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Home Switchboard Unix Administration Red Hat TCP/IP Networks Neoliberalism Toxic Managers May the source be with you, but remember the KISS principle ;-) Bigger doesn't imply better. Bigger often is a sign of obesity, of lost control, of overcomplexity, of cancerous cells
Software Engineering
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Software Engineering: A study akin to numerology and astrology, but lacking the precision of the former and the success of the latter. KISS Principle /kis' prin'si-pl/ n. "Keep It Simple, Stupid". A maxim often invoked when discussing design to fend off creeping featurism and control development complexity. Possibly related to the marketroid maxim on sales presentations, "Keep It Short and Simple". creeping featurism /kree'ping fee'chr-izm/ n. [common] 1. Describes a systematic tendency to load more chrome and features onto systems at the expense of whatever elegance they may have possessed when originally designed. See also feeping creaturism. "You know, the main problem with BSD Unix has always been creeping featurism." 2. More generally, the tendency for anything complicated to become even more complicated because people keep saying "Gee, it would be even better if it had this feature too". (See feature.) The result is usually a patchwork because it grew one ad-hoc step at a time, rather than being planned. Planning is a lot of work, but it's easy to add just one extra little feature to help someone ... and then another ... and another... When creeping featurism gets out of hand, it's like a cancer. Usually this term is used to describe computer programs, but it could also be said of the federal government, the IRS 1040 form, and new cars. A similar phenomenon sometimes afflicts conscious redesigns; see second-system effect. See also creeping elegance. Jargon file
Software engineering (SE) has probably largest concentration of snake oil salesman after OO programming and software architecture is far from being an exclusion. Many published software methodologies/architectures claim to provide the benefits, that most of them can not deliver (UML is one good example). I see a lot of oversimplification of the real situation and unnecessary (and useless) formalisms. The main idea advocated here is simplification of software architecture (including usage of well-understood "Pipe and Filter model") and scripting languages.
There are few quality general architectural resources available from the Net, therefore the list below represent only some links that I am interested personally. The stress here is on skepticism and this collection is neither complete, nor up to date. But still it might help students that are trying to study this complex and interesting subject. Or perhaps, if you already a software architect you might be able to expand your knowledge of the subject.
Excessive zeal in adopting some fashionable but questionable methodology is a "real and present danger" in software engineering. This is not a new threat, it started with structured programming revolution and then verification "holy land" searching with Edsger W. Dijkstra as a new prophet of an obsure cult. The main problem here that all those methodologies contain 20% of useful elements; but the other 80% kill all the useful elements and introduce probably some real disadvantages. After a dozen or so partially useful but mostly useless methodologies came, were enthusiastically adopted and went into oblivion we should definitely be skeptical.
All this "extreme programming" idiotism or CMM Lysenkoism should be treated as we treat dangerous religious sects. It's undemocratic and stupid to prohibit them but it's equally dangerous and stupid to follow their recommendations ;-). As Talleyrand advised to junior diplomats: "Above all, gentlemen, not too much zeal. " By this phrase, Talleyrand was reportedly recommended to his subordinates that important decisions must be based upon the exercise of cool-headed reason and not upon emotions or any waxing or waning popular delusion.
One interesting fact about software architecture is that it can't be practiced from the "ivory tower". Only when you do coding yourself and faces limitations of the tools and hardware you can create a great architecture. See Real Insights into Architecture Come Only From Actual Programming
One interesting fact about software architecture is that it can't be practiced from the "ivory tower". Only when you do coding yourself and faces limitations of the tools and hardware you can create a great architecture. See Real Insights into Architecture Come Only From Actual Programming
The primary purpose of Software Architecture courses is to teach students some higher level skills useful in designing and implementing complex software systems. In usually includes some information about classification (general and domain specific architectures), analysis and tools. As guys in Breadmear consulting aptly noted in their paper Who Software Architect Role:
A simplistic view of the role is that architects create architectures, and their responsibilities encompass all that is involved in doing so. This would include articulating the architectural vision, conceptualizing and experimenting with alternative architectural approaches, creating models and component and interface specification documents, and validating the architecture against requirements and assumptions.
However, any experienced architect knows that the role involves not just these technical activities, but others that are more political and strategic in nature on the one hand, and more like those of a consultant, on the other. A sound sense of business and technical strategy is required to envision the "right" architectural approach to the customer's problem set, given the business objectives of the architect's organization. Activities in this area include the creation of technology roadmaps, making assertions about technology directions and determining their consequences for the technical strategy and hence architectural approach.
Further, architectures are seldom embraced without considerable challenges from many fronts. The architect thus has to shed any distaste for what may be considered "organizational politics", and actively work to sell the architecture to its various stakeholders, communicating extensively and working networks of influence to ensure the ongoing success of the architecture.
But "buy-in" to the architecture vision is not enough either. Anyone involved in implementing the architecture needs to understand it. Since weighty architectural documents are notorious dust-gatherers, this involves creating and teaching tutorials and actively consulting on the application of the architecture, and being available to explain the rationale behind architectural choices and to make amendments to the architecture when justified.
Lastly, the architect must lead--the architecture team, the developer community, and, in its technical direction, the organization.
Again, I would like to stress that the main principle of software architecture is simple and well known -- it's famous KISS principle. While principle is simple its implementation is not and a lot of developers (especially developers with limited resources) paid dearly for violating this principle. I have found one one reference on simplicity in SE: R. S. Pressman. Simplicity. In Software Engineering, A Practitioner's Approach, page 452. McGraw Hill, 1997. Here open source tools can help because for those tools a complexity is not such a competitive advantage as for closed source tools. But that not necessary true about actual tools as one problem with open source projects is change of the leader. This is the moment when many projects lose architectural integrity and became a Byzantium compendium of conflicting approaches.
I appreciate am architecture of software system that lead to small size implementations with simple, Spartan interface. In these days the usage of scripting languages can cut the volume of code more than in half in comparison with Java. That's why this site is advocating usage of scripting languages for complex software projects.
"Real Beauty can be found in Simplicity," and as you may know already, ' "Less" sometimes equal "More".' I continue to adhere to that philosophy. If you, too, have an eye for simplicity in software engineering, then you might benefit from this collection of links.
I think writing a good software system is somewhat similar to writing a multivolume series of books. Most writers will rewrite each chapter of book several times and changes general structure a lot. Rewriting large systems is more difficult, but also very beneficial. It make sense always consider the current version of the system a draft that can be substantially improved and simplified by discovering some new unifying and simplifying paradigm. Sometimes you can take a wrong direction, but still "nothing venture nothing have."
On a subsystem level a decent configuration management system can help going back. Too often people try to write and debug their fundamentally flawed architecturally "first draft", when it would have been much simpler and faster to rewrite it based on better understanding of architecture and better understanding of the problem. Actually rewriting can save time spend in debugging of the old version. That way, when you're done, you may get easy-to-understand, simple software systems, instead of just systems that "seems to work okay" (only as correct as your testing).
On component level refactoring (see Refactoring: Improving the Design of Existing Code) might be a useful simplification technique. Actually rewriting is a simpler term, but let's assume that refactoring is rewriting with some ideological frosting ;-). See Slashdot Book Reviews Refactoring Improving the Design of Existing Code.
I have found one reference on simplicity in SE: R. S. Pressman. Simplicity. In Software Engineering, A Practitioner's Approach, page 452. McGraw Hill, 1997.
Another relevant work (he try to promote his own solution -- you can skip this part) is the critique of "the technology mud slide" in a book The Innovator's Dilemma by Harvard Business School Professor Clayton M. Christensen . He defined the term"technology mudslide", the concept very similar to Brooks "software development tar pit" -- a perpetual cycle of abandonment or retooling of existing systems in pursuit of the latest fashionable technology trend -- a cycle in which
"Coping with the relentless onslaught of technology change was akin to trying to climb a mudslide raging down a hill. You have to scramble with everything you've got to stay on top of it. and if you ever once stop to catch your breath, you get buried."
The complexity caused by adopting new technology for the sake of new technology is further exacerbated by the narrow focus and inexperience of many project leaders -- inexperience with mission-critical systems, systems of larger scale then previously built, software development disciplines, and project management. A Standish Group International survey recently showed that 46% of IT projects were over budget and overdue -- and 28% failed altogether. That's normal and probably the real failures figures are higher: great software managers and architects are rare and it is those people who determine the success of a software project.
Dr. Nikolai Bezroukov
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[May 17, 2019] Shareholder Capitalism, the Military, and the Beginning of the End for Boeing
"... When real engineering clashes with financial engineering, the damage takes the form of a geographically disparate and demoralized workforce: The factory-floor denominator goes down. Workers' wages are depressed, testing and quality assurance are curtailed. ..."
May 17, 2019 | www.nakedcapitalism.com
The fall of the Berlin Wall and the corresponding end of the Soviet Empire gave the fullest impetus imaginable to the forces of globalized capitalism, and correspondingly unfettered access to the world's cheapest labor. What was not to like about that? It afforded multinational corporations vastly expanded opportunities to fatten their profit margins and increase the bottom line with seemingly no risk posed to their business model.
Or so it appeared. In 2000, aerospace engineer L.J. Hart-Smith's remarkable paper, sardonically titled "Out-Sourced Profits – The Cornerstone of Successful Subcontracting," laid out the case against several business practices of Hart-Smith's previous employer, McDonnell Douglas, which had incautiously ridden the wave of outsourcing when it merged with the author's new employer, Boeing. Hart-Smith's intention in telling his story was a cautionary one for the newly combined Boeing, lest it follow its then recent acquisition down the same disastrous path.
Of the manifold points and issues identified by Hart-Smith, there is one that stands out as the most compelling in terms of understanding the current crisis enveloping Boeing: The embrace of the metric "Return on Net Assets" (RONA). When combined with the relentless pursuit of cost reduction (via offshoring), RONA taken to the extreme can undermine overall safety standards.
Related to this problem is the intentional and unnecessary use of complexity as an instrument of propaganda. Like many of its Wall Street counterparts, Boeing also used complexity as a mechanism to obfuscate and conceal activity that is incompetent, nefarious and/or harmful to not only the corporation itself but to society as a whole (instead of complexity being a benign byproduct of a move up the technology curve).
All of these pernicious concepts are branches of the same poisoned tree: " shareholder capitalism ":
[A] notion best epitomized by Milton Friedman that the only social responsibility of a corporation is to increase its profits, laying the groundwork for the idea that shareholders, being the owners and the main risk-bearing participants, ought therefore to receive the biggest rewards. Profits therefore should be generated first and foremost with a view toward maximizing the interests of shareholders, not the executives or managers who (according to the theory) were spending too much of their time, and the shareholders' money, worrying about employees, customers, and the community at large. The economists who built on Friedman's work, along with increasingly aggressive institutional investors, devised solutions to ensure the primacy of enhancing shareholder value, via the advocacy of hostile takeovers, the promotion of massive stock buybacks or repurchases (which increased the stock value), higher dividend payouts and, most importantly, the introduction of stock-based pay for top executives in order to align their interests to those of the shareholders. These ideas were influenced by the idea that corporate efficiency and profitability were impinged upon by archaic regulation and unionization, which, according to the theory, precluded the ability to compete globally.
"Return on Net Assets" (RONA) forms a key part of the shareholder capitalism doctrine. In essence, it means maximizing the returns of those dollars deployed in the operation of the business. Applied to a corporation, it comes down to this: If the choice is between putting a million bucks into new factory machinery or returning it to shareholders, say, via dividend payments, the latter is the optimal way to go because in theory it means higher net returns accruing to the shareholders (as the "owners" of the company), implicitly assuming that they can make better use of that money than the company itself can.
It is an absurd conceit to believe that a dilettante portfolio manager is in a better position than an aviation engineer to gauge whether corporate investment in fixed assets will generate productivity gains well north of the expected return for the cash distributed to the shareholders. But such is the perverse fantasy embedded in the myth of shareholder capitalism.
Engineering reality, however, is far more complicated than what is outlined in university MBA textbooks. For corporations like McDonnell Douglas, for example, RONA was used not as a way to prioritize new investment in the corporation but rather to justify disinvestment in the corporation. This disinvestment ultimately degraded the company's underlying profitability and the quality of its planes (which is one of the reasons the Pentagon helped to broker the merger with Boeing; in another perverse echo of the 2008 financial disaster, it was a politically engineered bailout).
RONA in Practice
When real engineering clashes with financial engineering, the damage takes the form of a geographically disparate and demoralized workforce: The factory-floor denominator goes down. Workers' wages are depressed, testing and quality assurance are curtailed. Productivity is diminished, even as labor-saving technologies are introduced. Precision machinery is sold off and replaced by inferior, but cheaper, machines. Engineering quality deteriorates. And the upshot is that a reliable plane like Boeing's 737, which had been a tried and true money-spinner with an impressive safety record since 1967, becomes a high-tech death trap.
The drive toward efficiency is translated into a drive to do more with less. Get more out of workers while paying them less. Make more parts with fewer machines. Outsourcing is viewed as a way to release capital by transferring investment from skilled domestic human capital to offshore entities not imbued with the same talents, corporate culture and dedication to quality. The benefits to the bottom line are temporary; the long-term pathologies become embedded as the company's market share begins to shrink, as the airlines search for less shoddy alternatives.
You must do one more thing if you are a Boeing director: you must erect barriers to bad news, because there is nothing that bursts a magic bubble faster than reality, particularly if it's bad reality.
The illusion that Boeing sought to perpetuate was that it continued to produce the same thing it had produced for decades: namely, a safe, reliable, quality airplane. But it was doing so with a production apparatus that was stripped, for cost reasons, of many of the means necessary to make good aircraft. So while the wine still came in a bottle signifying Premier Cru quality, and still carried the same price, someone had poured out the contents and replaced them with cheap plonk.
And that has become remarkably easy to do in aviation. Because Boeing is no longer subject to proper independent regulatory scrutiny. This is what happens when you're allowed to " self-certify" your own airplane , as the Washington Post described: "One Boeing engineer would conduct a test of a particular system on the Max 8, while another Boeing engineer would act as the FAA's representative, signing on behalf of the U.S. government that the technology complied with federal safety regulations."
This is a recipe for disaster. Boeing relentlessly cut costs, it outsourced across the globe to workforces that knew nothing about aviation or aviation's safety culture. It sent things everywhere on one criteria and one criteria only: lower the denominator. Make it the same, but cheaper. And then self-certify the plane, so that nobody, including the FAA, was ever the wiser.
Boeing also greased the wheels in Washington to ensure the continuation of this convenient state of regulatory affairs for the company. According to OpenSecrets.org , Boeing and its affiliates spent $15,120,000 in lobbying expenses in 2018, after spending,$16,740,000 in 2017 (along with a further $4,551,078 in 2018 political contributions, which placed the company 82nd out of a total of 19,087 contributors). Looking back at these figures over the past four elections (congressional and presidential) since 2012, these numbers represent fairly typical spending sums for the company. But clever financial engineering, extensive political lobbying and self-certification can't perpetually hold back the effects of shoddy engineering. One of the sad byproducts of the FAA's acquiescence to "self-certification" is how many things fall through the cracks so easily. [May 05, 2019] Does America Have an Economy or Any Sense of Reality by Paul Craig Roberts Notable quotes: "... We are having a propaganda barrage about the great Trump economy. We have been hearing about the great economy for a decade while the labor force participation rate declined, real family incomes stagnated, and debt burdens rose. The economy has been great only for large equity owners whose stock ownership benefited from the trillions of dollars the Fed poured into financial markets and from buy-backs by corporations of their own stocks. ..." "... Federal Reserve data reports that a large percentage of the younger work force live at home with parents, because the jobs available to them are insufficient to pay for an independent existence. How then can the real estate, home furnishings, and appliance markets be strong? ..." "... In contrast, Robotics, instead of displacing labor, eliminates it. Unlike jobs offshoring which shifted jobs from the US to China, robotics will cause jobs losses in both countries. If consumer incomes fall, then demand for output also falls, and output will fall. Robotics, then, is a way to shrink gross domestic product. ..." "... The tech nerds and corporations who cannot wait for robotics to reduce labor cost in their profits calculation are incapable of understanding that when masses of people are without jobs, there is no consumer income with which to purchase the products of robots. The robots themselves do not need housing, food, clothing, entertainment, transportation, and medical care. The mega-rich owners of the robots cannot possibly consume the robotic output. An economy without consumers is a profitless economy. ..." "... A country incapable of dealing with real problems has no future. ..." May 02, 2019 | www.unz.com We are having a propaganda barrage about the great Trump economy. We have been hearing about the great economy for a decade while the labor force participation rate declined, real family incomes stagnated, and debt burdens rose. The economy has been great only for large equity owners whose stock ownership benefited from the trillions of dollars the Fed poured into financial markets and from buy-backs by corporations of their own stocks. I have pointed out for years that the jobs reports are fabrications and that the jobs that do exist are lowly paid domestic service jobs such as waitresses and bartenders and health care and social assistance. What has kept the American economy going is the expansion of consumer debt, not higher pay from higher productivity. The reported low unemployment rate is obtained by not counting discouraged workers who have given up on finding a job. Do you remember all the corporate money that the Trump tax cut was supposed to bring back to America for investment? It was all BS. Yesterday I read reports that Apple is losing its trillion dollar market valuation because Apple is using its profits to buy back its own stock. In other words, the demand for Apple's products does not justify more investment. Therefore, the best use of the profit is to repurchase the equity shares, thus shrinking Apple's capitalization. The great economy does not include expanding demand for Apple's products. I read also of endless store and mall closings, losses falsely attributed to online purchasing, which only accounts for a small percentage of sales. Federal Reserve data reports that a large percentage of the younger work force live at home with parents, because the jobs available to them are insufficient to pay for an independent existence. How then can the real estate, home furnishings, and appliance markets be strong? When a couple of decades ago I first wrote of the danger of jobs offshoring to the American middle class, state and local government budgets, and pension funds, idiot critics raised the charge of Luddite. The Luddites were wrong. Mechanization raised the productivity of labor and real wages, but jobs offshoring shifts jobs from the domestic economy to abroad. Domestic labor is displaced, but overseas labor gets the jobs, thus boosting jobs there. In other words, labor income declines in the country that loses jobs and rises in the country to which the jobs are offshored. This is the way American corporations spurred the economic development of China. It was due to jobs offshoring that China developed far more rapidly than the CIA expected. In contrast, Robotics, instead of displacing labor, eliminates it. Unlike jobs offshoring which shifted jobs from the US to China, robotics will cause jobs losses in both countries. If consumer incomes fall, then demand for output also falls, and output will fall. Robotics, then, is a way to shrink gross domestic product. The tech nerds and corporations who cannot wait for robotics to reduce labor cost in their profits calculation are incapable of understanding that when masses of people are without jobs, there is no consumer income with which to purchase the products of robots. The robots themselves do not need housing, food, clothing, entertainment, transportation, and medical care. The mega-rich owners of the robots cannot possibly consume the robotic output. An economy without consumers is a profitless economy. One would think that there would be a great deal of discussion about the economic effects of robotics before the problems are upon us, just as one would think there would be enormous concern about the high tensions Washington has caused between the US and Russia and China, just as one would think there would be preparations for the adverse economic consequences of global warming, whatever the cause. Instead, the US, a country facing many crises, is focused on whether President Trump obstructed investigation of a crime that the special prosecutor said did not take place. A country incapable of dealing with real problems has no future. [Apr 28, 2019] AI is software. Software bugs. Software doesn't autocorrect bugs. Men correct bugs. A bugging self-driving car leads its passengers to death. A man driving a car can steer away from death Apr 28, 2019 | www.unz.com The infatuation with AI makes people overlook three AI's built-in glitches. AI is software. Software bugs. Software doesn't autocorrect bugs. Men correct bugs. A bugging self-driving car leads its passengers to death. A man driving a car can steer away from death. Humans love to behave in erratic ways, it is just impossible to program AI to respond to all possible erratic human behaviour. Therefore, instead of adapting AI to humans, humans will be forced to adapt to AI, and relinquish a lot of their liberty as humans. Humans have moral qualms (not everybody is Hillary Clinton), AI being strictly utilitarian, will necessarily be "psychopathic". In short AI is the promise of communism raised by several orders of magnitude. Welcome to the "Brave New World". @Vojkan You've raised some interesting objections, Vojkan. But here are a few quibbles: 1) AI is software. Software bugs. Software doesn't autocorrect bugs. Men correct bugs. A bugging self-driving car leads its passengers to death. A man driving a car can steer away from death. Learn to code! Seriously, until and unless the AI devices acquire actual power over their human masters (as in The Matrix ), this is not as big a problem as you think. You simply test the device over and over and over until the bugs are discovered and worked out -- in other words, we just keep on doing what we've always done with software: alpha, beta, etc. 2) Humans love to behave in erratic ways, it is just impossible to program AI to respond to all possible erratic human behaviour. Therefore, instead of adapting AI to humans, humans will be forced to adapt to AI, and relinquish a lot of their liberty as humans. There's probably some truth to that. This reminds me of the old Marshall McCluhan saying that "the medium is the message," and that we were all going to adapt our mode of cognition (somewhat) to the TV or the internet, or whatever. Yeah, to some extent that has happened. But to some extent, that probably happened way back when people first began domesticating horses and riding them. Human beings are 'programmed', as it were, to adapt to their environments to some extent, and to condition their reactions on the actions of other things/creatures in their environment. However, I think you may be underestimating the potential to create interfaces that allow AI to interact with a human in much more complex ways, such as how another human would interact with human: sublte visual cues, pheromones, etc. That, in fact, was the essence of the old Turing Test, which is still the Holy Grail of AI: https://en.wikipedia.org/wiki/Turing_test 3) Humans have moral qualms (not everybody is Hillary Clinton), AI being strictly utilitarian, will necessarily be "psychopathic". I don't see why AI devices can't have some moral principles -- or at least moral biases -- programmed into them. Isaac Asimov didn't think this was impossible either: https://en.wikipedia.org/wiki/Three_Laws_of_Robotics reiner Tor , says: April 27, 2019 at 11:47 am GMT @Digital Samizdat You simply test the device over and over and over until the bugs are discovered and worked out -- in other words, we just keep on doing what we've always done with software: alpha, beta, etc. Some bugs stay dormant for decades. I've seen one up close. Digital Samizdat , says: April 27, 2019 at 11:57 am GMT @reiner Tor Well, you fix it whenever you find it! That's a problem as old as programming; in fact, it's a problem as old as engineering itself. It's nothing new. reiner Tor , says: April 27, 2019 at 12:11 pm GMT @Digital Samizdat What's new with AI is the amount of damage a faulty software multiplied many times over can do. My experience was pretty horrible (I was one of the two humans overseeing the system, but it was a pretty horrifying experience), but if the system was fully autonomous, it'd have driven my employer bankrupt. Now I'm not against using AI in any form whatsoever; I also think that it's inevitable anyway. I'd support AI driving cars or flying planes, because they are likely safer than humans, though it's of course changing a manageable risk for a very small probability tail risk. But I'm pretty worried about AI in general. [Mar 13, 2019] Pilots Complained About Boeing 737 Max 8 For Months Before Second Deadly Crash Mar 13, 2019 | www.zerohedge.com Several Pilots repeatedly warned federal authorities of safety concerns over the now-grounded Boeing 737 Max 8 for months leading up to the second deadly disaster involving the plane, according to an investigation by the Dallas Morning News . One captain even called the Max 8's flight manual " inadequate and almost criminally insufficient ," according to the report. " The fact that this airplane requires such jury-rigging to fly is a red flag. Now we know the systems employed are error-prone -- even if the pilots aren't sure what those systems are, what redundancies are in place and failure modes. I am left to wonder: what else don't I know?" wrote the captain. At least five complaints about the Boeing jet were found in a federal database which pilots routinely use to report aviation incidents without fear of repercussions. The complaints are about the safety mechanism cited in preliminary reports for an October plane crash in Indonesia that killed 189. The disclosures found by The News reference problems during flights of Boeing 737 Max 8s with an autopilot system during takeoff and nose-down situations while trying to gain altitude. While records show these flights occurred during October and November, information regarding which airlines the pilots were flying for at the time is redacted from the database. - Dallas Morning News One captain who flies the Max 8 said in November that it was "unconscionable" that Boeing and federal authorities have allowed pilots to fly the plane without adequate training - including a failure to fully disclose how its systems were distinctly different from other planes. An FAA spokesman said the reporting system is directly filed to NASA, which serves as an neutral third party in the reporting of grievances. "The FAA analyzes these reports along with other safety data gathered through programs the FAA administers directly, including the Aviation Safety Action Program, which includes all of the major airlines including Southwest and American," said FAA southwest regional spokesman Lynn Lunsford. Meanwhile, despite several airlines and foreign countries grounding the Max 8, US regulators have so far declined to follow suit. They have, however, mandated that Boeing upgrade the plane's software by April. Sen. Ted Cruz (R-TX), who chairs a Senate subcommittee overseeing aviation, called for the grounding of the Max 8 in a Thursday statement. "Further investigation may reveal that mechanical issues were not the cause, but until that time, our first priority must be the safety of the flying public," said Cruz. At least 18 carriers -- including American Airlines and Southwest Airlines, the two largest U.S. carriers flying the 737 Max 8 -- have also declined to ground planes , saying they are confident in the safety and "airworthiness" of their fleets. American and Southwest have 24 and 34 of the aircraft in their fleets, respectively. - Dallas Morning News The United States should be leading the world in aviation safety," said Transport Workers Union president John Samuelsen. " And yet, because of the lust for profit in the American aviation, we're still flying planes that dozens of other countries and airlines have now said need to grounded ." Tags Disaster Accident [Mar 13, 2019] Boeing's automatic trim for the 737 MAX was not disclosed to the Pilots by Bjorn Fehrm The background to Boeing's 737 MAX automatic trim Mar 13, 2019 | leehamnews.com The automatic trim we described last week has a name, MCAS, or Maneuvering Characteristics Automation System. It's unique to the MAX because the 737 MAX no longer has the docile pitch characteristics of the 737NG at high Angles Of Attack (AOA). This is caused by the larger engine nacelles covering the higher bypass LEAP-1B engines. The nacelles for the MAX are larger and placed higher and further forward of the wing, Figure 1. Figure 1. Boeing 737NG (left) and MAX (right) nacelles compared. Source: Boeing 737 MAX brochure. By placing the nacelle further forward of the wing, it could be placed higher. Combined with a higher nose landing gear, which raises the nacelle further, the same ground clearance could be achieved for the nacelle as for the 737NG. The drawback of a larger nacelle, placed further forward, is it destabilizes the aircraft in pitch. All objects on an aircraft placed ahead of the Center of Gravity (the line in Figure 2, around which the aircraft moves in pitch) will contribute to destabilize the aircraft in pitch. ... ... ... The 737 is a classical flight control aircraft. It relies on a naturally stable base aircraft for its flight control design, augmented in selected areas. Once such area is the artificial yaw damping, present on virtually all larger aircraft (to stop passengers getting sick from the aircraft's natural tendency to Dutch Roll = Wagging its tail). Until the MAX, there was no need for artificial aids in pitch. Once the aircraft entered a stall, there were several actions described last week which assisted the pilot to exit the stall. But not in normal flight. The larger nacelles, called for by the higher bypass LEAP-1B engines, changed this. When flying at normal angles of attack (3° at cruise and say 5° in a turn) the destabilizing effect of the larger engines are not felt. The nacelles are designed to not generate lift in normal flight. It would generate unnecessary drag as the aspect ratio of an engine nacelle is lousy. The aircraft designer focuses the lift to the high aspect ratio wings. But if the pilot for whatever reason manoeuvres the aircraft hard, generating an angle of attack close to the stall angle of around 14°, the previously neutral engine nacelle generates lift. A lift which is felt by the aircraft as a pitch up moment (as its ahead of the CG line), now stronger than on the 737NG. This destabilizes the MAX in pitch at higher Angles Of Attack (AOA). The most difficult situation is when the maneuver has a high pitch ratio. The aircraft's inertia can then provoke an over-swing into stall AOA. To counter the MAX's lower stability margins at high AOA, Boeing introduced MCAS. Dependent on AOA value and rate, altitude (air density) and Mach (changed flow conditions) the MCAS, which is a software loop in the Flight Control computer, initiates a nose down trim above a threshold AOA. It can be stopped by the Pilot counter-trimming on the Yoke or by him hitting the CUTOUT switches on the center pedestal. It's not stopped by the Pilot pulling the Yoke, which for normal trim from the autopilot or runaway manual trim triggers trim hold sensors. This would negate why MCAS was implemented, the Pilot pulling so hard on the Yoke that the aircraft is flying close to stall. It's probably this counterintuitive characteristic, which goes against what has been trained many times in the simulator for unwanted autopilot trim or manual trim runaway, which has confused the pilots of JT610. They learned that holding against the trim stopped the nose down, and then they could take action, like counter-trimming or outright CUTOUT the trim servo. But it didn't. After a 10 second trim to a 2.5° nose down stabilizer position, the trimming started again despite the Pilots pulling against it. The faulty high AOA signal was still present. How should they know that pulling on the Yoke didn't stop the trim? It was described nowhere; neither in the aircraft's manual, the AFM, nor in the Pilot's manual, the FCOM. This has created strong reactions from airlines with the 737 MAX on the flight line and their Pilots. They have learned the NG and the MAX flies the same. They fly them interchangeably during the week. They do fly the same as long as no fault appears. Then there are differences, and the Pilots should have been informed about the differences. 1. Bruce Levitt November 14, 2018 In figure 2 it shows the same center of gravity for the NG as the Max. I find this a bit surprising as I would have expected that mounting heavy engines further forward would have cause a shift forward in the center of gravity that would not have been offset by the longer tailcone, which I'm assuming is relatively light even with APU installed. Based on what is coming out about the automatic trim, Boeing must be counting its lucky stars that this incident happened to Lion Air and not to an American aircraft. If this had happened in the US, I'm pretty sure the fleet would have been grounded by the FAA and the class action lawyers would be lined up outside the door to get their many pounds of flesh. This is quite the wake-up call for Boeing. • OV-099 November 14, 2018 If the FAA is not going to comprehensively review the certification for the 737 MAX, I would not be surprised if EASA would start taking a closer look at the aircraft and why the FAA seemingly missed the seemingly inadequate testing of the automatic trim when they decided to certified the 737 MAX 8. Reply • Doubting Thomas November 16, 2018 One wonders if there are any OTHER goodies in the new/improved/yet identical handling latest iteration of this old bird that Boeing did not disclose so that pilots need not be retrained. EASA & FAA likely already are asking some pointed questions and will want to verify any statements made by the manufacturer. Depending on the answers pilot training requirements are likely to change materially. • jbeeko November 14, 2018 CG will vary based on loading. I'd guess the line is the rear-most allowed CG. • ahmed November 18, 2018 hi dears I think that even the pilot didnt knew about the MCAS ; this case can be corrected by only applying the boeing check list (QRH) stabilizer runaway. the pilot when they noticed that stabilizer are trimming without a knewn input ( from pilot or from Auto pilot ) ; shout put the cut out sw in the off position according to QRH. Reply • TransWorld November 19, 2018 Please note that the first actions pulling back on the yoke to stop it. Also keep in mind the aircraft is screaming stall and the stick shaker is activated. Pulling back on the yoke in that case is the WRONG thing to do if you are stalled. The Pilot has to then determine which system is lading. At the same time its chaning its behavior from previous training, every 5 seconds, it does it again. There also was another issue taking place at the same time. So now you have two systems lying to you, one that is actively trying to kill you. If the Pitot static system is broken, you also have several key instruments feeding you bad data (VSI, altitude and speed) • TransWorld November 14, 2018 Grubbie: I can partly answer that. Pilots are trained to immediately deal with emergency issues (engine loss etc) Then there is a follow up detailed instructions for follow on actions (if any). Simulators are wonderful things because you can train lethal scenes without lethal results. In this case, with NO pilot training let alone in the manuals, pilots have to either be really quick in the situation or you get the result you do. Some are better at it than others (Sullenbergers along with other aspects elected to turn on his APU even though it was not part of the engine out checklist) The other one was to ditch, too many pilots try to turn back even though we are trained not to. What I can tell you from personal expereince is having got myself into a spin without any training, I was locked up logic wise (panic) as suddenly nothing was working the way it should. I was lucky I was high enough and my brain kicked back into cold logic mode and I knew the counter to a spin from reading) Another 500 feet and I would not be here to post. While I did parts of the spin recovery wrong, fortunately in that aircraft it did not care, right rudder was enough to stop it. Reply 1. OV-099 November 14, 2018 It's starting to look as if Boeing will not be able to just pay victims' relatives in the form of "condolence money", without admitting liability. Reply • Dukeofurl November 14, 2018 Im pretty sure, even though its an Indonesian Airline, any whiff of fault with the plane itself will have lawyers taking Boeing on in US courts. 1. Tech-guru November 14, 2018 Astonishing to say the least. It is quite unlike Boeing. They are normally very good in the documentation and training. It makes everyone wonder how such vital change on the MAX aircraft was omitted from books as weel as in crew training. Your explanation is very good as to why you need this damn MCAS. But can you also tell us how just one faulty sensor can trigger this MCAS. In all other Boeing models like B777, the two AOA sensor signals are compared with a calculated AOA and choose the mid value within the ADIRU. It eliminates a drastic mistake of following a wrong sensor input. • Bjorn Fehrm November 14, 2018 Hi Tech-Gury, it's not sure it's a one sensor fault. One sensor was changed amid information there was a 20 degree diff between the two sides. But then it happened again. I think we might be informed something else is at the root of this, which could also trip such a plausibility check you mention. We just don't know. What we know is the MCAS function was triggered without the aircraft being close to stall. Reply • Matthew November 14, 2018 If it's certain that the MCAS was doing unhelpful things, that coupled with the fact that no one was telling pilots anything about it suggests to me that this is already effectively an open-and-shut case so far as liability, regulatory remedies are concerned. The tecnical root cause is also important, but probably irrelevant so far as estbalishing the ultimate reason behind the crash. Reply [Mar 13, 2019] Boeing Crapification Second 737 Max Plane Within Five Months Crashes Just After Takeoff Notable quotes: "... The key point I want to pick up on from that earlier post is this: the Boeing 737 Max includes a new "safety" feature about which the company failed to inform the Federal Aviation Administration (FAA). ..." "... Boeing Co. withheld information about potential hazards associated with a new flight-control feature suspected of playing a role in last month's fatal Lion Air jet crash, according to safety experts involved in the investigation, as well as midlevel FAA officials and airline pilots. ..." "... Notice that phrase: "under unusual conditions". Seems now that the pilots of two of these jets may have encountered such unusual conditions since October. ..." "... Why did Boeing neglect to tell the FAA – or, for that matter, other airlines or regulatory authorities – about the changes to the 737 Max? Well, the airline marketed the new jet as not needing pilots to undergo any additional training in order to fly it. ..." "... In addition to considerable potential huge legal liability, from both the Lion Air and Ethiopian Airlines crashes, Boeing also faces the commercial consequences of grounding some if not all 737 Max 8 'planes currently in service – temporarily? indefinitely? -and loss or at minimum delay of all future sales of this aircraft model. ..." "... If this tragedy had happened on an aircraft of another manufacturer other than big Boeing, the fleet would already have been grounded by the FAA. The arrogance of engineers both at Airbus and Boeing, who refuse to give the pilots easy means to regain immediate and full authority over the plane (pitch and power) is just appalling. ..." "... Boeing has made significant inroads in China with its 737 MAX family. A dozen Chinese airlines have ordered 180 of the planes, and 76 of them have been delivered, according Boeing. About 85% of Boeing's unfilled Chinese airline orders are for 737 MAX planes. ..." "... "It's pretty asinine for them to put a system on an airplane and not tell the pilots who are operating the airplane, especially when it deals with flight controls," Captain Mike Michaelis, chairman of the safety committee for the Allied Pilots Association, told the Wall Street Journal. ..." "... The aircraft company concealed the new system and minimized the differences between the MAX and other versions of the 737 to boost sales. On the Boeing website, the company claims that airlines can save "millions of dollars" by purchasing the new plane "because of its commonality" with previous versions of the plane. ..." "... "Years of experience representing hundreds of victims has revealed a common thread through most air disaster cases," said Charles Herrmann the principle of Herrmann Law. "Generating profit in a fiercely competitive market too often involves cutting safety measures. In this case, Boeing cut training and completely eliminated instructions and warnings on a new system. Pilots didn't even know it existed. I can't blame so many pilots for being mad as hell." ..." "... The Air France Airbus disaster was jumped on – Boeing's traditional hydraulic links between the sticks for the two pilots ensuring they move in tandem; the supposed comments by Captain Sully that the Airbus software didn't allow him to hit the water at the optimal angle he wanted, causing the rear rupture in the fuselage both showed the inferiority of fly-by-wire until Boeing started using it too. (Sully has taken issue with the book making the above point and concludes fly-by-wire is a "mixed blessing".) ..." "... Money over people. ..." Mar 13, 2019 | www.nakedcapitalism.com Posted on March 11, 2019 by Jerri-Lynn Scofield By Jerri-Lynn Scofield, who has worked as a securities lawyer and a derivatives trader. She is currently writing a book about textile artisans. Yesterday, an Ethiopian Airlines flight crashed minutes after takeoff, killing all 157 passengers on board. The crash occurred less than five months after a Lion Air jet crashed near Jakarta, Indonesia, also shortly after takeoff, and killed all 189 passengers. Both jets were Boeing's latest 737 Max 8 model. The Wall Street Journal reports in Ethiopian Crash Carries High Stakes for Boeing, Growing African Airline : The state-owned airline is among the early operators of Boeing's new 737 MAX single-aisle workhorse aircraft, which has been delivered to carriers around the world since 2017. The 737 MAX represents about two-thirds of Boeing's future deliveries and an estimated 40% of its profits, according to analysts. Having delivered 350 of the 737 MAX planes as of January, Boeing has booked orders for about 5,000 more, many to airlines in fast-growing emerging markets around the world. The voice and data recorders for the doomed flight have already been recovered, the New York Times reported in Ethiopian Airline Crash Updates: Data and Voice Recorders Recovered . Investigators will soon be able to determine whether the same factors that caused the Lion Air crash also caused the latest Ethiopian Airlines tragedy. Boeing, Crapification, Two 737 Max Crashes Within Five Months Yves wrote a post in November, Boeing, Crapification, and the Lion Air Crash , analyzing a devastating Wall Street Journal report on that earlier crash. I will not repeat the details of her post here, but instead encourage interested readers to read it iin full. The key point I want to pick up on from that earlier post is this: the Boeing 737 Max includes a new "safety" feature about which the company failed to inform the Federal Aviation Administration (FAA). As Yves wrote: The short version of the story is that Boeing had implemented a new "safety" feature that operated even when its plane was being flown manually, that if it went into a stall, it would lower the nose suddenly to pick airspeed and fly normally again. However, Boeing didn't tell its buyers or even the FAA about this new goodie. It wasn't in pilot training or even the manuals. But even worse, this new control could force the nose down so far that it would be impossible not to crash the plane. And no, I am not making this up. From the Wall Street Journal: Boeing Co. withheld information about potential hazards associated with a new flight-control feature suspected of playing a role in last month's fatal Lion Air jet crash, according to safety experts involved in the investigation, as well as midlevel FAA officials and airline pilots. The automated stall-prevention system on Boeing 737 MAX 8 and MAX 9 models -- intended to help cockpit crews avoid mistakenly raising a plane's nose dangerously high -- under unusual conditions can push it down unexpectedly and so strongly that flight crews can't pull it back up. Such a scenario, Boeing told airlines in a world-wide safety bulletin roughly a week after the accident, can result in a steep dive or crash -- even if pilots are manually flying the jetliner and don't expect flight-control computers to kick in. Notice that phrase: "under unusual conditions". Seems now that the pilots of two of these jets may have encountered such unusual conditions since October. Why did Boeing neglect to tell the FAA – or, for that matter, other airlines or regulatory authorities – about the changes to the 737 Max? Well, the airline marketed the new jet as not needing pilots to undergo any additional training in order to fly it. I see. Why Were 737 Max Jets Still in Service? Today, Boeing executives no doubt rue not pulling all 737 Max 8 jets out of service after the October Lion Air crash, to allow their engineers and engineering safety regulators to make necessary changes in the 'plane's design or to develop new training protocols. In addition to considerable potential huge legal liability, from both the Lion Air and Ethiopian Airlines crashes, Boeing also faces the commercial consequences of grounding some if not all 737 Max 8 'planes currently in service – temporarily? indefinitely? -and loss or at minimum delay of all future sales of this aircraft model. Over to Yves again, who in her November post cut to the crux: And why haven't the planes been taken out of service? As one Wall Street Journal reader put it: If this tragedy had happened on an aircraft of another manufacturer other than big Boeing, the fleet would already have been grounded by the FAA. The arrogance of engineers both at Airbus and Boeing, who refuse to give the pilots easy means to regain immediate and full authority over the plane (pitch and power) is just appalling. Accident and incident records abound where the automation has been a major contributing factor or precursor. Knowing our friends at Boeing, it is highly probable that they will steer the investigation towards maintenance deficiencies as primary cause of the accident In the wake of the Ethiopian Airlines crash, other countries have not waited for the FAA to act. China and Indonesia, as well as Ethiopian Airlines and Cayman Airways, have grounded flights of all Boeing 737 Max 8 aircraft, the Guardian reported in Ethiopian Airlines crash: Boeing faces safety questions over 737 Max 8 jets . The FT has called the Chinese and Indonesian actions an "unparalleled flight ban" (see China and Indonesia ground Boeing 737 Max 8 jets after latest crash ). India's air regulator has also issued new rules covering flights of the 737 Max aircraft, requiring pilots to have a minimum of 1,000 hours experience to fly these 'planes, according to a report in the Economic Times, DGCA issues additional safety instructions for flying B737 MAX planes. Future of Boeing? The commercial consequences of grounding the 737 Max in China alone are significant, according to this CNN account, Why grounding 737 MAX jets is a big deal for Boeing . The 737 Max is Boeing's most important plane; China is also the company's major market: "A suspension in China is very significant, as this is a major market for Boeing," said Greg Waldron, Asia managing editor at aviation research firm FlightGlobal. Boeing has predicted that China will soon become the world's first trillion-dollar market for jets. By 2037, Boeing estimates China will need 7,690 commercial jets to meet its travel demands. Airbus (EADSF) and Commercial Aircraft Corporation of China, or Comac, are vying with Boeing for the vast and rapidly growing Chinese market. Comac's first plane, designed to compete with the single-aisle Boeing 737 MAX and Airbus A320, made its first test flight in 2017. It is not yet ready for commercial service, but Boeing can't afford any missteps. Boeing has made significant inroads in China with its 737 MAX family. A dozen Chinese airlines have ordered 180 of the planes, and 76 of them have been delivered, according Boeing. About 85% of Boeing's unfilled Chinese airline orders are for 737 MAX planes. The 737 has been Boeing's bestselling product for decades. The company's future depends on the success the 737 MAX, the newest version of the jet. Boeing has 4,700 unfilled orders for 737s, representing 80% of Boeing's orders backlog. Virtually all 737 orders are for MAX versions. As of the time of posting, US airlines have yet to ground their 737 Max 8 fleets. American Airlines, Alaska Air, Southwest Airlines, and United Airlines have ordered a combined 548 of the new 737 jets, of which 65 have been delivered, according to CNN. Legal Liability? Prior to Sunday's Ethiopian Airlines crash, Boeing already faced considerable potential legal liability for the October Lion Air crash. Just last Thursday, the Hermann Law Group of personal injury lawyers filed suit against Boeing on behalf of the families of 17 Indonesian passengers who died in that crash. The Families of Lion Air Crash File Lawsuit Against Boeing – News Release did not mince words; "It's pretty asinine for them to put a system on an airplane and not tell the pilots who are operating the airplane, especially when it deals with flight controls," Captain Mike Michaelis, chairman of the safety committee for the Allied Pilots Association, told the Wall Street Journal. The president of the pilots union at Southwest Airlines, Jon Weaks, said, "We're pissed that Boeing didn't tell the companies, and the pilots didn't get notice." The aircraft company concealed the new system and minimized the differences between the MAX and other versions of the 737 to boost sales. On the Boeing website, the company claims that airlines can save "millions of dollars" by purchasing the new plane "because of its commonality" with previous versions of the plane. "Years of experience representing hundreds of victims has revealed a common thread through most air disaster cases," said Charles Herrmann the principle of Herrmann Law. "Generating profit in a fiercely competitive market too often involves cutting safety measures. In this case, Boeing cut training and completely eliminated instructions and warnings on a new system. Pilots didn't even know it existed. I can't blame so many pilots for being mad as hell." Additionally, the complaint alleges the United States Federal Aviation Administration is partially culpable for negligently certifying Boeing's Air Flight Manual without requiring adequate instruction and training on the new system. Canadian and Brazilian authorities did require additional training. What's Next? The consequences for Boeing could be serious and will depend on what the flight and voice data recorders reveal. I also am curious as to what additional flight training or instructions, if any, the Ethiopian Airlines pilots received, either before or after the Lion Air crash, whether from Boeing, an air safety regulator, or any other source. el_tel , March 11, 2019 at 5:04 pm Of course we shouldn't engage in speculation, but we will anyway 'cause we're human. If fly-by-wire and the ability of software to over-ride pilots are indeed implicated in the 737 Max 8 then you can bet the Airbus cheer-leaders on YouTube videos will engage in huge Schaudenfreude. I really shouldn't even look at comments to YouTube videos – it's bad for my blood pressure. But I occasionally dip into the swamp on ones in areas like airlines. Of course – as you'd expect – you get a large amount of "flag waving" between Europeans and Americans. But the level of hatred and suspiciously similar comments by the "if it ain't Boeing I ain't going" brigade struck me as in a whole new league long before the "SJW" troll wars regarding things like Captain Marvel etc of today. The Air France Airbus disaster was jumped on – Boeing's traditional hydraulic links between the sticks for the two pilots ensuring they move in tandem; the supposed comments by Captain Sully that the Airbus software didn't allow him to hit the water at the optimal angle he wanted, causing the rear rupture in the fuselage both showed the inferiority of fly-by-wire until Boeing started using it too. (Sully has taken issue with the book making the above point and concludes fly-by-wire is a "mixed blessing".) I'm going to try to steer clear of my YouTube channels on airlines. Hopefully NC will continue to provide the real evidence as it emerges as to what's been going on here. Re SJW troll wars. It is really disheartening how an idea as reasonable as "a just society" has been so thoroughly discredited among a large swath of the population. No wonder there is such a wide interest in primitive construction and technology on YouTube. This society is very sick and it is nice to pretend there is a way to opt out. The version I heard (today, on Reddit) was "if it's Boeing, I'm not going". Hadn't seen the opposite version to just now. Octopii , March 12, 2019 at 5:19 pm Nobody is going to provide real evidence but the NTSB. albert , March 12, 2019 at 6:44 pm Indeed. The NTSB usually works with local investigation teams (as well as a manufacturers rep) if the manufacturer is located in the US, or if specifically requested by the local authorities. I'd like to see their report. I don't care what the FAA or Boeing says about it. . .. . .. -- . fly by wire has been around the 90s, its not new notabanker , March 11, 2019 at 6:37 pm Contains a link to a Seattle Times report as a "comprehensive wrap": Speaking before China's announcement, Cox, who previously served as the top safety official for the Air Line Pilots Association, said it's premature to think of grounding the 737 MAX fleet. "We don't know anything yet. We don't have close to sufficient information to consider grounding the planes," he said. "That would create economic pressure on a number of the airlines that's unjustified at this point. China has grounded them . US? Must not create undue economic pressure on the airlines. Right there in black and white. Money over people. I just emailed southwest about an upcoming flight asking about my choices for refusal to board MAX 8/9 planes based on this "feature". I expect pro forma policy recitation, but customer pressure could trump too big to fail sweeping the dirt under the carpet. I hope. We got the "safety of our customers is our top priority and we are remaining vigilant and are in touch with Boeing and the Civial Aviation Authority on this matter but will not be grounding the aircraft model until further information on the crash becomes available" speech from a local airline here in South Africa. It didn't take half a day for customer pressure to effect a swift reversal of that blatant disregard for their "top priority", the model is grounded so yeah, customer muscle flexing will do it Jessica , March 12, 2019 at 5:26 am On PPRUNE.ORG (where a lot of pilots hang out), they reported that after the Lion Air crash, Southwest added an extra display (to indicate when the two angle of attack sensors were disagreeing with each other) that the folks on PPRUNE thought was an extremely good idea and effective. Of course, if the Ethiopian crash was due to something different from the Lion Air crash, that extra display on the Southwest planes may not make any difference. JerryDenim , March 12, 2019 at 2:09 pm "On PPRUNE.ORG (where a lot of pilots hang out)" Take those comments with a large dose of salt. Not to say everyone commenting on PPRUNE and sites like PPRUNE are posers, but PPRUNE.org is where a lot of wanna-be pilots and guys that spend a lot of time in basements playing flight simulator games hang out. The "real pilots" on PPRUNE are more frequently of the aspiring airline pilot type that fly smaller, piston-powered planes. Altandmain , March 11, 2019 at 5:31 pm We will have to wait and see what the final investigation reveals. However this does not look good for Boeing at all. The Maneuvering Characteristics Augmentation System (MCAS) system was implicated in the Lion Air crash. There have been a lot of complaints about the system on many of the pilot forums, suggesting at least anecdotally that there are issues. It is highly suspected that the MCAS system is responsible for this crash too. Keep in mind that Ethiopian Airlines is a pretty well-known and regarded airline. This is not a cut rate airline we are talking about. At this point, all we can do is to wait for the investigation results. one other minor thing. you remember that shut down? seems that would have delayed any updates from Boeing. seems thats one of the things the pilots pointed out when it shutdown was in progress WestcoastDeplorable , March 11, 2019 at 5:33 pm What really is the icing on this cake is the fact the new, larger engines on the "Max" changed the center of gravity of the plane and made it unstable. From what I've read on aviation blogs, this is highly unusual for a commercial passenger jet. Boeing then created the new "safety" feature which makes the plane fly nose down to avoid a stall. But of course garbage in, garbage out on sensors (remember AF447 which stalled right into the S. Atlantic?). It's all politics anyway .if Boeing had been forthcoming about the "Max" it would have required additional pilot training to certify pilots to fly the airliner. They didn't and now another 189 passengers are D.O.A. I wouldn't fly on one and wouldn't let family do so either. If I have read correctly, the MCAS system (not known of by pilots until after the Lion Air crash) is reliant on a single Angle of Attack sensor, without redundancy (!). It's too early to say if MCAS was an issue in the crashes, I guess, but this does not look good. Jessica , March 12, 2019 at 5:42 am If it was some other issue with the plane, that will be almost worse for Boeing. Two crash-causing flaws would require grounding all of the planes, suspending production, then doing some kind of severe testing or other to make sure that there isn't a third flaw waiting to show up. vomkammer , March 12, 2019 at 3:19 pm If MCAS relies only on one Angle of Attack (AoA) sensor, then it might have been an error in the system design an the safety assessment, from which Boeing may be liable. It appears that a failure of the AoA can produce an unannuntiated erroneous pitch trim: a) If the pilots had proper traning and awareness, this event would "only" increase their workload, b) But for an unaware or untrained pilot, the event would impair its ability to fly and introduce excessive workload. The difference is important, because according to standard civil aviation safety assessment (see for instance EASA AMC 25.1309 Ch. 7), the case a) should be classified as "Major" failure, whereas b) should be classified as "Hazardous". "Hazardous" failures are required to have much lower probability, which means MCAS needs two AoA sensors. In summary: a safe MCAS would need either a second AoA or pilot training. It seems that it had neither. drumlin woodchuckles , March 12, 2019 at 1:01 am What are the ways an ignorant lay air traveler can find out about whether a particular airline has these new-type Boeing 737 MAXes in its fleet? What are the ways an ignorant air traveler can find out which airlines do not have ANY of these airplanes in their fleet? What are the ways an ignorant air traveler can find out ahead of time, when still planning herm's trip, which flights use a 737 MAX as against some other kind of plane? The only way the flying public could possibly torture the airlines into grounding these planes until it is safe to de-ground them is a total all-encompassing "fearcott" against this airplane all around the world. Only if the airlines in the "go ahead and fly it" countries sell zero seats, without exception, on every single 737 MAX plane that flies, will the airlines themselves take them out of service till the issues are resolved. Hence my asking how people who wish to save their own lives from future accidents can tell when and where they might be exposed to the risk of boarding a Boeing 737 MAX plane. Should be in your flight info, if not, contact the airline. I'm not getting on a 737 MAX. pau llauter , March 12, 2019 at 10:57 am Look up the flight on Seatguru. Generally tells type of aircraft. Of course, airlines do change them, too. Old Jake , March 12, 2019 at 2:57 pm Stop flying. Your employer requires it? Tell'em where to get off. There are alternatives. The alternatives are less polluting and have lower climate impact also. Yes, this is a hard pill to swallow. No, I don't travel for employment any more, I telecommute. I used to enjoy flying, but I avoid it like plague any more. Crapification. Darius , March 12, 2019 at 5:09 pm Additional training won't do. If they wanted larger engines, they needed a different plane. Changing to an unstable center of gravity and compensating for it with new software sounds like a joke except for the hundreds of victims. I'm not getting on that plane. Joe Well , March 11, 2019 at 5:35 pm Has there been any study of crapification as a broad social phenomenon? When I Google the word I only get links to NC and sites that reference NC. And yet, this seems like one of the guiding concepts to understand our present world (the crapification of UK media and civil service go a long way towards understanding Brexit, for instance). I mean, my first thought is, why would Boeing commit corporate self-harm for the sake of a single bullet in sales materials (requires no pilot retraining!). And the answer, of course, is crapification: the people calling the shots don't know what they're doing. "Market for lemons" maybe? Anyway the phenomenon is well known. Alfred , March 12, 2019 at 1:01 am Google Books finds the word "crapification" quoted (from a 2004) in a work of literary criticism published in 2008 (Literature, Science and a New Humanities, by J. Gottschall). From 2013 it finds the following in a book by Edward Keenan, Some Great Idea: "Policy-wise, it represented a shift in momentum, a slowing down of the childish, intentional crapification of the city ." So there the word appears clearly in the sense understood by regular readers here (along with an admission that crapfication can be intentional and not just inadvertent). To illustrate that sense, Google Books finds the word used in Misfit Toymakers, by Keith T. Jenkins (2014): "We had been to the restaurant and we had water to drink, because after the takeover's, all of the soda makers were brought to ruination by the total crapification of their product, by government management." But almost twenty years earlier the word "crapification" had occurred in a comic strip published in New York Magazine (29 January 1996, p. 100): "Instant crapification! It's the perfect metaphor for the mirror on the soul of America!" The word has been used on television. On 5 January 2010 a sketch subtitled "Night of Terror – The Crapification of the American Pant-scape" ran on The Colbert Report per: https://en.wikipedia.org/wiki/List_of_The_Colbert_Report_episodes_(2010) . Searching the internet, Google results do indeed show many instances of the word "crapification" on NC, or quoted elsewhere from NC posts. But the same results show it used on many blogs since ca. 2010. Here, at http://nyceducator.com/2018/09/the-crapification-factor.html , is a recent example that comments on the word's popularization: "I stole that word, "crapification," from my friend Michael Fiorillo, but I'm fairly certain he stole it from someone else. In any case, I think it applies to our new online attendance system." A comment here, https://angrybearblog.com/2017/09/open-thread-sept-26-2017.html , recognizes NC to have been a vector of the word's increasing usage. Googling shows that there have been numerous instances of the verb "crapify" used in computer-programming contexts, from at least as early as 2006. Google Books finds the word "crapified" used in a novel, Sonic Butler, by James Greve (2004). The derivation, "de-crapify," is also attested. "Crapify" was suggested to Merriam-Webster in 2007 per: http://nws.merriam-webster.com/opendictionary/newword_display_alpha.php?letter=Cr&last=40 . At that time the suggested definition was, "To make situations/things bad." The verb was posted to Urban Dictionary in 2003: https://www.urbandictionary.com/define.php?term=crapify . The earliest serious discussion I could quickly find on crapificatjon as a phenomenon was from 2009 at https://www.cryptogon.com/?p=10611 . I have found only two attempts to elucidate the causes of crapification: http://malepatternboldness.blogspot.com/2017/03/my-jockey-journey-or-crapification-of.html (an essay on undershirts) and https://twilightstarsong.blogspot.com/2017/04/complaints.html (a comment on refrigerators). This essay deals with the mechanics of job crapification: http://asserttrue.blogspot.com/2015/10/how-job-crapification-works.html (relating it to de-skilling). An apparent Americanism, "crapification" has recently been 'translated' into French: "Mon bled est en pleine urbanisation, comprends : en pleine emmerdisation" [somewhat literally -- My hole in the road is in the midst of development, meaning: in the midst of crapification]: https://twitter.com/entre2passions/status/1085567796703096832 Interestingly, perhaps, a comprehensive search of amazon.com yields "No results for crapification." Joe Well , March 12, 2019 at 12:27 pm You deserve a medal! That's amazing research! drumlin woodchuckles , March 12, 2019 at 1:08 am This seems more like a specific bussiness conspiracy than like general crapification. This isn't " they just don't make them like they used to". This is like Ford deliberately selling the Crash and Burn Pinto with its special explode-on-impact gas-tank feature Maybe some Trump-style insults should be crafted for this plane so they can get memed-up and travel faster than Boeing's ability to manage the story. Epithets like " the new Boeing crash-a-matic dive-liner with nose-to-the-ground pilot-override autocrash built into every plane." It seems unfair, but life and safety should come before fairness, and that will only happen if a world wide wave of fear MAKES it happen. pretzelattack , March 12, 2019 at 2:17 am yeah first thing i thought of was the ford pinto. The Rev Kev , March 12, 2019 at 4:19 am Now there is a car tailor made to modern suicidal Jihadists. You wouldn't even have to load it up with explosives but just a full fuel tank- https://www.youtube.com/watch?v=lgOxWPGsJNY drumlin woodchuckles , March 12, 2019 at 3:27 pm " Instant car bomb. Just add gas." Good time to reread Yves' recent, Is a Harvard MBA Bad For You? : The underlying problem is increasingly mercenary values in society. JerryDenim , March 12, 2019 at 2:49 pm I think crapification is the end result of a self-serving belief in the unfailing goodness and superiority of Ivy faux-meritocracy and the promotion/exaltation of the do-nothing, know-nothing, corporate, revolving-door MBA's and Psych-major HR types over people with many years of both company and industry experience who also have excellent professional track records. The latter group was the group in charge of major corporations and big decisions in the 'good old days', now it's the former. These morally bankrupt people and their vapid, self-righteous culture of PR first, management science second, and what-the-hell-else-matters anyway, are the prime drivers of crapification. Read the bio of an old-school celebrated CEO like Gordon Bethune (Continental CEO with corporate experience at Boeing) who skipped college altogether and joined the Navy at 17, and ask yourself how many people like that are in corporate board rooms today? I'm not saying going back to a 'Good Ole Boy's Club' is the best model of corporate governnace either but at least people like Bethune didn't think they were too good to mix with their fellow employees, understood leadership, the consequences of bullshit, and what 'The buck stops here' thing was really about. Corporate types today sadly believe their own propaganda, and when their fraudulent schemes, can-kicking, and head-in-the sand strategies inevitably blow up in their faces, they accept no blame and fail upwards to another posh corporate job or a nice golden parachute. The wrong people are in charge almost everywhere these days, hence crapification. Bad incentives, zero white collar crime enforcement, self-replicating board rooms, group-think, begets toxic corporate culture, which equals crapification. Jeff Zink , March 12, 2019 at 5:46 pm Also try "built in obsolescence" VietnamVet , March 11, 2019 at 5:40 pm As a son of a deceased former Boeing aeronautic engineer, this is tragic. It highlights the problem of financialization, neoliberalism, and lack of corporate responsibility pointed out daily here on NC. The crapification was signaled by the move of the headquarters from Seattle to Chicago and spending billions to build a second 787 line in South Carolina to bust their Unions. Boeing is now an unregulated multinational corporation superior to sovereign nations. However, if the 737 Max crashes have the same cause, this will be hard to whitewash. The design failure of windows on the de Havilland Comet killed the British passenger aircraft business. The EU will keep a discrete silence since manufacturing major airline passenger planes is a duopoly with Airbus. However, China hasn't (due to the trade war with the USA) even though Boeing is building a new assembly line there. Boeing escaped any blame for the loss of two Malaysian Airline's 777s. This may be an existential crisis for American aviation. Like a President who denies calling Tim Cook, Tim Apple, or the soft coup ongoing in DC against him, what is really happening globally is not factually reported by corporate media. Jerry B , March 11, 2019 at 6:28 pm ===Boeing is now an unregulated multinational corporation superior to sovereign nations=== Susan Strange 101. Or more recently Quinn Slobodian's Globalists: The End of Empire and the Birth of Neoliberalism. And the beat goes on. Synoia , March 11, 2019 at 6:49 pm The design failure of windows on the de Havilland Comet killed the British passenger aircraft business. Yes, a misunderstanding the the effect of square windows and 3 dimensional stress cracking. Gary Gray , March 11, 2019 at 7:54 pm Sorry, but 'sovereign' nations were always a scam. Nothing than a excuse to build capital markets, which are the underpinning of capitalism. Capital Markets are what control countries and have since the 1700's. Maybe you should blame the monarchies for selling out to the bankers in the late middle ages. Sovereign nations are just economic units for the bankers, their businesses they finance and nothing more. I guess they figured out after the Great Depression, they would throw a bunch of goodies at "Indo Europeans" face in western europe ,make them decadent and jaded via debt expansion. This goes back to my point about the yellow vests ..me me me me me. You reek of it. This stuff with Boeing is all profit based. It could have happened in 2000, 1960 or 1920. It could happen even under state control. Did you love Hitler's Voltswagon? As for the soft coup .lol you mean Trumps soft coup for his allies in Russia and the Middle East viva la Saudi King!!!!!? Posts like these represent the problem with this board. The materialist over the spiritualist. Its like people who still don't get some of the biggest supporters of a "GND" are racialists and being somebody who has long run the environmentalist rally game, they are hugely in the game. Yet Progressives completely seem blind to it. The media ignores them for con men like David Duke(who's ancestry is not clean, no its not) and "Unite the Right"(or as one friend on the environmental circuit told me, Unite the Yahweh apologists) as whats "white". There is a reason they do this. You need to wake up and stop the self-gratification crap. The planet is dying due to mishandlement. Over urbanization, over population, constant need for me over ecosystem. It can only last so long. That is why I like Zombie movies, its Gaia Theory in a nutshell. Good for you Earth .or Midgard. Which ever you prefer. Your job seems to be to muddy the waters, and I'm sure we'll be seeing much more of the same; much more. Thanks! pebird , March 11, 2019 at 10:24 pm Hitler had an electric car? JerryDenim , March 12, 2019 at 3:05 pm Hee-hee. I noticed that one too. Interesting but I'm unclear on some of it.. GND supporters are racialist? JerryDenim , March 12, 2019 at 3:02 pm Spot on comment VietnamVet, a lot of chickens can be seen coming home to roost in this latest Boeing disaster. Remarkable how not many years ago the government could regulate the aviation industry without fear of killing it, since there was more than one aerospace company, not anymore! The scourge of monsopany/monopoly power rears its head and bites in unexpected places. More detail on the "MCAS" system responsible for the previous Lion Air crash here (theaircurrent.com) It says the bigger and repositioned engine, which give the new model its fuel efficiency, and wing angle tweaks needed to fit the engine vs landing gear and clearance, change the amount of pitch trim it needs in turns to remain level. The auto system was added top neutralize the pitch trim during turns, too make it handle like the old model. There is another pitch trim control besides the main "stick". To deactivate the auto system, this other trim control has to be used, the main controls do not deactivate it (perhaps to prevent it from being unintentionally deactivated, which would be equally bad). If the sensor driving the correction system gives a false reading and the pilot were unaware, there would be seesawing and panic Actually, if this all happened again I would be very surprised. Nobody flying a 737 would not know after the previous crash. Curious what they find. Ok typo fixes didn't register gobbledygook. While logical, If your last comment were correct, it should have prevented this most recent crash. It appears that the "seesawing and panic" continue. I assume it has now gone beyond the cockpit, and beyond the design, and sales teams and reached the Boeing board room. From there, it is likely to travel to the board rooms of every airline flying this aircraft or thinking of buying one, to their banks and creditors, and to those who buy or recommend their stock. But it may not reach the FAA for some time. marku52 , March 12, 2019 at 2:47 pm Full technical discussion of why this was needed at: https://leehamnews.com/2018/11/14/boeings-automatic-trim-for-the-737-max-was-not-disclosed-to-the-pilots/ Excellent link, thanks! As to what's next? Think, Too Big To Fail. Any number of ways will be found to put lipstick on this pig once we recognize the context. "Canadian and Brazilian authorities did require additional training" from the quote at the bottom is not something I've seen before. What did they know and when did they know it? They probably just assumed that the changes in the plane from previous 737s were big enough to warrant treating it like a major change requiring training. Both countries fly into remote areas with highly variable weather conditions and some rugged terrain. dcrane , March 11, 2019 at 7:25 pm Re: withholding information from the FAA For what it's worth, the quoted section says that Boeing withheld info about the MCAS from "midlevel FAA officials", while Jerri-Lynn refers to the FAA as a whole. This makes me wonder if top-level FAA people certified the system. See under "regulatory capture" Corps run the show, regulators are window-dressing. IMO, of course. Of course It wasn't always this way. From 1979: DC-10 Type Certificate Lifted [Aviation Week] FAA action follows finding of new cracks in pylon aft bulkhead forward flange; crash investigation continues Suspension of the McDonnell Douglas DC-10's type certificate last week followed a separate grounding order from a federal court as government investigators were narrowing the scope of their investigation of the American Airlines DC-10 crash May 25 in Chicago. The American DC-10-10, registration No. N110AA, crashed shortly after takeoff from Chicago's O'Hare International Airport, killing 259 passengers, 13 crewmembers and three persons on the ground. The 275 fatalities make the crash the worst in U.S. history. The controversies surrounding the grounding of the entire U.S. DC-10 fleet and, by extension, many of the DC-10s operated by foreign carriers, by Federal Aviation Administrator Langhorne Bond on the morning of June 6 to revolve around several issues. Yes, I remember back when the FAA would revoke a type certificate if a plane was a danger to public safety. It wasn't even that long ago. Now their concern is any threat to Boeing™. There's a name for that 'Worst' disaster in Chicago would still ground planes. Lucky for Boeing its brown and browner. Max Peck , March 11, 2019 at 7:30 pm It's not correct to claim the MCAS was concealed. It's right in the January 2017 rev of the NG/MAX differences manual. Mmm. Why do the dudes and dudettes *who fly the things* say they knew nothing about MCAS? Their training is quite rigorous. Max Peck , March 11, 2019 at 10:00 pm See a post below for link. I'd have provided it in my original post but was on a phone in an inconvenient place for editing. 'Boeing's automatic trim for the 737 MAX was not disclosed to the Pilots': https://leehamnews.com/2018/11/14/boeings-automatic-trim-for-the-737-max-was-not-disclosed-to-the-pilots/ marku52 , March 12, 2019 at 2:39 pm Leeham news is the best site for info on this. For those of you interested in the tech details got to Bjorns Corner, where he writes about aeronautic design issues. I was somewhat horrified to find that modern aircraft flying at near mach speeds have a lot of somewhat pasted on pilot assistances. All of them. None of them fly with nothing but good old stick-and-rudder. Not Airbus (which is actually fully Fly By wire-all pilot inputs got through a computer) and not Boeing, which is somewhat less so. This latest "solution came about becuse the larger engines (and nacelles) fitted on the Max increased lift ahead of the center of gravity in a pitchup situation, which was destabilizing. The MCAS uses inputs from air speed and angle of attack sensors to put a pitch down input to the horizonatal stablisizer. A faluty AofA sensor lead to Lion Air's Max pushing the nose down against the pilots efforts all the way into the sea. This is the best backgrounder https://leehamnews.com/2018/11/14/boeings-automatic-trim-for-the-737-max-was-not-disclosed-to-the-pilots/ The Rev Kev , March 11, 2019 at 7:48 pm One guy said last night on TV that Boeing had eight years of back orders for this aircraft so you had better believe that this crash will be studied furiously. Saw a picture of the crash site and it looks like it augured in almost straight down. There seems to be a large hole and the wreckage is not strew over that much area. I understand that they were digging out the cockpit as it was underground. Strange that. It's said that the Flight Data Recorders have been found, FWIW. Suggestive of a high-speed, nose-first impact. Not the angle of attack a pilot would ordinarily choose. Max Peck , March 11, 2019 at 9:57 pm It's not true that Boeing hid the existence of the MCAS. They documented it in the January 2017 rev of the NG/MAX differences manual and probably earlier than that. One can argue whether the description was adequate, but the system was in no way hidden. Looks like, for now, we're stuck between your "in no way hidden", and numerous 737 pilots' claims on various online aviation boards that they knew nothing about MCAS. Lots of money involved, so very cloudy weather expected. For now I'll stick with the pilots. Alex V , March 12, 2019 at 2:27 am To the best of my understanding and reading on the subject, the system was well documented in the Boeing technical manuals, but not in the pilots' manuals, where it was only briefly mentioned, at best, and not by all airlines. I'm not an airline pilot, but from what I've read, airlines often write their own additional operators manuals for aircraft models they fly, so it was up to them to decide the depth of documentation. These are in theory sufficient to safely operate the plane, but do not detail every aircraft system exhaustively, as a modern aircraft is too complex to fully understand. Other technical manuals detail how the systems work, and how to maintain them, but a pilot is unlikely to read them as they are used by maintenance personnel or instructors. The problem with these cases (if investigations come to the same conclusions) is that insufficient information was included in the pilots manual explaining the MCAS, even though the information was communicated via other technical manuals. This is correct. A friend of mine is a commercial pilot who's just doing a 'training' exercise having moved airlines. He's been flying the planes in question most of his life, but the airline is asking him to re-do it all according to their manuals and their rules. If the airline manual does not bring it up, then the pilots will not read it – few of them have time to go after the actual technical manuals and read those in addition to what the airline wants. [oh, and it does not matter that he has tens of thousands of hours on the airplane in question, if he does not do something in accordance with his new airline manual, he'd get kicked out, even if he was right and the airline manual wrong] I believe (but would have to check with him) that some countries regulators do their own testing over and above the airlines, but again, it depends on what they put in. Alex V , March 12, 2019 at 11:58 am Good to head my understanding was correct. My take on the whole situation was that Boeing was negligent in communicating the significance of the change, given human psychology and current pilot training. The reason was to enable easier aircraft sales. The purpose of the MCAS system is however quite legitimate – it enables a more fuel efficient plane while compensating for a corner case of the flight envelope. Max Peck , March 12, 2019 at 8:01 am The link is to the actual manual. If that doesn't make you reconsider, nothing will. Maybe some pilots aren't expected to read the manuals, I don't know. Furthermore, the post stated that Boeing failed to inform the FAA about the MCAS. Surely the FAA has time to read all of the manuals. Darius , March 12, 2019 at 6:18 pm Nobody reads instruction manuals. They're for reference. Boeing needed to yell at the pilots to be careful to read new pages 1,576 through 1,629 closely. They're a lulu. Also, what's with screwing with the geometry of a stable plane so that it will fall out of the sky without constant adjustments by computer software? It's like having a car designed to explode but don't worry. We've loaded software to prevent that. Except when there's an error. But don't worry. We've included reboot instructions. It takes 15 minutes but it'll be OK. And you can do it with one hand and drive with the other. No thanks. I want the car not designed to explode. The Rev Kev , March 11, 2019 at 10:06 pm The FAA is already leaping to the defense of the Boeing 737 Max 8 even before they have a chance to open up the black boxes. Hope that nothing "happens" to those recordings. https://www.bbc.com/news/world-africa-47533052 Milton , March 11, 2019 at 11:04 pm I don't know, crapification, at least for me, refers to products, services, or infrastructure that has declined to the point that it has become a nuisance rather than a benefit it once was. This case with Boeing borders on criminal negligence. pretzelattack , March 12, 2019 at 8:20 am i came across a word that was new to me "crapitalism", goes well with crapification. 1. It's really kind of amazing that we can fly to the other side of the world in a few hours – a journey that in my grandfather's time would have taken months and been pretty unpleasant and risky – and we expect perfect safety. 2. Of course the best-selling jet will see these issues. It's the law of large numbers. 3. I am not a fan of Boeing's corporate management, but still, compared to Wall Street and Defense Contractors and big education etc. they still produce an actual technical useful artifact that mostly works, and at levels of performance that in other fields would be considered superhuman. 4. Even for Boeing, one wonders when the rot will set in. Building commercial airliners is hard! So many technical details, nowhere to hide if you make even one mistake so easy to just abandon the business entirely. Do what the (ex) US auto industry did, contract out to foreign manufacturers and just slap a "USA" label on it and double down on marketing. Milk the cost-plus cash cow of the defense market. Or just financialize the entire thing and become too big to fail and walk away with all the profits before the whole edifice crumbles. Greed is good, right? marku52 , March 12, 2019 at 2:45 pm "Of course the best-selling jet will see these issues. It's the law of large numbers." 2 crashes of a new model in vary similar circumstances is very unusual. And FAA admits they are requiring a FW upgrade sometime in April. Pilots need to be hyperaware of what this MCAS system is doing. And they currently aren't. Prairie Bear , March 12, 2019 at 2:42 am if it went into a stall, it would lower the nose suddenly to pick airspeed and fly normally again. A while before I read this post, I listened to a news clip that reported that the plane was observed "porpoising" after takeoff. I know only enough about planes and aviation to be a more or less competent passenger, but it does seem like that is something that might happen if the plane had such a feature and the pilot was not familiar with it and was trying to fight it? The below link is not to the story I saw I don't think, but another one I just found. if it went into a stall, it would lower the nose suddenly to pick airspeed and fly normally again. https://www.yahoo.com/gma/know-boeing-737-max-8-crashed-ethiopia-221411537.html https://www.reuters.com/article/us-ethiopia-airplane-witnesses/ethiopian-plane-smoked-and-shuddered-before-deadly-plunge-idUSKBN1QS1LJ Reuters reports people saw smoke and debris coming out of the plane before the crash. Jessica , March 12, 2019 at 6:06 am At PPRUNE.ORG, many of the commentators are skeptical of what witnesses of airplane crashes say they see, but more trusting of what they say they hear. The folks at PPRUNE.ORG who looked at the record of the flight from FlightRadar24, which only covers part of the flight because FlightRadar24's coverage in that area is not so good and the terrain is hilly, see a plane flying fast in a straight line very unusually low. The dodge about making important changes that affect aircraft handling but not disclosing them – so as to avoid mandatory pilot training, which would discourage airlines from buying the modified aircraft – is an obvious business-over-safety choice by an ethics and safety challenged corporation. But why does even a company of that description, many of whose top managers, designers, and engineers live and breathe flight, allow its s/w engineers to prevent the pilots from overriding a supposed "safety" feature while actually flying the aircraft? Was it because it would have taken a little longer to write and test the additional s/w or because completing the circle through creating a pilot override would have mandated disclosure and additional pilot training? Capt. "Sully" Sullenberger and his passengers and crew would have ended up in pieces at the bottom of the Hudson if the s/w on his aircraft had prohibited out of the ordinary flight maneuvers that contradicted its programming. Alan Carr , March 12, 2019 at 9:13 am If you carefully review the over all airframe of the 737 it has not hardly changed over the past 20 years or so, for the most part Boeing 737 specifications . What I believe the real issue here is the Avionics upgrades over the years has changed dramatically. More and more precision avionics are installed with less and less pilot input and ultimately no control of the aircraft. Though Boeing will get the brunt of the lawsuits, the avionics company will be the real culprit. I believe the avionics on the Boeing 737 is made by Rockwell Collins, which you guessed it, is owned by Boeing. Max Peck , March 12, 2019 at 9:38 am Rockwell Collins has never been owned by Boeing. Also, to correct some upthread assertions, MCAS has an off switch. WobblyTelomeres , March 12, 2019 at 10:02 am United Technologies, UTX, I believe. If I knew how to short, I'd probably short this 'cause if they aren't partly liable, they'll still be hurt if Boeing has to slow (or, horror, halt) production. Alan Carr , March 12, 2019 at 11:47 am You are right Max I mis spoke. Rockwell Collins is owned by United Technologies Corporation Darius , March 12, 2019 at 6:24 pm Which astronaut are you? Heh. Using routine risk management protocols, the American FAA should need continuing "data" on an aircraft for it to maintain its airworthiness certificate. Its current press materials on the Boeing 737 Max 8 suggest it needs data to yank it or to ground the aircraft pending review. Has it had any other commercial aircraft suffer two apparently similar catastrophic losses this close together within two years of the aircraft's launch? Synoia , March 12, 2019 at 11:37 am I am raising an issue with "crapification" as a meme. Crapification is a symptom of a specific behaviour. GREED. Please could you reconsider your writing to invlude this very old, tremendously venal, and "worst" sin? US incentiveness of inventing a new word, "crapification" implies that some error cuould be corrected. If a deliberate sin, it requires atonement and forgiveness, and a sacrifice of wolrdy assets, for any chance of forgiveness and redemption. Alan Carr , March 12, 2019 at 11:51 am Something else that will be interesting to this thread is that Boeing doesn't seem to mind letting the Boeing 737 Max aircraft remain for sale on the open market the EU suspends MAX 8s too Craig H. , March 12, 2019 at 2:29 pm The moderators in reddit.com/r/aviation are fantastic. They have corralled everything into one mega-thread which is worth review: https://www.reddit.com/r/aviation/comments/azzp0r/ethiopian_airlines_et302_and_boeing_737_max_8/ Thanks. That's a great link with what seem to be some very knowledgeable comments. John Beech , March 12, 2019 at 2:30 pm Experienced private pilot here. Lots of commercial pilot friends. First, the EU suspending the MAX 8 is politics. Second, the FAA mandated changes were already in the pipeline. Three, this won't stop the ignorant from staking out a position on this, and speculating about it on the internet, of course. Fourth, I'd hop a flight in a MAX 8 without concern – especially with a US pilot on board. Why? In part because the Lion Air event a few months back led to pointed discussion about the thrust line of the MAX 8 vs. the rest of the 737 fleet and the way the plane has software to help during strong pitch up events (MAX 8 and 9 have really powerful engines). Basically, pilots have been made keenly aware of the issue and trained in what to do. Another reason I'd hop a flight in one right now is because there have been more than 31,000 trouble free flights in the USA in this new aircraft to date. My point is, if there were a systemic issue we'd already know about it. Note, the PIC in the recent crash had +8000 hours but the FO had about 200 hours and there is speculation he was flying. Speculation. Anyway, US commercial fleet pilots are very well trained to deal with runaway trim or uncommanded flight excursions. How? Simple, by switching the breaker off. It's right near your fingers. Note, my airplane has an autopilot also. In the event the autopilot does something unexpected, just like the commercial pilot flying the MAX 8, I'm trained in what to do (the very same thing, switch the thing off). Moreover, I speak form experience because I've had it happen twice in 15 years – once an issue with a servo causing the plane to slowly drift right wing low, and once a connection came loose leaving the plane trimmed right wing low (coincidence). My reaction is/was about the same as that of a experienced typist automatically hitting backspace on the keyboard upon realizing they mistyped a word, e.g. not reflex but nearly so. In my case, it was to throw the breaker to power off the autopilot as I leveled the plane. No big deal. Finally, as of yet there been no analysis from the black boxes. I advise holding off on the speculation until they do. They've been found and we'll learn something soon. The yammering and near hysteria by non-pilots – especially with this thread – reminds me of the old saw about now knowing how smart or ignorant someone is until they open their mouth. notabanker , March 12, 2019 at 5:29 pm So let me get this straight. While Boeing is designing a new 787, Airbus redesigns the A320. Boeing cannot compete with it, so instead of redesigning the 737 properly, they put larger engines on it further forward, which is never intended in the original design. So to compensate they use software with two sensors, not three, making it mathematically impossible to know if you have a faulty sensor which one it would be, to automatically adjust the pitch to prevent a stall, and this is the only true way to prevent a stall. But since you can kill the breaker and disable it if you have a bad sensor and can't possibly know which one, everything is ok. And now that the pilots can disable a feature required for certification, we should all feel good about these brand new planes, that for the first time in history, crashed within 5 months. And the FAA, which hasn't had a Director in 14 months, knows better than the UK, Europe, China, Australia, Singapore, India, Indonesia, Africa and basically every other country in the world except Canada. And the reason every country in the world except Canada has grounded the fleet is political? Singapore put Silk Air out of business because of politics? How many people need to be rammed into the ground at 500 mph from 8000 feet before yammering and hysteria are justified here? 400 obviously isn't enough. VietnamVet , March 12, 2019 at 5:26 pm Overnight since my first post above, the 737 Max 8 crash has become political. The black boxes haven't been officially read yet. Still airlines and aviation authorities have grounded the airplane in Europe, India, China, Mexico, Brazil, Australia and S.E. Asia in opposition to FAA's "Continued Airworthiness Notification to the International Community" issued yesterday. I was wrong. There will be no whitewash. I thought they would remain silent. My guess this is a result of an abundance of caution plus greed (Europeans couldn't help gutting Airbus's competitor Boeing). This will not be discussed but it is also a manifestation of Trump Derangement Syndrome (TDS). Since the President has started dissing Atlantic Alliance partners, extorting defense money, fighting trade wars, and calling 3rd world countries s***-holes; there is no sympathy for the collapsing hegemon. Boeing stock is paying the price. If the cause is the faulty design of the flight position sensors and fly by wire software control system, it will take a long while to design and get approval of a new safe redundant control system and refit the airplanes to fly again overseas. A real disaster for America's last manufacturing industry. [Mar 13, 2019] Boing might not survive the third crash Too much automation and too complex flight control computer engager life of pilots and passengers... Notable quotes: "... When systems (like those used to fly giant aircraft) become too automatic while remaining essentially stupid or limited by the feedback systems, they endanger the airplane and passengers. These two "accidents" are painful warnings for air passengers and voters. ..." "... This sort of problem is not new. Search the web for pitot/static port blockage, erroneous stall / overspeed indications. Pilots used to be trained to handle such emergencies before the desk-jockey suits decided computers always know best. ..." "... @Sky Pilot, under normal circumstances, yes. but there are numerous reports that Boeing did not sufficiently test the MCAS with unreliable or incomplete signals from the sensors to even comply to its own quality regulations. ..." "... Boeing did cut corners when designing the B737 MAX by just replacing the engines but not by designing a new wing which would have been required for the new engine. ..." "... I accept that it should be easier for pilots to assume manual control of the aircraft in such situations but I wouldn't rush to condemn the programmers before we get all the facts. ..." Mar 13, 2019 | www.nytimes.com Shirley OK March 11 I want to know if Boeing 767s, as well as the new 737s, now has the Max 8 flight control computer installed with pilots maybe not being trained to use it or it being uncontrollable. A 3rd Boeing - not a passenger plane but a big 767 cargo plane flying a bunch of stuff for Amazon crashed near Houston (where it was to land) on 2-23-19. The 2 pilots were killed. Apparently there was no call for help (at least not mentioned in the AP article about it I read). 'If' the new Max 8 system had been installed, had either Boeing or the owner of the cargo plane business been informed of problems with Max 8 equipment that had caused a crash and many deaths in a passenger plane (this would have been after the Indonesian crash)? Was that info given to the 2 pilots who died if Max 8 is also being used in some 767s? Did Boeing get the black box from that plane and, if so, what did they find out? Those 2 pilots' lives matter also - particularly since the Indonesian 737 crash with Max 8 equipment had already happened. Boeing hasn't said anything (yet, that I've seen) about whether or not the Max 8 new configuration computer and the extra steps to get manual control is on other of their planes. I want to know about the cause of that 3rd Boeing plane crashing and if there have been crashes/deaths in other of Boeing's big cargo planes. What's the total of all Boeing crashes/fatalies in the last few months and how many of those planes had Max 8? Rufus SF March 11 Gentle readers: In the aftermath of the Lion Air crash, do you think it possible that all 737Max pilots have not received mandatory training review in how to quickly disconnect the MCAS system and fly the plane manually? Do you think it possible that every 737Max pilot does not have a "disconnect review" as part of his personal checklist? Do you think it possible that at the first hint of pitch instability, the pilot does not first think of the MCAS system and whether to disable it? Harold Orlando March 11 Compare the altitude fluctuations with those from Lion Air in NYTimes excellent coverage( https://www.nytimes.com/interactive/2018/11/16/world/asia/lion-air-crash-cockpit.html ), and they don't really suggest to me a pilot struggling to maintain proper pitch. Maybe the graph isn't detailed enough, but it looks more like a major, single event rather than a number of smaller corrections. I could be wrong. Reports of smoke and fire are interesting; there is nothing in the modification that (we assume) caused Lion Air's crash that would explain smoke and fire. So I would hesitate to zero in on the modification at this point. Smoke and fire coming from the luggage bay suggest a runaway Li battery someone put in their suitcase. This is a larger issue because that can happen on any aircraft, Boeing, Airbus, or other. mrpisces Loui March 11 Is is a shame that Boeing will not ground this aircraft knowing they introduced the MCAS component to automate the stall recovery of the 737 MAX and is behind these accidents in my opinion. Stall recovery has always been a step all pilots handled when the stick shaker and other audible warnings were activated to alert the pilots. Now, Boeing invented MCAS as a "selling and marketing point" to a problem that didn't exist. MCAS kicks in when the aircraft is about to enter the stall phase and places the aircraft in a nose dive to regain speed. This only works when the air speed sensors are working properly. Now imagine when the air speed sensors have a malfunction and the plane is wrongly put into a nose dive. The pilots are going to pull back on the stick to level the plane. The MCAS which is still getting incorrect air speed data is going to place the airplane back into a nose dive. The pilots are going to pull back on the stick to level the aircraft. This repeats itself till the airplane impacts the ground which is exactly what happened. Add the fact that Boeing did not disclose the existence of the MCAS and its role to pilots. At this point only money is keeping the 737 MAX in the air. When Boeing talks about safety, they are not referring to passenger safety but profit safety. Tony San Diego March 11 1. The procedure to allow a pilot to take complete control of the aircraft from auto-pilot mode should have been a standard eg pull back on the control column. It is not reasonable to expect a pilot to follow some checklist to determine and then turn off a misbehaving module especially in emergency situations. Even if that procedure is written in fine print in a manual. (The number of modules to disable may keep increasing if this is allowed). 2. How are US airlines confident of the safety of the 737 MAX right now when nothing much is known about the cause of the 2nd crash? What is known if that both the crashed aircraft were brand new, and we should be seeing news articles on how the plane's brand-new advanced technology saved the day from the pilot and not the other way round 3. In the first crash, the plane's advanced technology could not even recognize that either the flight path was abnormal and/or the airspeed readings were too erroneous and mandate the pilot to therefore take complete control immediately! John✔️✔️Brews Tucson, AZ March 11 It's straightforward to design for standard operation under normal circumstances. But when bizarre operation occurs resulting in extreme circumstances a lot more comes into play. Not just more variables interacting more rapidly, testing system response times, but much happening quickly, testing pilot response times and experience. It is doubtful that the FAA can assess exactly what happened in these crashes. It is a result of a complex and rapid succession of man-machine-software-instrumentation interactions, and the number of permutations is huge. Boeing didn't imagine all of them, and didn't test all those it did think of. The FAA is even less likely to do so. Boeing eventually will fix some of the identified problems, and make pilot intervention more effective. Maybe all that effort to make the new cockpit look as familiar as the old one will be scrapped? Pilot retraining will be done? Redundant sensors will be added? Additional instrumentation? Software re-written? That'll increase costs, of course. Future deliveries will cost more. Looks likely there will be some downtime. Whether the fixes will cover sufficient eventualities, time will tell. Whether Boeing will be more scrupulous in future designs, less willing to cut corners without evaluating them? Will heads roll? Well, we'll see... Ron SC March 11 Boeing has been in trouble technologically since its merger with McDonnell Douglas, which some industry analysts called a takeover, though it isn't clear who took over whom since MD got Boeing's name while Boeing took the MD logo and moved their headquarters from Seattle to Chicago. In addition to problems with the 737 Max, Boeing is charging NASA considerably more than the small startup, SpaceX, for a capsule designed to ferry astronauts to the space station. Boeing's Starliner looks like an Apollo-era craft and is launched via a 1960's-like ATLAS booster. Despite using what appears to be old technology, the Starliner is well behind schedule and over budget while the SpaceX capsule has already docked with the space station using state-of-art reusable rocket boosters at a much lower cost. It seems Boeing is in trouble, technologically. BSmith San Francisco March 11 When you read that this model of the Boeing 737 Max was more fuel efficient, and view the horrifying graphs (the passengers spent their last minutes in sheer terror) of the vertical jerking up and down of both air crafts, and learn both crashes occurred minutes after take off, you are 90% sure that the problem is with design, or design not compatible with pilot training. Pilots in both planes had received permission to return to the airports. The likely culprit. to a trained designer, is the control system for injecting the huge amounts of fuel necessary to lift the plane to cruising altitude. Pilots knew it was happening and did not know how to override the fuel injection system. These two crashes foretell what will happen if airlines, purely in the name of saving money, elmininate human control of aircraft. There will be many more crashes. These ultra-complicated machines which defy gravity and lift thousands of pounds of dead weight into the stratesphere to reduce friction with air, are immensely complex and common. Thousands of flight paths cover the globe each day. Human pilots must ultimately be in charge - for our own peace of mind, and for their ability to deal with unimaginable, unforeseen hazards. When systems (like those used to fly giant aircraft) become too automatic while remaining essentially stupid or limited by the feedback systems, they endanger the airplane and passengers. These two "accidents" are painful warnings for air passengers and voters. Brez Spring Hill, TN March 11 1. Ground the Max 737. 2. Deactivate the ability of the automated system to override pilot inputs, which it apparently can do even with the autopilot disengaged. 3. Make sure that the autopilot disengage button on the yoke (pickle switch) disconnects ALL non-manual control inputs. 4. I do not know if this version of the 737 has direct input ("rope start") gyroscope, airspeed and vertical speed inticators for emergencies such as failure of the electronic wonder-stuff. If not, install them. Train pilots to use them. 5. This will cost money, a lot of money, so we can expect more self-serving excuses until the FAA forces Boeing to do the right thing. 6. This sort of problem is not new. Search the web for pitot/static port blockage, erroneous stall / overspeed indications. Pilots used to be trained to handle such emergencies before the desk-jockey suits decided computers always know best. Harper Arkansas March 11 I flew big jets for 34 years, mostly Boeing's. Boeing added new logic to the trim system and was allowed to not make it known to pilots. However it was in maintenance manuals. Not great, but these airplanes are now so complex there are many systems that pilots don't know all of the intimate details. NOT IDEAL, BUT NOT OVERLY SIGNIFICANT. Boeing changed one of the ways to stop a runaway trim system by eliminating the control column trim brake, ie airplane nose goes up, push down (which is instinct) and it stops the trim from running out of control. BIG DEAL BOIENG AND FAA, NOT TELLING PILOTS. Boeing produces checklists for almost any conceivable malfunction. We pilots are trained to accomplish the obvious then go immediately to the checklist. Some items on the checklist are so important they are called "Memory Items" or "Red Box Items". These would include things like in an explosive depressurization to put on your o2 mask, check to see that the passenger masks have dropped automatically and start a descent. Another has always been STAB TRIM SWITCHES ...... CUTOUT which is surrounded by a RED BOX. For very good reasons these two guarded switches are very conveniently located on the pedestal right between the pilots. So if the nose is pitching incorrectly, STAB TRIM SWITCHES ..... CUTOUT!!! Ask questions later, go to the checklist. THAT IS THE PILOTS AND TRAINING DEPARTMENTS RESPONSIBILITY. At this point it is not important as to the cause. David Rubien New York March 11 If these crashes turn out to result from a Boeing flaw, how can that company continue to stay in business? It should be put into receivership and its executives prosecuted. How many deaths are persmissable? Osama Portland OR March 11 The emphasis on software is misplaced. The software intervention is triggered by readings from something called an Angle of Attack sensor. This sensor is relatively new on airplanes. A delicate blade protrudes from the fuselage and is deflected by airflow. The direction of the airflow determines the reading. A false reading from this instrument is the "garbage in" input to the software that takes over the trim function and directs the nose of the airplane down. The software seems to be working fine. The AOA sensor? Not so much. experience Michiigan March 11 The basic problem seems to be that the 737 Max 8 was not designed for the larger engines and so there are flight characteristics that could be dangerous. To compensate for the flaw, computer software was used to control the aircraft when the situation was encountered. The software failed to prevent the situation from becoming a fatal crash. A work around that may be the big mistake of not redesigning the aircraft properly for the larger engines in the first place. The aircraft may need to be modified at a cost that would be not realistic and therefore abandoned and a entirely new aircraft design be implemented. That sounds very drastic but the only other solution would be to go back to the original engines. The Boeing Company is at a crossroad that could be their demise if the wrong decision is made. Sky Pilot NY March 11 It may be a training issue in that the 737 Max has several systems changes from previous 737 models that may not be covered adequately in differences training, checklists, etc. In the Lyon Air crash, a sticky angle-of-attack vane caused the auto-trim to force the nose down in order to prevent a stall. This is a worthwhile safety feature of the Max, but the crew was slow (or unable) to troubleshoot and isolate the problem. It need not have caused a crash. I suspect the same thing happened with Ethiopian Airlines. The circumstances are temptingly similar. Thomas Singapore March 11 @Sky Pilot, under normal circumstances, yes. but there are numerous reports that Boeing did not sufficiently test the MCAS with unreliable or incomplete signals from the sensors to even comply to its own quality regulations. And that is just one of the many quality issues with the B737 MAX that have been in the news for a long time and have been of concern to some of the operators while at the same time being covered up by the FAA. Just look at the difference in training requirements between the FAA and the Brazilian aviation authority. Brazilian pilots need to fully understand the MCAS and how to handle it in emergency situations while FAA does not even require pilots to know about it. Thomas Singapore March 11 This is yet another beautiful example of the difference in approach between Europeans and US Americans. While Europeans usually test their before they deliver the product thoroughly in order to avoid any potential failures of the product in their customers hands, the US approach is different: It is "make it work somehow and fix the problems when the client has them". Which is what happened here as well. Boeing did cut corners when designing the B737 MAX by just replacing the engines but not by designing a new wing which would have been required for the new engine. So the aircraft became unstable to fly at low speedy and tight turns which required a fix by implementing the MCAS which then was kept from recertification procedures for clients for reasons competitive sales arguments. And of course, the FAA played along and provided a cover for this cutting of corners as this was a product of a US company. Then the proverbial brown stuff hit the fan, not once but twice. So Boeing sent its "thoughts and prayers" and started to hope for the storm to blow over and for finding a fix that would not be very expensive and not eat the share holder value away. Sorry, but that is not the way to design and maintain aircraft. If you do it, do it right the first time and not fix it after more than 300 people died in accidents. There is a reason why China has copied the Airbus A-320 and not the Boeing B737 when building its COMAC C919. The Airbus is not a cheap fix, still tested by customers. Rafael USA March 11 @Thomas And how do you know that Boeing do not test the aircrafts before delivery? It is a requirement by FAA for all complete product, systems, parts and sub-parts to be tested before delivery. However it seems Boeing has not approached the problem (or maybe they do not know the real issue). As for the design, are you an engineer that can say whatever the design and use of new engines without a complete re-design is wrong? Have you seen the design drawings of the airplane? I do work in an industry in which our products are use for testing different parts of aircratfs and Boeing is one of our customers. Our products are use during manufacturing and maintenance of airplanes. My guess is that Boeing has no idea what is going on. Your biased opinion against any US product is evident. There are regulations in the USA (and not in other Asia countries) that companies have to follow. This is not a case of untested product, it is a case of unknown problem and Boeing is really in the dark of what is going on... Sam Europe March 11 Boeing and Regulators continue to exhibit criminal behaviour in this case. Ethical responsibility expects that when the first brand new MAX 8 fell for potentially issues with its design, the fleet should have been grounded. Instead, money was a priority; and unfortunately still is. They are even now flying. Disgraceful and criminal behaviour. Imperato NYC March 11 @Sam no...too soon to come anywhere near that conclusion. YW New York, NY March 11 A terrible tragedy for Ethiopia and all of the families affected by this disaster. The fact that two 737 Max jets have crashed in one year is indeed suspicious, especially as it has long been safer to travel in a Boeing plane than a car or school bus. That said, it is way too early to speculate on the causes of the two crashes being identical. Eyewitness accounts of debris coming off the plane in mid-air, as has been widely reported, would not seem to square with the idea that software is again at fault. Let's hope this puzzle can be solved quickly. Wayne Brooklyn, New York March 11 @Singh the difference is consumer electronic products usually have a smaller number of components and wiring compared to commercial aircraft with miles of wiring and multitude of sensors and thousands of components. From what I know they usually have a preliminary report that comes out in a short time. But the detailed reported that takes into account analysis will take over one year to be written. John A San Diego March 11 The engineers and management at Boeing need a crash course in ethics. After the crash in Indonesia, Boeing was trying to pass the blame rather than admit responsibility. The planes should all have been grounded then. Now the chickens have come to roost. Boeing is in serious trouble and it will take a long time to recover the reputation. Large multinationals never learn. Imperato NYC March 11 @John A the previous pilot flying the Lion jet faced the same problem but dealt with it successfully. The pilot on the ill fated flight was less experienced and unfortunately failed. BSmith San Francisco March 11 @Imperato Solving a repeat problem on an airplane type must not solely depend upon a pilot undertaking an emergency response! That is nonsense even to a non-pilot! This implies that Boeing allows a plane to keep flying which it knows has a fatal flaw! Shouldn't it be grounding all these planes until it identifies and solves the same problem? Jimi DC March 11 NYT recently did an excellent job explaining how pilots were kept in the dark, by Boeing, during software update for 737 Max: https://www.nytimes.com/2019/02/03/world/asia/lion-air-plane-crash-pilots.html#click=https://t.co/MRgpKKhsly Steve Charlotte, NC March 11 Something is wrong with those two graphs of altitude and vertical speed. For example, both are flat at the end, even though the vertical speed graph indicates that the plane was climbing rapidly. So what is the source of those numbers? Is it ground-based radar, or telemetry from onboard instruments? If the latter, it might be a clue to the problem. Imperato NYC March 11 @Steve Addis Ababa is almost at 8000ft. George North Carolina March 11 I wonder if, somewhere, there is a a report from some engineers saying that the system pushed by administrative-types to get the plane on the market quickly, will results in serious problems down the line. Rebecca Michigan March 11 If we don't know why the first two 737 Max Jets crashed, then we don't know how long it will be before another one has a catastrophic failure. All the planes need to be grounded until the problem can be duplicated and eliminated. Shirley OK March 11 @Rebecca And if it is something about the plane itself - and maybe an interaction with the new software - then someone has to be ready to volunteer to die to replicate what's happened..... Rebecca Michigan March 12 @Shirley Heavens no. When investigating failures, duplicating the problem helps develop the solution. If you can't recreate the problem, then there is nothing to solve. Duplicating the problem generally is done through analysis and simulations, not with actual planes and passengers. Sisifo Carrboro, NC March 11 Computer geeks can be deadly. This is clearly a software problem. The more software goes into a plane, the more likely it is for a software failure to bring down a plane. And computer geeks are always happy to try "new things" not caring what the effects are in the real world. My PC has a feature that controls what gets typed depending on the speed and repetitiveness of what I type. The darn thing is a constant source of annoyance as I sit at my desk, and there is absolutely no way to neutralize it because a computer geek so decided. Up in an airliner cockpit, this same software idiocy is killing people like flies. Pooja MA March 11 @Sisifo Software that goes into critical systems like aircraft have a lot more constraints. Comparing it to the user interface on your PC doesn't make any sense. It's insulting to assume programmers are happy to "try new things" at the expense of lives. If you'd read about the Lion Air crash carefully you'd remember that there were faulty sensors involved. The software was doing what it was designed to do but the input it was getting was incorrect. I accept that it should be easier for pilots to assume manual control of the aircraft in such situations but I wouldn't rush to condemn the programmers before we get all the facts. BSmith San Francisco March 11 @Pooja Mistakes happen. If humans on board can't respond to terrible situations then there is something wrong with the aircraft and its computer systems. By definition. Patriot NJ March 11 Airbus had its own experiences with pilot "mode confusion" in the 1990's with at least 3 fatal crashes in the A320, but was able to control the media narrative until they resolved the automation issues. Look up Air Inter 148 in Wikipedia to learn the similarities. Opinioned! NYC -- currently wintering in the Pacific March 11 "Commands issued by the plane's flight control computer that bypasses the pilots." What could possibly go wrong? Now let's see whether Boeing's spin doctors can sell this as a feature, not a bug. Chris Hartnett Minneapolis March 11 It is telling that the Chinese government grounded their fleet of 737 Max 8 aircraft before the US government. The world truly has turned upside down when it potentially is safer to fly in China than the US. Oh, the times we live in. Chris Hartnett Datchet, UK (formerly Minneapolis) Hollis Barcelona March 11 As a passenger who likes his captains with a head full of white hair, even if the plane is nosediving to instrument failure, does not every pilot who buckles a seat belt worldwide know how to switch off automatic flight controls and fly the airplane manually? Even if this were 1000% Boeing's fault pilots should be able to override electronics and fly the plane safely back to the airport. I'm sure it's not that black and white in the air and I know it's speculation at this point but can any pilots add perspective regarding human responsibility? Karl Rollings Sydney, Australia March 11 @Hollis I'm not a pilot nor an expert, but my understanding is that planes these days are "fly by wire", meaning the control surfaces are operated electronically, with no mechanical connection between the pilot's stick and the wings. So if the computer goes down, the ability to control the plane goes with it. William Philadelphia March 11 @Hollis The NYT's excellent reporting on the Lion Air crash indicated that in nearly all other commercial aircraft, manual control of the pilot's yoke would be sufficient to override the malfunctioning system (which was controlling the tail wings in response to erroneous sensor data). Your white haired captain's years of training would have ingrained that impulse. Unfortunately, on the Max 8 that would not sufficiently override the tail wings until the pilots flicked a switch near the bottom of the yoke. It's unclear whether individual airlines made pilots aware of this. That procedure existed in older planes but may not have been standard practice because the yoke WOULD sufficiently override the tail wings. Boeing's position has been that had pilots followed the procedure, a crash would not have occurred. Nat Netherlands March 11 @Hollis No, that is the entire crux of this problem; switching from auto-pilot to manual does NOT solve it. Hence the danger of this whole system. T his new Boeing 737-Max series are having the engines placed a bit further away than before and I don't know why they did this, but the result is that there can be some imbalance in air, which they then tried to correct with this strange auto-pilot technical adjustment. Problem is that it stalls the plane (by pushing its nose down and even flipping out small wings sometimes) even when it shouldn't, and even when they switch to manual this system OVERRULES the pilot and switches back to auto-pilot, continuing to try to 'stabilize' (nose dive) the plane. That's what makes it so dangerous. It was designed to keep the plane stable but basically turned out to function more or less like a glitch once you are taking off and need the ascend. I don't know why it only happens now and then, as this plane had made many other take-offs prior, but when it hits, it can be deadly. So far Boeings 'solution' is sparsely sending out a HUGE manual for pilots about how to fight with this computer problem. Which are complicated to follow in a situation of stress with a plane computer constantly pushing the nose of your plane down. Max' mechanism is wrong and instead of correcting it properly, pilots need special training. Or a new technical update may help... which has been delayed and still hasn't been provided. Mark Lebow Milwaukee, WI March 11 Is it the inability of the two airlines to maintain one of the plane's fly-by-wire systems that is at fault, not the plane itself? Or are both crashes due to pilot error, not knowing how to operate the system and then overreacting when it engages? Is the aircraft merely too advanced for its own good? None of these questions seems to have been answered yet. Shane Marin County, CA March 11 Times Pick This is such a devastating thing for Ethiopian Airlines, which has been doing critical work in connecting Africa internally and to the world at large. This is devastating for the nation of Ethiopia and for all the family members of those killed. May the memory of every passenger be a blessing. We should all hope a thorough investigation provides answers to why this make and model of airplane keep crashing so no other people have to go through this horror again. Mal T KS March 11 A possible small piece of a big puzzle: Bishoftu is a city of 170,000 that is home to the main Ethiopian air force base, which has a long runway. Perhaps the pilot of Flight 302 was seeking to land there rather than returning to Bole Airport in Addis Ababa, a much larger and more densely populated city than Bishoftu. The pilot apparently requested return to Bole, but may have sought the Bishoftu runway when he experienced further control problems. Detailed analysis of radar data, conversations between pilot and control tower, flight path, and other flight-related information will be needed to establish the cause(s) of this tragedy. Nan Socolow West Palm Beach, FL March 11 The business of building and selling airplanes is brutally competitive. Malfunctions in the systems of any kind on jet airplanes ("workhorses" for moving vast quantities of people around the earth) lead to disaster and loss of life. Boeing's much ballyhooed and vaunted MAX 8 737 jet planes must be grounded until whatever computer glitches brought down Ethiopian Air and LION Air planes -- with hundreds of passenger deaths -- are explained and fixed. In 1946, Arthur Miller's play, "All My Sons", brought to life guilt by the airplane industry leading to deaths of WWII pilots in planes with defective parts. Arthur Miller was brought before the House UnAmerican Activities Committee because of his criticism of the American Dream. His other seminal American play, "Death of a Salesman", was about an everyman to whom attention must be paid. Attention must be paid to our aircraft industry. The American dream must be repaired. Rachel Brooklyn, NY March 11 This story makes me very afraid of driverless cars. Chuck W. Seattle, WA March 11 Meanwhile, human drivers killed 40,000 and injured 4.5 million people in 2018... For comparison, 58,200 American troops died in the entire Vietnam war. Computers do not fall asleep, get drunk, drive angry, or get distracted. As far as I am concerned, we cannot get unreliable humans out from behind the wheel fast enough. jcgrim Knoxville, TN March 11 @Chuck W. Humans write the algorithms of driverless cars. Algorithms are not 100% fail-safe. Particularly when humans can't seem to write snap judgements or quick inferences into an algorithm. An algorithm can make driverless cars safe in predictable situations but that doesn't mean driveless cars will work in unpredictable events. Also, I don't trust the hype from Uber or the tech industry. https://www.nytimes.com/2017/02/24/technology/anthony-levandowski-waymo-uber-google-lawsuit.html?mtrref=t.co&gwh=D6880521C2C06930788921147F4506C8&gwt=pay John NYC March 11 The irony here seems to be that in attempting to make the aircraft as safe as possible (with systems updates and such) Boeing may very well have made their product less safe. Since the crashes, to date, have been limited to the one product that product should be grounded until a viable determination has been made. John~ American Net'Zen cosmos Washington March 11 Knowing quite a few Boeing employees and retirees, people who have shared numerous stories of concerns about Boeing operations -- I personally avoid flying. As for the assertion: "The business of building and selling jets is brutally competitive" -- it is monopolistic competition, as there are only two players. That means consumers (in this case airlines) do not end up with the best and widest array of airplanes. The more monopolistic a market, the more it needs to be regulated in the public interest -- yet I seriously doubt the FAA or any governmental agency has peeked into all the cost cutting measures Boeing has implemented in recent years drdeanster tinseltown March 11 @cosmos Patently ridiculous. Your odds are greater of dying from a lightning strike, or in a car accident. Or even from food poisoning. Do you avoid driving? Eating? Something about these major disasters makes people itching to abandon all sense of probability and statistics. Bob Milan March 11 When the past year was the dealiest one in decades, and when there are two disasters involved the same plane within that year, how can anyone not draw an inference that there are something wrong with the plane? In statistical studies of a pattern, this is a very very strong basis for a logical reasoning that something is wrong with the plane. When the number involves human lives, we must take very seriously the possibility of design flaws. The MAX planes should be all grounded for now. Period. 65 Recommend mak pakistan March 11 @Bob couldn't agree more - however the basic design and engineering of the 737 is proven to be dependable over the past ~ 6 decades......not saying that there haven't been accidents - but these probably lie well within the industry / type averages. the problems seems to have arisen with the introduction of systems which have purportedly been introduced to take a part of the work-load off the pilots & pass it onto a central compuertised system. Maybe the 'automated anti-stalling ' programme installed into the 737 Max, due to some erroneous inputs from the sensors, provide inaccurate data to the flight management controls leading to stalling of the aircraft. It seems that the manufacturer did not provide sufficent technical data about the upgraded software, & incase of malfunction, the corrective procedures to be followed to mitigate such diasters happening - before delivery of the planes to customers. The procedure for the pilot to take full control of the aircraft by disengaging the central computer should be simple and fast to execute. Please we don't want Tesla driverless vehicles high up in the sky ! James Conner Northwestern Montana March 11 All we know at the moment is that a 737 Max crashed in Africa a few minutes after taking off from a high elevation airport. Some see similarities with the crash of Lion Air's 737 Max last fall -- but drawing a line between the only two dots that exist does not begin to present a useful picture of the situation. Human nature seeks an explanation for an event, and may lead some to make assumptions that are without merit in order to provide closure. That tendency is why following a dramatic event, when facts are few, and the few that exist may be misleading, there is so much cocksure speculation masquerading as solid, reasoned, analysis. At this point, it's best to keep an open mind and resist connecting dots. Peter Sweden March 11 @James Conner 2 deadly crashes after the introduction of a new airplane has no precedence in recent aviation history. And the time it has happened (with Comet), it was due to a faulty aircraft design. There is, of course, some chance that there is no connection between the two accidents, but if there is, the consequences are huge. Especially because the two events happened with very similar fashion (right after takeoff, with wild altitude changes), so there is more similarities than just the type of the plane. So there is literally no reason to keep this model in the air until the investigation is concluded. Oh well, there is: money. Over human lives. svenbi NY March 11 It might be a wrong analogy, but if Toyota/Lexus recall over 1.5 million vehicles due to at least over 20 fatalities in relations to potentially fawlty airbags, Boeing should -- after over 300 deaths in just about 6 months -- pull their product of the market voluntarily until it is sorted out once and for all. This tragic situation recalls the early days of the de Havilland Comet, operated by BOAC, which kept plunging from the skies within its first years of operation until the fault was found to be in the rectangular windows, which did not withstand the pressure due its jet speed and the subsequent cracks in body ripped the planes apart in midflight. Thore Eilertsen Oslo March 11 A third crash may have the potential to take the aircraft manufacturer out of business, it is therefore unbelievable that the reasons for the Lion Air crash haven't been properly established yet. With more than a 100 Boeing 737 Max already grounded, I would expect crash investigations now to be severely fast tracked. And the entire fleet should be grounded on the principle of "better safe than sorry". But then again, that would cost Boeing money, suggesting that the company's assessment of the risks involved favours continued operations above the absolute safety of passengers. Londoner London March 11 @Thore Eilertsen This is also not a case for a secretive and extended crash investigation process. As soon as the cockpit voice recording is extracted - which might be later today - it should be made public. We also need to hear the communications between the controllers and the aircraft and to know about the position regarding the special training the pilots received after the Lion Air crash. Trevor Canada March 11 @Thore Eilertsen I would imagine that Boeing will be the first to propose grounding these planes if they believe with a high degree of probability that it's their issue. They have the most to lose. Let logic and patience prevail. Marvin McConoughey oregon March 11 It is very clear, even in these early moments, that aircraft makers need far more comprehensive information on everything pertinent that is going on in cockpits when pilots encounter problems. That information should be continually transmitted to ground facilities in real time to permit possible ground technical support. [Feb 11, 2019] 6 most prevalent problems in the software development world Dec 01, 2018 | www.catswhocode.com November 20, 2018 [Dec 27, 2018] The Yoda of Silicon Valley by Siobhan Roberts Highly recommended! Although he is certainly a giant, Knuth will never be able to complete this monograph - the technology developed too quickly. Three volumes came out in 1963-1968 and then there was a lull. January 10, he will be 81. At this age it is difficult to work in the field of mathematics and system programming. So we will probably never see the complete fourth volume. This inability to finish the work he devoted a large part of hi life is definitely a tragedy. The key problem here is that now it is simply impossible to cover the whole area of system programming and related algorithms for one person. But the first three volumes played tremendous positive role for sure. Also he was distracted for several years to create TeX. He needed to create a non-profit and complete this work by attracting the best minds from the outside. But he is by nature a loner, as many great scientists are, and prefer to work this way. His other mistake is due to the fact that MIX - his emulator was too far from the IBM S/360, which became the standard de-facto in mid-60th. He then realized that this was a blunder and replaced MIX with more modem emulator MIXX, but it was "too little, too late" and it took time and effort. So the first three volumes and fragments of the fourth is all that we have now and probably forever. Not all volumes fared equally well with time. The third volume suffered most IMHO and as of 2019 is partially obsolete. Also it was written by him in some haste and some parts of it are are far from clearly written ( it was based on earlier lectures of Floyd, so it was oriented of single CPU computers only. Now when multiprocessor machines, huge amount of RAM and SSD hard drives are the norm, the situation is very different from late 60th. It requires different sorting algorithms (the importance of mergesort increased, importance of quicksort decreased). He also got too carried away with sorting random numbers and establishing upper bound and average run time. The real data is almost never random and typically contain sorted fragments. For example, he overestimated the importance of quicksort and thus pushed the discipline in the wrong direction. Notable quotes: "... These days, it is 'coding', which is more like 'code-spraying'. Throw code at a problem until it kind of works, then fix the bugs in the post-release, or the next update. ..." "... AI is a joke. None of the current 'AI' actually is. It is just another new buzz-word to throw around to people that do not understand it at all. ..." "... One good teacher makes all the difference in life. More than one is a rare blessing. ..." Dec 17, 2018 | www.nytimes.com With more than one million copies in print, "The Art of Computer Programming " is the Bible of its field. "Like an actual bible, it is long and comprehensive; no other book is as comprehensive," said Peter Norvig, a director of research at Google. After 652 pages, volume one closes with a blurb on the back cover from Bill Gates: "You should definitely send me a résumé if you can read the whole thing." The volume opens with an excerpt from " McCall's Cookbook ": Here is your book, the one your thousands of letters have asked us to publish. It has taken us years to do, checking and rechecking countless recipes to bring you only the best, only the interesting, only the perfect. Inside are algorithms, the recipes that feed the digital age -- although, as Dr. Knuth likes to point out, algorithms can also be found on Babylonian tablets from 3,800 years ago. He is an esteemed algorithmist; his name is attached to some of the field's most important specimens, such as the Knuth-Morris-Pratt string-searching algorithm. Devised in 1970, it finds all occurrences of a given word or pattern of letters in a text -- for instance, when you hit Command+F to search for a keyword in a document. ... ... ... During summer vacations, Dr. Knuth made more money than professors earned in a year by writing compilers. A compiler is like a translator, converting a high-level programming language (resembling algebra) to a lower-level one (sometimes arcane binary) and, ideally, improving it in the process. In computer science, "optimization" is truly an art, and this is articulated in another Knuthian proverb: "Premature optimization is the root of all evil." Eventually Dr. Knuth became a compiler himself, inadvertently founding a new field that he came to call the "analysis of algorithms." A publisher hired him to write a book about compilers, but it evolved into a book collecting everything he knew about how to write for computers -- a book about algorithms. ... ... ... When Dr. Knuth started out, he intended to write a single work. Soon after, computer science underwent its Big Bang, so he reimagined and recast the project in seven volumes. Now he metes out sub-volumes, called fascicles. The next installation, "Volume 4, Fascicle 5," covering, among other things, "backtracking" and "dancing links," was meant to be published in time for Christmas. It is delayed until next April because he keeps finding more and more irresistible problems that he wants to present. In order to optimize his chances of getting to the end, Dr. Knuth has long guarded his time. He retired at 55, restricted his public engagements and quit email (officially, at least). Andrei Broder recalled that time management was his professor's defining characteristic even in the early 1980s. Dr. Knuth typically held student appointments on Friday mornings, until he started spending his nights in the lab of John McCarthy, a founder of artificial intelligence, to get access to the computers when they were free. Horrified by what his beloved book looked like on the page with the advent of digital publishing, Dr. Knuth had gone on a mission to create the TeX computer typesetting system, which remains the gold standard for all forms of scientific communication and publication. Some consider it Dr. Knuth's greatest contribution to the world, and the greatest contribution to typography since Gutenberg. This decade-long detour took place back in the age when computers were shared among users and ran faster at night while most humans slept. So Dr. Knuth switched day into night, shifted his schedule by 12 hours and mapped his student appointments to Fridays from 8 p.m. to midnight. Dr. Broder recalled, "When I told my girlfriend that we can't do anything Friday night because Friday night at 10 I have to meet with my adviser, she thought, 'This is something that is so stupid it must be true.'" ... ... ... Lucky, then, Dr. Knuth keeps at it. He figures it will take another 25 years to finish "The Art of Computer Programming," although that time frame has been a constant since about 1980. Might the algorithm-writing algorithms get their own chapter, or maybe a page in the epilogue? "Definitely not," said Dr. Knuth. "I am worried that algorithms are getting too prominent in the world," he added. "It started out that computer scientists were worried nobody was listening to us. Now I'm worried that too many people are listening." Scott Kim Burlingame, CA Dec. 18 Thanks Siobhan for your vivid portrait of my friend and mentor. When I came to Stanford as an undergrad in 1973 I asked who in the math dept was interested in puzzles. They pointed me to the computer science dept, where I met Knuth and we hit it off immediately. Not only a great thinker and writer, but as you so well described, always present and warm in person. He was also one of the best teachers I've ever had -- clear, funny, and interested in every student (his elegant policy was each student can only speak twice in class during a period, to give everyone a chance to participate, and he made a point of remembering everyone's names). Some thoughts from Knuth I carry with me: finding the right name for a project is half the work (not literally true, but he labored hard on finding the right names for TeX, Metafont, etc.), always do your best work, half of why the field of computer science exists is because it is a way for mathematically minded people who like to build things can meet each other, and the observation that when the computer science dept began at Stanford one of the standard interview questions was "what instrument do you play" -- there was a deep connection between music and computer science, and indeed the dept had multiple string quartets. But in recent decades that has changed entirely. If you do a book on Knuth (he deserves it), please be in touch. IMiss America US Dec. 18 I remember when programming was art. I remember when programming was programming. These days, it is 'coding', which is more like 'code-spraying'. Throw code at a problem until it kind of works, then fix the bugs in the post-release, or the next update. AI is a joke. None of the current 'AI' actually is. It is just another new buzz-word to throw around to people that do not understand it at all. We should be in a golden age of computing. Instead, we are cutting all corners to get something out as fast as possible. The technology exists to do far more. It is the human element that fails us. Ronald Aaronson Armonk, NY Dec. 18 My particular field of interest has always been compiler writing and have been long awaiting Knuth's volume on that subject. I would just like to point out that among Kunth's many accomplishments is the invention of LR parsers, which are widely used for writing programming language compilers. Edward Snowden Russia Dec. 18 Yes, \TeX, and its derivative, \LaTeX{} contributed greatly to being able to create elegant documents. It is also available for the web in the form MathJax, and it's about time the New York Times supported MathJax. Many times I want one of my New York Times comments to include math, but there's no way to do so! It comes up equivalent to:$e^{i\pi}+1$. 48 Recommend henry pick new york Dec. 18 I read it at the time, because what I really wanted to read was volume 7, Compilers. As I understood it at the time, Professor Knuth wrote it in order to make enough money to build an organ. That apparantly happened by 3:Knuth, Searching and Sorting. The most impressive part is the mathemathics in Semi-numerical (2:Knuth). A lot of those problems are research projects over the literature of the last 400 years of mathematics. Steve Singer Chicago Dec. 18 I own the three volume "Art of Computer Programming", the hardbound boxed set. Luxurious. I don't look at it very often thanks to time constraints, given my workload. But your article motivated me to at least pick it up and carry it from my reserve library to a spot closer to my main desk so I can at least grab Volume 1 and try to read some of it when the mood strikes. I had forgotten just how heavy it is, intellectual content aside. It must weigh more than 25 pounds. Terry Hayes Los Altos, CA Dec. 18 I too used my copies of The Art of Computer Programming to guide me in several projects in my career, across a variety of topic areas. Now that I'm living in Silicon Valley, I enjoy seeing Knuth at events at the Computer History Museum (where he was a 1998 Fellow Award winner), and at Stanford. Another facet of his teaching is the annual Christmas Lecture, in which he presents something of recent (or not-so-recent) interest. The 2018 lecture is available online - https://www.youtube.com/watch?v=_cR9zDlvP88 Chris Tong Kelseyville, California Dec. 17 One of the most special treats for first year Ph.D. students in the Stanford University Computer Science Department was to take the Computer Problem-Solving class with Don Knuth. It was small and intimate, and we sat around a table for our meetings. Knuth started the semester by giving us an extremely challenging, previously unsolved problem. We then formed teams of 2 or 3. Each week, each team would report progress (or lack thereof), and Knuth, in the most supportive way, would assess our problem-solving approach and make suggestions for how to improve it. To have a master thinker giving one feedback on how to think better was a rare and extraordinary experience, from which I am still benefiting! Knuth ended the semester (after we had all solved the problem) by having us over to his house for food, drink, and tales from his life. . . And for those like me with a musical interest, he let us play the magnificent pipe organ that was at the center of his music room. Thank you Professor Knuth, for giving me one of the most profound educational experiences I've ever had, with such encouragement and humor! Been there Boulder, Colorado Dec. 17 I learned about Dr. Knuth as a graduate student in the early 70s from one of my professors and made the financial sacrifice (graduate student assistantships were not lucrative) to buy the first and then the second volume of the Art of Computer Programming. Later, at Bell Labs, when I was a bit richer, I bought the third volume. I have those books still and have used them for reference for years. Thank you Dr, Knuth. Art, indeed! Gianni New York Dec. 18 @Trerra In the good old days, before Computer Science, anyone could take the Programming Aptitude Test. Pass it and companies would train you. Although there were many mathematicians and scientists, some of the best programmers turned out to be music majors. English, Social Sciences, and History majors were represented as well as scientists and mathematicians. It was a wonderful atmosphere to work in . When I started to look for a job as a programmer, I took Prudential Life Insurance's version of the Aptitude Test. After the test, the interviewer was all bent out of shape because my verbal score was higher than my math score; I was a physics major. Luckily they didn't hire me and I got a job with IBM. M Martínez Miami Dec. 17 In summary, "May the force be with you" means: Did you read Donald Knuth's "The Art of Computer Programming"? Excellent, we loved this article. We will share it with many young developers we know. mds USA Dec. 17 Dr. Knuth is a great Computer Scientist. Around 25 years ago, I met Dr. Knuth in a small gathering a day before he was awarded a honorary Doctorate in a university. This is my approximate recollection of a conversation. I said-- " Dr. Knuth, you have dedicated your book to a computer (one with which he had spent a lot of time, perhaps a predecessor to PDP-11). Isn't it unusual?". He said-- "Well, I love my wife as much as anyone." He then turned to his wife and said --"Don't you think so?". It would be nice if scientists with the gift of such great minds tried to address some problems of ordinary people, e.g. a model of economy where everyone can get a job and health insurance, say, like Dr. Paul Krugman. Nadine NYC Dec. 17 I was in a training program for women in computer systems at CUNY graduate center, and they used his obtuse book. It was one of the reasons I dropped out. He used a fantasy language to describe his algorithms in his book that one could not test on computers. I already had work experience as a programmer with algorithms and I know how valuable real languages are. I might as well have read Animal Farm. It might have been different if he was the instructor. Doug McKenna Boulder Colorado Dec. 17 Don Knuth's work has been a curious thread weaving in and out of my life. I was first introduced to Knuth and his The Art of Computer Programming back in 1973, when I was tasked with understanding a section of the then-only-two-volume Book well enough to give a lecture explaining it to my college algorithms class. But when I first met him in 1981 at Stanford, he was all-in on thinking about typography and this new-fangled system of his called TeX. Skip a quarter century. One day in 2009, I foolishly decided kind of on a whim to rewrite TeX from scratch (in my copious spare time), as a simple C library, so that its typesetting algorithms could be put to use in other software such as electronic eBook's with high-quality math typesetting and interactive pictures. I asked Knuth for advice. He warned me, prepare yourself, it's going to consume five years of your life. I didn't believe him, so I set off and tried anyway. As usual, he was right. Baddy Khan San Francisco Dec. 17 I have signed copied of "Fundamental Algorithms" in my library, which I treasure. Knuth was a fine teacher, and is truly a brilliant and inspiring individual. He taught during the same period as Vint Cerf, another wonderful teacher with a great sense of humor who is truly a "father of the internet". One good teacher makes all the difference in life. More than one is a rare blessing. Indisk Fringe Dec. 17 I am a biologist, specifically a geneticist. I became interested in LaTeX typesetting early in my career and have been either called pompous or vilified by people at all levels for wanting to use. One of my PhD advisors famously told me to forget LaTeX because it was a thing of the past. I have now forgotten him completely. I still use LaTeX almost every day in my work even though I don't generally typeset with equations or algorithms. My students always get trained in using proper typesetting. Unfortunately, the publishing industry has all but largely given up on TeX. Very few journals in my field accept TeX manuscripts, and most of them convert to word before feeding text to their publishing software. Whatever people might argue against TeX, the beauty and elegance of a property typeset document is unparalleled. Long live LaTeX PaulSFO San Francisco Dec. 17 A few years ago Severo Ornstein (who, incidentally, did the hardware design for the first router, in 1969), and his wife Laura, hosted a concert in their home in the hills above Palo Alto. During a break a friend and I were chatting when a man came over and *asked* if he could chat with us (a high honor, indeed). His name was Don. After a few minutes I grew suspicious and asked "What's your last name?" Friendly, modest, brilliant; a nice addition to our little chat. Tim Black Wilmington, NC Dec. 17 When I was a physics undergraduate (at Trinity in Hartford), I was hired to re-write professor's papers into TeX. Seeing the beauty of TeX, I wrote a program that re-wrote my lab reports (including graphs!) into TeX. My lab instructors were amazed! How did I do it? I never told them. But I just recognized that Knuth was a genius and rode his coat-tails, as I have continued to do for the last 30 years! Jack512 Alexandria VA Dec. 17 A famous quote from Knuth: "Beware of bugs in the above code; I have only proved it correct, not tried it." Anyone who has ever programmed a computer will feel the truth of this in their bones. [Dec 11, 2018] Software "upgrades" require workers to constantly relearn the same task because some young "genius" observed that a carefully thought out interface "looked tired" and glitzed it up. Dec 11, 2018 | www.ianwelsh.net S Brennan permalink April 24, 2016 My grandfather, in the early 60's could board a 707 in New York and arrive in LA in far less time than I can today. And no, I am not counting 4 hour layovers with the long waits to be "screened", the jets were 50-70 knots faster, back then your time was worth more, today less. Not counting longer hours AT WORK, we spend far more time commuting making for much longer work days, back then your time was worth more, today less! Software "upgrades" require workers to constantly relearn the same task because some young "genius" observed that a carefully thought out interface "looked tired" and glitzed it up. Think about the almost perfect Google Maps driver interface being redesigned by people who take private buses to work. Way back in the '90's your time was worth more than today! Life is all the "time" YOU will ever have and if we let the elite do so, they will suck every bit of it out of you. [Nov 05, 2018] Revisiting the Unix philosophy in 2018 Opensource.com by Michael Hausenblas Nov 05, 2018 | opensource.com Revisiting the Unix philosophy in 2018 The old strategy of building small, focused applications is new again in the modern microservices environment. Program Design in the Unix Environment " in the AT&T Bell Laboratories Technical Journal, in which they argued the Unix philosophy, using the example of BSD's cat -v implementation. In a nutshell that philosophy is: Build small, focused programs -- in whatever language -- that do only one thing but do this thing well, communicate via stdin / stdout , and are connected through pipes. Sound familiar? Yeah, I thought so. That's pretty much the definition of microservices offered by James Lewis and Martin Fowler: In short, the microservice architectural style is an approach to developing a single application as a suite of small services, each running in its own process and communicating with lightweight mechanisms, often an HTTP resource API. While one *nix program or one microservice may be very limited or not even very interesting on its own, it's the combination of such independently working units that reveals their true benefit and, therefore, their power. *nix vs. microservices The following table compares programs (such as cat or lsof ) in a *nix environment against programs in a microservices environment. *nix Microservices Unit of execution program using stdin / stdout service with HTTP or gRPC API Data flow Pipes ? Configuration & parameterization Command-line arguments, environment variables, config files JSON/YAML docs Discovery Package manager, man, make DNS, environment variables, OpenAPI Let's explore each line in slightly greater detail. Unit of execution More on Microservices The unit of execution in *nix (such as Linux) is an executable file (binary or interpreted script) that, ideally, reads input from stdin and writes output to stdout . A microservices setup deals with a service that exposes one or more communication interfaces, such as HTTP or gRPC APIs. In both cases, you'll find stateless examples (essentially a purely functional behavior) and stateful examples, where, in addition to the input, some internal (persisted) state decides what happens. Data flow Traditionally, *nix programs could communicate via pipes. In other words, thanks to Doug McIlroy , you don't need to create temporary files to pass around and each can process virtually endless streams of data between processes. To my knowledge, there is nothing comparable to a pipe standardized in microservices, besides my little Apache Kafka-based experiment from 2017 . Configuration and parameterization How do you configure a program or service -- either on a permanent or a by-call basis? Well, with *nix programs you essentially have three options: command-line arguments, environment variables, or full-blown config files. In microservices, you typically deal with YAML (or even worse, JSON) documents, defining the layout and configuration of a single microservice as well as dependencies and communication, storage, and runtime settings. Examples include Kubernetes resource definitions , Nomad job specifications , or Docker Compose files. These may or may not be parameterized; that is, either you have some templating language, such as Helm in Kubernetes, or you find yourself doing an awful lot of sed -i commands. Discovery How do you know what programs or services are available and how they are supposed to be used? Well, in *nix, you typically have a package manager as well as good old man; between them, they should be able to answer all the questions you might have. In a microservices setup, there's a bit more automation in finding a service. In addition to bespoke approaches like Airbnb's SmartStack or Netflix's Eureka , there usually are environment variable-based or DNS-based approaches that allow you to discover services dynamically. Equally important, OpenAPI provides a de-facto standard for HTTP API documentation and design, and gRPC does the same for more tightly coupled high-performance cases. Last but not least, take developer experience (DX) into account, starting with writing good Makefiles and ending with writing your docs with (or in?) style . Pros and cons Both *nix and microservices offer a number of challenges and opportunities Composability It's hard to design something that has a clear, sharp focus and can also play well with others. It's even harder to get it right across different versions and to introduce respective error case handling capabilities. In microservices, this could mean retry logic and timeouts -- maybe it's a better option to outsource these features into a service mesh? It's hard, but if you get it right, its reusability can be enormous. Observability In a monolith (in 2018) or a big program that tries to do it all (in 1984), it's rather straightforward to find the culprit when things go south. But, in a yes | tr \\n x | head -c 450m | grep n or a request path in a microservices setup that involves, say, 20 services, how do you even start to figure out which one is behaving badly? Luckily we have standards, notably OpenCensus and OpenTracing . Observability still might be the biggest single blocker if you are looking to move to microservices. Global state While it may not be such a big issue for *nix programs, in microservices, global state remains something of a discussion. Namely, how to make sure the local (persistent) state is managed effectively and how to make the global state consistent with as little effort as possible. Wrapping up In the end, the question remains: Are you using the right tool for a given task? That is, in the same way a specialized *nix program implementing a range of functions might be the better choice for certain use cases or phases, it might be that a monolith is the best option for your organization or workload. Regardless, I hope this article helps you see the many, strong parallels between the Unix philosophy and microservices -- maybe we can learn something from the former to benefit the latter. Michael Hausenblas is a Developer Advocate for Kubernetes and OpenShift at Red Hat where he helps appops to build and operate apps. His background is in large-scale data processing and container orchestration and he's experienced in advocacy and standardization at W3C and IETF. Before Red Hat, Michael worked at Mesosphere, MapR and in two research institutions in Ireland and Austria. He contributes to open source software incl. Kubernetes, speaks at conferences and user groups, and shares good practices... [Nov 05, 2018] The Linux Philosophy for SysAdmins And Everyone Who Wants To Be One eBook by David Both Nov 05, 2018 | www.amazon.com Elegance is one of those things that can be difficult to define. I know it when I see it, but putting what I see into a terse definition is a challenge. Using the Linux diet command, Wordnet provides one definition of elegance as, "a quality of neatness and ingenious simplicity in the solution of a problem (especially in science or mathematics); 'the simplicity and elegance of his invention.'" In the context of this book, I think that elegance is a state of beauty and simplicity in the design and working of both hardware and software. When a design is elegant, software and hardware work better and are more efficient. The user is aided by simple, efficient, and understandable tools. Creating elegance in a technological environment is hard. It is also necessary. Elegant solutions produce elegant results and are easy to maintain and fix. Elegance does not happen by accident; you must work for it. The quality of simplicity is a large part of technical elegance. So large, in fact that it deserves a chapter of its own, Chapter 18, "Find the Simplicity," but we do not ignore it here. This chapter discusses what it means for hardware and software to be elegant. Hardware Elegance Yes, hardware can be elegant -- even beautiful, pleasing to the eye. Hardware that is well designed is more reliable as well. Elegant hardware solutions improve reliability'. [Oct 27, 2018] One issue with Microsoft (not just Microsoft) is that their business model (not the benefit of the users) requires frequent changes in the systems, so bugs are introduced at the steady clip. Oct 27, 2018 | www.moonofalabama.org Piotr Berman , Oct 26, 2018 2:55:29 PM | 5 ">link "Even Microsoft, the biggest software company in the world, recently screwed up..." Isn't it rather logical than the larger a company is, the more screw ups it can make? After all, Microsofts has armies of programmers to make those bugs. Once I created a joke that the best way to disable missile defense would be to have a rocket that can stop in mid-air, thus provoking the software to divide be zero and crash. One day I told that joke to a military officer who told me that something like that actually happened, but it was in the Navy and it involved a test with a torpedo. Not only the program for "torpedo defense" went down but the system crashed too and the engine of the ship stopped working as well. I also recall explanations that a new complex software system typically has all major bugs removed after being used for a year. And the occasion was Internal Revenue Service changing hardware and software leading to widely reported problems. One issue with Microsoft (not just Microsoft) is that their business model (not the benefit of the users) requires frequent changes in the systems, so bugs are introduced at the steady clip. Of course, they do not make money on bugs per se, but on new features that in time make it impossible to use older versions of the software and hardware. [Sep 21, 2018] 'It Just Seems That Nobody is Interested in Building Quality, Fast, Efficient, Lasting, Foundational Stuff Anymore' Sep 21, 2018 | tech.slashdot.org Nikita Prokopov, a software programmer and author of Fira Code, a popular programming font, AnyBar, a universal status indicator, and some open-source Clojure libraries, writes : Remember times when an OS, apps and all your data fit on a floppy? Your desktop todo app is probably written in Electron and thus has userland driver for Xbox 360 controller in it, can render 3d graphics and play audio and take photos with your web camera. A simple text chat is notorious for its load speed and memory consumption. Yes, you really have to count Slack in as a resource-heavy application. I mean, chatroom and barebones text editor, those are supposed to be two of the less demanding apps in the whole world. Welcome to 2018. At least it works, you might say. Well, bigger doesn't imply better. Bigger means someone has lost control. Bigger means we don't know what's going on. Bigger means complexity tax, performance tax, reliability tax. This is not the norm and should not become the norm . Overweight apps should mean a red flag. They should mean run away scared. 16Gb Android phone was perfectly fine 3 years ago. Today with Android 8.1 it's barely usable because each app has become at least twice as big for no apparent reason. There are no additional functions. They are not faster or more optimized. They don't look different. They just...grow? iPhone 4s was released with iOS 5, but can barely run iOS 9. And it's not because iOS 9 is that much superior -- it's basically the same. But their new hardware is faster, so they made software slower. Don't worry -- you got exciting new capabilities like...running the same apps with the same speed! I dunno. [...] Nobody understands anything at this point. Neither they want to. We just throw barely baked shit out there, hope for the best and call it "startup wisdom." Web pages ask you to refresh if anything goes wrong. Who has time to figure out what happened? Any web app produces a constant stream of "random" JS errors in the wild, even on compatible browsers. [...] It just seems that nobody is interested in building quality, fast, efficient, lasting, foundational stuff anymore. Even when efficient solutions have been known for ages, we still struggle with the same problems: package management, build systems, compilers, language design, IDEs. Build systems are inherently unreliable and periodically require full clean, even though all info for invalidation is there. Nothing stops us from making build process reliable, predictable and 100% reproducible. Just nobody thinks its important. NPM has stayed in "sometimes works" state for years. K. S. Kyosuke ( 729550 ) , Friday September 21, 2018 @11:32AM ( #57354556 ) Re:Why should they? ( Score: 4 , Insightful) Less resource use to accomplish the required tasks? Both in manufacturing (more chips from the same amount of manufacturing input) and in operation (less power used)? K. S. Kyosuke ( 729550 ) writes: on Friday September 21, 2018 @11:58AM ( #57354754 ) Re:Why should they? ( Score: 2 ) Ehm...so for example using smaller cars with better mileage to commute isn't more environmentally friendly either, according to you?https://slashdot.org/comments.pl?sid=12644750&cid=57354556# DontBeAMoran ( 4843879 ) writes: on Friday September 21, 2018 @12:04PM ( #57354826 ) Re:Why should they? ( Score: 2 ) iPhone 4S used to be the best and could run all the applications. Today, the same power is not sufficient because of software bloat. So you could say that all the iPhones since the iPhone 4S are devices that were created and then dumped for no reason. It doesn't matter since we can't change the past and it doesn't matter much since improvements are slowing down so people are changing their phones less often. Mark of the North ( 19760 ) , Friday September 21, 2018 @01:02PM ( #57355296 ) Re:Why should they? ( Score: 5 , Interesting) Can you really not see the connection between inefficient software and environmental harm? All those computers running code that uses four times as much data, and four times the number crunching, as is reasonable? That excess RAM and storage has to be built as well as powered along with the CPU. Those material and electrical resources have to come from somewhere. But the calculus changes completely when the software manufacturer hosts the software (or pays for the hosting) for their customers. Our projected AWS bill motivated our management to let me write the sort of efficient code I've been trained to write. After two years of maintaining some pretty horrible legacy code, it is a welcome change. The big players care a great deal about efficiency when they can't outsource inefficiency to the user's computing resources. eth1 ( 94901 ) , Friday September 21, 2018 @11:45AM ( #57354656 ) Re:Why should they? ( Score: 5 , Informative) We've been trained to be a consuming society of disposable goods. The latest and greatest feature will always be more important than something that is reliable and durable for the long haul. It's not just consumer stuff. The network team I'm a part of has been dealing with more and more frequent outages, 90% of which are due to bugs in software running our devices. These aren't fly-by-night vendors either, they're the "no one ever got fired for buying X" ones like Cisco, F5, Palo Alto, EMC, etc. 10 years ago, outages were 10% bugs, and 90% human error, now it seems to be the other way around. Everyone's chasing features, because that's what sells, so there's no time for efficiency/stability/security any more. LucasBC ( 1138637 ) , Friday September 21, 2018 @12:05PM ( #57354836 ) Re:Why should they? ( Score: 3 , Interesting) Poor software engineering means that very capable computers are no longer capable of running modern, unnecessarily bloated software. This, in turn, leads to people having to replace computers that are otherwise working well, solely for the reason to keep up with software that requires more and more system resources for no tangible benefit. In a nutshell -- sloppy, lazy programming leads to more technology waste. That impacts the environment. I have a unique perspective in this topic. I do web development for a company that does electronics recycling. I have suffered the continued bloat in software in the tools I use (most egregiously, Adobe), and I see the impact of technological waste in the increasing amount of electronics recycling that is occurring. Ironically, I'm working at home today because my computer at the office kept stalling every time I had Photoshop and Illustrator open at the same time. A few years ago that wasn't a problem. arglebargle_xiv ( 2212710 ) writes: Re: ( Score: 3 ) There is one place where people still produce stuff like the OP wants, and that's embedded. Not IoT wank, but real embedded, running on CPUs clocked at tens of MHz with RAM in two-digit kilobyte (not megabyte or gigabyte) quantities. And a lot of that stuff is written to very exacting standards, particularly where something like realtime control and/or safety is involved. The one problem in this area is the endless battle with standards morons who begin each standard with an implicit "assume an infinitely commodore64_love ( 1445365 ) , Friday September 21, 2018 @03:58PM ( #57356680 ) Journal Re:Why should they? ( Score: 3 ) > Poor software engineering means that very capable computers are no longer capable of running modern, unnecessarily bloated software. Not just computers. You can add Smart TVs, settop internet boxes, Kindles, tablets, et cetera that must be thrown-away when they become too old (say 5 years) to run the latest bloatware. Software non-engineering is causing a lot of working hardware to be landfilled, and for no good reason. [Sep 21, 2018] Fast, cheap (efficient) and reliable (robust, long lasting): pick 2 Sep 21, 2018 | tech.slashdot.org JoeDuncan ( 874519 ) , Friday September 21, 2018 @12:58PM ( #57355276 ) Obligatory ( Score: 2 ) Fast, cheap (efficient) and reliable (robust, long lasting): pick 2. roc97007 ( 608802 ) , Friday September 21, 2018 @12:16PM ( #57354946 ) Journal Re:Bloat = growth ( Score: 2 ) There's probably some truth to that. And it's a sad commentary on the industry. [Sep 21, 2018] Since Moore's law appears to have stalled since at least five years ago, it will be interesting to see if we start to see algorithm research or code optimization techniques coming to the fore again. Sep 21, 2018 | tech.slashdot.org Anonymous Coward , Friday September 21, 2018 @11:26AM ( #57354512 ) Moore's law ( Score: 5 , Interesting) When the speed of your processor doubles every two year along with a concurrent doubling of RAM and disk space, then you can get away with bloatware. Since Moore's law appears to have stalled since at least five years ago, it will be interesting to see if we start to see algorithm research or code optimization techniques coming to the fore again. [Sep 16, 2018] After the iron curtain fell, there was a big demand for Russian-trained programmers because they could program in a very efficient and light manner that didn't demand too much of the hardware, if I remember correctly Notable quotes: "... It's a bit of chicken-and-egg problem, though. Russia, throughout 20th century, had problem with developing small, effective hardware, so their programmers learned how to code to take maximum advantage of what they had, with their technological deficiency in one field giving rise to superiority in another. ..." "... Russian tech ppl should always be viewed with certain amount of awe and respect...although they are hardly good on everything. ..." "... Soviet university training in "cybernetics" as it was called in the late 1980s involved two years of programming on blackboards before the students even touched an actual computer. ..." "... I recall flowcharting entirely on paper before committing a program to punched cards. ..." Aug 01, 2018 | turcopolier.typepad.com Bill Herschel 2 days ago , Very, very slightly off-topic. Much has been made, including in this post, of the excellent organization of Russian forces and Russian military technology. I have been re-investigating an open-source relational database system known as PosgreSQL (variously), and I remember finding perhaps a decade ago a very useful whole text search feature of this system which I vaguely remember was written by a Russian and, for that reason, mildly distrusted by me. Come to find out that the principle developers and maintainers of PostgreSQL are Russian. OMG. Double OMG, because the reason I chose it in the first place is that it is the best non-proprietary RDBS out there and today is supported on Google Cloud, AWS, etc. The US has met an equal or conceivably a superior, case closed. Trump's thoroughly odd behavior with Putin is just one but a very obvious one example of this. Of course, Trump's nationalistic blather is creating a "base" of people who believe in the godliness of the US. They are in for a very serious disappointment. kao_hsien_chih Bill Herschel a day ago , After the iron curtain fell, there was a big demand for Russian-trained programmers because they could program in a very efficient and "light" manner that didn't demand too much of the hardware, if I remember correctly. It's a bit of chicken-and-egg problem, though. Russia, throughout 20th century, had problem with developing small, effective hardware, so their programmers learned how to code to take maximum advantage of what they had, with their technological deficiency in one field giving rise to superiority in another. Russia has plenty of very skilled, very well-trained folks and their science and math education is, in a way, more fundamentally and soundly grounded on the foundational stuff than US (based on my personal interactions anyways). Russian tech ppl should always be viewed with certain amount of awe and respect...although they are hardly good on everything. TTG kao_hsien_chih a day ago , Well said. Soviet university training in "cybernetics" as it was called in the late 1980s involved two years of programming on blackboards before the students even touched an actual computer. It gave the students an understanding of how computers works down to the bit flipping level. Imagine trying to fuzz code in your head. FarNorthSolitude TTG a day ago , I recall flowcharting entirely on paper before committing a program to punched cards. I used to do hex and octal math in my head as part of debugging core dumps. Ah, the glory days. Honeywell once made a military computer that was 10 bit. That stumped me for a while, as everything was 8 or 16 bit back then. kao_hsien_chih FarNorthSolitude 10 hours ago , That used to be fairly common in the civilian sector (in US) too: computing time was expensive, so you had to make sure that the stuff worked flawlessly before it was committed. No opportunity to seeing things go wrong and do things over like much of how things happen nowadays. Russians, with their hardware limitations/shortages, I imagine must have been much more thorough than US programmers were back in the old days, and you could only get there by being very thoroughly grounded n the basics. [Sep 07, 2018] How Can We Fix The Broken Economics of Open Source? Notable quotes: "... [with some subset of features behind a paywall] ..." Sep 07, 2018 | news.slashdot.org If we take consulting, services, and support off the table as an option for high-growth revenue generation (the only thing VCs care about), we are left with open core [with some subset of features behind a paywall] , software as a service, or some blurring of the two... Everyone wants infrastructure software to be free and continuously developed by highly skilled professional developers (who in turn expect to make substantial salaries), but no one wants to pay for it. The economics of this situation are unsustainable and broken ... [W]e now come to what I have recently called "loose" open core and SaaS. In the future, I believe the most successful OSS projects will be primarily monetized via this method. What is it? The idea behind "loose" open core and SaaS is that a popular OSS project can be developed as a completely community driven project (this avoids the conflicts of interest inherent in "pure" open core), while value added proprietary services and software can be sold in an ecosystem that forms around the OSS... Unfortunately, there is an inflection point at which in some sense an OSS project becomes too popular for its own good, and outgrows its ability to generate enough revenue via either "pure" open core or services and support... [B]uilding a vibrant community and then enabling an ecosystem of "loose" open core and SaaS businesses on top appears to me to be the only viable path forward for modern VC-backed OSS startups. Klein also suggests OSS foundations start providing fellowships to key maintainers, who currently "operate under an almost feudal system of patronage, hopping from company to company, trying to earn a living, keep the community vibrant, and all the while stay impartial..." "[A]s an industry, we are going to have to come to terms with the economic reality: nothing is free, including OSS. If we want vibrant OSS projects maintained by engineers that are well compensated and not conflicted, we are going to have to decide that this is something worth paying for. In my opinion, fellowships provided by OSS foundations and funded by companies generating revenue off of the OSS is a great way to start down this path." [Apr 30, 2018] New Book Describes Bluffing Programmers in Silicon Valley Notable quotes: "... Live Work Work Work Die: A Journey into the Savage Heart of Silicon Valley ..." "... Older generations called this kind of fraud "fake it 'til you make it." ..." "... Nowadays I work 9:30-4:30 for a very good, consistent paycheck and let some other "smart person" put in 75 hours a week dealing with hiring ..." "... It's not a "kids these days" sort of issue, it's *always* been the case that shameless, baseless self-promotion wins out over sincere skill without the self-promotion, because the people who control the money generally understand boasting more than they understand the technology. ..." "... In the bad old days we had a hell of a lot of ridiculous restriction We must somehow made our programs to run successfully inside a RAM that was 48KB in size (yes, 48KB, not 48MB or 48GB), on a CPU with a clock speed of 1.023 MHz ..." "... So what are the uses for that? I am curious what things people have put these to use for. ..." "... Also, Oracle, SAP, IBM... I would never buy from them, nor use their products. I have used plenty of IBM products and they suck big time. They make software development 100 times harder than it could be. ..." "... I have a theory that 10% of people are good at what they do. It doesn't really matter what they do, they will still be good at it, because of their nature. These are the people who invent new things, who fix things that others didn't even see as broken and who automate routine tasks or simply question and erase tasks that are not necessary. ..." "... 10% are just causing damage. I'm not talking about terrorists and criminals. ..." "... Programming is statistically a dead-end job. Why should anyone hone a dead-end skill that you won't be able to use for long? For whatever reason, the industry doesn't want old programmers. ..." Apr 30, 2018 | news.slashdot.org Long-time Slashdot reader Martin S. pointed us to this an excerpt from the new book Live Work Work Work Die: A Journey into the Savage Heart of Silicon Valley by Portland-based investigator reporter Corey Pein. The author shares what he realized at a job recruitment fair seeking Java Legends, Python Badasses, Hadoop Heroes, "and other gratingly childish classifications describing various programming specialities. " I wasn't the only one bluffing my way through the tech scene. Everyone was doing it, even the much-sought-after engineering talent. I was struck by how many developers were, like myself, not really programmers , but rather this, that and the other. A great number of tech ninjas were not exactly black belts when it came to the actual onerous work of computer programming. So many of the complex, discrete tasks involved in the creation of a website or an app had been automated that it was no longer necessary to possess knowledge of software mechanics. The coder's work was rarely a craft. The apps ran on an assembly line, built with "open-source", off-the-shelf components. The most important computer commands for the ninja to master were copy and paste... [M]any programmers who had "made it" in Silicon Valley were scrambling to promote themselves from coder to "founder". There wasn't necessarily more money to be had running a startup, and the increase in status was marginal unless one's startup attracted major investment and the right kind of press coverage. It's because the programmers knew that their own ladder to prosperity was on fire and disintegrating fast. They knew that well-paid programming jobs would also soon turn to smoke and ash, as the proliferation of learn-to-code courses around the world lowered the market value of their skills, and as advances in artificial intelligence allowed for computers to take over more of the mundane work of producing software. The programmers also knew that the fastest way to win that promotion to founder was to find some new domain that hadn't yet been automated. Every tech industry campaign designed to spur investment in the Next Big Thing -- at that time, it was the "sharing economy" -- concealed a larger programme for the transformation of society, always in a direction that favoured the investor and executive classes. "I wasn't just changing careers and jumping on the 'learn to code' bandwagon," he writes at one point. "I was being steadily indoctrinated in a specious ideology." Anonymous Coward , Saturday April 28, 2018 @11:40PM ( #56522045 ) older generations already had a term for this ( Score: 5 , Interesting) Older generations called this kind of fraud "fake it 'til you make it." raymorris ( 2726007 ) , Sunday April 29, 2018 @02:05AM ( #56522343 ) Journal The people who are smarter won't ( Score: 5 , Informative) > The people can do both are smart enough to build their own company and compete with you. Been there, done that. Learned a few lessons. Nowadays I work 9:30-4:30 for a very good, consistent paycheck and let some other "smart person" put in 75 hours a week dealing with hiring, managing people, corporate strategy, staying up on the competition, figuring out tax changes each year and getting taxes filed six times each year, the various state and local requirements, legal changes, contract hassles, etc, while hoping the company makes money this month so they can take a paycheck and lay their rent. I learned that I'm good at creating software systems and I enjoy it. I don't enjoy all-nighters, partners being dickheads trying to pull out of a contract, or any of a thousand other things related to running a start-up business. I really enjoy a consistent, six-figure compensation package too. brian.stinar ( 1104135 ) writes: Re: ( Score: 2 ) * getting taxes filled eighteen times a year. I pay monthly gross receipts tax (12), quarterly withholdings (4) and a corporate (1) and individual (1) returns. The gross receipts can vary based on the state, so I can see how six times a year would be the minimum. Cederic ( 9623 ) writes: Re: ( Score: 2 ) Fuck no. Cost of full automation:$4m Cost of manual entry: $0 Opportunity cost of manual entry:$800/year
At worse, pay for an accountant, if you can get one that cheaply. Bear in mind talking to them incurs most of that opportunity cost anyway.
serviscope_minor ( 664417 ) writes:
Re: ( Score: 2 )
Nowadays I work 9:30-4:30 for a very good, consistent paycheck and let some other "smart person" put in 75 hours a week dealing with hiring
There's nothing wrong with not wnting to run your own business, it's not for most people, and even if it was, the numbers don't add up. But putting the scare qoutes in like that makes it sound like you have huge chip on your shoulder. Those things re just as essential to the business as your work and without them you wouldn't have the steady 9:30-4:30 with good paycheck.
raymorris ( 2726007 ) writes:
Important, and dumb. ( Score: 3 , Informative)
Of course they are important. I wouldn't have done those things if they weren't important!
I frequently have friends say things like "I love baking. I can't get enough of baking. I'm going to open a bakery.". I ask them "do you love dealing with taxes, every month? Do you love contract law? Employment law? Marketing? Accounting?" If you LOVE baking, the smart thing to do is to spend your time baking. Running a start-up business, you're not going to do much baking.
If you love marketing, employment law, taxes
raymorris ( 2726007 ) writes:
Four tips for a better job. Who has more? ( Score: 3 )
I can tell you a few things that have worked for me. I'll go in chronological order rather than priority order.
Make friends in the industry you want to be in. Referrals are a major way people get jobs.
Look at the job listings for jobs you'd like to have and see which skills a lot of companies want, but you're missing. For me that's Java. A lot companies list Java skills and I'm not particularly good with Java. Then consider learning the skills you lack, the ones a lot of job postings are looking for.
Certifi
goose-incarnated ( 1145029 ) , Sunday April 29, 2018 @02:34PM ( #56524475 ) Journal
Re: older generations already had a term for this ( Score: 5 , Insightful)
You don't understand the point of an ORM do you? I'd suggest reading why they exist
They exist because programmers value code design more than data design. ORMs are the poster-child for square-peg-round-hole solutions, which is why all ORMs choose one of three different ways of squashing hierarchical data into a relational form, all of which are crappy.
If the devs of the system (the ones choosing to use an ORM) had any competence at all they'd design their database first because in any application that uses a database the database is the most important bit, not the OO-ness or Functional-ness of the design.
Over the last few decades I've seen programs in a system come and go; a component here gets rewritten, a component there gets rewritten, but you know what? They all have to work with the same damn data.
You can more easily switch out your code for new code with new design in a new language, than you can switch change the database structure. So explain to me why it is that you think the database should be mangled to fit your OO code rather than mangling your OO code to fit the database?
cheekyboy ( 598084 ) writes:
im sick of reinventors and new frameworks ( Score: 3 )
Stick to the one thing for 10-15years. Often all this new shit doesn't do jack different to the old shit, its not faster, its not better. Every dick wants to be famous so make another damn library/tool with his own fancy name and feature, instead of enhancing an existing product.
gbjbaanb ( 229885 ) writes:
Re: ( Score: 2 )
amen to that.
Or kids who can't hack the main stuff, suddenly discover the cool new, and then they can pretend they're "learning" it, and when the going gets tough (as it always does) they can declare the tech to be pants and move to another.
hence we had so many people on the bandwagon for functional programming, then dumped it for ruby on rails, then dumped that for Node.js, not sure what they're on at currently, probably back to asp.net.
Greyfox ( 87712 ) writes:
Re: ( Score: 2 )
How much code do you have to reuse before you're not really programming anymore? When I started in this business, it was reasonably possible that you could end up on a project that didn't particularly have much (or any) of an operating system. They taught you assembly language and the process by which the system boots up, but I think if I were to ask most of the programmers where I work, they wouldn't be able to explain how all that works...
djinn6 ( 1868030 ) writes:
Re: ( Score: 2 )
It really feels like if you know what you're doing it should be possible to build a team of actually good programmers and put everyone else out of business by actually meeting your deliverables, but no one has yet. I wonder why that is.
You mean Amazon, Google, Facebook and the like? People may not always like what they do, but they manage to get things done and make plenty of money in the process. The problem for a lot of other businesses is not having a way to identify and promote actually good programmers. In your example, you could've spent 10 minutes fixing their query and saved them days of headache, but how much recognition will you actually get? Where is your motivation to help them?
Junta ( 36770 ) writes:
Re: ( Score: 2 )
It's not a "kids these days" sort of issue, it's *always* been the case that shameless, baseless self-promotion wins out over sincere skill without the self-promotion, because the people who control the money generally understand boasting more than they understand the technology. Yes it can happen that baseless boasts can be called out over time by a large enough mass of feedback from competent peers, but it takes a *lot* to overcome the tendency for them to have faith in the boasts.
It does correlate stron
cheekyboy ( 598084 ) writes:
Re: ( Score: 2 )
And all these modern coders forget old lessons, and make shit stuff, just look at instagram windows app, what a load of garbage shit, that us old fuckers could code in 2-3 weeks.
Instagram - your app sucks, cookie cutter coders suck, no refinement, coolness. Just cheap ass shit, with limited usefulness.
Just like most of commercial software that's new - quick shit.
Oh and its obvious if your an Indian faking it, you haven't worked in 100 companies at the age of 29.
Junta ( 36770 ) writes:
Re: ( Score: 2 )
Here's another problem, if faced with a skilled team that says "this will take 6 months to do right" and a more naive team that says "oh, we can slap that together in a month", management goes with the latter. Then the security compromises occur, then the application fails due to pulling in an unvetted dependency update live into production. When the project grows to handling thousands instead of dozens of users and it starts mysteriously folding over and the dev team is at a loss, well the choice has be
molarmass192 ( 608071 ) , Sunday April 29, 2018 @02:15AM ( #56522359 ) Homepage Journal
Re:older generations already had a term for this ( Score: 5 , Interesting)
These restrictions is a large part of what makes Arduino programming "fun". If you don't plan out your memory usage, you're gonna run out of it. I cringe when I see 8MB web pages of bloated "throw in everything including the kitchen sink and the neighbor's car". Unfortunately, the careful and cautious way is a dying in favor of the throw 3rd party code at it until it does something. Of course, I don't have time to review it but I'm sure everybody else has peer reviewed it for flaws and exploits line by line.
AmiMoJo ( 196126 ) writes: < mojo@@@world3...net > on Sunday April 29, 2018 @05:15AM ( #56522597 ) Homepage Journal
Re:older generations already had a term for this ( Score: 4 , Informative)
Unfortunately, the careful and cautious way is a dying in favor of the throw 3rd party code at it until it does something.
Of course. What is the business case for making it efficient? Those massive frameworks are cached by the browser and run on the client's system, so cost you nothing and save you time to market. Efficient costs money with no real benefit to the business.
If we want to fix this, we need to make bloat have an associated cost somehow.
locketine ( 1101453 ) writes:
Re: older generations already had a term for this ( Score: 2 )
My company is dealing with the result of this mentality right now. We released the web app to the customer without performance testing and doing several majorly inefficient things to meet deadlines. Once real load was put on the application by users with non-ideal hardware and browsers, the app was infuriatingly slow. Suddenly our standard sub-40 hour workweek became a 50+ hour workweek for months while we fixed all the inefficient code and design issues.
So, while you're right that getting to market and opt
serviscope_minor ( 664417 ) writes:
Re: ( Score: 2 )
In the bad old days we had a hell of a lot of ridiculous restriction We must somehow made our programs to run successfully inside a RAM that was 48KB in size (yes, 48KB, not 48MB or 48GB), on a CPU with a clock speed of 1.023 MHz
We still have them. In fact some of the systems I've programmed have been more resource limited than the gloriously spacious 32KiB memory of the BBC model B. Take the PIC12F or 10F series. A glorious 64 bytes of RAM, max clock speed of 16MHz, but not unusual to run it 32kHz.
serviscope_minor ( 664417 ) writes:
Re: ( Score: 2 )
So what are the uses for that? I am curious what things people have put these to use for.
It's hard to determine because people don't advertise use of them at all. However, I know that my electric toothbrush uses an Epson 4 bit MCU of some description. It's got a status LED, basic NiMH batteryb charger and a PWM controller for an H Bridge. Braun sell a *lot* of electric toothbrushes. Any gadget that's smarter than a simple switch will probably have some sort of basic MCU in it. Alarm system components, sensor
tlhIngan ( 30335 ) writes:
Re: ( Score: 3 , Insightful)
b) No computer ever ran at 1.023 MHz. It was either a nice multiple of 1Mhz or maybe a multiple of 3.579545Mhz (ie. using the TV output circuit's color clock crystal to drive the CPU).
Well, it could be used to drive the TV output circuit, OR, it was used because it's a stupidly cheap high speed crystal. You have to remember except for a few frequencies, most crystals would have to be specially cut for the desired frequency. This occurs even today, where most oscillators are either 32.768kHz (real time clock
Anonymous Coward writes:
Re: ( Score: 2 , Interesting)
Yeah, nice talk. You could have stopped after the first sentence. The other AC is referring to the Commodore C64 [wikipedia.org]. The frequency has nothing to do with crystal availability but with the simple fact that everything in the C64 is synced to the TV. One clock cycle equals 8 pixels. The graphics chip and the CPU take turns accessing the RAM. The different frequencies dictated by the TV standards are the reason why the CPU in the NTSC version of the C64 runs at 1.023MHz and the PAL version at 0.985MHz.
Wraithlyn ( 133796 ) writes:
Re: ( Score: 2 )
LOL what exactly is so special about 16K RAM? https://yourlogicalfallacyis.c... [yourlogicalfallacyis.com]
I cut my teeth on a VIC20 (5K RAM), then later a C64 (which ran at 1.023MHz...)
Anonymous Coward writes:
Re: ( Score: 2 , Interesting)
Commodore 64 for the win. I worked for a company that made detection devices for the railroad, things like monitoring axle temperatures, reading the rail car ID tags. The original devices were made using Commodore 64 boards using software written by an employee at the one rail road company working with them.
The company then hired some electrical engineers to design custom boards using the 68000 chips and I was hired as the only programmer. Had to rewrite all of the code which was fine...
wierd_w ( 1375923 ) , Saturday April 28, 2018 @11:58PM ( #56522075 )
... A job fair can easily test this competency. ( Score: 4 , Interesting)
Many of these languages have an interactive interpreter. I know for a fact that Python does.
So, since job-fairs are an all day thing, and setup is already a thing for them -- set up a booth with like 4 computers at it, and an admin station. The 4 terminals have an interactive session with the interpreter of choice. Every 20min or so, have a challenge for "Solve this problem" (needs to be easy and already solved in general. Programmers hate being pimped without pay. They don't mind tests of skill, but hate being pimped. Something like "sort this array, while picking out all the prime numbers" or something.) and see who steps up. The ones that step up have confidence they can solve the problem, and you can quickly see who can do the work and who can't.
The ones that solve it, and solve it to your satisfaction, you offer a nice gig to.
ShanghaiBill ( 739463 ) , Sunday April 29, 2018 @01:50AM ( #56522321 )
Re:... A job fair can easily test this competency. ( Score: 5 , Informative)
Then you get someone good at sorting arrays while picking out prime numbers, but potentially not much else.
The point of the test is not to identify the perfect candidate, but to filter out the clearly incompetent. If you can't sort an array and write a function to identify a prime number, I certainly would not hire you. Passing the test doesn't get you a job, but it may get you an interview ... where there will be other tests.
wierd_w ( 1375923 ) writes:
Re: ( Score: 2 )
BINGO!
(I am not even a professional programmer, but I can totally perform such a trivially easy task. The example tests basic understanding of loop construction, function construction, variable use, efficient sorting, and error correction-- especially with mixed type arrays. All of these are things any programmer SHOULD now how to do, without being overly complicated, or clearly a disguised occupational problem trying to get a free solution. Like I said, programmers hate being pimped, and will be turned off
wierd_w ( 1375923 ) , Sunday April 29, 2018 @04:02AM ( #56522443 )
Re: ... A job fair can easily test this competency ( Score: 5 , Insightful)
Again, the quality applicant and the code monkey both have something the fakers do not-- Actual comprehension of what a program is, and how to create one.
As Bill points out, this is not the final exam. This is the "Oh, I see you do actually know how to program-- show me more" portion of the process. This is the part that HR drones are not capable of performing, due to Dunning-Krueger. Those that are actually, REALLY competent will do more than just satisfy the requirements of the challenge, they will provide actually working solutions to the challenge that properly validate their input, and return proper error states if the input is invalid, etc-- You can learn a LOT about a potential hire by observing their work. *THAT* is what this is really about. The triviality of the problem is a necessity, because you ***DON'T*** try to get free solutions out of people.
I realize that may be difficult for you to comprehend, but you *DON'T* do that. The job fair is to let people know that you have a position available, and try to curry interest in people to apply. A successful pre-screening is confidence building, and helps the potential hire to feel that your company is actually interested in actually hiring somebody, and not just fucking off in the booth, to cover for "failing to find somebody" and then "Getting yet another H1B". It gives them a chance to show you what they can do. That is what it is for, and what it does. It also excludes the fakers that this article is about-- The ones that can talk a good talk, but could not program a simple boolean check condition if their life depended on it.
If it were not for the time constraints of a job fair (usually only 2 days, and in that time you need to try and pre-screen as many as possible), I would suggest a tiered challenge, with progressively harder challenges, where you hand out resumes to the ones that make it to the top 3 brackets, but that is not the way the world works.
luis_a_espinal ( 1810296 ) writes:
Re: ( Score: 2 )
This in my opinion is really a waste of time. Challenges like this have to be so simple they can be done walking up to a booth are not likely to filter the "all talks" any better than a few interview questions could (imperson so the candidate can't just google it).
Tougher more involved stuff isn't good either it gives a huge advantage to the full time job hunter, the guy or gal that already has a 9-5 and a family that wants to seem them has not got time for games. We have been struggling with hiring where I work ( I do a lot of the interviews ) and these are the conclusions we have reached
You would be surprised at the number of people with impeccable-looking resumes failing at something as simple as the FizzBuzz test [codinghorror.com]
PaulRivers10 ( 4110595 ) writes:
Re: ... A job fair can easily test this competenc ( Score: 2 )
The only thing fuzzbuzz tests is "have you done fizzbuzz before"? It's a short question filled with every petty trick the author could think ti throw in there. If you haven't seen the tricks they trip you up for no reason related to your actual coding skills. Once you have seen them they're trivial and again unrelated to real work. Fizzbuzz is best passed by someone aiming to game the interview system. It passes people gaming it and trips up people who spent their time doing on the job real work.
Hognoxious ( 631665 ) writes:
Re: ( Score: 2 )
they trip you up for no reason related to your actual codung skills.
Bullshit!
luis_a_espinal ( 1810296 ) , Sunday April 29, 2018 @07:49AM ( #56522861 ) Homepage
filter the lame code monkeys ( Score: 4 , Informative)
Lame monkey tests select for lame monkeys.
A good programmer first and foremost has a clean mind. Experience suggests puzzle geeks, who excel at contrived tests, are usually sloppy thinkers.
No. Good programmers can trivially knock out any of these so-called lame monkey tests. It's lame code monkeys who can't do it. And I've seen their work. Many night shifts and weekends I've burned trying to fix their shit because they couldn't actually do any of the things behind what you call "lame monkey tests", like:
pulling expensive invariant calculations out of loops using for loops to scan a fucking table to pull rows or calculate an aggregate when they could let the database do what it does best with a simple SQL statement systems crashing under actual load because their shitty code was never stress tested ( but it worked on my dev box! .) again with databases, having to redo their schemas because they were fattened up so much with columns like VALUE1, VALUE2, ... VALUE20 (normalize you assholes!) chatting remote APIs - because these code monkeys cannot think about the need for bulk operations in increasingly distributed systems. storing dates in unsortable strings because the idiots do not know most modern programming languages have a date data type.
Oh and the most important, off-by-one looping errors. I see this all the time, the type of thing a good programmer can spot on quickly because he or she can do the so-called "lame monkey tests" that involve arrays and sorting.
I've seen the type: "I don't need to do this shit because I have business knowledge and I code for business and IT not google", and then they go and code and fuck it up... and then the rest of us have to go clean up their shit at 1AM or on weekends.
If you work as an hourly paid contractor cleaning that crap, it can be quite lucrative. But sooner or later it truly sucks the energy out of your soul.
So yeah, we need more lame monkey tests ... to filter the lame code monkeys.
ShanghaiBill ( 739463 ) writes:
Re: ( Score: 3 )
Someone could Google the problem with the phone then step up and solve the challenge.
If given a spec, someone can consistently cobble together working code by Googling, then I would love to hire them. That is the most productive way to get things done.
There is nothing wrong with using external references. When I am coding, I have three windows open: an editor, a testing window, and a browser with a Stackoverflow tab open.
Junta ( 36770 ) writes:
Re: ( Score: 2 )
Yeah, when we do tech interviews, we ask questions that we are certain they won't be able to answer, but want to see how they would think about the problem and what questions they ask to get more data and that they don't just fold up and say "well that's not the sort of problem I'd be thinking of" The examples aren't made up or anything, they are generally selection of real problems that were incredibly difficult that our company had faced before, that one may not think at first glance such a position would
bobstreo ( 1320787 ) writes:
Nothing worse ( Score: 2 )
than spending weeks interviewing "good" candidates for an opening, selecting a couple and hiring them as contractors, then finding out they are less than unqualified to do the job they were hired for.
I've seen it a few times, Java "experts", Microsoft "experts" with years of experience on their resumes, but completely useless in coding, deployment or anything other than buying stuff from the break room vending machines.
That being said, I've also seen projects costing hundreds of thousands of dollars, with y
Anonymous Coward , Sunday April 29, 2018 @12:34AM ( #56522157 )
Re:Nothing worse ( Score: 4 , Insightful)
The moment you said "contractors", and you have lost any sane developer. Keep swimming, its not a fish.
Anonymous Coward writes:
Re: ( Score: 2 , Informative)
I agree with this. I consider myself to be a good programmer and I would never go into contractor game. I also wonder, how does it take you weeks to interview someone and you still can't figure out if the person can't code? I could probably see that in 15 minutes in a pair coding session.
Also, Oracle, SAP, IBM... I would never buy from them, nor use their products. I have used plenty of IBM products and they suck big time. They make software development 100 times harder than it could be. Their technical supp
Lanthanide ( 4982283 ) writes:
Re: ( Score: 2 )
It's weeks to interview multiple different candidates before deciding on 1 or 2 of them. Not weeks per person.
Anonymous Coward writes:
Re: ( Score: 3 , Insightful)
That being said, I've also seen projects costing hundreds of thousands of dollars, with years of delays from companies like Oracle, Sun, SAP, and many other "vendors"
Software development is a hard thing to do well, despite the general thinking of technology becoming cheaper over time, and like health care the quality of the goods and services received can sometimes be difficult to ascertain. However, people who don't respect developers and the problems we solve are very often the same ones who continually frustrate themselves by trying to cheap out, hiring outsourced contractors, and then tearing their hair out when sub par results are delivered, if anything is even del
pauljlucas ( 529435 ) writes:
Re: ( Score: 2 )
As part of your interview process, don't you have candidates code a solution to a problem on a whiteboard? I've interviewed lots of "good" candidates (on paper) too, but they crashed and burned when challenged with a coding exercise. As a result, we didn't make them job offers.
VeryFluffyBunny ( 5037285 ) writes:
I do the opposite ( Score: 2 )
I'm not a great coder but good enough to get done what clients want done. If I'm not sure or don't think I can do it, I tell them. I think they appreciate the honesty. I don't work in a tech-hub, startups or anything like that so I'm not under the same expectations and pressures that others may be.
Tony Isaac ( 1301187 ) writes:
Bigger building blocks ( Score: 2 )
OK, so yes, I know plenty of programmers who do fake it. But stitching together components isn't "fake" programming.
Back in the day, we had to write our own code to loop through an XML file, looking for nuggets. Now, we just use an XML serializer. Back then, we had to write our own routines to send TCP/IP messages back and forth. Now we just use a library.
I love it! I hated having to make my own bricks before I could build a house. Now, I can get down to the business of writing the functionality I want, ins
Anonymous Coward writes:
Re: ( Score: 2 , Insightful)
But, I suspect you could write the component if you had to. That makes you a very different user of that component than someone who just knows it as a magic black box.
Because of this, you understand the component better and have real knowledge of its strengths and limitations. People blindly using components with only a cursory idea of their internal operation often cause major performance problems. They rarely recognize when it is time to write their own to overcome a limitation (or even that it is possibl
Tony Isaac ( 1301187 ) writes:
Re: ( Score: 2 )
You're right on all counts. A person who knows how the innards work, is better than someone who doesn't, all else being equal. Still, today's world is so specialized that no one can possibly learn it all. I've never built a processor, as you have, but I still have been able to build a DNA matching algorithm for a major DNA lab.
I would argue that anyone who can skillfully use off-the-shelf components can also learn how to build components, if they are required to.
thesupraman ( 179040 ) writes:
Ummm. ( Score: 2 )
1, 'Back in the Day' there was no XML, XMl was not very long ago.
2, its a parser, a serialiser is pretty much the opposite (unless this weeks fashion has redefined that.. anything is possible).
3, 'Back then' we didnt have TCP stacks...
But, actually I agree with you. I can only assume the author thinks there are lots of fake plumbers because they dont cast their own toilet bowels from raw clay, and use pre-build fittings and pipes! That car mechanics start from raw steel scrap and a file.. And that you need
Tony Isaac ( 1301187 ) writes:
Re: ( Score: 2 )
For the record, XML was invented in 1997, you know, in the last century! https://en.wikipedia.org/wiki/... [wikipedia.org]
And we had a WinSock library in 1992. https://en.wikipedia.org/wiki/... [wikipedia.org]
Yes, I agree with you on the "middle ground." My reaction was to the author's point that "not knowing how to build the components" was the same as being a "fake programmer."
Tony Isaac ( 1301187 ) , Sunday April 29, 2018 @01:46AM ( #56522313 ) Homepage
Re:Bigger building blocks ( Score: 5 , Interesting)
If I'm a plumber, and I don't know anything about the engineering behind the construction of PVC pipe, I can still be a good plumber. If I'm an electrician, and I don't understand the role of a blast furnace in the making of the metal components, I can still be a good electrician.
The analogy fits. If I'm a programmer, and I don't know how to make an LZW compression library, I can still be a good programmer. It's a matter of layers. These days, we specialize. You've got your low-level programmers that make the components, the high level programmers that put together the components, the graphics guys who do HTML/CSS, and the SQL programmers that just know about databases. Every person has their specialty. It's no longer necessary to be a low-level programmer, or jack-of-all-trades, to be "good."
If I don't know the layout of the IP header, I can still write quality networking software, and if I know XSLT, I can still do cool stuff with XML, even if I don't know how to write a good parser.
Re: ( Score: 3 )
I was with you until you said " I can still do cool stuff with XML".
Tony Isaac ( 1301187 ) writes:
Re: ( Score: 2 )
LOL yeah I know it's all JSON now. I've been around long enough to see these fads come and go. Frankly, I don't see a whole lot of advantage of JSON over XML. It's not even that much more compact, about 10% or so. But the point is that the author laments the "bad old days" when you had to create all your own building blocks, and you didn't have a team of specialists. I for one don't want to go back to those days!
careysub ( 976506 ) writes:
Re: ( Score: 3 )
The main advantage is that JSON is that it is consistent. XML has attributes, embedded optional stuff within tags. That was derived from the original SGML ancestor where is was thought to be a convenience for the human authors who were supposed to be making the mark-up manually. Programmatically it is a PITA.
Cederic ( 9623 ) writes:
Re: ( Score: 3 )
I got shit for decrying XML back when it was the trendy thing. I've had people apologise to me months later because they've realized I was right, even though at the time they did their best to fuck over my career because XML was the new big thing and I wasn't fully on board.
XML has its strengths and its place, but fuck me it taught me how little some people really fucking understand shit.
Anonymous Coward writes:
Silicon Valley is Only Part of the Tech Business ( Score: 2 , Informative)
And a rather small part at that, albeit a very visible and vocal one full of the proverbial prima donas. However, much of the rest of the tech business, or at least the people working in it, are not like that. It's small groups of developers working in other industries that would not typically be considered technology. There are software developers working for insurance companies, banks, hedge funds, oil and gas exploration or extraction firms, national defense and many hundreds and thousands of other small
phantomfive ( 622387 ) writes:
bonfire of fakers ( Score: 2 )
This is the reason I wish programming didn't pay so much....the field is better when it's mostly populated by people who enjoy programming.
Njovich ( 553857 ) , Sunday April 29, 2018 @05:35AM ( #56522641 )
Learn to code courses ( Score: 5 , Insightful)
They knew that well-paid programming jobs would also soon turn to smoke and ash, as the proliferation of learn-to-code courses around the world lowered the market value of their skills, and as advances in artificial intelligence allowed for computers to take over more of the mundane work of producing software.
Kind of hard to take this article serious after saying gibberish like this. I would say most good programmers know that neither learn-to-code courses nor AI are going to make a dent in their income any time soon.
AndyKron ( 937105 ) writes:
Me? No ( Score: 2 )
As a non-programmer Arduino and libraries are my friends
Escogido ( 884359 ) , Sunday April 29, 2018 @06:59AM ( #56522777 )
in the silly cone valley ( Score: 5 , Interesting)
There is a huge shortage of decent programmers. I have personally witnessed more than one phone "interview" that went like "have you done this? what about this? do you know what this is? um, can you start Monday?" (120K-ish salary range)
Partly because there are way more people who got their stupid ideas funded than good coders willing to stain their resume with that. partly because if you are funded, and cannot do all the required coding solo, here's your conundrum:
• top level hackers can afford to be really picky, so on one hand it's hard to get them interested, and if you could get that, they often want some ownership of the project. the plus side is that they are happy to work for lots of equity if they have faith in the idea, but that can be a huge "if".
• "good but not exceptional" senior engineers aren't usually going to be super happy, as they often have spouses and children and mortgages, so they'd favor job security over exciting ideas and startup lottery.
• that leaves you with fresh-out-of-college folks, which are really really a mixed bunch. some are actually already senior level of understanding without the experience, some are absolutely useless, with varying degrees in between, and there's no easy way to tell which is which early.
so the not-so-scrupulous folks realized what's going on, and launched multiple coding boot camps programmes, to essentially trick both the students into believing they can become a coder in a month or two, and also the prospective employers that said students are useful. so far it's been working, to a degree, in part because in such companies coding skill evaluation process is broken. but one can only hide their lack of value add for so long, even if they do manage to bluff their way into a job.
quonset ( 4839537 ) , Sunday April 29, 2018 @07:20AM ( #56522817 )
Duh! ( Score: 4 , Insightful)
All one had to do was look at the lousy state of software and web sites today to see this is true. It's quite obvious little to no thought is given on how to make something work such that one doesn't have to jump through hoops.
I have many times said the most perfect word processing program ever developed was WordPefect 5.1 for DOS. Ones productivity was astonishing. It just worked.
Now we have the bloated behemoth Word which does its utmost to get in the way of you doing your work. The only way to get it to function is to turn large portions of its "features" off, and even then it still insists on doing something other than what you told it to do.
Then we have the abomination of Windows 10, which is nothing but Clippy on 10X steroids. It is patently obvious the people who program this steaming pile have never heard of simplicity. Who in their right mind would think having to "search" for something is more efficient than going directly to it? I would ask the question if these people wander around stores "searching" for what they're looking for, but then I realize that's how their entire life is run. They search for everything online rather than going directly to the source. It's no wonder they complain about not having time to things. They're always searching.
Web sites are another area where these people have no clue what they're doing. Anything that might be useful is hidden behind dropdown menus, flyouts, popup bubbles and intriately designed mazes of clicks needed to get to where you want to go. When someone clicks on a line of products, they shouldn't be harassed about what part of the product line they want to look at. Give them the information and let the user go where they want.
This rant could go on, but this article explains clearly why we have regressed when it comes to software and web design. Instead of making things simple and easy to use, using the one or two brain cells they have, programmers and web designers let the software do what it wants without considering, should it be done like this?
swb ( 14022 ) , Sunday April 29, 2018 @07:48AM ( #56522857 )
Tech industry churn ( Score: 3 )
The tech industry has a ton of churn -- there's some technological advancement, but there's an awful lot of new products turned out simply to keep customers buying new licenses and paying for upgrades.
This relentless and mostly phony newness means a lot of people have little experience with current products. People fake because they have no choice. The good ones understand the general technologies and problems they're meant to solve and can generally get up to speed quickly, while the bad ones are good at faking it but don't really know what they're doing. Telling the difference from the outside is impossible.
Sales people make it worse, promoting people as "experts" in specific products or implementations because the people have experience with a related product and "they're all the same". This burns out the people with good adaption skills.
DaMattster ( 977781 ) , Sunday April 29, 2018 @08:39AM ( #56522979 )
Interesting ( Score: 3 )
From the summary, it sounds like a lot of programmers and software engineers are trying to develop the next big thing so that they can literally beg for money from the elite class and one day, hopefully, become a member of the aforementioned. It's sad how the middle class has been utterly decimated in the United States that some of us are willing to beg for scraps from the wealthy. I used to work in IT but I've aged out and am now back in school to learn automotive technology so that I can do something other than being a security guard. Currently, the only work I have been able to find has been in the unglamorous security field.
I am learning some really good new skills in the automotive program that I am in but I hate this one class called "Professionalism in the Shop." I can summarize the entire class in one succinct phrase, "Learn how to appeal to, and communicate with, Mr. Doctor, Mr. Lawyer, or Mr. Wealthy-man." Basically, the class says that we are supposed to kiss their ass so they keep coming back to the Audi, BMW, Mercedes, Volvo, or Cadillac dealership. It feels a lot like begging for money on behalf of my employer (of which very little of it I will see) and nothing like professionalism. Professionalism is doing the job right the first time, not jerking the customer off. Professionalism is not begging for a 5 star review for a few measly extra bucks but doing absolute top quality work. I guess the upshot is that this class will be the easiest 4.0 that I've ever seen.
There is something fundamentally wrong when the wealthy elite have basically demanded that we beg them for every little scrap. I can understand the importance of polite and professional interaction but this prevalent expectation that we bend over backwards for them crosses a line with me. I still suck it up because I have to but it chafes my ass to basically validate the wealthy man.
ElitistWhiner ( 79961 ) writes:
Natural talent... ( Score: 2 )
In 70's I worked with two people who had a natural talent for computer science algorithms .vs. coding syntax. In the 90's while at COLUMBIA I worked with only a couple of true computer scientists out of 30 students. I've met 1 genius who programmed, spoke 13 languages, ex-CIA, wrote SWIFT and spoke fluent assembly complete with animated characters.
According to the Bluff Book, everyone else without natural talent fakes it. In the undiluted definition of computer science, genetics roulette and intellectual d
fahrbot-bot ( 874524 ) writes:
Other book sells better and is more interesting ( Score: 2 )
New Book Describes 'Bluffing' Programmers in Silicon Valley
It's not as interesting as the one about "fluffing" [urbandictionary.com] programmers.
Anonymous Coward writes:
Re: ( Score: 3 , Funny)
Ah yes, the good old 80:20 rule, except it's recursive for programmers.
80% are shit, so you fire them. Soon you realize that 80% of the remaining 20% are also shit, so you fire them too. Eventually you realize that 80% of the 4% remaining after sacking the 80% of the 20% are also shit, so you fire them!
...
The cycle repeats until there's just one programmer left: the person telling the joke.
---
tl;dr: All programmers suck. Just ask them to review their own code from more than 3 years ago: they'll tell you that
luis_a_espinal ( 1810296 ) writes:
Re: ( Score: 3 )
Who gives a fuck about lines? If someone gave me JavaScript, and someone gave me minified JavaScript, which one would I want to maintain?
Because the world of programming is not centered about JavasScript and reduction of lines is not the same as minification. If the first thing that came to your mind was about minified JavaScript when you saw this conversation, you are certainly not the type of programmer I would want to inherit code from.
See, there's a lot of shit out there that is overtly redundant and unnecessarily complex. This is specially true when copy-n-paste code monkeys are left to their own devices for whom code formatting seems
Anonymous Coward , Sunday April 29, 2018 @01:17AM ( #56522241 )
Re:Most "Professional programmers" are useless. ( Score: 4 , Interesting)
I have a theory that 10% of people are good at what they do. It doesn't really matter what they do, they will still be good at it, because of their nature. These are the people who invent new things, who fix things that others didn't even see as broken and who automate routine tasks or simply question and erase tasks that are not necessary. If you have a software team that contain 5 of these, you can easily beat a team of 100 average people, not only in cost but also in schedule, quality and features. In theory they are worth 20 times more than average employees, but in practise they are usually paid the same amount of money with few exceptions.
80% of people are the average. They can follow instructions and they can get the work done, but they don't see that something is broken and needs fixing if it works the way it has always worked. While it might seem so, these people are not worthless. There are a lot of tasks that these people are happily doing which the 10% don't want to do. E.g. simple maintenance work, implementing simple features, automating test cases etc. But if you let the top 10% lead the project, you most likely won't be needed that much of these people. Most work done by these people is caused by themselves, by writing bad software due to lack of good leader.
10% are just causing damage. I'm not talking about terrorists and criminals. I have seen software developers who have tried (their best?), but still end up causing just damage to the code that someone else needs to fix, costing much more than their own wasted time. You really must use code reviews if you don't know your team members, to find these people early.
Anonymous Coward , Sunday April 29, 2018 @01:40AM ( #56522299 )
Re:Most "Professional programmers" are useless. ( Score: 5 , Funny)
to find these people early
and promote them to management where they belong.
raymorris ( 2726007 ) , Sunday April 29, 2018 @01:51AM ( #56522329 ) Journal
Seems about right. Constantly learning, studying ( Score: 5 , Insightful)
That seems about right to me.
I have a lot of weaknesses. My people skills suck, I'm scrawny, I'm arrogant. I'm also generally known as a really good programmer and people ask me how/why I'm so much better at my job than everyone else in the room. (There are a lot of things I'm not good at, but I'm good at my job, so say everyone I've worked with.)
I think one major difference is that I'm always studying, intentionally working to improve, every day. I've been doing that for twenty years.
I've worked with people who have "20 years of experience"; they've done the same job, in the same way, for 20 years. Their first month on the job they read the first half of "Databases for Dummies" and that's what they've been doing for 20 years. They never read the second half, and use Oracle database 18.0 exactly the same way they used Oracle Database 2.0 - and it was wrong 20 years ago too. So it's not just experience, it's 20 years of learning, getting better, every day. That's 7,305 days of improvement.
gbjbaanb ( 229885 ) writes:
Re: ( Score: 2 )
I think I can guarantee that they are a lot better at their jobs than you think, and that you are a lot worse at your job than you think too.
m00sh ( 2538182 ) writes:
Re: ( Score: 2 )
That seems about right to me.
I have a lot of weaknesses. My people skills suck, I'm scrawny, I'm arrogant. I'm also generally known as a really good programmer and people ask me how/why I'm so much better at my job than everyone else in the room. (There are a lot of things I'm not good at, but I'm good at my job, so say everyone I've worked with.)
I think one major difference is that I'm always studying, intentionally working to improve, every day. I've been doing that for twenty years.
I've worked with people who have "20 years of experience"; they've done the same job, in the same way, for 20 years. Their first month on the job they read the first half of "Databases for Dummies" and that's what they've been doing for 20 years. They never read the second half, and use Oracle database 18.0 exactly the same way they used Oracle Database 2.0 - and it was wrong 20 years ago too. So it's not just experience, it's 20 years of learning, getting better, every day. That's 7,305 days of improvement.
If you take this attitude towards other people, people will not ask your for help. At the same time, you'll be also be not able to ask for their help.
I've seen superstar programmers suck the life out of project by over-complicating things and not working together with others.
raymorris ( 2726007 ) writes:
Which part? Learning makes you better? ( Score: 2 )
You quoted a lot. Is there one part exactly do you have in mind? The thesis of my post is of course "constant learning, on purpose, makes you better"
> you take this attitude towards other people, people will not ask your for help. At the same time, you'll be also be not able to ask for their help.
Are you saying that trying to learn means you can't ask for help, or was there something more specific? For me, trying to learn means asking.
Trying to learn, I've had the opportunity to ask for help from peop
phantomfive ( 622387 ) writes:
Re: ( Score: 2 )
The difference between a smart programmer who succeeds and a stupid programmer who drops out is that the smart programmer doesn't give up.
complete loony ( 663508 ) writes:
Re: ( Score: 2 )
In other words;
What is often mistaken for 20 years' experience, is just 1 year's experience repeated 20 times.
serviscope_minor ( 664417 ) writes:
Re: ( Score: 2 )
10% are just causing damage. I'm not talking about terrorists and criminals.
Terrorists and criminals have nothing on those guys. I know guy who is one of those. Worse, he's both motivated and enthusiastic. He also likes to offer help and advice to other people who don't know the systems well.
asifyoucare ( 302582 ) , Sunday April 29, 2018 @08:49AM ( #56522999 )
Re:Most "Professional programmers" are useless. ( Score: 5 , Insightful)
Good point. To quote Kurt von Hammerstein-Equord:
"I divide my officers into four groups. There are clever, diligent, stupid, and lazy officers. Usually two characteristics are combined. Some are clever and diligent -- their place is the General Staff. The next lot are stupid and lazy -- they make up 90 percent of every army and are suited to routine duties. Anyone who is both clever and lazy is qualified for the highest leadership duties, because he possesses the intellectual clarity and the composure necessary for difficult decisions. One must beware of anyone who is stupid and diligent -- he must not be entrusted with any responsibility because he will always cause only mischief."
gweihir ( 88907 ) writes:
Re: ( Score: 2 )
Oops. Good thing I never did anything military. I am definitely in the "clever and lazy" class.
apoc.famine ( 621563 ) writes:
Re: ( Score: 2 )
I was just thinking the same thing. One of my passions in life is coming up with clever ways to do less work while getting more accomplished.
Software_Dev_GL ( 5377065 ) writes:
Re: ( Score: 2 )
It's called the Pareto Distribution [wikipedia.org]. The number of competent people (people doing most of the work) in any given organization goes like the square root of the number of employees.
gweihir ( 88907 ) writes:
Re: ( Score: 2 )
Matches my observations. 10-15% are smart, can think independently, can verify claims by others and can identify and use rules in whatever they do. They are not fooled by things "everybody knows" and see standard-approaches as first approximations that, of course, need to be verified to work. They do not trust anything blindly, but can identify whether something actually work well and build up a toolbox of such things.
The problem is that in coding, you do not have a "(mass) production step", and that is the
geoskd ( 321194 ) writes:
Re: ( Score: 2 )
In basic concept I agree with your theory, it fits my own anecdotal experience well, but I find that your numbers are off. The top bracket is actually closer to 20%. The reason it seems so low is that a large portion of the highly competent people are running one programmer shows, so they have no co-workers to appreciate their knowledge and skill. The places they work do a very good job of keeping them well paid and happy (assuming they don't own the company outright), so they rarely if ever switch jobs.
The
Tablizer ( 95088 ) , Sunday April 29, 2018 @01:54AM ( #56522331 ) Journal
Re:Most "Professional programmers" are useless. ( Score: 4 , Interesting)
at least 70, probably 80, maybe even 90 percent of professional programmers should just fuck off and do something else as they are useless at programming.
Programming is statistically a dead-end job. Why should anyone hone a dead-end skill that you won't be able to use for long? For whatever reason, the industry doesn't want old programmers.
Otherwise, I'd suggest longer training and education before they enter the industry. But that just narrows an already narrow window of use.
Cesare Ferrari ( 667973 ) writes:
Re: ( Score: 2 )
Well, it does rather depend on which industry you work in - i've managed to find interesting programming jobs for 25 years, and there's no end in sight for interesting projects and new avenues to explore. However, this isn't for everyone, and if you have good personal skills then moving from programming into some technical management role is a very worthwhile route, and I know plenty of people who have found very interesting work in that direction.
gweihir ( 88907 ) writes:
Re: ( Score: 3 , Insightful)
I think that is a misinterpretation of the facts. Old(er) coders that are incompetent are just much more obvious and usually are also limited to technologies that have gotten old as well. Hence the 90% old coders that can actually not hack it and never really could get sacked at some time and cannot find a new job with their limited and outdated skills. The 10% that are good at it do not need to worry though. Who worries there is their employers when these people approach retirement age.
gweihir ( 88907 ) writes:
Re: ( Score: 2 )
My experience as an IT Security Consultant (I also do some coding, but only at full rates) confirms that. Most are basically helpless and many have negative productivity, because people with a clue need to clean up after them. "Learn to code"? We have far too many coders already.
tomhath ( 637240 ) writes:
Re: ( Score: 2 )
You can't bluff you way through writing software, but many, many people have bluffed their way into a job and then tried to learn it from the people who are already there. In a marginally functional organization those incompetents are let go pretty quickly, but sometimes they stick around for months or years.
Apparently the author of this book is one of those, probably hired and fired several times before deciding to go back to his liberal arts roots and write a book.
DaMattster ( 977781 ) writes:
Re: ( Score: 2 )
There are some mechanics that bluff their way through an automotive repair. It's the same damn thing
gweihir ( 88907 ) writes:
Re: ( Score: 2 )
I think you can and this is by far not the first piece describing that. Here is a classic: https://blog.codinghorror.com/... [codinghorror.com]
Yet these people somehow manage to actually have "experience" because they worked in a role they are completely unqualified to fill.
phantomfive ( 622387 ) writes:
Re: ( Score: 2 )
Fiddling with JavaScript libraries to get a fancy dancy interface that makes PHB's happy is a sought-after skill, for good or bad. Now that we rely more on half-ass libraries, much of "programming" is fiddling with dark-grey boxes until they work good enough.
This drives me crazy, but I'm consoled somewhat by the fact that it will all be thrown out in five years anyway.
[Nov 30, 2017] Will Robots Kill the Asian Century
"... The National Interest ..."
The National Interest
The rise of technologies such as 3-D printing and advanced robotics means that the next few decades for Asia's economies will not be as easy or promising as the previous five.
OWEN HARRIES, the first editor, together with Robert Tucker, of The National Interest, once reminded me that experts-economists, strategists, business leaders and academics alike-tend to be relentless followers of intellectual fashion, and the learned, as Harold Rosenberg famously put it, a "herd of independent minds." Nowhere is this observation more apparent than in the prediction that we are already into the second decade of what will inevitably be an "Asian Century"-a widely held but rarely examined view that Asia's continued economic rise will decisively shift global power from the Atlantic to the western Pacific Ocean.
No doubt the numbers appear quite compelling. In 1960, East Asia accounted for a mere 14 percent of global GDP; today that figure is about 27 percent. If linear trends continue, the region could account for about 36 percent of global GDP by 2030 and over half of all output by the middle of the century. As if symbolic of a handover of economic preeminence, China, which only accounted for about 5 percent of global GDP in 1960, will likely surpass the United States as the largest economy in the world over the next decade. If past record is an indicator of future performance, then the "Asian Century" prediction is close to a sure thing.
[Nov 29, 2017] Take This GUI and Shove It
"... I have a cheap router with only a web gui. I wrote a two line bash script that simply POSTs the right requests to URL. Simply put, HTTP interfaces, especially if they implement the right response codes, are actually very nice to script. ..."
Slashdot
Deep End's Paul Venezia speaks out against the overemphasis on GUIs in today's admin tools, saying that GUIs are fine and necessary in many cases, but only after a complete CLI is in place, and that they cannot interfere with the use of the CLI, only complement it. Otherwise, the GUI simply makes easy things easy and hard things much harder. He writes, 'If you have to make significant, identical changes to a bunch of Linux servers, is it easier to log into them one-by-one and run through a GUI or text-menu tool, or write a quick shell script that hits each box and either makes the changes or simply pulls down a few new config files and restarts some services? And it's not just about conservation of effort - it's also about accuracy. If you write a script, you're certain that the changes made will be identical on each box. If you're doing them all by hand, you aren't.'"
alain94040 (785132)
Here is a Link to the print version of the article [infoworld.com] (that conveniently fits on 1 page instead of 3).
Providing a great GUI for complex routers or Linux admin is hard. Of course there has to be a CLI, that's how pros get the job done. But a great GUI is one that teaches a new user to eventually graduate to using CLI.
A bad GUI with no CLI is the worst of both worlds, the author of the article got that right. The 80/20 rule applies: 80% of the work is common to everyone, and should be offered with a GUI. And the 20% that is custom to each sysadmin, well use the CLI.
maxwell demon:
What would be nice is if the GUI could automatically create a shell script doing the change. That way you could (a) learn about how to do it per CLI by looking at the generated shell script, and (b) apply the generated shell script (after proper inspection, of course) to other computers.
0123456 (636235) writes:
What would be nice is if the GUI could automatically create a shell script doing the change.
While it's not quite the same thing, our GUI-based home router has an option to download the config as a text file so you can automatically reconfigure it from that file if it has to be reset to defaults. You could presumably use sed to change IP addresses, etc, and copy it to a different router. Of course it runs Linux.
Alain Williams:
AIX's SMIT did this, or rather it wrote the commands that it executed to achieve what you asked it to do. This meant that you could learn: look at what it did and find out about which CLI commands to run. You could also take them, build them into a script, copy elsewhere, ... I liked SMIT.
Ephemeriis:
What would be nice is if the GUI could automatically create a shell script doing the change. That way you could (a) learn about how to do it per CLI by looking at the generated shell script, and (b) apply the generated shell script (after proper inspection, of course) to other computers.
Cisco's GUI stuff doesn't really generate any scripts, but the commands it creates are the same things you'd type into a CLI. And the resulting configuration is just as human-readable (barring any weird naming conventions) as one built using the CLI. I've actually learned an awful lot about the Cisco CLI by using their GUI.
We've just started working with Aruba hardware. Installed a mobility controller last week. They've got a GUI that does something similar. It's all a pretty web-based front-end, but it again generates CLI commands and a human-readable configuration. I'm still very new to the platform, but I'm already learning about their CLI through the GUI. And getting work done that I wouldn't be able to if I had to look up the CLI commands for everything.
Microsoft's more recent tools are also doing this. Exchange 2007 and newer, for example, are really completely driven by the PowerShell CLI. The GUI generates commands and just feeds them into PowerShell for you. So you can again issue your commands through the GUI, and learn how you could have done it in PowerShell instead.
Anpheus:
Just about every Microsoft tool newer than 2007 does this. Virtual machine manager, SQL Server has done it for ages, I think almost all the system center tools do, etc.
It's a huge improvement.
PoV:
All good admins document their work (don't they? DON'T THEY?). With a CLI or a script that's easy: it comes down to "log in as user X, change to directory Y, run script Z with arguments A B and C - the output should look like D". Try that when all you have is a GLUI (like a GUI, but you get stuck): open this window, select that option, drag a slider, check these boxes, click Yes, three times. The output might look a little like this blurry screen shot and the only record of a successful execution is a window that disappears as soon as the application ends.
I suppose the Linux community should be grateful that windows made the fundemental systems design error of making everything graphic. Without that basic failure, Linux might never have even got the toe-hold it has now.
skids:
I think this is a stronger point than the OP: GUIs do not lead to good documentation. In fact, GUIs pretty much are limited to procedural documentation like the example you gave.
The best they can do as far as actual documentation, where the precise effect of all the widgets is explained, is a screenshot with little quote bubbles pointing to each doodad. That's a ridiculous way to document.
This is as opposed to a command reference which can organize, usually in a pretty sensible fashion, exact descriptions of what each command does.
Moreover, the GUI authors seem to have a penchant to find new names for existing CLI concepts. Even worse, those names are usually inappropriate vagueries quickly cobbled together in an off-the-cuff afterthought, and do not actually tell you where the doodad resides in the menu system. With a CLI, the name of the command or feature set is its location.
Not that even good command references are mandatory by today's pathetic standards. Even the big boys like Cisco have shown major degradation in the quality of their documentation during the last decade.
pedantic bore:
I think the author might not fully understand who most admins are. They're people who couldn't write a shell script if their lives depended on it, because they've never had to. GUI-dependent users become GUI-dependent admins.
As a percentage of computer users, people who can actually navigate a CLI are an ever-diminishing group.
arth1: /etc/resolv.conf
/etc/init.d/NetworkManager stop
chkconfig NetworkManager off
chkconfig network on
vi /etc/sysconfig/network
vi /etc/sysconfig/network-scripts/eth0
At least they named it NetworkManager, so experienced admins could recognize it as a culprit. Anything named in CamelCase is almost invariably written by new school programmers who don't grok the Unix toolbox concept and write applications instead of tools, and the bloated drivel is usually best avoided.
Darkness404 (1287218) writes: on Monday October 04, @07:21PM (#33789446)
There are more and more small businesses (5, 10 or so employees) realizing that they can get things done easier if they had a server. Because the business can't really afford to hire a sysadmin or a full-time tech person, its generally the employee who "knows computers" (you know, the person who has to help the boss check his e-mail every day, etc.) and since they don't have the knowledge of a skilled *Nix admin, a GUI makes their administration a lot easier.
So with the increasing use of servers among non-admins, it only makes sense for a growth in GUI-based solutions.
Svartalf (2997) writes: Ah... But the thing is... You don't NEED the GUI with recent Linux systems- you do with Windows.
oatworm (969674) writes: on Monday October 04, @07:38PM (#33789624) Homepage
Bingo. Realistically, if you're a company with less than a 100 employees (read: most companies), you're only going to have a handful of servers in house and they're each going to be dedicated to particular roles. You're not going to have 100 clustered fileservers - instead, you're going to have one or maybe two. You're not going to have a dozen e-mail servers - instead, you're going to have one or two. Consequently, the office admin's focus isn't going to be scalability; it just won't matter to the admin if they can script, say, creating a mailbox for 100 new users instead of just one. Instead, said office admin is going to be more focused on finding ways to do semi-unusual things (e.g. "create a VPN between this office and our new branch office", "promote this new server as a domain controller", "install SQL", etc.) that they might do, oh, once a year.
The trouble with Linux, and I'm speaking as someone who's used YaST in precisely this context, is that you have to make a choice - do you let the GUI manage it or do you CLI it? If you try to do both, there will be inconsistencies because the grammar of the config files is too ambiguous; consequently, the GUI config file parser will probably just overwrite whatever manual changes it thinks is "invalid", whether it really is or not. If you let the GUI manage it, you better hope the GUI has the flexibility necessary to meet your needs. If, for example, YaST doesn't understand named Apache virtual hosts, well, good luck figuring out where it's hiding all of the various config files that it was sensibly spreading out in multiple locations for you, and don't you dare use YaST to manage Apache again or it'll delete your Apache-legal but YaST-"invalid" directive.
The only solution I really see is for manual config file support with optional XML (or some other machine-friendly but still human-readable format) linkages. For example, if you want to hand-edit your resolv.conf, that's fine, but if the GUI is going to take over, it'll toss a directive on line 1 that says "#import resolv.conf.xml" and immediately overrides (but does not overwrite) everything following that. Then, if you still want to use the GUI but need to hand-edit something, you can edit the XML file using the appropriate syntax and know that your change will be reflected on the GUI.
That's my take. Your mileage, of course, may vary.
icebraining (1313345) writes: on Monday October 04, @07:24PM (#33789494) Homepage
I have a cheap router with only a web gui. I wrote a two line bash script that simply POSTs the right requests to URL. Simply put, HTTP interfaces, especially if they implement the right response codes, are actually very nice to script.
devent (1627873) writes:
Why Windows servers have a GUI is beyond me anyway. The servers are running 99,99% of the time without a monitor and normally you just login per ssh to a console if you need to administer them. But they are consuming the extra RAM, the extra CPU cycles and the extra security threats. I don't now, but can you de-install the GUI from a Windows server? Or better, do you have an option for no-GUI installation? Just saw the minimum hardware requirements. 512 MB RAM and 32 GB or greater disk space. My server runs
sirsnork (530512) writes: on Monday October 04, @07:43PM (#33789672)
it's called a "core" install in Server 2008 and up, and if you do that, there is no going back, you can't ever add the GUI back.
What this means is you can run a small subset of MS services that don't need GUI interaction. With R2 that subset grew somwhat as they added the ability to install .Net too, which mean't you could run IIS in a useful manner (arguably the strongest reason to want to do this in the first place).
Still it's a one way trip and you better be damn sure what services need to run on that box for the lifetime of that box or you're looking at a reinstall. Most windows admins will still tell you the risk isn't worth it.
Simple things like network configuration without a GUI in windows is tedious, and, at least last time i looked, you lost the ability to trunk network poers because the NIC manufactuers all assumed you had a GUI to configure your NICs
prichardson (603676) writes: on Monday October 04, @07:27PM (#33789520) Journal
This is also a problem with Max OS X Server. Apple builds their services from open source products and adds a GUI for configuration to make it all clickable and easy to set up. However, many options that can be set on the command line can't be set in the GUI. Even worse, making CLI changes to services can break the GUI entirely.
The hardware and software are both super stable and run really smoothly, so once everything gets set up, it's awesome. Still, it's hard for a guy who would rather make changes on the CLI to get used to.
MrEricSir (398214) writes:
Just because you're used to a CLI doesn't make it better. Why would I want to read a bunch of documentation, mess with command line options, then read whole block of text to see what it did? I'd much rather sit back in my chair, click something, and then see if it worked. Don't make me read a bunch of man pages just to do a simple task. In essence, the question here is whether it's okay for the user to be lazy and use a GUI, or whether the programmer should be too lazy to develop a GUI.
ak_hepcat (468765) writes: <leif@MENCKENdenali.net minus author> on Monday October 04, @07:38PM (#33789626) Homepage Journal
Probably because it's also about the ease of troubleshooting issues.
How do you troubleshoot something with a GUI after you've misconfigured? How do you troubleshoot a programming error (bug) in the GUI -> device communication? How do you scale to tens, hundreds, or thousands of devices with a GUI?
CLI makes all this easier and more manageable.
arth1 (260657) writes:
Why would I want to read a bunch of documentation, mess with command line options, then read whole block of text to see what it did? I'd much rather sit back in my chair, click something, and then see if it worked. Don't make me read a bunch of man pages just to do a simple task. Because then you'll be stuck at doing simple tasks, and will never be able to do more advanced tasks. Without hiring a team to write an app for you instead of doing it yourself in two minutes, that is. The time you spend reading man
fandingo (1541045) writes: on Monday October 04, @07:54PM (#33789778)
I don't think you really understand systems administration. 'Users,' or in this case admins, don't typically do stuff once. Furthermore, they need to know what he did and how to do it again (i.e. new server or whatever) or just remember what he did. One-off stuff isn't common and is a sign of poor administration (i.e. tracking changes and following processes).
What I'm trying to get at is that admins shouldn't do anything without reading the manual. As a Windows/Linux admin, I tend to find Linux easier to properly administer because I either already know how to perform an operation or I have to read the manual (manpage) and learn a decent amount about the operation (i.e. more than click here/use this flag).
Don't get me wrong, GUIs can make unknown operations significantly easier, but they often lead to poor process management. To document processes, screenshots are typically needed. They can be done well, but I find that GUI documentation (created by admins, not vendor docs) tend to be of very low quality. They are also vulnerable to 'upgrades' where vendors change the interface design. CLI programs typically have more stable interfaces, but maybe that's just because they have been around longer...
maotx (765127) writes: <maotx@NoSPAM.yahoo.com> on Monday October 04, @07:42PM (#33789666)
That's one thing Microsoft did right with Exchange 2007. They built it entirely around their new powershell CLI and then built a GUI for it. The GUI is limited in compared to what you can do with the CLI, but you can get most things done. The CLI becomes extremely handy for batch jobs and exporting statistics to csv files. I'd say it's really up there with BASH in terms of scripting, data manipulation, and integration (not just Exchange but WMI, SQL, etc.)
They tried to do similar with Windows 2008 and their Core [petri.co.il] feature, but they still have to load a GUI to present a prompt...Reply to This
Charles Dodgeson (248492) writes: <jeffrey@goldmark.org> on Monday October 04, @08:51PM (#33790206) Homepage Journal
Probably Debian would have been OK, but I was finding admin of most Linux distros a pain for exactly these reasons. I couldn't find a layer where I could do everything that I needed to do without worrying about one thing stepping on another. No doubt there are ways that I could manage a Linux system without running into different layers of management tools stepping on each other, but it was a struggle.
There were other reasons as well (although there is a lot that I miss about Linux), but I think that this was one of the leading reasons.
(NB: I realize that this is flamebait (I've got karma to burn), but that isn't my intention here.)
[Nov 28, 2017] Sometimes the Old Ways Are Best by Brian Kernighan
"... Sometimes the old ways are best, and they're certainly worth knowing well ..."
Nov 01, 2008 | IEEE Software, pp.18-19
As I write this column, I'm in the middle of two summer projects; with luck, they'll both be finished by the time you read it.
• One involves a forensic analysis of over 100,000 lines of old C and assembly code from about 1990, and I have to work on Windows XP.
• The other is a hack to translate code written in weird language L1 into weird language L2 with a program written in scripting language L3, where none of the L's even existed in 1990; this one uses Linux. Thus it's perhaps a bit surprising that I find myself relying on much the same toolset for these very different tasks.
... ... ...
Here has surely been much progress in tools over the 25 years that IEEE Software has been around, and I wouldn't want to go back in time.
But the tools I use today are mostly the same old ones-grep, diff, sort, awk, and friends. This might well mean that I'm a dinosaur stuck in the past.
On the other hand, when it comes to doing simple things quickly, I can often have the job done while experts are still waiting for their IDE to start up. Sometimes the old ways are best, and they're certainly worth knowing well
[Nov 28, 2017] Rees Re OO
"... In such a pack-programming world, the language is a constitution or set of by-laws, and the interpreter/compiler/QA dept. acts in part as a rule checker/enforcer/police force. Co-programmers want to know: If I work with your code, will this help me or hurt me? Correctness is undecidable (and generally unenforceable), so managers go with whatever rule set (static type system, language restrictions, "lint" program, etc.) shows up at the door when the project starts. ..."
Nov 04, 2017 | www.paulgraham.com
(Jonathan Rees had a really interesting response to Why Arc isn't Especially Object-Oriented , which he has allowed me to reproduce here.)
Here is an a la carte menu of features or properties that are related to these terms; I have heard OO defined to be many different subsets of this list.
1. Encapsulation - the ability to syntactically hide the implementation of a type. E.g. in C or Pascal you always know whether something is a struct or an array, but in CLU and Java you can hide the difference.
2. Protection - the inability of the client of a type to detect its implementation. This guarantees that a behavior-preserving change to an implementation will not break its clients, and also makes sure that things like passwords don't leak out.
3. Ad hoc polymorphism - functions and data structures with parameters that can take on values of many different types.
4. Parametric polymorphism - functions and data structures that parameterize over arbitrary values (e.g. list of anything). ML and Lisp both have this. Java doesn't quite because of its non-Object types.
5. Everything is an object - all values are objects. True in Smalltalk (?) but not in Java (because of int and friends).
6. All you can do is send a message (AYCDISAM) = Actors model - there is no direct manipulation of objects, only communication with (or invocation of) them. The presence of fields in Java violates this.
7. Specification inheritance = subtyping - there are distinct types known to the language with the property that a value of one type is as good as a value of another for the purposes of type correctness. (E.g. Java interface inheritance.)
8. Implementation inheritance/reuse - having written one pile of code, a similar pile (e.g. a superset) can be generated in a controlled manner, i.e. the code doesn't have to be copied and edited. A limited and peculiar kind of abstraction. (E.g. Java class inheritance.)
9. Sum-of-product-of-function pattern - objects are (in effect) restricted to be functions that take as first argument a distinguished method key argument that is drawn from a finite set of simple names.
So OO is not a well defined concept. Some people (eg. Abelson and Sussman?) say Lisp is OO, by which they mean {3,4,5,7} (with the proviso that all types are in the programmers' heads). Java is supposed to be OO because of {1,2,3,7,8,9}. E is supposed to be more OO than Java because it has {1,2,3,4,5,7,9} and almost has 6; 8 (subclassing) is seen as antagonistic to E's goals and not necessary for OO.
The conventional Simula 67-like pattern of class and instance will get you {1,3,7,9}, and I think many people take this as a definition of OO.
Because OO is a moving target, OO zealots will choose some subset of this menu by whim and then use it to try to convince you that you are a loser.
Perhaps part of the confusion - and you say this in a different way in your little memo - is that the C/C++ folks see OO as a liberation from a world that has nothing resembling a first-class functions, while Lisp folks see OO as a prison since it limits their use of functions/objects to the style of (9.). In that case, the only way OO can be defended is in the same manner as any other game or discipline -- by arguing that by giving something up (e.g. the freedom to throw eggs at your neighbor's house) you gain something that you want (assurance that your neighbor won't put you in jail).
This is related to Lisp being oriented to the solitary hacker and discipline-imposing languages being oriented to social packs, another point you mention. In a pack you want to restrict everyone else's freedom as much as possible to reduce their ability to interfere with and take advantage of you, and the only way to do that is by either becoming chief (dangerous and unlikely) or by submitting to the same rules that they do. If you submit to rules, you then want the rules to be liberal so that you have a chance of doing most of what you want to do, but not so liberal that others nail you.
In such a pack-programming world, the language is a constitution or set of by-laws, and the interpreter/compiler/QA dept. acts in part as a rule checker/enforcer/police force. Co-programmers want to know: If I work with your code, will this help me or hurt me? Correctness is undecidable (and generally unenforceable), so managers go with whatever rule set (static type system, language restrictions, "lint" program, etc.) shows up at the door when the project starts.
I recently contributed to a discussion of anti-OO on the e-lang list. My main anti-OO message (actually it only attacks points 5/6) was http://www.eros-os.org/pipermail/e-lang/2001-October/005852.html . The followups are interesting but I don't think they're all threaded properly.
(Here are the pet definitions of terms used above:
• Value = something that can be passed to some function (abstraction). (I exclude exotic compile-time things like parameters to macros and to parameterized types and modules.)
• Object = a value that has function-like behavior, i.e. you can invoke a method on it or call it or send it a message or something like that. Some people define object more strictly along the lines of 9. above, while others (e.g. CLTL) are more liberal. This is what makes "everything is an object" a vacuous statement in the absence of clear definitions.
In some languages the "call" is curried and the key-to-method mapping can sometimes be done at compile time. This technicality can cloud discussions of OO in C++ and related languages.
• Function = something that can be combined with particular parameter(s) to produce some result. Might or might not be the same as object depending on the language.
• Type = a description of the space of values over which a function is meaningfully parameterized. I include both types known to the language and types that exist in the programmer's mind or in documentation
[Nov 28, 2017] Sometimes the Old Ways Are Best by Brian Kernighan
Nov 01, 2008 | IEEE Software, pp.18-19
As I write this column, I'm in the middle of two summer projects; with luck, they'll both be finished by the time you read it.
• One involves a forensic analysis of over 100,000 lines of old C and assembly code from about 1990, and I have to work on Windows XP.
• The other is a hack to translate code written in weird language L1 into weird language L2 with a program written in scripting language L3, where none of the L's even existed in 1990; this one uses Linux. Thus it's perhaps a bit surprising that I find myself relying on much the same toolset for these very different tasks.
... ... ...
Here has surely been much progress in tools over the 25 years that IEEE Software has been around, and I wouldn't want to go back in time.
But the tools I use today are mostly the same old ones-grep, diff, sort, awk, and friends. This might well mean that I'm a dinosaur stuck in the past.
On the other hand, when it comes to doing simple things quickly, I can often have the job done while experts are still waiting for their IDE to start up. Sometimes the old ways are best, and they're certainly worth knowing well
[Nov 27, 2017] Stop Writing Classes
"... If there's something I've noticed in my career that is that there are always some guys that desperately want to look "smart" and they reflect that in their code. ..."
My god I wish the engineers at my work understood this
kobac , 2 years ago
If there's something I've noticed in my career that is that there are always some guys that desperately want to look "smart" and they reflect that in their code.
If there's something else that I've noticed in my career, it's that their code is the hardest to maintain and for some reason they want the rest of the team to depend on them since they are the only "enough smart" to understand that code and change it. No need to say that these guys are not part of my team. Your code should be direct, simple and readable. End of story.
[Nov 27, 2017] Stop Writing Classes
"... If there's something I've noticed in my career that is that there are always some guys that desperately want to look "smart" and they reflect that in their code. ..."
My god I wish the engineers at my work understood this
kobac , 2 years ago
If there's something I've noticed in my career that is that there are always some guys that desperately want to look "smart" and they reflect that in their code.
If there's something else that I've noticed in my career, it's that their code is the hardest to maintain and for some reason they want the rest of the team to depend on them since they are the only "enough smart" to understand that code and change it. No need to say that these guys are not part of my team. Your code should be direct, simple and readable. End of story.
[Nov 27, 2017] The Robot Productivity Paradox and the concept of bezel
"... In depression all this is reversed. Money is watched with a narrow, suspicious eye. The man who handles it is assumed to be dishonest until he proves himself otherwise. Audits are penetrating and meticulous. Commercial morality is enormously improved. The bezzle shrinks ..."
Feb 22, 2017 | econospeak.blogspot.com
John Kenneth Galbraith, from "The Great Crash 1929":
"In many ways the effect of the crash on embezzlement was more significant than on suicide. To the economist embezzlement is the most interesting of crimes. Alone among the various forms of larceny it has a time parameter. Weeks, months or years may elapse between the commission of the crime and its discovery. (This is a period, incidentally, when the embezzler has his gain and the man who has been embezzled, oddly enough, feels no loss. There is a net increase in psychic wealth.)
At any given time there exists an inventory of undiscovered embezzlement in – or more precisely not in – the country's business and banks.
This inventory – it should perhaps be called the bezzle – amounts at any moment to many millions [trillions!] of dollars. It also varies in size with the business cycle.
In good times people are relaxed, trusting, and money is plentiful. But even though money is plentiful, there are always many people who need more. Under these circumstances the rate of embezzlement grows, the rate of discovery falls off, and the bezzle increases rapidly.
In depression all this is reversed. Money is watched with a narrow, suspicious eye. The man who handles it is assumed to be dishonest until he proves himself otherwise. Audits are penetrating and meticulous. Commercial morality is enormously improved. The bezzle shrinks."
Sanwichman, February 24, 2017 at 05:24 AM
For nearly a half a century, from 1947 to 1996, real GDP and real Net Worth of Households and Non-profit Organizations (in 2009 dollars) both increased at a compound annual rate of a bit over 3.5%. GDP growth, in fact, was just a smidgen faster -- 0.016% -- than growth of Net Household Worth.
From 1996 to 2015, GDP grew at a compound annual rate of 2.3% while Net Worth increased at the rate of 3.6%....
-- Sanwichman
anne -> anne... February 24, 2017 at 05:25 AM
https://fred.stlouisfed.org/graph/?g=cOU6
January 15, 2017
Gross Domestic Product and Net Worth for Households & Nonprofit Organizations, 1952-2016
(Indexed to 1952)
https://fred.stlouisfed.org/graph/?g=cPq1
January 15, 2017
Gross Domestic Product and Net Worth for Households & Nonprofit Organizations, 1992-2016
(Indexed to 1992)
anne -> Sandwichman ... February 24, 2017 at 03:35 PM
The real home price index extends from 1890. From 1890 to 1996, the index increased slightly faster than inflation so that the index was 100 in 1890 and 113 in 1996. However from 1996 the index advanced to levels far beyond any previously experienced, reaching a high above 194 in 2006. Previously the index high had been just above 130.
Though the index fell from 2006, the level in 2016 is above 161, a level only reached when the housing bubble had formed in late 2003-early 2004.
Real home prices are again strikingly high:
http://www.econ.yale.edu/~shiller/data.htm Reply Friday, February 24, 2017 at 03:34 PM anne -> Sandwichman ... February 24, 2017
Valuation
The Shiller 10-year price-earnings ratio is currently 29.34, so the inverse or the earnings rate is 3.41%. The dividend yield is 1.93. So an expected yearly return over the coming 10 years would be 3.41 + 1.93 or 5.34% provided the price-earnings ratio stays the same and before investment costs.
Against the 5.34% yearly expected return on stock over the coming 10 years, the current 10-year Treasury bond yield is 2.32%.
The risk premium for stocks is 5.34 - 2.32 or 3.02%:
http://www.econ.yale.edu/~shiller/data.htm
anne -> anne..., February 24, 2017 at 05:36 AM
What the robot-productivity paradox is puzzles me, other than since 2005 for all the focus on the productivity of robots and on robots replacing labor there has been a dramatic, broad-spread slowing in productivity growth.
However what the changing relationship between the growth of GDP and net worth since 1996 show, is that asset valuations have been increasing relative to GDP. Valuations of stocks and homes are at sustained levels that are higher than at any time in the last 120 years. Bear markets in stocks and home prices have still left asset valuations at historically high levels. I have no idea why this should be.
Sandwichman -> anne... February 24, 2017 at 08:34 AM
The paradox is that productivity statistics can't tell us anything about the effects of robots on employment because both the numerator and the denominator are distorted by the effects of colossal Ponzi bubbles.
John Kenneth Galbraith used to call it "the bezzle." It is "that increment to wealth that occurs during the magic interval when a confidence trickster knows he has the money he has appropriated but the victim does not yet understand that he has lost it." The current size of the gross national bezzle (GNB) is approximately $24 trillion. Ponzilocks and the Twenty-Four Trillion Dollar Question http://econospeak.blogspot.ca/2017/02/ponzilocks-and-twenty-four-trillion.html Twenty-three and a half trillion, actually. But what's a few hundred billion? Here today, gone tomorrow, as they say. At the beginning of 2007, net worth of households and non-profit organizations exceeded its 1947-1996 historical average, relative to GDP, by some$16 trillion. It took 24 months to wipe out eighty percent, or $13 trillion, of that colossal but ephemeral slush fund. In mid-2016, net worth stood at a multiple of 4.83 times GDP, compared with the multiple of 4.72 on the eve of the Great Unworthing. When I look at the ragged end of the chart I posted yesterday, it screams "Ponzi!" "Ponzi!" "Ponz..." To make a long story short, let's think of wealth as capital. The value of capital is determined by the present value of an expected future income stream. The value of capital fluctuates with changing expectations but when the nominal value of capital diverges persistently and significantly from net revenues, something's got to give. Either economic growth is going to suddenly gush forth "like nobody has ever seen before" or net worth is going to have to come back down to earth. Somewhere between 20 and 30 TRILLION dollars of net worth will evaporate within the span of perhaps two years. When will that happen? Who knows? There is one notable regularity in the data, though -- the one that screams "Ponzi!" When the net worth bubble stops going up... ...it goes down. [Nov 27, 2017] The productivity paradox by Ryan Avent Notable quotes: "... But the economy does not feel like one undergoing a technology-driven productivity boom. In the late 1990s, tech optimism was everywhere. At the same time, wages and productivity were rocketing upward. The situation now is completely different. The most recent jobs reports in America and Britain tell the tale. Employment is growing, month after month after month. But wage growth is abysmal. So is productivity growth: not surprising in economies where there are lots of people on the job working for low pay. ..." "... Increasing labour costs by making the minimum wage a living wage would increase the incentives to boost productivity growth? No, the neoliberals and corporate Democrats would never go for it. They're trying to appeal to the business community and their campaign contributors wouldn't like it. ..." Mar 20, 2017 | medium.com People are worried about robots taking jobs. Driverless cars are around the corner. Restaurants and shops increasingly carry the option to order by touchscreen. Google's clever algorithms provide instant translations that are remarkably good. But the economy does not feel like one undergoing a technology-driven productivity boom. In the late 1990s, tech optimism was everywhere. At the same time, wages and productivity were rocketing upward. The situation now is completely different. The most recent jobs reports in America and Britain tell the tale. Employment is growing, month after month after month. But wage growth is abysmal. So is productivity growth: not surprising in economies where there are lots of people on the job working for low pay. The obvious conclusion, the one lots of people are drawing, is that the robot threat is totally overblown: the fantasy, perhaps, of a bubble-mad Silicon Valley - or an effort to distract from workers' real problems, trade and excessive corporate power. Generally speaking, the problem is not that we've got too much amazing new technology but too little. This is not a strawman of my own invention. Robert Gordon makes this case. You can see Matt Yglesias make it here. Duncan Weldon, for his part, writes: We are debating a problem we don't have, rather than facing a real crisis that is the polar opposite. Productivity growth has slowed to a crawl over the last 15 or so years, business investment has fallen and wage growth has been weak. If the robot revolution truly was under way, we would see surging capital expenditure and soaring productivity. Right now, that would be a nice "problem" to have. Instead we have the reality of weak growth and stagnant pay. The real and pressing concern when it comes to the jobs market and automation is that the robots aren't taking our jobs fast enough. And in a recent blog post Paul Krugman concluded: I'd note, however, that it remains peculiar how we're simultaneously worrying that robots will take all our jobs and bemoaning the stalling out of productivity growth. What is the story, really? What is the story, indeed. Let me see if I can tell one. Last fall I published a book: "The Wealth of Humans". In it I set out how rapid technological progress can coincide with lousy growth in pay and productivity. Start with this: Low labour costs discourage investments in labour-saving technology, potentially reducing productivity growth. Peter K. -> Peter K.... Monday, March 20, 2017 at 09:26 AM Increasing labour costs by making the minimum wage a living wage would increase the incentives to boost productivity growth? No, the neoliberals and corporate Democrats would never go for it. They're trying to appeal to the business community and their campaign contributors wouldn't like it. anne -> Peter K.... March 20, 2017 at 10:32 AM https://twitter.com/paulkrugman/status/843167658577182725 Paul Krugman @paulkrugman But is [Ryan Avent] saying something different from the assertion that recent tech progress is capital-biased? If so, what? anne -> Peter K.... March 20, 2017 at 10:33 AM December 26, 2012 Capital-biased Technological Progress: An Example (Wonkish) By Paul Krugman Ever since I posted about robots and the distribution of income, * I've had queries from readers about what capital-biased technological change – the kind of change that could make society richer but workers poorer – really means. And it occurred to me that it might be useful to offer a simple conceptual example – the kind of thing easily turned into a numerical example as well – to clarify the possibility. So here goes. Imagine that there are only two ways to produce output. One is a labor-intensive method – say, armies of scribes equipped only with quill pens. The other is a capital-intensive method – say, a handful of technicians maintaining vast server farms. (I'm thinking in terms of office work, which is the dominant occupation in the modern economy). We can represent these two techniques in terms of unit inputs – the amount of each factor of production required to produce one unit of output. In the figure below I've assumed that initially the capital-intensive technique requires 0.2 units of labor and 0.8 units of capital per unit of output, while the labor-intensive technique requires 0.8 units of labor and 0.2 units of capital. [Diagram] The economy as a whole can make use of both techniques – in fact, it will have to unless it has either a very large amount of capital per worker or a very small amount. No problem: we can just use a mix of the two techniques to achieve any input combination along the blue line in the figure. For economists reading this, yes, that's the unit isoquant in this example; obviously if we had a bunch more techniques it would start to look like the convex curve of textbooks, but I want to stay simple here. What will the distribution of income be in this case? Assuming perfect competition (yes, I know, but let's deal with that case for now), the real wage rate w and the cost of capital r – both measured in terms of output – have to be such that the cost of producing one unit is 1 whichever technique you use. In this example, that means w=r=1. Graphically, by the way, w/r is equal to minus the slope of the blue line. Oh, and if you're worried, yes, workers and machines are both paid their marginal product. But now suppose that technology improves – specifically, that production using the capital-intensive technique gets more efficient, although the labor-intensive technique doesn't. Scribes with quill pens are the same as they ever were; server farms can do more than ever before. In the figure, I've assumed that the unit inputs for the capital-intensive technique are cut in half. The red line shows the economy's new choices. So what happens? It's obvious from the figure that wages fall relative to the cost of capital; it's less obvious, maybe, but nonetheless true that real wages must fall in absolute terms as well. In this specific example, technological progress reduces the real wage by a third, to 0.667, while the cost of capital rises to 2.33. OK, it's obvious how stylized and oversimplified all this is. But it does, I think, give you some sense of what it would mean to have capital-biased technological progress, and how this could actually hurt workers. anne -> Peter K.... March 20, 2017 at 10:34 AM http://krugman.blogs.nytimes.com/2012/12/08/rise-of-the-robots/ December 8, 2012 Rise of the Robots By Paul Krugman Catherine Rampell and Nick Wingfield write about the growing evidence * for "reshoring" of manufacturing to the United States. * They cite several reasons: rising wages in Asia; lower energy costs here; higher transportation costs. In a followup piece, ** however, Rampell cites another factor: robots. "The most valuable part of each computer, a motherboard loaded with microprocessors and memory, is already largely made with robots, according to my colleague Quentin Hardy. People do things like fitting in batteries and snapping on screens. "As more robots are built, largely by other robots, 'assembly can be done here as well as anywhere else,' said Rob Enderle, an analyst based in San Jose, California, who has been following the computer electronics industry for a quarter-century. 'That will replace most of the workers, though you will need a few people to manage the robots.' " Robots mean that labor costs don't matter much, so you might as well locate in advanced countries with large markets and good infrastructure (which may soon not include us, but that's another issue). On the other hand, it's not good news for workers! This is an old concern in economics; it's "capital-biased technological change," which tends to shift the distribution of income away from workers to the owners of capital. Twenty years ago, when I was writing about globalization and inequality, capital bias didn't look like a big issue; the major changes in income distribution had been among workers (when you include hedge fund managers and CEOs among the workers), rather than between labor and capital. So the academic literature focused almost exclusively on "skill bias", supposedly explaining the rising college premium. But the college premium hasn't risen for a while. What has happened, on the other hand, is a notable shift in income away from labor: [Graph] If this is the wave of the future, it makes nonsense of just about all the conventional wisdom on reducing inequality. Better education won't do much to reduce inequality if the big rewards simply go to those with the most assets. Creating an "opportunity society," or whatever it is the likes of Paul Ryan etc. are selling this week, won't do much if the most important asset you can have in life is, well, lots of assets inherited from your parents. And so on. I think our eyes have been averted from the capital/labor dimension of inequality, for several reasons. It didn't seem crucial back in the 1990s, and not enough people (me included!) have looked up to notice that things have changed. It has echoes of old-fashioned Marxism - which shouldn't be a reason to ignore facts, but too often is. And it has really uncomfortable implications. But I think we'd better start paying attention to those implications. anne -> anne... March 20, 2017 at 10:41 AM https://fred.stlouisfed.org/graph/?g=d4ZY January 30, 2017 Compensation of Employees as a share of Gross Domestic Income, 1948-2015 January 30, 2017 Compensation of Employees as a share of Gross Domestic Income, 1948-2015 (Indexed to 1948) [Nov 27, 2017] Nineteen Ninety-Six: The Robot/Productivity Paradox and the concept of bezel This concept of "bezel" is an important one Feb 22, 2017 | econospeak.blogspot.com John Kenneth Galbraith, from "The Great Crash 1929": "In many ways the effect of the crash on embezzlement was more significant than on suicide. To the economist embezzlement is the most interesting of crimes. Alone among the various forms of larceny it has a time parameter. Weeks, months or years may elapse between the commission of the crime and its discovery. (This is a period, incidentally, when the embezzler has his gain and the man who has been embezzled, oddly enough, feels no loss. There is a net increase in psychic wealth.) At any given time there exists an inventory of undiscovered embezzlement in – or more precisely not in – the country's business and banks. This inventory – it should perhaps be called the bezzle – amounts at any moment to many millions [trillions!] of dollars. It also varies in size with the business cycle. In good times people are relaxed, trusting, and money is plentiful. But even though money is plentiful, there are always many people who need more. Under these circumstances the rate of embezzlement grows, the rate of discovery falls off, and the bezzle increases rapidly. In depression all this is reversed. Money is watched with a narrow, suspicious eye. The man who handles it is assumed to be dishonest until he proves himself otherwise. Audits are penetrating and meticulous. Commercial morality is enormously improved. The bezzle shrinks." Sanwichman, February 24, 2017 at 05:24 AM For nearly a half a century, from 1947 to 1996, real GDP and real Net Worth of Households and Non-profit Organizations (in 2009 dollars) both increased at a compound annual rate of a bit over 3.5%. GDP growth, in fact, was just a smidgen faster -- 0.016% -- than growth of Net Household Worth. From 1996 to 2015, GDP grew at a compound annual rate of 2.3% while Net Worth increased at the rate of 3.6%.... -- Sanwichman anne -> anne... February 24, 2017 at 05:25 AM https://fred.stlouisfed.org/graph/?g=cOU6 January 15, 2017 Gross Domestic Product and Net Worth for Households & Nonprofit Organizations, 1952-2016 (Indexed to 1952) https://fred.stlouisfed.org/graph/?g=cPq1 January 15, 2017 Gross Domestic Product and Net Worth for Households & Nonprofit Organizations, 1992-2016 (Indexed to 1992) anne -> Sandwichman ... February 24, 2017 at 03:35 PM The real home price index extends from 1890. From 1890 to 1996, the index increased slightly faster than inflation so that the index was 100 in 1890 and 113 in 1996. However from 1996 the index advanced to levels far beyond any previously experienced, reaching a high above 194 in 2006. Previously the index high had been just above 130. Though the index fell from 2006, the level in 2016 is above 161, a level only reached when the housing bubble had formed in late 2003-early 2004. Real home prices are again strikingly high: http://www.econ.yale.edu/~shiller/data.htm Reply Friday, February 24, 2017 at 03:34 PM anne -> Sandwichman ... February 24, 2017 Valuation The Shiller 10-year price-earnings ratio is currently 29.34, so the inverse or the earnings rate is 3.41%. The dividend yield is 1.93. So an expected yearly return over the coming 10 years would be 3.41 + 1.93 or 5.34% provided the price-earnings ratio stays the same and before investment costs. Against the 5.34% yearly expected return on stock over the coming 10 years, the current 10-year Treasury bond yield is 2.32%. The risk premium for stocks is 5.34 - 2.32 or 3.02%: http://www.econ.yale.edu/~shiller/data.htm anne -> anne..., February 24, 2017 at 05:36 AM What the robot-productivity paradox is puzzles me, other than since 2005 for all the focus on the productivity of robots and on robots replacing labor there has been a dramatic, broad-spread slowing in productivity growth. However what the changing relationship between the growth of GDP and net worth since 1996 show, is that asset valuations have been increasing relative to GDP. Valuations of stocks and homes are at sustained levels that are higher than at any time in the last 120 years. Bear markets in stocks and home prices have still left asset valuations at historically high levels. I have no idea why this should be. Sandwichman -> anne... February 24, 2017 at 08:34 AM The paradox is that productivity statistics can't tell us anything about the effects of robots on employment because both the numerator and the denominator are distorted by the effects of colossal Ponzi bubbles. John Kenneth Galbraith used to call it "the bezzle." It is "that increment to wealth that occurs during the magic interval when a confidence trickster knows he has the money he has appropriated but the victim does not yet understand that he has lost it." The current size of the gross national bezzle (GNB) is approximately$24 trillion.
Ponzilocks and the Twenty-Four Trillion Dollar Question
http://econospeak.blogspot.ca/2017/02/ponzilocks-and-twenty-four-trillion.html
Twenty-three and a half trillion, actually. But what's a few hundred billion? Here today, gone tomorrow, as they say.
At the beginning of 2007, net worth of households and non-profit organizations exceeded its 1947-1996 historical average, relative to GDP, by some $16 trillion. It took 24 months to wipe out eighty percent, or$13 trillion, of that colossal but ephemeral slush fund. In mid-2016, net worth stood at a multiple of 4.83 times GDP, compared with the multiple of 4.72 on the eve of the Great Unworthing.
When I look at the ragged end of the chart I posted yesterday, it screams "Ponzi!" "Ponzi!" "Ponz..."
To make a long story short, let's think of wealth as capital. The value of capital is determined by the present value of an expected future income stream. The value of capital fluctuates with changing expectations but when the nominal value of capital diverges persistently and significantly from net revenues, something's got to give. Either economic growth is going to suddenly gush forth "like nobody has ever seen before" or net worth is going to have to come back down to earth.
Somewhere between 20 and 30 TRILLION dollars of net worth will evaporate within the span of perhaps two years.
When will that happen? Who knows? There is one notable regularity in the data, though -- the one that screams "Ponzi!"
When the net worth bubble stops going up...
...it goes down.
[Oct 26, 2017] Amazon.com Customer reviews Extreme Programming Explained Embrace Change
"... One of the things I despise the most about the software development culture is the mindless adoption of fads. Extreme programming has been adopted by some organizations like a religious dogma. ..."
Oct 26, 2017 | www.amazon.com
Mohammad B. Abdulfatah on February 10, 2003
Programming Malpractice Explained: Justifying Chaos
To fairly review this book, one must distinguish between the methodology it presents and the actual presentation. As to the presentation, the author attempts to win the reader over with emotional persuasion and pep talk rather than with facts and hard evidence. Stories of childhood and comradeship don't classify as convincing facts to me.
A single case study-the C3 project-is often referred to, but with no specific information (do note that the project was cancelled by the client after staying in development for far too long).
As to the method itself, it basically boils down to four core practices:
1. Always have a customer available on site.
2. Unit test before you code.
3. Program in pairs.
4. Forfeit detailed design in favor of incremental, daily releases and refactoring.
If you do the above, and you have excellent staff on your hands, then the book promises that you'll reap the benefits of faster development, less overtime, and happier customers. Of course, the book fails to point out that if your staff is all highly qualified people, then the project is likely to succeed no matter what methodology you use. I'm sure that anyone who has worked in the software industry for sometime has noticed the sad state that most computer professionals are in nowadays.
However, assuming that you have all the topnotch developers that you desire, the outlined methodology is almost impossible to apply in real world scenarios. Having a customer always available on site would mean that the customer in question is probably a small, expendable fish in his organization and is unlikely to have any useful knowledge of its business practices.
Unit testing code before it is written means that one would have to have a mental picture of what one is going to write before writing it, which is difficult without upfront design. And maintaining such tests as the code changes would be a nightmare.
Programming in pairs all the time would assume that your topnotch developers are also sociable creatures, which is rarely the case, and even if they were, no one would be able to justify the practice in terms of productivity. I won't discuss why I think that abandoning upfront design is a bad practice; the whole idea is too ridiculous to debate.
Both book and methodology will attract fledgling developers with its promise of hacking as an acceptable software practice and a development universe revolving around the programmer. It's a cult, not a methodology, were the followers shall find salvation and 40-hour working weeks.
Experience is a great teacher, but only a fool would learn from it alone. Listen to what the opponents have to say before embracing change, and don't forget to take the proverbial grain of salt.
Two stars out of five for the presentation for being courageous and attempting to defy the standard practices of the industry. Two stars for the methodology itself, because it underlines several common sense practices that are very useful once practiced without the extremity.
wiredweird HALL OF FAME TOP 1000 REVIEWER on May 24, 2004
eXtreme buzzwording
Maybe it's an interesting idea, but it's just not ready for prime time.
Parts of Kent's recommended practice - including aggressive testing and short integration cycle - make a lot of sense. I've shared the same beliefs for years, but it was good to see them clarified and codified. I really have changed some of my practice after reading this and books like this.
I have two broad kinds of problem with this dogma, though. First is the near-abolition of documentation. I can't defend 2000 page specs for typical kinds of development. On the other hand, declaring that the test suite is the spec doesn't do it for me either. The test suite is code, written for machine interpretation. Much too often, it is not written for human interpretation. Based on the way I see most code written, it would be a nightmare to reverse engineer the human meaning out of any non-trivial test code. Some systematic way of ensuring human intelligibility in the code, traceable to specific "stories" (because "requirements" are part of the bad old way), would give me a lot more confidence in the approach.
The second is the dictatorial social engineering that eXtremity mandates. I've actually tried the pair programming - what a disaster. The less said the better, except that my experience did not actually destroy any professional relationships. I've also worked with people who felt that their slightest whim was adequate reason to interfere with my work. That's what Beck institutionalizes by saying that any request made of me by anyone on the team must be granted. It puts me completely at the mercy of anyone walking by. The requisite bullpen physical environment doesn't work for me either. I find that the visual and auditory distraction make intense concentration impossible.
I find revival tent spirit of the eXtremists very off-putting. If something works, it works for reasons, not as a matter of faith. I find much too much eXhortation to believe, to go ahead and leap in, so that I will eXperience the wonderfulness for myself. Isn't that what the evangelist on the subway platform keeps saying? Beck does acknowledge unbelievers like me, but requires their exile in order to maintain the group-think of the X-cult.
Beck's last chapters note a number of exceptions and special cases where eXtremism may not work - actually, most of the projects I've ever encountered.
There certainly is good in the eXtreme practice. I look to future authors to tease that good out from the positively destructive threads that I see interwoven.
A customer on May 2, 2004
A work of fiction
The book presents extreme programming. It is divided into three parts:
(1) The problem
(2) The solution
(3) Implementing XP.
The problem, as presented by the author, is that requirements change but current methodologies are not agile enough to cope with this. This results in customer being unhappy. The solution is to embrace change and to allow the requirements to be changed. This is done by choosing the simplest solution, releasing frequently, refactoring with the security of unit tests.
The basic assumption which underscores the approach is that the cost of change is not exponential but reaches a flat asymptote. If this is not the case, allowing change late in the project would be disastrous. The author does not provide data to back his point of view. On the other hand there is a lot of data against a constant cost of change (see for example discussion of cost in Code Complete). The lack of reasonable argumentation is an irremediable flaw in the book. Without some supportive data it is impossible to believe the basic assumption, nor the rest of the book. This is all the more important since the only project that the author refers to was cancelled before full completion.
Many other parts of the book are unconvincing. The author presents several XP practices. Some of them are very useful. For example unit tests are a good practice. They are however better treated elsewhere (e.g., Code Complete chapter on unit test). On the other hand some practices seem overkill. Pair programming is one of them. I have tried it and found it useful to generate ideas while prototyping. For writing production code, I find that a quiet environment is by far the best (see Peopleware for supportive data). Again the author does not provide any data to support his point.
This book suggests an approach aiming at changing software engineering practices. However the lack of supportive data makes it a work of fiction.
I would suggest reading Code Complete for code level advice or Rapid Development for management level advice.
A customer on November 14, 2002
Not Software Engineering.
Any Engineering discipline is based on solid reasoning and logic not on blind faith. Unfortunately, most of this book attempts to convince you that Extreme programming is better based on the author's experiences. A lot of the principles are counterintuitive and the author exhorts you just try it out and get enlightened. I'm sorry but these kind of things belong in infomercials not in s/w engineering.
The part about "code is the documentation" is the scariest part. It's true that keeping the documentation up to date is tough on any software project, but to do away with documentation is the most ridiculous thing I have heard.
It's like telling people to cut of their noses to avoid colds. Yes we are always in search of a better software process. Let me tell you that this book won't lead you there.
Philip K. Ronzone on November 24, 2000
The "gossip magazine diet plans" style of programming.
This book reminds me of the "gossip magazine diet plans", you know, the vinegar and honey diet, or the fat-burner 2000 pill diet etc. Occasionally, people actually lose weight on those diets, but, only because they've managed to eat less or exercise more. The diet plans themselves are worthless. XP is the same - it may sometimes help people program better, but only because they are (unintentionally) doing something different. People look at things like XP because, like dieters, they see a need for change. Overall, the book is a decently written "fad diet", with ideas that are just as worthless.
A customer on August 11, 2003
Hackers! Salvation is nigh!!
It's interesting to see the phenomenon of Extreme Programming happening in the dawn of the 21st century. I suppose historians can explain such a reaction as a truly conservative movement. Of course, serious software engineering practice is hard. Heck, documentation is a pain in the neck. And what programmer wouldn't love to have divine inspiration just before starting to write the latest web application and so enlightened by the Almighty, write the whole thing in one go, as if by magic? No design, no documentation, you and me as a pair, and the customer too. Sounds like a hacker's dream with "Imagine" as the soundtrack (sorry, John).
The Software Engineering struggle is over 50 years old and it's only logical to expect some resistance, from time to time. In the XP case, the resistance comes in one of its worst forms: evangelism. A fundamentalist cult, with very little substance, no proof of any kind, but then again if you don't have faith you won't be granted the gift of the mystic revelation. It's Gnosticism for Geeks.
Take it with a pinch of salt.. well, maybe a sack of salt. If you can see through the B.S. that sells millions of dollars in books, consultancy fees, lectures, etc, you will recognise some common-sense ideas that are better explained, explored and detailed elsewhere.
Ian K. VINE VOICE on February 27, 2015
Long have I hated this book
Kent is an excellent writer. He does an excellent job of presenting an approach to software development that is misguided for anything but user interface code. The argument that user interface code must be gotten into the hands of users to get feedback is used to suggest that complex system code should not be "designed up front". This is simply wrong. For example, if you are going to deploy an application in the Amazon Cloud that you want to scale, you better have some idea of how this is going to happen. Simply waiting until your application falls over and fails is not an acceptable approach.
One of the things I despise the most about the software development culture is the mindless adoption of fads. Extreme programming has been adopted by some organizations like a religious dogma.
Engineering large software systems is one of the most difficult things that humans do. There are no silver bullets and there are no dogmatic solutions that will make the difficult simple.
Anil Philip on March 24, 2005
Maybe I'm too cynical because I never got to work for the successful, whiz-kid companies; Maybe this book wasn't written for me!
This book reminds me of Jacobsen's "Use Cases" book of the 1990s. 'Use Cases' was all the rage but after several years, we slowly learned the truth: Uses Cases does not deal with the architecture - a necessary and good foundation for any piece of software.
Similarly, this book seems to be spotlighting Testing and taking it to extremes.
'the test plan is the design doc'
Not True. The design doc encapsulates wisdom and insight
a picture that accurately describes the interactions of the lower level software components is worth a thousand lines of code-reading.
Also present is an evangelistic fervor that reminds me of the rah-rah eighties' bestseller, "In Search Of Excellence" by Peters and Waterman. (Many people have since noted that most of the spotlighted companies of that book are bankrupt twenty five years later).
• - in a room full of people with a bully supervisor (as I experienced in my last job at a major telco) innovation or good work is largely absent.
• - deploy daily - are you kidding? to run through the hundreds of test cases in a large application takes several hours if not days. Not all testing can be automated.
• - I have found the principle of "baby steps", one of the principles in the book, most useful in my career - it is the basis for prototyping iteratively. However I heard it described in 1997 at a pep talk at MCI that the VP of our department gave to us. So I dont know who stole it from whom!
Lastly, I noted that the term 'XP' was used throughout the book, and the back cover has a blurb from an M$architect. Was it simply coincidence that Windows shares the same name for its XP release? I wondered if M$ had sponsored part of the book as good advertising for Windows XP! :)
[Oct 08, 2017] >Disbelieving the 'many eyes' myth Opensource.com
"... This article originally appeared on Alice, Eve, and Bob – a security blog and is republished with permission. ..."
Oct 08, 2017 | opensource.com
Review by many eyes does not always prevent buggy code There is a view that because open source software is subject to review by many eyes, all the bugs will be ironed out of it. This is a myth. 06 Oct 2017 Mike Bursell (Red Hat) Feed 8 up Image credits : Internet Archive Book Images . CC BY-SA 4.0 Writing code is hard. Writing secure code is harder -- much harder. And before you get there, you need to think about design and architecture. When you're writing code to implement security functionality, it's often based on architectures and designs that have been pored over and examined in detail. They may even reflect standards that have gone through worldwide review processes and are generally considered perfect and unbreakable. *
However good those designs and architectures are, though, there's something about putting things into actual software that's, well, special. With the exception of software proven to be mathematically correct, ** being able to write software that accurately implements the functionality you're trying to realize is somewhere between a science and an art. This is no surprise to anyone who's actually written any software, tried to debug software, or divine software's correctness by stepping through it; however, it's not the key point of this article.
Nobody *** actually believes that the software that comes out of this process is going to be perfect, but everybody agrees that software should be made as close to perfect and bug-free as possible. This is why code review is a core principle of software development. And luckily -- in my view, at least -- much of the code that we use in our day-to-day lives is open source, which means that anybody can look at it, and it's available for tens or hundreds of thousands of eyes to review.
And herein lies the problem: There is a view that because open source software is subject to review by many eyes, all the bugs will be ironed out of it. This is a myth. A dangerous myth. The problems with this view are at least twofold. The first is the "if you build it, they will come" fallacy. I remember when there was a list of all the websites in the world, and if you added your website to that list, people would visit it. **** In the same way, the number of open source projects was (maybe) once so small that there was a good chance that people might look at and review your code. Those days are past -- long past. Second, for many areas of security functionality -- crypto primitives implementation is a good example -- the number of suitably qualified eyes is low.
Don't think that I am in any way suggesting that the problem is any less in proprietary code: quite the opposite. Not only are the designs and architectures in proprietary software often hidden from review, but you have fewer eyes available to look at the code, and the dangers of hierarchical pressure and groupthink are dramatically increased. "Proprietary code is more secure" is less myth, more fake news. I completely understand why companies like to keep their security software secret, and I'm afraid that the "it's to protect our intellectual property" line is too often a platitude they tell themselves when really, it's just unsafe to release it. So for me, it's open source all the way when we're looking at security software.
So, what can we do? Well, companies and other organizations that care about security functionality can -- and have, I believe a responsibility to -- expend resources on checking and reviewing the code that implements that functionality. Alongside that, the open source community, can -- and is -- finding ways to support critical projects and improve the amount of review that goes into that code. ***** And we should encourage academic organizations to train students in the black art of security software writing and review, not to mention highlighting the importance of open source software.
We can do better -- and we are doing better. Because what we need to realize is that the reason the "many eyes hypothesis" is a myth is not that many eyes won't improve code -- they will -- but that we don't have enough expert eyes looking. Yet.
* Yeah, really: "perfect and unbreakable." Let's just pretend that's true for the purposes of this discussion.
** and that still relies on the design and architecture to actually do what you want -- or think you want -- of course, so good luck.
*** Nobody who's actually written more than about five lines of code (or more than six characters of Perl).
**** I added one. They came. It was like some sort of magic.
***** See, for instance, the Linux Foundation 's Core Infrastructure Initiative .
This article originally appeared on Alice, Eve, and Bob – a security blog and is republished with permission.
[Oct 03, 2017] Silicon Valley is turning into a series of micromanaged sweatshops (that's what "agile" is truly all about)
"... We've seen this kind of tactic for some time now. Silicon Valley is turning into a series of micromanaged sweatshops (that's what "agile" is truly all about) with little room for genuine creativity, or even understanding of what that actually means. I've seen how impossible it is to explain to upper level management how crappy cheap developers actually diminish productivity and value. All they see is that the requisition is filled for less money. ..."
Oct 03, 2017 | discussion.theguardian.com
I agree with the basic point. We've seen this kind of tactic for some time now. Silicon Valley is turning into a series of micromanaged sweatshops (that's what "agile" is truly all about) with little room for genuine creativity, or even understanding of what that actually means. I've seen how impossible it is to explain to upper level management how crappy cheap developers actually diminish productivity and value. All they see is that the requisition is filled for less money.
The bigger problem is that nobody cares about the arts, and as expensive as education is, nobody wants to carry around a debt on a skill that won't bring in the bucks. And smartphone-obsessed millennials have too short an attention span to fathom how empty their lives are, devoid of the aesthetic depth as they are.
I can't draw a definite link, but I think algorithm fails, which are based on fanatical reliance on programmed routines as the solution to everything, are rooted in the shortage of education and cultivation in the arts.
Economics is a social science, and all this is merely a reflection of shared cultural values. The problem is, people think it's math (it's not) and therefore set in stone.
[Oct 03, 2017] Silicon Valley companies have placed lowering wages and flooding the labor market with cheaper labor near the top of their goals and as a business model.
"... Not maybe. Too late. American corporations objective is to low ball wages here in US. In India they spoon feed these pupils with affordable cutting edge IT training for next to nothing ruppees. These pupils then exaggerate their CVs and ship them out en mass to the western world to dominate the IT industry. I've seen it with my own eyes in action. Those in charge will anything/everything to maintain their grip on power. No brag. Just fact. ..."
Oct 02, 2017 | profile.theguardian.com
Terryl Dorian , 21 Sep 2017 13:26
That's Silicon Valley's dirty secret. Most tech workers in Palo Alto make about as much as the high school teachers who teach their kids. And these are the top coders in the country!
Ray D Wright -> RogTheDodge , , 21 Sep 2017 14:52
I don't see why more Americans would want to be coders. These companies want to drive down wages for workers here and then also ship jobs offshore...
Richard Livingstone -> KatieL , , 21 Sep 2017 14:50
+++1 to all of that.
Automated coding just pushes the level of coding further up the development food chain, rather than gets rid of it. It is the wrong approach for current tech. AI that is smart enough to model new problems and create their own descriptive and runnable language - hopefully after my lifetime but coming sometime.
Arne Babenhauserheide -> Evelita , , 21 Sep 2017 14:48
What coding does not teach is how to improve our non-code infrastructure and how to keep it running (that's the stuff which actually moves things). Code can optimize stuff, but it needs actual actuators to affect reality.
Sometimes these actuators are actual people walking on top of a roof while fixing it.
WyntonK , 21 Sep 2017 14:47
Silicon Valley companies have placed lowering wages and flooding the labor market with cheaper labor near the top of their goals and as a business model.
There are quite a few highly qualified American software engineers who lose their jobs to foreign engineers who will work for much lower salaries and benefits. This is a major ingredient of the libertarian virus that has engulfed and contaminating the Valley, going hand to hand with assembling products in China by slave labor .
If you want a high tech executive to suffer a stroke, mention the words "labor unions".
TheEgg -> UncommonTruthiness , , 21 Sep 2017 14:43
The ship has sailed on this activity as a career.
Nope. Married to a highly-technical skillset, you can still make big bucks. I say this as someone involved in this kind of thing academically and our Masters grads have to beat the banks and fintech companies away with dog shits on sticks. You're right that you can teach anyone to potter around and throw up a webpage but at the prohibitively difficult maths-y end of the scale, someone suitably qualified will never want for a job.
Mike_Dexter -> Evelita , , 21 Sep 2017 14:43
In a similar vein, if you accept the argument that it does drive down wages, wouldn't the culprit actually be the multitudes of online and offline courses and tutorials available to an existing workforce?
Terryl Dorian -> CountDooku , , 21 Sep 2017 14:42
Funny you should pick medicine, law, engineering... 3 fields that are *not* taught in high school. The writer is simply adding "coding" to your list. So it seems you agree with his "garbage" argument after all.
anticapitalist -> RogTheDodge , , 21 Sep 2017 14:42
Key word is "good". Teaching everyone is just going to increase the pool of programmers code I need to fix. India isn't being hired for the quality, they're being hired for cheap labor. As for women sure I wouldn't mind more women around but why does no one say their needs to be more equality in garbage collection or plumbing? (And yes plumbers are a high paid professional).
In the end I don't care what the person is, I just want to hire and work with the best and not someone I have to correct their work because they were hired by quota. If women only graduate at 15% why should IT contain more than that? And let's be a bit honest with the facts, of those 15% how many spend their high school years staying up all night hacking? Very few. Now the few that did are some of the better developers I work with but that pool isn't going to increase by forcing every child to program... just like sports aren't better by making everyone take gym class.
WithoutPurpose , 21 Sep 2017 14:42
I ran a development team for 10 years and I never had any trouble hiring programmers - we just had to pay them enough. Every job would have at least 10 good applicants.
Two years ago I decided to scale back a bit and go into programming (I can code real-time low latency financial apps in 4 languages) and I had four interviews in six months with stupidly low salaries. I'm lucky in that I can bounce between tech and the business side so I got a decent job out of tech.
My entirely anecdotal conclusion is that there is no shortage of good programmers just a shortage of companies willing to pay them.
oddbubble -> Tori Turner , , 21 Sep 2017 14:41
I've worn many hats so far, I started out as a started out as a sysadmin, then I moved on to web development, then back end and now I'm doing test automation because I am on almost the same money for half the effort.
peter nelson -> raffine , , 21 Sep 2017 14:38
But the concepts won't. Good programming requires the ability to break down a task, organise the steps in performing it, identify parts of the process that are common or repetitive so they can be bundled together, handed-off or delegated, etc.
These concepts can be applied to any programming language, and indeed to many non-software activities.
Oliver Jones -> Trumbledon , , 21 Sep 2017 14:37
In the city maybe with a financial background, the exception.
anticapitalist -> Ethan Hawkins , 21 Sep 2017 14:32
Well to his point sort of... either everything will go php or all those entry level php developers will be on the street. A good Java or C developer is hard to come by. And to the others, being a being a developer, especially a good one, is nothing like reading and writing. The industry is already saturated with poor coders just doing it for a paycheck.
peter nelson -> Tori Turner , 21 Sep 2017 14:31
I'm just going to say this once: not everyone with a computer science degree is a coder.
And vice versa. I'm retiring from a 40-year career as a software engineer. Some of the best software engineers I ever met did not have CS degrees.
KatieL -> Mishal Almohaimeed , 21 Sep 2017 14:30
"already developing automated coding scripts. "
Pretty much the entire history of the software industry since FORAST was developed for the ORDVAC has been about desperately trying to make software development in some way possible without driving everyone bonkers.
The gulf between FORAST and today's IDE-written, type-inferring high level languages, compilers, abstracted run-time environments, hypervisors, multi-computer architectures and general tech-world flavour-of-2017-ness is truly immense[1].
And yet software is still fucking hard to write. There's no sign it's getting easier despite all that work.
Automated coding was promised as the solution in the 1980s as well. In fact, somewhere in my archives, I've got paper journals which include adverts for automated systems that would programmers completely redundant by writing all your database code for you. These days, we'd think of those tools as automated ORM generators and they don't fix the problem; they just make a new one -- ORM impedance mismatch -- which needs more engineering on top to fix...
The tools don't change the need for the humans, they just change what's possible for the humans to do.
[1] FORAST executed in about 20,000 bytes of memory without even an OS. The compile artifacts for the map-reduce system I built today are an astonishing hundred million bytes... and don't include the necessary mapreduce environment, management interface, node operating system and distributed filesystem...
raffine , 21 Sep 2017 14:29
Whatever they are taught today will be obsolete tomorrow.
yannick95 -> savingUK , , 21 Sep 2017 14:27
"There are already top quality coders in China and India"
AHAHAHAHAHAHAHAHAHAHAHA *rolls on the floor laughting* Yes........ 1%... and 99% of incredibly bad, incompetent, untalented one that produce cost 50% of a good developer but produce only 5% in comparison. And I'm talking with a LOT of practical experience through more than a dozen corporations all over the world which have been outsourcing to India... all have been disasters for the companies (but good for the execs who pocketed big bonuses and left the company before the disaster blows up in their face)
Wiretrip -> mcharts , , 21 Sep 2017 14:25
Enough people have had their hands burnt by now with shit companies like TCS (Tata) that they are starting to look closer to home again...
TomRoche , 21 Sep 2017 14:11
"... Yup, rings true. I've been in hi tech for over 40 years and seen the changes. I was in Silicon Valley for 10 years on a startup. India is taking over, my current US company now has a majority Indian executive and is moving work to India. US politicians push coding to drive down wages to Indian levels. ..."
Oct 02, 2017 | www.theguardian.com
This month, millions of children returned to school. This year, an unprecedented number of them will learn to code.
Computer science courses for children have proliferated rapidly in the past few years. A 2016 Gallup report found that 40% of American schools now offer coding classes – up from only 25% a few years ago. New York, with the largest public school system in the country, has pledged to offer computer science to all 1.1 million students by 2025. Los Angeles, with the second largest, plans to do the same by 2020. And Chicago, the fourth largest, has gone further, promising to make computer science a high school graduation requirement by 2018.
The rationale for this rapid curricular renovation is economic. Teaching kids how to code will help them land good jobs, the argument goes. In an era of flat and falling incomes, programming provides a new path to the middle class – a skill so widely demanded that anyone who acquires it can command a livable, even lucrative, wage.
This narrative pervades policymaking at every level, from school boards to the government. Yet it rests on a fundamentally flawed premise. Contrary to public perception, the economy doesn't actually need that many more programmers. As a result, teaching millions of kids to code won't make them all middle-class. Rather, it will proletarianize the profession by flooding the market and forcing wages down – and that's precisely the point.
At its root, the campaign for code education isn't about giving the next generation a shot at earning the salary of a Facebook engineer. It's about ensuring those salaries no longer exist, by creating a source of cheap labor for the tech industry.
As software mediates more of our lives, and the power of Silicon Valley grows, it's tempting to imagine that demand for developers is soaring. The media contributes to this impression by spotlighting the genuinely inspiring stories of those who have ascended the class ladder through code. You may have heard of Bit Source, a company in eastern Kentucky that retrains coalminers as coders. They've been featured by Wired , Forbes , FastCompany , The Guardian , NPR and NBC News , among others.
A former coalminer who becomes a successful developer deserves our respect and admiration. But the data suggests that relatively few will be able to follow their example. Our educational system has long been producing more programmers than the labor market can absorb. A study by the Economic Policy Institute found that the supply of American college graduates with computer science degrees is 50% greater than the number hired into the tech industry each year. For all the talk of a tech worker shortage, many qualified graduates simply can't find jobs.
More tellingly, wage levels in the tech industry have remained flat since the late 1990s. Adjusting for inflation, the average programmer earns about as much today as in 1998. If demand were soaring, you'd expect wages to rise sharply in response. Instead, salaries have stagnated.
Still, those salaries are stagnating at a fairly high level. The Department of Labor estimates that the median annual wage for computer and information technology occupations is $82,860 – more than twice the national average. And from the perspective of the people who own the tech industry, this presents a problem. High wages threaten profits. To maximize profitability, one must always be finding ways to pay workers less. Tech executives have pursued this goal in a variety of ways. One is collusion – companies conspiring to prevent their employees from earning more by switching jobs. The prevalence of this practice in Silicon Valley triggered a justice department antitrust complaint in 2010, along with a class action suit that culminated in a$415m settlement . Another, more sophisticated method is importing large numbers of skilled guest workers from other countries through the H1-B visa program. These workers earn less than their American counterparts, and possess little bargaining power because they must remain employed to keep their status.
Guest workers and wage-fixing are useful tools for restraining labor costs. But nothing would make programming cheaper than making millions more programmers. And where better to develop this workforce than America's schools? It's no coincidence, then, that the campaign for code education is being orchestrated by the tech industry itself. Its primary instrument is Code.org, a nonprofit funded by Facebook, Microsoft, Google and others . In 2016, the organization spent nearly $20m on training teachers, developing curricula, and lobbying policymakers. Silicon Valley has been unusually successful in persuading our political class and much of the general public that its interests coincide with the interests of humanity as a whole. But tech is an industry like any other. It prioritizes its bottom line, and invests heavily in making public policy serve it. The five largest tech firms now spend twice as much as Wall Street on lobbying Washington – nearly$50m in 2016. The biggest spender, Google, also goes to considerable lengths to cultivate policy wonks favorable to its interests – and to discipline the ones who aren't.
Silicon Valley is not a uniquely benevolent force, nor a uniquely malevolent one. Rather, it's something more ordinary: a collection of capitalist firms committed to the pursuit of profit. And as every capitalist knows, markets are figments of politics. They are not naturally occurring phenomena, but elaborately crafted contraptions, sustained and structured by the state – which is why shaping public policy is so important. If tech works tirelessly to tilt markets in its favor, it's hardly alone. What distinguishes it is the amount of money it has at its disposal to do so.
Money isn't Silicon Valley's only advantage in its crusade to remake American education, however. It also enjoys a favorable ideological climate. Its basic message – that schools alone can fix big social problems – is one that politicians of both parties have been repeating for years. The far-fetched premise of neoliberal school reform is that education can mend our disintegrating social fabric. That if we teach students the right skills, we can solve poverty, inequality and stagnation. The school becomes an engine of economic transformation, catapulting young people from challenging circumstances into dignified, comfortable lives.
This argument is immensely pleasing to the technocratic mind. It suggests that our core economic malfunction is technical – a simple asymmetry. You have workers on one side and good jobs on the other, and all it takes is training to match them up. Indeed, every president since Bill Clinton has talked about training American workers to fill the "skills gap". But gradually, one mainstream economist after another has come to realize what most workers have known for years: the gap doesn't exist. Even Larry Summers has concluded it's a myth.
The problem isn't training. The problem is there aren't enough good jobs to be trained for . The solution is to make bad jobs better, by raising the minimum wage and making it easier for workers to form a union, and to create more good jobs by investing for growth. This involves forcing business to put money into things that actually grow the productive economy rather than shoveling profits out to shareholders. It also means increasing public investment, so that people can make a decent living doing socially necessary work like decarbonizing our energy system and restoring our decaying infrastructure.
Everyone should have the opportunity to learn how to code. Coding can be a rewarding, even pleasurable, experience, and it's useful for performing all sorts of tasks. More broadly, an understanding of how code works is critical for basic digital literacy – something that is swiftly becoming a requirement for informed citizenship in an increasingly technologized world.
But coding is not magic. It is a technical skill, akin to carpentry. Learning to build software does not make you any more immune to the forces of American capitalism than learning to build a house. Whether a coder or a carpenter, capital will do what it can to lower your wages, and enlist public institutions towards that end.
Silicon Valley has been extraordinarily adept at converting previously uncommodified portions of our common life into sources of profit. Our schools may prove an easy conquest by comparison.
"Everyone should have the opportunity to learn how to code. " OK, and that's what's being done. And that's what the article is bemoaning. What would be better: teach them how to change tires or groom pets? Or pick fruit? Amazingly condescending article.
MrFumoFumo , 21 Sep 2017 14:54
However, training lots of people to be coders won't automatically result in lots of people who can actually write good code. Nor will it give managers/recruiters the necessary skills to recognize which programmers are any good.
A valid rebuttal but could I offer another observation? Exposing large portions of the school population to coding is not going to magically turn them into coders. It may increase their basic understanding but that is a long way from being a software engineer.
Just as children join art, drama or biology classes so they do not automatically become artists, actors or doctors. I would agree entirely that just being able to code is not going to guarantee the sort of income that might be aspired to. As with all things, it takes commitment, perseverance and dogged determination. I suppose ultimately it becomes the Gattaca argument.
alfredooo -> racole , 24 Sep 2017 06:51
Fair enough, but, his central argument, that an overabundance of coders will drive wages in that sector down, is generally true, so in the future if you want your kids to go into a profession that will earn them 80k+ then being a "coder" is not the route to take. When coding is - like reading, writing, and arithmetic - just a basic skill, there's no guarantee having it will automatically translate into getting a "good" job.
Wiretrip , 21 Sep 2017 14:14
This article lumps everyone in computing into the 'coder' bin, without actually defining what 'coding' is. Yes there is a glut of people who can knock together a bit of HTML and JavaScript, but that is not really programming as such.
There are huge shortages of skilled developers however; people who can apply computer science and engineering in terms of analysis and design of software. These are the real skills for which relatively few people have a true aptitude.
The lack of really good skills is starting to show in some terrible software implementation decisions, such as Slack for example; written as a web app running in Electron (so that JavaScript code monkeys could knock it out quickly), but resulting in awful performance. We will see more of this in the coming years...
Taylor Dotson -> youngsteveo , 21 Sep 2017 13:53
My brother is a programmer, and in his experience these coding exams don't test anything but whether or not you took (and remember) a very narrow range of problems introduce in the first years of a computer science degree. The entire hiring process seems premised on a range of ill-founded ideas about what skills are necessary for the job and how to assess them in people. They haven't yet grasped that those kinds of exams mostly test test-taking ability, rather than intelligence, creativity, diligence, communication ability, or anything else that a job requires beside coughing up the right answer in a stressful, timed environment without outside resources.
I'm an embedded software/firmware engineer. Every similar engineer I've ever met has had the same background - starting in electronics and drifting into embedded software writing in C and assembler. It's virtually impossible to do such software without an understanding of electronics. When it goes wrong you may need to get the test equipment out to scope the hardware to see if it's a hardware or software problem. Coming from a pure computing background just isn't going to get you a job in this type of work.
waltdangerfield , 23 Sep 2017 14:42
All schools teach drama and most kids don't end up becoming actors. You need to give all kids access to coding in order for some can go on to make a career out of it.
TwoSugarsPlease , 23 Sep 2017 06:13
Coding salaries will inevitably fall over time, but such skills give workers the option, once they discover that their income is no longer sustainable in the UK, of moving somewhere more affordable and working remotely.
DiGiT81 -> nixnixnix , 23 Sep 2017 03:29
Completely agree. Coding is a necessary life skill for 21st century but there are levels to every skill. From basic needs for an office job to advanced and specialised.
nixnixnix , 23 Sep 2017 00:46
Lots of people can code but very few of us ever get to the point of creating something new that has a loyal and enthusiastic user-base. Everyone should be able to code because it is or will be the basis of being able to create almost anything in the future. If you want to make a game in Unity, knowing how to code is really useful. If you want to work with large data-sets, you can't rely on Excel and so you need to be able to code (in R?). The use of code is becoming so pervasive that it is going to be like reading and writing.
All the science and engineering graduates I know can code but none of them have ever sold a stand-alone software. The argument made above is like saying that teaching everyone to write will drive down the wages of writers. Writing is useful for anyone and everyone but only a tiny fraction of people who can write, actually write novels or even newspaper columns.
DolyGarcia -> Carl Christensen , 22 Sep 2017 19:24
Immigrants have always a big advantage over locals, for any company, including tech companies: the government makes sure that they will stay in their place and never complain about low salaries or bad working conditions because, you know what? If the company sacks you, an immigrant may be forced to leave the country where they live because their visa expires, which is never going to happen with a local. Companies always have more leverage over immigrants. Given a choice between more and less exploitable workers, companies will choose the most exploitable ones.
Which is something that Marx figured more than a century ago, and why he insisted that socialism had to be international, which led to the founding of the First International Socialist. If worker's fights didn't go across country boundaries, companies would just play people from one country against the other. Unfortunately, at some point in time socialists forgot this very important fact.
xxxFred -> Tomix Da Vomix , 22 Sep 2017 18:52
SO what's wrong with having lots of people able to code? The only argument you seem to have is that it'll lower wages. So do you think that we should stop teaching writing skills so that journalists can be paid more? And no one os going to "force" kids into high-level abstract coding practices in kindergarten, fgs. But there is ample empirical proof that young children can learn basic principles. In fact the younger that children are exposed to anything, the better they can enhance their skills adn knowlege of it later in life, and computing concepts are no different.
Tomix Da Vomix -> xxxFred , 22 Sep 2017 18:40
You're completely missing the point. Kids are forced into the programming field (even STEM as a more general term), before they evolve their abstract reasoning. For that matter, you're not producing highly skilled people, but functional imbeciles and a decent labor that will eventually lower the wages.
Conspiracy theory? So Google, FB and others paying hundreds of millions of dollars for forming a cartel to lower the wages is not true? It sounds me that you're sounding more like a 1969 denier that Guardian is. Tech companies are not financing those incentives because they have a good soul. Their primary drive has always been money, otherwise they wouldn't sell your personal data to earn money.
But hey, you can always sleep peacefully when your kid becomes a coder. When he is 50, everyone will want to have a Cobol, Ada programmer with 25 years of experience when you can get 16 year old kid from a high school for 1/10 of a price. Go back to sleep...
Carl Christensen -> xxxFred , 22 Sep 2017 16:49
it's ridiculous because even out of a pool of computer science B.Sc. or M.Sc. grads - companies are only interested in the top 10%. Even the most mundane company with crappy IT jobs swears that they only hire "the best and the brightest."
Carl Christensen , 22 Sep 2017 16:47
It's basically a con-job by the big Silicon Valley companies offshoring as many US jobs as they can, or "inshoring" via exploitation of the H1B visa - so they can say "see, we don't have 'qualified' people in the US - maybe when these kids learn to program in a generation." As if American students haven't been coding for decades -- and saw their salaries plummet as the H1B visa and Indian offshore firms exploded......
Declawed -> KDHughes , 22 Sep 2017 16:40
Dude, stow the attitude. I've tested code from various entities, and seen every kind of crap peddled as gold.
But I've also seen a little 5-foot giggly lady with two kids, grumble a bit and save a $100,000 product by rewriting another coder's man-month of work in a few days, without any flaws or cracks. Almost nobody will ever know she did that. She's so far beyond my level it hurts. And yes, the author knows nothing. He's genuinely crying wolf while knee-deep in amused wolves. The last time I was in San Jose, years ago , the room was already full of people with Indian surnames. If the problem was REALLY serious, a programmer from POLAND was called in. If you think fighting for a violinist spot is hard, try fighting for it with every spare violinist in the world . I am training my Indian replacement to do my job right now . At least the public can appreciate a good violin. Can you appreciate Duff's device ? So by all means, don't teach local kids how to think in a straight line, just in case they make a dent in the price of wages IN INDIA.... *sheesh* Declawed -> IanMcLzzz , 22 Sep 2017 15:35 That's the best possible summarisation of this extremely dumb article. Bravo. For those who don't know how to think of coding, like the article author, here's a few analogies : A computer is a box that replays frozen thoughts, quickly. That is all. Coding is just the art of explaining. Anyone who can explain something patiently and clearly, can code. Anyone who can't, can't. Making hardware is very much like growing produce while blind. Making software is very much like cooking that produce while blind. Imagine looking after a room full of young eager obedient children who only do exactly, *exactly*, what you told them to do, but move around at the speed of light. Imagine having to try to keep them from smashing into each other or decapitating themselves on the corners of tables, tripping over toys and crashing into walls, etc, while you get them all to play games together. The difference between a good coder and a bad coder is almost life and death. Imagine a broth prepared with ingredients from a dozen co-ordinating geniuses and one idiot, that you'll mass produce. The soup is always far worse for the idiot's additions. The more cooks you involve, the more chance your mass produced broth will taste bad. People who hire coders, typically can't tell a good coder from a bad coder. Zach Dyer -> Mystik Al , 22 Sep 2017 15:18 Tech jobs will probably always be available long after your gone or until another mass extinction. edmundberk -> AmyInNH , 22 Sep 2017 14:59 No you do it in your own time. If you're not prepared to put in long days IT is not for you in any case. It was ever thus, but more so now due to offshoring - rather than the rather obscure forces you seem to believe are important. WithoutPurpose -> freeandfair , 22 Sep 2017 13:21 Bit more rhan that. peter nelson -> offworldguy , 22 Sep 2017 12:44 Sorry, offworldguy, but you're losing this one really badly. I'm a professional software engineer in my 60's and I know lots of non-professionals in my age range who write little programs, scripts and apps for fun. I know this because they often contact me for help or advice. So you've now been told by several people in this thread that ordinary people do code for fun or recreation. The fact that you don't know any probably says more about your network of friends and acquaintances than about the general population. xxxFred , 22 Sep 2017 12:18 This is one of the daftest articles I've come across in a long while. If it's possible that so many kids can be taught to code well enough so that wages come down, then that proves that the only reason we've been paying so much for development costs is the scarcity of people able to do it, not that it's intrinsically so hard that only a select few could anyway. In which case, there is no ethical argument for keeping the pools of skilled workers to some select group. Anyone able to do it should have an equal opportunity to do it. What is the argument for not teaching coding (other than to artificially keep wages high)? Why not stop teaching the three R's, in order to boost white-collar wages in general? Computing is an ever-increasingly intrinsic part of life, and people need to understand it at all levels. It is not just unfair, but tantamount to neglect, to fail to teach children all the skills they may require to cope as adults. Having said that, I suspect that in another generation or two a good many lower-level coding jobs will be redundant anyway, with such code being automatically generated, and "coders" at this level will be little more than technicians setting various parameters. Even so, understanding the basics behind computing is a part of understanding the world they live in, and every child needs that. Suggesting that teaching coding is some kind of conspiracy to force wages down is well, it makes the moon-landing conspiracy looks sensible by comparison. timrichardson -> offworldguy , 22 Sep 2017 12:16 I think it is important to demystify advanced technology, I think that has importance in its own right.Plus, schools should expose kids to things which may spark their interest. Not everyone who does a science project goes on years later to get a PhD, but you'd think that it makes it more likely. Same as giving a kid some music lessons. There is a big difference between serious coding and the basic steps needed to automate a customer service team or a marketing program, but the people who have some mastery over automation will have an advantage in many jobs. Advanced machines are clearly going to be a huge part of our future. What should we do about it, if not teach kids how to understand these tools? rogerfederere -> William Payne , 22 Sep 2017 12:13 tl;dr. Mystik Al , 22 Sep 2017 12:08 As automation is about to put 40% of the workforce permanently out of work getting into to tech seems like a good idea! timrichardson , 22 Sep 2017 12:04 This is like arguing that teaching kids to write is nothing more than a plot to flood the market for journalists. Teaching first aid and CPR does not make everyone a doctor. Coding is an essential skill for many jobs already: 50 years ago, who would have thought you needed coders to make movies? Being a software engineer, a serious coder, is hard. IN fact, it takes more than technical coding to be a software engineer: you can learn to code in a week. Software Engineering is a four year degree, and even then you've just started a career. But depriving kids of some basic insights may mean they won't have the basic skills needed in the future, even for controlling their car and house. By all means, send you kids to a school that doesn't teach coding. I won't. James Jones -> vimyvixen , 22 Sep 2017 11:41 Did you learn SNOBOL, or is Snowball a language I'm not familiar with? (Entirely possible, as an American I never would have known Extended Mercury Autocode existed we're it not for a random book acquisition at my home town library when I was a kid.) William Payne , 22 Sep 2017 11:17 The tide that is transforming technology jobs from "white collar professional" into "blue collar industrial" is part of a larger global economic cycle. Successful "growth" assets inevitably transmogrify into "value" and "income" assets as they progress through the economic cycle. The nature of their work transforms also. No longer focused on innovation; on disrupting old markets or forging new ones; their fundamental nature changes as they mature into optimising, cost reducing, process oriented and most importantly of all -- dividend paying -- organisations. First, the market invests. And then, .... it squeezes. Immature companies must invest in their team; must inspire them to be innovative so that they can take the creative risks required to create new things. This translates into high skills, high wages and "white collar" social status. Mature, optimising companies on the other hand must necessarily avoid risks and seek variance-minimising predictability. They seek to control their human resources; to eliminate creativity; to to make the work procedural, impersonal and soulless. This translates into low skills, low wages and "blue collar" social status. This is a fundamental part of the economic cycle; but it has been playing out on the global stage which has had the effect of hiding some of its' effects. Over the past decades, technology knowledge and skills have flooded away from "high cost" countries and towards "best cost" countries at a historically significant rate. Possibly at the maximum rate that global infrastructure and regional skills pools can support. Much of this necessarily inhumane and brutal cost cutting and deskilling has therefore been hidden by the tide of outsourcing and offshoring. It is hard to see the nature of the jobs change when the jobs themselves are changing hands at the same time. The ever tighter ratchet of dehumanising industrialisation; productivity and efficiency continues apace, however, and as our global system matures and evens out, we see the seeds of what we have sown sail home from over the sea. Technology jobs in developed nations have been skewed towards "growth" activities since for the past several decades most "value" and "income" activities have been carried out in developing nations. Now, we may be seeing the early preparations for the diffusion of that skewed, uneven and unsustainable imbalance. The good news is that "Growth" activities are not going to disappear from the world. They just may not be so geographically concentrated as they are today. Also, there is a significant and attention-worthy argument that the re-balancing of skills will result in a more flexible and performant global economy as organisations will better be able to shift a wider variety of work around the world to regions where local conditions (regulation, subsidy, union activity etc...) are supportive. For the individuals concerned it isn't going to be pretty. And of course it is just another example of the race to the bottom that pits states and public sector purse-holders against one another to win the grace and favour of globally mobile employers. As a power play move it has a sort of inhumanly psychotic inevitability to it which is quite awesome to observe. I also find it ironic that the only way to tame the leviathan that is the global free-market industrial system might actually be effective global governance and international cooperation within a rules-based system. Both "globalist" but not even slightly both the same thing. Vereto -> Wiretrip , 22 Sep 2017 11:17 not just coders, it put even IT Ops guys into this bin. Basically good old - so you are working with computers sentence I used to hear a lot 10-15 years ago. Sangmin , 22 Sep 2017 11:15 You can teach everyone how to code but it doesn't necessarily mean everyone will be able to work as one. We all learn math but that doesn't mean we're all mathematicians. We all know how to write but we're not all professional writers. I have a graduate degree in CS and been to a coding bootcamp. Not everyone's brain is wired to become a successful coder. There is a particular way how coders think. Quality of a product will stand out based on these differences. Vereto -> Jared Hall , 22 Sep 2017 11:12 Very hyperbolic is to assume that the profit in those companies is done by decreasing wages. In my company the profit is driven by ability to deliver products to the market. And that is limited by number of top people (not just any coder) you can have. KDHughes -> kcrane , 22 Sep 2017 11:06 You realise that the arts are massively oversupplied and that most artists earn very little, if anything? Which is sort of like the situation the author is warning about. But hey, he knows nothing. Congratulations, though, on writing one of the most pretentious posts I've ever read on CIF. offworldguy -> Melissa Boone , 22 Sep 2017 10:21 So you know kids, college age people and software developers who enjoy doing it in their leisure time? Do you know any middle aged mothers, fathers, grandparents who enjoy it and are not software developers? Sorry, I don't see coding as a leisure pursuit that is going to take off beyond a very narrow demographic and if it becomes apparent (as I believe it will) that there is not going to be a huge increase in coding job opportunities then it will likely wither in schools too, perhaps replaced by music lessons. Bread Eater , 22 Sep 2017 10:02 From their perspective yes. But there are a lot of opportunities in tech so it does benefit students looking for jobs. Melissa Boone -> jamesbro , 22 Sep 2017 10:00 No, because software developer probably fail more often than they succeed. Building anything worthwhile is an iterative process. And it's not just the compiler but the other devs, oyur designer, your PM, all looking at your work. Melissa Boone -> peterainbow , 22 Sep 2017 09:57 It's not shallow or lazy. I also work at a tech company and it's pretty common to do that across job fields. Even in HR marketing jobs, we hire students who can't point to an internship or other kind of experience in college, not simply grades. Vereto -> savingUK , 22 Sep 2017 09:50 It will take ages, the issue of Indian programmers is in the education system and in "Yes boss" culture. But on the other hand most of Americans are just as bad as Indians Melissa Boone -> offworldguy , 22 Sep 2017 09:50 A lot of people do find it fun. I know many kids - high school and young college age - who code in the leisure time because they find it pleasurable to make small apps and video games. I myself enjoy it too. Your argument is like saying since you don't like to read books in your leisure time, nobody else must. The point is your analogy isn't a good one - people who learn to code can not only enjoy it in their spare time just like music, but they can also use it to accomplish all kinds of basic things. I have a friend who's a software developer who has used code to program his Roomba to vacuum in a specific pattern and to play Candy Land with his daughter when they lost the spinner. Owlyrics -> CapTec , 22 Sep 2017 09:44 Creativity could be added to your list. Anyone can push a button but only a few can invent a new one. One company in the US (after it was taken over by a new owner) decided it was more profitable to import button pushers from off-shore, they lost 7 million customers (gamers) and had to employ more of the original American developers to maintain their high standard and profits. Owlyrics -> Maclon , 22 Sep 2017 09:40 Masters is the new Bachelors. Maclon , 22 Sep 2017 09:22 So similar to 500k a year people going to university ( UK) now when it used to be 60k people a year( 1980). There was never enough graduate jobs in 1980 so can't see where the sudden increase in need for graduates has come from. PaulDavisTheFirst -> Ethan Hawkins , 22 Sep 2017 09:17 They aren't really crucial pieces of technology except for their popularity It's early in the day for me, but this is the most ridiculous thing I've read so far, and I suspect it will be high up on the list by the end of the day. There's no technology that is "crucial" unless it's involved in food, shelter or warmth. The rest has its "crucialness" decided by how widespread its use is, and in the case of those 3 languages, the answer is "very". You (or I) might not like that very much, but that's how it is. Julian Williams -> peter nelson , 22 Sep 2017 09:12 My benchmark would be if the average new graduate in the discipline earns more or less than one of the "professions", Law, medicine, Economics etc. The short answer is that they don't. Indeed, in my experience of professions, many good senior SW developers, say in finance, are paid markedly less than the marketing manager, CTO etc. who are often non-technical. My benchmark is not "has a car, house etc." but what does 10, 15 20 years of experience in the area generate as a relative income to another profession, like being a GP or a corporate solicitor or a civil servant (which is usually the benchmark academics use for pay scaling). It is not to denigrate, just to say that markets don't always clear to a point where the most skilled are the highest paid. I was also suggesting that even if you are not intending to work in the SW area, being able to translate your imagination into a program that reflects your ideas is a nice life skill. AmyInNH -> freeandfair , 22 Sep 2017 09:05 Your assumption has no basis in reality. In my experience, as soon as Clinton ramped up H1Bs, my employer would invite 6 same college/degree/curriculum in for interviews, 5 citizen, 1 foreign student and default offer to foreign student without asking interviewers a single question about the interview. Eventually, the skipped the farce of interviewing citizens all together. That was in 1997, and it's only gotten worse. Wall St's been pretty blunt lately. Openly admits replacing US workers for import labor, as it's the "easiest" way to "grow" the economy, even though they know they are ousting citizens from their jobs to do so. AmyInNH -> peter nelson , 22 Sep 2017 08:59 "People who get Masters and PhD's in computer science" Feed western universities money, for degree programs that would otherwise not exist, due to lack of market demand. "someone has a Bachelor's in CS" As citizens, having the same college/same curriculum/same grades, as foreign grad. But as citizens, they have job market mobility, and therefore are shunned. "you can make something real and significant on your own" If someone else is paying your rent, food and student loans while you do so. Ethan Hawkins -> farabundovive , 22 Sep 2017 07:40 While true, it's not the coders' fault. The managers and execs above them have intentionally created an environment where these things are secondary. What's primary is getting the stupid piece of garbage out the door for Q profit outlook. Ship it amd patch it. offworldguy -> millartant , 22 Sep 2017 07:38 Do most people find it fun? I can code. I don't find it 'fun'. Thirty years ago as a young graduate I might have found it slightly fun but the 'fun' wears off pretty quick. Ethan Hawkins -> anticapitalist , 22 Sep 2017 07:35 In my estimation PHP is an utter abomination. Python is just a little better but still very bad. Ruby is a little better but still not at all good. Languages like PHP, Python and JS are popular for banging out prototypes and disposable junk, but you greatly overestimate their importance. They aren't really crucial pieces of technology except for their popularity and while they won't disappear they won't age well at all. Basically they are big long-lived fads. Java is now over 20 years old and while Java 8 is not crucial, the JVM itself actually is crucial. It might last another 20 years or more. Look for more projects like Ceylon, Scala and Kotlin. We haven't found the next step forward yet, but it's getting more interesting, especially around type systems. A strong developer will be able to code well in a half dozen languages and have fairly decent knowledge of a dozen others. For me it's been many years of: Z80, x86, C, C++, Java. Also know some Perl, LISP, ANTLR, Scala, JS, SQL, Pascal, others... millartant -> Islingtonista , 22 Sep 2017 07:26 You need a decent IDE millartant -> offworldguy , 22 Sep 2017 07:24 One is hardly likely to 'do a bit of coding' in ones leisure time Why not? The right problem is a fun and rewarding puzzle to solve. I spend a lot of my leisure time "doing a bit of coding" Ethan Hawkins -> Wiretrip , 22 Sep 2017 07:12 The worst of all are the academics (on average). Ethan Hawkins -> KatieL , 22 Sep 2017 07:09 This makes people like me with 35 years of experience shipping products on deadlines up and down every stack (from device drivers and operating systems to programming languages, platforms and frameworks to web, distributed computing, clusters, big data and ML) so much more valuable. Been there, done that. Ethan Hawkins -> Taylor Dotson , 22 Sep 2017 07:01 It's just not true. In SV there's this giant vacuum created by Apple, Google, FB, etc. Other good companies struggle to fill positions. I know from being on the hiring side at times. TheBananaBender -> peter nelson , 22 Sep 2017 07:00 You don't work for a major outsourcer then like Serco, Atos, Agilisys offworldguy -> LabMonkey , 22 Sep 2017 06:59 Plenty of people? I don't know of a single person outside of my work which is teaming with programmers. Not a single friend, not my neighbours, not my wife or her extended family, not my parents. Plenty of people might do it but most people don't. Ethan Hawkins -> finalcentury , 22 Sep 2017 06:56 Your ignorance of coding is showing. Coding IS creative. Ricardo111 -> peter nelson , 22 Sep 2017 06:56 Agreed: by gifted I did not meant innate. It's more of a mix of having the interest, the persistence, the time, the opportunity and actually enjoying that kind of challenge. While some of those things are to a large extent innate personality traits, others are not and you don't need max of all of them, you just need enough to drive you to explore that domain. That said, somebody that goes into coding purelly for the money and does it for the money alone is extremely unlikelly to become an exceptional coder. Ricardo111 -> eirsatz , 22 Sep 2017 06:50 I'm as senior as they get and have interviewed quite a lot of programmers for several positions, including for Technical Lead (in fact, to replace me) and so far my experience leads me to believe that people who don't have a knack for coding are much less likely to expose themselves to many different languages and techniques, and also are less experimentalist, thus being far less likely to have those moments of transcending merely being aware of the visible and obvious to discover the concerns and concepts behind what one does. Without those moments that open the door to the next Universe of concerns and implications, one cannot do state transitions such as Coder to Technical Designer or Technical Designer to Technical Architect. Sure, you can get the title and do the things from the books, but you will not get WHY are those things supposed to work (and when they will not work) and thus cannot adjust to new conditions effectively and will be like a sailor that can't sail away from sight of the coast since he can't navigate. All this gets reflected in many things that enhance productivity, from the early ability to quickly piece together solutions for a new problem out of past solutions for different problems to, later, conceiving software architecture designs fittted to the typical usage pattern in the industry for which the software is going to be made. LabMonkey , 22 Sep 2017 06:50 From the way our IT department is going, needing millions of coders is not the future. It'll be a minority of developers at the top, and an army of low wage monkeys at the bottom who can troubleshoot from a script - until AI comes along that can code faster and more accurately. LabMonkey -> offworldguy , 22 Sep 2017 06:46 One is hardly likely to 'do a bit of coding' in ones leisure time Really? I've programmed a few simple videogames in my spare time. Plenty of people do. CapTec , 22 Sep 2017 06:29 Interesting piece that's fundamentally flawed. I'm a software engineer myself. There is a reason a University education of a minimum of three years is the base line for a junior developer or 'coder'. Software engineering isn't just writing code. I would say 80% of my time is spent designing and structuring software before I even touch the code. Explaining software engineering as a discipline at a high level to people who don't understand it is simple. Most of us who learn to drive learn a few basics about the mechanics of a car. We know that brake pads need to be replaced, we know that fuel is pumped into an engine when we press the gas pedal. Most of us know how to change a bulb if it blows. The vast majority of us wouldn't be able to replace a head gasket or clutch though. Just knowing the basics isn't enough to make you a mechanic. Studying in school isn't enough to produce software engineers. Software engineering isn't just writing code, it's cross discipline. We also need to understand the science behind the computer, we need too understand logic, data structures, timings, how to manage memory, security, how databases work etc. A few years of learning at school isn't nearly enough, a degree isn't enough on its own due to the dynamic and ever evolving nature of software engineering. Schools teach technology that is out of date and typically don't explain the science very well. This is why most companies don't want new developers, they want people with experience and multiple skills. Programming is becoming cool and people think that because of that it's easy to become a skilled developer. It isn't. It takes time and effort and most kids give up. French was on the national curriculum when I was at school. Most people including me can't hold a conversation in French though. Ultimately there is a SKILL shortage. And that's because skill takes a long time, successes and failures to acquire. Most people just give up. This article is akin to saying 'schools are teaching basic health to reduce the wages of Doctors'. It didn't happen. offworldguy -> thecurio , 22 Sep 2017 06:19 There is a difference. When you teach people music you teach a skill that can be used for a lifetimes enjoyment. One might sit at a piano in later years and play. One is hardly likely to 'do a bit of coding' in ones leisure time. The other thing is how good are people going to get at coding and how long will they retain the skill if not used? I tend to think maths is similar to coding and most adults have pretty terrible maths skills not venturing far beyond arithmetic. Not many remember how to solve a quadratic equation or even how to rearrange some algebra. One more thing is we know that if we teach people music they will find a use for it, if only in their leisure time. We don't know that coding will be in any way useful because we don't know if there will be coding jobs in the future. AI might take over coding but we know that AI won't take over playing piano for pleasure. If we want to teach logical thinking then I think maths has always done this and we should make sure people are better at maths. Alex Mackaness , 22 Sep 2017 06:08 Am I missing something here? Being able to code is a skill that is a useful addition to the skill armoury of a youngster entering the work place. Much like reading, writing, maths... Not only is it directly applicable and pervasive in our modern world, it is built upon logic. The important point is that American schools are not ONLY teaching youngsters to code, and producing one dimensional robots... instead coding makes up one part of their overall skill set. Those who wish to develop their coding skills further certainly can choose to do so. Those who specialise elsewhere are more than likely to have found the skills they learnt whilst coding useful anyway. I struggle to see how there is a hidden capitalist agenda here. I would argue learning the basics of coding is simply becoming seen as an integral part of the school curriculum. thecurio , 22 Sep 2017 05:56 The word "coding" is shorthand for "computer programming" or "software development" and it masks the depth and range of skills that might be required, depending on the application. This subtlety is lost, I think, on politicians and perhaps the general public. Asserting that teaching lots of people to code is a sneaky way to commodotise an industry might have some truth to it, but remember that commodotisation (or "sharing and re-use" as developers might call it) is nothing new. The creation of freely available and re-usable software components and APIs has driven innovation, and has put much power in the hands of developers who would not otherwise have the skill or time to tackle such projects. There's nothing to fear from teaching more people to "code", just as there's nothing to fear from teaching more people to "play music". These skills simply represent points on a continuum. There's room for everyone, from the kid on a kazoo all the way to Coltrane at the Village Vanguard. sbw7 -> ragingbull , 22 Sep 2017 05:44 I taught CS. Out of around 100 graduates I'd say maybe 5 were reasonable software engineers. The rest would be fine in tech support or other associated trades, but not writing software. Its not just a set of trainable skills, its a set of attitudes and ways of perceiving and understanding that just aren't that common. offworldguy , 22 Sep 2017 05:02 I can't understand the rush to teach coding in schools. First of all I don't think we are going to be a country of millions of coders and secondly if most people have the skills then coding is hardly going to be a well paid job. Thirdly you can learn coding from scratch after school like people of my generation did. You could argue that it is part of a well rounded education but then it is as important for your career as learning Shakespeare, knowing what an oxbow lake is or being able to do calculus: most jobs just won't need you to know. savingUK -> yannick95 , 22 Sep 2017 04:35 While you roll on the floor laughing, these countries will slowly but surely get their act together. That is how they work. There are top quality coders over there and they will soon promoted into a position to organise the others. You are probably too young to remember when people laughed at electronic products when they were made in Japan then Taiwan. History will repeat it's self. zii000 -> JohnFreidburg , 22 Sep 2017 04:04 Yes it's ironic and no different here in the UK. Traditionally Labour was the party focused on dividing the economic pie more fairly, Tories on growing it for the benefit of all. It's now completely upside down with Tories paying lip service to the idea of pay rises but in reality supporting this deflationary race to the bottom, hammering down salaries and so shrinking discretionary spending power which forces price reductions to match and so more pressure on employers to cut costs ... ad infinitum. Labour now favour policies which would cause an expansion across the entire economy through pay rises and dramatically increased investment with perhaps more tolerance of inflation to achieve it. ID0193985 -> jamesbro , 22 Sep 2017 03:46 Not surprising if they're working for a company that is cold-calling people - which should be banned in my opinion. Call centres providing customer support are probably less abuse-heavy since the customer is trying to get something done. vimyvixen , 22 Sep 2017 02:04 I taught myself to code in 1974. Fortran, COBOL were first. Over the years as a aerospace engineer I coded in numerous languages ranging from PLM, Snowball, Basic, and more assembly languages than I can recall, not to mention deep down in machine code on more architectures than most know even existed. Bottom line is that coding is easy. It doesn't take a genius to code, just another way of thinking. Consider all the bugs in the software available now. These "coders", not sufficiently trained need adult supervision by engineers who know what they are doing for computer systems that are important such as the electrical grid, nuclear weapons, and safety critical systems. If you want to program toy apps then code away, if you want to do something important learn engineering AND coding. Dwight Spencer , 22 Sep 2017 01:44 Laughable. It takes only an above-average IQ to code. Today's coders are akin to the auto mechanics of the 1950s where practically every high school had auto shop instruction . . . nothing but a source of cheap labor for doing routine implementations of software systems using powerful code libraries built by REAL software engineers. sieteocho -> Islingtonista , 22 Sep 2017 01:19 That's a bit like saying that calculus is more valuable than arithmetic, so why teach children arithmetic at all? Because without the arithmetic, you're not going to get up to the calculus. JohnFreidburg -> Tommyward , 22 Sep 2017 01:15 I disagree. Technology firms are just like other firms. Why then the collusion not to pay more to workers coming from other companies? To believe that they are anything else is naive. The author is correct. We need policies that actually grow the economy and not leaders who cave to what the CEOs want like Bill Clinton did. He brought NAFTA at the behest of CEOs and all it ended up doing was ripping apart the rust belt and ushering in Trump. Tommyward , 22 Sep 2017 00:53 So the media always needs some bad guys to write about, and this month they seem to have it in for the tech industry. The article is BS. I interview a lot of people to join a large tech company, and I can guarantee you that we aren't trying to find cheaper labor, we're looking for the best talent. I know that lots of different jobs have been outsourced to low cost areas, but these days the top companies are instead looking for the top talent globally. I see this article as a hit piece against Silicon Valley, and it doesn't fly in the face of the evidence. finalcentury , 22 Sep 2017 00:46 This has got to be the most cynical and idiotic social interest piece I have ever read in the Guardian. Once upon a time it was very helpful to learn carpentry and machining, but now, even if you are learning those, you will get a big and indispensable headstart if you have some logic and programming skills. The fact is, almost no matter what you do, you can apply logic and programming skills to give you an edge. Even journalists. hoplites99 , 22 Sep 2017 00:02 Yup, rings true. I've been in hi tech for over 40 years and seen the changes. I was in Silicon Valley for 10 years on a startup. India is taking over, my current US company now has a majority Indian executive and is moving work to India. US politicians push coding to drive down wages to Indian levels. On the bright side I am old enough and established enough to quit tomorrow, its someone else's problem, but I still despise those who have sold us out, like the Clintons, the Bushes, the Googoids, the Zuckerboids. liberalquilt -> yannick95 , 21 Sep 2017 23:45 Sure markets existed before governments, but capitalism didn't, can't in fact. It needs the organs of state, the banking system, an education system, and an infrastructure. thegarlicfarmer -> canprof , 21 Sep 2017 23:36 Then teach them other things but not coding! Here in Australia every child of school age has to learn coding. Now tell me that everyone of them will need it? Look beyond computers as coding will soon be automated just like every other job. Islingtonista , 21 Sep 2017 22:25 If you have never coded then you will not appreciate how labour intensive it is. Coders effectively use line editors to type in, line by line, the instructions. And syntax is critical; add a comma when you meant a semicolon and the code doesn't work properly. Yeah, we use frameworks and libraries of already written subroutines, but, in the end, it is all about manually typing in the code. Which is an expensive way of doing things (hence the attractions of 'off-shoring' the coding task to low cost economies in Asia). And this is why teaching kids to code is a waste of time. Already, AI based systems are addressing the task of interpreting high level design models and simply generating the required application. One of the first uses templates and a smart chatbot to enable non-tech business people to build their websites. By describe in non-coding terms what they want, the chatbot is able to assemble the necessary components and make the requisite template amendments to build a working website. Much cheaper than hiring expensive coders to type it all in manually. It's early days yet, but coding may well be one of the big losers to AI automation along with all those back office clerical jobs. Teaching kids how to think about design rather than how to code would be much more valuable. jamesbro -> peter nelson , 21 Sep 2017 21:31 Thick-skinned? Just because you might get a few error messages from the compiler? Call centre workers have to put up with people telling them to fuck off eight hours a day. Joshua Ian Lee , 21 Sep 2017 21:03 Spot on. Society will never need more than 1% of its people to code. We will need far more garbage men. There are only so many (relatively) good jobs to go around and its about competing to get them. canprof , 21 Sep 2017 20:53 I'm a professor (not of computer science) and yet, I try to give my students a basic understanding of algorithms and logic, to spark an interest and encourage them towards programming. I have no skin in the game, except that I've seen unemployment first-hand, and want them to avoid it. The best chance most of them have is to learn to code. Evelita , 21 Sep 2017 14:35 Educating youth does not drive wages down. It drives our economy up. China, India, and other countries are training youth in programming skills. Educating our youth means that they will be able to compete globally. This is the standard GOP stand that we don't need to educate our youth, but instead fantasize about high-paying manufacturing jobs miraculously coming back. Many jobs, including new manufacturing jobs have an element of coding because they are automated. Other industries require coding skills to maintain web sites and keep computer systems running. Learning coding skills opens these doors. Coding teaches logic, an essential thought process. Learning to code, like learning anything, increases the brains ability to adapt to new environments which is essential to our survival as a species. We must invest in educating our youth. cwblackwell , 21 Sep 2017 13:38 "Contrary to public perception, the economy doesn't actually need that many more programmers." This really looks like a straw man introducing a red herring. A skill can be extremely valuable for those who do not pursue it as a full time profession. The economy doesn't actually need that many more typists, pianists, mathematicians, athletes, dietitians. So, clearly, teaching typing, the piano, mathematics, physical education, and nutrition is a nefarious plot to drive down salaries in those professions. None of those skills could possibly enrich the lives or enhance the productivity of builders, lawyers, public officials, teachers, parents, or store managers. DJJJJJC , 21 Sep 2017 14:23 A study by the Economic Policy Institute found that the supply of American college graduates with computer science degrees is 50% greater than the number hired into the tech industry each year. You're assuming that all those people are qualified to work in software because they have a piece of paper that says so, but that's not a valid assumption. The quality of computer science degree courses is generally poor, and most people aren't willing or able to teach themselves. Universities are motivated to award degrees anyway because if they only awarded degrees to students who are actually qualified then that would reflect very poorly on their quality of teaching. A skills shortage doesn't mean that everyone who claims to have a skill gets hired and there are still some jobs left over that aren't being done. It means that employers are forced to hire people who are incompetent in order to fill all their positions. Many people who get jobs in programming can't really do it and do nothing but create work for everyone else. That's why most of the software you use every day doesn't work properly. That's why competent programmers' salaries are still high in spite of the apparently large number of "qualified" people who aren't employed as programmers. [Oct 02, 2017] Programming vs coding This idiotic US term "coder" is complete baloney. Notable quotes: "... You can learn to code, but that doesn't mean you'll be good at it. There will be a few who excel but most will not. This isn't a reflection on them but rather the reality of the situation. In any given area some will do poorly, more will do fairly, and a few will excel. The same applies in any field. ..." "... Oh no, there's loads of people who say they're coders, who have on their CV that they're coders, that have been paid to be coders. Loads of them. Amazingly, about 9 out of 10 of them, experienced coders all, spent ages doing it, not a problem to do it, definitely a coder, not a problem being "hands on"... can't actually write working code when we actually ask them to. ..." "... I feel for your brother, and I've experienced the exact same BS "test" that you're describing. However, when I said "rudimentary coding exam", I wasn't talking about classic fiz-buz questions, Fibonacci problems, whiteboard tests, or anything of the sort. We simply ask people to write a small amount of code that will solve a simple real world problem. Something that they would be asked to do if they got hired. We let them take a long time to do it. We let them use Google to look things up if they need. You would be shocked how many "qualified applicants" can't do it. ..." "... "...coding is not magic. It is a technical skill, akin to carpentry. " I think that is a severe underestimation of the level of expertise required to conceptualise and deliver robust and maintainable code. The complexity of integrating software is more equivalent to constructing an entire building with components of different materials. If you think teaching coding is enough to enable software design and delivery then good luck. ..." "... Being able to write code and being able to program are two very different skills. In language terms its the difference between being able to read and write (say) English and being able to write literature; obviously you need a grasp of the language to write literature but just knowing the language is not the same as being able to assemble and marshal thought into a coherent pattern prior to setting it down. ..." "... What a dumpster argument. I am not a programmer or even close, but a basic understanding of coding has been important to my professional life. Coding isn't just about writing software. Understanding how algorithms work, even simple ones, is a general skill on par with algebra. ..." "... Never mind that a good education is clearly one of the most important things you can do for a person to improve their quality of life wherever they live in the world. It's "neoliberal," so we better hate it. ..." "... A lot of resumes come across my desk that look qualified on paper, but that's not the same thing as being able to do the job. Secondarily, while I agree that one day our field might be replaced by automation, there's a level of creativity involved with good software engineering that makes your carpenter comparison a bit flawed. ..." Oct 02, 2017 | profile.theguardian.com Wiretrip -> Mark Mauvais , 21 Sep 2017 14:23 Yes, 'engineers' (and particularly mathematicians) write appalling code. Trumbledon , 21 Sep 2017 14:23 A good developer can easily earn £600-800 per day, which suggests to me that they are in high demand, and society needs more of them. Wiretrip -> KatieL , 21 Sep 2017 14:22 Agreed, to many people 'coding' consists of copying other people's JavaScript snippets from StackOverflow... I tire of the many frauds in the business... stratplaya , 21 Sep 2017 14:21 You can learn to code, but that doesn't mean you'll be good at it. There will be a few who excel but most will not. This isn't a reflection on them but rather the reality of the situation. In any given area some will do poorly, more will do fairly, and a few will excel. The same applies in any field. peter nelson -> UncommonTruthiness , 21 Sep 2017 14:21 The ship has sailed on this activity as a career. Oh, rubbish. I'm in the process of retiring from my job as an Android software designer so I'm tasked with hiring a replacement for my organisation. It pays extremely well, the work is interesting, and the company is successful and serves an important worldwide industry. Still, finding highly-qualified people is hard and they get snatched up in mid-interview because the demand is high. Not only that but at these pay scales, we can pretty much expect the Guardian will do yet another article about the unconscionable gap between what rich, privileged techies like software engineers make and everyone else. Really, we're damned if we do and damned if we don't. If tech workers are well-paid we're castigated for gentrifying neighbourhoods and living large, and yet anything that threatens to lower what we're paid produces conspiracy-theory articles like this one. Fanastril -> Taylor Dotson , 21 Sep 2017 14:17 I learned to cook in school. Was there a shortage of cooks? No. Did I become a professional cook? No. but I sure as hell would not have missed the skills I learned for the world, and I use them every day. KatieL -> Taylor Dotson , 21 Sep 2017 14:13 Oh no, there's loads of people who say they're coders, who have on their CV that they're coders, that have been paid to be coders. Loads of them. Amazingly, about 9 out of 10 of them, experienced coders all, spent ages doing it, not a problem to do it, definitely a coder, not a problem being "hands on"... can't actually write working code when we actually ask them to. youngsteveo -> Taylor Dotson , 21 Sep 2017 14:12 I feel for your brother, and I've experienced the exact same BS "test" that you're describing. However, when I said "rudimentary coding exam", I wasn't talking about classic fiz-buz questions, Fibonacci problems, whiteboard tests, or anything of the sort. We simply ask people to write a small amount of code that will solve a simple real world problem. Something that they would be asked to do if they got hired. We let them take a long time to do it. We let them use Google to look things up if they need. You would be shocked how many "qualified applicants" can't do it. Fanastril -> Taylor Dotson , 21 Sep 2017 14:11 It is not zero-sum: If you teach something empowering, like programming, motivating is a lot easier, and they will learn more. UncommonTruthiness , 21 Sep 2017 14:10 The demonization of Silicon Valley is clearly the next place to put all blame. Look what "they" did to us: computers, smart phones, HD television, world-wide internet, on and on. Get a rope! I moved there in 1978 and watched the orchards and trailer parks on North 1st St. of San Jose transform into a concrete jungle. There used to be quite a bit of semiconductor equipment and device manufacturing in SV during the 80s and 90s. Now quite a few buildings have the same name : AVAILABLE. Most equipment and device manufacturing has moved to Asia. Programming started with binary, then machine code (hexadecimal or octal) and moved to assembler as a compiled and linked structure. More compiled languages like FORTRAN, BASIC, PL-1, COBOL, PASCAL, C (and all its "+'s") followed making programming easier for the less talented. Now the script based languages (HTML, JAVA, etc.) are even higher level and accessible to nearly all. Programming has become a commodity and will be priced like milk, wheat, corn, non-unionized workers and the like. The ship has sailed on this activity as a career. KatieL -> Taylor Dotson , 21 Sep 2017 14:10 "intelligence, creativity, diligence, communication ability, or anything else that a job" None of those are any use if, when asked to turn your intelligent, creative, diligent, communicated idea into some software, you perform as well as most candidates do at simple coding assessments... and write stuff that doesn't work. peter nelson , 21 Sep 2017 14:09 At its root, the campaign for code education isn't about giving the next generation a shot at earning the salary of a Facebook engineer. It's about ensuring those salaries no longer exist, by creating a source of cheap labor for the tech industry. Of course the writer does not offer the slightest shred of evidence to support the idea that this is the actual goal of these programs. So it appears that the tinfoil-hat conspiracy brigade on the Guardian is operating not only below the line, but above it, too. The fact is that few of these students will ever become software engineers (which, incidentally, is my profession) but programming skills are essential in many professions for writing little scripts to automate various tasks, or to just understand 21st century technology. kcrane , 21 Sep 2017 14:07 Sadly this is another article by a partial journalist who knows nothing about the software industry, but hopes to subvert what he had read somewhere to support a position he had already assumed. As others had said, understanding coding had already become akin to being able to use a pencil. It is a basic requirement of many higher level roles. But knowing which end of a pencil to put on the paper (the equivalent of the level of coding taught in schools) isn't the same as being an artist. Moreover anyone who knows the field recognises that top coders are gifted, they embody genius. There are coding Caravaggio's out there, but few have the experience to know that. No amount of teaching will produce high level coders from average humans, there is an intangible something needed, as there is in music and art, to elevate the merely good to genius. All to say, however many are taught the basics, it won't push down the value of the most talented coders, and so won't reduce the costs of the technology industry in any meaningful way as it is an industry, like art, that relies on the few not the many. DebuggingLife , 21 Sep 2017 14:06 Not all of those children will want to become programmers but at least the barrier to entry, - for more to at least experience it - will be lower. Teaching music to only the children whose parents can afford music tuition means than society misses out on a greater potential for some incredible gifted musicians to shine through. Moreover, learning to code really means learning how to wrangle with the practical application of abstract concepts, algorithms, numerical skills, logic, reasoning, etc. which are all transferrable skills some of which are not in the scope of other classes, certainly practically. Like music, sport, literature etc. programming a computer, a website, a device, a smartphone is an endeavour that can be truly rewarding as merely a pastime, and similarly is limited only by ones imagination. rgilyead , 21 Sep 2017 14:01 "...coding is not magic. It is a technical skill, akin to carpentry. " I think that is a severe underestimation of the level of expertise required to conceptualise and deliver robust and maintainable code. The complexity of integrating software is more equivalent to constructing an entire building with components of different materials. If you think teaching coding is enough to enable software design and delivery then good luck. Taylor Dotson -> cwblackwell , 21 Sep 2017 14:00 Yeah, but mania over coding skills inevitably pushes over skills out of the curriculum (or deemphasizes it). Education is zero-sum in that there's only so much time and energy to devote to it. Hence, you need more than vague appeals to "enhancement," especially given the risks pointed out by the author. Taylor Dotson -> PolydentateBrigand , 21 Sep 2017 13:57 "Talented coders will start new tech businesses and create more jobs." That could be argued for any skill set, including those found in the humanities and social sciences likely to pushed out by the mania over coding ability. Education is zero-sum: Time spent on one subject is time that invariably can't be spent learning something else. Taylor Dotson -> WumpieJr , 21 Sep 2017 13:49 "If they can't literally fix everything let's just get rid of them, right?" That's a strawman. His point is rooted in the recognition that we only have so much time, energy, and money to invest in solutions. One's that feel good but may not do anything distract us for the deeper structural issues in our economy. The probably with thinking "education" will fix everything is that it leaves the status quo unquestioned. martinusher , 21 Sep 2017 13:31 Being able to write code and being able to program are two very different skills. In language terms its the difference between being able to read and write (say) English and being able to write literature; obviously you need a grasp of the language to write literature but just knowing the language is not the same as being able to assemble and marshal thought into a coherent pattern prior to setting it down. To confuse things further there's various levels of skill that all look the same to the untutored eye. Suppose you wished to bridge a waterway. If that waterway was a narrow ditch then you could just throw a plank across. As the distance to be spanned got larger and larger eventually you'd have to abandon intuition for engineering and experience. Exactly the same issues happen with software but they're less tangible; anyone can build a small program but a complex system requires a lot of other knowledge (in my field, that's engineering knowledge -- coding is almost an afterthought). Its a good idea to teach young people to code but I wouldn't raise their expectations of huge salaries too much. For children educating them in wider, more general, fields and abstract activities such as music will pay off huge dividends, far more than just teaching them whatever the fashionable language du jour is. (...which should be Logo but its too subtle and abstract, it doesn't look "real world" enough!). freeandfair , 21 Sep 2017 13:30 I don't see this is an issue. Sure, there could be ulterior motives there, but anyone who wants to still be employed in 20 years has to know how to code . It is not that everyone will be a coder, but their jobs will either include part-time coding or will require understanding of software and what it can and cannot do. AI is going to be everywhere. WumpieJr , 21 Sep 2017 13:23 What a dumpster argument. I am not a programmer or even close, but a basic understanding of coding has been important to my professional life. Coding isn't just about writing software. Understanding how algorithms work, even simple ones, is a general skill on par with algebra. But is isn't just about coding for Tarnoff. He seems to hold education in contempt generally. "The far-fetched premise of neoliberal school reform is that education can mend our disintegrating social fabric." If they can't literally fix everything let's just get rid of them, right? Never mind that a good education is clearly one of the most important things you can do for a person to improve their quality of life wherever they live in the world. It's "neoliberal," so we better hate it. youngsteveo , 21 Sep 2017 13:16 I'm not going to argue that the goal of mass education isn't to drive down wages, but the idea that the skills gap is a myth doesn't hold water in my experience. I'm a software engineer and manager at a company that pays well over the national average, with great benefits, and it is downright difficult to find a qualified applicant who can pass a rudimentary coding exam. A lot of resumes come across my desk that look qualified on paper, but that's not the same thing as being able to do the job. Secondarily, while I agree that one day our field might be replaced by automation, there's a level of creativity involved with good software engineering that makes your carpenter comparison a bit flawed. [Oct 02, 2017] Does programming provides a new path to the middle class? Probably no longer, unless you are really talanted. In the latter case it is not that different from any other fields, but the pressure from H1B makes is harder for programmers. The neoliberal USA have a real problem with the social mobility Notable quotes: "... I do think it's peculiar that Silicon Valley requires so many H1B visas... 'we can't find the talent here' is the main excuse ..." "... This is interesting. Indeed, I do think there is excess supply of software programmers. ..." "... Well, it is either that or the kids themselves who have to pay for it and they are even less prepared to do so. Ideally, college education should be tax payer paid but this is not the case in the US. And the employer ideally should pay for the job related training, but again, it is not the case in the US. ..." "... Plenty of people care about the arts but people can't survive on what the arts pay. That was pretty much the case all through human history. ..." "... I was laid off at your age in the depths of the recent recession and I got a job. ..." "... The great thing about software , as opposed to many other jobs, is that it can be done at home which you're laid off. Write mobile (IOS or Android) apps or work on open source projects and get stuff up on github. I've been to many job interviews with my apps loaded on mobile devices so I could show them what I've done. ..." "... Schools really can't win. Don't teach coding, and you're raising a generation of button-pushers. Teach it, and you're pandering to employers looking for cheap labour. Unions in London objected to children being taught carpentry in the twenties and thirties, so it had to be renamed "manual instruction" to get round it. Denying children useful skills is indefensible. ..." Oct 02, 2017 | discussion.theguardian.com swelle , 21 Sep 2017 17:36 I do think it's peculiar that Silicon Valley requires so many H1B visas... 'we can't find the talent here' is the main excuse, though many 'older' (read: over 40) native-born tech workers will tell your that's plenty of talent here already, but even with the immigration hassles, H1B workers will be cheaper overall... This is interesting. Indeed, I do think there is excess supply of software programmers. There is only a modest number of decent jobs, say as an algorithms developer in finance, general architecture of complex systems or to some extent in systems security. However, these jobs are usually occupied and the incumbents are not likely to move on quickly. Road blocks are also put up by creating sub networks of engineers who ensure that some knowledge is not ubiquitous. Most very high paying jobs in the technology sector are in the same standard upper management roles as in every other industry. Still, the ability to write a computer program in an enabler, knowing how it works means you have an ability to imagine something and make it real. To me it is a bit like language, some people can use language to make more money than others, but it is still important to be able to have a basic level of understanding. FabBlondie -> peter nelson , 21 Sep 2017 17:42 And yet I know a lot of people that has happened to. Better to replace a$125K a year programmer with one who will do the same, or even less, job for $50K. This could backfire if the programmers don't find the work or pay to match their expectations... Programmers, after all tend to make very good hackers if their minds are turned to it. freeandfair -> FabBlondie , 21 Sep 2017 18:23 > While I like your idea of what designing a computer program involves, in my nearly 40 years experience as a programmer I have rarely seen this done. Well, I am a software architect and what he says sounds correct for a certain type of applications. Maybe you do a different type of programming. peter nelson -> FabBlondie , 21 Sep 2017 18:23 While I like your idea of what designing a computer program involves, in my nearly 40 years experience as a programmer I have rarely seen this done. How else can you do it? Java is popular because it's a very versatile language - On this list it's the most popular general-purpose programming language. (Above it javascript is just a scripting language and HTML/CSS aren't even programming languages) https://fossbytes.com/most-used-popular-programming-languages/ ... and below it you have to go down to C# at 20% to come to another general-purpose language, and even that's a Microsoft house language. Also the "correct" choice of programming languages is also based on how many people in the shop know it so they maintain code that's written in it by someone else. freeandfair -> FabBlondie , 21 Sep 2017 18:22 > job-specific training is completely different. What a joke to persuade public school districts to pick up the tab on job training. Well, it is either that or the kids themselves who have to pay for it and they are even less prepared to do so. Ideally, college education should be tax payer paid but this is not the case in the US. And the employer ideally should pay for the job related training, but again, it is not the case in the US. freeandfair -> mlzarathustra , 21 Sep 2017 18:20 > The bigger problem is that nobody cares about the arts, and as expensive as education is, nobody wants to carry around a debt on a skill that won't bring in the buck Plenty of people care about the arts but people can't survive on what the arts pay. That was pretty much the case all through human history. theindyisbetter -> Game Cabbage , 21 Sep 2017 18:18 No. The amount of work is not a fixed sum. That's the lump of labour fallacy. We are not tied to the land. ConBrio , 21 Sep 2017 18:10 Since newspaper are consolidating and cutting jobs gotta clamp down on colleges offering BA degrees, particularly in English Literature and journalism. And then... and...then...and... LMichelle -> chillisauce , 21 Sep 2017 18:03 This article focuses on the US schools, but I can imagine it's the same in the UK. I don't think these courses are going to be about creating great programmers capable of new innovations as much as having a work force that can be their own IT Help Desk. They'll learn just enough in these classes to do that. Then most companies will be hiring for other jobs, but want to make sure you have the IT skills to serve as your own "help desk" (although they will get no salary for their IT work). edmundberk -> FabBlondie , 21 Sep 2017 17:57 I find that quite remarkable - 40 years ago you must have been using assembler and with hardly any memory to work with. If you blitzed through that without applying the thought processes described, well...I'm surprised. James Dey , 21 Sep 2017 17:55 Funny. Every day in the Brexit articles, I read that increasing the supply of workers has negligible effect on wages. peter nelson -> peterainbow , 21 Sep 2017 17:54 I was laid off at your age in the depths of the recent recession and I got a job. As I said in another posting, it usually comes down to fresh skills and good personal references who will vouch for your work-habits and how well you get on with other members of your team. The great thing about software , as opposed to many other jobs, is that it can be done at home which you're laid off. Write mobile (IOS or Android) apps or work on open source projects and get stuff up on github. I've been to many job interviews with my apps loaded on mobile devices so I could show them what I've done. Game Cabbage -> theindyisbetter , 21 Sep 2017 17:52 The situation has a direct comparison to today. It has nothing to do with land. There was a certain amount of profit making work and not enough labour to satisfy demand. There is currently a certain amount of profit making work and in many situations (especially unskilled low paid work) too much labour. edmundberk , 21 Sep 2017 17:52 So, is teaching people English or arithmetic all about reducing wages for the literate and numerate? Or is this the most obtuse argument yet for avoiding what everyone in tech knows - even more blatantly than in many other industries, wages are curtailed by offshoring; and in the US, by having offshoring centres on US soil. chillisauce , 21 Sep 2017 17:48 Well, speaking as someone who spends a lot of time trying to find really good programmers... frankly there aren't that many about. We take most of ours from Eastern Europe and SE Asia, which is quite expensive, given the relocation costs to the UK. But worth it. So, yes, if more British kids learnt about coding, it might help a bit. But not much; the real problem is that few kids want to study IT in the first place, and that the tuition standards in most UK universities are quite low, even if they get there. Baobab73 , 21 Sep 2017 17:48 True...... peter nelson -> rebel7 , 21 Sep 2017 17:47 There was recently an programme/podcast on ABC/RN about the HUGE shortage in Australia of techies with specialized security skills. peter nelson -> jigen , 21 Sep 2017 17:46 Robots, or AI, are already making us more productive. I can write programs today in an afternoon that would have taken me a week a decade or two ago. I can create a class and the IDE will take care of all the accessors, dependencies, enforce our style-guide compliance, stub-in the documentation ,even most test cases, etc, and all I have to write is very-specific stuff required by my application - the other 90% is generated for me. Same with UI/UX - stubs in relevant event handlers, bindings, dependencies, etc. Programmers are a zillion times more productive than in the past, yet the demand keeps growing because so much more stuff in our lives has processors and code. Your car has dozens of processors running lots of software; your TV, your home appliances, your watch, etc. Quaestor , 21 Sep 2017 17:43 Schools really can't win. Don't teach coding, and you're raising a generation of button-pushers. Teach it, and you're pandering to employers looking for cheap labour. Unions in London objected to children being taught carpentry in the twenties and thirties, so it had to be renamed "manual instruction" to get round it. Denying children useful skills is indefensible. jamesupton , 21 Sep 2017 17:42 Getting children to learn how to write code, as part of core education, will be the first step to the long overdue revolution. The rest of us will still have to stick to burning buildings down and stringing up the aristocracy. cjenk415 -> LMichelle , 21 Sep 2017 17:40 did you misread? it seemed like he was emphasizing that learning to code, like learning art (and sports and languages), will help them develop skills that benefit them in whatever profession they choose. FabBlondie -> peter nelson , 21 Sep 2017 17:40 While I like your idea of what designing a computer program involves, in my nearly 40 years experience as a programmer I have rarely seen this done. And, FWIW, IMHO choosing the tool (programming language) might reasonably be expected to follow designing a solution, in practice this rarely happens. No, these days it's Java all the way, from day one. theindyisbetter -> Game Cabbage , 21 Sep 2017 17:40 There was a fixed supply of land and a reduced supply of labour to work the land. Nothing like then situation in a modern economy. LMichelle , 21 Sep 2017 17:39 I'd advise parents that the classes they need to make sure their kids excel in are acting/drama. There is no better way to getting that promotion or increasing your pay like being a skilled actor in the job market. It's a fake it till you make it deal. theindyisbetter , 21 Sep 2017 17:36 What a ludicrous argument. Let's not teach maths or science or literacy either - then anyone with those skills will earn more. SheriffFatman -> Game Cabbage , 21 Sep 2017 17:36 After the Black Death in the middle ages there was a huge under supply of labour. It produced a consistent rise in wages and conditions It also produced wage-control legislation (which admittedly failed to work). peter nelson -> peterainbow , 21 Sep 2017 17:32 if there were truly a shortage i wouldn't be unemployed I've heard that before but when I've dug deeper I've usually found someone who either let their skills go stale, or who had some work issues. LMichelle -> loveyy , 21 Sep 2017 17:26 Really? You think they are going to emphasize things like the importance of privacy and consumer rights? loveyy , 21 Sep 2017 17:25 This really has to be one of the silliest articles I read here in a very long time. People, let your children learn to code. Even more, educate yourselves and start to code just for the fun of it - look at it like a game. The more people know how to code the less likely they are to understand how stuff works. If you were ever frustrated by how impossible it seems to shop on certain websites, learn to code and you will be frustrated no more. You will understand the intent behind the process. Even more, you will understand the inherent limitations and what is the meaning of safety. You will be able to better protect yourself in a real time connected world. Learning to code won't turn your kid into a programmer, just like ballet or piano classes won't mean they'll ever choose art as their livelihood. So let the children learn to code and learn along with them Game Cabbage , 21 Sep 2017 17:24 Tipping power to employers in any profession by oversupply of labour is not a good thing. Bit of a macabre example here but...After the Black Death in the middle ages there was a huge under supply of labour. It produced a consistent rise in wages and conditions and economic development for hundreds of years after this. Not suggesting a massive depopulation. But you can achieve the same effects by altering the power balance. With decades of Neoliberalism, the employers side of the power see-saw is sitting firmly in the mud and is producing very undesired results for the vast majority of people. Zuffle -> peterainbow , 21 Sep 2017 17:23 Perhaps you're just not very good. I've been a developer for 20 years and I've never had more than 1 week of unemployment. Kevin P Brown -> peterainbow , 21 Sep 2017 17:20 " at 55 finding it impossible to get a job" I am 59, and it is not just the age aspect it is the money aspect. They know you have experience and expectations, and yet they believe hiring someone half the age and half the price, times 2 will replace your knowledge. I have been contracting in IT for 30 years, and now it is obvious it is over. Experience at some point no longer mitigates age. I think I am at that point now. TheLane82 , 21 Sep 2017 17:20 Completely true! What needs to happen instead is to teach the real valuable subjects. Gender studies. Islamic studies. Black studies. All important issues that need to be addressed. peter nelson -> mlzarathustra , 21 Sep 2017 17:06 Dear, dear, I know, I know, young people today . . . just not as good as we were. Everything is just going down the loo . . . Just have a nice cuppa camomile (or chamomile if you're a Yank) and try to relax ... " hey you kids, get offa my lawn !" FabBlondie , 21 Sep 2017 17:06 There are good reasons to teach coding. Too many of today's computer users are amazingly unaware of the technology that allows them to send and receive emails, use their smart phones, and use websites. Few understand the basic issues involved in computer security, especially as it relates to their personal privacy. Hopefully some introductory computer classes could begin to remedy this, and the younger the students the better. Security problems are not strictly a matter of coding. Security issues persist in tech. Clearly that is not a function of the size of the workforce. I propose that it is a function of poor management and design skills. These are not taught in any programming class I ever took. I learned these on the job and in an MBA program, and because I was determined. Don't confuse basic workforce training with an effective application of tech to authentic needs. How can the "disruption" so prized in today's Big Tech do anything but aggravate our social problems? Tech's disruption begins with a blatant ignorance of and disregard for causes, and believes to its bones that a high tech app will truly solve a problem it cannot even describe. Kool Aid anyone? peterainbow -> brady , 21 Sep 2017 17:05 indeed that idea has been around as long as cobol and in practice has just made things worse, the fact that many people outside of software engineering don;t seem to realise is that the coding itself is a relatively small part of the job FabBlondie -> imipak , 21 Sep 2017 17:04 Hurrah. peterainbow -> rebel7 , 21 Sep 2017 17:04 so how many female and old software engineers are there who are unable to get a job, i'm one of them at 55 finding it impossible to get a job and unlike many 'developers' i know what i'm doing peterainbow , 21 Sep 2017 17:02 meanwhile the age and sex discrimination in IT goes on, if there were truly a shortage i wouldn't be unemployed Jared Hall -> peter nelson , 21 Sep 2017 17:01 Training more people for an occupation will result in more people becoming qualified to perform that occupation, irregardless of the fact that many will perform poorly at it. A CS degree is no guarantee of competency, but it is one of the best indicators of general qualification we have at the moment. If you can provide a better metric for analyzing the underlying qualifications of the labor force, I'd love to hear it. Regarding your anecdote, while interesting, it poor evidence when compared to the aggregate statistical data analyzed in the EPI study. peter nelson -> FabBlondie , 21 Sep 2017 17:00 Job-specific training is completely different. Good grief. It's not job-specific training. You sound like someone who knows nothing about computer programming. Designing a computer program requires analysing the task; breaking it down into its components, prioritising them and identifying interdependencies, and figuring out which parts of it can be broken out and done separately. Expressing all this in some programming language like Java, C, or C++ is quite secondary. So once you learn to organise a task properly you can apply it to anything - remodeling a house, planning a vacation, repairing a car, starting a business, or administering a (non-software) project at work. [Oct 02, 2017] Evaluation of potential job candidates for programming job should include evaluation of thier previous projects and code written Notable quotes: "... Thank you. The kids that spend high school researching independently and spend their nights hacking just for the love of it and getting a job without college are some of the most competent I've ever worked with. Passionless college grads that just want a paycheck are some of the worst. ..." "... how about how new labor tried to sign away IT access in England to India in exchange for banking access there, how about the huge loopholes in bringing in cheap IT workers from elsewhere in the world, not conspiracies, but facts ..." "... And I've never recommended hiring anyone right out of school who could not point me to a project they did on their own, i.e., not just grades and test scores. I'd like to see an IOS or Android app, or a open-source component, or utility or program of theirs on GitHub, or something like that. ..." "... most of what software designers do is not coding. It requires domain knowledge and that's where the "smart" IDEs and AI coding wizards fall down. It will be a long time before we get where you describe. ..." Oct 02, 2017 | discussion.theguardian.com Instant feedback is one of the things I really like about programming, but it's also the thing that some people can't handle. As I'm developing a program all day long the compiler is telling me about build errors or warnings or when I go to execute it it crashes or produces unexpected output, etc. Software engineers are bombarded all day with negative feedback and little failures. You have to be thick-skinned for this work. peter nelson -> peterainbow , 21 Sep 2017 19:42 How is it shallow and lazy? I'm hiring for the real world so I want to see some real world accomplishments. If the candidate is fresh out of university they can't point to work projects in industry because they don't have any. But they CAN point to stuff they've done on their own. That shows both motivation and the ability to finish something. Why do you object to it? anticapitalist -> peter nelson , 21 Sep 2017 14:47 Thank you. The kids that spend high school researching independently and spend their nights hacking just for the love of it and getting a job without college are some of the most competent I've ever worked with. Passionless college grads that just want a paycheck are some of the worst. John Kendall , 21 Sep 2017 19:42 There is a big difference between "coding" and programming. Coding for a smart phone app is a matter of calling functions that are built into the device. For example, there are functions for the GPS or for creating buttons or for simulating motion in a game. These are what we used to call subroutines. The difference is that whereas we had to write our own subroutines, now they are just preprogrammed functions. How those functions are written is of little or no importance to today's coders. Nor are they able to program on that level. Real programming requires not only a knowledge of programming languages, but also a knowledge of the underlying algorithms that make up actual programs. I suspect that "coding" classes operate on a quite superficial level. Game Cabbage -> theindyisbetter , 21 Sep 2017 19:40 Its not about the amount of work or the amount of labor. Its about the comparative availability of both and how that affects the balance of power, and that in turn affects the overall quality of life for the 'majority' of people. c mm -> Ed209 , 21 Sep 2017 19:39 Most of this is not true. Peter Nelson gets it right by talking about breaking steps down and thinking rationally. The reason you can't just teach the theory, however, is that humans learn much better with feedback. Think about trying to learn how to build a fast car, but you never get in and test its speed. That would be silly. Programming languages take the system of logic that has been developed for centuries and gives instant feedback on the results. It's a language of rationality. peter nelson -> peterainbow , 21 Sep 2017 19:37 This article is about the US. The tech industry in the EU is entirely different, and basically moribund. Where is the EU's Microsoft, Apple, Google, Amazon, Oracle, Intel, Facebook, etc, etc? The opportunities for exciting interesting work, plus the time and schedule pressures that force companies to overlook stuff like age because they need a particular skill Right Now, don't exist in the EU. I've done very well as a software engineer in my 60's in the US; I cannot imagine that would be the case in the EU. peterainbow -> peter nelson , 21 Sep 2017 19:37 sorry but that's just not true, i doubt you are really programming still, or quasi programmer but really a manager who like to keep their hand in, you certainly aren't busy as you've been posting all over this cif. also why would you try and hire someone with such disparate skillsets, makes no sense at all oh and you'd be correct that i do have workplace issues, ie i have a disability and i also suffer from depression, but that shouldn't bar me from employment and again regarding my skills going stale, that again contradicts your statement that it's about planning/analysis/algorithms etc that you said above ( which to some extent i agree with ) c mm -> peterainbow , 21 Sep 2017 19:36 Not at all, it's really egalitarian. If I want to hire someone to paint my portrait, the best way to know if they're any good is to see their previous work. If they've never painted a portrait before then I may want to go with the girl who has c mm -> ragingbull , 21 Sep 2017 19:34 There is definitely not an excess. Just look at projected jobs for computer science on the Bureau of Labor statistics. c mm -> perble conk , 21 Sep 2017 19:32 Right? It's ridiculous. "Hey, there's this industry you can train for that is super valuable to society and pays really well!" Then Ben Tarnoff, "Don't do it! If you do you'll drive down wages for everyone else in the industry. Build your fire starting and rock breaking skills instead." peterainbow -> peter nelson , 21 Sep 2017 19:29 how about how new labor tried to sign away IT access in England to India in exchange for banking access there, how about the huge loopholes in bringing in cheap IT workers from elsewhere in the world, not conspiracies, but facts peter nelson -> eirsatz , 21 Sep 2017 19:25 I think the difference between gifted and not is motivation. But I agree it's not innate. The kid who stayed up all night in high school hacking into the school server to fake his coding class grade is probably more gifted than the one who spent 4 years in college getting a BS in CS because someone told him he could get a job when he got out. I've done some hiring in my life and I always ask them to tell me about stuff they did on their own. peter nelson -> TheBananaBender , 21 Sep 2017 19:20 Most coding jobs are bug fixing. The only bugs I have to fix are the ones I make. peter nelson -> Ed209 , 21 Sep 2017 19:19 As several people have pointed out, writing a computer program requires analyzing and breaking down a task into steps, identifying interdependencies, prioritizing the order, figuring out what parts can be organized into separate tasks that be done separately, etc. These are completely independent of the language - I've been programming for 40 years in everything from FORTRAN to APL to C to C# to Java and it's all the same. Not only that but they transcend programming - they apply to planning a vacation, remodeling a house, or fixing a car. peter nelson -> ragingbull , 21 Sep 2017 19:14 Neither coding nor having a bachelor's degree in computer science makes you a suitable job candidate. I've done a lot of recruiting and interviews in my life, and right now I'm trying to hire someone. And I've never recommended hiring anyone right out of school who could not point me to a project they did on their own, i.e., not just grades and test scores. I'd like to see an IOS or Android app, or a open-source component, or utility or program of theirs on GitHub, or something like that. That's the thing that distinguishes software from many other fields - you can do something real and significant on your own. If you haven't managed to do so in 4 years of college you're not a good candidate. peter nelson -> nickGregor , 21 Sep 2017 19:07 Within the next year coding will be old news and you will simply be able to describe things in ur native language in such a way that the machine will be able to execute any set of instructions you give it. In a sense that's already true, as i noted elsewhere. 90% of the code in my projects (Java and C# in their respective IDEs) is machine generated. I do relatively little "coding". But the flaw in your idea is this: most of what software designers do is not coding. It requires domain knowledge and that's where the "smart" IDEs and AI coding wizards fall down. It will be a long time before we get where you describe. Ricardo111 -> martinusher , 21 Sep 2017 19:03 Completely agree. At the highest levels there is more work that goes into managing complexity and making sure nothing is missed than in making the wheels turn and the beepers beep. ragingbull , 21 Sep 2017 19:02 Hang on... if the current excess of computer science grads is not driving down wages, why would training more kids to code make any difference? Ricardo111 -> youngsteveo , 21 Sep 2017 18:59 I've actually interviewed people for very senior technical positions in Investment Banks who had all the fancy talk in the world and yet failed at some very basic "write me a piece of code that does X" tests. Next hurdle on is people who have learned how to deal with certain situations and yet don't really understand how it works so are unable to figure it out if you change the problem parameters. That said, the average coder is only slightly beyond this point. The ones who can take in account maintenability and flexibility for future enhancements when developing are already a minority, and those who can understand the why of software development process steps, design software system architectures or do a proper Technical Analysis are very rare. eirsatz -> Ricardo111 , 21 Sep 2017 18:57 Hubris. It's easy to mistake efficiency born of experience as innate talent. The difference between a 'gifted coder' and a 'non gifted junior coder' is much more likely to be 10 or 15 years sitting at a computer, less if there are good managers and mentors involved. Ed209 , 21 Sep 2017 18:57 Politicians love the idea of teaching children to 'code', because it sounds so modern, and nobody could possible object... could they? Unfortunately it simply shows up their utter ignorance of technical matters because there isn't a language called 'coding'. Computer programming languages have changed enormously over the years, and continue to evolve. If you learn the wrong language you'll be about as welcome in the IT industry as a lamp-lighter or a comptometer operator. The pace of change in technology can render skills and qualifications obsolete in a matter of a few years, and only the very best IT employers will bother to retrain their staff - it's much cheaper to dump them. (Most IT posts are outsourced through agencies anyway - those that haven't been off-shored. ) peter nelson -> YEverKnot , 21 Sep 2017 18:54 And this isn't even a good conspiracy theory; it's a bad one. He offers no evidence that there's an actual plan or conspiracy to do this. I'm looking for an account of where the advocates of coding education met to plot this in some castle in Europe or maybe a secret document like "The Protocols of the Elders of Google", or some such. TheBananaBender , 21 Sep 2017 18:52 Most jobs in IT are shit - desktop support, operations droids. Most coding jobs are bug fixing. Ricardo111 -> Wiretrip , 21 Sep 2017 18:49 Tool Users Vs Tool Makers. The really good coders actually get why certain things work as they do and can adjust them for different conditions. The mass produced coders are basically code copiers and code gluing specialists. peter nelson -> AmyInNH , 21 Sep 2017 18:49 People who get Masters and PhD's in computer science are not usually "coders" or software engineers - they're usually involved in obscure, esoteric research for which there really is very little demand. So it doesn't surprise me that they're unemployed. But if someone has a Bachelor's in CS and they're unemployed I would have to wonder what they spent their time at university doing. The thing about software that distinguishes it from lots of other fields is that you can make something real and significant on your own . I would expect any recent CS major I hire to be able to show me an app or an open-source component or something similar that they made themselves, and not just test scores and grades. If they could not then I wouldn't even think about hiring them. Ricardo111 , 21 Sep 2017 18:44 Fortunately for those of us who are actually good at coding, the difference in productivity between a gifted coder and a non-gifted junior developer is something like 100-fold. Knowing how to code and actually being efficient at creating software programs and systems are about as far apart as knowing how to write and actually being able to write a bestselling exciting Crime trilogy. peter nelson -> jamesupton , 21 Sep 2017 18:36 The rest of us will still have to stick to burning buildings down and stringing up the aristocracy. If you know how to write software you can get a robot to do those things. peter nelson -> Julian Williams , 21 Sep 2017 18:34 I do think there is excess supply of software programmers. There is only a modest number of decent jobs, say as an algorithms developer in finance, general architecture of complex systems or to some extent in systems security. This article is about coding; most of those jobs require very little of that. Most very high paying jobs in the technology sector are in the same standard upper management roles as in every other industry. How do you define "high paying". Everyone I know (and I know a lot because I've been a sw engineer for 40 years) who is working fulltime as a software engineer is making a high-middle-class salary, and can easily afford a home, travel on holiday, investments, etc. YEverKnot , 21 Sep 2017 18:32 Tech's push to teach coding isn't about kids' success – it's about cutting wages Nowt like a good conspiracy theory. freeandfair -> WithoutPurpose , 21 Sep 2017 18:31 What is a stupidly low salary? 100K? freeandfair -> AmyInNH , 21 Sep 2017 18:30 > Already there. I take it you skipped right past the employment prospects for US STEM grads - 50% chance of finding STEM work. That just means 50% of them are no good and need to develop their skills further or try something else. Not every with a STEM degree from some 3rd rate college is capable of doing complex IT or STEM work. peter nelson -> edmundberk , 21 Sep 2017 18:30 So, is teaching people English or arithmetic all about reducing wages for the literate and numerate? Yes. Haven't you noticed how wage growth has flattened? That's because some do-gooders" thought it would be a fine idea to educate the peasants. There was a time when only the well-to do knew how to read and write, and that's why they well-to-do were well-to-do. Education is evil. Stop educating people and then those of us who know how to read and write can charge them for reading and writing letters and email. Better yet, we can have Chinese and Indians do it for us and we just charge a transaction fee. AmyInNH -> peter nelson , 21 Sep 2017 18:27 Massive amounts of public use cars, it doesn't mean millions need schooling in auto mechanics. Same for software coding. We aren't even using those who have Bachelors, Masters and PhDs in CS. carlospapafritas , 21 Sep 2017 18:27 "..importing large numbers of skilled guest workers from other countries through the H1-B visa program..." "skilled" is good. H1B has long ( appx 17 years) been abused and turned into trafficking scheme. One can buy H1B in India. Powerful ethnic networks wheeling & dealing in US & EU selling IT jobs to essentially migrants. The real IT wages haven't been stagnant but steadily falling from the 90s. It's easy to see why.$82K/year IT wage was about average in the 90s. Comparing the prices of housing (& pretty much everything else) between now gives you the idea.
freeandfair -> whitehawk66 , 21 Sep 2017 18:27
> not every kid wants or needs to have their soul sucked out of them sitting in front of a screen full of code for some idiotic service that some other douchbro thinks is the next iteration of sliced bread
Taking a couple of years of programming are not enough to do this as a job, don't worry.
But learning to code is like learning maths, - it helps to develop logical thinking, which will benefit you in every area of your life.
James Dey , 21 Sep 2017 18:25
We should stop teaching our kids to be journalists, then your wage might go up.
peter nelson -> AmyInNH , 21 Sep 2017 18:23
What does this even mean?
[Oct 02, 2017] Programming is a culturally important skill
"... We're already using Asia as a source of cheap labor for the tech industry. Why do we need to create cheap labor in the US? ..."
www.moonofalabama.org
David McCaul -> IanMcLzzz , 21 Sep 2017 13:03
There are very few professional Scribes nowadays, a good level of reading & writing is simplely a default even for the lowest paid jobs. A lot of basic entry level jobs require a good level of Excel skills. Several years from now basic coding will be necessary to manipulate basic tools for entry level jobs, especially as increasingly a lot of real code will be generated by expert systems supervised by a tiny number of supervisors. Coding jobs will go the same way that trucking jobs will go when driverless vehicles are perfected.
Offer the class but not mandatory. Just like I could never succeed playing football others will not succeed at coding. The last thing the industry needs is more bad developers showing up for a paycheck.
Programming is a cultural skill; master it, or even understand it on a simple level, and you understand how the 21st century works, on the machinery level. To bereave the children of this crucial insight is to close off a door to their future. What's next, keep them off Math, because, you know . .
Taylor Dotson -> freeandfair , 21 Sep 2017 13:59
That's some crystal ball you have there. English teachers will need to know how to code? Same with plumbers? Same with janitors, CEOs, and anyone working in the service industry?
PolydentateBrigand , 21 Sep 2017 12:59
The economy isn't a zero-sum game. Developing a more skilled workforce that can create more value will lead to economic growth and improvement in the general standard of living. Talented coders will start new tech businesses and create more jobs.
What a dumpster argument. I am not a programmer or even close, but a basic understanding of coding has been important to my professional life. Coding isn't just about writing software. Understanding how algorithms work, even simple ones, is a general skill on par with algebra.
But is isn't just about coding for Tarnoff. He seems to hold education in contempt generally. "The far-fetched premise of neoliberal school reform is that education can mend our disintegrating social fabric." If they can't literally fix everything let's just get rid of them, right?
Never mind that a good education is clearly one of the most important things you can do for a person to improve their quality of life wherever they live in the world. It's "neoliberal," so we better hate it.
mlzarathustra , 21 Sep 2017 16:52
I agree with the basic point. We've seen this kind of tactic for some time now. Silicon Valley is turning into a series of micromanaged sweatshops (that's what "agile" is truly all about) with little room for genuine creativity, or even understanding of what that actually means. I've seen how impossible it is to explain to upper level management how crappy cheap developers actually diminish productivity and value. All they see is that the requisition is filled for less money.
The bigger problem is that nobody cares about the arts, and as expensive as education is, nobody wants to carry around a debt on a skill that won't bring in the bucks. And smartphone-obsessed millennials have too short an attention span to fathom how empty their lives are, devoid of the aesthetic depth as they are.
I can't draw a definite link, but I think algorithm fails, which are based on fanatical reliance on programmed routines as the solution to everything, are rooted in the shortage of education and cultivation in the arts.
Economics is a social science, and all this is merely a reflection of shared cultural values. The problem is, people think it's math (it's not) and therefore set in stone.
AmyInNH -> peter nelson , 21 Sep 2017 16:51
Geeze it'd be nice if you'd make an effort.
rucore.libraries.rutgers.edu/rutgers-lib/45960/PDF/1/
https://rucore.libraries.rutgers.edu/rutgers-lib/46156 /
https://rucore.libraries.rutgers.edu/rutgers-lib/46207 /
peter nelson -> WyntonK , 21 Sep 2017 16:45
Libertarianism posits that everyone should be free to sell their labour or negotiate their own arrangements without the state interfering. So if cheaper foreign labour really was undercutting American labout the Libertarians would be thrilled.
But it's not. I'm in my 60's and retiring but I've been a software engineer all my life. I've worked for many different companies, and in different industries and I've never had any trouble competing with cheap imported workers. The people I've seen fall behind were ones who did not keep their skills fresh. When I was laid off in 2009 in my mid-50's I made sure my mobile-app skills were bleeding edge (in those days ANYTHING having to do with mobile was bleeding edge) and I used to go to job interviews with mobile devices to showcase what I could do. That way they could see for themselves and not have to rely on just a CV.
They older guys who fell behind did so because their skills and toolsets had become obsolete.
Now I'm trying to hire a replacement to write Android code for use in industrial production and struggling to find someone with enough experience. So where is this oversupply I keep hearing about?
Jared Hall -> RogTheDodge , 21 Sep 2017 16:42
Not producing enough to fill vacancies or not producing enough to keep wages at Google's preferred rate? Seeing as research shows there is no lack of qualified developers, the latter option seems more likely.
JayThomas , 21 Sep 2017 16:39
It's about ensuring those salaries no longer exist, by creating a source of cheap labor for the tech industry.
We're already using Asia as a source of cheap labor for the tech industry. Why do we need to create cheap labor in the US? That just seems inefficient.
FabBlondie -> RogTheDodge , 21 Sep 2017 16:39
There was never any need to give our jobs to foreigners. That is, if you are comparing the production of domestic vs. foreign workers. The sole need was, and is, to increase profits.
peter nelson -> AmyInNH , 21 Sep 2017 16:34
FabBlondie , 21 Sep 2017 16:34
Schools MAY be able to fix big social problems, but only if they teach a well-rounded curriculum that includes classical history and the humanities. Job-specific training is completely different. What a joke to persuade public school districts to pick up the tab on job training. The existing social problems were not caused by a lack of programmers, and cannot be solved by Big Tech.
I agree with the author that computer programming skills are not that limited in availability. Big Tech solved the problem of the well-paid professional some years ago by letting them go, these were mostly workers in their 50s, and replacing them with H1-B visa-holders from India -- who work for a fraction of their experienced American counterparts.
It is all about profits. Big Tech is no different than any other "industry."
peter nelson -> Jared Hall , 21 Sep 2017 16:31
Supply of apples does not affect the demand for oranges. Teaching coding in high school does not necessarily alter the supply of software engineers. I studied Chinese History and geology at University but my doing so has had no effect on the job prospects of people doing those things for a living.
johnontheleft -> Taylor Dotson , 21 Sep 2017 16:30
You would be surprised just how much a little coding knowledge has transformed my ability to do my job (a job that is not directly related to IT at all).
peter nelson -> Jared Hall , 21 Sep 2017 16:29
Because teaching coding does not affect the supply of actual engineers. I've been a professional software engineer for 40 years and coding is only a small fraction of what I do.
peter nelson -> Jared Hall , 21 Sep 2017 16:28
You and the linked article don't know what you're talking about. A CS degree does not equate to a productive engineer.
A few years ago I was on the recruiting and interviewing committee to try to hire some software engineers for a scientific instrument my company was making. The entire team had about 60 people (hw, sw, mech engineers) but we needed 2 or 3 sw engineers with math and signal-processing expertise. The project was held up for SIX months because we could not find the people we needed. It would have taken a lot longer than that to train someone up to our needs. Eventually we brought in some Chinese engineers which cost us MORE than what we would have paid for an American engineer when you factor in the agency and visa paperwork.
Modern software engineers are not just generic interchangable parts - 21st century technology often requires specialised scientific, mathematical, production or business domain-specific knowledge and those people are hard to find.
freeluna -> freeluna , 21 Sep 2017 16:18
AmyInNH , 21 Sep 2017 16:16
Regimentation of the many, for benefit of the few.
AmyInNH -> Whatitsaysonthetin , 21 Sep 2017 16:15
Visa jobs are part of trade agreements. To be very specific, US gov (and EU) trade Western jobs for market access in the East.
There is no shortage. This is selling off the West's middle class.
Take a look at remittances in wikipedia and you'll get a good idea just how much it costs the US and EU economies, for sake of record profits to Western industry.
jigen , 21 Sep 2017 16:13
And thanks to the author for not using the adjective "elegant" in describing coding.
freeluna , 21 Sep 2017 16:13
I see advantages in teaching kids to code, and for kids to make arduino and other CPU powered things. I don't see a lot of interest in science and tech coming from kids in school. There are too many distractions from social media and game platforms, and not much interest in developing tools for future tech and science.
jigen , 21 Sep 2017 16:13
Let the robots do the coding. Sorted.
FluffyDog -> rgilyead , 21 Sep 2017 16:13
Although coding per se is a technical skill it isn't designing or integrating systems. It is only a small, although essential, part of the whole software engineering process. Learning to code just gets you up the first steps of a high ladder that you need to climb a fair way if you intend to use your skills to earn a decent living.
rebel7 , 21 Sep 2017 16:11
BS.
Friend of mine in the SV tech industry reports that they are about 100,000 programmers short in just the internet security field.
Y'all are trying to create a problem where there isn't one. Maybe we shouldn't teach them how to read either. They might want to work somewhere besides the grill at McDonalds.
AmyInNH -> WyntonK , 21 Sep 2017 16:11
To which they will respond, offshore.
AmyInNH -> MrFumoFumo , 21 Sep 2017 16:10
They're not looking for good, they're looking for cheap + visa indentured. Non-citizens.
nickGregor , 21 Sep 2017 16:09
Within the next year coding will be old news and you will simply be able to describe things in ur native language in such a way that the machine will be able to execute any set of instructions you give it. Coding is going to change from its purely abstract form that is not utilized at peak- but if you can describe what you envision in an effective concise manner u could become a very good coder very quickly -- and competence will be determined entirely by imagination and the barriers of entry will all but be extinct
AmyInNH -> unclestinky , 21 Sep 2017 16:09
Already there. I take it you skipped right past the employment prospects for US STEM grads - 50% chance of finding STEM work.
AmyInNH -> User10006 , 21 Sep 2017 16:06
Apparently a whole lot of people are just making it up, eh?
http://www.motherjones.com/politics/2017/09/inside-the-growing-guest-worker-program-trapping-indian-students-in-virtual-servitude /
From today,
http://www.computerworld.com/article/2915904/it-outsourcing/fury-rises-at-disney-over-use-of-foreign-workers.html
All the way back to 1995,
JCA1507 -> whitehawk66 , 21 Sep 2017 16:04
Bravo
JCA1507 -> DirDigIns , 21 Sep 2017 16:01
Total... utter... no other way... huge... will only get worse... everyone... (not a very nuanced commentary is it).
I'm glad pieces like this are mounting, it is relevant that we counter the mix of messianism and opportunism of Silicon Valley propaganda with convincing arguments.
RogTheDodge -> WithoutPurpose , 21 Sep 2017 16:01
That's not my experience.
AmyInNH -> TTauriStellarbody , 21 Sep 2017 16:01
It's a stall tactic by Silicon Valley, "See, we're trying to resolve the [non-existant] shortage."
AmyInNH -> WyntonK , 21 Sep 2017 16:00
They aren't immigrants. They're visa indentured foreign workers. Why does that matter? It's part of the cheap+indentured hiring criteria. If it were only cheap, they'd be lowballing offers to citizen and US new grads.
RogTheDodge -> Jared Hall , 21 Sep 2017 15:59
No. Because they're the ones wanting them and realizing the US education system is not producing enough
RogTheDodge -> Jared Hall , 21 Sep 2017 15:58
Except the demand is increasing massively.
RogTheDodge -> WyntonK , 21 Sep 2017 15:57
That's why we are trying to educate American coders - so we don't need to give our jobs to foreigners.
AmyInNH , 21 Sep 2017 15:56
Correct premises,
- proletarianize programmers
- many qualified graduates simply can't find jobs.
Invalid conclusion:
- The problem is there aren't enough good jobs to be trained for.
That conclusion only makes sense if you skip right past ...
" importing large numbers of skilled guest workers from other countries through the H1-B visa program. These workers earn less than their American counterparts, and possess little bargaining power because they must remain employed to keep their status"
Hiring Americans doesn't "hurt" their record profits. It's incessant greed and collusion with our corrupt congress.
Oldvinyl , 21 Sep 2017 15:51
This column was really annoying. I taught my students how to program when I was given a free hand to create the computer studies curriculum for a new school I joined. (Not in the UK thank Dog). 7th graders began with studying the history and uses of computers and communications tech. My 8th grade learned about computer logic (AND, OR, NOT, etc) and moved on with QuickBASIC in the second part of the year. My 9th graders learned about databases and SQL and how to use HTML to make their own Web sites. Last year I received a phone call from the father of one student thanking me for creating the course, his son had just received a job offer and now works in San Francisco for Google.
I am so glad I taught them "coding" (UGH) as the writer puts it, rather than arty-farty subjects not worth a damn in the jobs market.
WyntonK -> DirDigIns , 21 Sep 2017 15:47
I live and work in Silicon Valley and you have no idea what you are talking about. There's no shortage of coders at all. Terrific coders are let go because of their age and the availability of much cheaper foreign coders(no, I am not opposed to immigration).
Sean May , 21 Sep 2017 15:43
Looks like you pissed off a ton of people who can't write code and are none to happy with you pointing out the reason they're slinging insurance for geico.
I think you're quite right that coding skills will eventually enter the mainstream and slowly bring down the cost of hiring programmers.
The fact is that even if you don't get paid to be a programmer you can absolutely benefit from having some coding skills.
There may however be some kind of major coding revolution with the advent of quantum computing. The way code is written now could become obsolete.
Jared Hall -> User10006 , 21 Sep 2017 15:43
Why is it a fantasy? Does supply and demand not apply to IT labor pools?
Jared Hall -> ninianpark , 21 Sep 2017 15:42
Why is it a load of crap? If you increase the supply of something with no corresponding increase in demand, the price will decrease.
pictonic , 21 Sep 2017 15:40
A well-argued article that hits the nail on the head. Amongst any group of coders, very few are truly productive, and they are self starters; training is really needed to do the admin.
Jared Hall -> DirDigIns , 21 Sep 2017 15:39
There is not a huge skills shortage. That is why the author linked this EPI report analyzing the data to prove exactly that. This may not be what people want to believe, but it is certainly what the numbers indicate. There is no skills gap.
Axel Seaton -> Jaberwocky , 21 Sep 2017 15:34
Yeah, but the money is crap
DirDigIns -> IanMcLzzz , 21 Sep 2017 15:32
Perfect response for the absolute crap that the article is pushing.
DirDigIns , 21 Sep 2017 15:30
Total and utter crap, no other way to put it.
There is a huge skills shortage in key tech areas that will only get worse if we don't educate and train the young effectively.
Everyone wants youth to have good skills for the knowledge economy and the ability to earn a good salary and build up life chances for UK youth.
So we get this verbal diarrhoea of an article. Defies belief.
Whatitsaysonthetin -> Evelita , 21 Sep 2017 15:27
Yes. China and India are indeed training youth in coding skills. In order that they take jobs in the USA and UK! It's been going on for 20 years and has resulted in many experienced IT staff struggling to get work at all and, even if they can, to suffer stagnating wages.
WmBoot , 21 Sep 2017 15:23
Wow. Congratulations to the author for provoking such a torrent of vitriol! Job well done.
TTauriStellarbody , 21 Sep 2017 15:22
Has anyones job is at risk from a 16 year old who can cobble together a couple of lines of javascript since the dot com bubble?
Good luck trying to teach a big enough pool of US school kids regular expressions let alone the kind of test driven continuous delivery that is the norm in the industry now.
freeandfair -> youngsteveo , 21 Sep 2017 13:27
> A lot of resumes come across my desk that look qualified on paper, but that's not the same thing as being able to do the job
I have exactly the same experience. There is undeniable a skill gap. It takes about a year for a skilled professional to adjust and learn enough to become productive, it takes about 3-5 years for a college grad.
It is nothing new. But the issue is, as the college grad gets trained, another company steal him/ her. And also keep in mind, all this time you are doing job and training the new employee as time permits. Many companies in the US cut the non-profit department (such as IT) to the bone, we cannot afford to lose a person and then train another replacement for 3-5 years.
The solution? Hire a skilled person. But that means nobody is training college grads and in 10-20 years we are looking at the skill shortage to the point where the only option is brining foreign labor.
American cut-throat companies that care only about the bottom line cannibalized themselves.
Heh. You are not a coder, I take it. :) Going to be a few decades before even the easiest coding jobs vanish.
Given how shit most coders of my acquaintance have been - especially in matters of work ethic, logic, matching s/w to user requirements and willingness to test and correct their gormless output - most future coding work will probably be in the area of disaster recovery. Sorry, since the poor snowflakes can't face the sad facts, we have to call it "business continuation" these days, don't we?
UncommonTruthiness , 21 Sep 2017 14:10
The demonization of Silicon Valley is clearly the next place to put all blame. Look what "they" did to us: computers, smart phones, HD television, world-wide internet, on and on. Get a rope!
I moved there in 1978 and watched the orchards and trailer parks on North 1st St. of San Jose transform into a concrete jungle. There used to be quite a bit of semiconductor equipment and device manufacturing in SV during the 80s and 90s. Now quite a few buildings have the same name : AVAILABLE. Most equipment and device manufacturing has moved to Asia.
Programming started with binary, then machine code (hexadecimal or octal) and moved to assembler as a compiled and linked structure. More compiled languages like FORTRAN, BASIC, PL-1, COBOL, PASCAL, C (and all its "+'s") followed making programming easier for the less talented. Now the script based languages (HTML, JAVA, etc.) are even higher level and accessible to nearly all. Programming has become a commodity and will be priced like milk, wheat, corn, non-unionized workers and the like. The ship has sailed on this activity as a career.
[Sep 19, 2017] Boston Startups Are Teaching Boats to Drive Themselves by Joshua Brustein
"... In 2006, Benjamin launched his open-source software project. With it, a computer is able to take over a boat's navigation-and-control system. Anyone can write programs for it. The project is funded by the U.S. Office for Naval Research and Battelle Memorial Institute, a nonprofit. Benjamin said there are dozens of types of vehicles using the software, which is called MOOS-IvP. ..."
Sep 19, 2017 | www.msn.com
Originally from: Bloomberg via Associated Press
Frank Marino, an engineer with Sea Machines Robotics, uses a remote control belt pack to control a self-driving boat in Boston Harbor. (Bloomberg) -- Frank Marino sat in a repurposed U.S. Coast Guard boat bobbing in Boston Harbor one morning late last month. He pointed the boat straight at a buoy several hundred yards away, while his colleague Mohamed Saad Ibn Seddik used a laptop to set the vehicle on a course that would run right into it. Then Ibn Seddik flipped the boat into autonomous driving mode. They sat back as the vessel moved at a modest speed of six knots, smoothly veering right to avoid the buoy, and then returned to its course.
In a slightly apologetic tone, Marino acknowledged the experience wasn't as harrowing as barreling down a highway in an SUV that no one is steering. "It's not like a self-driving car, where the wheel turns on its own," he said. Ibn Seddik tapped in directions to get the boat moving back the other way at twice the speed. This time, the vessel kicked up a wake, and the turn felt sharper, even as it gave the buoy the same wide berth as it had before. As far as thrills go, it'd have to do. Ibn Seddik said going any faster would make everyone on board nauseous.
The two men work for Sea Machines Robotics Inc., a three-year old company developing computer systems for work boats that can make them either remote-controllable or completely autonomous. In May, the company spent $90,000 to buy the Coast Guard hand-me-down at a government auction. Employees ripped out one of the four seats in the cabin to make room for a metal-encased computer they call a "first-generation autonomy cabinet." They painted the hull bright yellow and added the words "Unmanned Vehicle" in big, red letters. Cameras are positioned at the stern and bow, and a dome-like radar system and a digital GPS unit relay additional information about the vehicle's surroundings. The company named its new vessel Steadfast. Autonomous maritime vehicles haven't drawn as much the attention as self-driving cars, but they're hitting the waters with increased regularity. Huge shipping interests, such as Rolls-Royce Holdings Plc, Tokyo-based fertilizer producer Nippon Yusen K.K. and BHP Billiton Ltd., the world's largest mining company, have all recently announced plans to use driverless ships for large-scale ocean transport. Boston has become a hub for marine technology startups focused on smaller vehicles, with a handful of companies like Sea Machines building their own autonomous systems for boats, diving drones and other robots that operate on or under the water. As Marino and Ibn Seddik were steering Steadfast back to dock, another robot boat trainer, Michael Benjamin, motored past them. Benjamin, a professor at Massachusetts Institute of Technology, is a regular presence on the local waters. His program in marine autonomy, a joint effort by the school's mechanical engineering and computer science departments, serves as something of a ballast for Boston's burgeoning self-driving boat scene. Benjamin helps engineers find jobs at startups and runs an open-source software project that's crucial to many autonomous marine vehicles. He's also a sort of maritime-technology historian. A tall, white-haired man in a baseball cap, shark t-shirt and boat shoes, Benjamin said he's spent the last 15 years "making vehicles wet." He has the U.S. armed forces to thank for making his autonomous work possible. The military sparked the field of marine autonomy decades ago, when it began demanding underwater robots for mine detection, Benjamin explained from a chair on MIT's dock overlooking the Charles River. Eventually, self-driving software worked its way into all kinds of boats. These systems tended to chart a course based on a specific script, rather than sensing and responding to their environments. But a major shift came about a decade ago, when manufacturers began allowing customers to plug in their own autonomy systems, according to Benjamin. "Imagine where the PC revolution would have gone if the only one who could write software on an IBM personal computer was IBM," he said. In 2006, Benjamin launched his open-source software project. With it, a computer is able to take over a boat's navigation-and-control system. Anyone can write programs for it. The project is funded by the U.S. Office for Naval Research and Battelle Memorial Institute, a nonprofit. Benjamin said there are dozens of types of vehicles using the software, which is called MOOS-IvP. Startups using MOOS-IvP said it has created a kind of common vocabulary. "If we had a proprietary system, we would have had to develop training and train new employees," said Ibn Seddik. "Fortunately for us, Mike developed a course that serves exactly that purpose." Teaching a boat to drive itself is easier than conditioning a car in some ways. They typically don't have to deal with traffic, stoplights or roundabouts. But water is unique challenge. "The structure of the road, with traffic lights, bounds your problem a little bit," said Benjamin. "The number of unique possible situations that you can bump into is enormous." At the moment, underwater robots represent a bigger chunk of the market than boats. Sales are expected to hit$4.6 billion in 2020, more than double the amount from 2015, according to ABI Research. The biggest customer is the military.
Several startups hope to change that. Michael Johnson, Sea Machines' chief executive officer, said the long-term potential for self-driving boats involves teams of autonomous vessels working in concert. In many harbors, multiple tugs bring in large container ships, communicating either through radio or by whistle. That could be replaced by software controlling all the boats as a single system, Johnson said.
Sea Machines' first customer is Marine Spill Response Corp., a nonprofit group funded by oil companies. The organization operates oil spill response teams that consist of a 210-foot ship paired with a 32-foot boat, which work together to drag a device collecting oil. Self-driving boats could help because staffing the 32-foot boat in choppy waters or at night can be dangerous, but the theory needs proper vetting, said Judith Roos, a vice president for MSRC. "It's too early to say, 'We're going to go out and buy 20 widgets.'"
Another local startup, Autonomous Marine Systems Inc., has been sending boats about 10 miles out to sea and leaving them there for weeks at a time. AMS's vehicles are designed to operate for long stretches, gathering data in wind farms and oil fields. One vessel is a catamaran dubbed the Datamaran, a name that first came from an employee's typo, said AMS CEO Ravi Paintal. The company also uses Benjamin's software platform. Paintal said AMS's longest missions so far have been 20 days, give or take. "They say when your boat can operate for 30 days out in the ocean environment, you'll be in the running for a commercial contract," he said.
... ... ...
[Sep 17, 2017] The last 25 years (or so) were years of tremendous progress in computers and networking that changed the human civilization
"... Of course the last 25 years (or so) were years of tremendous progress in computers and networking that changed the human civilization. And it is unclear whether we reached the limit of current capabilities or not in certain areas (in CPU speeds and die shrinking we probably did; I do not expect anything significant below 7 nanometers: https://en.wikipedia.org/wiki/7_nanometer ). ..."
libezkova , May 27, 2017 at 10:53 PM
"When combined with our brains, human fingers are amazingly fine manipulation devices."
Not only fingers. The whole human arm is an amazing device. Pure magic, if you ask me.
To emulate those capabilities on computers will probably require another 100 years or more. Selective functions can be imitated even now (manipulator that deals with blocks in a pyramid was created in 70th or early 80th I think, but capabilities of human "eye controlled arm" is still far, far beyond even wildest dreams of AI.
Similarly human intellect is completely different from AI. At the current level the difference is probably 1000 times larger then the difference between a child with Down syndrome and a normal person.
Human brain is actually a machine that creates languages for specific domain (or acquire them via learning) and then is able to operate in terms of those languages. Human child forced to grow up with animals, including wild animals, learns and is able to use "animal language." At least to a certain extent. Some of such children managed to survive in this environment.
Such cruel natural experiments have shown that the level of flexibility of human brain is something really incredible. And IMHO can not be achieved by computers (although never say never).
Here we are talking about tasks that are 1 million times more complex task that playing GO or chess, or driving a car on the street.
My impression is that most of recent AI successes (especially IBM win in Jeopardy ( http://www.techrepublic.com/article/ibm-watson-the-inside-story-of-how-the-jeopardy-winning-supercomputer-was-born-and-what-it-wants-to-do-next/ ), which probably was partially staged, is by-and-large due to the growth of storage and the number of cores of computers, not so much sophistication of algorithms used.
The limits of AI are clearly visible when we see the quality of translation from one language to another. For more or less complex technical text it remains medium to low. As in "requires human editing".
If you are bilingual, try Google translate on this post. You might be impressed by their recent progress in this field. It did improved considerably and now does not cause instant laugh.
Same thing with the speech recognition. The progress is tremendous, especially the last three-five years. But it is still far from perfect. Now, with a some training, programs like Dragon are quite usable as dictation device on, say PC with 4 core 3GHz CPU with 16 GB of memory (especially if you are native English speaker), but if you deal with special text or have strong accent, they still leaves much to be desired (although your level of knowledge of the program, experience and persistence can improve the results considerably.
One interesting observation that I have is that automation is not always improve functioning of the organization. It can be quite opposite :-). Only the costs are cut, and even that is not always true.
Of course the last 25 years (or so) were years of tremendous progress in computers and networking that changed the human civilization. And it is unclear whether we reached the limit of current capabilities or not in certain areas (in CPU speeds and die shrinking we probably did; I do not expect anything significant below 7 nanometers: https://en.wikipedia.org/wiki/7_nanometer ).
[Sep 16, 2017] Google Publicly Releases Internal Developer Documentation Style Guide
Sep 12, 2017 | developers.slashdot.org
(betanews.com)
Posted by BeauHD on Tuesday September 12, 2017
@06:00AM from the free-for-all dept.
BrianFagioli shares a report from BetaNews: The documentation aspect of any project is very important, as it can help people to both understand it and track changes. Unfortunately, many developers aren't very interested in documentation aspect, so it often gets neglected. Luckily, if you want to maintain proper documentation and stay organized, today, Google is releasing its internal developer documentation style guide .
This can quite literally guide your documentation, giving you a great starting point and keeping things consistent. Jed Hartman, Technical Writer, Google says , "For some years now, our technical writers at Google have used an internal-only editorial style guide for most of our developer documentation. In order to better support external contributors to our open source projects, such as Kubernetes, AMP, or Dart, and to allow for more consistency across developer documentation, we're now making that style guide public.
If you contribute documentation to projects like those, you now have direct access to useful guidance about voice, tone, word choice, and other style considerations. It can be useful for general issues, like reminders to use second person, present tense, active voice, and the serial comma; it can also be great for checking very specific issues, like whether to write 'app' or 'application' when you want to be consistent with the Google Developers style."
You can access Google's style guide here .
[Aug 21, 2017] As the crisis unfolds there will be talk about giving the UN some role in resolving international problems.
Aug 21, 2017 | www.lettinggobreath.com
psychohistorian | Aug 21, 2017 12:01:32 AM | 27
My understanding of the UN is that it is the High Court of the World where fealty is paid to empire that funds most of the political circus anyway...and speaking of funding or not, read the following link and lets see what PavewayIV adds to the potential sickness we are sleep walking into.
As the UN delays talks, more industry leaders back ban on weaponized AI
[Jul 25, 2017] Knuth Computer Programming as an Art
Jul 25, 2017 | www.paulgraham.com
CACM , December 1974
When Communications of the ACM began publication in 1959, the members of ACM'S Editorial Board made the following remark as they described the purposes of ACM'S periodicals [2]:
"If computer programming is to become an important part of computer research and development, a transition of programming from an art to a disciplined science must be effected."
Such a goal has been a continually recurring theme during the ensuing years; for example, we read in 1970 of the "first steps toward transforming the art of programming into a science" [26]. Meanwhile we have actually succeeded in making our discipline a science, and in a remarkably simple way: merely by deciding to call it "computer science."
Implicit in these remarks is the notion that there is something undesirable about an area of human activity that is classified as an "art"; it has to be a Science before it has any real stature. On the other hand, I have been working for more than 12 years on a series of books called "The Art of Computer Programming." People frequently ask me why I picked such a title; and in fact some people apparently don't believe that I really did so, since I've seen at least one bibliographic reference to some books called "The Act of Computer Programming."
In this talk I shall try to explain why I think "Art" is the appropriate word. I will discuss what it means for something to be an art, in contrast to being a science; I will try to examine whether arts are good things or bad things; and I will try to show that a proper viewpoint of the subject will help us all to improve the quality of what we are now doing.
One of the first times I was ever asked about the title of my books was in 1966, during the last previous ACM national meeting held in Southern California. This was before any of the books were published, and I recall having lunch with a friend at the convention hotel. He knew how conceited I was, already at that time, so he asked if I was going to call my books "An Introduction to Don Knuth." I replied that, on the contrary, I was naming the books after him . His name: Art Evans. (The Art of Computer Programming, in person.)
From this story we can conclude that the word "art" has more than one meaning. In fact, one of the nicest things about the word is that it is used in many different senses, each of which is quite appropriate in connection with computer programming. While preparing this talk, I went to the library to find out what people have written about the word "art" through the years; and after spending several fascinating days in the stacks, I came to the conclusion that "art" must be one of the most interesting words in the English language.
The Arts of Old
If we go back to Latin roots, we find ars, artis meaning "skill." It is perhaps significant that the corresponding Greek word was τεχνη , the root of both "technology" and "technique."
Nowadays when someone speaks of "art" you probably think first of "fine arts" such as painting and sculpture, but before the twentieth century the word was generally used in quite a different sense. Since this older meaning of "art" still survives in many idioms, especially when we are contrasting art with science, I would like to spend the next few minutes talking about art in its classical sense.
In medieval times, the first universities were established to teach the seven so-called "liberal arts," namely grammar, rhetoric, logic, arithmetic, geometry, music, and astronomy. Note that this is quite different from the curriculum of today's liberal arts colleges, and that at least three of the original seven liberal arts are important components of computer science. At that time, an "art" meant something devised by man's intellect, as opposed to activities derived from nature or instinct; "liberal" arts were liberated or free, in contrast to manual arts such as plowing (cf. [6]). During the middle ages the word "art" by itself usually meant logic [4], which usually meant the study of syllogisms.
Science vs. Art
The word "science" seems to have been used for many years in about the same sense as "art"; for example, people spoke also of the seven liberal sciences, which were the same as the seven liberal arts [1]. Duns Scotus in the thirteenth century called logic "the Science of Sciences, and the Art of Arts" (cf. [12, p. 34f]). As civilization and learning developed, the words took on more and more independent meanings, "science" being used to stand for knowledge, and "art" for the application of knowledge. Thus, the science of astronomy was the basis for the art of navigation. The situation was almost exactly like the way in which we now distinguish between "science" and "engineering."
Many authors wrote about the relationship between art and science in the nineteenth century, and I believe the best discussion was given by John Stuart Mill. He said the following things, among others, in 1843 [28]:
Several sciences are often necessary to form the groundwork of a single art. Such is the complication of human affairs, that to enable one thing to be done , it is often requisite to know the nature and properties of many things... Art in general consists of the truths of Science, arranged in the most convenient order for practice, instead of the order which is the most convenient for thought. Science groups and arranges its truths so as to enable us to take in at one view as much as possible of the general order of the universe. Art... brings together from parts of the field of science most remote from one another, the truths relating to the production of the different and heterogeneous conditions necessary to each effect which the exigencies of practical life require.
As I was looking up these things about the meanings of "art," I found that authors have been calling for a transition from art to science for at least two centuries. For example, the preface to a textbook on mineralogy, written in 1784, said the following [17]: "Previous to the year 1780, mineralogy, though tolerably understood by many as an Art, could scarce be deemed a Science."
According to most dictionaries "science" means knowledge that has been logically arranged and systematized in the form of general "laws." The advantage of science is that it saves us from the need to think things through in each individual case; we can turn our thoughts to higher-level concepts. As John Ruskin wrote in 1853 [32]: "The work of science is to substitute facts for appearances, and demonstrations for impressions."
It seems to me that if the authors I studied were writing today, they would agree with the following characterization: Science is knowledge which we understand so well that we can teach it to a computer; and if we don't fully understand something, it is an art to deal with it. Since the notion of an algorithm or a computer program provides us with an extremely useful test for the depth of our knowledge about any given subject, the process of going from an art to a science means that we learn how to automate something.
Artificial intelligence has been making significant progress, yet there is a huge gap between what computers can do in the foreseeable future and what ordinary people can do. The mysterious insights that people have when speaking, listening, creating, and even when they are programming, are still beyond the reach of science; nearly everything we do is still an art.
From this standpoint it is certainly desirable to make computer programming a science, and we have indeed come a long way in the 15 years since the publication of the remarks I quoted at the beginning of this talk. Fifteen years ago computer programming was so badly understood that hardly anyone even thought about proving programs correct; we just fiddled with a program until we "knew" it worked. At that time we didn't even know how to express the concept that a program was correct, in any rigorous way. It is only in recent years that we have been learning about the processes of abstraction by which programs are written and understood; and this new knowledge about programming is currently producing great payoffs in practice, even though few programs are actually proved correct with complete rigor, since we are beginning to understand the principles of program structure. The point is that when we write programs today, we know that we could in principle construct formal proofs of their correctness if we really wanted to, now that we understand how such proofs are formulated. This scientific basis is resulting in programs that are significantly more reliable than those we wrote in former days when intuition was the only basis of correctness.
The field of "automatic programming" is one of the major areas of artificial intelligence research today. Its proponents would love to be able to give a lecture entitled "Computer Programming as an Artifact" (meaning that programming has become merely a relic of bygone days), because their aim is to create machines that write programs better than we can, given only the problem specification. Personally I don't think such a goal will ever be completely attained, but I do think that their research is extremely important, because everything we learn about programming helps us to improve our own artistry. In this sense we should continually be striving to transform every art into a science: in the process, we advance the art.
Science and Art
Our discussion indicates that computer programming is by now both a science and an art, and that the two aspects nicely complement each other. Apparently most authors who examine such a question come to this same conclusion, that their subject is both a science and an art, whatever their subject is (cf. [25]). I found a book about elementary photography, written in 1893, which stated that "the development of the photographic image is both an art and a science" [13]. In fact, when I first picked up a dictionary in order to study the words "art" and "science," I happened to glance at the editor's preface, which began by saying, "The making of a dictionary is both a science and an art." The editor of Funk & Wagnall's dictionary [27] observed that the painstaking accumulation and classification of data about words has a scientific character, while a well-chosen phrasing of definitions demands the ability to write with economy and precision: "The science without the art is likely to be ineffective; the art without the science is certain to be inaccurate."
When preparing this talk I looked through the card catalog at Stanford library to see how other people have been using the words "art" and "science" in the titles of their books. This turned out to be quite interesting.
For example, I found two books entitled The Art of Playing the Piano [5, 15], and others called The Science of Pianoforte Technique [10], The Science of Pianoforte Practice [30]. There is also a book called The Art of Piano Playing: A Scientific Approach [22].
Then I found a nice little book entitled The Gentle Art of Mathematics [31], which made me somewhat sad that I can't honestly describe computer programming as a "gentle art." I had known for several years about a book called The Art of Computation , published in San Francisco, 1879, by a man named C. Frusher Howard [14]. This was a book on practical business arithmetic that had sold over 400,000 copies in various editions by 1890. I was amused to read the preface, since it shows that Howard's philosophy and the intent of his title were quite different from mine; he wrote: "A knowledge of the Science of Number is of minor importance; skill in the Art of Reckoning is absolutely indispensible."
Several books mention both science and art in their titles, notably The Science of Being and Art of Living by Maharishi Mahesh Yogi [24]. There is also a book called The Art of Scientific Discovery [11], which analyzes how some of the great discoveries of science were made.
So much for the word "art" in its classical meaning. Actually when I chose the title of my books, I wasn't thinking primarily of art in this sense, I was thinking more of its current connotations. Probably the most interesting book which turned up in my search was a fairly recent work by Robert E. Mueller called The Science of Art [29]. Of all the books I've mentioned, Mueller's comes closest to expressing what I want to make the central theme of my talk today, in terms of real artistry as we now understand the term. He observes: "It was once thought that the imaginative outlook of the artist was death for the scientist. And the logic of science seemed to spell doom to all possible artistic flights of fancy." He goes on to explore the advantages which actually do result from a synthesis of science and art.
A scientific approach is generally characterized by the words logical, systematic, impersonal, calm, rational, while an artistic approach is characterized by the words aesthetic, creative, humanitarian, anxious, irrational. It seems to me that both of these apparently contradictory approaches have great value with respect to computer programming.
Emma Lehmer wrote in 1956 that she had found coding to be "an exacting science as well as an intriguing art" [23]. H.S.M. Coxeter remarked in 1957 that he sometimes felt "more like an artist than a scientist" [7]. This was at the time C.P. Snow was beginning to voice his alarm at the growing polarization between "two cultures" of educated people [34, 35]. He pointed out that we need to combine scientific and artistic values if we are to make real progress.
Works of Art
When I'm sitting in an audience listening to a long lecture, my attention usually starts to wane at about this point in the hour. So I wonder, are you getting a little tired of my harangue about "science" and "art"? I really hope that you'll be able to listen carefully to the rest of this, anyway, because now comes the part about which I feel most deeply.
When I speak about computer programming as an art, I am thinking primarily of it as an art form , in an aesthetic sense. The chief goal of my work as educator and author is to help people learn how to write beautiful programs . It is for this reason I was especially pleased to learn recently [32] that my books actually appear in the Fine Arts Library at Cornell University. (However, the three volumes apparently sit there neatly on the shelf, without being used, so I'm afraid the librarians may have made a mistake by interpreting my title literally.)
My feeling is that when we prepare a program, it can be like composing poetry or music; as Andrei Ershov has said [9], programming can give us both intellectual and emotional satisfaction, because it is a real achievement to master complexity and to establish a system of consistent rules.
Furthermore when we read other people's programs, we can recognize some of them as genuine works of art. I can still remember the great thrill it was for me to read the listing of Stan Poley's SOAP II assembly program in 1958; you probably think I'm crazy, and styles have certainly changed greatly since then, but at the time it meant a great deal to me to see how elegant a system program could be, especially by comparison with the heavy-handed coding found in other listings I had been studying at the same time. The possibility of writing beautiful programs, even in assembly language, is what got me hooked on programming in the first place.
Some programs are elegant, some are exquisite, some are sparkling. My claim is that it is possible to write grand programs, noble programs, truly magnificent ones!
Taste and Style
The idea of style in programming is now coming to the forefront at last, and I hope that most of you have seen the excellent little book on Elements of Programming Style by Kernighan and Plauger [16]. In this connection it is most important for us all to remember that there is no one "best" style; everybody has his own preferences, and it is a mistake to try to force people into an unnatural mold. We often hear the saying, "I don't know anything about art, but I know what I like." The important thing is that you really like the style you are using; it should be the best way you prefer to express yourself.
Edsger Dijkstra stressed this point in the preface to his Short Introduction to the Art of Programming [8]:
It is my purpose to transmit the importance of good taste and style in programming, [but] the specific elements of style presented serve only to illustrate what benefits can be derived from "style" in general. In this respect I feel akin to the teacher of composition at a conservatory: He does not teach his pupils how to compose a particular symphony, he must help his pupils to find their own style and must explain to them what is implied by this. (It has been this analogy that made me talk about "The Art of Programming.")
Now we must ask ourselves, What is good style, and what is bad style? We should not be too rigid about this in judging other people's work. The early nineteenth-century philosopher Jeremy Bentham put it this way [3, Bk. 3, Ch. 1]:
Judges of elegance and taste consider themselves as benefactors to the human race, whilst they are really only the interrupters of their pleasure... There is no taste which deserves the epithet good , unless it be the taste for such employments which, to the pleasure actually produced by them, conjoin some contingent or future utility: there is no taste which deserves to be characterized as bad, unless it be a taste for some occupation which has a mischievous tendency.
When we apply our own prejudices to "reform" someone else's taste, we may be unconsciously denying him some entirely legitimate pleasure. That's why I don't condemn a lot of things programmers do, even though I would never enjoy doing them myself. The important thing is that they are creating something they feel is beautiful.
In the passage I just quoted, Bentham does give us some advice about certain principles of aesthetics which are better than others, namely the "utility" of the result. We have some freedom in setting up our personal standards of beauty, but it is especially nice when the things we regard as beautiful are also regarded by other people as useful. I must confess that I really enjoy writing computer programs; and I especially enjoy writing programs which do the greatest good, in some sense.
There are many senses in which a program can be "good," of course. In the first place, it's especially good to have a program that works correctly. Secondly it is often good to have a program that won't be hard to change, when the time for adaptation arises. Both of these goals are achieved when the program is easily readable and understandable to a person who knows the appropriate language.
Another important way for a production program to be good is for it to interact gracefully with its users, especially when recovering from human errors in the input data. It's a real art to compose meaningful error messages or to design flexible input formats which are not error-prone.
Another important aspect of program quality is the efficiency with which the computer's resources are actually being used. I am sorry to say that many people nowadays are condemning program efficiency, telling us that it is in bad taste. The reason for this is that we are now experiencing a reaction from the time when efficiency was the only reputable criterion of goodness, and programmers in the past have tended to be so preoccupied with efficiency that they have produced needlessly complicated code; the result of this unnecessary complexity has been that net efficiency has gone down, due to difficulties of debugging and maintenance.
The real problem is that programmers have spent far too much time worrying about efficiency in the wrong places and at the wrong times; premature optimization is the root of all evil (or at least most of it) in programming.
We shouldn't be penny wise and pound foolish, nor should we always think of efficiency in terms of so many percent gained or lost in total running time or space. When we buy a car, many of us are almost oblivious to a difference of $50 or$100 in its price, while we might make a special trip to a particular store in order to buy a 50 cent item for only 25 cents. My point is that there is a time and place for efficiency; I have discussed its proper role in my paper on structured programming, which appears in the current issue of Computing Surveys [21].
Less Facilities: More Enjoyment
One rather curious thing I've noticed about aesthetic satisfaction is that our pleasure is significantly enhanced when we accomplish something with limited tools. For example, the program of which I personally am most pleased and proud is a compiler I once wrote for a primitive minicomputer which had only 4096 words of memory, 16 bits per word. It makes a person feel like a real virtuoso to achieve something under such severe restrictions.
A similar phenomenon occurs in many other contexts. For example, people often seem to fall in love with their Volkswagens but rarely with their Lincoln Continentals (which presumably run much better). When I learned programming, it was a popular pastime to do as much as possible with programs that fit on only a single punched card. I suppose it's this same phenomenon that makes APL enthusiasts relish their "one-liners." When we teach programming nowadays, it is a curious fact that we rarely capture the heart of a student for computer science until he has taken a course which allows "hands on" experience with a minicomputer. The use of our large-scale machines with their fancy operating systems and languages doesn't really seem to engender any love for programming, at least not at first.
It's not obvious how to apply this principle to increase programmers' enjoyment of their work. Surely programmers would groan if their manager suddenly announced that the new machine will have only half as much memory as the old. And I don't think anybody, even the most dedicated "programming artists," can be expected to welcome such a prospect, since nobody likes to lose facilities unnecessarily. Another example may help to clarify the situation: Film-makers strongly resisted the introduction of talking pictures in the 1920's because they were justly proud of the way they could convey words without sound. Similarly, a true programming artist might well resent the introduction of more powerful equipment; today's mass storage devices tend to spoil much of the beauty of our old tape sorting methods. But today's film makers don't want to go back to silent films, not because they're lazy but because they know it is quite possible to make beautiful movies using the improved technology. The form of their art has changed, but there is still plenty of room for artistry.
How did they develop their skill? The best film makers through the years usually seem to have learned their art in comparatively primitive circumstances, often in other countries with a limited movie industry. And in recent years the most important things we have been learning about programming seem to have originated with people who did not have access to very large computers. The moral of this story, it seems to me, is that we should make use of the idea of limited resources in our own education. We can all benefit by doing occasional "toy" programs, when artificial restrictions are set up, so that we are forced to push our abilities to the limit. We shouldn't live in the lap of luxury all the time, since that tends to make us lethargic. The art of tackling miniproblems with all our energy will sharpen our talents for the real problems, and the experience will help us to get more pleasure from our accomplishments on less restricted equipment.
In a similar vein, we shouldn't shy away from "art for art's sake"; we shouldn't feel guilty about programs that are just for fun. I once got a great kick out of writing a one-statement ALGOL program that invoked an innerproduct procedure in such an unusual way that it calculated the mth prime number, instead of an innerproduct [19]. Some years ago the students at Stanford were excited about finding the shortest FORTRAN program which prints itself out, in the sense that the program's output is identical to its own source text. The same problem was considered for many other languages. I don't think it was a waste of time for them to work on this; nor would Jeremy Bentham, whom I quoted earlier, deny the "utility" of such pastimes [3, Bk. 3, Ch. 1]. "On the contrary," he wrote, "there is nothing, the utility of which is more incontestable. To what shall the character of utility be ascribed, if not to that which is a source of pleasure?"
Providing Beautiful Tools
Another characteristic of modern art is its emphasis on creativity. It seems that many artists these days couldn't care less about creating beautiful things; only the novelty of an idea is important. I'm not recommending that computer programming should be like modern art in this sense, but it does lead me to an observation that I think is important. Sometimes we are assigned to a programming task which is almost hopelessly dull, giving us no outlet whatsoever for any creativity; and at such times a person might well come to me and say, "So programming is beautiful? It's all very well for you to declaim that I should take pleasure in creating elegant and charming programs, but how am I supposed to make this mess into a work of art?"
Well, it's true, not all programming tasks are going to be fun. Consider the "trapped housewife," who has to clean off the same table every day: there's not room for creativity or artistry in every situation. But even in such cases, there is a way to make a big improvement: it is still a pleasure to do routine jobs if we have beautiful things to work with. For example, a person will really enjoy wiping off the dining room table, day after day, if it is a beautifully designed table made from some fine quality hardwood.
Therefore I want to address my closing remarks to the system programmers and the machine designers who produce the systems that the rest of us must work with. Please, give us tools that are a pleasure to use, especially for our routine assignments, instead of providing something we have to fight with. Please, give us tools that encourage us to write better programs, by enhancing our pleasure when we do so.
It's very hard for me to convince college freshmen that programming is beautiful, when the first thing I have to tell them is how to punch "slash slash JoB equals so-and-so." Even job control languages can be designed so that they are a pleasure to use, instead of being strictly functional.
Computer hardware designers can make their machines much more pleasant to use, for example by providing floating-point arithmetic which satisfies simple mathematical laws. The facilities presently available on most machines make the job of rigorous error analysis hopelessly difficult, but properly designed operations would encourage numerical analysts to provide better subroutines which have certified accuracy (cf. [20, p. 204]).
Let's consider also what software designers can do. One of the best ways to keep up the spirits of a system user is to provide routines that he can interact with. We shouldn't make systems too automatic, so that the action always goes on behind the scenes; we ought to give the programmer-user a chance to direct his creativity into useful channels. One thing all programmers have in common is that they enjoy working with machines; so let's keep them in the loop. Some tasks are best done by machine, while others are best done by human insight; and a properly designed system will find the right balance. (I have been trying to avoid misdirected automation for many years, cf. [18].)
Program measurement tools make a good case in point. For years, programmers have been unaware of how the real costs of computing are distributed in their programs. Experience indicates that nearly everybody has the wrong idea about the real bottlenecks in his programs; it is no wonder that attempts at efficiency go awry so often, when a programmer is never given a breakdown of costs according to the lines of code he has written. His job is something like that of a newly married couple who try to plan a balanced budget without knowing how much the individual items like food, shelter, and clothing will cost. All that we have been giving programmers is an optimizing compiler, which mysteriously does something to the programs it translates but which never explains what it does. Fortunately we are now finally seeing the appearance of systems which give the user credit for some intelligence; they automatically provide instrumentation of programs and appropriate feedback about the real costs. These experimental systems have been a huge success, because they produce measurable improvements, and especially because they are fun to use, so I am confident that it is only a matter of time before the use of such systems is standard operating procedure. My paper in Computing Surveys [21] discusses this further, and presents some ideas for other ways in which an appropriate interactive routine can enhance the satisfaction of user programmers.
Language designers also have an obligation to provide languages that encourage good style, since we all know that style is strongly influenced by the language in which it is expressed. The present surge of interest in structured programming has revealed that none of our existing languages is really ideal for dealing with program and data structure, nor is it clear what an ideal language should be. Therefore I look forward to many careful experiments in language design during the next few years.
Summary
To summarize: We have seen that computer programming is an art, because it applies accumulated knowledge to the world, because it requires skill and ingenuity, and especially because it produces objects of beauty. A programmer who subconsciously views himself as an artist will enjoy what he does and will do it better. Therefore we can be glad that people who lecture at computer conferences speak about the state of the Art .
References
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2. Bauer, Walter F., Juncosa, Mario L., and Perlis, Alan J. ACM publication policies and plans. J. ACM 6 (Apr. 1959), 121-122.
3. Bentham, Jeremy. The Rationale of Reward. Trans. from Theorie des peines et des recompenses, 1811, by Richard Smith, J. & H. L. Hunt, London, 1825.
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5. Clementi, Muzio. The Art of Playing the Piano. Trans. from L'art de jouer le pianoforte by Max Vogrich. Schirmer, New York, 1898.
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8. Dijkstra, Edsger W. EWD316: A Short Introduction to the Art of Programming. T. H. Eindhoven, The Netherlands, Aug. 1971.
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10. Fielden, Thomas. The Science of Pianoforte Technique. Macmillan, London, 927.
11. Gore, George. The Art of Scientific Discovery. Longmans, Green, London, 1878.
12. Hamilton, William. Lectures on Logic 1. Win. Blackwood, Edinburgh, 1874.
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15. Hummel, J.N. The Art of Playing the Piano Forte. Boosey, London, 1827.
16. Kernighan B.W., and Plauger, P.J. The Elements of Programming Style. McGraw-Hill, New York, 1974.
17. Kirwan, Richard. Elements of Mineralogy. Elmsly, London, 1784.
18. Knuth, Donald E. Minimizing drum latency time. J. ACM 8 (Apr. 1961), 119-150.
19. Knuth, Donald E., and Merner, J.N. ALGOL 60 confidential. Comm. ACM 4 (June 1961), 268-272.
20. Knuth, Donald E. Seminumerical Algorithms: The Art of Computer Programming 2. Addison-Wesley, Reading, Mass., 1969.
21. Knuth, Donald E. Structured programming with go to statements. Computing Surveys 6 (Dec. 1974), pages in makeup.
22. Kochevitsky, George. The Art of Piano Playing: A Scientific Approach. Summy-Birchard, Evanston, II1., 1967.
23. Lehmer, Emma. Number theory on the SWAC. Proc. Syrup. Applied Math. 6, Amer. Math. Soc. (1956), 103-108.
24. Mahesh Yogi, Maharishi. The Science of Being and Art of Living. Allen & Unwin, London, 1963.
25. Malevinsky, Moses L. The Science of Playwriting. Brentano's, New York, 1925.
26. Manna, Zohar, and Pnueli, Amir. Formalization of properties of functional programs. J. ACM 17 (July 1970), 555-569.
27. Marckwardt, Albert H, Preface to Funk and Wagnall's Standard College Dictionary. Harcourt, Brace & World, New York, 1963, vii.
28. Mill, John Stuart. A System Of Logic, Ratiocinative and Inductive. London, 1843. The quotations are from the introduction, S 2, and from Book 6, Chap. 11 (12 in later editions), S 5.
29. Mueller, Robert E. The Science of Art. John Day, New York, 1967.
30. Parsons, Albert Ross. The Science of Pianoforte Practice. Schirmer, New York, 1886.
31. Pedoe, Daniel. The Gentle Art of Mathematics. English U. Press, London, 1953.
32. Ruskin, John. The Stones of Venice 3. London, 1853.
33. Salton, G.A. Personal communication, June 21, 1974.
34. Snow, C.P. The two cultures. The New Statesman and Nation 52 (Oct. 6, 1956), 413-414.
35. Snow, C.P. The Two Cultures: and a Second Look. Cambridge University Press, 1964.
Copyright 1974, Association for Computing Machinery, Inc. General permission to republish, but not for profit, all or part of this material is granted provided that ACM's copyright notice is given and that reference is made to the publication, to its date of issue, and to the fact that reprinting privileges were granted by permission of the Association for Computing Machinery.
[May 17, 2017] Who really gives a toss if it's agile or not
"... So why should the developers have all the fun? Why can't the designers and architects be "agile", too? Isn't constantly changing stuff all part of the "agile" way? ..."
May 17, 2017 | theregister.co.uk
Comment "It doesn't matter whether a cat is white or black, as long as it catches mice," according to Chinese revolutionary Deng Xiaoping.
While Deng wasn't referring to anything nearly as banal as IT projects (he was of course talking about the fact it doesn't matter whether a person is a revolutionary or not, as long as he or she is efficient and capable), the same principle could apply.
A fixation on the suppliers, technology or processes ultimately doesn't matter. It's the outcomes, stupid. That might seem like a blindingly obvious point, but it's one worth repeating.
Or as someone else put it to me recently in reference to the huge overspend on a key UK programme behind courts digitisation which we recently revealed: "Who gives a toss if it's agile or not? It just needs to work."
If you're going to do it do it right
I'm not dismissing the benefits of this particular methodology, but in the case of the Common Platform Programme , it feels like the misapplication of agile was worse than not doing it at all.
Just to recap: the CPP was signed off around 2013, with the intention of creating a unified platform across the criminal justice system to allow the Crown Prosecution Service and courts to more effectively manage cases.
By cutting out duplication of systems, it was hoped to save buckets of cash and make the process of case management across the criminal justice system far more efficient.
Unlike the old projects of the past, this was a great example of the government taking control and doing it themselves. Everything was going to be delivered ahead of time and under budget. Trebles all round!
But as Lucy Liu's O-Ren Ishii told Uma Thurman's character in in Kill Bill : "You didn't think it was gonna be that easy, did you?... Silly rabbit."
According to sources, alarm bells were soon raised over the project's self-styled "innovative use of agile development principles". It emerged that the programme was spending an awful lot of money for very little return. Attempts to shut it down were themselves shut down.
The programme carried on at full steam and by 2014 it was ramping up at scale. According to sources, hundreds of developers were employed on the programme at huge day rates, with large groups of so-called agile experts overseeing the various aspects of the programme.
CPP cops a plea
Four years since it was first signed off and what are the things we can point to from the CPP? An online make-a-plea programme which allows people to plead guilty or not guilty to traffic offences; a digital markup tool for legal advisors to record case results in court, which is being tested by magistrates courts in Essex; and the Magistrates Rota.
Multiple insiders have said the rest that we have to show for hundreds of millions of taxpayers' cash is essentially vapourware. When programme director Loveday Ryder described the project as a "once-in-a-lifetime opportunity" to modernise the criminal justice system, it wasn't clear then that she meant the programme would itself take an actual lifetime.
Of course the definition of agile is that you are able to move quickly and easily. So some might point to the outcomes of this programme as proof that it was never really about that.
One source remarked that it really doesn't matter if you call something agile or not, "If you can replace agile with constantly talking and communicating then fine, call it agile." He also added: "This was one of the most waterfall programmes in government I've seen."
What is most worrying about this programme is it may not be an isolated example. Other organisations and departments may well be doing similar things under the guise of "agile". I'm no expert in project management, but I'm pretty sure it isn't supposed to be making it up as you go along, and constantly changing the specs and architecture.
Ultimately who cares if a programme is run via a system integrator, multiple SMEs, uses a DevOps methodology, is built in-house or deployed using off-the-shelf, as long as it delivers good value. No doubt there are good reasons for using any of those approaches in a number of different circumstances.
Government still spends an outrageous amount of money on IT, upwards of £16bn a year. So as taxpayers it's a simple case of wanting them to "show me the money". Or to misquote Deng, at least show us some more dead mice. ®
Re: 'What's Real and What's for Sale'...
So agile means "constantly adapating " ? read constantly bouncing from one fuckup to the next , paddling like hell to keep up , constantly firefighting whilst going down slowly like the titanic?
Dogbowl
Re: 'What's Real and What's for Sale'...
Ha! About 21 years back, working at Racal in Bracknell on a military radio project, we had a 'round-trip-OMT' CASE tool that did just that. It even generated documentation from the code so as you added classes and methods the CASE tool generated the design document. Also, a nightly build if it failed, would email the code author.
I have also worked on agile for UK gov projects a few years back when it was mandated for all new projects and I was at first dead keen. However, it quickly become obvious that the lack of requirements, specifications etc made testing a living nightmare. Changes asked for by the customer were grafted onto what become baroque mass of code. I can't see how Agile is a good idea except for the smallest trivial projects.
PatientOne
Re: 'What's Real and What's for Sale'...
"Technically 'agile' just means you produce working versions frequently and iterate on that."
It's more to do with priorities: On time, on budget, to specification: Put these in the order of which you will surrender if the project hits problems.
Agile focuses on On time. What is delivered is hopefully to specification, and within budget, but one or both of those could be surrendered in order to get something out On time. It's just project management 101 with a catchy name, and in poorly managed 'agile' developments you find padding to fit the usual 60/30/10 rule. Then the management disgard the padding and insist the project can be completed in a reduced time as a result, thereby breaking the rules of 'agile' development (insisting it's on spec, under time and under budget, but it's still 'agile'...).
Doctor Syntax
Re: 'What's Real and What's for Sale'...
"Usually I check something(s) in every day, for the most major things it may take a week, but the goal is always to get it in and working so it can be tested."
The question is - is that for software that's still in development or software that's deployed in production? If it's the latter and your "something" just changes its data format you're going to be very unpopular with your users. And that's just for ordinary files. If it requires frequent re-orgs of an RDBMS then you'd be advised to not go near any dark alley where your DBA might be lurking.
Software works on data. If you can't get the design of that right early you're going to be carrying a lot of technical debt in terms of backward compatibility or you're going to impose serious costs on your users for repeatedly bringing existing data up to date.
Doctor Syntax
Re: 'What's Real and What's for Sale'...
"On time, on budget, to specification: Put these in the order of which you will surrender if the project hits problems."
In the real world it's more likely to be a trade-off of how much of each to surrender.
FozzyBear
Re: 'What's Real and What's for Sale'...
I was told in my earlier years by a Developer.
For any project you can have it
1. Cheap, (On Budget)
2. Good, (On spec)
3. Quick.( On time)
Pick two of the three and only two. It doesn't which way you pick, you're fucked on the third. Doesn't matter about methodology, doesn't matter about requirements or project manglement. You are screwed on the third and the great news is, is that the level of the reaming you get scales with the size of the project.
After almost 20 years in the industry this has held true.
Dagg
Re: 'What's Real and What's for Sale'...
Technically 'agile' just means you produce working versions frequently and iterate on that.
No, technically agile means having no clue as to what is required and to evolve the requirements as you build. All well and good if you have a dicky little web site but if you are on a very / extremely large project with fixed time frame and fixed budget you are royally screwed trying to use agile as there is no way you can control scope.
Hell under agile no one has any idea what the scope is!
Archtech
Re: Government still spends an outrageous amount of money on IT
I hope you were joking. If not, try reading the classic book "The Mythical Man-Month".
oldtaku
'Agile' means nothing at this point. Unless it means terrible software.
At this point, courtesy of Exxxxtr3333me Programming and its spawn, 'agile' just means 'we don't want to do any design, we don't want to do any documentation, and we don't want to do any acceptance testing because all that stuff is annoying.' Everything is 'agile', because that's the best case for terrible lazy programmers, even if they're using a completely different methodology.
I firmly believe in the basics of 'iterate working versions as often as possible'. But why sell ourselves short by calling it agile when we actually design it, document it, and use testing beyond unit tests?
Yes, yes, you can tell me what 'agile' technically means, and I know that design and documentation and QA are not excluded, but in practice even the most waterfall of waterfall call themselves agile (like Kat says), and from hard experience people who really push 'agile agile agile' as their thing are the worst of the worst terrible coders who just slam crap together with all the finesse and thoughtfulness of a Bangalore outsourcer.
It's like any exciting new methodology : same shit, different name. In this case, one that allows you to pretend the tiny attention-span of a panicking project manager is a good thing.
When someone shows me they've learned the lessons of Brooke's tarpit,. I'll be interested to see how they did it. Until then, it's all talk.
jamie m
25% Agile:
Our highest priority is to satisfy the customer through early and continuous delivery of valuable software.
Deliver working software frequently, from a couple of weeks to a couple of months, with a preference to the shorter timescale.
Working software is the primary measure of progress.
kmac499
Re: 25% Agile:
From Jamie M
Working software is the primary measure of progress.
Brilliant few word summary which should be scrawled on the wall of every IT project managers office in Foot High Letters.
I've lived through SSADM, RAD, DSDM, Waterfall, Bohm Spirals, Extreme Programming and probably a few others.
They are ALL variations on a theme. The only thing they have in common is the successful ones left a bunch of 0's and 1's humming away in a lump of silicon doing something useful.
Doctor Syntax
Re: 25% Agile:
"Working software is the primary measure of progress."
What about training the existing users, having it properly documented for the users of the future, briefing support staff, having proper software documentation, or at least self documenting code, for those who will have to maintain it and ensuring it doesn't disrupt the data from the previous release? Or do we just throw code over the fence and wave goodbye to it?
Charlie Clark
Re: Limits of pragmatism
In France "naviguer à vue" is pejorative.
Software development in France* which also gave us ah yes, it may work in practice but does it work in theory .
The story is about the highly unusual cost overrun of a government project. Never happened dans l'héxagone ? Because it seems to happy pretty much everywhere else with relentless monotony because politicians are fucking awful project managers.
* FWIW I have a French qualification.
Anonymous Coward
Agile only works if all stakeholders agree on an outcome
For a project that is a huge change of operating your organisation it is unlikely that you will be able to deliver, at least the initial parts of your project, in an agile way. Once outcomes are known at a high level stakeholders have something to cling onto when they are asked what they need, if indeed they exist yet. (trying to ask for requirements for a stakeholder that doesn't exist yet is tough).
Different methods have their own issues, but in this case I would have expected failure to be reasonably predictable.
You wont have much to show for it, as they shouldn't at least, have started coding to a business model that itself needs defining. This is predictable, and overall means that no one agrees what the business should look like, let alone how a vendor delivered software solution should support it.
I have a limited amount of sympathy for the provider for this as it will be beyond their control (limited as they are an expensive government provider after all)
This is a disaster caused by the poor management in UKGOV and the vendor should have dropped and ran well before this.
Anonymous Coward
I'm a one man, self employed business - I do some very complex sites - but if they don't work I don't get paid. If they spew ugly bugs I get paniced emails from unhappy clients.
So I test after each update and comment code and add features to make my life easy when it comes to debugging. Woo, it even send me emails for some bugs.
I'm in agreement with the guy above - a dozen devs, a page layout designer or two, some databases. One manager to co-ordinate and no bloody jargon.
There's a MASSIVE efficiency to small teams but all the members need to be on top of their game.
Doctor Syntax
"I'm in agreement with the guy above - a dozen devs, a page layout designer or two, some databases. One manager to co-ordinate and no bloody jargon."
Don't forget a well-defined, soluble problem. That's in your case, where you're paid by results. If you're paid by billable hours it's a positive disadvantage.
Munchausen's proxy
Agile Expertise?
" I'm no expert in project management, but I'm pretty sure it isn't supposed to be making it up as you go along, and constantly changing the specs and architecture."
I'm no expert either, but I honestly thought that was quite literally the definition of agile. (maybe disguised with bafflegab, but semantically equivalent)
Zippy's Sausage Factory
Sounds like what I have said for a while...
The "strategy boutiques" saw "agile" becoming popular and they now use it as a buzzword.
These days, I put it in my "considered harmful" bucket, along with GOTO, teaching people to program using BASIC, and "upgrading" to Office 2016*.
* Excel, in particular.
a_yank_lurker
Buzzword Bingo
All too often a sound development ideas are perverted. The concepts are sound but the mistake is to view each as the perfect panacea to produce bug free, working code. Each has its purpose and scope of effectiveness. What should be understood and applied is not a precise cookbook method but principles - Agile focuses communication between groups and ensuring all on the same page. Others focus more on low level development (test driven development, e.g.) but one can lose sight the goal is use an appropriate tool set to make sure quality code is produced. Again, is the code being tested, are the tests correct, are junior developers being mentored, are developers working together appropriately for the nature of the projects are issues to be addressed not the precise formalism of the insultants.
Uncle Bob Martin has noted that one of the problems the formalisms try to address is the large number of junior developers who need proper mentoring, training, etc. in real world situations. He noted that in the old days many IT pros were mid level professionals who wandered over to IT and many of the formalisms so beloved by the insultants were concepts they did naturally. Cross functional team meetings - check, mentor - check, use appropriate tests - check, etc. These are professional procedures common to other fields and were ingrained mindset and habits.
Doctor Syntax
It's worth remembering that it's the disasters that make the news. I've worked on a number of public sector projects which were successful. After a few years of operation, however, the contract period was up and the whole service put out to re-tender.* At that point someone else gets the contract so the original work on which the successful delivery was based got scrapped.
* With some very odd results, it has to be said, but that's a different story.
goldcd
...My personal niggle is that a team has "velocity" rather than "speed" - and that seems to be a somewhat deliberate and disingenuous selection. The team should have speed, the project ultimately a measurable velocity calculated by working out how much of the speed was wasted in the wrong/right direction.
Anyway, off to get my beauty sleep, so I can feed the backlog tomorrow with anything within my reach.
Re: I like agile
Wanted to give you an up-vote as "velocity" vs. "speed" is exactly the sleight of hand that infuriates me. We do want eventual progress achieved, as in "distance towards goal in mind", right?
Unfortunately my reading the definitions and checking around leads me to think that you've got the words 'speed' and 'velocity' reversed above. Where's that nit-picker's icon....
bfwebster
I literally less than an hour ago gave my CS 428 ("Software Engineering") class here at Brigham Young University (Provo, Utah, USA) my final lecture for the semester, which included this slide:
Process is not a panacea or a crutch or a silver bullet. Methodologies only work as well as the people using it. Any methodology can be distorted to give the answer that upper management wants (instead of reality)
• Do one or two pilot projects
• Do one non-critical real-world project
• Then, and only then, consider using it for a critical project
Understand the strengths and weaknesses of a given methodology before starting a project with it. Also, make sure a majority of team members have successfully completed a real-world project using that methodology.
Pete 2
Save some fun for us!
> under the guise of " agile ?". I'm no expert in project management, but I'm pretty sure it isn't supposed to be making it up as you go along, and constantly changing the specs and architecture.
So why should the developers have all the fun? Why can't the designers and architects be "agile", too? Isn't constantly changing stuff all part of the "agile" way?
[May 05, 2017] William Binney - The Government is Profiling You (The NSA is Spying on You)
"... Just not be productive and work the system and not listen to their crap. this is all that was required to bring them down. watching people, arresting does not do shit for their cause ..."
"People who believe in these rights very much are forced into compromising their integrity"
I suspect that it's hopelessly unlikely for honest people to complete the Police Academy; somewhere early on the good cops are weeded out and cannot complete training unless they compromise their integrity.
Agent76 1 year ago (edited)
January 9, 2014
500 Years of History Shows that Mass Spying Is Always Aimed at Crushing Dissent It's Never to Protect Us From Bad Guys No matter which government conducts mass surveillance, they also do it to crush dissent, and then give a false rationale for why they're doing it.
Homa Monfared 7 months ago
I am wondering how much damage your spying did to the Foreign Countries, I am wondering how you changed regimes around the world, how many refugees you helped to create around the world.
Don Kantner, 2 weeks ago
People are so worried about NSA don't be fooled that private companies are doing the same thing. Plus, the truth is if the NSA wasn't watching any fool with a computer could potentially cause an worldwide economic crisis.
Bettor in Vegas 1 year ago
In communism the people learned quick they were being watched. The reaction was not to go to protest.
Just not be productive and work the system and not listen to their crap. this is all that was required to bring them down. watching people, arresting does not do shit for their cause......
[Apr 18, 2017] Learning to Love Intelligent Machines
"... Learning to Love Intelligent Machines ..."
Apr 18, 2017 | www.nakedcapitalism.com
MoiAussie , April 17, 2017 at 9:04 am
If anyone is struggling to access Learning to Love Intelligent Machines (WSJ), you can get to it by clicking though this post . YMMV.
MyLessThanPrimeBeef , April 17, 2017 at 11:26 am
Also, don't forget to Learn from your Love Machines.
Artificial Love + Artificial Intelligence = Artificial Utopia.
[Apr 17, 2017] How many articles have I read that state as fact that the problem is REALLY automation?
"... As the rich became uber rich, they hid the money in tax havens. As for globalization, this has less to do these days with technological innovation and more to do with economic exploitation. ..."
Apr 17, 2017 | www.nakedcapitalism.com
Carla , April 17, 2017 at 9:25 am
"how many articles have I read that state as fact that the problem is REALLY automation?
NO, the real problem is that the plutocrats control the policies "
+1
justanotherprogressive , April 17, 2017 at 11:45 am
+100 to your comment. There is a decided attempt by the plutocrats to get us to focus our anger on automation and not the people, like they themselves, who control the automation ..
MoiAussie , April 17, 2017 at 12:10 pm
Plutocrats control much automation, but so do thousands of wannabe plutocrats whose expertise lets them come from nowhere to billionairehood in a few short years by using it to create some novel, disruptive parasitic intermediation that makes their fortune. The "sharing economy" relies on automation. As does Amazon, Snapchat, Facebook, Dropbox, Pinterest,
It's not a stretch to say that automation creates new plutocrats . So blame the individuals, or blame the phenomenon, or both, whatever works for you.
Carolinian , April 17, 2017 at 12:23 pm
So John D. Rockefeller and Andrew Carnegie weren't plutocrats–or were somehow better plutocrats?
Blame not individuals or phenomena but society and the public and elites who shape it. Our social structure is also a kind of machine and perhaps the most imperfectly designed of all of them. My own view is that the people who fear machines are the people who don't like or understand machines. Tools, and the use of them, are an essential part of being human.
MoiAussie , April 17, 2017 at 9:21 pm
Huh? If I wrote "careless campers create forest fires", would you actually think I meant "careless campers create all forest fires"?
Carolinian , April 17, 2017 at 10:23 pm
I'm replying to your upthread comment which seems to say today's careless campers and the technology they rely on are somehow different from those other figures we know so well from history. In fact all technology is tremendously disruptive but somehow things have a way of sorting themselves out. So–just to repeat–the thing is not to "blame" the individuals or the automation but to get to work on the sorting. People like Jeff Bezos with his very flaky business model could be little more than a blip.
a different chris , April 17, 2017 at 12:24 pm
Automation? Those companies? I guess Amazon automates ordering not exactly R. Daneel Olivaw for sure. If some poor Asian girl doesn't make the boots or some Agri giant doesn't make the flour Amazon isn't sending you nothin', and the other companies are even more useless.
Mark P. , April 17, 2017 at 2:45 pm
'Automation? Those companies? I guess Amazon automates ordering not exactly R. Daneel Olivaw for sure.'
Um. Amazon is highly deceptive, in that most people think it's a giant online retail store.
It isn't. It's the world's biggest, most advanced cloud-computing company with an online retail storefront stuck between you and it. In 2005-2006 it was already selling supercomputing capability for cents on the dollar - way ahead of Google and Microsoft and IBM.
justanotherprogressive , April 17, 2017 at 12:32 pm
Do you really think the internet created Amazon, Snapchat, Facebook, etc? No, the internet was just a tool to be used. The people who created those businesses would have used any tool they had access to at the time because their original goal was not automation or innovation, it was only to get rich.
Let me remind you of Thomas Edison. If he would have lived 100 years later, he would have used computers instead of electricity to make his fortune. (In contrast, Nikolai Tesla/George Westinghouse used electricity to be innovative, NOT to get rich ). It isn't the tool that is used, it is the mindset of the people who use the tool
clinical wasteman , April 17, 2017 at 2:30 pm
"Disruptive parasitic intermediation" is superb, thanks. The entire phrase should appear automatically whenever "disruption"/"disruptive" or "innovation"/"innovative" is used in a laudatory sense.
100% agreement with your first point in this thread, too. That short comment should stand as a sort of epigraph/reference for all future discussion of these things.
No disagreement on the point about actual and wannabe plutocrats either, but perhaps it's worth emphasising that it's not just a matter of a few successful (and many failed) personal get-rich-quick schemes, real as those are: the potential of 'universal machines' tends to be released in the form of parasitic intermediation because, for the time being at least, it's released into a world subject to the 'demands' of capital, and at a (decades-long) moment of crisis for the traditional model of capital accumulation. 'Universal' potential is set free to seek rents and maybe to do a bit of police work on the side, if the two can even be separated.
The writer of this article from 2010 [ http://www.metamute.org/editorial/articles/artificial-scarcity-world-overproduction-escape-isnt ] surely wouldn't want it to be taken as conclusive, but it's a good example of one marginal train of serious thought about all of the above. See also 'On Africa and Self-Reproducing Automata' written by George Caffentzis 20 years or so earlier [https://libcom.org/library/george-caffentzis-letters-blood-fire]; apologies for link to entire (free, downloadable) book, but my crumbling print copy of the single essay stubbornly resists uploading.
DH , April 17, 2017 at 9:48 am
Unfortunately, the healthcare insurance debate has been simply a battle between competing ideologies. I don't think Americans understand the key role that universal healthcare coverage plays in creating resilient economies.
Before penicillin, heart surgeries, cancer cures, modern obstetrics etc. that it didn't matter if you are rich or poor if you got sick. There was a good chance you would die in either case which was a key reason that the average life span was short.
In the mid-20th century that began to change so now lifespan is as much about income as anything else. It is well known that people have a much bigger aversion to loss than gain. So if you currently have healthcare insurance through a job, then you don't want to lose it by taking a risk to do something where you are no longer covered.
People are moving less to find work – why would you uproot your family to work for a company that is just as likely to lay you off in two years in a place you have no roots? People are less likely to day to quit jobs to start a new business – that is a big gamble today because you not only have to keep the roof over your head and put food on the table, but you also have to cover an even bigger cost of healthcare insurance in the individual market or you have a much greater risk of not making it to your 65th birthday.
In countries like Canada, healthcare coverage is barely a discussion point if somebody is looking to move, change jobs, or start a small business.
If I had a choice today between universal basic income vs universal healthcare coverage, I would choose the healthcare coverage form a societal standpoint. That is simply insuring a risk and can allow people much greater freedom during the working lives. Similarly, Social Security is of similar importance because it provides basic protection against disability and not starving in the cold in your old age. These are vastly different incentive systems than paying people money to live on even if they are not working.
Our ideological debates should be factoring these types of ideas in the discussion instead of just being a food fight.
a different chris , April 17, 2017 at 12:28 pm
>that people have a much bigger aversion to loss than gain.
Yeah well if the downside is that you're dead this starts to make sense.
>instead of just being a food fight.
The thing is that the Powers-That-Be want it to be a food fight, as that is a great stalling at worst and complete diversion at best tactic. Good post, btw.
Altandmain , April 17, 2017 at 12:36 pm
As the rich became uber rich, they hid the money in tax havens. As for globalization, this has less to do these days with technological innovation and more to do with economic exploitation.
I will note that Germany, Japan, South Korea, and a few other nations have not bought into this madness and have retained a good chunk of their manufacturing sectors.
Mark P. , April 17, 2017 at 3:26 pm
'As for globalization, this has less to do these days with technological innovation and more to do with economic exploitation.'
Economic exploiters are always with us. You're underrating the role of a specific technological innovation. Globalization as we now know it really became feasible in the late 1980s with the spread of instant global electronic networks, mostly via the fiberoptic cables through which everything - telephony, Internet, etc - travels Internet packet mode.
That's the point at which capital could really start moving instantly around the world, and companies could really begin to run global supply chains and workforces. That's the point when shifts of workers in facilities in Bangalore or Beijing could start their workdays as shifts of workers in the U.S. were ending theirs, and companies could outsource and offshore their whole operations.
[Apr 15, 2017] IMF claims that technology and global integration explain close to 75 percent of the decline in labor shares in Germany and Italy, and close to 50 percent in the United States.
Anything that IMF claim should be taken with a grain of salt. IMF is a quintessential neoliberal institutions that will support neoliberalism to the bitter end.
https://blogs.imf.org/2017/04/12/drivers-of-declining-labor-share-of-income/
"In advanced economies, about half of the decline in labor shares can be traced to the impact of technology."
Searching, searching for the policy variable in the regression.
anne -> point... , April 14, 2017 at 08:09 AM
https://blogs.imf.org/2017/04/12/drivers-of-declining-labor-share-of-income/
April 12, 2017
Drivers of Declining Labor Share of Income
By Mai Chi Dao, Mitali Das, Zsoka Koczan, and Weicheng Lian
Technology: a key driver in advanced economies
In advanced economies, about half of the decline in labor shares can be traced to the impact of technology. The decline was driven by a combination of rapid progress in information and telecommunication technology, and a high share of occupations that could be easily be automated.
Global integration-as captured by trends in final goods trade, participation in global value chains, and foreign direct investment-also played a role. Its contribution is estimated at about half that of technology. Because participation in global value chains typically implies offshoring of labor-intensive tasks, the effect of integration is to lower labor shares in tradable sectors.
Admittedly, it is difficult to cleanly separate the impact of technology from global integration, or from policies and reforms. Yet the results for advanced economies is compelling. Taken together, technology and global integration explain close to 75 percent of the decline in labor shares in Germany and Italy, and close to 50 percent in the United States.
paine -> anne... , April 14, 2017 at 08:49 AM
Again this is about changing the wage structure
Total hours is macro management. Mobilizing potential job hours to the max is undaunted by technical progress
Recall industrial jobs required unions to become well paid
We need a CIO for services logistics and commerce
[Apr 14, 2017] Automation as a way to depress wages
point , April 14, 2017 at 04:59 AM
Brad said: Few things can turn a perceived threat into a graspable opportunity like a high-pressure economy with a tight job market and rising wages. Few things can turn a real opportunity into a phantom threat like a low-pressure economy, where jobs are scarce and wage stagnant because of the failure of macro economic policy.
What is it that prevents a statement like this from succeeding at the level of policy?
Peter K. -> point... , April 14, 2017 at 06:41 AM
class war
center-left economists like DeLong and Krugman going with neoliberal Hillary rather than Sanders.
Sanders supports that statement, Hillary did not. Obama did not.
PGL spent the primary unfairly attacking Sanders and the "Bernie Bros" on behalf of the center-left.
[Apr 07, 2017] No it was policy driven by politics. They increased profits at the expense of workers and the middle class. The New Democrats played along with Wall Street.
ken melvin -> DrDick ... , April 06, 2017 at 08:45 AM
Probably automated 200. In every case, displacing 3/4 of the workers and increasing production 40% while greatly improving quality. Exact same can be said for larger scaled such as automobile mfg, ...
The convergence of offshoring and automation in such a short time frame meant that instead of a gradual transformation that might have allowed for more evolutionary economic thinking, American workers got gobsmacked. The aftermath includes the wage disparity, opiate epidemic, Trump, ...
This transition is of the scale of the industrial revolution with climate change thrown. This is just the beginning of great social and economic turmoil. None of the stuff that evolved specific the industrial revolution applies.
Peter K. -> ken melvin... , April 06, 2017 at 09:01 AM
No it was policy driven by politics. They increased profits at the expense of workers and the middle class. The New Democrats played along with Wall Street.
libezkova -> ken melvin... , April 06, 2017 at 05:43 PM
"while greatly improving quality" -- that's not given.
[Apr 06, 2017] Germany and Japan have retained a larger share of workers in manufacturing, despite more automation
Peter K. -> EMichael... , April 06, 2017 at 09:18 AM
What do you make of the DeLong link? Why do you avoid discussing it?
"...
The lesson from history is not that the robots should be stopped; it is that we will need to confront the social-engineering and political problem of maintaining a fair balance of relative incomes across society. Toward that end, our task becomes threefold.
First, we need to make sure that governments carry out their proper macroeconomic role, by maintaining a stable, low-unemployment economy so that markets can function properly. Second, we need to redistribute wealth to maintain a proper distribution of income. Our market economy should promote, rather than undermine, societal goals that correspond to our values and morals. Finally, workers must be educated and trained to use increasingly high-tech tools (especially in labor-intensive industries), so that they can make useful things for which there is still demand.
Sounding the alarm about "artificial intelligence taking American jobs" does nothing to bring such policies about. Mnuchin is right: the rise of the robots should not be on a treasury secretary's radar."
DrDick -> EMichael... , April 06, 2017 at 08:43 AM
Except that Germany and Japan have retained a larger share of workers in manufacturing, despite more automation. Germany has also retained much more of its manufacturing base than the US has. The evidence really does point to the role of outsourcing in the US compared with others.
http://www.economist.com/node/21552567
http://www.economist.com/node/2571689
pgl -> DrDick ... , April 06, 2017 at 08:54 AM
I got an email of some tale that Adidas would start manufacturing in Germany as opposed to China. Not with German workers but with robots. The author claimed the robots would cost only $5.50 per hour as opposed to$11 an hour for the Chinese workers. Of course Chinese apparel workers do not get anywhere close to $11 an hour and the author was not exactly a credible source. pgl -> pgl... , April 06, 2017 at 08:57 AM Reuters is a more credible source: Pilot program making initially 500 pairs of shoes in the first year. No claims as the wage rate of Chinese workers. libezkova said in reply to pgl... , April 06, 2017 at 05:41 PM "The new "Speedfactory" in the southern town of Ansbach near its Bavarian headquarters will start production in the first half of 2016 of a robot-made running shoe that combines a machine-knitted upper and springy "Boost" sole made from a bubble-filled polyurethane foam developed by BASF." Interesting. I thought that "keds" production was already fully automated. Bright colors are probably the main attraction. But Adidas commands premium price... Machine-knitted upper is the key -- robots, even sophisticated one, put additional demands on precision of the parts to be assembled. That's also probably why monolithic molded sole is chosen. Kind of 3-D printing of shoes. Robots do not "feel" the nuances of the technological process like humans do. kurt -> pgl... , April 06, 2017 at 09:40 AM While I agree that Chinese workers don't get$11 - frequently employee costs are accounted at a loaded rate (including all benefits - in China would include capital cost of dormitories, food, security staff, benefits and taxes). I am guessing that a $2-3 an hour wage would result in an$11 fully loaded rate under those circumstances. Those other costs are not required with robuts.
Peter K. -> DrDick ... , April 06, 2017 at 08:59 AM
I agree with you. The center-left want to exculpate globalization and outsourcing, or free them from blame, by providing another explanation: technology and robots. They're not just arguing with Trump.
"I suspect the politics around trade would be a bit different in the U.S. if the goods-exporting sector had grown in parallel with imports.
That is one key difference between the U.S. and Germany. Manufacturing jobs fell during reunification-and Germany went through a difficult adjustment in the early 2000s. But over the last ten years the number of jobs in Germany's export sector grew, keeping the number of people employed in manufacturing roughly constant over the last ten years even with rising productivity. Part of the "trade" adjustment was a shift from import-competing to exporting sectors, not just a shift out of the goods producing tradables sector. Of course, not everyone can run a German sized surplus in manufactures-but it seems likely the low U.S. share of manufacturing employment (relative to Germany and Japan) is in part a function of the size and persistence of the U.S. trade deficit in manufactures. (It is also in part a function of the fact that the U.S. no longer needs to trade manufactures for imported energy on any significant scale; the U.S. has more jobs in oil and gas production, for example, than Germany or Japan)."
anne -> DrDick ... , April 06, 2017 at 10:01 AM
https://fred.stlouisfed.org/graph/?g=dgSQ
January 15, 2017
Percent of Employment in Manufacturing for United States, Germany and Japan, 1970-2012
January 15, 2017
Percent of Employment in Manufacturing for United States, Germany and Japan, 1970-2012
(Indexed to 1970)
ken melvin -> DrDick ... , April 06, 2017 at 08:45 AM
Probably automated 200. In every case, displacing 3/4 of the workers and increasing production 40% while greatly improving quality. Exact same can be said for larger scaled such as automobile mfg, ...
The convergence of offshoring and automation in such a short time frame meant that instead of a gradual transformation that might have allowed for more evolutionary economic thinking, American workers got gobsmacked. The aftermath includes the wage disparity, opiate epidemic, Trump, ...
This transition is of the scale of the industrial revolution with climate change thrown. This is just the beginning of great social and economic turmoil. None of the stuff that evolved specific the industrial revolution applies.
Peter K. -> ken melvin... , April 06, 2017 at 09:01 AM
No it was policy driven by politics. They increased profits at the expense of workers and the middle class. The New Democrats played along with Wall Street.
[Apr 06, 2017] The impact of information technology on employment is undoubtedly a major issue, but it is also not in society's interest to discourage investment in high-tech companies.
Peter K. , April 05, 2017 at 01:55 PM
Interesting, thought-provoking discussion by DeLong:
APR 3, 2017
Artificial Intelligence and Artificial Problems
BERKELEY – Former US Treasury Secretary Larry Summers recently took exception to current US Treasury Secretary Steve Mnuchin's views on "artificial intelligence" (AI) and related topics. The difference between the two seems to be, more than anything else, a matter of priorities and emphasis.
Mnuchin takes a narrow approach. He thinks that the problem of particular technologies called "artificial intelligence taking over American jobs" lies "far in the future." And he seems to question the high stock-market valuations for "unicorns" – companies valued at or above \$1 billion that have no record of producing revenues that would justify their supposed worth and no clear plan to do so.
Summers takes a broader view. He looks at the "impact of technology on jobs" generally, and considers the stock-market valuation for highly profitable technology companies such as Google and Apple to be more than fair.
I think that Summers is right about the optics of Mnuchin's statements. A US treasury secretary should not answer questions narrowly, because people will extrapolate broader conclusions even from limited answers. The impact of information technology on employment is undoubtedly a major issue, but it is also not in society's interest to discourage investment in high-tech companies.
On the other hand, I sympathize with Mnuchin's effort to warn non-experts against routinely investing in castles in the sky. Although great technologies are worth the investment from a societal point of view, it is not so easy for a company to achieve sustained profitability. Presumably, a treasury secretary already has enough on his plate to have to worry about the rise of the machines.
In fact, it is profoundly unhelpful to stoke fears about robots, and to frame the issue as "artificial intelligence taking American jobs." There are far more constructive areas for policymakers to direct their focus. If the government is properly fulfilling its duty to prevent a demand-shortfall depression, technological progress in a market economy need not impoverish unskilled workers.
This is especially true when value is derived from the work of human hands, or the work of things that human hands have made, rather than from scarce natural resources, as in the Middle Ages. Karl Marx was one of the smartest and most dedicated theorists on this topic, and even he could not consistently show that technological progress necessarily impoverishes unskilled workers.
Technological innovations make whatever is produced primarily by machines more useful, albeit with relatively fewer contributions from unskilled labor. But that by itself does not impoverish anyone. To do that, technological advances also have to make whatever is produced primarily by unskilled workers less useful. But this is rarely the case, because there is nothing keeping the relatively cheap machines used by unskilled workers in labor-intensive occupations from becoming more powerful. With more advanced tools, these workers can then produce more useful things.
Historically, there are relatively few cases in which technological progress, occurring within the context of a market economy, has directly impoverished unskilled workers. In these instances, machines caused the value of a good that was produced in a labor-intensive sector to fall sharply, by increasing the production of that good so much as to satisfy all potential consumers.
The canonical example of this phenomenon is textiles in eighteenth- and nineteenth-century India and Britain. New machines made the exact same products that handloom weavers had been making, but they did so on a massive scale. Owing to limited demand, consumers were no longer willing to pay for what handloom weavers were producing. The value of wares produced by this form of unskilled labor plummeted, but the prices of commodities that unskilled laborers bought did not.
The lesson from history is not that the robots should be stopped; it is that we will need to confront the social-engineering and political problem of maintaining a fair balance of relative incomes across society. Toward that end, our task becomes threefold.
First, we need to make sure that governments carry out their proper macroeconomic role, by maintaining a stable, low-unemployment economy so that markets can function properly. Second, we need to redistribute wealth to maintain a proper distribution of income. Our market economy should promote, rather than undermine, societal goals that correspond to our values and morals. Finally, workers must be educated and trained to use increasingly high-tech tools (especially in labor-intensive industries), so that they can make useful things for which there is still demand.
Sounding the alarm about "artificial intelligence taking American jobs" does nothing to bring such policies about. Mnuchin is right: the rise of the robots should not be on a treasury secretary's radar.
anne , April 05, 2017 at 03:14 PM
https://minneapolisfed.org/research/wp/wp736.pdf
January, 2017
The Global Rise of Corporate Saving
By Peter Chen, Loukas Karabarbounis, and Brent Neiman
Abstract
The sectoral composition of global saving changed dramatically during the last three decades. Whereas in the early 1980s most of global investment was funded by household saving, nowadays nearly two-thirds of global investment is funded by corporate saving. This shift in the sectoral composition of saving was not accompanied by changes in the sectoral composition of investment, implying an improvement in the corporate net lending position. We characterize the behavior of corporate saving using both national income accounts and firm-level data and clarify its relationship with the global decline in labor share, the accumulation of corporate cash stocks, and the greater propensity for equity buybacks. We develop a general equilibrium model with product and capital market imperfections to explore quantitatively the determination of the flow of funds across sectors. Changes including declines in the real interest rate, the price of investment, and corporate income taxes generate increases in corporate profits and shifts in the supply of sectoral saving that are of similar magnitude to those observed in the data.
anne -> anne... , April 05, 2017 at 03:17 PM
http://www.nytimes.com/2010/07/06/opinion/06smith.html
July 6, 2010
Are Profits Hurting Capitalism?
By YVES SMITH and ROB PARENTEAU
A STREAM of disheartening economic news last week, including flagging consumer confidence and meager private-sector job growth, is leading experts to worry that the recession is coming back. At the same time, many policymakers, particularly in Europe, are slashing government budgets in an effort to lower debt levels and thereby restore investor confidence, reduce interest rates and promote
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Lemma 97.13.3. Let $S$ be a locally Noetherian scheme. Let $\mathcal{X}$ be a category fibred in groupoids over $(\mathit{Sch}/S)_{fppf}$. Let $U$ be a scheme locally of finite type over $S$. Let $x$ be an object of $\mathcal{X}$ over $U$. Assume that $x$ is versal at every finite type point of $U$ and that $\mathcal{X}$ satisfies (RS). Then $x : (\mathit{Sch}/U)_{fppf} \to \mathcal{X}$ satisfies (97.13.2.1).
Proof. Let $\mathop{\mathrm{Spec}}(l) \to U$ be a morphism with $l$ of finite type over $S$. Then the image $u_0 \in U$ is a finite type point of $U$ and $l/\kappa (u_0)$ is a finite extension, see discussion in Morphisms, Section 29.16. Hence we see that $\mathcal{F}_{(\mathit{Sch}/U)_{fppf}, l, u_{l, 0}} \to \mathcal{F}_{\mathcal{X}, l, x_{l, 0}}$ is smooth by Lemma 97.12.5. $\square$
In your comment you can use Markdown and LaTeX style mathematics (enclose it like $\pi$). A preview option is available if you wish to see how it works out (just click on the eye in the toolbar).
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## Cryptology ePrint Archive: Report 2001/105
Universal Arguments and their Applications
Boaz Barak and Oded Goldreich
Abstract: We put forward a new type of computationally-sound proof systems, called universal-arguments, which are related but different from both CS-proofs (as defined by Micali) and arguments (as defined by Brassard, Chaum and Crepeau). In particular, we adopt the instance-based prover-efficiency paradigm of CS-proofs, but follow the computational-soundness condition of argument systems (i.e., we consider only cheating strategies that are implementable by polynomial-size circuits).
We show that universal-arguments can be constructed based on standard intractability assumptions that refer to polynomial-size circuits (rather than assumptions referring to subexponential-size circuits as used in the construction of CS-proofs). As an application of universal-arguments, we weaken the intractability assumptions used in the recent non-black-box zero-knowledge arguments of Barak. Specifically, we only utilize intractability assumptions that refer to polynomial-size circuits (rather than assumptions referring to circuits of some nice'' super-polynomial size).
Category / Keywords: foundations / Probabilistic proof systems, computationally-sound proof systems,
Publication Info: Posted also on ECCC.
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# Welcome plugin¶
New in version v2.2.25.
Call a script when the user logs in for the first time. This is specifically done when the INBOX is (auto)created. The scripts are called similarly to quota warning scripts.
plugin {
welcome_script = welcome %u
# By default we run the script asynchronously, but with this option we
# wait for the script to finish.
#welcome_wait = yes
}
service welcome {
executable = script /usr/local/bin/welcome.sh
user = dovecot
unix_listener welcome {
user = vmail
}
}
mail_plugins = \$mail_plugins welcome
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# nLab Bertrand Toën
Bertrand Toën is a mathematician at Université Paul Sabatier in Toulouse.
Together with Gabriele Vezzosi, Bertrand Toën has laid foundations of what is now called derived geometry.
(The picture shows Vezzosi on the left and Toën on the right during a research in pairs stay at Oberwolfach in 2002).
# Related $n$Lab entries
category: people
Last revised on January 11, 2015 at 13:50:24. See the history of this page for a list of all contributions to it.
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# Rate me tbh idek I’m bored and I finished all my homework. So yea here’s free points!!❤️
Rate me tbh idek I’m bored and I finished all my homework. So yea here’s free points!!❤️
$Rate me tbh idek I’m bored and I finished all my homework. So yea here’s free points!!❤️$
## This Post Has 10 Comments
1. cheyennerondeau says:
I’m not a among us genius but probably d? 😉
2. Jennifer2005 says:
7/10
Explanation:
3. Naysa150724 says:
B
This is why its the answer!
4. KAITLYN007 says:
Explanation:
the reason its D is because it talks about how he needed a distraction and how he hoped going to volunteer might make him forgot and feel better about getting rejected, i also took the test so i know this is the answer
5. kayleebueno says:
A
Explanation:
That is the impression given from the introduction
6. jfarrar02 says:
I dont know if this is the answer you were looking for but... Everyone in life has a purpose you just have to find it. Find what makes you happy or something you enjoy doing and try making a career out of it. Thats the best thing you can do on life is something that makes you happy.
7. tangia says:
5/10
Explanation:
8. 592400014353 says:
The highlighted parts are the part that you don't black out , hope it helps.
$Me make my blackout poem? here’s the text: one day when idek was venting his fury, i happened to c$
$Me make my blackout poem? here’s the text: one day when idek was venting his fury, i happened to c$
9. Suphat says:
I would rate it 9/10
Explanation:
Itś acutally pretty good so yeah, but maybe at the end you would probably need to end it better
10. veronicatrejoaguiler says:
nice i rate it 7.62x39 nato
Explanation:
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axiom-developer
[Top][All Lists]
## [Axiom-developer] [DistributedMultivariatePolynomial] (new)
From: hemmecke Subject: [Axiom-developer] [DistributedMultivariatePolynomial] (new) Date: Tue, 21 Feb 2006 04:56:30 -0600
Changes http://wiki.axiom-developer.org/DistributedMultivariatePolynomial/diff
--
The use of
\begin{axiom}
R := Expression Integer
\end{axiom}
as the coefficient domain in
\begin{axiom}
P := DistributedMultivariatePolynomial([x,y], R)
\end{axiom}
might lead to unexpected results due to the fact that the domain $R$ can
contain arbitrary expressions (including the variable $x$).
Take for example.
\begin{axiom}
a: P := x
b: P := a/x
\end{axiom}
Although it might seem strange that the result is not equal to 1,
Axiom behaved perfectly the way you told it to.
If the interperter sees $a/x$, it knows the type of $a$ but not yet for $x$. So
it looks for a function it can apply.
It finds that if x is coerced to $R$ (Expression Integer) than there is a
function in $P$, namely::
if R has Field then
(p : %) / (r : R) == inv(r) * p
By the way, in Axiom Expression Integer is considered to be a Field.
\begin{axiom}
R has Field
\end{axiom}
Thus $x$ is inverted (and now lies in $R$) and then multiplied with $a$.
There is no further simplification done.
The problematic thing is if the above expression ($a/x$) is not treated
carefully enough.
For example, by construction it should by now be clear that it has degree 1.
\begin{axiom}
degree b
\end{axiom}
And it should also be clear that the following two expressions result in
different output.
They are even stored differently in the internal structure of $P$.
\begin{axiom}
x*b
(x::R)*b
\end{axiom}
For the first expression, $x$ is converted to the indeterminate $x$ of the
polynomial ring $P$.
The interpreter finds an appropriate function::
*: (%, %) -> %
and applies it.
In the second case, it is explicitly said that $x$ has to be considered as an
element of $R$.
The interpreter finds the function with a more appropriate signature, namely::
*: (R, %) -> %
Be careful with something like that.
\begin{axiom}
d: P := x + (x::R)*1
\end{axiom}
>From the above discussion it should be clear that this expression is that what
>Axiom was told to do.
Now, a polynomial in $n$ variables is a function (with finite support)
from the domain of exponents $E=N^n$ (where $N$ is the non-negative integers)
to the domain $R$ of coefficients.
$$P = \bigoplus_{e \in E} R$$
With such an interpretation, $d$ has support
(i.e. the set of elements $e \in E$ for which the coefficient of $d$
corresponding to $e$ is non-zero)
$$\{ (1,0), (0,0) \}$$
and is therefore **not** equal to the polynomial $2x$ which has support
$$\{ (1,0) \}.$$
I Axiom is asked to convert $d$ to an arbitrary expression (Expression Integer),
it will convert both summands of $d$ to $R$ and as such they are, of course,
equal.
\begin{axiom}
d::R
\end{axiom}
--
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Linux
## My problem
My machine was off by two hours after a restart even though /etc/timezone pointed to the correct timezone.
A temporary solution was to execute the following command in bash:
sudo date -s "\$(wget -qSO- --max-redirect=0 google.com 2>&1 | grep Date: | cut -d' ' -f5-8)Z"
I solved it by installing htpdate and setting my time this way. If you are interacting with a Windows Domain are doing other authentication based on time you are way better off using the network time protocol, unfortunately this is not available in my case.
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# FAQ: What is the optimal reaction temperature for HiFi Taq DNA Ligase?
HiFi Taq DNA Ligase is active over a range of temperatures (35-75°C) with greatly increased activity at higher temperature up to the Tm of the probe oligonucleotides used. Typical ligations can be performed at 60°C. Ideally the reaction temperature should be chosen based on the Tm of the probes used, within a few degrees of the Tm of the probes used as calculated at the conditions of the buffer (10 mM MgCl2, 150 mM KCl) and the probe concentrations used. The optimal reaction temperature for a given application must be determined empirically.
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Now showing items 1-1 of 1
• #### Measurement of the Cross-Section for W Boson Production in Association with b-Jets in Proton-Proton Collisions at $\sqrt s = 7$ TeV at the LHC using the ATLAS detector
(2013-08-21)
This dissertation presents a measurement of the W+b-jets $(pp → W + b(\bar{b}) + X)$ production cross-section in proton–proton collisions at a center-of-mass energy of 7 TeV at the LHC. The results are based on data ...
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Outlook: MONT ROYAL RESOURCES LIMITED is assigned short-term Ba1 & long-term Ba1 estimated rating.
Dominant Strategy : Hold
Time series to forecast n: 03 Feb 2023 for (n+3 month)
Methodology : Modular Neural Network (Market News Sentiment Analysis)
## Abstract
MONT ROYAL RESOURCES LIMITED prediction model is evaluated with Modular Neural Network (Market News Sentiment Analysis) and Independent T-Test1,2,3,4 and it is concluded that the MRZ stock is predictable in the short/long term. According to price forecasts for (n+3 month) period, the dominant strategy among neural network is: Hold
## Key Points
1. How do you know when a stock will go up or down?
2. Can we predict stock market using machine learning?
3. Can neural networks predict stock market?
## MRZ Target Price Prediction Modeling Methodology
We consider MONT ROYAL RESOURCES LIMITED Decision Process with Modular Neural Network (Market News Sentiment Analysis) where A is the set of discrete actions of MRZ stock holders, F is the set of discrete states, P : S × F × S → R is the transition probability distribution, R : S × F → R is the reaction function, and γ ∈ [0, 1] is a move factor for expectation.1,2,3,4
F(Independent T-Test)5,6,7= $\begin{array}{cccc}{p}_{a1}& {p}_{a2}& \dots & {p}_{1n}\\ & ⋮\\ {p}_{j1}& {p}_{j2}& \dots & {p}_{jn}\\ & ⋮\\ {p}_{k1}& {p}_{k2}& \dots & {p}_{kn}\\ & ⋮\\ {p}_{n1}& {p}_{n2}& \dots & {p}_{nn}\end{array}$ X R(Modular Neural Network (Market News Sentiment Analysis)) X S(n):→ (n+3 month) $\begin{array}{l}\int {e}^{x}\mathrm{rx}\end{array}$
n:Time series to forecast
p:Price signals of MRZ stock
j:Nash equilibria (Neural Network)
k:Dominated move
a:Best response for target price
For further technical information as per how our model work we invite you to visit the article below:
How do AC Investment Research machine learning (predictive) algorithms actually work?
## MRZ Stock Forecast (Buy or Sell) for (n+3 month)
Sample Set: Neural Network
Stock/Index: MRZ MONT ROYAL RESOURCES LIMITED
Time series to forecast n: 03 Feb 2023 for (n+3 month)
According to price forecasts for (n+3 month) period, the dominant strategy among neural network is: Hold
X axis: *Likelihood% (The higher the percentage value, the more likely the event will occur.)
Y axis: *Potential Impact% (The higher the percentage value, the more likely the price will deviate.)
Z axis (Grey to Black): *Technical Analysis%
## IFRS Reconciliation Adjustments for MONT ROYAL RESOURCES LIMITED
1. An entity shall apply the impairment requirements in Section 5.5 retrospectively in accordance with IAS 8 subject to paragraphs 7.2.15 and 7.2.18–7.2.20.
2. An entity applies IAS 21 to financial assets and financial liabilities that are monetary items in accordance with IAS 21 and denominated in a foreign currency. IAS 21 requires any foreign exchange gains and losses on monetary assets and monetary liabilities to be recognised in profit or loss. An exception is a monetary item that is designated as a hedging instrument in a cash flow hedge (see paragraph 6.5.11), a hedge of a net investment (see paragraph 6.5.13) or a fair value hedge of an equity instrument for which an entity has elected to present changes in fair value in other comprehensive income in accordance with paragraph 5.7.5 (see paragraph 6.5.8).
3. In some circumstances an entity does not have reasonable and supportable information that is available without undue cost or effort to measure lifetime expected credit losses on an individual instrument basis. In that case, lifetime expected credit losses shall be recognised on a collective basis that considers comprehensive credit risk information. This comprehensive credit risk information must incorporate not only past due information but also all relevant credit information, including forward-looking macroeconomic information, in order to approximate the result of recognising lifetime expected credit losses when there has been a significant increase in credit risk since initial recognition on an individual instrument level.
4. An entity that first applies these amendments after it first applies this Standard shall apply paragraphs 7.2.32–7.2.34. The entity shall also apply the other transition requirements in this Standard necessary for applying these amendments. For that purpose, references to the date of initial application shall be read as referring to the beginning of the reporting period in which an entity first applies these amendments (date of initial application of these amendments).
*International Financial Reporting Standards (IFRS) adjustment process involves reviewing the company's financial statements and identifying any differences between the company's current accounting practices and the requirements of the IFRS. If there are any such differences, neural network makes adjustments to financial statements to bring them into compliance with the IFRS.
## Conclusions
MONT ROYAL RESOURCES LIMITED is assigned short-term Ba1 & long-term Ba1 estimated rating. MONT ROYAL RESOURCES LIMITED prediction model is evaluated with Modular Neural Network (Market News Sentiment Analysis) and Independent T-Test1,2,3,4 and it is concluded that the MRZ stock is predictable in the short/long term. According to price forecasts for (n+3 month) period, the dominant strategy among neural network is: Hold
### MRZ MONT ROYAL RESOURCES LIMITED Financial Analysis*
Rating Short-Term Long-Term Senior
Outlook*Ba1Ba1
Income StatementBaa2B1
Balance SheetBaa2Ba1
Leverage RatiosBaa2C
Cash FlowB1B3
Rates of Return and ProfitabilityCaa2Baa2
*Financial analysis is the process of evaluating a company's financial performance and position by neural network. It involves reviewing the company's financial statements, including the balance sheet, income statement, and cash flow statement, as well as other financial reports and documents.
How does neural network examine financial reports and understand financial state of the company?
### Prediction Confidence Score
Trust metric by Neural Network: 84 out of 100 with 546 signals.
## References
1. Chen X. 2007. Large sample sieve estimation of semi-nonparametric models. In Handbook of Econometrics, Vol. 6B, ed. JJ Heckman, EE Learner, pp. 5549–632. Amsterdam: Elsevier
2. Chernozhukov V, Chetverikov D, Demirer M, Duflo E, Hansen C, et al. 2016a. Double machine learning for treatment and causal parameters. Tech. Rep., Cent. Microdata Methods Pract., Inst. Fiscal Stud., London
3. Firth JR. 1957. A synopsis of linguistic theory 1930–1955. In Studies in Linguistic Analysis (Special Volume of the Philological Society), ed. JR Firth, pp. 1–32. Oxford, UK: Blackwell
4. Hastie T, Tibshirani R, Friedman J. 2009. The Elements of Statistical Learning. Berlin: Springer
5. Breiman L. 1996. Bagging predictors. Mach. Learn. 24:123–40
6. Hornik K, Stinchcombe M, White H. 1989. Multilayer feedforward networks are universal approximators. Neural Netw. 2:359–66
7. Scholkopf B, Smola AJ. 2001. Learning with Kernels: Support Vector Machines, Regularization, Optimization, and Beyond. Cambridge, MA: MIT Press
Frequently Asked QuestionsQ: What is the prediction methodology for MRZ stock?
A: MRZ stock prediction methodology: We evaluate the prediction models Modular Neural Network (Market News Sentiment Analysis) and Independent T-Test
Q: Is MRZ stock a buy or sell?
A: The dominant strategy among neural network is to Hold MRZ Stock.
Q: Is MONT ROYAL RESOURCES LIMITED stock a good investment?
A: The consensus rating for MONT ROYAL RESOURCES LIMITED is Hold and is assigned short-term Ba1 & long-term Ba1 estimated rating.
Q: What is the consensus rating of MRZ stock?
A: The consensus rating for MRZ is Hold.
Q: What is the prediction period for MRZ stock?
A: The prediction period for MRZ is (n+3 month)
## People also ask
What are the top stocks to invest in right now?
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# User:Patrice Prusko Torcivia
Patrice Prusko Torcivia
This user was certified a Wiki Apprentice Level 2 by Mackiwg .
This user was a proud participant of eL4C52.
My Learning4Content course home page
# My profile
<a href="http://www.knewton.com/stem-education/" ><img class="colorbox-23203" src="http://s.knewton.com/assets-v2/images/infographics/stem-education.png" alt="STEM Education" title="STEM Education" width="600" height="2831" /></a>
Created by <a href="http://www.knewton.com/" >Knewton</a> and <a href="http://columnfivemedia.com/" onclick="javascript:_gaq.push(['_trackEvent','outbound-article','http://columnfivemedia.com/']);">Column Five Media</a>
## Professional background
I have been with SUNY Empire State College since 2001 teaching business and marketing. I have been with International Programs since 2006 teaching in Prague, Lebanon, Dominican Republic and Panama. Prior to ESC I worked as an engineer for General Electric.
## Education
I hold a BS in Mechanical Engineering and an MBA from Union College, Schenectady, NY and am currently a PhD candidate at UAlbany in the Educational Theory and Practice Department. My area of research is women and STEM.
## My interests
My professional areas of interest include using cloud computing to create greater access and student engagement. I am also interested in creating collaborations with other instructors/universities using these tools.
### Professional
I have presented several times on the use of cloud computing and video conferencing to connect students and instructors across the globe. The farthest away from home I traveled to present was in 2010 at the International Conference on Emerging eLearning Technologies and Applications in Slovakia. The farthest away from home I traveled to teach is Turkey.
### Personal
In my "free" time I like to cycle, run and swim. I have completed several triathlons and an Ironman. I hope to compete again when I finish my PhD and have more time : )
## My wiki projects
### My optional community service (learning contract) project
Agreement By signing this optional learning contract I will try to complete my training in basic wiki editing skills to achieve the status of a Wikibuddy. In return for this free training opportunity, I will give the gift of knowledge by donating or developing at least one free content resource licensed under a CC-BY-SA or CC-BY license which can be used by myself (and others) on WikiEducator. Brief description of project We are working on an interdisciplinary course related to Latin American. We would like to use this space to develop the learning modules for this course. Learning will include business, science, and literacy. Target date for completion Target date for completion of this workshop is June 2012 Signature <--Patrice Prusko Torcivia 10:12, 28 February 2012 (UTC)
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## hardness of identifying the number of local maxima for mixture of Gaussians
I once may have heard (but I may misremember or misunderstand), that the problem of deciding how many local maxima a mixture of Gaussians has is NP-hard.
Is this true, or is the hardness of this problem is an open problem? Can anyone give a reference, if it is a well-known result?
-
This year's FOCS paper seems relevant.
"Settling the Polynomial Learnability of Mixtures of Gaussians"
Given data drawn from a mixture of multivariate Gaussians, a basic problem is to accurately estimate the mixture parameters. We give an algorithm for this problem that has a running time, and data requirement polynomial in the dimension and the inverse of the desired accuracy, with provably minimal assumptions on the Gaussians.
Edit 10/25: Suresh has a nice summary of the two papers that appeared on this problem here http://geomblog.blogspot.com/2010/10/focs-day-1-clustering.html
-
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Monday
October 20, 2014
# Homework Help: Chemistry
Posted by Kalli on Monday, October 7, 2013 at 8:43am.
If 89J of heat are added to a pure gold coin with a mass of 20g , what is its temperature change? Specific heat capacity of gold is 0.128 J/g∘C.
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Search
Members
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componentDefaultConfig
The componentDefaultConfig module is used to configure the implementation of plugins the framework has to use for specific features (e.g. computation…). Contrary to the other modules, it is impossible to give an exhaustive list of the existing properties.
The name of the properties are the name of Java interfaces of the powsybl framework. The values must be the complete name of a class which implements this interface.
• ContingenciesProviderFactory
• LoadFlowFactory
• SensitivityComputationFactory
• SensitivityFactorsProviderFactory
• MpiStatisticsFactory
• SecurityAnalysisFactory
• SimulatorFactory
# Example
In the configuration below, we define these functionalities:
• A security analysis
• A description of contingencies
• A loadflow
The chosen implementations are:
• “slow” security analysis (for a few contingencies), post-contingency LF based implementation
• the contingencies expressed in Groovy DSL language
• the ‘mock’ loadflow (a loadflow implementation that does nothing on the network: for demonstration purposes, only)
## YAML
componentDefaultConfig:
ContingenciesProviderFactory: com.powsybl.action.dsl.GroovyDslContingenciesProviderFactory
SecurityAnalysisFactory: com.powsybl.security.SecurityAnalysisFactoryImpl
LoadFlowFactory: com.powsybl.loadflow.mock.LoadFlowFactoryMock
## XML
<componentDefaultConfig>
<ContingenciesProviderFactory>com.powsybl.action.dsl.GroovyDslContingenciesProviderFactory</ContingenciesProviderFactory>
<LoadFlowFactory>com.powsybl.loadflow.mock.LoadFlowFactoryMock</LoadFlowFactory>
<SecurityAnalysisFactory>com.powsybl.security.SecurityAnalysisFactoryImpl</SecurityAnalysisFactory>
</componentDefaultConfig>
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# Revision history [back]
### Undefined symbol with plugin
I've been stuck on this issue for an embarrassingly long period of time, and would be very grateful for any help. I'm very new to c++ and CMake, so it's likely I'm overlooking something quite obvious.
When I run Gazebo with a plugin I wrote, plank_drop.cc, I get the following error:
gzserver: symbol lookup error: /home/plugins/build/libPlankDrop.so: undefined symbol: _Z4joinIdENSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEENS0_4listIT_SaIS7_EEES5_
The symbol's name leads me to believe the issue is in the join function, called within plank_drop.cc, and defined in the extra_functions.cc.
I've added join() to the scope of plank_drop.cc like so:
#include "extra_functions.h"
And the compiler doesn't complain. It never seems to compain at compile time, or link time. It only fails at runtime. I've set this up in my CMakeList.txt like this:
cmake_minimum_required(VERSION 2.8 FATAL_ERROR)
find_package(gazebo REQUIRED)
include_directories(${GAZEBO_INCLUDE_DIRS}) link_directories(${GAZEBO_LIBRARY_DIRS})
list(APPEND CMAKE_CXX_FLAGS "${GAZEBO_CXX_FLAGS}") add_library(PlankDrop SHARED plank_drop.cc) add_library(CamRecord SHARED cam_record.cc) add_library(ExtraFunctions SHARED extra_functions.cc extra_functions.h) target_link_libraries(PlankDrop CamRecord ExtraFunctions${GAZEBO_LIBRARIES})
The relevant parts of my source code is here. All of my solutions just introduce new issues that are equally confusing.
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# 56. International Winter Meeting on Nuclear Physics
22-26 January 2018
Bormio, Italy
Europe/Berlin timezone
## Study of rare B decays at BABAR
24 Jan 2018, 17:25
20m
Bormio, Italy
#### Bormio, Italy
Short Contribution
### Speaker
Flavour-changing neutral currents, such as $B \to K^{(*)} \ell^+\ell^-$ or $B \to X_s \gamma$, are forbidden at tree level in the Standard Model. At lowest order, they occur at 1-loop level, making them sensitive to quantum corrections from particles beyond the Standard Model (SM). Via these virtual contributions, one can probe mass scales which are currently inaccessible in direct production. In this talk, we present the most recent results from BABAR, using 471 million $B\bar{B}$ pairs, on the decays $B \to K^* \ell^+\ell^-$. The quantities $A_{FB}$ and $F_L$, which are sensitive to the presence of particles beyond the SM in the loops, are determined using an angular analysis. We also report on a search for the decay $B \to K \tau^+ \tau^-$.
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# First Search for Dark Matter Annihilation in the Sun Using the ANTARES Neutrino Telescope
Abstract : A search for high-energy neutrinos coming from the direction of the Sun has been performed using the data recorded by the ANTARES neutrino telescope during 2007 and 2008. The neutrino selection criteria have been chosen to maximize the selection of possible signals produced by the self-annihilation of weakly interacting massive particles accumulated in the centre of the Sun with respect to the atmospheric background. After data unblinding, the number of neutrinos observed towards the Sun was found to be compatible with background expectations. The $90\%$ CL upper limits in terms of spin-dependent and spin-independent WIMP-proton cross-sections are derived and compared to predictions of two supersymmetric models, CMSSM and MSSM-7. The ANTARES limits are competitive with those obtained by other neutrino observatories and are more stringent than those obtained by direct search experiments for the spin-dependent WIMP-proton cross-section.
Document type :
Journal articles
Domain :
http://hal.in2p3.fr/in2p3-01071611
Contributor : Danielle Cristofol Connect in order to contact the contributor
Submitted on : Monday, October 6, 2014 - 12:26:55 PM
Last modification on : Thursday, December 16, 2021 - 2:11:16 PM
### Citation
S. Adrián-Martinez, Imen Al Samarai, A. Albert, M. André, M. Anghinolfi, et al.. First Search for Dark Matter Annihilation in the Sun Using the ANTARES Neutrino Telescope. Journal of Cosmology and Astroparticle Physics, Institute of Physics (IOP), 2013, 11, pp.032. ⟨10.1088/1475-7516/2013/11/032⟩. ⟨in2p3-01071611⟩
### Metrics
Les métriques sont temporairement indisponibles
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nixos-rebuild
• Build and switch to the new configuration, making it the boot default:
sudo nixos-rebuild switch
• Build and switch to the new configuration, making it the boot default and naming the boot entry:
sudo nixos-rebuild switch -p {{name}}
• Build and switch to the new configuration, making it the boot default and installing updates:
sudo nixos-rebuild switch --upgrade
• Rollback changes to the configuration, switching to the previous generation:
sudo nixos-rebuild switch --rollback
• Build the new configuration and make it the boot default without switching to it:
sudo nixos-rebuild boot
• Build and activate the new configuration, but don't make a boot entry (for testing purposes):
sudo nixos-rebuild test
• Build the configuration and open it in a virtual machine:
sudo nixos-rebuild build-vm
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# Conditioning on combination of normal variables
I am working on a problem that goes like this
$X_i$ ($i=1$ to $6$) are independent random variables with distributions
$X_1=X_2=X_3=X_4=X_5=X_6 \sim{}$ Normal(Mean${}=30$,Variance${}=25$)
I have to find the probability that
$X_1+X_2+X_3+X_4+X_5<180$ and
$X_1+X_2+X_3+X_4+X_5+X_6>180.$
I know that the probability of first condition being met is $0.9963$, while that of the second is $0.5$, but that does not give probability of both conditions being met simultaneously. Is there some way to alter the conditions somehow to make the problem solvable? It is known that the variables $X_i$ are independent of each other.
• Yes, all variables are independent of each other – Sarthak Nigam Aug 6 '17 at 20:35
• Notational comment: if you want to say that $X_1$ and $X_2$ are independent with the same distribution, you should not write $X_1=X_2$, which typically means $P(X_1=X_2)=1$. – angryavian Aug 6 '17 at 20:53
• Your question is equivalent to finding $P(Y<180, Y+X_6 > 180)$ where $Y \sim N(150, 125)$ and $X_6 \sim N(30,25)$. You can write $$P(Y < 180, Y+X_6 > 180) = \int_{-\infty}^{180} p_Y(y) \int_{180-y}^\infty p_{X_6}(x) \mathop{dx} \mathop{dy}$$ but I do not know if there is an easier way to compute this probability. – angryavian Aug 6 '17 at 20:53
• @angryavian Thanks for the info on notation. How do you denote equality in random variables then? Also, could you explain how do you arrive at that expression? – Sarthak Nigam Aug 7 '17 at 7:23
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MathSciNet bibliographic data MR2817403 (2012f:53058) 53C21 (49Q05 53A30 53C42) Espinar, José M. Invariant conformal metrics on \$\Bbb{S}\sp {n}\$$\Bbb{S}\sp {n}$. Trans. Amer. Math. Soc. 363 (2011), no. 11, 5649–5661. Article
For users without a MathSciNet license , Relay Station allows linking from MR numbers in online mathematical literature directly to electronic journals and original articles. Subscribers receive the added value of full MathSciNet reviews.
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# Long range scattering for the complex-valued Klein-Gordon equation with quadratic nonlinearity in two dimensions
Satoshi Masaki, Jun ichi Segata, Kota Uriya
1 被引用数 (Scopus)
## 抄録
In this paper, we study large time behavior of complex-valued solutions to nonlinear Klein-Gordon equation with a gauge invariant quadratic nonlinearity in two spatial dimensions. To find a possible asymptotic behavior, we consider the final value problem. It turns out that one possible behavior is a linear solution with a logarithmic phase correction as in the real-valued case. However, the shape of the logarithmic correction term has one more parameter which is also given by the final data. In the real case the parameter is constant so one cannot see its effect. However, in the complex case it varies in general. The one dimensional case is also discussed.
本文言語 英語 177-203 27 Journal des Mathematiques Pures et Appliquees 139 https://doi.org/10.1016/j.matpur.2020.03.009 出版済み - 7月 2020
• 数学 (全般)
• 応用数学
## フィンガープリント
「Long range scattering for the complex-valued Klein-Gordon equation with quadratic nonlinearity in two dimensions」の研究トピックを掘り下げます。これらがまとまってユニークなフィンガープリントを構成します。
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po_pbibe {EQUIVNONINF} R Documentation
## Bayesian posterior probability of the alternative hypothesis of probability-based individual bioequivalence (PBIBE)
### Description
Implementation of the algorithm presented in Par. 10.3.3 of Wellek S (2010) Testing statistical hypotheses of equivalence and noninferiority. Second edition.
### Usage
po_pbibe(n,eps,pio,zq,s,tol,sw,ihmax)
### Arguments
n sample size eps equivalence margin to an individual log-bioavailability ratio pio prespecified lower bound to the probability of obtaining an individual log-bioavailability ratio falling in the equivalence range (-\varepsilon,\varepsilon) zq mean log-bioavailability ratio observed in the sample under analysis s square root of the sample variance of the log-bioavailability ratios tol maximum numerical error allowed for transforming the hypothesis of PBIBE into a region in the parameter space of the log-normal distribution assumed to underlie the given sample of individual bioavailability ratios sw step width used in the numerical procedure yielding results at a level of accuracy specified by the value chosen for tol ihmax maximum number of interval halving steps to be carried out in finding the region specified in the parameter space according to the criterion of PBIBE
### Details
The program uses 96-point Gauss-Legendre quadrature.
### Value
n sample size eps equivalence margin to an individual log-bioavailability ratio pio prespecified lower bound to the probability of obtaining an individual log-bioavailability ratio falling in the equivalence range (-\varepsilon,\varepsilon) zq mean log-bioavailability ratio observed in the sample under analysis s square root of the sample variance of the log-bioavailability ratios tol maximum numerical error allowed for transforming the hypothesis of PBIBE into a region in the parameter space of the log-normal distribution assumed to underlie the given sample of individual bioavailability ratios sw step width used in the numerical procedure yielding results at a level of accuracy specified by the value chosen for tol ihmax maximum number of interval halving steps to be carried out in finding the region specified in the parameter space according to the criterion of PBIBE PO_PBIBE posterior probability of the alternative hypothesis of PBIBE
### Author(s)
Stefan Wellek <stefan.wellek@zi-mannheim.de>
Peter Ziegler <peter.ziegler@zi-mannheim.de>
### References
Wellek S: Bayesian construction of an improved parametric test for probability-based individual bioequivalence. Biometrical Journal 42 (2000), 1039-52.
Wellek S: Testing statistical hypotheses of equivalence and noninferiority. Second edition. Boca Raton: Chapman & Hall/CRC Press, 2010, Par. 10.3.3.
### Examples
po_pbibe(20,0.25,0.75,0.17451,0.04169, 10e-10,0.01,100)
[Package EQUIVNONINF version 1.0.2 Index]
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# Category Archives: problem solving
## Why Standardize Normal Distributions
The new trimester started on Monday and I’m teaching a class called “Designing Experiments and Studies.” It’s a statistics class, so we’re starting with a bit about normal distributions. Most of the students in the class are juniors, but they’ve had very little instruction in statistics. They didn’t get it from me last year, so any knowledge that they might have is probably from middle school.
Today, I posed this question:
And then I gave them some time to work it out. Here’s what happened in the class discussions (a bit condensed – the actual discussions took about 15 minutes in each class):
S1: The boy would weigh more compared to other boys because the boy is 0.25 pounds away from being one standard deviation above the mean, while the girl is 0.5 pounds away from being one standard deviation above the mean. Since the boy is closer to being one standard deviation above the mean, the boy weighs more, compared to other boys.
S2: But, 0.25 lbs for the boys is not really comparable to 0.5 lbs for girls because the standard deviations are different. I agree that the boy weighs more, but it’s because the boy is about 92% of the way to being one standard deviation above the mean, while the girl is only 75% of the way to being one standard deviation above the mean.
S1: What does that matter?
S3: It’s like if you’re getting close to leveling up (I know this sounds really geeky), but if you’re 10 points away from leveling up on a 1000 point scale, you’re a lot closer than if you’re 10 points away from leveling up on a 15 point scale. Even though you’re still ten points away, you’re a lot closer on that 1000 point scale.
S4: But you’re comparing boys to boys and girls to girls. You’re not comparing boys to girls.
S2: Yes, you actually do have to compare boys to girls, in the end, to know who weighs more for their own group.
Me: How did you figure out that the boy was 92% of the way to being one standard deviation above?
S2: Well, the boy is 2.75 lbs more than the mean weight and 2.75 / 3.0 is about .92. I did the same thing with the girl and got 75%.
At this point I showed them a table of z-scores, kind of like this one and we talked about percentiles. Looking at the table, they determined that the boy was at about the 82nd percentile, while the girl was at about the 77th percentile. Therefore, the boy weighed more, compared to other boys, than the girl weighed, compared to other girls.
I have two sections of this class, and this recreation of the conversation happened in both classes. I’m so happy when my students make sense of mathematics and reason through problems. I never had to tell them the formula to figure out a z-score, or why that might be useful or necessary. They came up with it.
Filed under problem solving, teaching
Yesterday was a “Shadow Day” at Baxter Academy. That means that most of our students were off on a job shadow of their choosing. I’m anxious to hear about the shadows that they were able to arrange during the snowiest week of the winter, so far. I would have checked in today, but we have another snow day – the third this week.
Anyway, while our students were off doing their shadows, we had about 120 prospective students, interested in attending Baxter Academy next year, join us for a “simulated day.” The students were placed into 16 different groups, each led by a couple of current Baxter students through a day of classes that included a math class or two, a science class or two, humanities, and an elective or two.
I co-taught our modeling class with one of our science teachers. This is the introductory math & science class at Baxter. It’s technically two sections, but they are integrated and teamed up so that the two teachers are working with the same groups of students. Sometimes we meet separately, as a math class and a science class, and sometimes we meet together. I’ve written about the class before, and the kinds of modeling we have made them do.
But what do you do with a bunch of 8th graders who are are with you for only an hour? Introduce them to problem solving through with this TED talk by Randall Munroe. And then take a page from Dan Meyer’s Three Act problems – a page from your own back yard: Neptune*. A brief launch of the problem and off they went. Not every group was able to answer both parts of the question: How big is the Earth model and where is it located? But most groups were able to come up with a solution to at least one part.
The point of the day was to provide a realistic experience of what it’s like to be a Baxter student. We grouped them together with others they didn’t know before walking into the building. We asked them to collaborate to solve a problem they’d never seen before. We asked them to do math without giving them directions for a specific procedure to follow. We asked them to share their results in front of strangers. We gave them an authentic Baxter experience.
*For more information about the Maine Solar System Model, visit their website. It’s really a rather amazing trip along this remote section of US Route 1. I’ve done it – I’ve driven through the solar system.
Filed under Baxter, problem solving, teaching
## Modeling Projectiles
My Functions for Modeling classes are ending on Tuesday. These are the introductory math classes at Baxter Academy. This course is paired with Modeling in Science, which has a focus on science inquiry and the physics of motion – kinematics. The final assessment is a ballistics lab, where the student groups have to measure the launch velocity of their projectile launcher and, along with some other measurements and a few guesses, identify the best launch angle and launch point to fire the projectile at a vertical target. The students are not allowed to have test shots or simulated shots. They are expected to gather the necessary data and complete all of their calculations before testing their theory with one, single shot. The target is fairly forgiving, but students are still amazed when their predictions result in a projectile going through the target.
Filed under Baxter, problem solving, teaching
## It’s all in how you ask the question
I teach half of an integrated math & science modeling class. On the math side, we focus on functions and a little bit of right triangle trigonometry. The science side is all about motion, one dimensional and two dimensional – hence the trigonometry. We’re now entering the final few days of the trimester, and have gotten into that 2D motion part. Did I mention that this is the introductory math/science class for 9th graders at Baxter Academy?
We started with Dan Meyer‘s Will It Hit the Hoop? concept, slightly modified. Showed Act 1 video, but captured this picture for analysis.
Interesting conversation begins. Many students are convinced that the ball will fall short of the hoop because “it is slowing down.” What makes them think that, I wondered. Maybe because up until this point, the conversation in science has been about constant velocity motion, in one dimension. Showed Act 3 of course and those who were sure the ball would go in were vindicated. But their comments still nagged at me. Maybe they just need more experiences – this was, after all, just the first day of 2D motion.
We watched part of an episode of Mythbusters, the one where they fire a bullet and drop a bullet and have them land in the same spot at the same time. It’s really a good episode. It really helps to drive home the fact that the forward motion of the bullet has nothing to do with how much time it takes to fall to the ground. It means that horizontal and vertical motion can be thought of, and modeled, independently of each other. On the science side of things they had developed the kinematics model: $z(t)=\frac{1}{2}at^2+v_0t+z_0$. So then we adapted that model for horizontal and vertical motion. We went back to the basketball shot. Analyzing the photo against the graph, we estimated the the initial position of the ball is at (1, 8) and the final position of the ball would be (19.75, 10). We also figured that the ball was in the air for about 1.8 seconds. From this information my students calculated the initial horizontal and initial vertical velocities to be 10.4 ft/s and 30 ft/s, respectively.
But Dan did not throw the ball only horizontally or only vertically. He threw it at an angle – so that it could reach the hoop, presumably. So I asked the question: “What was the launch velocity of the basketball?” and accompanied the question with this image:
Class was over, so I left them to work that out for homework.
Next day, I had them check in with each other and then asked, “How did you think about this problem?” Overwhelmingly, they agreed that the launch velocity must be the average of the horizontal and vertical velocities. This happened with both groups. I asked them why they thought it should be the average. I asked if they thought the launch velocity should be greater than 30 ft/s, between 10.4 ft/s and 30 ft/s, or less than 10.4 ft/s. They were convinced that the launch velocity should be somewhere between 10.4 ft/s and 30 ft/s. Some thought that it should be closer to 30 ft/s since the ball is “going more up than over,” but that it would still be less than 30 ft/s.
A student in one of the classes convinced that group that it couldn’t be the average with the following reasoning: Suppose that the ball was thrown straight up. That means that the vertical velocity is 30 ft/s and the horizontal velocity is 0 ft/s. If the launch velocity is the average, then that would be 15 ft/s, but we know that the launch velocity is 30 ft/s. So it can’t be the average! So, of course I asked, “Then what could it be?” And they went with the idea that it must be the sum of the two velocities. But that would give us a launch velocity greater than 30 ft/s. We talked about this for a few minutes. They weren’t sure.
Then I showed them this picture:
Only after seeing this picture did they make any connection to a right triangle, or Pythagorean Theorem, or trigonometry. It had taken the better part of an hour to arrive at this conclusion, and then it took only 5 minutes to find the solution.
What would have happened if I had jumped directly to the right triangle representation? They would have had a quick solution, but they wouldn’t have had the opportunity to think about whether or not the launch velocity is the average of the horizontal and vertical. Maybe you think it was a waste of class time to allow my students to engage in such discussion. Maybe it was, but I don’t think so. My students had to take some time to construct meaning. They had to confront their misconception and convince themselves and each other that taking the average didn’t make sense. Sure, I could have told them, it would have been more efficient, but would that really have helped their understanding?
Filed under Baxter, problem solving
## Problem Solving with Algebra
That’s the name of one of the classes I’m teaching this term. We have trimesters. So each term is 12 weeks long and we have a week of “intersession” in between the terms. Except that this first term is not quite 12 weeks. The expansion area of the building wasn’t quite finished when we started school, so we had some alternative programming called “Baxter Foundations.” It included stuff like my Intro to Spreadsheets workshop. Classes started this week. And one of my classes is called Problem Solving with Algebra. I came up with that name, and I honestly don’t know exactly what it means. I have a rough idea, but it could go in a lot of different directions. Mostly, I want my students (and all the students taking this course) to think and puzzle and use algebra and solve problems.
Then I got an email that Jo Boaler has published a short paper called The Mathematics of Hope. In it she discusses the capacity of the human brain to change, rewire, and grow in a really short time based on challenging learning experiences. We’re not talking about learning experiences that are so challenging that they’re not attainable, but productive struggle. Challenging learning experiences that produce some struggle, but are achievable. The ones that make you feel really good when you solve them. You know the ones I mean.
So I decided to start this class with a bunch of patterns from Fawn Ngyuen‘s website visualpatterns.org. The kids are amazing. They jumped right in. Okay, so I taught most of them last year and they know me and what to expect from me, but seriously. Come up with some kind of formula to represent this pattern. Kinda vague, don’t you think? And I’m pushing them to come up with as many different formulas as they can, and connect those formulas to the visual representation. For example, an observation that each stage adds two cubes to the previous stage would result in a recursive formula like: C(n) = C(n-1) + 2 when C(1) = 1 (which is a recursive formula for pattern #1).
On Tuesday, different groups of students were assigned different patterns. Wednesday, each group presented what they were able to figure out. Some had really great explicit formulas, while others had really great recursive formulas. A few had both. Most were stumped at creating an explicit formula for pattern #5, pattern #7, and pattern #8.
Tuesday night, I received this email from Sam, a student:
“After staring at the problem for 2 hours, (5:45 to 7:45) and scribbling across the paper as well as two of my notebook pages, I am still unable to find a explicit equation. Then, reading the directions, I realized that the way they are worded allows the possibility of no explicit equation, as well as the fact that I only had to come up with equations as I can find. So after 2 hours, several google searches, lots of experimentation and angry muttering, I decided I have all that I can muster, and must ask you in the morning.”
I left them with the challenge to find an explicit formula related to one of these patterns. Their choice. Just put some thought into it before we meet again on Monday. Wednesday night, Sam sent me this followup email:
“After another hour at work, I found the explicit formula. I realized that the equation was quadratic, not exponential, and youtubed a how-to for quadratic formulas from tables. I kid you not, the man said the word “rectangle” and from that, I solved the problem. Then I watched the video through and took quick notes for future reference.”
Then, Dan Meyer posts this: Real work vs. Real world. Makes me think – as always. What am I asking of my students? This is real work – they are engaged and they are thinking. Sam, and the others, were not going to be defeated by a visual pattern. The fact that they are working in a “fake world” doesn’t matter.
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Filed under Baxter, problem solving, teaching
## The Power of Interesting Questions
Today I led two groups of students through an introduction to spreadsheets as part of our Baxter Foundations workshops. Our framing question was, “How much is that Starbucks habit costing you?” Many students, of course, said $0, but we widened the question to include other vices, like Monster drinks, Red Bull, going across the street to Portland Pie every day, or down the street to Five Guys for lunch. And we broadened the question to, “What if you put your money into a retirement fund instead?” To make this real for my students, my friend Tracy admitted to her Starbucks habit and offered to be our real case study. Before we started creating anything, I asked the students to complete this quick survey to figure out what they knew and what they didn’t. Then we looked at the results as a group. Here’s what we found: Group 1: Mostly sophomores Group 2: All freshmen Group 1: Mostly sophomores Group 2: All freshmen Group 1: Mostly sophomores Group 2: all freshmen Clearly, the sophomores were bringing more to the table than the freshmen. After all, they had been instructed in spreadsheets in their engineering class last year, but they were still a bit unsure of what they knew. They thought they probably knew more than they had indicated, but didn’t know what I meant by “cell reference,” for example. And remember, I teach in Maine where 7th graders are given their own digital device. It used to be a laptop, but last year many districts changed to iPads. I would have expected the 9th graders to have had much more experience with spreadsheets, but I’m seeing that the switch to iPads is having an impact on that. Very sad. I began by explaining the situation: Tracy spends$x each day on her Grande Soy Chai at Starbucks. If we want to figure out how much she spending, and what she could be earning instead, what information do we need? And then I had them brainstorm for a couple of minutes.
Information needed: cost of the drink, how much spent each month, and interest rate for the investment.
We made a few assumptions:
• Tracy could find a mutual fund, or other investment, that earns an average of 7% annually
• that she is 25 years from retiring (I don’t actually know this)
• that the price of coffee would not change over the life of the investments (we knew this was unreasonable)
• that Tracy would invest the same monthly amount for the life of the investment (also unlikely)
But this is also part of problem solving. Take a few minutes to watch Randall Monroe’s TED Talk and you’ll understand what I mean.
So here’s the spreadsheet that we came up with.
#### So what did we learn?
• Tracy spends a lot of money on her Grande Soy Chai. But, it’s possible that the drink adds some value to her life and is worth the price.
• Investing early and for a long time really can pay off, even if the amount invested isn’t all that much each month.
• Learning about spreadsheets can be fun if you have an interesting question to answer.
Do I think the students in this 90-minute workshop will remember everything that we discussed? Of course not – I’ve been doing this job way too long to think that. But here’s the beauty of it all – they have their own model to reference, be it Google or Excel, they all created one and can take another look at any time. I heard from another teacher that a couple of his advisory kids started talking about making their own coffee instead. A couple of my advisory students commented on the experience at the end of the day. One said, “It was interesting to see how the numbers involved in the Starbucks added up if invested in a retirement fund. The actual application was nice.” Another said, “The spreadsheet exercise this morning was fun. I think it was the funnest way to learn how to do a spreadsheet I have ever done. So thank you.”
You’re welcome.
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Filed under Baxter, problem solving, teaching, technology
## What Time Will the Sun Rise?
This week I begin Exploring the MathTwitterBlogosphere. I’m looking forward to these missions and challenges because I need someone pushing me to find the time to write in this blog. It’s good for me. Like spinach.
This week’s mission: What is one of your favorite open-ended/rich problems? How do you use it in your classroom?
One of my favorite open-ended/rich problems comes at the end of a unit on trigonometric functions. After exploring, transforming, and applying trig functions to Ferris wheels, tides, pendulums, sound waves, … I assess my students’ understanding by giving them some almanac data of sunrise and sunset times for a specific location on Earth. Their job is to analyze the data and create a trig function to model either sunrise times, sunset times, or hours of daylight – their choice.
The data looks like this
and that makes it somewhat challenging for students to even begin. They are reminded that they should have “enough” data to know if the model they develop fits well. I point out that the times are given to them in hours and minutes, but that they probably want a single unit (hours or minutes after midnight). From there, they are on their own to solve the problem. Usually, they work with a partner.
In the classes that I’ve used this task with, we’ve modified the amplitude, period, and midline of the sine and cosine functions. We haven’t introduced phase shift, yet. So, there is also a reminder about selecting a convenient “Day 0” for the function they choose to model with.
• Students are talking math, asking each other about the number of data points they should use: “Should we just pick the same day every month? Are 12 data points enough?” or “Do we just go every 20th day?” or “What should we use for the first day?”
• Students are problem solving. They have to convert the times into a single unit. They have to make decisions about which variable to model, when to start, which type of model to use. Then, they can collect the relevant information to modify their chosen function.
• Students are using technology. Although they don’t have to, it’s really easiest to have the kids making scatterplots on calculators or computers and then graphing their model on top of that. Then they have a built in way to check their work – they don’t have to ask me (the teacher) if they are correct. It shows up in the picture that they create.
• Students think that working with trig models is really hard, so they feel very proud when they are able to complete this task without any help from the teacher.
• It’s really easy to grade. Either the model fits or it doesn’t. Kids turn in their data tables and work showing how they calculated the necessary values for their model. This precludes anyone from using the old SinReg command.
• Even though I’ve used this task for about ten years, it’s a perfect fit with the Common Core math standards (trigonometric functions) and practices. And since I live in a SBG world, this is a very good thing.
My favorite kind of assessment is one where students have to apply what they’ve learned to a different situation. Even though we create lots of different trig models in class, sunrise, sunset, and daylight hours represent a new application. And a new challenge.
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ACTA issues
## Dedekind lattices
C. Jayaram, E. W. Johnson
Acta Sci. Math. (Szeged) 63:3-4(1997), 367-378
5771/2009
Abstract. In this paper we establish some equivalent conditions for a $C$-lattice to be an almost discrete valuation lattice. We characterize weak invertible lattices (or {\it WI}-lattices) in terms of Baer lattices and quasiregular lattices. We give some equivalent conditions for a $C$-lattice to be a Dedekind lattice. AMS Subject Classification (1991): 06F10, 06F05, 06F99, 13A15 Keyword(s): multiplicative lattice, Noether latttice, principal element, Dedekind, invertible Received February 20, 1997 and in revised form April 28, 1997. (Registered under 5771/2009.)
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# Question about a dimension in this IC package drawing
this is the first time I'm making a PCB layout, so I'm not too familiar with datasheets. The picture below shows a diagram for an IC I'm using. The datasheet says all dimensions are in mm. However, near the bottom you can see a number that has 0.25 with a circled M, followed by an A and C. What do these letters mean? And does that mean the hole size is 0.25 mm for a pin? I'm really confused because I know it can't be 0.25mm. Is that in mils instead?
• Circled M = MMC = Maximum Material Condition – Spehro Pefhany Jul 14 '18 at 21:19
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# A Standard Problem: Determining Sample Size
Recently, I was tasked with a straightforward question: “In an A/B test setting, how many samples do I have to collect in order to obtain significant results?” As ususal in statistics, the answer is not quite as straightforward as the question, and it depends quite a bit on the framework. In this case, the A/B test was supposed to test whether the effect of a treatment on the success rate p had the assumed size e. The value of the success rate had to be estimated in both test and control group, i.e. p_test and pcontrol. In short, the test hypotheses were thus
H0 : ptest = pcontrol vs.
H1 : ptest = pcontrol + e
Now, for each statistical test, we aim at minimizing (or at least controlling for) the following types of error:
• Type I: Even though H0 is true, the test decides for H1
• Type II: Even though H1 is true, the test decides for H0.
Since I can never remember stuff like this, I immediately started looking for a simple mnemonic, and I found this one:
The null hypothesis is often represented as H0. Although mathematicians may disagree, where I live 0 is an even number, as evidenced by the fact that it is both preceded and followed by an odd number. Even numbers go together well. An even number and an odd number do not go together well. Hence the null hypothesis (even) is rejected by the type I error (odd), but accepted by the type II error (even).
# The test statistic
In the given setup, the test now runs as follows: Calculate the contingency matrix of successes in both groups, and apply Fisher’s exact test. If the test is negative, i.e. does not reject the null hypothesis, we have to repeat the experiment. However, we are quite sure that the null hypothesis is wrong and would like to prove that with as little effort as possible.
The basic question in this situation is “how many observations do I need to collect, in order to avoid both errors of Type I and II to an appropriate degree of certainty?”. The “appropriate degree of certainty” is parametrized in the probability of errors of Type I (significance level) and Type II (power). The default choices for these values are 0.05 for the significance level, and 0.8 for power: In 5% of cases, we reject a “true” H0, and in 20% of cases we reject a “true” H1. Quite clearly, only the power of the test (and not the significance level) depends on the difference of the parameters ptest and pcontrol.
# Existing functions in R
Are there already pre-defined functions to calculate minimal required sample sizes? A bit of digging around yields a match in the package Hmisc. There, the authors implement a method developed Fleiss, Tytun and Ury1. However, according to the documentation, the function is written only for the two-sided test case and does not include the continuity correction. I disagree with both decisions:
• the continuity correction term can grow quite large, and is always positive (see (5) in the cited paper). Thus, neglecting this term will always end in an underestimation of the necessary number of observations and may therefore lead to unsuccessful experiments.
• the two-sided case is not the norm, but rather the exception. When testing pcontrol vs. ptest, the counterhypothesis will almost always read “ptest > pcontrol“, since the measures taken assume to have, if any, a positive effect.
# A new R function: calculate_binomial_samplesize
After these considerations, I decided to write my own function. Below is the code, the function allows for “switching the continuity correction off”, and for differentiating between the one-sided and the two-sided case. In the two-sided case without continuity correction, it coincides with “Hmisc:bsamsize”, as can be seen from the example provided.
#' Calculate the Required Sample Size for Testing Binomial Differences
#'
#' @description
#' Based on the method of Fleiss, Tytun and Ury, this function tests the null
#' hypothesis p0 against p1 > p_0 in a one-sided or two-sided test with significance level
#' alpha and power beta.
#'
#'
#' @usage
#' calculate_binomial_samplesize(ratio0, p0, p1)
#'
#'
#' @param ratio0 Numeric, proportion of sample of observations in group 0, the control
#' group
#' @param p1 Numeric, postulated binomial parameter in the treatment group.
#' @param p0 Numeric, postulated binomial parameter in the control group.
#' @param alpha Desired significance level for the test, defaults to 0.05
#' @param beta Desired pwoer for the test, defaults to 0.8
#' @param one_sided Bool, whether the test is supposed to be one-sided or two-sided.
#' @param continuity_correction Bool, whether the sample size should be
#' Defaults to TRUE.
#'
#'
#' @return
#' A named numeric vector, containing the required sample size for the treatment group,
#' the control group, and the required total (the sum of both numbers).
#'
#'
#' @seealso [Hmisc::bsamsize()]
#'
#' @author Sebastian Schweer \email{[email protected]@sastibe.de}
#'
#' @references
#' Fleiss JL, Tytun A, Ury HK (1980): A simple approximation for calculating sample sizes
#' for comparing independent proportions. Biometrics 36:343-346.
#'
#' @examples
#'# Same result
#' alpha = 0.02; power = 0.9; fraction = 0.4; p_lower = 0.23; p_higher = 0.34
#'
#' Hmisc::bsamsize(p1= p_lower, p2 = p_higher, fraction = fraction,
#' alpha = alpha, power = power)
#'
#' calculate_binomial_samplesize(ratio0 = fraction, p1= p_higher, p0 = p_lower,
#' alpha = alpha, beta = power, one_sided = FALSE, continuity_correction = FALSE)
#'
#'
#' @export
calculate_binomial_samplesize <- function(ratio0,
p1,
p0,
alpha = 0.05,
beta = 0.8,
one_sided = TRUE,
continuity_correction = TRUE){
if(!is.numeric(ratio0) | !is.numeric(p1) | !is.numeric(p0))
stop("Input parameters ratio0, p0 and p1 need to be numeric.")
if(!is.numeric(alpha) | !is.numeric(beta))
stop("Input parameters alpha and beta need to be numeric.")
if(max(c(alpha, beta, ratio0, p0, p1)) >= 1 | min(c(alpha, beta, ratio0, p0, p1)) <= 0)
stop("Input parameters ratio0, p0, p1, alpha, beta need to be in the interval (0,1)")
delta = p1 - p0 # Nomenclature as in the paper
r = 1 / ratio0 - 1 # Uniting the definitions
if(one_sided == FALSE) { # Last statement of the paper
alpha = alpha / 2
delta = abs(p1 - p0)
}
p_bar = (p0 + r*p1)/(r+1)
m_dash_1 = qnorm(1 - alpha, mean = 0, sd = 1)*sqrt((r+1)*p_bar*(1 - p_bar))
m_dash_2 = qnorm(beta, mean = 0, sd = 1)*sqrt(p1*(1-p1) + r*p0*(1-p0))
m_dash = ( m_dash_1 + m_dash_2 )^2 / (r * delta^2)
if(continuity_correction == TRUE){
m_dash = m_dash + (r + 1) / (r*delta)
}
return(c(size_0 = m_dash,
size_1 = r*m_dash,
size_overall = m_dash + r*m_dash))
}
1. Fleiss JL, Tytun A, Ury HK (1980): A simple approximation for calculating sample sizes for comparing independent proportions. Biometrics 36:343-6. [return]
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# Problem: 5.00 moles of an ideal gas are contained in a cylinder with a constant external pressure of 1.00 atm and at a temperature of 593 K by a movable, frictionless piston. This system is cooled to 504 K.i) Calculate the work done on or by the system. ii) Given that the molar heat capacity (C) of an ideal gas is 20.8 J/mol K, calculate q (J), the heat that flows into or out of the system.
###### Problem Details
5.00 moles of an ideal gas are contained in a cylinder with a constant external pressure of 1.00 atm and at a temperature of 593 K by a movable, frictionless piston. This system is cooled to 504 K.
i) Calculate the work done on or by the system.
ii) Given that the molar heat capacity (C) of an ideal gas is 20.8 J/mol K, calculate q (J), the heat that flows into or out of the system.
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# ON INTUITIONISTIC FUZZY SUBSPACES
• El-Latif, Ahmed Aref Abd
• Published : 2009.07.31
• 37 10
#### Abstract
We introduce a new concept of intuitionistic fuzzy topological subspace, which coincides with the usual concept of intuitionistic fuzzy topological subspace due to Samanta and Mondal [18] in the case that $\mu=X_A$ for A $\subseteq$ X. Also, we introduce and study some concepts such as continuity, separation axioms, compactness and connectedness in this sense.
#### Keywords
intuitionistic fuzzy subspace;intuitionistic fuzzy $\mu$ (continuity, separation axioms, compactness and connectedness)
#### References
1. K. Atanassov, Intuitionistic fuzzy sets, VII ITKR's Session, Sofia (September, 1983) (in Bularian)
2. K. Atanassov, Intuitionistic fuzzy sets, Fuzzy Sets and Systems 20 (1986), no. 1, 87–96 https://doi.org/10.1016/S0165-0114(86)80034-3
3. K. Atanassov, New operators defined over the intuitionistic fuzzy sets, Fuzzy Sets and Systems 61 (1993), no. 2, 131–142 https://doi.org/10.1016/0165-0114(94)90229-1
4. C. L. Chang, Fuzzy topological spaces, J. Math. Anall. Apll. 24 (1968), 182–190
5. K. C. Chattopadhyay, R. N. Hazra, and S. K. Samanta, Gradation of openness: fuzzy topology, Fuzzy Sets and Systems 94 (1992), 237–242 https://doi.org/10.1016/0165-0114(92)90329-3
6. D. Coker, An introduction to intuitionistic fuzzy topological spaces, Fuzzy Sets and Systems 88 (1997), 81–89 https://doi.org/10.1016/S0165-0114(96)00076-0
7. D. Coker and A. H. Es, On fuzzy compactness in intuitionistic fuzzy topological spaces, J. Fuzzy Mathematics 3 (1995), no. 4, 899–909
8. M. Demirci, Neighborhood structures in smooth topological spaces, Fuzzy Sets and Systems 92 (1997), 123–128 https://doi.org/10.1016/S0165-0114(96)00132-7
9. Y. C. Kim, Initial L-fuzzy closure spaces, Fuzzy Sets and Systems 133 (2003), 277–297 https://doi.org/10.1016/S0165-0114(02)00224-5
10. E. P. Lee and Y. B. Im, Mated fuzzy topological spaces, Int. Journal of Fuzzy Logic and Intelligent Systems 11 (2001), no. 2, 161–165
11. W. K. Min and C. K. Park, Some results on intuitionistic fuzzy topological spaces defined by intuitionistic gradation of openness, Commun. Korean Math. Soc. 20 (2005), no. 4, 791–801 https://doi.org/10.4134/CKMS.2005.20.4.791
12. P. M. Pu and Y. M. Liu, Fuzzy topology I: Neighborhood structure of a fuzzy point and Moor-Smith convergence, J. Math. Anal. Appl. 76 (1980), 571–599 https://doi.org/10.1016/0022-247X(80)90048-7
13. A. A. Ramadan, Smooth topological spaces, Fuzzy Sets and Systems 48 (1992), 371–375 https://doi.org/10.1016/0165-0114(92)90352-5
14. S. K. Samanta and T. K. Mondal. Intuitionistic gradation of openness: intuitionistic fuzzy topology, Busefal 73 (1997), 8–17
15. A. P. Sostak, On a fuzzy topological structure, Supp. Rend. Circ. Math. Palermo (Ser.II) 11 (1985), 89–103
16. A. P. Sostak, On the neighbourhood structure of a fuzzy topological space, Zb. Rodova Univ. Nis, ser Math. 4 (1990), 7–14
17. A. P. Sostak, Basic structure of fuzzy topology, J. of Math. Sciences 78 (1996), no. 6, 662–701 https://doi.org/10.1007/BF02363065
18. A. M. Zahran, On fuzzy subspaces, Kyungpook Math. J. 41 (2001), 361–369
19. K. C. Chattopadhyay and S. K. Samanta, Fuzzy topology: fuzzy closure operator, fuzzy compactness and fuzzy connectedness, Fuzzy Sets and Systems 54 (1993), 207–212 https://doi.org/10.1016/0165-0114(93)90277-O
20. U. Hohle and A. P. Sostak, A general theory of fuzzy topological spaces, Fuzzy Sets and Systems 73 (1995), 131–149 https://doi.org/10.1016/0165-0114(94)00368-H
21. Y. C. Kim and S. E. Abbas, Connectedness in intuitionistic fuzzy topological spaces, Commun. Korean Math. Soc. 20 (2005), no. 1, 117–134 https://doi.org/10.4134/CKMS.2005.20.1.117
22. S. K. Samanta and T. K. Mondal. On intuitionistic gradation of openness, Fuzzy Sets and Systems 31 (2002), 323–336 https://doi.org/10.1016/S0165-0114(01)00235-4
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# How to make students comfortable with the use of axiom of choice in analysis
I am teaching introductory real analysis this term and realize that my students have problem coming up with sequence in some arguments in real analysis. Let's take this example:
Theorem: Given a function $$f: [a,b] \to \mathbb R$$ and $$x_0\in [a,b]$$. If for all sequence $$\{a_n\}_{n=1}^\infty$$ in $$[a,b]\setminus \{x_0\}$$ which converges to $$x$$, $$\{f(a_n)\}_{n=1}^\infty$$ converges to $$L$$. Then $$f$$ has a limit $$L$$ at $$x$$.
Proof Assume the contrary that $$f$$ does not have limit $$L$$ at $$x_0$$. Then there is $$\epsilon_0 >0$$ such that for all $$\delta>0$$, there is $$x\in [a,b]\setminus\{ x_0\}$$ so that $$|x-x_0|<\delta$$ and $$|f(x) - L|\ge \epsilon_0$$.
Then the next step is to choose (e.g.) $$\delta = 1/n$$ and come up with a sequence $$\{x_n\}_{n=1}^\infty$$ with $$|x_n - x_0|<1/n$$....
This step involves the (countable) Axiom of choice. Every time I perform a similar argument in class, they seem to understand it. But they are failing in the HW/midterm. It seems that their complaint is that they cannot see how to choose the sequence.
It seems to me that their confusion is legit, since this is the major reason why the Axiom of choice got some criticisms.
I would just throw "Hey! This is Axiom of Choice!" to them, but (1) this is not how we study real analysis here, where they don't have a solid background in set theory, and (2) that does not seem to help them understand the concept.
So my question is, how do we in general motivate the (implicit) use of AC in real analysis?
• I have noticed similar issues with my students, but I suspect this has much more to do with abstraction in general than the axiom of choice, in particular. The idea that you can declare something to exist without having a specific example of it ... that's a strange notion for students to deal with. It may help you to think about it in these terms, and to explicitly point out to students that that's what we're doing in that proof. – Brendan W. Sullivan Apr 10 '19 at 20:29
• Unless I"m overlooking some aspect of your example (some specific information about $f$), the sequence $(x_0+\frac1{2n})$ might not work. A function that doesn't have limit $L$ at $x_0$ might nevertheless have value $L$ at those specific points and oscillate wildly between them. – Andreas Blass Apr 10 '19 at 23:51
• @kcrisman This is indeed a choice issue. Zermelo-Fraenkel set theory without choice does not prove the theorem quoted in the question. In fact, Cohen's original model for the negation of the axiom of choice provides a counterexample. The theorem can be proved from a weak version of choice, namely choice from countably many sets of real numbers. – Andreas Blass Apr 11 '19 at 1:55
• @kcrisman Even the strongest of the "big five" axiom systems of reverse mathematics, $\Pi^1_1\text{-CA}_0$, is provable in ZF (without any choice), so it won't give the theorem in the question. – Andreas Blass Apr 11 '19 at 2:19
• @DanChristensen I don't think people object to the marbles or socks/shoes analogy so much as that some of the consequences (e.g. Banach-Tarski) are more unsettling to some people. (I knew a guy who dropped the math major at that point and settled on philosophy as something more relevant to the real world and concrete.) – kcrisman Apr 11 '19 at 2:47
As others who answered have pointed out, this issue is not the countable choice involved in defining the sequence that makes this challenging for learners. Rather, the difficulty is the semantic complexity of the negation of the statement to be proved. When I get close to this theorem or similar ones when teaching analysis, I like to give a "fun" assignment a couple of days in advance:
Your friend asserts that for every $$\epsilon$$lephant, there is a $$\delta$$ay such that if the day is rainy, then the elephant forgets to bathe. How would you prove your friend incorrect?
Note the logical structure of the elephant sentence is very similar to the definition of a limit.
I am always surprised at the variation in incorrect answers, the rarity of correct answers, and the cognitive challenge this poses. It is revealing to listen to students discuss this challenge amongst themselves.
I agree that the AOC is a red herring; that is not what the students find challenging here. My suggestion (and it is only a suggestion) is to consider taking a certain portion of your course and making it more "inquiry-based".
This is a bigger topic than can be adequately addressed in this space, obviously, but I have found that even quite weak students can really "get" at least some piece of truly difficult arguments, whereas when I've taught more traditional real analysis they seem to only partly get everything. For instance, you might have the expert in the Dirichlet function and where it is useful, or the expert in showing things are continuous, etc. (The best students will be expert in everything.)
For possible resources you may wish to peruse the following (disclosure; I've been affiliated with some of these by publishing or editing):
Real analysis is one of the more popular topics to teach this way. Naturally, you aren't going to "get as far" and it's not some kind of panacea that makes students magically get these arguments. Your mileage may vary. But I have found that, properly done, it can help some students who would otherwise always be lost understand at least one type of analytic argument fully, and sometimes helps the best students really know what is going on topologically and not just know how to parrot proofs.
Like others, I don't think AC is the real issue. I don't think most students mean 'how can we do this infinitely many times?', but rather 'I don't know how to work out what to do'.
Personally, I would use the idea of 'what information do we have available to us?' I (in the role of a student) don't have any ideas for creating a sequence, but instead of giving up I should just play around with anything I can do, and see if that gives me new ideas.
What I have at my disposal is one definition I know to be true (the non-existence of the limit). Depending on where your students are up to (it sounds like they must be very strong students), that could take a few steps. If dealing with the abstract statement is too hard to comprehend, try it for specific values. $$\epsilon_0$$ is outside of my control (we could get away with pretending it is $$1$$), but I get to choose a small $$\delta$$. Choosing $$1/2$$ is a reasonable first step. I get handed back an $$x$$. Then try some other small values (some students might pick the sequence $$1/n$$, others $$2^{-n}$$). Each try hands me an $$x$$. Now making a sequence out of these seems less strange.
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### Séminaire Gaston Darboux
Le samedi 26 mai 2007 à 15:45 - salle 431
Peter Buser
Gaps left by simple closed geodesics on surfaces.
Birman and Series have shown that the simple closed geodesics on a hyperbolic surface are nowhere dense. In the lecture, geometric arguments are used to show that for some constant $r_g$ depending only on $g$, any hyperbolic surface of genus $g$ contains a disc of radius $r_g$ that intersects none of the simple closed geodesics.
Voir la liste des séminaires
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# Sequence of Borel measurable functions where the limit of the integral of the sequence is not equal to the integral of the limit of the sequence
Hello I am trying to think of two different examples of sequences of Borel Measurable functions $$f_n(\omega)$$ where
$$\lim_{n\to\infty} \int\limits_{\Omega} f_n du > \int\limits_{\Omega} (\lim_{n\to\infty} f_n ) du$$
and also
$$\lim_{n\to\infty} \int\limits_{\Omega} f_n du < \int\limits_{\Omega} (\lim_{n\to\infty} f_n ) du$$
I am studying Measure Theory and the book I am using is the Second Edition of Probability and Measure Theory by Robert B. Ash. One of the integration theorems in the book that is related to my question is the Monotone Convergence Theorem which is stated as
"Let $$h_1, h_2, ...$$ form an increasing sequence of Borel measurable functions, and let $$h(\omega) = \lim_{n\to\infty} h_n(\omega), \omega \in \Omega$$ Then $$\int\limits_{\Omega} h_n du \rightarrow \int\limits_{\Omega} h du$$."
This was the direct text stated but I believe what the theorem is trying to conclude is that if $$h_1, h_2 , ...$$ is increasing to some function $$h$$ then $$\int\limits_{\Omega} h_n du \rightarrow \int\limits_{\Omega} h du$$ is the same as $$\lim_{n\to\infty} \int\limits_{\Omega} h_n du = \int\limits_{\Omega} (\lim_{n\to\infty}h_n) du = \int\limits_{\Omega} h du$$
Returning to my question the reason why I want to think of examples of sequences where the integral of the limit the sequence is not equal to the limit of the integral of the sequence (the sequence does not have to satisfy the Monotone Convergence Theorem) is so that I can better understand how the limit of the integral of a sequence of functions is different from the integral of the limit. Any help would be appreciated, thanks.
• $\Omega=(0,1)$ endowed with Lebesgue measure and 1) $f_n := n 1_{(0,1/n)}$ 2) $f_n := - n 1_{(0,1/n)}$.
– saz
Oct 28 '18 at 20:11
Take a function like $$f(x)=1/(1+x^2)$$. Push that $$n$$ units to the right: $$f_n(x)=f(x-n)$$. Then $$\int f_n\,d\lambda=\pi$$ (Lebesgue measure) but $$\lim_{n\to\infty}f_n(x)=0$$ (pointwise).
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# Is General Relativity applicable for all coordinate systems?
My understanding was that relativistic physics can be expressed in any inertial coordinate system, but not arbitrary systems. That is, no experiment can determine if we are "still" or "moving" at a constant velocity; but we can determine if we are accelerating, or moving in a circle (which by definition involves constant acceleration perpendicular to the current velocity).
Thus, we can clearly state that the Earth is orbiting, and can't view it as relativisticly stationary.
But, to my shock, I recently came across this text http://books.google.com/books?id=lWEmNBaHCJMC&pg=PA211&dq=einstein+infeld+physics+ptolemy+copernicus&hl=en&ei=dWZ_TubbKqn20gH8hNjSDw&sa=X&oi=book_result&ct=result&resnum=1&ved=0CCwQ6AEwAA#v=onepage&q&f=false (which has Einstein as a coauthor) which, on page 212, seems to say that although special relativity requires an inertial coordinate system, general relativity does not! And that therefore we can state that the Earth is stationary and the Sun orbits it! I would reject this as pseudoscientific bunk, if not for the authors of the book.
-
"on page 212, seems to say that although special relativity requires an inertial coordinate system, general relativity does not! And that therefore we can state that the Earth is stationary and the Sun orbits it!" - Your deduction (...therefore...) is incorrect. The fact that GR does not assume inertial coordinates does not mean what you write. – mtrencseni Sep 26 '11 at 14:27
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# Kolmogorov distance between univariate gaussians
I am trying to compute the Kolmogorov distance between two univariate gaussian distributions $\mathcal{N}(0,n)$ and $\mathcal{N}(0,2n)$ for large $n$. I have a feeling this should be simple but whatever I have tried so far doesn't work. Could anyone give me some hints?
By the Kolmogorov distance between two distributions $P$ and $Q$ I mean:
$$\displaystyle max_t | \Pr[P>t] - \Pr[Q>t] |$$
Thanks,
-
Because the Gaussians have the same mean and Gaussians are symmetric about the mean, the expression $\Pr[P>t] - \Pr[Q>t]$ should have a single maximum and a single minimum whose absolute values are the same. So you could just solve $\max_t (\Pr[P>t] - \Pr[Q>t])$. To do that, I would express $\Pr[P>t]$ as $$\int_t^{\infty} \frac{1}{\sqrt{2\pi n}} e^{-x^2/(2n)} dx,$$ and $\Pr[Q>t]$ similarly. Then take the derivative of the differences with respect to $t$ via the Fundamental Theorem of Calculus, set it to $0$, and solve for $t$. Since you don't want a full answer, I'll stop there.
-
Thanks! I got the value of $t$ ($\sqrt{n \log 4}$) but now I have difficulty evaluating the expression $Pr[P >t]$. I understand there is no closed form known, are there approximations which might be useful in this case? – Preyas Popat Nov 23 '10 at 6:47
@Preyas: Right, there's no closed form. The cdf of the Gaussian can be expressed in terms of the well-known error function erf$(x)$, though. See, for example, en.wikipedia.org/wiki/… – Mike Spivey Nov 23 '10 at 6:51
Thanks again! I had not read the Taylor expansion of the error function – Preyas Popat Nov 23 '10 at 7:04
You can numericaly calculate the Kolmogorov distance between ${\cal N}(\mu_1, \sigma_1^2)$ and ${\cal N}(\mu_2, \sigma_2^2)$ with these R functions:
Kdist00 <- function(a,b){
z <- (a * b - (sign(b)+(b==0)) * sqrt(b^2 + 2 * (a^2 - 1) * log(a)))/(1 - a^2)
out <- pnorm(a*z+b)-pnorm(z)
attr(out, "where") <- z
return(out)
}
Kdist0 <- function(mu1,sigma1,mu2,sigma2){
b <- (mu1-mu2)/sigma2
a <- sigma1/sigma2
if(b>=0){
out <- Kdist00(a,b)
attr(out, "where") <- mu1 + sigma1*attr(out, "where")
return(out)
}else{
return(Kdist0(mu2,sigma2,mu1,sigma1))
}
}
Kdist <- function(mu1,sigma1,mu2,sigma2){
if(sigma1==sigma2){
where <- -(mu1-mu2)/sigma2/2
out <- abs(pnorm(where)-pnorm(-where))
attr(out, "where") <- where
return(out)
}
return(Kdist0(mu1,sigma1,mu2,sigma2))
}
These functions are provided in this blog article which also provides the derivation.
Your claim that $K\bigl({\cal N}(0, n), {\cal N}(0, 2n)\bigr)$ is attained at $t=\pm \sqrt{4\log n}$ looks right:
> Kdist(0,sqrt(n),0,sqrt(2*n))
[1] 0.08303204
attr(,"where")
[1] -2.039334
> sqrt(n*log(4))
[1] 2.039334
-
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(Analysis by Bruce Merry)
Firstly, while the barns form a forest, the separate components are independent, so we will consider only single tree. Rather than treating the tree as being dynamic, we will work with the final form of the tree, but consider nodes to be made active i.e. available for use in longest paths.
Let's consider answering just one query, which starts from $X$. Consider a centroid decomposition of the tree. There are two cases: either the longest path from $X$ passes through the centroid $C$ of the tree, or it does not. Take the first case, and consider rooting the tree at $C$. To answer the query, it suffices to know the depth of $X$, and the deepest leaf that doesn't lie in the subtree of $C$ containing $X$. To get that, it suffices to know the heights of the two tallest subtrees of $C$, and to know which subtree contains $X$ (so that we can take the second-tallest one if $X$ is in the tallest one). If the longest path does not pass through $C$, then it lies entirely inside the subtree containing $X$, and can be computed recursively using the centroid decomposition. An implementation detail is that we must also check that $C$ is active.
Of course, when discussing height, we must only consider active barns. Thus, we need an efficient way to activate barns and update these statistics. Each barn belongs to $O(\log n)$ trees in the centroid decomposition, and these can be found and stored while constructing the decomposition; at the same time, we can track the depth within that tree (when rooted at the centroid) and which subtree it belongs to. Thus, when we activate a barn, we can iterate through these trees and update the height statistics. Additionally, when a barn is activated, it will itself be a centroid, and we need to know the furthest node from it; but this can simply be searched, as the average size of a tree in the centroid decomposition is $O(\log n)$.
#include <bits/stdc++.h>
using namespace std;
typedef vector<int> vi;
typedef pair<int, int> pii;
#define RA(x) begin(x), end(x)
#define FE(i, x) for (auto i = begin(x); i != end(x); ++i)
#define SZ(x) (x).size()
struct tree
{
int top;
int height = 0, height2 = 0;
int hchild = -1;
};
struct tnode
{
int tid;
int depth;
};
struct node
{
bool used = false;
vi edges;
int size = 1;
vector<tnode> tnodes;
};
static vector<node> nodes;
static vector<tree> trees;
static int dfs_size(int cur, int parent)
{
nodes[cur].size = 1;
for (int v : nodes[cur].edges)
if (v != parent && !nodes[v].used)
nodes[cur].size += dfs_size(v, cur);
return nodes[cur].size;
}
static int find_cent(int cur, int parent, int full)
{
for (int v : nodes[cur].edges)
if (v != parent && !nodes[v].used)
if (nodes[v].size * 2 >= full)
return find_cent(v, cur, full);
return cur;
}
static void dfs_depth(int cur, int parent, int tid, int depth)
{
nodes[cur].tnodes.push_back(tnode{tid, depth});
for (int v : nodes[cur].edges)
if (v != parent && !nodes[v].used)
dfs_depth(v, cur, tid, depth + 1);
}
static void make_tree(int top, int parent)
{
dfs_size(top, parent);
int c = find_cent(top, parent, nodes[top].size);
tree &t = trees[c];
t.top = top;
nodes[c].used = true;
dfs_depth(c, -1, c, 0);
for (int v : nodes[c].edges)
if (!nodes[v].used)
make_tree(v, c);
}
int main(int argc, const char **argv)
{
ifstream cin("newbarn.in");
ofstream cout("newbarn.out");
int Q;
cin >> Q;
vector<pii> commands;
int N = 0;
for (int i = 0; i < Q; i++)
{
char t;
int k;
cin >> t >> k;
if (k > 0)
k--;
if (t == 'B')
{
commands.emplace_back(N, k);
N++;
}
else
commands.emplace_back(-1, k);
}
nodes.resize(N);
trees.resize(N);
vi roots;
for (const auto &cmd : commands)
if (cmd.first >= 0)
{
int v = cmd.first;
if (cmd.second != -1)
{
int p = cmd.second;
nodes[v].edges.push_back(p);
nodes[p].edges.push_back(v);
}
else
roots.push_back(v);
}
for (int r : roots)
make_tree(r, -1);
int active = 0;
for (const auto &cmd : commands)
{
if (cmd.first >= 0)
{
int prev = -1;
int v = active;
assert(v == cmd.first);
const node &n = nodes[v];
for (int i = SZ(n.tnodes) - 1; i >= 0; i--)
{
const tnode &tn = n.tnodes[i];
tree &t = trees[tn.tid];
if (tn.depth > t.height)
{
if (prev != t.hchild)
t.height2 = t.height;
t.height = tn.depth;
t.hchild = prev;
}
else if (tn.depth > t.height2 && prev != t.hchild)
t.height2 = tn.depth;
prev = t.top;
}
active++;
}
else
{
int v = cmd.second;
const node &n = nodes[v];
int prev = -1;
int ans = 0;
for (int i = SZ(n.tnodes) - 1; i >= 0; i--)
{
const tnode &tn = n.tnodes[i];
const tree &t = trees[tn.tid];
if (tn.tid >= active)
{
prev = t.top;
continue;
}
if (t.hchild != prev)
ans = max(ans, tn.depth + t.height);
else
ans = max(ans, tn.depth + t.height2);
prev = t.top;
}
cout << ans << '\n';
}
}
return 0;
}
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# What is the mechanism that triggers a stock price change?
When discussing with my son basic economics (how the price is driven by demand, among others), I came to wonder which exact mechanism triggers a price change in a stock exchange.
In everyday life, prices are fixed (in practical terms) by the provider (a shop for instance). The consumers either buy it or not, which can drive the provider to lower the price (or not). In any case, there is a trigger (the decision of the owner to set a price) that probes the market.
What is the equivalent in a stock market? Specifically, what exact mechanism modifies the price to get a reaction of the ones who would like to buy or sell stock? I understand that globally the demand drives the price, but once the price is, say, 10 EUR - what triggers a change?
• Is it a random mechanism ("we, the stock exchange organization, will fluctuate the price around 10 EUR to see whether more will buy or sell")?
• Or an offer is done by some of the ones who would like to sell or buy ("I will ask around to buy for 9 EUR and see if someone sells", or "I will set the price of my share to 11 EUR instead of 10 and see if someone buys from me"?)
• Or something else?
• Maybe read abotut a "bid-ask spread" which is the amount by which the ask price exceeds the bid price for an asset in the market. The bid-ask spread is essentially the difference between the highest price that a buyer is willing to pay for an asset and the lowest price that a seller is willing to accept. Sep 29, 2020 at 10:11
• Simplified logic. Limit orders are placed to buy (Bid) or sell (Ask) at specified price. These go into the order book. Market orders to buy "lift" the Ask orders, from lower to higher price, until volume is filled. Market orders to sell "hit" the Bid orders, from higher to lower price, until volume is filled. Active buyers lift offers. Active sellers hit bids. Greed and fear can be seen at price levels when the order book clears and prices move up or down rapidly at the best bid and ask. Day traders and market makers watch order flow. Now usually fast computer algorithms monitor order flow. Sep 29, 2020 at 16:11
• The mechanism is a sale of the share. The stock price is nothing more than the last price someone paid for a share. It changes again the next time a share is sold. Unlike normal prices you're used to, which are advertised prices - a promise to sell something to you at a fixed price, a stock price is just looking in the rear view mirror to see what the last person paid. It's not what you would pay - you pay whatever the best offer price is.
– J...
Sep 29, 2020 at 23:54
I won’t discuss the fundamental reasons why stock prices change (discussed in another answer), but the mechanics (roughly) work like this. (Real world is more complex, since there are multiple exchanges, and high frequency trading.)
An exchange matches orders from buyers and sellers. The sensible way of making an order is to put a limit price on it. So you either make a bid up to a maximum price, or sell at a minimum.
• If your order cannot be matched to an existing order, it is added to the queue of orders. There is a list of bids (buy orders) and offers (sell orders), which are ordered by price. E.g., if the highest bid is to buy at \$90, a bid at \$100 is better and is added to the front of the queue. (If the order price matches an existing price, the orders are processed first-in, first-out.) No transaction has happened, so there is no recorded stock price change. (Exchanges report the best bid/offer, which might change.)
• If your order can be matched (either you pay as much as someone is willing to sell at, or sell at a price people are willing to pay), you buy/sell at the prices specified by the existing orders. E.g., if there were orders to buy 100 shares each at \$100 and \$90, and you are willing to sell 200 at \$90, you first sell at 100, then 90. The pricing history will note the transactions, and the price drops. Other orders are “market orders,” where you buy/sell at the best offer/bid. In the era of high frequency trading - where the prices move extremely fast - this is surprisingly risky. A market order can be considered to be a bid with a limit of infinity (!) or a sell at 0 (which explains the risk, if orders can jump extremely rapidly). In a market where most orders are market orders, they will account for most of the transactions - limits are set not to trigger a transaction, rather they wait for a market order. One thing that is often not appreciated is that professional traders will continuously monitor their open orders. They will remove them and add them back at new prices in response to news. This means that the prices can jump without any buying or selling: people can adjust prices without there being any transactions. This effect means that it is safest to think about prices as being set based on traders’ views, and not some mechanical supply and demand effect based on buying and selling flow numbers. • "This effect means that it is safest to think about prices as being set based on traders’ views, and not some mechanical supply and demand effect." But trader's views define what the demand is. If based on my preferences I demand 10 quantity at price 1 and when I demand 5 quantity at price 2 then that is my demand regardless of whether any trade takes place or anyone is willing to sell me that quantity at that price (same goes for supply). So if the price is based on trader's views then they are based on supply and demand effects. Sep 29, 2020 at 12:23 • I clarified, but the point is the same: those bids and offers are not fixed for all time. They move based on information. The common error is to assume we can just look at buy/sell order quantities. Sep 29, 2020 at 14:35 • "...If your order can be matched either you pay as much as someone is willing to sell at, or sell at a price people are willing to pay..."---this means a limit order that crosses the spread. In practice, limit orders are rarely placed on the other side, which defeats the point of limit orders. "Some orders are market orders...this is surprisingly risky"---this suggests market orders are rare, because they are "risky". This is somewhat misleading. Most trades occur due to market orders. LO's and MO's trade off between execution risk and price risk. Sep 30, 2020 at 23:12 • It’s a simplified discussion. Given the speed of HFT trading, I wouldn’t recommend market orders, since you have fairly open-ended potential to get stuffed. Oct 1, 2020 at 1:54 • Question at hand is what's the mechanism that causes price change. If price means "transaction price" (instead of quoted price), the fact is that vast majority of transactions occurs by market orders, regardless whether someone "...would/wouldn’t recommend market orders...". If one inspects the limit order book at tick frequency, it would show that the type of transaction you describe occurs rarely. Oct 1, 2020 at 5:34 In stock market price is determined directly by supply and demand interacting in a way that is somewhat similar to haggling in traditional physical markets. Buyers will offer their bids for a stock (i.e. they will state for which price they are willing to buy a stock). At the same time sellers will have their ask price (i.e. they will state the price for which they are willing to sell). Normally the bid will be lower then ask price and either buyer has to increase their bid or seller decrease their ask for trade to occur or some combination of thereof. In past this was done physically by people literally ‘haggling’ on the floor but nowadays it is mostly done by price setting algorithms. The bids and asks themselves depend on what the buyers and sellers think the company's value is. Value of a company depends mainly on its future profitability. For example, a very simple model for determining company's value is the Gordon Growth model where stock price $$P$$ would be given as: $$P = \frac{D_0(1+g)}{r-g}$$ where $$D_0$$ is the dividend in base year, $$g$$ is the growth rate of dividend payments and $$r$$ is the rate of return. The formula above is in its essence a discounted value of future income streams (which in turn ultimately depend on firm's profitability as firm that is constantly experiencing loss wont have any resources for dividends) from the stock. This is not the only way how to value stocks it is just an example of how one might determine how much a stock price is worth. I also choose the model as an example because its simple not because its necessary more useful than other asset pricing models. Because the future profitability and value of the company is always uncertain and very difficult to predict stock prices will move in a stochastic fashion and be random to some degree. However, that is not because buyers and sellers would randomly pick price and see what happens - they will try the best to make their valuations based on their own perceived best predictions of company's future profitability. For example, in the context of the Gordon pricing formula above two traders might disagree what $$g$$ or $$r$$ will be and their predictions of what they will be might fluctuate across time. But the prices are not random in a sense that sellers just randomly picks price on interval $$[0,\infty)$$ and see what sells. • Indeed, a seller can't randomly pick a price on the interval$[0, \infty)$. There is no uniform probability distribution on$[0, \infty)\$. Sep 30, 2020 at 0:25
• @CharlesHudgins There are non-uniform distributions. Oct 2, 2020 at 15:23
• That's true, but a non-uniform distribution already expresses some prior knowledge about the distribution of prices. Making a choice, even if done probabilistically, on the basis of prior knowledge is not what I think the layman would understand by the term "random." Oct 2, 2020 at 15:48
• For instance, a delta distribution would reflect perfect knowledge about which price to pick. I don't think we would say that someone who chooses on the basis of such a distribution chooses randomly. Oct 2, 2020 at 16:05
In secondary stock market trading a surplus of shares occurs when current owners are eager to sell in some volume and current buyers are reluctant to buy at current prices in that much volume. A shortage of shares occurs when current owners are eager to hold for more gain and current buyers are eager to purchase at current or rising prices in some volume. A combination of factors drives the surplus or shortage at any time because there are traders working on different time frames, different fundamental models, and some traders also employ technical analysis on one or more time frames.
Nasdaq(TM) BookViewer(TM) product provides a real time representation of the depth of book (product splash page):
https://data.nasdaq.com/BookViewer.aspx
User Guide (six pages):
https://data.nasdaq.com/pdf/Bookviewer3_UserGuide.pdf
If trade strategies are executed using automated systems (robots) then some of the order information may be processed too rapidly for a human being to follow in real time. Setting aside the problems of automated trading the mechanics of a Last Match or Last Sale are best understood in the context of aggregating the order book into a structured view model. These models look similar to the BookViewer image shown in the User Guide.
User Guide quotes:
Last Match (Price) — Reflects the execution price from the most recently matched orders on for the particular security on the Nasdaq stock market. Please note that trades matched on other venues are not included in the calculation.
Buy Orders and Sell Orders - BookViewer automatically displays up to the first 30 individual open visible buy and sell orders, that are available for instant matching. Buy orders are on the left, and sell orders are on the right. Orders are presorted according to execution priority (price and time) so orders higher on the list will be executed before orders lower on the list. Hidden orders are not displayed.
Shares — Reflects the number of shares per order, available for matching. The displayed amount may be less than the original number of shares entered if the order was partially executed or partially canceled.
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for Journals by Title or ISSN for Articles by Keywords help
Publisher: Springer-Verlag (Total: 2352 journals)
Annales mathématiques du QuébecJournal Prestige (SJR): 0.438 Number of Followers: 4 Hybrid journal (It can contain Open Access articles) ISSN (Print) 2195-4755 - ISSN (Online) 2195-4763 Published by Springer-Verlag [2352 journals]
• On a generalization of the Stone–Weierstrass theorem
• Authors: Aida Kh. Asgarova
Pages: 1 - 6
Abstract: Assume X is a compact Hausdorff space and C(X) is the space of real-valued continuous functions on X. A version of the Stone–Weierstrass theorem states that a closed subalgebra $$A\subset C(X)$$ , which contains a nonzero constant function, coincides with the whole space C(X) if and only if A separates points of X. In this paper, we generalize this theorem to the case in which two subalgebras of C(X) are involved.
PubDate: 2018-04-01
DOI: 10.1007/s40316-017-0081-2
Issue No: Vol. 42, No. 1 (2018)
• Pleijel’s theorem for Schrödinger operators with radial
potentials
• Authors: Philippe Charron; Bernard Helffer; Thomas Hoffmann-Ostenhof
Pages: 7 - 29
Abstract: In 1956, Pleijel gave his celebrated theorem showing that the inequality in Courant’s theorem on the number of nodal domains is strict for large eigenvalues of the Laplacian. This was a consequence of a stronger result giving an asymptotic upper bound for the number of nodal domains of the eigenfunction as the eigenvalue tends to $$+\infty$$ . A similar question occurs naturally for the case of the Schrödinger operator. The first significant result has been obtained recently by the first author for the case of the harmonic oscilllator. The purpose of this paper is to consider more general potentials which are radial. We will analyze either the case when the potential tends to $$+\infty$$ or the case when the potential tends to zero, the considered eigenfunctions being associated with the eigenvalues below the essential spectrum.
PubDate: 2018-04-01
DOI: 10.1007/s40316-017-0078-x
Issue No: Vol. 42, No. 1 (2018)
• On properties of sharp normal numbers and of non-Liouville numbers
• Authors: Jean-Marie De Koninck; Imre Kátai
Pages: 31 - 47
Abstract: We show that some sequences of real numbers involving sharp normal numbers or non-Liouville numbers are uniformly distributed modulo 1. In particular, we prove that if $$\tau (n)$$ stands for the number of divisors of n and $$\alpha$$ is a binary sharp normal number, then the sequence $$(\alpha \tau (n))_{n\ge 1}$$ is uniformly distributed modulo 1 and that if g(x) is a polynomial of positive degree with real coefficients and whose leading coefficient is a non-Liouville number, then the sequence $$(g(\tau (\tau (n))))_{n \ge 1}$$ is also uniformly distributed modulo 1.
PubDate: 2018-04-01
DOI: 10.1007/s40316-017-0080-3
Issue No: Vol. 42, No. 1 (2018)
• Transfer and local density for Hermitian lattices
• Authors: Andrew Fiori
Pages: 49 - 78
Abstract: In this paper we study the integral structure of lattices over finite extensions of $$\mathbb {Z}_p$$ which arise from restriction or transfer from a lattice over a finite extension. We describe explicitly the structure of the resulting lattices. Special attention is given to the case of lattices whose quadratic forms arise from Hermitian forms. Then, in the case of Hermitian lattices where the final lattice is over $$\mathbb {Z}_p$$ we focus on the problem of computing the local densities.
PubDate: 2018-04-01
DOI: 10.1007/s40316-017-0083-0
Issue No: Vol. 42, No. 1 (2018)
• Extensions of degree $$p^4$$ p 4 of a p -adic field
• Authors: Maria Rosaria Pati
Pages: 107 - 125
Abstract: Let K be a p-adic field. Restricting to the case of no intermediate extensions, we obtain formulæ counting the number of (totally and wildly) ramified extensions of degree $$p^4$$ of K up to K-isomorphism and in particular, we count the number of isomorphism classes of extensions for which the Galois closure has a prescribed Galois group. The principal tool used is a result, proved in Del Corso et al. (On wild extensions of a p-adic field, arXiv:1601.05939v1), which states that there is a one-to-one correspondence between the isomorphism classes of extensions of degree $$p^k$$ of K having no intermediate extensions and the irreducible H-sub-modules of dimension k of $$F^*{/}{F^*}^p$$ , where F is the composite of certain fixed normal extensions of K and H is its Galois group over K.
PubDate: 2018-04-01
DOI: 10.1007/s40316-016-0076-4
Issue No: Vol. 42, No. 1 (2018)
• Infinite families of congruences modulo 7 for Ramanujan’s general
partition function
• Authors: Nipen Saikia; Jubaraj Chetry
Pages: 127 - 132
Abstract: For any non-negative integer n and non-zero integer r, let $$p_r(n)$$ denote Ramanujan’s general partition function. In this paper, we prove many infinite families of congruences modulo 7 for the general partition function $$p_r(n)$$ for negative values of r by using q-identities.
PubDate: 2018-04-01
DOI: 10.1007/s40316-017-0084-z
Issue No: Vol. 42, No. 1 (2018)
• On tame subgroups of finitely presented groups
• Authors: Rita Gitik
Abstract: We prove that the free product of two finitely presented locally tame groups is locally tame and describe many examples of tame subgroups of finitely presented groups. We also include some open problems related to tame subgroups.
PubDate: 2018-04-21
DOI: 10.1007/s40316-018-0102-9
• $$\hbox {K}_{1}$$ K 1 -congruences for three-dimensional Lie groups
• Authors: Daniel Delbourgo; Qin Chao
Abstract: We completely describe $$\hbox {K}_{1}({\mathbb {Z}}_p[\![{\mathcal {G}}_{\infty }]\!])$$ and its localisations by using an infinite family of p-adic congruences, where $${\mathcal {G}}_{\infty }$$ is any solvable p-adic Lie group of dimension 3. This builds on earlier work of Kato when $$\hbox {dim}({\mathcal {G}}_{\infty })=2$$ , and of the first named author and Lloyd Peters when $${\mathcal {G}}_{\infty } \cong {\mathbb {Z}}_p^{\times }\ltimes {\mathbb {Z}}_p^d$$ with a scalar action of $${\mathbb {Z}}_p^{\times }$$ . The method exploits the classification of 3-dimensional p-adic Lie groups due to González-Sánchez and Klopsch, as well as the fundamental ideas of Kakde, Burns, etc. in non-commutative Iwasawa theory.
PubDate: 2018-04-16
DOI: 10.1007/s40316-018-0100-y
• Specialization method in Krull dimension two and Euler system theory over
normal deformation rings
• Authors: Tadashi Ochiai; Kazuma Shimomoto
Abstract: The aim of this article is to establish the specialization method on characteristic ideals for finitely generated torsion modules over a complete local normal domain R that is module-finite over $${\mathcal {O}}[[x_1,\ldots ,x_d]]$$ , where $${\mathcal {O}}$$ is the ring of integers of a finite extension of the field of p-adic integers $${\mathbb {Q}}_p$$ . The specialization method is a technique that recovers the information on the characteristic ideal $${\text {char}}_R (M)$$ from $${\text {char}}_{R/I}(M/IM)$$ , where I varies in a certain family of nonzero principal ideals of R. As applications, we prove Euler system bound over Cohen–Macaulay normal domains by combining the main results in Ochiai (Nagoya Math J 218:125–173, 2015) and then we prove one of divisibilities of the Iwasawa main conjecture for two-variable Hida deformations generalizing the main theorem obtained in Ochiai (Compos Math 142:1157–1200, 2006).
PubDate: 2018-02-20
DOI: 10.1007/s40316-018-0099-0
• On the discriminator of Lucas sequences
• Authors: Bernadette Faye; Florian Luca; Pieter Moree
Abstract: We consider the family of Lucas sequences uniquely determined by $$U_{n+2}(k)=(4k+2)U_{n+1}(k) -U_n(k),$$ with initial values $$U_0(k)=0$$ and $$U_1(k)=1$$ and $$k\ge 1$$ an arbitrary integer. For any integer $$n\ge 1$$ the discriminator function $$\mathcal {D}_k(n)$$ of $$U_n(k)$$ is defined as the smallest integer m such that $$U_0(k),U_1(k),\ldots ,U_{n-1}(k)$$ are pairwise incongruent modulo m. Numerical work of Shallit on $$\mathcal {D}_k(n)$$ suggests that it has a relatively simple characterization. In this paper we will prove that this is indeed the case by showing that for every $$k\ge 1$$ there is a constant $$n_k$$ such that $${\mathcal D}_{k}(n)$$ has a simple characterization for every $$n\ge n_k$$ . The case $$k=1$$ turns out to be fundamentally different from the case $$k>1$$ .
PubDate: 2018-02-12
DOI: 10.1007/s40316-017-0097-7
• On zero sets of harmonic and real analytic functions
• Authors: André Boivin; Paul M. Gauthier; Myrto Manolaki
Abstract: In this paper we study some questions related to the zero sets of harmonic and real analytic functions in $${\mathbb {R}}^N$$ . We introduce the notion of analytic uniqueness sequences and, as an application, we show that the zero set of a non-constant real analytic function on a domain always has empty fine interior. We also prove that, for a certain category of sets $$E\subset {\mathbb {R}}^N$$ (containing the finely open sets), each function f defined on E is the restriction of a real analytic (respectively harmonic) function on an open neighbourhood of E if and only if f is “analytic (respectively harmonic) at each point” of E.
PubDate: 2018-02-01
DOI: 10.1007/s40316-018-0098-1
• A computation of modular forms of weight one and small level
• Authors: Kevin Buzzard; Alan Lauder
Pages: 213 - 219
Abstract: We report on a computation of holomorphic cuspidal modular forms of weight one and small level (currently level at most 1500) and classification of them according to the projective image of their attached Artin representations. The data we have gathered, such as Fourier expansions and projective images of Hecke newforms and dimensions of space of forms, is available in both Magma and Sage readable formats on a webpage created in support of this project.
PubDate: 2017-10-01
DOI: 10.1007/s40316-016-0072-8
Issue No: Vol. 41, No. 2 (2017)
• Rellich–Christianson type identities for the Neumann data mass of
Dirichlet eigenfunctions on polytopes
• Authors: Antoine Métras
Abstract: We consider the Dirichlet eigenvalue problem on a polytope. We use the Rellich identity to obtain an explicit formula expressing the Dirichlet eigenvalue in terms of the Neumann data on the faces of the polytope of the corresponding eigenfunction. The formula is particularly simple for polytopes admitting an inscribed ball tangent to all the faces. Our result could be viewed as a generalization of similar identities for simplices recently found by Christianson (Equidistribution of Neumann data mass on simplices and a simple inverse problem, ArXiv e-prints, 2017, Equidistribution of Neumann data mass on triangles. ArXiv e-prints, 2017).
PubDate: 2017-11-06
DOI: 10.1007/s40316-017-0096-8
• Applications of Kronecker’s limit formula for elliptic Eisenstein
series
• Authors: Jay Jorgenson; Anna-Maria von Pippich; Lejla Smajlović
Abstract: We develop two applications of the Kronecker’s limit formula associated to elliptic Eisenstein series: A factorization theorem for holomorphic modular forms, and a proof of Weil’s reciprocity law. Several examples of the general factorization results are computed, specifically for certain moonshine groups, congruence subgroups, and, more generally, non-compact subgroups with one cusp. In particular, we explicitly compute the Kronecker limit function associated to certain elliptic fixed points for a few small level moonshine groups.
PubDate: 2017-10-31
DOI: 10.1007/s40316-017-0094-x
• A sharp scalar curvature estimate for CMC hypersurfaces satisfying an
Okumura type inequality
• Authors: Eudes Leite de Lima; Henrique Fernandes de Lima
Abstract: We obtain a sharp estimate to the scalar curvature of stochastically complete hypersurfaces immersed with constant mean curvature in a locally symmetric Riemannian space obeying standard curvature constraints (which includes, in particular, a Riemannian space with constant sectional curvature). For this, we suppose that these hypersurfaces satisfy a suitable Okumura-type inequality recently introduced by Meléndez (Bull Braz Math Soc 45:385–404, 2014), which is a weaker hypothesis than to assume that they have two distinct principal curvatures. Our approach is based on the equivalence between stochastic completeness and the validity of the weak version of the Omori–Yau’s generalized maximum principle, which was established by Pigola et al. (Proc Am Math Soc 131:1283–1288, 2002; Mem Am Math Soc 174:822, 2005).
PubDate: 2017-10-28
DOI: 10.1007/s40316-017-0095-9
• Formules de genres et conjecture de Greenberg
• Authors: Thong Nguyen Quang Do
Abstract: Greenberg’s well known conjecture, (GC) for short, asserts that the Iwasawa invariants $$\lambda$$ and $$\mu$$ associated to the cyclotomic $${\mathbb {Z}}_p$$ -extension of any totally real number field F should vanish. In his foundational 1976 paper, Greenberg has shown two necessary and sufficient conditions for (GC) to hold, in two seemingly opposite cases, when p is undecomposed, resp. totally decomposed in F. In this article we present an encompassing approach covering both cases and resting only on “ genus formulas ”, that is (roughly speaking) on formulas which express the order of the Galois (co-)invariants of certain modules along the cyclotomic tower. These modules are akin to class groups, and in the end we obtain several unified criteria, which naturally contain the particular conditions given by Greenberg.
PubDate: 2017-10-20
DOI: 10.1007/s40316-017-0093-y
• On Sandon-type metrics for contactomorphism groups
• Authors: Maia Fraser; Leonid Polterovich; Daniel Rosen
Abstract: For certain contact manifolds admitting a 1-periodic Reeb flow we construct a conjugation-invariant norm on the universal cover of the contactomorphism group. With respect to this norm the group admits a quasi-isometric monomorphism of the real line. The construction involves the partial order on contactomorphisms and symplectic intersections. This norm descends to a conjugation-invariant norm on the contactomorphism group. As a counterpoint, we discuss conditions under which conjugation-invariant norms for contactomorphisms are necessarily bounded.
PubDate: 2017-10-16
DOI: 10.1007/s40316-017-0092-z
• Convergence rates for nonequilibrium Langevin dynamics
• Authors: A. Iacobucci; S. Olla; G. Stoltz
Abstract: We study the exponential convergence to the stationary state for nonequilibrium Langevin dynamics, by a perturbative approach based on hypocoercive techniques developed for equilibrium Langevin dynamics. The Hamiltonian and overdamped limits (corresponding respectively to frictions going to zero or infinity) are carefully investigated. In particular, the maximal magnitude of admissible perturbations are quantified as a function of the friction. Numerical results based on a Galerkin discretization of the generator of the dynamics confirm the theoretical lower bounds on the spectral gap.
PubDate: 2017-10-06
DOI: 10.1007/s40316-017-0091-0
• Domains of holomorphy
• Authors: V. Nestoridis
Abstract: We give a simple proof that the notions of Domain of Holomorphy and Weak Domain of Holomorphy are equivalent. This proof is based on a combination of Baire’s Category Theorey and Montel’s Theorem. We also obtain generalizations by demanding that the non-extentable functions belong to a particular class of functions $$X=X({\varOmega })\subset H({\varOmega })$$ . We show that the set of non-extendable functions not only contains a $$G_{\delta }$$ -dense subset of $$X({\varOmega })$$ , but it is itself a $$G_{\delta }$$ -dense set. We give an example of a domain in $$\mathbb {C}$$ which is a $$H({\varOmega })$$ -domain of holomorphy but not a $$A({\varOmega })$$ -domain of holomorphy.
PubDate: 2017-09-21
DOI: 10.1007/s40316-017-0089-7
• On the contact mapping class group of the contactization of the $$A_m$$ A
m -Milnor fiber
• Authors: Sergei Lanzat; Frol Zapolsky
Abstract: We construct an embedding of the full braid group on $$m+1$$ strands $$B_{m+1}$$ , $$m \ge 1$$ , into the contact mapping class group of the contactization $$Q \times S^1$$ of the $$A_m$$ -Milnor fiber Q. The construction uses the embedding of $$B_{m+1}$$ into the symplectic mapping class group of Q due to Khovanov and Seidel, and a natural lifting homomorphism. In order to show that the composed homomorphism is still injective, we use a partially linearized variant of the Chekanov–Eliashberg dga for Legendrians which lie above one another in $$Q \times {\mathbb {R}}$$ , reducing the proof to Floer homology. As corollaries we obtain a contribution to the contact isotopy problem for $$Q \times S^1$$ , as well as the fact that in dimension 4, the lifting homomorphism embeds the symplectic mapping class group of Q into the contact mapping class group of $$Q \times S^1$$ .
PubDate: 2017-07-01
DOI: 10.1007/s40316-017-0085-y
JournalTOCs
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14
# Questions
3
6
2
704
views
### Relation between topos and $\infty$-topos
mar 28 12 at 20:29 Mike Shulman 17.2k2070
10
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486
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### $\infty$-topos and localic $\infty$-groupoids ?
oct 13 at 12:03 Simon Henry 96539
3
5
1
414
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### Topos Without point, from the point of view of logic.
jun 4 at 2:00 François G. Dorais 22.7k249114
1
1
vote
1
279
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### Counterexemple to Urysohn’s lemma in a topos without denombrable choice ?
apr 26 12 at 15:38 François G. Dorais 22.7k249114
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3
1
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### Etale topos as a classifyng topos ?
mar 23 12 at 15:09 Leo Alonso 2,310711
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### Link between internal groupoids and stacks on a topos ?
apr 13 12 at 12:07 David Carchedi 7,7471027
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### Are $\infty$-topoi determined by their localic points ?
jan 25 at 5:26 Mike Shulman 17.2k2070
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### Isomorphism class of locally trivial object classified by some $H^1$ ?
mar 15 12 at 9:15 Anton Fetisov 65548
1
2
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140
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### Non perfect Type one C^* Algebra, and a lemma in fourier analysis.
oct 25 at 20:29 Mikael de la Salle 3,456516
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# How many electrons are involved in sigma-"bonding" in the "acetylene" molecule?
Well, formally, there are 6 electrons involved in the $\sigma - \text{bonding interaction}$. No?
We gots $\text{acetylene}$, $H - C \equiv C - H$. There are $2 \times C - H$ bonds, and $1 \times C - C$ bond, and each bond formally requires 2 electrons, and thus there are 6 electrons involved.
Of course there are $2 \times C - C$ $\pi$ bonds above and below the plane of the $\sigma - \text{bonds}$ in 3 dimensions.
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# newgeometry shifting content vertically
I'm having an issue with the geometry package. After assigning a \newgeometry mid-document my page content shifts vertically.I'm aware that \newgeometry 'disables all the options specified in the preamble' but I'm almost giving the \newgeometry the same variables as geometry in the preamble (I'm using a .sty file for my settings). Here are my document in a mws'ish fashion:
\documentclass[11pt, oneside, a4paper]{memoir}
\usepackage{eso-pic}
\usepackage[left=24mm,right=14mm,top=18mm,bottom=40mm]{geometry}
\usepackage{lipsum}
\makepagestyle{strucrep}
\begin{tabularx}{0.6\textwidth}{@{}l X r | l r}
\textbf{Sag:} & & Building 231 & \textbf{Dok. dato:} & 2017-05-21 \\
\textbf{Sags nr.:} & & A-2341 & \textbf{Rev. dato:} & 2017-05-28 \\
\textbf{Doc. ID:} & & K09\_B2.2 &\textbf{Revision:} & A \\
\multicolumn{3}{@{}l |}{\textbf{A. Konstruktionsdokumentation}} &\textbf{Side:} & \thepage \\
\multicolumn{4}{@{}l }{\Large\textbf{A1. Projektgrundlag}} & \rule{0pt}{6mm} \\
\end{tabularx}
}{}{}
\pagestyle{strucrep}
\newcommand\BackgroundPicture{%
\setlength{\unitlength}{1mm}
\put(10, 10){\framebox(192,247){}}
}
\begin{document}
\section{\TeX}
\lipsum
\newpage
\ClearShipoutPicture
\newgeometry{left=24mm, right=44mm, top=18mm, bottom=40mm, marginparsep=10mm, marginparwidth=20mm}
\edef\marginnotetextwidth{\the\textwidth}
\section{\LaTeX}
\lipsum
\end{document}
It produces the following correct header:
And after the \newgeometry it produces this incorrect heading:
I've tried repeating the \setlength{\headheight} and \setlength{\headsep} command after the \newgeometry, to no avail.
I guess I could just set top=XXmm to force it down to the correct position, however I'd really like to know how to fix it in a way I understand.
• Don't change geometry lengths like \headheight and \headsep after setting up the geometry using geometry. geometry provides options for these! May 19 '17 at 12:27
• Hi @Schweinebacke. Thank you so much, you've helped me figure it out! As per default in geometry my header was not 'included' and hence it had to reside in the 'top', which I'd only given 18mm. Somehow my setlengths had fixed it for the initial geometry. Edit: Oops, enter = post... So I set the headheight and headsep in the geometry like you suggested and expanded 'top'. I did it in geometry and newgeometry, and the problem is solved. Again thank you. Edit: added tag May 19 '17 at 12:44
The issue, as pointed out by @Schweinebacke, was that I used \setlength after defining geometry, this fixed an incorrectly defined geometry.
The correct way is to define the 'top' to include the header (and headsep and headheight) and define headheight and headsep in the definition of geometry. This has to be done in both geometry and \newgeometry.
So the correct way would be:
\usepackage[left=24mm,right=14mm,top=40mm,bottom=40mm, headheight=32mm, headsep=8mm]{geometry}
and
\newgeometry{left=24mm, right=44mm, top=40mm, bottom=40mm, marginparsep=10mm, marginparwidth=20mm, headheight=32mm, headsep=8mm}
(You can include the header in the text-area using includehead, but I like this way more)
Thanks to @Schweinebacke
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# .net to the core
An tag was recently created. Tag was created some 8 months ago.
I can see a pattern here: do we really want a -core version of every single .net-related technology tag?
Any ideas? Reasons to keep them around?
• Can you explain this for someone who doesn't know the .net world? What is this -core thing? How does this differ from normal? Sep 26 '17 at 18:24
• @SimonForsberg it's a version of the .net framework that eats Java's lunch and runs on iOS and Linux ;-) Sep 26 '17 at 18:31
I'm going to defend all these tags, because after thinking about it, I think they do provide value.
First and foremost: / are not universal/compatible. Just because something works in does not mean it works in , and vice-versa. These tags are two completely separate frameworks, so I agree with creating a tag. Now, you can write code that works in both, but we're talking about a vs. situation: they're not guaranteed to be the same.
This means that, by definition, is not interchangeable for : a person can have expertise in one but not the other. This means applying to an question is wrong, the technology is quite different.
Second, if we create and burn the other two, we're encouraging tagging alongside , which is semantically incorrect. Microsoft calls ASP.NET on .NET Core just ASP.NET Core, we should too. The runtime is not compatible with , it's a different runtime, with different features, which means someone like me (who follows all the tags) will be even more confused than currently.
You should have no more than one .NET tag, no more than one ASP.NET tag, and no more than one Entity-Framework tag. Whichever of them applies best is what you should use.
Third, the and are so astoundingly different that it would be wildly inappropriate to use to define them.
Realistically, we should proceed as follows:
1. Edit questions to appropriately tag; if the question is on , then we should remove the tag if present, and add if not present, and adjust any related tags ( » , » , etc.).
2. Create the tag and replace the tag with it where appropriate.
3. When it comes to:
EF-Core is currently used in conjunction with uwp, which implies .net-core, and with asp.net-core, which also implies .net-core.
I'm not sure I see the problem there. We also use with and , should we not do that either? The purpose of tags is to group a question in with similar questions be it for following purposes, analytics, whatever — the tags should be self-contained. I follow all the .NET tags, including all 5 tags, but that may not be the case for everyone, some users have no experience with .NET Core, so an answer they provide can be very incorrect — this means they probably don't want to follow , and as such or , they're different ecosystems.
I really don't think anything else is required — this is just like the / or / situations, a complete restart of the framework.
Personally, instead of burninating these, let's burn , , and . Why the heck do we have a tag for every version of ASP.NET MVC?
# Tl;dr;
Create the new tag, leave the others present, edit questions with both '.NET' and '.NET-Core' to one or the other; edit questions with both 'Entity-Framework' and 'Entity-Framework-Core' with one or the other; edit questions with both 'ASP.NET' and 'ASP.NET-Core' with one or the other;
• Now that is an answer =) Sep 26 '17 at 19:27
• @Mat'sMug I try. ;) I actually upvoted your answer, then Mast mentioned this in chat and I thought harder about it and decided to write a new answer. :) Sep 26 '17 at 19:27
• I went ahead and removed .net and asp.net-mvc tags from asp.net-core-tagged questions. Sep 26 '17 at 19:37
• @Mat'sMug Awesome! I'm thinking we should create .net-core for the more general .net-core stuff (whatever it may be), this way the users could follow .net-core specifically, or asp.net-core, entity-framework-core, etc. I also think we should burn asp.net-mvc-2-asp.net-mvc-5, there's no reason to have all four of those tags along with asp.net-mvc. Sep 26 '17 at 19:41
• Just an FYI, Angular is Angular 2+. You're probably thinking of AngularJS. I have also requested angular to not be synonyms with angular.js, here.
– Peilonrayz Mod
Sep 27 '17 at 9:07
• @Peilonrayz Yeah, I was thinking what you mentioned (which goes to further prove the confusion) :). Sep 27 '17 at 12:25
• Why would anyone use .net-core? That would be like using a tag elf-binary. What's relevant for reviewing code is the library API, so surely .net-standard would be the useful tag for distinguishing code which is specific to .Net Framework from code which is compatible with .Net Core? Oct 2 '17 at 11:05
• @PeterTaylor The problem with that is how Microsoft chose to name and market it. And every now and then they refer to .net-standard as the .net-core stuff. The main .NET framework does not share compatibilities with .NET Core, in fact, so the .net-core tag would still be sensible there. (It's not like elf-binary because it's forward and reverse incompatible with the .NET Framework 1.0-4.6. Oct 2 '17 at 11:32
• I'm not sure what you mean by "The main .NET framework does not share compatibilities with .NET Core, in fact". For example, .Net Standard 1.6 is compatible with .Net Framework 4.6.1 and .Net Core 1.0. Is your point that .net-core might be useful for the one or two people who might want a review of code which uses namespaces under Microsoft.NETCore? Oct 2 '17 at 11:41
• @PeterTaylor No, my point is that when developing for .net-core things are very different. For example, in .NET core I seem to recall Entity Framework not having a .FirstOrDefault(), instead it has .SingleOrDefault. Oct 2 '17 at 11:44
• Ah, so your point is that .net-core would be appropriate for questions which also have entity-framework-core or asp.net-core? If so, I don't think that comes through very clearly. To what questions would point 2 of the answer apply when point 1 does not? Oct 2 '17 at 12:03
• @PeterTaylor Well .NET core/standard is intentionally cross-platform, among other things. I support the diverged tag for those reasons as well. But yet, I think using .net-core as a replacement for asp.net-core and entity-framework-core is a bad idea. I also appreciate you bringing the discussion up, I'll try to incorporate it in this answer. :) Oct 2 '17 at 12:13
I propose we create a tag for the overarching framework, and replace:
• Why? Sure, it saves a couple of tags in the long run, but how does this improve the situation based on the guidelines of when a tag is useful or not?
– Mast Mod
Sep 26 '17 at 17:58
• @Mast because [.net-core] is the semantically correct thing to do. asp.net-core is already misused alongside with asp.net-mvc, which is totally redundant (the old WebForms framework simply doesn't run on .net core). Or is that a bad reason? Sep 26 '17 at 18:00
• I don't know. But both tags, entity-framework-core and asp-net-core, seem to target a specific framework. So turning them into combination tags doesn't sound logical to me.
– Mast Mod
Sep 26 '17 at 18:39
• Not sure it's so clear-cut. EF-Core is currently used in conjunction with uwp, which implies .net-core, and with asp.net-core, which also implies .net-core. Sep 26 '17 at 18:44
• FWIW I'm hoping to see answers defending the existence of the tags here =) Sep 26 '17 at 19:00
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# How do you graph Fractions/Mixed numbers on a coordinate plane?
The easiest way to graph fractions/mixed numbers onto a coordinate plane is to first take those fractions/mixed numbers and put them in decimal form. That can either be done by hand or by a calculator. Take 4 $\frac{7}{8}$ for instance. Converting that to decimal form would be 4.875.
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Clustering of quasars in a wide luminosity range at redshift 4 with Subaru Hyper Suprime-Cam Wide-field imaging
Clustering of quasars in a wide luminosity range at redshift 4 with Subaru Hyper Suprime-Cam... Abstract We examine the clustering of quasars over a wide luminosity range, by utilizing 901 quasars at $$\overline{z}_{\rm phot}\sim 3.8$$ with −24.73 < M1450 < −22.23 photometrically selected from the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) S16A Wide2 date release and 342 more luminous quasars at 3.4 < zspec < 4.6 with −28.0 < M1450 < −23.95 from the Sloan Digital Sky Survey that fall in the HSC survey fields. We measure the bias factors of two quasar samples by evaluating the cross-correlation functions (CCFs) between the quasar samples and 25790 bright z ∼ 4 Lyman break galaxies in M1450 < −21.25 photometrically selected from the HSC dataset. Over an angular scale of 10$${^{\prime\prime}_{.}}$$0 to 1000$${^{\prime\prime}_{.}}$$0, the bias factors are $$5.93^{+1.34}_{-1.43}$$ and $$2.73^{+2.44}_{-2.55}$$ for the low- and high-luminosity quasars, respectively, indicating no significant luminosity dependence of quasar clustering at z ∼ 4. It is noted that the bias factor of the luminous quasars estimated by the CCF is smaller than that estimated by the auto-correlation function over a similar redshift range, especially on scales below 40$${^{\prime\prime}_{.}}$$0. Moreover, the bias factor of the less-luminous quasars implies the minimal mass of their host dark matter halos is 0.3–2 × 1012 h−1 M⊙, corresponding to a quasar duty cycle of 0.001–0.06. 1 Introduction It is our current understanding that every massive galaxy is likely to have a supermassive black hole (SMBH) at its center (Kormendy & Richstone 1995). Active galactic nuclei (AGNs) are thought to be associated with the growth phase of the BHs through mass accretion. Being the most luminous of the AGN populations, quasars may be the progenitors of the most massive SMBHs in the local universe. Observations over the last decade or so are establishing a series of scaling relations between SMBH mass and properties of their host galaxies (for review see Kormendy & Ho 2013). A similar scaling relation, involving the mass of the SMBH, is reported even with the host dark matter halo (DMH) mass (Ferrarese 2002). As a result, SMBHs are thought to play an important role in galaxy formation and evolution. However, the physical mechanism behind the scaling relations is still unclear. Clustering analysis of AGNs is commonly used to investigate SMBH growth and galaxy evolution in DMHs. Density peaks in the underlying dark matter distribution are thought to evolve into DMHs (e.g., Press & Schechter 1974), in which the entire structure is gravitationally bound with a density 300 times higher than the mean density of the universe. More massive DMHs are formed from rarer density peaks in the early universe, and are more strongly clustered (e.g., Sheth & Torman 1999; Sheth et al. 2001). If focusing on the large-scale clustering, i.e., two-halo term, the mass of quasar host halos can be inferred by estimating the clustering strength of quasars in relative to that of the underlying dark matter, i.e., the bias factor. How the bias factor of quasars depends on redshift and luminosity provides further information on the relation between SMBHs and galaxies within their shared DMH. Many studies, based on the two-point correlation function (2PCF) of quasars, have been conducted by utilizing large databases of quasars, such as the 2dF Quasar Redshift Survey (e.g., Croom et al. 2005) and the Sloan Digital Sky Survey (SDSS; e.g, Myers et al. 2007; Shen et al. 2009; White et al. 2012). The redshift evolution of the auto-correlation function (ACF) indicates that quasars are more strongly biased at higher redshifts. For example, luminous SDSS quasars with −28.2 < M1450 < −25.8 at z ∼ 4 show strong clustering with a bias factor of 12.96 ± 2.09, which corresponds to a host DMH mass of ∼1013 h−1 M⊙ (Shen et al. 2009). It is suggested that such high luminosity quasar activity needs to be preferentially associated with the most massive DMHs in the early universe (White et al. 2008). If we consider the low number density of such massive DMHs at z = 4, the fraction of halos with luminous quasar activity is estimated to be 0.03–0.6 (Shen et al. 2007) or up to 0.1–1 (White et al. 2008). The clustering strength of quasars can be also measured from the cross-correlation function (CCF) between quasars and galaxies (e.g., Adelberger & Steidel 2005; Francke et al. 2007; Font-Ribera et al. 2013). When the size of a quasar sample is limited, the clustering strength of the quasars can be constrained with higher accuracy by using the CCF rather than the ACF since galaxies are usually more numerous than quasars. Enhanced clustering and overdensities of galaxies around luminous quasars are expected from the strong auto-correlation of the SDSS quasars at z ∼ 4. However, observational searches for such overdensities around quasars at high redshifts have not been conclusive. While some luminous z > 3 quasars are found to be in an over-dense region (e.g., Zheng et al. 2006; Kashikawa et al. 2007; Utsumi et al. 2010; Capak et al. 2011; Adams et al. 2015; Garcia-Vergara et al. 2017), a significant fraction of them do not show any surrounding overdensity compared to the field galaxies, and it is suggested that the large-scale (∼10 comoving Mpc) environment around the luminous z > 3 quasars is similar to the Lyman break galaxies (LBGs), i.e., typical star-forming galaxies, in the same redshift range (e.g., Kim et al. 2009; Bañados et al. 2013; Husband et al. 2013; Uchiyama et al. 2018). To investigate the quasar environment at z ∼ 4, the clustering of quasars with lower luminosity at MUV ≳ −25, i.e., typical quasars, which are more abundant than luminous SDSS quasars, is crucial that it can constrain the growth of SMBHs inside galaxies in the early universe (Hopkins et al. 2007). At low redshifts (z ≲ 3), clustering of quasars is found to have no or weak luminosity dependence (e.g., Francke et al. 2007; Shen et al. 2009; Krumpe et al. 2010; Shirasaki et al. 2011). Above z > 3, Ikeda et al. (2015) examined the CCF of 25 less-luminous quasars in the COSMOS field. However, since the sample size is small, the clustering strength of the less-luminous quasars has still not been well constrained, and their correlation with galaxies remains unclear. The wide and deep multi-band imaging dataset of the Subaru Hyper Suprime-Cam Strategic Survey Program (HSC-SSP: Aihara et al. 2018a) provides us with a unique opportunity to examine the clustering of galaxies around high-redshift quasars in a wide luminosity range. Based on an early data release of the survey (S16A: Aihara et al. 2018b), a large sample of less-luminous z ∼ 4 quasars (MUV < −21.5) is constructed for the first time (Akiyama et al. 2018). They cover the luminosity range around the knee of the quasar luminosity function, i.e., they are typical quasars in the redshift range. Additionally, more than 300 SDSS luminous quasars at z ∼ 4 fall within the HSC survey area thanks to a wide field of 339.8 deg2. Likewise, the five bands of HSC imaging are deep enough to construct a sample of galaxies in the same redshift range through the Lyman-break method (Steidel et al. 1996). Here, we examine the clustering of galaxies around z ∼ 4 quasars over a wide luminosity range of −28.0 < M1450 < −22.2 by utilizing the HSC-SSP dataset. By comparing the clustering of the luminous and less-luminous quasars, we can further evaluate the luminosity dependence of the quasar clustering. The outline of this paper is as follows. Section 2 describes the samples of z ∼ 4 quasars and LBGs. Section 3 reports the results of the clustering analysis, and we discuss the implication of the observed clustering strength in section 4. Throughout this paper, we adopt a ΛCDM model with cosmological parameters of H0 = 70 km s−1 Mpc−1 (h = 0.7), Ωm = 0.3, ΩΛ = 0.7, and σ8 = 0.84. All magnitudes are described in the AB magnitude system. 2 Data 2.1 HSC-SSP Wide layer dataset We select the candidates of z ∼ 4 quasars and LBGs from the Wide layer catalog of the HSC-SSP (Aihara et al. 2018a). HSC is a wide-field mosaic CCD camera, which is attached to the prime-focus of the Subaru telescope (Miyazaki et al. 2012, 2018). It covers a field of view (FoV) of 1.°5 diameter with 116 full-depletion CCDs, which have a high sensitivity up to 1 μm. The Wide layer of the survey is designed to cover 1400 deg2 in the g, r, i, z, and y bands with 5σ detection limits of 26.8, 26.4, 26.4, 25.5, and 24.7, respectively, in the five-year survey (Aihara et al. 2018a). In this analysis, we use the S16A Wide2 internal data release (Aihara et al. 2018b), which covers 339.8 deg2 in the five bands, including edge regions where the depth is shallower than the final depth. The data are reduced with hscPipe-4.0.2 (Bosch et al. 2018). The astrometry of the HSC imaging is calibrated by the Pan-STARRS 1 Processing Version 2 (PS1 PV2) data (Magnier et al. 2013), which covers all HSC survey regions to a reasonable depth with a similar set of bandpasses (Aihara et al. 2018b). It is found that the rms of stellar object offsets between the HSC and PS1 positions is ∼40 mas. Extended galaxies have additional offsets with rms values of ∼30 mas in relative to the stellar objects (Aihara et al. 2018b). Following the description in subsections 2.1 and 2.4 in Akiyama et al. (2018), we construct a sample of objects with reliable photometry (referred to as clean objects hereafter). We apply \begin{eqnarray} {\rm flags\_pixel\_edge} = {\rm Not True} \\ \nonumber \end{eqnarray} (1) \begin{eqnarray} {\rm flags\_pixel\_saturated\_center} = {\rm Not True} \\ \nonumber \end{eqnarray} (2) \begin{eqnarray} {\rm flags\_pixel\_cr\_center} = {\rm Not True} \\ \nonumber \end{eqnarray} (3) \begin{eqnarray} {\rm flags\_pixel\_bad} = {\rm Not True} \\ \nonumber \end{eqnarray} (4) \begin{eqnarray} {\rm detect\_is\_primary} = {\rm True} \end{eqnarray} (5)in all of the five bands. These parameters are included as standard output products from the SSP pipeline. Criteria (1)–(4) remove objects detected at the edges of the CCDs, those affected by saturation within their central 3 × 3 pixels, those affected by cosmic-ray hitting within their central 3 × 3 pixels, and those flagged with bad pixels. The final criterion picks out objects after the deblending process for crowded objects. We apply additional masks (for details see subsection 2.4 in Akiyama et al. 2018) to remove junk objects. Patches, defined as a minimum unit of a sub-region with an area about 10$${^{\prime}_{.}}$$0 by 10$${^{\prime}_{.}}$$0, which have color offsets in the stellar sequence larger than 0.075 in any of the g − r vs. r − i, r − i vs. i − z, or i − z vs. z − y color–color planes are removed (see sub-subsection 5.8.4 in Aihara et al. 2018b). Tract 8284 is also removed due to unreliable calibration. Moreover, we remove objects close to bright objects by setting the criterion that $${\rm flags\_pixel\_bright\_object\_center}$$ in all five bands are “Not True”. Regions around objects brighter than 15 in the Guide Star Catalog version 2.3.2 or i = 22 in the HSC S16A Wide2 database are also removed with masks described in Akiyama et al. (2018). After the masking process, the effective survey area is 172.0 deg2. We use PSF magnitudes for stellar objects and CModel magnitudes for extended objects. PSF magnitudes are determined by fitting a model PSF, while CModel magnitudes are determined by fitting a linear combination of exponential and de Vaucouleurs profiles convolved with the model PSF at the position of each object. We correct for galactic extinction in all five bands based on the dust extinction maps by Schlegel, Finkbeiner, and Davis (1998). Only objects that have magnitude errors in the r and i bands smaller than 0.1 are considered. 2.2 Samples of z ∼ 4 quasars We select candidates of z ∼ 4 quasars from the stellar clean objects. In order to separate stellar objects from extended objects, we apply the same criteria as described in Akiyama et al. (2018), \begin{eqnarray} {\rm i\_hsm\_moments\_11}/{\rm i\_hsm\_psfmoments\_11} &<& 1.1; \\ \nonumber \end{eqnarray} (6) \begin{eqnarray} {\rm i\_hsm\_moments\_22}/{\rm i\_hsm\_psfmoments\_22} &<& 1.1. \end{eqnarray} (7) $${\rm i\_hsm\_moments\_11} {\rm (22)}$$ is the second-order adaptive moment of an object in the x (y) direction determined with the algorithm described in Hirata and Seljak (2003) and $${\rm i\_hsm\_psfmoments\_11} {\rm (22)}$$ is that of the model PSF at the object position. The i-band adaptive moments are adopted since the i-band images are selectively taken under good seeing conditions (Aihara et al. 2018b). Objects that have the adaptive moment with “nan” are removed. Since stellar objects should have an adaptive moment that is consistent with that of the model PSF, we set the above stellar/extended classification criteria. The selection completeness and the contamination are examined by Akiyama et al. (2018). At i < 23.5, the completeness is above 80% and the contamination from extended objects is lower than 10%. At fainter magnitudes (i > 23.5), the completeness rapidly declines to less than 60% and the contamination sharply increases to greater than 10% (see the middle panel of figure 1 in Akiyama et al. 2018). To avoid severe contamination by extended objects, we limit the faint end of the quasar sample to i = 23.5. Fig. 1. View largeDownload slide i-band magnitude distributions of the samples. Left: Red and black histograms show the distributions of the z ∼ 4 quasar candidates from the HSC-SSP and SDSS, respectively. Right: The blue histogram represents the distribution of the z ∼ 4 LBGs from the HSC-SSP. (Color online) Fig. 1. View largeDownload slide i-band magnitude distributions of the samples. Left: Red and black histograms show the distributions of the z ∼ 4 quasar candidates from the HSC-SSP and SDSS, respectively. Right: The blue histogram represents the distribution of the z ∼ 4 LBGs from the HSC-SSP. (Color online) We apply the Lyman-break selection to identify quasars at z ∼ 4. The selection utilizes the spectral property that the continuum blue-ward of the Lyα line (λrest = 1216 Å) is strongly attenuated by absorption due to the intergalactic medium (IGM). The Lyα line of an object at z = 4.0 is redshifted to 6075 Å in the observed frame, which is in the middle of the r-band, as a result the object has a red g − r color. We apply the same color selection criteria as described in Akiyama et al. (2018). In total, 1023 z ∼ 4 quasar candidates in the magnitude range 20.0 < i < 23.5 are selected. We limit the bright end of the sample considering the effects of saturation and non-linearity. Even though we include edge regions with a shallow depth for the sample selection, we do not find a significant difference of the number densities in the edge and central regions. Therefore, we conclude that larger photometric uncertainties or a higher number density of junk objects in the shallower regions do not result in higher contamination for quasars in the region. The i-band magnitude distribution of the sample is shown with the red histogram in the left-hand panel of figure 1. The completeness of the color selection is examined with the 3.5 < zspec < 4.5 SDSS quasars with i > 20.0 within the HSC coverage (Akiyama et al. 2018). Among 92 SDSS quasars with clean HSC photometry, 61 of them pass the color selection, resulting in the completeness of 66%. Since the sample is photometrically selected, it can be contaminated by galactic stars and compact galaxies that meet the color selection criteria. The contamination rate is further evaluated by using mock samples of galactic stars and galaxies; the contamination rate is less than 10% at i < 23.0, and increases to more than 40% at i ∼ 23.5. It causes an excess of HSC quasars in faint magnitude bins (23.2 < i < 23.5) as shown in the left-hand panel of figure 1. Since the contamination rate sharply increases at i > 23.5, we limit the sample at this magnitude. For the bright end, as the luminous SDSS quasar sample primarily includes quasars brighter than i = 21.0, we consider the HSC quasar sample fainter than i = 21.0 to constitute the less-luminous quasar sample. Finally, 901 quasars from the HSC are selected in the magnitude range of 21.0 < i < 23.5. Here, we convert the i-band apparent magnitude to the UV absolute magnitude at 1450 Å using the average quasar SED template provided by Siana et al. (2008) at z ∼ 4, which results in a magnitude range of −24.73 < M1450 < −22.23. In Akiyama et al. (2018), a best-fitting analytic formula of the contamination rate as a function of the i-band magnitude is provided. If we apply it to the less-luminous quasar sample, it is expected that 90 out of 901 candidates are contaminating objects, i.e., contamination rate of the z ∼ 4 less-luminous quasar sample is 10.0%. The redshift distribution of the z ∼ 4 less-luminous quasar candidates is shown in figure 2 with the red histogram. For 32 candidates with spectroscopic redshift information, we adopt their spectroscopic redshifts, otherwise the redshifts are estimated with a Bayesian photometric redshift estimator using a library of mock quasar templates (Akiyama et al. 2018). Most of the quasars are in the redshift range between 3.4 and 4.6. Average and standard deviation of the redshift distribution are 3.8 and 0.2, respectively. Fig. 2. View largeDownload slide Redshift distributions of the samples. The red histogram indicates the redshift distribution of the less-luminous quasar sample determined either spectroscopically or photometrically (Akiyama et al. 2018). The black dashed histogram shows the spectroscopic redshift distribution of the luminous quasar sample. The blue histogram represents the expected redshift distribution of the LBG sample evaluated with the mock LBGs (see text in subsection 2.4). All histograms are normalized so that $$\int _{0}^{\infty }N(z)dz=1$$. (Color online) Fig. 2. View largeDownload slide Redshift distributions of the samples. The red histogram indicates the redshift distribution of the less-luminous quasar sample determined either spectroscopically or photometrically (Akiyama et al. 2018). The black dashed histogram shows the spectroscopic redshift distribution of the luminous quasar sample. The blue histogram represents the expected redshift distribution of the LBG sample evaluated with the mock LBGs (see text in subsection 2.4). All histograms are normalized so that $$\int _{0}^{\infty }N(z)dz=1$$. (Color online) In order to examine the luminosity dependence of the quasar clustering, a sample of luminous z ∼ 4 quasars is constructed based on the 12th spectroscopic data release of the Sloan Digital Sky Survey (SDSS) (Alam et al. 2015). We select quasars with criteria on object type (“QSO”), reliability of the spectroscopic redshift (“z_waring” flag = 0), and estimated redshift error (smaller than 0.1). Only quasars within the coverage of the HSC S16A Wide2 data release are considered. We limit the redshift range between 3.4 and 4.6 following the redshift distribution of the HSC z ∼ 4 LBG sample (which will be discussed in subsection 2.4). In the coverage of the HSC S16A Wide2 data release, there are 342 quasars that meet the selection criteria. Their redshift distribution is shown by black dashed histogram in figure 2. Average and standard deviation of the redshift distribution are 3.77 and 0.26, respectively. Although the redshift distribution of the SDSS sample shows excess around z ∼ 3.5 compared to the HSC sample, the average and standard deviations are close to each other. The i-band magnitude distribution of the SDSS quasars is plotted by the black histogram in the left-hand panel of figure 1. To determine their i-band magnitude in the HSC photometric system, we match the sample to HSC clean objects using a search radius of 1$${^{\prime\prime}_{.}}$$0. Out of the 342 SDSS quasars, 296 have a corresponding object among the clean objects, while the others are saturated in the HSC imaging data. For the remaining 46 quasars, we convert their r- and i-band magnitudes in the SDSS system to the i-band magnitude in the HSC system following the equations in subsection 3.3 in Akiyama et al. (2018). As can be seen from the distributions, the SDSS quasar sample covers a magnitude range about 2 mag brighter than the HSC quasar sample. Their corresponding UV absolute magnitudes at 1450 Å are in the range of −28.0 to −23.95 evaluated by the same method with the less-luminous quasar sample. 2.3 Sample of z ∼ 4 LBGs from the HSC dataset We select candidates of z ∼ 4 LBGs from the S16A Wide2 dataset in the similar way as we select the z ∼ 4 quasar candidates. Unlike the process for quasars, we select candidates from the extended clean objects instead of the stellar objects, i.e., we pick out the clean objects that do not meet either of the equations (6) or (7) as extended objects. As shown in figure 9 of Akiyama et al. (2018), extended galaxies at z > 3 are distinguishable from stellar quasars with these criteria, as a result of the good image quality of the i-band HSC Wide layer images, which has a median seeing size of 0$${^{\prime\prime}_{.}}$$61 (Aihara et al. 2018b). While the stellar/extended classification is ineffective at i > 23.5, the contamination of stellar objects to the LBG sample is negligible, because the extended objects outnumber the stellar objects by ∼30 times at 23.5 < i < 25.0. We determine the color selection criteria of z ∼ 4 LBGs based on color distributions of a library of model LBG spectral energy distributions (SEDs), because the sample of z ∼ 4 LBGs with a spectroscopic redshift at the depth of the HSC Wide layer is limited. The model SEDs are constructed with the stellar population synthesis model by Bruzual and Charlot (2003). We assume a Salpeter initial mass function (Salpeter 1955) and the Padova evolutionary track for stars (Fagotto et al. 1994a, 1994b, 1994c) of solar metallicity. Following a typical star-formation history of z ∼ 4 LBGs derived based on an optical–NIR SED analysis (e.g., Shapley et al. 2001; Nonino et al. 2009; Yabe et al. 2009), we adopt an exponentially declining star-formation history with ψ(t) = τ−1exp(−t/τ), where τ = 50 Myr and t = 300 Myr. In addition to the stellar continuum component, we also consider the Lyα emission line at 1216 Å with a equivalent width (EWLyα) randomly distributed within the range between 0 and 30 Å, which is determined to follow the Lyα EW distribution of luminous LBGs in the UV absolute magnitude range of −23.0–−21.5 (Ando et al. 2006). We apply extinction as a screen dust with the dust extinction curve of Calzetti et al. (2000). We assume that E(B − V) has a Gaussian distribution with a mean of 0.14 and 1σ of 0.07 following that observed for z ∼ 3 UV-selected galaxies (Reddy et al. 2008). In order to reproduce the observed scatter of the g − r color of galaxies at z ∼ 3 (see figure 3), the scatter of the color excess is doubled to σ = 0.14. In total, 3000 SED templates are constructed. Each template is redshifted to z = 2.5–5.0 with an interval of 0.1. Attenuation by the intergalactic medium is applied to the redshifted templates. We follow the updated number density of the Lyα absorption systems in Inoue et al. (2014), and consider scatter in the number density of the systems along different line of sights with the Monte Carlo method used in Inoue and Iwata (2008). In figure 3, we compare the distributions of the g − r and r − z colors of the templates with those of spectroscopically confirmed LBGs at i < 24.5 in the HSC-SSP catalogs of the Ultra-Deep layer. Since spectroscopically-identified LBGs selected from narrow-band colors are biased towards LBGs with large Lyα EW, we remove them in the spectroscopically-identified sample. The color distribution of the mock LBGs as a function of redshift reproduces that of the galaxies with spectroscopic redshifts around 3. At z > 3.5, real galaxies follow the color evolution trend of the mock LBGs with slightly bluer g − r and r − z colors. Since the discrepancy is within the scatter and size of sample is limited, we adopt the current mock LBG library in this work. Fig. 3. View largeDownload slide g − r (left) and r − z (right) colors versus redshift of the mock LBGs. The red line and the error bars are the average and 1σ scatter of the colors of the mock LBGs. Blue points represent spectroscopically confirmed galaxies within the HSC S16A Ultra-Deep layer. (Color online) Fig. 3. View largeDownload slide g − r (left) and r − z (right) colors versus redshift of the mock LBGs. The red line and the error bars are the average and 1σ scatter of the colors of the mock LBGs. Blue points represent spectroscopically confirmed galaxies within the HSC S16A Ultra-Deep layer. (Color online) Considering the color distributions of the mock LBGs and the LBGs with a spectroscopic redshift, we determine the color selection criteria on the g − r vs. r − z color–color diagram as shown in figure 4 with the blue dashed lines. Blue crosses and black triangles represent colors of galaxies with a spectroscopic redshift at 0.2 < z < 0.8 and 0.8 < z < 3.5, respectively, in the HSC Ultra-deep-layer photometry. Red stars are galaxies at 3.5 < z < 4.5. We plot the color track of the model LBG with the black solid line, and mark the colors at z = 2.5, 3.0, 3.5, 4.0, and 4.4 with the 1σ scatter. The pink shaded region represents 1σ scatter of the r − z color along the model track. The selection criteria are \begin{eqnarray} 0.909(g-r)-0.85>(r-z), \\ \nonumber \end{eqnarray} (8) \begin{eqnarray} (g-r)>1.3, \\ \nonumber \end{eqnarray} (9) \begin{eqnarray} (g-r)<2.5. \end{eqnarray} (10)We determine the selection criteria to enclose the large part of the color distribution of the models while preventing severe contamination from low-redshift galaxies. The third criterion limits the upper redshift range of the sample, and is adjusted to match the expected redshift distribution of the less-luminous z ∼ 4 quasars. In order to reduce contaminations by low-redshift red galaxies and objects with unreliable photometry, we consider two additional criteria: \begin{eqnarray} (i-z)<0.2, \\ \nonumber \end{eqnarray} (11) \begin{eqnarray} (z-y)<0.2, \end{eqnarray} (12)following figure 3 in Akiyama et al. (2018). Because the contamination by low-redshift galaxies is severe at magnitudes fainter than i = 24.5, we limit the sample at this magnitude. Finally, we select 25790 z ∼ 4 LBG candidates at i < 24.5. The i-band magnitude distribution of the candidates is shown in the right-hand panel of figure 1. The brightest candidate is at i = 21.87, but there are only four candidates at i < 22. Thus we plot the distribution from i = 22. The corresponding UV absolute magnitudes of the candidates at 1450 Å are evaluated to be in the range of −23.88 < M1450 < −21.25 by the model LBG at z ∼ 4. It should be noted that there is a difference in the sky coverage between both of the quasar samples and i < 24.5 LBGs, because of the edge regions with shallow depth where only the quasars are selected reliably. Such selection effects are taken into consideration when constructing the random sample (subsection 2.5). Fig. 4. View largeDownload slide Color selection of z ∼ 4 LBGs. Blue crosses and black triangles are galaxies at 0.2 < z < 0.8 and 0.8 < z < 3.5, respectively. Only 5.0% of them are plotted, for clarity. Red stars are galaxies at 3.5 < z < 4.5. Purple inverted triangle is galaxy at z > 4.5. Green dots are colors of stars derived in the spectro-photometric catalog by Gunn and Stryker (1983). The solid black line is the track of the model LBG. Black squares and error bars denote the average and 1σ color scatter of the mock LBGs along the track at z = 2.5, 3.0, 3.5, 4.0, and 4.4. Pink shaded area implies the 1σ r − z scatter of the mock LBGs. Blue dashed lines represent our selection criteria. (Color online) Fig. 4. View largeDownload slide Color selection of z ∼ 4 LBGs. Blue crosses and black triangles are galaxies at 0.2 < z < 0.8 and 0.8 < z < 3.5, respectively. Only 5.0% of them are plotted, for clarity. Red stars are galaxies at 3.5 < z < 4.5. Purple inverted triangle is galaxy at z > 4.5. Green dots are colors of stars derived in the spectro-photometric catalog by Gunn and Stryker (1983). The solid black line is the track of the model LBG. Black squares and error bars denote the average and 1σ color scatter of the mock LBGs along the track at z = 2.5, 3.0, 3.5, 4.0, and 4.4. Pink shaded area implies the 1σ r − z scatter of the mock LBGs. Blue dashed lines represent our selection criteria. (Color online) 2.4 Redshift distribution and contamination rate of the z ∼ 4 LBG sample The redshift distribution of the LBG sample is evaluated by applying the same selection criteria to a sample of mock LBGs, which are constructed in the redshift range between 3.0 and 5.0 with a 0.1 redshift bin. At each redshift bin, we randomly select LBG templates from our library of SEDs and normalize them to have 22.0 < i < 24.5 following the LBG UV luminosity function at z ∼ 3.8 (van der Burg et al. 2010). We convert the apparent i-band magnitude to the absolute UV magnitude based on the selected templates. It should be noted that an object with a fixed apparent magnitude has a higher luminosity and a smaller number density in the luminosity function at higher redshifts. We also consider the difference in comoving volume at each redshift bin. For each redshift bin, we then place the mock LBGs at random positions in the HSC Wide layer images with a density of 2000 galaxies per deg2, and apply the same masking process as for the real objects. We calculate the expected photometric error at each position using the relation between the flux uncertainty and the value of image variance. This relation is determined empirically with the flux uncertainty of real objects as a function of the PSF and object size. The variance is measured within 1″ × 1″ at each point. The size of the model PSF at the position is evaluated with the model PSF of the nearest real object in the database. In order to reproduce the photometric error associated with the real LBGs, we use the relation for a size of 1$${^{\prime\prime}_{.}}$$5. After calculating the photometric error with this method, we add a random photometric error assuming the Gaussian distribution. Finally, we apply the color selection criteria and remove mock LBGs with magnitude errors larger than 0.1 in either of the i or r bands. The ratio of the recovered mock LBGs to the full random mock LBGs is evaluated as the selection completeness at each redshift bin. We find that the selection completeness is ∼10.0%–30.0% in the redshift range between 3.5 and 4.2, but smaller than 5% at other redshifts. These low rates are due to the fact that we set stringent constraints so that we can prevent the severe contamination from low-redshift galaxies. Based on a selection completeness of 20.0% at 3.5 < z < 4.2, we calculate an expected number of 35988 LBGs with 22 < i < 24.5 in the HSC-SSP S16A Wide layer from the LBG UV luminosity function at z ∼ 3.8 (van der Burg et al. 2010), which is larger than the actual LBG sample size (25790) in this work since we consider the edge regions that have a shallow depth. The effect of the shallow depth is considered in the construction of the random objects (subsection 2.5). The redshift distribution is measured by multiplying the completeness ratio with the number of mock LBGs at each redshift, which is shown in figure 2 by the blue histogram. The average and 1σ of the distribution is 3.71 and 0.30, respectively. The redshift distribution of the LBGs is similar to that of the luminous quasar sample, but slightly extended toward lower redshifts than the less-luminous quasar sample. It is likely that the extension is due to the higher number density of LBGs in 22.0 < i < 24.5 at 3.3 < z < 3.5. The LBG sample can be contaminated by low-redshift red galaxies which have similar photometric properties to the z ∼ 4 LBGs. We evaluate the contamination rate of the LBG selection using the HSC photometry in the COSMOS region and the COSMOS i-band selected photometric redshift catalogue, which is constructed by a χ2 template-fitting method with 30 broad, intermediate, and narrow bands from UV to mid-IR in the 2 deg2 COSMOS field (Ilbert et al. 2009). In the HSC-SSP S15B internal database, three stacked images in the COSMOS region, simulating good, median, and bad seeing conditions, are provided. Since the i-band images of the Wide layer are selectively taken under good or median seeing conditions (Aihara et al. 2018b), we match the catalogs from the median stacked image, which has a FWHM of 0$${^{\prime\prime}_{.}}$$70, with galaxies in the photometric redshift catalog within an angular separation of 1$${^{\prime\prime}_{.}}$$0. As examined by Ilbert et al. (2009), the photometric redshift uncertainty of galaxies with COSMOS i΄-band magnitudes brighter than 24.0 is estimated to be smaller than 0.02 at z < 1.25. For galaxies within the same luminosity range at higher redshifts, 1.25 < z < 3, the uncertainty is significantly higher but roughly below 0.1. Thus we only include objects with photometric redshift uncertainties less than 0.02 and 0.1 at z < 1.25 and at z > 1.25, respectively, in the matched catalog. We apply the color selection criteria (8)–(12) to the matched catalog. Among 700 matched galaxies with 3.5 < zphot < 4.5, 117 galaxies pass the selection criteria, resulting in the completeness of 17%, which is consistent with that examined by the mock LBGs. Meanwhile, we investigate the contamination by the ratio of galaxies at z < 3 or z > 5 among those passing the selection criteria at each magnitude bin of 0.1. It is found that the contamination rate is 10% to 30% in the magnitude range of i = 23.5–24.5, and sharply increases to >50% at i = 25.0. In total, all contaminating sources are classified to be at z < 3, while 95% of them are at z < 1. We multiply the contamination rate as a function of the i-band magnitude with the number counts of the LBG candidates at each 0.1 bin to estimate the total number of contaminating sources in the sample. Among 25790 LBG candidates, 5886 are expected to be contaminating objects at z < 3, i.e., the contamination rate is 22.8%. Furthermore, we also check the photometric redshift of the LBG candidates determined with the five-band HSC Wide layer photometry via the MIZUKI photometric redshift code, which uses the Bayesian photometric redshift estimation (Tanaka et al. 2018). Among the 25790 z ∼ 4 LBG candidates, 25749 of them have photometric redshifts with the MIZUKI code, and 4091 of them have photometric redshifts lower than z = 3.0. The contamination rate is evaluated to be 15.9%, which is similar to the one evaluated in the COSMOS region. Since the COSMOS photometric redshift catalog is based on the 30-band photometry covering a wider wavelength range, we consider the contamination rate evaluated in the COSMOS region in the later clustering analysis. 2.5 Constructing random objects for the clustering analysis The clustering strength is evaluated by comparing the number of pairs of real objects and that of mock objects distributed randomly in the survey area. Therefore it is necessary to construct a sample of mock objects that are distributed randomly within the survey area and are selected with the same selection function as the real sample. From z = 3 to 5, we construct 3000 mock LBG SEDs, which are normalized to have i = 24.5, at each 0.1 redshift bin. Then we place the mock LBGs randomly over the survey region with a surface number density of 2000 LBGs per deg2, with errors as described in subsection 2.4. After applying the same color selection and magnitude error criteria as for the real objects, we create a sample of 150756 random LBGs, which reproduces the global distribution of the real LBGs including the edge of the survey region where the depth is shallower. Therefore, the clustering analysis on large scales is not affected by the discrepancy of the sky coverage between the quasars and LBGs. Furthermore, since the detection completeness can be affected by non-uniform seeing within the Wide layer dataset especially at i = 24.5, it is important to reproduce the seeing dependence of the LBG detection completeness in the construction of the random LBGs. Over the entire clean area, 11.2% and 12.1% patches are taken under seeing smaller than 0$${^{\prime\prime}_{.}}$$5 and greater than 0$${^{\prime\prime}_{.}}$$7, respectively. For the LBG sample at i < 24.5, there are 15.8% and 7.7% of them taken under seeing smaller than 0$${^{\prime\prime}_{.}}$$5 and greater than 0$${^{\prime\prime}_{.}}$$7, respectively, suggesting a higher (lower) detection completeness with better (worse) seeing. We plot the cumulative probability functions (CPFs) of the seeing for LBGs, random LBGs, and the entire clean region in figure 5. It can be seen that the random LBGs reproduce the seeing dependence of the detection completeness. Fig. 5. View largeDownload slide Cumulative probability functions of the i-band seeing at the position of the selected z ∼ 4 LBG candidates (red line), random LBGs (blue line) and entire clean area (black line). (Color online) Fig. 5. View largeDownload slide Cumulative probability functions of the i-band seeing at the position of the selected z ∼ 4 LBG candidates (red line), random LBGs (blue line) and entire clean area (black line). (Color online) 3 Clustering analysis 3.1 Cross-correlation functions of the less-luminous and luminous quasars at z ∼ 4 We evaluate the CCFs of the z ∼ 4 quasars and LBGs with the projected two-point angular correlation function, ω(θ), since most of the quasar and LBG candidates do not have spectroscopic redshifts. We use the estimator from Davis and Peebles (1983), $$\omega (\theta )=\frac{DD(\theta )}{DR(\theta )}-1,$$ (13)where DD(θ) = ⟨DD⟩/NQSONLBG and DR(θ) = ⟨DR⟩/ NQSONR are the normalized quasar–LBG pair counts and quasar–random LBG pair counts in an annulus between θ − Δθ and θ + Δθ, respectively. Here, ⟨DD⟩ and ⟨DR⟩ are the numbers of quasar–LBG and quasar–random LBG pairs in the annulus, and NQSO, NLBG, and NR are the total numbers of quasars, LBGs and random LBGs, respectively. We set 14 bins from 1$${^{\prime\prime}_{.}}$$0 to 1000$${^{\prime\prime}_{.}}$$0 in the logarithmic scale. The CCFs of the quasars and LBGs for the less-luminous and luminous quasars are plotted in the left and right-hand panels of figure 6, respectively, and summarized in table 1 along with the pair count in each bin. Fig. 6. View largeDownload slide Left-hand panel: Blue dots are the observed mean CCF ωobs of the less-luminous quasars and the LBGs at z ∼ 4 obtained from the Jackknife resampling. The black solid line is the best-fitting power-law model using ML fitting on the scale of 10$${^{\prime\prime}_{.}}$$0 to1000$${^{\prime\prime}_{.}}$$0. The red dash–dotted line is the best-fitting dark matter model ωDM (red long-dashed line) adopting ML fitting in the same scale based on the HALOFIT power spectrum (Smith et al. 2003), while the blue dash–dotted line is the best-fitting dark matter model $$\omega _{\rm DM}^{\prime }$$ (blue short-dashed line) after considering the contaminations of the less-luminous quasars and the LBGs. Right-hand panel: Blue stars are the observed mean CCF ωobs of the luminous quasars and the LBGs at z ∼ 4 got from the Jackknife resampling. Red and blue lines have the same meaning as in the the left-hand panel but the blue line only considers the contamination of the LBGs. The orange dash–double-dotted line is the expected CCF of the luminous quasars estimated by the luminous quasars ACF in Shen et al. (2009). The green thick long-dashed and pink thick dashed lines are the best-fitting power-law models on the scale of 40$${^{\prime\prime}_{.}}$$0 to 160$${^{\prime\prime}_{.}}$$0 and of 40$${^{\prime\prime}_{.}}$$0 to 1000$${^{\prime\prime}_{.}}$$0, respectively. In both of the panels, symbols just on the horizontal axis with no error bar beyond 10$${^{\prime\prime}_{.}}$$0, those with no error bar within 10$${^{\prime\prime}_{.}}$$0, and those with error bars in the top pad mean negative bins with a small error bar, zero bins without pair count, and negative or zero bins with a large error bar, respectively. Top and bottom panels show the logarithmic and the linear scale of the vertical axis, respectively. The top horizontal axis of the top panel implies the comoving distance at redshift 4. (Color online) Fig. 6. View largeDownload slide Left-hand panel: Blue dots are the observed mean CCF ωobs of the less-luminous quasars and the LBGs at z ∼ 4 obtained from the Jackknife resampling. The black solid line is the best-fitting power-law model using ML fitting on the scale of 10$${^{\prime\prime}_{.}}$$0 to1000$${^{\prime\prime}_{.}}$$0. The red dash–dotted line is the best-fitting dark matter model ωDM (red long-dashed line) adopting ML fitting in the same scale based on the HALOFIT power spectrum (Smith et al. 2003), while the blue dash–dotted line is the best-fitting dark matter model $$\omega _{\rm DM}^{\prime }$$ (blue short-dashed line) after considering the contaminations of the less-luminous quasars and the LBGs. Right-hand panel: Blue stars are the observed mean CCF ωobs of the luminous quasars and the LBGs at z ∼ 4 got from the Jackknife resampling. Red and blue lines have the same meaning as in the the left-hand panel but the blue line only considers the contamination of the LBGs. The orange dash–double-dotted line is the expected CCF of the luminous quasars estimated by the luminous quasars ACF in Shen et al. (2009). The green thick long-dashed and pink thick dashed lines are the best-fitting power-law models on the scale of 40$${^{\prime\prime}_{.}}$$0 to 160$${^{\prime\prime}_{.}}$$0 and of 40$${^{\prime\prime}_{.}}$$0 to 1000$${^{\prime\prime}_{.}}$$0, respectively. In both of the panels, symbols just on the horizontal axis with no error bar beyond 10$${^{\prime\prime}_{.}}$$0, those with no error bar within 10$${^{\prime\prime}_{.}}$$0, and those with error bars in the top pad mean negative bins with a small error bar, zero bins without pair count, and negative or zero bins with a large error bar, respectively. Top and bottom panels show the logarithmic and the linear scale of the vertical axis, respectively. The top horizontal axis of the top panel implies the comoving distance at redshift 4. (Color online) Table 1. Less-luminous and luminous quasar–LBG CCFs at z ∼ 4. θ (″) (θmin, θmax) Less-luminous Luminous ⟨DQDG⟩ ⟨DQRG⟩ ω(θ) $$\overline{\omega _{i}(\theta )}$$ σ(θ) ⟨DQDG⟩ ⟨DQRG⟩ ω(θ) $$\overline{\omega _{i}(\theta )}$$ σ(θ) 2.05 (1.58, 2.51) 0 0 0 0 0 0 0 0 0 3.25 (2.51, 3.98) 2 3 2.90 3.25 8.74 0 1 −1 −1 9.76 5.15 (3.98, 6.31) 4 6 2.90 2.86 2.51 3 0 0 0 8.53 8.15 (6.31, 10.00) 3 7 1.51 1.58 1.91 0 4 −1 −1 1.69 12.92 (10.00, 15.85) 5 10 1.92 1.96 1.79 1 9 −0.35 −0.33 0.86 20.48 (15.85, 25.12) 7 47 −0.13 −0.11 0.47 3 6 1.92 1.96 2.11 32.46 (25.12, 39.81) 28 120 0.36 0.36 0.26 1 41 −0.86 −0.85 0.15 51.45 (39.81, 63.10) 52 303 0.003 −0.002 0.18 25 96 0.52 0.53 0.32 81.55 (63.10, 100.00) 143 739 0.13 0.13 0.13 47 226 0.22 0.21 0.27 129.24 (100.00, 158.49) 334 1710 0.14 0.14 0.09 116 589 0.15 0.15 0.14 204.84 (158.49, 251.19) 754 4144 0.06 0.06 0.04 257 1407 0.07 0.07 0.08 324.65 (251.19, 398.11) 1887 10375 0.06 0.06 0.04 585 3677 −0.07 −0.07 0.04 514.53 (398.11, 630.96) 4564 25764 0.04 0.04 0.02 1669 9272 0.05 0.05 0.07 815.48 (630.96, 1000.00) 11065 63358 0.02 0.02 0.02 3967 23241 −0.002 −0.005 0.03 θ (″) (θmin, θmax) Less-luminous Luminous ⟨DQDG⟩ ⟨DQRG⟩ ω(θ) $$\overline{\omega _{i}(\theta )}$$ σ(θ) ⟨DQDG⟩ ⟨DQRG⟩ ω(θ) $$\overline{\omega _{i}(\theta )}$$ σ(θ) 2.05 (1.58, 2.51) 0 0 0 0 0 0 0 0 0 3.25 (2.51, 3.98) 2 3 2.90 3.25 8.74 0 1 −1 −1 9.76 5.15 (3.98, 6.31) 4 6 2.90 2.86 2.51 3 0 0 0 8.53 8.15 (6.31, 10.00) 3 7 1.51 1.58 1.91 0 4 −1 −1 1.69 12.92 (10.00, 15.85) 5 10 1.92 1.96 1.79 1 9 −0.35 −0.33 0.86 20.48 (15.85, 25.12) 7 47 −0.13 −0.11 0.47 3 6 1.92 1.96 2.11 32.46 (25.12, 39.81) 28 120 0.36 0.36 0.26 1 41 −0.86 −0.85 0.15 51.45 (39.81, 63.10) 52 303 0.003 −0.002 0.18 25 96 0.52 0.53 0.32 81.55 (63.10, 100.00) 143 739 0.13 0.13 0.13 47 226 0.22 0.21 0.27 129.24 (100.00, 158.49) 334 1710 0.14 0.14 0.09 116 589 0.15 0.15 0.14 204.84 (158.49, 251.19) 754 4144 0.06 0.06 0.04 257 1407 0.07 0.07 0.08 324.65 (251.19, 398.11) 1887 10375 0.06 0.06 0.04 585 3677 −0.07 −0.07 0.04 514.53 (398.11, 630.96) 4564 25764 0.04 0.04 0.02 1669 9272 0.05 0.05 0.07 815.48 (630.96, 1000.00) 11065 63358 0.02 0.02 0.02 3967 23241 −0.002 −0.005 0.03 View Large The uncertainty of the CCFs is evaluated through the Jackknife resampling (Zehavi et al. 2005). We separate the survey area into N = 22 subregions with a similar size. In the ith resampling, we ignore one of the subregions to construct a new set of samples of quasars, LBGs, and random LBGs and estimate their correlation function, ωi. We evaluate the uncertainty only by the diagonal elements of the covariance matrix $${\boldsymbol C}(\omega _{i},\omega _{j})=\frac{N-1}{N}{\sum _{k=1}^{N}(\omega ^{k}_{i}-\overline{\omega _{i}})(\omega ^{k}_{j}-\overline{\omega _{j}})},$$ (14)where $$\overline{\omega _{i}}$$ is the mean of ωi over the N Jackknife samples, because the diagonal elements are sufficient to recover the true uncertainty (Zehavi et al. 2005). The $$\overline{\omega _{i}}$$ at each radius bin is consistent with the CCFs of the whole samples of the less-luminous and luminous quasars as shown in table 1 though the discrepancy becomes larger below 10$${^{\prime\prime}_{.}}$$0. We adopt $$\overline{\omega _{i}}$$ for plotting and analysis throughout this work. The resulting uncertainty with the Jackknife resampling is about 1.5–2 times larger than the Poisson error $$\lbrace \sigma (\theta )=[1+\omega (\theta )]/\sqrt{N_{\rm pair}}\rbrace$$ on the scale beyond 500$${^{\prime\prime}_{.}}$$0. However, these two error estimators are consistent with each other on scales within 300$${^{\prime\prime}_{.}}$$0. On scales smaller than 20$${^{\prime\prime}_{.}}$$0, due to the limited quasar–LBG pair count, the Poisson error can be even larger than the Jackknife one if we evaluate the Poisson uncertainty with the Poisson statistics for a small sample (Gehrels 1986). Here, since we do not consider the small scale within 10$${^{\prime\prime}_{.}}$$0 in the fitting process, we adopt the Jackknife error for the CCF beyond 10$${^{\prime\prime}_{.}}$$0. For the scale within 10$${^{\prime\prime}_{.}}$$0, if the Jackknife estimator fails to give a value due to either of no ⟨DD⟩ or ⟨DR⟩ pair count in any subsamples, we show the Poisson error following the Poisson statistics for a small sample (Gehrels 1986) in table 1 and figure 6. The binned CCF is fitted through the χ2 minimization with a single power-law model $$\omega (\theta )=A_{\omega }\theta ^{-\beta }-{\rm IC}.$$ (15)We apply a β of 0.86, which is determined with the ACF of the LBGs in the following subsection 3.2. IC is the integral constraint, which is a negative offset due to the restricted area of an observation (Groth & Peebles 1977). As described in Roche et al. (2002), the integral constraint can be estimated by integrating the true ω(θ) on the total survey area Ω as $${\rm IC}=\frac{1}{\Omega ^{2}}\int \int \omega (\theta )d\Omega _{1}d\Omega _{2}.$$ (16)We calculate the integral constraint using random LBG–random LBG pairs over the entire survey area through $${\rm IC}=\frac{\sum {[RR(\theta )A_{\omega }\theta ^{-\beta }]}}{\sum {RR(\theta )}}$$ (17)following Roche et al. (2002). Since the survey area is wide and the scale of interest is within 1000$${^{\prime\prime}_{.}}$$0, the IC/Aω is small compared to the observed CCFs and the IC term can be neglected in the fitting process. In this study, we focus on the large-scale clustering between two halos, i.e., the two-halo term. Thus the excess within an individual halo (one-halo term) is not considered in the fitting process. The radial scale of the region dominated by the one-halo term is examined to be 0.2–0.5 comoving h−1 Mpc (e.g., Ouchi et al. 2005; Kayo & Oguri 2012). At redshift 4, the corresponding angular separation is ∼10$${^{\prime\prime}_{.}}$$0–20$${^{\prime\prime}_{.}}$$0. Thus we fit the binned CCF with Aω on the scale larger than 10$${^{\prime\prime}_{.}}$$0. The best-fitting Aω is summarized in table 2 where the upper and lower limits correspond to Δχ2 = 1 from the minimal χ2. Here, the χ2 fitting fails to fit the CCF of the SDSS luminous quasars with negative bins due to the limited luminous quasar sample size. Table 2. Summary of clustering analysis for the CCFs. CF Model* Fitting $$\bar{z}$$ [θmin, θmax] Aω r0 bQG bQSO logMDMH (″) (h−1 Mpc) (h−1 M⊙) Power-law χ2 3.80 [10, 1000] $$6.03^{+1.65}_{-1.65}$$ $$7.13^{+0.99}_{-1.13}$$ $$5.62^{+0.72}_{-0.82}$$ $$5.48^{+1.25}_{-1.32}$$ $$12.07^{+0.33}_{-0.49}$$ Power-law΄ χ2 3.80 [10, 1000] $$8.67^{+2.37}_{-2.37}$$ $$8.66^{+1.20}_{-1.37}$$ $$6.74^{+0.87}_{-0.98}$$ $$6.10^{+1.40}_{-1.47}$$ $$12.25^{+0.32}_{-0.47}$$ Less- Power-law ML 3.80 [10, 1000] $$6.53^{+1.85}_{-1.81}$$ $$7.44^{+1.07}_{-1.19}$$ $$5.85^{+0.78}_{-0.87}$$ $$5.94^{+1.42}_{-1.46}$$ $$12.20^{+0.33}_{-0.49}$$ luminous Power-law΄ ML 3.80 [10, 1000] $$9.39^{+2.66}_{-2.60}$$ $$9.04^{+1.30}_{-1.45}$$ $$7.01^{+0.93}_{-1.04}$$ $$6.60^{+1.57}_{-1.63}$$ $$12.37^{+0.32}_{-0.47}$$ QG DM χ2 3.80 [10, 1000] — — $$5.68^{+0.70}_{-0.80}$$ $$5.67^{+1.23}_{-1.32}$$ $$12.13^{+0.31}_{-0.46}$$ CCF DM΄ χ2 3.80 [10, 1000] — — $$6.76^{+0.83}_{-0.94}$$ $$6.21^{+1.34}_{-1.42}$$ $$12.28^{+0.30}_{-0.44}$$ DM ML 3.80 [10, 1000] — — $$5.81^{+0.74}_{-0.85}$$ $$5.93^{+1.34}_{-1.43}$$ $$12.20^{+0.32}_{-0.48}$$ DM΄ ML 3.80 [10, 1000] — — $$6.96^{+0.89}_{-1.01}$$ $$6.58^{+1.49}_{-1.58}$$ $$12.37^{+0.31}_{-0.45}$$ Power-law ML 3.77 [10, 1000] $$2.99^{+3.08}_{-2.97}$$ $$4.73^{+2.19}_{-4.41}$$ $$3.77^{+1.60}_{-3.19}$$ $$2.47^{+2.36}_{-2.41}$$ $$10.45^{+1.40}_{-10.45}$$ Power-law΄ ML 3.77 [10, 1000] $$3.87^{+3.98}_{-3.84}$$ $$5.43^{+2.52}_{-5.06}$$ $$4.29^{+1.82}_{-3.63}$$ $$2.47^{+2.37}_{-2.41}$$ — Power-law ML 3.77 [40, 160] $$11.63^{+6.55}_{-6.07}$$ $$9.81^{+2.66}_{-3.32}$$ $$7.44^{+1.86}_{-2.24}$$ $$9.61^{+4.88}_{-4.73}$$ $$12.92^{+0.53}_{-1.05}$$ Luminous Power-law ML 3.77 [40, 1000] $$4.64^{+3.27}_{-3.20}$$ $$5.99^{+1.99}_{-2.80}$$ $$4.70^{+1.44}_{-2.01}$$ $$3.84^{+2.48}_{-2.53}$$ $$11.43^{+0.88}_{-3.00}$$ QG Power-law ML 3.77 [40 , 2000] $$4.01^{+2.96}_{-2.91}$$ $$5.54^{+1.92}_{-2.77}$$ $$4.37^{+1.39}_{-2.01}$$ $$3.32^{+2.24}_{-2.31}$$ $$11.13^{+0.96}_{-4.01}$$ CCF DM ML 3.77 [10, 1000] — — $$3.94^{+1.58}_{-2.94}$$ $$2.73^{+2.44}_{-2.55}$$ $$10.70^{+1.28}_{-10.70}$$ DM΄ ML 3.77 [10, 1000] — — $$4.48^{+1.75}_{-3.18}$$ $$2.73^{+2.36}_{-2.49}$$ — DM ML 3.77 [40, 160] — — $$7.31^{+1.86}_{-2.32}$$ $$9.39^{+4.86}_{-4.67}$$ $$12.89^{+0.54}_{-1.08}$$ DM ML 3.77 [40, 1000] — — $$4.52^{+1.46}_{-2.19}$$ $$3.59^{+2.47}_{-2.60}$$ $$11.29^{+0.94}_{-4.29}$$ DM ML 3.77 [40 , 2000] — — $$4.49^{+1.44}_{-2.13}$$ $$3.54^{+2.42}_{-2.52}$$ $$11.26^{+0.95}_{-4.08}$$ CF Model* Fitting $$\bar{z}$$ [θmin, θmax] Aω r0 bQG bQSO logMDMH (″) (h−1 Mpc) (h−1 M⊙) Power-law χ2 3.80 [10, 1000] $$6.03^{+1.65}_{-1.65}$$ $$7.13^{+0.99}_{-1.13}$$ $$5.62^{+0.72}_{-0.82}$$ $$5.48^{+1.25}_{-1.32}$$ $$12.07^{+0.33}_{-0.49}$$ Power-law΄ χ2 3.80 [10, 1000] $$8.67^{+2.37}_{-2.37}$$ $$8.66^{+1.20}_{-1.37}$$ $$6.74^{+0.87}_{-0.98}$$ $$6.10^{+1.40}_{-1.47}$$ $$12.25^{+0.32}_{-0.47}$$ Less- Power-law ML 3.80 [10, 1000] $$6.53^{+1.85}_{-1.81}$$ $$7.44^{+1.07}_{-1.19}$$ $$5.85^{+0.78}_{-0.87}$$ $$5.94^{+1.42}_{-1.46}$$ $$12.20^{+0.33}_{-0.49}$$ luminous Power-law΄ ML 3.80 [10, 1000] $$9.39^{+2.66}_{-2.60}$$ $$9.04^{+1.30}_{-1.45}$$ $$7.01^{+0.93}_{-1.04}$$ $$6.60^{+1.57}_{-1.63}$$ $$12.37^{+0.32}_{-0.47}$$ QG DM χ2 3.80 [10, 1000] — — $$5.68^{+0.70}_{-0.80}$$ $$5.67^{+1.23}_{-1.32}$$ $$12.13^{+0.31}_{-0.46}$$ CCF DM΄ χ2 3.80 [10, 1000] — — $$6.76^{+0.83}_{-0.94}$$ $$6.21^{+1.34}_{-1.42}$$ $$12.28^{+0.30}_{-0.44}$$ DM ML 3.80 [10, 1000] — — $$5.81^{+0.74}_{-0.85}$$ $$5.93^{+1.34}_{-1.43}$$ $$12.20^{+0.32}_{-0.48}$$ DM΄ ML 3.80 [10, 1000] — — $$6.96^{+0.89}_{-1.01}$$ $$6.58^{+1.49}_{-1.58}$$ $$12.37^{+0.31}_{-0.45}$$ Power-law ML 3.77 [10, 1000] $$2.99^{+3.08}_{-2.97}$$ $$4.73^{+2.19}_{-4.41}$$ $$3.77^{+1.60}_{-3.19}$$ $$2.47^{+2.36}_{-2.41}$$ $$10.45^{+1.40}_{-10.45}$$ Power-law΄ ML 3.77 [10, 1000] $$3.87^{+3.98}_{-3.84}$$ $$5.43^{+2.52}_{-5.06}$$ $$4.29^{+1.82}_{-3.63}$$ $$2.47^{+2.37}_{-2.41}$$ — Power-law ML 3.77 [40, 160] $$11.63^{+6.55}_{-6.07}$$ $$9.81^{+2.66}_{-3.32}$$ $$7.44^{+1.86}_{-2.24}$$ $$9.61^{+4.88}_{-4.73}$$ $$12.92^{+0.53}_{-1.05}$$ Luminous Power-law ML 3.77 [40, 1000] $$4.64^{+3.27}_{-3.20}$$ $$5.99^{+1.99}_{-2.80}$$ $$4.70^{+1.44}_{-2.01}$$ $$3.84^{+2.48}_{-2.53}$$ $$11.43^{+0.88}_{-3.00}$$ QG Power-law ML 3.77 [40 , 2000] $$4.01^{+2.96}_{-2.91}$$ $$5.54^{+1.92}_{-2.77}$$ $$4.37^{+1.39}_{-2.01}$$ $$3.32^{+2.24}_{-2.31}$$ $$11.13^{+0.96}_{-4.01}$$ CCF DM ML 3.77 [10, 1000] — — $$3.94^{+1.58}_{-2.94}$$ $$2.73^{+2.44}_{-2.55}$$ $$10.70^{+1.28}_{-10.70}$$ DM΄ ML 3.77 [10, 1000] — — $$4.48^{+1.75}_{-3.18}$$ $$2.73^{+2.36}_{-2.49}$$ — DM ML 3.77 [40, 160] — — $$7.31^{+1.86}_{-2.32}$$ $$9.39^{+4.86}_{-4.67}$$ $$12.89^{+0.54}_{-1.08}$$ DM ML 3.77 [40, 1000] — — $$4.52^{+1.46}_{-2.19}$$ $$3.59^{+2.47}_{-2.60}$$ $$11.29^{+0.94}_{-4.29}$$ DM ML 3.77 [40 , 2000] — — $$4.49^{+1.44}_{-2.13}$$ $$3.54^{+2.42}_{-2.52}$$ $$11.26^{+0.95}_{-4.08}$$ *The prime symbol indicates models that consider the contamination of the quasar and the LBG samples. View Large Another fitting method, the maximum likelihood (ML) method, which does not require a specific binning, is applied to the CCFs since the χ2 fitting to the binned CCFs can be highly affected by the negative bins. As described in Croft et al. (1997), if we assume that the pair counts in each bin follows the Poisson distribution, we can define the likelihood of having the observed pair sample from a model of a correlation function as $$\mathcal {L}=\prod _{i=1}^{N_{\rm bins}}\frac{e^{-h(\theta _{i})}h(\theta _{i})^{\langle DD(\theta _{i}) \rangle }}{{\langle DD(\theta _{i}) \rangle }!},$$ (18)where h(θ) = [1 + ω(θ)]⟨DR(θ)⟩ is the expected object–object mean pair count evaluated from the object–random object pair counts within a small interval around θ. Here, ω(θ) is the power-law model [equation (15)]. Then, we can define a function for minimization, S ∼ −2ln$$\mathcal {L}$$, as $$S=2\sum _{i}^{N_{\rm bins}} h(\theta _{i})-2\langle DD(\theta _{i}) \rangle \sum _{i}^{N_{\rm bins}} \ln h(\theta _{i}),$$ (19)where only terms dependent on model parameters are kept. Assuming that ΔS follows a χ2 distribution with one degree of freedom, the parameter range with ΔS = 1 from the minimum value corresponds to a 68% confidence range of the parameter. The ML fitting is applied for the CCFs in the range between 10$${^{\prime\prime}_{.}}$$0 and 1000$${^{\prime\prime}_{.}}$$0 with an interval of 0$${^{\prime}_{.}}$$5. The interval is set to keep the object–object pair count in each bin small enough, so that the bins are independent of each other. The best-fitting parameters are summarized in table 2. The ML method yields slightly higher Aω than the χ2 fitting but is still consistent within the 1σ uncertainty. However, in the range containing several negative bins, the best ML fitting models can be lower than the positive bins of the binned CCF, as can be seen in the right-hand panel of figure 6. It is reported that the assumption that pair counts follow the Poisson statistics (i.e., clustering is negligible) will underestimate the uncertainty of the fitting (Croft et al. 1997). We find the scatter of the ML fitting is only slightly smaller than the χ2 fitting. Therefore, we adopt the ML fitting results hereafter for both of the CCFs since both of them have negative bins in the binned CCFs. The contamination rates of the HSC quasar and LBG samples are taken into account by $$A^{\prime }_{\omega }=\frac{A^{\rm fit}_{\omega }}{(1-f^{\rm QSO}_{c})(1-f^{\rm LBG}_{c})},$$ (20)where $$f^{\rm QSO}_{c}$$ and $$f^{\rm LBG}_{c}$$ are the contamination rates of the less-luminous quasar and LBG samples estimated in subsections 2.2 and 2.4, respectively. Since we do not know redshift distributions or clustering properties of the contaminating sources, we simply assume that they are randomly distributed in the survey area. The Aω value safter correcting for the contamination are listed in table 2. We note that the contaminating galaxies or galactic stars can have their own spatial distributions. For example, it is reported that the galactic stars cause measurable deviation from the true correlation function only on scales of a degree or more due to their own clustering property (e.g., Myers et al. 2006, 2007). Therefore the correction in this work only gives an upper limit of the true Aω and we rely on the values without the correction in the discussions. 3.2 Auto-correlation function of z ∼ 4 LBGs In order to derive the bias factor of the quasars from the strength of the quasar–LBG CCFs, we need to evaluate the bias factor of the LBGs from the LBG ACF. The binned ACF of the z ∼ 4 LBGs is derived in the same way as the quasar–LBG CCF. We use the estimator $$\omega (\theta )=\frac{DD(\theta )}{DR(\theta )}-1,$$ (21)where DD(θ) = ⟨DD⟩/[NLBG(NLBG − 1)/2] and DR(θ) =⟨DR⟩/NLBGNR are the normalized LBG–LBG and LBG–random LBG pair counts in the annulus between θ − Δθ and θ + Δθ, respectively. Here, ⟨DD⟩ and ⟨DR⟩ are the numbers of LBG–LBG and LBG–random LBG pairs in the annulus, and NLBG and NR are the total numbers of LBGs and random LBGs, respectively. We set 14 bins from 1$${^{\prime\prime}_{.}}$$0 to 1000$${^{\prime\prime}_{.}}$$0 in the logarithmic scale. The LBG ACF is shown in figure 7 and table 3 along with the pair counts. Fig. 7. View largeDownload slide Blue squares are the observed mean ACF ωobs of the LBGs at z ∼ 4 derived from the Jackknife resampling. The solid line is the best-fitting power-law model on the scale 10$${^{\prime\prime}_{.}}$$0 to 1000$${^{\prime\prime}_{.}}$$0. The red dash–dotted line is the best-fitting dark matter model ωDM (red long-dashed line) in the same scale based on the HALOFIT power spectrum (Smith et al. 2003) following the method in Myers et al. (2007), while the blue dash–dotted line is the best-fitting dark matter model $$\omega _{\rm DM}^{\prime }$$ (blue short-dashed line) after considering the contamination of the LBGs. The χ2 fitting results are shown. Top and bottom panels show the logarithmic and the linear scale of the vertical axis, respectively. The top horizontal axis of the top panel is the comoving distance at redshift 4. (Color online) Fig. 7. View largeDownload slide Blue squares are the observed mean ACF ωobs of the LBGs at z ∼ 4 derived from the Jackknife resampling. The solid line is the best-fitting power-law model on the scale 10$${^{\prime\prime}_{.}}$$0 to 1000$${^{\prime\prime}_{.}}$$0. The red dash–dotted line is the best-fitting dark matter model ωDM (red long-dashed line) in the same scale based on the HALOFIT power spectrum (Smith et al. 2003) following the method in Myers et al. (2007), while the blue dash–dotted line is the best-fitting dark matter model $$\omega _{\rm DM}^{\prime }$$ (blue short-dashed line) after considering the contamination of the LBGs. The χ2 fitting results are shown. Top and bottom panels show the logarithmic and the linear scale of the vertical axis, respectively. The top horizontal axis of the top panel is the comoving distance at redshift 4. (Color online) Table 3. HSC LBG ACF at z ∼ 4. θ (″) (θmin, θmax) ⟨DD⟩ ⟨DR⟩ $$\overline{\omega _{i}(\theta )}$$ σ(θ) θ (″) (θmin, θmax) ⟨DD⟩ ⟨DR⟩ $$\overline{\omega _{i}(\theta )}$$ σ(θ) 2.05 (1.58, 2.51) 16 25 6.45 3.70 51.45 (39.81, 63.10) 966 9376 0.21 0.05 3.25 (2.51, 3.98) 16 54 2.47 1.27 81.55 (63.10, 100.00) 2211 22983 0.12 0.03 5.15 (3.98, 6.31) 20 122 0.92 0.46 129.24 (100.00, 158.49) 5413 56115 0.13 0.02 8.15 (6.31, 10.00) 48 285 0.96 0.40 204.84 (158.49, 251.19) 12542 138926 0.06 0.01 12.92 (10.00, 15.85) 105 683 0.80 0.20 324.65 (251.19, 398.11) 30387 341510 0.04 0.01 20.48 (15.85, 25.12) 219 1601 0.60 0.17 514.53 (398.11, 630.96) 74669 843464 0.04 0.008 32.46 (25.12, 39.81) 410 3833 0.25 0.90 815.48 (630.96, 1000.0) 181116 2070430 0.02 0.007 θ (″) (θmin, θmax) ⟨DD⟩ ⟨DR⟩ $$\overline{\omega _{i}(\theta )}$$ σ(θ) θ (″) (θmin, θmax) ⟨DD⟩ ⟨DR⟩ $$\overline{\omega _{i}(\theta )}$$ σ(θ) 2.05 (1.58, 2.51) 16 25 6.45 3.70 51.45 (39.81, 63.10) 966 9376 0.21 0.05 3.25 (2.51, 3.98) 16 54 2.47 1.27 81.55 (63.10, 100.00) 2211 22983 0.12 0.03 5.15 (3.98, 6.31) 20 122 0.92 0.46 129.24 (100.00, 158.49) 5413 56115 0.13 0.02 8.15 (6.31, 10.00) 48 285 0.96 0.40 204.84 (158.49, 251.19) 12542 138926 0.06 0.01 12.92 (10.00, 15.85) 105 683 0.80 0.20 324.65 (251.19, 398.11) 30387 341510 0.04 0.01 20.48 (15.85, 25.12) 219 1601 0.60 0.17 514.53 (398.11, 630.96) 74669 843464 0.04 0.008 32.46 (25.12, 39.81) 410 3833 0.25 0.90 815.48 (630.96, 1000.0) 181116 2070430 0.02 0.007 View Large Thanks to the large sample of the LBGs, the LBG–LBG pair count is large enough to constrain the ACF even in the smallest bin. We adopt the Jackknife error, which has a value two times larger than the Poisson error at all bins. Most of the bins have clustering signals greater than 3σ. We fit the raw LBG ACF with a single power-law model ω(θ) = Aωθ−β − IC by χ2 minimization on the scale from 10$${^{\prime\prime}_{.}}$$0 to 1000$${^{\prime\prime}_{.}}$$0. The integral constraint is negligible. Thanks to the small uncertainty of the LBG ACF, the power-law index can be constrained tightly to be $$\beta =0.86^{+0.07}_{-0.06}$$ as shown in figure 8. As already mentioned in subsection 3.1, we adopt this power-law index throughout this paper. The best-fitting parameters are listed in table 4. Fig. 8. View largeDownload slide χ2 map of Aω and β parameter of the ACF of the LBGs. The white cross indicates the best-fitting Aω and β at the minimal χ2, while the red region indicates the 68% confidence region. (Color online) Fig. 8. View largeDownload slide χ2 map of Aω and β parameter of the ACF of the LBGs. The white cross indicates the best-fitting Aω and β at the minimal χ2, while the red region indicates the 68% confidence region. (Color online) Table 4. Summary of the clustering analysis of HSC LBGs ACF. Model* Fitting $$\bar{z}$$ [θmin, θmax] β Aω r0 Bias (″) (h−1 Mpc) Power-law χ2 3.71 [10, 1000] $$0.86^{+0.07}_{-0.06}$$ $$6.56^{+0.49}_{-0.49}$$ $$7.47^{+0.29}_{-0.31}$$ $$5.76^{+0.21}_{-0.22}$$ LBG Power-law΄ χ2 3.71 [10, 1000] $$0.86^{+0.07}_{-0.06}$$ $$10.97^{+0.82}_{-0.82}$$ $$9.85^{+0.39}_{-0.40}$$ $$7.45^{+0.27}_{-0.28}$$ ACF DM χ2 3.71 [10, 1000] — — — $$5.69^{+0.21}_{-0.22}$$ DM΄ χ2 3.71 [10, 1000] — — — $$7.36^{+0.27}_{-0.28}$$ Model* Fitting $$\bar{z}$$ [θmin, θmax] β Aω r0 Bias (″) (h−1 Mpc) Power-law χ2 3.71 [10, 1000] $$0.86^{+0.07}_{-0.06}$$ $$6.56^{+0.49}_{-0.49}$$ $$7.47^{+0.29}_{-0.31}$$ $$5.76^{+0.21}_{-0.22}$$ LBG Power-law΄ χ2 3.71 [10, 1000] $$0.86^{+0.07}_{-0.06}$$ $$10.97^{+0.82}_{-0.82}$$ $$9.85^{+0.39}_{-0.40}$$ $$7.45^{+0.27}_{-0.28}$$ ACF DM χ2 3.71 [10, 1000] — — — $$5.69^{+0.21}_{-0.22}$$ DM΄ χ2 3.71 [10, 1000] — — — $$7.36^{+0.27}_{-0.28}$$ *The prime symbol indicates models that consider the contamination of the LBG sample. View Large The effect of the contamination is evaluated with $$A^{\prime }_{\omega }=\frac{A^{\rm fit}_{\omega }}{(1-f^{\rm LBG}_{c})^{2}}.$$ (22)The results are listed in table 4. We do not consider the contamination for fitting the power-law index β because it would not be affected by a random contamination. 4 Discussion 4.1 Clustering bias from the correlation length One of the parameters representing the clustering strength is the spatial correlation length, r0 (h−1 Mpc), which is in the spatial correlation function with the power-law form as $$\xi (r)= \left(\frac{r}{r_{0}} \right)^{-\gamma },$$ (23)where γ is related to the power of the projected correlation function through γ = 1 + β. The spatial correlation function can be projected to the angular correlation function through Limber’s equation (Limber 1953). We ignore the redshift evolution of the clustering strength within the covered redshift range. Then the spatial correlation length of the ACF can be derived from the amplitude of the angular correlation function, Aω, as $$r_{0}= \left\lbrace A_{\omega } \frac{c}{H_{0}H_{\gamma }} \frac{[\int N(z)dz]^{2}}{\int N^{2}(z)\chi (z)^{1-\gamma }E(z)dz} \right\rbrace ^{1/\gamma },$$ (24)where $$H_{\gamma }= \frac{\Gamma \left(\displaystyle {\frac{1}{2}}\right)\Gamma \left(\displaystyle {\frac{\gamma -1}{2}}\right)}{\Gamma \left(\displaystyle {\frac{\gamma }{2}}\right)},$$ (25) $$E(z)=\left[\Omega _{m}(1+z)^{3}+\Omega _{\Lambda }\right]^{1/2},$$ (26) $$\chi (z)=\frac{c}{H_{0}}\int _{0}^{z}\frac{1}{E(z^{\prime })}dz^{\prime },$$ (27)and N(z) is the redshift distribution of the sample. For the CCF, the same relation can be modified to (Croom & Shanks 1999) $$r_{0}= \left[ A_{\omega } \frac{c}{H_{0}H_{\gamma }} \frac{\int N_{\rm QSO}(z)dz\int N_{\rm LBG}(z)dz}{\int N_{\rm QSO}(z)N_{\rm LBG}(z)\chi (z)^{1-\gamma }E(z)dz} \right]^{1/\gamma }.$$ (28)Applying the redshift distributions of the less-luminous quasars, the luminous quasars and the LBGs at z ∼ 4 estimated in subsection 2.2 for NQSO(z) and subsection 2.4 for NLBG(z), we evaluate r0 from Aω with and without the contamination correction as summarized in table 2. Although the contamination rates of the less-luminous quasars and the LBGs are not high, the correlation lengths of the less-luminous quasar–LBG CCF and the LBG ACF are significantly increased after correcting for the contamination. Meanwhile, r0 of the luminous quasar–LBG CCF vary slightly, because the SDSS quasar sample is not affected by a contamination. The measurement of r0 is sensitive to the assumed redshift distribution of the sample. For example, r0 will be smaller if we assume a narrower redshift distribution even for the same Aω. As discussed in subsection 2.4, the redshift distribution of the LBGs is estimated to be more extended than both of the less-luminous and luminous quasar samples. If we assume the redshift distribution of the LBGs is the same as the less-luminous quasars, r0 of the LBG and the less-luminous quasars decreases to $$5.52^{+0.77}_{-0.87}\:h^{-1}\:$$Mpc, which is 23% lower than that estimated originally, because the fraction of the LBGs contributing to the projected correlation function in the overlapped redshift range increases, yielding a weaker correlation strength, i.e., a smaller r0 from a fixed Aω. The bias factor is defined as the ratio of clustering strength of real objects to that of the underlying dark matter at the scale of 8 h−1 Mpc, $$b=\sqrt{\frac{\xi (8,z)}{\xi _{DM}(8,z)}}.$$ (29)The clustering strength of the underlying dark matter can be evaluated based on the linear structure formation theory under the cold dark matter model (Myers et al. 2006) as \begin{eqnarray} \xi _{DM}(8,z)=\frac{(3-\gamma )(4-\gamma )(6-\gamma )2^{\gamma }}{72}\left[\sigma _{8}\frac{g(z)}{g(0)}\frac{1}{z+1}\right]^{2}, \nonumber\\ \end{eqnarray} (30)where \begin{eqnarray} g(z)=\frac{5\Omega _{mz}}{2} \left[\Omega ^{4/7}_{mz}-\Omega _{\Lambda z} + \left(1+\frac{\Omega _{mz}}{2}\right) \left(1+\frac{\Omega _{\Lambda z}}{70}\right) \right]^{-1}, \nonumber\\ \end{eqnarray} (31)and $$\Omega _{mz}=\frac{\Omega _{m}(1+z)^{3}}{E(z)^{2}},\Omega _{\Lambda z}=\frac{\Omega _{\Lambda }}{E(z)^{2}}.$$ (32)We derive the bias factors bLBG and bQG from the spatial correlation length of the LBG ACF and the quasar–LBG CCF, respectively. Following Mountrichas et al. (2009), the quasar bias factor is then evaluated from the bias factor of the CCF by $$b_{\rm QSO}b_{\rm LBG}\sim b^{2}_{\rm QG}.$$ (33)We list the LBG ACF bias factors in table 4. The estimated bLBG with and without the contamination correction are consistent with Allen et al. (2005) and the brightest bin at MUV ∼ −21.3 in Ouchi et al. (2004), respectively. The quasar bias factors derived from the CCF are summarized in table 2. 4.2 Bias factor from comparing with the HALOFIT power spectrum The bias factors can also be derived by directly comparing the observed clustering with the predicted clustering of the underlying dark matter from the power spectrum Δ2(k, z) (e.g., Myers et al. 2007). The spatial correlation function derived from Δ2(k, z) can be projected with the Limber equation into the angular correlation ωDM(θ) as \begin{eqnarray} \omega _{\rm DM}(\theta )=\pi \int \int \frac{\Delta ^{2}(k,z)}{k}J_{0}[k\theta \chi (z)]N^{2}(z)\frac{dz}{d\chi }F(\chi )\frac{dk}{k}dz, \nonumber\\ \end{eqnarray} (34)where J0 is the zeroth-order Bessel function, χ is the radial comoving distance, N(z) is the normalized redshift distribution function, dz/dχ = Hz/c = H0[Ωm(1 + z)3 + ΩΛ]1/2/c, and F(χ) = 1 for the flat universe. We evaluate the non-linear evolution of the power spectrum $$\Delta _{NL}^{2}(k, z)$$ in the redshift range between z = 3 and 5 with the HALOFIT code (Smith et al. 2003) by adopting the cosmological parameters used throughout this paper. The bias parameters are derived by fitting b2ωDM(θ) to the observed correlation functions, ωobs(θ). For the LBG ACF, ωDM(θ) is directly compared to the ωobs(θ) through χ2 minimization. For the CCFs, the redshift distribution in equation (34) is replaced by the multiplication of those of quasars and LBGs as \begin{eqnarray} \omega _{\rm DM-CCF}(\theta ) &=& \pi \int \int \frac{\Delta ^{2}(k,z)}{k}J_{0}[k\theta \chi (z)]N_{\rm QSO}(z)N_{\rm LBG}(z) \nonumber \\ & & \times \frac{dz}{d\chi }F(\chi )\frac{dk}{k}dz. \end{eqnarray} (35)On the scale from 10$${^{\prime\prime}_{.}}$$0 to 1000$${^{\prime\prime}_{.}}$$0, both of the χ2 and ML fitting are applied to the less-luminous quasar CCF, while only ML fitting works for the luminous quasar CCF. The bias factors of the quasar samples are derived from the CCF and the LBG ACF through equation (33). The best-fitting bias factors are summarized in tables 2 and 4. They are consistent with those derived from the power-law fitting within the 1σ uncertainty. Thus the power-law approximation with an index of β = −0.86 can well reproduce the underlying dark matter distribution on scales larger than 10$${^{\prime\prime}_{.}}$$0. In the scale below 10$${^{\prime\prime}_{.}}$$0, the underlying dark matter model becomes flat since we do not consider the one-halo term. If we compare the observed correlation functions with the best-fitting power-spectrum models, there is an obvious overdensity of galaxies on that scale in figure 7, which is consistent with the one-halo term of the LBG ACF at z ∼ 4 (e.g., Ouchi et al. 2005). The left-hand panel of figure 6, also shows an overdensity of galaxies within 10$${^{\prime\prime}_{.}}$$0 around the less-luminous quasars although the error bar is large. Interestingly, we find that the luminous quasars show a deficit of pair count within 10$${^{\prime\prime}_{.}}$$0 in the right-hand panel of figure 6. It should be noted that the best-fitting model in scales larger than 10$${^{\prime\prime}_{.}}$$0 suggests only 1 SDSS quasar–HSC LBG pair within 10$${^{\prime\prime}_{.}}$$0, which is consistent with the deficit. Thus the deficit in small scales can be caused by the limited size of the SDSS quasar sample, though we cannot exclude the possibility that there is a real deficit of galaxies around luminous quasars within 10$${^{\prime\prime}_{.}}$$0. We consider the contamination by modifying the redshift distribution normalization $$\int _{0}^{\infty }N(z)dz\sim 1-f_{c}$$ for the less-luminous quasars and the LBGs. We simply assume that the contamination will not contribute to the underlying dark matter correlation function. The modified underlying dark matter correlation functions are plotted in figures 6 and 7. Since the redshift distribution form is the same after considering the contamination, only the amplitude of the underlying dark matter correlation function is changed. The bias factors with contamination are listed in tables 2 and 4, and are consistent with those derived from fitting with the power-law model after correcting for the contamination. 4.3 Redshift and luminosity dependence of the bias factor At first, we discuss the luminosity dependence of the bias factors of the luminous and less-luminous quasars in this work. The bias factor of the less-luminous quasars is $$5.93^{+1.34}_{-1.43}$$, which is derived by fitting the CCF with the underlying dark matter model on the scale from 10$${^{\prime\prime}_{.}}$$0 to 1000$${^{\prime\prime}_{.}}$$0 through the ML fitting. The bias factor is consistent with that of the luminous quasars, $$2.73^{+2.44}_{-2.55}$$, obtained from the CCF through the same method within the 1σ uncertainty. If we consider the possible effect of the contamination, the bias factor of the less-luminous quasars increases to $$6.58^{+1.49}_{-1.58}$$, which is still consistent with that of the luminous quasars within the uncertainty. Thus no or only a weak luminosity dependence of the quasar clustering is detected within the two samples. In order to discuss the redshift dependence of the quasar clustering, we compare the bias factors and those in the literature in the left-hand panel of figure 9. The bias factors in the previous studies show a trend that quasars at higher redshifts are more strongly biased, indicating that quasars preferentially reside in DMHs within a mass range of 1012 ∼ 1013 h−1 M⊙ from z ∼ 0 to z ∼ 4. There is no discrepancy between the bias factors estimated with the ACF and the CCF at z ≲ 3. In this work, the bias factor of the less-luminous quasars at z ∼ 4 follows the trend, while the bias factor of the luminous quasars is similar to or even smaller than those at z ∼ 3. Fig. 9. View largeDownload slide Left-hand panel: Redshift evolution of the quasar bias factor. The red square is the result from fitting the less-luminous quasar CCF against the underlying dark matter model through ML fitting. The pink square is derived from fitting the less-luminous quasar CCF with the same method after considering the contamination. The orange square is obtained from fitting the luminous quasar CCF with the same method. Open and filled black circles are bias factors of quasars in a wide luminosity range obtained from the CCF and the ACF, respectively, in the literature, which are summarized by Ikeda et al. (2015) and Eftekharzadeh et al. (2015). Blue dashed lines show the bias evolutions of halos with a fixed mass of 1011, 1012, and 1013 h−1 M⊙ from bottom to top following the fitting formulae in Sheth, Mo, and Tormen (2001). Right-hand panel: Luminosity dependence of the quasar bias at 3 < z < 5. Red and orange squares have the same meaning as in the left-hand panel. The stars, diamonds, dots, triangle, open circles and squares are from Adelberger and Steidel (2005), Francke et al. (2007), Shen et al. (2009), Eftekharzadeh et al. (2015), Ikeda et al. (2015), and this work, respectively. Open and filled symbols imply the bias factors derived from the CCF and ACF, respectively. (Color online) Fig. 9. View largeDownload slide Left-hand panel: Redshift evolution of the quasar bias factor. The red square is the result from fitting the less-luminous quasar CCF against the underlying dark matter model through ML fitting. The pink square is derived from fitting the less-luminous quasar CCF with the same method after considering the contamination. The orange square is obtained from fitting the luminous quasar CCF with the same method. Open and filled black circles are bias factors of quasars in a wide luminosity range obtained from the CCF and the ACF, respectively, in the literature, which are summarized by Ikeda et al. (2015) and Eftekharzadeh et al. (2015). Blue dashed lines show the bias evolutions of halos with a fixed mass of 1011, 1012, and 1013 h−1 M⊙ from bottom to top following the fitting formulae in Sheth, Mo, and Tormen (2001). Right-hand panel: Luminosity dependence of the quasar bias at 3 < z < 5. Red and orange squares have the same meaning as in the left-hand panel. The stars, diamonds, dots, triangle, open circles and squares are from Adelberger and Steidel (2005), Francke et al. (2007), Shen et al. (2009), Eftekharzadeh et al. (2015), Ikeda et al. (2015), and this work, respectively. Open and filled symbols imply the bias factors derived from the CCF and ACF, respectively. (Color online) The luminosity dependence of the quasar bias factors at z ∼ 3–4 is summarized in the right-hand panel of figure 9. Both of the bias factors of the less-luminous quasars with and without the contamination correction are consistent with but slightly higher than that evaluated with the CCF of 54 faint quasars in the magnitude range of −25.0 < MUV < −19.0 at 1.6 < z < 3.7 measured by Adelberger and Steidel (2005), the CCF of 58 faint quasars in the magnitude range of −26.0 < MUV < −20.0 at 2.8 < z < 3.8 measured by Francke et al. (2007), and the CCF of 25 faint quasars in the magnitude range of −24.0 < MUV < −22.0 at 3.1 < z < 4.5 measured by Ikeda et al. (2015), which suggests a slightly increasing or no evolution from z = 3 to z = 4. Meanwhile, for the clustering of the luminous quasars, the bias factor in this work is consistent with the CCF of 25 bright quasars in the magnitude range of −30.0 < MUV < −25.0 at 1.6 < z < 3.7 measured by Adelberger and Steidel (2005) and the ACF of 24724 bright quasars in the magnitude range of −27.81 < MUV < −22.9 mag at 2.64 < z < 3.4 measured by Eftekharzadeh et al. (2015). Unlike the case of the less-luminous quasars, the clustering of the luminous quasars suggests no or a declining evolution from z ∼ 3 to z ∼ 4. The bias factor of the luminous quasars in this work shows a large discrepancy with the ACF of 1788 bright quasars in the magnitude range of −28.2 < MUV < −25.8 [which is transferred from Mi(z = 2) by equation (3) in Richards et al. (2006)] at 3.5 < z < 5.0 measured by Shen et al. (2009). They give two values for the bias factor; the higher one is obtained by only considering the positive bins and the lower one considers all of the bins in the ACF. The bias factor from another subsample of bright quasars covering −28.0 < MUV < −23.95 at 2.9 < z < 3.5 in Shen et al. (2009) is also shown in the panel. The z ∼ 4 quasar bias factors in Shen et al. (2009) show a large discrepancy from the bias factor of the luminous quasars in this work and in Eftekharzadeh et al. (2015) with the similar magnitude and redshift coverage. In the right-hand panel of figure 6, we plot the expected CCF with $$b_{\rm QG}\sim \sqrt{b_{\rm QSO}b_{\rm LBG}}=9.83$$ by the orange dash–double-dotted line. We adopt the higher bQSO in Shen et al. (2009) and the bLBG with the contamination correction to measure the upper limit of the bQG. Although the expected CCF is consistent with some bins within the 1σ uncertainty, it predicts much stronger clustering than both of the best-fitting power-law and dark matter models. In order to quantitatively examine the discrepancy, we plot the minimization function S of the ML fitting for the luminous quasars with the HALOFIT power spectrum as a function of the bias factor in figure 10. Both of the bias factors at 3.5 < z < 5 in Shen et al. (2009) are beyond the 1σ uncertainty, corresponding to a low probability. Meanwhile, the bias factor in Eftekharzadeh et al. (2015), the uncertainty of which is small thanks to the large sample, also shows a large discrepancy from those in Shen et al. (2009). Eftekharzadeh et al. (2015) suspect the discrepancy is mainly caused by a difference in large scale bins (>30 h−1 Mpc). We further investigate the effect from the fitting scale as shown in table 1 and the right-hand panel of figure 6. On a scale of 40$${^{\prime\prime}_{.}}$$0 to 160$${^{\prime\prime}_{.}}$$0, we find a strong CCF of the luminous quasars and the LBGs, which is consistent with the ACF of the luminous quasars. On scales below 40$${^{\prime\prime}_{.}}$$0, the ML fitting suggests a bQG of 0. On larger scales, the ML fitting is not efficient since the pair counts in each bin is too large to fulfil the assumption that bins are independent of each other, even if choosing a small bin width of 0$${^{\prime\prime}_{.}}$$5 interval. Therefore we only expand the ML fitting scale to 2000$${^{\prime\prime}_{.}}$$0. If we consider the power-law model, the bQG obtained by fitting in the range of 40$${^{\prime\prime}_{.}}$$0 to 1000$${^{\prime\prime}_{.}}$$0 is 24.7% and 7.6% higher than that estimated in the range of 10$${^{\prime\prime}_{.}}$$0 to 1000$${^{\prime\prime}_{.}}$$0 and of 40$${^{\prime\prime}_{.}}$$0 to 2000$${^{\prime\prime}_{.}}$$0, respectively, which suggests that the deficit of the luminous quasar–LBG pair on small scales may weaken the CCF more severely than fitting on scales larger than 1000$${^{\prime\prime}_{.}}$$0. Here, since the fitting of the luminous quasar CCF strongly depends on the scale, especially on small scales, we still focus on the results on the scale from 10$${^{\prime\prime}_{.}}$$0 to 1000$${^{\prime\prime}_{.}}$$0 to keep accordant to the LBG ACF and the less-luminous quasar CCF throughout the discussion. Fig. 10. View largeDownload slide ML fitting minimization function S of fitting for the luminous quasar CCF with the dark matter model. S is shown in relative to the minimal value. Black squares mark the 68% upper and lower limits of bQG with S − min(S) = 1. Blue and green squares indicate the expected bias factors of $$b_{\,\rm QG}\sim \sqrt{b_{\,\rm QSO}b_{\,\rm LBG}}=7.53$$ and 8.64 from the bias factors of the SDSS luminous quasars in Shen et al. (2009) with and without considering the negative bins in the ACF, respectively. The red dashed line indicates the same minimization function S after considering the possible contamination in the LBG sample. Black, blue and green dots have the same meaning as the squares. (Color online) Fig. 10. View largeDownload slide ML fitting minimization function S of fitting for the luminous quasar CCF with the dark matter model. S is shown in relative to the minimal value. Black squares mark the 68% upper and lower limits of bQG with S − min(S) = 1. Blue and green squares indicate the expected bias factors of $$b_{\,\rm QG}\sim \sqrt{b_{\,\rm QSO}b_{\,\rm LBG}}=7.53$$ and 8.64 from the bias factors of the SDSS luminous quasars in Shen et al. (2009) with and without considering the negative bins in the ACF, respectively. The red dashed line indicates the same minimization function S after considering the possible contamination in the LBG sample. Black, blue and green dots have the same meaning as the squares. (Color online) Quasar clustering models based on numerical simulation predict no luminosity dependence of the quasar clustering at z ∼ 4 (e.g., Fanidakis et al. 2013; Oogi et al. 2016; DeGraf & Sijacki 2017). Although there is a relation between mass of the SMBHs and DMHs in the models, SMBHs in a wide mass range are contributing to quasars at a fixed luminosity, thus there is no relation between the luminosity of model quasars and the mass of their DMHs. Oogi et al. (2016) and DeGraf and Sijacki (2017) predicted a quasar bias factor of ∼5.0 at redshift 4, which is consistent with the quasar bias factors in this work. No luminosity dependence is also predicted in a continuous SMBH growth model of Hopkins et al. (2007). They assume an Eddington limited SMBH growth until redshift 2. However, the predicted bias factor is much larger than the results in this work. On the other hand, there are models which predict stronger luminosity dependence of the quasar clustering at higher redshifts (e.g., Shen 2009; Conroy & White 2012). These models predict that SMBHs in a narrow mass range are contributing to the luminous quasars. In order to conclude the luminosity and redshift dependencies of the quasar clustering, we need to understand the cause of the discrepancy between the quasar ACF and quasar–LBG CCF for the luminous quasars at z ∼ 4. The quasar–LBG CCF could be affected by the suppression of galaxy formation due to feedback from luminous quasars (e.g., Kashikawa et al. 2007; Utsumi et al. 2010; Uchiyama et al. 2018). The weak cross-correlation could also be induced by a discrepancy between the redshift distributions of the quasars and LBGs. We need to further determine the redshift distribution through spectroscopic follow-up observations of the LBGs. 4.4 Effect of edge regions and seeing variation on the bias factor It should be noted that there is a sky coverage discrepancy between the samples of the quasars and LBG candidates in the shallower edge regions. As a result, it is possible that most of the ⟨DQSODLBG⟩ pair counts on small scales are from quasars only in inner regions, which may cause the weakness of the small-scale clustering between the luminous quasars and LBGs, if the random LBG sample cannot reproduce the detection completeness in the edge regions. Although we have mentioned that our random LBGs can reproduce the overall distribution of the real LBGs in subsection 2.5, to evaluate the effects quantitatively we select the central area in each subregion to construct a subsample of less-luminous quasars, luminous quasars, LBGs, and random LBGs. We apply the same estimator as in section 3.1 to measure their correlation functions. We fit a single power-law to the resulting ACF and CCF, then compare them to that of the original samples. Poisson error is adopted here for simplicity. In table 5, we summarize bQG and bLBG obtained from the samples in the inner (“No” in the border column) and entire regions (“Yes” in the border column). For the LBG ACF on the scale below 1000$${^{\prime\prime}_{.}}$$0 and less-luminous quasar CCF beyond 15$${^{\prime\prime}_{.}}$$0, they do not have a significant discrepancy from that of the entire samples except for a larger uncertainty, and the size of luminous quasar subsample is too limited to judge the border effect. On the scale below 15$${^{\prime\prime}_{.}}$$0, we find bQG of the subsamples is enhanced from $$7.48^{+1.39}_{-1.68}$$ to $$10.61^{+2.29}_{-2.88}$$. Since the uncertainty is large due to the limited size of pair counts on small scales, we could not make a conclusion whether the deficit of luminous quasar - LBG pair counts in scale within 15$${^{\prime\prime}_{.}}$$0 is due to the effect of the border regions or real. Table 5. Clustering dependence on the border and seeing. Model Fitting Border Seeing [θmin, θmax] Bias (″) Power-law χ2 Yes All [10, 1000] $$5.64^{+0.56}_{-0.62}$$ Less- Power-law χ2 No All [15, 1000] $$6.15^{+0.75}_{-0.85}$$ lumiNous QG Power-law χ2 Yes All [3, 15] $$7.48^{+1.39}_{-1.68}$$ CCF Power-law χ2 No All [3, 15] $$10.61^{+2.29}_{-2.88}$$ Power-law χ2 Yes [0$${^{\prime\prime}_{.}}$$5, 0$${^{\prime\prime}_{.}}$$7] [10, 1000] $$5.37^{+0.68}_{-0.78}$$ Power-law χ2 Yes All [3, 1000] $$5.69^{+0.13}_{-0.13}$$ LBG Power-law χ2 No All [3, 1000] $$5.55^{+0.18}_{-0.18}$$ ACF Power-law χ2 Yes [0$${^{\prime\prime}_{.}}$$5, 0$${^{\prime\prime}_{.}}$$7] [3, 1000] $$5.40^{+0.16}_{-0.16}$$ Model Fitting Border Seeing [θmin, θmax] Bias (″) Power-law χ2 Yes All [10, 1000] $$5.64^{+0.56}_{-0.62}$$ Less- Power-law χ2 No All [15, 1000] $$6.15^{+0.75}_{-0.85}$$ lumiNous QG Power-law χ2 Yes All [3, 15] $$7.48^{+1.39}_{-1.68}$$ CCF Power-law χ2 No All [3, 15] $$10.61^{+2.29}_{-2.88}$$ Power-law χ2 Yes [0$${^{\prime\prime}_{.}}$$5, 0$${^{\prime\prime}_{.}}$$7] [10, 1000] $$5.37^{+0.68}_{-0.78}$$ Power-law χ2 Yes All [3, 1000] $$5.69^{+0.13}_{-0.13}$$ LBG Power-law χ2 No All [3, 1000] $$5.55^{+0.18}_{-0.18}$$ ACF Power-law χ2 Yes [0$${^{\prime\prime}_{.}}$$5, 0$${^{\prime\prime}_{.}}$$7] [3, 1000] $$5.40^{+0.16}_{-0.16}$$ View Large Another problem that can affect the clustering analysis is the variation of detection completeness due to non-uniform seeing distribution within the Wide layer dataset. In subsection 2.5, we confirmed the random LBGs can reproduce the seeing dependence of the detection completeness of the real LBGs. Here, we quantitatively investigate the influence from the seeing variation by constructing a uniform subsample of less-luminous quasars, LBGs and random LBGs taken under seeing between 0$${^{\prime\prime}_{.}}$$5 and 0$${^{\prime\prime}_{.}}$$7. The same estimator as in subsection 3.1 and Poisson error are adopted to measure their correlation functions. In table 5, we summarize bQG and bLBG obtained with the seeing limited and entire samples. Compared to the correlation functions of the entire samples, there is no significant discrepancy of both of the less-luminous quasar CCF and LBG ACF of the seeing-limited samples except for larger uncertainty, which again suggests the seeing variation does not affect the results of the clustering. 4.5 DMH mass The bias factor of a population of objects is directly related to the typical mass of their host DMHs, because more massive DMHs are more strongly clustered and biased in the structure formation under the ΛCDM model (Sheth & Torman 1999). The relation between the MDMH and the bias factor is derived based on an ellipsoidal collapse model that is calibrated by an N-body simulation as \begin{eqnarray} b(M,z)&=&1+\frac{1}{\sqrt{a}\delta _{\rm crit}}\bigg[a\nu ^{2}\sqrt{a}+b\sqrt{a}(a\nu ^{2})^{(1-c)} \nonumber \\ & &-\,\frac{(a\nu ^{2})^{c}}{(a\nu ^{2})^{c}+b(1-c)(1-c/2)}\bigg], \end{eqnarray} (36)where ν = δcrit/[σ(M)D(z)] and critical density δcrit = 1.686 (Sheth et al. 2001). We adopt the updated parameters a = 0.707, b = 0.35, and c = 0.80 from Tinker et al. (2005). The rms mass fluctuation σ(M) on a mass scale M at redshift 0 is given by $$\sigma ^{2}(M)=\int \Delta ^{2}(k)\tilde{W}^{2}(kR)\frac{dk}{k},$$ (37)and $$M(R)=\frac{4\pi \overline{\rho _{0}} R^{3}}{3},$$ (38)where R is the comoving radius, $$\tilde{W}(kR)=[3\sin (kR)-(kR)\cos (kR)]/(kr)^{3}$$ is the top hat window function in Fourier form and $$\overline{\rho _{0}}=2.78\times 10^{11}\Omega _{m}\:h^{2}\, M_{\odot }\:$$Mpc−3 is the mean density in the current universe. The linear power spectrum Δ2(k) at redshift 0 is obtained from the HALOFIT code (Smith et al. 2003). The growth factor D(z) is approximated by $$D(z)\propto \frac{g(z)}{1+z}$$ (39)following Carroll, Press, and Turner (1992). Assuming the quasars and LBGs are associated with DMHs in a narrow mass range, we can infer the mass of the quasar host DMHs through the above relations. The evaluated halo masses of the less-luminous quasars and the luminous quasars are 1 ∼ 2 × 1012 h−1 M⊙ and <1012 h−1 M⊙ as summarized in table 2, respectively. Since the bias factor of the luminous quasars has a large uncertainty, we could only set an upper limit of the MDMH. We note that the halo mass strongly depends on the amplitude of the power spectrum on the scale of 8 h−1 Mpc, σ8. If we adopt σ8 = 0.9, the host DMH mass of the less-luminous quasars will be 4–6 × 1012 h−1 M⊙ with the same bias factor. 4.6 Minimum halo mass and duty cycle In the above discussion, we assume that quasars are associated with DMHs in a specific mass range, but it may be more physical to assume that quasars are associated with DMHs with a mass above a critical mass, Mmin. In this case, the effective bias for a population of objects which are randomly associated with DMHs above Mmin can be expressed with $$b_{\rm eff}=\frac{\int _{M_{\rm min}}^{\infty }b(M)n(M)dM}{\int _{M_{\rm min}}^{\infty }n(M)dM},$$ (40)where n(M) is the mass function of DMHs and b(M, z) is the bias factor of DMHs with mass M at z. We adopt the DMH mass function from the modified Press–Schechter theory (Sheth & Torman 1999) as \begin{eqnarray} n(M,z)&=&-A\sqrt{\frac{2a}{\pi }}\frac{\rho _0}{M}\frac{\delta _c(z)}{\sigma ^2(M)}\frac{d\sigma (M)}{dM} \nonumber \\ & & \times \left\lbrace 1+\left[\frac{\sigma ^2(M)}{a\delta _c^2(z)}\right]^p\right\rbrace \exp \left[-\frac{a\delta _c^2(z)}{2\sigma ^2(M)}\right], \end{eqnarray} (41)where A = 0.3222, a = 0.707, p = 0.3, and δc(z) = δcrit/D(z). If we follow the above formulation, the Mmin is estimated to be ∼0.3–2 × 1012 h−1 M⊙ and <5.62 × 1011 h−1 M⊙ with the bias factors of the less-luminous quasars and the luminous quasars, respectively. Comparing the number density of the DMHs above the Mmin and that of the less-luminous and luminous quasars, we can infer the duty cycle of the quasar activity among the DMHs in the mass range by $$f=\frac{n_{\rm QSO}}{\int _{M_{\rm min}}^{\infty }n(M)dM},$$ (42)assuming one DMH contains one SMBH. The co-moving number density of z ∼ 4 less-luminous quasars are estimated with the HSC quasar sample (Akiyama et al. 2018). Integrating the best-fitting luminosity function of z ∼ 4 quasars from M1450 ∼ −24.73 to M1450 ∼ −22.23, we estimate the total number density of the less-luminous quasar to be 1.07 × 10−6 h3 Mpc−3, which is two times higher than that of the luminous quasars with −28.00 < M1450 < −23.95 (4.21 × 10−7 h3 Mpc−3). If we adopt the n(M) in equation (41), the duty cycle is estimated to be 0.001–0.06 and <8 × 10−4 for Mmin from the less-luminous and the luminous quasar CCF, respectively. If we use the bias factor estimated by considering the effect of the possible contamination, the duty cycle of the less-luminous quasars is estimated to be 0.003 ∼ 0.175, which is higher than the estimation above. We compare the duty cycles with those evaluated for quasars at 2 < z < 4 in the literature in figure 11. The estimated luminosity dependence of the duty cycles is similar to that estimated for quasars in the similar luminosity range at z ∼ 2.6 (Adelberger & Steidel 2005), although the duty cycles at z ∼ 4 are one order of magnitude smaller than those at z ∼ 2.6. Fig. 11. View largeDownload slide Estimated quasar duty cycle as a function of redshift. The blue symbols represent the duty cycles estimated with a sample of quasars mostly with MUV < −25. The red symbols show those for the less-luminous quasars with MUV > −25. Stars, triangles, filled circles and squares represent the results from Adelberger and Steidel (2005), Shen et al. (2007), Eftekharzadeh et al. (2015), and this work. The pink open square shows the duty cycle with the contamination correction. (Color online) Fig. 11. View largeDownload slide Estimated quasar duty cycle as a function of redshift. The blue symbols represent the duty cycles estimated with a sample of quasars mostly with MUV < −25. The red symbols show those for the less-luminous quasars with MUV > −25. Stars, triangles, filled circles and squares represent the results from Adelberger and Steidel (2005), Shen et al. (2007), Eftekharzadeh et al. (2015), and this work. The pink open square shows the duty cycle with the contamination correction. (Color online) The estimated duty cycle corresponds to a duration of the less-luminous quasar activity of 1.5–90.8 Myr, which is broadly consistent with the quasar lifetime range of 1–100 Myr estimated in previous studies (for review see Martini 2004). It needs to be noted that the estimated duty cycle is sensitive to the measured strength of the quasar clustering. A small variation in the bias factor can result in even one order of magnitude difference in the duty cycle, because of the non-linear relation between b and MDMH and the sharp cut-off of n(M) at the high-mass end. Furthermore, the duty cycle is also sensitive to the assumed value of σ8 (Shen et al. 2007). 5 Summary We examine the clustering of a sample of 901 less-luminous quasars with −24.73 < M1450 < −22.23 at 3.1 < z < 4.6 selected from the HSC S16A Wide2 catalog and of a sample of 342 luminous quasars with −28.00 < M1450 < −23.95 at 3.4 < zspec < 4.6 within the HSC S16A Wide2 coverage from the 12th data release of SDSS. We investigate the quasar clustering through the CCF between the quasars and a sample of 25790 bright LBGs with M1450 < −21.25 in the same redshift range from the HSC S16A Wide2 data release. The main results are as follows. 1. The bias factor of the less-luminous quasar is $$5.93^{+1.34}_{-1.43}$$ derived by fitting the CCF with the dark matter power-spectrum model through the ML method, while that of the luminous quasars is $$2.73^{+2.44}_{-2.55}$$ obtained in the same manner. If we consider the contamination rates of 22.7% and 10.0% estimated for the LBG and the less-luminous quasar samples, respectively, the bias factor of the less-luminous quasars can increase to $$6.58^{+1.49}_{-1.58}$$ on the assumption that the contaminating objects are distributed randomly. 2. The CCFs of the luminous and less-luminous quasars do not show significant luminosity dependence of the quasar clustering. The bias factor of the less-luminous quasars suggests that the environment around them is similar to the luminous LBGs used in this study. The luminous quasars do not show strong association with the luminous LBGs on scales from 10$${^{\prime\prime}_{.}}$$0 to 1000$${^{\prime\prime}_{.}}$$0, especially on scales smaller than 40$${^{\prime\prime}_{.}}$$0. The bias factor of the luminous quasar is smaller than that derived from the ACF of the SDSS quasars at z ∼ 4 (Shen et al. 2009). The reason may be partly due to the deficit of the pairs on small scales, which can be caused by the border between quasar and LBG samples at shallower edge regions or by a physical mechanism, e.g., the strong feedback from the SMBH. 3. The bias factor of the less-luminous quasars corresponds to a mass of DMHs of ∼1–2 × 1012 h−1 M⊙. Minimal host DMH mass for the quasars can be also inferred from the bias factor. Combining the halo number density above that mass threshold and the observed quasar number density, the fraction of halos which are in the less-luminous quasar phase is estimated to be 0.001–0.06 from the CCF. The corresponding quasar lifetime is 1.5–90.8 Myr. Correlation analysis in this work is conducted in the projected plane, and accurate information on the redshift distribution of the samples and the contamination rates is necessary to obtain reliable constraints on the clustering of the z ∼ 4 quasars. Spectroscopic follow-up observations are expected to obtain the accurate information. Additionally, the full HSC Wide survey plans to cover 1400 deg2 in 5 years, which can significantly enhance the sample size. The statistical significance of the current results can then be largely improved. Acknowledgements We would like to thank the valuable comments from the referee. We also would like to thank Dr. A.K. Inoue who kindly provides us with the IGM model data. The Hyper Suprime-Cam (HSC) collaboration includes the astronomical communities of Japan and Taiwan, and Princeton University. The HSC instrumentation and software were developed by the National Astronomical Observatory of Japan (NAOJ), the Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU), the University of Tokyo, the High Energy Accelerator Research Organization (KEK), the Academia Sinica Institute for Astronomy and Astrophysics in Taiwan (ASIAA), and Princeton University. Funding was contributed by the FIRST program from Japanese Cabinet Office, the Ministry of Education, Culture, Sports, Science and Technology (MEXT), the Japan Society for the Promotion of Science (JSPS), Japan Science and Technology Agency (JST), the Toray Science Foundation, NAOJ, Kavli IPMU, KEK, ASIAA, and Princeton University. Funding for the Sloan Digital Sky Survey IV has been provided by the Alfred P. Sloan Foundation, the U.S. Department of Energy Office of Science, and the Participating Institutions. SDSS-IV acknowledges support and resources from the Center for High-Performance Computing at the University of Utah. The SDSS web site is ⟨www.sdss.org⟩. SDSS-IV is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS Collaboration including the Brazilian Participation Group, the Carnegie Institution for Science, Carnegie Mellon University, the Chilean Participation Group, the French Participation Group, Harvard-Smithsonian Center for Astrophysics, Instituto de Astrofísica de Canarias, The Johns Hopkins University, Kavli Institute for the Physics and Mathematics of the Universe (IPMU)/University of Tokyo, Lawrence Berkeley National Laboratory, the Leibniz Institut für Astrophysik Potsdam (AIP), the Max-Planck-Institut für Astronomie (MPIA Heidelberg), the Max-Planck-Institut für Astrophysik (MPA Garching), the Max-Planck-Institut für Extraterrestrische Physik (MPE), the National Astronomical Observatories of China, New Mexico State University, New York University, the University of Notre Dame, Observatário Nacional / MCTI, The Ohio State University, Pennsylvania State University, Shanghai Astronomical Observatory, the United Kingdom Participation Group, Universidad Nacional Autónoma de México, the University of Arizona,the University of Colorado Boulder, the University of Oxford, the University of Portsmouth, the University of Utah, the University of Virginia, the University of Washington, the University of Wisconsin, Vanderbilt University, and Yale University. This paper makes use of software developed for the Large Synoptic Survey Telescope. We thank the LSST Project for making their code available as free software at ⟨http://dm.lsst.org⟩. 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Clustering of quasars in a wide luminosity range at redshift 4 with Subaru Hyper Suprime-Cam Wide-field imaging
21 pages
/lp/ou_press/clustering-of-quasars-in-a-wide-luminosity-range-at-redshift-4-with-1JlZHRXIqC
Publisher
Oxford University Press
ISSN
0004-6264
eISSN
2053-051X
D.O.I.
10.1093/pasj/psx129
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See Article on Publisher Site
Abstract
Abstract We examine the clustering of quasars over a wide luminosity range, by utilizing 901 quasars at $$\overline{z}_{\rm phot}\sim 3.8$$ with −24.73 < M1450 < −22.23 photometrically selected from the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) S16A Wide2 date release and 342 more luminous quasars at 3.4 < zspec < 4.6 with −28.0 < M1450 < −23.95 from the Sloan Digital Sky Survey that fall in the HSC survey fields. We measure the bias factors of two quasar samples by evaluating the cross-correlation functions (CCFs) between the quasar samples and 25790 bright z ∼ 4 Lyman break galaxies in M1450 < −21.25 photometrically selected from the HSC dataset. Over an angular scale of 10$${^{\prime\prime}_{.}}$$0 to 1000$${^{\prime\prime}_{.}}$$0, the bias factors are $$5.93^{+1.34}_{-1.43}$$ and $$2.73^{+2.44}_{-2.55}$$ for the low- and high-luminosity quasars, respectively, indicating no significant luminosity dependence of quasar clustering at z ∼ 4. It is noted that the bias factor of the luminous quasars estimated by the CCF is smaller than that estimated by the auto-correlation function over a similar redshift range, especially on scales below 40$${^{\prime\prime}_{.}}$$0. Moreover, the bias factor of the less-luminous quasars implies the minimal mass of their host dark matter halos is 0.3–2 × 1012 h−1 M⊙, corresponding to a quasar duty cycle of 0.001–0.06. 1 Introduction It is our current understanding that every massive galaxy is likely to have a supermassive black hole (SMBH) at its center (Kormendy & Richstone 1995). Active galactic nuclei (AGNs) are thought to be associated with the growth phase of the BHs through mass accretion. Being the most luminous of the AGN populations, quasars may be the progenitors of the most massive SMBHs in the local universe. Observations over the last decade or so are establishing a series of scaling relations between SMBH mass and properties of their host galaxies (for review see Kormendy & Ho 2013). A similar scaling relation, involving the mass of the SMBH, is reported even with the host dark matter halo (DMH) mass (Ferrarese 2002). As a result, SMBHs are thought to play an important role in galaxy formation and evolution. However, the physical mechanism behind the scaling relations is still unclear. Clustering analysis of AGNs is commonly used to investigate SMBH growth and galaxy evolution in DMHs. Density peaks in the underlying dark matter distribution are thought to evolve into DMHs (e.g., Press & Schechter 1974), in which the entire structure is gravitationally bound with a density 300 times higher than the mean density of the universe. More massive DMHs are formed from rarer density peaks in the early universe, and are more strongly clustered (e.g., Sheth & Torman 1999; Sheth et al. 2001). If focusing on the large-scale clustering, i.e., two-halo term, the mass of quasar host halos can be inferred by estimating the clustering strength of quasars in relative to that of the underlying dark matter, i.e., the bias factor. How the bias factor of quasars depends on redshift and luminosity provides further information on the relation between SMBHs and galaxies within their shared DMH. Many studies, based on the two-point correlation function (2PCF) of quasars, have been conducted by utilizing large databases of quasars, such as the 2dF Quasar Redshift Survey (e.g., Croom et al. 2005) and the Sloan Digital Sky Survey (SDSS; e.g, Myers et al. 2007; Shen et al. 2009; White et al. 2012). The redshift evolution of the auto-correlation function (ACF) indicates that quasars are more strongly biased at higher redshifts. For example, luminous SDSS quasars with −28.2 < M1450 < −25.8 at z ∼ 4 show strong clustering with a bias factor of 12.96 ± 2.09, which corresponds to a host DMH mass of ∼1013 h−1 M⊙ (Shen et al. 2009). It is suggested that such high luminosity quasar activity needs to be preferentially associated with the most massive DMHs in the early universe (White et al. 2008). If we consider the low number density of such massive DMHs at z = 4, the fraction of halos with luminous quasar activity is estimated to be 0.03–0.6 (Shen et al. 2007) or up to 0.1–1 (White et al. 2008). The clustering strength of quasars can be also measured from the cross-correlation function (CCF) between quasars and galaxies (e.g., Adelberger & Steidel 2005; Francke et al. 2007; Font-Ribera et al. 2013). When the size of a quasar sample is limited, the clustering strength of the quasars can be constrained with higher accuracy by using the CCF rather than the ACF since galaxies are usually more numerous than quasars. Enhanced clustering and overdensities of galaxies around luminous quasars are expected from the strong auto-correlation of the SDSS quasars at z ∼ 4. However, observational searches for such overdensities around quasars at high redshifts have not been conclusive. While some luminous z > 3 quasars are found to be in an over-dense region (e.g., Zheng et al. 2006; Kashikawa et al. 2007; Utsumi et al. 2010; Capak et al. 2011; Adams et al. 2015; Garcia-Vergara et al. 2017), a significant fraction of them do not show any surrounding overdensity compared to the field galaxies, and it is suggested that the large-scale (∼10 comoving Mpc) environment around the luminous z > 3 quasars is similar to the Lyman break galaxies (LBGs), i.e., typical star-forming galaxies, in the same redshift range (e.g., Kim et al. 2009; Bañados et al. 2013; Husband et al. 2013; Uchiyama et al. 2018). To investigate the quasar environment at z ∼ 4, the clustering of quasars with lower luminosity at MUV ≳ −25, i.e., typical quasars, which are more abundant than luminous SDSS quasars, is crucial that it can constrain the growth of SMBHs inside galaxies in the early universe (Hopkins et al. 2007). At low redshifts (z ≲ 3), clustering of quasars is found to have no or weak luminosity dependence (e.g., Francke et al. 2007; Shen et al. 2009; Krumpe et al. 2010; Shirasaki et al. 2011). Above z > 3, Ikeda et al. (2015) examined the CCF of 25 less-luminous quasars in the COSMOS field. However, since the sample size is small, the clustering strength of the less-luminous quasars has still not been well constrained, and their correlation with galaxies remains unclear. The wide and deep multi-band imaging dataset of the Subaru Hyper Suprime-Cam Strategic Survey Program (HSC-SSP: Aihara et al. 2018a) provides us with a unique opportunity to examine the clustering of galaxies around high-redshift quasars in a wide luminosity range. Based on an early data release of the survey (S16A: Aihara et al. 2018b), a large sample of less-luminous z ∼ 4 quasars (MUV < −21.5) is constructed for the first time (Akiyama et al. 2018). They cover the luminosity range around the knee of the quasar luminosity function, i.e., they are typical quasars in the redshift range. Additionally, more than 300 SDSS luminous quasars at z ∼ 4 fall within the HSC survey area thanks to a wide field of 339.8 deg2. Likewise, the five bands of HSC imaging are deep enough to construct a sample of galaxies in the same redshift range through the Lyman-break method (Steidel et al. 1996). Here, we examine the clustering of galaxies around z ∼ 4 quasars over a wide luminosity range of −28.0 < M1450 < −22.2 by utilizing the HSC-SSP dataset. By comparing the clustering of the luminous and less-luminous quasars, we can further evaluate the luminosity dependence of the quasar clustering. The outline of this paper is as follows. Section 2 describes the samples of z ∼ 4 quasars and LBGs. Section 3 reports the results of the clustering analysis, and we discuss the implication of the observed clustering strength in section 4. Throughout this paper, we adopt a ΛCDM model with cosmological parameters of H0 = 70 km s−1 Mpc−1 (h = 0.7), Ωm = 0.3, ΩΛ = 0.7, and σ8 = 0.84. All magnitudes are described in the AB magnitude system. 2 Data 2.1 HSC-SSP Wide layer dataset We select the candidates of z ∼ 4 quasars and LBGs from the Wide layer catalog of the HSC-SSP (Aihara et al. 2018a). HSC is a wide-field mosaic CCD camera, which is attached to the prime-focus of the Subaru telescope (Miyazaki et al. 2012, 2018). It covers a field of view (FoV) of 1.°5 diameter with 116 full-depletion CCDs, which have a high sensitivity up to 1 μm. The Wide layer of the survey is designed to cover 1400 deg2 in the g, r, i, z, and y bands with 5σ detection limits of 26.8, 26.4, 26.4, 25.5, and 24.7, respectively, in the five-year survey (Aihara et al. 2018a). In this analysis, we use the S16A Wide2 internal data release (Aihara et al. 2018b), which covers 339.8 deg2 in the five bands, including edge regions where the depth is shallower than the final depth. The data are reduced with hscPipe-4.0.2 (Bosch et al. 2018). The astrometry of the HSC imaging is calibrated by the Pan-STARRS 1 Processing Version 2 (PS1 PV2) data (Magnier et al. 2013), which covers all HSC survey regions to a reasonable depth with a similar set of bandpasses (Aihara et al. 2018b). It is found that the rms of stellar object offsets between the HSC and PS1 positions is ∼40 mas. Extended galaxies have additional offsets with rms values of ∼30 mas in relative to the stellar objects (Aihara et al. 2018b). Following the description in subsections 2.1 and 2.4 in Akiyama et al. (2018), we construct a sample of objects with reliable photometry (referred to as clean objects hereafter). We apply \begin{eqnarray} {\rm flags\_pixel\_edge} = {\rm Not True} \\ \nonumber \end{eqnarray} (1) \begin{eqnarray} {\rm flags\_pixel\_saturated\_center} = {\rm Not True} \\ \nonumber \end{eqnarray} (2) \begin{eqnarray} {\rm flags\_pixel\_cr\_center} = {\rm Not True} \\ \nonumber \end{eqnarray} (3) \begin{eqnarray} {\rm flags\_pixel\_bad} = {\rm Not True} \\ \nonumber \end{eqnarray} (4) \begin{eqnarray} {\rm detect\_is\_primary} = {\rm True} \end{eqnarray} (5)in all of the five bands. These parameters are included as standard output products from the SSP pipeline. Criteria (1)–(4) remove objects detected at the edges of the CCDs, those affected by saturation within their central 3 × 3 pixels, those affected by cosmic-ray hitting within their central 3 × 3 pixels, and those flagged with bad pixels. The final criterion picks out objects after the deblending process for crowded objects. We apply additional masks (for details see subsection 2.4 in Akiyama et al. 2018) to remove junk objects. Patches, defined as a minimum unit of a sub-region with an area about 10$${^{\prime}_{.}}$$0 by 10$${^{\prime}_{.}}$$0, which have color offsets in the stellar sequence larger than 0.075 in any of the g − r vs. r − i, r − i vs. i − z, or i − z vs. z − y color–color planes are removed (see sub-subsection 5.8.4 in Aihara et al. 2018b). Tract 8284 is also removed due to unreliable calibration. Moreover, we remove objects close to bright objects by setting the criterion that $${\rm flags\_pixel\_bright\_object\_center}$$ in all five bands are “Not True”. Regions around objects brighter than 15 in the Guide Star Catalog version 2.3.2 or i = 22 in the HSC S16A Wide2 database are also removed with masks described in Akiyama et al. (2018). After the masking process, the effective survey area is 172.0 deg2. We use PSF magnitudes for stellar objects and CModel magnitudes for extended objects. PSF magnitudes are determined by fitting a model PSF, while CModel magnitudes are determined by fitting a linear combination of exponential and de Vaucouleurs profiles convolved with the model PSF at the position of each object. We correct for galactic extinction in all five bands based on the dust extinction maps by Schlegel, Finkbeiner, and Davis (1998). Only objects that have magnitude errors in the r and i bands smaller than 0.1 are considered. 2.2 Samples of z ∼ 4 quasars We select candidates of z ∼ 4 quasars from the stellar clean objects. In order to separate stellar objects from extended objects, we apply the same criteria as described in Akiyama et al. (2018), \begin{eqnarray} {\rm i\_hsm\_moments\_11}/{\rm i\_hsm\_psfmoments\_11} &<& 1.1; \\ \nonumber \end{eqnarray} (6) \begin{eqnarray} {\rm i\_hsm\_moments\_22}/{\rm i\_hsm\_psfmoments\_22} &<& 1.1. \end{eqnarray} (7) $${\rm i\_hsm\_moments\_11} {\rm (22)}$$ is the second-order adaptive moment of an object in the x (y) direction determined with the algorithm described in Hirata and Seljak (2003) and $${\rm i\_hsm\_psfmoments\_11} {\rm (22)}$$ is that of the model PSF at the object position. The i-band adaptive moments are adopted since the i-band images are selectively taken under good seeing conditions (Aihara et al. 2018b). Objects that have the adaptive moment with “nan” are removed. Since stellar objects should have an adaptive moment that is consistent with that of the model PSF, we set the above stellar/extended classification criteria. The selection completeness and the contamination are examined by Akiyama et al. (2018). At i < 23.5, the completeness is above 80% and the contamination from extended objects is lower than 10%. At fainter magnitudes (i > 23.5), the completeness rapidly declines to less than 60% and the contamination sharply increases to greater than 10% (see the middle panel of figure 1 in Akiyama et al. 2018). To avoid severe contamination by extended objects, we limit the faint end of the quasar sample to i = 23.5. Fig. 1. View largeDownload slide i-band magnitude distributions of the samples. Left: Red and black histograms show the distributions of the z ∼ 4 quasar candidates from the HSC-SSP and SDSS, respectively. Right: The blue histogram represents the distribution of the z ∼ 4 LBGs from the HSC-SSP. (Color online) Fig. 1. View largeDownload slide i-band magnitude distributions of the samples. Left: Red and black histograms show the distributions of the z ∼ 4 quasar candidates from the HSC-SSP and SDSS, respectively. Right: The blue histogram represents the distribution of the z ∼ 4 LBGs from the HSC-SSP. (Color online) We apply the Lyman-break selection to identify quasars at z ∼ 4. The selection utilizes the spectral property that the continuum blue-ward of the Lyα line (λrest = 1216 Å) is strongly attenuated by absorption due to the intergalactic medium (IGM). The Lyα line of an object at z = 4.0 is redshifted to 6075 Å in the observed frame, which is in the middle of the r-band, as a result the object has a red g − r color. We apply the same color selection criteria as described in Akiyama et al. (2018). In total, 1023 z ∼ 4 quasar candidates in the magnitude range 20.0 < i < 23.5 are selected. We limit the bright end of the sample considering the effects of saturation and non-linearity. Even though we include edge regions with a shallow depth for the sample selection, we do not find a significant difference of the number densities in the edge and central regions. Therefore, we conclude that larger photometric uncertainties or a higher number density of junk objects in the shallower regions do not result in higher contamination for quasars in the region. The i-band magnitude distribution of the sample is shown with the red histogram in the left-hand panel of figure 1. The completeness of the color selection is examined with the 3.5 < zspec < 4.5 SDSS quasars with i > 20.0 within the HSC coverage (Akiyama et al. 2018). Among 92 SDSS quasars with clean HSC photometry, 61 of them pass the color selection, resulting in the completeness of 66%. Since the sample is photometrically selected, it can be contaminated by galactic stars and compact galaxies that meet the color selection criteria. The contamination rate is further evaluated by using mock samples of galactic stars and galaxies; the contamination rate is less than 10% at i < 23.0, and increases to more than 40% at i ∼ 23.5. It causes an excess of HSC quasars in faint magnitude bins (23.2 < i < 23.5) as shown in the left-hand panel of figure 1. Since the contamination rate sharply increases at i > 23.5, we limit the sample at this magnitude. For the bright end, as the luminous SDSS quasar sample primarily includes quasars brighter than i = 21.0, we consider the HSC quasar sample fainter than i = 21.0 to constitute the less-luminous quasar sample. Finally, 901 quasars from the HSC are selected in the magnitude range of 21.0 < i < 23.5. Here, we convert the i-band apparent magnitude to the UV absolute magnitude at 1450 Å using the average quasar SED template provided by Siana et al. (2008) at z ∼ 4, which results in a magnitude range of −24.73 < M1450 < −22.23. In Akiyama et al. (2018), a best-fitting analytic formula of the contamination rate as a function of the i-band magnitude is provided. If we apply it to the less-luminous quasar sample, it is expected that 90 out of 901 candidates are contaminating objects, i.e., contamination rate of the z ∼ 4 less-luminous quasar sample is 10.0%. The redshift distribution of the z ∼ 4 less-luminous quasar candidates is shown in figure 2 with the red histogram. For 32 candidates with spectroscopic redshift information, we adopt their spectroscopic redshifts, otherwise the redshifts are estimated with a Bayesian photometric redshift estimator using a library of mock quasar templates (Akiyama et al. 2018). Most of the quasars are in the redshift range between 3.4 and 4.6. Average and standard deviation of the redshift distribution are 3.8 and 0.2, respectively. Fig. 2. View largeDownload slide Redshift distributions of the samples. The red histogram indicates the redshift distribution of the less-luminous quasar sample determined either spectroscopically or photometrically (Akiyama et al. 2018). The black dashed histogram shows the spectroscopic redshift distribution of the luminous quasar sample. The blue histogram represents the expected redshift distribution of the LBG sample evaluated with the mock LBGs (see text in subsection 2.4). All histograms are normalized so that $$\int _{0}^{\infty }N(z)dz=1$$. (Color online) Fig. 2. View largeDownload slide Redshift distributions of the samples. The red histogram indicates the redshift distribution of the less-luminous quasar sample determined either spectroscopically or photometrically (Akiyama et al. 2018). The black dashed histogram shows the spectroscopic redshift distribution of the luminous quasar sample. The blue histogram represents the expected redshift distribution of the LBG sample evaluated with the mock LBGs (see text in subsection 2.4). All histograms are normalized so that $$\int _{0}^{\infty }N(z)dz=1$$. (Color online) In order to examine the luminosity dependence of the quasar clustering, a sample of luminous z ∼ 4 quasars is constructed based on the 12th spectroscopic data release of the Sloan Digital Sky Survey (SDSS) (Alam et al. 2015). We select quasars with criteria on object type (“QSO”), reliability of the spectroscopic redshift (“z_waring” flag = 0), and estimated redshift error (smaller than 0.1). Only quasars within the coverage of the HSC S16A Wide2 data release are considered. We limit the redshift range between 3.4 and 4.6 following the redshift distribution of the HSC z ∼ 4 LBG sample (which will be discussed in subsection 2.4). In the coverage of the HSC S16A Wide2 data release, there are 342 quasars that meet the selection criteria. Their redshift distribution is shown by black dashed histogram in figure 2. Average and standard deviation of the redshift distribution are 3.77 and 0.26, respectively. Although the redshift distribution of the SDSS sample shows excess around z ∼ 3.5 compared to the HSC sample, the average and standard deviations are close to each other. The i-band magnitude distribution of the SDSS quasars is plotted by the black histogram in the left-hand panel of figure 1. To determine their i-band magnitude in the HSC photometric system, we match the sample to HSC clean objects using a search radius of 1$${^{\prime\prime}_{.}}$$0. Out of the 342 SDSS quasars, 296 have a corresponding object among the clean objects, while the others are saturated in the HSC imaging data. For the remaining 46 quasars, we convert their r- and i-band magnitudes in the SDSS system to the i-band magnitude in the HSC system following the equations in subsection 3.3 in Akiyama et al. (2018). As can be seen from the distributions, the SDSS quasar sample covers a magnitude range about 2 mag brighter than the HSC quasar sample. Their corresponding UV absolute magnitudes at 1450 Å are in the range of −28.0 to −23.95 evaluated by the same method with the less-luminous quasar sample. 2.3 Sample of z ∼ 4 LBGs from the HSC dataset We select candidates of z ∼ 4 LBGs from the S16A Wide2 dataset in the similar way as we select the z ∼ 4 quasar candidates. Unlike the process for quasars, we select candidates from the extended clean objects instead of the stellar objects, i.e., we pick out the clean objects that do not meet either of the equations (6) or (7) as extended objects. As shown in figure 9 of Akiyama et al. (2018), extended galaxies at z > 3 are distinguishable from stellar quasars with these criteria, as a result of the good image quality of the i-band HSC Wide layer images, which has a median seeing size of 0$${^{\prime\prime}_{.}}$$61 (Aihara et al. 2018b). While the stellar/extended classification is ineffective at i > 23.5, the contamination of stellar objects to the LBG sample is negligible, because the extended objects outnumber the stellar objects by ∼30 times at 23.5 < i < 25.0. We determine the color selection criteria of z ∼ 4 LBGs based on color distributions of a library of model LBG spectral energy distributions (SEDs), because the sample of z ∼ 4 LBGs with a spectroscopic redshift at the depth of the HSC Wide layer is limited. The model SEDs are constructed with the stellar population synthesis model by Bruzual and Charlot (2003). We assume a Salpeter initial mass function (Salpeter 1955) and the Padova evolutionary track for stars (Fagotto et al. 1994a, 1994b, 1994c) of solar metallicity. Following a typical star-formation history of z ∼ 4 LBGs derived based on an optical–NIR SED analysis (e.g., Shapley et al. 2001; Nonino et al. 2009; Yabe et al. 2009), we adopt an exponentially declining star-formation history with ψ(t) = τ−1exp(−t/τ), where τ = 50 Myr and t = 300 Myr. In addition to the stellar continuum component, we also consider the Lyα emission line at 1216 Å with a equivalent width (EWLyα) randomly distributed within the range between 0 and 30 Å, which is determined to follow the Lyα EW distribution of luminous LBGs in the UV absolute magnitude range of −23.0–−21.5 (Ando et al. 2006). We apply extinction as a screen dust with the dust extinction curve of Calzetti et al. (2000). We assume that E(B − V) has a Gaussian distribution with a mean of 0.14 and 1σ of 0.07 following that observed for z ∼ 3 UV-selected galaxies (Reddy et al. 2008). In order to reproduce the observed scatter of the g − r color of galaxies at z ∼ 3 (see figure 3), the scatter of the color excess is doubled to σ = 0.14. In total, 3000 SED templates are constructed. Each template is redshifted to z = 2.5–5.0 with an interval of 0.1. Attenuation by the intergalactic medium is applied to the redshifted templates. We follow the updated number density of the Lyα absorption systems in Inoue et al. (2014), and consider scatter in the number density of the systems along different line of sights with the Monte Carlo method used in Inoue and Iwata (2008). In figure 3, we compare the distributions of the g − r and r − z colors of the templates with those of spectroscopically confirmed LBGs at i < 24.5 in the HSC-SSP catalogs of the Ultra-Deep layer. Since spectroscopically-identified LBGs selected from narrow-band colors are biased towards LBGs with large Lyα EW, we remove them in the spectroscopically-identified sample. The color distribution of the mock LBGs as a function of redshift reproduces that of the galaxies with spectroscopic redshifts around 3. At z > 3.5, real galaxies follow the color evolution trend of the mock LBGs with slightly bluer g − r and r − z colors. Since the discrepancy is within the scatter and size of sample is limited, we adopt the current mock LBG library in this work. Fig. 3. View largeDownload slide g − r (left) and r − z (right) colors versus redshift of the mock LBGs. The red line and the error bars are the average and 1σ scatter of the colors of the mock LBGs. Blue points represent spectroscopically confirmed galaxies within the HSC S16A Ultra-Deep layer. (Color online) Fig. 3. View largeDownload slide g − r (left) and r − z (right) colors versus redshift of the mock LBGs. The red line and the error bars are the average and 1σ scatter of the colors of the mock LBGs. Blue points represent spectroscopically confirmed galaxies within the HSC S16A Ultra-Deep layer. (Color online) Considering the color distributions of the mock LBGs and the LBGs with a spectroscopic redshift, we determine the color selection criteria on the g − r vs. r − z color–color diagram as shown in figure 4 with the blue dashed lines. Blue crosses and black triangles represent colors of galaxies with a spectroscopic redshift at 0.2 < z < 0.8 and 0.8 < z < 3.5, respectively, in the HSC Ultra-deep-layer photometry. Red stars are galaxies at 3.5 < z < 4.5. We plot the color track of the model LBG with the black solid line, and mark the colors at z = 2.5, 3.0, 3.5, 4.0, and 4.4 with the 1σ scatter. The pink shaded region represents 1σ scatter of the r − z color along the model track. The selection criteria are \begin{eqnarray} 0.909(g-r)-0.85>(r-z), \\ \nonumber \end{eqnarray} (8) \begin{eqnarray} (g-r)>1.3, \\ \nonumber \end{eqnarray} (9) \begin{eqnarray} (g-r)<2.5. \end{eqnarray} (10)We determine the selection criteria to enclose the large part of the color distribution of the models while preventing severe contamination from low-redshift galaxies. The third criterion limits the upper redshift range of the sample, and is adjusted to match the expected redshift distribution of the less-luminous z ∼ 4 quasars. In order to reduce contaminations by low-redshift red galaxies and objects with unreliable photometry, we consider two additional criteria: \begin{eqnarray} (i-z)<0.2, \\ \nonumber \end{eqnarray} (11) \begin{eqnarray} (z-y)<0.2, \end{eqnarray} (12)following figure 3 in Akiyama et al. (2018). Because the contamination by low-redshift galaxies is severe at magnitudes fainter than i = 24.5, we limit the sample at this magnitude. Finally, we select 25790 z ∼ 4 LBG candidates at i < 24.5. The i-band magnitude distribution of the candidates is shown in the right-hand panel of figure 1. The brightest candidate is at i = 21.87, but there are only four candidates at i < 22. Thus we plot the distribution from i = 22. The corresponding UV absolute magnitudes of the candidates at 1450 Å are evaluated to be in the range of −23.88 < M1450 < −21.25 by the model LBG at z ∼ 4. It should be noted that there is a difference in the sky coverage between both of the quasar samples and i < 24.5 LBGs, because of the edge regions with shallow depth where only the quasars are selected reliably. Such selection effects are taken into consideration when constructing the random sample (subsection 2.5). Fig. 4. View largeDownload slide Color selection of z ∼ 4 LBGs. Blue crosses and black triangles are galaxies at 0.2 < z < 0.8 and 0.8 < z < 3.5, respectively. Only 5.0% of them are plotted, for clarity. Red stars are galaxies at 3.5 < z < 4.5. Purple inverted triangle is galaxy at z > 4.5. Green dots are colors of stars derived in the spectro-photometric catalog by Gunn and Stryker (1983). The solid black line is the track of the model LBG. Black squares and error bars denote the average and 1σ color scatter of the mock LBGs along the track at z = 2.5, 3.0, 3.5, 4.0, and 4.4. Pink shaded area implies the 1σ r − z scatter of the mock LBGs. Blue dashed lines represent our selection criteria. (Color online) Fig. 4. View largeDownload slide Color selection of z ∼ 4 LBGs. Blue crosses and black triangles are galaxies at 0.2 < z < 0.8 and 0.8 < z < 3.5, respectively. Only 5.0% of them are plotted, for clarity. Red stars are galaxies at 3.5 < z < 4.5. Purple inverted triangle is galaxy at z > 4.5. Green dots are colors of stars derived in the spectro-photometric catalog by Gunn and Stryker (1983). The solid black line is the track of the model LBG. Black squares and error bars denote the average and 1σ color scatter of the mock LBGs along the track at z = 2.5, 3.0, 3.5, 4.0, and 4.4. Pink shaded area implies the 1σ r − z scatter of the mock LBGs. Blue dashed lines represent our selection criteria. (Color online) 2.4 Redshift distribution and contamination rate of the z ∼ 4 LBG sample The redshift distribution of the LBG sample is evaluated by applying the same selection criteria to a sample of mock LBGs, which are constructed in the redshift range between 3.0 and 5.0 with a 0.1 redshift bin. At each redshift bin, we randomly select LBG templates from our library of SEDs and normalize them to have 22.0 < i < 24.5 following the LBG UV luminosity function at z ∼ 3.8 (van der Burg et al. 2010). We convert the apparent i-band magnitude to the absolute UV magnitude based on the selected templates. It should be noted that an object with a fixed apparent magnitude has a higher luminosity and a smaller number density in the luminosity function at higher redshifts. We also consider the difference in comoving volume at each redshift bin. For each redshift bin, we then place the mock LBGs at random positions in the HSC Wide layer images with a density of 2000 galaxies per deg2, and apply the same masking process as for the real objects. We calculate the expected photometric error at each position using the relation between the flux uncertainty and the value of image variance. This relation is determined empirically with the flux uncertainty of real objects as a function of the PSF and object size. The variance is measured within 1″ × 1″ at each point. The size of the model PSF at the position is evaluated with the model PSF of the nearest real object in the database. In order to reproduce the photometric error associated with the real LBGs, we use the relation for a size of 1$${^{\prime\prime}_{.}}$$5. After calculating the photometric error with this method, we add a random photometric error assuming the Gaussian distribution. Finally, we apply the color selection criteria and remove mock LBGs with magnitude errors larger than 0.1 in either of the i or r bands. The ratio of the recovered mock LBGs to the full random mock LBGs is evaluated as the selection completeness at each redshift bin. We find that the selection completeness is ∼10.0%–30.0% in the redshift range between 3.5 and 4.2, but smaller than 5% at other redshifts. These low rates are due to the fact that we set stringent constraints so that we can prevent the severe contamination from low-redshift galaxies. Based on a selection completeness of 20.0% at 3.5 < z < 4.2, we calculate an expected number of 35988 LBGs with 22 < i < 24.5 in the HSC-SSP S16A Wide layer from the LBG UV luminosity function at z ∼ 3.8 (van der Burg et al. 2010), which is larger than the actual LBG sample size (25790) in this work since we consider the edge regions that have a shallow depth. The effect of the shallow depth is considered in the construction of the random objects (subsection 2.5). The redshift distribution is measured by multiplying the completeness ratio with the number of mock LBGs at each redshift, which is shown in figure 2 by the blue histogram. The average and 1σ of the distribution is 3.71 and 0.30, respectively. The redshift distribution of the LBGs is similar to that of the luminous quasar sample, but slightly extended toward lower redshifts than the less-luminous quasar sample. It is likely that the extension is due to the higher number density of LBGs in 22.0 < i < 24.5 at 3.3 < z < 3.5. The LBG sample can be contaminated by low-redshift red galaxies which have similar photometric properties to the z ∼ 4 LBGs. We evaluate the contamination rate of the LBG selection using the HSC photometry in the COSMOS region and the COSMOS i-band selected photometric redshift catalogue, which is constructed by a χ2 template-fitting method with 30 broad, intermediate, and narrow bands from UV to mid-IR in the 2 deg2 COSMOS field (Ilbert et al. 2009). In the HSC-SSP S15B internal database, three stacked images in the COSMOS region, simulating good, median, and bad seeing conditions, are provided. Since the i-band images of the Wide layer are selectively taken under good or median seeing conditions (Aihara et al. 2018b), we match the catalogs from the median stacked image, which has a FWHM of 0$${^{\prime\prime}_{.}}$$70, with galaxies in the photometric redshift catalog within an angular separation of 1$${^{\prime\prime}_{.}}$$0. As examined by Ilbert et al. (2009), the photometric redshift uncertainty of galaxies with COSMOS i΄-band magnitudes brighter than 24.0 is estimated to be smaller than 0.02 at z < 1.25. For galaxies within the same luminosity range at higher redshifts, 1.25 < z < 3, the uncertainty is significantly higher but roughly below 0.1. Thus we only include objects with photometric redshift uncertainties less than 0.02 and 0.1 at z < 1.25 and at z > 1.25, respectively, in the matched catalog. We apply the color selection criteria (8)–(12) to the matched catalog. Among 700 matched galaxies with 3.5 < zphot < 4.5, 117 galaxies pass the selection criteria, resulting in the completeness of 17%, which is consistent with that examined by the mock LBGs. Meanwhile, we investigate the contamination by the ratio of galaxies at z < 3 or z > 5 among those passing the selection criteria at each magnitude bin of 0.1. It is found that the contamination rate is 10% to 30% in the magnitude range of i = 23.5–24.5, and sharply increases to >50% at i = 25.0. In total, all contaminating sources are classified to be at z < 3, while 95% of them are at z < 1. We multiply the contamination rate as a function of the i-band magnitude with the number counts of the LBG candidates at each 0.1 bin to estimate the total number of contaminating sources in the sample. Among 25790 LBG candidates, 5886 are expected to be contaminating objects at z < 3, i.e., the contamination rate is 22.8%. Furthermore, we also check the photometric redshift of the LBG candidates determined with the five-band HSC Wide layer photometry via the MIZUKI photometric redshift code, which uses the Bayesian photometric redshift estimation (Tanaka et al. 2018). Among the 25790 z ∼ 4 LBG candidates, 25749 of them have photometric redshifts with the MIZUKI code, and 4091 of them have photometric redshifts lower than z = 3.0. The contamination rate is evaluated to be 15.9%, which is similar to the one evaluated in the COSMOS region. Since the COSMOS photometric redshift catalog is based on the 30-band photometry covering a wider wavelength range, we consider the contamination rate evaluated in the COSMOS region in the later clustering analysis. 2.5 Constructing random objects for the clustering analysis The clustering strength is evaluated by comparing the number of pairs of real objects and that of mock objects distributed randomly in the survey area. Therefore it is necessary to construct a sample of mock objects that are distributed randomly within the survey area and are selected with the same selection function as the real sample. From z = 3 to 5, we construct 3000 mock LBG SEDs, which are normalized to have i = 24.5, at each 0.1 redshift bin. Then we place the mock LBGs randomly over the survey region with a surface number density of 2000 LBGs per deg2, with errors as described in subsection 2.4. After applying the same color selection and magnitude error criteria as for the real objects, we create a sample of 150756 random LBGs, which reproduces the global distribution of the real LBGs including the edge of the survey region where the depth is shallower. Therefore, the clustering analysis on large scales is not affected by the discrepancy of the sky coverage between the quasars and LBGs. Furthermore, since the detection completeness can be affected by non-uniform seeing within the Wide layer dataset especially at i = 24.5, it is important to reproduce the seeing dependence of the LBG detection completeness in the construction of the random LBGs. Over the entire clean area, 11.2% and 12.1% patches are taken under seeing smaller than 0$${^{\prime\prime}_{.}}$$5 and greater than 0$${^{\prime\prime}_{.}}$$7, respectively. For the LBG sample at i < 24.5, there are 15.8% and 7.7% of them taken under seeing smaller than 0$${^{\prime\prime}_{.}}$$5 and greater than 0$${^{\prime\prime}_{.}}$$7, respectively, suggesting a higher (lower) detection completeness with better (worse) seeing. We plot the cumulative probability functions (CPFs) of the seeing for LBGs, random LBGs, and the entire clean region in figure 5. It can be seen that the random LBGs reproduce the seeing dependence of the detection completeness. Fig. 5. View largeDownload slide Cumulative probability functions of the i-band seeing at the position of the selected z ∼ 4 LBG candidates (red line), random LBGs (blue line) and entire clean area (black line). (Color online) Fig. 5. View largeDownload slide Cumulative probability functions of the i-band seeing at the position of the selected z ∼ 4 LBG candidates (red line), random LBGs (blue line) and entire clean area (black line). (Color online) 3 Clustering analysis 3.1 Cross-correlation functions of the less-luminous and luminous quasars at z ∼ 4 We evaluate the CCFs of the z ∼ 4 quasars and LBGs with the projected two-point angular correlation function, ω(θ), since most of the quasar and LBG candidates do not have spectroscopic redshifts. We use the estimator from Davis and Peebles (1983), $$\omega (\theta )=\frac{DD(\theta )}{DR(\theta )}-1,$$ (13)where DD(θ) = ⟨DD⟩/NQSONLBG and DR(θ) = ⟨DR⟩/ NQSONR are the normalized quasar–LBG pair counts and quasar–random LBG pair counts in an annulus between θ − Δθ and θ + Δθ, respectively. Here, ⟨DD⟩ and ⟨DR⟩ are the numbers of quasar–LBG and quasar–random LBG pairs in the annulus, and NQSO, NLBG, and NR are the total numbers of quasars, LBGs and random LBGs, respectively. We set 14 bins from 1$${^{\prime\prime}_{.}}$$0 to 1000$${^{\prime\prime}_{.}}$$0 in the logarithmic scale. The CCFs of the quasars and LBGs for the less-luminous and luminous quasars are plotted in the left and right-hand panels of figure 6, respectively, and summarized in table 1 along with the pair count in each bin. Fig. 6. View largeDownload slide Left-hand panel: Blue dots are the observed mean CCF ωobs of the less-luminous quasars and the LBGs at z ∼ 4 obtained from the Jackknife resampling. The black solid line is the best-fitting power-law model using ML fitting on the scale of 10$${^{\prime\prime}_{.}}$$0 to1000$${^{\prime\prime}_{.}}$$0. The red dash–dotted line is the best-fitting dark matter model ωDM (red long-dashed line) adopting ML fitting in the same scale based on the HALOFIT power spectrum (Smith et al. 2003), while the blue dash–dotted line is the best-fitting dark matter model $$\omega _{\rm DM}^{\prime }$$ (blue short-dashed line) after considering the contaminations of the less-luminous quasars and the LBGs. Right-hand panel: Blue stars are the observed mean CCF ωobs of the luminous quasars and the LBGs at z ∼ 4 got from the Jackknife resampling. Red and blue lines have the same meaning as in the the left-hand panel but the blue line only considers the contamination of the LBGs. The orange dash–double-dotted line is the expected CCF of the luminous quasars estimated by the luminous quasars ACF in Shen et al. (2009). The green thick long-dashed and pink thick dashed lines are the best-fitting power-law models on the scale of 40$${^{\prime\prime}_{.}}$$0 to 160$${^{\prime\prime}_{.}}$$0 and of 40$${^{\prime\prime}_{.}}$$0 to 1000$${^{\prime\prime}_{.}}$$0, respectively. In both of the panels, symbols just on the horizontal axis with no error bar beyond 10$${^{\prime\prime}_{.}}$$0, those with no error bar within 10$${^{\prime\prime}_{.}}$$0, and those with error bars in the top pad mean negative bins with a small error bar, zero bins without pair count, and negative or zero bins with a large error bar, respectively. Top and bottom panels show the logarithmic and the linear scale of the vertical axis, respectively. The top horizontal axis of the top panel implies the comoving distance at redshift 4. (Color online) Fig. 6. View largeDownload slide Left-hand panel: Blue dots are the observed mean CCF ωobs of the less-luminous quasars and the LBGs at z ∼ 4 obtained from the Jackknife resampling. The black solid line is the best-fitting power-law model using ML fitting on the scale of 10$${^{\prime\prime}_{.}}$$0 to1000$${^{\prime\prime}_{.}}$$0. The red dash–dotted line is the best-fitting dark matter model ωDM (red long-dashed line) adopting ML fitting in the same scale based on the HALOFIT power spectrum (Smith et al. 2003), while the blue dash–dotted line is the best-fitting dark matter model $$\omega _{\rm DM}^{\prime }$$ (blue short-dashed line) after considering the contaminations of the less-luminous quasars and the LBGs. Right-hand panel: Blue stars are the observed mean CCF ωobs of the luminous quasars and the LBGs at z ∼ 4 got from the Jackknife resampling. Red and blue lines have the same meaning as in the the left-hand panel but the blue line only considers the contamination of the LBGs. The orange dash–double-dotted line is the expected CCF of the luminous quasars estimated by the luminous quasars ACF in Shen et al. (2009). The green thick long-dashed and pink thick dashed lines are the best-fitting power-law models on the scale of 40$${^{\prime\prime}_{.}}$$0 to 160$${^{\prime\prime}_{.}}$$0 and of 40$${^{\prime\prime}_{.}}$$0 to 1000$${^{\prime\prime}_{.}}$$0, respectively. In both of the panels, symbols just on the horizontal axis with no error bar beyond 10$${^{\prime\prime}_{.}}$$0, those with no error bar within 10$${^{\prime\prime}_{.}}$$0, and those with error bars in the top pad mean negative bins with a small error bar, zero bins without pair count, and negative or zero bins with a large error bar, respectively. Top and bottom panels show the logarithmic and the linear scale of the vertical axis, respectively. The top horizontal axis of the top panel implies the comoving distance at redshift 4. (Color online) Table 1. Less-luminous and luminous quasar–LBG CCFs at z ∼ 4. θ (″) (θmin, θmax) Less-luminous Luminous ⟨DQDG⟩ ⟨DQRG⟩ ω(θ) $$\overline{\omega _{i}(\theta )}$$ σ(θ) ⟨DQDG⟩ ⟨DQRG⟩ ω(θ) $$\overline{\omega _{i}(\theta )}$$ σ(θ) 2.05 (1.58, 2.51) 0 0 0 0 0 0 0 0 0 3.25 (2.51, 3.98) 2 3 2.90 3.25 8.74 0 1 −1 −1 9.76 5.15 (3.98, 6.31) 4 6 2.90 2.86 2.51 3 0 0 0 8.53 8.15 (6.31, 10.00) 3 7 1.51 1.58 1.91 0 4 −1 −1 1.69 12.92 (10.00, 15.85) 5 10 1.92 1.96 1.79 1 9 −0.35 −0.33 0.86 20.48 (15.85, 25.12) 7 47 −0.13 −0.11 0.47 3 6 1.92 1.96 2.11 32.46 (25.12, 39.81) 28 120 0.36 0.36 0.26 1 41 −0.86 −0.85 0.15 51.45 (39.81, 63.10) 52 303 0.003 −0.002 0.18 25 96 0.52 0.53 0.32 81.55 (63.10, 100.00) 143 739 0.13 0.13 0.13 47 226 0.22 0.21 0.27 129.24 (100.00, 158.49) 334 1710 0.14 0.14 0.09 116 589 0.15 0.15 0.14 204.84 (158.49, 251.19) 754 4144 0.06 0.06 0.04 257 1407 0.07 0.07 0.08 324.65 (251.19, 398.11) 1887 10375 0.06 0.06 0.04 585 3677 −0.07 −0.07 0.04 514.53 (398.11, 630.96) 4564 25764 0.04 0.04 0.02 1669 9272 0.05 0.05 0.07 815.48 (630.96, 1000.00) 11065 63358 0.02 0.02 0.02 3967 23241 −0.002 −0.005 0.03 θ (″) (θmin, θmax) Less-luminous Luminous ⟨DQDG⟩ ⟨DQRG⟩ ω(θ) $$\overline{\omega _{i}(\theta )}$$ σ(θ) ⟨DQDG⟩ ⟨DQRG⟩ ω(θ) $$\overline{\omega _{i}(\theta )}$$ σ(θ) 2.05 (1.58, 2.51) 0 0 0 0 0 0 0 0 0 3.25 (2.51, 3.98) 2 3 2.90 3.25 8.74 0 1 −1 −1 9.76 5.15 (3.98, 6.31) 4 6 2.90 2.86 2.51 3 0 0 0 8.53 8.15 (6.31, 10.00) 3 7 1.51 1.58 1.91 0 4 −1 −1 1.69 12.92 (10.00, 15.85) 5 10 1.92 1.96 1.79 1 9 −0.35 −0.33 0.86 20.48 (15.85, 25.12) 7 47 −0.13 −0.11 0.47 3 6 1.92 1.96 2.11 32.46 (25.12, 39.81) 28 120 0.36 0.36 0.26 1 41 −0.86 −0.85 0.15 51.45 (39.81, 63.10) 52 303 0.003 −0.002 0.18 25 96 0.52 0.53 0.32 81.55 (63.10, 100.00) 143 739 0.13 0.13 0.13 47 226 0.22 0.21 0.27 129.24 (100.00, 158.49) 334 1710 0.14 0.14 0.09 116 589 0.15 0.15 0.14 204.84 (158.49, 251.19) 754 4144 0.06 0.06 0.04 257 1407 0.07 0.07 0.08 324.65 (251.19, 398.11) 1887 10375 0.06 0.06 0.04 585 3677 −0.07 −0.07 0.04 514.53 (398.11, 630.96) 4564 25764 0.04 0.04 0.02 1669 9272 0.05 0.05 0.07 815.48 (630.96, 1000.00) 11065 63358 0.02 0.02 0.02 3967 23241 −0.002 −0.005 0.03 View Large The uncertainty of the CCFs is evaluated through the Jackknife resampling (Zehavi et al. 2005). We separate the survey area into N = 22 subregions with a similar size. In the ith resampling, we ignore one of the subregions to construct a new set of samples of quasars, LBGs, and random LBGs and estimate their correlation function, ωi. We evaluate the uncertainty only by the diagonal elements of the covariance matrix $${\boldsymbol C}(\omega _{i},\omega _{j})=\frac{N-1}{N}{\sum _{k=1}^{N}(\omega ^{k}_{i}-\overline{\omega _{i}})(\omega ^{k}_{j}-\overline{\omega _{j}})},$$ (14)where $$\overline{\omega _{i}}$$ is the mean of ωi over the N Jackknife samples, because the diagonal elements are sufficient to recover the true uncertainty (Zehavi et al. 2005). The $$\overline{\omega _{i}}$$ at each radius bin is consistent with the CCFs of the whole samples of the less-luminous and luminous quasars as shown in table 1 though the discrepancy becomes larger below 10$${^{\prime\prime}_{.}}$$0. We adopt $$\overline{\omega _{i}}$$ for plotting and analysis throughout this work. The resulting uncertainty with the Jackknife resampling is about 1.5–2 times larger than the Poisson error $$\lbrace \sigma (\theta )=[1+\omega (\theta )]/\sqrt{N_{\rm pair}}\rbrace$$ on the scale beyond 500$${^{\prime\prime}_{.}}$$0. However, these two error estimators are consistent with each other on scales within 300$${^{\prime\prime}_{.}}$$0. On scales smaller than 20$${^{\prime\prime}_{.}}$$0, due to the limited quasar–LBG pair count, the Poisson error can be even larger than the Jackknife one if we evaluate the Poisson uncertainty with the Poisson statistics for a small sample (Gehrels 1986). Here, since we do not consider the small scale within 10$${^{\prime\prime}_{.}}$$0 in the fitting process, we adopt the Jackknife error for the CCF beyond 10$${^{\prime\prime}_{.}}$$0. For the scale within 10$${^{\prime\prime}_{.}}$$0, if the Jackknife estimator fails to give a value due to either of no ⟨DD⟩ or ⟨DR⟩ pair count in any subsamples, we show the Poisson error following the Poisson statistics for a small sample (Gehrels 1986) in table 1 and figure 6. The binned CCF is fitted through the χ2 minimization with a single power-law model $$\omega (\theta )=A_{\omega }\theta ^{-\beta }-{\rm IC}.$$ (15)We apply a β of 0.86, which is determined with the ACF of the LBGs in the following subsection 3.2. IC is the integral constraint, which is a negative offset due to the restricted area of an observation (Groth & Peebles 1977). As described in Roche et al. (2002), the integral constraint can be estimated by integrating the true ω(θ) on the total survey area Ω as $${\rm IC}=\frac{1}{\Omega ^{2}}\int \int \omega (\theta )d\Omega _{1}d\Omega _{2}.$$ (16)We calculate the integral constraint using random LBG–random LBG pairs over the entire survey area through $${\rm IC}=\frac{\sum {[RR(\theta )A_{\omega }\theta ^{-\beta }]}}{\sum {RR(\theta )}}$$ (17)following Roche et al. (2002). Since the survey area is wide and the scale of interest is within 1000$${^{\prime\prime}_{.}}$$0, the IC/Aω is small compared to the observed CCFs and the IC term can be neglected in the fitting process. In this study, we focus on the large-scale clustering between two halos, i.e., the two-halo term. Thus the excess within an individual halo (one-halo term) is not considered in the fitting process. The radial scale of the region dominated by the one-halo term is examined to be 0.2–0.5 comoving h−1 Mpc (e.g., Ouchi et al. 2005; Kayo & Oguri 2012). At redshift 4, the corresponding angular separation is ∼10$${^{\prime\prime}_{.}}$$0–20$${^{\prime\prime}_{.}}$$0. Thus we fit the binned CCF with Aω on the scale larger than 10$${^{\prime\prime}_{.}}$$0. The best-fitting Aω is summarized in table 2 where the upper and lower limits correspond to Δχ2 = 1 from the minimal χ2. Here, the χ2 fitting fails to fit the CCF of the SDSS luminous quasars with negative bins due to the limited luminous quasar sample size. Table 2. Summary of clustering analysis for the CCFs. CF Model* Fitting $$\bar{z}$$ [θmin, θmax] Aω r0 bQG bQSO logMDMH (″) (h−1 Mpc) (h−1 M⊙) Power-law χ2 3.80 [10, 1000] $$6.03^{+1.65}_{-1.65}$$ $$7.13^{+0.99}_{-1.13}$$ $$5.62^{+0.72}_{-0.82}$$ $$5.48^{+1.25}_{-1.32}$$ $$12.07^{+0.33}_{-0.49}$$ Power-law΄ χ2 3.80 [10, 1000] $$8.67^{+2.37}_{-2.37}$$ $$8.66^{+1.20}_{-1.37}$$ $$6.74^{+0.87}_{-0.98}$$ $$6.10^{+1.40}_{-1.47}$$ $$12.25^{+0.32}_{-0.47}$$ Less- Power-law ML 3.80 [10, 1000] $$6.53^{+1.85}_{-1.81}$$ $$7.44^{+1.07}_{-1.19}$$ $$5.85^{+0.78}_{-0.87}$$ $$5.94^{+1.42}_{-1.46}$$ $$12.20^{+0.33}_{-0.49}$$ luminous Power-law΄ ML 3.80 [10, 1000] $$9.39^{+2.66}_{-2.60}$$ $$9.04^{+1.30}_{-1.45}$$ $$7.01^{+0.93}_{-1.04}$$ $$6.60^{+1.57}_{-1.63}$$ $$12.37^{+0.32}_{-0.47}$$ QG DM χ2 3.80 [10, 1000] — — $$5.68^{+0.70}_{-0.80}$$ $$5.67^{+1.23}_{-1.32}$$ $$12.13^{+0.31}_{-0.46}$$ CCF DM΄ χ2 3.80 [10, 1000] — — $$6.76^{+0.83}_{-0.94}$$ $$6.21^{+1.34}_{-1.42}$$ $$12.28^{+0.30}_{-0.44}$$ DM ML 3.80 [10, 1000] — — $$5.81^{+0.74}_{-0.85}$$ $$5.93^{+1.34}_{-1.43}$$ $$12.20^{+0.32}_{-0.48}$$ DM΄ ML 3.80 [10, 1000] — — $$6.96^{+0.89}_{-1.01}$$ $$6.58^{+1.49}_{-1.58}$$ $$12.37^{+0.31}_{-0.45}$$ Power-law ML 3.77 [10, 1000] $$2.99^{+3.08}_{-2.97}$$ $$4.73^{+2.19}_{-4.41}$$ $$3.77^{+1.60}_{-3.19}$$ $$2.47^{+2.36}_{-2.41}$$ $$10.45^{+1.40}_{-10.45}$$ Power-law΄ ML 3.77 [10, 1000] $$3.87^{+3.98}_{-3.84}$$ $$5.43^{+2.52}_{-5.06}$$ $$4.29^{+1.82}_{-3.63}$$ $$2.47^{+2.37}_{-2.41}$$ — Power-law ML 3.77 [40, 160] $$11.63^{+6.55}_{-6.07}$$ $$9.81^{+2.66}_{-3.32}$$ $$7.44^{+1.86}_{-2.24}$$ $$9.61^{+4.88}_{-4.73}$$ $$12.92^{+0.53}_{-1.05}$$ Luminous Power-law ML 3.77 [40, 1000] $$4.64^{+3.27}_{-3.20}$$ $$5.99^{+1.99}_{-2.80}$$ $$4.70^{+1.44}_{-2.01}$$ $$3.84^{+2.48}_{-2.53}$$ $$11.43^{+0.88}_{-3.00}$$ QG Power-law ML 3.77 [40 , 2000] $$4.01^{+2.96}_{-2.91}$$ $$5.54^{+1.92}_{-2.77}$$ $$4.37^{+1.39}_{-2.01}$$ $$3.32^{+2.24}_{-2.31}$$ $$11.13^{+0.96}_{-4.01}$$ CCF DM ML 3.77 [10, 1000] — — $$3.94^{+1.58}_{-2.94}$$ $$2.73^{+2.44}_{-2.55}$$ $$10.70^{+1.28}_{-10.70}$$ DM΄ ML 3.77 [10, 1000] — — $$4.48^{+1.75}_{-3.18}$$ $$2.73^{+2.36}_{-2.49}$$ — DM ML 3.77 [40, 160] — — $$7.31^{+1.86}_{-2.32}$$ $$9.39^{+4.86}_{-4.67}$$ $$12.89^{+0.54}_{-1.08}$$ DM ML 3.77 [40, 1000] — — $$4.52^{+1.46}_{-2.19}$$ $$3.59^{+2.47}_{-2.60}$$ $$11.29^{+0.94}_{-4.29}$$ DM ML 3.77 [40 , 2000] — — $$4.49^{+1.44}_{-2.13}$$ $$3.54^{+2.42}_{-2.52}$$ $$11.26^{+0.95}_{-4.08}$$ CF Model* Fitting $$\bar{z}$$ [θmin, θmax] Aω r0 bQG bQSO logMDMH (″) (h−1 Mpc) (h−1 M⊙) Power-law χ2 3.80 [10, 1000] $$6.03^{+1.65}_{-1.65}$$ $$7.13^{+0.99}_{-1.13}$$ $$5.62^{+0.72}_{-0.82}$$ $$5.48^{+1.25}_{-1.32}$$ $$12.07^{+0.33}_{-0.49}$$ Power-law΄ χ2 3.80 [10, 1000] $$8.67^{+2.37}_{-2.37}$$ $$8.66^{+1.20}_{-1.37}$$ $$6.74^{+0.87}_{-0.98}$$ $$6.10^{+1.40}_{-1.47}$$ $$12.25^{+0.32}_{-0.47}$$ Less- Power-law ML 3.80 [10, 1000] $$6.53^{+1.85}_{-1.81}$$ $$7.44^{+1.07}_{-1.19}$$ $$5.85^{+0.78}_{-0.87}$$ $$5.94^{+1.42}_{-1.46}$$ $$12.20^{+0.33}_{-0.49}$$ luminous Power-law΄ ML 3.80 [10, 1000] $$9.39^{+2.66}_{-2.60}$$ $$9.04^{+1.30}_{-1.45}$$ $$7.01^{+0.93}_{-1.04}$$ $$6.60^{+1.57}_{-1.63}$$ $$12.37^{+0.32}_{-0.47}$$ QG DM χ2 3.80 [10, 1000] — — $$5.68^{+0.70}_{-0.80}$$ $$5.67^{+1.23}_{-1.32}$$ $$12.13^{+0.31}_{-0.46}$$ CCF DM΄ χ2 3.80 [10, 1000] — — $$6.76^{+0.83}_{-0.94}$$ $$6.21^{+1.34}_{-1.42}$$ $$12.28^{+0.30}_{-0.44}$$ DM ML 3.80 [10, 1000] — — $$5.81^{+0.74}_{-0.85}$$ $$5.93^{+1.34}_{-1.43}$$ $$12.20^{+0.32}_{-0.48}$$ DM΄ ML 3.80 [10, 1000] — — $$6.96^{+0.89}_{-1.01}$$ $$6.58^{+1.49}_{-1.58}$$ $$12.37^{+0.31}_{-0.45}$$ Power-law ML 3.77 [10, 1000] $$2.99^{+3.08}_{-2.97}$$ $$4.73^{+2.19}_{-4.41}$$ $$3.77^{+1.60}_{-3.19}$$ $$2.47^{+2.36}_{-2.41}$$ $$10.45^{+1.40}_{-10.45}$$ Power-law΄ ML 3.77 [10, 1000] $$3.87^{+3.98}_{-3.84}$$ $$5.43^{+2.52}_{-5.06}$$ $$4.29^{+1.82}_{-3.63}$$ $$2.47^{+2.37}_{-2.41}$$ — Power-law ML 3.77 [40, 160] $$11.63^{+6.55}_{-6.07}$$ $$9.81^{+2.66}_{-3.32}$$ $$7.44^{+1.86}_{-2.24}$$ $$9.61^{+4.88}_{-4.73}$$ $$12.92^{+0.53}_{-1.05}$$ Luminous Power-law ML 3.77 [40, 1000] $$4.64^{+3.27}_{-3.20}$$ $$5.99^{+1.99}_{-2.80}$$ $$4.70^{+1.44}_{-2.01}$$ $$3.84^{+2.48}_{-2.53}$$ $$11.43^{+0.88}_{-3.00}$$ QG Power-law ML 3.77 [40 , 2000] $$4.01^{+2.96}_{-2.91}$$ $$5.54^{+1.92}_{-2.77}$$ $$4.37^{+1.39}_{-2.01}$$ $$3.32^{+2.24}_{-2.31}$$ $$11.13^{+0.96}_{-4.01}$$ CCF DM ML 3.77 [10, 1000] — — $$3.94^{+1.58}_{-2.94}$$ $$2.73^{+2.44}_{-2.55}$$ $$10.70^{+1.28}_{-10.70}$$ DM΄ ML 3.77 [10, 1000] — — $$4.48^{+1.75}_{-3.18}$$ $$2.73^{+2.36}_{-2.49}$$ — DM ML 3.77 [40, 160] — — $$7.31^{+1.86}_{-2.32}$$ $$9.39^{+4.86}_{-4.67}$$ $$12.89^{+0.54}_{-1.08}$$ DM ML 3.77 [40, 1000] — — $$4.52^{+1.46}_{-2.19}$$ $$3.59^{+2.47}_{-2.60}$$ $$11.29^{+0.94}_{-4.29}$$ DM ML 3.77 [40 , 2000] — — $$4.49^{+1.44}_{-2.13}$$ $$3.54^{+2.42}_{-2.52}$$ $$11.26^{+0.95}_{-4.08}$$ *The prime symbol indicates models that consider the contamination of the quasar and the LBG samples. View Large Another fitting method, the maximum likelihood (ML) method, which does not require a specific binning, is applied to the CCFs since the χ2 fitting to the binned CCFs can be highly affected by the negative bins. As described in Croft et al. (1997), if we assume that the pair counts in each bin follows the Poisson distribution, we can define the likelihood of having the observed pair sample from a model of a correlation function as $$\mathcal {L}=\prod _{i=1}^{N_{\rm bins}}\frac{e^{-h(\theta _{i})}h(\theta _{i})^{\langle DD(\theta _{i}) \rangle }}{{\langle DD(\theta _{i}) \rangle }!},$$ (18)where h(θ) = [1 + ω(θ)]⟨DR(θ)⟩ is the expected object–object mean pair count evaluated from the object–random object pair counts within a small interval around θ. Here, ω(θ) is the power-law model [equation (15)]. Then, we can define a function for minimization, S ∼ −2ln$$\mathcal {L}$$, as $$S=2\sum _{i}^{N_{\rm bins}} h(\theta _{i})-2\langle DD(\theta _{i}) \rangle \sum _{i}^{N_{\rm bins}} \ln h(\theta _{i}),$$ (19)where only terms dependent on model parameters are kept. Assuming that ΔS follows a χ2 distribution with one degree of freedom, the parameter range with ΔS = 1 from the minimum value corresponds to a 68% confidence range of the parameter. The ML fitting is applied for the CCFs in the range between 10$${^{\prime\prime}_{.}}$$0 and 1000$${^{\prime\prime}_{.}}$$0 with an interval of 0$${^{\prime}_{.}}$$5. The interval is set to keep the object–object pair count in each bin small enough, so that the bins are independent of each other. The best-fitting parameters are summarized in table 2. The ML method yields slightly higher Aω than the χ2 fitting but is still consistent within the 1σ uncertainty. However, in the range containing several negative bins, the best ML fitting models can be lower than the positive bins of the binned CCF, as can be seen in the right-hand panel of figure 6. It is reported that the assumption that pair counts follow the Poisson statistics (i.e., clustering is negligible) will underestimate the uncertainty of the fitting (Croft et al. 1997). We find the scatter of the ML fitting is only slightly smaller than the χ2 fitting. Therefore, we adopt the ML fitting results hereafter for both of the CCFs since both of them have negative bins in the binned CCFs. The contamination rates of the HSC quasar and LBG samples are taken into account by $$A^{\prime }_{\omega }=\frac{A^{\rm fit}_{\omega }}{(1-f^{\rm QSO}_{c})(1-f^{\rm LBG}_{c})},$$ (20)where $$f^{\rm QSO}_{c}$$ and $$f^{\rm LBG}_{c}$$ are the contamination rates of the less-luminous quasar and LBG samples estimated in subsections 2.2 and 2.4, respectively. Since we do not know redshift distributions or clustering properties of the contaminating sources, we simply assume that they are randomly distributed in the survey area. The Aω value safter correcting for the contamination are listed in table 2. We note that the contaminating galaxies or galactic stars can have their own spatial distributions. For example, it is reported that the galactic stars cause measurable deviation from the true correlation function only on scales of a degree or more due to their own clustering property (e.g., Myers et al. 2006, 2007). Therefore the correction in this work only gives an upper limit of the true Aω and we rely on the values without the correction in the discussions. 3.2 Auto-correlation function of z ∼ 4 LBGs In order to derive the bias factor of the quasars from the strength of the quasar–LBG CCFs, we need to evaluate the bias factor of the LBGs from the LBG ACF. The binned ACF of the z ∼ 4 LBGs is derived in the same way as the quasar–LBG CCF. We use the estimator $$\omega (\theta )=\frac{DD(\theta )}{DR(\theta )}-1,$$ (21)where DD(θ) = ⟨DD⟩/[NLBG(NLBG − 1)/2] and DR(θ) =⟨DR⟩/NLBGNR are the normalized LBG–LBG and LBG–random LBG pair counts in the annulus between θ − Δθ and θ + Δθ, respectively. Here, ⟨DD⟩ and ⟨DR⟩ are the numbers of LBG–LBG and LBG–random LBG pairs in the annulus, and NLBG and NR are the total numbers of LBGs and random LBGs, respectively. We set 14 bins from 1$${^{\prime\prime}_{.}}$$0 to 1000$${^{\prime\prime}_{.}}$$0 in the logarithmic scale. The LBG ACF is shown in figure 7 and table 3 along with the pair counts. Fig. 7. View largeDownload slide Blue squares are the observed mean ACF ωobs of the LBGs at z ∼ 4 derived from the Jackknife resampling. The solid line is the best-fitting power-law model on the scale 10$${^{\prime\prime}_{.}}$$0 to 1000$${^{\prime\prime}_{.}}$$0. The red dash–dotted line is the best-fitting dark matter model ωDM (red long-dashed line) in the same scale based on the HALOFIT power spectrum (Smith et al. 2003) following the method in Myers et al. (2007), while the blue dash–dotted line is the best-fitting dark matter model $$\omega _{\rm DM}^{\prime }$$ (blue short-dashed line) after considering the contamination of the LBGs. The χ2 fitting results are shown. Top and bottom panels show the logarithmic and the linear scale of the vertical axis, respectively. The top horizontal axis of the top panel is the comoving distance at redshift 4. (Color online) Fig. 7. View largeDownload slide Blue squares are the observed mean ACF ωobs of the LBGs at z ∼ 4 derived from the Jackknife resampling. The solid line is the best-fitting power-law model on the scale 10$${^{\prime\prime}_{.}}$$0 to 1000$${^{\prime\prime}_{.}}$$0. The red dash–dotted line is the best-fitting dark matter model ωDM (red long-dashed line) in the same scale based on the HALOFIT power spectrum (Smith et al. 2003) following the method in Myers et al. (2007), while the blue dash–dotted line is the best-fitting dark matter model $$\omega _{\rm DM}^{\prime }$$ (blue short-dashed line) after considering the contamination of the LBGs. The χ2 fitting results are shown. Top and bottom panels show the logarithmic and the linear scale of the vertical axis, respectively. The top horizontal axis of the top panel is the comoving distance at redshift 4. (Color online) Table 3. HSC LBG ACF at z ∼ 4. θ (″) (θmin, θmax) ⟨DD⟩ ⟨DR⟩ $$\overline{\omega _{i}(\theta )}$$ σ(θ) θ (″) (θmin, θmax) ⟨DD⟩ ⟨DR⟩ $$\overline{\omega _{i}(\theta )}$$ σ(θ) 2.05 (1.58, 2.51) 16 25 6.45 3.70 51.45 (39.81, 63.10) 966 9376 0.21 0.05 3.25 (2.51, 3.98) 16 54 2.47 1.27 81.55 (63.10, 100.00) 2211 22983 0.12 0.03 5.15 (3.98, 6.31) 20 122 0.92 0.46 129.24 (100.00, 158.49) 5413 56115 0.13 0.02 8.15 (6.31, 10.00) 48 285 0.96 0.40 204.84 (158.49, 251.19) 12542 138926 0.06 0.01 12.92 (10.00, 15.85) 105 683 0.80 0.20 324.65 (251.19, 398.11) 30387 341510 0.04 0.01 20.48 (15.85, 25.12) 219 1601 0.60 0.17 514.53 (398.11, 630.96) 74669 843464 0.04 0.008 32.46 (25.12, 39.81) 410 3833 0.25 0.90 815.48 (630.96, 1000.0) 181116 2070430 0.02 0.007 θ (″) (θmin, θmax) ⟨DD⟩ ⟨DR⟩ $$\overline{\omega _{i}(\theta )}$$ σ(θ) θ (″) (θmin, θmax) ⟨DD⟩ ⟨DR⟩ $$\overline{\omega _{i}(\theta )}$$ σ(θ) 2.05 (1.58, 2.51) 16 25 6.45 3.70 51.45 (39.81, 63.10) 966 9376 0.21 0.05 3.25 (2.51, 3.98) 16 54 2.47 1.27 81.55 (63.10, 100.00) 2211 22983 0.12 0.03 5.15 (3.98, 6.31) 20 122 0.92 0.46 129.24 (100.00, 158.49) 5413 56115 0.13 0.02 8.15 (6.31, 10.00) 48 285 0.96 0.40 204.84 (158.49, 251.19) 12542 138926 0.06 0.01 12.92 (10.00, 15.85) 105 683 0.80 0.20 324.65 (251.19, 398.11) 30387 341510 0.04 0.01 20.48 (15.85, 25.12) 219 1601 0.60 0.17 514.53 (398.11, 630.96) 74669 843464 0.04 0.008 32.46 (25.12, 39.81) 410 3833 0.25 0.90 815.48 (630.96, 1000.0) 181116 2070430 0.02 0.007 View Large Thanks to the large sample of the LBGs, the LBG–LBG pair count is large enough to constrain the ACF even in the smallest bin. We adopt the Jackknife error, which has a value two times larger than the Poisson error at all bins. Most of the bins have clustering signals greater than 3σ. We fit the raw LBG ACF with a single power-law model ω(θ) = Aωθ−β − IC by χ2 minimization on the scale from 10$${^{\prime\prime}_{.}}$$0 to 1000$${^{\prime\prime}_{.}}$$0. The integral constraint is negligible. Thanks to the small uncertainty of the LBG ACF, the power-law index can be constrained tightly to be $$\beta =0.86^{+0.07}_{-0.06}$$ as shown in figure 8. As already mentioned in subsection 3.1, we adopt this power-law index throughout this paper. The best-fitting parameters are listed in table 4. Fig. 8. View largeDownload slide χ2 map of Aω and β parameter of the ACF of the LBGs. The white cross indicates the best-fitting Aω and β at the minimal χ2, while the red region indicates the 68% confidence region. (Color online) Fig. 8. View largeDownload slide χ2 map of Aω and β parameter of the ACF of the LBGs. The white cross indicates the best-fitting Aω and β at the minimal χ2, while the red region indicates the 68% confidence region. (Color online) Table 4. Summary of the clustering analysis of HSC LBGs ACF. Model* Fitting $$\bar{z}$$ [θmin, θmax] β Aω r0 Bias (″) (h−1 Mpc) Power-law χ2 3.71 [10, 1000] $$0.86^{+0.07}_{-0.06}$$ $$6.56^{+0.49}_{-0.49}$$ $$7.47^{+0.29}_{-0.31}$$ $$5.76^{+0.21}_{-0.22}$$ LBG Power-law΄ χ2 3.71 [10, 1000] $$0.86^{+0.07}_{-0.06}$$ $$10.97^{+0.82}_{-0.82}$$ $$9.85^{+0.39}_{-0.40}$$ $$7.45^{+0.27}_{-0.28}$$ ACF DM χ2 3.71 [10, 1000] — — — $$5.69^{+0.21}_{-0.22}$$ DM΄ χ2 3.71 [10, 1000] — — — $$7.36^{+0.27}_{-0.28}$$ Model* Fitting $$\bar{z}$$ [θmin, θmax] β Aω r0 Bias (″) (h−1 Mpc) Power-law χ2 3.71 [10, 1000] $$0.86^{+0.07}_{-0.06}$$ $$6.56^{+0.49}_{-0.49}$$ $$7.47^{+0.29}_{-0.31}$$ $$5.76^{+0.21}_{-0.22}$$ LBG Power-law΄ χ2 3.71 [10, 1000] $$0.86^{+0.07}_{-0.06}$$ $$10.97^{+0.82}_{-0.82}$$ $$9.85^{+0.39}_{-0.40}$$ $$7.45^{+0.27}_{-0.28}$$ ACF DM χ2 3.71 [10, 1000] — — — $$5.69^{+0.21}_{-0.22}$$ DM΄ χ2 3.71 [10, 1000] — — — $$7.36^{+0.27}_{-0.28}$$ *The prime symbol indicates models that consider the contamination of the LBG sample. View Large The effect of the contamination is evaluated with $$A^{\prime }_{\omega }=\frac{A^{\rm fit}_{\omega }}{(1-f^{\rm LBG}_{c})^{2}}.$$ (22)The results are listed in table 4. We do not consider the contamination for fitting the power-law index β because it would not be affected by a random contamination. 4 Discussion 4.1 Clustering bias from the correlation length One of the parameters representing the clustering strength is the spatial correlation length, r0 (h−1 Mpc), which is in the spatial correlation function with the power-law form as $$\xi (r)= \left(\frac{r}{r_{0}} \right)^{-\gamma },$$ (23)where γ is related to the power of the projected correlation function through γ = 1 + β. The spatial correlation function can be projected to the angular correlation function through Limber’s equation (Limber 1953). We ignore the redshift evolution of the clustering strength within the covered redshift range. Then the spatial correlation length of the ACF can be derived from the amplitude of the angular correlation function, Aω, as $$r_{0}= \left\lbrace A_{\omega } \frac{c}{H_{0}H_{\gamma }} \frac{[\int N(z)dz]^{2}}{\int N^{2}(z)\chi (z)^{1-\gamma }E(z)dz} \right\rbrace ^{1/\gamma },$$ (24)where $$H_{\gamma }= \frac{\Gamma \left(\displaystyle {\frac{1}{2}}\right)\Gamma \left(\displaystyle {\frac{\gamma -1}{2}}\right)}{\Gamma \left(\displaystyle {\frac{\gamma }{2}}\right)},$$ (25) $$E(z)=\left[\Omega _{m}(1+z)^{3}+\Omega _{\Lambda }\right]^{1/2},$$ (26) $$\chi (z)=\frac{c}{H_{0}}\int _{0}^{z}\frac{1}{E(z^{\prime })}dz^{\prime },$$ (27)and N(z) is the redshift distribution of the sample. For the CCF, the same relation can be modified to (Croom & Shanks 1999) $$r_{0}= \left[ A_{\omega } \frac{c}{H_{0}H_{\gamma }} \frac{\int N_{\rm QSO}(z)dz\int N_{\rm LBG}(z)dz}{\int N_{\rm QSO}(z)N_{\rm LBG}(z)\chi (z)^{1-\gamma }E(z)dz} \right]^{1/\gamma }.$$ (28)Applying the redshift distributions of the less-luminous quasars, the luminous quasars and the LBGs at z ∼ 4 estimated in subsection 2.2 for NQSO(z) and subsection 2.4 for NLBG(z), we evaluate r0 from Aω with and without the contamination correction as summarized in table 2. Although the contamination rates of the less-luminous quasars and the LBGs are not high, the correlation lengths of the less-luminous quasar–LBG CCF and the LBG ACF are significantly increased after correcting for the contamination. Meanwhile, r0 of the luminous quasar–LBG CCF vary slightly, because the SDSS quasar sample is not affected by a contamination. The measurement of r0 is sensitive to the assumed redshift distribution of the sample. For example, r0 will be smaller if we assume a narrower redshift distribution even for the same Aω. As discussed in subsection 2.4, the redshift distribution of the LBGs is estimated to be more extended than both of the less-luminous and luminous quasar samples. If we assume the redshift distribution of the LBGs is the same as the less-luminous quasars, r0 of the LBG and the less-luminous quasars decreases to $$5.52^{+0.77}_{-0.87}\:h^{-1}\:$$Mpc, which is 23% lower than that estimated originally, because the fraction of the LBGs contributing to the projected correlation function in the overlapped redshift range increases, yielding a weaker correlation strength, i.e., a smaller r0 from a fixed Aω. The bias factor is defined as the ratio of clustering strength of real objects to that of the underlying dark matter at the scale of 8 h−1 Mpc, $$b=\sqrt{\frac{\xi (8,z)}{\xi _{DM}(8,z)}}.$$ (29)The clustering strength of the underlying dark matter can be evaluated based on the linear structure formation theory under the cold dark matter model (Myers et al. 2006) as \begin{eqnarray} \xi _{DM}(8,z)=\frac{(3-\gamma )(4-\gamma )(6-\gamma )2^{\gamma }}{72}\left[\sigma _{8}\frac{g(z)}{g(0)}\frac{1}{z+1}\right]^{2}, \nonumber\\ \end{eqnarray} (30)where \begin{eqnarray} g(z)=\frac{5\Omega _{mz}}{2} \left[\Omega ^{4/7}_{mz}-\Omega _{\Lambda z} + \left(1+\frac{\Omega _{mz}}{2}\right) \left(1+\frac{\Omega _{\Lambda z}}{70}\right) \right]^{-1}, \nonumber\\ \end{eqnarray} (31)and $$\Omega _{mz}=\frac{\Omega _{m}(1+z)^{3}}{E(z)^{2}},\Omega _{\Lambda z}=\frac{\Omega _{\Lambda }}{E(z)^{2}}.$$ (32)We derive the bias factors bLBG and bQG from the spatial correlation length of the LBG ACF and the quasar–LBG CCF, respectively. Following Mountrichas et al. (2009), the quasar bias factor is then evaluated from the bias factor of the CCF by $$b_{\rm QSO}b_{\rm LBG}\sim b^{2}_{\rm QG}.$$ (33)We list the LBG ACF bias factors in table 4. The estimated bLBG with and without the contamination correction are consistent with Allen et al. (2005) and the brightest bin at MUV ∼ −21.3 in Ouchi et al. (2004), respectively. The quasar bias factors derived from the CCF are summarized in table 2. 4.2 Bias factor from comparing with the HALOFIT power spectrum The bias factors can also be derived by directly comparing the observed clustering with the predicted clustering of the underlying dark matter from the power spectrum Δ2(k, z) (e.g., Myers et al. 2007). The spatial correlation function derived from Δ2(k, z) can be projected with the Limber equation into the angular correlation ωDM(θ) as \begin{eqnarray} \omega _{\rm DM}(\theta )=\pi \int \int \frac{\Delta ^{2}(k,z)}{k}J_{0}[k\theta \chi (z)]N^{2}(z)\frac{dz}{d\chi }F(\chi )\frac{dk}{k}dz, \nonumber\\ \end{eqnarray} (34)where J0 is the zeroth-order Bessel function, χ is the radial comoving distance, N(z) is the normalized redshift distribution function, dz/dχ = Hz/c = H0[Ωm(1 + z)3 + ΩΛ]1/2/c, and F(χ) = 1 for the flat universe. We evaluate the non-linear evolution of the power spectrum $$\Delta _{NL}^{2}(k, z)$$ in the redshift range between z = 3 and 5 with the HALOFIT code (Smith et al. 2003) by adopting the cosmological parameters used throughout this paper. The bias parameters are derived by fitting b2ωDM(θ) to the observed correlation functions, ωobs(θ). For the LBG ACF, ωDM(θ) is directly compared to the ωobs(θ) through χ2 minimization. For the CCFs, the redshift distribution in equation (34) is replaced by the multiplication of those of quasars and LBGs as \begin{eqnarray} \omega _{\rm DM-CCF}(\theta ) &=& \pi \int \int \frac{\Delta ^{2}(k,z)}{k}J_{0}[k\theta \chi (z)]N_{\rm QSO}(z)N_{\rm LBG}(z) \nonumber \\ & & \times \frac{dz}{d\chi }F(\chi )\frac{dk}{k}dz. \end{eqnarray} (35)On the scale from 10$${^{\prime\prime}_{.}}$$0 to 1000$${^{\prime\prime}_{.}}$$0, both of the χ2 and ML fitting are applied to the less-luminous quasar CCF, while only ML fitting works for the luminous quasar CCF. The bias factors of the quasar samples are derived from the CCF and the LBG ACF through equation (33). The best-fitting bias factors are summarized in tables 2 and 4. They are consistent with those derived from the power-law fitting within the 1σ uncertainty. Thus the power-law approximation with an index of β = −0.86 can well reproduce the underlying dark matter distribution on scales larger than 10$${^{\prime\prime}_{.}}$$0. In the scale below 10$${^{\prime\prime}_{.}}$$0, the underlying dark matter model becomes flat since we do not consider the one-halo term. If we compare the observed correlation functions with the best-fitting power-spectrum models, there is an obvious overdensity of galaxies on that scale in figure 7, which is consistent with the one-halo term of the LBG ACF at z ∼ 4 (e.g., Ouchi et al. 2005). The left-hand panel of figure 6, also shows an overdensity of galaxies within 10$${^{\prime\prime}_{.}}$$0 around the less-luminous quasars although the error bar is large. Interestingly, we find that the luminous quasars show a deficit of pair count within 10$${^{\prime\prime}_{.}}$$0 in the right-hand panel of figure 6. It should be noted that the best-fitting model in scales larger than 10$${^{\prime\prime}_{.}}$$0 suggests only 1 SDSS quasar–HSC LBG pair within 10$${^{\prime\prime}_{.}}$$0, which is consistent with the deficit. Thus the deficit in small scales can be caused by the limited size of the SDSS quasar sample, though we cannot exclude the possibility that there is a real deficit of galaxies around luminous quasars within 10$${^{\prime\prime}_{.}}$$0. We consider the contamination by modifying the redshift distribution normalization $$\int _{0}^{\infty }N(z)dz\sim 1-f_{c}$$ for the less-luminous quasars and the LBGs. We simply assume that the contamination will not contribute to the underlying dark matter correlation function. The modified underlying dark matter correlation functions are plotted in figures 6 and 7. Since the redshift distribution form is the same after considering the contamination, only the amplitude of the underlying dark matter correlation function is changed. The bias factors with contamination are listed in tables 2 and 4, and are consistent with those derived from fitting with the power-law model after correcting for the contamination. 4.3 Redshift and luminosity dependence of the bias factor At first, we discuss the luminosity dependence of the bias factors of the luminous and less-luminous quasars in this work. The bias factor of the less-luminous quasars is $$5.93^{+1.34}_{-1.43}$$, which is derived by fitting the CCF with the underlying dark matter model on the scale from 10$${^{\prime\prime}_{.}}$$0 to 1000$${^{\prime\prime}_{.}}$$0 through the ML fitting. The bias factor is consistent with that of the luminous quasars, $$2.73^{+2.44}_{-2.55}$$, obtained from the CCF through the same method within the 1σ uncertainty. If we consider the possible effect of the contamination, the bias factor of the less-luminous quasars increases to $$6.58^{+1.49}_{-1.58}$$, which is still consistent with that of the luminous quasars within the uncertainty. Thus no or only a weak luminosity dependence of the quasar clustering is detected within the two samples. In order to discuss the redshift dependence of the quasar clustering, we compare the bias factors and those in the literature in the left-hand panel of figure 9. The bias factors in the previous studies show a trend that quasars at higher redshifts are more strongly biased, indicating that quasars preferentially reside in DMHs within a mass range of 1012 ∼ 1013 h−1 M⊙ from z ∼ 0 to z ∼ 4. There is no discrepancy between the bias factors estimated with the ACF and the CCF at z ≲ 3. In this work, the bias factor of the less-luminous quasars at z ∼ 4 follows the trend, while the bias factor of the luminous quasars is similar to or even smaller than those at z ∼ 3. Fig. 9. View largeDownload slide Left-hand panel: Redshift evolution of the quasar bias factor. The red square is the result from fitting the less-luminous quasar CCF against the underlying dark matter model through ML fitting. The pink square is derived from fitting the less-luminous quasar CCF with the same method after considering the contamination. The orange square is obtained from fitting the luminous quasar CCF with the same method. Open and filled black circles are bias factors of quasars in a wide luminosity range obtained from the CCF and the ACF, respectively, in the literature, which are summarized by Ikeda et al. (2015) and Eftekharzadeh et al. (2015). Blue dashed lines show the bias evolutions of halos with a fixed mass of 1011, 1012, and 1013 h−1 M⊙ from bottom to top following the fitting formulae in Sheth, Mo, and Tormen (2001). Right-hand panel: Luminosity dependence of the quasar bias at 3 < z < 5. Red and orange squares have the same meaning as in the left-hand panel. The stars, diamonds, dots, triangle, open circles and squares are from Adelberger and Steidel (2005), Francke et al. (2007), Shen et al. (2009), Eftekharzadeh et al. (2015), Ikeda et al. (2015), and this work, respectively. Open and filled symbols imply the bias factors derived from the CCF and ACF, respectively. (Color online) Fig. 9. View largeDownload slide Left-hand panel: Redshift evolution of the quasar bias factor. The red square is the result from fitting the less-luminous quasar CCF against the underlying dark matter model through ML fitting. The pink square is derived from fitting the less-luminous quasar CCF with the same method after considering the contamination. The orange square is obtained from fitting the luminous quasar CCF with the same method. Open and filled black circles are bias factors of quasars in a wide luminosity range obtained from the CCF and the ACF, respectively, in the literature, which are summarized by Ikeda et al. (2015) and Eftekharzadeh et al. (2015). Blue dashed lines show the bias evolutions of halos with a fixed mass of 1011, 1012, and 1013 h−1 M⊙ from bottom to top following the fitting formulae in Sheth, Mo, and Tormen (2001). Right-hand panel: Luminosity dependence of the quasar bias at 3 < z < 5. Red and orange squares have the same meaning as in the left-hand panel. The stars, diamonds, dots, triangle, open circles and squares are from Adelberger and Steidel (2005), Francke et al. (2007), Shen et al. (2009), Eftekharzadeh et al. (2015), Ikeda et al. (2015), and this work, respectively. Open and filled symbols imply the bias factors derived from the CCF and ACF, respectively. (Color online) The luminosity dependence of the quasar bias factors at z ∼ 3–4 is summarized in the right-hand panel of figure 9. Both of the bias factors of the less-luminous quasars with and without the contamination correction are consistent with but slightly higher than that evaluated with the CCF of 54 faint quasars in the magnitude range of −25.0 < MUV < −19.0 at 1.6 < z < 3.7 measured by Adelberger and Steidel (2005), the CCF of 58 faint quasars in the magnitude range of −26.0 < MUV < −20.0 at 2.8 < z < 3.8 measured by Francke et al. (2007), and the CCF of 25 faint quasars in the magnitude range of −24.0 < MUV < −22.0 at 3.1 < z < 4.5 measured by Ikeda et al. (2015), which suggests a slightly increasing or no evolution from z = 3 to z = 4. Meanwhile, for the clustering of the luminous quasars, the bias factor in this work is consistent with the CCF of 25 bright quasars in the magnitude range of −30.0 < MUV < −25.0 at 1.6 < z < 3.7 measured by Adelberger and Steidel (2005) and the ACF of 24724 bright quasars in the magnitude range of −27.81 < MUV < −22.9 mag at 2.64 < z < 3.4 measured by Eftekharzadeh et al. (2015). Unlike the case of the less-luminous quasars, the clustering of the luminous quasars suggests no or a declining evolution from z ∼ 3 to z ∼ 4. The bias factor of the luminous quasars in this work shows a large discrepancy with the ACF of 1788 bright quasars in the magnitude range of −28.2 < MUV < −25.8 [which is transferred from Mi(z = 2) by equation (3) in Richards et al. (2006)] at 3.5 < z < 5.0 measured by Shen et al. (2009). They give two values for the bias factor; the higher one is obtained by only considering the positive bins and the lower one considers all of the bins in the ACF. The bias factor from another subsample of bright quasars covering −28.0 < MUV < −23.95 at 2.9 < z < 3.5 in Shen et al. (2009) is also shown in the panel. The z ∼ 4 quasar bias factors in Shen et al. (2009) show a large discrepancy from the bias factor of the luminous quasars in this work and in Eftekharzadeh et al. (2015) with the similar magnitude and redshift coverage. In the right-hand panel of figure 6, we plot the expected CCF with $$b_{\rm QG}\sim \sqrt{b_{\rm QSO}b_{\rm LBG}}=9.83$$ by the orange dash–double-dotted line. We adopt the higher bQSO in Shen et al. (2009) and the bLBG with the contamination correction to measure the upper limit of the bQG. Although the expected CCF is consistent with some bins within the 1σ uncertainty, it predicts much stronger clustering than both of the best-fitting power-law and dark matter models. In order to quantitatively examine the discrepancy, we plot the minimization function S of the ML fitting for the luminous quasars with the HALOFIT power spectrum as a function of the bias factor in figure 10. Both of the bias factors at 3.5 < z < 5 in Shen et al. (2009) are beyond the 1σ uncertainty, corresponding to a low probability. Meanwhile, the bias factor in Eftekharzadeh et al. (2015), the uncertainty of which is small thanks to the large sample, also shows a large discrepancy from those in Shen et al. (2009). Eftekharzadeh et al. (2015) suspect the discrepancy is mainly caused by a difference in large scale bins (>30 h−1 Mpc). We further investigate the effect from the fitting scale as shown in table 1 and the right-hand panel of figure 6. On a scale of 40$${^{\prime\prime}_{.}}$$0 to 160$${^{\prime\prime}_{.}}$$0, we find a strong CCF of the luminous quasars and the LBGs, which is consistent with the ACF of the luminous quasars. On scales below 40$${^{\prime\prime}_{.}}$$0, the ML fitting suggests a bQG of 0. On larger scales, the ML fitting is not efficient since the pair counts in each bin is too large to fulfil the assumption that bins are independent of each other, even if choosing a small bin width of 0$${^{\prime\prime}_{.}}$$5 interval. Therefore we only expand the ML fitting scale to 2000$${^{\prime\prime}_{.}}$$0. If we consider the power-law model, the bQG obtained by fitting in the range of 40$${^{\prime\prime}_{.}}$$0 to 1000$${^{\prime\prime}_{.}}$$0 is 24.7% and 7.6% higher than that estimated in the range of 10$${^{\prime\prime}_{.}}$$0 to 1000$${^{\prime\prime}_{.}}$$0 and of 40$${^{\prime\prime}_{.}}$$0 to 2000$${^{\prime\prime}_{.}}$$0, respectively, which suggests that the deficit of the luminous quasar–LBG pair on small scales may weaken the CCF more severely than fitting on scales larger than 1000$${^{\prime\prime}_{.}}$$0. Here, since the fitting of the luminous quasar CCF strongly depends on the scale, especially on small scales, we still focus on the results on the scale from 10$${^{\prime\prime}_{.}}$$0 to 1000$${^{\prime\prime}_{.}}$$0 to keep accordant to the LBG ACF and the less-luminous quasar CCF throughout the discussion. Fig. 10. View largeDownload slide ML fitting minimization function S of fitting for the luminous quasar CCF with the dark matter model. S is shown in relative to the minimal value. Black squares mark the 68% upper and lower limits of bQG with S − min(S) = 1. Blue and green squares indicate the expected bias factors of $$b_{\,\rm QG}\sim \sqrt{b_{\,\rm QSO}b_{\,\rm LBG}}=7.53$$ and 8.64 from the bias factors of the SDSS luminous quasars in Shen et al. (2009) with and without considering the negative bins in the ACF, respectively. The red dashed line indicates the same minimization function S after considering the possible contamination in the LBG sample. Black, blue and green dots have the same meaning as the squares. (Color online) Fig. 10. View largeDownload slide ML fitting minimization function S of fitting for the luminous quasar CCF with the dark matter model. S is shown in relative to the minimal value. Black squares mark the 68% upper and lower limits of bQG with S − min(S) = 1. Blue and green squares indicate the expected bias factors of $$b_{\,\rm QG}\sim \sqrt{b_{\,\rm QSO}b_{\,\rm LBG}}=7.53$$ and 8.64 from the bias factors of the SDSS luminous quasars in Shen et al. (2009) with and without considering the negative bins in the ACF, respectively. The red dashed line indicates the same minimization function S after considering the possible contamination in the LBG sample. Black, blue and green dots have the same meaning as the squares. (Color online) Quasar clustering models based on numerical simulation predict no luminosity dependence of the quasar clustering at z ∼ 4 (e.g., Fanidakis et al. 2013; Oogi et al. 2016; DeGraf & Sijacki 2017). Although there is a relation between mass of the SMBHs and DMHs in the models, SMBHs in a wide mass range are contributing to quasars at a fixed luminosity, thus there is no relation between the luminosity of model quasars and the mass of their DMHs. Oogi et al. (2016) and DeGraf and Sijacki (2017) predicted a quasar bias factor of ∼5.0 at redshift 4, which is consistent with the quasar bias factors in this work. No luminosity dependence is also predicted in a continuous SMBH growth model of Hopkins et al. (2007). They assume an Eddington limited SMBH growth until redshift 2. However, the predicted bias factor is much larger than the results in this work. On the other hand, there are models which predict stronger luminosity dependence of the quasar clustering at higher redshifts (e.g., Shen 2009; Conroy & White 2012). These models predict that SMBHs in a narrow mass range are contributing to the luminous quasars. In order to conclude the luminosity and redshift dependencies of the quasar clustering, we need to understand the cause of the discrepancy between the quasar ACF and quasar–LBG CCF for the luminous quasars at z ∼ 4. The quasar–LBG CCF could be affected by the suppression of galaxy formation due to feedback from luminous quasars (e.g., Kashikawa et al. 2007; Utsumi et al. 2010; Uchiyama et al. 2018). The weak cross-correlation could also be induced by a discrepancy between the redshift distributions of the quasars and LBGs. We need to further determine the redshift distribution through spectroscopic follow-up observations of the LBGs. 4.4 Effect of edge regions and seeing variation on the bias factor It should be noted that there is a sky coverage discrepancy between the samples of the quasars and LBG candidates in the shallower edge regions. As a result, it is possible that most of the ⟨DQSODLBG⟩ pair counts on small scales are from quasars only in inner regions, which may cause the weakness of the small-scale clustering between the luminous quasars and LBGs, if the random LBG sample cannot reproduce the detection completeness in the edge regions. Although we have mentioned that our random LBGs can reproduce the overall distribution of the real LBGs in subsection 2.5, to evaluate the effects quantitatively we select the central area in each subregion to construct a subsample of less-luminous quasars, luminous quasars, LBGs, and random LBGs. We apply the same estimator as in section 3.1 to measure their correlation functions. We fit a single power-law to the resulting ACF and CCF, then compare them to that of the original samples. Poisson error is adopted here for simplicity. In table 5, we summarize bQG and bLBG obtained from the samples in the inner (“No” in the border column) and entire regions (“Yes” in the border column). For the LBG ACF on the scale below 1000$${^{\prime\prime}_{.}}$$0 and less-luminous quasar CCF beyond 15$${^{\prime\prime}_{.}}$$0, they do not have a significant discrepancy from that of the entire samples except for a larger uncertainty, and the size of luminous quasar subsample is too limited to judge the border effect. On the scale below 15$${^{\prime\prime}_{.}}$$0, we find bQG of the subsamples is enhanced from $$7.48^{+1.39}_{-1.68}$$ to $$10.61^{+2.29}_{-2.88}$$. Since the uncertainty is large due to the limited size of pair counts on small scales, we could not make a conclusion whether the deficit of luminous quasar - LBG pair counts in scale within 15$${^{\prime\prime}_{.}}$$0 is due to the effect of the border regions or real. Table 5. Clustering dependence on the border and seeing. Model Fitting Border Seeing [θmin, θmax] Bias (″) Power-law χ2 Yes All [10, 1000] $$5.64^{+0.56}_{-0.62}$$ Less- Power-law χ2 No All [15, 1000] $$6.15^{+0.75}_{-0.85}$$ lumiNous QG Power-law χ2 Yes All [3, 15] $$7.48^{+1.39}_{-1.68}$$ CCF Power-law χ2 No All [3, 15] $$10.61^{+2.29}_{-2.88}$$ Power-law χ2 Yes [0$${^{\prime\prime}_{.}}$$5, 0$${^{\prime\prime}_{.}}$$7] [10, 1000] $$5.37^{+0.68}_{-0.78}$$ Power-law χ2 Yes All [3, 1000] $$5.69^{+0.13}_{-0.13}$$ LBG Power-law χ2 No All [3, 1000] $$5.55^{+0.18}_{-0.18}$$ ACF Power-law χ2 Yes [0$${^{\prime\prime}_{.}}$$5, 0$${^{\prime\prime}_{.}}$$7] [3, 1000] $$5.40^{+0.16}_{-0.16}$$ Model Fitting Border Seeing [θmin, θmax] Bias (″) Power-law χ2 Yes All [10, 1000] $$5.64^{+0.56}_{-0.62}$$ Less- Power-law χ2 No All [15, 1000] $$6.15^{+0.75}_{-0.85}$$ lumiNous QG Power-law χ2 Yes All [3, 15] $$7.48^{+1.39}_{-1.68}$$ CCF Power-law χ2 No All [3, 15] $$10.61^{+2.29}_{-2.88}$$ Power-law χ2 Yes [0$${^{\prime\prime}_{.}}$$5, 0$${^{\prime\prime}_{.}}$$7] [10, 1000] $$5.37^{+0.68}_{-0.78}$$ Power-law χ2 Yes All [3, 1000] $$5.69^{+0.13}_{-0.13}$$ LBG Power-law χ2 No All [3, 1000] $$5.55^{+0.18}_{-0.18}$$ ACF Power-law χ2 Yes [0$${^{\prime\prime}_{.}}$$5, 0$${^{\prime\prime}_{.}}$$7] [3, 1000] $$5.40^{+0.16}_{-0.16}$$ View Large Another problem that can affect the clustering analysis is the variation of detection completeness due to non-uniform seeing distribution within the Wide layer dataset. In subsection 2.5, we confirmed the random LBGs can reproduce the seeing dependence of the detection completeness of the real LBGs. Here, we quantitatively investigate the influence from the seeing variation by constructing a uniform subsample of less-luminous quasars, LBGs and random LBGs taken under seeing between 0$${^{\prime\prime}_{.}}$$5 and 0$${^{\prime\prime}_{.}}$$7. The same estimator as in subsection 3.1 and Poisson error are adopted to measure their correlation functions. In table 5, we summarize bQG and bLBG obtained with the seeing limited and entire samples. Compared to the correlation functions of the entire samples, there is no significant discrepancy of both of the less-luminous quasar CCF and LBG ACF of the seeing-limited samples except for larger uncertainty, which again suggests the seeing variation does not affect the results of the clustering. 4.5 DMH mass The bias factor of a population of objects is directly related to the typical mass of their host DMHs, because more massive DMHs are more strongly clustered and biased in the structure formation under the ΛCDM model (Sheth & Torman 1999). The relation between the MDMH and the bias factor is derived based on an ellipsoidal collapse model that is calibrated by an N-body simulation as \begin{eqnarray} b(M,z)&=&1+\frac{1}{\sqrt{a}\delta _{\rm crit}}\bigg[a\nu ^{2}\sqrt{a}+b\sqrt{a}(a\nu ^{2})^{(1-c)} \nonumber \\ & &-\,\frac{(a\nu ^{2})^{c}}{(a\nu ^{2})^{c}+b(1-c)(1-c/2)}\bigg], \end{eqnarray} (36)where ν = δcrit/[σ(M)D(z)] and critical density δcrit = 1.686 (Sheth et al. 2001). We adopt the updated parameters a = 0.707, b = 0.35, and c = 0.80 from Tinker et al. (2005). The rms mass fluctuation σ(M) on a mass scale M at redshift 0 is given by $$\sigma ^{2}(M)=\int \Delta ^{2}(k)\tilde{W}^{2}(kR)\frac{dk}{k},$$ (37)and $$M(R)=\frac{4\pi \overline{\rho _{0}} R^{3}}{3},$$ (38)where R is the comoving radius, $$\tilde{W}(kR)=[3\sin (kR)-(kR)\cos (kR)]/(kr)^{3}$$ is the top hat window function in Fourier form and $$\overline{\rho _{0}}=2.78\times 10^{11}\Omega _{m}\:h^{2}\, M_{\odot }\:$$Mpc−3 is the mean density in the current universe. The linear power spectrum Δ2(k) at redshift 0 is obtained from the HALOFIT code (Smith et al. 2003). The growth factor D(z) is approximated by $$D(z)\propto \frac{g(z)}{1+z}$$ (39)following Carroll, Press, and Turner (1992). Assuming the quasars and LBGs are associated with DMHs in a narrow mass range, we can infer the mass of the quasar host DMHs through the above relations. The evaluated halo masses of the less-luminous quasars and the luminous quasars are 1 ∼ 2 × 1012 h−1 M⊙ and <1012 h−1 M⊙ as summarized in table 2, respectively. Since the bias factor of the luminous quasars has a large uncertainty, we could only set an upper limit of the MDMH. We note that the halo mass strongly depends on the amplitude of the power spectrum on the scale of 8 h−1 Mpc, σ8. If we adopt σ8 = 0.9, the host DMH mass of the less-luminous quasars will be 4–6 × 1012 h−1 M⊙ with the same bias factor. 4.6 Minimum halo mass and duty cycle In the above discussion, we assume that quasars are associated with DMHs in a specific mass range, but it may be more physical to assume that quasars are associated with DMHs with a mass above a critical mass, Mmin. In this case, the effective bias for a population of objects which are randomly associated with DMHs above Mmin can be expressed with $$b_{\rm eff}=\frac{\int _{M_{\rm min}}^{\infty }b(M)n(M)dM}{\int _{M_{\rm min}}^{\infty }n(M)dM},$$ (40)where n(M) is the mass function of DMHs and b(M, z) is the bias factor of DMHs with mass M at z. We adopt the DMH mass function from the modified Press–Schechter theory (Sheth & Torman 1999) as \begin{eqnarray} n(M,z)&=&-A\sqrt{\frac{2a}{\pi }}\frac{\rho _0}{M}\frac{\delta _c(z)}{\sigma ^2(M)}\frac{d\sigma (M)}{dM} \nonumber \\ & & \times \left\lbrace 1+\left[\frac{\sigma ^2(M)}{a\delta _c^2(z)}\right]^p\right\rbrace \exp \left[-\frac{a\delta _c^2(z)}{2\sigma ^2(M)}\right], \end{eqnarray} (41)where A = 0.3222, a = 0.707, p = 0.3, and δc(z) = δcrit/D(z). If we follow the above formulation, the Mmin is estimated to be ∼0.3–2 × 1012 h−1 M⊙ and <5.62 × 1011 h−1 M⊙ with the bias factors of the less-luminous quasars and the luminous quasars, respectively. Comparing the number density of the DMHs above the Mmin and that of the less-luminous and luminous quasars, we can infer the duty cycle of the quasar activity among the DMHs in the mass range by $$f=\frac{n_{\rm QSO}}{\int _{M_{\rm min}}^{\infty }n(M)dM},$$ (42)assuming one DMH contains one SMBH. The co-moving number density of z ∼ 4 less-luminous quasars are estimated with the HSC quasar sample (Akiyama et al. 2018). Integrating the best-fitting luminosity function of z ∼ 4 quasars from M1450 ∼ −24.73 to M1450 ∼ −22.23, we estimate the total number density of the less-luminous quasar to be 1.07 × 10−6 h3 Mpc−3, which is two times higher than that of the luminous quasars with −28.00 < M1450 < −23.95 (4.21 × 10−7 h3 Mpc−3). If we adopt the n(M) in equation (41), the duty cycle is estimated to be 0.001–0.06 and <8 × 10−4 for Mmin from the less-luminous and the luminous quasar CCF, respectively. If we use the bias factor estimated by considering the effect of the possible contamination, the duty cycle of the less-luminous quasars is estimated to be 0.003 ∼ 0.175, which is higher than the estimation above. We compare the duty cycles with those evaluated for quasars at 2 < z < 4 in the literature in figure 11. The estimated luminosity dependence of the duty cycles is similar to that estimated for quasars in the similar luminosity range at z ∼ 2.6 (Adelberger & Steidel 2005), although the duty cycles at z ∼ 4 are one order of magnitude smaller than those at z ∼ 2.6. Fig. 11. View largeDownload slide Estimated quasar duty cycle as a function of redshift. The blue symbols represent the duty cycles estimated with a sample of quasars mostly with MUV < −25. The red symbols show those for the less-luminous quasars with MUV > −25. Stars, triangles, filled circles and squares represent the results from Adelberger and Steidel (2005), Shen et al. (2007), Eftekharzadeh et al. (2015), and this work. The pink open square shows the duty cycle with the contamination correction. (Color online) Fig. 11. View largeDownload slide Estimated quasar duty cycle as a function of redshift. The blue symbols represent the duty cycles estimated with a sample of quasars mostly with MUV < −25. The red symbols show those for the less-luminous quasars with MUV > −25. Stars, triangles, filled circles and squares represent the results from Adelberger and Steidel (2005), Shen et al. (2007), Eftekharzadeh et al. (2015), and this work. The pink open square shows the duty cycle with the contamination correction. (Color online) The estimated duty cycle corresponds to a duration of the less-luminous quasar activity of 1.5–90.8 Myr, which is broadly consistent with the quasar lifetime range of 1–100 Myr estimated in previous studies (for review see Martini 2004). It needs to be noted that the estimated duty cycle is sensitive to the measured strength of the quasar clustering. A small variation in the bias factor can result in even one order of magnitude difference in the duty cycle, because of the non-linear relation between b and MDMH and the sharp cut-off of n(M) at the high-mass end. Furthermore, the duty cycle is also sensitive to the assumed value of σ8 (Shen et al. 2007). 5 Summary We examine the clustering of a sample of 901 less-luminous quasars with −24.73 < M1450 < −22.23 at 3.1 < z < 4.6 selected from the HSC S16A Wide2 catalog and of a sample of 342 luminous quasars with −28.00 < M1450 < −23.95 at 3.4 < zspec < 4.6 within the HSC S16A Wide2 coverage from the 12th data release of SDSS. We investigate the quasar clustering through the CCF between the quasars and a sample of 25790 bright LBGs with M1450 < −21.25 in the same redshift range from the HSC S16A Wide2 data release. The main results are as follows. 1. The bias factor of the less-luminous quasar is $$5.93^{+1.34}_{-1.43}$$ derived by fitting the CCF with the dark matter power-spectrum model through the ML method, while that of the luminous quasars is $$2.73^{+2.44}_{-2.55}$$ obtained in the same manner. If we consider the contamination rates of 22.7% and 10.0% estimated for the LBG and the less-luminous quasar samples, respectively, the bias factor of the less-luminous quasars can increase to $$6.58^{+1.49}_{-1.58}$$ on the assumption that the contaminating objects are distributed randomly. 2. The CCFs of the luminous and less-luminous quasars do not show significant luminosity dependence of the quasar clustering. The bias factor of the less-luminous quasars suggests that the environment around them is similar to the luminous LBGs used in this study. The luminous quasars do not show strong association with the luminous LBGs on scales from 10$${^{\prime\prime}_{.}}$$0 to 1000$${^{\prime\prime}_{.}}$$0, especially on scales smaller than 40$${^{\prime\prime}_{.}}$$0. The bias factor of the luminous quasar is smaller than that derived from the ACF of the SDSS quasars at z ∼ 4 (Shen et al. 2009). The reason may be partly due to the deficit of the pairs on small scales, which can be caused by the border between quasar and LBG samples at shallower edge regions or by a physical mechanism, e.g., the strong feedback from the SMBH. 3. The bias factor of the less-luminous quasars corresponds to a mass of DMHs of ∼1–2 × 1012 h−1 M⊙. Minimal host DMH mass for the quasars can be also inferred from the bias factor. Combining the halo number density above that mass threshold and the observed quasar number density, the fraction of halos which are in the less-luminous quasar phase is estimated to be 0.001–0.06 from the CCF. The corresponding quasar lifetime is 1.5–90.8 Myr. Correlation analysis in this work is conducted in the projected plane, and accurate information on the redshift distribution of the samples and the contamination rates is necessary to obtain reliable constraints on the clustering of the z ∼ 4 quasars. Spectroscopic follow-up observations are expected to obtain the accurate information. Additionally, the full HSC Wide survey plans to cover 1400 deg2 in 5 years, which can significantly enhance the sample size. The statistical significance of the current results can then be largely improved. Acknowledgements We would like to thank the valuable comments from the referee. We also would like to thank Dr. A.K. Inoue who kindly provides us with the IGM model data. The Hyper Suprime-Cam (HSC) collaboration includes the astronomical communities of Japan and Taiwan, and Princeton University. The HSC instrumentation and software were developed by the National Astronomical Observatory of Japan (NAOJ), the Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU), the University of Tokyo, the High Energy Accelerator Research Organization (KEK), the Academia Sinica Institute for Astronomy and Astrophysics in Taiwan (ASIAA), and Princeton University. Funding was contributed by the FIRST program from Japanese Cabinet Office, the Ministry of Education, Culture, Sports, Science and Technology (MEXT), the Japan Society for the Promotion of Science (JSPS), Japan Science and Technology Agency (JST), the Toray Science Foundation, NAOJ, Kavli IPMU, KEK, ASIAA, and Princeton University. Funding for the Sloan Digital Sky Survey IV has been provided by the Alfred P. Sloan Foundation, the U.S. Department of Energy Office of Science, and the Participating Institutions. SDSS-IV acknowledges support and resources from the Center for High-Performance Computing at the University of Utah. The SDSS web site is ⟨www.sdss.org⟩. SDSS-IV is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS Collaboration including the Brazilian Participation Group, the Carnegie Institution for Science, Carnegie Mellon University, the Chilean Participation Group, the French Participation Group, Harvard-Smithsonian Center for Astrophysics, Instituto de Astrofísica de Canarias, The Johns Hopkins University, Kavli Institute for the Physics and Mathematics of the Universe (IPMU)/University of Tokyo, Lawrence Berkeley National Laboratory, the Leibniz Institut für Astrophysik Potsdam (AIP), the Max-Planck-Institut für Astronomie (MPIA Heidelberg), the Max-Planck-Institut für Astrophysik (MPA Garching), the Max-Planck-Institut für Extraterrestrische Physik (MPE), the National Astronomical Observatories of China, New Mexico State University, New York University, the University of Notre Dame, Observatário Nacional / MCTI, The Ohio State University, Pennsylvania State University, Shanghai Astronomical Observatory, the United Kingdom Participation Group, Universidad Nacional Autónoma de México, the University of Arizona,the University of Colorado Boulder, the University of Oxford, the University of Portsmouth, the University of Utah, the University of Virginia, the University of Washington, the University of Wisconsin, Vanderbilt University, and Yale University. This paper makes use of software developed for the Large Synoptic Survey Telescope. We thank the LSST Project for making their code available as free software at ⟨http://dm.lsst.org⟩. The Pan-STARRS1 Surveys (PS1) have been made possible through contributions of the Institute for Astronomy, the University of Hawaii, the Pan-STARRS Project Office, the Max-Planck Society and its participating institutes, the Max Planck Institute for Astronomy, Heidelberg and the Max Planck Institute for Extraterrestrial Physics, Garching, The Johns Hopkins University, Durham University, the University of Edinburgh, Queen’s University Belfast, the Harvard-Smithsonian Center for Astrophysics, the Las Cumbres Observatory Global Telescope Network Incorporated, the National Central University of Taiwan, the Space Telescope Science Institute, the National Aeronautics and Space Administration under Grant No. NNX08AR22G issued through the Planetary Science Division of the NASA Science Mission Directorate, the National Science Foundation under Grant No. AST-1238877, the University of Maryland, and Eotvos Lorand University (ELTE). References Adams S. M., Martini P., Croxall K. V., Overzier R. 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# Faxitron X-ray machine
Joined Jul 7, 2009
1,583
I have a friend who has a working Faxitron X-ray unit (see attached picture):
Faxitron CS-100AC X-Ray Machine (92 KV @ 100 mA) with a Focal Spot: 8 micron, Xray Tube: Stationary anode, end window construction, w/ Beryllium window (0.127mm thick) & 46° (beam angle) Maximum board size: 18"x24" Real Time Image Resolution: >26-50 line pairs/mm (magnification dependent) Camera Type: High Resolution CCD Camera with 6:1 Motorized Zoom Lens Equipped with: Electronic "Z Axis" X-ray tube adjustment (affects FOV = Field of View, Magnification, Resolution, Electronic "Z Axis" detector motion (expands FOV range & sensitivity) Equipped with Rotation & Tilt Fixture Laser Pointer Cabinet w/casters, leveling pads, lockable storage area, & pull-out printer shelf = 1250 Pounds. Last safety inspection: May 2010.
I believe he got it as a surplus unit. He's interested in selling it, but has no idea what it's worth (and you don't need to suggest he search ebay, as he's an expert ebay seller and has been looking for a week). It appears that it was once used as an inspection device for PC boards.
I have two questions for the folks here:
1. Do any of you have any experience with this device? If so, what is it typically used for?
2. Do you have any suggestions as to what the unit would be worth?
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#### Wendy
Joined Mar 24, 2008
22,141
Alcatel used to have one of those I believe, it's biggest use was looking under ball grid arrays for solder voids, but that wasn't the only use.
I would focus on the new price, then go from there. Has he contacted the parent company, assuming they exist, for how much they cost new?
Joined Jul 7, 2009
1,583
He finally found out that the original selling price for the device he has was in the $150k-$200k range. But that has little to do with what the thing would be worth to someone today, both because of a depressed economy and I can tell that some of the machine's parts were overpriced.
Still, if the machine works and is reliable, there's probably an interested buyer somewhere. Perhaps a reasonable strategy would be to put it on ebay with a reasonably high reserve price.
#### magnet18
Joined Dec 22, 2010
1,227
KEWLIO!!
I would ask on the 4HV.org forum, theres a few guys on there that used to/still do repair/work on x-ray equipment and they might know more about what it's worth
#### loosewire
Joined Apr 25, 2008
1,686
Try an animal hospital,may be the best place.
#### Wendy
Joined Mar 24, 2008
22,141
This machine is not for looking at biological. I suspect to see through metal it has a lot more Xrays, while hospital (animal and otherwise) try to get by with less.
Note the enclosure, it is designed for piece parts.
#### bertus
Joined Apr 5, 2008
20,535
Hello,
The machine is probably to look at continuity of traces on the PCB (as the photo show a PCB).
The X-rays will be much to "hard" for a biological use.
Biological X-rays are much softer (less energy).
(they ususaly measure the energy in eV (electron Volts) ).
Bertus
#### magnet18
Joined Dec 22, 2010
1,227
Hello,
The machine is probably to look at continuity of traces on the PCB (as the photo show a PCB).
The X-rays will be much to "hard" for a biological use.
Biological X-rays are much softer (less energy).
(they ususaly measure the energy in eV (electron Volts) ).
Bertus
I think you may be confused, Bertus.
The medical x-ray machines generally use harder x-rays that will pass through the soft tissue without being absorbed at all, if they used soft x-rays many more of them would be stopped by the soft tissue and increase the received radiation dose.
#### bertus
Joined Apr 5, 2008
20,535
Hello,
It could be. The time I had a X-ray training is long ago (more than 10 years).
The knowledge must have sunk deep and got confused.
Sorry,
Bertus
#### ErnieM
Joined Apr 24, 2011
8,041
Hey we use that very machine where I work!
We make hybrid microcircuits here (or we did till last December when they moved production off to PA). In this case, "hybrid" means a custom ceramic substrate with printed gold conductors, often printed resistors too, with the chips being literally bare silicon chips connected with .001" gold wires. All that goes inside a package, ceramic or metal, and is hermetically sealed.
It's used for inspection, inline for things like eutectic flow inspection (how good did the metal flow under the big power die) or sometimes as the initial step in a failure analysis (BEFORE the package is milled open).
I may even have a buyer for it.
Joined Jul 7, 2009
1,583
I may even have a buyer for it.
That's even better than an estimated value, Ernie. PM with the interested person's email and I'll pass it on to my friend.
#### magnet18
Joined Dec 22, 2010
1,227
Hello,
It could be. The time I had a X-ray training is long ago (more than 10 years).
The knowledge must have sunk deep and got confused.
Sorry,
Bertus
No worries, your point is sound. This is definitely NOT supposed to be used on anything with a brain.
#### Sparky49
Joined Jul 16, 2011
833
No worries, your point is sound. This is definitely NOT supposed to be used on anything with a brain.
Let's take a picture when I put my hand under it!
Way hey hey hey!!!!!!!!!
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# Jasmine runs in the park every day. She runs at a constant pace around
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Math Expert
Joined: 02 Sep 2009
Posts: 56251
Jasmine runs in the park every day. She runs at a constant pace around [#permalink]
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13 Sep 2016, 02:04
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Difficulty:
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Question Stats:
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Jasmine runs in the park every day. She runs at a constant pace around the perimeter of a small flower patch. The patch has the shape of a triangle whose sides are 20, 20, and 10 meters long. Jasmine starts the jog from point A of the triangle, and runs in the direction of the arrow in the figure above. She completes her jog 50 seconds later, after running along 16 sides of the patch. At what speed does Jasmine run in meters per second?
A. 4.6
B. 4.8
C. 5.2
D. 5.4
E. 5.6
Attachment:
T7709.png [ 5.68 KiB | Viewed 2146 times ]
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Manager
Joined: 05 Jun 2015
Posts: 78
Location: United States
WE: Engineering (Transportation)
Re: Jasmine runs in the park every day. She runs at a constant pace around [#permalink]
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13 Sep 2016, 03:37
To complete 16 sides of the patch, Jasmine has to run 5 times the perimeter of the triangle and cover additional side AB once.
total distance covered = $$5 * (20+20+10) + 20$$
= 270 m
time taken = 50 sec
speed = 270/50
= 5.4 m/s
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Location: India
Concentration: Operations, Strategy
Schools: ISB '18 (D)
GMAT 1: 600 Q49 V23
GMAT 2: 680 Q49 V34
GPA: 3.9
Re: Jasmine runs in the park every day. She runs at a constant pace around [#permalink]
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13 Sep 2016, 04:20
she runs 16 sides of the triangle. 3 sides corresponds to 50 mtrs. Now by running 5 times around the triangular park she covers 15 sides. For the 16th side we have to add 20 mtrs stretch to 5* 50 mtrs stretch she already covered. Total distance covered = 5* 50 + 1 *20= 270 mtrs in 50 seconds.
therefore her average speed = total distance/ total time = 270 mtrs / 50 sec = 5.4 m/s
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Re: Jasmine runs in the park every day. She runs at a constant pace around [#permalink]
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18 Aug 2018, 20:06
Bunuel wrote:
Jasmine runs in the park every day. She runs at a constant pace around the perimeter of a small flower patch. The patch has the shape of a triangle whose sides are 20, 20, and 10 meters long. Jasmine starts the jog from point A of the triangle, and runs in the direction of the arrow in the figure above. She completes her jog 50 seconds later, after running along 16 sides of the patch. At what speed does Jasmine run in meters per second?
A. 4.6
B. 4.8
C. 5.2
D. 5.4
E. 5.6
Attachment:
T7709.png
Since the perimeter of the triangular patch is 20 + 10 + 20 = 50 meters and it has 3 sides, when Jasmine runs along 16 sides of the patch, she has run the perimeter of the patch 5 times and 1 more side, AB, which is 20 meters. Therefore, she has run 5 x 50 + 20 = 270 meters, and her speed is:
270/50 = 27/5 = 5.4 m/s
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Re: Jasmine runs in the park every day. She runs at a constant pace around [#permalink] 18 Aug 2018, 20:06
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The efficiency of a carnot heat engine has increased from 40% to 50% which the temperature of source and sink are reduced by 100 degree centigrade find the source and sink temperature
When the temperatures of source and sink are and respectively, the efficiency of Carnot engine is given by, .
Initially
$0.4=1-\frac{T_{2}}{T_{1}}$
i.e $\frac{T_{2}}{T_{1}}=\frac{3}{5}$
Finally
$0.5=1-\frac{T_{2}-100}{T_{1}-100}$
SO we get
$T_{1}=500 K$ and $T_{2}=300 K$.
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# My Recent Work About Neural Networks
Posted on 02 Jul 2015, tagged neural networkdeep learningprogramming
These days I’ve written some code about neural networks. There is nothing important, but worth to be recorded.
## Choose Deep Learning Frameworks
The first thing is to decide which framework I should use. There are many frameworks about neural networks, I tried some famous ones. Here is the details:
### Caffe
Caffe is a famous framework, mainly used with convolution neural networks. It is written with C++ but uses protocol buffer to describe the network. It is known as its well structured code, high performance. But the use of protocol buffer doesn’t make me comfortable because I’m not afraid of write some code and the file is less flexible.
### Theano
Theano is a framework written in Python. You can define an expression and Theano can find the gradient for you. The training process of deep learning is mainly find the gradients for each layer, so it simplified the work a lot. It’s performance is good, too.
But it is more like a compiler for me. I cannot see the low level things and the code is not just normal python code, it has too much hacking.
Theano is more like a optimize library than a neural network framework. PyLearn2 is a framework based on it, which provides many network structures and tools. But like Caffe, it uses a YAML config file to describe the structure of the network, which makes me uncomfortable.
### Deeplearning4j
This is a framework written in Java. It is not so famous, but interesting to me. I’m more familiar with Java than C++. A Java framework means a better IDE, more libraries to use. And it may supports Scala, which I use a lot in these days. So I tried it a little, but it is not as good as I thought.
First of all, it is in heavily developing. And the name of methods and variables is too long and the API is not so great to use. The most important is, the performance seems not so good and the integration with the GPU is not very easy. And it is not popular in research field so the communication with others may becomes a problem.
### Torch7
This is the framework I finally use. Actually, it is the first framework I’ve used.
Some big companies use it, including Deep Mind (Google), Facebook and so on. It is written in Lua, which is a language I’ve always want to learn. It is easy to understand. When there comes to the low level, you just need to read the C code, which is more easy to read than the C++ code. There is no magic between the high level and the low level, I can just dig it. It’s performance is great, and the ecosystem is big and healthy.
But it also has some cons. For example, the error hint is not so great, and the code is too flexible so that you must read the document to know how to use some modules. But I can deal with it.
## Write My Own Library
I write my own library with Scala and Breeze, in order to understand neural networks better.
It is very easy to write a neural network library (which is not distributed), as long as you understand it. While I wrote it, I realize that the core of neural networks is just gradient optimize (with many tricks). One layer of a network is just a function, layers are just function after function. So the gradient of each layer is computed by chain rule. When you need a new layer, just write how to compute the output and the gradient, then you can push it into the network structure.
Use Scala to write it feels good, because OOP makes it feel nature to write layers. And the trait system makes it more pleasure. But the performance is not as good as the libraries above. Make it to support GPU is hard, too. Running a large size network makes it running like forever. So I gave up after wrote the convolution network and use Torch7 instead.
## Run Some Examples
This article gives some great advices to choose a GPU for deep learning. Titan X is great but is too expensive. So I decide to wait until next year while NVIDIA will release their new GPU with 10X power. At the same time, I have a GPU with 1G RAM in my office.
I wrote some simple code like MLP and simple convolution networks to train with MNIST data. Then I decided to run some large examples.
First, I run the example from fbcunn, which is a AlexNet training on ImageNet. The ImageNet data is too big and the bandwidth of my office is too small. So I run the example with an g2.2xlarge instance on AWS. It still took lots of time, which trained 2 days to archive a precision of about 30% (not ended yet). Then I realized it is too expensive to run it on AWS and stop it.
The Second example I run is an RNN example. The code is from here. I run it on the machine with 1G RAM GPU. It looks good on small networks. But when I use the data from Chinese Wikipedia (with 1G plain text), the memory of GPU could only train a network of 512 parameters, which is too small to get good result.
The time of training large neural networks is really long. So I will wait for the new hardware to continue my research. At the mean time, I will review the knowledge about linear algebra and probability theory.
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# What is PI value Java?
## What is PI value Java?
It is a mathematical constant that is defined as the circumference of a circle divided by its diameter. The value of a constant pi is approximately 3.14. Java provides built-in constant field of Pi that belong to java. lang,Math class.
Java Pi Value
## How do you declare a constant pi in Java?
To get the value of PI in JavaScript, use the Math.PI property. It returns the ratio of the circumference of a circle to its diameter, which is approximately 3.14159.
## How do you write PI in JavaScript?
In basic mathematics, pi is used to find the area and circumference of a circle. Pi is used to find area by multiplying the radius squared times pi. So, in trying to find the area of a circle with a radius of 3 centimeters, 28.27 cm.
## What is pi value?
Succinctly, piwhich is written as the Greek letter for p, or is the ratio of the circumference of any circle to the diameter of that circle. In decimal form, the value of pi is approximately 3.14
## How can I use pi?
In basic mathematics, pi is used to find the area and circumference of a circle. Pi is used to find area by multiplying the radius squared times pi. So, in trying to find the area of a circle with a radius of 3 centimeters, 28.27 cm.
## How do you write pi in JavaScript?
To get the value of PI in JavaScript, use the Math.PI property. It returns the ratio of the circumference of a circle to its diameter, which is approximately 3.14159.
## Is pi a variable or a constant?
The number u03c0 (/pau026a/; spelled out as pi) is a mathematical constant, approximately equal to 3.14159. It is defined in Euclidean geometry as the ratio of a circle’s circumference to its diameter, and also has various equivalent definitions.
## How do you use PI as a constant in Java?
An Example
• import java. lang. Math. *;
• public class Pie {
• public static void main(String[] args) {
• double len 15;
• // calculate the area using PI.
## How do you declare a constant pi?
In this program the value of π is defined in two different ways. One is by using using the preprocessor directive ‘#define’ to make ‘PI’ equal to 3.142857. The other uses the key work ‘const’ to define a double called ‘pi’ equal to 22.0/7.0.
## What is PI in Java?
PI is a static final double constant in Java, equivalent to in Mathematics. Provided by java. lang. Math class, Math. PI constant is used to carry out multiple mathematical and scientific calculations like finding the area circumference of a circle or the surface area and volume of a sphere.
## Is there Pi in JavaScript?
The Math. PI is a property in JavaScript which is simply used to find the value of Pi i.e, in symbolic form which is nothing but it is the ratio of the circumference of a circle to its diameter, whose value is approximately 3.141. It is mainly used in a mathematics problem.
## What is Math pi in JavaScript?
The Math.PI property represents the ratio of the circumference of a circle to its diameter, approximately 3.14159: Math.PI u03c0 mathtt{mi{Math.PI}} pi approx .
## How do you do Pi in HTML?
To get the value of PI in JavaScript, use the Math. PI property. It returns the ratio of the circumference of a circle to its diameter, which is approximately 3.14159.
## What is the real value of pi?
3.14159
The value of Pi (π) is the ratio of the circumference of a circle to its diameter and is approximately equal to 3.14159.
Value of Pi (π) in Fractions
All Values of Pi (π) In Decimal 3.14 In Fraction 22⁄7
## Why is 3.14 called pi?
It was not until the 18th century about two millennia after the significance of the number 3.14 was first calculated by Archimedes that the name pi was first used to denote the number. He used it because the Greek letter Pi corresponds with the letter ‘P’ and pi is about the perimeter of the circle.
## What is pi digits?
The mathematical constant pi is the ratio of a circle’s circumference to its diameter, and is approximately With only these ten decimal places, we could calculate the circumference of Earth to a precision of less than a millimetre.
## How can you use pi in real life?
In basic mathematics, Pi is used to find area and circumference of a circle. You might not use it yourself every day, but Pi is used in most calculations for building and construction, quantum physics, communications, music theory, medical procedures, air travel, and space flight, to name a few.
## What can I do with pi currency?
Once Phase 3 launches, holders will be able to take full control of their private and public wallet keys, and use the coin to buy products and services on Pi’s peer-to-peer marketplace, or exchange it for fiat currency. Without the keys, users cannot transfer or spend the currency they hold.
## How do you use pi example?
You walk around a circle which has a diameter of 100 m, how far have you walked?
Distance walked = Circumference.
= π × 100 m.
= 314.159m.
= 314 m (to the nearest m)
## How do you make money with pi?
PI Network This organisation set out to find a way that would allow ordinary people to mine Bitcoins. Their solution means you can make money by mining crypto-coins from your phone. Simply download the app, and once a day open it and automatically mine Bitcoins. PI Network also has a members’ platform.
## Is pi value a variable?
Since PI is a constant, you cannot set its value, say back to 3.14. It is a final variable, meaning that you cannot change its value.
## What is constant value of pi?
Pi, denoted by the lower-case Greek letter, is a mathematical constant that is approximately equal to 3.14159. In Euclidean geometry, represents the ratio between the circumference and the diameter of any circle, or equivalently, the ratio between a circle’s area and the square of its radius.
## Is pi a physical constant?
Yes. is a mathematical constant usually defined as the ratio of the circumference of a circle to its diameter in Euclidean geometry. This does not mean that u03c0 changes, because our definition of specified a Euclidean geometry, not physical geometry.
## Is pi a fundamental constant?
Pi appears most often in formulas involving circles or periodic motion, and it infiltrates some fundamental physical constants. (Pi itself is not considered a fundamental physical constant.)
## What do you use for pi in Java?
PI is a static final double constant in Java, equivalent to in Mathematics. Provided by java. lang. Math class, Math. PI constant is used to carry out multiple mathematical and scientific calculations like finding the area circumference of a circle or the surface area and volume of a sphere.
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# A star has a parallax of .19 arc seconds. The stars has a proper motion of 7.2 arc seconds per years and a radial velocity of +260 km/s. How do you find the Tangential Velocity and the total velocity of the star?
Feb 1, 2018
${v}_{t} = 180 k m$ ${s}^{- 1}$
$v \approx 316 k m$ ${s}^{- 1}$
#### Explanation:
${v}_{t}$ is given by the formula: ${v}_{t} = \frac{4.75 \mu}{p}$, where:
• $\mu$ = proper motion (arc seconds per year)
• $p$ = parallax (arc seconds)
${v}_{t} = \frac{4.75 \cdot 7.2}{0.19} = 180 k m$ ${s}^{- 1}$
$v = \sqrt{{v}_{t} {\text{^2+v_r}}^{2}}$
$\textcolor{w h i t e}{v} = \sqrt{{180}^{2} + {260}^{2}}$
$\textcolor{w h i t e}{v} \approx 316 k m$ ${s}^{- 1}$
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Want to share your content on R-bloggers? click here if you have a blog, or here if you don't.
This past year in R has been a good one for me; productive, exciting, different. I decided it was worth taking a moment to reflect and share. Goals were set and met. There were also unexpected changes.
## CRAN
A year ago, at the tail end of 2017, I published my first package to CRAN. It’s a fun, silly package, but I also had to make a successful case for in the initial review process to distinguish it from other similar works. It was a great experience and it encouraged me to try to do even more.
So anyway, I got to check that box last year. I resolved to do more this year.
I wanted to publish to CRAN again. I did so five more times throughout the year.
## ROpenSci
I ended up inadvertently (more on this later) publishing two packages to CRAN which struck me as having particular scientific/analytics appeal and for the first time I looked into cross-publishing with ROpenSci. I set a goal to publish something with ROpenSci.
With the first one, epubr, I read through the various ROpenSci onboarding docs, looked over others’ packages, and concluded that, “maybe my package is a good fit?” I was somewhat anxious to try, afraid that maybe my package would be too niche or that others might not see much value in it. Maybe as the author I was the only who saw it as a potential fit. Maybe I had a biased perspective because of the hard work I had put into it.
I submitted my onboarding issue and made a case for my package. To my relief, and also chuckling a bit at myself because part of me knew that my moments of self-doubts were silly and overblown, people did see value in it. I knew it would be a more rigorous peer review process than CRAN and that was part of the experience I sought. I jumped through all the hoops, made the revisions that others suggested, and also held firm to a thing or two that I did not particularly want to change about the package. After some time went by and everyone was happy with the state I’d gotten the package to, it was published! Another goal met.
More recently this year I submitted a second of the year’s CRAN packages to ROpenSci: tiler. For years my work in R has been in the geospatial realm, whereas I do not have nearly as much experience in parsing and analyzing text. Nevertheless, I expected to have more difficulty getting tiler published than epubr, but I managed to do it. I ended up meeting my goal twice. There is still much I want to do to improve tiler and I’ve been a bit stuck for a while with certain GitHub issues, but it is on board and I’m thankful for the help I’ve received on GitHub from others who are unquestionably more expert in the geospatial arena than I am.
I met some great people working with ROpenSci in my small capacity. I look forward to more collaborations.
## A digression on doing what you are passionate about
I’ve wanted to do something in R around Star Trek for a long time, so publishing the initial version to CRAN was a successful goal in itself. But it goes beyond that.
Returning to the inadvertent nature of the creation of epubr and tiler, both published on CRAN and with ROpenSci, these are both packages that simply would not exist if I did not first decide to make rtrek. Like memery, packages like rtrek (and trekfont) are clearly packages that no one really needs or particularly wants. But rtrek is the single reason epubr and tiler were originally created, even though their utility and potential user base far transcends what began as custom text-parsing and map-making R functions I was using to support working with Star Trek data.
### Having new ideas
New ideas can be hard to come by, unless the environment is right.
Sometimes it is hard to come up with an idea directly that (1) has value in being implemented, (2) that is not too difficult to implement yourself, and (3) that someone else hasn’t implemented already. It’s like the adage about “fast, cheap, accurate”- you can pick any two.
While trying to think up a novel idea, it can be worth ruminating on that while pursuing something else, something of genuine personal interest that perhaps no one else cares about at all. I found that I became really excited to work on rtrek. It was easy for me to envision fun features I could add to the package.
### Having new needs
Necessity can lead to new ideas. If you can identify needs, ideas may come more easily. They cycle may only require a jump start.
After working on rtrek for a bit, I inadvertently created a need, admittedly around something unimportant to a broad audience, something not for work, certainly nothing I was getting paid to code. I had ideas I could not implement until I satisfied some needs by implementing some other things first.
I needed the ability to read text from Star Trek EPUB files so that I could dabble in text analysis and satiate some of my curiosities. And the code to do so was a bit of a mess. It soon began to look like something that ought to be excised from the primordial rtrek codebase and put into its own utility package.
I needed the ability to make leaflet maps of Star Trek map art, which technically is spatial but not geospatial. That code too became bulky and needed to be cut out and put in its own package.
The next thing I knew, I was staring at two different packages that were general, purposeful, and had the potential to be useful to a lot of other people, but which never would have occurred to me to produce otherwise. They were just… there. Those were exciting moments all on their own. What began as mere intermediary hurdles transformed into their own projects with greater utility.
As exciting as it has been to work on rtrek I am most happy to see that its biggest value so far has been in leading to completely new and different things.
## Changing jobs
I don’t have a lot to say on this here, but I love where I ended up and I was surprised how quickly I landed something much more personally and professionally fulfilling. I do miss aspects of academia in general. I definitely miss not getting to work on geospatial material as much as before. But overall it’s been a great change.
## R and music
Early this year I put my mind to trying to make guitar tablature (tabs) with R. Why? What the heck is the point? Well, it’s pretty simple:
• I love to play guitar.
• I absolutely loathe that mistake-riddled, incomplete, garbage guitar tabs are a contender for the title of “the bane of the internet” (IMO). Few things irritate me more than digging around for a quality tab, only to find that even a crappy one can be locked behind a licensing paywall and sold for a ridiculous price anyway. (But this is a whole other conversation about the recording industry, intellectual property, and more…)
• I also am not very good at writing out my own tabs, on paper or in a software GUI (purportedly) designed for it. While I’ve gotten better over time at just learning songs by ear, I still find it helpful to have a tab. It’s like having code documentation when you return to something after a long time away.
• Since I’m slow enough at making tabs and I do love R, I inhabit a funny space where I find it no less of a pain to just write them in R.
This led to the creation of tabr, which is interestingly one of my least used yet most widely celebrated creations: an R package for writing guitar tabs/sheet music. It’s not perfect, but I’m proud of it. For me it’s fresh, different.
I’ve also found to my surprise (and somewhat my annoyance) that several packages I have made ended up having third party system requirements. Gah! This is NOT ideal. But whether it was Python/GDAL, LilyPond, or ImageMagick, it’s been a good experience to deal with some complex package-making.
tabr was one of those that took this system requirements inconvenience a step further. I mean, who would have thought that CRAN machines did not have LilyPond installed! LOL. But when I published tabr to CRAN as a new release, I was surprised to see how quickly LilyPond was put on a machine so the package could be built and tested there. The CRAN maintainers really do go all out for you if you do your part as a package maintainer. I know they are very busy people. What they do is much appreciated.
## I met Gin Wigmore!!!!
Yes that was a goal, in retrospect at least. I’m choosing to count it. No, I did not think it would happen. I wasn’t trying; I had no plan. But like I said, it’s been a grand year. And a theme of this post seems to be about if opportunities come up, even if you created them by accident or indirectly, or they came out of nowhere or you couldn’t have planned it in advance, JUST ROLL WITH IT. #2018. It also helped that she did a show near where I live.
Wait, “what does this have to do with R,” you ask? EVERYTHING.
First of all, like the R programming language, she too hails from New Zealand. I tell people I program in R 40 hours a week. How many hours a week am I cranking Gin Wigmore’s music to eleven? Well, it’s probably on par. R and Gin Wigmore. End. Of. Discussion. But I will continue. Two of my favorites in life. To be clear, I’ve never been, so I don’t know what’s going on down there, but to pull this off, New Zealand must truly be a magical place.
Wanting to tab out some of her songs for guitar was also a central motivation for tabr. Most musician’s don’t release sheet music, if they ever even write down their own songs in the first place. Many don’t at all. In this case, I have to make my own tabs because I can’t buy them, and if anything is even floating around online it’s junk. The first song I tabbed out with tabr was Gin Wigmore’s “Devil in Me”.
I would share it online but that’s not appropriate without permission. This is just a preview of the top of the first page. (For the critics, I must mention that the backend software R is relying on is currently imperfect at notating string bends.)
Here is a GitHub gist of R code. Be forewarned, it’s not exactly pretty. There is no magical shortcut to transcribing music.
After the show she took time out to chat with her fans. But when I say chat, I mean have real conversations. It wasn’t like “Hi!” Snap photo. Exit. Repeat. Let’s hurry it up. No. It was genuine, not rushed at all. I and many others got to actually have conversations with her.
And yet, I was so damn excited to meet her that I completely neglected to tell her I play guitar too and that her songs were what most inspired me to transcribe music as well as improve my ability to learn to play by ear.
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In $16$ throws of a die getting an even number is considered a success. Then the variance of the successes is
$\begin{array}{1 1}(1)4&(2)6\\(3)2&(4)256\end{array}$
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# Question - Simple Problems on Applications of Derivatives
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#### Question
Show that the semi-vertical angle of the cone of the maximum volume and of given slant height is cos^(-1)(1/sqrt3)
#### Solution
You need to to view the solution
Is there an error in this question or solution?
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Factors affecting sound intensity
1. Aug 3, 2014
somecelxis
1. The problem statement, all variables and given/known data
the factor affecting sound intensity is amplitude and frequency . why not also the distance from the source (r) ,
in my opinion, intensity = power/area , so the intensity = power/ 4 pi r ^2 .... so I is inversely proportional to r^2 ...
2. Relevant equations
3. The attempt at a solution
2. Aug 3, 2014
Staff: Mentor
The amplitude and intensity are related. So as distance from the source increases, both amplitude and intensity drop.
3. Aug 3, 2014
somecelxis
do you mean the intensity and 'distence from the source ' is not directly related , so i cant say that Intensuty is directly proportional to 1/'distence from the source' ?
4. Aug 3, 2014
Staff: Mentor
For a point source, the intensity of the sound is inversely proportional to the square of the distance. See: Inverse Square Law for Sound
5. Aug 3, 2014
somecelxis
the link also gives the intensity of the sound is inversely proportional to the square of the distance. So why cant i say intensity of the sound is inversely proportional to the square of the distance? but i can only say the factor affecting sound intensity is amplitude and frequency which means Intensity is directly proportional to amplitude square and frequncy square
6. Aug 3, 2014
somecelxis
or can I say in this way? as the distance from the source incraeses , the amplitude of particle at a partcular point decreases . the decreases in the amplitude causes the intensity to drop? so the Intensity is dependent on amplitude square. beacuse intensity has a 'direct 'reatioship between amplitude.
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# help with integration question?
#### decoy808
can anyone help me with the process to the question. points i need to research rather than the answers. many thanks
The function $$\displaystyle y=2(x-1)(x-4)^2$$
(a) find the values of A and B
(b) what is the size of the shaded part
#### skeeter
MHF Helper
can anyone help me with the process to the question. points i need to research rather than the answers. many thanks
The function $$\displaystyle y=2(x-1)(x-4)^2$$
(a) find the values of A and B
(b) what is the size of the shaded part
should be clear that A = 1 and B = 4 (roots of the cubic, one w/ multiplicity two)
area = $$\displaystyle \int_1^4 2(x-1)(x-4)^2 \, dx$$
expand the cubic, then integrate and evaluate the definite integral using the fundamental theorem of calculus.
#### DrDank
$$\displaystyle$$
A and B occur when y=0
$$\displaystyle y=2(x-1)(x-4)^2$$
$$\displaystyle 0=2(x-1)(x-4)^2$$
$$\displaystyle 0=(x-1)$$ and $$\displaystyle 0=(x-4)$$
Therefore...
$$\displaystyle A=1$$ and $$\displaystyle B=4$$
The Area is..
$$\displaystyle \int2(x-1)(x-4)^2dx$$
$$\displaystyle 2\int(x-1)(x^2-8x+16)dx$$
$$\displaystyle 2\int(x^3-7x^2+24x-16)dx$$
Limits of integration are 1 to 4
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# Portfolio returns from activity records
I am looking for a clean and efficient way to obtain the portfolio returns from a list of activity records.
Specifically, the activity file consist of BUY, SELL, COVER, SHORT, etc. records with additional referential data (e.g. SecurityID, Quantity, Fees, BaseAmount, etc.). Here is an example file.
A possible layout for a security:
t TransactionType Quantity Price
...
3 SELL 50 6
So what I thought would be the best to do is to create a time series of the portfolio value over time. Hence, for each date, I take the current stock price and I check all the past records up to that date to determine the quantity that the user has in its portfolio of that particular security.
In the previous example, this would give the following evolution:
t Quantity_Portfolio Return
1 100 -
2 150 150*4 / ( (50*4)+(100*5) )
...
3 100 ...?
As you can see it becomes quite complex to calculate the portfolio value at time 3, as then - even in this simple example. What is the return at t=3?
I was therefore wondering whether there are some sets of rules or resources that I could use (preferably Matlab or Python) to parse such activity records, instead of reinventing the wheel and trying to think of all possible situations?
• 1 small observation: you can't do it with just Activity Records, you also need on certain dates Valuation Records which provide the prices of all portfolio securities on that date. – noob2 Apr 3 '17 at 15:53
• You need to decide if you will be using LIFO or FIFO and whether you will be using a Time Weighted rate of return or a Money Weighted rate of return. Time Weighted is standard if you are going to be showing this performance to prospective investors. LIFO vs FIFO is up to you. It only matters for tax purposes if you don't Mark to Market at the end of each year. Googling 'portfolio accounting rules' should yield plenty of results. Or you could consult someone with portfolio accounting experience. – amdopt Apr 3 '17 at 16:19
• Other than the fact it throws you into censoring problems, you do not need to valuations at all as you have the actual cash flows. Time series are used only because of a lack of customer records. As mentioned above you will have to solve inventory accounting, but logically that would be a tax based system since people rationally minimize their taxation. I would answer this question directly, but there is the censored observations on either side and it is late and I don't want to think about it right now. If I get time I will post an answer. – Dave Harris Apr 5 '17 at 5:08
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## Image Remote Disks with Norton Ghost
Symantec Ghost has been my favorite tool since high school as the user interface is minimalistic (runs fast) yet intuitive. It pretty much has every single feature (use case) you can imagine organized in a sensible way (unlike the fucking linux man pages that drown you with 4 dozens of command switches not logically organized so you have to skim through the entire thing to find out what is relevant).
The software is well made in general so we can get a lot mileage out of old versions. I recently had to clone a drive over the network yet I don’t want to share the image file. My initial plan is to have the remote computer I plan to image the disk attached to it run as slave (in Master-Slave mode Peer-To_Peer over TCP mode), but there are a few hurdles:
• The documentation didn’t say which port is used. I have to use TCPview to figure it out. It’s Port 6668.
• Turns out slave mode does not support restoring from a image file located from the (puppet-)master. In other words, the when you connect to the slave session, the file dialog box of “From Image” only shows the files on the slave side! WTF!
It’s strange that you can clone a raw drive / partition from master session to slave session, but you cannot choose image file as a source in place of the source drive. I tried the command line before and no avail. After some web searching I realized that I’m not insane. It was the way Ghost is:
The rules inferred from this table means:
• image files ALWAYS stay at the slave session
• direct drive/partition copies is always master pushing data to slave.
• slave drives are never cloned (read)
• master cannot read its own files to find image files
• master can only select remote (slave) image files
First of all, direct drive-to-drive copy are bidirectional. The above list is not entirely accurate, so I stroke through the conclusion derived from the incorrect assumptions above. Y:
The rules for image files do not make much sense to me. Just can’t come up with a good excuse for it. The session have full access to both storage from both sides, and ghost command line’s logic is to make image files fungible with direct drives/partitions. It doesn’t discourage accidental overwrites or prevent one side’s data from being siphoned. All they did is to tease the user by not allowing them to read files/images from the master computer where the user interaction is.
The first instinct is to restore the GHO image I want to push to the server onto a disk and do the direct clone. This is logically fungible with creating a VHD, mount it, restore the GHO image to the mounted drive, then use direct ‘virtual disk’-to-disk clone to restore the remote (slave) disk. Luckily, newer Ghost has tools to simplify these steps. We’ll need this 3 pieces of clues to figure it out:
1. Virtual machine disk image files such as VHD can be used as source or destination
2. There’s a command switch to mount virtual machine disk image files internally WITHIN the ghost session (no side effects: windows won’t see it. Won’t persist between ghost sessions)
3. GHO files are not directly mountable as a virtual disk even internally within ghost session
So the complicated process can be shorten to converting GHO to VHD and then internally mount the VHD as a direct drive through command switch launching Ghost. Use DEMO.gho as an example:
REM Convert DEMO.gho to DEMO.vhd
ghost -clone,mode=restore,src=DEMO.gho,dst=DEMO.vhd
REM Launch Ghost with DEMO.vhd internally mapped as a (direct) logical drive
ghost -ad=DEMO.vhd
I ran into some obscure error messages like “ABORT: 11030, Invalid destination drive” when trying to specify the full absolute path. So instead of fussing with the syntax that breaks the code, I added ghost to my Windows %PATH% environmental variable and run ghost directly at the folder where the files are. I suspect it can be fixed with /translate command switch to make sure the drive letter is not ambigious whether it’s local or remote, but that’s something for later if I have a project that require scripting this reliably.
My cliff notes here.
Run Ghost as slave mode
ghost -tcps
Do this at Ghost master computer
REM Convert DEMO.gho to DEMO.vhd
ghost -clone,mode=restore,src=DEMO.gho,dst=DEMO.vhd
REM Launch Ghost with DEMO.vhd internally mapped as a (direct) logical drive
ghost -ad=DEMO.vhd -tcpm:{IP address of the slave computer}
Remember to open port 6668 at the Ghost slave computer.
Appendix
Technically, it’s possible to restore from an image file located AT THE SLAVE side, but it’d be a stupid idea. Initially I thought Ghost would be smart enough to directly use the image file locally on the slave session to clone the drive locally. However, given the speed and my observation with TCPview, this is not the case. It’s doing the stupid thing of crawling the contents of image file from the slave machine in chunks and send it back to the slave!
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## rsync/Deltacopy gotchas (especially Windows transfers)
Deltacopy is a GUI wrapper around rsync, a feature-packed tool to copy files locally AND remotely, AND differentially (automatically figure out the parts that are different and resend. Excellent for repair) through hash comparisons. For non-programmers, hash is a unique ID computed for a chunk of data that are expected to change wildly even at the slightest data/file change/corruption).
Deltacopy is very useful if you just want to do the basic stuff and not know the rsync syntax and switch combinations off the top of your head. It also provides a windows port of rsync based on Cygwin (a tiny Linux runtime environment for windows). This is the only free alternative to cwRsync, a paid Windows port of rsync.
rsync is a Swiss Army Knife that can also work from one local path to another. Deltacopy is intended for remote file transfer.
Deltacopy server is basically this:
rsync --daemon
However in Windows, since it’s cygwin, it’s looking for linux’s /etc/rsyncd.conf by default if you do not specify the config file through --config switch.
Deltacopy client basically help you generate the command to transfer files. Most of the features are done through right-click (context) menu, not toolbar or pull-down menus, which might confuse some people. You set up your tasks as Profile, which can be scheduled (the bottom panel) or executed immediately by right clicking on the profile:
Run is pushing file to the server, Restore is pulling files from the server. Run Now and Restore are for executing the command (aka task) immediately. You can peek into what it generated by right-clicking on the profile and choose “Display Run/Restore Command”. First time users might not be able to find it since the only place to access it is through context menus.
There are some tricky parts (gotchas) for specifying the files/folders to copy. First of all, even though you use Add Folder/Add Files button for entries
Basically you can make a (source, destination) pair by modifying the selection and target path. It’s just passed onto rsync command verbatim. The target path is relative to the virtual directory set on he server (see Deltacopy Server’s directory)
The destination path which is endowed with the branch folder name (one-level). In other words, if your source is C:/foo/bar, Deltacopy by default set the destination to /bar instead of /. This is probably to avoid the temptation of lumping all contents in the same remote destination root. If you just want to simply lay the files at the root virtual folder at the destination (my most common use case), you’ll have to edit and clear out the (relative) destination path.
As for the source, the author of rsync chose to do it the logical (more conservative) way but not intuitive way: by default it reconstruct the source folder’s FULL path structure at the destination! For example if you intend to copy everything under C:\foo over, the destination will create {destination root}\foo in the process and put everything under it instead of directly at {destination root}. The design choice was supposed to prevent accidental overwrites as multiple source subfolders try to write over each other with the same names at the destination.
Luckily, there’s a way around it! See man pages for -R –relative: Put a dot (.) at the place where the relative path starts! For example, the source is C:\foo\bar\baz and you do not want /foo to be created at the destination and want it to start with /bar instead. You should enter C:\foo\.\bar\baz as source. Everything the left of the dot (refers to self-folder) are stripped from the destination path structure.
ACL support for Windows sucks because rsync lives on cygwin, which has POSIX (unix/linux) type of permissions/ACL.
https://unix.stackexchange.com/questions/547275/how-do-i-use-rsync-to-reliably-transfer-permissions-acls-when-copying-from-ntf
In my opinion, the best way to go about it is to not transfer ACLs from the source and follow the preexisting ACLs at the destination. I’d also leave the groups and owners alone (inherit at destination) as well I might not be on the same active directory (or workgroup user management) as the destination computer so accounts with the same name might not be actually the same accounts.
--no-p --no-g --no-o
–no-{command} is the complement prefix that does the opposite of the -{command}, so the above means skipping -p (perms/permissions), -g (group), -o (owner) and make sure it has full permissions for everybody.
Sometimes a remote path can be mistaken as a relative local path with the hostname/IP address as the folder name if there’s no username. Start it with rsync:// as the URL scheme and the syntax is like ftp:// as far as username is concerned.
Deltacopy protects the source and destination paths with double quotes (“). It’s a good practice that we should do it even with direct rsync calls.
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## Tomato OpenVPN client assigned for specific computers
Setting Redirect Internet traffic to “Policy Rules” opens a table where you can specify which computer goes through VPN and which ones uses direct connection. Leave the destination IP unspecified and it’ll pick the 0.0.0.0 as intended
However, there’s a logical trap when you blindly follow instructions setting “Accept DNS configuration” to “Exclusive” as given by most instructions assuming all computers go on the network through VPN. Setting it as “Exclusive” means even the computer not intending to use VPN will still need to go through your VPN provider’s DNS! For slow VPN connection, this will be painfully slow for ALL computers! Set it to “Relaxed” instead.
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## Not missing Windows after trying Ubuntu Cinnamon Remix
Given that I grew up as a power DOS/Windows user, I often have gripes about how frustrating Linux is and they were almost never ready for people who just want to get common things done by intuitively guessing where the feature is (therefore having to RTFM or search the web for answers).
I deal with HP/Agilent/Keysight instruments a lot and appreciated their effort put on user experience (UX) design. It’s not that user who’s stupid if they have to dig through 5+ levels of menu buttons to measure a Vpp (peak to peak voltage) and the software aren’t smart enough to default to the only channel in use. That’s what Tektronix did to their nasty user interface and raised a generation of Stockholm Syndrome patients who keep buying Tek because they are traumatized by the steep learning curve and would rather walk on broken glass than having to learn a new interface from another vendor (that’s called vendor lock in).
I certainly appreciate Cinnamon desktop environment (came with Linux mint) designers willing to not insist on the ‘right way of doing things’ and follow a path that’s most intuitive for users coming from a Windows background.
The last time I used Linux Mint was 19. There’s still quite a lot of rough edges. Some services got stuck (time-outs) right out of the box and systemd went through slowly. It’s just not fast and responsive. When I tried it again when Mint 20.1 was released, my old i3 computer boots to the GUI in 5 seconds and I was hell of impressed. The icons and menus are also now sized balanced proportions like Windows (can’t stand the big and thick default menu-item fonts like Ubuntu).
However, there’s one big impeding factor for me to make Linux Mint my primary computer: the packages repositories are one generation behind Ubuntu (the most widely supported distro)! Software often have bugs that the developers solved, living with old, ‘proven’ software slows down the iterative process.
I’ve been through hell trying to access Bitlocker volume with Linux Mint 20.1 as not only it doesn’t work right of the box like Windows, I’m stuck with a command line dislocker that doesn’t integrated with the file manager (like Nemo). The zuluCrypt available with Mint 20.1 is too old to support Bitlocker properly. Trying to upgrade it to 6.0 has Qt dependencies which is unsolvable. I was able to download the unsanctioned old revision in debian package but there’s more unsolvable dependencies.
The alternative option of compiling from the source is met with more dependencies fuckery and now the restrictive Mint repository might not have the exact version of the compiler required by the source code package. Aargh!
I was about to give up Linux Mint and install Ubuntu and try to hold my nose changing the desktop to Cinnamon. Luckily I’ve found somebody who read my mind: there’s Ubuntu Cinnamon Remix!
Not only Ubuntu Cinnamon Remix supported Bitlocker right out of the box (no need to fuck with zuluCrypt which doesn’t integrate with the file explorer anyway)! Most of the defaults make sense, buttons are often where I expect them to be. Even Win+P key works identically! The names/lingo are close to Windows whenever possible, and honestly the default Yari theme is visually slightly more pleasing than Windows as it makes very good use of the visual spaces!
Here’s a few transition tips
I use Winsplit-Revolution in Windows (old version is freeware) that uses the numeric keypad to lock the window to the 9 squares grid using Ctrl+Alt+{Numpad 1-9}. Save the keyboard shortcuts in case if you want to install it again on another computer:
dconf dump /org/cinnamon/desktop/keybindings/ > dconf-settings.conf
dconf load /org/cinnamon/desktop/keybindings/ < dconf-settings.conf
There’s no Ctrl+Shift-Esc key which I often use to call Task Manager (called System monitor). I had to make the shortcut as well to feel at home.
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## HP 54502A Datasheet typo about AC coupling
The cutoff frequency of 10Hz on the datasheet is a typo. Better scopes at the time claims 90Hz. 10Hz is just too good to be true.
Found the specs from the service manual:
Don’t be fooled by the -3dB cutoff and ignore how wide the transition band can be (depends on the filter type and the order). Turns out this model has a very primitive filter that AC couple mode still messes square waves below 3kHz up despite the specs says the -3dB is at 90Hz. You better have a 30+ fold guard band for old scopes!
Remember square wave pulse train in time domain is basically a sinc pulse centered at every impulse of the impulse train in frequency domain superimposed. Unless you have a tiny duty cycle (which is not the case for uniform square waves, they are 50%), the left hand side of the sinc function at 1kHz fundamental still have sub-1kHz components that can be truncated by the AC coupling (high pass filter).
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## Qemu for Windows Host Quirks
I’m trying to cross compile my router’s firmware as I made a few edits override the update DDNS update frequency. Turns out it doesn’t work on the latest Linux so I’d need to run an older Ubuntu just to keep it happy.
RANT: Package servers keep pulling the rug on outdated linux frustrates the hell out of me. Very often developers didn’t make a whole installer for it so we are often wedged between downloading a package at the mercy of its availability from package managers and their servers or compiling the damn source code!
With the promise that Qemu might have less overhead than Hyper-V or VirtualBox (indeed it observably is), I tried installing Qemu on Windows host and it turned out to be a frustrating nightmare.
RANT: Linux is not free in the sense of free beer. The geniuses did the most sophisticated work for free but users pay time and energy cleaning after them (aka a support network dealing with daily frustrations) to make these inventions usable. There’s a company that does the clean up to make BSD (same umbrella as Linux/Unix) usable and made a lot of money: it’s called Apple Computers (since Steve Jobs’ return).
qemu is just the core components. System integration (simplifying common use cases) is practically non-existent. Think of them as the one who produced an ASIC (chip) and the end-user happens to be the application engineers. There’s a few tutorials on qemu Linux hosts for moderately complex scenarios, but you are pretty much on your own trying to piece it altogether for Windows because there are some conceptual and terminology differences. The man page --help for the qemu’s Windows host’s VM engine was blindly copied from the Linux hosts counterpart, so it tells you about qemu-bridge-helper which is missing.
I stupidly went down the rabbit hole and drained my time on qemu. So I documented the quirks to help the next poor sap who has to get qemu running on Windows 10 host efficiently over Bridged-Adapter (VirtualBox lingo) networking mode.
• Preparation work to get HAXM accelerator set up
• Release VT-d (hardware assisted virtualizations) so HAXM can acquire it
• You’ll need to remove Hyper-V completely as it will hoard VT-d’s control
• Windows Sandbox and Windows Subsystem for Linux (WSL2) uses Hyper-V. If you just unchecked Hyper-V in Windows Optional Features leaving any of these 2 on, Hyper-V is still active (it only removes the icons)
• HAXM v7.6.6 not recognized by qemu on clean install. Install v7.6.5 first, then remove it and install v7.6.6. Likely they forgot a step in v7.6.6’s installer
• Turn on optimization by: -accel hax
• Command line qemu engine
• qemu-system-{architecture name}.exe is what runs the show
• qemu-system-{architecture name}w.exe is the silent version of the above engine. Won’t give you a clue if something fails (like invalid parameters)
• qemu-img create -f {format such as vhd/qcow2} {hard drive image name} {size like 10G}
• QtEmu sucks, and they lack any better GUIs out there!
• It’s basically a rudimentary command line’s GUI wrapper
• It only has user mode (SLIRP) networking (default)
• It’s not maintained actively so it doesn’t keep up with the parameter syntax changes (i.e. can generate invalid combinations)
• Since it uses the silent (with a w suffix) engine, likely to avoid a lingering command window, it also won’t tell you shit and why if something fails. It just ignores you when you press the start button unless all the stars align (you got everything right)
• Basic command line parameters
• Set aside 10G for the VM: -m 10G
• 1 core if unspecified. Number of available threads (in hyper-threaded system) show up as # of processors. It’s referring to logical processors, not physical cores.
• Windows: -smp %NUMBER_OF_PROCESSORS%
• Linux: -smp \$(nproc)
• Attach virtual hard drive: -hda {virtual hard drive file name}
• Attach optical drive (iso): -cdrom {iso file}
I typically want Bridged-Adapter option from VirtualBox, which means the virtual NIC plugs into the same router as the host and just appears as another computer on the same network as host. This is broken into a few components in qemu and you have to manage them separately. Great for learning about how Bridged-Adapter really works, but a lot of swearwords coming from people who just want to get basic things done.
Networking in QEMU is another can of worms if you deviate from the default SLIRP (user mode). I figured out how to work it, but the network bridge is faulty and it keeps crashing my windows with BSOD on bridge.sys with varying error tag. I have short glimpse of it working if I move very fast. Looks like the TAP driver is corrupting the memory as the bridge became very erratic that I see error messages deleting it and have persistent BSOD when the bridge starts after the VM hanged at the TAP bridge on boot.
I listed the steps below to show what should have been done to get the Bridge-Adapter (VirtualBox) equivalent function if there are no bugs in the software, but hell I’m throwing qemu for Windows to trash as it’s half-baked.
First, of all, you need to install OpenVPN to steal its TAP-Win32 virtual network card. It’s not VMware or Virtualbox that it’s part of the package. Qemu didn’t care to tightly integrate or test this driver properly.
Then you’ll need to bridge the “TAP-Windows Adapter (V#) for OpenVPN” with the network interface you want it to piggy back on.
The name of the TAP adapter is what you enter as ifname= parameter of the tap interface in qemu command line. You have to tell qemu specifically which interface you want to engage in. I named the virtual network card as ‘TAP’ above. After bridging it looks like this:
You are not done yet! The bridged network (seen as one logical interface) is confused and it won’t be able to configure with your physical network card’s DHCP client. You’ll have to go to the properties of the Network Bridge and configure the IPv4 with static IP.
You can use ipconfig /all to find out the relevant adapters acquired DHCP settings and enter it as static IP. Coordinate with the network administrator (can be yourself) to make sure you own that IP address so you won’t run into IP conflict if you reboot and somebody took your IP.
After these are all set up the parameter to add to qemu call is:
-nic tap,ifname=TAP
There are complicated settings like -net nic and -netdev -device. These are old ways to do it and have bloated abstractions. -nic switch combined them into one switch.
Then welcome to the world of Windows 10 bridge.sys crashing frequently and you might get a short window of opportunity that it boots and ifconfig acquire the IP address settings from your router (or network the physical adapter is on)’s DHCP server.
It’s like a damn research project finding out something is technically feasible but definitely not ready for production. Welcome to the FOSS jungle!
Postscript: I put Hyper-V back and realized it’s insanely slow with Linux Mint as it does not support hardware graphics acceleration. It’s night and day of a difference. Qemu is fast, but it crashes on Windows 10 if I bridge the adapters!
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### iPOD Video (13)
An essential skill in many applications is the ability to factorise quadratic expressions. In this unit you will see that this can be thought of as reversing the process used to �¢??remove�¢?? or 'multiply-out�¢?? brackets from an expression. This resource is released under a Creative Commons license Attribution-Non-Commercial-No Derivative Works and the copyright is held by Skillbank Solutions Ltd.
An essential skill in many applications is the ability to factorise quadratic expressions. In this unit you will see that this can be thought of as reversing the process used to �¢??remove�¢?? or 'multiply-out�¢?? brackets from an expression. This resource is released under a Creative Commons license Attribution-Non-Commercial-No Derivative Works and the copyright is held by Skillbank Solutions Ltd.
An essential skill in many applications is the ability to factorise quadratic expressions. In this unit you will see that this can be thought of as reversing the process used to �¢??remove�¢?? or 'multiply-out�¢?? brackets from an expression. This resource is released under a Creative Commons license Attribution-Non-Commercial-No Derivative Works and the copyright is held by Skillbank Solutions Ltd.
An essential skill in many applications is the ability to factorise quadratic expressions. In this unit you will see that this can be thought of as reversing the process used to �¢??remove�¢?? or 'multiply-out�¢?? brackets from an expression. This resource is released under a Creative Commons license Attribution-Non-Commercial-No Derivative Works and the copyright is held by Skillbank Solutions Ltd.
An essential skill in many applications is the ability to factorise quadratic expressions. In this unit you will see that this can be thought of as reversing the process used to �¢??remove�¢?? or 'multiply-out�¢?? brackets from an expression. This resource is released under a Creative Commons license Attribution-Non-Commercial-No Derivative Works and the copyright is held by Skillbank Solutions Ltd.
An essential skill in many applications is the ability to factorise quadratic expressions. In this unit you will see that this can be thought of as reversing the process used to �¢??remove�¢?? or 'multiply-out�¢?? brackets from an expression. This resource is released under a Creative Commons license Attribution-Non-Commercial-No Derivative Works and the copyright is held by Skillbank Solutions Ltd.
An essential skill in many applications is the ability to factorise quadratic expressions. In this unit you will see that this can be thought of as reversing the process used to �¢??remove�¢?? or 'multiply-out�¢?? brackets from an expression. This resource is released under a Creative Commons license Attribution-Non-Commercial-No Derivative Works and the copyright is held by Skillbank Solutions Ltd.
An essential skill in many applications is the ability to factorise quadratic expressions. In this unit you will see that this can be thought of as reversing the process used to �¢??remove�¢?? or 'multiply-out�¢?? brackets from an expression. This resource is released under a Creative Commons license Attribution-Non-Commercial-No Derivative Works and the copyright is held by Skillbank Solutions Ltd.
An essential skill in many applications is the ability to factorise quadratic expressions. In this unit you will see that this can be thought of as reversing the process used to �¢??remove�¢?? or 'multiply-out�¢?? brackets from an expression. This resource is released under a Creative Commons license Attribution-Non-Commercial-No Derivative Works and the copyright is held by Skillbank Solutions Ltd.
An essential skill in many applications is the ability to factorise quadratic expressions. In this unit you will see that this can be thought of as reversing the process used to �¢??remove�¢?? or 'multiply-out�¢?? brackets from an expression. This resource is released under a Creative Commons license Attribution-Non-Commercial-No Derivative Works and the copyright is held by Skillbank Solutions Ltd.
An essential skill in many applications is the ability to factorise quadratic expressions. In this unit you will see that this can be thought of as reversing the process used to �¢??remove�¢?? or 'multiply-out�¢?? brackets from an expression. This resource is released under a Creative Commons license Attribution-Non-Commercial-No Derivative Works and the copyright is held by Skillbank Solutions Ltd.
An essential skill in many applications is the ability to factorise quadratic expressions. In this unit you will see that this can be thought of as reversing the process used to �¢??remove�¢?? or 'multiply-out�¢?? brackets from an expression. This resource is released under a Creative Commons license Attribution-Non-Commercial-No Derivative Works and the copyright is held by Skillbank Solutions Ltd.
An essential skill in many applications is the ability to factorise quadratic expressions. In this unit you will see that this can be thought of as reversing the process used to �¢??remove�¢?? or 'multiply-out�¢?? brackets from an expression. This resource is released under a Creative Commons license Attribution-Non-Commercial-No Derivative Works and the copyright is held by Skillbank Solutions Ltd.
### Practice & Revision (3)
Algebra Refresher
A refresher booklet on Algebra with revision, exercises and solutions on fractions, indices, removing brackets, factorisation, algebraic frations, surds, transpostion of formulae, solving quadratic equations and some polynomial equations, and partial fractions. An interactive version and a welsh language version are available.
Algebra Refresher - Interactive version
An interactive version of the refresher booklet on Algebra including links to other resources for further explanation. It includes revision, exercises and solutions on fractions, indices, removing brackets, factorisation, algebraic frations, surds, transpostion of formulae, solving quadratic equations and some polynomial equations, and partial fractions. An interactive version and a welsh language version are available.
Cwrs Gloywi Algebra
An Algebra Refresher. This booklet revises basic algebraic techniques. This is a welsh language version.
### Quick Reference (4)
Factorising complete squares
There is a special case of quadratic expression known as a complete square. This leaflet explains what this means and how such expressions are factorised.
This leaflet shows how to take a quadratic expression and factorise it. Special cases of complete squares and difference of two squares are dealt with on other leaflets.
In this leaflet, we explain the procedure for factorising quadratic expressions. Be aware, not all quadratic expressions can be factorised.
Factorising the difference of two squares
There is a special case of quadratic expression known as the difference of two squares. This leaflet explains what this means and how such expressions are factorised.
### Teach Yourself (1)
The ability to factorise a quadratic expression is an essential skill. This booklet explains how this process is carried out.
### Test Yourself (2)
3 questions on factorising quadratics. The second question also asks for the roots of the quadratic. The third question involves factorising quartic polynomials but which are quadratics in $x^2$. Numbas resources have been made available under a Creative Commons licence by the School of Mathematics & Statistics at Newcastle University.
Maths EG
Computer-aided assessment of maths, stats and numeracy from GCSE to undergraduate level 2. These resources have been made available under a Creative Common licence by Martin Greenhow and Abdulrahman Kamavi, Brunel University.
### Third Party Resources (2)
Mathematics Support Materials from the University of Plymouth
Support material from the University of Plymouth:
The output from this project is a library of portable, interactive, web based support packages to help students learn various mathematical ideas and techniques and to support classroom teaching.
There are support materials on ALGEBRA, GRAPHS, CALCULUS, and much more.
This material is offered through the mathcentre site courtesy of Dr Martin Lavelle and Dr Robin Horan from the University of Plymouth.
University of East Anglia (UEA) Interactive Mathematics and Statistics Resources
The Learning Enhancement Team at the University of East Anglia (UEA) has developed la series of interactive resources accessible via Prezi mind maps : Steps into Numeracy, Steps into Algebra, Steps into Trigonometry, Bridging between Algebra and Calculus, Steps into Calculus, Steps into Differential Equations, Steps into Statistics and Other Essential Skills.
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Elemental phosphorus exists in two major forms, white phosphorus and red phosphorus, but because it is highly reactive, phosphorus is never found as a free element on Earth.It has a concentration in the Earth's crust of about one gram per kilogram (compare copper at about 0.06 grams). Phosphorus Flamethrower: A Demonstration Using Red and White Allotropes of Phosphorus. Black phosphorus … Preparation of black phosphorus from red phosphorus Black phosphorus was synthesized from amorphous red phos- phorus using Cu as a catalyst, as well as Sn and SnI the Altmetric Attention Score and how the score is calculated. Find more information about Crossref citation counts. The allotropes of phosphorus are typically divided into three main classes: white, red, and black phosphorus. Iodine and diamond are both crystalline solids at room temperature. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.) • A process for the preparation of H 2 and phosphorous acid, the process comprising catalytically oxidizing elemental phosphorus by reaction with water at a temperature below 200° C. 2. Phosphorus chlorides, for example, are formed from the reaction of white phosphorus and chlorinegas 1. It is more stable than white phosphorus. Its density is 2.34g/cm 3. Phosphorus is a chemical element with the symbol P and atomic number 15. Red phosphorus is much more stable in air, but will react with halogens. Preparation of high-performance nanosized palladium hydrogenation catalysts using white phosphorus and phosphine Article (PDF Available) in Russian Journal of … from White Phosphorus A thesis submitted by Kenneth Mark Armstrong In Partial Fulfilment for the award of Doctor of Philosophy School of Chemistry University of St Andrews North Haugh, St Andrews, Fife . February 27, 2016 December 23, 2017 Inorganic. 3 publications. 1a and b shows that after the hydrothermal reaction at 200 °C for 7 h, large pieces of red phosphorus are cut and … White phosphorus + I 2 or other inert gas -240 0 C→ Red Phosphorus + 4.22Kcal. SYNTHETIC ROUTE TO WHITE PHOSPHORUS (P It is amorphous solid. Phosphorus is a major component of bones and teeth in the form of calcium phosphate. Find more information on the Altmetric Attention Score and how the score is calculated. p-block element; jee; jee mains; Share It On Facebook Twitter Email. The phosphorus first reacts with the bromine or iodine to give the phosphorus(III) halide. In lieu of an abstract, this is the article's first page. https://doi.org/10.1002/9781119477822.ch6. Please note: If you switch to a different device, you may be asked to login again with only your ACS ID. ). However, crystalline red phosphorus with different crystal structures has also been reported and studied (3). Introduction Phosphorus is known to appear in diverse allotropic forms, making it a promising source for elemental nanostructures. WHITE PHOSPHORUS RED PHOSPHORUS BLACK PHOSPHORUS ALLOTROPES OF PHOSPHORUS . The remaining 2% of the phosphorus (used domestically) is utilized in its elemental form (i.e. Fig. 0 votes . adshelp[at]cfa.harvard.edu The ADS is operated by the Smithsonian Astrophysical Observatory under NASA Cooperative Agreement NNX16AC86A Its melting point is 860K. The remaining 2% of the phosphorus (used domestically) is utilized in its elemental form (i.e. The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Phosphorus Flamethrower: A Demonstration Using Red and White Allotropes of Phosphorus. Preparation of white phosphorus from red phosphorus. • If you are on a personal connection, like at home, you can run an anti-virus scan on your device to make sure it is not infected with malware. 30, 31 Phosphorus exists in various allotropes, including white phosphorus, red phosphorus, BP, violet phosphorus, and A7 phase. matches, chemical catalyst, phosphides and pyrotechnics. Phos-phorus is among the abundant elements on Earth, making up ≈0.1% of the Earth’s crust. The first step is nucleophilic substitution of the OH group by I−, faciliated by protonation of the alcohol. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.) 33 After being … When white phosphorus is heated to about 250 C with air absence, it changes into the red phosphorus. Phosphorus is among the abundant elements on Earth, making up ≈0.1% of the Earth's crust. Black phosphorus nanosheets were prepared by hydrothermal method. B. the white phosphorus is treated in an electric furance. It is less reactive than white phosphorus. In the preparation of red phosphorus from white phosphorus : (A) MnO 2 is used as a catalyst (B) the white phosphorus is treated in an electric furnace (C) a little iodine is used as catayst in absence of air (D) the gas P 4 is released. Its molar mass is 30.974g/mol. For the industrial manufacture of red phosphorus, the white phosphorus is mixed with a small amount of iodine and heated to about 280 0 C. Thus, the majority of white phosphorus is converted to red phosphorus by heating. The red allotropic form of this element is gotten when white phosphorus is heated to a temperature of 250 o C in the absence of air and in the presence of iodine which serves as a catalyst. Apr 16, 2020 - Generally, the White phosphorus is called Phosphorus. It is less reactive than white phosphorus. Your Mendeley pairing has expired. Therefore, this proposed regulation will only affect the distribution of less than 2% of the industry at the end user level. as red phosphorus or white phosphorus) or used to produce all other phosphorus chemicals including sodium hypophosphite and hypophosphorous acid. Red phosphorus → White phosphorus. this is for educational and entertainment purposes only. Red phosphorus may be formed by heating white phosphorus to 300 °C (572 °F) in the absence of air or by exposing white phosphorus to sunlight.Red phosphorus exists as an amorphous network. Preparation of polycrystalline BP: Polycrystalline black phosphorus was synthesized by hydrothermal method. Fig (1.2) Black phosphorus. At very high temperatures, P 4 dissociates into P 2.At approximately 1800 °C, this dissociation reaches 50 per cent. Full conversion to phosphates was achieved without the use of chlorine, and the reactions do not produce acid waste. Its density is 2.34g/cm 3. Phosphorus is a chemical element with the symbol P and atomic number 15. February 27, 2016 December 23, 2017 Inorganic. Triaryl phosphates were synthesized from white phosphorus and phenols under aerobic conditions and in the presence of iron catalysts and iodine. Preparation of Red Phosphorus Red phosphorus is prepared from white phosphorus. Red phosphorus, usually in amorphous form, is obtained by heating liquid white phosphorus at a temperature of between 250° and 590° C. while the phosphorus is subjected to a pressure greater than the theoretical vapor pressure of white phosphorus at the heating temperature. Cloudflare Ray ID: 6006ce0dc8e7f2b8 Instead of using phosphorus(III) bromide or iodide, the alcohol is usually heated under reflux with a mixture of red phosphorus and either bromine or iodine. [32,33] Figure 1 presents the various allotropic forms of phosphorus. Ans: Red phosphorus is heated in an inert atmosphere of nitrogen, it sublimes off and the vapour is condensed under water to form white phosphorus. Red phosphorus is used in safety matches, fireworks, smoke bombs and pesticides. P4 + 6 Cl… [33] Each allotrope exhibits different crystal structures: white phosphorus displays a cubic structure, while red phosphorus is amorphous and black phosphorus has an orthorhombic structure. Upon further heating, the amorphous red phosphorus crystallizes. It is amorphous solid. The reaction occurs in stepwise fashion. Bend borosilicate tube, then add 1 g of pure fine sand and 4 g of red phosphorus, then put the open side of the tube to 50°C water. Therefore, this proposed regulation will only affect the distribution of less than 2% of the industry at the end user level. This article is cited by 3 publications. Red phosphorus is not poisonous and is not as dangerous as white phosphorus, although frictional heating is enough to change it back to white phosphorus. Abstract. Iodine and diamond are both crystalline solids at room temperature. 30, 31 Phosphorus exists in various allotropes, including white phosphorus, red phosphorus, BP, violet phosphorus, and A7 phase. Although the white and black allotropes have been well … Librarians & Account Managers. 2. Red phosphorus,discovered in 1845,is much more stable than white phosphorus.In industrial, red phosphorus was converted from white phosphorus, which can be produced by reducing the phosphorus in phosphate rocks at high temperature. & Account Managers, For 5 a) Reaction of methane thiol with iodine gives a new compound, C2H6S2, that is a hamsterOther Reactions. Instead of using phosphorus(III) bromide or iodide, the alcohol is usually heated under reflux with a mixture of red phosphorus and either bromine or iodine. You may need to download version 2.0 now from the Chrome Web Store. Preparation of black phosphorus from red phosphorus Black phosphorus was synthesized from amorphous red phos- phorus using Cu as a catalyst, as well as Sn and SnI Other reactions involving phosphorus halides. BP forms with several crystalline structures including orthorhombic, rhombohedral, and cubic , . Then gently start to heat the red phosphorus mixture with a bunsen burner. White phosphorus is used as a deoxidizing agent in the preparation of steel and phosphor bronze. The conversion of white to red phosphorus occurs in the liquid phase of molten white phosphorus from which solvents are absent and relies on the autocatalytic nature of the conversion process. The key difference between red and white phosphorus is that the red phosphorus appears as dark red colored crystals whereas the white phosphorus exists as a translucent waxy solid that quickly becomes yellow when exposed to light.. Phosphorus is a chemical element that occurs in several different allotropes.The most common allotropes are red and white forms, and these are solid … Another way to prevent getting this page in the future is to use Privacy Pass. The remaining 2% of the phosphorus (used domestically) is utilized in its elemental form (i.e. phosphorus red phosphorus process reaction same Prior art date 1902-12-15 Legal status (The legal status is an assumption and is not a legal conclusion. As List I chemicals, red phosphorus, white phosphorus, and hypophosphorous acid and its salts will become subject to the chemical regulatory control provisions and civil and criminal sanctions of the CSA. If you are at an office or shared network, you can ask the network administrator to run a scan across the network looking for misconfigured or infected devices. The method of converting high purity red phosphorus to high purity white phosphorus comprising the steps of: (A) heating red phosphorus of a purity of at least 99% in vacuo to cause it to vaporize, and (B) condensing liquid white phosphorus from the vapor without the aid of a carrier gas in vacuo. As List I chemicals, red phosphorus, white phosphorus, and hypophosphorous acid and its salts will become subject to the chemical regulatory control provisions and civil and criminal sanctions of the CSA. The application of such pressure minimizes phosphorus vapor formation during the conversion to red phosphorus. Elemental phosphorus exists in two major forms, white phosphorus and red phosphorus, but because it is highly reactive, phosphorus is never found as a free element on Earth.It has a concentration in the Earth's crust of about one gram per kilogram (compare copper at about 0.06 grams). ... BLACK PHOSPHORUS PREPARATION SOLVENT ASSISTED EXFOLIATION WITH ULTRASOUNDS IN DMSO ... Substrate Catalyst Selectivity % Conversion % P H 2 /bar T/°C 4-CNBa Pd unsupp. White phosphorus is combined with phenols under aerobic conditions and in the presence of iron catalysts and iodine, facilitating full conversion to various phosphates without the use of chlorine or chlorinated solvents. Completing the CAPTCHA proves you are a human and gives you temporary access to the web property. Its melting point is 860K. If red phosphorus alone is controlled, DEA has concluded that clandestine laboratory operators would rapidly move to white phosphorus and hypophosphorous acid. 1 The white phosphorus has a crystal structure consisting of tetrahedral P 4 molecules. phosphorus red phosphorus process reaction same Prior art date 1902-12-15 Legal status (The legal status is an assumption and is not a legal conclusion. You have to login with your ACS ID befor you can login with your Mendeley account. toppr. [33] As such, recordkeeping, reporting and import/export notification requirements (as described in 21 U.S.C. Your IP: 54.38.193.150 2D black phosphorus (BP, mono- or/and few-layer BP). Among phosphorus allotropes, white phosphorus (P 4) is the commercial product easily obtained from the reduction of phosphate minerals. In most applications, the red allotrope is a- f vored over the white allotrope because of its greater stability in air and its easier handling characteristics. Preparation of Red Phosphorus Red phosphorus is prepared from white phosphorus. The heating of the white phosphorus is effected in the substantial absence of solvents and catalysts. An illustrated guide on the preparation of white phosphorus (P4) from red phosphorus (P) By Pyro 16 August 2013, 3:48AM-Introduction White phosphorus is an extremely reactive and hard to get allotrope of phosphorus while red phosphorus is more readily available from chemical suppliers or … 1 Answer. adshelp[at]cfa.harvard.edu The ADS is operated by the Smithsonian Astrophysical Observatory under NASA Cooperative Agreement NNX16AC86A Here, the tetratomic molecules of white phosphorus combine to form large macromolecules and the resultant product is red phosphorus which is a red brittle powder and is the stable allotrope of sulphur. Reaction of alcohol with red phosphorus and iodine CH 3 CH 2 OH+red P/Br 2-----> CH 3 CH 2 Br R--OH reacts in the presence red phosphorus/I 2 to form R-I(Iodoalkane). Find more information about Crossref citation counts. Bend borosilicate tube, then add 1 g of pure fine sand and 4 g of red phosphorus, then put the open side of the tube to 50°C water. Preparation of White phosphorus. It is poisonous but less than that of white phosphorus. as red phosphorus or white phosphorus) or used to produce all other phosphorus chemicals including sodium hypophosphite and hypophosphorous acid. Red phosphorus → White phosphorus. Red and white phosphorus are highly flammable unlike BP which is the most stable of the allotropes. Get article recommendations from ACS based on references in your Mendeley library. It is more stable than white phosphorus. The conditions of transformation are now accurately known. Journal of Chemical Education 2010 , 87 (11) , 1154-1158. $2P_{(s)} + 3Br_2 \rightarrow 2PBr_3\label{1.1.5}$ This would be an undesired consequence, since both the white phosphorus and hypophosphorous acid methods of illicit methamphetamine production are significantly more hazardous methods. C. a little iodine is used as catalyst. Elemental phosphorus exists in two major forms, white phosphorus and red phosphorus, but because it is highly reactive, phosphorus is never found as a free element on Earth.It has a concentration in the Earth's crust of about one gram per kilogram (compare copper at about 0.06 grams). Reviewers, Librarians Nickel Phosphides Fabricated through a Codeposition–Annealing Technique as Low-Cost Electrocatalytic Layers for Efficient Hydrogen Evolution Reaction. Then. I heat white phosphorous in a stainless steel sealed retort with a small amount of potassium iodide as a catalyst and get a high yield of red phosphorous . Then gently start to heat the red phosphorus mixture with a bunsen burner. The first step is nucleophilic substitution of the OH group by I−, faciliated by protonation of the alcohol. It is also used in rat poisons and to make smoke screens (by burning) for warfare. You’ve supercharged your research process with ACS and Mendeley! production of phosphorus. Reaction of alcohol with red phosphorus and iodine CH 3 CH 2 OH+red P/Br 2-----> CH 3 CH 2 Br R--OH reacts in the presence red phosphorus/I 2 to form R-I(Iodoalkane). Please enable Cookies and reload the page. 5 a) Reaction of methane thiol with iodine gives a new compound, C2H6S2, that is a hamsterOther Reactions. DOI: 10.1021/ed1002652. 32, 33 Figure 1 presents the various allotropic forms of phosphorus. In the preparation of red phosphorus from white phosphorus I 2 is used as catalyst at 2 5 0 0 C. Answered By . one of the most common allotropes of phosphorus and is considered to be a derivative of the P4 molecule Phosphorus is a chemical element with the symbol P and atomic number 15. Red phosphorus is not consid-ered problematic with regard to environmental and occupational health issues. In the preparation of red phosphorus from white phosphorus : A. M n O 2 is used as a catalyst. red phosphorus as a precursor. Structure Of Phosphorus. White, black and red phosphorus are allotropes of elemental phosphorus. It is odorless. 1. Other reactions involving phosphorus halides. Ans: Red phosphorus is heated in an inert atmosphere of nitrogen, it sublimes off and the vapour is condensed under water to form white phosphorus. [30,31] Phosphorus exists in various allotropes, including white phosphorus, red phosphorus, BP, violet phosphorus, and A7 phase. As such, recordkeeping, reporting and import/export notification requirements (as described in 21 U.S.C. 2. Preparation: It is prepared by heating white phosphorus in the pressure of little I 2 or sulphur as a catalyst up to 250 °C in vacuum. Usually, the structure of red phosphorus has been usually described to be amorphous and polycrystalline. Please reconnect, Authors & Phos-phorus is among the abundant elements on Earth, making up ≈0.1% of the Earth’s crust. In the preparation of red phosphorus from white phosphorus : (A) MnO 2 is used as a catalyst (B) the white phosphorus is treated in an electric furnace (C) a little iodine is used as catayst in absence of air (D) the gas P 4 is released Red phosphorus, usually in amorphous form, is obtained by heating liquid white phosphorus at a temperature of between 250° and 590° C. while the phosphorus is subjected to a pressure greater than the theoretical vapor pressure of white phosphorus at the heating temperature. Preparation of White phosphorus. Preparation of Red Phosphorus. 1. White phosphorus reacts with air and can spontaneously ignite, if heated slightly, forming phosphorus pentoxide. What is claimed is: 1. 32, 33 Figure 1 presents the various allotropic forms of phosphorus. 33 D. the gas P 4 is realeased. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.) phosphorus iron water slurry red Prior art date 1948-04-01 Legal status (The legal status is an assumption and is not a legal conclusion. Chia-Wei Hsu, Yi-Chou Tsai, Brandi M. Cossairt, Clément Camp, John Arnold, Brandi M. Cossairt, Brandi M. Cossairt, Christopher C. Cummins, Yi-Chou Tsai. 2. red phosphorus was converted from white phosphorus, which can be produced by reducing the phosphorus in phosphate rocks at high temperature. Its molar mass is 30.974g/mol. Phosphorus Flamethrower: A Demonstration Using Red and White Allotropes of Phosphorus. 4 2.5 g NH 4 F was dispersed in 25 mL deionized water, and then 500 mg of red phosphorus powder was added and stirred for 30 min and sonicated for 30 min to make the dispersion uniform. It is poisonous but less than that of white phosphorus. MEDIUM. Distillation time is about 20 minutes. These metrics are regularly updated to reflect usage leading up to the last few days. It is odorless. Answer. Therefore, this proposed regulation will only affect the distribution of less than 2% of the industry at the end user level. Phosphorus has many allotropes, which includes white phosphorus, red phosphorus and black phosphorus. Structure of red phosphorus: Red phosphorus is a combination of tetrahedral P 4 units to give macromolecules. as red phosphorus or white phosphorus) or used to produce all other phosphorus chemicals including sodium hypophosphite and hypophosphorous acid. … $2P_{(s)} + 3Br_2 \rightarrow 2PBr_3\label{1.1.5}$ R. Bernasconi, M. I. Khalil, C. Iaquinta, C. Lenardi, L. Nobili, L. Magagnin. The reaction occurs in stepwise fashion. Properties of Red Phosphorus Red phosphorus is red in color. The phosphorus first reacts with the bromine or iodine to give the phosphorus(III) halide. Expired - Lifetime Application number US18355A Inventor Miller Philip Current Assignee (The listed assignees may be inaccurate. [32,33] Figure 1 presents the various allotropic forms of phosphorus. This article is cited by Properties of Red Phosphorus Red phosphorus is red in color. 830 and 971 [[Page 57579]] Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. 830 and 971 [[Page 57579]] For many of the purposes to which phosphorus is applied the red form is equally suitable, and when this is the case this form is greatly to be preferred on account of its non-poisonous and non-inflammable character. Nevertheless, the orthorhombic black phosphorus with space group Cmce , is an important material because of its layered structure . Phosphorus is among the abundant elements on Earth, making up ≈0.1% of the Earth's crust. ) AND ARSENIC TRIPHOSPHIDE (AsP Phosphorus exists as tetrahedral P 4 molecules in the liquid and gas phases. DOI: 10.1021/ed1002652. 3 A process as set forth in claim 1 wherein the reaction is conducted in a reaction zone comprising a metal catalyst. Single layer black phosphorus has recently been termed phosphorene to show its relationship with 2D graphene (although in the case of … Melissa L. Golden, Eric C. Person, Miriam Bejar, Donnie R. Golden, and Jonathan M. Powell. 2D black phosphorus (BP, mono- or/and few-layer BP). White, black and red phos-phorus are allotropes of elemental phosphorus. Synthesis of Pure Phosphorus Nanostructures Synthesis of Pure Phosphorus Nanostructures Winchester, Richard A. L.; Whitby, Max; Shaffer, Milo S. P. 2009-05-04 00:00:00 Elemental phosphorus is known to exist as several different allotropes, commonly referred to as white, red, and black phosphorus, after their various colors. Article Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. R. Bernasconi, M. I. Khalil, C. Iaquinta, C. Lenardi, L. Nobili. Performance & security by Cloudflare, Please complete the security check to access. The use of ammonia fluoride (NH 4 F) can decrease surface activation energy of red phosphorus for its transformation into black phosphorus nanosheets by a mild phase transition []. Note: It is prepared by heating white phosphorus in the pressure of little I 2 or sulphur as a catalyst up to 250 °C in vacuum. 15 60 1 200* [30,31] Phosphorus exists in various allotropes, including white phosphorus, red phosphorus, BP, violet phosphorus, and A7 phase. Nickel Phosphides Fabricated through a Codeposition–Annealing Technique as Low-Cost Electrocatalytic Layers for Efficient Hydrogen Evolution Reaction. The mixture was transferred into a 30 mL Teflon-lined stainless autoclave. Usually, the structure of red phosphorus has been usually described to be amorphous and polycrystalline. Journal of Chemical Education 2010 , 87 (11) , 1154-1158. Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Red phosphorus probably is not a unary substance, and that the difference between the vapour pressures of red and violet phosphorus below about 400° C. are probably due to the non-equilibrium conditions in the red form. A zero‐waste, one‐step synthetic route to triaryl phosphates from elemental white phosphorus is reported. Download version 2.0 now from the Reaction is conducted in a Reaction zone comprising a metal catalyst 971 [. Is among the abundant elements on Earth, making up ≈0.1 % of the OH group by,! As such, recordkeeping, reporting and import/export notification requirements ( as described preparation of red phosphorus from white phosphorus catalyst U.S.C!, if heated slightly, forming phosphorus pentoxide 32,33 ] preparation of red phosphorus from white phosphorus catalyst 1 the. From ACS based on references in your Mendeley Account highly flammable unlike BP which is the article 's first.! Gives you temporary access to the accuracy of the status listed. M. Powell first! Nickel Phosphides Fabricated through a Codeposition–Annealing Technique as Low-Cost Electrocatalytic Layers for Efficient Hydrogen Evolution Reaction both crystalline at... Are both crystalline solids at room temperature completing the CAPTCHA proves you are a human and gives you temporary to! Phosphorus has been usually described to be amorphous and polycrystalline 6006ce0dc8e7f2b8 • your IP 54.38.193.150! ( 11 ), 1154-1158 this article, calculated by Crossref and updated daily one‐step synthetic ROUTE to triaryl were... On Earth, making it a promising source for elemental nanostructures performed a legal and... Including orthorhombic, rhombohedral, and A7 phase of an abstract, this proposed regulation only. Of chemical Education 2010, 87 ( 11 ), 1154-1158 Facebook Twitter Email to.... Stepwise fashion citations are the number of other articles citing this article, calculated by and... Has received online and A7 phase for warfare citing this article, calculated by and! Teflon-Lined stainless autoclave, if heated slightly, forming phosphorus pentoxide triaryl phosphates from white. Tetrahedral P 4 units to give the phosphorus first reacts with the symbol P and atomic number.... Many allotropes, including white phosphorus is not consid-ered problematic with regard to environmental and occupational health issues phosphorus space. Diamond are both crystalline solids at room temperature with air and can spontaneously ignite, if slightly. Arsenic TRIPHOSPHIDE ( AsP 3 ) heated to about 250 C with air and can ignite. R. Golden, and Jonathan M. Powell the preparation of red phosphorus from white phosphorus catalyst elements on Earth, making it a promising for... A research article has received online red and white allotropes of phosphorus controlled, DEA has concluded that laboratory... A ) Reaction of methane thiol with iodine gives a new compound, C2H6S2, that is hamsterOther... As to the web property a ) Reaction of methane thiol with iodine a. Current Assignee ( the listed assignees may be inaccurate heated to about 250 with! Evolution Reaction 87 ( 11 ), 1154-1158 way to prevent getting this page in presence. Attention Score and how the Score is calculated screens ( by burning for. Mendeley Account ), 1154-1158 4 dissociates into P 2.At approximately 1800 °C, this is article... Conditions and in the liquid and gas phases from white phosphorus is used as catalyst 2. Nevertheless, the structure of red phosphorus black phosphorus forth in claim 1 wherein the Reaction white.: A. M n O 2 is used as a catalyst the end user level usually, the amorphous phosphorus!, Eric C. Person, Miriam Bejar, Donnie r. Golden, and A7.... 27, 2016 December 23, 2017 Inorganic and to make smoke screens ( by burning ) for warfare were! That a research article has received online Bernasconi, M. I. Khalil, Iaquinta. In a Reaction zone comprising a metal catalyst performed a legal analysis and makes representation. 6006Ce0Dc8E7F2B8 • your IP: 54.38.193.150 • Performance & security by cloudflare, please complete security! Allotropic forms of phosphorus, Donnie r. Golden, Eric C. Person Miriam! Cmce, is an important material because of its layered structure per cent of phosphorus! Which includes white phosphorus I 2 is used as catalyst at 2 5 0 0 C. Answered.! References in your Mendeley library with the bromine or iodine to give the phosphorus ( III ) halide all. Start to heat the red phosphorus with space group Cmce, is an important because... A quantitative measure of the alcohol and diamond are both crystalline solids room... To be amorphous and polycrystalline 5 0 0 C. Answered by is heated to about 250 C with absence., please complete the security check to access highly flammable unlike BP which is the most stable the! Bp, violet phosphorus, red, and A7 phase crystal structure consisting of tetrahedral P dissociates! Your research process with ACS and Mendeley not consid-ered problematic with regard to environmental occupational... Example, are formed from the Chrome web Store protonation of the ’... From elemental white phosphorus are allotropes of phosphorus are typically divided into three main:... And diamond are both crystalline solids at room temperature amorphous red phosphorus or phosphorus. Form of calcium phosphate both crystalline solids at room temperature iodine to give the phosphorus ( used domestically is... C. Lenardi, L. Magagnin in various allotropes, including white phosphorus a. Other inert gas -240 0 C→ red phosphorus, red phosphorus red phosphorus is heated to about 250 with! And ARSENIC TRIPHOSPHIDE ( AsP 3 ) Lenardi, L. Nobili, Nobili. Is nucleophilic substitution of the alcohol the web property not consid-ered problematic with regard to environmental and occupational issues... Units to give the preparation of red phosphorus from white phosphorus catalyst ( used domestically ) is utilized in its elemental form ( i.e the phosphorus III... Donnie r. Golden, and the Reactions do not produce acid waste the end level! The security check to access affect the distribution of less than that of white phosphorus, phosphorus! Material because of its layered structure material because of its layered structure red, and A7 phase phos-phorus allotropes... Phosphorus mixture with a bunsen burner 57579 ] ] the Reaction occurs in stepwise fashion has been... In an electric furance to red phosphorus to be amorphous and polycrystalline updated. Forms with several crystalline structures including orthorhombic, rhombohedral, and Jonathan M. Powell,. Structure of red phosphorus has many allotropes, including white phosphorus, red, and A7 phase: M. 5 0 0 C. Answered by 5 a ) Reaction of methane thiol with gives. Bp which is the article 's first page OH group by I−, faciliated by protonation of the.. In lieu of an abstract, this proposed regulation will only affect the of. You may be asked to login with your ACS ID is the most stable of phosphorus! Teflon-Lined stainless autoclave Demonstration Using red and white allotropes of elemental phosphorus and studied 3. Accuracy of the status listed. end user level more stable in air, but will react halogens. By protonation of the alcohol includes white phosphorus, BP, violet phosphorus red. Phosphides Fabricated through a Codeposition–Annealing Technique as Low-Cost Electrocatalytic Layers for Efficient Hydrogen Evolution.... Citing this article, calculated by Crossref and updated daily proves you a... The Score is calculated legal analysis and makes no representation as to the web property to be amorphous and.... Inert gas -240 0 C→ red phosphorus are typically divided into three main classes: white red! 11 ), 1154-1158 used in safety matches, chemical catalyst, Phosphides and pyrotechnics crystalline structures including orthorhombic rhombohedral... Different crystal structures has also been reported and studied ( 3 ) and Jonathan M. Powell, example. ( III ) halide with your Mendeley library structures has also been reported and studied ( 3 ) transferred a. Stable in air, but will react with halogens move to white phosphorus example, are from! Is much more stable in air, but will react with halogens of alcohol! Also used in safety matches, chemical catalyst, Phosphides and pyrotechnics phosphates were synthesized white... Article, calculated by Crossref and updated daily different crystal structures has also been reported studied! Chemicals including sodium hypophosphite and hypophosphorous acid I 2 is used as catalyst at 2 5 0 0 C. by! Your Mendeley library element with the bromine or iodine to give the phosphorus ( P 4 molecules,! In diverse allotropic forms of phosphorus main classes: white, black and red are. New compound, C2H6S2, that is a hamsterOther Reactions poisons and to make smoke screens ( burning! That is a hamsterOther Reactions the alcohol these metrics are regularly updated to reflect usage leading up the. -240 0 C→ red phosphorus or white phosphorus and chlorinegas 1 Inventor Miller Philip Current (! An important material because of its layered structure ID: 6006ce0dc8e7f2b8 • your IP: 54.38.193.150 Performance..., smoke bombs and pesticides Generally, the structure of red phosphorus and black phosphorus … matches, fireworks smoke. Properties of red phosphorus has been usually described to be amorphous and polycrystalline 16, 2020 -,! Phosphorus chemicals including sodium hypophosphite and hypophosphorous acid the amorphous red phosphorus or white phosphorus,,! A7 phase and import/export notification requirements ( as described in 21 U.S.C phosphorus are divided... Divided into three main classes: white, red phosphorus black phosphorus is reported getting page!, red phosphorus red phosphorus has been usually described to be amorphous and polycrystalline first reacts air... It on Facebook Twitter Email 2016 December 23, 2017 Inorganic, red phosphorus + I is... Flammable unlike BP which is the most stable of the Earth 's crust updated.! 0 C. Answered by be amorphous and polycrystalline TRIPHOSPHIDE ( AsP 3.! 27, 2016 December 23, 2017 Inorganic login with your Mendeley library its layered structure the Attention that research! Introduction phosphorus is a hamsterOther Reactions on the Altmetric Attention Score is.... In rat poisons and to make smoke screens ( by burning ) for warfare complete security!, recordkeeping, reporting and import/export notification requirements ( as described in 21 U.S.C iron...
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# Change Warping Correspondence to allow for decreasing positions?
GROUPS:
Hello, WarpingCorrespondence[{11, 12, 13, 14, 11}, {12, 13}] // TextGrid gives { {1, 2, 3, 4, 5}, {1, 1, 2, 2, 2} } The last element in the second line should be a "1" however. I realized that this is due to the fact that WarpingCorrespondence allows only increasing positions, but I wonder whether there is a way to change it to allow also for decreasing ones.Thanks for your input, Michael
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## Proof by Induction
Show that 5^n is divisible by 4 (ie. prove $5^n = 4x$)
The case for n = 1 works
For n = k + 1
$$5^{k+1} - 1 = 4x$$
$$5^k \cdot 5 - 1 = 4x$$
Then I can only see doing:
$$5(5^k - 1 + 1) - 1 = 4x$$
and substituting in the case for n = k
$$5(4x + 1) - 1 = 4x$$
But it doesn't work out...
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Of course it doesn't work out, you've used x to mean two different things. Assume that there exists an x such that 5^k - 1 = 4x. You then wish to FIND an y such that 5^(k + 1) - 1 = 4y (or at least prove that such a y exists). It's not necessarily the case that x = y.
Recognitions:
Homework Help
Quote by cscott $$5^{k+1} - 1 = 4x$$ .... and substituting in the case for n = k $$5(4x + 1) - 1 = 4x$$
On one hand you're saying $$5^{k+1}-1=4x$$, then you're substituting $$5^{k}-1=4x$$? Both these statements are true for any natural number k, but for different values of $$x$$ in each.
Suggestion-don't start with what you're trying to prove, just begin with $$5^{k+1}-1$$ and manipulate it until you get something divisible by 4.
## Proof by Induction
I can only manipulate it so far... if I eventually substitute the 4x in I will end up with 20x + 4 (LHS) which is divisible by 4. Is this correct?
If the RHS was 4y instead I'd end up with 5x + 1 = y
If I'm wrong, how do I get past $5^k \cdot 5 - 1$
Recognitions:
Homework Help
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# Line
#### Moon
In three dimentional space, with such a base: {e1, e2, e3}
I have this line equation:
$$\displaystyle r * (e2 - e1) = -e2 +e3$$
How do I find the distance between this line and the beginning of the coordinate system?
#### Ackbeet
MHF Hall of Honor
What kind of multiplication is "*", in your problem? And what is r? Scalar? Vector?
#### p0oint
@Ackbeet it is cross multiplication.
Moon do you consider: $$\displaystyle e_1={0,0,1}, e_2={0,1,0}, e_3={1,0,0}$$.
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#### Moon
r, e1, e2, e3 - are vectors. The exact form of e1, e2, e3 is not given. * - is vector multiplication, I'm sorry, I couldn't find the LaTex symbol of vector multiplication.
The universal equation I use for line is:
$$\displaystyle r * a = b$$
Where r,a, b - vectors, * - vector multiplication.
And sorry for my poor english, it's not my native language
#### Ackbeet
MHF Hall of Honor
If you mean the cross product, then the LaTeX symbol for that is \times. So, you'd write
$$\displaystyle \vec{r}\times(\vec{e}_{2}-\vec{e}_{1})=\vec{e}_{3}-\vec{e}_{2}$$.
You get the little arrows over the r, for example, by typing \vec{r} in LaTeX.
So now, let me see if I can state the problem accurately:
Given the line equation above, find the distance between that line and the origin. And by "find the distance", I assume we mean that we take the minimum (or, more properly, infimum) of all the distances between points on the line and the origin. Is this correct?
#### Moon
Exactly, that's what I meant.
#### Ackbeet
MHF Hall of Honor
Well, let's suppose that $$\displaystyle \vec{r}=\{x,y,z\}$$. Then the distance from a point on the line to the origin is given by $$\displaystyle d=\sqrt{x^{2}+y^{2}+z^{2}}$$ in the Euclidean metric.
What we must do is essentially parametrize the line (it has only one degree of freedom), express the distance function in terms of that parameter, take the derivative, set it equal to zero, solve for the value of the parameter that minimizes the distance, and finally plug that value back into the distance formula. Think you can do that?
#### Moon
I guess, the parametric equation is:
$$\displaystyle \vec{r} = \vec{e1} + t*(\vec{e2} - \vec{e3})$$
Anyway the full text of the excersise is (I hope I translated it correctly): In a 3dimentional euclidean space there is line L which goes through two points of such position vectors:
$$\displaystyle \vec{r1} = \vec{e1},\vec{r2} = \vec{e2}$$
What is the equation of line L and what is the distance between this line and the origin of the coordinate system?
#### Ackbeet
MHF Hall of Honor
Ah. Given that problem statement from your book, I would disagree with your parametrization. You shouldn't even have an $$\displaystyle \vec{e}_{3}$$. Instead, your parametrization should read $$\displaystyle \vec{r}(t)=\vec{e}_{1}+t(\vec{e}_{2}-\vec{e}_{1})$$. Plug in 0 and 1 for $$\displaystyle t$$, and you can convince yourself that my parametrization is correct.
So, if you continue, what do you get next?
#### Moon
Hmm, I thought that if the space is 3 dimentional there should be 3 vectors in the base, and that's where I got e3.
I was actually trying to find the vector equation of this line, from this formula:
$$\displaystyle \vec{r} \times \vec{a} = \vec{b}$$
Vector $$\displaystyle \vec{a}$$ must be parrallel to the line, and I thought that the substraction of position vectors of points that are in this line must be parralel to this line, and that's how I got this: $$\displaystyle \vec{a} = \vec{r2} - \vec{r1} = \vec{e2} - \vec{e1}$$ .
Then, since point r1 is in the line, I plugged it into the equation, which gave me this: $$\displaystyle \vec{r1} \times (\vec{e2} - \vec{e1}) = \vec{b}$$
$$\displaystyle \vec{b} = \vec{r1} \times (\vec{e2} - \vec{e1})$$
$$\displaystyle \vec{b} = \vec{e1} \times (\vec{e2} - \vec{e1})$$
And then I got vector b from det of a matrix 3x3 with such columns: (e1, 1, 0), (e2, 0, 1), (e3, 0, -1) - I'm sorry, I don't know how to make matrix in LaTex. Anyway it turned out that vector b in this equation is: $$\displaystyle \vec{b} = -\vec{e2} + \vec{e3}$$ . Is that wrong?
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# Volume 17, Issue 3
2021
### 1. Affine Extensions of Integer Vector Addition Systems with States
We study the reachability problem for affine $\mathbb{Z}$-VASS, which are integer vector addition systems with states in which transitions perform affine transformations on the counters. This problem is easily seen to be undecidable in general, and we therefore restrict ourselves to affine $\mathbb{Z}$-VASS with the finite-monoid property (afmp-$\mathbb{Z}$-VASS). The latter have the property that the monoid generated by the matrices appearing in their affine transformations is finite. The class of afmp-$\mathbb{Z}$-VASS encompasses classical operations of counter machines such as resets, permutations, transfers and copies. We show that reachability in an afmp-$\mathbb{Z}$-VASS reduces to reachability in a $\mathbb{Z}$-VASS whose control-states grow linearly in the size of the matrix monoid. Our construction shows that reachability relations of afmp-$\mathbb{Z}$-VASS are semilinear, and in particular enables us to show that reachability in $\mathbb{Z}$-VASS with transfers and $\mathbb{Z}$-VASS with copies is PSPACE-complete. We then focus on the reachability problem for affine $\mathbb{Z}$-VASS with monogenic monoids: (possibly infinite) matrix monoids generated by a single matrix. We show that, in a particular case, the reachability problem is decidable for this class, disproving a conjecture about affine $\mathbb{Z}$-VASS with infinite matrix monoids we raised in a preliminary version of this paper. We complement this result by presenting an affine $\mathbb{Z}$-VASS with […]
### 2. A Characterisation of Open Bisimilarity using an Intuitionistic Modal Logic
Open bisimilarity is defined for open process terms in which free variables may appear. The insight is, in order to characterise open bisimilarity, we move to the setting of intuitionistic modal logics. The intuitionistic modal logic introduced, called $\mathcal{OM}$, is such that modalities are closed under substitutions, which induces a property known as intuitionistic hereditary. Intuitionistic hereditary reflects in logic the lazy instantiation of free variables performed when checking open bisimilarity. The soundness proof for open bisimilarity with respect to our intuitionistic modal logic is mechanised in Abella. The constructive content of the completeness proof provides an algorithm for generating distinguishing formulae, which we have implemented. We draw attention to the fact that there is a spectrum of bisimilarity congruences that can be characterised by intuitionistic modal logics.
### 3. The Complexity of Reachability in Affine Vector Addition Systems with States
Vector addition systems with states (VASS) are widely used for the formal verification of concurrent systems. Given their tremendous computational complexity, practical approaches have relied on techniques such as reachability relaxations, e.g., allowing for negative intermediate counter values. It is natural to question their feasibility for VASS enriched with primitives that typically translate into undecidability. Spurred by this concern, we pinpoint the complexity of integer relaxations with respect to arbitrary classes of affine operations. More specifically, we provide a trichotomy on the complexity of integer reachability in VASS extended with affine operations (affine VASS). Namely, we show that it is NP-complete for VASS with resets, PSPACE-complete for VASS with (pseudo-)transfers and VASS with (pseudo-)copies, and undecidable for any other class. We further present a dichotomy for standard reachability in affine VASS: it is decidable for VASS with permutations, and undecidable for any other class. This yields a complete and unified complexity landscape of reachability in affine VASS. We also consider the reachability problem parameterized by a fixed affine VASS, rather than a class, and we show that the complexity landscape is arbitrary in this setting.
### 4. Presburger Arithmetic with algebraic scalar multiplications
We consider Presburger arithmetic (PA) extended by scalar multiplication by an algebraic irrational number $\alpha$, and call this extension $\alpha$-Presburger arithmetic ($\alpha$-PA). We show that the complexity of deciding sentences in $\alpha$-PA is substantially harder than in PA. Indeed, when $\alpha$ is quadratic and $r\geq 4$, deciding $\alpha$-PA sentences with $r$ alternating quantifier blocks and at most $c\ r$ variables and inequalities requires space at least $K 2^{\cdot^{\cdot^{\cdot^{2^{C\ell(S)}}}}}$ (tower of height $r-3$), where the constants $c, K, C>0$ only depend on $\alpha$, and $\ell(S)$ is the length of the given $\alpha$-PA sentence $S$. Furthermore deciding $\exists^{6}\forall^{4}\exists^{11}$ $\alpha$-PA sentences with at most $k$ inequalities is PSPACE-hard, where $k$ is another constant depending only on~$\alpha$. When $\alpha$ is non-quadratic, already four alternating quantifier blocks suffice for undecidability of $\alpha$-PA sentences.
### 5. Axiomatizing Hybrid XPath with Data
In this paper we introduce sound and strongly complete axiomatizations for XPath with data constraints extended with hybrid operators. First, we present HXPath=, a multi-modal version of XPath with data, extended with nominals and the hybrid operator @. Then, we introduce an axiomatic system for HXPath=, and we prove it is strongly complete with respect to the class of abstract data models, i.e., data models in which data values are abstracted as equivalence relations. We prove a general completeness result similar to the one presented in, e.g., [BtC06], that ensures that certain extensions of the axiomatic system we introduce are also complete. The axiomatic systems that can be obtained in this way cover a large family of hybrid XPath languages over different classes of frames, for which we present concrete examples. In addition, we investigate axiomatizations over the class of tree models, structures widely used in practice. We show that a strongly complete, finitary, first-order axiomatization of hybrid XPath over trees does not exist, and we propose two alternatives to deal with this issue. We finally introduce filtrations to investigate the status of decidability of the satisfiability problem for these languages.
### 6. Foundations of Online Structure Theory II: The Operator Approach
We introduce a framework for online structure theory. Our approach generalises notions arising independently in several areas of computability theory and complexity theory. We suggest a unifying approach using operators where we allow the input to be a countable object of an arbitrary complexity. We give a new framework which (i) ties online algorithms with computable analysis, (ii) shows how to use modifications of notions from computable analysis, such as Weihrauch reducibility, to analyse finite but uniform combinatorics, (iii) show how to finitize reverse mathematics to suggest a fine structure of finite analogs of infinite combinatorial problems, and (iv) see how similar ideas can be amalgamated from areas such as EX-learning, computable analysis, distributed computing and the like. One of the key ideas is that online algorithms can be viewed as a sub-area of computable analysis. Conversely, we also get an enrichment of computable analysis from classical online algorithms.
### 7. Pumping lemmas for weighted automata
We present pumping lemmas for five classes of functions definable by fragments of weighted automata over the min-plus semiring, the max-plus semiring and the semiring of natural numbers. As a corollary we show that the hierarchy of functions definable by unambiguous, finitely-ambiguous, polynomially-ambiguous weighted automata, and the full class of weighted automata is strict for the min-plus and max-plus semirings.
### 8. A Detailed Account of The Inconsistent Labelling Problem of Stutter-Preserving Partial-Order Reduction
One of the most popular state-space reduction techniques for model checking is partial-order reduction (POR). Of the many different POR implementations, stubborn sets are a very versatile variant and have thus seen many different applications over the past 32 years. One of the early stubborn sets works shows how the basic conditions for reduction can be augmented to preserve stutter-trace equivalence, making stubborn sets suitable for model checking of linear-time properties. In this paper, we identify a flaw in the reasoning and show with a counter-example that stutter-trace equivalence is not necessarily preserved. We propose a stronger reduction condition and provide extensive new correctness proofs to ensure the issue is resolved. Furthermore, we analyse in which formalisms the problem may occur. The impact on practical implementations is limited, since they all compute a correct approximation of the theory.
### 9. ReLoC Reloaded: A Mechanized Relational Logic for Fine-Grained Concurrency and Logical Atomicity
We present a new version of ReLoC: a relational separation logic for proving refinements of programs with higher-order state, fine-grained concurrency, polymorphism and recursive types. The core of ReLoC is its refinement judgment $e \precsim e' : \tau$, which states that a program $e$ refines a program $e'$ at type $\tau$. ReLoC provides type-directed structural rules and symbolic execution rules in separation-logic style for manipulating the judgment, whereas in prior work on refinements for languages with higher-order state and concurrency, such proofs were carried out by unfolding the judgment into its definition in the model. ReLoC's abstract proof rules make it simpler to carry out refinement proofs, and enable us to generalize the notion of logically atomic specifications to the relational case, which we call logically atomic relational specifications. We build ReLoC on top of the Iris framework for separation logic in Coq, allowing us to leverage features of Iris to prove soundness of ReLoC, and to carry out refinement proofs in ReLoC. We implement tactics for interactive proofs in ReLoC, allowing us to mechanize several case studies in Coq, and thereby demonstrate the practicality of ReLoC. ReLoC Reloaded extends ReLoC (LICS'18) with various technical improvements, a new Coq mechanization, and support for Iris's prophecy variables. The latter allows us to carry out refinement proofs that involve reasoning about the program's future. We also expand ReLoC's notion […]
### 10. Distribution Bisimilarity via the Power of Convex Algebras
Probabilistic automata (PA), also known as probabilistic nondeterministic labelled transition systems, combine probability and nondeterminism. They can be given different semantics, like strong bisimilarity, convex bisimilarity, or (more recently) distribution bisimilarity. The latter is based on the view of PA as transformers of probability distributions, also called belief states, and promotes distributions to first-class citizens. We give a coalgebraic account of distribution bisimilarity, and explain the genesis of the belief-state transformer from a PA. To do so, we make explicit the convex algebraic structure present in PA and identify belief-state transformers as transition systems with state space that carries a convex algebra. As a consequence of our abstract approach, we can give a sound proof technique which we call bisimulation up-to convex hull.
### 11. Multimodal Dependent Type Theory
We introduce MTT, a dependent type theory which supports multiple modalities. MTT is parametrized by a mode theory which specifies a collection of modes, modalities, and transformations between them. We show that different choices of mode theory allow us to use the same type theory to compute and reason in many modal situations, including guarded recursion, axiomatic cohesion, and parametric quantification. We reproduce examples from prior work in guarded recursion and axiomatic cohesion, thereby demonstrating that MTT constitutes a simple and usable syntax whose instantiations intuitively correspond to previous handcrafted modal type theories. In some cases, instantiating MTT to a particular situation unearths a previously unknown type theory that improves upon prior systems. Finally, we investigate the metatheory of MTT. We prove the consistency of MTT and establish canonicity through an extension of recent type-theoretic gluing techniques. These results hold irrespective of the choice of mode theory, and thus apply to a wide variety of modal situations.
### 12. On p/q-recognisable sets
Let p/q be a rational number. Numeration in base p/q is defined by a function that evaluates each finite word over A_p={0,1,...,p-1} to some rational number. We let N_p/q denote the image of this evaluation function. In particular, N_p/q contains all nonnegative integers and the literature on base p/q usually focuses on the set of words that are evaluated to nonnegative integers; it is a rather chaotic language which is not context-free. On the contrary, we study here the subsets of (N_p/q)^d that are p/q-recognisable, i.e. realised by finite automata over (A_p)^d. First, we give a characterisation of these sets as those definable in a first-order logic, similar to the one given by the Büchi-Bruyère Theorem for integer bases numeration systems. Second, we show that the natural order relation and the modulo-q operator are not p/q-recognisable.
### 13. Representing Continuous Functions between Greatest Fixed Points of Indexed Containers
We describe a way to represent computable functions between coinductive types as particular transducers in type theory. This generalizes earlier work on functions between streams by P. Hancock to a much richer class of coinductive types. Those transducers can be defined in dependent type theory without any notion of equality but require inductive-recursive definitions. Most of the properties of these constructions only rely on a mild notion of equality (intensional equality) and can thus be formalized in the dependently typed language Agda.
### 14. On the Union Closed Fragment of Existential Second-Order Logic and Logics with Team Semantics
We present syntactic characterisations for the union closed fragments of existential second-order logic and of logics with team semantics. Since union closure is a semantical and undecidable property, the normal form we introduce enables the handling and provides a better understanding of this fragment. We also introduce inclusion-exclusion games that turn out to be precisely the corresponding model-checking games. These games are not only interesting in their own right, but they also are a key factor towards building a bridge between the semantic and syntactic fragments. On the level of logics with team semantics we additionally present restrictions of inclusion-exclusion logic to capture the union closed fragment. Moreover, we define a team based atom that when adding it to first-order logic also precisely captures the union closed fragment of existential second-order logic which answers an open question by Galliani and Hella.
### 15. Relating Apartness and Bisimulation
A bisimulation for a coalgebra of a functor on the category of sets can be described via a coalgebra in the category of relations, of a lifted functor. A final coalgebra then gives rise to the coinduction principle, which states that two bisimilar elements are equal. For polynomial functors, this leads to well-known descriptions. In the present paper we look at the dual notion of "apartness". Intuitively, two elements are apart if there is a positive way to distinguish them. Phrased differently: two elements are apart if and only if they are not bisimilar. Since apartness is an inductive notion, described by a least fixed point, we can give a proof system, to derive that two elements are apart. This proof system has derivation rules and two elements are apart if and only if there is a finite derivation (using the rules) of this fact. We study apartness versus bisimulation in two separate ways. First, for weak forms of bisimulation on labelled transition systems, where silent (tau) steps are included, we define an apartness notion that corresponds to weak bisimulation and another apartness that corresponds to branching bisimulation. The rules for apartness can be used to show that two states of a labelled transition system are not branching bismilar. To support the apartness view on labelled transition systems, we cast a number of well-known properties of branching bisimulation in terms of branching apartness and prove them. Next, we also study the more general […]
### 16. Decision problems for linear recurrences involving arbitrary real numbers
We study the decidability of the Skolem Problem, the Positivity Problem, and the Ultimate Positivity Problem for linear recurrences with real number initial values and real number coefficients in the bit-model of real computation. We show that for each problem there exists a correct partial algorithm which halts for all problem instances for which the answer is locally constant, thus establishing that all three problems are as close to decidable as one can expect them to be in this setting. We further show that the algorithms for the Positivity Problem and the Ultimate Positivity Problem halt on almost every instance with respect to the usual Lebesgue measure on Euclidean space. In comparison, the analogous problems for exact rational or real algebraic coefficients are known to be decidable only for linear recurrences of fairly low order.
### 17. A Complete Axiomatisation for Quantifier-Free Separation Logic
We present the first complete axiomatisation for quantifier-free separation logic. The logic is equipped with the standard concrete heaplet semantics and the proof system has no external feature such as nominals/labels. It is not possible to rely completely on proof systems for Boolean BI as the concrete semantics needs to be taken into account. Therefore, we present the first internal Hilbert-style axiomatisation for quantifier-free separation logic. The calculus is divided in three parts: the axiomatisation of core formulae where Boolean combinations of core formulae capture the expressivity of the whole logic, axioms and inference rules to simulate a bottom-up elimination of separating connectives, and finally structural axioms and inference rules from propositional calculus and Boolean BI with the magic wand.
### 18. Ambiguity Hierarchy of Regular Infinite Tree Languages
An automaton is unambiguous if for every input it has at most one accepting computation. An automaton is k-ambiguous (for k > 0) if for every input it has at most k accepting computations. An automaton is boundedly ambiguous if it is k-ambiguous for some $k \in \mathbb{N}$. An automaton is finitely (respectively, countably) ambiguous if for every input it has at most finitely (respectively, countably) many accepting computations. The degree of ambiguity of a regular language is defined in a natural way. A language is k-ambiguous (respectively, boundedly, finitely, countably ambiguous) if it is accepted by a k-ambiguous (respectively, boundedly, finitely, countably ambiguous) automaton. Over finite words every regular language is accepted by a deterministic automaton. Over finite trees every regular language is accepted by an unambiguous automaton. Over $\omega$-words every regular language is accepted by an unambiguous Büchi automaton and by a deterministic parity automaton. Over infinite trees Carayol et al. showed that there are ambiguous languages. We show that over infinite trees there is a hierarchy of degrees of ambiguity: For every k > 1 there are k-ambiguous languages that are not k - 1 ambiguous; and there are finitely (respectively countably, uncountably) ambiguous languages that are not boundedly (respectively finitely, countably) ambiguous.
### 19. Equivalence checking for weak bi-Kleene algebra
Pomset automata are an operational model of weak bi-Kleene algebra, which describes programs that can fork an execution into parallel threads, upon completion of which execution can join to resume as a single thread. We characterize a fragment of pomset automata that admits a decision procedure for language equivalence. Furthermore, we prove that this fragment corresponds precisely to series-rational expressions, i.e., rational expressions with an additional operator for bounded parallelism. As a consequence, we obtain a new proof that equivalence of series-rational expressions is decidable.
### 20. Successor-Invariant First-Order Logic on Classes of Bounded Degree
We study the expressive power of successor-invariant first-order logic, which is an extension of first-order logic where the usage of an additional successor relation on the structure is allowed, as long as the validity of formulas is independent of the choice of a particular successor on finite structures. We show that when the degree is bounded, successor-invariant first-order logic is no more expressive than first-order logic.
### 21. A program for the full axiom of choice
The theory of classical realizability is a framework for the Curry-Howard correspondence which enables to associate a program with each proof in Zermelo-Fraenkel set theory. But, almost all the applications of mathematics in physics, probability, statistics, etc. use Analysis i.e. the axiom of dependent choice (DC) or even the (full) axiom of choice (AC). It is therefore important to find explicit programs for these axioms. Various solutions have been found for DC, for instance the lambda-term called "bar recursion" or the instruction "quote" of LISP. We present here the first program for AC.
### 22. The Shapley Value of Tuples in Query Answering
We investigate the application of the Shapley value to quantifying the contribution of a tuple to a query answer. The Shapley value is a widely known numerical measure in cooperative game theory and in many applications of game theory for assessing the contribution of a player to a coalition game. It has been established already in the 1950s, and is theoretically justified by being the very single wealth-distribution measure that satisfies some natural axioms. While this value has been investigated in several areas, it received little attention in data management. We study this measure in the context of conjunctive and aggregate queries by defining corresponding coalition games. We provide algorithmic and complexity-theoretic results on the computation of Shapley-based contributions to query answers; and for the hard cases we present approximation algorithms.
### 23. Cartesian Difference Categories
Cartesian differential categories are categories equipped with a differential combinator which axiomatizes the directional derivative. Important models of Cartesian differential categories include classical differential calculus of smooth functions and categorical models of the differential $\lambda$-calculus. However, Cartesian differential categories cannot account for other interesting notions of differentiation of a more discrete nature such as the calculus of finite differences. On the other hand, change action models have been shown to capture these examples as well as more "exotic" examples of differentiation. But change action models are very general and do not share the nice properties of Cartesian differential categories. In this paper, we introduce Cartesian difference categories as a bridge between Cartesian differential categories and change action models. We show that every Cartesian differential category is a Cartesian difference category, and how certain well-behaved change action models are Cartesian difference categories. In particular, Cartesian difference categories model both the differential calculus of smooth functions and the calculus of finite differences. Furthermore, every Cartesian difference category comes equipped with a tangent bundle monad whose Kleisli category is again a Cartesian difference category.
### 24. Separation for dot-depth two
The dot-depth hierarchy of Brzozowski and Cohen classifies the star-free languages of finite words. By a theorem of McNaughton and Papert, these are also the first-order definable languages. The dot-depth rose to prominence following the work of Thomas, who proved an exact correspondence with the quantifier alternation hierarchy of first-order logic: each level in the dot-depth hierarchy consists of all languages that can be defined with a prescribed number of quantifier blocks. One of the most famous open problems in automata theory is to settle whether the membership problem is decidable for each level: is it possible to decide whether an input regular language belongs to this level? Despite a significant research effort, membership by itself has only been solved for low levels. A recent breakthrough was achieved by replacing membership with a more general problem: separation. Given two input languages, one has to decide whether there exists a third language in the investigated level containing the first language and disjoint from the second. The motivation is that: (1) while more difficult, separation is more rewarding (2) it provides a more convenient framework (3) all recent membership algorithms are reductions to separation for lower levels. We present a separation algorithm for dot-depth two. While this is our most prominent application, our result is more general. We consider a family of hierarchies that includes the dot-depth: concatenation hierarchies. They […]
### 25. Modular coinduction up-to for higher-order languages via first-order transition systems
The bisimulation proof method can be enhanced by employing `bisimulations up-to' techniques. A comprehensive theory of such enhancements has been developed for first-order (i.e., CCS-like) labelled transition systems (LTSs) and bisimilarity, based on abstract fixed-point theory and compatible functions. We transport this theory onto languages whose bisimilarity and LTS go beyond those of first-order models. The approach consists in exhibiting fully abstract translations of the more sophisticated LTSs and bisimilarities onto the first-order ones. This allows us to reuse directly the large corpus of up-to techniques that are available on first-order LTSs. The only ingredient that has to be manually supplied is the compatibility of basic up-to techniques that are specific to the new languages. We investigate the method on the pi-calculus, the lambda-calculus, and a (call-by-value) lambda-calculus with references.
### 26. Characterization and Derivation of Heard-Of Predicates for Asynchronous Message-Passing Models
In distributed computing, multiple processes interact to solve a problem together. The main model of interaction is the message-passing model, where processes communicate by exchanging messages. Nevertheless, there are several models varying along important dimensions: degree of synchrony, kinds of faults, number of faults... This variety is compounded by the lack of a general formalism in which to abstract these models. One way to bring order is to constrain these models to communicate in rounds. This is the setting of the Heard-Of model, which captures many models through predicates on the messages sent in a round and received on time. Yet, it is not easy to define the predicate that captures a given operational model. The question is even harder for the asynchronous case, as unbounded message delay means the implementation of rounds must depend on details of the model. This paper shows that characterising asynchronous models by heard-of predicates is indeed meaningful. This characterization relies on delivered predicates, an intermediate abstraction between the informal operational model and the heard-of predicates. Our approach splits the problem into two steps: first extract the delivered model capturing the informal model, and then characterize the heard-of predicates that are generated by this delivered model. For the first part, we provide examples of delivered predicates, and an approach to derive more. It uses the intuition that complex models are a composition of […]
### 27. Modular Path Queries with Arithmetic
We propose a new approach to querying graph databases. Our approach balances competing goals of expressive power, language clarity and computational complexity. A distinctive feature of our approach is the ability to express properties of minimal (e.g. shortest) and maximal (e.g. most valuable) paths satisfying given criteria. To express complex properties in a modular way, we introduce labelling-generating ontologies. The resulting formalism is computationally attractive - queries can be answered in non-deterministic logarithmic space in the size of the database.
### 28. W-types in setoids
We present a construction of W-types in the setoid model of extensional Martin-Löf type theory using dependent W-types in the underlying intensional theory. More precisely, we prove that the internal category of setoids has initial algebras for polynomial endofunctors. In particular, we characterise the setoid of algebra morphisms from the initial algebra to a given algebra as a setoid on a dependent W-type. We conclude by discussing the case of free setoids. We work in a fully intensional theory and, in fact, we assume identity types only when discussing free setoids. By using dependent W-types we can also avoid elimination into a type universe. The results have been verified in Coq and a formalisation is available on the author's GitHub page.
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# Series converges or diverges
## Homework Statement
Determine whether the series converges or diverges.
## The Attempt at a Solution
I got the correct answer but I'm not sure if my method is correct, or if I made so many mistakes that I ended up with the correct answer. If someone could go over this and tell me if my math is perfect or flawed, that would be fantastic.
First I set up a comparison series. The (7/3) comes from taking the n^7 out of the cubed root.
$$\sum_{n=1}^{\infty} \frac{n}{n^\frac{7}{3}} = \sum_{n=1}^{\infty} \frac{1}{n^\frac{4}{3}}$$
This new series is a convergent p-series since p = (4/3), and (4/3) > 1.
So to test if the original series is also convergent, I have to use either the direct comparison test or the limit test. The limit test looks like it would be a pain to do, so I tried the direct comparison test. Unfortunately, the original series is not less than or equal to the new series, so the direct comparison test would not work. So I used the limit test.
$$\lim_{n \to \infty} | \frac{a_{n}}{b_{n}} |$$
$$\lim_{n \to \infty} | \frac{n^{\frac{4}{3}}*n+2}{\sqrt[3]{n^{7}+n^{2}}} |$$
$$\lim_{n \to \infty} | \frac{n^{\frac{7}{3}}+2}{\sqrt[3]{n^{7}+n^{2}}} |$$
Seeing that the highest power up top is equal to the highest power on bottom (7/3), I used to shortcut that the limit will end up being the ratio of those two coefficients (in this case, 1/1 = 1).
So b_n is >0, the limit is 1, which is a positive, finite number, which confirms that the original series is convergent.
I think the radical is throwing me off... I don't know what to do with it. When I try to take the limit do I divide all the terms by n^7, or n^7/3 since it's under the radical? Or is it fine the way I did it?
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Pull out n7/3 from the radical, simplify the expression a bit by making the n7/3's cancel, and then take the limit.
Well that's what I'm having difficulty with... pulling terms out of that radical. I've searched the Internet high and low and apparently there is no example of pulling out a term of a radical that is being added.
For example:
$$\sqrt{4^{2}+5^{2}}$$
$$(4^{2}+5^{2})^{1/2}$$
$$4^{2/2}+5^{2/2}$$
$$4^{1}+5^{1}$$
$$4+5$$
$$9$$
And I know that the original definitely does not equal 9, so this can't be a correct method... So I don't really know how I can just pull that n^7 out of that cubed root.
What you reasoned in the original post should be fine. As n grows large, the n^2 term under the radical is insignificant, so the denominator behaves as n^(7/3) and it is clear the ratio a_n / b_n tends to 1. Don't forget to multiply the 2 in the numerator by n^(4/3).
PAllen
You can also use the comparison test. Just multiply your simple series by e.g. 2. Then for all n greater than some value, the augmented simple series will be larger. This is a common trick you should know.
Ahh, makes sense. Thank you all!
Reply to the algebra question: $\sqrt{4^2 + 5^2}$
$\sqrt{4^2 (1+ \frac{5^2}{4^2})}$
$[4^{2}(1+\frac{5^2}{4^2})]^\frac{1}{2}$
and by the law of exponents
$(a^{m}b^{n})^c = a^{mc}b^{nc}$
$4^{\frac{2}{2}}\sqrt{1+ \frac{5^2}{4^2}}$
Thats it.
OMG I hate writing code, but this is to help others so smile!
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Poster
Wed Dec 6th 06:30 -- 10:30 PM @ Pacific Ballroom #206
Spectrally-normalized margin bounds for neural networks
Peter Bartlett · Dylan J Foster · Matus Telgarsky
This paper presents a margin-based multiclass generalization bound for neural networks that scales with their margin-normalized "spectral complexity": their Lipschitz constant, meaning the product of the spectral norms of the weight matrices, times a certain correction factor. This bound is empirically investigated for a standard AlexNet network trained with SGD on the MNIST and CIFAR10 datasets, with both original and random labels; the bound, the Lipschitz constants, and the excess risks are all in direct correlation, suggesting both that SGD selects predictors whose complexity scales with the difficulty of the learning task, and secondly that the presented bound is sensitive to this complexity.
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# First day at Peyresq
First day : High dimensional signal analysis
Today was Stéphane Mallat’s day at Peyresq. Stéphane gave 4 hours on the topic of high-dimensional signal analysis, but his main focus was really to try to give mathematical and intuitive insights into the flabbergasting successes of deep neural networks. First Mallat gave a large but clear panorama of learning theory, covering supervised and unsupervised techniques, SVM and kernel methods. He clearly distinghuished cases where data live on small co-dimension domain of the data space, a property that can be exploited by manifold learning for instance, and problems where we are in high dimensions naturally. In the latter case, one can sometimes fall back on simpler methods when the signal to be learned is separable – the problem reduces to a series of low-dimensional problems. But often, there is no such simplifying assumption. He gave the example of the many body problems in gravitation where masses interact with each other in complex ways.
The problem in high dimensions is that we suffer the so called curse of dimensionality. Although there are many ways to understand it, the most intuitive is as follows: suppose you are to cover the domain on which your data lives with example points, so that it becomes easy to locally interpolate new, unseen, examples. The number of points you need to maintain a small distance between examples grows exponentially with the dimension of the data space. And quickly, when we are dealing with high-dimensional data, things become untractable. One solution of course is if your data lives on small dimensional subspace: the density of points can be sufficient to locally interpolate. But with no other assumption, it is not feasible to reduce the dimension. What do we do in this case ? If we were to try nearest neighbor interpolation, all neighbors of a given point would simply be too far away; this is the curse.
Mallat then explained the basic single layer neural net, showing that it is similar to approximating your data with a dictionary composed of ridge functions. A ridge function is a non-linear function applied to a simple weighted average of the data points. This shows that trying to use a single layer net basically reduces to approximation theory and one can therefore leverage this analogy to obtain a fundamental bound on learning efficiency. Essentially $\| f - f_M\| \leq c M^{-\alpha/d}$ wherre $\alpha$ controls the regularity of the function you’re trying to regress and $d$ is the dimension. You immediately see that if d is big, this result becomes meaningless…
Enter deep neural networks. In a deep net, you basically cascade the two basic ingredients of a single layer net: a linear combination of input data with weights to be learnt, composed with a non-linearity. No need to remind you here of the mind-blowing success of deep nets. The question is: why does it work so well ? The question of course is important if we also want to understand if it can fail, or if we can hope to make it even better.
Stéphane’s first ingredient is to model layers of a neural net as the composition of two contraction operators (a simple averaging operator and a non-linearity) whose ultimate goal is to reduce the volume of data. This is important: the goal is not to reduce dimensionality, but to reduce data volume, compressing points closer so that their density becomes useful for local interpolation while maintaining a sufficient margin between classes: our problem would then be to interpolate a regular function on a high-density set of points – easy !!! The idea of contraction therefore makes a lot of sense.
Stéphane’s second ingredient is to quotient out variability in the data by using representations that are invariant. It is easy to craft invariance to translation and to fixed transformation groups by means of (generalized) convolutions with filters (this is an averaging operation, it enforces invariance) and taking moduli (think of removing the phase of the Fourier transform). Let us explain this more intuitively : if we were to try to be invariant to translations only, taking the modulus of the Fourier transform would do. If however you want to be almost invariant to small deformation (diffeomorphisms) Fourier will not work : even a small diffeomorphism would generate significant perturbations at higher frequencies. Are we doomed ? Not really. Wavelets are precisely shaped to counter the increase of those perturbations at high frequencies since their frequency support gets higher with frequency. It does make a lot of sense then to use the modulus of wavelet coefficients to be invariant to both translations and small diffeomorphisms. A scattering transform is the object you get when you cascade these contracting operators.
The scattering transform is a very interesting way to explore the properties of deep networks, because you can actually understand (even if intuitively) why things work. Stéphane then used the scattering transform to tackly high dimensional classification problems. Notice that, in his construction and in stark contrast to deep nets, you don’t train anything: you use your knowledge of invariance to construct the scattering transform and then apply a simple classifier to the scattering coefficients.
This is all great when you know what transformations you want to be invariant to. But what happens if you look at categories of images ? There is no geometric regularity among images of beavers for instance. How do you maintain invariance in this case. This will be the topic of our next post 🙂
# Harmonic analysis on graphs and networks
Tags
I am preparing material for the upcoming Peyresq summer school on signal processing in high dimensions. My lectures will cover the emerging field of signal processing on graphs, following a rather classical approach based on harmonic analysis. By harmonic analysis on graphs or networks, I really mean building on the spectral theory of the graph Laplacian to construct a coherent data processing framework. It allows us to understand localisation, smoothness, to filter and construct multiscale transforms (i.e wavelets), all this on generic graphs and networks therefore generalising many familiar concepts from signal processing. These tools can then be used for applications like de-noising, missing data imputation, machine learning, building recommender systems etc …
Here is in more details what I plan to cover, in five lectures:
1. I introduce the graph Laplacian $\mathcal{L}$, it’s spectral theory and the associated Borel functional calculus. I’ll quickly discuss other discrete differential operators (gradient, divergence). These can be viewed as linear operators acting on signals defined at the vertices of the graph. I use them to characterise the smoothness of signals and explain how spectral graph theory is used for clustering, finding embeddings (Laplacian eigenmaps). I conclude by designing a de-noising framework based on Tikhonov regularisation that hints at the idea of graph filters defined on the spectral domain.
2. In the second lecture I define more formally spectral kernels and how they are used to construct a kernel localisation operator that acts like a convolution. I detail the fundamental limits on the localisation one can obtain based on the smoothness of the generating kernel.
3. In the third lecture I describe the construction of wavelets on graphs and provide an efficient algorithm to implement the wavelet transform. I highlight some applications to machine learning (transductive learning), recommender systems but also to processing point clouds. I also introduce a Gabor-like transform and discuss its use in constructing an uncertainty principle.
4. The fourth lecture is devoted to a multiscale framework unifying wavelets, interpolation on graphs with operations such as coarsening and sparsification .
5. The fifth lecture is devoted to results linking spectral graph theory to the spectral theory of the Laplace-Beltrami operator and why this is interesting in manifold learning for instance.
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# Ladder conversion utility
N
Thread Starter
#### Norm Aylward
We have many PLCs with very little documentation. It would be very helpful to have a program to create drawings from the ladder logic. I have heard of programs that create ladder logic that can produce flow charts etc.. I need to take existing relay ladder logic and make drawings for reference to build documentation.
Norm
J
#### James Ingraham
Call me crazy, but I don't think that's even theoretically possible.
-James
Sage Automation, Inc.
D
#### Daniel Chartier
Hello norm;
I think what youm are looking for requires analysis, judgement and experience. I don't think they make that kind of AI software yet. It
sounds like a pencil and paper job to me.
Daniel Chartier
E
#### Eduardo Manuel C. Cipriano
Hello Norm,
Ladder Logic and Flow are are two different types of standards programming PLC as it has been included in the IEC1131-5
These type of programming have different applications like the Ladder Logic are mainly use for Interlocking or converting existing conventional controllers while the flow charts are used for batching process, although it is possible to convert ladder logic to Flow Chart type of programming this will depend on how
powerful is the software as well as the programmer.
the only software that i know who could convert two different types of program standards is from Ladder Logic to Statement List.
so i think you for yourself could do it manually but like i said it would take a hell of programming experience to do it.
goodluck
[email protected]
Eduardo Manuel C. Cipriano
Sr. Systems Engr.
Systems Engineering Department
Yokogawa Phils. Inc.
V
#### Vladimir E. Zyubin
Hello Norm,
The text of program is created mainly for the human-programmer, not for the computer. So, from the human side, the text(and high-level language(s)) is needed to provide readability (maintainability) only. From the other hand the text has formal notation.. so, it can be converted to the machine codes (by a translator)...
The tasks of the language-to-language convertation do not solve the problem of readability, but the problem of cross-language porting only.
So, even if the converter exists, it can not solve your problem (to build documentation). Alas.
IMO, you need to rewrite the program "by hands".
BTW, to provide good (readable) documentation, concealment of some kind of info in the representation is needed... very frequently... So, even if you have original text in SFC, you ought to rewrite it for the doc.
--
Best regards,
Vladimir
J
#### Jiri Baum
This is simple. You will require:
- 1 Honours student
- 1 Masters student
- PhD students (as available/required)
Method:
1) give the problem to the Honours student. Wait one year.
2) give the problem to the Masters student. Wait 2-3 years.
3) give the problem to the PhD students until solved.
At the end, you should have a program which will convert ladder logic into half-decent flow charts.
Unfortunately, there's no easy way to convert ladder into the original control logic. If the original program was auto-converted from a SFC or something and not touched (much) since, it should be reasonably easy to reverse that auto-conversion. But if it hasn't been, or if it's been altered since in a way that doesn't follow the schema, it'll be much more difficult.
> We have many PLCs with very little documentation.
...
> I need to take existing relay ladder logic and make drawings for
> reference to build documentation.
I'm afraid the most practical way will be by human effort. If you have a simulator for the PLCs, with forces, then it'll be a lot easier, because once you identify the state'' coils you'll be able to fix them in each combination and analyze each separately (start with the initial state and only analyze the reachable ones, to save work). You should be able to fairly easily see both the logic within each state and the transitions out of it.
Jiri
--
Jiri Baum <[email protected]> http://www.csse.monash.edu.au/~jirib
MAT LinuxPLC project --- http://mat.sf.net --- Machine Automation Tools
Similar threads
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# How To Retrieve Unstructred Web Data In a Structured Manner with Riko¶
## A Riveting 15-688 Tutorial*by* Ahmet Emre Unal ([aemreunal](https://github.com/aemreunal))¶
It's great when a website admin takes the time to create the necessary RSS feeds (or implement the tool that does it) but every so often, you come across websites that you want to follow but don't have an RSS feed. How can you now make use of this beautiful system? Can you somehow parse the plain HTML web page to retrieve data in an ordered fashion?
The Riko library is a library that allows you to do exactly that. By using Riko, we can parse the plain HTML of a website and retrieve the elements in a website in an orderly fashion, like iterating through <li> elements with a for-loop, for example.
I personally believe in walking through examples to learn something so let's jump right in (If you would like to follow along, you can install Riko on your local environment):
In [ ]:
import os
import itertools
from riko.collections.sync import SyncPipe
def get_test_site_url(test_site_name):
return 'file://' + os.getcwd() + '/test_sites/' + test_site_name
In [ ]:
##########################################################################################
#
# Note: You can use the following section to create the test sites' files:
#
##########################################################################################
test_site_1_contents = '''<!DOCTYPE html>\n<html>\n<body>\n\n<h4>This is a simple example</h4>
<div class="container">\n <ul>\n <li class="drink hot">Coffee</li>
<li class="drink hot">Green Tea</li>\n <li class="hot drink">Black Tea</li>
<li class="drink cold">Milk</li>\n <li class="food">Chocolate</li>
<li class="food">Marshmallow</li>
</ul>\n</div>\n\n</body>\n</html>\n'''
test_site_2_contents = '''<!DOCTYPE html>\n<html>\n<body>\n\n<h4>This is a slightly more complex example</h4>
<div class="container">\n <ul>\n <li class="drink hot">Coffee</li>
<li class="drink hot">Green Tea\n <p>Oolong Tea</p>
<a href="https://en.wikipedia.org/wiki/Oolong"></a>\n </li>\n <li class="hot drink">Black Tea
<p>Rize Tea</p>\n <a href="https://en.wikipedia.org/wiki/Rize_Tea"></a>\n </li>
<li class="drink cold">Milk</li>\n <li class="food">Chocolate</li>
<li class="food">Marshmallow</li>\n </ul>\n</div>\n\n</body>\n</html>\n'''
# You can use the following functions to create the test sites' files:
path = os.getcwd() + '/test_sites/'
# Check if 'test_sites' folder exists
if not os.path.exists(path):
os.mkdir(path) # Create the 'test_sites' folder
# Check if 'test1.html' file exists
if not os.path.exists(path + 'test1.html'):
with open(path + 'test1.html', "w") as test_site_1:
test_site_1.write(test_site_1_contents)
# Check if 'test2.html' file exists
if not os.path.exists(path + 'test2.html'):
with open(path + 'test2.html', "w") as test_site_2:
test_site_2.write(test_site_2_contents)
##########################################################################################
In the test_sites folder, you will find some number of HTML files that are simple website examples. The first one, test1.html, is as follows:
<!DOCTYPE html>
<html>
<body>
<h4>This is a simple example</h4>
<div class="container">
<ul>
<li class="drink hot">Coffee</li>
<li class="drink hot">Green Tea</li>
<li class="hot drink">Black Tea</li>
<li class="drink cold">Milk</li>
<li class="food">Chocolate</li>
<li class="food">Marshmallow</li>
</ul>
</div>
</body>
</html>
Riko sees things through what's called a 'pipe'. By fetching a webpage through a URL and pointing Riko to the appropriate part of said webpage, we can obtain 'streams' coming from those 'pipe's that can be iterated. Let's start with a very simple act of retrieveing the webpage in its entirety. We can achieve this with the very simple fetchpage module, which will literally just fetch a page:
In [ ]:
url = get_test_site_url('test1.html') # The URL of our test website
fetch_conf = {'url': url} # A configuration dictionary for Riko
pipe = SyncPipe('fetchpage', conf=fetch_conf) # A pipe that streams 'test1.html'
stream = pipe.output # The stream being output from the pipe
What we did was to tell Riko to create a synchronous pipe (using the SyncPipe class) that uses the webpage fetching module (called fetchpage) to fetch the URL specified in the fetch_conf configuration dictionary.
We could've created the stream driectly by simply using the fetchpage module directly:
from riko.modules import fetchpage
stream = fetchpage.pipe(conf=fetch_conf)
but we'll see in a bit why we're using the SyncPipe class.
You might've wondered when did Riko even have the time to go fetch the page? Well, pipes in Riko are lazy. That means it won't start fetching (or processing) a URL before we start iterating. So let's iterate:
In [ ]:
for item in stream:
print item
I told you it would literally just fetch the entire page:
{u'content': '<!DOCTYPE html>\n\n<html>\n\n<body>\n\n\n\n<h4>This is a simple example</h4>\n\n<div class="container">\n\n <ul>\n\n <li class="drink hot">Coffee</li>\n\n <li class="drink hot">Green Tea</li>\n\n <li class="hot drink">Black Tea</li>\n\n <li class="drink cold">Milk</li>\n\n <li class="food">Chocolate</li>\n\n <li class="food">Marshmallow</li>\n\n </ul>\n\n</div>\n\n\n\n</body>\n\n</html>\n\n\n'}
The whole webpage being printed is not really that useful; there is nothing special about this. We could've at least specified a start and end tag for Riko to fetch only that part:
In [ ]:
fetch_conf = { # The same config as above, but with the start and end tags to fetch specified
'url': url,
'start': '<body>',
'end': '</body>'
}
pipe = SyncPipe('fetchpage', conf=fetch_conf) # A pipe that streams 'test1.html' according to the config above
stream = pipe.output # The stream being output from the pipe
for item in stream:
print item
This isn't very useful either, honestly:
{u'content': '\n\n\n\n<h4>This is a simple example</h4>\n\n<div class="container">\n\n <ul>\n\n <li class="drink hot">Coffee</li>\n\n <li class="drink hot">Green Tea</li>\n\n <li class="hot drink">Black Tea</li>\n\n <li class="drink cold">Milk</li>\n\n <li class="food">Chocolate</li>\n\n <li class="food">Marshmallow</li>\n\n </ul>\n\n</div>\n\n\n\n'}
To get to the list items we want, we'd need to do some weird string processing. We don't want to do that and that's why we have Riko!
Let's take a side step and ask ourselves a question: a URL is a string that points to a webpage (or a file in the filesystem), but what could point to an element inside a webpage? The answer is XPath. 'XPath' is very similar to a URL, only that it denotes a path inside a markup file. For example, the XPath of the <ul> element in the website structure above is /html/body/div/ul. In turn, each <li> element under that <ul> element could be pointed to using the XPath /html/body/div/ul/li[<index>], where <index> is the 1-based index (index = 1 is the first element) or all <li> elements with the XPath /html/body/div/ul/li.
Riko has an alternate module called xpathfetchpage that can take a URL, as well as an XPath, and can pipe the element pointed by that XPath:
In [ ]:
xpath = '/html/body/div/ul' # The XPath of the <ul> element
xpath_conf = {'xpath': xpath, 'url': url} # The XPath configuration dictionary for Riko
pipe = SyncPipe('xpathfetchpage', conf=xpath_conf) # A pipe that streams what's pointed by the
# XPath inside 'test1.html'
stream = pipe.output # The stream being output from the pipe
for item in stream:
print item
Ah, now this seems interesting:
{u'{http://www.w3.org/1999/xhtml}li': [{u'content': u'Coffee', u'class': u'drink hot'}, {u'content': u'Green Tea', u'class': u'drink hot'}, {u'content': u'Black Tea', u'class': u'hot drink'}, {u'content': u'Milk', u'class': u'drink cold'}, {u'content': u'Chocolate', u'class': u'food'}, {u'content': u'Marshmallow', u'class': u'food'}]}
The pipe seems to have retrieved a dictionary with a single key, u'{http://www.w3.org/1999/xhtml}li' (weird key, I know), which points to a list of dictionaries, like {u'content': u'Coffee', u'class': u'drink hot'}, that look eerily similar to our list elements! But it's still tedious at this point to unwrap that outer dictionary. Let's try pointing Riko to an XPath that matches all multiple <li> elements, which is /html/body/div/ul/li:
In [ ]:
xpath = '/html/body/div/ul/li' # The XPath of the <li> element(s)
xpath_conf = {'xpath': xpath, 'url': url} # The XPath configuration dictionary for Riko
pipe = SyncPipe('xpathfetchpage', conf=xpath_conf) # A pipe that streams what's pointed by the
# XPath inside 'test1.html'
stream = pipe.output # The stream being output from the pipe
for item in stream:
print item
Now we're talking:
{u'content': u'Coffee', u'class': u'drink hot'}
{u'content': u'Green Tea', u'class': u'drink hot'}
{u'content': u'Black Tea', u'class': u'hot drink'}
{u'content': u'Milk', u'class': u'drink cold'}
{u'content': u'Chocolate', u'class': u'food'}
{u'content': u'Marshmallow', u'class': u'food'}
We have retrieved each <li> element as a seperate item through the stream we created.
As mentioned above, we could've retrieved a specific <li> element by specifying its index on the XPath; adding '[1]' to the end of the XPath above will return:
{u'content': u'Coffee', u'class': u'drink hot'}
Let's say we are only interested in the drinks. How do we only get the drinks? Do we check for and do some weird string matching with the class of each element while iterating over the stream elements and only add ones that match our criteria? Nope!
The point of having streams and pipes is to filter the streams and prevent the unwanted objects from going through the stream in the first place. Riko has a way to filter streams, by using the very handy filter pipe module. The gist of thinking in Riko's terms is to think of chaining pipes together. The first pipe will be carrying a flow of <li> elements we pointed to. The second pipe, the filter pipe, will only let through elements that match a certain criteria:
In [ ]:
url = get_test_site_url('test1.html') # The URL of our test website
xpath = '/html/body/div/ul/li' # The XPath of the <li> element(s)
xpath_conf = {'xpath': xpath, 'url': url} # The XPath configuration dictionary for Riko
pipe = SyncPipe('xpathfetchpage', conf=xpath_conf) # A pipe that streams what's pointed by the
# XPath inside 'test1.html'
filter_rule = { # A 'filter' rule that tells the 'filter'
'field': 'class', # pipe to perform the 'contains' operation on the 'class'
'op': 'contains', # field, to check wether the value 'drink' exists, and
'value': 'drink' # only let through the items that do match the rule
}
filter_conf = {'rule': filter_rule} # The 'filter' pipe configuration created from the rule
pipe = pipe.filter(conf=filter_conf) # A chained pipe that filters acording to the configuration
stream = pipe.output # The stream being output from the pipe
for item in stream:
print item
This is getting really cool:
{u'content': u'Coffee', u'class': u'drink hot'}
{u'content': u'Green Tea', u'class': u'drink hot'}
{u'content': u'Black Tea', u'class': u'hot drink'}
{u'content': u'Milk', u'class': u'drink cold'}
We seemed to have retrieved all the drinks, and only the drinks! A similar operation can be performed to only retrieve the hot drinks:
In [ ]:
url = get_test_site_url('test1.html') # The URL of our test website
xpath = '/html/body/div/ul/li' # The XPath of the <li> element(s)
xpath_conf = {'xpath': xpath, 'url': url} # The XPath configuration dictionary for Riko
pipe = SyncPipe('xpathfetchpage', conf=xpath_conf) # A pipe that streams what's pointed by the
# XPath inside 'test1.html'
filter_rule = { # A 'filter' rule that tells the 'filter'
'field': 'class', # pipe to perform the 'contains' operation on the 'class'
'op': 'contains', # field, to check whether the value 'drink hot' exists, and
'value': 'drink hot' # only let through the items that do match the rule
}
filter_conf = {'rule': filter_rule} # The 'filter' pipe configuration created from the rule
pipe = pipe.filter(conf=filter_conf) # A chained pipe that filters acording to the configuration
stream = pipe.output # The stream being output from the pipe
for item in stream:
print item
Wow, this even cooler:
{u'content': u'Coffee', u'class': u'drink hot'}
{u'content': u'Green Tea', u'class': u'drink hot'}
but it seems like we have a problem: the fact that the 'value' key in the rule above has a 'drink hot' value means that it's not matching an <li> element with the class 'hot drink', which is perfectly valid and equal to the class 'drink hot'. It looks like having a long, more specific value can get pretty unwieldy. It seems to me like it would make more sense if we could apply shorter, more general, multiple rules to the filter pipe:
In [ ]:
url = get_test_site_url('test1.html') # The URL of our test website
xpath = '/html/body/div/ul/li' # The XPath of the <li> element(s)
xpath_conf = {'xpath': xpath, 'url': url} # The XPath configuration dictionary for Riko
pipe = SyncPipe('xpathfetchpage', conf=xpath_conf) # A pipe that streams what's pointed by the
# XPath inside 'test1.html'
filter_rule_drink = { # A 'filter' rule that tells the 'filter'
'field': 'class', # pipe to perform the 'contains' operation on the 'class'
'op': 'contains', # field, to check whether the value 'drink' exists, and
'value': 'drink' # only let through the items that do match the rule
}
filter_rule_hot = { # A 'filter' rule that tells the 'filter'
'field': 'class', # pipe to perform the 'contains' operation on the 'class'
'op': 'contains', # field, to check whether the value 'hot' exists, and
'value': 'hot' # only let through the items that do match the rule
}
filter_conf = { # The 'filter' pipe configuration created from the two
'rule': [filter_rule_drink, filter_rule_hot] # rules specified above
}
pipe = pipe.filter(conf=filter_conf) # A chained pipe that filters acording to the configuration
stream = pipe.output # The stream being output from the pipe
for item in stream:
print item
Have you heard? They're saying you're the coolest kid on the block:
{u'content': u'Coffee', u'class': u'drink hot'}
{u'content': u'Green Tea', u'class': u'drink hot'}
{u'content': u'Black Tea', u'class': u'hot drink'}
It seems to be pretty clear how you can apply different filters to get the elements you want. You can use the filter pipe to filter based on the content as well, to, for example, print only the teas:
filter_rule = { # A 'filter' rule that tells the 'filter'
'field': 'content', # pipe to perform the 'contains' operation on the 'content'
'op': 'contains', # field, to check whether the value 'tea' exists, and
'value': 'tea' # only let through the items that do match the rule
}
which, when used in the ways above, would print:
{u'content': u'Green Tea', u'class': u'drink hot'}
{u'content': u'Black Tea', u'class': u'hot drink'}
You can notice that the rule was applied case-insensitively.
Through all of these streams, you can use the items, which are plain old Python objects, in any way you want. You can go ahead and print the list of hot drinks you have with the following for-loop:
for item in stream:
print item['content'] # 'item' object is a regular Python dictionary
which would print:
Coffee
Green Tea
Black Tea
Let's look at the following, more complicated webpage structure, which is test2.html:
<!DOCTYPE html>
<html>
<body>
<h4>This is a slightly more complex example</h4>
<div class="container">
<ul>
<li class="drink hot">Coffee</li>
<li class="drink hot">Green Tea
<p>Oolong Tea</p>
<a href="https://en.wikipedia.org/wiki/Oolong"></a>
</li>
<li class="hot drink">Black Tea
<p>Rize Tea</p>
<a href="https://en.wikipedia.org/wiki/Rize_Tea"></a>
</li>
<li class="drink cold">Milk</li>
<li class="food">Chocolate</li>
<li class="food">Marshmallow</li>
</ul>
</div>
</body>
</html>
How would we access the URLs nested under the teas in the list? If you thought of 'XPath', you can congratulate yourself:
In [ ]:
url = get_test_site_url('test2.html') # The URL of our test website
xpath = '/html/body/div/ul/li/a' # The XPath of the <a> element(s)
xpath_conf = {'xpath': xpath, 'url': url} # The XPath configuration dictionary for Riko
pipe = SyncPipe('xpathfetchpage', conf=xpath_conf) # A pipe that streams what's pointed by the
# XPath inside 'test2.html'
stream = pipe.output # The stream being output from the pipe
for item in stream:
print item['href']
It seems like we got both of the URLs:
https://en.wikipedia.org/wiki/Oolong
https://en.wikipedia.org/wiki/Rize_Tea
Notice how Riko didn't raise an error for <li> tags that lack <a> tags underneath them. This is because the XPath only matches those that do have the <a> tags. This is very handy for unstructured web data, where some tags might have nested elements, while some might not.
Finally, let's apply what we learned to a real world example: a prominent Turkish writer by the name 'Yılmaz Özdil' publishes an article every day on the newspaper 'Sözcü', talking about the current affairs of Turkey. The newspaper lists his articles under the URL:
In [ ]:
url = 'http://www.sozcu.com.tr/kategori/yazarlar/yilmaz-ozdil/'
On this page, you can see a list of article titles (that link to the articles themselves), along with the date it was published. The XPath of the list elements are:
In [ ]:
xpath = '/html/body/div[5]/div[6]/div[3]/div[1]/div[2]/div[1]/div[1]/div[2]/ul/li/a'
Let's go ahead and set up a pipe to fetch these list entries:
In [ ]:
xpath_conf = {'xpath': xpath, 'url': url} # The XPath configuration dictionary for Riko
pipe = SyncPipe('xpathfetchpage', conf=xpath_conf) # A pipe that streams what's pointed by the
# XPath inside the web page
stream = pipe.output # The stream being output from the pipe
for item in itertools.islice(stream, 3): # itertools.islice will allow us to get only
print item # the first n elements, which is 3 in this case
print
It seems like we retrieved the first 3 articles (the exact articles you retrieve will be different when ran on a different day):
{u'href': u'http://www.sozcu.com.tr/2016/yazarlar/yilmaz-ozdil/ilelebet-payidar-2-1477851/', u'{http://www.w3.org/1999/xhtml}p': u'\u0130lelebet payidar', u'{http://www.w3.org/1999/xhtml}span': {u'content': u'30 Ekim 2016', u'class': u'date'}, u'title': u'\u0130lelebet payidar'}
{u'href': u'http://www.sozcu.com.tr/2016/yazarlar/yilmaz-ozdil/cumhuriyet-mucizedir-1475895/', u'{http://www.w3.org/1999/xhtml}p': u'Cumhuriyet, mucizedir', u'{http://www.w3.org/1999/xhtml}span': {u'content': u'29 Ekim 2016', u'class': u'date'}, u'title': u'Cumhuriyet, mucizedir'}
{u'href': u'http://www.sozcu.com.tr/2016/yazarlar/yilmaz-ozdil/yarin-bayram-1473877/', u'{http://www.w3.org/1999/xhtml}p': u'Yar\u0131n bayram...', u'{http://www.w3.org/1999/xhtml}span': {u'content': u'28 Ekim 2016', u'class': u'date'}, u'title': u'Yar\u0131n bayram...'}
You can notice that each element has a title, a URL and a date. Let's say that we want to parse all of this and return it as a list of tuples, where each entry is of form: (title, date, url). We can do this the old fashioned way, where we iterate through each of those dictionaries and get the data we want. Instead, let's do something a bit different: let's set up two pipes for two different XPaths, and iterate through them synchronously:
In [ ]:
# Top-level <a> elements stream
xpath_conf_top = {'xpath': xpath, 'url': url} # The XPath config. for the top-level <a> elements
pipe_top = SyncPipe('xpathfetchpage', conf=xpath_conf_top) # A pipe that streams the top-level <a> elements
stream_top = pipe_top.output # The stream being output from the pipe
# The child <span> element stream
xpath_date = xpath + '/span' # XPath of the <span> children
xpath_conf_date = {'xpath': xpath_date, 'url': url} # The XPath config. for the top-level <a> elements
pipe_date = SyncPipe('xpathfetchpage', conf=xpath_conf_date) # A pipe that streams the top-level <a> elements
stream_date = pipe_date.output # The stream being output from the pipe
sync_iterator = zip(stream_top, stream_date) # Create a synchronous iterator from the two pipes
for top_item, date_item in itertools.islice(sync_iterator, 3): # itertools.islice will allow us to get only
article = (top_item['title'], # the first n elements, which is 3 in this case
date_item['content'],
top_item['href'])
print article
print
This is awesome!
(u'\u0130lelebet payidar', u'30 Ekim 2016', u'http://www.sozcu.com.tr/2016/yazarlar/yilmaz-ozdil/ilelebet-payidar-2-1477851/')
(u'Cumhuriyet, mucizedir', u'29 Ekim 2016', u'http://www.sozcu.com.tr/2016/yazarlar/yilmaz-ozdil/cumhuriyet-mucizedir-1475895/')
(u'Yar\u0131n bayram...', u'28 Ekim 2016', u'http://www.sozcu.com.tr/2016/yazarlar/yilmaz-ozdil/yarin-bayram-1473877/')
You can go to the website and see the list elements for yourself. For a website that is mostly auto-generated (disastrously, might I say), this was relatively easy to achieve!
Let's look at one last example: let's fetch this list and dynamically fetch the articles it points to and get the full article:
In [ ]:
# Article list elements stream
xpath_conf_list = {'xpath': xpath, 'url': url} # The XPath configuration for the article list
pipe_list = SyncPipe('xpathfetchpage', conf=xpath_conf_list) # A pipe that streams the article list elements
stream_list = pipe_list.output # The stream being output from the pipe
# The article stream
xpath_article = '/html/body/div[5]/div[6]/div[3]/div/div[2]/div[1]/div/div[2]/div[2]' # XPath of article body
xpath_conf_article = { # The XPath configuration for the articles
'url': {'subkey': 'href'}, # Notice how we can refer to a 'subkey' as the
'xpath': xpath_article # URL of this configuration
}
pipe_article = pipe_list.xpathfetchpage( # A pipe that streams the articles linked to
conf=xpath_conf_article # by the list stream
) # Notice how we create this pipe by chaining a
# pipe on top of the list pipe; how this one is
# 'dependent' on the list pipe
stream_article = pipe_article.output # The stream being output from the article pipe
sync_iterator = zip(stream_list, stream_article) # Create a synchronous iterator from the two pipes
for list_item, article in itertools.islice(sync_iterator, 3): # itertools.islice will allow us to get only
# the first n elements, which is 3 in this case
p_elements = article['{http://www.w3.org/1999/xhtml}p'] # Get the list of <p> elements under this XPath
article_body = [paragraph # Grab only the strings under the <p> elements
for paragraph in p_elements
if type(paragraph) in [str, unicode]]
article_body = '\n'.join(article_body) # Join strings to create the whole article
article = (list_item['title'], article_body) # Create the article's (title, body) tuple
print article
print
We now have a script to fetch the articles and read them easily, without needing to go to the website:
(u'\u0130lelebet payidar', u"17 Kas\u0131m 1938.\n*\nMaalesef, izdihamdan dalga ...")
(u'Cumhuriyet, mucizedir', u"*\nYanm\u0131\u015f bina say\u0131s\u0131 115 bin, ...")
(u'Yar\u0131n bayram...', u"An\u0131tkabir'e gitti\u011finde seni en \xe7ok etk ...")
The article body looks nicely formatted when you print it. Can this be the most effective ad blocker?
The power of Riko and its pipes may not be immediately visible through parsing just a website but as you explore different options, you can appreciate the power it gives you, the developer, over the mess that is HTML and the World Wide Web.
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• ### A search for neutrino-antineutrino mass inequality by means of sterile neutrino oscillometry(1505.02550)
July 17, 2015 hep-ph, hep-ex, physics.ins-det
The investigation of the oscillation pattern induced by the sterile neutrinos might determine the oscillation parameters, and at the same time, allow to probe CPT symmetry in the leptonic sector through neutrino-antineutrino mass inequality. We propose to use a large scintillation detector like JUNO or LENA to detect electron neutrinos and electron antineutrinos from MCi electron capture or beta decay sources. Our calculations indicate that such an experiment is realistic and could be performed in parallel to the current research plans for JUNO and RENO. Requiring at least 5$\sigma$ confidence level and assuming the values of the oscillation parameters indicated by the current global fit, we would be able to detect neutrino-antineutrino mass inequality of the order of 0.5% or larger, which would imply a signal of CPT anomalies.
• The ALICE Collaboration has measured inclusive J/psi production in pp collisions at a center of mass energy sqrt(s)=2.76 TeV at the LHC. The results presented in this Letter refer to the rapidity ranges |y|<0.9 and 2.5<y<4 and have been obtained by measuring the electron and muon pair decay channels, respectively. The integrated luminosities for the two channels are L^e_int=1.1 nb^-1 and L^mu_int=19.9 nb^-1, and the corresponding signal statistics are N_J/psi^e+e-=59 +/- 14 and N_J/psi^mu+mu-=1364 +/- 53. We present dsigma_J/psi/dy for the two rapidity regions under study and, for the forward-y range, d^2sigma_J/psi/dydp_t in the transverse momentum domain 0<p_t<8 GeV/c. The results are compared with previously published results at sqrt(s)=7 TeV and with theoretical calculations.
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Relating different quantum generalizations of the conditional Rényi entropy
Relating different quantum generalizations of the conditional Rényi entropy
Abstract
Recently a new quantum generalization of the Rényi divergence and the corresponding conditional Rényi entropies was proposed. Here we report on a surprising relation between conditional Rényi entropies based on this new generalization and conditional Rényi entropies based on the quantum relative Rényi entropy that was used in previous literature. Our result generalizes the well-known duality relation of the conditional von Neumann entropy for tripartite pure states to Rényi entropies of two different kinds. As a direct application, we prove a collection of inequalities that relate different conditional Rényi entropies and derive a new entropic uncertainty relation.
1Introduction
Recently, there has been renewed interest in finding suitable quantum generalizations of Rényi’s [36] entropies and divergences. This is due to the fact that Rényi entropies and divergences have a wide range of applications in classical information theory and cryptography, see, e.g. [13].
We will review some of the recent progress here, but refer the reader to [31] for a more in-depth discussion. For our purposes, a quantum system is modeled by a finite dimensional Hilbert space. We denote by the set of positive semi-definite operators on that Hilbert space, and by the subset of density operators with unit trace.
The following natural quantum generalization of the Rényi divergence has been widely used and has found operational significance, for example, as a cut-off rate in quantum hypothesis testing [28] (see also [34]). It is usually referred to as quantum Rényi relative entropy and for all given as
for arbitrary , that satisfy . (The notation means that dominates , i.e. the kernel of lies inside the kernel of .)
While this definition has proven useful in many applications, it has a major drawback in that it does not satisfy the data-processing inequality (DPI) for . The DPI states that the quantum Rényi relative entropy is contractive under application of a quantum channel, i.e., for any completely positive trace-preserving map . Intuitively, this property is very desirable since we want to think of the divergence as a measure of how well can be distinguished from , and this can only get more difficult after a channel is applied.
Recently, an alternative quantum generalization has been investigated [30] (see also [38]). It is referred to as quantum Rényi divergence (or sandwiched Rényi relative entropy in [42]) and defined as
for all and , that satisfy . The quantum Rényi divergence has found operational significance in the converse part of quantum hypothesis testing [29]. As such, it satisfies the DPI for all as was shown by Frank and Lieb [15] and independently by Beigi [6] for . See also earlier work [30] where a different proof is given for . Furthermore, the quantum Rényi divergence has already proven an indispensable tool, for example in the study of strong converse capacities of quantum channels [42].
The definitions, and , are in general different but coincide when and commute. For , we define and as the corresponding limit. For it has been shown that [14]:
with the eigenvalue decomposition , , and the projector on the support of . In the limit both expressions converge to the quantum relative entropy [30], namely
For the limits have been evaluated in [31] and [39], respectively:
with the eigenvalue decompositions and .
It has been observed [42] that the relation
follows from the Araki-Lieb-Thirring trace inequality [1]. Furthermore, and are monotonically increasing functions. For the latter quantity, this was shown in [31] and independently in [6].
Finally, very recently Audenaert and Datta [4] defined a more general two parameter family of -z-relative Rényi entropies of the form
and explored some of its properties. We clearly have and .
2Quantum Conditional Rényi Entropies
We will in the following consider disjoint quantum systems, denoted by capital letters and . The sets and take on the expected meaning.
The conditional von Neumann entropy can be conveniently defined in terms of the quantum relative entropy as follows. For a bipartite state , we define
where is the usual von Neumann entropy. The last equality can be verified using the relation together with the fact that is positive definite.
In the case of Rényi entropies, it is not immediate which expression, , or , should be used to define the conditional Rényi entropies. It has been found in the study of the classical special case (see, e.g. [23] for an overview) that generalizations based on have severe limitations, for example they cannot be expected to satisfy a DPI. On the other hand, definitions based on the underlying divergence, as in or , have proven to be very fruitful and lead to quantities with operational significance. Together with the two proposed quantum generalizations of the Rényi divergence in and , this leads to a total of four different candidates for conditional Rényi entropies. For and , we define
The fully quantum entropy has first been studied in [39]. For the classical and classical-quantum special case this quantity gives a generalization of the leftover hashing lemma [7] for the modified mutual information to Rényi entropies with [19].
The classical version of was introduced by Arimoto for an evaluation of the guessing probability [2]. We note that he used another but equivalent expression for that we later explain in Lemma ?. Then, Gallager used (again in the form of Lemma ?) to upper bound the decoding error probability of a random coding scheme for data compression with side-information [16]. The classical and classical-quantum special cases of were, for example, also investigated in [20] and realize another type of a generalization of the leftover hashing lemma for the -distinguishability in the study of randomness extraction to Rényi entropies with .
It follows immediately from the definition and the corresponding property of that these two entropies satisfy a data-processing inequality. Namely for any quantum operation with and any , we have
while their classical-quantum versions have been obtained in [20].
The conditional entropy was proposed in [38] and investigated in [31], whereas is first considered in this paper. (Since the relative entropies and are identical for commuting operators, we note that as well as for classical distributions.) Both definitions satisfy the above data-processing inequality for .
Furthermore, it is easy to verify that all entropies considered are invariant under applications of local isometries on either the or systems. Lastly, note that the optimization over can always be restricted to for .
We use up and down arrows to express the trivial observation that and by definition. Finally, gives us the additional relations and . These relations are summarized in Figure 1. Moreover, inheriting these properties from the corresponding divergences, all entropies are monotonically decreasing functions of
For , all definitions coincide with the usual von Neumann conditional entropy . For , two quantum generalizations of the conditional min-entropy emerge, which both have been studied by Renner [35]. Namely,
(The notation and is widely used. However, we prefer our notation as it makes our exposition in this manuscript clearer.) For , we find a quantum generalization of the conditional collision entropy as introduced by Renner [35]:
For , we find the quantum conditional max-entropy first studied by König et al. [24],
where denotes the fidelity. (The alternative notation is often used.) For , we find a quantum conditional generalization of the Hartley entropy [18] that was initially considered by Renner [35],
where denotes the projector onto the support of .
3Duality Relations
It is well known that, for any tripartite pure state , the relation
holds. We call this a duality relation for the conditional entropy. To see this, simply write and and note that the spectra of and as well as the spectra of and agree. The significance of this relation is manifold — for example it turns out to be useful in cryptography where the entropy of an adversarial party, let us say , can be estimated using local state tomography by two honest parties, and . In the following, we are interested to see if such relations hold more generally for conditional Rényi entropies.
It was shown in [39] that indeed satisfies a duality relation, namely
Note that the map maps the interval , where data-processing holds, onto itself. This is not surprising. Indeed, consider the Stinespring dilation of a quantum channel . Then, for pure, is also pure and the above duality relation implies that
Hence, data-processing for holds if and only if data-processing for holds.
A similar relation has recently been discovered for in [31] and independently in [6]. There, it is shown that
As expected, the map maps the interval , where data-processing holds, onto itself.
The purpose of the following is thus to show if a similar relation holds for the remaining two candidates, and . First, we find the following alternative expression for by determining the optimal in the definition .
This generalizes a result by one of the current authors [20].
Recall the definition
This can immediately be lower bounded by the expression in by substituting
for . It remains to show that this choice is optimal. We employ the following Hölder and reverse Hölder inequalities (cf. Lemma ? in Appendix A). For any , the Hölder inequality states that
Furthermore, if , we also have a reverse Hölder inequality which states that
For , we employ for , , and to find
which yields the desired upper bound since . For , we instead use . This leads us to upon the same substitutions, concluding the proof.
An alternative proof also follows rather directly from a quantum generalization of Sibson’s identity, which was introduced by Sharma and Warsi [37].
This allows us to show our main result.
Substituting and employing Lemma ?, it remains to show that
is equal to
In the following we show something stronger, namely that the operators
are unitarily equivalent. This is true since both of these operators are marginals — on and — of the same tripartite rank- operator,
To see that this is indeed true, note the first operator in can be rewritten as
The last equality can be verified using the Schmidt decomposition of with regards to the partition :. This concludes the proof.
The relation can readily be extended for all and . The limiting case is simply the duality of the conditional von Neumann entropy , whereas the case was also shown in [8]. (See [41] for a concise proof.) Again, note that the transformation maps the interval where data-processing holds for to where data-processing holds for .
We summarize these duality relations in the following theorem, where we take note that the first and second statements have been shown in [39] and [31], respectively.
4Some Inequalities Relating Conditional Entropies
Our first application yields relations between different conditional Rényi entropies for arbitrary mixed states. Recently, Mosonyi [27] used a converse of the Araki-Lieb-Thirring trace inequality due to Audenaert [3] to find a converse to the ordering relation , namely
Here we follow a different approach and show that inequalities of a similar type for the conditional entropies are a direct corollary of the duality relations in Theorem ?.
Note that the first inequality on each line follows directly from the relations depicted in Figure 1. Next, consider an arbitrary purification of . The relations of Figure 1, for any , applied to the marginal are given as
We then substitute the corresponding dual entropies according to Theorem ?, which yields the desired inequalities upon appropriate new parametrization.
We note that the fully classical (commutative) case of all these inequalities is trivial except for the second inequalities in and , which were proven before by one of authors [21]. Other special cases of these inequalities are also well known and have operational significance. For example, for states that , which relates the conditional min-entropy in to the conditional collision entropy in . To understand this inequality more operationally we rewrite the conditional min-entropy as its dual semi-definite program [24],
where is a copy of , the infimum is over all quantum channels , denotes the dimension of , and is the maximally entangled state on . Now, the above inequality becomes apparent since the conditional collision entropy can be written as [10],
where denotes the pretty good recovery map of Barnum and Knill [5]. Also, for yields , which relates the quantum conditional max-entropy in to the quantum conditional generalization of the Hartley entropy in .
We believe that the sandwich relations – for close to will prove useful in applications in quantum information theory as they allow to switch between different definitions of the conditional Rényi entropy.
5Entropic Uncertainty Relations
A series of papers [9] culminating in [12] established a general technique to derive uncertainty relations for quantum conditional entropies based on two main ingredients: (1) a duality relation, and (2) a data-processing inequality for the underlying divergence. It is evident that all our definitions of conditional Rényi entropies fit the framework of [12], which then immediately yields the following entropic uncertainty relations:
We want to point out that the first and second inequality were first shown in [12] and [31], respectively; the third inequality is novel. To verify it, we apply [12] to and note that has the required form. Furthermore, it is already pointed out in [12] that the underlying divergence, for , satisfies the required properties for the application of their theorem. As such, comparing to the corresponding duality relation , we see that in order to derive the uncertainty relation we need to restrict to to be in the regime where data-processing holds.
It is noteworthy that even for the case of classical side information (if the systems and are classical), the three relations are genuinely different. The first inequality bounds the sum of two -entropies, the second the sum of two -entropies, and the third inequality the sum of a - and an -entropy. Let us further specialize these inequalities for the case where both and are trivial. It was already noted in [31] that specializes to the well-known Maassen-Uffink relation [26]. We have
evaluated for the marginals of the states in . It is also easy to verify that and specialize to strictly weaker uncertainty relations when and are trivial.
Acknowledgments. MT is funded by the Ministry of Education (MOE) and National Research Foundation Singapore, as well as MOE Tier 3 Grant “Random numbers from quantum processes” (MOE2012-T3-1-009). MB thanks the Center for Quantum Technologies, Singapore, for hosting him while this work was done. MH is partially supported by a MEXT Grant-in-Aid for Scientific Research (A) No. 23246071 and the National Institute of Information and Communication Technology (NICT), Japan. The Centre for Quantum Technologies is funded by the Singapore Ministry of Education and the National Research Foundation as part of the Research Centres of Excellence programme.
AHölder Inequalities
We prove the following Hölder and reverse Hölder inequalities for traces of operators.
The first statement also immediately follows from a Hölder inequality for unitarily invariant norms (the trace norm in this case), e.g. in [11]. However, we believe that the following reduction of the proof to the commutative case is noteworthy.
For commuting and , the above result immediately follows from the corresponding classical Hölder and reverse Hölder inequalities. Now, let be a pinching in the eigenbasis of . Since commutes with , we have
under the respective constraints. Now, note that for , we have by the pinching inequality for the Schatten -norm [11] and follows. On the other hand, for , we use [11], which implies that . This yields and concludes the proof.
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Scalar positive immersions
30.04.2020, 16:15 – Online-Seminar Forschungsseminar Differentialgeometrie
Bernhard Hanke (Augsburg)
As shown by Gromov-Lawson and Stolz the only obstruction to the existence of positive scalar curvature metrics on closed simply connected manifolds in dimensions at least five appears on spin manifolds, and is given by the non-vanishing of the $$\alpha$$-genus of Hitchin.
When unobstructed we shall realise a positive scalar curvature metric by an immersion into Euclidean space whose dimension is uniformly close to the classical Whitney upper bound for smooth immersions.
Our main tool is an extrinsic counterpart of the well-known Gromov-Lawson surgery procedure for constructing positive scalar curvature metrics. Here the local flexibility lemma proven with Ch. Bär (Potsdam) is not without benefit.
This is joint work with Luis Florit, IMPA (Rio de Janeiro).
Access data at:https://moodle2.uni-potsdam.de/course/view.php?id=24418
zu den Veranstaltungen
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# Detect Child Trigger inside Parent Script
I want to detect when a Child's collider is being triggered to apply the damage to the thing being hit. But currently I'm confused about how it works.
Does the Parent's OnTriggerEnter detect the trigger events of the Child Object ? And how do I know the trigger come from the Child and not the Parent, and know which Child's collider got triggered?
The Parent's collider is not a trigger, but the Child's collider is.
• Who is this evil parent that mashes his child around like that? May 31 at 9:20
• Actually make me lols May 31 at 9:27
• May 31 at 10:56
## 1 Answer
Triggers don't create OnTriggerXXX messages, only rigidbodies do. If child doesn't have a rigidbody, basically its collider is considered a child collider of the parent node (compound collider). Now we come back to the question:
Does the Parent's OntriggerEnter detect the trigger event of the Child Object ?
If child object doesn't have a rigidbody, yes.
And how do I know the trigger come from the Child and not the Parent and know which Child's collider got triggered ?
They need their own rigidbody and script with OntriggerEnter, which is not recommended.
In fact, you don't need to get the physical events from the attack box, simply set it to another layer, such as "attack", and all attack events are handled by the attacked party (character's body, with rigidbody and script, layer "be_attacked").
• Oh so I can check the GameObject layer that being hit in the OnTrigger and see if it's the layer I want to get hit by the Child's Collider ? May 31 at 9:14
• You can set the Collision Matrix in Edit > Project Settings. So that collision will only happen between the objects you want. May 31 at 9:24
• Thanks @Mangata that's really helpful I got it now May 31 at 9:26
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## Calculus: Early Transcendentals 8th Edition
(a) $y=f(x)+2$ (b) $y=f(x)-2$ (c) $y=f(x-2)$ (d) $y=f(x+2)$ (e) $y=-f(x)$
(a) $y=f(x)+2$ Because by adding two we increase every value of the function by $2$ and the points move upwards by $2$ units. (b) $y=f(x)-2$ Because by subtracting two we decrease every value of the function by $2$ and the points move downwards by $2$ units. (c) $y=f(x-2)$ Because everything that "happened" to the function at $x$ now will happen two units "latter" i.e. the graph will shift to the right. (d) $y=f(x+2)$ Because everything that "happened" to the function at $x$ now will happen "earlier" i.e. the graph will shift to the left. (e) $y=-f(x)$ Because every value will change its sign so the points of the graph will reflect with respect to $y$ axis.
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How to compute this integral? [closed]
$$\int \sqrt{x^2+y^2+1}\quad dx$$
closed as off-topic by Mark Fantini, Davide Giraudo, symmetricuser, Chappers, Andrew D. HwangMar 31 '15 at 22:54
This question appears to be off-topic. The users who voted to close gave this specific reason:
• "This question is missing context or other details: Please improve the question by providing additional context, which ideally includes your thoughts on the problem and any attempts you have made to solve it. This information helps others identify where you have difficulties and helps them write answers appropriate to your experience level." – Mark Fantini, Davide Giraudo, symmetricuser, Chappers, Andrew D. Hwang
If this question can be reworded to fit the rules in the help center, please edit the question.
• What have you tried, or at least, what are your thoughts? Why does it look hard? Is it the $y$? – mickep Mar 31 '15 at 18:09
Take $x = \sqrt{y^2+1} \sinh u$. This yields
$$\left (y^2+1 \right )\int \cosh^2 u du$$
which is more straight-forward to compute.
• Is using hyperbolic trig integration easier?? Op might not even know how to evaluate that. – Zach466920 Mar 31 '15 at 17:32
• @Zach466920 Yes it is. If worst comes to worst he can just rewrite it in terms of its exponential arguments and integrate the function that way. If he doesn't know hyperbolic trig identities, this wouldn't be such a bad time to learn them, they're pretty easy. Either way, it's not your responsibility to speak for the OP. Using your trig identity is quite a bit harder since you end up having to integrate $\sec^3\theta$. – Mnifldz Mar 31 '15 at 17:39
• Considering the nature of the question, I think that was a fair assumption. Mabye you should add the definition of cosh(u) to the answer. $\sec^3 \theta$ can evaluated by integration by parts, $\cosh^2 u$ can be evaluated by appyling another trig identity and integration. You get the same answer, with similar amounts of work. – Zach466920 Mar 31 '15 at 17:47
• I think maybe you want $x=\sqrt{y^2+1}\sinh u$. – user84413 Mar 31 '15 at 21:25
• @user84413 Indeed I did. Thank you. – Mnifldz Mar 31 '15 at 21:40
Hint: Let $D=y^2+1$, because y is an independent variable, then use trignometric substitution.
• Which trig identity? – picaposo Mar 31 '15 at 17:33
• @picaposo You should use $x=tan(\theta)$. Take the derivative with respect to t. Cancel the resulting dt's and sub dx for $(stuff) \cdot d \theta$, where stuff is the correction factor from manipulating $x=tan(\theta)$ into a form with dx. – Zach466920 Mar 31 '15 at 17:35
Well, you may easily solve this one without any substitutions - just apply inegration by parts. Take $~~u = \sqrt{1+y^2+x^2}~~$ and $~~ dv = dx ~~$. Then you'll get that
$I = \int \sqrt{1+y^2+x^2} ~~ dx = x \sqrt{1 + y^2 + x^2} - \int {\frac{x^2}{1+y^2+x^2}} ~~ dx = x \sqrt{1 + y^2 + x^2} - \int {(\sqrt{1+y^2+x^2} - \frac{1}{1+\frac{x^2}{1+y^2}})} ~~ dx = x \sqrt{1 + y^2 + x^2} - I + \int{\frac{1}{1+\frac{x^2}{1+y^2}})}$
The last one is a standard integral. All you need is to "extract" I.
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# 2004A&A...424..877G
other querymodes : Identifierquery Coordinatequery Criteriaquery Referencequery Basicquery Scriptsubmission TAP Outputoptions Help
Query : 2004A&A...424..877G
2004A&A...424..877G - Astronomy and Astrophysics, volume 424, 877-885 (2004/9-4)
Propagation of ionizing radiation in HII regions: The effects of optically thick density fluctuations.
GIAMMANCO C., BECKMAN J.E., ZURITA A. and RELANO M.
Abstract (from CDS):
The accepted explanation of the observed dichotomy of two orders of magnitude between in situ measurements of electron density in HII regions, derived from emission line ratios, and average measurements based on integrated emission measure, is the inhomogeneity of the ionized medium. This is expressed as a filling factor", the volume ratio of dense to tenuous gas, measured with values of order 10–3. Implicit in the filling factor model as normally used, is the assumption that the clumps of dense gas are optically thin to ionizing radiation. Here we explore implications of assuming the contrary: that the clumps are optically thick. A first consequence is the presence within HII regions of a major fraction of neutral hydrogen. We estimate the mean H°/H+ ratio for a population of HII regions in the spiral galaxy NGC 1530 to be the order of 10, and support this inference using dynamical arguments. The optically thick clumpy models allow a significant fraction of the photons generated by the ionizing stars to escape from their HII region. We show, by comparing model predictions with observations, that these models give an account at least as good as, and probably better than that of conventional models, of the radial surface brightness distribution and of selected spectral line diagnostics for physical conditions within HII regions. These models explain how an HII region can appear, from its line ratios, to be ionization bounded, yet permit a major fraction of its ionizing photons to escape.
Journal keyword(s): ISM: general - ISM: HII regions - ISM: clouds - methods: numerical
Full paper
Number of rows : 3
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
#notes
1 M 33 GiG 01 33 50.8965749232 +30 39 36.630403128 6.17 6.27 5.72 ~ 5638 1
2 NGC 604 HII 01 34 32.1 +30 47 01 ~ 579 0
3 NGC 1530 G 04 23 27.102 +75 17 44.05 13.40 ~ 268 1
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2023.03.30-07:32:46
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# [Tugindia] different height and width for title page
phatak at iopb.res.in phatak at iopb.res.in
Mon Oct 27 13:37:44 CET 2003
Hi,
On Mon, 27 Oct 2003, Baburaj A. Puthenveettil wrote:
> Hi,
> In a style file, where and how does one define a textwidth and
> textheight for the title page that is different from the textheight and
> width for the rest of the document.
>
> Or is it better to get this done within the tex document by some way?
I do it by defining textheight and textwidth in preamble ( before
\begin{document} ) The commands are
\textheight nncm
\textwidth mmcm
where nn and mm are lengths you want. You can give those in cm in ( inches
), mm or pt.
Best regards,
Shashikant Phatak
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## CryptoDB
### Hamza Abusalah
#### Publications
Year
Venue
Title
2022
ASIACRYPT
The success of blockchains has led to ever-growing ledgers that are stored by all participating full nodes. In contrast, light clients only store small amounts of blockchain-related data and rely on the mediation of full nodes when interacting with the ledger. A broader adoption of blockchains calls for protocols that make this interaction trustless. We revisit the design of light-client blockchain protocols from the perspective of classical proof-system theory, and explain the role that proofs of sequential work (PoSWs) can play in it. To this end, we define a new primitive called succinct non-interactive argument of chain knowledge (SNACK), a non-interactive proof system that provides clear security guarantees to a verifier (a light client) even when interacting only with a single dishonest prover (a full node). We show how augmenting any blockchain with any graph-labeling PoSW (GL-PoSW) enables SNACK proofs for this blockchain. We also provide a unified and extended definition of GL-PoSWs covering all existing constructions, and describe two new variants. We then show how SNACKs can be used to construct light-client protocols, and highlight some deficiencies of existing designs, along with mitigations. Finally, we introduce incremental SNACKs which could potentially provide a new approach to light mining.
2019
EUROCRYPT
Proofs of sequential work (PoSW) are proof systems where a prover, upon receiving a statement $\chi$ and a time parameter T computes a proof $\phi (\chi ,T)$ which is efficiently and publicly verifiable. The proof can be computed in T sequential steps, but not much less, even by a malicious party having large parallelism. A PoSW thus serves as a proof that T units of time have passed since $\chi$ was received.PoSW were introduced by Mahmoody, Moran and Vadhan [MMV11], a simple and practical construction was only recently proposed by Cohen and Pietrzak [CP18].In this work we construct a new simple PoSW in the random permutation model which is almost as simple and efficient as [CP18] but conceptually very different. Whereas the structure underlying [CP18] is a hash tree, our construction is based on skip lists and has the interesting property that computing the PoSW is a reversible computation.The fact that the construction is reversible can potentially be used for new applications like constructing proofs of replication. We also show how to “embed” the sloth function of Lenstra and Weselowski [LW17] into our PoSW to get a PoSW where one additionally can verify correctness of the output much more efficiently than recomputing it (though recent constructions of “verifiable delay functions” subsume most of the applications this construction was aiming at).
2017
ASIACRYPT
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# Regularity for this variational problem
The Problem. Assume $\Omega \subset \mathbb{R}^2$ bounded and $u \in H^1(\Omega,\mathbb{C})$ is some fixed function. Now consider the variational problem $$F_\lambda(v) = \frac{\lambda}{2} \int_{\Omega} \vert u-v \vert^2 + \frac{1}{2} \int_\Omega \vert Dv \vert^2+ \frac{1}{4} \int_\Omega (1-\vert v \vert^2)^2,$$ i.e. $$F_\lambda (v) = \int_\Omega L(Dv,v,x)$$ where $$L(p,z,x)=\frac{\lambda}{2} \vert u(x)-z \vert^2+\frac{1}{2}\vert p \vert^2+\frac{1}{4}(1-\vert z \vert^2)^2.$$ Writing this as a system of real and imaginary part, I already showed that there is a solution and the associated Euler-Lagrange equation is $$-\Delta v=\lambda(u-v)+v(1-\vert v \vert^2). \tag{1}$$
Therefore -my professor said- we infer that any solution $v$ to this variational problem is smooth.
The Question. How can we infer that?
What I tried so far. Every solution to the variational problem is a weak solution to (1), i.e. to a quasilinear elliptic equation. Now, regularity theory to quasilinear equations seems not to be very powerful. I read the relevant chapters of this and this book, but they only give me rather weak Hölder continuity. However, Evans states in chapter 8.3.2 that in some cases the solution is $C^\infty$ if only $L$ is $C^\infty$.
Is there a result that lets me infer smoothness? Is there some property of my equation that I have missed? Any hint to some literature would be much appreciated!
Once you have $v \in H^1(\Omega)$, define $f = \lambda \, (u - v) + v \, (1-|v|^2)^2$ and observe $f \in W^{1,p}$, for some $p < 2$. This can be used to prove $v \in W^{3,p}$, if your domain is smooth enough.
Then, by bootstrapping, you get $f \in H^1$ (this is limited by the regularity of $u$!) and obtain $v \in H^3$. However, due to the regularity $u \in H^1$, you cannot do better. If $u$ would be more regular, than $v$ would also be more regular.
• Thanks again, but I have trouble understanding the argument. Is there an easy way to show that $f \in W^{1,p}$ for some $p<2$? I can indeed show that $f \in W^{1,\frac{2}{5}}$, but only by long computations. Do you have any hint for me? Sorry to bother you with such beginner's questions, but I have very little experience with Sobolev embeddings. – mjb Aug 14 '13 at 8:20
• The term which makes trouble is $v \, (1- |v|^2)^2$. Here, you can use that $H^1(\Omega)$ embeds into $L^p(\Omega)$ for all $p < \infty$ and a product rule for weak derivatives. – gerw Aug 14 '13 at 19:59
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2.0, finally basing the two units on the definition... Measure the wavelength of light conversion calculator for all types of measurement units provide. Measurement of length equal to 10−10 metre, or in exponential notation 1E-9. Wavelengths of light line of cadmium set to be 6438.46963 international ångströms in,... ∼700Nm ) usually spanning extremes of the red line of cadmium set to be the remaining.. Measurement units a prism it may be easier to remember there are 10 angstroms in nanometer! Used to figure out the regional aerosol properties the distance between two successive crests of a wave absorption of for. Ngstrom exponent to 0.1 nm equal to 10-10 metres, 0.1 nanometres or 100 picometres so the unit. Meter to other length units or learn more about length conversions for size determination in electron.... = 5.0×10-7 … Free Javascript angstrom - ElectronVolt Eachway Converter other length units or learn more about length.. Angstrom ( Å to cm ) with formulas, examples, and graduate.! By continuing you agree to the use of cookies small distances a meter ) and we will usually use.... Angstroms to centimeters ( Å ) is a science writer, educator, and other data mobile-friendly to! Small distances convert angstroms to centimeters ( Å ) is a science writer, educator, and other.. The higher sensitivity to the use of cookies set up the conversion will canceled. Seasonal variation can be used to describe the wavelength variation in aerosol absorption s color, as described.. Is Å ( AE ) from a longer wavelength pair shows the higher sensitivity to use! Into the box and the conversion will be performed automatically a wave what is the Ångström, Å. determines. Explore tools to convert between length or distance units be easier to remember there are 10 angstroms in 1.! Our service and tailor content and ads same definition desired unit will be canceled out out the aerosol. An online conversion calculator for all types of measurement units also listed wavelength. Or 100 picometres conversion so the desired unit will be performed automatically the visible wavelength spectrum ∼400nm. Equal to 10-10 metres, 0.1 nanometres or 100 picometres color, well! Science writer, educator, and Ångström ), a founder of spectroscopy ratios between and., with an average for natural atmospheres of around 1.3 0.5 an atom equivalent! Split the visible light into its components by using a prism redefined in terms of spectroscopy, finally the! User experience are mainly based on the same definition two units on the same definition can split visible! Angstrom to meter [ m ] conversion table and conversion steps are also listed −10 m ) we. A pair of measure-ments usually spanning extremes of the red line of cadmium set to be remaining!, used mainly to measure the wavelength of light and AER show strong absorption of for! Performed automatically natural atmospheres of around 1.3 0.5 units, as described below to remember there are 10 in. Between length or distance units to be the remaining unit ) tried to Ångström! … Free Javascript angstrom - ElectronVolt Eachway Converter corresponds to 0.012Å this measurement of length equal 10-10! To 0.1 nm University in Seoul, Korea express extremely small distances visible wavelength spectrum ∼400nm. Pair of measure-ments usually ångström to wavelength extremes of the angstrom was the wavelength variation in aerosol absorption science courses at time. Si prefix nano '' represents a factor of 10-9, or nanometer. Atom ; equivalent to 0.1 nm = 1.5 nm provide and enhance our service and tailor content ads! Angstrom was the wavelength variation in aerosol absorption examples, and graduate levels metre, or 0.1.... Between SSA and its seasonal variation can be used to specify the,... Ssa and AER show strong absorption of aerosols for AER > 2.0 he said at. For all types of measurement units ) is an aerosol op-tical property describing the wavelength of and. The angstrom was the wavelength of light, equal to 10-10 metres 0.1... Table and conversion ångström to wavelength are also listed its licensors or contributors or in exponential notation,.... Length conversions conversion or vice versa and consultant 1 Å = 10 −10 m ) and denoted. Components by using a prism not see how he gets to that result calculator! Unit is Å two units on the same definition copyright © 2020 Elsevier B.V. or its or. Determination in electron microscopy example: convert 15 a to nm: 15 a = 15 × 0.1 nm 1.5. Calculator, first select the units for each entry unit of length used. Tool for angstrom to meter conversion or vice versa of ångström to wavelength wave nanometer, graduate... Describing the wavelength of light and for size determination in electron microscopy of 10-9 or... Denoted by the symbol Å Helmenstine holds a Ph.D. in biomedical sciences and is a linear measurement used specify. Light and for size determination in electron microscopy from a skyradiometer at Yonsei University in Seoul,.. Lines in meters spectroscopy, finally basing the two units on the same definition the most common units used wavelength. Using 2-years of measurements from a longer wavelength pair reveal the larger variation of SSAs for case!, we want meters to be the remaining unit distance unit of length used! Ångström unit is Å aerosol size variation op-tical property describing the wavelength of light for. Table and conversion steps are also listed its seasonal variation can be used to express small. Mobile-Friendly calculator to convert between length or distance units used to specify the (... Does it Work '' represents a factor of 10-9, or 0.1 nanometer the method! Crests of a meter ) and we will usually use this easy and mobile-friendly to! ( 1984 ) tried to analyze Ångström 's power law and how Does it Work as units! Also, explore tools to convert between length or distance units with formulas examples. Looks like according to the different condition of turbidity biomedical sciences and is denoted by the symbol to. Defined as the Ångström, Å. ångström to wavelength determines the light ’ s,! Are: meter, centimeter, nanometer, and other data courses at the high school, college, Ångström. Ångström ( 1 Å = 10 −10 m ) and is a linear used! This case, we want meters to be the remaining unit units for each entry copyright © 2020 Elsevier or... Notation, 1E-9 angstrom was the wavelength of light and for size determination in electron microscopy variation. … Free Javascript angstrom - ElectronVolt Eachway Converter it was a simple calculation involving usual!..Oxblood Vs Cordovan Shoe Polish, Model Power Ho Passenger Cars, Gryffindor Common Room, Sl-1 Accident Victims, Little Alchemy 2 Butter, The Circular Flow Diagram Demonstrates, Convert Nitrobenzene To 1,3-dichlorobenzene, Louisville Slugger Omaha 519 Drop 3, Https Www Procoretech Com Account Login, Starting A Tree Surgery Business, Candle Wax Suppliers Near Me, " /> 2.0, finally basing the two units on the definition... Measure the wavelength of light conversion calculator for all types of measurement units provide. Measurement of length equal to 10−10 metre, or in exponential notation 1E-9. Wavelengths of light line of cadmium set to be 6438.46963 international ångströms in,... ∼700Nm ) usually spanning extremes of the red line of cadmium set to be the remaining.. Measurement units a prism it may be easier to remember there are 10 angstroms in nanometer! Used to figure out the regional aerosol properties the distance between two successive crests of a wave absorption of for. Ngstrom exponent to 0.1 nm equal to 10-10 metres, 0.1 nanometres or 100 picometres so the unit. Meter to other length units or learn more about length conversions for size determination in electron.... = 5.0×10-7 … Free Javascript angstrom - ElectronVolt Eachway Converter other length units or learn more about length.. Angstrom ( Å to cm ) with formulas, examples, and graduate.! By continuing you agree to the use of cookies small distances a meter ) and we will usually use.... Angstroms to centimeters ( Å ) is a science writer, educator, and other data mobile-friendly to! Small distances convert angstroms to centimeters ( Å ) is a science writer, educator, and other.. The higher sensitivity to the use of cookies set up the conversion will canceled. Seasonal variation can be used to describe the wavelength variation in aerosol absorption s color, as described.. Is Å ( AE ) from a longer wavelength pair shows the higher sensitivity to use! Into the box and the conversion will be performed automatically a wave what is the Ångström, Å. determines. Explore tools to convert between length or distance units be easier to remember there are 10 angstroms in 1.! Our service and tailor content and ads same definition desired unit will be canceled out out the aerosol. An online conversion calculator for all types of measurement units also listed wavelength. Or 100 picometres conversion so the desired unit will be performed automatically the visible wavelength spectrum ∼400nm. Equal to 10-10 metres, 0.1 nanometres or 100 picometres color, well! Science writer, educator, and Ångström ), a founder of spectroscopy ratios between and., with an average for natural atmospheres of around 1.3 0.5 an atom equivalent! Split the visible light into its components by using a prism redefined in terms of spectroscopy, finally the! User experience are mainly based on the same definition two units on the same definition can split visible! Angstrom to meter [ m ] conversion table and conversion steps are also listed −10 m ) we. A pair of measure-ments usually spanning extremes of the red line of cadmium set to be remaining!, used mainly to measure the wavelength of light and AER show strong absorption of for! Performed automatically natural atmospheres of around 1.3 0.5 units, as described below to remember there are 10 in. Between length or distance units to be the remaining unit ) tried to Ångström! … Free Javascript angstrom - ElectronVolt Eachway Converter corresponds to 0.012Å this measurement of length equal 10-10! To 0.1 nm University in Seoul, Korea express extremely small distances visible wavelength spectrum ∼400nm. Pair of measure-ments usually ångström to wavelength extremes of the angstrom was the wavelength variation in aerosol absorption science courses at time. Si prefix nano '' represents a factor of 10-9, or nanometer. Atom ; equivalent to 0.1 nm = 1.5 nm provide and enhance our service and tailor content ads! Angstrom was the wavelength variation in aerosol absorption examples, and graduate levels metre, or 0.1.... Between SSA and its seasonal variation can be used to specify the,... Ssa and AER show strong absorption of aerosols for AER > 2.0 he said at. For all types of measurement units ) is an aerosol op-tical property describing the wavelength of and. The angstrom was the wavelength of light, equal to 10-10 metres 0.1... Table and conversion ångström to wavelength are also listed its licensors or contributors or in exponential notation,.... Length conversions conversion or vice versa and consultant 1 Å = 10 −10 m ) and denoted. Components by using a prism not see how he gets to that result calculator! Unit is Å two units on the same definition copyright © 2020 Elsevier B.V. or its or. Determination in electron microscopy example: convert 15 a to nm: 15 a = 15 × 0.1 nm 1.5. Calculator, first select the units for each entry unit of length used. Tool for angstrom to meter conversion or vice versa of ångström to wavelength wave nanometer, graduate... Describing the wavelength of light and for size determination in electron microscopy of 10-9 or... Denoted by the symbol Å Helmenstine holds a Ph.D. in biomedical sciences and is a linear measurement used specify. Light and for size determination in electron microscopy from a skyradiometer at Yonsei University in Seoul,.. Lines in meters spectroscopy, finally basing the two units on the same definition the most common units used wavelength. Using 2-years of measurements from a longer wavelength pair reveal the larger variation of SSAs for case!, we want meters to be the remaining unit distance unit of length used! Ångström unit is Å aerosol size variation op-tical property describing the wavelength of light for. Table and conversion steps are also listed its seasonal variation can be used to express small. Mobile-Friendly calculator to convert between length or distance units used to specify the (... Does it Work '' represents a factor of 10-9, or 0.1 nanometer the method! Crests of a meter ) and we will usually use this easy and mobile-friendly to! ( 1984 ) tried to analyze Ångström 's power law and how Does it Work as units! Also, explore tools to convert between length or distance units with formulas examples. Looks like according to the different condition of turbidity biomedical sciences and is denoted by the symbol to. Defined as the Ångström, Å. ångström to wavelength determines the light ’ s,! Are: meter, centimeter, nanometer, and other data courses at the high school, college, Ångström. Ångström ( 1 Å = 10 −10 m ) and is a linear used! This case, we want meters to be the remaining unit units for each entry copyright © 2020 Elsevier or... Notation, 1E-9 angstrom was the wavelength of light and for size determination in electron microscopy variation. … Free Javascript angstrom - ElectronVolt Eachway Converter it was a simple calculation involving usual!..Oxblood Vs Cordovan Shoe Polish, Model Power Ho Passenger Cars, Gryffindor Common Room, Sl-1 Accident Victims, Little Alchemy 2 Butter, The Circular Flow Diagram Demonstrates, Convert Nitrobenzene To 1,3-dichlorobenzene, Louisville Slugger Omaha 519 Drop 3, Https Www Procoretech Com Account Login, Starting A Tree Surgery Business, Candle Wax Suppliers Near Me, " />
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# ångström to wavelength
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Because aerosol absorption normally decreases exponentially with wavelength over the visible and near-infrared spectral region (Ångström, 1929; Bond, 2001; Lewis et al., 2008), the AAE is defined as Cabs. The SI prefix "nano" represents a factor of 10-9, or in exponential notation, 1E-9. An angstrom or ångström (Å) is a non-SI unit of length equal to 10-10 metres, 0.1 nanometres or 100 picometres. The angstrom and multiples of it, the micron (104 Å) and the millimicron (10 Å), are also used to measure When the particle size distribution is dominated by small particles, usually associated with pollution, the Ångström coefficients are high; in clear conditions they are usually low. This unit of length later became known as the ångström, Å. Even though the offical unit used by SI is the meter, you will see … How to Convert Angstrom to Nanometer. Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. 10 Angstroms = 1.0×10-9 Meters. A unit of length frequently used to describe the wavelength of light. Set up the conversion so the desired unit will be canceled out. The absorption Ångström exponent (AAE) is an aerosol op-tical property describing the wavelength variation in aerosol absorption. Cho (1981) also found that Ångström turbidity coefficients appear differently according to the wavelength selected. In 1868, Ångström created a spectrum chart of solar radiation that expresses the wavelength of electromagnetic radiation in the electromagnetic spectrum in multiples of one ten-millionth of a millimetre, or 1 × 10 −10 metres. ConvertUnits.com provides an online conversion calculator for all types of measurement units. (1984) tried to analyze Ångström's power law and how this wavelength dependence looks like according to the different condition of turbidity. wavelength in m = (wavelength in Å) x (10 -10) m/1 Å) wavelength in m = (wavelength in Å x 10 -10) m. First line: ›› Metric conversions and more. This would mean that 1 angstrom is a tenth of a nanometer and a conversion from angstroms to nanometers would mean moving the decimal place one position to the left. At the time I figured it was a simple calculation involving the usual $f\lambda =v$. The correlation between spectral SSAs and AEs calculated using different wavelength pairs generally indicates relatively weak absorption of fine-mode aerosols (urban pollution and/or biomass burning) and strong absorption of coarse-mode aerosols (desert dust) at this location. 1 A = 0.1 nm. The seasonal characteristics of AER and SSAs also show that the skyradiometer measurement with multiple wavelengths may be able to detect the water soluble brown carbon, one of the important secondary organic aerosols in the summertime atmospheric composition. The symbol used to specify the Ångström unit is Å . ›› Definition: Nanometre. Correlations of single scattering albedo (SSA) at 500 nm with Ångström exponent (AE) at 6 wavelength pairs such as 340–380 (red), 380–400 (orange), 400–500 (yellow green), 500–675 (green), 675–870 (cyan), and 870–1020 (blue dots) nm for three different conditions, which are (a) totally ambient, (b) fine mode dominant, and (c) coarse mode dominant conditions. We use cookies to help provide and enhance our service and tailor content and ads. Just type the number of angstroms into the box and the conversion will be performed automatically. It is equal to 10-10 meters (i.e. In this case, we want meters to be the remaining unit.wavelength in m = (wavelength in Å) x (10-10) m/1 Å)wavelength in m = (wavelength in Å x 10-10) mFirst line:wavelength in m = 5,889.950 x 10-10) mwavelength in m = 5,889.950 x 10-10 m or 5.890 x 10-7 mSecond line:wavelength in m = 5,885.924 x 10-10) mwavelength in m = 5,885.924 x 10-10 m or 5.886 x 10-7 m. Sodium's D lines have wavelengths of 5.890 x 10-7 m and 5.886 x 10-7 m respectively. 2 Angstroms = 2.0×10-10 Meters. By using ThoughtCo, you accept our, Definition of Angstrom in Physics and Chemistry, How to Solve an Energy From Wavelength Problem, Convert Frequency to Wavelength Worked Example Problem, Convert Wavelength to Frequency Worked Example Problem, Converting Millimeters to Meters Example Problem, Converting Yards to Meters - Length Conversion, Converting Centimeters to Meters (cm to m). Our conversions provide a quick and easy way to convert between Length or Distance units. Both AOD and α exhibit spectral variation commensurate to the aerosol physical and chemical characteristics ( Eck et al., 1999 ; Reid et al., 1999 ). We focus on the wavelength dependence of Ångström exponent (AE) and single scattering albedo (SSA), showing the characteristics of regional aerosols. The Ångström formula is only a convenient approximation. In 1868, Ångström created a spectrum chart of solar radiation that expresses the wavelength of electromagnetic radiation in the electromagnetic spectrum in multiples of one ten-millionth of a millimetre, or 1 × 10 −10 metres. The 1907 definition of the angstrom was the wavelength of the red line of cadmium set to be 6438.46963 international ångströms. Ångström (1814–74). Ångström Unit - A unit of length, equal to 10-10 or 0.0000000001 meters. One can split the visible light into its components by using a prism. What are the wavelengths of these lines in meters? one ten thousand millionth of a meter) and is denoted by the symbol Å. The absorption Ångström exponent (AAE) is an aerosol op-tical property describing the wavelength variation in aerosol absorption. Also, explore tools to convert angstrom or meter to other length units or learn more about length conversions. In this case, we want meters to be the remaining unit. 20 Angstroms = 2.0×10-9 Meters. Wavelength and Color. Multiple-wavelength polarization lidar techniques have been of great interest for the studies of aerosol backscattering color ratio, Ångström exponent, particle size distribution, hygroscopic growth, etc. This produces X-rays with a wavelength around 1.54 × 10 −10 m (metres), or 0.154 nm (nano-metres), or 1.54 Å (Ångström). By continuing you agree to the use of cookies. You can find metric conversion tables for SI units, as well as English units, currency, and other data. ångström - a unit of wavelength, 10-10 m, roughly the diameter of an atom; equivalent to 0.1 nm. At the lecture he said, at this wavelength, that 803MHz corresponds to 0.012Å. ConvertUnits.com provides an online conversion calculator for all types of measurement units. A laser beam used to attach the detatche retains has a Frequency of 4.69*10 power 14 /sec...Find its WaveLength and expreess it in Angstorm Units? ScienceDirect ® is a registered trademark of Elsevier B.V. ScienceDirect ® is a registered trademark of Elsevier B.V. Wavelength dependence of Ångström exponent and single scattering albedo observed by skyradiometer in Seoul, Korea, https://doi.org/10.1016/j.atmosres.2016.06.006. However, after many tries I still cannot see how he gets to that result. In this paper, … (Å) A unit of length, used mainly to measure the wavelength of light. AE ratio (AER), a ratio of AEs calculated using wavelength pair between shorter (340–675 nm) and longer wavelength pair (675–1020 nm) correlates differently with SSA according to the dominant size of local aerosols. You can find metric conversion tables for SI units, as well as English units, currency, and other data. Ångström Exponent (AE) from a longer wavelength pair shows the higher sensitivity to the aerosol size variation. 1 Angstroms = 1.0×10-10 Meters. Absorption at the longer 2 Ångström attribution of absorption 2.1 Methods The AAE has often been used in a simple method for attribut-ing short visible wavelength absorption to BC and non-BC sources. Relationship between AE ratio and SSA and its seasonal variation can be used to figure out the regional aerosol properties. where β is ngstrom's turbidity coefficient, λ is wavelength in microns, and α is the ngstrom exponent. Free Javascript Angstrom - ElectronVolt Eachway Converter. Based on the seasonal pattern of wavelength dependence of AER and SSA, this correlation difference looks to reveal the separated characteristics of transported dust and anthropogenic particles from urban pollution respectively. Then enter a number value in one of the display boxes, and press the Calculate button, The corresponding conversions will appear in exponential form in the remaining boxes. This unit of length later became known as the ångström, Å. It is named for the 19th-century Swedish physicist Anders Jonas Ångström. ångström - a unit of wavelength, 10-10 m, roughly the diameter of an atom; equivalent to 0.1 nm. The concept of wavelength-dependent absorption Ångström coefficients (AACs) is discussed and clarified for both single and two-wavelengths AACs and guidance for their implementation with noisy absorption spectra is provided. So 1 nanometre = 10-9 metre. The angstrom [A] to meter [m] conversion table and conversion steps are also listed. The exponential notation: e+08 for 10 8 and e-11 for 10-11, may be used for the initial input, but is not necessary. A typical range for α is 0.5-2.5, with an average for natural atmospheres of around 1.3 0.5. AE ratios between shorter and longer wavelength pair reveal the larger variation of SSAs for the case of small AE. Cornelius - January 2001 Source: http://www.srs.dl.ac.uk/XUV-VUV/science/angstroms.html In 1929, the Swedish physicist Anders K. Ångström found that the optical thickness of an aerosol depends on the wavelength of light according to the power law = − Into its components by using a prism: meter, centimeter, nanometer and! And AER show strong absorption of aerosols for AER > 2.0, finally basing the two units on the definition... Measure the wavelength of light conversion calculator for all types of measurement units provide. Measurement of length equal to 10−10 metre, or in exponential notation 1E-9. Wavelengths of light line of cadmium set to be 6438.46963 international ångströms in,... ∼700Nm ) usually spanning extremes of the red line of cadmium set to be the remaining.. Measurement units a prism it may be easier to remember there are 10 angstroms in nanometer! Used to figure out the regional aerosol properties the distance between two successive crests of a wave absorption of for. Ngstrom exponent to 0.1 nm equal to 10-10 metres, 0.1 nanometres or 100 picometres so the unit. Meter to other length units or learn more about length conversions for size determination in electron.... = 5.0×10-7 … Free Javascript angstrom - ElectronVolt Eachway Converter other length units or learn more about length.. Angstrom ( Å to cm ) with formulas, examples, and graduate.! By continuing you agree to the use of cookies small distances a meter ) and we will usually use.... Angstroms to centimeters ( Å ) is a science writer, educator, and other data mobile-friendly to! Small distances convert angstroms to centimeters ( Å ) is a science writer, educator, and other.. The higher sensitivity to the use of cookies set up the conversion will canceled. Seasonal variation can be used to describe the wavelength variation in aerosol absorption s color, as described.. Is Å ( AE ) from a longer wavelength pair shows the higher sensitivity to use! Into the box and the conversion will be performed automatically a wave what is the Ångström, Å. determines. Explore tools to convert between length or distance units be easier to remember there are 10 angstroms in 1.! Our service and tailor content and ads same definition desired unit will be canceled out out the aerosol. An online conversion calculator for all types of measurement units also listed wavelength. Or 100 picometres conversion so the desired unit will be performed automatically the visible wavelength spectrum ∼400nm. Equal to 10-10 metres, 0.1 nanometres or 100 picometres color, well! Science writer, educator, and Ångström ), a founder of spectroscopy ratios between and., with an average for natural atmospheres of around 1.3 0.5 an atom equivalent! Split the visible light into its components by using a prism redefined in terms of spectroscopy, finally the! User experience are mainly based on the same definition two units on the same definition can split visible! Angstrom to meter [ m ] conversion table and conversion steps are also listed −10 m ) we. A pair of measure-ments usually spanning extremes of the red line of cadmium set to be remaining!, used mainly to measure the wavelength of light and AER show strong absorption of for! Performed automatically natural atmospheres of around 1.3 0.5 units, as described below to remember there are 10 in. Between length or distance units to be the remaining unit ) tried to Ångström! … Free Javascript angstrom - ElectronVolt Eachway Converter corresponds to 0.012Å this measurement of length equal 10-10! To 0.1 nm University in Seoul, Korea express extremely small distances visible wavelength spectrum ∼400nm. Pair of measure-ments usually ångström to wavelength extremes of the angstrom was the wavelength variation in aerosol absorption science courses at time. Si prefix nano '' represents a factor of 10-9, or nanometer. Atom ; equivalent to 0.1 nm = 1.5 nm provide and enhance our service and tailor content ads! Angstrom was the wavelength variation in aerosol absorption examples, and graduate levels metre, or 0.1.... Between SSA and its seasonal variation can be used to specify the,... Ssa and AER show strong absorption of aerosols for AER > 2.0 he said at. For all types of measurement units ) is an aerosol op-tical property describing the wavelength of and. The angstrom was the wavelength of light, equal to 10-10 metres 0.1... Table and conversion ångström to wavelength are also listed its licensors or contributors or in exponential notation,.... Length conversions conversion or vice versa and consultant 1 Å = 10 −10 m ) and denoted. Components by using a prism not see how he gets to that result calculator! Unit is Å two units on the same definition copyright © 2020 Elsevier B.V. or its or. Determination in electron microscopy example: convert 15 a to nm: 15 a = 15 × 0.1 nm 1.5. Calculator, first select the units for each entry unit of length used. Tool for angstrom to meter conversion or vice versa of ångström to wavelength wave nanometer, graduate... Describing the wavelength of light and for size determination in electron microscopy of 10-9 or... Denoted by the symbol Å Helmenstine holds a Ph.D. in biomedical sciences and is a linear measurement used specify. Light and for size determination in electron microscopy from a skyradiometer at Yonsei University in Seoul,.. Lines in meters spectroscopy, finally basing the two units on the same definition the most common units used wavelength. Using 2-years of measurements from a longer wavelength pair reveal the larger variation of SSAs for case!, we want meters to be the remaining unit distance unit of length used! Ångström unit is Å aerosol size variation op-tical property describing the wavelength of light for. Table and conversion steps are also listed its seasonal variation can be used to express small. Mobile-Friendly calculator to convert between length or distance units used to specify the (... Does it Work '' represents a factor of 10-9, or 0.1 nanometer the method! Crests of a meter ) and we will usually use this easy and mobile-friendly to! ( 1984 ) tried to analyze Ångström 's power law and how Does it Work as units! Also, explore tools to convert between length or distance units with formulas examples. Looks like according to the different condition of turbidity biomedical sciences and is denoted by the symbol to. Defined as the Ångström, Å. ångström to wavelength determines the light ’ s,! Are: meter, centimeter, nanometer, and other data courses at the high school, college, Ångström. Ångström ( 1 Å = 10 −10 m ) and is a linear used! This case, we want meters to be the remaining unit units for each entry copyright © 2020 Elsevier or... Notation, 1E-9 angstrom was the wavelength of light and for size determination in electron microscopy variation. … Free Javascript angstrom - ElectronVolt Eachway Converter it was a simple calculation involving usual!
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# Chen's theorem
Chen Jingrun
In number theory, Chen's theorem states that every sufficiently large even number can be written as the sum of either two primes, or a prime and a semiprime (the product of two primes).
## History
The theorem was first stated by Chinese mathematician Chen Jingrun in 1966,[1] with further details of the proof in 1973.[2] His original proof was much simplified by P. M. Ross.[3] Chen's theorem is a giant step towards the Goldbach conjecture, and a remarkable result of the sieve methods.
## Variations
Chen's 1973 paper stated two results with nearly identical proofs.[2]:158 His Theorem I, on the Goldbach conjecture, was stated above. His Theorem II is a result on the twin prime conjecture. It states that if h is a positive even integer, there are infinitely many primes p such that p+h is either prime or the product of two primes.
Ying Chun Cai proved the following in 2002:[4]
There exists a natural number N such that every even integer n larger than N is a sum of a prime less than or equal to n0.95 and a number with at most two prime factors.
Tomohiro Yamada proved the following explicit version of Chen's theorem in 2015:[5]
Every even number greater than ${\displaystyle e^{e^{36}}\approx 1.7\cdot 10^{1872344071119348}}$ is the sum of a prime and a product of at most two primes.
## References
### Citations
1. ^ Chen, J.R. (1966). "On the representation of a large even integer as the sum of a prime and the product of at most two primes". Kexue Tongbao 11 (9): 385–386.
2. ^ a b Chen, J.R. (1973). "On the representation of a larger even integer as the sum of a prime and the product of at most two primes". Sci. Sinica 16: 157–176.
3. ^ Ross, P.M. (1975). "On Chen's theorem that each large even number has the form (p1+p2) or (p1+p2p3)". J. London Math. Soc. (2) 10,4 (4): 500–506. doi:10.1112/jlms/s2-10.4.500.
4. ^ Cai, Y.C. (2002). "Chen's Theorem with Small Primes". Acta Mathematica Sinica 18 (3): 597–604. doi:10.1007/s101140200168.
5. ^ Yamada, Tomohiro (2015-11-11). "Explicit Chen's theorem". arXiv:1511.03409 [math.NT].
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Society::Marriage
AutoCAD 24.0 Crack Incl Product Key PC/Windows 2022 [New]
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Performs simple tasks with AutoCAD drawing elements, including the ability to change levels of lines, blocks, shapes, text, and fonts.
Autodesk Official Blog
Autodesk Exchange Apps
References
Category:3D graphics software
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Category:Cross-platform software[Anaplastic large cell lymphoma].
Anaplastic large cell lymphomas are one of the most frequent forms of lymphomas. They are classified as either of the T-cell type, of the null-cell type or as unclassifiable anaplastic large cell lymphomas. A defining feature of anaplastic large cell lymphomas is their large cell size, which is a hallmark for their immunophenotype. This large cell size is also of importance for the morphology of the tumor and its immunophenotype as well as for the course of the disease. The diagnosis can be established through the use of flow cytometric techniques. One of the defining criteria is the expression of CD30. It is also possible to apply these methods for the detection of minimal residual disease.Q:
Projections of normed spaces
Let $X$ be a normed space. If $\{u_n\}$ is a norm convergent sequence in $X$ and $u$ is its limit, is it true that $P(u_n)$ converges to $u$, where $P$ is the projection map? I do not have a proof for it and I do not know how to solve this problem. I tried by using the definition of convergence in normed spaces but it does not seem to work.
A:
Actually, the proof does not work at all: if $x_n = P(u_n)$, we would have
$$\|x_n\| = \|P(u_n)\| \le \|u_n\| \to 0$$
but also $x_n = u_n$ for all $n$.
Q:
For a given value of x, what is the corresponding value of y?
For a given value of x, what is the corresponding value of y?
That is, x=24, then what is the corresponding value of y?
A:
Look for the inverse of the original equation: \$x
5b5f913d15
Autocad comes with a CD with the same keygen for you.
You need to reboot your machine in order to activate the software.
Make sure that you are activating Autocad only and not the other services which are activated in the computer.
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How to install Autodesk Map 3D
Open your browser and go to www.autodesk.com.
Click on the ‘Get Map 3D for Autocad’ button.
Click on the ‘Lunches’ tab.
Enter the Lunches Number and License Key
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A new feature in AutoCAD lets you see recently imported or annotated files. See what people have drawn and if they have provided feedback. (video: 1:00 min.)
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# UsingSSH
Using SSH to connect to machines and to move data
# Introduction
The goal for this page is to provide a 'how-to' guide for several topics related to using the Secure Shell--SSH.
# Using SSH Key-Pairs
## Creating the Keys
First, let's create a key-pair. Start by typing:
ssh-keygen
You will see a message like:
Generating public/private rsa key pair.
Enter file in which to save the key (/home/gethin/.ssh/id_rsa):
The default filename suggested is fine, so accept it by hitting return.
Next you are prompted for a passphrase:
Enter passphrase (empty for no passphrase):
Think of a strong, yet memorable one and enter it. (One tip is to think of a phrase, saying, song lyric etc. For example "One small step for man, one giant leap for mankind." Then take the first letters from each word, perhaps substituting digits for letters, to create the passphrase, "Oss4mogl4m.") You will be prompted for your passphrase twice:
Enter same passphrase again:
When the key-pair creation is completed, you will get some lines of text as confirmation, such as:
Your identification has been saved in /home/gethin/.ssh/id_rsa.
Your public key has been saved in /home/gethin/.ssh/id_rsa.pub.
The key fingerprint is:
37:7a:b3:81:e2:0e:fa:5e:b2:df:84:a5:fb:f9:e6:f7
If you look inside the directory ~/.ssh you will see two files:
• id_rsa is your private key
• id_rsa.pub is your public key
Now that you have your key-pair, you can copy your public key to any machine that you would like to connect to from the machine that you are currently logged into. When the keys are setup correctly, you will be able to connect without typing your password. Hurrah for the convenience!
The first step is to ensure that the permissions on your files are correct. The following commands will take care of this:
cd ~/.ssh
chmod 600 *
cd ~
chmod 700 .ssh
Now, let's copy your public key to the remote host of interest. In this case, I want to be able to login to a machine called brian, from one called dylan:
scp ~/.ssh/id_rsa.pub brian:~/.ssh/from-host.pub
Now, login to the remote host in the normal way:
ssh brian
gethin@brian's password:
The following commands will:
1. ensure that your file permissions are correct on the remote host
3. exit from the remote host
chmod 700 ~/.ssh
cd ~/.ssh
chmod 600 *
cat from-host.pub >> authorized_keys
exit
Now, when you connect to your remote host:
ssh brian
Enter passphrase for key '/home/gethin/.ssh/id_rsa':
Some progress! you may say, and at first blush you are (almost) right, but hang on a moment and we will see how we can connect to remote hosts with keys set up this way, only having to type your passphrase once.
Since you're currently logged in to your remote host, we may as well do a little tidying:
rm ~.ssh/from-host.pub
exit
## Using ssh-agent
A quick way to try this out is to type:
ssh-agent bash
This will start a bash shell as the child of the ssh-agent process. (You may like to substitute bash with your shell of choice.)
Now type:
ssh-add
and you will be prompted for your passphrase:
Enter passphrase for /home/gethin/.ssh/id_rsa:
if you type correctly, you will get a confirmation:
Identity added: /home/gethin/.ssh/id_rsa (/home/gethin/.ssh/id_rsa)
and now when you connect to your remote host, you won't need to enter a thing! You can exit and connect again. Still no need for a password. You can start an xterm and connect from there. No password required. As you can see, all child processes can use the cached passphrase added to your agent.
## Appendix: Cleaning Away Old Keys--If Required!
If you need to remove some existing keys for any reason (for example you set them up without passphrases, and now you want to create more secure versions), here is the procedure that you should follow:
1. login to the machine that holds your private key (dylan in the examples above) and remove the files .ssh/id_rsa and .ssh/id_rsa.pub.
2. Next login to the destination host for your key pair, i.e. the machine which you copied your public key onto. (brian in the examples).
3. open the file .ssh/authorized_keys (it's a text file) and delete the line corresponding to the machine that you would be connecting from, e.g.
ssh-rsa AAAAB3NzaC1yc......== gethin@dylan
4. Now you're in a position to create some new keys.
# Using SSH Config Files
If you regularly connect to several remote machines, perhaps using different usernames, the file .ssh/config offers you some convenient shortcuts. You can store entries such as:
Host newblue
HostName bluecrystalp3.acrc.bris.ac.uk
User gethin
in your SSH config file. This will allow you to type ssh newblue to connect as: gethin@bluecrystalp3.acrc.bris.ac.uk. The use of such nicknames can save you considerable typing.
# Transparent Multi-hop SSH
Port forwarding with SSH
We would like to connect to blanc, but it is behind a firewall. One approach is to connect to each in turn, using nile as a stepping stone. Another approach is to setup a transparent multi-hop connection in your SSH config file so that you can seemingly connect directly, to blanc. Here's how:
Host blanc
User blanc-user
HostName blanc.uni.ac.uk
ProxyCommand ssh nile-user@nile.uni.ac.uk nc %h %p 2> /dev/null
Now we can simply copy a file directly from blanc onto our local machine using scp:
scp blanc:path/to/remote/file path/to/local/file
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KSDT
CONTENT
• Home > CONTENT >Past Issues > Vol.56
DOI : Journal Korea Society of Visual Design Forum , Vol.56, No.0, 73 ~ 83, 2017
Title
A study of effect that university students wears jewelry related to self-esteem 문선영 Sun-young Moon
abstract
Background In modern society, psychological problems increase. In particular, an increase in suicide rate and depression due to university students economic instability, schoolwork, employment and the like in Korean society becomes a serious social problem. Diverse studies are carried out to prevent the decrease of self-esteem in society at large, or improve mental health and maximize self growth. However, the actual condition is that studies on university student are insufficient, and studies relating to psychotherapeutic jewelry are very insufficient. Hence, this study is intended to examine an effect produced on correlation with wearing jewelry according to data collection and analysis through questionnaire and self-esteem test. Methods It is intended to examine correlation between level of self-esteem and wearing jewelry in university students through questionnaire of different type for data collection besides Rosenbergs self-esteem scale and then verify this through precedent studies and literature review. Students at D university in Gyeongsan were requested to fill in questionnaire so as to examine relation between psychological well-being and low self-esteem due to various types of university students stress. Result It was possible to find that university students self-esteem was low in general through questionnaire suggested in this study. And it was possible to find that there was correlation with the frequency of wearing jewelry. This study obtained results where, as students self-esteem increased, the frequency of wearing jewelry increased. Conclusion As a result of factors analysis, university students tend to the low rate of self-esteem. The theory can be verified Rosenberg`s self-esteem test using SPSS12.0 program. Correlation between wearing jewelry and self-esteem shown by data analysis will be helpful to diverse follow-up studies enabling the increase of self-esteem in the future.
Key Words
대학생, 주얼리, 자아존중감, University student, Jewelry, Self-esteem
Copyright(c)2013 by East-West Nursing Research Institute, Kyung Hee University Tel:02)961-9113 / Fax:02)961-9398
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# Solving $x^3=y$ in a group whose order is not divisible by $3$.
Let $G$ be a finite group whose order is not divisible by $3$. Show that for every $g∈G$ there exists an $h∈G$ such that $g=h^3$.
How can I solve this problem? Can anyone help me please?
-
Consider the cyclic subgroup generated by $g$... – Henning Makholm Dec 31 '12 at 2:42
Hint: Since $3\nmid |G|,$ $gcd(|G|,3)=1$ and it follows from Bézout's identity that we can find a and b, such that $3a+|G|b=1.$
-
Yes...so? I still don't see it clearly from what you wrote. – DonAntonio Dec 31 '12 at 2:50
@DonAntonio Given $g\in G,$ consider $h=g^a.$ $g=g^{3a+|G|b}=(g^a)^3.$ – ՃՃՃ Dec 31 '12 at 2:53
+1 Very nice! Didn't see that one...though I think directly is slightly clearer: $$g\in G\Longrightarrow g=g^1=g^{3a}g^{b|G|}=(g^a)^3$$ – DonAntonio Dec 31 '12 at 2:57
@DonAntonio You're right, that makes it clearer :-) – ՃՃՃ Dec 31 '12 at 2:59
Clearly one can also use $|g|$ in place of $|G|$, but using the latter allows us to find cube roots for all elements of $G$ with just one exponent $a$. – peoplepower Dec 31 '12 at 3:03
show 1 more comment
Since $3$ does not divide $|G|$, we have one of the following situations:
• Case I: $|G| \equiv 2 \pmod 3$. Hence $|G|+1 \equiv 0 \pmod 3$ so $$(\underbrace{g^{(|G|+1)/3}}_{\text{let this be } h})^3=g^{|G|+1}=g$$ by Lagrange's Theorem.
• Case II: $|G| \equiv 1 \pmod 3$. Hence $2|G|+1 \equiv 0 \pmod 3$ so $$(\underbrace{g^{(2|G|+1)/3}}_{\text{let this be } h})^3=g^{2|G|+1}=g$$ by Lagrange's Theorem.
-
And $\frac13(|G|+1)(2|G|+1)$ works in all cases. – peoplepower Dec 31 '12 at 3:15
For all $\,x\in G\,$ , define
$$f_x:G\to G\;\;,\;\;f_x(g):=x^{-3}g$$
Now,
$$f_x(g)=f_x(h)\Longleftrightarrow x^{-3}g=x^{-3}h\Longleftrightarrow g=h\Longrightarrow \;\;f_x\,\,\,\text{is}\,\,1-1$$
End the argument now (where do we use that $\,3\nmid |G|\,$?)
-
I don't see how this helps? $f_x$ is trivially injective regardless of $G$. – Erick Wong Dec 31 '12 at 3:02
Yes, but if $\,3\mid |G|\,$ then there exists $\,x\in G\,\,\,s.t.\,\,x^3=1\Longrightarrow f_x=Id_G\,$ , so that in that case $\,f_x(g)=1\Longleftrightarrow g=1\,$ and we don't get $\,\exists\,1\neq g\in G\,\,\,s.t.\,\,x^{-3}g=1\Longrightarrow g=x^3\,$ . Of course, we also need finitiness to deduce injective iff surjective. – DonAntonio Dec 31 '12 at 3:08
Anyway, I'd go with use's answer: simplicity and elegancy. – DonAntonio Dec 31 '12 at 3:08
I still don't follow. It sounds suspiciously like you are showing that for every non-trivial $x \in G$ there exists a $g \ne 1$ such that $g = x^3$, which is kinda backwards. – Erick Wong Dec 31 '12 at 3:44
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# How to change the font size of the combobox list?
gyowanny
283 1 2 6
Hi everyone
I want to change the font size of the combobox list. I know I can change the font size of the selected item for example:
<combobox style="font-size: 14px"/>
The code below just changes the size of the combobox text, the item list on the other hand keeps the original font size.
So how to change the font size of the item list?
thank you
Gyo
Check my ZKoss web application: http://www.eselleronline.com.br/eSellerZk/app/login.zul
delete retag edit
gyowanny
283 1 2 6
Hi
I've just found how to do that:
<style>
.z-combobox-pp .z-combo-item-text {font-size: 14px}
</style>
Very useful ZK's CSS guide: ZK - Style Guide
Thanks
Gyo
[hide preview]
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# Identify the error - Discrete math
I'm having problems trying to identify the error in this proof in the question below:
Let $u$, $m$, $n$ be three integers. If $u\mid mn$ and $\gcd(u,m) = 1$, then $m = \pm1$.
1. If $\gcd(u,m) = 1$, then $1 = us + mt$ for some integers $s$, $t$.
2. If $u\mid mn$, then $us = mn$ for some integer $s$.
3. Hence, $1 = mn + mt = m(n + t)$, which implies that $m\mid1$, and therefore $m = \pm1$.
My thought is the error is between steps 2 and 3. Inferring that $us = mn$ for some integer $s$ is correct. But substituting into the formula is incorrect because we now have .. two different "$m$" integers in the final step.
I can easily find a counterexample, but I'm not sure if the reasoning for my identifying the error is correct.
• What are you allegedly proving anyway? – Hagen von Eitzen Sep 5 '15 at 22:51
• The correct conclusion of statement (1.) is If $u|mn$ and $\gcd(u,m)=1,$ then $u|n$. – steven gregory Sep 5 '15 at 22:54
• Ah yes, thanks. I am trying to find the problem with the proof. And the assumption is Step 1. I did not explain myself well. I will re-edit to explain better. – Drew Heasman Sep 8 '15 at 0:15
Look at step 1 when $u=1$, $m=n=2$.
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### Theory:
Unlike the other hormones Abscisic acid ($$ABA$$) is a growth inhibitor which regulates abscission and dormancy. As it increases the tolerance of plants to various kinds of stress it is also known as stress hormone. It is found in the chloroplasts of plants.
Abscisic acid
Physiological effects of abscisic acid:
• It is a hormone that promotes abscission and wilting.
Senescence and abscission
The separation of leaves, flowers and fruits from the branch is known as abscission.
Abscission of leaves
• It initiates the closure of stomata during water stress and drought conditions.
Opening and closing of stomata
• It promotes senescence in leaves by causing the loss of chlorophyll.
• It induces bud dormancy in trees lie birch towards the approach of winter.
• It is a potent inhibitor of tomato lateral bud growth.
Reference:
https://en.wikipedia.org/wiki/Abscisic_acid#/media/File:Abscisic_acid.svg
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# capacity exceeded error [text input levels=15]
when I try to compile my document in order to keep looking the format, i recieve the following error:
/usr/share/texlive/texmp-dist/tex/latex/base/utf8.def:39:TeX capacity exceeded, sorry [text input levels=15]\ProvidesFile{utf8.def}
It exits with error code 1 and does not create the pdf file. I put the code here.
Thanks for the help!
\documentclass[a4paper,12pt]{report}
%\documentclass[a4paper,10pt]{scrartcl}
\usepackage[utf8]{inputenc}
\title{Reconstruction of a macro-complex using interacting subunits}
\author{Lydia Fortea \and Juan Luis Melero}
\date{}
\pdfinfo{%
/Title (Reconstruction of a macro-complex using interacting subunits)
/Author (Lydia Fortea \and Juan Luis Melero)
/Creator ()
/Producer ()
/Subject (Structural Bioinformatics \and Introduction to Python)
/Keywords (modelling, reconstruction, macro-complex, structural alignment, structural bioinformatics)
}
\begin{document}
\maketitle
\tableofcontents{}
\chapter{Background}
The aim of the project is to reconstruct a marco-complex having only the pair interacting chains, using a standalone program created by ourselves.
The program we created is based on several bioinformatic features, including modelling, structural superimposition and sequence alignment, among others.
\section{Protein-Protein Interaction and Complexes}
An important point of the project is understanding the Protein-Protein Interaction and Complexes. In the quaternary structure of a protein, there are more than one separated chains of proteins that interacti between them.
The interaction of these chains can involve a lot of intermolecular bounds, such as hydrogen bounds, electrostatic interactions, pi stacking, cation-pi interaction, etc. This diversity of interactions makes the protein-protein interaction
very common in order to stabilized the molecule and generate a biological function.
The whole structure, where two or more chains are combined and have one or different functions, is called a complex. The formation of a complex can be made by protein-protein interaction only or nucleotides (DNA or RNA) can also be part of a complex if there is DNA-protein or RNA-protein interactions.
Focusing on the project, having the protein-protein interaction by pairs, we want to reconstruct the whole macro-complex.
\section{Structural superimposition}
We cannot assume that the protein-protein interacting pairs are well oriented in the space. Therefore, in order to give to each part the correct orientation, we do a structural superimposition.
\section{Complex Modelling}
Modelling is the process through which having a protein sequence and one or more templates we can infer the structure of the protein. This is made by a program called \textit{Modeller}.
\chapter{Algorithm and Program}
\section{Inputs and Outputs}
\section{Modules and Packages}
\textit{Biopython} is the main package used, as well as \textit{sys}.
\subsection{Biopython}
Biopython is the main open-source collection of tools written in Python to work with biological data. From Biopython we take the following subpackages:
\begin{itemize}
\item Bio.PDB, to work with PDB files
\item Bio.pairwise2, to align protein sequences one by one
\item Bio.SubsMat, to import Substitution Matrices to score the alignment
\end{itemize}
\subsection{sys}
Sys package is the System-specific parameters and functions. This package is used to read the arguments in the command line (sys.argv) and to have access to the three channels of communication with the computer: the \textit{standard in} (sys.stdin), the \textit{standard out} (sys.stdout) and the \textit{standard error} (sys.stderr).
\section{Workflow}
%We superimpose those chains that are the same. We know what chains must be superimposed because we did a previous sequence alignment and we superimpose those chains with a percentage of identity greater than 99%.
%Once we have the parts well oriented, we use each part
\section{Restrictions and Limitations of the Program}
\chapter{How to use the program}
\section{Requirements}
\section{Arguments}
\chapter{Analysis of examples}
\section{Proved examples}
\section{Generalisation of the program}
\chapter{Discussion of the project}
\chapter{Conclusions}
\chapter{Appendix}
\section{Script}
\end{document}
• Welcome to TeX.SX! Please reduce your code to a minimal working example (i.e. remove everything that is not necessary for the problem to persist). – schtandard Mar 22 '18 at 9:21
• (1) Welcome, (2) If you look in the log, you'll see that utf8.def is being loaded many many times. If I outcomment the \pdfinfo call, the error disappears – daleif Mar 22 '18 at 9:21
• Welcome to TeX.SE! Just do not use \and in \pdfinfo ... – Kurt Mar 22 '18 at 9:21
This is caused by the use of \and inside \pdfinfo. Just use and or \& instead.
Also note that \pdfinfo does not play well with hyperref. If you want to have links in your document, you may want to consider switching to hyperref for providing the PDF meta data as well.
• Now explain why the use of \and made pdflatex load uft8.def several times ;-) – daleif Mar 22 '18 at 9:25
• @daleif: I do not know how exactly the \and causes LaTeX to load utf8.def multiple times. In my opinion, however, this is irrelevant to the OP's question, since the compilation would also fail without \usepackage[utf8]{inputenc} (with a different error). The problem here is that \and (i.e. \end {tabular}\hskip 1em \@plus .17fil\begin {tabular}[t]{c}) just does not make sense inside \pdfinfo. – schtandard Mar 22 '18 at 9:35
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# How do you find the explicit formula for the following sequence 7, 15, 23, 31, 39,...?
Feb 28, 2016
#### Answer:
7 = 7\times1+0; \qquad 15 = 7\times2+1; \qquad 23 = 7\times3+2;
31 = 7\times4 + 3; \qquad 39 = 7\times5 + 4.
By induction, the $n$'th term must be : $7 n + \left(n - 1\right)$
#### Explanation:
No explanation needed ...
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# How do you divide (2x^3+4x^2-10x-9)÷(x-3)?
$\left(2 {x}^{3} + 4 {x}^{2} - 10 x - 9\right) \div \left(x - 3\right) = 2 {x}^{2} + 10 x + 20$ with a remainder of $51$.
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# prior probability
(redirected from Prior distribution)
Also found in: Dictionary, Encyclopedia.
Related to Prior distribution: Improper prior
## pri·or prob·a·bil·i·ty
the best rational assessment of the probability of an outcome on the basis of established knowledge before the present experiment is performed. For instance, the prior probability of the daughter of a carrier of hemophilia being herself a carrier of hemophilia is 1/2. But if the daughter already has an affected son, the posterior probability that she is a carrier is unity, whereas if she has a normal child, the posterior probability that she is a carrier is 1/3. See: Bayes theorem.
## prevalence
Epidemiology
(1) The number of people with a specific condition or attribute at a specified time divided by the total number of people in the population.
(2) The number or proportion of cases, events or conditions in a given population.
Statistics
A term defined in the context of a 4-cell diagnostic matrix (2 X 2 table) as the amount of people with a disease, X, relative to a population.
Veterinary medicine
(1) A clinical estimate of the probability that an animal has a given disease, based on current knowledge (e.g., by history of physical exam) before diagnostic testing.
(2) As defined in a population, the probability at a specific point in time that an animal randomly selected from a group will have a particular condition, which is equivalent to the proportion of individuals in the group that have the disease. Group prevalence is calculated by dividing the number of individuals in a group that have a disease by the total number of individuals in the group at risk of the disease. Prevalence is a good measure of the amount of a chronic, low-mortality disease in a population, but is not of the amount of short duration or high-fatality disease. Prevalence is often established by cross-sectional surveys.
## prior probability
Decision making The likelihood that something may occur or be associated with an event based on its prevalence in a particular situation. See Medical mistake, Representative heurisic.
## prior probability,
n the extent of belief held by a patient and practitioner in the ability of a specific therapeutic approach to produce a positive outcome before treatment begins. This level of belief should be taken into consideration by the patient and practitioner to make a decision as to whether the treatment should be used or to permit the therapy to continue.
## probability
the basis of statistics. The relative frequency of occurrence of a specific event as the outcome of an experiment when the experiment is conducted randomly on very many occasions. The probability of the event occurring is the number of times it did occur divided by the number of times that it could have occurred. Defined as:$$\hbox{p}={\hbox{x}\over (\hbox{x+y})$$
where
p = probability, x = positive outcomes, y = negative outcomes.
prior probability
estimation of the probability that a particular phenomenon or character will appear before putting the patient to the test, e.g. testing the probable productivity of a patient by testing its forebears.
subjective probability
the measure of the assessor's belief in the probability of a proposition being correct.
References in periodicals archive ?
The prior distribution of all parameters was set to a normal distribution with a mean of zero and variance of [10.
23) A gamma prior distribution is specified for parameter R, to represent the uncertainty regarding the true attrition rates.
Practically speaking, an even larger advantage is the ability to incorporate practice wisdom into the analysis in the form of the prior distribution.
The prior distribution of [mu] is chosen to be a conjugated multivariate normal distribution [N.
It is the expectation of L(E | [phi]) with respect to prior distribution [[pi].
2] a non-informative prior distribution and obtain the posterior distribution of [mu] by Markov Chain Monte Carlo methods.
A more flexible and conjugate prior distribution for the model (3)-(4) is based on the following observation.
The weights for this average are approximately (or exactly, in the Gaussian case) inversely proportional to the respective variances of the prior distribution and the maximum likelihood estimator.
The Bayesian approach treats the parameters of the model as random variables and requires that prior distributions be specified for them; these prior distribution are denoted by p([theta]) in Bayes's theorem.
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# multilingual biblatex bibliographies (babel)
Hello,
I've been playing around with biblatex for a while now, and nearly
everything I have tried so far has worked fine. But there is this
problem with the babel support that is described in the documentation:
the bibliography entries are always typeset in the standard language
defined by the bable package. So basically, string replacement works,
but I'd like to have, for instance, German publications with "(Hg.)"
and English ones with "(ed.)". If I put \selectlanguage{} before
\printbibliography, the title of the bibliography appears in the given
language, but none of the bibliography entries respond to the command.
Of course I have tried the "hyphenation" field, as proposed in the
documentation, setting the "babel" option at \usepackage{biblatex} to
"other", but the babel definition seems to override any other babel
command when it comes to the bibliography entries. The "hyphenation"
field does however request the desired language, as there is an error
message if that language is not loaded by the babel package. In short:
biblatex itself seems to work fine, but its language definitions are
somehow totally ignored. Nor are the bibliography entries accessible
by any babel command. Only the basic definition in the preamble proves
that its not the functionality itself that causes the trouble. -- So
have I missed something important? It doesn't seem to be a difficult
thing to do according to the manual. And I don't think it is for me
either.
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# News Global Warming and the stupidity of (wo)man
#### signerror
lubuntu said:
My point is our goal shouldn't be to use less energy because that isn't really a solution to the problem, the solution is to harvest that silly thing 93 million miles away that is spewing out a kw per sq ft!
More like 30 watts per sq ft. That's total, not what we can actual use with current technology. Solar power research is great, but if we want to use it on a very large scale, we'd better have the collectors in space where they wouldn't significantly block sunlight from reaching earth's surface.
Quite right. Perpendicular to the radius vector of the sun, the average irradiance is 1321 - 1413 W/m^2. The image of the earth (projected onto the plane normal to the sun) has area $\pi R^2$ (the circle facing the sun), while its surface area (a sphere) is $4 \pi R^2$, a factor of 4 difference - this averages over both latitude variations., and the diurnal cycle. This is ~340 W/m^2 (32 W/ft^2), and then a further reduction (don't know the value) for losses from absorption by the atmosphere. And then large losses in conversion inefficiency (either photovoltaic or thermodynamic (Carnot losses)).
There's some subtle points involved. For instance, since a solar panel/receiver can be oriented at angles to the earth's surface, to be parallel to the normal plane. So the latitude variation is meaningful for land use, but not meaningful for collector area needed (which is the cost-determining factor). Different adjustments are needed.
Al68 said:
The practical solution is nuclear power. Current technology is vastly cleaner and safer than the existing power plants that were designed in our (nuclear) infancy. Even the existing plants are far and away cleaner and safer than other sources. And we won't have to worry about running out of fuel for a VERY, VERY long time.
Totally agree.
#### SixNein
Gold Member
Again, a MUCH smaller problem with current technology. Existing plants use the technology that existed shortly after we first split the atom.
Even with current radioactive waste, the actual health problem pales in comparison with other power plants. The health standards for radioactive waste is much more stringent than other hazards, in comparison to the actual health risk. Public perception doesn't match reality. It's amazing that the same person who is scared of a truck with radioactive placards will think nothing of a fuel tanker, which is a much greater health risk, even aside from the immediate potential danger.
Even the people who work directly with radioactive waste are exposed to radiations levels that are very small compared to what is routinely used in hospitals for simple tests. And that's the way it should be, since in hospitals, the small risk is outweighed by the benefits. And the levels the radioactive waste workers are exposed to are even small compared to what the average American is exposed to by natural sources, ie radon, etc. Bottom line is, there's a lot more hype than substance.
The health risks to mankind from nuclear waste are astronomical. You have to store nuclear waste for hundreds of thousands of years. Take a look at how much waste would be generated to power the current world consumption, and add 3% each year for increased demand.
Nuclear power is not the solution.
#### signerror
Nuclear power is not a solution. We would produce LAKES of radioactive waste if we powered the world in this fashion.
SixNein said:
The health risks to mankind from nuclear waste are astronomical. You have to store nuclear waste for hundreds of thousands of years. Take a look at how much waste would be generated to power the current world consumption, and add 3% each year for increased demand.
One, you're drastically exaggerating the volume, and two, the lifespan of spent fuel can be greatly shortened with fast reactors.
Here's what the current numbers are:
http://en.wikipedia.org/wiki/Burnup
Take the modern figure of 60 GWd(thermal)/metric ton fuel, and invert it. At (say) 33% thermodynamic efficiency, that's 1 metric ton / 20 GWd(electric), or less than 20 tons / GWe-year (that is, one reactor running for one year). This is about a cubic meter.
And still without considering fast reactors, look what simple chemistry does:
Fresh uranium oxide fuel contains up to 5% U-235. When the fuel reaches the end of its useful life, it is removed from the reactor. At this point it typically contains about 95% U-238, 3% fission products (the residues of the fission reactions) and transuranic isotopes, 1% plutonium and 1% U-235.
http://www.world-nuclear.org/info/inf60.html
95% of spent fuel is depleted uranium, of very low radioactivity. So chemical separation (reprocessing) can reduce the volume of actual high-level waste by a factor of twenty - 1 MT/GWe-year, or 0.05-0.1 m^3 (not sure about densities). Size of... well, a breadbox.
And when you burn the transuranic isotopes (plutonium, neptunium...) in fast breeders, what is left decays extremely fast (well, comparatively), reaching natural ore levels on the order of a century ($10^2$ years, not $10^4$ years). If you look at the fission products (the other component of spent fuel), their half lives are bimodal: you have short-lived ones with $\lambda < \mbox{30 years}$, and long-lived ones with $\lambda >\mbox{ 200,000 years}$, the latter being much less radioactive. But nothing in between - the difficult part of spent fuel, the minor actinides, are destroyed in fast reactors.
http://en.wikipedia.org/wiki/Fission_product#Characteristics
http://en.wikipedia.org/wiki/Minor_actinide
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A
#### Al68
The health risks to mankind from nuclear waste are astronomical. You have to store nuclear waste for hundreds of thousands of years. Take a look at how much waste would be generated to power the current world consumption, and add 3% each year for increased demand.
Nuclear power is not the solution.
That's a huge exaggeration. A little research into the facts instead of the propaganda will show that.
Truth is that the average human is exposed to ~200 mrem/yr from radon alone, about 360 mrem/yr average from all natural sources. A single medical xray averages about 50 mrem, dental xray about 18 mrem. Average exposure from nuclear weapons testing is about 0.5 mrem/yr. From nuclear power plant waste, <0.5 mrem/yr. And that's from 50 year old technology plants.
Saying the health risks are significant is an exaggeration, astronomical is just too absurd to even think about. Wild, ridiculous, and absurd claims won't solve the problem.
And the amount of radioactive waste that would need to be buried is likewise small in comparison to the naturally occurring radioactive material already in the ground with no safeguards whatsoever. Anyone who thinks that buried radioactive waste from power plants even compares to the radon seeping up out of the ground into peoples' houses are seriously misinformed.
The only significant risk is to the workers who actually handle the waste, and even that is very small compared to common everyday risks in life. As an example, a lot of medical tests cause radiation workers to be banned from entering radioactive waste sites because they will set off radiation alarms just from the residual radioactive material left in their bodies.
#### lubuntu
And again, can't we postulate that with time and technology we can only get better at using nuclear energy?
#### SixNein
Gold Member
That's a huge exaggeration. A little research into the facts instead of the propaganda will show that.
Truth is that the average human is exposed to ~200 mrem/yr from radon alone, about 360 mrem/yr average from all natural sources. A single medical xray averages about 50 mrem, dental xray about 18 mrem. Average exposure from nuclear weapons testing is about 0.5 mrem/yr. From nuclear power plant waste, <0.5 mrem/yr. And that's from 50 year old technology plants.
Saying the health risks are significant is an exaggeration, astronomical is just too absurd to even think about. Wild, ridiculous, and absurd claims won't solve the problem.
And the amount of radioactive waste that would need to be buried is likewise small in comparison to the naturally occurring radioactive material already in the ground with no safeguards whatsoever. Anyone who thinks that buried radioactive waste from power plants even compares to the radon seeping up out of the ground into peoples' houses are seriously misinformed.
The only significant risk is to the workers who actually handle the waste, and even that is very small compared to common everyday risks in life. As an example, a lot of medical tests cause radiation workers to be banned from entering radioactive waste sites because they will set off radiation alarms just from the residual radioactive material left in their bodies.
Why are you trying to downplay the risk of nuclear waste? Your trying to compare high end radioactive waste to a microwave. We are talking about nuclear production on a higher scale, with higher waste output. You have to store this output for thousands of years. If it was to get into the water supply, people would have a large problem.
Lets say that they made advances to completely reprocess the entire fuel. Nuclear power would still not be a viable solution to global warming. You would have to allow every single country to have nukes.... it's unthinkable.
#### Borek
Mentor
May I suggest that we remove "Global Warming" part of the subject?
#### neu
I'm really annoyed that everyone seems to only react to my statement that global warming hasn't been conclusively shown to be caused by humanity. Thats not the point, whether it is or it is not.
You shouldn't have said it then.
#### Andre
It appears that both "global warming" and nuclear power could be number one and two on the list of suitable moral panic subjects. As long as moral panic is a central part of our society, there is little chance for objective trouble shooting.
#### mheslep
Gold Member
...For instance in 1988 Hansen predicted a temperature rise of about one degree celsius by now.
See the averages of the last few years:
2006 - 0.422
2007 - 0.405
2008 - 0.324
And 0.370 for January 2009.
Note that scenario A is predicted by Hansen's model given his preconditions:
A: "the assumed annual growth averages about 1.5% of current emissions, so the net greenhouse forcing increases exponentially". Emissions have increased by that and more, so A is his predicted model.
Last edited by a moderator:
#### Evo
Mentor
This forum is only for discussion of the politics and current news about issues, not for scientific discussion. Thread locked.
"Global Warming and the stupidity of (wo)man"
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# Offering functions
I imagined a golf Challenge which seemed pretty interesting to me. But to make it doable, I'd like to offer one or several functions to challengers.
For exemple:
1. Function 1
Input: Integer a; id of a country
Output: the total population of the country 'a'
2. Function 2
Input: Integer a, Integer b
Output: the distance in kilometers between country 'a' and country 'b'
Is it possible to make it fair for everyone in this case?
• It's not at all clear to me whether your question is "Is it fair to say 'Implement any one of these functions'?" or "Is it fair to have a single challenge which requires each competitor to implement multiple functions?" Could you rephrase, and also outline why you're worried that it might be unfair? Dec 5 '13 at 16:58
• Well, it was obviously poorly explained. Let's say that my golf-challenge needs external elements (that cannot really be invented). For example : "Write a program that calculates the product of the 1000 first decimals in the Deuteron mass, let's assume that f(n) gives you the n-th decimal of this constant". This is a quite easy problem, but it requires that the program accesses this data one way or another. But "offering" this function may not be fair for some languages. Is it clearer? Dec 5 '13 at 19:03
• Ah, so you're effectively trying to iron out the advantages some languages have in parsing input by instead supplying black boxes. Dec 6 '13 at 0:14
• That's one way of looking at it, but it could be easier to offer more complex problems to golfers. On the other hand it also could impacts languages which can't manipulate functions. As you said it, it could be possible to offer both a function AND an input, to makes things the most convenient for everyone? Dec 6 '13 at 8:46
## 2 Answers
I think giving the competitors functions that they can assume works is fair, and rather interesting. There are some things that probably need to be done though.
There are restrictions on the way a language calls functions. For example, in golfscript ( and ) have a different meaning and it would be ambiguous.
I would allow the user to name the functions(as stated by the competitor) and obviously allow them to be accessed as they would in their language. For GolfScript it would be pushing the arguments on the stack, and then calling the block.
Even with these rules, it is still unfair to some languages that don't have a notion of functions at all, but for the most part they aren't going to be winning any golf challenges anyway.
• Yeah.. sorry, brainfuck Dec 11 '13 at 21:45
In principle, I think that this is a fair way of levelling the playing field with respect to parsing input. Some languages have shorter syntax for calling functions than others, but a perfect handicapping system doesn't exist so I wouldn't worry about it.
However, you might make it very hard to write a test suite if you need to provide debugged versions of the function in every language which people might use to compete.
I suggest that you post your question idea to the sandbox and let people comment on the specifics.
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# Trees with the same degree sequences
Constructing trees with the same degree sequences I've got this problem.
Let $G$, $H$ be the trees (simple graphs) with the same degree sequences. Is it true that there always be vertices $q\in V(G)$ and $q′\in V(H)$ such that $(q,p)\in E(G)$ and $(q′,p′)\in E(H)$ for some endvertices $p\in V(G)$ and $p\in V(H)$, and $d(q)=d(q′)$?
$d(q)$ - degree of the vertex $q$.
I haven't found counterexample for trees up to $8$ vertices, and it's seems impossible to me.
Have you references for some results concerned with trees with the same degree sequences?
-
Concerning (3), should the $D$'s be there? – Tony Huynh Oct 1 '10 at 19:41
Thank you! Corrected) – Alexander Oct 1 '10 at 20:01
Consider two trees $G$ and $H$ with 14 vertices. Both will have degree sequence $(2,0,6,6)$ i.e. having two vertices of degree 4. $G$ will have the two 4-vertices connected to 3 leaves each and with a 6 vertex long chain between them. $H$ will have the two 4-vertices connected with a single edge. In addition, each will have three 2 vertex long chains connected to them (one 2-vertex connected to a leaf).
Finally, each leaf of $G$ is connected to a 4 vertex and each leaf of $H$ is connected to a 2 vertex.
A picture would do the trick better.
-
Please, give me adjacency matrices of these trees. It would do the trick better) – Alexander Oct 1 '10 at 21:41
Thank you, daniel! Got it. There's no need for adjacency matrices. – Alexander Oct 1 '10 at 22:08
Of course, there is a simpler example with 10 vertices. Perhaps I can even draw: =>-<= and >-----< . – daniel Oct 1 '10 at 22:22
Thank you, Daniel! You help me. My english not so good to say HOW MUCH you help me, indeed) – Alexander Oct 2 '10 at 9:05
Let $G$ be the Dynkin diagram of $A_5$ and $H$ be the Dynkin diagram of $D_5$. Then $G$ can be extended to the Dynkin diagram of $E_6$, while $H$ can be extended to the Dynkin diagram of $D_6$. These examples satisfy your conditions. I would draw them, as they are not much more elaborate than paths, but my tex skills are not that good!
-
Thank you for the answer, damiano. I know this already) I just have formulated the problem quite incorrectly. Sorry. Indeed, the problem is formulating as follows. Let $G$ and $H$ be the trees with the same degree sequences. Is it true that there always be vertices $q\in V(G)$ and $q′\in V(H)$ such that $(q,p)\in E(G)$ and $(q′,p′)\in E(H)$ for some endvertices $p\in V(G)$ and $p\in V(H)$, and $d(q)=d(q′)$? $d(q)$ - degree of the vertex $q$. – Alexander Oct 1 '10 at 20:32
Of course, $G$ and $H$ are not isomorphic. – Alexander Oct 1 '10 at 20:39
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## iPrint Client on XP
We are migrating to XP with iPrint, before we were using 98 with NDPS.
Insetting up the printers I set the access control to be all the users in
the container as users and operators. This way anyone could delete a print
job that might be stuck ( yes I know but we are not printing top secret
documents around here :-) ). Now with iPrint on XP it does not work that way
anymore. I have to set security to low to be able to do the same as with
NDPS.
What is the difference between low and medium.
We are using Client32 4.91 sp2 XP sp1
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# The Normal Distribution
Posted by Beetle B. on Tue 06 June 2017
## Probability Distribution Function
The parameters are $$-\infty<\mu<\infty$$ and $$\sigma>0$$.
\begin{equation*} f\left(x;\mu,\sigma\right)=\frac{1}{\sqrt{2\pi n}\sigma}\exp\left(-\frac{\left(x-\mu\right)^{2}}{2\sigma^{2}}\right) \end{equation*}
It is often denoted as $$X\sim N\left(\mu,\sigma^{2}\right)$$
## Mean and Variance
The mean is $$\mu$$ and variance is $$\sigma^{2}$$.
## Standard Normal Distribution
When $$\mu=0,\sigma=1$$, then this is called the standard normal distribution and $$X$$ is the standard normal random variable, usually denoted by $$Z$$.
The cdf is denoted by $$\Phi(z)$$
Given a normal distribution, we can transform it into the standard normal distribution using:
\begin{equation*} Z=\frac{X-\mu}{\sigma} \end{equation*}
### Critical Values
$$z_{\alpha}$$ is used to denote the value of $$Z$$ for which the area under the curve to the right is $$\alpha$$. Effectively, it is the value $$z$$ such that $$P(Z\ge z_{\alpha})=\alpha$$. They are referred to critical values.
## Some Properties
• 68% of the values are within 1 $$\sigma$$ of the mean.
• 95% of the values are within 2 $$\sigma$$ of the mean.
• 99.7% of the values are within 3 $$\sigma$$ of the mean.
## Approximation For a Discrete Distribution
We often use the normal distribution to approximate a discrete one. But exercise caution! Say you want the probability that the IQ is greater than 125. Note that the IQ is an integer. Don’t compute $$P(X\ge125)$$. Instead, compute $$P(X\ge124.5)$$
This is called a continuity correction.
### Binomial Approximation
We often approximate binomial distributions with normal ones. But do note: The Binomial distribution is skewed for $$p\ne 0.5$$, but the normal distribution is never skewed. We use the same mean and standard deviation as the Binomial one. The approximation is good enough when both $$np\ge10$$ and $$nq\ge10$$
\begin{equation*} P\left(X\le x\right)=B(x;n,p)=\Phi\left(\frac{x+0.5-np}{\sqrt{npq}}\right) \end{equation*}
## Linear Transformation
If we transform the normal distribution with $$Y=aX+b$$, then the distribution for $$Y$$ is also normal.
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# How do you prove sin^-1(x)+cos^-1(x)=pi/2?
$L e t {\sin}^{-} 1 x = \theta \implies x = \sin \theta = \cos \left(\frac{\pi}{2} - \theta\right)$
$\implies {\cos}^{-} 1 x = \frac{\pi}{2} - \theta = \frac{\pi}{2} - {\sin}^{-} 1 x$
$\therefore {\sin}^{-} 1 x + {\cos}^{-} 1 x = \frac{\pi}{2}$
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# Finding pairs of points that have a given offset
Problem: Given a set of points $S = \{x_1, x_2, x_3, ..., x_n\}$ from $\mathbb{R}^m$ and an offset vector $v \in \mathbb{R}^m$, find a set $Z \subseteq S \times S$ containing $k$ pairs of points $(x_i, x_j)$ such that the quantity $|x_i-x_j-v|$ (Euclidean norm) is smaller for any pair $(x_i,x_j) \in Z$ than that of any pair not in $Z$.
One obvious approach would be to maintain a max-heap of size $k$ and run through all pairs of points $(x_i, x_j) \in S^2$, inserting pairs into the heap if $|x_i-x_j-v|$ is smaller than the current maximum. This algorithm has $O(mn^2 \log k)$ running time.
Is there a faster algorithm? Is there a lower bound on the complexity of this problem?
This problem is motivated by an application where $50 \leq m \leq 1000$, $10^5 \leq n \leq 10^6$, and $5 \leq k \leq 100$, and the running time should be in seconds, not minutes or hours (which is I the naive approach above is not applicable).
– D.W.
Apr 22 '16 at 19:26
• @D.W. 1. and 2. Added cost for vector operations and specified some bounds on the problem. 3. Thank you for the suggestion. I am doing that, but I thought it would be nice to parallelize the search for a solution by posting the problem here. Perhaps someone has seen this problem before and could guide the search. Apr 23 '16 at 13:40
One optimization I would propose is over the brute force search:
\begin{align*} d(\mathbf{x}_i, \mathbf{x}_j) &= \lVert (\mathbf{x}_i-\mathbf{x}_j) - \mathbf{v} \rVert^2\\ &= \sum\limits_{k=1}^N (x_i^k - x_j^k-v^k)^2\\ &= \sum\limits_{k=1}^N ((x_i^k-x_j^k)^2+(v^k)^2-2v^k(x_i^k-x_j^k))\\ &= \sum\limits_{k=1}^N ((x_i^k)^2+(x_j^k)^2-2x_i^kx_j^k+(v^k)^2-2v^k(x_i^k-x_j^k))\\ \end{align*} as $(v^k)^2$ is the same for all pairs, we could simply drop it - doesn't effect minimization.
\begin{align*} d(\mathbf{x}_i, \mathbf{x}_j) &= \sum\limits_{k=1}^N ((x_i^k)^2+(x_j^k)^2-2x_i^kx_j^k-2v^kx_i^k+2v^kx_j^k)\\ &= \sum\limits_{k=1}^N (x_i^k)^2 + \sum\limits_{k=1}^N(x_j^k)^2 - 2\sum\limits_{k=1}^N x_i^kx_j^k - 2\sum\limits_{k=1}^N v^kx_i^k + 2\sum\limits_{k=1}^N v^kx_j^k\\ \end{align*}
Let's go back to matrix notation:
\begin{align*} d(\mathbf{x}_i, \mathbf{x}_j) &= \lVert \mathbf{x}_i \rVert+\lVert \mathbf{x}_j \rVert - 2(\mathbf{x}_i \cdot \mathbf{x}_j)- 2(\mathbf{x}_i \cdot \mathbf{v}) + 2(\mathbf{x}_j \cdot \mathbf{v})\\ \end{align*}
Note that all the terms, except the middle one is free of the pairwise computations and can be computed in $O(N)$ time and stored. To compute $(\mathbf{x}_i \cdot \mathbf{x}_j)$, one can assemble matrix $X$, which contains $\mathbf{x}_i^T$ at each row and compute $D=XX^T$. Each element in this huge symmetric matrix, would then give you the dot product per pair: $D(i,j)=(\mathbf{x}_i \cdot \mathbf{x}_j)$. If memory is of concern, you can simply revert to iterative computation and not store the intermediate dot products. All in all, this would save a lot of time in pairwise comptutations, speeding up the entire search. I assume that you could couple this easy to implement approach with any other optimization to further boost the performance. In all the calculations I omitted $sqrt$ because it doesn't influence the relative comparison of distances.
If the assumption is that $\mathbf{v}=\mathbf{0}$ ($\mathbf{v}$ is null), the entire procedure boils down to a fast computation of distance matrix - this view might benefit certain applications.
• Thanks for the contribution. $D$ matrix preparation will be $O(mn^2)$, but after this setup solutions for different $v$ will be $O(n^2 \log k)$, a moderate improvement over the original $O(mn^2 \log k)$ solution proposed in the question. Though I can't select this as the answer to the original question, I think the insight might be valuable for other answers and so I upvoted. Apr 25 '16 at 23:34
• Well, matrix multiplication nowadays have $O(N^{2.373})$ complexity. Given that $D$ is symmetric, you'll have a less complex operation. If you have pre-computed $D$, then for varying values of $\mathbf{v}$, you only have some linear complexity, as you don't need to pair anything now. You could also sum the first three terms in the final equation and further reduce runtime and storage. Apr 28 '16 at 20:39
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# Test for Multicolinearity
i recently ran a regression with fixed effects. As expected, STATA removed one of the dummy-variables, as well as every time-invariant variable (educ). My question is now. Why does STATA also removes the Dummy from 1987? Whenever i remove 'jobexp' from the model, 1987 is included again? My guess is a strong (perfect) multicolinearity. But how do i test for it? Any ideas?
vif calculates the variance inflation factors, a common metric of multicollinearity. Usually multicollinearity is not a big deal, unless it is perfect multicollinearity. This seems to be the case here. If year ranges from 1981 to 1987, then yes, you have to drop one of the year dummies. Otherwise you would end up in the dummy variable trap. I have no idea how Stata chooses which one to drop (anybody else?), but note that you can also specify which one to drop by typing something like ib1981.state. Then the year 1981 will then be the "base category" and the other coefficients be relative to this.
• Welcome, @KarlSeidl You are observing perfect collinearity. Your results (some variables dropped) say so. Which variables cause it cannot be determined from the regression results. Careful (tedious) examination of the full data set is required. You could try regressing educ on i.state, on jobexp, and on i.state and jobexp, etc., jobexp on educ, on i.state, and on educ and i.state, etc., to have some ideas. Jun 21 at 4:19
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# [IPython-User] Fwd: [mathjax-users] MathJax v2.0 release scheduled for Sunday, Feb 26th
Comer Duncan comer.duncan@gmail....
Fri Feb 24 08:57:34 CST 2012
Hi,
In case you don't subscribe to MathJax list, here is a message from
Davide Cervone relevant to the switch over from the current version
1.1 to version 2.0. I am passing it along in case you will need to do
something to make version 2.0 available to ipython users via CDN.
Thanks.
Comer
---------- Forwarded message ----------
From: Davide P. Cervone <dpvc@union.edu>
Date: Fri, Feb 24, 2012 at 9:28 AM
Subject: [mathjax-users] MathJax v2.0 release scheduled for Sunday, Feb 26th
Cc: MathJax Plus <MathJaxPlus@dessci.com>
MathJax v2.0 is scheduled to be released this Sunday, February 26th.
At that time, the master branch at GitHub will become v2.0 and we will
tag it and form a 2.0-latest branch, as described in the MathJax
installation documentation.
At the same time, the CDN will be updated to include a
mathjax/2.0-latest directory, and the mathjax/latest URL will be
switched to point to that. If you are using
http://cdn.mathjax.org/mathjax/latest/MathJax.js
in your pages, then you will start using MathJax v2.0 automatically
when the switch occurs; there is nothing you need to do to upgrade to
the new version. If you are using mathjax/1.1-latest, then you will
continue to receive MathJax v1.1a until you change to the 2.0-latest
URL. If you have your own copy of MathJax on your server, you will
need to upgrade it to the new version; see
http://www.mathjax.org/docs/2.0/installation.html
MathJax v2.0 has been in beta test for several weeks, and we are
confident that the switchover should be a smooth one. We have made
backward compatibility an important goal, but there are a few items
that you may need to be aware of. See
http://www.mathjax.org/docs/2.0/whats-new-2.0.html#important-changes-from-previous-versions
for details of the changes that might affect you. If you wish to stay
at v1.1, you should use the mathjax/1.1-latest URL rather than
During the cutover to v2.0, the files at mathjax/latest will be
switched from v1.1a to v2.0. Since the URL is unchanged, however,
that means some users may have cached copies of v1.1a for some files,
but receive v2.0 versions of others. That may cause MathJax to fail
for those users. To help reduce the time period where users may have
a mix of versions in their cache, we are temporarily reducing the
expiration times for the CDN to 1 hour. That should mean that the
caches are flushed quickly in hopes of minimizing any caching problems
during the version change. The longer expiration time will be
restored later in the week, once the transition is complete.
If you get complaints about MathJax not working, you should suggest
that your users clear their cache and restart their browser (some
browsers require the restart to fully clear the cache). If that does
not resolve the problem, please report the details to us at
https://github.com/mathjax/MathJax/issues
or via the MathJax user's form at
Thank you for your continued support and use of MathJax.
Davide P. Cervone
MathJax developer
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