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https://en.wikipedia.org/wiki/Haruna%20Tunnel | is a tunnel on JR East-Joetsu Shinkansen line in Japan that runs from Nakazato-cho, Takasaki city to Kawashima, Shibukawa city, in Gunma prefecture with approximate length of 15.350 km. It was completed and opened in 1981.
References
See also
List of tunnels in Japan
Seikan Tunnel Tappi Shakō Line
Sakhalin–Hokkaido Tunnel
Bohai Strait tunnel
External links
Mapion maps
Haruna Tunnel (in Japanese)
Railway tunnels in Japan
Japan
Tunnels completed in 1981 |
https://en.wikipedia.org/wiki/Emotional%20selection%20%28evolution%29 | Emotional selection is a form of evolutionary selection where decisions are made based primarily on emotional factors.
The German philosopher Ferdinand Fellmann proposed in 2009 emotional selection as a third form of evolutionary selection besides natural and sexual selection. Loving, monogamous pair-bonding seems to be the favored field where sexual selection is being transformed in emotional selection specific for human courtship and mating.
The concept of emotional selection fits the recent trend of evolutionary psychology which suggests that individual differences are more than the raw material upon which natural selection operates as a homogenizing force. Instead, personality and individual differences are created by "psychosocial selection" in the more intense forms of pair-bonding in primate sociality. Pair-bonds are based on detecting and supporting emotional complexity in partners with whom we maintain long-term intimate intercourse.
References
Selection
Evolutionary biology
Ecological processes
Emotion |
https://en.wikipedia.org/wiki/265%20%28number%29 | 265 is the natural number following 264 and preceding 266.
In mathematics
265 is an odd composite number with two prime factors.
265's sum of its proper divisors is 59.
265 is the number of derangements possible with 6 digits. That means that it is equivalent to !6.
The number 265 is associated with the geometric shape known as the Vesica Piscis. This is shown by having 2 circles overlap in a way that the circumference of each circle touches the center of the other. Archimedes estimated that the ratio of the height of this shape to the width was 265:153 or approximately √3.
265 is the 22nd Padovan number which is defined by the two equations P(0)=P(1)=P(2)=1 and P(n)=P(n-2)+P(n-3) similar to the Fibonacci sequence.
265 is the 7th number to be the hypotenuse for two separate Pythagorean Triples. The other two values would be 23 and 264 or 96 and 247.
265 is the sum of two sets of two perfect squares. Those being 11 and 12 or 16 and 3.
In technology
High Efficiency Video Coding also known as "H-265," is built upon H.264 and can compress 4k graphicsat a quicker rate.
In 2021, scientists developed waveguide-coupled germanium photodiodes, which produced a bandwidth of 265 GHz.
The Garmin Forerunner 265 is a running watch that has both the functionality of a smartwatch and that of an exercising watch. It provides comprehensive exercising data for the user.
World Records
The record for skipping rope on one leg in one minute was set by Gbenga Ezekiel at 265 times.
On October 14, 2021, Johnson & Johnson achieved the Guinness World Record for the number of people simultaneously making heart hand gestures. There were 265 participants.
On March 5, 2022, Sony achieved the largest synchronized car dance of 265 cars in Dubai.
On May 16, 2010, Sai Manapragada received the Guinness World Record for the most languages sung in a single song which was 265.
Other fields
The calendar years 265 AD and 265 BC.
In the French Republican calendar, The year 265 would be a year 1 cycle |
https://en.wikipedia.org/wiki/Emotional%20selection%20%28dreaming%29 | Emotional selection is a psychological theory of dreaming that describes dreams as modifiers and tests of mental schemas that improve their fitness to meet waking human needs. It was introduced in 2008 and extended in 2010. According to emotional selection, during non-REM sleep, the mind processes dreams with content intended to improve the adaptability of mental schemas. For example, individuals struggling with self-perceptions of incompetence may process dreams in which they successfully navigate complex situations, those who struggle to meet belongingness needs may have dreams of entering a partner relationship, and so forth. The theme of the non-REM dream is tentatively accommodated by mental schemas. Because schemas coexist as a network, accommodations can introduce accidental, maladaptive conflicts and therefore are ideally tested prior to full integration. Therefore, during subsequent REM sleep, a second set of dreams is executed in the form of test scenarios. If schema accommodations alleviate anxiety, frustration, sadness, or in other ways appear emotionally adaptive during REM dream tests, they are selected for retention. Those accommodations that compare negatively to existing, unchanged schemas are abandoned or further modified and tested.
REM dreams are often described in the academic literature as having bizarre themes. This description fits neatly in emotional selection. During the development of complex systems, engineers often test with rigorous, outwardly bizarre scenarios, such as intentionally crashing expensive automobiles, dropping functioning electronics onto hard surfaces, or vibrating scale models of buildings on shake tables. Such extreme, costly tests assure that designs meet specifications. The themes of REM dreams are often likewise extreme and bizarre, such as being chase down an alley by a monster, finding oneself naked in the presence of a crowd of people, or realizing that one's teeth or hair are falling out. When such themes are re |
https://en.wikipedia.org/wiki/Emotional%20selection%20%28information%29 | Emotional selection describes the perpetuation and evolution of information based on its ability to evoke emotions. The hypothesis posits that information spreads throughout populations not just based on their factual accuracy or utility, but also based on the emotional impact it has on recipients. Emotional selection suggests that if a meme or piece of information evokes strong emotions—whether positive or negative—it is more likely to be shared and propagated. The emotional response effectively acts as a selection mechanism, giving certain memes an advantage in the competition for attention and dissemination. This hypothesis underscores the importance of emotional resonance in the virality and longevity of information in cultural evolution.
References
Selection
Evolutionary biology
Ecological processes
Emotion |
https://en.wikipedia.org/wiki/Asiatech%20Data%20Transmission | Asiatech Data Transmission traded Asiatech is an Iranian content delivery network, mobile virtual network operator, VPS, website hosting service and broadband provider based in Tehran. Asiatech operates a National datacenter based in Milad Tower.
In October 2023 it started cloud.ir content delivery network platform.
The asiatech is sanctioned by United States for breaching human right through helping Iranian government develop NIN walled internet. It received united network services license, FTTX license and finance from Iranian Minister of ICT in 2023.
In 2020s Iranian ISP Hiweb which was backed by Vodafon tried to acquire asiatech and parsonline but ultimately asiatech was not merged due to corporate structural decisions.
Products
It also runs streaming service تماشاخونه
Iaas
Paas
Saas
When Abr Arvan was hacked in 2022 it offered to provide colocation enabled datacenters.
References
CDN.IR (آزمایشی)
Economy of Iran
Internet in Iran
Mobile virtual network operators
Virtual private network services
Web hosting
Internet service providers of Iran |
https://en.wikipedia.org/wiki/285%20%28number%29 | 285 is the natural number following 284 and preceding 286.
In mathematics
285 is an odd composite number.
285 is the 9th square pyramidal number. That means it is the sum of a number of consecutive perfect squares starting with 1. For 285, it is the sum of all of the single digits' perfect squares.
285 is the number of variations possible with a binary rooted tree with 13 points. A binary rooted tree means that it always begins with 1 point that is rooted. From there, each point can branch in up to two directions.
285 is a sphenic number which means that it has three prime factors.
285 is a Harshad number. That means that it is divisible by the sum of its digits. 285 is divisible by 15.
285 is a repdigit number in base 7. In base 7, 285 is 555.
285 is a very symmetric number. If flipped horizontally, these numbers are symmetrical.
In technology
The Turbojet 285 is a variation of the Williams Jet Tenders motorboat that is smaller than its other designs. It is designed for personal use.
The area code 285 does not exist. If you are receiving a call from a number that begins with 285, it is likely a spam call.
World Records
On December 9, 2022, Peter Thomson received the Guinness World Record for the greatest number of crossovers while jumping rope in a row.
On October 7, 2015, Camelot UK Lotteries Limited achieved the Guinness World Record for the longest champagne cork popping relay.
The Guinness World Record for the greatest number of people in an online video toast chain as of December 16, 2022, is 285. It was achieved in Cereser, Brazil.
On April 12, 2018, the Narraghmore Vintage Club received the Guinness World Record for having the largest parade of 285 tractors
Other fields
The calendar years 285 AD and 285 BC.
In the French Republican calendar, The year 285 would be a year 9 cycle and be in 2077.
285 Regina is a Main belt asteroid that was discovered in 1889 by Auguste Charlois in Nice, France.
In 1980 the 285th Civil Engineering Squadron in the United Stat |
https://en.wikipedia.org/wiki/274%20%28number%29 | 274 is the natural number following 273 and preceding 275.
In mathematics
274 is an even composite number.
274's sum of its proper divisors is 140.
The number 274 is the 13th tribonacci number. This is defined by the equations P(0)=P(1)=0 P(2)=1 and P(n)=P(n-1)+P(n-2)+P(n-3).
274 is the sum of 5 perfect cubes. It is the sum of 2³+2³+2³+5³+5³.
274 is a Stirling number of the first kind which counts the number of permutations and their number of cycles.
In technology
The number 274 is an area code in Northeast Wisconsin. The previous code in this area was 920 and the switch was made in May 2023.
MiR-274 is a type of microRNA which can mediate the communication between certain organs and tissues. This one in particular is used between neurons and tracheal cells.
The Heinkel He 274 was a German Bomber that was created during World War II. It was designed for long-distance trips to disrupt American involvement in Europe.
World Records
On June 2, 2021, Namco received a Guinness World Record by releasing its 274th intellectual property license in a single role-playing game series.
On July 13, 2019, 274 participants participated in a perfume appreciation relay race. Bath & Body Works (USA) received the record for organizing this event.
On April 15, 2023, Ronald Sarchain received the Guinness World Record for snapping 274 chopsticks using karate chops in one minute.
On September 14, 2013, Kabushikigaisha Shiseido Kamakurakoujou received the Guinness World Record for organizing an event in Fujisawa, Japan, where 274 people were painting their toenails simultaneously.
On April 19, 2022, Fayis Nazer achieved 274 hula hoop rotations on one arm in one minute in Abu Dhabi.
Other fields
The calendar years 274 AD and 274 BC.
In the French Republican calendar, The year 274 would be a year 9 cycle and be in 2064.
274 is the number of several highways in Canada, Japan, and the United States
References
Integers |
https://en.wikipedia.org/wiki/289%20%28number%29 | 289 is the natural number following 288 and preceding 290.
In mathematics
289 is an odd composite number with only one prime factor.
289 is the 9th Friedman number. Friedman numbers are numbers that can be written by using its own digits the exact number of times they show up in the number. This one can be expressed as (8+9)².
289 is a perfect square being equal to 17². It is also the 7th number to only have 3 factors because it is a square of a prime number.
289 is the sum of perfect cubes. It is the sum of 1³+2³+4³+6³.
289 is equivalent to the sum of the first 5 whole numbers to their respective powers. It is equal to 0⁰+1¹+2²+3³+4⁴.
In technology
The area code 289 is shared with 905 in the area in southern Ontario surrounding the greater Toronto metropolitan area.
The Fluke 289 True-RMS Industrial Logging Digital Multimeter with Trendcapture is a tool designed to find signal in certain areas. It has a graphic visualization of this information that it displays on its screen. It can store up to 15,000 data points.
The 289 series is a style of train that is operated by the West Japan Railway Company. It uses a DC EMU as opposed to the dual-voltage 683 series that preceded it.
World Records
On February 2, 2021, Ariel Chahi grew a strawberry that weighed 289 g in Israel. This was confirmed to be the world's heaviest strawberry.
On December 2, 2022, the longest flight by a paper aircraft was achieved by Dillon Ruble, Nathaniel Erickson, and Garret Jensen at a distance of 289 ft.
On March 21, 2017, e.motion21 Inc received the Guinness World Record for 289 people drumming on Swiss Balls simultaneously.
In the 2001-2002 horse racing season, Tom McCoy received the world record for achieving 289 steeplechase wins.
In the US Masters golf tournament, Sam Snead, Jack Burke Jr., and Zach Johnson all won the competition in 1954, 1956, and 2007 respectively. They all won with a score of 289 which is the highest winning score for this event.
Other fields
The calendar years 289 |
https://en.wikipedia.org/wiki/293%20%28number%29 | 293 is the natural number following 292 and preceding 294.
In mathematics
293 is an odd prime number with one prime factor, being itself.
293's sum of its proper divisors is 1.
293 is equivalent to the sum of the first three tetradic primes. Tetradic numbers are numbers that are the same if written backwards, flipped upside-down, or mirrored upside-down and tetradic primes are tetradic numbers that are also prime. It is the sum of 11 + 101 + 181.
293 can be written as the sum of perfect cubes. It is 2³+2³+3³+5³+5³
The total number of ways to make change for a dollar in US minted coins including the half-dollar and the dollar coin.
In technology
There is no area code in the United States with 293. There is an area code for +46 293 in Tierp, Sweden. The +46 part locates the code in Sweden and the 293 part locates it as Tierp.
293T is a cell line in humans that can assist in gene expression or DNA replication. It is has been tested on its ability to use certain viruses such as adenoviruses and other mammalian viruses.
The Omni-293 is a type of omni-directional antenna that includes 3.5 GHz of 5G bands. It is designed to be used in both rural and urban locations.<ref</ref>
World Records
In 1995, the Bagger 293 was developed by Takraf and was the heaviest machine that could move by itself. It weighs in a 31.3 million lbs.
On December 31, 2012, it was reported that in 2011, the United States was told to have the highest average watch time of TV per day at a 293 minutes.
On April 23, 2019, Jules and You in the Netherlands organized an event where 293 participants were fire breathing simultaneously.
On August 23, 2015, the Purple House Cancer Support in Ireland received the Guinness World Record for the greatest number of people dressed as sumo wrestlers at 293 people.
On May 15, 2018, Alberto Pires in Portugal, at the Lisbon Bar Show, hosted the largest port tasting event with a total of 293 people.
Other fields
The calendar years 293 AD and 293 BC.
In the French Repub |
https://en.wikipedia.org/wiki/Cryptomator | Cryptomator is an open source encryption software that provides encryption for cloud drives. It provides transparent, client-side encryption for personal cloud storage. Cryptomator encrypts each file separately and then allows the user to sync files with a cloud or local storage of choice. It is available for all major operating system including Android, iOS, Windows, Mac, Linux.
Cryptomator uses AES-256 standard encryption and WebDAV and relies on its open-source model for software verifiability, trust and bug fixing. The software encrypts each file individually.
History
In 2017, Cure53 audited the software. Cryptomator was lauded for its high degree of robustness in cryptographic implementation, but criticized use of AES in insecure ECB mode. Hagemann however did this was a false positive,"This is due to the Java Cryptography Extension, where the ECB mode must be specified for the creation of the SIV mode, even though this is and was never used by Cryptomator."
In December 2021, Cryptomator 2.0 was released for iOS, which was rewritten in Swift and integrated with apple file browser.
In January 2022, an update was released for a bug that leaked file path to Apple, because of the integration with Apple's file and use of File Provider Extension API.
Reception
Cryptomator got CeBIT innovation award in 2016.
References
External links
Cryptomator Community
Cryptographic software
Free and open-source software
Java platform software |
https://en.wikipedia.org/wiki/282%20%28number%29 | 282 is the natural number following 281 and preceding 283.
In mathematics
282 is an even composite number with three prime factors.
282 is a palindromic number. This is a number that is the same backwards as it is forwards. 282 is the smallest multi-digit palindromic number that is between twin primes, numbers that are prime and are 2 away from another prime number.
282 is equal to the sum of its divisors containing the number 4. It is the sum of 47 + 94 + 141.
282 is the number of planar partitions of 9. This means that 282 is the number of ways to separate 9 units.
In technology
The area code 282 is not in use in the North American numbering plan, but the area code is in use in Libya as +218 282. The +218 portion is the country code that places the phone number in Libya and the 282 piece labels it as Agelat.
The Haynes 282 alloy is a superalloy that is nickel-based and can withstand high temperatures. It was designed for use in industrial gas turbine engines.
A method for Dynamic Nuclear Polarization which uses microwaves to irradiate substances utilizes an electron frequency of 282 GHz.
World Records
On April 20, 2010, Dr.M completed, with a time of 2.82 seconds, the "Break the Targets" challenge in Super Smash Bros. Melee with the character Mr. Game and Watch.
On July 26, 2012, Curt Markwardt received the Guinness World Record for the highest backflip on a pogo stick. It totaled a height of 2.82 meters.
In 1998, several surfers managed to stack 282 surfboards on top of a Humvee and managed to drive 100 ft without the surfboards falling.
In the 2018 season, basketball player Sylvia Fowles received the Guinness World Record for grabbing 282 defensive rebounds for the Minnesota Lynx.
On June 18, 2005, Cristian Sterling achieved the longest golf carry with a total distance of 282 yards. This was achieved as St. Andrews Bay Golf Resort and Spa in Scotland.
On March 21, 2019, the fastest autonomous car was declared as the Robocar at Roborace with a speed of 282.42 |
https://en.wikipedia.org/wiki/267%20%28number%29 | 267 is the natural number following 266 and preceding 268.
In mathematics
267 is an odd composite number with two prime factors.
267 is the number of planar partitions of the number 12. Planar partitions are the number of ways in which the given number can be organized as split in an array.
267 is the sum of perfect cubes in two different ways. It is the sum of 1³+2³+2³+5³+5³ and 2³+2³+2³+3³+6³
In technology
The area code 267 is used for Philadelphia and the greater Philadelphia metropolitan area in Pennsylvania. It began use in 1999.
+267 is also a country code. This calling code comes from Botswana.
A scientific discovery that in 267 GHz observation of Venus, it presents phosphine was shown by ALMA. It has been declared that it is not statistically significant enough to consider.
The Setra's Model is a low differential pressure transducer, which measures the pressure in an area. It is primarily composed of its stainless steel capacitive sensing element that is good for long-term usage.
The Masters 267 is a Fishing Boat that is designed to comfortably fit 4 people and fishing gear. Its entire designs based on the comfort of the user.
World records
In 1985, E. Stone grew the heaviest rhubarb in Wiltshire, in the UK. It weighed in at 2.67 kg.
On November 13, 2021, the largest number of birthday wishes uploaded to a bespoke platform in an hour was 267 by Mecca Bingo (UK).
On On May 10, 2017, Leon Walraven received the Guinness World Record for the greatest number of football (soccer) touches with the shin with 267 touches in one minute.
On March 16, 2022, Current Food, Inc. produced the largest serving of ceviche with a total mass of 267 kg.
The highest concentration of male centenarians is in Sardinia, Italy with a percentage of 1.267%. Most areas on the other hand have a rate closer to .5%.
Other fields
The calendar years 267 AD and 267 BC.
In the French Republican calendar, The year 267 would be a year 3 cycle and be in 2059.
267 is the number for several hig |
https://en.wikipedia.org/wiki/Overhaul%20hook%20ball | An overhaul hook ball, also known as an overhaul ball or headache ball, is a heavy weight that is attached to the end of a crane's cable, above the lifting hook. It is used to keep the cable under sufficient tension even when no load is attached. Although commonly spherical as the name suggests, overhaul balls may also be ellipsoidal or cylindrical.
Overhaul balls should be distinguished from wrecking balls, which although superficially similar looking, are different and serve a different purpose.
References
Lifting equipment |
https://en.wikipedia.org/wiki/294%20%28number%29 | 294 is the natural number following 293 and preceding 295.
In mathematics
294 is an even composite number with three prime factors.
294 is the number of planar biconnected graphs with 7 vertices. Biconnected graphs are two dimensional graphs with a given number of points and 294 is the number of ways to organize 7 vertices in different ways.
11115² - 294² = 123456789
The Magic Inscribed Lotus was created by Nārāyaṇa, and Indian Mathematician in the 14th century. In this inscription, each group of 12 numbers has a sum of 294. It was constructed with a 12 x 4 magic rectangle.
In 1930, George A. Miller determined that there are 294 isomorphic groups in the order of 64. Isomorphism is making a map that preserves relationships. This was later disproven as there are 267 isomorphic groups in the order of 64. See List of incomplete proofs.
In technology
The area code +52 294 is in use in Mexico, specifically in Veracruz.The +52 locates the phone number in Mexico and the 294 locates it as Veracruz.
A CMOS THz transmitter is used for short range links. It produces .47 mW with an output power of 294 GHz.
The UL Standard 294 is a number of guidelines that many facilities follow regarding the electronic access of control devices.
World Records
On October 20, 2019, Doshisha Kori Alumni Association in Japan received the Guinness World Record for writing 294 signatures on a t-shirt in one hour.
On November 29, 2015, in Mexico City, 294 participants were Beatles impersonators. A Beatles cover band lead them in a sing-along.
2008 was declared as the worst year regarding Afghan insurrection. By NATO's calculations, there were a total of 294 military deaths.
On December 3, 2011, in Saint-Genis-les-Ollières, the Guinness World Record for the greatest number of people in an indoor volleyball exhibition match was achieved with 294 people.
On December 21, 2000, Jessie Frankson kicked the highest martial arts kick at a height of 2.94m.
Other fields
The calendar years 294 AD and 294 BC.
|
https://en.wikipedia.org/wiki/279%20%28number%29 | 279 is the natural number following 278 and preceding 280.
In mathematics
279 is an odd composite number with two prime factors.
Waring’s Conjecture is g(n)=2n+⌊(3/2)n⌋-2. When 8 is plugged in for n, the result is 279. That means that any positive integer can be formed with at most 279 numbers to the 8th power.
279 is the smallest number whose product of digits is 7 times the sum of its digits.
279 can be written as the sum of 4 nonzero perfect squares.
In technology
The area code of 279 was added to the Sacramento metropolitan area in California. It was added to the code of 916 in that area.
Tyrosine Kinase 2 Inhibitor or TAK-279 Inhibitor is a mediator of IL12 and IL23. TAK-279 is involved with certain inflammatory diseases like lupus and arthritis. TAK-279 inhibition is a possible way to treat these diseases.
World Records
On March 1, 2019, Benjamin Comparot and Carnival du Cor received the Guinness World Record for the largest French horn ensemble. It contained 279 people.
On October 6, 2023, EO Discover Okinawa had 279 people we simultaneously breaking roof tiles as a multi-day event.
On February 21, 2017? Dude Perfect achieved the Guinness World Record for the fastest time to make 5 3 point basketball shots in a time of 2.79 seconds.
On November 11, 2016, the tallest cake pyramid was built by Stratford University. It reached a total height of 2.79m.
In 2011, according to Twinning across the Developing World, Benin has the greatest rate of twins. It has 279 twins per 10000 births. Although some countries have a greater rate, this study is done without modern medicine.
Other fields
The calendar years 279 AD and 279 BC.
In the French Republican calendar, The year 279 would be a year 2 cycle and be in 2069.
279 is the number for several highways across the countries of Canada, Japan, and the United States.
279 Thule is a D-type asteroid in the asteroid belt. It was discovered by Johann Palisa in Vienna and was named after the land of Thule.
In Greenland, for t |
https://en.wikipedia.org/wiki/266%20%28number%29 | 266 is the natural number following 265 and preceding 267.
In mathematics
266 is an even composite number with three prime factors.
266 is a repdigit in base 11. In base 11, 266 is 222.
266 is a sphenic number being the product of 3 prime numbers.
266 is a nontotient number which is an even number, not in Euler’s totient function.
266 is an inconsummate number.
In technology
+266 is the calling code in Lesotho.
H.266 or Versatile Video Coding (VVC) is a video compression service. It was created by the Joint Video Experts Team as ITU and was created in 2017. It is designed to handle anywhere between 4k and 16k streaming.
World Records
On September 10, 2022, Delgadill’s Snow Cap offered 266 milkshake varieties. In support of Route 66, they created 266 flavors of milkshake.
On November 2, 2019, the Guinness World Record for the greatest number of people in the shape of a gemstone ring was completed in Kunming, China. There were 266 participants
On October 27, 2017, Casio Computer Co., LTD, and Hamura R&D Center created the largest human image of a watch with 266 people.
On February 13, 2022, Team Hantare Nacs received the Guinnes World Record for setting up 266 dominoes and knocking them down in one minute by a team of 8.
On October 17, 2013, 266 people in Quitman, Georgia were tossing skillets simultaneously.
Other fields
The calendar years 266 AD and 266 BC.
In the French Republican calendar, The year 266 would be a year 2 cycle and be in 2058.
266 is the number for several highways across the countries of Canada, Japan, and the United States.
266 Aline is an asteroid in the asteroid belt. It was discovered by Johann Palisa in Vienna. He named it after fellow astronomer Edmund Weiss' daughter.
Jorge Mario Bergoglio was elected the 266th pope on March 13, 2013 as Pope Francis.
References |
https://en.wikipedia.org/wiki/Fernando%20Zalamea | Fernando Zalamea Traba (Bogota, 28 February 1959) is a Colombian mathematician, essayist, critic, philosopher and popularizer, known by his contributions to the philosophy of mathematics, being the creator of the synthetic philosophy of mathematics. He is the author of around twenty books and is one of the world's leading experts on the mathematical and philosophical work of Alexander Grothendieck, as well as in the logical work of Charles S. Peirce.
Currently, he is a full professor in the Department of Mathematics of the National University of Colombia, where he has established a mathematical school, primarily through his ongoing seminar of epistemology, history and philosophy of mathematics, which he conducted for eleven years at the university. He is also known for his creative, critical, and constructive teaching of mathematics. Zalamea has supervised approximately 50 thesis projects at the undergraduate, master's and doctoral levels in various fields, including mathematics, philosophy, logic, category theory, semiology, medicine, culture, among others. Since 2018, he has been an honorary member of the Colombian Academy of Physical Exact Sciences and Natural. In 2016, he was recognized as one of the 100 most outstanding contemporary interdisciplinary global minds by "100 Global Minds, the most daring cross-disciplinary thinkers in the world," being the only Latin American included in this recognition.
References
National University of Colombia
Living people
Mathematics and culture
Academic staff of the National University of Colombia
1959 births
Colombian mathematicians
es:Fernando Zalamea |
https://en.wikipedia.org/wiki/Tuomas%20Sandholm | Tuomas Sandholm is the Angel Jordan University Professor of Computer Science at Carnegie Mellon University and a serial entrepreneur with a research focus on the intersection of artificial intelligence, economics, and operations research.
Early life and education
Sandholm was born in Finland. He earned a Dipl. Eng. (M.S. with B.S. included) with distinction in Industrial Engineering and Management Science. He continued his education in the United States, where he obtained his M.S. and Ph.D. in computer science from the University of Massachusetts Amherst.
Career and research
Sandholm has contributed to several domains including AI, game theory, and real-world applications like organ exchanges and electronic marketplaces. His achievements in AI and game theory include the development of Libratus and Pluribus, AI systems that have defeated top human players in poker, attracting global attention.
He has impacted practical applications by implementing algorithms for national kidney exchange and founded several companies, including CombineNet, Inc., and Strategy Robot, Inc., that have applied his research to sectors like advertising and defense.
Awards and honors
Sandholm's work has garnered numerous awards, such as the IJCAI John McCarthy Award and the Vannevar Bush Faculty Fellowship. He is a Fellow of the ACM, AAAI, INFORMS, and AAAS.
Personal life
In his early years, Sandholm was a pilot second lieutenant in the Finnish Air Force. Additionally, he attained recognition in sports, securing the #1 ranking in windsurfing in Finland in 1987.
References
American computer scientists
Finnish computer scientists
Artificial intelligence researchers
Game theorists
Carnegie Mellon University faculty
Living people
Year of birth missing (living people) |
https://en.wikipedia.org/wiki/Anne%20van%20den%20Nouweland | Anne van den Nouweland is a Dutch-American game theorist specializing in cooperative game theory, the game-based formation of complex networks, and their application in the design of communication networks. She works as a professor of economics at the University of Oregon.
Education and career
Van den Nouweland studied mathematics as an undergraduate at Nijmegen University in the Netherlands, graduating in 1984, and earned a master's degree there in 1989. Her doctoral research applied intuitionism to the understanding of the Riemann–Stieltjes integral, supervised by Arnoud van Rooij and Wim Veldman. After two more years as a teaching assistant in the mathematics department at Nijmegen, she moved to the econometrics department at Tilburg University, also in the Netherlands, completing her Ph.D. there in 1993. Her doctoral dissertation, Games and Graphs in Economic Situations, was promoted by Stef Tijs.
After completing her doctorate, she stayed on at Tilburg as an assistant professor and member of the CentER for Economic Research. She moved to the University of Oregon in 1996, was tenured there as an associate professor in 2001, and was promoted to full professor in 2007.
Book
Van den Nouweland is the coauthor of Social and Economic Networks in Cooperative Game Theory (with Marco Slikker, Kluwer Academic Publishers, 2001).
References
External links
Home page
Year of birth missing (living people)
Living people
Dutch emigrants to the United States
Dutch economists
Dutch mathematicians
Dutch women economists
Dutch women mathematicians
American economists
American mathematicians
American women economists
American women mathematicians
Game theorists
Radboud University Nijmegen alumni
Tilburg University alumni
Academic staff of Tilburg University
University of Oregon faculty |
https://en.wikipedia.org/wiki/268%20%28number%29 | 268 is the natural number following 267 and preceding 269.
In mathematics
268 is an even composite number with two prime factors, but one of the prime factors is repeated: 268 = 67*2*2.
268 is the smallest number whose product of digits is 6 times the sum of its digits.
268 is untouchable which means that it is not the sum of the proper divisors of any number
268 is the sum of the consecutive primes 131 and 137.
In technology
The area code for 268 is in Antigua and Barbuda.
The country code +268 is the calling code for Eswatini, formerly Swaziland.
MF 268 is a chemical compound with the formula of C28H46N4O3. It reacts at the abiotic site of the enzyme.
World records
Youtuber Hassan Suliman (AboFlah) received 2 world records during a live stream. The first was the longest video live stream with a total length of 268 hours. The second was the most viewers on a charity live stream on youtube with 698000 viewers.
On January 17, 2013, The Procter & Gamble Company received the Guinness World Record for the most people using teeth-whitening strips simultaneously. There were 268 participants.
On December 9, 2012, 268 people were brushing dog’s teeth. It was an event to promote dog’s dental health awareness.
On April 17, 2016, there were 268 people in Hikone, Japan dressed as ninjas. https://www.guinnessworldrecords.com/world-records/95237-largest-gathering-of-people-dressed-as-ninjas
On June 19, 2011, the lowest score in the golf US Open was achieved by Rory McIlroy. The score was 268 in 72 holes.
Other fields
The calendar years 268 AD and 268 BC.
In the French Republican calendar, The year 268 would be a year 4 cycle and be in 2060.
267 is the number for several highways across the countries of Canada, Japan, and the United States.
268 Adorea is an asteroid in the asteroid belt. It was discovered by Alphonse Borrelly in Marseilles. It was named after adorea liba which were split cakes made by the Romans as sacrificial offerings. This was controversial because all a |
https://en.wikipedia.org/wiki/10G | 10G is a term used by some cable Internet access providers and industry groups in the United States in reference to broadband networks with a maximum potential download rate of ten gigabits per second (10 Gbit/s). The term was first used in this regard by industry association NCTA in January 2019, which said it had filed for a trademark on the term, and expanded on by CableLabs in a summer 2019 white paper.
The term "10G" has no connection to the numbered generations of cellular network standards such as 5G (fifth generation). Some articles discussing the term have posited that 10G suggests to casual readers that service would be twice as fast as 5G, when in fact the 5G standard already encompasses even faster speeds of up to 20 Gbit/s.
In early 2023, Comcast began referring to its Xfinity Internet service as now being on a "10G network", despite the fact that the top-speed service available in the vast majority of homes served by Comcast was still only 1 Gbit/s.
In October 2023, the National Advertising Division (NAD) of the Better Business Bureau ruled that it considered Comcast's use of 10G to be false or misleading, as it constituted an express claim that Comcast was using a tenth-generation network or was promising 10 Gbit/s speeds to all customers. The NAD recommended that Comcast should either discontinue its claims or clarify 10G as an "aspirational" technology. Comcast said it would appeal the decision by the self-regulatory body.
See also
10 Gigabit Ethernet – a set of technologies for Ethernet communications that support up to 10 Gbit/s speeds
10G-PON and 10G-EPON – passive optical network standards that support up to 10 Gbit/s speeds
References
Internet access
Internet terminology
Comcast |
https://en.wikipedia.org/wiki/Common%20symbiosis%20signaling%20pathway | The common symbiosis signaling pathway (CSSP) is a signaling cascade in plants that allows them to interact with symbiotic microbes. It corresponds to an ancestral pathway that plants use to interact with arbuscular mycorrhizal fungi (AMF). It is known as "common" because different evolutionary younger symbioses also use this pathway, notably the root nodule symbiosis with nitrogen-fixing rhizobia bacteria. The pathway is activated by both Nod-factor perception (for nodule forming rhizobia), as well as by Myc-factor perception that are released from AMF. The pathway is distinguished from the pathogen recognition pathways, but may have some common receptors involved in both pathogen recognition as well as CSSP. A recent work by Kevin Cope and colleagues showed that ectomycorrhizae (a different type of mycorrhizae) also uses CSSP components such as Myc-factor recognition.
The AMF colonization requires the following chain of events that can be roughly divided into the following steps:
1: Pre-Contact Signaling
2: The CSSP2: A: Perception
2: B: Transmission
2: C: Transcription3: The Accommodation program
Outline
To accurately recognize the infection thread of a different species of organism, and to establish a mutually beneficial association requires robust signaling. AM fungi are also fatty acid auxotrophs; therefore they depend on plant for supply of fatty acids.
At the pre-symbiotic signaling, plants and AMF release chemical factors in their surroundings so that the partners can recognise and find each other.' Plant root exudates play roles in complex microbial interaction, by releasing a variety of compounds, among which strigolactone has been identified to facilitate both AMF colonisation and pathogen infection.
Phosphate starvation in plant induces strigolactone production as well as AMF colonisation. Plants release strigolactone, a class of caroteinoid-based plant hormone which also attracts the fungal symbionts and stimulate the fungal oxidative metabo |
https://en.wikipedia.org/wiki/Graphs%20with%20few%20cliques | In graph theory, a class of graphs is said to have few cliques if every member of the class has a polynomial number of maximal cliques. Certain generally NP-hard computational problems are solvable in polynomial time on such classes of graphs, making graphs with few cliques of interest in computational graph theory, network analysis, and other branches of applied mathematics. Informally, a family of graphs has few cliques if the graphs do not have a large number of large clusters.
Definition
A clique of a graph is a complete subgraph, while a maximal clique is a clique that is not properly contained in another clique. One can regard a clique as a cluster of vertices, since they are by definition all connected to each other by an edge. The concept of clusters is ubiquitous in data analysis, such as on the analysis of social networks. For that reason, limiting the number of possible maximal cliques has computational ramifications for algorithms on graphs or networks.
Formally, let be a class of graphs. If for every -vertex graph in , there exists a polynomial such that has maximal cliques, then is said to be a class of graphs with few cliques.
Examples
The Turán graph has an exponential number of maximal cliques. In particular, this graph has exactly maximal cliques when , which is asymptotically greater than any polynomial function. This graph is sometimes called the Moon-Moser graph, after Moon & Moser showed in 1965 that this graph has the largest number of maximal cliques among all graphs on vertices. So the class of Turán graphs does not have few cliques.
A tree on vertices has as many maximal cliques as edges, since it contains no triangles by definition. Any tree has exactly edges, and therefore that number of maximal cliques. So the class of trees has few cliques.
A chordal graph on vertices has at most maximal cliques, so chordal graphs have few cliques.
Any planar graph on vertices has at most maximal cliques, so the class of planar |
https://en.wikipedia.org/wiki/275%20%28number%29 | 275 is the natural number following 274 and preceding 276.
In mathematics
275 is an odd composite number with 2 prime factors.
275 is equivalent to the number of partitions of 28 when no partition occurs only once. Partitions are the number of ways of writing a number as a sum of other positive integers.
275 is the sum of fifth powers of the first two primes (2^5 + 3^5 = 275).
275 is the maximum number of pieces made by cutting an annulus with 22 cuts.
275 is the smallest non semiprime that follows the equations n>1 and the greatest common denominator of n and b^n-b is 1 for some value of b.
World Records
In May 2011, Angry Birds ended its 275 day streak of the best-selling app in the Apple App Store.
On November 14, 2007, the Guinness World Record for the greatest number of people dressed as mobile phones at 275 people. It was completed in Puerto Rico.
On April 11, 2015, the largest welding lesson was completed in Willowbrook, Illinois. There were 275 attendees.
The greatest number of certificates that a show dog earned as 275 certificates. It was earned by German Shepherd Mystique.
Other fields
The calendar years 275 AD and 275 BC.
In the French Republican calendar, The year 275 would be a year 10 cycle and be in 2065.
275 is the number of several highways in Canada, India, Japan, and the United States
275 Sapientia is an asteroid in the asteroid belt. It is a C-type asteroid that was discovered by Johann Palisa.
References |
https://en.wikipedia.org/wiki/Monotone%20dualization | In theoretical computer science, monotone dualization is a computational problem of constructing the dual of a monotone Boolean function. Equivalent problems can also be formulated as constructing the transversal hypergraph of a given hypergraph, of listing all minimal hitting sets of a family of sets, or of listing all minimal set covers of a family of sets. These problems can be solved in quasi-polynomial time in the combined size of its input and output, but whether they can be solved polynomial time is an open problem.
Definitions
A Boolean function takes as input an assignment of truth values to its arguments, and produces as output another truth value. It is monotone when changing an argument from false to true cannot change the output from true to false. Every monotone Boolean function can be expressed as a Boolean expression using only logical disjunction ("or") and logical conjunction ("and"), without using logical negation ("not"). Such an expression is called a monotone Boolean expression. Every monotone Boolean expression describes a monotone Boolean function.
There may be many different expressions for the same function. Among them are two special expressions, the conjunctive normal form and disjunctive normal form. For monotone functions these two special forms can also be restricted to be monotone:
The conjunctive normal form of a monotone function expresses the function as a conjunction ("and") of clauses, each of which is a disjunction ("or") of some of the variables. A clause may appear in the conjunctive normal form if it is true whenever the overall function is true; in this case it is called an implicate, because the truth of the function implies the truth of the clause. This expression may be made canonical by restricting it to use only prime implicates, the implicates that use a minimal set of variables. The conjunctive normal form using only prime implicates is called the prime CNF.
The disjunctive normal form of a monotone function express |
https://en.wikipedia.org/wiki/278%20%28number%29 | 278 is the natural number following 277 and preceding 279.
In mathematics
278 is an even composite number with 2 prime factors.
278 is equal to Φ(30). It is the sum of the totient function.
278 is a nontotient number which means that it is an even number that doesn't follow Euler's totient function.
278 is the smallest semiprime number that has an anagram that is also semiprime. The other number is 287.
World Records
On October 29, 2011, April Mathis lifted the heaviest squat weight by a female at 278 kg in Orlando, Florida.
On November, 10, 1993, Tom Rodden received the Guinness World Record for shaving 278 people in one hour.
On March 25, 2000, in Meadowhall Center, there were 278 human mannequins in the shopping center. They were in a total of 114 stores.
On December 5, 2006, James Cripps received the Guinness World Record for the highest score in backwards bowling. The score was 278.
Other fields
The calendar years 278 AD and 278 BC.
278 is the number of several highways in Canada, Japan, and the United States.
278 Paulina is an asteroid in the asteroid belt. It was discovered by Johann Palisa in Vienna.
References |
https://en.wikipedia.org/wiki/Charles%20Hamilton%20Mitchell | Charles Hamilton Mitchell, CB, CMG, DSO (1872-1941) was a Civil Engineer and an Intelligence Officer of the Canadian Armed Forces in World War I, with the rank of Brigadier-General. He served in France, Italy, and England during the war as an Intelligence Officer, winning several honours, becoming the most decorated Intelligence Officer in Canadian military intelligence history. After the war, he returned to Canada to serve as the Dean of Engineering at the University of Toronto Faculty of Applied Science and Engineering. He helped greatly expand and improve the faculty during his tenure and served in that role until 1941.
Early life and education
Charles Hamilton Mitchell was born to George Mitchell and Agnes Becket in 1872 at Petrolia, Ontario. His father, George Mitchell, was a clergyman and a graduate of Upper Canada College and the University of Toronto in mathematics. He was the great-grandson of a United Empire Loyalist.
He attended the School of Practical Science at the University of Toronto, studying Civil Engineering at the School. He received his SPS diploma in 1892 and his B.A.Sc. in 1894. After graduating from the University of Toronto, he worked as a Civil Engineer (officially qualifying as a C.E. in 1898), specializing in hydraulic and hydro-electric power development. He took employment as the Assistant City Engineer in Niagara Falls and later served as the City Engineer. After leaving that post, he set up a Toronto-based consulting firm in 1906 in partnership with his brother Percival, working largely in hydroelectric power plant construction. He was responsible for the design and construction of several plants in the Maritimes, Ontario, and Western Canada.
In 1901 he married Myra Ethlyn Stanton, daughter of John N. Stanton and Martha Hubbs of St Catharines. They had one son, Donald Russell Mitchell in 1902, though Donald Russel survived for only 3 weeks.
Military service
Mitchell joined the Militia in 1899. Prior to World War I, he served in t |
https://en.wikipedia.org/wiki/283%20%28number%29 | 283 is the natural number following 282 and preceding 284.
In mathematics
283 is an odd prime number with 1 prime factors.
283 is a twin prime number and a super prime. The former are two prime numbers that are only separated by a single number with 281. The latter is a prime number that is the nth prime where n is a prime number as well.
283 is a strictly non palindromic number. That means that between base 2 and base n-2, that number is never palindromic.
283 is such a number where 4283-3238 is prime.
283 is equivalent to 25+8+35.
World Records
In 2015, Kris Russell set the Guinness World Record for the greatest number of shots blocked in an NHL season. The record was 283 shots blocked.
According to Professor Olu Tomori, the English language has the greatest number of irregular verbs as 283.
On November 21, 2012, the fastest time to climb a vertical corridor was achieved in Beijing by Zhisheng Fang with a time of 28.3 seconds.
In the Marshall Islands, the largest atoll is found with a length of 283 km.
On May 13, 2023, the longest standing jump was completed by Lorenz Wetsher with a grand total of 2.83 m distance.
Other fields
The calendar years 283 AD and 283 BC.
283 is the number of several highways in Canada, Japan, and the United States.
283 Emma is an asteroid in the asteroid belt. It was discovered by Auguste Charlois in Nice, France.
References |
https://en.wikipedia.org/wiki/BBM%20Enterprise | BBM Enterprise (abbreviated as BBMe) is a centralized instant messaging client provided by Canadian company BlackBerry Limited. BBMe is marketed as a secure messenger with end-to-end encryption.
BBMe was launched in 2014 originally as BBM Protected, based on a revamped version of BBM (BlackBerry Messenger), the company's consumer-oriented instant messenger. Initially offered only for enterprise customers, BBMe was opened up to all customers in 2019 after the shutting down of the older consumer BBM service.
From the client to server, messages in BBMe are encrypted using TLS. Each message has its own random encryption public and private key. It uses a FIPS 140-2 certified cryptographic library for generating the keys. According to BlackBerry Ltd., BBMe complies with the following standards:
Digital signature FIPS 186-4
AES symmetric encryption standard FIPS 197
HMAC standard FIPS 198-1 based on based on SHA2-256
Cryptographic key generation standard NIST SP 800-133
Secure Hash standard FIPS 180-4
In addition, it makes use of EC-SPEKE, KDF and One-Pass DH (all National Institute of Standards and Technology algorithm standards) with "256-bit equivalent security".
The service consists of group chats, voice and video calls. Unlike its predecessor, BBMe is not entirely free, lasting for a year before costing $2.49 for six months.
References
BlackBerry
Instant messaging
Instant messaging clients
BlackBerry Limited
BlackBerry software
Cryptographic software
Secure communication
Internet privacy software |
https://en.wikipedia.org/wiki/Pictet%27s%20experiment | Pictet's experiment refers to the demonstration of the reflection of heat and the apparent reflection of cold in a series of experiments performed in 1790 (reported in English in 1791 in An Essay on Fire) by Marc-Auguste Pictet. After "demonstrating that radiant heat, even when it was not accompanied by any light, could be reflected and focused like light", Pictet used the same apparatus to demonstrate the apparent reflection of cold in a similar manner. This demonstration was important to Benjamin Thompson, Count Rumford who argued for the existence of 'frigorific rays' conveying cold. Rumford's continuation of the experiments and promotion of the topic caused the name to be attached to the experiment.
The apparatus for the experiment used two concave mirrors facing one another at a distance. An object placed at the focus of one mirror would have heat and light reflected by the mirror and focused. An object at the focus of the counterpart mirror would do the same. Placing a hot object at one focus and a thermometer at the other would register an increase in temperature on the thermometer. This was sometimes demonstrated with the explosion of a flammable mix of gasses in a blackened balloon, as described and depicted by John Tyndall in 1863.
The apparent reflection of cold if a cold object is placed in one focus surprised Pictet and two scholars writing about the experiment in 1985 noted "most physicists, on seeing it demonstrated for the first time, find it surprising and even puzzling." The confusion may be dispensed with by imagining that all objects in the system—thermometers or otherwise—are constantly radiating heat. Pictet described this as "the thermometer acts the fame part relatively to the snow as the bullet [heat source] in relation to the thermometer." Addition of a very cold object adds an effective heat sink versus a room temperature object which would not, in the net, cool or warm a thermometer in the other focus.
The experiment was performed 10 y |
https://en.wikipedia.org/wiki/284%20%28number%29 | 284 is the natural number following 283 and preceding 285.
In mathematics
284 is an even composite number with 2 prime factors.
284 is in the first pair of amicable numbers with 220. That means that the sum of the proper divisors are the same between the two numbers.
284 can be written as a sum of exactly 4 nonzero perfect squares.
284 is a nontotient number which are numbers where phi(x) equaling that number has no solution.
284 is a number that is the nth prime plus n. It is the 51st prime number (233) plus 51.
World Records
On July 3, 2010, Eduaedo Nakagawa achieved the Guinness World Record as the most prolific holder of records on Picross. He has the record for 284 of the 345 levels.
On June 21, 2019, the largest rhythmic yoga lesson was completed in Hefei, China. It had 284 attendees.
On October 25, 2005, Soulcalibur III was released on the PlayStation 2 with the most weapons in any video game. It had 284 weapons.
On October 17, 2022, the students of Tabla Talim Sanstha in Ahmedabad, India completed the longest hand-drumming relay with 284 people.
Other fields
The calendar years 284 AD and 284 BC.
283 is the number of several highways in Japan and the United States.
284 Amalia is an asteroid in the asteroid belt. It was discovered by Auguste Charlois in Nice, France and is a Ch-type asteroid.
References |
https://en.wikipedia.org/wiki/286%20%28number%29 | 286 is the natural number following 285 and preceding 287.
In mathematics
286 is an even composite number with 3 prime factors.
286 is in the smallest pair of nontotient anagrams with 268.
286 is a tetrahedral number which means that represents a tetrahedron.
286 is a sphenic number which means that it has exactly 3 prime factors.
286 the first even pseudoprime to base 3.
World Records
On November 7, 2013, Alastair Galpin received the Guinness World Record for the fastest time to slice 10 matches in half. He completed it in 2.86 seconds.
On April 27, 2013, the largest tiramisu-making lesson ensued in Japan with 286 participants.
On September 21, 2007, the largest steel drum ensemble was achieved in Poznan, Poland. There were 286 members.
On November 12, 2017, Toyota achieved the Guinness World Record for the greatest number of toy cars launched simultaneously. There were 286 toy cars.
Other fields
The calendar years 286 AD and 286 BC.
286 is the number of several highways in Japan and the United States.
286 Iclea is an asteroid in the asteroid belt. It was discovered by Johann Palisa in Vienna, Austria.
References |
https://en.wikipedia.org/wiki/DMT%20%28company%29 | DMT GmbH & Co. KG is an engineering and consulting company based in Essen, Germany. Founded in 1990, DMT has been a subsidiary of TÜV NORD AG since 2007. It operates within the TÜV NORD GROUP, providing engineering and consulting services.
The DMT Group consists of 16 engineering and consulting firms with global locations and around 1,100 employees. The group's annual revenue is approximately €130 million. DMT collaborates on research projects with industry, research institutions, and universities internationally.
History
DMT GmbH & Co. KG traces its corporate history to 1990. It evolved from a series of corporate mergers dating back to 1737 when the Märkische Gewerkschaftskasse was founded. In the 1990s, the business lines were integrated into the newly created Deutsche Montan Technologie für Rohstoff, Energie, Umwelt e.V., where two companies emerged:
DMT-Gesellschaft für Forschung und Prüfung mbH
DMT-Gesellschaft für Lehre und Bildung mbH
Organization
DMT GmbH & Co. KG operates 19 testing and specialist centers for safety, with 17 of them being accredited or officially recognized. The company employs approximately 100 recognized experts.
Service Areas
DMT provides engineering services in areas such as plant construction, process engineering, civil engineering, mining, and oil and gas. Its core activities include engineering, consulting, geotechnics, and exploration. The company also develops measurement and monitoring systems for various industries.
Geo Engineering and Exploration
In this sector, DMT offers services for the development, planning, and monitoring of infrastructure projects, including geotechnical and site investigation, route engineering, and geomonitoring.
Mining Consulting and Engineering
DMT assists investors, governments, and mining operators throughout the entire lifecycle of a mine, offering services such as resource prospecting, feasibility studies, and mine planning.
Industrial Engineering
DMT designs and constructs process |
https://en.wikipedia.org/wiki/Graphitization | Graphitization is a process of transforming a carbonaceous material, such as coal, graphite or certain forms of iron alloys, into graphite.
Process
The graphitization process involves a restructuring of the molecular structure of the carbon material. In the initial state, these materials can have an amorphous structure or a crystalline structure different from graphite. Graphitization generally occurs at high temperatures (up to ), and can be accelerated by catalysts such as iron or nickel.
When carbonaceous material is exposed to high temperatures for an extended period of time, the carbon atoms begin to rearrange and form layered crystal planes. In the structure of graphite, carbon atoms are arranged in flat hexagonal sheets that are stacked on top of each other. These crystal planes give graphite its characteristic flake structure, giving it specific properties such as good electrical and thermal conductivity, low friction and excellent lubrication.
Interest
Graphitization can be observed in various contexts. For example, it occurs naturally during the formation of certain types of coal or graphite in the Earth's crust. It can also be artificially induced during the manufacture of specific carbon materials, such as graphite electrodes used in fuel cells, nuclear reactors or metallurgical applications.
Graphitization is of particular interest in the field of metallurgy. Some iron alloys, such as cast iron, can undergo graphitization heat treatment to improve their mechanical properties and machinability. During this process, the carbon dissolved in the iron alloy matrix separates and restructures as graphite, which gives the cast iron its specific characteristics, such as improved ductility and wear resistance.
Notes and references
Molecular physics
Metallurgy
Materials science
Materials |
https://en.wikipedia.org/wiki/International%20Conference%20on%20Formal%20Power%20Series%20and%20Algebraic%20Combinatorics | The International Conference on Formal Power Series and Algebraic Combinatorics (FPSAC) is an annual academic conference in the areas of algebraic and enumerative combinatorics and their applications and relations with other areas of mathematics, physics, biology and computer science.
History
FPSAC was first held in 1988 and has been held annually since 1990, typically in June, July or August.
The most recent conference in the series, FPSAC'23, was held in July 2023 at the University of California, Davis. The 2024 meeting is slated to take place at Ruhr-Universität Bochum in Bochum, Germany on July 22-26, 2024.
The proceedings of conferences in the series have appeared as a Springer volume,
and in the journals Discrete Mathematics, Discrete Mathematics and Theoretical Computer Science, and Séminaire Lotharingien de Combinatoire.
References
External Links
Mathematics conferences |
https://en.wikipedia.org/wiki/287%20%28number%29 | 287 is the natural number following 286 and preceding 288.
In mathematics
287 is an odd composite number with 2 prime factors.
287 is the sum of consecutive primes in three different ways, 89+97+101, 43+53+59+61+67, and 17+19+23+29+31+37+41+43+47
287 is a pentagonal number which follows the concept of triangular numbers.
287 is an odd semiprime number.
287 is the sum of exactly 4 nonzero squares.
287 is a number where 2(287)-1 and 2(287)+1 are both prime.
World Records
On November 15, 2012, in the United Kingdom, the largest toy construction lesson was achieved with 287 participants.
On August 8, 2018, in Japan, the largest blind soccer (football) lesson was completed with 287 members.
On February 28, 2020, the largest Welsh folk dance was completed in Swansea in the United Kingdom. There were 287 participants.
On June 20, 2009, Bora Milutinović completed the Guinness World Record for the greatest number of international soccer matches a coach has been in charge of. He was at 287 games.
On December 20, 2020, the largest group of people dressed as the sun was completed in Guangzhou, China. There were 287 participants.
Other fields
The calendar years 287 AD and 287 BC.
287 is the number of several highways in Brazil, Canada, Japan, and the United States.
287 Nephthys is an S-type asteroid in the asteroid belt. It was discovered by Christian Heinrich Friedrich Peters in Clinton, Oneida County, New York. It was named after Nephthys in Egyptian mythology.
References |
https://en.wikipedia.org/wiki/Journal%20of%20Functional%20Foods | Journal of Functional Foods is a monthly peer-reviewed scientific journal covering various aspects of food research. It is published by Elsevier and was established in 2009. The editor-in-chief is Vincenzo Fogliano (Wageningen University) and Mingfu Wang (Shenzhen University).
The journal publishes research articles, reviews, and commentaries related to functional foods, including the role of food ingredients, food digestion, safety, and processing.
Abstracting and indexing
The journal is abstracted and indexed, for example, in:
According to the Journal Citation Reports, the journal has a 2022 impact factor of 5.6.
References
External links
English-language journals
Elsevier academic journals
Academic journals established in 2009
Food science journals
Monthly journals |
https://en.wikipedia.org/wiki/Food%20Research%20International | Food Research International is a monthly peer-reviewed scientific journal covering various aspects of food science. It is published by Elsevier and was established in 1992. The editor-in-chief is Anderson Sant'Ana (University of Campinas).
The journal publishes research articles, reviews, and commentaries related to food research, including food chemistry, food toxicology, food engineering, and quality.
Abstracting and indexing
The journal is abstracted and indexed, for example, in:
According to the Journal Citation Reports, the journal has a 2022 impact factor of 8.1.
References
External links
English-language journals
Elsevier academic journals
Academic journals established in 1992
Food science journals
Monthly journals |
https://en.wikipedia.org/wiki/310%20%28number%29 | 310 is the natural number following 309 and preceding 311.
In mathematics
310 is an even composite number with 3 prime factors.
310 is a sphenic number meaning that it has 3 prime factors.
310 is a noncototient number which means that m − φ(m) = n has no solution for n=310.
310 is the number of Dyks 11 paths with strictly intersecting peaks.
310 base 6 it is 1234
The sum of the divisors of 310 is a perfect square.
World Records
On September 14, 2016, Siamand Rahman achieved the heaviest power lift for a paralympic male at 310 kg lifted.
On July 21, 2023, the Guinness World Record for the longest microphone passing relay was completed in Zhangjiakou, China. There were 310 participants.
On October 21, 2018, the largest football tournament was achieved in Colorado. There were 310 participants.
On September 29, 2012, the greatest number of consecutive football appearances was 310 completed by Brad Friedel.
Other fields
The calendar years 310 AD and 310 BC.
310 is the number of several highways in Canada, China, Costa Rica, Japan, and the United States.
310 Margarita is an asteroid in the asteroid belt. It was discovered by Auguste Charlois in Nice, France.
References |
https://en.wikipedia.org/wiki/Finite%20subgroups%20of%20SU%282%29 | In applied mathematics, finite subgroups of are groups composed of rotations and related transformations, employed particularly in the field of physical chemistry. The symmetry group of a physical body generally contains a subgroup (typically finite) of the 3D rotation group. It may occur that the group with two elements acts also on the body; this is typically the case in magnetism for the exchange of north and south poles, or in quantum mechanics for the change of spin sign. In this case, the symmetry group of a body may be a central extension of the group of spatial symmetries by the group with two elements. Hans Bethe introduced the term "double group" (Doppelgruppe) for such a group, in which two different elements induce the spatial identity, and a rotation of may correspond to an element of the double group that is not the identity.
The classification of the finite double groups and their character tables is therefore physically meaningful and is thus the main part of the theory of double groups. Finite double groups include the binary polyhedral groups.
In physical chemistry, double groups are used in the treatment of the magnetochemistry of complexes of metal ions that have a single unpaired electron in the d-shell or f-shell. Instances when a double group is commonly used include 6-coordinate complexes of copper(II), titanium(III) and cerium(III). In these double groups rotation by 360° is treated as a symmetry operation separate from the identity operation; the double group is formed by combining these two symmetry operations with a point group such as a dihedral group or the full octahedral group.
Definition and theory
Let be a finite subgroup of SO(3), the three-dimensional rotation group. There is a natural homomorphism of SU(2) onto SO(3) which has kernel {±I}. This double cover can be realised using the adjoint action of SU(2) on the Lie algebra of traceless 2-by-2 skew-adjoint matrices or using the action by conjugation of unit quaternions. |
https://en.wikipedia.org/wiki/Gaspy | Gaspy is a crowd-sourced petrol price monitoring application for New Zealand. It based in Tauranga and available for both iPhone and Android. Prices are entered into the app by motorists. the app has half a million users. A founder of Gaspy says that 97 percent of the app's data is accurate, and that the data is externally audited.
History
Gaspy was started in 2016 by Larry Green and three other directors of Hwem, a technology company. It was a "philantropic sideproject, 'for kicks'". Originally Gaspy was made to demonstrate engineering capabilities of Hwem to potential clients. It was also created as a game, where members would play as characters who would achieve spy ranks depending on how much they contribute to the app.
Once the app reached 200,000, the Commerce Commission, who was studying fuel prices, used Gaspy's data. The study found that consumers were paying too much for fuel, and made propositions on how to make the market more competitive. In 2020 Gaspy reached 500,000 members.
In 2023 after the 2022 New Zealand fuel tax subsidy was removed, Gaspy membership numbers surged. In one day, it received an increase of 6500 members, compared to its usual 500 new members per day. During this time, Gaspy reached 146,500 active users in a day, compared to numbers averaging between 35,000 and 60,000.
References
Companies based in Tauranga
New Zealand companies established in 2016
Software companies of New Zealand
Crowdsourcing
Online databases
Price indices |
https://en.wikipedia.org/wiki/291%20%28number%29 | 291 is the natural number following 290 and preceding 292.
In mathematics
291 is an odd composite number with two prime factor.
291 is a semiprime number meaning that it has 2 prime factors.
291 can be written as the sum of the nth prime plus n. It is the 52nd prime (239) plus 52.
291 is one of the positions of “c” in the tribonacci word abacabaab… defined by a->ab, b->ac, c->a.
291 is the sum of 6 different 4th powers. It is the sum of 44+24+24+14+14+14.
World Records
On March 6, 2022, Tamara Walcott received the Guinness World Record for the elephant bar deadlift achieved by a woman. She lifted a weight of 291 kg.
On December 19, 2021, the greatest number of cakes eaten online simultaneously was achieved in Tanba, Japan. There were 291 cakes.
On October 25, 2014, the longest string instrument was created in Singapore. It was the ‘Earth Harp’ at a length of 291 m.
On August 7, 2011, Fred Grsybowski achieved the Guinness World Record for the tallest usable pogo stick in Toronto. It was 2.91 m tall.
Other fields
The calendar years 291 AD and 291 BC.
291 is the number for several highways across the countries of Canada, Japan, and the United States.
291 Alice is an asteroid in the asteroid belt. It was discovered by Johann Palisa in Vienna, Austria.
References |
https://en.wikipedia.org/wiki/304%20%28number%29 | 304 is the natural number following 303 and preceding 305.
In mathematics
304 is an even composite number with two prime factor.
304 is the sum of consecutive primes in two different ways. It is the sum of 41+43+47+53+59+61 and of 23+29+31+37+41+43+47+53.3
304 is a primitive semiperfect number meaning that it is a semiperfect number that is not divisible by any other semiperfect number.
304 is an untouchable number meaning that it is not equal to the sum of any number’s proper divisors.
304 is a nontotient number meaning that it is an even number where phi(x) cannot result in that number.
World Records
In 2021, Tom Brady completed his 304th touchdown during his football career in Gillette Stadium. This is the most by one quarterback in one stadium.
On October 20, 2018, the Guinness World Record for the greatest number of participants in a Beetle drive game was achieved. There were 304 participants.
On August 25, 2014, David Chapple attended the most performances in the Edinburgh Fringe Festival. There were 304 shows with David attending around 11 shows each day.
On December 31, 2021, the greatest number of people passing a squash ball over a video chain was achieved by SquashSmarts.
Other fields
The calendar years 304 AD and 304 BC.
289 is the number for several highways across the countries of Brazil, Canada, China, Costa Rica, Hungary, Japan, the Thailand and the United States.
304 Olga is an asteroid in the asteroid belt. It was discovered by Johann Palisa in Vienna.
References |
https://en.wikipedia.org/wiki/History%20sniffing | History sniffing is the tracking of a user's web browsing history activities by recording which websites a user has visited and which the user has not.
References
Web security exploits
Internet privacy |
https://en.wikipedia.org/wiki/Interdigitation | Interdigitation is the interlinking of biological components that resembles the fingers of two hands being locked together. It can be a naturally occurring or man-made state.
Examples
Naturally occurring interdigitation includes skull sutures that develop during periods of brain growth, and which remain thin and straight, and later develop complex fractal interdigitations that provide interlocking strength. A layer of the retina where photoreception occurs is called the interdigitation zone. Adhesion or diffusive bonding occurs when sections of polymer chains from one surface interdigitate with those of an adjacent surface. In the dermis, dermal papillae (DP) (singular papilla, diminutive of Latin papula, 'pimple') are small, nipple-like extensions of the dermis into the epidermis, also known as interdigitations. The distal convoluted tubule (DCT), a portion of kidney nephron, can be recognized by several distinct features, including lateral membrane interdigitations with neighboring cells.
Some hypotheses contend that crown shyness, the interdigitation of canopy branches, leads to "reciprocal pruning" of adjacent trees.
Interdigitation is also found in biological research. Interdigitation fusion is a method of preparing calcium- and phosphate-loaded liposomes. Drugs inserted in the bilayer biomembrane may influence the lateral organization of the lipid membrane, with interdigitation of the membrane to fill volume voids. A similar interdigitation process involves investigating dissipative particle dynamics (DPD) simulations by adding alcohol molecules to the bilayers of double-tail lipids. Pressure-induced interdigitation is used to study hydrostatic pressure of bicellular dispersions containing anionic lipids.
References
Biology
Research |
https://en.wikipedia.org/wiki/Pickled%20oysters | Pickled oysters are a traditional way of preserving oysters by pickling or curing. To pickle oysters, they are usually cooked for a short period after removal from the shell, cooled, and placed in glass jars with vinegar and other spices.
History
In 1646, Humphrey Mill described pickled oysters being served to customers in brothels in England. Another early reference to pickled oysters appears in the writings of Samuel Pepys, who wrote about them as early as 1661.
According to Rowan Jacobsen, pickled oysters were "standard fare in every city on the Eastern Seaboard in that heady pre-canning era when oysters were in demand far and wide." Pickled oysters were a popular dish among both the upper and lower classes. Pickled oysters were also served at the Governor’s Palace in Williamsburg, Virginia. In Colonial America, pickled oysters were a commonly traded commodity as a part of the slave trade. The papers of George Washington indicate that he enjoyed pickled oysters in the 1780s and received them as a gift.
In the 1840s and 1850s, Thomas Downing served pickled oysters at his establishment in New York City.
In 1881, U.S. President James A. Garfield's inauguration dinner included over 100 gallons of pickled oysters. Victorian-era cookbooks often include pickled oyster recipes.
Pickled oysters were a frequent holiday staple in American homes of the 1800s.
The 1903 Le guide culinaire includes a pickled oyster preparation. Pickled oysters are still a common staple in Southern cuisine of the United States, and have been a featured recipe by Mashama Bailey and Thomas Keller.
See also
Citations
American seafood dishes
Oyster dishes
Pickles
Food preservation |
https://en.wikipedia.org/wiki/292%20%28number%29 | 292 is the natural number following 291 and preceding 293.
In mathematics
292 is an even composite number with two prime factor.
292 is a noncototient number meaning that phi(x) cannot result in 292.
292 is an untouchable number meaning that the proper divisors of any number do not add up to 292.
292 is a repdigit in base 8 with it being 444.
In the simplified continued fraction for pi, 292 is the 5th number.
World Records
Between December 16, 2021, and March 15, 2022, Arnaud Clein watched Spider-Man: No Way Home a grand total of 292 times with a total run time of 720 hours.
On May 30, 2016, in Tokyo, Japan, the greatest number of people using vacuum cleaners was achieved with 292 participants.
On April 23, 2019, the largest Shakespeare recital was completed in London. There were 292 participants.
On December 19, 2010, the Guinness World Record for the longest paper airplane flight time was 29.2 seconds achieved in Fukuyama City, Japan.
Other fields
The calendar years 292 AD and 292 BC.
292 is the number for several highways across the countries of Japan and the United States.
292 Ludovica is an asteroid in the asteroid belt. It was discovered by Johann Palisa in Vienna.
References |
https://en.wikipedia.org/wiki/295%20%28number%29 | 295 is the natural number following 294 and preceding 296.
In mathematics
295 is an odd composite number with two prime factor.
295 is a centered tetrahedral number meaning that it can be represented as a tetrahedron.
295 Is a structured deltoidal hexecontahedral number which can be represented as a deltoidal hexecontahedron.
295 can be written as the sum of 4 nonzero perfect squares.
In binary, 295 would be a decimal prime number.
World Records
On September 28, 2018, the greatest number of people filling in the eyebrows was achieved in San Francisco. There were 295 participants.
On December 18, 2014, in Chengdu, China, the greatest number of handheld lasers were lit simultaneously. There were 295 lasers.
The largest lunar crater is Bailly, near the South Pole of the moon. It is 295 km in diameter.
On September 16, 2006, the Guinness World Record for the longest jump on a unicycle was achieved. It was a distance of 2.95 m achieved by David Weichenberger in Vienna.
Other fields
The calendar years 295 AD and 295 BC.
295 is the number for several highways across the countries of Canada, Japan, and the United States.
295 Theresia is an asteroid in the asteroid belt. It was discovered by Johann Palisa in Vienna.
295 is a song recorded by Punjabi singer Sidhu Moose Wala.
References |
https://en.wikipedia.org/wiki/Faraday%20cage | A Faraday cage or Faraday shield is an enclosure used to block electromagnetic fields. A Faraday shield may be formed by a continuous covering of conductive material, or in the case of a Faraday cage, by a mesh of such materials. Faraday cages are named after scientist Michael Faraday, who invented them in 1836.
A Faraday cage operates because an external electrical field causes the electric charges within the cage's conducting material to be distributed so that they cancel the field's effect in the cage's interior. This phenomenon is used to protect sensitive electronic equipment (for example RF receivers) from external radio frequency interference (RFI) often during testing or alignment of the device. They are also used to protect people and equipment against actual electric currents such as lightning strikes and electrostatic discharges, since the enclosing cage conducts current around the outside of the enclosed space and none passes through the interior.
Faraday cages cannot block stable or slowly varying magnetic fields, such as the Earth's magnetic field (a compass will still work inside). To a large degree, though, they shield the interior from external electromagnetic radiation if the conductor is thick enough and any holes are significantly smaller than the wavelength of the radiation. For example, certain computer forensic test procedures of electronic systems that require an environment free of electromagnetic interference can be carried out within a screened room. These rooms are spaces that are completely enclosed by one or more layers of a fine metal mesh or perforated sheet metal. The metal layers are grounded to dissipate any electric currents generated from external or internal electromagnetic fields, and thus they block a large amount of the electromagnetic interference. See also electromagnetic shielding. They provide less attenuation of outgoing transmissions than incoming: they can block electromagnetic pulse (EMP) waves from natural phenomen |
https://en.wikipedia.org/wiki/Deception | Deception or falsehood is an act or statement that misleads, hides the truth, or promotes a belief, concept, or idea that is not true. It is often done for personal gain or advantage. Deception can involve dissimulation, propaganda and sleight of hand as well as distraction, camouflage or concealment. There is also self-deception, as in bad faith. It can also be called, with varying subjective implications, beguilement, deceit, bluff, mystification, ruse, or subterfuge.
Deception is a major relational transgression that often leads to feelings of betrayal and distrust between relational partners. Deception violates relational rules and is considered to be a negative violation of expectations. Most people expect friends, relational partners, and even strangers to be truthful most of the time. If people expected most conversations to be untruthful, talking and communicating with others would require distraction and misdirection to acquire reliable information. A significant amount of deception occurs between some romantic and relational partners.
Deceit and dishonesty can also form grounds for civil litigation in tort, or contract law (where it is known as misrepresentation or fraudulent misrepresentation if deliberate), or give rise to criminal prosecution for fraud. It also forms a vital part of psychological warfare in denial and deception.
Types
Communication
Deception includes several types of communications or omissions that serve to distort or omit the whole truth. Examples of deception range from false statements to misleading claims in which relevant information is omitted, leading the receiver to infer false conclusions. For example, a claim that "sunflower oil is beneficial to brain health due to the presence of omega-3 fatty acids" may be misleading, as it leads the receiver to believe sunflower oil will benefit brain health more so than other foods. In fact, sunflower oil is relatively low in omega-3 fatty acids and is not particularly good for bra |
https://en.wikipedia.org/wiki/Authorization | Authorization or authorisation (see spelling differences) is the function of specifying access rights/privileges to resources, which is related to general information security and computer security, and to access control in particular. More formally, "to authorize" is to define an access policy. For example, human resources staff are normally authorized to access employee records and this policy is often formalized as access control rules in a computer system. During operation, the system uses the access control rules to decide whether access requests from (authenticated) consumers shall be approved (granted) or disapproved (rejected). Resources include individual files or an item's data, computer programs, computer devices and functionality provided by computer applications. Examples of consumers are computer users, computer software and other hardware on the computer.
Overview
Access control in computer systems and networks rely on access policies. The access control process can be divided into the following phases: policy definition phase where access is authorized, and policy enforcement phase where access requests are approved or disapproved. Authorization is the function of the policy definition phase which precedes the policy enforcement phase where access requests are approved or disapproved based on the previously defined authorizations.
Most modern, multi-user operating systems include role-based access control (RBAC) and thereby rely on authorization. Access control also uses authentication to verify the identity of consumers. When a consumer tries to access a resource, the access control process checks that the consumer has been authorized to use that resource. Authorization is the responsibility of an authority, such as a department manager, within the application domain, but is often delegated to a custodian such as a system administrator. Authorizations are expressed as access policies in some types of "policy definition application", e.g. in the fo |
https://en.wikipedia.org/wiki/One-instruction%20set%20computer | A one-instruction set computer (OISC), sometimes referred to as an ultimate reduced instruction set computer (URISC), is an abstract machine that uses only one instructionobviating the need for a machine language opcode. With a judicious choice for the single instruction and given arbitrarily many resources, an OISC is capable of being a universal computer in the same manner as traditional computers that have multiple instructions. OISCs have been recommended as aids in teaching computer architecture and have been used as computational models in structural computing research. The first carbon nanotube computer is a 1-bit one-instruction set computer (and has only 178 transistors).
Machine architecture
In a Turing-complete model, each memory location can store an arbitrary integer, anddepending on the modelthere may be arbitrarily many locations. The instructions themselves reside in memory as a sequence of such integers.
There exists a class of universal computers with a single instruction based on bit manipulation such as bit copying or bit inversion. Since their memory model is finite, as is the memory structure used in real computers, those bit manipulation machines are equivalent to real computers rather than to Turing machines.
Currently known OISCs can be roughly separated into three broad categories:
Bit-manipulating machines
Transport triggered architecture machines
Arithmetic-based Turing-complete machines
Bit-manipulating machines
Bit-manipulating machines are the simplest class.
FlipJump
The FlipJump machine has 1 instruction, a;b - flips the bit a, then jumps to b. This is the most primitive OISC, but it's still useful. It can successfully do Math/Logic calculations, branching, pointers, and calling functions with the help of its standard library.
BitBitJump
A bit copying machine, called BitBitJump, copies one bit in memory and passes the execution unconditionally to the address specified by one of the operands of the instruction. This proc |
https://en.wikipedia.org/wiki/Zu%20Chongzhi | Zu Chongzhi (; 429–500 AD), courtesy name Wenyuan (), was a Chinese astronomer, mathematician, politician, inventor, and writer during the Liu Song and Southern Qi dynasties. He was most notable for calculating pi as between 3.1415926 and 3.1415927, a record in accuracy which would not be surpassed for over 800 years.
Life and works
Chongzhi's ancestry was from modern Baoding, Hebei. To flee from the ravages of war, Zu's grandfather Zu Chang moved to the Yangtze, as part of the massive population movement during the Eastern Jin. Zu Chang () at one point held the position of Chief Minister for the Palace Buildings () within the Liu Song and was in charge of government construction projects. Zu's father, Zu Shuozhi (), also served the court and was greatly respected for his erudition.
Zu was born in Jiankang. His family had historically been involved in astronomical research, and from childhood Zu was exposed to both astronomy and mathematics. When he was only a youth his talent earned him much repute. When Emperor Xiaowu of Liu Song heard of him, he was sent to the Hualin Xuesheng () academy, and later the Imperial Nanjing University (Zongmingguan) to perform research. In 461 in Nanxu (today Zhenjiang, Jiangsu), he was engaged in work at the office of the local governor.
Zu Chongzhi, along with his son Zu Gengzhi, wrote a mathematical text entitled Zhui Shu (; "Methods for Interpolation"). It is said that the treatise contained formulas for the volume of a sphere, cubic equations and an accurate value of pi. This book has been lost since the Song Dynasty.
His mathematical achievements included
the Daming calendar () introduced by him in 465.
distinguishing the sidereal year and the tropical year. He measured 45 years and 11 months per degree between those two; today we know the difference is 70.7 years per degree.
calculating one year as 365.24281481 days, which is very close to 365.24219878 days as we know today.
calculating the number of overlaps between sun |
https://en.wikipedia.org/wiki/Stirling%27s%20approximation | In mathematics, Stirling's approximation (or Stirling's formula) is an approximation for factorials. It is a good approximation, leading to accurate results even for small values of . It is named after James Stirling, though a related but less precise result was first stated by Abraham de Moivre.
One way of stating the approximation involves the logarithm of the factorial:
where the big O notation means that, for all sufficiently large values of , the difference between and will be at most proportional to the logarithm. In computer science applications such as the worst-case lower bound for comparison sorting, it is convenient to instead use the binary logarithm, giving the equivalent form
The error term in either base can be expressed more precisely as , corresponding to an approximate formula for the factorial itself,
Here the sign means that the two quantities are asymptotic, that is, that their ratio tends to 1 as tends to infinity. The following version of the bound holds for all , rather than only asymptotically:
Derivation
Roughly speaking, the simplest version of Stirling's formula can be quickly obtained by approximating the sum
with an integral:
The full formula, together with precise estimates of its error, can be derived as follows. Instead of approximating , one considers its natural logarithm, as this is a slowly varying function:
The right-hand side of this equation minus
is the approximation by the trapezoid rule of the integral
and the error in this approximation is given by the Euler–Maclaurin formula:
where is a Bernoulli number, and is the remainder term in the Euler–Maclaurin formula. Take limits to find that
Denote this limit as . Because the remainder in the Euler–Maclaurin formula satisfies
where big-O notation is used, combining the equations above yields the approximation formula in its logarithmic form:
Taking the exponential of both sides and choosing any positive integer , one obtains a formula involving an unknown |
https://en.wikipedia.org/wiki/Divergence%20theorem | In vector calculus, the divergence theorem, also known as Gauss's theorem or Ostrogradsky's theorem, is a theorem which relates the flux of a vector field through a closed surface to the divergence of the field in the volume enclosed.
More precisely, the divergence theorem states that the surface integral of a vector field over a closed surface, which is called the "flux" through the surface, is equal to the volume integral of the divergence over the region inside the surface. Intuitively, it states that "the sum of all sources of the field in a region (with sinks regarded as negative sources) gives the net flux out of the region".
The divergence theorem is an important result for the mathematics of physics and engineering, particularly in electrostatics and fluid dynamics. In these fields, it is usually applied in three dimensions. However, it generalizes to any number of dimensions. In one dimension, it is equivalent to integration by parts. In two dimensions, it is equivalent to Green's theorem.
Explanation using liquid flow
Vector fields are often illustrated using the example of the velocity field of a fluid, such as a gas or liquid. A moving liquid has a velocity—a speed and a direction—at each point, which can be represented by a vector, so that the velocity of the liquid at any moment forms a vector field. Consider an imaginary closed surface S inside a body of liquid, enclosing a volume of liquid. The flux of liquid out of the volume at any time is equal to the volume rate of fluid crossing this surface, i.e., the surface integral of the velocity over the surface.
Since liquids are incompressible, the amount of liquid inside a closed volume is constant; if there are no sources or sinks inside the volume then the flux of liquid out of S is zero. If the liquid is moving, it may flow into the volume at some points on the surface S and out of the volume at other points, but the amounts flowing in and out at any moment are equal, so the net flux of liqui |
https://en.wikipedia.org/wiki/All%20horses%20are%20the%20same%20color | All horses are the same color is a falsidical paradox that arises from a flawed use of mathematical induction to prove the statement All horses are the same color. There is no actual contradiction, as these arguments have a crucial flaw that makes them incorrect. This example was originally raised by George Pólya in a 1954 book in different terms: "Are any numbers equal?" or "Any girls have eyes of the same color", as an exercise in mathematical induction. It has also been restated as "All cows have the same color".
The "horses" version of the paradox was presented in 1961 in a satirical article by Joel E. Cohen. It was stated as a lemma, which in particular allowed the author to "prove" that Alexander the Great did not exist, and he had an infinite number of limbs.
The argument
The argument is proof by induction. First, we establish a base case for one horse (). We then prove that if horses have the same color, then horses must also have the same color.
Base case: One horse
The case with just one horse is trivial. If there is only one horse in the "group", then clearly all horses in that group have the same color.
Inductive step
Assume that horses always are the same color. Consider a group consisting of horses.
First, exclude one horse and look only at the other horses; all these are the same color, since horses always are the same color. Likewise, exclude some other horse (not identical to the one first removed) and look only at the other horses. By the same reasoning, these, too, must also be of the same color. Therefore, the first horse that was excluded is of the same color as the non-excluded horses, who in turn are of the same color as the other excluded horse. Hence, the first horse excluded, the non-excluded horses, and the last horse excluded are all of the same color, and we have proven that:
If horses have the same color, then horses will also have the same color.
We already saw in the base case that the rule ("all horses have the sam |
https://en.wikipedia.org/wiki/Del | Del, or nabla, is an operator used in mathematics (particularly in vector calculus) as a vector differential operator, usually represented by the nabla symbol ∇. When applied to a function defined on a one-dimensional domain, it denotes the standard derivative of the function as defined in calculus. When applied to a field (a function defined on a multi-dimensional domain), it may denote any one of three operations depending on the way it is applied: the gradient or (locally) steepest slope of a scalar field (or sometimes of a vector field, as in the Navier–Stokes equations); the divergence of a vector field; or the curl (rotation) of a vector field.
Del is a very convenient mathematical notation for those three operations (gradient, divergence, and curl) that makes many equations easier to write and remember. The del symbol (or nabla) can be formally defined as a three-dimensional vector operator whose three components are the corresponding partial derivative operators. As a vector operator, it can act on scalar and vector fields in three different ways, giving rise to three different differential operations: first, it can act on scalar fields by a "formal" scalar multiplication—to give a vector field called the gradient; second, it can act on vector fields by a "formal" dot product—to give a scalar field called the divergence; and lastly, it can act on vector fields by a "formal" cross product—to give a vector field called the curl. These "formal" products do not necessarily commute with other operators or products. These three uses, detailed below, are summarized as:
Gradient:
Divergence:
Curl:
Definition
In the Cartesian coordinate system with coordinates and standard basis , del is a vector operator whose components are the partial derivative operators ; that is,
Where the expression in parentheses is a row vector. In three-dimensional Cartesian coordinate system with coordinates and standard basis or unit vectors of axes , del is written as
As |
https://en.wikipedia.org/wiki/S-100%20bus | The S-100 bus or Altair bus, IEEE 696-1983 (withdrawn), is an early computer bus designed in 1974 as a part of the Altair 8800. The bus was the first industry standard expansion bus for the microcomputer industry. computers, consisting of processor and peripheral cards, were produced by a number of manufacturers. The bus formed the basis for homebrew computers whose builders (e.g., the Homebrew Computer Club) implemented drivers for CP/M and MP/M. These microcomputers ran the gamut from hobbyist toy to small business workstation and were common in early home computers until the advent of the IBM PC.
Architecture
The bus is a passive backplane of 100-pin printed circuit board edge connectors wired in parallel. Circuit cards measuring 5 × 10-inches serving the functions of CPU, memory, or I/O interface plugged into these connectors. The bus signal definitions closely follow those of an 8080 microprocessor system, since the Intel 8080 microprocessor was the first microprocessor hosted on the bus. The 100 lines of the bus can be grouped into four types: 1) Power, 2) Data, 3) Address, and 4) Clock and control.
Power supplied on the bus is bulk unregulated +8 Volt DC and ±16 Volt DC, designed to be regulated on the cards to +5 V (used by TTL ICs), -5 V and +12 V for Intel 8080 CPU IC, ±12 V RS-232 line driver ICs, +12 V for disk drive motors. The onboard voltage regulation is typically performed by devices of the 78xx family (for example, a 7805 device to produce +5 volts). These were linear regulators which are commonly mounted on heat sinks.
The bi-directional 8-bit data bus of the Intel 8080 is split into two unidirectional 8-bit data buses. The processor could use only one of these at a time. The Sol-20 used a variation that had only a single 8-bit bus and used the now-unused pins as signal grounds to reduce electronic noise. The direction of the bus, in or out, was signaled using the otherwise unused DBIN pin. This became universal in the market as well |
https://en.wikipedia.org/wiki/Karyotype | A karyotype is the general appearance of the complete set of chromosomes in the cells of a species or in an individual organism, mainly including their sizes, numbers, and shapes. Karyotyping is the process by which a karyotype is discerned by determining the chromosome complement of an individual, including the number of chromosomes and any abnormalities.
A karyogram or idiogram is a graphical depiction of a karyotype, wherein chromosomes are generally organized in pairs, ordered by size and position of centromere for chromosomes of the same size. Karyotyping generally combines light microscopy and photography in the metaphase of the cell cycle, and results in a photomicrographic (or simply micrographic) karyogram. In contrast, a schematic karyogram is a designed graphic representation of a karyotype. In schematic karyograms, just one of the sister chromatids of each chromosome is generally shown for brevity, and in reality they are generally so close together that they look as one on photomicrographs as well unless the resolution is high enough to distinguish them. The study of whole sets of chromosomes is sometimes known as karyology.
Karyotypes describe the chromosome count of an organism and what these chromosomes look like under a light microscope. Attention is paid to their length, the position of the centromeres, banding pattern, any differences between the sex chromosomes, and any other physical characteristics. The preparation and study of karyotypes is part of cytogenetics.
The basic number of chromosomes in the somatic cells of an individual or a species is called the somatic number and is designated 2n. In the germ-line (the sex cells) the chromosome number is n (humans: n = 23).p28 Thus, in humans 2n = 46.
So, in normal diploid organisms, autosomal chromosomes are present in two copies. There may, or may not, be sex chromosomes. Polyploid cells have multiple copies of chromosomes and haploid cells have single copies.
Karyotypes can be used for |
https://en.wikipedia.org/wiki/Inter-process%20communication | In computer science, inter-process communication (IPC), also spelled interprocess communication, are the mechanisms provided by an operating system for processes to manage shared data. Typically, applications can use IPC, categorized as clients and servers, where the client requests data and the server responds to client requests. Many applications are both clients and servers, as commonly seen in distributed computing.
IPC is very important to the design process for microkernels and nanokernels, which reduce the number of functionalities provided by the kernel. Those functionalities are then obtained by communicating with servers via IPC, leading to a large increase in communication when compared to a regular monolithic kernel. IPC interfaces generally encompass variable analytic framework structures. These processes ensure compatibility between the multi-vector protocols upon which IPC models rely.
An IPC mechanism is either synchronous or asynchronous. Synchronization primitives may be used to have synchronous behavior with an asynchronous IPC mechanism.
Approaches
Different approaches to IPC have been tailored to different software requirements, such as performance, modularity, and system circumstances such as network bandwidth and latency.
Applications
Remote procedure call interfaces
Java's Remote Method Invocation (RMI)
ONC RPC
XML-RPC or SOAP
JSON-RPC
Message Bus (Mbus) (specified in RFC 3259) (not to be confused with M-Bus)
.NET Remoting
gRPC
Platform communication stack
The following are messaging, and information systems that utilize IPC mechanisms but don't implement IPC themselves:
KDE's Desktop Communications Protocol (DCOP) deprecated by D-Bus
D-Bus
OpenWrt uses ubus micro bus architecture
MCAPI Multicore Communications API
SIMPL The Synchronous Interprocess Messaging Project for Linux (SIMPL)
9P (Plan 9 Filesystem Protocol)
Distributed Computing Environment (DCE)
Thrift
ZeroC's Internet Communications Engine (ICE)
ØMQ
Endu |
https://en.wikipedia.org/wiki/Scalable%20Coherent%20Interface | The Scalable Coherent Interface or Scalable Coherent Interconnect (SCI), is a high-speed interconnect standard for shared memory multiprocessing and message passing. The goal was to scale well, provide system-wide memory coherence and a simple interface; i.e. a standard to replace existing buses in multiprocessor systems with one with no inherent scalability and performance limitations.
The IEEE Std 1596-1992, IEEE Standard for Scalable Coherent Interface (SCI) was approved by the IEEE standards board on March 19, 1992. It saw some use during the 1990s, but never became widely used and has been replaced by other systems from the early 2000s.
History
Soon after the Fastbus (IEEE 960) follow-on Futurebus (IEEE 896) project in 1987, some engineers predicted it would already be too slow for the high performance computing marketplace by the time it would be released in the early 1990s.
In response, a "Superbus" study group was formed in November 1987.
Another working group of the standards association of the Institute of Electrical and Electronics Engineers (IEEE) spun off to form a standard targeted at this market in July 1988.
It was essentially a subset of Futurebus features that could be easily implemented at high speed, along with minor additions to make it easier to connect to other systems, such as VMEbus. Most of the developers had their background from high-speed computer buses. Representatives from companies in the computer industry and research community included Amdahl, Apple Computer, BB&N, Hewlett-Packard, CERN, Dolphin Server Technology, Cray Research, Sequent, AT&T, Digital Equipment Corporation, McDonnell Douglas, National Semiconductor, Stanford Linear Accelerator Center, Tektronix, Texas Instruments, Unisys, University of Oslo, University of Wisconsin.
The original intent was a single standard for all buses in the computer.
The working group soon came up with the idea of using point-to-point communication in the form of insertion rings. This avoided |
https://en.wikipedia.org/wiki/Forcing%20%28mathematics%29 | In the mathematical discipline of set theory, forcing is a technique for proving consistency and independence results. Intuitively, forcing can be thought of as a technique to expand the set theoretical universe to a larger universe by introducing a new "generic" object .
Forcing was first used by Paul Cohen in 1963, to prove the independence of the axiom of choice and the continuum hypothesis from Zermelo–Fraenkel set theory. It has been considerably reworked and simplified in the following years, and has since served as a powerful technique, both in set theory and in areas of mathematical logic such as recursion theory. Descriptive set theory uses the notions of forcing from both recursion theory and set theory. Forcing has also been used in model theory, but it is common in model theory to define genericity directly without mention of forcing.
Intuition
Forcing is usually used to construct an expanded universe that satisfies some desired property. For example, the expanded universe might contain many new real numbers (at least of them), identified with subsets of the set of natural numbers, that were not there in the old universe, and thereby violate the continuum hypothesis.
In order to intuitively justify such an expansion, it is best to think of the "old universe" as a model of the set theory, which is itself a set in the "real universe" . By the Löwenheim–Skolem theorem, can be chosen to be a "bare bones" model that is externally countable, which guarantees that there will be many subsets (in ) of that are not in . Specifically, there is an ordinal that "plays the role of the cardinal " in , but is actually countable in . Working in , it should be easy to find one distinct subset of per each element of . (For simplicity, this family of subsets can be characterized with a single subset .)
However, in some sense, it may be desirable to "construct the expanded model within ". This would help ensure that "resembles" in certain aspects, such as b |
https://en.wikipedia.org/wiki/Compactness%20theorem | In mathematical logic, the compactness theorem states that a set of first-order sentences has a model if and only if every finite subset of it has a model. This theorem is an important tool in model theory, as it provides a useful (but generally not effective) method for constructing models of any set of sentences that is finitely consistent.
The compactness theorem for the propositional calculus is a consequence of Tychonoff's theorem (which says that the product of compact spaces is compact) applied to compact Stone spaces, hence the theorem's name. Likewise, it is analogous to the finite intersection property characterization of compactness in topological spaces: a collection of closed sets in a compact space has a non-empty intersection if every finite subcollection has a non-empty intersection.
The compactness theorem is one of the two key properties, along with the downward Löwenheim–Skolem theorem, that is used in Lindström's theorem to characterize first-order logic. Although there are some generalizations of the compactness theorem to non-first-order logics, the compactness theorem itself does not hold in them, except for a very limited number of examples.
History
Kurt Gödel proved the countable compactness theorem in 1930. Anatoly Maltsev proved the uncountable case in 1936.
Applications
The compactness theorem has many applications in model theory; a few typical results are sketched here.
Robinson's principle
The compactness theorem implies the following result, stated by Abraham Robinson in his 1949 dissertation.
Robinson's principle: If a first-order sentence holds in every field of characteristic zero, then there exists a constant such that the sentence holds for every field of characteristic larger than This can be seen as follows: suppose is a sentence that holds in every field of characteristic zero. Then its negation together with the field axioms and the infinite sequence of sentences
is not satisfiable (because there is no field o |
https://en.wikipedia.org/wiki/Zermelo%E2%80%93Fraenkel%20set%20theory | In set theory, Zermelo–Fraenkel set theory, named after mathematicians Ernst Zermelo and Abraham Fraenkel, is an axiomatic system that was proposed in the early twentieth century in order to formulate a theory of sets free of paradoxes such as Russell's paradox. Today, Zermelo–Fraenkel set theory, with the historically controversial axiom of choice (AC) included, is the standard form of axiomatic set theory and as such is the most common foundation of mathematics. Zermelo–Fraenkel set theory with the axiom of choice included is abbreviated ZFC, where C stands for "choice", and ZF refers to the axioms of Zermelo–Fraenkel set theory with the axiom of choice excluded.
Informally, Zermelo–Fraenkel set theory is intended to formalize a single primitive notion, that of a hereditary well-founded set, so that all entities in the universe of discourse are such sets. Thus the axioms of Zermelo–Fraenkel set theory refer only to pure sets and prevent its models from containing urelements (elements of sets that are not themselves sets). Furthermore, proper classes (collections of mathematical objects defined by a property shared by their members where the collections are too big to be sets) can only be treated indirectly. Specifically, Zermelo–Fraenkel set theory does not allow for the existence of a universal set (a set containing all sets) nor for unrestricted comprehension, thereby avoiding Russell's paradox. Von Neumann–Bernays–Gödel set theory (NBG) is a commonly used conservative extension of Zermelo–Fraenkel set theory that does allow explicit treatment of proper classes.
There are many equivalent formulations of the axioms of Zermelo–Fraenkel set theory. Most of the axioms state the existence of particular sets defined from other sets. For example, the axiom of pairing says that given any two sets and there is a new set containing exactly and . Other axioms describe properties of set membership. A goal of the axioms is that each axiom should be true if interprete |
https://en.wikipedia.org/wiki/Rooibos | Rooibos ( ; , meaning "red bush"), or Aspalathus linearis, is a broom-like member of the plant family Fabaceae that grows in South Africa's fynbos biome.
The leaves are used to make a herbal tea that is called rooibos (especially in Southern Africa), bush tea, red tea, or redbush tea (predominantly in Great Britain).
The tea has been popular in Southern Africa for generations, and since the 2000s has gained popularity internationally.
The tea has an earthy flavour that is similar to yerba mate or tobacco.
Rooibos was formerly classified as Psoralea but is now thought to be part of Aspalathus following Dahlgren (1980).
The specific name of linearis was given by Burman (1759)
for the plant's linear growing structure and needle-like leaves.
The name rooibos is Afrikaans, and derived from the Dutch words 'rood bos' (red forest).
Production and processing
Rooibos is usually grown in the Cederberg, a small mountainous area in the West Coast District of the Western Cape province of South Africa.
Generally, the leaves undergo oxidation. This process produces the distinctive reddish-brown colour of rooibos and enhances the flavour. Unoxidised green rooibos is also produced, but the more demanding production process for green rooibos (similar to the method by which green tea is produced) makes it more expensive than traditional rooibos. It carries a malty and slightly grassy flavour somewhat different from its red counterpart.
Use
Rooibos is commonly prepared as a tisane by steeping in hot water, in the same manner as black tea. The infusion is consumed on its own or flavored by addition of milk, lemon, sugar or honey. It is also served as lattes, cappuccinos or iced tea.
Chemical composition
As a fresh leaf, rooibos contains a high content of ascorbic acid (vitamin C).
Rooibos tea does not contain caffeine and has low tannin levels compared to black tea or green tea. Rooibos contains polyphenols, including flavanols, flavones, flavanones, dihydrochalcones, aspal |
https://en.wikipedia.org/wiki/Babylonian%20cuneiform%20numerals | Babylonian cuneiform numerals, also used in Assyria and Chaldea, were written in cuneiform, using a wedge-tipped reed stylus to print a mark on a soft clay tablet which would be exposed in the sun to harden to create a permanent record.
The Babylonians, who were famous for their astronomical observations (Observations of the sky), as well as their calculations (aided by their invention of the abacus), used a sexagesimal (base-60) positional numeral system inherited from either the Sumerian or the Akkadian civilizations. Neither of the predecessors was a positional system (having a convention for which 'end' of the numeral represented the units).
Origin
This system first appeared around 2000 BC; its structure reflects the decimal lexical numerals of Semitic languages rather than Sumerian lexical numbers. However, the use of a special Sumerian sign for 60 (beside two Semitic signs for the same number) attests to a relation with the Sumerian system.
Symbols
The Babylonian system is credited as being the first known positional numeral system, in which the value of a particular digit depends both on the digit itself and its position within the number. This was an extremely important development because non-place-value systems require unique symbols to represent each power of a base (ten, one hundred, one thousand, and so forth), which can make calculations more difficult.
Only two symbols ( to count units and to count tens) were used to notate the 59 non-zero digits. These symbols and their values were combined to form a digit in a sign-value notation quite similar to that of Roman numerals; for example, the combination represented the digit for 23 (see table of digits above).
These digits were used to represent larger numbers in the base 60 (sexagesimal) positional system. For example, would represent 2×602+23×60+3 = 8583.
A space was left to indicate a place without value, similar to the modern-day zero. Babylonians later devised a sign to represent this |
https://en.wikipedia.org/wiki/Passphrase | A passphrase is a sequence of words or other text used to control access to a computer system, program or data. It is similar to a password in usage, but a passphrase is generally longer for added security. Passphrases are often used to control both access to, and the operation of, cryptographic programs and systems, especially those that derive an encryption key from a passphrase. The origin of the term is by analogy with password. The modern concept of passphrases is believed to have been invented by Sigmund N. Porter in 1982.
Security
Considering that the entropy of written English is less than 1.1 bits per character, passphrases can be relatively weak. NIST has estimated that the 23-character passphrase "IamtheCapitanofthePina4" contains a 45-bit strength. The equation employed here is:
4 bits (1st character) + 14 bits (characters 2–8) + 18 bits (characters 9–20) + 3 bits (characters 21–23) + 6 bits (bonus for upper case, lower case, and alphanumeric) = 45 bits
(This calculation does not take into account that this is a well-known quote from the operetta H.M.S. Pinafore. An MD5 hash of this passphrase can be cracked in 4 seconds using crackstation.net, indicating that the phrase is found in password cracking databases.)
Using this guideline, to achieve the 80-bit strength recommended for high security (non-military) by NIST, a passphrase would need to be 58 characters long, assuming a composition that includes uppercase and alphanumeric.
There is room for debate regarding the applicability of this equation, depending on the number of bits of entropy assigned. For example, the characters in five-letter words each contain 2.3 bits of entropy, which would mean only a 35-character passphrase is necessary to achieve 80 bit strength.
If the words or components of a passphrase may be found in a language dictionary—especially one available as electronic input to a software program—the passphrase is rendered more vulnerable to dictionary attack. This is a particul |
https://en.wikipedia.org/wiki/Ceva%27s%20theorem | In Euclidean geometry, Ceva's theorem is a theorem about triangles. Given a triangle , let the lines be drawn from the vertices to a common point (not on one of the sides of ), to meet opposite sides at respectively. (The segments are known as cevians.) Then, using signed lengths of segments,
In other words, the length is taken to be positive or negative according to whether is to the left or right of in some fixed orientation of the line. For example, is defined as having positive value when is between and and negative otherwise.
Ceva's theorem is a theorem of affine geometry, in the sense that it may be stated and proved without using the concepts of angles, areas, and lengths (except for the ratio of the lengths of two line segments that are collinear). It is therefore true for triangles in any affine plane over any field.
A slightly adapted converse is also true: If points are chosen on respectively so that
then are concurrent, or all three parallel. The converse is often included as part of the theorem.
The theorem is often attributed to Giovanni Ceva, who published it in his 1678 work De lineis rectis. But it was proven much earlier by Yusuf Al-Mu'taman ibn Hűd, an eleventh-century king of Zaragoza.
Associated with the figures are several terms derived from Ceva's name: cevian (the lines are the cevians of ), cevian triangle (the triangle is the cevian triangle of ); cevian nest, anticevian triangle, Ceva conjugate. (Ceva is pronounced Chay'va; cevian is pronounced chev'ian.)
The theorem is very similar to Menelaus' theorem in that their equations differ only in sign. By re-writing each in terms of cross-ratios, the two theorems may be seen as projective duals.
Proofs
Several proofs of the theorem have been given.
Two proofs are given in the following.
The first one is very elementary, using only basic properties of triangle areas. However, several cases have to be considered, depending on the position of the point .
The second |
https://en.wikipedia.org/wiki/Futurebus | Futurebus, or IEEE 896, is a computer bus standard, intended to replace all local bus connections in a computer, including the CPU, memory, plug-in cards and even, to some extent, LAN links between machines. The effort started in 1979 and didn't complete until 1987, and then immediately went into a redesign that lasted until 1994. By this point, implementation of a chip-set based on the standard lacked industry leadership. It has seen little real-world use, although custom implementations continue to be designed and used throughout industry.
History
In the late 1970s, VMEbus was faster than the parts plugged into it. It was quite reasonable to connect a CPU and RAM to VME on separate cards to build a computer. However, as the speed of the CPUs and RAM rapidly increased, VME was quickly overwhelmed. Increasing the speed of VME was not easy, because all of the parts plugged into it would have to be able to support these faster speeds as well.
Futurebus looked to fix these problems and create a successor to systems like VMEbus with a system that could grow in speed without affecting existing devices. In order to do this the primary technology of Futurebus was built using asynchronous links, allowing the devices plugged into it to talk at whatever speed they wished. Another problem that needed to be addressed was the ability to have several cards in the system as "masters", allowing Futurebus to build multiprocessor machines. This required some form of "distributed arbitration" to allow the various cards to gain access to the bus at any point, as opposed to VME, which put a single master in slot 0 with overall control. In order to have a clear performance benefit, Futurebus was designed to have the performance needed ten years in the future.
Typical IEEE standards start with a company building a device, and then submitting it to the IEEE for the standardization effort. In the case of Futurebus this was reversed, the whole system was being designed during the standar |
https://en.wikipedia.org/wiki/QuickRing | QuickRing was a gigabit-rate interconnect that combined the functions of a computer bus and a network. It was designed at Apple Computer as a multimedia system to run "on top" of existing local bus systems inside a computer, but was later taken over by National Semiconductor and repositioned as an interconnect for parallel computing. It appears to have seen little use in either role, and is no longer being actively worked on. However it appears to have been an inspiration for other more recent technologies, such as HyperTransport.
History
QuickRing started as an offshoot of the fabled Futurebus project, which started in the late 1970s under the aegis of the IEEE. The Futurebus process quickly bogged down, and concluding it was doomed, several of the main designers left the effort in 1987 to try again on smaller projects, leading to both QuickRing and SCI. In the case of QuickRing the main proponent was Paul Sweazey of National Semiconductor, who had hosted Futurebus's cache coherency group. Sweazey left National Semiconductor and moved to Apple Computer's Advanced Technology Group, where the new system was developed.
The system was first announced publicly at the 1992 Worldwide Developers Conference, positioned primarily as a secondary bus for computer systems to carry multiple streams of digital video without using the existing backplane bus. Apple was particularly interested in this role due to the limitations of their current NuBus systems in terms of speed. They envisioned various video cards using a second connector located near the top of the card, opposite the NuBus connector on the bottom, to talk to each other. Optionally, one of the cards would produce compressed output, which could be sent over the NuBus for storage or display. Before any commercial use of QuickRing, newer versions of PCI started appearing that offered performance close enough to QuickRing to make its role redundant. Apple switched to an all-PCI based computer lineup starting in 1995, |
https://en.wikipedia.org/wiki/Susning.nu | Susning.nu (in English literally meaning "") was a Swedish language wiki website created by Lars Aronsson (also the founder of Project Runeberg) in 2001 and active until 2009. In its first three years, the website ran as an open wiki that anyone could edit. Susning did not have a pronounced ambition and could be compared in scope to Everything2; Aronsson's stated original aim for Susning was "to make it into whatever the users want it to be". As such, Susning was an encyclopedia, a dictionary, and a discussion forum about any concept of interest to its users. Because of this, Susning grew and became Sweden's biggest and the world's next biggest wiki.
At its peak in April 2004, Susning had over 60,000 articles on various topics, which was more than any other Swedish wiki at that time. During its first few years, it was in direct competition with the Swedish Wikipedia. However, because of the website's popularity and open nature, Susning was highly affected by vandals, eventually leading to the complete shutdown of the project. In attempt at preventing vandalism, many efforts were made by Susning's founder Lars Aronsson, which were mostly unsuccessful. Users who regularly edited at Susning were called "susare".
History
Susning.nu was started on August 31, 2001, by Lars Aronsson and functioned as part of his personal website. It changed to Susning.nu on September 29, and was released on October 1. During October that year, Susning.nu was indexed by the bigger web search engines, and the article collection firmly increased. In one year, Susning.nu grew with 10,000 articles, and more features were added. Among them were link statistics for all pages, and date searching which automatically generated dates and search links in several languages. The first edit war broke out on July 31, 2002.
Susning used a heavily modified version of UseModWiki as its wiki engine. Its domain name , which belongs to the island of Niue in Oceania but which is sold primarily to foreigners, |
https://en.wikipedia.org/wiki/Abel%E2%80%93Ruffini%20theorem | In mathematics, the Abel–Ruffini theorem (also known as Abel's impossibility theorem) states that there is no solution in radicals to general polynomial equations of degree five or higher with arbitrary coefficients. Here, general means that the coefficients of the equation are viewed and manipulated as indeterminates.
The theorem is named after Paolo Ruffini, who made an incomplete proof in 1799 (which was refined and completed in 1813 and accepted by Cauchy) and Niels Henrik Abel, who provided a proof in 1824.
Abel–Ruffini theorem refers also to the slightly stronger result that there are equations of degree five and higher that cannot be solved by radicals. This does not follow from Abel's statement of the theorem, but is a corollary of his proof, as his proof is based on the fact that some polynomials in the coefficients of the equation are not the zero polynomial. This improved statement follows directly from . Galois theory implies also that
is the simplest equation that cannot be solved in radicals, and that almost all polynomials of degree five or higher cannot be solved in radicals.
The impossibility of solving in degree five or higher contrasts with the case of lower degree: one has the quadratic formula, the cubic formula, and the quartic formula for degrees two, three, and four, respectively.
Context
Polynomial equations of degree two can be solved with the quadratic formula, which has been known since antiquity. Similarly the cubic formula for degree three, and the quartic formula for degree four, were found during the 16th century. At that time a fundamental problem was whether equations of higher degree could be solved in a similar way.
The fact that every polynomial equation of positive degree has solutions, possibly non-real, was asserted during the 17th century, but completely proved only at the beginning of the 19th century. This is the fundamental theorem of algebra, which does not provide any tool for computing exactly the solutions, alth |
https://en.wikipedia.org/wiki/Bisection | In geometry, bisection is the division of something into two equal or congruent parts (having the same shape and size). Usually it involves a bisecting line, also called a bisector. The most often considered types of bisectors are the segment bisector, a line that passes through the midpoint of a given segment, and the angle bisector, a line that passes through the apex of an angle (that divides it into two equal angles).
In three-dimensional space, bisection is usually done by a bisecting plane, also called the bisector.
Perpendicular line segment bisector
Definition
The perpendicular bisector of a line segment is a line which meets the segment at its midpoint perpendicularly.
The perpendicular bisector of a line segment also has the property that each of its points is equidistant from segment AB's endpoints:
(D).
The proof follows from and Pythagoras' theorem:
Property (D) is usually used for the construction of a perpendicular bisector:
Construction by straight edge and compass
In classical geometry, the bisection is a simple compass and straightedge construction, whose possibility depends on the ability to draw arcs of equal radii and different centers:
The segment is bisected by drawing intersecting circles of equal radius , whose centers are the endpoints of the segment. The line determined by the points of intersection of the two circles is the perpendicular bisector of the segment.
Because the construction of the bisector is done without the knowledge of the segment's midpoint , the construction is used for determining as the intersection of the bisector and the line segment.
This construction is in fact used when constructing a line perpendicular to a given line at a given point : drawing a circle whose center is such that it intersects the line in two points , and the perpendicular to be constructed is the one bisecting segment .
Equations
If are the position vectors of two points , then its midpoint is and vector is a normal vect |
https://en.wikipedia.org/wiki/Aerospike%20engine | The aerospike engine is a type of rocket engine that maintains its aerodynamic efficiency across a wide range of altitudes. It belongs to the class of altitude compensating nozzle engines. Aerospike engines were proposed for many single-stage-to-orbit (SSTO) designs. They were a contender for the Space Shuttle main engine. However, as of 2023 no such engine was in commercial production, although some large-scale aerospikes were in testing phases.
The term aerospike was originally used for a truncated plug nozzle with a rough conical taper and some gas injection, forming an "air spike" to help make up for the absence of the plug tail. However, a full-length plug nozzle may also be called an aerospike.
Principles
The purpose of any engine bell is to direct the exhaust of a rocket engine in one direction, generating thrust in the opposite direction. The exhaust, a high-temperature mix of gases, has an effectively random momentum distribution (i.e., the exhaust pushes in any direction it can). If the exhaust is allowed to escape in this form, only a small part of the flow will be moving in the correct direction and thus contribute to forward thrust. The bell redirects exhaust moving in the wrong direction so that it generates thrust in the correct direction. Ambient air pressure also imparts a small pressure against the exhaust, helping to keep it moving in the "right" direction as it exits the engine. As the vehicle travels upward through the atmosphere, ambient air pressure is reduced. This causes the thrust-generating exhaust to begin to expand outside the edge of the bell. Since this exhaust begins traveling in the "wrong" direction (i.e., outward from the main exhaust plume), the efficiency of the engine is reduced as the rocket travels because this escaping exhaust is no longer contributing to the thrust of the engine. An aerospike rocket engine seeks to eliminate this loss of efficiency.
Instead of firing the exhaust out of a small hole in the middle of |
https://en.wikipedia.org/wiki/Generalized%20Riemann%20hypothesis | The Riemann hypothesis is one of the most important conjectures in mathematics. It is a statement about the zeros of the Riemann zeta function. Various geometrical and arithmetical objects can be described by so-called global L-functions, which are formally similar to the Riemann zeta-function. One can then ask the same question about the zeros of these L-functions, yielding various generalizations of the Riemann hypothesis. Many mathematicians believe these generalizations of the Riemann hypothesis to be true. The only cases of these conjectures which have been proven occur in the algebraic function field case (not the number field case).
Global L-functions can be associated to elliptic curves, number fields (in which case they are called Dedekind zeta-functions), Maass forms, and Dirichlet characters (in which case they are called Dirichlet L-functions). When the Riemann hypothesis is formulated for Dedekind zeta-functions, it is known as the extended Riemann hypothesis (ERH) and when it is formulated for Dirichlet L-functions, it is known as the generalized Riemann hypothesis or generalised Riemann hypothesis (see spelling differences) (GRH). These two statements will be discussed in more detail below. (Many mathematicians use the label generalized Riemann hypothesis to cover the extension of the Riemann hypothesis to all global L-functions,
not just the special case of Dirichlet L-functions.)
Generalized Riemann hypothesis (GRH)
The generalized Riemann hypothesis (for Dirichlet L-functions) was probably formulated for the first time by Adolf Piltz in 1884. Like the original Riemann hypothesis, it has far reaching consequences about the distribution of prime numbers.
The formal statement of the hypothesis follows. A Dirichlet character is a completely multiplicative arithmetic function χ such that there exists a positive integer k with for all n and whenever . If such a character is given, we define the corresponding Dirichlet L-function by
for every comp |
https://en.wikipedia.org/wiki/Cellular%20differentiation | Cellular differentiation is the process in which a stem cell changes from one type to a differentiated one. Usually, the cell changes to a more specialized type. Differentiation happens multiple times during the development of a multicellular organism as it changes from a simple zygote to a complex system of tissues and cell types. Differentiation continues in adulthood as adult stem cells divide and create fully differentiated daughter cells during tissue repair and during normal cell turnover. Some differentiation occurs in response to antigen exposure. Differentiation dramatically changes a cell's size, shape, membrane potential, metabolic activity, and responsiveness to signals. These changes are largely due to highly controlled modifications in gene expression and are the study of epigenetics. With a few exceptions, cellular differentiation almost never involves a change in the DNA sequence itself. However, metabolic composition does get altered quite dramatically where stem cells are characterized by abundant metabolites with highly unsaturated structures whose levels decrease upon differentiation. Thus, different cells can have very different physical characteristics despite having the same genome.
A specialized type of differentiation, known as terminal differentiation, is of importance in some tissues, including vertebrate nervous system, striated muscle, epidermis and gut. During terminal differentiation, a precursor cell formerly capable of cell division permanently leaves the cell cycle, dismantles the cell cycle machinery and often expresses a range of genes characteristic of the cell's final function (e.g. myosin and actin for a muscle cell). Differentiation may continue to occur after terminal differentiation if the capacity and functions of the cell undergo further changes.
Among dividing cells, there are multiple levels of cell potency, which is the cell's ability to differentiate into other cell types. A greater potency indicates a larger n |
https://en.wikipedia.org/wiki/Z3%20%28computer%29 | The Z3 was a German electromechanical computer designed by Konrad Zuse in 1938, and completed in 1941. It was the world's first working programmable, fully automatic digital computer. The Z3 was built with 2,600 relays, implementing a 22-bit word length that operated at a clock frequency of about 5–10 Hz. Program code was stored on punched film. Initial values were entered manually.
The Z3 was completed in Berlin in 1941. It was not considered vital, so it was never put into everyday operation. Based on the work of the German aerodynamics engineer Hans Georg Küssner (known for the Küssner effect), a "Program to Compute a Complex Matrix" was written and used to solve wing flutter problems. Zuse asked the German government for funding to replace the relays with fully electronic switches, but funding was denied during World War II since such development was deemed "not war-important".
The original Z3 was destroyed on 21 December 1943 during an Allied bombardment of Berlin. That Z3 was originally called V3 (Versuchsmodell 3 or Experimental Model 3) but was renamed so that it would not be confused with Germany's V-weapons. A fully functioning replica was built in 1961 by Zuse's company, Zuse KG, which is now on permanent display at Deutsches Museum in Munich.
The Z3 was demonstrated in 1998 to be, in principle, Turing-complete. However, because it lacked conditional branching, the Z3 only meets this definition by speculatively computing all possible outcomes of a calculation.
Thanks to this machine and its predecessors, Konrad Zuse has often been suggested as the inventor of the computer.
Design and development
Zuse designed the Z1 in 1935 to 1936 and built it from 1936 to 1938. The Z1 was wholly mechanical and only worked for a few minutes at a time at most. Helmut Schreyer advised Zuse to use a different technology. As a doctoral student at the Berlin Institute of Technology in 1937 he worked on the implementation of Boolean operations and (in today's terminolog |
https://en.wikipedia.org/wiki/Tractor | A tractor is an engineering vehicle specifically designed to deliver a high tractive effort (or torque) at slow speeds, for the purposes of hauling a trailer or machinery such as that used in agriculture, mining or construction. Most commonly, the term is used to describe a farm vehicle that provides the power and traction to mechanize agricultural tasks, especially (and originally) tillage, and now many more. Agricultural implements may be towed behind or mounted on the tractor, and the tractor may also provide a source of power if the implement is mechanised.
Etymology
The word tractor was taken from Latin, being the agent noun of trahere "to pull". The first recorded use of the word meaning "an engine or vehicle for pulling wagons or plows" occurred in 1896, from the earlier term "traction motor" (1859).
National variations
In the UK, Ireland, Australia, India, Spain, Argentina, Slovenia, Serbia, Croatia, the Netherlands, and Germany, the word "tractor" usually means "farm tractor", and the use of the word "tractor" to mean other types of vehicles is familiar to the vehicle trade, but unfamiliar to much of the general public. In Canada and the US, the word may also refer to the road tractor portion of a tractor trailer truck, but also usually refers to the piece of farm equipment.
History
Traction engines
The first powered farm implements in the early 19th century were portable engines – steam engines on wheels that could be used to drive mechanical farm machinery by way of a flexible belt. Richard Trevithick designed the first 'semi-portable' stationary steam engine for agricultural use, known as a "barn engine" in 1812, and it was used to drive a corn threshing machine. The truly portable engine was invented in 1893 by William Tuxford of Boston, Lincolnshire who started manufacture of an engine built around a locomotive-style boiler with horizontal smoke tubes. A large flywheel was mounted on the crankshaft, and a stout leather belt was used to transfe |
https://en.wikipedia.org/wiki/BARK%20%28computer%29 | BARK () was an early electromechanical computer. BARK was built using standard telephone relays, implementing a 32-bit binary machine. It could perform addition in 150 ms and multiplication in 250 ms. It had a memory with 50 registers and 100 constants. It was later expanded to double the memory. Howard Aiken stated in reference to BARK "This is the first computer I have seen outside Harvard that actually works."
History
BARK was developed by Matematikmaskinnämnden (Swedish Board for Computing Machinery) a few years before BESK. The machine was built with 8,000 standard telephone relays, 80 km of cable and with 175,000 soldering points. Programming was done by plugboard. It was completed in February 1950 at a cost of 400,000 Swedish kronor (less than $100,000), became operational on April 28, 1950, and was taken offline on September 22, 1954. The engineers on the team led by Conny Palm were Harry Freese, Gösta Neovius, Olle Karlqvist, Carl-Erik Fröberg, G. Kellberg, Björn Lind, Arne Lindberger, P. Petersson and Madeline Wallmark.
See also
BESK - Binär Elektronisk Sekvens-Kalkylator - Sweden's second computer.
Elsa-Karin Boestad-Nilsson, a programmer on BARK and BESK
SMIL - SifferMaskinen I Lund (The Number Machine in Lund)
History of computing hardware
References
External links
Tekn. lic. Olle Karlqvist in memoriam (in Swedish), Google translation, memorial site of one of the engineers behind BARK and BESK. On BARK page there's a technical pdf document (in English): The BARK, A Swedish General Purpose Relay Computer
One-of-a-kind computers
Electro-mechanical computers
Science and technology in Sweden |
https://en.wikipedia.org/wiki/Hilbert%27s%20third%20problem | The third of Hilbert's list of mathematical problems, presented in 1900, was the first to be solved. The problem is related to the following question: given any two polyhedra of equal volume, is it always possible to cut the first into finitely many polyhedral pieces which can be reassembled to yield the second? Based on earlier writings by Carl Friedrich Gauss, David Hilbert conjectured that this is not always possible. This was confirmed within the year by his student Max Dehn, who proved that the answer in general is "no" by producing a counterexample.
The answer for the analogous question about polygons in 2 dimensions is "yes" and had been known for a long time; this is the Wallace–Bolyai–Gerwien theorem.
Unknown to Hilbert and Dehn, Hilbert's third problem was also proposed independently by Władysław Kretkowski for a math contest of 1882 by the Academy of Arts and Sciences of Kraków, and was solved by Ludwik Antoni Birkenmajer with a different method than Dehn's. Birkenmajer did not publish the result, and the original manuscript containing his solution was rediscovered years later.
History and motivation
The formula for the volume of a pyramid,
had been known to Euclid, but all proofs of it involve some form of limiting process or calculus, notably the method of exhaustion or, in more modern form, Cavalieri's principle. Similar formulas in plane geometry can be proven with more elementary means. Gauss regretted this defect in two of his letters to Christian Ludwig Gerling, who proved that two symmetric tetrahedra are equidecomposable.
Gauss' letters were the motivation for Hilbert: is it possible to prove the equality of volume using elementary "cut-and-glue" methods? Because if not, then an elementary proof of Euclid's result is also impossible.
Dehn's answer
Dehn's proof is an instance in which abstract algebra is used to prove an impossibility result in geometry. Other examples are doubling the cube and trisecting the angle.
Two polyhedra are called |
https://en.wikipedia.org/wiki/Hilbert%27s%20second%20problem | In mathematics, Hilbert's second problem was posed by David Hilbert in 1900 as one of his 23 problems. It asks for a proof that the arithmetic is consistent – free of any internal contradictions. Hilbert stated that the axioms he considered for arithmetic were the ones given in , which include a second order completeness axiom.
In the 1930s, Kurt Gödel and Gerhard Gentzen proved results that cast new light on the problem. Some feel that Gödel's theorems give a negative solution to the problem, while others consider Gentzen's proof as a partial positive solution.
Hilbert's problem and its interpretation
In one English translation, Hilbert asks:
"When we are engaged in investigating the foundations of a science, we must set up a system of axioms which contains an exact and complete description of the relations subsisting between the elementary ideas of that science. ... But above all I wish to designate the following as the most important among the numerous questions which can be asked with regard to the axioms: To prove that they are not contradictory, that is, that a definite number of logical steps based upon them can never lead to contradictory results. In geometry, the proof of the compatibility of the axioms can be effected by constructing a suitable field of numbers, such that analogous relations between the numbers of this field correspond to the geometrical axioms. ... On the other hand a direct method is needed for the proof of the compatibility of the arithmetical axioms."
Hilbert's statement is sometimes misunderstood, because by the "arithmetical axioms" he did not mean a system equivalent to Peano arithmetic, but a stronger system with a second-order completeness axiom. The system Hilbert asked for a completeness proof of is more like second-order arithmetic than first-order Peano arithmetic.
As a nowadays common interpretation, a positive solution to Hilbert's second question would in particular provide a proof that Peano arithmetic is consis |
https://en.wikipedia.org/wiki/Hilbert%27s%20fifth%20problem | Hilbert's fifth problem is the fifth mathematical problem from the problem list publicized in 1900 by mathematician David Hilbert, and concerns the characterization of Lie groups.
The theory of Lie groups describes continuous symmetry in mathematics; its importance there and in theoretical physics (for example quark theory) grew steadily in the twentieth century. In rough terms, Lie group theory is the common ground of group theory and the theory of topological manifolds. The question Hilbert asked was an acute one of making this precise: is there any difference if a restriction to smooth manifolds is imposed?
The expected answer was in the negative (the classical groups, the most central examples in Lie group theory, are smooth manifolds). This was eventually confirmed in the early 1950s. Since the precise notion of "manifold" was not available to Hilbert, there is room for some debate about the formulation of the problem in contemporary mathematical language.
Formulation of the problem
A modern formulation of the problem (in its simplest interpretation) is as follows:
An equivalent formulation of this problem closer to that of Hilbert, in terms of composition laws, goes as follows:
In this form the problem was solved by Montgomery–Zippin and Gleason.
A stronger interpretation (viewing as a transformation group rather than an abstract group) results in the Hilbert–Smith conjecture about group actions on manifolds, which in full generality is still open. It is known classically for actions on 2-dimensional manifolds and has recently been solved for three dimensions by John Pardon.
Solution
The first major result was that of John von Neumann in 1933, giving an affirmative answer for compact groups. The locally compact abelian group case was solved in 1934 by Lev Pontryagin. The final resolution, at least in the interpretation of what Hilbert meant given above, came with the work of Andrew Gleason, Deane Montgomery and Leo Zippin in the 1950s.
In 1953, Hide |
https://en.wikipedia.org/wiki/Organ%20%28biology%29 | In a multicellular organism, an organ is a collection of tissues joined in a structural unit to serve a common function. In the hierarchy of life, an organ lies between tissue and an organ system. Tissues are formed from same type cells to act together in a function. Tissues of different types combine to form an organ which has a specific function. The intestinal wall for example is formed by epithelial tissue and smooth muscle tissue. Two or more organs working together in the execution of a specific body function form an organ system, also called a biological system or body system.
An organ's tissues can be broadly categorized as parenchyma, the functional tissue, and stroma, the structural tissue with supportive, connective, or ancillary functions. For example, the gland's tissue that makes the hormones is the parenchyma, whereas the stroma includes the nerves that innervate the parenchyma, the blood vessels that oxygenate and nourish it and carry away its metabolic wastes, and the connective tissues that provide a suitable place for it to be situated and anchored. The main tissues that make up an organ tend to have common embryologic origins, such as arising from the same germ layer. Organs exist in most multicellular organisms. In single-celled organisms such as members of the eukaryotes, the functional analogue of an organ is known as an organelle. In plants, there are three main organs.
The number of organs in any organism depends on the definition used. By one widely adopted definition, 79 organs have been identified in the human body.
Animals
Except for placozoans, multicellular animals including humans have a variety of organ systems. These specific systems are widely studied in human anatomy. The functions of these organ systems often share significant overlap. For instance, the nervous and endocrine system both operate via a shared organ, the hypothalamus. For this reason, the two systems are combined and studied as the neuroendocrine system. The sam |
https://en.wikipedia.org/wiki/Finitism | Finitism is a philosophy of mathematics that accepts the existence only of finite mathematical objects. It is best understood in comparison to the mainstream philosophy of mathematics where infinite mathematical objects (e.g., infinite sets) are accepted as legitimate.
Main idea
The main idea of finitistic mathematics is not accepting the existence of infinite objects such as infinite sets. While all natural numbers are accepted as existing, the set of all natural numbers is not considered to exist as a mathematical object. Therefore quantification over infinite domains is not considered meaningful. The mathematical theory often associated with finitism is Thoralf Skolem's primitive recursive arithmetic.
History
The introduction of infinite mathematical objects occurred a few centuries ago when the use of infinite objects was already a controversial topic among mathematicians. The issue entered a new phase when Georg Cantor in 1874 introduced what is now called naive set theory and used it as a base for his work on transfinite numbers. When paradoxes such as Russell's paradox, Berry's paradox and the Burali-Forti paradox were discovered in Cantor's naive set theory, the issue became a heated topic among mathematicians.
There were various positions taken by mathematicians. All agreed about finite mathematical objects such as natural numbers. However there were disagreements regarding infinite mathematical objects.
One position was the intuitionistic mathematics that was advocated by L. E. J. Brouwer, which rejected the existence of infinite objects until they are constructed.
Another position was endorsed by David Hilbert: finite mathematical objects are concrete objects, infinite mathematical objects are ideal objects, and accepting ideal mathematical objects does not cause a problem regarding finite mathematical objects. More formally, Hilbert believed that it is possible to show that any theorem about finite mathematical objects that can be obtained using i |
https://en.wikipedia.org/wiki/Data%20link%20layer | The data link layer, or layer 2, is the second layer of the seven-layer OSI model of computer networking. This layer is the protocol layer that transfers data between nodes on a network segment across the physical layer. The data link layer provides the functional and procedural means to transfer data between network entities and may also provide the means to detect and possibly correct errors that can occur in the physical layer.
The data link layer is concerned with local delivery of frames between nodes on the same level of the network. Data-link frames, as these protocol data units are called, do not cross the boundaries of a local area network. Inter-network routing and global addressing are higher-layer functions, allowing data-link protocols to focus on local delivery, addressing, and media arbitration. In this way, the data link layer is analogous to a neighborhood traffic cop; it endeavors to arbitrate between parties contending for access to a medium, without concern for their ultimate destination. When devices attempt to use a medium simultaneously, frame collisions occur. Data-link protocols specify how devices detect and recover from such collisions, and may provide mechanisms to reduce or prevent them.
Examples of data link protocols are Ethernet, the IEEE 802.11 WiFi protocols, ATM and Frame Relay. In the Internet Protocol Suite (TCP/IP), the data link layer functionality is contained within the link layer, the lowest layer of the descriptive model, which is assumed to be independent of physical infrastructure.
Function
The data link provides for the transfer of data frames between hosts connected to the physical link. Within the semantics of the OSI network architecture, the protocols of the data link layer respond to service requests from the network layer, and perform their function by issuing service requests to the physical layer. That transfer can be reliable or unreliable; many data link protocols do not have acknowledgments of successf |
https://en.wikipedia.org/wiki/Eutectic%20system | A eutectic system or eutectic mixture ( ) is a homogeneous mixture that has a melting point lower than those of the constituents. The lowest possible melting point over all of the mixing ratios of the constituents is called the eutectic temperature. On a phase diagram, the eutectic temperature is seen as the eutectic point (see plot on the right).
Non-eutectic mixture ratios would have different melting temperatures for their different constituents, since one component's lattice will melt at a lower temperature than the other's. Conversely, as a non-eutectic mixture cools down, each of its components would solidify (form a lattice) at a different temperature, until the entire mass is solid.
Not all binary alloys have eutectic points, since the valence electrons of the component species are not always compatible, in any mixing ratio, to form a new type of joint crystal lattice. For example, in the silver-gold system the melt temperature (liquidus) and freeze temperature (solidus) "meet at the pure element endpoints of the atomic ratio axis while slightly separating in the mixture region of this axis".
The term was coined in 1884 by British physicist and chemist Frederick Guthrie (1833–1886). The word originates .
Eutectic phase transition
The eutectic solidification is defined as follows:
This type of reaction is an invariant reaction, because it is in thermal equilibrium; another way to define this is the change in Gibbs free energy equals zero. Tangibly, this means the liquid and two solid solutions all coexist at the same time and are in chemical equilibrium. There is also a thermal arrest for the duration of the change of phase during which the temperature of the system does not change.
The resulting solid macrostructure from a eutectic reaction depends on a few factors, with the most important factor being how the two solid solutions nucleate and grow. The most common structure is a lamellar structure, but other possible structures include rodlike, globu |
https://en.wikipedia.org/wiki/Radio%20navigation | Radio navigation or radionavigation is the application of radio frequencies to determine a position of an object on the Earth, either the vessel or an obstruction. Like radiolocation, it is a type of radiodetermination.
The basic principles are measurements from/to electric beacons, especially
Angular directions, e.g. by bearing, radio phases or interferometry,
Distances, e.g. ranging by measurement of time of flight between one transmitter and multiple receivers or vice versa,
Distance differences by measurement of times of arrival of signals from one transmitter to multiple receivers or vice versa
Partly also velocity, e.g. by means of radio Doppler shift.
Combinations of these measurement principles also are important—e.g., many radars measure range and azimuth of a target.
Bearing-measurement systems
These systems used some form of directional radio antenna to determine the location of a broadcast station on the ground. Conventional navigation techniques are then used to take a radio fix. These were introduced prior to World War I, and remain in use today.
Radio direction finding
The first system of radio navigation was the Radio Direction Finder, or RDF. By tuning in a radio station and then using a directional antenna, one could determine the direction to the broadcasting antenna. A second measurement using another station was then taken. Using triangulation, the two directions can be plotted on a map where their intersection reveals the location of the navigator. Commercial AM radio stations can be used for this task due to their long range and high power, but strings of low-power radio beacons were also set up specifically for this task, especially near airports and harbours.
Early RDF systems normally used a loop antenna, a small loop of metal wire that is mounted so it can be rotated around a vertical axis. At most angles the loop has a fairly flat reception pattern, but when it is aligned perpendicular to the station the signal received on one |
https://en.wikipedia.org/wiki/Normal%20closure%20%28group%20theory%29 | In group theory, the normal closure of a subset of a group is the smallest normal subgroup of containing
Properties and description
Formally, if is a group and is a subset of the normal closure of is the intersection of all normal subgroups of containing :
The normal closure is the smallest normal subgroup of containing in the sense that is a subset of every normal subgroup of that contains
The subgroup is generated by the set of all conjugates of elements of in
Therefore one can also write
Any normal subgroup is equal to its normal closure. The conjugate closure of the empty set is the trivial subgroup.
A variety of other notations are used for the normal closure in the literature, including and
Dual to the concept of normal closure is that of or , defined as the join of all normal subgroups contained in
Group presentations
For a group given by a presentation with generators and defining relators the presentation notation means that is the quotient group where is a free group on
References
Group theory
Closure operators |
https://en.wikipedia.org/wiki/Dedekind%20group | In group theory, a Dedekind group is a group G such that every subgroup of G is normal.
All abelian groups are Dedekind groups.
A non-abelian Dedekind group is called a Hamiltonian group.
The most familiar (and smallest) example of a Hamiltonian group is the quaternion group of order 8, denoted by Q8.
Dedekind and Baer have shown (in the finite and respectively infinite order case) that every Hamiltonian group is a direct product of the form , where B is an elementary abelian 2-group, and D is a torsion abelian group with all elements of odd order.
Dedekind groups are named after Richard Dedekind, who investigated them in , proving a form of the above structure theorem (for finite groups). He named the non-abelian ones after William Rowan Hamilton, the discoverer of quaternions.
In 1898 George Miller delineated the structure of a Hamiltonian group in terms of its order and that of its subgroups. For instance, he shows "a Hamilton group of order 2a has quaternion groups as subgroups". In 2005 Horvat et al used this structure to count the number of Hamiltonian groups of any order where o is an odd integer. When then there are no Hamiltonian groups of order n, otherwise there are the same number as there are Abelian groups of order o.
Notes
References
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Baer, R. Situation der Untergruppen und Struktur der Gruppe, Sitz.-Ber. Heidelberg. Akad. Wiss.2, 12–17, 1933.
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Group theory
Properties of groups |
https://en.wikipedia.org/wiki/Quaternion%20group | In group theory, the quaternion group Q8 (sometimes just denoted by Q) is a non-abelian group of order eight, isomorphic to the eight-element subset
of the quaternions under multiplication. It is given by the group presentation
where e is the identity element and commutes with the other elements of the group.
Another presentation of Q8 is
The quaternion group sprang full-blown from the mind of W. R. Hamilton, and there has been an effort to connect it with the wellspring of discrete groups in field extensions and the study of algebraic numbers. Richard Dedekind considered the field ℚ[√2, √3] in this effort. In field theory, extensions are generated by roots of polynomial irreducible over a ground field. Isomorphic fields are associated with permutation groups that move around the roots of the polynomial. This notion, pioneered by Évariste Galois (1830), now forms a standard study Galois theory in mathematics education. In 1936 Ernst Witt published his approach to the quaternion group through Galois theory. A definitive connection was published in 1981, see § Galois group.
Compared to dihedral group
The quaternion group Q8 has the same order as the dihedral group D4, but a different structure, as shown by their Cayley and cycle graphs:
In the diagrams for D4, the group elements are marked with their action on a letter F in the defining representation R2. The same cannot be done for Q8, since it has no faithful representation in R2 or R3. D4 can be realized as a subset of the split-quaternions in the same way that Q8 can be viewed as a subset of the quaternions.
Cayley table
The Cayley table (multiplication table) for Q8 is given by:
Properties
The elements i, j, and k all have order four in Q8 and any two of them generate the entire group. Another presentation of Q8 based in only two elements to skip this redundancy is:
One may take, for instance, and .
The quaternion group has the unusual property of being Hamiltonian: Q8 is non-abelian, but every |
https://en.wikipedia.org/wiki/Autocatalytic%20set | An autocatalytic set is a collection of entities, each of which can be created catalytically by other entities within the set, such that as a whole, the set is able to catalyze its own production. In this way the set as a whole is said to be autocatalytic. Autocatalytic sets were originally and most concretely defined in terms of molecular entities, but have more recently been metaphorically extended to the study of systems in sociology, ecology, and economics.
Autocatalytic sets also have the ability to replicate themselves if they are split apart into two physically separated spaces. Computer models illustrate that split autocatalytic sets will reproduce all of the reactions of the original set in each half, much like cellular mitosis. In effect, using the principles of autocatalysis, a small metabolism can replicate itself with very little high level organization. This property is why autocatalysis is a contender as the foundational mechanism for complex evolution.
Prior to Watson and Crick, biologists considered autocatalytic sets the way metabolism functions in principle, i.e. one protein helps to synthesize another protein and so on. After the discovery of the double helix, the central dogma of molecular biology was formulated, which is that DNA is transcribed to RNA which is translated to protein. The molecular structure of DNA and RNA, as well as the metabolism that maintains their reproduction, are believed to be too complex to have arisen spontaneously in one step from a soup of chemistry.
Several models of the origin of life are based on the notion that life may have arisen through the development of an initial molecular autocatalytic set which evolved over time. Most of these models which have emerged from the studies of complex systems predict that life arose not from a molecule with any particular trait (such as self-replicating RNA) but from an autocatalytic set. The first empirical support came from Lincoln and Joyce, who obtained autocatalyti |
https://en.wikipedia.org/wiki/System%20dynamics | System dynamics (SD) is an approach to understanding the nonlinear behaviour of complex systems over time using stocks, flows, internal feedback loops, table functions and time delays.
Overview
System dynamics is a methodology and mathematical modeling technique to frame, understand, and discuss complex issues and problems. Originally developed in the 1950s to help corporate managers improve their understanding of industrial processes, SD is currently being used throughout the public and private sector for policy analysis and design.
Convenient graphical user interface (GUI) system dynamics software developed into user friendly versions by the 1990s and have been applied to diverse systems. SD models solve the problem of simultaneity (mutual causation) by updating all variables in small time increments with positive and negative feedbacks and time delays structuring the interactions and control. The best known SD model is probably the 1972 The Limits to Growth. This model forecast that exponential growth of population and capital, with finite resource sources and sinks and perception delays, would lead to economic collapse during the 21st century under a wide variety of growth scenarios.
System dynamics is an aspect of systems theory as a method to understand the dynamic behavior of complex systems. The basis of the method is the recognition that the structure of any system, the many circular, interlocking, sometimes time-delayed relationships among its components, is often just as important in determining its behavior as the individual components themselves. Examples are chaos theory and social dynamics. It is also claimed that because there are often properties-of-the-whole which cannot be found among the properties-of-the-elements, in some cases the behavior of the whole cannot be explained in terms of the behavior of the parts.
History
System dynamics was created during the mid-1950s by Professor Jay Forrester of the Massachusetts Institute of Technology. In |
https://en.wikipedia.org/wiki/Working%20mass | Working mass, also referred to as reaction mass, is a mass against which a system operates in order to produce acceleration.
In the case of a chemical rocket, for example, the reaction mass is the product of the burned fuel shot backwards to provide propulsion. All acceleration requires an exchange of momentum, which can be thought of as the "unit of movement". Momentum is related to mass and velocity, as given by the formula P = mv, where P is the momentum, m the mass, and v the velocity. The velocity of a body is easily changeable, but in most cases the mass is not, which makes it important.
Rockets and rocket-like reaction engines
In rockets, the total velocity change can be calculated (using the Tsiolkovsky rocket equation) as follows:
Where:
v = ship velocity.
u = exhaust velocity.
M = ship mass, not including the working mass.
m = total mass ejected from the ship (working mass).
The term working mass is used primarily in the aerospace field. In more "down to earth" examples the working mass is typically provided by the Earth, which contains so much momentum in comparison to most vehicles that the amount it gains or loses can be ignored. However, in the case of an aircraft the working mass is the air, and in the case of a rocket, it is the rocket fuel itself. Most rocket engines use light-weight fuels (liquid hydrogen, oxygen, or kerosene) accelerated to super-sonic speeds. However, ion engines often use heavier elements like xenon as the reaction mass, accelerated to much higher speeds using electric fields.
In many cases the working mass is separate from the energy used to accelerate it. In a car the engine provides power to the wheels, which then accelerates the Earth backward to make the car move forward. This is not the case for most rockets however, where the rocket propellant is the working mass, as well as the energy source. This means that rockets stop accelerating as soon as they run out of fuel, regardless of other power sources they may have |
https://en.wikipedia.org/wiki/Local%20ring | In mathematics, more specifically in ring theory, local rings are certain rings that are comparatively simple, and serve to describe what is called "local behaviour", in the sense of functions defined on varieties or manifolds, or of algebraic number fields examined at a particular place, or prime. Local algebra is the branch of commutative algebra that studies commutative local rings and their modules.
In practice, a commutative local ring often arises as the result of the localization of a ring at a prime ideal.
The concept of local rings was introduced by Wolfgang Krull in 1938 under the name Stellenringe. The English term local ring is due to Zariski.
Definition and first consequences
A ring R is a local ring if it has any one of the following equivalent properties:
R has a unique maximal left ideal.
R has a unique maximal right ideal.
1 ≠ 0 and the sum of any two non-units in R is a non-unit.
1 ≠ 0 and if x is any element of R, then x or is a unit.
If a finite sum is a unit, then it has a term that is a unit (this says in particular that the empty sum cannot be a unit, so it implies 1 ≠ 0).
If these properties hold, then the unique maximal left ideal coincides with the unique maximal right ideal and with the ring's Jacobson radical. The third of the properties listed above says that the set of non-units in a local ring forms a (proper) ideal, necessarily contained in the Jacobson radical. The fourth property can be paraphrased as follows: a ring R is local if and only if there do not exist two coprime proper (principal) (left) ideals, where two ideals I1, I2 are called coprime if .
In the case of commutative rings, one does not have to distinguish between left, right and two-sided ideals: a commutative ring is local if and only if it has a unique maximal ideal.
Before about 1960 many authors required that a local ring be (left and right) Noetherian, and (possibly non-Noetherian) local rings were called quasi-local rings. In this article this requi |
https://en.wikipedia.org/wiki/IUCN%20Red%20List | The International Union for Conservation of Nature (IUCN) Red List of Threatened Species, also known as the IUCN Red List or Red Data Book, founded in 1964, is an inventory of the global conservation status and extinction risk of biological species. A series of Regional Red Lists are produced by countries and organizations, which assess the risk of extinction to species within a political management unit.
The goals of the Red List are to provide scientifically-based information on the status of species and subspecies at a global level, to draw attention to the magnitude and importance of threatened biodiversity, to influence national and international policy and decision-making, and to provide information to guide actions to conserve biological diversity.
Major species assessors include BirdLife International, the Institute of Zoology (the research division of the Zoological Society of London), the World Conservation Monitoring Centre, and many Specialist Groups within the IUCN Species Survival Commission (SSC). Collectively, assessments by these organizations and groups account for nearly half the species on the Red List.
The IUCN aims to have the category of every species re-evaluated at least every ten years, and every five years if possible. This is done in a peer reviewed manner through IUCN Species Survival Commission Specialist Groups (SSC), which are Red List Authorities (RLA) responsible for a species, group of species or specific geographic area, or in the case of BirdLife International, an entire class (Aves). The red list unit works with staff from the IUCN Global Species Programme as well as current program partners to recommend new partners or networks to join as new Red List Authorities.
The number of species which have been assessed for the Red List has been increasing over time. of 150,388 species surveyed, 42,108 are considered at risk of extinction because of human activity, in particular overfishing, hunting, and land development.
Hist |
https://en.wikipedia.org/wiki/RCA%20connector | The RCA connector is a type of electrical connector commonly used to carry audio and video signals. The name RCA derives from the company Radio Corporation of America, which introduced the design in the 1930s. The connector’s male plug and female jack are called RCA plug and RCA jack.
It is also called RCA phono connector or phono connector. The word phono in phono connector is an abbreviation of the word phonograph, because this connector was originally created to allow the connection of a phonograph turntable to a radio receiver. RCA jacks are often used in phono inputs, a set of input jacks usually located on the rear panel of a preamp, mixer or amplifier, especially on early radio sets, to which a phonograph or turntable is attached.
In some European countries (i.e. Germany) the older English name Cinch is still used.
History
The exact release date of this connector is still a little vague. The following dates were derived from historical RCA documentation.
By no later than 1937, RCA introduced this connector. In 1937, it was used inside a RCA model U-109 radio-phonograph and model R-97 phonograph. In the U-109, the internal amplifier chassis had female connectors which accepted male cables from the internal radio chassis and built-in phonograph player. Originally, the concept was intended as an easy method to unhook sources while troubleshooting the console during servicing.
By no later than 1938, RCA migrated the female connector to the rear panel of many of their desktop AM radio models to allow customers an easy method to attach an external phonograph or television at a later date. The connector was labeled on the back of radio with one of the following terms: "Victrola", "Phono", "Pick-up", "Television". RCA later marketed a special turntable for 45 RPM records, the model 9JY.
In 1939, RCA introduced two radio-television floor consoles (TRK-9, TRK-12) which used the same internal connection concept but the audio output of the television chass |
https://en.wikipedia.org/wiki/Cytokine | Cytokines are a broad and loose category of small proteins (~5–25 kDa) important in cell signaling. Due to their size, cytokines cannot cross the lipid bilayer of cells to enter the cytoplasm and therefore typically exert their functions by interacting with specific cytokine receptors on the target cell surface. Cytokines have been shown to be involved in autocrine, paracrine and endocrine signaling as immunomodulating agents.
Cytokines include chemokines, interferons, interleukins, lymphokines, and tumour necrosis factors, but generally not hormones or growth factors (despite some overlap in the terminology). Cytokines are produced by a broad range of cells, including immune cells like macrophages, B lymphocytes, T lymphocytes and mast cells, as well as endothelial cells, fibroblasts, and various stromal cells; a given cytokine may be produced by more than one type of cell. They act through cell surface receptors and are especially important in the immune system; cytokines modulate the balance between humoral and cell-based immune responses, and they regulate the maturation, growth, and responsiveness of particular cell populations. Some cytokines enhance or inhibit the action of other cytokines in complex ways. They are different from hormones, which are also important cell signaling molecules. Hormones circulate in higher concentrations, and tend to be made by specific kinds of cells. Cytokines are important in health and disease, specifically in host immune responses to infection, inflammation, trauma, sepsis, cancer, and reproduction.
The word comes from the ancient Greek language: cyto, from Greek κύτος, kytos, 'cavity, cell' + kines, from Greek κίνησις, kinēsis, 'movement'.
Discovery
Interferon-alpha, an interferon type I, was identified in 1957 as a protein that interfered with viral replication. The activity of interferon-gamma (the sole member of the interferon type II class) was described in 1965; this was the first identified lymphocyte-derived med |
https://en.wikipedia.org/wiki/Celestial%20equator | The celestial equator is the great circle of the imaginary celestial sphere on the same plane as the equator of Earth. By extension, it is also a plane of reference in the equatorial coordinate system. In other words, the celestial equator is an abstract projection of the terrestrial equator into outer space. Due to Earth's axial tilt, the celestial equator is currently inclined by about 23.44° with respect to the ecliptic (the plane of Earth's orbit), but has varied from about 22.0° to 24.5° over the past 5 million years due to perturbation from other planets.
An observer standing on Earth's equator visualizes the celestial equator as a semicircle passing through the zenith, the point directly overhead. As the observer moves north (or south), the celestial equator tilts towards the opposite horizon. The celestial equator is defined to be infinitely distant (since it is on the celestial sphere); thus, the ends of the semicircle always intersect the horizon due east and due west, regardless of the observer's position on Earth. At the poles, the celestial equator coincides with the astronomical horizon. At all latitudes, the celestial equator is a uniform arc or circle because the observer is only finitely far from the plane of the celestial equator, but infinitely far from the celestial equator itself.
Astronomical objects near the celestial equator appear above the horizon from most places on earth, but they culminate (reach the meridian) highest near the equator. The celestial equator currently passes through these constellations:
These are the most globally visible constellations.
Over thousands of years, the orientation of Earth's equator and thus the constellations the celestial equator passes through will change due to axial precession.
Celestial bodies other than Earth also have similarly defined celestial equators.
See also
Axial precession
Celestial pole
Declination
Rotation around a fixed axis (pole)
References
Equator
Dynamics of the Solar Syst |
https://en.wikipedia.org/wiki/I%20%3D%20PAT | I = (PAT) is the mathematical notation of a formula put forward to describe the impact of human activity on the environment.
I = P × A × T
The expression equates human impact on the environment to a function of three factors: population (P), affluence (A) and technology (T). It is similar in form to the Kaya identity which applies specifically to emissions of the greenhouse gas carbon dioxide.
The validity of expressing environmental impact as a simple product of independent factors, and the factors that should be included and their comparative importance, have been the subject of debate among environmentalists. In particular, some have drawn attention to potential inter-relationships among the three factors; and others have wished to stress other factors not included in the formula, such as political and social structures, and the scope for beneficial, as well as harmful, environmental actions.
History
The equation was developed in 1970 during the course of a debate between Barry Commoner, Paul R. Ehrlich and John Holdren. Commoner argued that environmental impacts in the United States were caused primarily by changes in its production technology following World War II and focused on present-day deteriorating environmental conditions in the United States. Ehrlich and Holdren argued that all three factors were important but emphasized the role of human population growth, focusing on a broader scale, being less specific in space and time.
The equation can aid in understanding some of the factors affecting human impacts on the environment, but it has also been cited as a basis for many of the dire environmental predictions of the 1970s by Paul Ehrlich, George Wald, Denis Hayes, Lester Brown, René Dubos, and Sidney Ripley that did not come to pass. Neal Koblitz classified equations of this type as "mathematical propaganda" and criticized Ehrlich's use of them in the media (e.g. on The Tonight Show) to sway the general public.
The dependent variable: Impact
The va |
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