source stringlengths 31 203 | text stringlengths 28 2k |
|---|---|
https://en.wikipedia.org/wiki/311%20%28number%29 | 311 (three hundred [and] eleven) is the natural number following 310 and preceding 312.
311 is the 64th prime; a twin prime with 313; an irregular prime; an emirp, an Eisenstein prime with no imaginary part and real part of the form ; a Gaussian prime with no imaginary part and real part of the form ; and a permutable prime with 113 and 131.
It can be expressed as a sum of consecutive primes in four different ways: as a sum of three consecutive primes (101 + 103 + 107), as a sum of five consecutive primes (53 + 59 + 61 + 67 + 71), as a sum of seven consecutive primes (31 + 37 + 41 + 43 + 47 + 53 + 59), and as a sum of eleven consecutive primes (11 + 13 + 17 + 19 + 23 + 29 + 31 + 37 + 41 + 43 + 47).
311 is a strictly non-palindromic number, as it is not palindromic in any base between base 2 and base 309.
311 is the smallest positive integer d such that the imaginary quadratic field Q() has class number = 19.
4311 - 3311 is prime
References
Integers |
https://en.wikipedia.org/wiki/Optimized%20Link%20State%20Routing%20Protocol | The Optimized Link State Routing Protocol (OLSR) is an IP routing protocol optimized for mobile ad hoc networks, which can also be used on other wireless ad hoc networks. OLSR is a proactive link-state routing protocol, which uses hello and topology control (TC) messages to discover and then disseminate link state information throughout the mobile ad hoc network. Individual nodes use this topology information to compute next hop destinations for all nodes in the network using shortest hop forwarding paths.
Features specific to OLSR
Link-state routing protocols such as Open Shortest Path First (OSPF) and Intermediate System to Intermediate System (IS-IS) elect a designated router on every link to perform flooding of topology information. In wireless ad hoc networks, there is different notion of a link, packets can and do go out the same interface; hence, a different approach is needed in order to optimize the flooding process. Using Hello messages the OLSR protocol at each node discovers 2-hop neighbor information and performs a distributed election of a set of multipoint relays (MPRs). Nodes select MPRs such that there exists a path to each of its 2-hop neighbors via a node selected as an MPR. These MPR nodes then source and forward TC messages that contain the MPR selectors. This functioning of MPRs makes OLSR unique from other link state routing protocols in a few different ways: The forwarding path for TC messages is not shared among all nodes but varies depending on the source, only a subset of nodes source link state information, not all links of a node are advertised but only those that represent MPR selections.
Since link-state routing requires the topology database to be synchronized across the network, OSPF and IS-IS perform topology flooding using a reliable algorithm. Such an algorithm is very difficult to design for ad hoc wireless networks, so OLSR doesn't bother with reliability; it simply floods topology data often enough to make sure that |
https://en.wikipedia.org/wiki/Divided%20differences | In mathematics, divided differences is an algorithm, historically used for computing tables of logarithms and trigonometric functions. Charles Babbage's difference engine, an early mechanical calculator, was designed to use this algorithm in its operation.
Divided differences is a recursive division process. Given a sequence of data points , the method calculates the coefficients of the interpolation polynomial of these points in the Newton form.
Definition
Given n + 1 data points
where the are assumed to be pairwise distinct, the forward divided differences are defined as:
To make the recursive process of computation clearer, the divided differences can be put in tabular form, where the columns correspond to the value of j above, and each entry in the table is computed from the difference of the entries to its immediate lower left and to its immediate upper left, divided by a difference of corresponding x-values:
Notation
Note that the divided difference depends on the values and , but the notation hides the dependency on the x-values. If the data points are given by a function f,
one sometimes writes the divided difference in the notation
Other notations for the divided difference of the function ƒ on the nodes x0, ..., xn are:
Example
Divided differences for and the first few values of :
Properties
Linearity
Leibniz rule
Divided differences are symmetric: If is a permutation then
Polynomial interpolation in the Newton form: if is a polynomial function of degree , and is the divided difference, then
If is a polynomial function of degree , then
Mean value theorem for divided differences: if is n times differentiable, then for a number in the open interval determined by the smallest and largest of the 's.
Matrix form
The divided difference scheme can be put into an upper triangular matrix:
Then it holds
if is a scalar
This follows from the Leibniz rule. It means that multiplication of such matrices is commutative. Summarised, |
https://en.wikipedia.org/wiki/Sergei%20Bernstein | Sergei Natanovich Bernstein (, sometimes Romanized as ; 5 March 1880 – 26 October 1968) was a Ukrainian and Russian mathematician of Jewish origin known for contributions to partial differential equations, differential geometry, probability theory, and approximation theory.
Bernstein was born into a Jewish family living in Odessa. After high school Bernstein went to Paris to study mathematics. He returned to Russia in 1905 and taught at Kharkiv University from 1908 to 1933. He was made an ordinary professor in 1920. Bernstein later worked at the Mathematical Institute of the USSR Academy of Sciences in Leningrad, and also taught at the University and Polytechnic Institute. From January 1939, Bernstein also worked also at Moscow University. He and his wife were evacuated to Borovoe, Kazakhstan in 1941. From 1943 he worked at the Mathematical Institute in Moscow, and edited Chebyshev’s complete works. In 1947 he was dismissed from the University and became Head of the Department of Constructive Function Theory at the Steklov Institute. He died in Moscow in 1968.
Work
Partial differential equations
In his doctoral dissertation, submitted in 1904 to the Sorbonne, Bernstein solved Hilbert's nineteenth problem on the analytic solution of elliptic differential equations. His later work was devoted to Dirichlet's boundary problem for non-linear equations of elliptic type, where, in particular, he introduced a priori estimates.
Probability theory
In 1917, Bernstein suggested the first axiomatic foundation of probability theory, based on the underlying algebraic structure. It was later superseded by the measure-theoretic approach of Kolmogorov.
In the 1920s, he introduced a method for proving limit theorems for sums of dependent random variables.
Approximation theory
Through his application of Bernstein polynomials, he laid the foundations of constructive function theory, a field studying the connection between smoothness properties of a function and its approximation |
https://en.wikipedia.org/wiki/Monomial%20basis | In mathematics the monomial basis of a polynomial ring is its basis (as a vector space or free module over the field or ring of coefficients) that consists of all monomials. The monomials form a basis because every polynomial may be uniquely written as a finite linear combination of monomials (this is an immediate consequence of the definition of a polynomial).
One indeterminate
The polynomial ring of univariate polynomials over a field is a -vector space, which has
as an (infinite) basis. More generally, if is a ring then is a free module which has the same basis.
The polynomials of degree at most form also a vector space (or a free module in the case of a ring of coefficients), which has as a basis.
The canonical form of a polynomial is its expression on this basis:
or, using the shorter sigma notation:
The monomial basis is naturally totally ordered, either by increasing degrees
or by decreasing degrees
Several indeterminates
In the case of several indeterminates a monomial is a product
where the are non-negative integers. As an exponent equal to zero means that the corresponding indeterminate does not appear in the monomial; in particular is a monomial.
Similar to the case of univariate polynomials, the polynomials in form a vector space (if the coefficients belong to a field) or a free module (if the coefficients belong to a ring), which has the set of all monomials as a basis, called the monomial basis.
The homogeneous polynomials of degree form a subspace which has the monomials of degree as a basis. The dimension of this subspace is the number of monomials of degree , which is
where is a binomial coefficient.
The polynomials of degree at most form also a subspace, which has the monomials of degree at most as a basis. The number of these monomials is the dimension of this subspace, equal to
In contrast to the univariate case, there is no natural total order of the monomial basis in the multivariate case. For problems which re |
https://en.wikipedia.org/wiki/Safe%20operating%20area | For power semiconductor devices (such as BJT, MOSFET, thyristor or IGBT), the safe operating area (SOA) is defined as the voltage and current conditions over which the device can be expected to operate without self-damage.
SOA is usually presented in transistor datasheets as a graph with VCE (collector-emitter voltage) on the abscissa and ICE (collector-emitter current) on the ordinate; the safe 'area' referring to the area under the curve. The SOA specification combines the various limitations of the device — maximum voltage, current, power, junction temperature, secondary breakdown — into one curve, allowing simplified design of protection circuitry.
Often, in addition to the continuous rating, separate SOA curves are also plotted for short duration pulse conditions (1 ms pulse, 10 ms pulse, etc.).
The safe operating area curve is a graphical representation of the power handling capability of the device under various conditions. The SOA curve takes into account the wire bond current carrying capability, transistor junction temperature, internal power dissipation and secondary breakdown limitations.
Limits of the safe operating area
Where both current and voltage are plotted on logarithmic scales, the borders of the SOA are straight lines:
IC = ICmax — current limit
VCE = VCEmax — voltage limit
IC VCE = Pmax — dissipation limit, thermal breakdown
IC VCEα = const — this is the limit given by the secondary breakdown (bipolar junction transistors only)
SOA specifications are useful to the design engineer working on power circuits such as amplifiers and power supplies as they allow quick assessment of the limits of device performance, the design of appropriate protection circuitry, or selection of a more capable device. SOA curves are also important in the design of foldback circuits.
Secondary breakdown
For a device that makes use of the secondary breakdown effect see Avalanche transistor
Secondary breakdown is a failure mode in bipolar power transistors. |
https://en.wikipedia.org/wiki/Template%20matching | Template matching is a technique in digital image processing for finding small parts of an image which match a template image. It can be used for quality control in manufacturing, navigation of mobile robots, or edge detection in images.
The main challenges in a template matching task are detection of occlusion, when a sought-after object is partly hidden in an image; detection of non-rigid transformations, when an object is distorted or imaged from different angles; sensitivity to illumination and background changes; background clutter; and scale changes.
Feature-based approach
The feature-based approach to template matching relies on the extraction of image features, such as shapes, textures, and colors, that match the target image or frame. This approach is usually achieved using neural networks and deep-learning classifiers such as VGG, AlexNet, and ResNet.Convolutional neural networks (CNNs), which many modern classifiers are based on, process an image by passing it through different hidden layers, producing a vector at each layer with classification information about the image. These vectors are extracted from the network and used as the features of the image. Feature extraction using deep neural networks, like CNNs, has proven extremely effective has become the standard in state-of-the-art template matching algorithms.
This feature-based approach is often more robust than the template-based approach described below. As such, it has become the state-of-the-art method for template matching, as it can match templates with non-rigid and out-of-plane transformations, as well as high background clutter and illumination changes.
Template-based approach
For templates without strong features, or for when the bulk of a template image constitutes the matching image as a whole, a template-based approach may be effective. Since template-based matching may require sampling of a large number of data points, it is often desirable to reduce the number of sampling points |
https://en.wikipedia.org/wiki/Joist | A joist is a horizontal structural member used in framing to span an open space, often between beams that subsequently transfer loads to vertical members. When incorporated into a floor framing system, joists serve to provide stiffness to the subfloor sheathing, allowing it to function as a horizontal diaphragm. Joists are often doubled or tripled, placed side by side, where conditions warrant, such as where wall partitions require support.
Joists are either made of wood, engineered wood, or steel, each of which has unique characteristics. Typically, wood joists have the cross section of a plank with the longer faces positioned vertically. However, engineered wood joists may have a cross section resembling the Roman capital letter ""; these joists are referred to as -joists. Steel joists can take on various shapes, resembling the Roman capital letters "C", "", "L" and "S".
Wood joists were also used in old-style timber framing. The invention of the circular saw for use in modern sawmills has made it possible to fabricate wood joists as dimensional lumber.
Strength characteristics
Joists must exhibit the strength to support the anticipated load over a long period of time. In many countries, the fabrication and installation of all framing members including joists must meet building code standards. Considering the cross section of a typical joist, the overall depth of the joist is critical in establishing a safe and stable floor or ceiling system. The wider the spacing between the joists, the deeper the joist will need to be to limit stress and deflection under load. Lateral support called dwang, blocking, or strutting increases its stability, preventing the joist from buckling under load. There are approved formulas for calculating the depth required and reducing the depth as needed; however, a rule of thumb for calculating the depth of a wooden floor joist for a residential property is to take half the span in feet, add two, and use the resulting number as the de |
https://en.wikipedia.org/wiki/Net.art | net.art refers to a group of artists who have worked in the medium of Internet art since 1994. Some of the early adopters and main members of this movement include Vuk Ćosić, Jodi.org, Alexei Shulgin, Olia Lialina, Heath Bunting, Daniel García Andújar, and Rachel Baker. Although this group was formed as a parody of avant garde movements by writers such as Tilman Baumgärtel, Josephine Bosma, Hans Dieter Huber and Pit Schultz, their individual works have little in common.
The term "net.art" is also used as a synonym for net art or Internet art and covers a much wider range of artistic practices. In this wider definition, net.art means art that uses the Internet as its medium and that cannot be experienced in any other way. Typically net.art has the Internet and the specific socio-culture that it spawned as its subject matter but this is not required.
The German critic Tilman Baumgärtel - building on the ideas of American critic Clement Greenberg - has frequently argued for a "media specificity" of net.art in his writings. According to the introduction to his book "net.art. Materialien zur Netzkunst", the specific qualities of net.art are "connectivity, global reach, multimediality, immateriality, interactivity and egality".
History of the net.art movement
The net.art movement arose in the context of the wider development of Internet art. As such, net.art is more of a movement and a critical and political landmark in Internet art history, than a specific genre. Early precursors of the net.art movement include the international fluxus (Nam June Paik) and avant-pop (Mark Amerika) movements. The avant-pop movement particularly became widely recognized in Internet circles from 1993, largely via the popular Alt-X site.
In 1995, the term "net.art" was used by nettime initiator Pit Schultz as a title for an exhibition in Berlin in 1995, in which Vuk Cosic and Alexei Shulgin both showed their work. It was later used with regard to the "net.art per se" meeting of artists |
https://en.wikipedia.org/wiki/Semi-local%20ring | In mathematics, a semi-local ring is a ring for which R/J(R) is a semisimple ring, where J(R) is the Jacobson radical of R.
The above definition is satisfied if R has a finite number of maximal right ideals (and finite number of maximal left ideals). When R is a commutative ring, the converse implication is also true, and so the definition of semi-local for commutative rings is often taken to be "having finitely many maximal ideals".
Some literature refers to a commutative semi-local ring in general as a
quasi-semi-local ring, using semi-local ring to refer to a Noetherian ring with finitely many maximal ideals.
A semi-local ring is thus more general than a local ring, which has only one maximal (right/left/two-sided) ideal.
Examples
Any right or left Artinian ring, any serial ring, and any semiperfect ring is semi-local.
The quotient is a semi-local ring. In particular, if is a prime power, then is a local ring.
A finite direct sum of fields is a semi-local ring.
In the case of commutative rings with unity, this example is prototypical in the following sense: the Chinese remainder theorem shows that for a semi-local commutative ring R with unit and maximal ideals m1, ..., mn
.
(The map is the natural projection). The right hand side is a direct sum of fields. Here we note that ∩i mi=J(R), and we see that R/J(R) is indeed a semisimple ring.
The classical ring of quotients for any commutative Noetherian ring is a semilocal ring.
The endomorphism ring of an Artinian module is a semilocal ring.
Semi-local rings occur for example in algebraic geometry when a (commutative) ring R is localized with respect to the multiplicatively closed subset S = ∩ (R \ pi), where the pi are finitely many prime ideals.
Textbooks
Ring theory
Localization (mathematics) |
https://en.wikipedia.org/wiki/Relativity%20%28M.%20C.%20Escher%29 | Relativity is a lithograph print by the Dutch artist M. C. Escher, first printed in December 1953. The first version of this work was a woodcut made earlier that same year.
It depicts a world in which the normal laws of gravity do not apply. The architectural structure seems to be the centre of an idyllic community, with most of its inhabitants casually going about their ordinary business, such as dining. There are windows and doorways leading to park-like outdoor settings. All of the figures are dressed in identical attire and have featureless bulb-shaped heads. Identical characters such as these can be found in many other Escher works.
In the world of Relativity, there are three sources of gravity, each being orthogonal to the two others. Each inhabitant lives in one of the gravity wells, where normal physical laws apply. There are sixteen characters, spread between each gravity source, six in one and five each in the other two. The apparent confusion of the lithograph print comes from the fact that the three gravity sources are depicted in the same space.
The structure has seven stairways, and each stairway can be used by people who belong to two different gravity sources. This creates interesting phenomena, such as in the top stairway, where two inhabitants use the same stairway in the same direction and on the same side, but each using a different face of each step; thus, one descends the stairway as the other climbs it, even while moving in the same direction nearly side by side. In the other stairways, inhabitants are depicted as climbing the stairways upside-down, but based on their own gravity source, they are climbing normally.
Each of the three parks belongs to one of the gravity wells. All but one of the doors seem to lead to basements below the parks. Though metaphysically possible, such basements are certainly unusual and add to the surreal effect of the picture.
In popular culture
Relativity is one of Escher's most popular works, and has been u |
https://en.wikipedia.org/wiki/Remote%20broadcast | In broadcast engineering, a remote broadcast (usually just called a remote or a live remote, or in news parlance, a live shot) is broadcasting done from a location away from a formal television studio and is considered an electronic field production (EFP). A remote pickup unit (RPU) is usually used to transmit the audio and/or video back to the television station, where it joins the normal airchain. Other methods include satellite trucks, production trucks and even regular telephone lines if necessary.
History
The first airing of a remote broadcast came in 1924, when Loew's Theater publicist and WHN (New York City) station manager Nils Granlund leased telegraph lines from Western Union to provide the first link in what became called cabaret broadcasting." By early 1925, Granlund had established remote lines between WHN and more than thirty New York City jazz nightclubs, including the Silver Slipper, The Parody Club, the Cotton Club, the Strand Roof, and Club Moritz. These big band remotes would become a staple of the old-time radio era, lasting well into the 1950s.
Nils T. Granlund cited the 1925 WHN airing of Senator James J. Walker's announcement of his New York City mayoral candidacy through a remote broadcast from the New York Press Club as the first such remote link for a political forum.
In Latin America on 27 October 1920, Dr Sussini made the first remote transmission in Argentina from the theatre El Coliseo in Buenos Aires. In Mexico on 27 September 1921, Adolfo Gomez Fernandez made a transmission from the Teatro Ideal, Mexico DF
The very first live remote broadcast to the nation was by the Canadian Broadcasting Corporation in 1938 when Frank Willis reported on the Moose River Gold Mine disaster in Nova Scotia http://archives.cbc.ca/economy_business/natural_resources/clips/3860/
On 11 June 1955, NBC, The National Broadcasting Company, provided the 1st live remote broadcast to the nation from Niagara Falls, New York.
Radio
In radio, remotes are often u |
https://en.wikipedia.org/wiki/Comparison%20of%20web%20browsers | This is a comparison of both historical and current web browsers based on developer, engine, platform(s), releases, license, and cost.
General information
Basic general information about the browsers. Browsers listed on a light purple background are discontinued. Platforms with a yellow background have limited support.
Operating system support
Browsers are compiled to run on certain operating systems, without emulation.
This list is not exhaustive, but rather reflects the most common OSes today (e.g. Netscape Navigator was also developed for OS/2 at a time when macOS 10 did not exist) but does not include the growing appliance segment (for example, the Opera web browser has gained a leading role for use in mobile phones, smartphones, the Nintendo DS and Wii, and Personal Digital Assistants, and is also used in some smart TVs).
Both the web browser and OS means most recent version, example: Windows 11 with Internet Explorer 11.
Browser features
Information about what common browser features are implemented natively (without third-party add-ons).
Accessibility features
Information about what common accessibility features are implemented natively (without third-party add-ons). Browsers that do not support pop-ups have no need for pop-up blocking abilities, so that field is marked as N/A.
Accessibility features (continued)
Information about what common accessibility features are implemented natively (without third-party add-ons).
Web technology support
Information about what web standards, and technologies the browsers support, except for JavaScript. External links lead to information about support in future versions of the browsers or extensions that provide such functionality.
Plugins and syndicated content support
Information about what web standards, and technologies the browsers support. External links lead to information about support in future versions of the browsers or extensions that provide such functionality.
JavaScript support
Information about wha |
https://en.wikipedia.org/wiki/Cyberduck | Cyberduck is an open-source client for FTP and SFTP, WebDAV, and cloud storage (OpenStack Swift, Amazon S3, Backblaze B2 and Microsoft Azure), available for macOS and Windows (as of version 4.0) licensed under the GPL. Cyberduck is written in Java and C# using the Cocoa user interface framework on macOS and Windows Forms on Windows. It supports FTP/TLS (FTP secured over SSL/TLS), using AUTH TLS as well as directory synchronization. The user interacts with the user interface (GUI), including file transfer by drag and drop and notifications via Growl. It is also able to open some files in external text editors.
Cyberduck includes a bookmark manager and supports Apple's Keychain and Bonjour networking. It supports multiple languages including English, Catalan, Czech, Chinese (Traditional and Simplified), Danish, Dutch, Finnish, French, German, Hebrew, Hungarian, Indonesian, Italian, Japanese, Korean, Norwegian, Polish, Portuguese, Russian, Slovak, Spanish, Swedish, Thai, Turkish, Ukrainian, and Welsh.
Cyberduck CLI
The Cyberduck creator also provides a version for the command-line interface (CLI), called duck, available for Windows, macOS and Linux. It has its own website at duck.sh. The program can be used as FTP and SFTP-client, for operations with different cloud services.
See also
Comparison of FTP client software
References
External links
Portable Cyberduck — packaged as portable application for external drive. (Mac only)
First Look: Cyberduck 3 is a great, free FTP client for Mac
How to mount almost any remote drive in your Mac’s Finder
Free FTP clients
SSH File Transfer Protocol clients
MacOS Internet software
Data synchronization
MacOS-only free software
Cloud storage |
https://en.wikipedia.org/wiki/Triple%20product | In geometry and algebra, the triple product is a product of three 3-dimensional vectors, usually Euclidean vectors. The name "triple product" is used for two different products, the scalar-valued scalar triple product and, less often, the vector-valued vector triple product.
Scalar triple product
The scalar triple product (also called the mixed product, box product, or triple scalar product) is defined as the dot product of one of the vectors with the cross product of the other two.
Geometric interpretation
Geometrically, the scalar triple product
is the (signed) volume of the parallelepiped defined by the three vectors given. Here, the parentheses may be omitted without causing ambiguity, since the dot product cannot be evaluated first. If it were, it would leave the cross product of a scalar and a vector, which is not defined.
Properties
The scalar triple product is unchanged under a circular shift of its three operands (a, b, c):
Swapping the positions of the operators without re-ordering the operands leaves the triple product unchanged. This follows from the preceding property and the commutative property of the dot product:
Swapping any two of the three operands negates the triple product. This follows from the circular-shift property and the anticommutativity of the cross product:
The scalar triple product can also be understood as the determinant of the matrix that has the three vectors either as its rows or its columns (a matrix has the same determinant as its transpose):
If the scalar triple product is equal to zero, then the three vectors a, b, and c are coplanar, since the parallelepiped defined by them would be flat and have no volume.
If any two vectors in the scalar triple product are equal, then its value is zero:
Also:
The simple product of two triple products (or the square of a triple product), may be expanded in terms of dot products:This restates in vector notation that the product of the determinants of two 3×3 matrices eq |
https://en.wikipedia.org/wiki/Orbital%20node | An orbital node is either of the two points where an orbit intersects a plane of reference to which it is inclined. A non-inclined orbit, which is contained in the reference plane, has no nodes.
Planes of reference
Common planes of reference include the following:
For a geocentric orbit, Earth's equatorial plane. In this case, non-inclined orbits are called equatorial.
For a heliocentric orbit, the ecliptic or invariable plane. In this case, non-inclined orbits are called ecliptic.
For an orbit outside the Solar System, the plane through the primary perpendicular to a line through the observer and the primary (called the plane of the sky).
Node distinction
If a reference direction from one side of the plane of reference to the other is defined, the two nodes can be distinguished. For geocentric and heliocentric orbits, the ascending node (or north node) is where the orbiting object moves north through the plane of reference, and the descending node (or south node) is where it moves south through the plane. In the case of objects outside the Solar System, the ascending node is the node where the orbiting secondary passes away from the observer, and the descending node is the node where it moves towards the observer., p. 137.
The position of the node may be used as one of a set of parameters, called orbital elements, which describe the orbit. This is done by specifying the longitude of the ascending node (or, sometimes, the longitude of the node.)
The line of nodes is the straight line resulting from the intersection of the object's orbital plane with the plane of reference; it passes through the two nodes.
Symbols and nomenclature
The symbol of the ascending node is (Unicode: U+260A, ☊), and the symbol of the descending node is (Unicode: U+260B, ☋).
In medieval and early modern times, the ascending and descending nodes of the Moon were called the "dragon's head" (, ) and "dragon's tail" (), respectively. These terms originally referred to the times wh |
https://en.wikipedia.org/wiki/Concepts%20of%20Modern%20Mathematics | Concepts of Modern Mathematics is a book by mathematician and science popularizer Ian Stewart about then-recent developments in mathematics. It was originally published by Penguin Books in 1975, updated in 1981, and reprinted by Dover publications in 1995 and 2015.
Overview
The book arose out of an extramural class that Ian Stewart taught at the University of Warwick about "Modern mathematics". In the 1995 Dover edition Stewart wrote that the aim of the class was:
to explain why the underlying abstract point of view had gained currency among research mathematicians, and to examine how it opened up entirely new realms of mathematical thought.
The book is aimed at non-mathematicians. However, there are frequent equations and diagrams and the level of presentation is more technical than some of Stewart's other popular books such as Flatterland. Topics covered include analytic geometry, set theory, abstract algebra, group theory, topology, and probability.
References
Books by Ian Stewart (mathematician)
1975 non-fiction books
Mathematics books |
https://en.wikipedia.org/wiki/Brittleness | A material is brittle if, when subjected to stress, it fractures with little elastic deformation and without significant plastic deformation. Brittle materials absorb relatively little energy prior to fracture, even those of high strength. Breaking is often accompanied by a sharp snapping sound.
When used in materials science, it is generally applied to materials that fail when there is little or no plastic deformation before failure. One proof is to match the broken halves, which should fit exactly since no plastic deformation has occurred.
Brittleness in different materials
Polymers
Mechanical characteristics of polymers can be sensitive to temperature changes near room temperatures. For example, poly(methyl methacrylate) is extremely brittle at temperature 4˚C, but experiences increased ductility with increased temperature.
Amorphous polymers are polymers that can behave differently at different temperatures. They may behave like a glass at low temperatures (the glassy region), a rubbery solid at intermediate temperatures (the leathery or glass transition region), and a viscous liquid at higher temperatures (the rubbery flow and viscous flow region). This behavior is known as viscoelastic behavior. In the glassy region, the amorphous polymer will be rigid and brittle. With increasing temperature, the polymer will become less brittle.
Metals
Some metals show brittle characteristics due to their slip systems. The more slip systems a metal has, the less brittle it is, because plastic deformation can occur along many of these slip systems. Conversely, with fewer slip systems, less plastic deformation can occur, and the metal will be more brittle. For example, HCP (hexagonal close packed) metals have few active slip systems, and are typically brittle.
Ceramics
Ceramics are generally brittle due to the difficulty of dislocation motion, or slip. There are few slip systems in crystalline ceramics that a dislocation is able to move along, which makes deformation di |
https://en.wikipedia.org/wiki/Customer%20service | Customer service is the assistance and advice provided by a company to those people who buy or use its products or services. Each industry requires different levels of customer service, but towards the end, the idea of a well-performed service is that of increasing revenues. The perception of success of the customer service interactions is dependent on employees "who can adjust themselves to the personality of the customer". Customer service is often practiced in a way that reflects the strategies and values of a firm. Good quality customer service is usually measured through customer retention. Customer service for some firms is part of the firm’s intangible assets and can differentiate it from others in the industry. One good customer service experience can change the entire perception a customer holds towards the organization.
Customer service does not only focus on the external aspect of the organization, but also the internal relations that facilitate the business activity. For service firms, customer service plays a vital role due to the close interaction with clients, as in the healthcare or legal industries.[2] When close interaction is not required, there are different methods to provide individuals with a sense of attention. For instance, when withdrawing money from an ATM or skipping the line in an amusement park. Customers still receive the service they are looking for in a direct level without face-to-face interaction.
The evolution in the service industry has identified the needs of consumers. Companies usually create policies or standards to guide their personnel to follow their particular service package. A service package is a combination of tangible and intangible characteristics a firm uses to take care of its clients.
Customer support
Customer support is a range of consumer services to assist customers in making cost-effective and correct use of a product. It includes assistance in planning, installation, training, troubleshooting, maintenanc |
https://en.wikipedia.org/wiki/Sodium%20metabisulfite | Sodium metabisulfite or sodium pyrosulfite (IUPAC spelling; Br. E. sodium metabisulphite or sodium pyrosulphite) is an inorganic compound of chemical formula Na2S2O5. The substance is sometimes referred to as disodium metabisulfite. It is used as a disinfectant, antioxidant, and preservative agent. When dissolved in water it forms sodium bisulfite.
Preparation
Sodium metabisulfite can be prepared by treating a solution of sodium hydroxide with sulfur dioxide. When conducted in warm water, Na2SO3 initially precipitates as a yellow solid. With more SO2, the solid dissolves to give the disulfite, which crystallises upon cooling.
SO2 + 2 NaOH → Na2SO3 + H2O
SO2 + Na2SO3 → Na2S2O5
which yields a residue of colourless solid Na2S2O5.
Chemical structure
The anion metabisulfite consists of an SO2 group linked to an SO3 group, with the negative charge more localised on the SO3 end. The S–S bond length is 2.22 Å, and the "thionate" and "thionite" S–O distances are 1.46 and 1.50 Å, respectively.
Reactivity
Upon dissolution in water, bisulfite is generated:
Na2S2O5 + H2O → 2 Na+ + 2 HSO3−
Uses
Sodium and potassium metabisulfite have many major and niche uses. It is widely used for preserving food and beverages.
Sodium metabisulfite is added as an excipient to medications which contain adrenaline (epinephrine), in order to prevent the oxidation of adrenaline. For example, it is added to combination drug formulations which contain a local anaesthetic and adrenaline, and to the formulation in epinephrine autoinjectors, such as the EpiPen. This lengthens the shelf life of the formulation, although the sodium metabisulphite reacts with adrenaline, causing it to degrade and form epinephrine sulphonate.
In combination with sodium hydrosulfite it is used as a rust-stain remover
It is used in photography.
Concentrated sodium metabisulfite can be used to remove tree stumps. Some brands contain 98% sodium metabisulfite, and cause degradation of lignin in the stu |
https://en.wikipedia.org/wiki/Graham%20number | The Graham number or Benjamin Graham number is a figure used in securities investing that measures a stock's so-called fair value. Named after Benjamin Graham, the founder of value investing, the Graham number can be calculated as follows:
The final number is, theoretically, the maximum price that a defensive investor should pay for the given stock. Put another way, a stock priced below the Graham Number would be considered a good value, if it also meets a number of other criteria.
The Number represents the geometric mean of the maximum that one would pay based on earnings and based on book value. Graham writes:
Alternative calculation
Earnings per share is calculated by dividing net income by shares outstanding. Book value is another way of saying shareholders' equity. Therefore, book value per share is calculated by dividing equity by shares outstanding. Consequently, the formula for the Graham number can also be written as follows:
References
Valuation (finance)
Mathematical finance |
https://en.wikipedia.org/wiki/Exatron%20Stringy%20Floppy | The Exatron Stringy Floppy (or ESF) is a continuous-loop tape drive developed by Exatron.
History
The company introduced an S-100 stringy floppy drive at the 1978 West Coast Computer Faire, and a version for the Radio Shack TRS-80 in 1979. Exatron sold about 4,000 TRS-80 drives by August 1981 for $249.50 each, stating that it was "our best seller by far". The tape cartridge is about the size of a business card, but about thick. The magnetic tape inside the cartridge is wide.
Format
There is no single catalog of files; to load a specific file the drive searches the entire tape, briefly stopping to read the header of each found file. The tape loop only moves in one direction, so a file that starts behind the current location cannot be read until the drive searches the entire loop for it. The device is capable of reading and writing random access data files (unlike a datacassette). If a record being sought has been overshot, the drive advances the tape until it loops around to the beginning and continues seeking from there.
According to Embedded Systems magazine, the Exatron Stringy Floppy uses Manchester encoding, achieving 14K read-write speeds and the code controlling the device was developed by Li-Chen Wang, who also wrote a Tiny BASIC, the basis for the TRS-80 Model I Level I BASIC.
Reception
In the July 1983 issue of Compute!'s Gazette, the Exatron Stringy Floppy for the VIC-20 and the Commodore 64 was reviewed. Calling the peripheral "a viable alternative" to tape or disk, the magazine noted that "under ideal conditions, a Stringy Floppy can outperform a VIC-1540/1541 disk drive". Texas Instruments licensed the Stringy Floppy as the Waferdrive for its cancelled TI 99/2 computer and a Compact Computer 40 peripheral which never shipped.
Use and distribution
The Exatron drive was initially used in the Prophet-10 music synthesizer and was later replaced with a micro-cassette drive from Braemar, reportedly due to unreliability and poor mutual compatibil |
https://en.wikipedia.org/wiki/Air%20vortex%20cannon | An air vortex cannon is a toy that releases doughnut-shaped air vortices — similar to smoke rings but larger, stronger and invisible. The vortices are able to ruffle hair, disturb papers or blow out candles after travelling several metres.
The design consists of a short and broad barrel with a slight taper, closed by a flexible diaphragm at the larger end. The diaphragm is internally attached to the barrel by elastic strips. The cannon is "armed" by pulling the diaphragm out, distending the elastic bands, and is "fired" by releasing the diaphragm. The diaphragm quickly pushes a quantity of air out of the open end, creating a vortex ring.
An air vortex cannon can be made easily at home, from just a cardboard box. A toy commercial version, with a barrel wide and useful range of is sold under the name Air bazooka or Airzooka.
Air cannons are used in some amusement parks such as Universal Studios to spook or surprise visitors.
The Wham-O Air Blaster toy introduced in 1965 could blow out a candle at . The commercial Airzooka was developed by Brian S. Jordan who claims to have conceived it when still a boy. A feature of the Airzooka is a loose non-elastic polythene membrane, tensioned by a bungee cord, rather than elastic membranes. This allows a much greater volume of air to be displaced.
A large air vortex cannon, with a wide barrel and a displacement volume of was built in March 2008 at the University of Minnesota, and was able to blow out candles at .
In 2012 a large air vortex cannon was built for Czech television show Zázraky přírody (English: Wonders of Nature). It was capable of bringing down a wall of cardboard boxes from in what was claimed to be a world record.
See also
Bubble ring
Vortex ring gun
References
External links
Home made vortex cannon using a cardboard box and a smoke machine from The URN Science Show.
Toy weapons
Vortices |
https://en.wikipedia.org/wiki/Playtest | A playtest is the process by which a game designer tests a new game for bugs and design flaws before releasing it to market. Playtests can be run "open", "closed", "beta", or otherwise, and are very common with board games, collectible card games, puzzle hunts, role-playing games, and video games, for which they have become an established part of the quality control process. An individual involved in testing a game is referred to as a playtester.
An open playtest could be considered open to anyone who wishes to join, or it may refer to game designers recruiting testers from outside the design group. Prospective testers usually must complete a survey or provide their contact information in order to be considered for participation. A closed playtest is an internal testing process not available to the public. Beta testing normally refers to the final stages of testing just before going to market with a product, and is often run semi-open with a limited form of the game in order to find any last-minute problems. With all forms of playtesting it is not unusual for participants to be required to sign a non-disclosure agreement, in order to protect the game designer's copyrights.
The word 'playtest' is also commonly used in unofficial situations where a game is being tested by a group of players for their own private use, or to denote a situation where a new strategy or game mechanic is being tested. Playtesting is a part of usability test in the process of game development.
Video games
In the video game industry, playtesting refers specifically to the process of exposing a game in development (or some specific parts of it) to its intended audience, to identify potential design flaws and gather feedback. Playtests are also used to help ensure that a product will be commercially viable upon release, by providing a way for consumers to play the game and provide their opinions. Playtesting should not be confused with quality assurance (QA) testing, in which professional te |
https://en.wikipedia.org/wiki/Ring%20species | In biology, a ring species is a connected series of neighbouring populations, each of which interbreeds with closely sited related populations, but for which there exist at least two "end populations" in the series, which are too distantly related to interbreed, though there is a potential gene flow between each "linked" population and the next. Such non-breeding, though genetically connected, "end populations" may co-exist in the same region (sympatry) thus closing a "ring". The German term , meaning a circle of races, is also used.
Ring species represent speciation and have been cited as evidence of evolution. They illustrate what happens over time as populations genetically diverge, specifically because they represent, in living populations, what normally happens over time between long-deceased ancestor populations and living populations, in which the intermediates have become extinct. The evolutionary biologist Richard Dawkins remarks that ring species "are only showing us in the spatial dimension something that must always happen in the time dimension".
Formally, the issue is that interfertility (ability to interbreed) is not a transitive relation; if A breeds with B, and B breeds with C, it does not mean that A breeds with C, and therefore does not define an equivalence relation. A ring species is a species with a counterexample to the transitivity of interbreeding. However, it is unclear whether any of the examples of ring species cited by scientists actually permit gene flow from end to end, with many being debated and contested.
History
The classic ring species is the Larus gull. In 1925 Jonathan Dwight found the genus to form a chain of varieties around the Arctic Circle. However, doubts have arisen as to whether this represents an actual ring species. In 1938, Claud Buchanan Ticehurst argued that the greenish warbler had spread from Nepal around the Tibetan Plateau, while adapting to each new environment, meeting again in Siberia where the ends no lon |
https://en.wikipedia.org/wiki/Mental%20abacus | The abacus system of mental calculation is a system where users mentally visualize an abacus to carry out arithmetical calculations. No physical abacus is used; only the answers are written down. Calculations can be made at great speed in this way. For example, in the Flash Anzan event at the All Japan Soroban Championship, champion Takeo Sasano was able to add fifteen three-digit numbers in just 1.7 seconds.
This system is being propagated in China, Singapore, South Korea, Thailand, Malaysia, and Japan. Mental calculation is said to improve mental capability, increases speed of response, memory power, and concentration power.
Many veteran and prolific abacus users in China, Japan, South Korea, and others who use the abacus daily, naturally tend to not use the abacus any more, but perform calculations by visualizing the abacus. This was verified when the right brain of visualisers showed heightened EEG activity when calculating, compared with others using an actual abacus to perform calculations.
The abacus can be used routinely to perform addition, subtraction, multiplication, and division; it can also be used to extract square and cube roots.
See also
Abacus logic
Abacus
References
External links
Mental abacus does away with words, New Scientist, August 9, 2011
Competitions
Games of mental skill
Mental calculation
Abacus
Mathematics competitions |
https://en.wikipedia.org/wiki/Frequency%20extender | In broadcast engineering, a frequency extender is an electronic device that allows high-fidelity analog audio to be sent over regular POTS telephone lines, without the loss of higher audio frequencies (treble). It is an extended concept of a telephone hybrid.
The concept uses frequency shifting to overcome the narrow bandwidth of regular telephone systems. The input signal is sent on one telephone line as-is, or in some cases upshifted to provide extra low-frequency response, and sent on a second line shifted down by 3 kHz, which is normally the upper bandpass limit in telephony. Thus, an audio frequency of 5 kHz is sent at 2 kHz. A receiver on the other end then shifts the second line back up and mixes it with the first. This results in greatly improved audio, adding a full octave of range, and pushing the total bandpass to 6 kHz. The sound is then acceptable for voice, if not for music.
It is also possible to add other lines, each increasing the bandpass by another 3 kHz. However, the law of diminishing returns takes over, because each successive octave is double the size of the last. A third line pushes the bandpass up 50% to 9 kHz, equivalent to AM radio. A fourth line would push it up 33% to 12 kHz. FM radio quality would require five telephone lines to be installed, pushing the bandpass up 25% to 15 kHz. The audio is shifted down by 6,9, and 12 kHz respectively for each additional line.
Frequency extenders have been nearly eliminated by POTS codecs.
See also
Remote broadcast
Broadcast engineering
Telephony |
https://en.wikipedia.org/wiki/Idris%20%28operating%20system%29 | Idris is a discontinued multi-tasking, Unix-like, multi-user, real-time operating system released by Whitesmiths, of Westford, Massachusetts. The product was commercially available from 1979 through 1988.
Background
Idris was originally written for the PDP-11 by P. J. Plauger, who started working on Idris in August 1978. It was binary compatible with Unix V6 on PDP-11, but it could run on non-memory managed systems (like LSI-11 or PDP-11/23) as well. The kernel required 31 KB of RAM, and the C compiler (provided along with the standard V6 toolset) had more or less the same size.
Ports
Although Idris was initially available for the PDP-11, it was later ported to run on a number of platforms, such as the VAX, Motorola 68000, System/370 and Intel 8086. There was also a version that used bank-switching for memory management, that ran on the Intel 8080.
In 1986, David M. Stanhope at Computer Tools International ported Idris to the Atari ST and developed its ROM boot cartridge. This work also included a port of X to Idris. Computer Tools and Whitesmiths offered it to Atari as a replacement for Atari TOS, but eventually marketed it directly to ST enthusiasts.
A specific version of Idris (CoIdris) was packaged as a .COM file under DOS and used it for low level I/O services.
Idris was ported to the Apple Macintosh (as MacIdris) by John O'Brien (of Whitesmiths Australia) and remained available until the early 1990s. MacIdris ran as an application under the Finder or MultiFinder.
After Whitesmiths had been merged with Intermetrics, Idris along with its development toolchain was ported by Real Time Systems Ltd to the INMOS T800 transputer architecture for the Parsytec SN1000 multiprocessor.
References
Discontinued operating systems
PDP-11
Unix variants
68k architecture |
https://en.wikipedia.org/wiki/Comparison%20of%20operating%20systems | These tables provide a comparison of operating systems, of computer devices, as listing general and technical information for a number of widely used and currently available PC or handheld (including smartphone and tablet computer) operating systems. The article "Usage share of operating systems" provides a broader, and more general, comparison of operating systems that includes servers, mainframes and supercomputers.
Because of the large number and variety of available Linux distributions, they are all grouped under a single entry; see comparison of Linux distributions for a detailed comparison. There is also a variety of BSD and DOS operating systems, covered in comparison of BSD operating systems and comparison of DOS operating systems.
General information
Technical information
Security
Commands
For POSIX compliant (or partly compliant) systems like FreeBSD, Linux, macOS or Solaris, the basic commands are the same because they are standardized.
NOTE: Linux systems may vary by distribution which specific program, or even 'command' is called, via the POSIX function. For example, if you wanted to use the DOS to give you a directory listing with one detailed file listing per line you could use (e.g. in a session configuration file).
See also
Comparison of command shells
Comparison of file systems
List of operating systems
Light-weight Linux distribution
Security-focused operating system
Timeline of operating systems
Usage share of operating systems
Operating system comparisons
Comparison of BSD operating systems
Comparison of DOS operating systems
Comparison of IPv6 support in operating systems
Comparison of operating system kernels
Comparison of Linux distributions
Comparison of netbook-oriented Linux distributions
Comparison of Microsoft Windows versions
Comparison of mobile operating systems
Comparison of open-source operating systems
Comparison of real-time operating systems
Comparison of OpenSolaris distributions
Comparison of |
https://en.wikipedia.org/wiki/Digital%20Audio%20Stationary%20Head | The Digital Audio Stationary Head or DASH standard is a reel-to-reel, digital audio tape format introduced by Sony in early 1982 for high-quality multitrack studio recording and mastering, as an alternative to analog recording methods. DASH is capable of recording two channels of audio on a quarter-inch tape, and 24 or 48 tracks on tape on open reels of up to 14 inches. The data is recorded on the tape linearly, with a stationary recording head, as opposed to the DAT format, where data is recorded helically with a rotating head, in the same manner as a VCR. The audio data is encoded as linear PCM and boasts strong cyclic redundancy check (CRC) error correction, allowing the tape to be physically edited with a razor blade as analog tape would, e.g. by cutting and splicing, and played back with no loss of signal. In a two-track DASH recorder, the digital data is recorded onto the tape across nine data tracks: eight for the digital audio data and one for the CRC data; there is also provision for two linear analog cue tracks and one additional linear analog track dedicated to recording time code.
Digital audio recorders are fundamentally high bit-rate data recorders storing PCM encoded audio data. The main advantage of any digital recording medium is that of consistent, flat frequency response, high dynamic range audio reproduction compared to analog tape recorders, which is why some of the first uses of digital audio recording were for classical music. To further increase usable dynamic range, early DASH recorders included a specialized circuit called "Emphasis" which was intended to help overcome the noise of analog to digital and digital to analog converters of the time by boosting high frequencies on the front end. This circuit required complimentary de-emphasis on playback after the DAC for accurate reproduction. While emphasis was almost a necessity in earlier units, the circuit, of course, had a sound of its own and was used less and less as converter design |
https://en.wikipedia.org/wiki/POP-2 | POP-2 (also referred to as POP2) is a programming language developed around 1970 from the earlier language POP-1 (developed by Robin Popplestone in 1968, originally named COWSEL) by Robin Popplestone and Rod Burstall at the University of Edinburgh. It drew roots from many sources: the languages LISP and ALGOL 60, and theoretical ideas from Peter J. Landin. It used an incremental compiler, which gave it some of the flexibility of an interpreted language, including allowing new function definitions at run time and modification of function definitions while a program was running (both of which are features of dynamic compilation), without the overhead of an interpreted language.
Description
Stack
POP-2's syntax was Algol-like, except that assignments were the other way round: instead of writing
a := 3;
one wrote
3 -> a;
The reason for this was that the language had explicit notion of an operand stack; thus, the previous assignment could be written as two separate statements:
3;
which evaluated the value 3 and left it on the stack, and
-> a;
which popped the top value off the stack and assigned it to the variable 'a'. Similarly, the function call
f(x, y, z);
could be written as
x, y, z; f();
(commas and semicolons being largely interchangeable) or even
x, y, z.f;
or
(x, y, z).f;
Because of the stack-based paradigm, there was no need to distinguish between statements and expressions; thus, the two constructs
if a > b then
c -> e
else
d -> e
close;
and
if a > b then
c
else
d
close -> e;
were equivalent (note the use of close, as endif hadn't become a common end-of-if-clause notation yet).
Arrays and doublet functions
There were no special language constructs for creating arrays or record structures as they are commonly understood: instead, these were created with the aid of special builtin functions, e.g. newarray (for arrays that could contain any type of item) and newanyarray for creating |
https://en.wikipedia.org/wiki/Failure%20mode%20and%20effects%20analysis | Failure mode and effects analysis (FMEA; often written with "failure modes" in plural) is the process of reviewing as many components, assemblies, and subsystems as possible to identify potential failure modes in a system and their causes and effects. For each component, the failure modes and their resulting effects on the rest of the system are recorded in a specific FMEA worksheet. There are numerous variations of such worksheets. An FMEA can be a qualitative analysis, but may be put on a quantitative basis when mathematical failure rate models are combined with a statistical failure mode ratio database. It was one of the first highly structured, systematic techniques for failure analysis. It was developed by reliability engineers in the late 1950s to study problems that might arise from malfunctions of military systems. An FMEA is often the first step of a system reliability study.
A few different types of FMEA analyses exist, such as:
Functional
Design
Process
Sometimes FMEA is extended to FMECA (failure mode, effects, and criticality analysis) to indicate that criticality analysis is performed too.
FMEA is an inductive reasoning (forward logic) single point of failure analysis and is a core task in reliability engineering, safety engineering and quality engineering.
A successful FMEA activity helps identify potential failure modes based on experience with similar products and processes—or based on common physics of failure logic. It is widely used in development and manufacturing industries in various phases of the product life cycle. Effects analysis refers to studying the consequences of those failures on different system levels.
Functional analyses are needed as an input to determine correct failure modes, at all system levels, both for functional FMEA or piece-part (hardware) FMEA. An FMEA is used to structure mitigation for risk reduction based on either failure (mode) effect severity reduction or based on lowering the probability of failure or bot |
https://en.wikipedia.org/wiki/Integer%20square%20root | In number theory, the integer square root (isqrt) of a non-negative integer is the non-negative integer which is the greatest integer less than or equal to the square root of ,
For example,
Introductory remark
Let and be non-negative integers.
Algorithms that compute (the decimal representation of) run forever on each input which is not a perfect square.
Algorithms that compute do not run forever. They are nevertheless capable of computing up to any desired accuracy .
Choose any and compute .
For example (setting ):
Compare the results with
It appears that the multiplication of the input by gives an accuracy of decimal digits.
To compute the (entire) decimal representation of , one can execute an infinite number of times, increasing by a factor at each pass.
Assume that in the next program () the procedure is already defined and — for the sake of the argument — that all variables can hold integers of unlimited magnitude.
Then will print the entire decimal representation of .
// Print sqrt(y), without halting
void sqrtForever(unsigned int y)
{
unsigned int result = isqrt(y);
printf("%d.", result); // print result, followed by a decimal point
while (true) // repeat forever ...
{
y = y * 100; // theoretical example: overflow is ignored
result = isqrt(y);
printf("%d", result % 10); // print last digit of result
}
}
The conclusion is that algorithms which compute are computationally equivalent to algorithms which compute .
Basic algorithms
The integer square root of a non-negative integer can be defined as
For example, because .
Algorithm using linear search
The following C-programs are straightforward implementations.
Linear search using addition
In the program above (linear search, ascending) one can replace multiplication by addition, using the equivalence
// Integer square root
// (linear search, ascending) using addition
unsigned int isqrt(unsigned int y)
{
unsigned int L = 0;
unsigned int a = 1;
unsigned int d = |
https://en.wikipedia.org/wiki/Requirements%20engineering | Requirements engineering (RE) is the process of defining, documenting, and maintaining requirements in the engineering design process. It is a common role in systems engineering and software engineering.
The first use of the term requirements engineering was probably in 1964 in the conference paper "Maintenance, Maintainability, and System Requirements Engineering", but it did not come into general use until the late 1990s with the publication of an IEEE Computer Society tutorial in March 1997 and the establishment of a conference series on requirements engineering that has evolved into the International Requirements Engineering Conference.
In the waterfall model, requirements engineering is presented as the first phase of the development process. Later development methods, including the Rational Unified Process (RUP) for software, assume that requirements engineering continues through a system's lifetime.
Requirements management, which is a sub-function of Systems Engineering practices, is also indexed in the International Council on Systems Engineering (INCOSE) manuals.
Activities
The activities involved in requirements engineering vary widely, depending on the type of system being developed and the organization's specific practice(s) involved. These may include:
Requirements inception or requirements elicitation – Developers and stakeholders meet; the latter are inquired concerning their needs and wants regarding the software product.
Requirements analysis and negotiation – Requirements are identified (including new ones if the development is iterative), and conflicts with stakeholders are solved. Both written and graphical tools (the latter commonly used in the design phase, but some find them helpful at this stage, too) are successfully used as aids. Examples of written analysis tools: use cases and user stories. Examples of graphical tools: UML and LML.
System modeling – Some engineering fields (or specific situations) require the product to be completel |
https://en.wikipedia.org/wiki/Rubble%20trench%20foundation | The rubble trench foundation, an ancient construction approach popularized by architect Frank Lloyd Wright, is a type of foundation that uses loose stone or rubble to minimize the use of concrete and improve drainage. It is considered more environmentally friendly than other types of foundation because cement manufacturing requires the use of enormous amounts of energy. However, some soil environments are not suitable for this kind of foundation, particularly expansive or poor load-bearing (< 1 ton/sf) soils. A rubble trench foundation with a concrete grade beam is not recommended for earthquake prone areas.
A foundation must bear the structural loads imposed upon it and allow proper drainage of ground water to prevent expansion or weakening of soils and frost heaving. While the far more common concrete foundation requires separate measures to ensure good soil drainage, the rubble trench foundation serves both foundation functions at once.
To construct a rubble trench foundation a narrow trench is dug down below the frost line. The bottom of the trench would ideally be gently sloped to an outlet. Drainage tile, graded 1":8' to daylight, is then placed at the bottom of the trench in a bed of washed stone protected by filter fabric. The trench is then filled with either screened stone (typically 1-1/2") or recycled rubble. A steel-reinforced concrete grade beam may be poured at the surface to provide ground clearance for the structure.
If an insulated slab is to be poured inside the grade beam, then the outer surface of the grade beam and the rubble trench should be insulated with rigid XPS foam board, which must be protected above grade from mechanical and UV degradation.
The rubble-trench foundation is a relatively simple, inexpensive, and environment-friendly alternative to a conventional foundation, but may require an engineer's approval if building officials are not familiar with it. Frank Lloyd Wright used them successfully for more than 50 years in the firs |
https://en.wikipedia.org/wiki/Double%20coset | In group theory, a field of mathematics, a double coset is a collection of group elements which are equivalent under the symmetries coming from two subgroups. More precisely, let be a group, and let and be subgroups. Let act on by left multiplication and let act on by right multiplication. For each in , the -double coset of is the set
When , this is called the -double coset of . Equivalently, is the equivalence class of under the equivalence relation
if and only if there exist in and in such that .
The set of all -double cosets is denoted by
Properties
Suppose that is a group with subgroups and acting by left and right multiplication, respectively. The -double cosets of may be equivalently described as orbits for the product group acting on by . Many of the basic properties of double cosets follow immediately from the fact that they are orbits. However, because is a group and and are subgroups acting by multiplication, double cosets are more structured than orbits of arbitrary group actions, and they have additional properties that are false for more general actions.
Two double cosets and are either disjoint or identical.
is the disjoint union of its double cosets.
There is a one-to-one correspondence between the two double coset spaces and given by identifying with .
If , then . If , then .
A double coset is a union of right cosets of and left cosets of ; specifically,
The set of -double cosets is in bijection with the orbits , and also with the orbits under the mappings and respectively.
If is normal, then is a group, and the right action of on this group factors through the right action of . It follows that . Similarly, if is normal, then .
If is a normal subgroup of , then the -double cosets are in one-to-one correspondence with the left (and right) -cosets.
Consider as the union of a -orbit of right -cosets. The stabilizer of the right -coset with respect to the right action of is . Similarl |
https://en.wikipedia.org/wiki/Coagulase | Coagulase is a protein enzyme produced by several microorganisms that enables the conversion of fibrinogen to fibrin. In the laboratory, it is used to distinguish between different types of Staphylococcus isolates. Importantly, S. aureus is generally coagulase-positive, meaning that a positive coagulase test would indicate the presence of S. aureus or any of the other 11 coagulase-positive Staphylococci. A negative coagulase test would instead show the presence of coagulase-negative organisms such as S. epidermidis or S. saprophyticus. However, it is now known that not all S. aureus are coagulase-positive. Whereas coagulase-positive Staphylococci are usually pathogenic, coagulase-negative Staphylococci are more often associated with opportunistic infection.
It is also produced by Yersinia pestis.
Coagulase reacts with prothrombin in the blood. The resulting complex is called staphylothrombin, which enables the enzyme to act as a protease to convert fibrinogen, a plasma protein produced by the liver, to fibrin. This results in clotting of the blood. Coagulase is tightly bound to the surface of the bacterium S. aureus and can coat its surface with fibrin upon contact with blood. The fibrin clot may protect the bacterium from phagocytosis and isolate it from other defenses of the host. The fibrin coat can therefore make the bacteria more virulent. Bound coagulase is part of the larger family of MSCRAMM adhesin proteins.
Coagulase test
The coagulase test has traditionally been used to differentiate Staphylococcus aureus from coagulase-negative staphylococci. S.aureus produces two forms of coagulase (i.e., bound coagulase and free coagulase). Bound coagulase, otherwise known as "clumping factor", can be detected by carrying out a slide coagulase test, and free coagulase can be detected using a tube coagulase test.
Slide test
A slide coagulase test is run with a negative control to rule out autoagglutination. Two drops of saline are put onto the slide labeled wit |
https://en.wikipedia.org/wiki/Mertens%27%20theorems | In analytic number theory, Mertens' theorems are three 1874 results related to the density of prime numbers proved by Franz Mertens.
In the following, let mean all primes not exceeding n.
First theorem
Mertens' first theorem is that
does not exceed 2 in absolute value for any . ()
Second theorem
Mertens' second theorem is
where M is the Meissel–Mertens constant (). More precisely, Mertens proves that the expression under the limit does not in absolute value exceed
for any .
Proof
The main step in the proof of Mertens' second theorem is
where the last equality needs which follows from .
Thus, we have proved that
.
Since the sum over prime powers with converges, this implies
.
A partial summation yields
.
Changes in sign
In a paper on the growth rate of the sum-of-divisors function published in 1983, Guy Robin proved that in Mertens' 2nd theorem the difference
changes sign infinitely often, and that in Mertens' 3rd theorem the difference
changes sign infinitely often. Robin's results are analogous to Littlewood's famous theorem that the difference π(x) − li(x) changes sign infinitely often. No analog of the Skewes number (an upper bound on the first natural number x for which π(x) > li(x)) is known in the case of Mertens' 2nd and 3rd theorems.
Relation to the prime number theorem
Regarding this asymptotic formula Mertens refers in his paper to "two curious formula of Legendre", the first one being Mertens' second theorem's prototype (and the second one being Mertens' third theorem's prototype: see the very first lines of the paper). He recalls that it is contained in Legendre's third edition of his "Théorie des nombres" (1830; it is in fact already mentioned in the second edition, 1808), and also that a more elaborate version was proved by Chebyshev in 1851. Note that, already in 1737, Euler knew the asymptotic behaviour of this sum.
Mertens diplomatically describes his proof as more precise and rigorous. In reality none of the previous pr |
https://en.wikipedia.org/wiki/Broadcast%20automation | Broadcast automation incorporates the use of broadcast programming technology to automate broadcasting operations. Used either at a broadcast network, radio station or a television station, it can run a facility in the absence of a human operator. They can also run in a live assist mode when there are on-air personnel present at the master control, television studio or control room.
The radio transmitter end of the airchain is handled by a separate automatic transmission system (ATS).
History
Originally, in the US, many (if not most) broadcast licensing authorities required a licensed board operator to run every station at all times, meaning that every DJ had to pass an exam to obtain a license to be on-air, if their duties also required them to ensure proper operation of the transmitter. This was often the case on overnight and weekend shifts when there was no broadcast engineer present, and all of the time for small stations with only a contract engineer on call.
In the U.S., it was also necessary to have an operator on duty at all times in case the Emergency Broadcast System (EBS) was used, as this had to be triggered manually. While there has not been a requirement to relay any other warnings, any mandatory messages from the U.S. president would have had to first be authenticated with a code word sealed in a pink envelope sent annually to stations by the Federal Communications Commission (FCC).
Gradually, the quality and reliability of electronic equipment improved, regulations were relaxed, and no operator had to be present (or even available) while a station was operating. In the U.S., this came about when the EAS replaced the EBS, starting the movement toward automation to assist, and sometimes take the place of, the live disc jockeys (DJs) and radio personalities. in 1999, The Weather Channel launched Weatherscan Local, a cable television channel that broadcast uninterrupted live local weather information and forecasts. Weatherscan Local became Weat |
https://en.wikipedia.org/wiki/L%20ring | The L-ring of the bacterial flagellum is the ring in the lipid outer cell membrane through which the axial filament (rod, hook, and flagellum) passes. that l ring stands for lipopolysaccharide.
References
Bacteria |
https://en.wikipedia.org/wiki/Waterfall%20%28M.%20C.%20Escher%29 | Waterfall () is a lithograph by the Dutch artist M. C. Escher, first printed in October 1961. It shows a perpetual motion machine where water from the base of a waterfall appears to run downhill along the water path before reaching the top of the waterfall.
While most two-dimensional artists use relative proportions to create an illusion of depth, Escher here and elsewhere uses conflicting proportions to create a visual paradox. The watercourse supplying the waterfall (its aqueduct or leat) has the structure of two Penrose triangles. A Penrose triangle is an impossible object designed by Oscar Reutersvärd in 1934, and found independently by Roger Penrose in 1958.
Description
The image depicts a watermill with an elevated aqueduct and waterwheel as the main feature. The aqueduct begins at the waterwheel and flows behind it. The walls of the aqueduct step downward, suggesting that it slopes downhill. The aqueduct turns sharply three times, first to the left, then to the right, and finally to the left again. The viewer looks down at the scene diagonally, which means that from the viewer's perspective the aqueduct appears to be slanted upward. The viewer is also looking across the scene diagonally from the lower right, which means that from the viewer's perspective the two left-hand turns are directly in line with each other, while the waterwheel, the forward turn and the end of the aqueduct are all in line. The second left-hand turn is supported by pillars from the first, while the other two corners are supported by a tower of pillars that begins at the waterwheel. The water falls off the edge of the aqueduct and over the waterwheel in an impossible infinite cycle; in his notes on the picture, Escher points out that some water must be periodically added to this perpetual motion machine to compensate for evaporation. The use of the Penrose stairs is paralleled by Escher's Ascending and Descending (1960), where instead of the flow of water, two lines of monks endlessly |
https://en.wikipedia.org/wiki/Video%20server | A video server is a computer-based device that is dedicated to delivering video. Video servers are used in a number of applications, and often have additional functions and capabilities that address the needs of particular applications. For example, video servers used in security, surveillance and inspection applications typically are designed to capture video from one or more cameras and deliver the video via a computer network. In video production and broadcast applications, a video server may have the ability to record and play recorded video, and to deliver many video streams simultaneously.
Video broadcast and production
In TV broadcast industries, a server is a device used to store broadcast quality images and allows several users to edit stories using the images they contain simultaneously.
The video server can be used in a number of contexts, some of which include:
News: providing short news video clips as part of a news broadcast as seen on networks such as CNN, Fox News and the BBC.
Production: enhance live events with instant replays and slow motion and highlights (sport production) (see OB Vans)
Instruction: delivering course material in video format.
Public Access: delivering city specific information to residents over a cable system.
Surveillance: deliver real-time video images of protected site.
Entertainment: deliver anything used for entertainment. It can be gaming, news, movie trailers, or movies.
A professional-grade video server performs recording, storage, and playout of multiple video streams without any degradation of the video signal. Broadcast quality video servers often store hundreds of hours of compressed audio and video (in different codecs), play out multiple and synchronised simultaneous streams of video by, and offer quality interfaces such as SDI for digital video and XLR for balanced analog audio, AES/EBU digital audio and also Time Code. A genlock input is usually provided to provide a means of synchronizing with the h |
https://en.wikipedia.org/wiki/Dujiangyan | The Dujiangyan () is an ancient irrigation system in Dujiangyan City, Sichuan, China. Originally constructed around 256 BC by the State of Qin as an irrigation and flood control project, it is still in use today. The system's infrastructure develops on the Min River (Minjiang), the longest tributary of the Yangtze. The area is in the west part of the Chengdu Plain, between the Sichuan Basin and the Tibetan Plateau. Originally, the Min would rush down from the Min Mountains and slow down abruptly after reaching the Chengdu Plain, filling the watercourse with silt, thus making the nearby areas extremely prone to floods. King Zhao of Qin commissioned the project, and the construction of the Dujiangyan harnessed the river using a new method of channeling and dividing the water rather than simply damming it. The water management scheme is still in use today to irrigate over of land in the region and has produced comprehensive benefits in flood control, irrigation, water transport and general water consumption. Begun over 2,250 years ago, it now irrigates 668,700 hectares of farmland. The Dujiangyan, the Zhengguo Canal in Shaanxi and the Lingqu Canal in Guangxi are collectively known as the "three great hydraulic engineering projects of the Qin."
Dujiangyan Irrigation System were inscribed on the World Heritage List in 2000. It has also been declared a State Priority Protected Site, among the first batch of National Scenic Areas and Historical Sites, and a National ISO14000 Demonstration Area.
History
Planning
During the Warring States period, people who lived in the area of the Min River were plagued by annual flooding. Qin hydrologist Li Bing investigated the problem and discovered that the river was swelled by fast flowing spring melt-water from the local mountains that burst the banks when it reached the slow moving and heavily silted stretch below.
One solution would have been to build a dam, but the Qin wanted to keep the waterway open for military vessels to |
https://en.wikipedia.org/wiki/Social%20complexity | In sociology, social complexity is a conceptual framework used in the analysis of society. In the sciences, contemporary definitions of complexity are found in systems theory, wherein the phenomenon being studied has many parts and many possible arrangements of the parts; simultaneously, what is complex and what is simple are relative and change in time.
Contemporary usage of the term complexity specifically refers to sociologic theories of society as a complex adaptive system, however, social complexity and its emergent properties are recurring subjects throughout the historical development of social philosophy and the study of social change.
Early theoreticians of sociology, such as Ferdinand Tönnies, Émile Durkheim, and Max Weber, Vilfredo Pareto and Georg Simmel, examined the exponential growth and interrelatedness of social encounters and social exchanges. The emphases on the interconnectivity among social relationships, and the emergence of new properties within society, is found in the social theory produced in the subfields of sociology. Social complexity is a basis for the connection of the phenomena reported in microsociology and macrosociology, and thus provides an intellectual middle-range for sociologists to formulate and develop hypotheses. Methodologically, social complexity is theory-neutral, and includes the phenomena studied in microsociology and the phenomena studied in macrosociology.
Theoretic background
In 1937, the sociologist Talcott Parsons continued the work of the early theoreticians of sociology with his work on action theory; and by 1951, Parson had developed action theory into formal systems theory in The Social System (1951). In the following decades, the synergy between general systems thinking and the development of social system theories is carried forward by Robert K. Merton in discussions of theories of the middle-range and social structure and agency. From the late 1970s until the early 1990s, sociological investigation conc |
https://en.wikipedia.org/wiki/Neuropeptide | Neuropeptides are chemical messengers made up of small chains of amino acids that are synthesized and released by neurons. Neuropeptides typically bind to G protein-coupled receptors (GPCRs) to modulate neural activity and other tissues like the gut, muscles, and heart.
There are over 100 known neuropeptides, representing the largest and most diverse class of signaling molecules in the nervous system. Neuropeptides are synthesized from large precursor proteins which are cleaved and post-translationally processed then packaged into dense core vesicles. Neuropeptides are often co-released with other neuropeptides and neurotransmitters in a single neuron, yielding a multitude of effects. Once released, neuropeptides can diffuse widely to affect a broad range of targets.
Synthesis
Neuropeptides are synthesized from large, inactive precursor proteins called prepropeptides. Prepropeptides contain sequences for a family of distinct peptides and often contain repeated copies of the same peptides, depending on the organism. In addition to the precursor peptide sequences, prepropeptides also contain a signal peptide, spacer peptides, and cleavage sites. The signal peptide sequence guides the protein to the secretory pathway, starting at the endoplasmic reticulum. The signal peptide sequence is removed in the endoplasmic reticulum, yielding a propeptide. The propeptide travels to the Golgi apparatus where it is proteolytically cleaved and processed into multiple peptides. Peptides are packaged into dense core vesicles, where further cleaving and processing, such as C-terminal amidation, can occur. Dense core vesicles are transported throughout the neuron and can release peptides at the synaptic cleft, cell body, and along the axon.
Mechanism
Neuropeptides are released by dense core vesicles after depolarization of the cell. Compared to classical neurotransmitter signaling, neuropeptide signaling is more sensitive. Neuropeptide receptor affinity is in the nanomolar to micr |
https://en.wikipedia.org/wiki/Lyapunov%20equation | In control theory, the discrete Lyapunov equation (also known as Stein equation) is of the form
where is a Hermitian matrix and is the conjugate transpose of .
The continuous Lyapunov equation is of the form
.
The Lyapunov equation occurs in many branches of control theory, such as stability analysis and optimal control. This and related equations are named after the Russian mathematician Aleksandr Lyapunov.
Application to stability
In the following theorems , and and are symmetric. The notation means that the matrix is positive definite.
Theorem (continuous time version). Given any , there exists a unique satisfying if and only if the linear system is globally asymptotically stable. The quadratic function is a Lyapunov function that can be used to verify stability.
Theorem (discrete time version). Given any , there exists a unique satisfying if and only if the linear system is globally asymptotically stable. As before, is a Lyapunov function.
Computational aspects of solution
The Lyapunov equation is linear, and so if contains entries can be solved in time using standard matrix factorization methods.
However, specialized algorithms are available which can yield solutions much quicker owing to the specific structure of the Lyapunov equation. For the discrete case, the Schur method of Kitagawa is often used. For the continuous Lyapunov equation the Bartels–Stewart algorithm can be used.
Analytic solution
Defining the vectorization operator as stacking the columns of a matrix and as the Kronecker product of and , the continuous time and discrete time Lyapunov equations can be expressed as solutions of a matrix equation. Furthermore, if the matrix is "stable", the solution can also be expressed as an integral (continuous time case) or as an infinite sum (discrete time case).
Discrete time
Using the result that , one has
where is a conformable identity matrix and is the element-wise complex conjugate of . One may then solve for |
https://en.wikipedia.org/wiki/Windows%20NT%203.1 | Windows NT 3.1 is the first major release of the Windows NT operating system developed by Microsoft, released on July 27, 1993.
At the time of Windows NT's release, Microsoft's Windows 3.1 desktop environment had established brand recognition and market share; but Windows 3.1 relied on the DOS operating system for essential functions, and it had a constrictive 16-bit architecture. Windows NT, however, was a complete, 32-bit operating system that retained a desktop environment familiar to Windows 3.1 users.
By extending the Windows brand and beginning Windows NT at version 3.1, Microsoft implied that consumers should expect a familiar user experience. The name Windows NT ("New Technology") advertised that this was a re-engineered version of Windows.
Windows NT began as a rewrite of the OS/2 operating system, which Microsoft had co-developed with IBM in the 1980s. For several reasons, including the market success of Windows 3.0 in 1990, Microsoft decided to advance Windows rather than OS/2. They relinquished their OS/2 development responsibilities to IBM, and forked their work on OS/2 v3.0 into a competing operating system. Windows NT 3.1 sold about 300,000 copies before it was succeeded by Windows NT 3.5 in 1994.
Windows NT 3.1 was available in two editions: Windows NT 3.1 for workstations, and Windows NT 3.1 Advanced Server for servers. When these premiered, their sales were limited by high system requirements, and a general lack of 32-bit applications to take advantage of the OS's data processing capabilities.
On December 31, 2000, Microsoft declared Windows NT 3.1 obsolete and stopped providing support and updates for the system.
Development history
The origins of Windows NT date back to 1988, where Microsoft had a major foothold on the personal computer market due to the use of its MS-DOS as the operating system of IBM PC compatibles. Nathan Myhrvold, who had joined Microsoft after its acquisition of Dynamical Systems Research, identified two major threats |
https://en.wikipedia.org/wiki/Windows%20NT%203.5 | Windows NT 3.5 is a major release of the Windows NT operating system developed by Microsoft and oriented towards businesses. It was released on September 21, 1994, as the successor to Windows NT 3.1 and the predecessor to Windows NT 3.51.
One of the primary goals during Windows NT 3.5 development was to improve the operating system's performance. As a result, the project was codenamed "Daytona", after the Daytona International Speedway in Daytona Beach, Florida.
On December 31, 2001, Microsoft declared Windows NT 3.5 obsolete and stopped providing support and updates for the system.
Features
Windows NT 3.5 comes in two editions: NT Workstation and NT Server. They respectively replace the NT and NT Advanced Server editions of Windows NT 3.1. The Workstation edition allows only 10 concurrent clients to access the file server and does not support Mac clients.
Windows NT 3.5 includes integrated Winsock and TCP/IP support. (Its predecessor, Windows NT 3.1, only includes an incomplete implementation of TCP/IP based on the AT&T UNIX System V "STREAMS" API.) TCP/IP and IPX/SPX stacks in Windows NT 3.5 are rewritten. NetBIOS over TCP/IP (NetBT) support as a compatibility layer for TCP/IP was introduced as also the Microsoft DHCP and WINS clients and DHCP and WINS servers.
Windows NT 3.5 can share files via the File Transfer Protocol, and printers through the Line Printer Daemon protocol. It can act as a Gopher, HTTP, or WAIS server, and includes Remote Access Service for remote dial-up modem access to LAN services using either SLIP or PPP protocols. Windows NT 3.5 Resource Kit includes the first implementation of Microsoft DNS.
Other new features in Windows NT 3.5 include support for the VFAT file system, Object Linking and Embedding (OLE) version 2.0 and support for input/output completion ports. Microsoft updated the graphical user interface to be consistent with that of Windows for Workgroups 3.11. NT 3.5 shows performance improvements over NT 3.1, and requires less |
https://en.wikipedia.org/wiki/Windows%20NT%203.51 | Windows NT 3.51 is a major release of the Windows NT operating system developed by Microsoft and oriented towards businesses. It is the third version of Windows NT and was released on May 30, 1995, eight months following the release of Windows NT 3.5. The most significant enhancement offered in this release was that it provides client/server support for inter-operating with Windows 95, which was released almost three months after NT 3.51. Windows NT 4.0 became its successor a year later. Mainstream support for Windows NT 3.51 Workstation ended on December 31, 2000, and extended support ended on December 31, 2001, while Windows NT 3.51 Server mainstream support ended on September 30, 2000, followed by extended support on September 30, 2002. Both editions were succeeded by Windows NT 4.0 Workstation and Windows NT 4.0 Server, respectively.
Overview
The release of Windows NT 3.51 was dubbed "the PowerPC release" at Microsoft. The original intention was to release a PowerPC edition of NT 3.5, but according to Microsoft's David Thompson, "we basically sat around for 9 months fixing bugs while we waited for IBM to finish the Power PC hardware". Editions of NT 3.51 were also released for the x86, MIPS, and Alpha architectures.
New features introduced in Windows NT 3.51 include PCMCIA support, NTFS file compression, replaceable WinLogon (GINA), 3D support in OpenGL, persistent IP routes when using TCP/IP, automatic display of textual descriptions when the mouse pointer was placed on toolbar buttons ("tooltips") and support for Windows 95 common controls.
In view of the significant difference in the kernel base, Windows NT 3.51 is readily able to run a large number of Win32 applications designed for Windows 95. More recent 32-bit applications will not work, as the developers have prevented their application from working with any Windows version earlier than Windows 98, and also because some applications do not work properly with the older Windows NT 3.51 interface.
Despi |
https://en.wikipedia.org/wiki/List%20of%20defunct%20hard%20disk%20manufacturers | At least 223 companies have manufactured hard disk drives. Most of that industry has vanished through bankruptcy or mergers and acquisitions. None of the first four entrants continue in the industry today. Only three manufacturers have survived: Seagate, Toshiba and Western Digital (WD)—all of which grew at least in part through mergers and acquisitions.
Partial list of defunct manufacturers
Some of the defunct manufacturers include:
Alps America
Amcodyne
Ampex
Anelex Corp.
Areal Technology – acquired by Tomen Corp in 1993
Atasi Technology, Inc.
Aura Associates
Avatar Systems
BASF
Brand Technologies
Bryant Computer Products
Bull
Burroughs Corporation – merged with Sperry Corporation to form Unisys in 1986
C. Itoh Electronics
Castlewood Systems
Caelus Memories|Caelus Memories, Inc.
CalComp
Calluna Technologies
Cardiff
Century Data
Cogito
Comport
Computer Memories Inc. (CMI) – left industry in 1986
Computer Memory Devices, Inc.
Conner Peripherals – merged with Seagate in 1996
Control Data Corporation (CDC) / Imprimis Technology – sold hard disk drive business to Seagate in 1989
Cornice LLC – bankrupt in 2007
Data General
Data Products Corp.
Data Recording Instruments (DRI)
Data Tech Memories
Diablo Systems - became Diablo Data Systems in 1972
Digital Equipment Corporation (DEC) – sold hard disk drive business to Quantum Corporation in 1994
Disc Tech One
Disctron
DMA
DZU (of Bulgaria) – converted from government-owned to private, and sold to Videoton in 1999
Ecol. 2
Emulex
Epson
Espert
ExcelStor Technology – left industry
Fuji Electric
Fujitsu – HDD division acquired by Toshiba in July 2009
General Electric (GE)
Gigastorage
GS Magicstor, Inc. – manufacturing 1-inch drives
Hewlett-Packard (HP) - 1976 to 1996, left industry
Hitachi Global Storage Technologies (HGST) – 2002 merger of Hitachi and IBM disk drive businesses, sold to Western Digital in 2012 with part of 3.5″ manufacturing facilities going to Toshiba
Hokus |
https://en.wikipedia.org/wiki/Agent-based%20model | An agent-based model (ABM) is a computational model for simulating the actions and interactions of autonomous agents (both individual or collective entities such as organizations or groups) in order to understand the behavior of a system and what governs its outcomes. It combines elements of game theory, complex systems, emergence, computational sociology, multi-agent systems, and evolutionary programming. Monte Carlo methods are used to understand the stochasticity of these models. Particularly within ecology, ABMs are also called individual-based models (IBMs). A review of recent literature on individual-based models, agent-based models, and multiagent systems shows that ABMs are used in many scientific domains including biology, ecology and social science. Agent-based modeling is related to, but distinct from, the concept of multi-agent systems or multi-agent simulation in that the goal of ABM is to search for explanatory insight into the collective behavior of agents obeying simple rules, typically in natural systems, rather than in designing agents or solving specific practical or engineering problems.
Agent-based models are a kind of microscale model that simulate the simultaneous operations and interactions of multiple agents in an attempt to re-create and predict the appearance of complex phenomena. The process is one of emergence, which some express as "the whole is greater than the sum of its parts". In other words, higher-level system properties emerge from the interactions of lower-level subsystems. Or, macro-scale state changes emerge from micro-scale agent behaviors. Or, simple behaviors (meaning rules followed by agents) generate complex behaviors (meaning state changes at the whole system level).
Individual agents are typically characterized as boundedly rational, presumed to be acting in what they perceive as their own interests, such as reproduction, economic benefit, or social status, using heuristics or simple decision-making rules. ABM agents |
https://en.wikipedia.org/wiki/Derived%20category | In mathematics, the derived category D(A) of an abelian category A is a construction of homological algebra introduced to refine and in a certain sense to simplify the theory of derived functors defined on A. The construction proceeds on the basis that the objects of D(A) should be chain complexes in A, with two such chain complexes considered isomorphic when there is a chain map that induces an isomorphism on the level of homology of the chain complexes. Derived functors can then be defined for chain complexes, refining the concept of hypercohomology. The definitions lead to a significant simplification of formulas otherwise described (not completely faithfully) by complicated spectral sequences.
The development of the derived category, by Alexander Grothendieck and his student Jean-Louis Verdier shortly after 1960, now appears as one terminal point in the explosive development of homological algebra in the 1950s, a decade in which it had made remarkable strides. The basic theory of Verdier was written down in his dissertation, published finally in 1996 in Astérisque (a summary had earlier appeared in SGA 4½). The axiomatics required an innovation, the concept of triangulated category, and the construction is based on localization of a category, a generalization of localization of a ring. The original impulse to develop the "derived" formalism came from the need to find a suitable formulation of Grothendieck's coherent duality theory. Derived categories have since become indispensable also outside of algebraic geometry, for example in the formulation of the theory of D-modules and microlocal analysis. Recently derived categories have also become important in areas nearer to physics, such as D-branes and mirror symmetry.
Motivations
In coherent sheaf theory, pushing to the limit of what could be done with Serre duality without the assumption of a non-singular scheme, the need to take a whole complex of sheaves in place of a single dualizing sheaf became apparent |
https://en.wikipedia.org/wiki/Cytolysis | Cytolysis, or osmotic lysis, occurs when a cell bursts due to an osmotic imbalance that has caused excess water to diffuse into the cell. Water can enter the cell by diffusion through the cell membrane or through selective membrane channels called aquaporins, which greatly facilitate the flow of water. It occurs in a hypotonic environment, where water moves into the cell by osmosis and causes its volume to increase to the point where the volume exceeds the membrane's capacity and the cell bursts. The presence of a cell wall prevents the membrane from bursting, so cytolysis only occurs in animal and protozoa cells which do not have cell walls. The reverse process is plasmolysis.
In bacteria
Osmotic lysis would be expected to occur when bacterial cells are treated with a hypotonic solution with added lysozyme, which destroys the bacteria's cell walls.
Prevention
Different cells and organisms have adapted different ways of preventing cytolysis from occurring. For example, the paramecium uses a contractile vacuole, which rapidly pumps out excessive water to prevent the build-up of water and the otherwise subsequent lysis.
See also
Cell disruption
Crenation
Lysis
Osmotic pressure
Plasmolysis
Water intoxication
References
Cell biology
Membrane biology
Articles containing video clips |
https://en.wikipedia.org/wiki/N-gram | n-gram is a series of n adjacent letters (including punctuation marks and blanks), syllables, or rarely whole words found in a language dataset; or adjacent phonemes extracted from a speech-recording dataset, or adjacent base pairs extracted from a genome. They are collected from a text or speech corpus. If Latin numerical prefixes are used, then n-gram of size 1 is called a "unigram", size 2 a "bigram" (or, less commonly, a "digram") etc. If, instead of the Latin ones, the English cardinal numbers are furtherly used, then they are called "four-gram", "five-gram", etc. Similarly, using Greek numerical prefixes such as "monomer", "dimer", "trimer", "tetramer", "pentamer", etc., or English cardinal numbers, "one-mer", "two-mer", "three-mer", etc. are used in computational biology, for polymers or oligomers of a known size, called k-mers. When the items are words, -grams may also be called shingles.
Examples
Figure 1 shows several example sequences and the corresponding 1-gram, 2-gram and 3-gram sequences.
Here are further examples; these are word-level 3-grams and 4-grams (and counts of the number of times they appeared) from the Google n-gram corpus.
3-grams
ceramics collectables collectibles (55)
ceramics collectables fine (130)
ceramics collected by (52)
ceramics collectible pottery (50)
ceramics collectibles cooking (45)
4-grams
serve as the incoming (92)
serve as the incubator (99)
serve as the independent (794)
serve as the index (223)
serve as the indication (72)
serve as the indicator (120)
References
Further reading
Christopher D. Manning, Hinrich Schütze, Foundations of Statistical Natural Language Processing, MIT Press: 1999. .
Frederick J. Damerau, Markov Models and Linguistic Theory. Mouton. The Hague, 1971.
External links
Ngram Extractor: Gives weight of n-gram based on their frequency.
Google's Google Books n-gram viewer and Web n-grams database (September 2006)
STATOPERATOR N-grams Project Weighted n-gram viewer for eve |
https://en.wikipedia.org/wiki/Information%20leakage | Information leakage happens whenever a system that is designed to be closed to an eavesdropper reveals some information to unauthorized parties nonetheless. In other words: Information leakage occurs when secret information correlates with, or can be correlated with, observable information. For example, when designing an encrypted instant messaging network, a network engineer without the capacity to crack encryption codes could see when messages are transmitted, even if he could not read them.
Risk vectors
A modern example of information leakage is the leakage of secret information via data compression, by using variations in data compression ratio to reveal correlations between known (or deliberately injected) plaintext and secret data combined in a single compressed stream. Another example is the key leakage that can occur when using some public-key systems when cryptographic nonce values used in signing operations are insufficiently random. Bad randomness cannot protect proper functioning of a cryptographic system, even in a benign circumstance, it can easily produce crackable keys that cause key leakage.
Information leakage can sometimes be deliberate: for example, an algorithmic converter may be shipped that intentionally leaks small amounts of information, in order to provide its creator with the ability to intercept the users' messages, while still allowing the user to maintain an illusion that the system is secure. This sort of deliberate leakage is sometimes known as a subliminal channel.
Generally, only very advanced systems employ defenses against information leakage.
Following are the commonly implemented countermeasures :
Use steganography to hide the fact that a message is transmitted at all.
Use chaffing to make it unclear to whom messages are transmitted (but this does not hide from others the fact that messages are transmitted).
For busy re-transmitting proxies, such as a Mixmaster node: randomly delay and shuffle the order of outbound pack |
https://en.wikipedia.org/wiki/Symbolic%20method%20%28combinatorics%29 | In combinatorics, the symbolic method is a technique for counting combinatorial objects. It uses the internal structure of the objects to derive formulas for their generating functions. The method is mostly associated with Philippe Flajolet and is detailed in Part A of his book with Robert Sedgewick, Analytic Combinatorics, while the rest of the book explains how to use complex analysis in order to get asymptotic and probabilistic results on the corresponding generating functions.
During two centuries, generating functions were popping up via the corresponding recurrences on their coefficients (as can be seen in the seminal works of Bernoulli, Euler, Arthur Cayley, Schröder,
Ramanujan, Riordan, Knuth, , etc.).
It was then slowly realized that the generating functions were capturing many other facets of the initial discrete combinatorial objects, and that this could be done in a more direct formal way: The recursive nature of some combinatorial structures
translates, via some isomorphisms, into noteworthy identities on the corresponding generating functions.
Following the works of Pólya, further advances were thus done in this spirit in the 1970s with generic uses of languages for specifying combinatorial classes and their generating functions, as found in works by Foata and Schützenberger on permutations,
Bender and Goldman on prefabs, and Joyal on combinatorial species.
Note that this symbolic method in enumeration is unrelated to "Blissard's symbolic method", which is just another old name for umbral calculus.
The symbolic method in combinatorics constitutes the first step of many analyses of combinatorial structures,
which can then lead to fast computation schemes, to asymptotic properties and limit laws, to random generation, all of them being suitable to automatization via computer algebra.
Classes of combinatorial structures
Consider the problem of distributing objects given by a generating function into a set of n slots, where a permutation group |
https://en.wikipedia.org/wiki/Combinatorial%20class | In mathematics, a combinatorial class is a countable set of mathematical objects, together with a size function mapping each object to a non-negative integer, such that there are finitely many objects of each size.
Counting sequences and isomorphism
The counting sequence of a combinatorial class is the sequence of the numbers of elements of size i for i = 0, 1, 2, ...; it may also be described as a generating function that has these numbers as its coefficients. The counting sequences of combinatorial classes are the main subject of study of enumerative combinatorics. Two combinatorial classes are said to be isomorphic if they have the same numbers of objects of each size, or equivalently, if their counting sequences are the same. Frequently, once two combinatorial classes are known to be isomorphic, a bijective proof of this equivalence is sought; such a proof may be interpreted as showing that the objects in the two isomorphic classes are cryptomorphic to each other.
For instance, the triangulations of regular polygons (with size given by the number of sides of the polygon, and a fixed choice of polygon to triangulate for each size) and the set of unrooted binary plane trees (up to graph isomorphism, with a fixed ordering of the leaves, and with size given by the number of leaves) are both counted by the Catalan numbers, so they form isomorphic combinatorial classes. A bijective isomorphism in this case is given by planar graph duality: a triangulation can be transformed bijectively into a tree with a leaf for each polygon edge, an internal node for each triangle, and an edge for each two (polygon edges?) or triangles that are adjacent to each other.
Analytic combinatorics
The theory of combinatorial species and its extension to analytic combinatorics provide a language for describing many important combinatorial classes, constructing new classes from combinations of previously defined ones, and automatically deriving their counting sequences. For example, two c |
https://en.wikipedia.org/wiki/Comparison%20of%20cross-platform%20instant%20messaging%20clients | The landscape for instant messaging involves cross-platform instant messaging clients that can handle one or multiple protocols. Clients that use the same protocol can typically federate and talk to one another. The following table compares general and technical information for cross-platform instant messaging clients in active development, each of which have their own article that provide further information.
General
Operating system support
Connectivity
Privacy
Some messaging services that are not designed for privacy require a unique phone number for sign-up, as a form of identity verification and to prevent users from creating multiple accounts.
Some messaging services that do not solely focus on a mobile-first experience, or enforce SMS authentication, may allow email addresses to be used for sign-up instead.
Some messaging services offer greater flexibility and privacy, by allowing users to create more than one account to compartmentalize personal & work purposes, or not requiring personally identifiable information for sign-up.
To find out if the software has end-to-end encryption, see "media" table below.
1: Apple iOS doesn't allow screenshot protection.
Message handling
Media
Miscellaneous
Messaging services can operate around different models, based on security and accessibility considerations.
A mobile-focused, phone number-based model operates on the concept of primary and secondary devices. Examples of such messaging services include: WhatsApp, Viber, Line, WeChat, Signal, etc. The primary device is a mobile phone and is required to login and send/receive messages. Only one mobile phone is allowed to be the primary device, as attempting to login to the messaging app on another mobile phone would trigger the previous phone to be logged out. The secondary device is a computer running a desktop operating system, which serves as a companion for the primary device. Desktop messaging clients on secondary devices do not function independently, a |
https://en.wikipedia.org/wiki/List%20of%20genetics%20research%20organizations | This is a list of organizations involved in genetics research.
Africa
Kenya
International Livestock Research Institute (ILRI), Nairobi
Namibia
The Life Technologies Conservation Genetics Laboratory (Cheetah Conservation Fund), Otjiwarongo
Asia
Pakistan
IBGE
Institute of Biomedical and Genetic Engineering
China
BGI Group
Chinese National Human Genome Center
India
Institute of Genomics and Integrative Biology
DNA Labs India
Iran
Royan Institute
Philippines
Philippine Genome Center
International Rice Research Institute
Singapore
Genome Institute of Singapore
Institute of Molecular and Cell Biology
Taiwan
National Health Research Institutes
Japan
National Institute of Genetics
Okinawa Institute of Science and Technology
RIKEN
Europe
Germany
Max Planck Institute for Molecular Genetics
Italy
Bioversity International
Sweden
Science for Life Laboratory
United Kingdom
The Genome Analysis Centre
Wellcome Sanger Institute
Wellcome Centre for Human Genetics (University of Oxford)
Russia
Research Centre for Medical Genetics (RCMG), Moscow
North America
Canada
The Centre for Applied Genomics (University of Toronto)
United States
Arizona
Translational Genomics Research Institute
California
Clear Labs
Genetic Information Research Institute
Joint Genome Institute (U.S. Department of Energy)
Salk Institute for Biological Studies
Illinois
Carl R. Woese Institute for Genomic Biology (University of Illinois, Urbana-Champaign)
Maine
The Jackson Laboratory
Maryland
Howard Hughes Medical Institute
J. Craig Venter Institute
Kennedy Krieger Institute
National Human Genome Research Institute
USC Institute Of Translational Genomics
Massachusetts
Broad Institute (Massachusetts Institute of Technology and Harvard University)
Dana–Farber Cancer Institute
Whitehead Institute for Biomedical Research (Massachusetts Institute of Technology)
Missouri
McDonnell Genome Institute (Washington University in St. Louis)
New Mexico
National Center for Genome Resources
New York
Cold Sprin |
https://en.wikipedia.org/wiki/Food%20browning | Browning is the process of food turning brown due to the chemical reactions that take place within. The process of browning is one of the chemical reactions that take place in food chemistry and represents an interesting research topic regarding health, nutrition, and food technology. Though there are many different ways food chemically changes over time, browning in particular falls into two main categories: enzymatic versus non-enzymatic browning processes.
Browning has many important implications on the food industry relating to nutrition, technology, and economic cost. Researchers are especially interested in studying the control (inhibition) of browning and the different methods that can be employed to maximize this inhibition and ultimately prolong the shelf life of food.
Enzymatic browning
Enzymatic browning is one of the most important reactions that takes place in most fruits and vegetables as well as in seafood. These processes affect the taste, color, and value of such foods. Generally, it is a chemical reaction involving polyphenol oxidase (PPO), catechol oxidase, and other enzymes that create melanins and benzoquinone from natural phenols. Enzymatic browning (also called oxidation of foods) requires exposure to oxygen. It begins with the oxidation of phenols by polyphenol oxidase into quinones, whose strong electrophilic state causes high susceptibility to a nucleophilic attack from other proteins. These quinones are then polymerized in a series of reactions, eventually resulting in the formation of brown pigments (melanosis) on the surface of the food. The rate of enzymatic browning is reflected by the amount of active polyphenol oxidases present in the food. Hence, most research into methods of preventing enzymatic browning has been directed towards inhibiting polyphenol oxidase activity. However, not all browning of food produces negative effects.
Examples of beneficial enzymatic browning:
Developing color and flavor in coffee, cocoa beans, a |
https://en.wikipedia.org/wiki/Salomon%20Bochner | Salomon Bochner (20 August 1899 – 2 May 1982) was an Austrian mathematician, known for work in mathematical analysis, probability theory and differential geometry.
Life
He was born into a Jewish family in Podgórze (near Kraków), then Austria-Hungary, now Poland. Fearful of a Russian invasion in Galicia at the beginning of World War I in 1914, his family moved to Germany, seeking greater security. Bochner was educated at a Berlin gymnasium (secondary school), and then at the University of Berlin. There, he was a student of Erhard Schmidt, writing a dissertation involving what would later be called the Bergman kernel. Shortly after this, he left the academy to help his family during the escalating inflation. After returning to mathematical research, he lectured at the University of Munich from 1924 to 1933. His academic career in Germany ended after the Nazis came to power in 1933, and he left for a position at Princeton University. He was a visiting scholar at the Institute for Advanced Study in 1945-48. He was appointed as Henry Burchard Fine Professor in 1959, retiring in 1968. Although he was seventy years old when he retired from Princeton, Bochner was appointed as Edgar Odell Lovett Professor of Mathematics at Rice University and went on to hold this chair until his death in 1982. He became Head of Department at Rice in 1969 and held this position until 1976. He died in Houston, Texas. He was an Orthodox Jew.
Mathematical work
In 1925 he started work in the area of almost periodic functions, simplifying the approach of Harald Bohr by use of compactness and approximate identity arguments. In 1933 he defined the Bochner integral, as it is now called, for vector-valued functions. Bochner's theorem on Fourier transforms appeared in a 1932 book. His techniques came into their own as Pontryagin duality and then the representation theory of locally compact groups developed in the following years.
Subsequently, he worked on multiple Fourier series, posing the questi |
https://en.wikipedia.org/wiki/Gram%20matrix | In linear algebra, the Gram matrix (or Gramian matrix, Gramian) of a set of vectors in an inner product space is the Hermitian matrix of inner products, whose entries are given by the inner product . If the vectors are the columns of matrix then the Gram matrix is in the general case that the vector coordinates are complex numbers, which simplifies to for the case that the vector coordinates are real numbers.
An important application is to compute linear independence: a set of vectors are linearly independent if and only if the Gram determinant (the determinant of the Gram matrix) is non-zero.
It is named after Jørgen Pedersen Gram.
Examples
For finite-dimensional real vectors in with the usual Euclidean dot product, the Gram matrix is , where is a matrix whose columns are the vectors and is its transpose whose rows are the vectors . For complex vectors in , , where is the conjugate transpose of .
Given square-integrable functions on the interval , the Gram matrix is:
where is the complex conjugate of .
For any bilinear form on a finite-dimensional vector space over any field we can define a Gram matrix attached to a set of vectors by . The matrix will be symmetric if the bilinear form is symmetric.
Applications
In Riemannian geometry, given an embedded -dimensional Riemannian manifold and a parametrization for the volume form on induced by the embedding may be computed using the Gramian of the coordinate tangent vectors: This generalizes the classical surface integral of a parametrized surface for :
If the vectors are centered random variables, the Gramian is approximately proportional to the covariance matrix, with the scaling determined by the number of elements in the vector.
In quantum chemistry, the Gram matrix of a set of basis vectors is the overlap matrix.
In control theory (or more generally systems theory), the controllability Gramian and observability Gramian determine properties of a linear system.
Gramian matrice |
https://en.wikipedia.org/wiki/Data%20logger | A data logger (also datalogger or data recorder) is an electronic device that records data over time or about location either with a built-in instrument or sensor or via external instruments and sensors. Increasingly, but not entirely, they are based on a digital processor (or computer), and called digital data loggers (DDL). They generally are small, battery-powered, portable, and equipped with a microprocessor, internal memory for data storage, and sensors. Some data loggers interface with a personal computer and use software to activate the data logger and view and analyze the collected data, while others have a local interface device (keypad, LCD) and can be used as a stand-alone device.
Data loggers vary from general-purpose types for a range of measurement applications to very specific devices for measuring in one environment or application type only. It is common for general purpose types to be programmable; however, many remain as static machines with only a limited number or no changeable parameters. Electronic data loggers have replaced chart recorders in many applications.
One of the primary benefits of using data loggers is the ability to automatically collect data on a 24-hour basis. Upon activation, data loggers are typically deployed and left unattended to measure and record information for the duration of the monitoring period. This allows for a comprehensive, accurate picture of the environmental conditions being monitored, such as air temperature and relative humidity.
The cost of data loggers has been declining over the years as technology improves and costs are reduced. Simple single-channel data loggers cost as little as $25. More complicated loggers may cost hundreds or thousands of dollars.
Data formats
Standardization of protocols and data formats has been a problem but is now growing in the industry and XML, JSON, and YAML are increasingly being adopted for data exchange. The development of the Semantic Web and the Internet of Things i |
https://en.wikipedia.org/wiki/Polygon%20mesh | In 3D computer graphics and solid modeling, a polygon mesh is a collection of , s and s that defines the shape of a polyhedral object. The faces usually consist of triangles (triangle mesh), quadrilaterals (quads), or other simple convex polygons (n-gons), since this simplifies rendering, but may also be more generally composed of concave polygons, or even polygons with holes.
The study of polygon meshes is a large sub-field of computer graphics (specifically 3D computer graphics) and geometric modeling. Different representations of polygon meshes are used for different applications and goals. The variety of operations performed on meshes may include: Boolean logic (Constructive solid geometry), smoothing, simplification, and many others. Algorithms also exist for ray tracing, collision detection, and rigid-body dynamics with polygon meshes. If the mesh's edges are rendered instead of the faces, then the model becomes a wireframe model.
Volumetric meshes are distinct from polygon meshes in that they explicitly represent both the surface and volume of a structure, while polygon meshes only explicitly represent the surface (the volume is implicit).
Several methods exist for mesh generation, including the marching cubes algorithm.
Elements
Objects created with polygon meshes must store different types of elements. These include vertices, edges, faces, polygons and surfaces. In many applications, only vertices, edges and either faces or polygons are stored. A renderer may support only 3-sided faces, so polygons must be constructed of many of these, as shown above. However, many renderers either support quads and higher-sided polygons, or are able to convert polygons to triangles on the fly, making it unnecessary to store a mesh in a triangulated form.
Representations
Polygon meshes may be represented in a variety of ways, using different methods to store the vertex, edge and face data. These include:
Each of the representations above have particular |
https://en.wikipedia.org/wiki/English%20Electric%20DEUCE | The DEUCE (Digital Electronic Universal Computing Engine) was one of the earliest British commercially available computers, built by English Electric from 1955. It was the production version of the Pilot ACE, itself a cut-down version of Alan Turing's ACE.
Hardware description
The DEUCE had 1450 thermionic valves, and used mercury delay lines for its main memory; each of the 12 delay lines could store 32 instructions or data words of 32 bits each. It adopted the then high 1 megahertz clock rate of the Pilot ACE. Input/output was via Hollerith 80-column punch-card equipment. The reader read cards at the rate of 200 per minute, while the card punch rate was 100 cards per minute. The DEUCE also had an 8192-word magnetic drum for main storage. To access any of the 256 tracks of 32 words, the drum had one group of 16 read and one group of 16 write heads, each group on independent moveable arms, each capable of moving to one of 16 positions. Access time was 15 milliseconds if the heads were already in position; an additional 35 milliseconds was required if the heads had to be moved. There was no rotational delay incurred when reading from and writing to drum. Data was transferred between the drum and one of the 32-word delay lines.
The DEUCE could be fitted with paper tape equipment; the reader speed was 850 characters per second, while the paper tape output speed was 25 characters per second. (The DEUCE at the University of New South Wales {UTECOM} had a Siemens M100 teleprinter attached in 1964, giving 10 characters per second input/output). Decca magnetic tape units could also be attached. The automatic multiplier and divider operated asynchronously (that is, other instructions could be executed while the multiplier/divider unit was in operation). Two arithmetic units were provided for integer operations: one of 32 bits and another capable of performing 32-bit operations and 64-bit operations. Auto-increment and auto-decrement were provided on eight registers fro |
https://en.wikipedia.org/wiki/Automatic%20Computing%20Engine | The Automatic Computing Engine (ACE) was a British early electronic serial stored-program computer design by Alan Turing. Turing completed the ambitious design in late 1945, having had experience in the years prior with the secret Colossus computer at Bletchley Park.
The ACE was not built, but a smaller version, the Pilot ACE, was constructed at the National Physical Laboratory and became operational in 1950. A larger implementation of the ACE design was the MOSAIC computer which became operational in 1955. ACE also led to the Bendix G-15 and other computers.
Background
The project was managed by John R. Womersley, superintendent of the Mathematics Division of the National Physical Laboratory (NPL). The use of the word Engine was in homage to Charles Babbage and his Difference Engine and Analytical Engine. Turing's technical design Proposed Electronic Calculator was the product of his theoretical work in 1936 "On Computable Numbers" and his wartime experience at Bletchley Park where the Colossus computers had been successful in breaking German military codes. In his 1936 paper, Turing described his idea as a "universal computing machine", but it is now known as the Universal Turing machine.
Turing was sought by Womersley to work in the NPL on the ACE project; he accepted and began work on 1 October 1945 and by the end of the year he completed his outline of his 'Proposed electronic calculator', which was the first reasonably complete design of a stored-program computer and, apart from being on a much larger scale than the final working machine, anticipated the final realisation in most important respects. However, because of the strict and long-lasting secrecy around the Bletchley Park work, he was prohibited (because of the Official Secrets Act) from explaining that he knew that his ideas could be implemented in an electronic device. The better-known EDVAC design presented in the First Draft of a Report on the EDVAC (dated 30 June 1945), by John von Neumann, |
https://en.wikipedia.org/wiki/Residue%20number%20system | A residue numeral system (RNS) is a numeral system representing integers by their values modulo several pairwise coprime integers called the moduli. This representation is allowed by the Chinese remainder theorem, which asserts that, if is the product of the moduli, there is, in an interval of length , exactly one integer having any given set of modular values. The arithmetic of a residue numeral system is also called multi-modular arithmetic.
Multi-modular arithmetic is widely used for computation with large integers, typically in linear algebra, because it provides faster computation than with the usual numeral systems, even when the time for converting between numeral systems is taken into account. Other applications of multi-modular arithmetic include polynomial greatest common divisor, Gröbner basis computation and cryptography.
Definition
A residue numeral system is defined by a set of integers
called the moduli, which are generally supposed to be pairwise coprime (that is, any two of them have a greatest common divisor equal to one). Residue number systems have been defined for non-coprime moduli, but are not commonly used because of worse properties. Therefore, they will not be considered in the remainder of this article.
An integer is represented in the residue numeral system by the set of its remainders
under Euclidean division by the moduli. That is
and
for every
Let be the product of all the . Two integers whose difference is a multiple of have the same representation in the residue numeral system defined by the s. More precisely, the Chinese remainder theorem asserts that each of the different sets of possible residues represents exactly one residue class modulo . That is, each set of residues represents exactly one integer in the interval . For signed numbers, the dynamic range is
(when is even, generally an extra negative value is represented).
Arithmetic operations
For adding, subtracting and multiplying numbers represented in a |
https://en.wikipedia.org/wiki/The%20Free%20Dictionary | The Free Dictionary is an American online dictionary and encyclopedia that aggregates information from various sources. It is accessible in fourteen languages.
History
The Free Dictionary was launched in 2005 by Farlex. In the same year, it was included in PCMag's Make Your Browser Better list.
Content
The site cross-references the contents of dictionaries such as The American Heritage Dictionary of the English Language, the Collins English Dictionary; encyclopedias such as the Columbia Encyclopedia, the Computer Desktop Encyclopedia, the Hutchinson Encyclopedia (subscription), and Wikipedia; book publishers such as McGraw-Hill, Houghton Mifflin, HarperCollins, as well as the Acronym Finder database, several financial dictionaries, legal dictionaries, and other content.
It has a feature that allows a user to preview an article while positioning the mouse cursor over a link. One can also double-click on any word to look it up in the dictionary. The website has sections such as Spelling Bee, Word Pronunciation, My Word List, and Match Up.
It is available as a mobile app called "Dictionary app by Farlex".
Wikipedia Mirror
Wikipedia content is hosted at the sub-domain encyclopedia.thefreedictionary.com, which is excluded from search-engine indexing in its entirety by Farlex with the use of meta tags. This is done to avoid duplicate content in the search-engine results and prevent user traffic that would otherwise go to Wikipedia.
Farlex
The site is run by Farlex, Inc., located in Huntingdon Valley, Pennsylvania.
Farlex also maintains a companion title, The Free Library, an online library of out-of-copyright classic books as well as a collection of periodicals of over four million articles dating back to 1984, and definition-of.com, a community dictionary of slang and other terms.
The Free LibraryThe Free Library has a separate homepage. It is a free reference website that offers full-text versions of classic literary works by hundreds of authors. It is also a ne |
https://en.wikipedia.org/wiki/Streaming%20television | Streaming television is the digital distribution of television content, such as television shows and films, as streaming media delivered over the Internet. Streaming television stands in contrast to dedicated terrestrial television delivered by over-the-air aerial systems, cable television, and/or satellite television systems.
History
Up until the 1990s, it was not thought possible that a television show could be squeezed into the limited telecommunication bandwidth of a copper telephone cable to provide a streaming service of acceptable quality, as the required bandwidth of a digital television signal was around 200Mbit/s, which was 2,000 times greater than the bandwidth of a speech signal over a copper telephone wire.
Streaming services started as a result of two major technological developments: MPEG (motion-compensated DCT) video compression and asymmetric digital subscriber line (ADSL) data communication.
The first worldwide live-streaming event was a radio live broadcast of a baseball game between the Seattle Mariners and the New York Yankees streamed by ESPN SportsZone on September 5, 1995. During the mid-2000s, the streaming media was based on UDP, whereas the basis of the majority of the Internet was HTTP and content delivery networks (CDNs). In 2007, HTTP-based adaptive streaming was introduced by Move Networks. This new technology would be a significant change for the industry. One year later the introduction of HTTP-based adaptive streaming, many companies such as Microsoft and Netflix developed their streaming technology. In 2009, Apple launched HTTP Live Streaming (HLS), and Adobe, in 2010, HTTP Dynamic Streaming (HDS). In addition, HTTP-based adaptive streaming was chosen for important streaming events such as Roland Garros, Wimbledon, Vancouver and London Olympic Games, and many others and on premium on-demand services (Netflix, Amazon Instant Video, etc.). The increase in streaming services required a new standardization, therefore in 2012, wit |
https://en.wikipedia.org/wiki/Software%20requirements%20specification | A software requirements specification (SRS) is a description of a software system to be developed. It is modeled after the business requirements specification (CONOPS). The software requirements specification lays out functional and non-functional requirements, and it may include a set of use cases that describe user interactions that the software must provide to the user for perfect interaction.
Software requirements specifications establish the basis for an agreement between customers and contractors or suppliers on how the software product should function (in a market-driven project, these roles may be played by the marketing and development divisions). Software requirements specification is a rigorous assessment of requirements before the more specific system design stages, and its goal is to reduce later redesign. It should also provide a realistic basis for estimating product costs, risks, and schedules. Used appropriately, software requirements specifications can help prevent software project failure.
The software requirements specification document lists sufficient and necessary requirements for the project development. To derive the requirements, the developer needs to have a clear and thorough understanding of the products under development. This is achieved through detailed and continuous communications with the project team and customer throughout the software development process.
The SRS may be one of a contract's deliverable data item descriptions or have other forms of organizationally-mandated content.
Typically a SRS is written by a technical writer, a systems architect, or a software programmer.
Structure
An example organization of an SRS is as follows:
Purpose
Definitions
Background
System overview
References
Overall description
Product perspective
System Interfaces
User interfaces
Hardware interfaces
Software interfaces
Communication Interfaces
Memory constraints
Design constraints
Operations
Site adaptation requirements
Product functi |
https://en.wikipedia.org/wiki/Ubuntu | Ubuntu ( ) is a Linux distribution based on Debian and composed mostly of free and open-source software. Ubuntu is officially released in multiple editions: Desktop, Server, and Core for Internet of things devices and robots. All of the editions can run on a computer alone, or in a virtual machine. Ubuntu is a popular operating system for cloud computing, with support for OpenStack.
An upgrade to Ubuntu is released every six months, with long-term support (LTS) releases every two years. , the most-recent release is 23.10 ("Mantic Minotaur"), and the current long-term support release is 22.04 ("Jammy Jellyfish").
Ubuntu is developed by the British company Canonical, and a community of other developers, under a meritocratic governance model. Canonical provides security updates and support for each Ubuntu release, starting from the release date until the release reaches its designated end-of-life (EOL) date. Canonical generates revenue through the sale of premium services related to Ubuntu and donations from those who download the Ubuntu software.
Ubuntu is named after the Nguni philosophy of , which Canonical indicates means "humanity to others" with a connotation of "I am what I am because of who we all are".
Ubuntu is also supported by Microsoft, in Windows 10 and 11, by enabling WSL (or WSLg for GUI applications).
Background
Ubuntu is built on Debian's architecture and infrastructure, and comprises Linux server, desktop and discontinued phone and tablet operating system versions. Ubuntu releases updated versions predictably every six months, and each release receives free support for nine months (eighteen months prior to 13.04) with security fixes, high-impact bug fixes and conservative, substantially beneficial low-risk bug fixes. The first release was in October 2004.
Current long-term support (LTS) releases are supported for five years, and are released every two years. Since the release of Ubuntu 6.06, every fourth release receives long-term support. Lo |
https://en.wikipedia.org/wiki/List%20of%20former%20IA-32%20compatible%20processor%20manufacturers | As the 32-bit Intel Architecture became the dominant computing platform during the 1980s and 1990s, multiple companies have tried to build microprocessors that are compatible with that Intel instruction set architecture. Most of these companies were not successful in the mainstream computing market. So far, only AMD has had any market presence in the computing market for more than a couple of product generations. Cyrix was successful during the 386 and 486 generations of products, but did not do well after the Pentium was introduced.
List of former IA-32 compatible microprocessor vendors:
Progressed into surviving companies
Centaur Technology – originally subsidiary of IDT, later acquired by VIA Technologies, still producing compatible low-end devices for VIA
Cyrix – acquired by National Semiconductor, later acquired by VIA Technologies, eventually shut down
NexGen – bought by AMD to help develop the successful K6 device
National Semiconductor – low-end 486 (designed in-house) never widely sold; first acquirer of Cyrix, later keeping only low-end IA-32 devices targeted for consumer System-on-a-chips, finally selling them to AMD
Product discontinued/transformed
Harris Corporation – sold radiation-hardened versions of the 8086 and 80286; product line discontinued. Produced 20 MHz and 25 MHz 80286s (some motherboards were equipped with cache memory, which was unusual for 80286 processors).
NEC – sold processors, such as NEC V20 and NEC V30, that were compatible with early Intel 16-bit architectures; product line transitioned to NEC-designed architectures.
Siemens – sold versions of the 8086 and 80286; product line discontinued.
VM Technology – developed VM860 (8086-compatible processor) and VM8600SP (386-compatible processor) for the Japanese market.
Left the market or closed
Chips and Technologies – left market after failed 386 compatible chip failed to boot the Windows operating system
IBM – Cyrix licensee and developer of Blue Lightning 486 line of pro |
https://en.wikipedia.org/wiki/Lindenbaum%E2%80%93Tarski%20algebra | In mathematical logic, the Lindenbaum–Tarski algebra (or Lindenbaum algebra) of a logical theory T consists of the equivalence classes of sentences of the theory (i.e., the quotient, under the equivalence relation ~ defined such that p ~ q exactly when p and q are provably equivalent in T). That is, two sentences are equivalent if the theory T proves that each implies the other. The Lindenbaum–Tarski algebra is thus the quotient algebra obtained by factoring the algebra of formulas by this congruence relation.
The algebra is named for logicians Adolf Lindenbaum and Alfred Tarski.
Starting in the academic year 1926-1927, Lindenbaum pioneered his method in Jan Łukasiewicz's mathematical logic seminar, and the method was popularized and generalized in subsequent decades through work
by Tarski.
The Lindenbaum–Tarski algebra is considered the origin of the modern algebraic logic.
Operations
The operations in a Lindenbaum–Tarski algebra A are inherited from those in the underlying theory T. These typically include conjunction and disjunction, which are well-defined on the equivalence classes. When negation is also present in T, then A is a Boolean algebra, provided the logic is classical. If the theory T consists of the propositional tautologies, the Lindenbaum–Tarski algebra is the free Boolean algebra generated by the propositional variables.
Related algebras
Heyting algebras and interior algebras are the Lindenbaum–Tarski algebras for intuitionistic logic and the modal logic S4, respectively.
A logic for which Tarski's method is applicable, is called algebraizable. There are however a number of logics where this is not the case, for instance the modal logics S1, S2, or S3, which lack the rule of necessitation (⊢φ implying ⊢□φ), so ~ (defined above) is not a congruence (because ⊢φ→ψ does not imply ⊢□φ→□ψ). Another type of logic where Tarski's method is inapplicable is relevance logics, because given two theorems an implication from one to the other may not it |
https://en.wikipedia.org/wiki/Interior%20algebra | In abstract algebra, an interior algebra is a certain type of algebraic structure that encodes the idea of the topological interior of a set. Interior algebras are to topology and the modal logic S4 what Boolean algebras are to set theory and ordinary propositional logic. Interior algebras form a variety of modal algebras.
Definition
An interior algebra is an algebraic structure with the signature
⟨S, ·, +, ′, 0, 1, I⟩
where
⟨S, ·, +, ′, 0, 1⟩
is a Boolean algebra and postfix I designates a unary operator, the interior operator, satisfying the identities:
xI ≤ x
xII = xI
(xy)I = xIyI
1I = 1
xI is called the interior of x.
The dual of the interior operator is the closure operator C defined by xC = ((x′)I)′. xC is called the closure of x. By the principle of duality, the closure operator satisfies the identities:
xC ≥ x
xCC = xC
(x + y)C = xC + yC
0C = 0
If the closure operator is taken as primitive, the interior operator can be defined as xI = ((x′)C)′. Thus the theory of interior algebras may be formulated using the closure operator instead of the interior operator, in which case one considers closure algebras of the form ⟨S, ·, +, ′, 0, 1, C⟩, where ⟨S, ·, +, ′, 0, 1⟩ is again a Boolean algebra and C satisfies the above identities for the closure operator. Closure and interior algebras form dual pairs, and are paradigmatic instances of "Boolean algebras with operators." The early literature on this subject (mainly Polish topology) invoked closure operators, but the interior operator formulation eventually became the norm following the work of Wim Blok.
Open and closed elements
Elements of an interior algebra satisfying the condition xI = x are called open. The complements of open elements are called closed and are characterized by the condition xC = x. An interior of an element is always open and the closure of an element is always closed. Interiors of closed elements are called regular open and closures of open elements are called regular clos |
https://en.wikipedia.org/wiki/Openswan | In the field of computer security, Openswan provides a complete IPsec implementation for Linux and FreeBSD.
Openswan, begun as a fork of the now-defunct FreeS/WAN project, continues to use the GNU General Public License. Unlike the FreeS/WAN project, it does not exclusively target the Linux operating system.
Libreswan forked from Openswan in 2012.
See also
Libreswan
strongSwan
External links
References
Virtual private networks
Software forks
Free security software
Cryptographic protocols
IPsec |
https://en.wikipedia.org/wiki/Norm%20%28mathematics%29 | In mathematics, a norm is a function from a real or complex vector space to the non-negative real numbers that behaves in certain ways like the distance from the origin: it commutes with scaling, obeys a form of the triangle inequality, and is zero only at the origin. In particular, the Euclidean distance in a Euclidean space is defined by a norm on the associated Euclidean vector space, called the Euclidean norm, the 2-norm, or, sometimes, the magnitude of the vector. This norm can be defined as the square root of the inner product of a vector with itself.
A seminorm satisfies the first two properties of a norm, but may be zero for vectors other than the origin. A vector space with a specified norm is called a normed vector space. In a similar manner, a vector space with a seminorm is called a seminormed vector space.
The term pseudonorm has been used for several related meanings. It may be a synonym of "seminorm".
A pseudonorm may satisfy the same axioms as a norm, with the equality replaced by an inequality "" in the homogeneity axiom.
It can also refer to a norm that can take infinite values, or to certain functions parametrised by a directed set.
Definition
Given a vector space over a subfield of the complex numbers a norm on is a real-valued function with the following properties, where denotes the usual absolute value of a scalar :
Subadditivity/Triangle inequality: for all
Absolute homogeneity: for all and all scalars
Positive definiteness/positiveness/: for all if then
Because property (2.) implies some authors replace property (3.) with the equivalent condition: for every if and only if
A seminorm on is a function that has properties (1.) and (2.) so that in particular, every norm is also a seminorm (and thus also a sublinear functional). However, there exist seminorms that are not norms. Properties (1.) and (2.) imply that if is a norm (or more generally, a seminorm) then and that also has the following property:
Non-neg |
https://en.wikipedia.org/wiki/Dynamical%20systems%20theory | Dynamical systems theory is an area of mathematics used to describe the behavior of complex dynamical systems, usually by employing differential equations or difference equations. When differential equations are employed, the theory is called continuous dynamical systems. From a physical point of view, continuous dynamical systems is a generalization of classical mechanics, a generalization where the equations of motion are postulated directly and are not constrained to be Euler–Lagrange equations of a least action principle. When difference equations are employed, the theory is called discrete dynamical systems. When the time variable runs over a set that is discrete over some intervals and continuous over other intervals or is any arbitrary time-set such as a Cantor set, one gets dynamic equations on time scales. Some situations may also be modeled by mixed operators, such as differential-difference equations.
This theory deals with the long-term qualitative behavior of dynamical systems, and studies the nature of, and when possible the solutions of, the equations of motion of systems that are often primarily mechanical or otherwise physical in nature, such as planetary orbits and the behaviour of electronic circuits, as well as systems that arise in biology, economics, and elsewhere. Much of modern research is focused on the study of chaotic systems.
This field of study is also called just dynamical systems, mathematical dynamical systems theory or the mathematical theory of dynamical systems.
Overview
Dynamical systems theory and chaos theory deal with the long-term qualitative behavior of dynamical systems. Here, the focus is not on finding precise solutions to the equations defining the dynamical system (which is often hopeless), but rather to answer questions like "Will the system settle down to a steady state in the long term, and if so, what are the possible steady states?", or "Does the long-term behavior of the system depend on its initial condition?" |
https://en.wikipedia.org/wiki/Dedicated%20short-range%20communications | Dedicated short-range communications (DSRC) is a technology for direct wireless exchange of vehicle-to-everything (V2X) and other intelligent transportation systems (ITS) data between vehicles, other road users (pedestrians, cyclists, etc.), and roadside infrastructure (traffic signals, electronic message signs, etc.). DSRC, which can be used for both one- and two-way data exchanges, uses channels in the licensed 5.9 GHz band. DSRC is based on IEEE 802.11p.
History
In October 1999, the United States Federal Communications Commission (FCC) allocated 75 MHz of spectrum in the 5.9 GHz band for DSRC-based ITS uses. By 2003, DSRC was used in Europe and Japan for electronic toll collection. In August 2008, the European Telecommunications Standards Institute (ETSI) allocated 30 MHz of spectrum in the 5.9 GHz band for ITS.
In November 2020, the FCC reallocated the lower 45 MHz of the 75 MHz spectrum to the neighboring 5.8 GHz ISM band for unlicensed non-ITS uses, citing DSRC's lack of adoption. Of the 30 MHz that remained for licensed ITS uses, 10 MHz was kept for DSRC (Channel 180, 5.895–5.905 GHz) and 20 MHz was reserved for a successor to DSRC, LTE-CV2X (Channel 183, 5.905–5.925 GHz).
Applications
Singapore's Electronic Road Pricing scheme plans to use DSRC technology for road use measurement (ERP2) to replace its ERP1 overhead gantry method.
In June 2017, the Utah Department of Transportation and the Utah Transit Authority (UTA) demonstrated the use of DSRC for transit signal priority on SR-68 (Redwood Road) in Salt Lake City, whereby several UTA transit buses equipped with DSRC equipment could request changes to signal timing if they were running behind schedule.
Other applications include:
Emergency warning system for vehicles
Cooperative Adaptive Cruise Control
Cooperative Forward Collision Warning
Intersection collision avoidance
Approaching emergency vehicle warning (Blue Waves)
Vehicle safety inspection
Emergency vehicle signal preemption
Electronic |
https://en.wikipedia.org/wiki/Programmer%20%28hardware%29 | A programmer, device programmer, chip programmer, device burner, or PROM writer is a piece of electronic equipment that arranges written software or firmware to configure programmable non-volatile integrated circuits, called programmable devices. The target devices include PROM, EPROM, EEPROM, Flash memory, eMMC, MRAM, FeRAM, NVRAM, PLDs, PLAs, PALs, GALs, CPLDs, FPGAs, and microcontrollers.
Function
Programmer hardware has two variants. One is configuring the target device itself with a socket on the programmer. Another is configuring the device on a printed circuit board.
In the former case, the target device is inserted into a socket (usually ZIF) on top of the programmer. If the device is not a standard DIP packaging, a plug-in adapter board, which converts the footprint with another socket, is used.
In the latter case, device programmer is directly connected to the printed circuit board by a connector, usually with a cable. This way is called on-board programming, in-circuit programming, or in-system programming.
Afterwards the data is transferred from the programmer into the device by applying signals through the connecting pins. Some devices have a serial interface
for receiving the programming data (including JTAG interface).
Other devices require the data on parallel pins, followed by a programming pulse with a higher voltage for programming the data into the device.
Usually device programmers are connected to a personal computer through a parallel port,
USB port,
or LAN interface.
A software program on the computer then transfers the data to the programmer,
selects the device and interface type, and starts the programming process to read/ write/ erase/ blank the data inside the device.
Types
There are four general types of device programmers:
Automated programmers (multi-programming sites, having a set of sockets) for mass production. These systems utilize robotic pick and place handlers with on-board sites. This allows for high volume and compl |
https://en.wikipedia.org/wiki/Line%20driver | A line driver is an electronic amplifier circuit designed for driving a load such as a transmission line. The amplifier's output impedance may be matched to the characteristic impedance of the transmission line.
Line drivers are commonly used within digital systems, e.g. to communicate digital signals across circuit-board traces and cables.
In analog audio, a line driver is typically used to drive line-level analog signal outputs, for example to connect a CD player to an amplified speaker system.
References
Electronic amplifiers |
https://en.wikipedia.org/wiki/Rodenticide | Rodenticides are chemicals made and sold for the purpose of killing rodents. While commonly referred to as "rat poison", rodenticides are also used to kill mice, squirrels, woodchucks, chipmunks, porcupines, nutria, beavers, and voles. Despite the crucial roles that rodents play in nature, there are times when they need to be controlled.
Some rodenticides are lethal after one exposure while others require more than one. Rodents are disinclined to gorge on an unknown food (perhaps reflecting an adaptation to their inability to vomit), preferring to sample, wait and observe whether it makes them or other rats sick. This phenomenon of poison shyness is the rationale for poisons that kill only after multiple doses.
Besides being directly toxic to the mammals that ingest them, including dogs, cats, and humans, many rodenticides present a secondary poisoning risk to animals that hunt or scavenge the dead corpses of rats.
Classes of rodenticides
Anticoagulants
Anticoagulants are defined as chronic (death occurs one to two weeks after ingestion of the lethal dose, rarely sooner), single-dose (second generation) or multiple-dose (first generation) rodenticides, acting by effective blocking of the vitamin-K cycle, resulting in inability to produce essential blood-clotting factors—mainly coagulation factors II (prothrombin) and VII (proconvertin).
In addition to this specific metabolic disruption, massive toxic doses of 4-hydroxycoumarin, 4-thiochromenone and 1,3-indandione anticoagulants cause damage to tiny blood vessels (capillaries), increasing their permeability, causing internal bleeding. These effects are gradual, developing over several days. In the final phase of the intoxication, the exhausted rodent collapses due to hemorrhagic shock or severe anemia and dies. The question of whether the use of these rodenticides can be considered humane has been raised.
The main benefit of anticoagulants over other poisons is that the time taken for the poison to induce dea |
https://en.wikipedia.org/wiki/Divisibility%20rule | A divisibility rule is a shorthand and useful way of determining whether a given integer is divisible by a fixed divisor without performing the division, usually by examining its digits. Although there are divisibility tests for numbers in any radix, or base, and they are all different, this article presents rules and examples only for decimal, or base 10, numbers. Martin Gardner explained and popularized these rules in his September 1962 "Mathematical Games" column in Scientific American.
Divisibility rules for numbers 1–30
The rules given below transform a given number into a generally smaller number, while preserving divisibility by the divisor of interest. Therefore, unless otherwise noted, the resulting number should be evaluated for divisibility by the same divisor. In some cases the process can be iterated until the divisibility is obvious; for others (such as examining the last n digits) the result must be examined by other means.
For divisors with multiple rules, the rules are generally ordered first for those appropriate for numbers with many digits, then those useful for numbers with fewer digits.
To test the divisibility of a number by a power of 2 or a power of 5 (2n or 5n, in which n is a positive integer), one only need to look at the last n digits of that number.
To test divisibility by any number expressed as the product of prime factors , we can separately test for divisibility by each prime to its appropriate power. For example, testing divisibility by 24 (24 = 8×3 = 23×3) is equivalent to testing divisibility by 8 (23) and 3 simultaneously, thus we need only show divisibility by 8 and by 3 to prove divisibility by 24.
Step-by-step examples
Divisibility by 2
First, take any number (for this example it will be 376) and note the last digit in the number, discarding the other digits. Then take that digit (6) while ignoring the rest of the number and determine if it is divisible by 2. If it is divisible by 2, then the original number is divis |
https://en.wikipedia.org/wiki/Logical%20unit%20number | In computer storage, a logical unit number, or LUN, is a number used to identify a logical unit, which is a device addressed by the SCSI protocol or by Storage Area Network protocols that encapsulate SCSI, such as Fibre Channel or iSCSI.
A LUN may be used with any device which supports read/write operations, such as a tape drive, but is most often used to refer to a logical disk as created on a SAN. Though not technically correct, the term "LUN" is often also used to refer to the logical disk itself.
Examples
To provide a practical example, a typical multi-disk drive has multiple physical SCSI ports, each with one SCSI target address assigned. An administrator may format the disk array as a RAID and then partition this RAID into several separate storage-volumes. To represent each volume, a SCSI target is configured to provide a logical unit. Each SCSI target may provide multiple logical units and thus represent multiple volumes, but this does not mean that those volumes are concatenated. The computer that accesses a volume on the disk array identifies which volume to read or write with the LUN of the associated logical unit.
In another example: a single disk-drive has one physical SCSI port. It usually provides just a single target, which in turn usually provides just a single logical unit whose LUN is zero. This logical unit represents the entire storage of the disk drive.
Use
How to select a LUN: In the early versions of SCSI, an initiator delivers a Command Descriptor Block (CDB) to a target (physical unit) and within the CDB is a 3-bit LUN field to identify the logical unit within the target. In current SCSI, the initiator delivers the CDB to a particular logical unit, so the LUN appears in the transport layer data structures and not in the CDB.
LUN vs. SCSI Device ID: The LUN is not the only way to identify a logical unit. There is also the SCSI Device ID, which identifies a logical unit uniquely in the world. Labels or serial numbers stored in a l |
https://en.wikipedia.org/wiki/Fibre%20Channel%20switch | In the computer storage field, a Fibre Channel switch is a network switch compatible with the Fibre Channel (FC) protocol. It allows the creation of a Fibre Channel fabric, that is the core component of a storage area network (SAN). The fabric is a network of Fibre Channel devices which allows many-to-many communication, device name lookup, security, and redundancy. FC switches implement zoning, a mechanism that disables unwanted traffic between certain fabric nodes.
Fibre Channel switches may be deployed one at a time or in larger multi-switch configurations. SAN administrators typically add new switches as their server and storage needs grow, connecting switches together via fiber optic cable using the standard device ports. Some switch vendors offer dedicated high-speed stacking ports to handle inter-switch connections (similar to existing stackable Ethernet switches), allowing high-performance multi-switch configurations to be created using fewer switches overall.
Major manufacturers of Fibre Channel switches include Brocade(Broadcom), Cisco Systems, and QLogic(Marvell).
Fibre Channel Director
A special variety of a FC switch is the Fibre Channel Director, a switch meant to provide backbone infrastructure in a fabric usually featuring at least 128 ports and high-availability attributes, however the term is loose and varies among to manufacturers. It does not differ from a switch in core FC protocol functionality. The director term itself is derived from legacy ESCON Directors such as the IBM 9032-005.
See also
List of Fibre Channel switches
Host Bus Adapter (HBA)
References
Fibre Channel |
https://en.wikipedia.org/wiki/Bob%20O.%20Evans | Bob Overton Evans (August 19, 1927 – September 2, 2004), also known as "Boe" Evans, was an American computer pioneer and corporate executive at IBM (International Business Machines). He led the groundbreaking development of compatible computers that changed the industry.
Early life and education
Evans was born in Grand Island, Nebraska. In 1951, after earning an engineering degree from Iowa State University, he joined IBM as a junior engineer.
Career
Bob O. Evans joined IBM in a low level engineering position in
1951
as it was developing a new range of "computers" based on vacuum tubes (earlier IBM computers used mechanical
switches). A natural and very
capable manager he moved up the company hierarchy to the position of vice president (development) in
the Data Systems division in 1962. This was apparently created as a position where he had responsibility for the
development of "System/360", a merger of IBMs separate scientific and business computing systems.
In the early 1960s, Evans persuaded IBM’s chairman, Thomas J. Watson Jr., to discontinue the company’s development of a hodgepodge of incompatible computers and instead to embark on the development of a single product line of general-purpose, compatible computers. Until then, researchers thought that the fields of scientific computing and commercial data processing each required their own type of special-purpose computer. Compatibility would ensure that the same software could run on any model of the product line, avoiding a re-programming of software.
Evans had overall responsibility for the hardware and software development of what was announced on April 7, 1964, as the IBM System/360 product line, with six models (later gradually expanded to 18 models) and a performance range factor of 50. IBM – in 1964 a company with an annual revenue of $3.2 billion – invested more than $5 billion in engineering, factories and equipment to develop and manufacture System/360, opening five plants and hiring 60,000 e |
https://en.wikipedia.org/wiki/Multiple%20instruction%2C%20single%20data | In computing, multiple instruction, single data (MISD) is a type of parallel computing architecture where many functional units perform different operations on the same data. Pipeline architectures belong to this type, though a purist might say that the data is different after processing by each stage in the pipeline. Fault tolerance executing the same instructions redundantly in order to detect and mask errors, in a manner known as task replication, may be considered to belong to this type. Applications for this architecture are much less common than MIMD and SIMD, as the latter two are often more appropriate for common data parallel techniques. Specifically, they allow better scaling and use of computational resources. However, one prominent example of MISD in computing are the Space Shuttle flight control computers.
Systolic arrays
Systolic arrays (< wavefront processors), first described by H. T. Kung and Charles E. Leiserson are an example of MISD architecture. In a typical systolic array, parallel input data flows through a network of hard-wired processor nodes, resembling the human brain which combine, process, merge or sort the input data into a derived result.
Systolic arrays are often hard-wired for a specific operation, such as "multiply and accumulate", to perform massively parallel integration, convolution, correlation, matrix multiplication or data sorting tasks. A systolic array typically consists of a large monolithic network of primitive computing nodes, which can be hardwired or software-configured for a specific application. The nodes are usually fixed and identical, while the interconnect is programmable. More general wavefront processors, by contrast, employ sophisticated and individually programmable nodes which may or may not be monolithic, depending on the array size and design parameters. Because the wave-like propagation of data through a systolic array resembles the pulse of the human circulatory system, the name systolic was coined |
https://en.wikipedia.org/wiki/Transglutaminase | Transglutaminases are enzymes that in nature primarily catalyze the formation of an isopeptide bond between γ-carboxamide groups ( -(C=O)NH2 ) of glutamine residue side chains and the ε-amino groups ( -NH2 ) of lysine residue side chains with subsequent release of ammonia ( NH3 ). Lysine and glutamine residues must be bound to a peptide or a protein so that this cross-linking (between separate molecules) or intramolecular (within the same molecule) reaction can happen. Bonds formed by transglutaminase exhibit high resistance to proteolytic degradation (proteolysis). The reaction is
Gln-(C=O)NH2 + NH2-Lys → Gln-(C=O)NH-Lys + NH3
Transglutaminases can also join a primary amine ( RNH2 ) to the side chain carboxyamide group of a protein/peptide bound glutamine residue thus forming an isopeptide bond
Gln-(C=O)NH2 + RNH2 → Gln-(C=O)NHR + NH3
These enzymes can also deamidate glutamine residues to glutamic acid residues in the presence of water
Gln-(C=O)NH2 + H2O → Gln-COOH + NH3
Transglutaminase isolated from Streptomyces mobaraensis -bacteria for example, is a calcium-independent enzyme. Mammalian transglutaminases among other transglutaminases require Ca2+ ions as a cofactor.
Transglutaminases were first described in 1959. The exact biochemical activity of transglutaminases was discovered in blood coagulation protein factor XIII in 1968.
Examples
Nine transglutaminases have been characterised in humans, eight of which catalyse transamidation reactions. These TGases have a three or four-domain organization, with immunoglobulin-like domains surrounding the central catalytic domain. The core domain belongs to the papain-like protease superfamily (CA clan) and uses a Cys-His-Asp catalytic triad. Protein 4.2 , also referred to as band 4.2, is a catalytically inactive member of the human transglutaminase family that has a Cys to Ala substitution at the catalytic triad.
Bacterial transglutaminases are single-domain proteins with a similarly-folded core. The transglutaminas |
https://en.wikipedia.org/wiki/Circumscribed%20sphere | In geometry, a circumscribed sphere of a polyhedron is a sphere that contains the polyhedron and touches each of the polyhedron's vertices. The word circumsphere is sometimes used to mean the same thing, by analogy with the term circumcircle. As in the case of two-dimensional circumscribed circles (circumcircles), the radius of a sphere circumscribed around a polyhedron is called the circumradius of , and the center point of this sphere is called the circumcenter of .
Existence and optimality
When it exists, a circumscribed sphere need not be the smallest sphere containing the polyhedron; for instance, the tetrahedron formed by a vertex of a cube and its three neighbors has the same circumsphere as the cube itself, but can be contained within a smaller sphere having the three neighboring vertices on its equator. However, the smallest sphere containing a given polyhedron is always the circumsphere of the convex hull of a subset of the vertices of the polyhedron.
In De solidorum elementis (circa 1630), René Descartes observed that, for a polyhedron with a circumscribed sphere, all faces have circumscribed circles, the circles where the plane of the face meets the circumscribed sphere. Descartes suggested that this necessary condition for the existence of a circumscribed sphere is sufficient, but it is not true: some bipyramids, for instance, can have circumscribed circles for their faces (all of which are triangles) but still have no circumscribed sphere for the whole polyhedron. However, whenever a simple polyhedron has a circumscribed circle for each of its faces, it also has a circumscribed sphere.
Related concepts
The circumscribed sphere is the three-dimensional analogue of the circumscribed circle.
All regular polyhedra have circumscribed spheres, but most irregular polyhedra do not have one, since in general not all vertices lie on a common sphere. The circumscribed sphere (when it exists) is an example of a bounding sphere, a sphere that contains a given |
https://en.wikipedia.org/wiki/Inscribed%20sphere | In geometry, the inscribed sphere or insphere of a convex polyhedron is a sphere that is contained within the polyhedron and tangent to each of the polyhedron's faces. It is the largest sphere that is contained wholly within the polyhedron, and is dual to the dual polyhedron's circumsphere.
The radius of the sphere inscribed in a polyhedron P is called the inradius of P.
Interpretations
All regular polyhedra have inscribed spheres, but most irregular polyhedra do not have all facets tangent to a common sphere, although it is still possible to define the largest contained sphere for such shapes. For such cases, the notion of an insphere does not seem to have been properly defined and various interpretations of an insphere are to be found:
The sphere tangent to all faces (if one exists).
The sphere tangent to all face planes (if one exists).
The sphere tangent to a given set of faces (if one exists).
The largest sphere that can fit inside the polyhedron.
Often these spheres coincide, leading to confusion as to exactly what properties define the insphere for polyhedra where they do not coincide.
For example, the regular small stellated dodecahedron has a sphere tangent to all faces, while a larger sphere can still be fitted inside the polyhedron. Which is the insphere? Important authorities such as Coxeter or Cundy & Rollett are clear enough that the face-tangent sphere is the insphere. Again, such authorities agree that the Archimedean polyhedra (having regular faces and equivalent vertices) have no inspheres while the Archimedean dual or Catalan polyhedra do have inspheres. But many authors fail to respect such distinctions and assume other definitions for the 'inspheres' of their polyhedra.
See also
Circumscribed sphere
Inscribed circle
Midsphere
Sphere packing
References
Coxeter, H.S.M. Regular Polytopes 3rd Edn. Dover (1973).
Cundy, H.M. and Rollett, A.P. Mathematical Models, 2nd Edn. OUP (1961).
External links
Elementary geometry
Polyhedra |
https://en.wikipedia.org/wiki/ISO%2015924 | ISO 15924, Codes for the representation of names of scripts, is an international standard defining codes for writing systems or scripts (a "set of graphic characters used for the written form of one or more languages"). Each script is given both a four-letter code and a numeric code.
Where possible the codes are derived from ISO 639-2, where the name of a script and the name of a language using the script are identical (example: Gujarātī ISO 639 guj, ISO 15924 Gujr). Preference is given to the 639-2 Bibliographical codes, which is different from the otherwise often preferred use of the Terminological codes.
4-letter ISO 15924 codes are incorporated into the IANA Language Subtag Registry for IETF language tags and so can be used in file formats that make use of such language tags. For example, they can be used in HTML and XML to help Web browsers determine which typeface to use for foreign text. This way one could differentiate, for example, between Serbian written in the Cyrillic (sr-Cyrl) or Latin (sr-Latn) script, or mark romanized or transliterated text as such.
Maintenance
ISO appointed the Unicode Consortium as the Registration Authority (RA) for the standard. The RA is responsible for appointing a registrar who works with a Joint Advisory Committee (JAC) in developing and implementing the standard. The registrar from 2004 to 2018 was Michael Everson, and from January 2019 the registrar has been Markus Scherer, a technical director of the Unicode Consortium. The JAC consists of six members: one representative of the RA (Markus Scherer), one representative of ISO 639-2 (Randall K. Barry of the Library of Congress), one representative of ISO TC37 (Christian Galinski), one representative of ISO TC46 (Peeter Päll), and two representatives of ISO/IEC JTC 1/SC 2 (Rick McGowan and Ken Whistler, both also officers of the Unicode Consortium).
Script codes
Numeric ranges
Hieroglyphic and cuneiform scripts
Right-to-left alphabetic scripts
Left-to-right alphabetic |
https://en.wikipedia.org/wiki/Black%20Chamber | The Black Chamber (1919–1929), also known as the Cipher Bureau, was the United States' first peacetime cryptanalytic organization, and a forerunner of the National Security Agency. The only prior codes and cypher organizations maintained by the US government had been some intermittent, and always abandoned, attempts by Armed Forces branches prior to World War I.
History
Headed by Herbert O. Yardley (1889–1958), the Black Chamber was founded in May 1919 following World War I. Yardley had commanded the U.S. Army cryptographic section of Military Intelligence (MI-8) during World War I. MI-8 was disbanded after the war. Jointly funded by the Army and the State Department, the Cipher Bureau was disguised as a New York City commercial code company; it actually produced and sold such codes for business use. Its true mission, however, was to break the communications (chiefly diplomatic) of other nations. During the Washington Naval Conference, it aided American negotiators by providing them with the decrypted traffic of many of the Conference delegations, including the Japanese.
According to intelligence historian James Bamford, the Black Chamber secured the cooperation of American telegraph companies, such as Western Union, in illegally turning over the cable traffic of foreign embassies and consulates in Washington and New York. Eventually, "almost the entire American cable industry" was part of this effort. However, these companies eventually withdrew their support—possibly spurred by the Radio Act of 1927, which broadened criminal offenses related to breaching the confidentiality of telegraph messages.
In 1929, the State Department withdrew its share of the funding, the Army declined to bear the entire load, and the Black Chamber closed down. New Secretary of State Henry L. Stimson made this decision, and years later in his memoirs made the oft-quoted comment: "Gentlemen do not read each other's mail." Stimson's ethical reservations about cryptanalysis focused on t |
https://en.wikipedia.org/wiki/The%20WELL | The Whole Earth 'Lectronic Link, normally shortened to The WELL or, alternatively, The Well, was launched in 1985. It is one of the oldest continuously operating virtual communities. By 1993 it had 7,000 members, a staff of 12, and gross annual income of $2 million. A 1997 feature in Wired magazine called it "The world's most influential online community." In 2012, when it was last publicly offered for sale, it had 2,693 members. It is best known for its Internet forums, but also provides email, shell accounts, and web pages. Discussion topics are organized into conferences that cover broad areas of interest. User anonymity is prohibited.
History
The WELL was started by Stewart Brand and Larry Brilliant in 1985. The name follows the naming of some of Brand's earlier projects, including the Whole Earth Catalog. Initially The WELL was owned 50% by The Point Foundation, publishers of the Whole Earth Catalog and Whole Earth Review, and 50% by NETI Technologies Inc. a Vancouver-based company of which Larry Brilliant was at that time chairman. Its original management team—Matthew McClure, soon joined by Cliff Figallo and John Coate—collaborated with its early users to foster a sense of virtual community. McClure, Coate and Figallo were all veterans of the 1970s commune called The Farm.
John Coate left the WELL to help create SFGate, the San Francisco Chronicle's first web site. In 1991 Figallo hired Gail Ann Williams as a community manager. Williams, one of the principals of the satirical group the Plutonium Players, had been working in nonprofit theater management and was already an active member of the WELL.
In 1992 Cliff Figallo also left his job at The WELL and long time WELL member Maurice Weitman was hired as general manager. Figallo's resignation letter to the Board cited changes in company approach: "I am too much identified with the permissive and accommodating attitude that has been part of The Well's growth to preside over a more restrictive régime."
From 1 |
https://en.wikipedia.org/wiki/Anatol%20Rapoport | Anatol Rapoport (; ; May 22, 1911January 20, 2007) was an American mathematical psychologist. He contributed to general systems theory, to mathematical biology and to the mathematical modeling of social interaction and stochastic models of contagion.
Biography
Rapoport was born in Lozova, Kharkov Governorate, Russia (in today's Kharkiv Oblast, Ukraine) into a secular Jewish family. In 1922, he came to the United States, and in 1928 he became a naturalized citizen. He started studying music in Chicago and continued with piano, conducting and composition at the Vienna Hochschule für Musik where he studied from 1929 to 1934. However, due to the rise of Nazism, he found it impossible to make a career as a pianist.
He shifted his career into mathematics, completing a Ph.D. in mathematics under Otto Schilling and Abraham Adrian Albert at the University of Chicago in 1941 on the thesis Construction of Non-Abelian Fields with Prescribed Arithmetic. According to The Globe and Mail, he was a member of the American Communist Party for three years, but quit before enlisting in the U.S. Army Air Forces in 1941, serving in Alaska and India during World War II.
After the war, he joined the Committee on Mathematical Biology at the University of Chicago (1947–54), publishing his first book, Science and the Goals of Man, co-authored with semanticist S. I. Hayakawa in 1950. He also received a one-year fellowship at the prestigious Center for Advanced Study in the Behavioral Sciences at Stanford University
From 1955 to 1970, Rapoport was Professor of Mathematical Biology and Senior Research Mathematician at the University of Michigan, as well as founding member, in 1955, of the Mental Health Research Institute (MHRI) at the University of Michigan. In 1970, during the Vietnam War, Rapoport moved to Toronto "to live in a country that was not committed to a messianic role—a small peaceful country with no aspiration to major power status". He was appointed professor of mathematics a |
https://en.wikipedia.org/wiki/Wireless%20distribution%20system | A wireless distribution system (WDS) is a system enabling the wireless interconnection of access points in an IEEE 802.11 network. It allows a wireless network to be expanded using multiple access points without the traditional requirement for a wired backbone to link them. The notable advantage of WDS over other solutions is that it preserves the MAC addresses of client frames across links between access points.
An access point can be either a main, relay, or remote base station.
A main base station is typically connected to the (wired) Ethernet.
A relay base station relays data between remote base stations, wireless clients, or other relay stations; to either a main, or another relay base station.
A remote base station accepts connections from wireless clients and passes them on to relay stations or to main stations. Connections between "clients" are made using MAC addresses.
All base stations in a wireless distribution system must be configured to use the same radio channel, method of encryption (none, WEP, WPA or WPA2) and the same encryption keys. They may be configured to different service set identifiers (SSIDs). WDS also requires every base station to be configured to forward to others in the system.
WDS may also be considered a repeater mode because it appears to bridge and accept wireless clients at the same time (unlike traditional bridging). However, with the repeater method, throughput is halved for all clients connected wirelessly. This is because Wi-Fi is an inherently half duplex medium and therefore any Wi-Fi device functioning as a repeater must use the Store and forward method of communication.
WDS may be incompatible between different products (even occasionally from the same vendor) since the IEEE 802.11-1999 standard does not define how to construct any such implementations or how stations interact to arrange for exchanging frames of this format. The IEEE 802.11-1999 standard merely defines the 4-address frame format that makes it pos |
https://en.wikipedia.org/wiki/Cisco%20PIX | Cisco PIX (Private Internet eXchange) was a popular IP firewall and network address translation (NAT) appliance. It was one of the first products in this market segment.
In 2005, Cisco introduced the newer Cisco Adaptive Security Appliance (Cisco ASA), that inherited many of the PIX features, and in 2008 announced PIX end-of-sale.
The PIX technology was sold in a blade, the FireWall Services Module (FWSM), for the Cisco Catalyst 6500 switch series and the 7600 Router series, but has reached end of support status as of September 26, 2007.
PIX
History
PIX was originally conceived in early 1994 by John Mayes of Redwood City, California and designed and coded by Brantley Coile of Athens, Georgia. The PIX name is derived from its creators' aim of creating the functional equivalent of an IP PBX to solve the then-emerging registered IP address shortage. At a time when NAT was just being investigated as a viable approach, they wanted to conceal a block or blocks of IP addresses behind a single or multiple registered IP addresses, much as PBXs do for internal phone extensions. When they began, RFC 1597 and RFC 1631 were being discussed, but the now-familiar RFC 1918 had not yet been submitted.
The design, and testing were carried out in 1994 by John Mayes, Brantley Coile and Johnson Wu of Network Translation, Inc., with Brantley Coile being the sole software developer. Beta testing of PIX serial number 000000 was completed and first customer acceptance was on December 21, 1994 at KLA Instruments in San Jose, California. The PIX quickly became one of the leading enterprise firewall products and was awarded the Data Communications Magazine "Hot Product of the Year" award in January 1995.
Shortly before Cisco acquired Network Translation in November 1995, Mayes and Coile hired two longtime associates, Richard (Chip) Howes and Pete Tenereillo, and shortly after acquisition 2 more longtime associates, Jim Jordan and Tom Bohannon. Together they continued development on Fine |
https://en.wikipedia.org/wiki/Apple%20event | Apple events are the message-based interprocess communication mechanism in Mac OS, first making an appearance in System 7 and supported by every version of the classic Mac OS since then and by macOS. Apple events describe "high-level" events such as "open document" or "print file", whereas earlier OSs had supported much more basic events, namely "click" and "keypress". Apple events form the basis of the Mac OS scripting system, the Open Scripting Architecture (the primary language of such being AppleScript).
The starting point is a dynamically-typed, extensible descriptor format called an AEDesc, which is just an OSType code specifying the data type, together with a block of type-dependent data. For instance, the OSType code inte indicates that the data was a four-byte signed integer in big-endian format.
Besides predefined type codes for various common simple types, there are two predefined structured descriptor types: an AERecord, which has data type reco (record), and AEList with type list (list or array). The internal structure of these contain recursively-nested AEDescs, while the AERecord also associates each element with a unique record field ID, which is an OSType. The Apple Event Manager provides API calls to construct these structures, as well as extract their contents and query the type of contents they hold.
The Apple Event Manager also supports coercions, which converts AEDescs from one data type to another. In addition to standard coercions, for instance between integer and real types, applications can install their own coercion handler callbacks, which handle conversions to and from custom data types.
An Apple event proper is an AERecord with fields that depended on the purpose of the event. In addition, it has attributes (which are distinct from record fields, which are now called the parameters of the event) from a set predefined by the Apple Event Manager. These specify what the event is supposed to do (through event class and event ID), the t |
https://en.wikipedia.org/wiki/OTRS | OTRS (originally Open-Source Ticket Request System) is a service management suite. The suite contains an agent portal, admin dashboard and customer portal. In the agent portal, teams process tickets and requests from customers (internal or external). There are various ways in which this information, as well as customer and related data can be viewed. As the name implies, the admin dashboard allows system administrators to manage the system: Options are many, but include roles and groups, process automation, channel integration, and CMDB/database options. The third component, the customer portal, is much like a customizable webpage where information can be shared with customers and requests can be tracked on the customer side.
History
In 2001, OTRS began as an open source help desk ticketing software.
In 2003, OTRS GmbH was formed and a professional company entered the EMEA market. This was followed in 2006 by entry into the North American market.
In 2007, the company was renamed to OTRS AG with the intention of going public, which it did in 2009. This is the same year in which OTRS was brought to Latin America with the Mexican subsidiary officially being founded in 2010. Entry into the APAC region occurred in 2011.
In 2015, a new version of the software, known as OTRS Business Solution, was launched. This proprietary version was designed for professional users who needed additional support, configuration and features.
Also in 2015, STORM powered by OTRS was launched.
In 2018, both OTRS-specific products were renamed: The open source version became ((OTRS)) Community Edition. The proprietary and managed version is named OTRS. A third offering, also proprietary, is called OTRS On-Premise for professional customers who intend to host the platform in their own data centers.
In December 2020, OTRS AG announced the end of life of support for the Community Edition which led to several forks. Alongside its customers was Wikimedia Foundation, which used ((OTRS)) Commu |
https://en.wikipedia.org/wiki/Contingent%20cooperator | In game theory, a contingent cooperator is a person or agent who is willing to act in the collective interest, rather than his short-term selfish interest, if he observes a majority of the other agents in the collective doing the same. The apparent contradiction in this stance is resolved by game theory, which shows that in the right circumstances, cooperation with a sufficient number of other participants will have a better outcome for cooperators than pursuing short-term selfish interests.
See also
Cooperation
Iterated prisoner's dilemma
Tit for tat
External links
Ronald A. Heiner. Robust Evolution of Contingent Cooperation in Pure One-Shot Prisoners' Dilemmas. Discussion Papers Nos. 2002-09 and 2002–09, Center for the Study of Law and Economics discussion paper series, 2002.
Christopher Wilson. “I Will if You Will: Facilitating Contingent Cooperation”, Optimum Online, Vol. 37, Issue 1, Apr 2007
Game theory |
https://en.wikipedia.org/wiki/Mobile%20office | A mobile office is an office built within a truck, motorhome, trailer or shipping container. The term is also used for people who don't work at a physical office location but instead carry their office materials with them. The mobile office can allow businesses to cut costs and avoid building physical locations where it would be too costly or simply unnecessary.
See also
Mobile home
Virtual office
References
Office work
Construction
Portable buildings and shelters |
https://en.wikipedia.org/wiki/Processor%20Direct%20Slot | A processor direct slot (PDS) is a slot incorporated into many older Macintosh models that allowed direct access to the signal pins of a CPU, similar to the functionality of a local bus in PCs. This would result in much higher speeds than having to go through a bus layer, such as NuBus, which typically ran at a slower 10 MHz speed.
Overview
Typically, if a machine had bus expansion slots it would feature multiple bus expansions slots. However, there was never more than one PDS slot, as rather than providing a sophisticated communication protocol with arbitration between different bits of hardware that might be trying to use the communication channel at the same time, the PDS slot, for the most part, just gave direct access to signal pins on the CPU, making it closer in nature to a local bus.
Thus, PDS slots tended to be CPU-specific, and therefore a card designed for the PDS slot in the Motorola 68030-based Macintosh SE/30, for example, would not work in the Motorola 68040-based Quadra 700.
The one notable exception to this was the PDS design for the original Motorola 68020-based Macintosh LC. This was Apple's first attempt at a "low-cost" Mac, and it was such a success that, when subsequent models replaced the CPU with a 68030, a 68040, and later a PowerPC processor, Apple found methods to keep the PDS slot compatible with the original LC, so that the same expansion cards would continue to work.
History
SE slot (Motorola 68000)
The SE "System Expansion" slot, introduced in the Macintosh SE in 1987, was the first processor direct slot, using a 96-pin Euro-DIN connector to interface with the Motorola 68000 processor. This slot was also used in the Macintosh Portable.
IIci slot (Motorola 68030)
The L2 cache slot of the Macintosh IIci, introduced in 1989, was a 32-bit version of a PDS which used a 120-pin Euro-DIN connector to support the Motorola 68030 processor. This slot also appeared in the Macintosh IIsi, IIvi, and IIvx. These allowed for 3rd party compan |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.