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https://en.wikipedia.org/wiki/Forward%20declaration
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In computer programming, a forward declaration is a declaration of an identifier (denoting an entity such as a type, a variable, a constant, or a function) for which the programmer has not yet given a complete definition.
It is required for a compiler to know certain properties of an identifier (size for memory allocation, data type for type checking, such as type signature of functions), but not other details, like the particular value it holds (in case of variables or constants) or definition (in the case of functions). This is particularly useful for one-pass compilers and separate compilation.
Forward declaration is used in languages that require declaration before use; it is necessary for mutual recursion in such languages, as it is impossible to define such functions (or data structures) without a forward reference in one definition: one of the functions (respectively, data structures) must be defined first. It is also useful to allow flexible code organization, for example if one wishes to place the main body at the top, and called functions below it.
In other languages forward declarations are not necessary, which generally requires instead a multi-pass compiler and for some compilation to be deferred to link time. In these cases identifiers must be defined (variables initialized, functions defined) before they can be employed during runtime without the need for pre-definition in the source code for either compilation or interpretation: identifiers do not need to be immediately resolved to an existing entity.
Examples
A basic example in C is:
void printThisInteger(int);
In C and C++, the line above represents a forward declaration of a function and is the function's prototype. After processing this declaration, the compiler would allow the program code to refer to the entity printThisInteger in the rest of the program. The definition for a function must be provided somewhere (same file or other, where it would be the responsibility of the linker to corr
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https://en.wikipedia.org/wiki/Tinning
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Tinning is the process of thinly coating sheets of wrought iron or steel with tin, and the resulting product is known as tinplate. The term is also widely used for the different process of coating a metal with solder before soldering.
It is most often used to prevent rust, but is also commonly applied to the ends of stranded wire used as electrical conductors to prevent oxidation (which increases electrical resistance), and to keep them from fraying or unraveling when used in various wire connectors like twist-ons, binding posts, or terminal blocks, where stray strands can cause a short circuit.
While once more widely used, the primary use of tinplate now is the manufacture of tin cans. Formerly, tinplate was used for cheap pots, pans, and other holloware. This kind of holloware was also known as tinware and the people who made it were tinplate workers.
The untinned sheets employed in the manufacture are known as black plates. They are now made of steel, either Bessemer steel or open-hearth. Formerly iron was used, and was of two grades, coke iron and charcoal iron; the latter, being the better, received a heavier coating of tin, and this circumstance is the origin of the terms coke plates and charcoal plates by which the quality of tinplate is still designated, although iron is no longer used. Tinplate was consumed in enormous quantities for the manufacture of the tin cans in which preserved meat, fish, fruit, biscuits, cigarettes, and numerous other products are packed, and also for the household utensils of various kinds made by the tinsmith.
History
The practice of tinning ironware to protect it against rust is an ancient one. According to Pliny the Elder tinning was invented by the Gallic Bituriges tribe (based near modern Bourges), who boiled copper objects in a tin solution in order to make them look as if they were made from silver. The first detailed account of the process appears in Zosimus of Panopolis, Book 6.62, part of a work on alchemy written in
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https://en.wikipedia.org/wiki/Marsden%20square
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Marsden square mapping or Marsden squares is a system that divides a world map with latitude-longitude gridlines (e.g. plate carrée projection, Mercator or other) between 80°N and 70°S latitudes (or 90°N and 80°S: refer chart at Ocean Teacher’s Ocean Geography page) into grid cells of 10° latitude by 10° longitude, each with a geocode, a unique numeric identifier. The method was devised by William Marsden (b. 1754, d. 1836), when first secretary of the British Admiralty, for collecting and combining geographically based information about the oceans.
Structure and design
On the plate carrée projection the grid cells appear square, although if the Mercator projection is used, the grid cells appear "stretched" vertically nearer the tops and bottoms of the map. On the actual surface of the globe, the cells are approximately "square" only adjacent to the equator, and become progressively narrower and tapered (also with curved northern and southern boundaries) as they approach the poles, and cells adjoining the poles are unique in possessing three faces rather than four. Each of the 540 10°x10° squares is allocated a unique number from 1 to 288 and from 300 to 551 (see image to the right), plus the sequence extends to 936 in higher latitudes; individual squares can also be subdivided into 100 one-degree squares numbered from 00 to 99 in order to improve precision.
Use
Marsden squares have mostly been used for identifying the geographic position of meteorological data, and are described further in various publications of the World Meteorological Organization (WMO). The 10°x10° square identifiers typically use a minimal number of characters (between 1 and 3 digits) which was/is an operational advantage for low bandwidth transmission systems.
However the rules for allocating numbers to squares do not follow a consistent pattern, so that reverse-engineering (decoding) the relevant square boundaries from any particular Marsden Square identifier is not particularly straig
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https://en.wikipedia.org/wiki/Fluent%20calculus
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The fluent calculus is a formalism for expressing dynamical domains in first-order logic. It is a variant of the situation calculus; the main difference is that situations are considered representations of states. A binary function symbol is used to concatenate the terms that represent facts that hold in a situation. For example, that the box is on the table in the situation is represented by the formula . The frame problem is solved by asserting that the situation after the execution of an action is identical to the one before but for the conditions changed by the action. For example, the action of moving the box from the table to the floor is formalized as:
This formula states that the state after the move is added the term and removed the term . Axioms specifying that is commutative and non-idempotent are necessary for such axioms to work.
See also
Fluent (artificial intelligence)
Frame problem
Situation calculus
Event calculus
References
M. Thielscher (1998). Introduction to the fluent calculus. Electronic Transactions on Artificial Intelligence, 2(3–4):179–192.
M. Thielscher (2005). Reasoning Robots - The Art and Science of Programming Robotic Agents. Volume 33 of Applied Logic Series. Springer, Dordrecht.
Logical calculi
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https://en.wikipedia.org/wiki/Spatial%20reference%20system
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A spatial reference system (SRS) or coordinate reference system (CRS) is a framework used to precisely measure locations on the surface of Earth as coordinates. It is thus the application of the abstract mathematics of coordinate systems and analytic geometry to geographic space. A particular SRS specification (for example, "Universal Transverse Mercator WGS 84 Zone 16N") comprises a choice of Earth ellipsoid, horizontal datum, map projection (except in the geographic coordinate system), origin point, and unit of measure. Thousands of coordinate systems have been specified for use around the world or in specific regions and for various purposes, necessitating transformations between different SRS.
Although they date to the Hellenic Period, spatial reference systems are now a crucial basis for the sciences and technologies of Geoinformatics, including cartography, geographic information systems, surveying, remote sensing, and civil engineering. This has led to their standardization in international specifications such as the EPSG codes and ISO 19111:2019 Geographic information—Spatial referencing by coordinates, prepared by ISO/TC 211, also published by the Open Geospatial Consortium as Abstract Specification, Topic 2: Spatial referencing by coordinate.
Types of systems
The thousands of spatial reference systems used today are based on a few general strategies, which have been defined in the EPSG, ISO, and OGC standards:
Geographic coordinate system (or geodetic)
A spherical coordinate system measuring locations directly on the Earth (modeled as a sphere or ellipsoid) using latitude (degrees north or south of the equator) and longitude (degrees west or east of a prime meridian).
Geocentric coordinate system (or Earth-centered Earth-fixed)
A three-dimensional cartesian coordinate system that models the Earth as a three-dimensional object, measuring locations from a center point, usually the center of mass of the Earth, along x, y, and z axes aligned with the equ
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https://en.wikipedia.org/wiki/Security%20operations%20center
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A security operations center (SOC) is responsible for protecting an organization against cyber threats. SOC analysts perform round-the-clock monitoring of an organization’s network and investigate any potential security incidents. If a cyberattack is detected, the SOC analysts are responsible for taking any steps necessary to remediate it. It comprises the three building blocks for managing and enhancing an organization's security posture: people, processes, and technology. Thereby, governance and compliance provide a framework, tying together these building blocks. A SOC within a building or facility is a central location from which staff supervises the site using data processing technology. Typically, a SOC is equipped for access monitoring and control of lighting, alarms, and vehicle barriers.
IT
An information security operations center (ISOC) is a dedicated site where enterprise information systems (web sites, applications, databases, data centers and servers, networks, desktops and other endpoints) are monitored, assessed, and defended.
The United States government
The Transportation Security Administration in the United States has implemented security operations centers for most airports that have federalized security. The primary function of TSA security operations centers is to act as a communication hub for security personnel, law enforcement, airport personnel and various other agencies involved in the daily operations of airports. SOCs are staffed 24-hours a day by SOC watch officers. Security operations center watch officers are trained in all aspects of airport and aviation security and are often required to work abnormal shifts. SOC watch officers also ensure that TSA personnel follow proper protocol in dealing with airport security operations. The SOC is usually the first to be notified of incidents at airports such as the discovery of prohibited items/contraband, weapons, explosives, hazardous materials as well as incidents regarding fligh
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https://en.wikipedia.org/wiki/Creepmeter
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A creepmeter is an instrument that monitors the slow surface displacement of an active geologic fault in the earth. Its function is to record the slow, aseismic creep between earthquakes. The measurement range of a creepmeter is usually limited to 10–30 mm. Approximately 40 creepmeters are in operation in California—most are operated by the United States Geological Survey (USGS), but nine are maintained by the University of Colorado.
References
Structural geology
Measuring instruments
Seismology
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https://en.wikipedia.org/wiki/Barracuda%20Networks
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Barracuda Networks, Inc. is a company providing security, networking and storage products based on network appliances and cloud services. The company's security products include products for protection against email, web surfing, web hackers and instant messaging threats such as spam, spyware, trojans, and viruses. The company's networking and storage products include web filtering, load balancing, application delivery controllers, message archiving, NG firewalls, backup services and data protection.
History
Barracuda Networks was founded in 2003 by Dean Drako (founding CEO), Michael Perone, and Zach Levow; the company introduced the Barracuda Spam and Virus Firewall in the same year. In 2007 the company moved its headquarters to Campbell, California, and opened an office in Ann Arbor, Michigan.
In January 2006, it closed its first outside investment of $40 million from Sequoia Capital and Francisco Partners.
On January 29, 2008, Barracuda Networks was sued by Trend Micro over their use of the open source anti-virus software Clam AntiVirus, which Trend Micro claimed to be in violation of their patent on 'anti-virus detection on an SMTP or FTP gateway'. In addition to providing samples of prior art in an effort to render Trend Micro's patent invalid, in July 2008 Barracuda launched a countersuit against Trend Micro claiming Trend Micro violated several antivirus patents Barracuda Networks had acquired from IBM.
In December 2008, the company launched the BRBL (Barracuda Reputation Block List), its proprietary and dynamic list of known spam servers, for free and public use in blocking spam at the gateway.
Soon after opening BRBL many IP addresses got blacklisted without apparent reason and without any technical explanation.
As of October 2009, Barracuda had over 85,000 customers. As of November 2011, Barracuda had more than 130,000 customers. As of January 2014, Barracuda has more than 150,000 customers worldwide.
In 2012, the company became a co-sponsor of the
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https://en.wikipedia.org/wiki/Captive%20breeding
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Captive breeding, also known as captive propagation, is the process of keeping plants or animals in controlled environments, such as wildlife reserves, zoos, botanic gardens, and other conservation facilities. It is sometimes employed to help species that are being threatened by the effects of human activities such as climate change, habitat loss, fragmentation, overhunting or fishing, pollution, predation, disease, and parasitism.
For many species, relatively little is known about the conditions needed for successful breeding. Information about a species' reproductive biology may be critical to the success of a captive breeding program. In some cases a captive breeding program can save a species from extinction, but for success, breeders must consider many factors—including genetic, ecological, behavioral, and ethical issues. Most successful attempts involve the cooperation and coordination of many institutions. The efforts put into captive breeding can aid in education about conservation because species in captivity are closer to the public than their wild conspecifics. These accomplishments from the continued breeding of species for generations in captivity is also aided by extensive research efforts ex-situ and in-situ.
History
Captive breeding techniques began with the first human domestication of animals such as goats, and plants like wheat, at least 10,000 years ago. These practices were expanded with the rise of the first zoos, which started as royal menageries such as the one at Hierakonpolis, capital in the Predynastic Period of Egypt.
The first actual captive breeding programs were only started in the 1960s. These programs, such as the Arabian Oryx breeding program from the Phoenix Zoo in 1962, were aimed at the reintroduction of these species into the wild. These programs expanded under The Endangered Species Act of 1973 of the Nixon Administration which focused on protecting endangered species and their habitats to preserve biodiversity. Since th
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https://en.wikipedia.org/wiki/Time%20reversal%20signal%20processing
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Time reversal signal processing is a signal processing technique that has three main uses: creating an optimal carrier signal for communication, reconstructing a source event, and focusing high-energy waves to a point in space. A Time Reversal Mirror (TRM) is a device that can focus waves using the time reversal method. TRMs are also known as time reversal mirror arrays since they are usually arrays of transducers. TRM are well-known and have been used for decades in the optical domain. They are also used in the ultrasonic domain.
Overview
If the source is passive, i.e. some type of isolated reflector, an iterative technique can be used to focus energy on it. The TRM transmits a plane wave which travels toward the target and is reflected off it. The reflected wave returns to the TRM, where it looks as if the target has emitted a (weak) signal. The TRM reverses and retransmits the signal as usual, and a more focused wave travels toward the target. As the process is repeated, the waves become more and more focused on the target.
Yet another variation is to use a single transducer and an ergodic cavity. Intuitively, an ergodic cavity is one that will allow a wave originating at any point to reach any other point. An example of an ergodic cavity is an irregularly shaped swimming pool: if someone dives in, eventually the entire surface will be rippling with no clear pattern. If the propagation medium is lossless and the boundaries are perfect reflectors, a wave starting at any point will reach all other points an infinite number of times. This property can be exploited by using a single transducer and recording for a long time to get as many reflections as possible.
Theory
The time reversal technique is based upon a feature of the wave equation known as reciprocity: given a solution to the wave equation, then the time reversal (using a negative time) of that solution is also a solution. This occurs because the standard wave equation only contains even order
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https://en.wikipedia.org/wiki/EFront
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eFront was an affiliate marketing network which purchased successful websites, such as Penny Arcade, SquareGamer, and BetaNews, and pooled traffic to those sites to command higher prices for advertising during an industrywide ad revenue slowdown. In 2001, there was a scandal when ICQ instant messaging logs between the CEO Sam P. Jain and other employees were leaked onto the internet through Fuckedcompany.com. The logs detailed activities such as not paying websites that had hosted their banner ads, sending legal threats to websites that spoke poorly of eFront, and threatening to "rape her and spit on her" (referring to a female webmaster angry about not receiving her check from the company). The logs also detailed how eFront attempted to hire, though never ended up paying, Something Awful founder and webmaster Richard "Lowtax" Kyanka, ostensibly to have him generate a positive buzz for the company.
Richard Kyanka stated during a presentation at the University of Illinois in October 2005 that he was still owed $40,000 by eFront, and that the company ran a number of competitions to attract clients, yet the prizes were awarded to employees.
As of July 2006, the company's former efront.com domain is owned by an unrelated French software firm, eFront Alternative Investment Solutions.
References
External links
eFront website from the Internet Archive
Original ICQ logs - Sam Jain detailing his activity
Betanews escapes eFront meltdown from The Register
eFront Fiasco Was an Affront to Advertisers' Trust
Online advertising services and affiliate networks
Companies disestablished in 2001
Defunct marketing companies of the United States
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https://en.wikipedia.org/wiki/Markov%20number
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A Markov number or Markoff number is a positive integer x, y or z that is part of a solution to the Markov Diophantine equation
studied by .
The first few Markov numbers are
1, 2, 5, 13, 29, 34, 89, 169, 194, 233, 433, 610, 985, 1325, ...
appearing as coordinates of the Markov triples
(1, 1, 1), (1, 1, 2), (1, 2, 5), (1, 5, 13), (2, 5, 29), (1, 13, 34), (1, 34, 89), (2, 29, 169), (5, 13, 194), (1, 89, 233), (5, 29, 433), (1, 233, 610), (2, 169, 985), (13, 34, 1325), ...
There are infinitely many Markov numbers and Markov triples.
Markov tree
There are two simple ways to obtain a new Markov triple from an old one (x, y, z). First, one may permute the 3 numbers x,y,z, so in particular one can normalize the triples so that x ≤ y ≤ z. Second, if (x, y, z) is a Markov triple then so is (x, y, 3xy − z). Applying this operation twice returns the same triple one started with. Joining each normalized Markov triple to the 1, 2, or 3 normalized triples one can obtain from this gives a graph starting from (1,1,1) as in the diagram. This graph is connected; in other words every Markov triple can be connected to by a sequence of these operations. If we start, as an example, with we get its three neighbors , and in the Markov tree if z is set to 1, 5 and 13, respectively. For instance, starting with and trading y and z before each iteration of the transform lists Markov triples with Fibonacci numbers. Starting with that same triplet and trading x and z before each iteration gives the triples with Pell numbers.
All the Markov numbers on the regions adjacent to 2's region are odd-indexed Pell numbers (or numbers n such that 2n2 − 1 is a square, ), and all the Markov numbers on the regions adjacent to 1's region are odd-indexed Fibonacci numbers (). Thus, there are infinitely many Markov triples of the form
where Fk is the kth Fibonacci number. Likewise, there are infinitely many Markov triples of the form
where Pk is the kth Pell number.
Proof that this generate
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https://en.wikipedia.org/wiki/Teardrop%20tattoo
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The teardrop tattoo or tear tattoo is a symbolic tattoo of a tear that is placed underneath the eye. The teardrop is one of the most widely recognised prison tattoos and has various meanings.
It can signify that the wearer has spent time in prison, or more specifically that the wearer was raped while incarcerated and tattooed by the rapist as a "property" mark and for humiliation, since facial tattoos cannot be concealed.
The tattoo is sometimes worn by the female companions of prisoners in solidarity with their loved ones. Amy Winehouse had a teardrop drawn on her face in eyeliner after her husband Blake entered the Pentonville prison hospital following a suspected drug overdose.
It can acknowledge the loss of a friend or family member: Basketball player Amar'e Stoudemire has had a teardrop tattoo since 2012 honouring his older brother Hazell Jr., who died in a car accident.
In West Coast gang culture (USA), the tattoo may signify that the wearer has killed someone and in some of those circles, the tattoo's meaning can change: an empty outline meaning the wearer attempted murder.
Sometimes the exact meaning of the tattoo is known only by the wearer:
Portuguese footballer Ricardo Quaresma has never explained his teardrop tattoos.
See also
Criminal tattoo
Prison rape
Prison tattooing
References
Symbols
Tattoo designs
Prison culture
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https://en.wikipedia.org/wiki/Behavior-driven%20development
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In software engineering, behavior-driven development (BDD) is a software development process that goes well with agile software development process that encourages collaboration among developers, quality assurance experts, and customer representatives in a software project. It encourages teams to use conversation and concrete examples to formalize a shared understanding of how the application should behave. It emerged from test-driven development (TDD). Behavior-driven development combines the general techniques and principles of TDD with ideas from domain-driven design and object-oriented analysis and design to provide software development and management teams with shared tools and a shared process to collaborate on software development.
Although BDD is principally an idea about how software development should be managed by both business interests and technical insight, the practice of BDD does assume the use of specialized software tools to support the development process. Although these tools are often developed specifically for use in BDD projects, they can be seen as specialized forms of the tooling that supports test-driven development. The tools serve to add automation to the ubiquitous language that is a central theme of BDD.
BDD is largely facilitated through the use of a simple domain-specific language (DSL) using natural-language constructs (e.g., English-like sentences) that can express the behaviour and the expected outcomes. Test scripts have long been a popular application of DSLs with varying degrees of sophistication. BDD is considered an effective technical practice especially when the "problem space" of the business problem to solve is complex.
History
Behavior-driven development, an extension of test-driven development, is a development process that makes use of a simple DSL. These DSLs convert structured natural language statements into executable tests. The result is a closer relationship to acceptance criteria for a given function and the
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https://en.wikipedia.org/wiki/CDC%203000%20series
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The CDC 3000 series ("thirty-six hundred" or "thirty-one hundred") are a family of mainframe computers from Control Data Corporation (CDC). The first member, the CDC 3600, was a 48-bit system introduced in 1963. The same basic design led to the cut-down CDC 3400 of 1964, and then the 24-bit CDC 3300, 3200 and 3100 introduced between 1964 and 1965. The 3000 series replaced the earlier CDC 1604 and CDC 924 systems.
The line was a great success and became CDC's cash cow through the 1960s. The series significantly outsold the much faster and more expensive machines in the CDC 6000 series, but the performance of the 3000's relative to other vendors quickly eroded. The line was phased out of production in the early 1970s in favour of new members of the 6000 series, and then the CDC Cyber series, initially based on the 6600 design but spanning a wide range of performance.
Specifications
Upper 3000 series
The upper 3000 series used a 48-bit word size. The first 3000 machine to be produced was the CDC 3600; first delivered in June 1963. First deliveries of the CDC 3400 and CDC 3800 were in December 1965. These machines were designed for scientific computing applications; they were the upgrade path for users of the CDC 1604 machines. However these machines were overshadowed by the upcoming 60-bit CDC 6000 series machines when the CDC 6600 was introduced in December 1964 and delivered in 1965. Some high-end computer labs purchased these machines as stopgaps, while waiting for delivery of their 6600 machine. (CDC had indicated that the 6600 machines would use the same assembler language.)
Lower 3000 series
The lower 3000 series used a 24-bit word size. They were based on the earlier CDC 924 - a 24-bit version of the (48-bit) CDC 1604. The first lower 3000 to be released was the CDC 3200 (May 1964), followed by the smaller CDC 3100 (February 1965), and the CDC 3300 (December 1965). The final machine in the series, the CDC 3500, was released in March 1967 and used
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https://en.wikipedia.org/wiki/241%20%28number%29
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241 (two hundred [and] forty-one) is the natural number between 240 and 242. It is also a prime number.
241 is the larger of the twin primes (239, 241). Twin primes are pairs of primes separated by 2.
241 is a regular prime and a lucky prime.
Since 241 = 15 × 24 + 1, it is a Proth prime.
241 is a repdigit in base 15 (111).
241 is the only known Lucas–Wieferich prime to (U, V) = (3, −1).
References
Integers
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https://en.wikipedia.org/wiki/Outer%20billiards
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Outer billiards is a dynamical system based on a convex shape in the plane. Classically, this system is defined for the Euclidean plane but one can also consider the system in the hyperbolic plane or in other spaces that suitably generalize the plane. Outer billiards differs from a usual dynamical billiard in that it deals with a discrete sequence of moves outside the shape rather than inside of it.
Definitions
The outer billiards map
Let P be a convex shape in the plane.
Given a point x0 outside P, there is typically a unique
point x1 (also outside P) so that the line segment connecting x0 to x1 is tangent to P at its midpoint and
a person walking from x0 to x1 would see P on the right. (See Figure.) The map
F: x0 -> x1 is called the outer billiards map.
The inverse (or backwards) outer billiards map is also defined, as the map x1 -> x0.
One gets the inverse map simply by replacing the word right by the word left in the definition given above.
The figure shows the situation in the Euclidean plane, but the definition in the
hyperbolic plane is essentially the same.
Orbits
An outer billiards orbit is the set of all iterations
of the point, namely ... x0 <--> x1 <--> x2 <--> x3 ... That is, start at x0 and
iteratively apply both the outer billiards map and the backwards outer billiards map.
When P is a strictly convex shape, such as an ellipse,
every point in the exterior of P has a well defined orbit. When P
is a polygon, some points might not have well-defined orbits, on account of the
potential ambiguity of choosing the midpoint of the relevant tangent line. Nevertheless, in
the polygonal case, almost every point has a well-defined orbit.
An orbit is called periodic if it eventually repeats.
An orbit is called aperiodic (or non-periodic) if it is not periodic.
An orbit is called bounded (or stable) if some bounded region in the plane contains the whole orbit.
An orbit is called unbounded (or unstable) if it is not bounded.
Higher-dimensional spaces
De
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https://en.wikipedia.org/wiki/Engel%20expansion
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The Engel expansion of a positive real number x is the unique non-decreasing sequence of positive integers such that
For instance, Euler's number e has the Engel expansion
1, 1, 2, 3, 4, 5, 6, 7, 8, ...
corresponding to the infinite series
Rational numbers have a finite Engel expansion, while irrational numbers have an infinite Engel expansion. If x is rational, its Engel expansion provides a representation of x as an Egyptian fraction. Engel expansions are named after Friedrich Engel, who studied them in 1913.
An expansion analogous to an Engel expansion, in which alternating terms are negative, is called a Pierce expansion.
Engel expansions, continued fractions, and Fibonacci
observe that an Engel expansion can also be written as an ascending variant of a continued fraction:
They claim that ascending continued fractions such as this have been studied as early as Fibonacci's Liber Abaci (1202). This claim appears to refer to Fibonacci's compound fraction notation in which a sequence of numerators and denominators sharing the same fraction bar represents an ascending continued fraction:
If such a notation has all numerators 0 or 1, as occurs in several instances in Liber Abaci, the result is an Engel expansion. However, Engel expansion as a general technique does not seem to be described by Fibonacci.
Algorithm for computing Engel expansions
To find the Engel expansion of x, let
and
where is the ceiling function (the smallest integer not less than r).
If for any i, halt the algorithm.
Iterated functions for computing Engel expansions
Another equivalent method is to consider the map
and set
where
and
Yet another equivalent method, called the modified Engel expansion calculated by
and
The transfer operator of the Engel map
The Frobenius–Perron transfer operator of the Engel map acts on functions with
since
and the inverse of the n-th component is which is found by solving for .
Relation to the Riemann ζ function
The Mellin tran
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https://en.wikipedia.org/wiki/Single%20address%20space%20operating%20system
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In computer science, a single address space operating system (or SASOS) is an operating system that provides only one globally shared address space for all processes. In a single address space operating system, numerically identical (virtual memory) logical addresses in different processes all refer to exactly the same byte of data.
Single address-space operating systems offer certain advantages. In a traditional OS with private per-process address space, memory protection is based on address space boundaries ("address space isolation"). Single address-space operating systems use a different approach for memory protection that is just as strong. One advantage is that the same virtual-to-physical map page table can be used with every process (and in some SASOS, the kernel as well). This makes context switches on a SASOS faster than on operating systems that must change the page table and flush the TLB caches on every context switch.
SASOS projects include the following:
Amiga family – AmigaOS, AROS and MorphOS
Angel
BareMetal
Br1X
Genera by Symbolics
IBM i (formerly called OS/400)
Iguana at NICTA, Australia
JX a research Java OS
IncludeOS
Mungi at NICTA, Australia
Nemesis
Opal
OS-9
Phantom OS
RTEMS
Scout
Singularity
Sombrero
TempleOS
Theseus OS
Torsion
VxWorks
Zephyr
See also
Exokernel
Hybrid kernel
Kernel
Microkernel
Nanokernel
Unikernel
Flat memory model
Virtual memory
References
Bibliography
.
Operating systems
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https://en.wikipedia.org/wiki/FFTW
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The Fastest Fourier Transform in the West (FFTW) is a software library for computing discrete Fourier transforms (DFTs) developed by Matteo Frigo and Steven G. Johnson at the Massachusetts Institute of Technology.
FFTW is one of the fastest free software implementations of the fast Fourier transform (FFT). It implements the FFT algorithm for real and complex-valued arrays of arbitrary size and dimension.
Library
FFTW expeditiously transforms data by supporting a variety of algorithms and choosing the one (a particular decomposition of the transform into smaller transforms) it estimates or measures to be preferable in the particular circumstances. It works best on arrays of sizes with small prime factors, with powers of two being optimal and large primes being worst case (but still O(n log n)). To decompose transforms of composite sizes into smaller transforms, it chooses among several variants of the Cooley–Tukey FFT algorithm (corresponding to different factorizations and/or different memory-access patterns), while for prime sizes it uses either Rader's or Bluestein's FFT algorithm. Once the transform has been broken up into subtransforms of sufficiently small sizes, FFTW uses hard-coded unrolled FFTs for these small sizes that were produced (at compile time, not at run time) by code generation; these routines use a variety of algorithms including Cooley–Tukey variants, Rader's algorithm, and prime-factor FFT algorithms.
For a sufficiently large number of repeated transforms it is advantageous to measure the performance of some or all of the supported algorithms on the given array size and platform. These measurements, which the authors refer to as "wisdom", can be stored in a file or string for later use.
FFTW has a "guru interface" that intends "to expose as much as possible of the flexibility in the underlying FFTW architecture". This allows, among other things, multi-dimensional transforms and multiple transforms in a single call (e.g., where the data is in
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https://en.wikipedia.org/wiki/Johnjoe%20McFadden
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Johnjoe McFadden (born 17 May 1956) is an Anglo-Irish scientist, academic and writer. He is Professor of Molecular Genetics at the University of Surrey, United Kingdom.
Life
McFadden was born in Donegal, Ireland but raised in the UK. He holds joint British and Irish Nationality. He obtained his BSc in Biochemistry University of London in 1977 and his PhD at Imperial College London in 1982. He went on to work on human genetic diseases and then infectious diseases, at St Mary's Hospital Medical School, London (1982–84) and St George's Hospital Medical School, London (1984–88) and then at the University of Surrey in Guildford, UK.
For more than a decade, McFadden has researched the genetics of microbes such as the agents of tuberculosis and meningitis and invented a test for the diagnosis of meningitis. He has published more than 100 articles in scientific journals on subjects as wide-ranging as bacterial genetics, tuberculosis, idiopathic diseases and computer modelling of evolution. He has contributed to more than a dozen books and has edited a book on the genetics of mycobacteria. He produced a widely reported artificial life computer model which modelled evolution in organisms.
McFadden has lectured extensively in the UK, Europe, the US and Japan and his work has been featured on radio, television and national newspaper articles particularly for the Guardian. His present post, which he has held since 2001, is Professor of Molecular Genetics at the University of Surrey. Living in London, he is married and has one son.
Quantum evolution
McFadden wrote the popular science book, Quantum Evolution. The book examines the role of quantum mechanics in life, evolution and consciousness. The book has been described as offering an alternative evolutionary mechanism, beyond the neo-Darwinian framework.
The book received positive reviews by Kirkus Reviews and Publishers Weekly. It was negatively reviewed in the journal Heredity by evolutionary biologist Wallace Arthur.
W
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https://en.wikipedia.org/wiki/Radiant%20flux
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In radiometry, radiant flux or radiant power is the radiant energy emitted, reflected, transmitted, or received per unit time, and spectral flux or spectral power is the radiant flux per unit frequency or wavelength, depending on whether the spectrum is taken as a function of frequency or of wavelength. The SI unit of radiant flux is the watt (W), one joule per second (), while that of spectral flux in frequency is the watt per hertz () and that of spectral flux in wavelength is the watt per metre ()—commonly the watt per nanometre ().
Mathematical definitions
Radiant flux
Radiant flux, denoted ('e' for "energetic", to avoid confusion with photometric quantities), is defined as
where
is the time;
is the radiant energy flux of the field out of a closed surface ;
is the Poynting vector, representing the current density of radiant energy;
is the normal vector of a point on ;
represents the area of .
But the time-average of the norm of the Poynting vector is used instead, because in radiometry it is the only quantity that radiation detectors are able to measure:
where is the time-average, and is the angle between and
Spectral flux
Spectral flux in frequency, denoted Φe,ν, is defined as
where is the frequency.
Spectral flux in wavelength, denoted , is defined as
where is the wavelength.
SI radiometry units
See also
Luminous flux
Heat flux
Power (physics)
Radiosity (heat transfer)
References
Further reading
Power (physics)
Physical quantities
Radiometry
Temporal rates
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https://en.wikipedia.org/wiki/Van%20Deemter%20equation
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The van Deemter equation in chromatography, named for Jan van Deemter, relates the variance per unit length of a separation column to the linear mobile phase velocity by considering physical, kinetic, and thermodynamic properties of a separation. These properties include pathways within the column, diffusion (axial and longitudinal), and mass transfer kinetics between stationary and mobile phases. In liquid chromatography, the mobile phase velocity is taken as the exit velocity, that is, the ratio of the flow rate in ml/second to the cross-sectional area of the ‘column-exit flow path.’ For a packed column, the cross-sectional area of the column exit flow path is usually taken as 0.6 times the cross-sectional area of the column. Alternatively, the linear velocity can be taken as the ratio of the column length to the dead time. If the mobile phase is a gas, then the pressure correction must be applied. The variance per unit length of the column is taken as the ratio of the column length to the column efficiency in theoretical plates. The van Deemter equation is a hyperbolic function that predicts that there is an optimum velocity at which there will be the minimum variance per unit column length and, thence, a maximum efficiency. The van Deemter equation was the result of the first application of rate theory to the chromatography elution process.
Van Deemter equation
The van Deemter equation relates height equivalent to a theoretical plate (HETP) of a chromatographic column to the various flow and kinetic parameters which cause peak broadening, as follows:
Where
HETP = a measure of the resolving power of the column [m]
A = Eddy-diffusion parameter, related to channeling through a non-ideal packing [m]
B = diffusion coefficient of the eluting particles in the longitudinal direction, resulting in dispersion [m2 s−1]
C = Resistance to mass transfer coefficient of the analyte between mobile and stationary phase [s]
u = speed [m s−1]
In open tubular capillar
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https://en.wikipedia.org/wiki/Trudinger%27s%20theorem
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In mathematical analysis, Trudinger's theorem or the Trudinger inequality (also sometimes called the Moser–Trudinger inequality) is a result of functional analysis on Sobolev spaces. It is named after Neil Trudinger (and Jürgen Moser).
It provides an inequality between a certain Sobolev space norm and an Orlicz space norm of a function. The inequality is a limiting case of Sobolev imbedding and can be stated as the following theorem:
Let be a bounded domain in satisfying the cone condition. Let and . Set
Then there exists the embedding
where
The space
is an example of an Orlicz space.
References
.
.
Sobolev spaces
Inequalities
Theorems in analysis
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https://en.wikipedia.org/wiki/Wabun%20code
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is a form of Morse code used to send Japanese language in kana characters. Unlike International Morse Code, which represents letters of the Latin script, in Wabun each symbol represents a Japanese kana. For this reason, Wabun code is also sometimes called Kana code.
When Wabun code is intermixed with International Morse code, the prosign DO () is used to announce the beginning of Wabun, and the prosign SN () is used to announce the return to International Code.
Chart
Kana in Iroha order.
Expanded chart
References
External links
CW Wabun
Japanese Code Wabun Morse
The Silent War Against the Japanese Navy
Code Breaking in the Pacific
Katakana Man, The Most Secret of all Allied Operations in World War II in the Pacific
Encodings of Japanese
Morse code
ja:モールス符号#和文モールス符号
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https://en.wikipedia.org/wiki/Tunnel%20injection
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Tunnel injection is a field electron emission effect; specifically a quantum process called Fowler–Nordheim tunneling, whereby charge carriers are injected to an electric conductor through a thin layer of an electric insulator.
It is used to program NAND flash memory. The process used for erasing is called tunnel release. This injection is achieved by creating a large voltage difference between the gate and the body of the MOSFET. When VGB >> 0, electrons are injected into the floating gate. When VGB << 0, electrons are forced out of the floating gate.
An alternative to tunnel injection is the spin injection.
See also
Hot carrier injection
References
Quantum mechanics
Semiconductors
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https://en.wikipedia.org/wiki/Penetron
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The penetron, short for penetration tube, is a type of limited-color television used in some military applications. Unlike a conventional color television, the penetron produces a limited color gamut, typically two colors and their combination. Penetrons, and other military-only cathode ray tubes (CRTs), have been replaced by LCDs in modern designs.
History
Basic television
A conventional black and white television (B&W) uses a tube that is uniformly coated with a phosphor on the inside face. When excited by high-speed electrons, the phosphor gives off light, typically white but other colors are also used in certain circumstances. An electron gun at the back of the tube provides a beam of high-speed electrons, and a set of electromagnets arranged near the gun allow the beam to be moved about the display. The television signal is sent as a series of stripes, each one of which is displayed as a separate line on the display. The strength of the signal increases or decreases the current in the beam, producing bright or dark points on the display as the beam sweeps across the tube.
In a color display, the uniform coating of white phosphor is replaced by dots or lines of three colored phosphors, producing red, green or blue light (RGB) when excited. These primary colors mix in the human eye to produce a single apparent color. This presents a problem for conventional electron guns, which cannot be focussed or positioned accurately enough to hit these much smaller individual patterns. A number of companies were working on various solutions to this problem in the late 1940s, using three separate tubes or a single white-output with colored filters placed in front of it. None of these proved practical and this was a field of considerable development interest.
Penetron
The penetron was original designed by Koller and Williams while working at General Electric (GE). It was initially developed as a novel way to build a single-gun color television with the simplicity of a co
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https://en.wikipedia.org/wiki/Penrose%20graphical%20notation
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In mathematics and physics, Penrose graphical notation or tensor diagram notation is a (usually handwritten) visual depiction of multilinear functions or tensors proposed by Roger Penrose in 1971. A diagram in the notation consists of several shapes linked together by lines.
The notation widely appears in modern quantum theory, particularly in matrix product states and quantum circuits. In particular, Categorical quantum mechanics which includes ZX-calculus is a fully comprehensive reformulation of quantum theory in terms of Penrose diagrams, and is now widely used in quantum industry.
The notation has been studied extensively by Predrag Cvitanović, who used it, along with Feynman's diagrams and other related notations in developing "birdtracks", a group-theoretical diagram to classify the classical Lie groups. Penrose's notation has also been generalized using representation theory to spin networks in physics, and with the presence of matrix groups to trace diagrams in linear algebra.
Interpretations
Multilinear algebra
In the language of multilinear algebra, each shape represents a multilinear function. The lines attached to shapes represent the inputs or outputs of a function, and attaching shapes together in some way is essentially the composition of functions.
Tensors
In the language of tensor algebra, a particular tensor is associated with a particular shape with many lines projecting upwards and downwards, corresponding to abstract upper and lower indices of tensors respectively. Connecting lines between two shapes corresponds to contraction of indices. One advantage of this notation is that one does not have to invent new letters for new indices. This notation is also explicitly basis-independent.
Matrices
Each shape represents a matrix, and tensor multiplication is done horizontally, and matrix multiplication is done vertically.
Representation of special tensors
Metric tensor
The metric tensor is represented by a U-shaped loop or an upside-
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https://en.wikipedia.org/wiki/Idempotent%20matrix
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In linear algebra, an idempotent matrix is a matrix which, when multiplied by itself, yields itself. That is, the matrix is idempotent if and only if . For this product to be defined, must necessarily be a square matrix. Viewed this way, idempotent matrices are idempotent elements of matrix rings.
Example
Examples of idempotent matrices are:
Examples of idempotent matrices are:
Real 2 × 2 case
If a matrix is idempotent, then
implying so or
implying so or
Thus, a necessary condition for a matrix to be idempotent is that either it is diagonal or its trace equals 1.
For idempotent diagonal matrices, and must be either 1 or 0.
If , the matrix will be idempotent provided so a satisfies the quadratic equation
or
which is a circle with center (1/2, 0) and radius 1/2. In terms of an angle θ,
is idempotent.
However, is not a necessary condition: any matrix
with is idempotent.
Properties
Singularity and regularity
The only non-singular idempotent matrix is the identity matrix; that is, if a non-identity matrix is idempotent, its number of independent rows (and columns) is less than its number of rows (and columns).
This can be seen from writing , assuming that has full rank (is non-singular), and pre-multiplying by to obtain .
When an idempotent matrix is subtracted from the identity matrix, the result is also idempotent. This holds since
If a matrix is idempotent then for all positive integers n, . This can be shown using proof by induction. Clearly we have the result for , as . Suppose that . Then, , since is idempotent. Hence by the principle of induction, the result follows.
Eigenvalues
An idempotent matrix is always diagonalizable. Its eigenvalues are either 0 or 1: if is a non-zero eigenvector of some idempotent matrix and its associated eigenvalue, then which implies This further implies that the determinant of an idempotent matrix is always 0 or 1. As stated above, if the determinant is equal to one, the matrix is i
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https://en.wikipedia.org/wiki/Belling-Lee%20connector
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The Belling-Lee connector (also type 9,52, but largely only in the context of its specification, IEC 61169, Part 2: Radio-frequency coaxial connector of type 9,52) is commonly used in Europe, parts of South-East Asia, and Australia, to connect coaxial cables with each other and with terrestrial VHF/UHF roof antennas, antenna signal amplifiers, CATV distribution equipment, TV sets, and FM and DAB radio receivers. In these countries, it is known colloquially as a PAL antenna connector, IEC antenna connector, or simply as a TV aerial plug. It is one of the oldest coaxial connectors still commonly used in consumer devices. For television signals, the convention is that the source has a male connector and the receptor has a female connector. For FM radio signals, the convention is that the source has a female connector and the receptor has a male connector. This is more or less universally adopted with TV signals, while it's not uncommon for FM radio receivers to deviate from this, especially FM radio receivers from companies not based in the areas that use this kind of connector.
It was invented at Belling & Lee Ltd in Enfield, United Kingdom around 1922 at the time of the first BBC broadcasts. Originally intended for use only at MF frequencies (up to 1.6 MHz) when adopted for Television they were used for frequencies as high as 957 MHz. Belling Lee Limited still exists as a wholly owned subsidiary of Dialight, since 1992.
In type 9,52, the 9,52, in French SI style, refers to the 9.525mm (, or 0.375in) male external and female internal connector body diameter.
In their most common form the connectors just slide together. There is, however, also a screw-coupled variant which is specified to have an M14×1 thread.
There is also a miniature Belling-Lee connector which was used for internal connections inside some equipment (including BBC RC5/3 Band II receiver and the STC AF101 Radio Telephone). The miniature version is only about in diameter.
See also
List of RF c
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https://en.wikipedia.org/wiki/Dependence%20relation
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In mathematics, a dependence relation is a binary relation which generalizes the relation of linear dependence.
Let be a set. A (binary) relation between an element of and a subset of is called a dependence relation, written , if it satisfies the following properties:
if , then ;
if , then there is a finite subset of , such that ;
if is a subset of such that implies , then implies ;
if but for some , then .
Given a dependence relation on , a subset of is said to be independent if for all If , then is said to span if for every is said to be a basis of if is independent and spans
Remark. If is a non-empty set with a dependence relation , then always has a basis with respect to Furthermore, any two bases of have the same cardinality.
Examples
Let be a vector space over a field The relation , defined by if is in the subspace spanned by , is a dependence relation. This is equivalent to the definition of linear dependence.
Let be a field extension of Define by if is algebraic over Then is a dependence relation. This is equivalent to the definition of algebraic dependence.
See also
matroid
Linear algebra
Binary relations
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https://en.wikipedia.org/wiki/Kolmogorov%27s%20inequality
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In probability theory, Kolmogorov's inequality is a so-called "maximal inequality" that gives a bound on the probability that the partial sums of a finite collection of independent random variables exceed some specified bound.
Statement of the inequality
Let X1, ..., Xn : Ω → R be independent random variables defined on a common probability space (Ω, F, Pr), with expected value E[Xk] = 0 and variance Var[Xk] < +∞ for k = 1, ..., n. Then, for each λ > 0,
where Sk = X1 + ... + Xk.
The convenience of this result is that we can bound the worst case deviation of a random walk at any point of time using its value at the end of time interval.
Proof
The following argument employs discrete martingales.
As argued in the discussion of Doob's martingale inequality, the sequence is a martingale.
Define as follows. Let , and
for all .
Then is also a martingale.
For any martingale with , we have that
Applying this result to the martingale , we have
where the first inequality follows by Chebyshev's inequality.
This inequality was generalized by Hájek and Rényi in 1955.
See also
Chebyshev's inequality
Etemadi's inequality
Landau–Kolmogorov inequality
Markov's inequality
Bernstein inequalities (probability theory)
References
(Theorem 22.4)
Stochastic processes
Probabilistic inequalities
Articles containing proofs
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https://en.wikipedia.org/wiki/Przemys%C5%82aw%20Prusinkiewicz
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Przemysław (Przemek) Prusinkiewicz is a Polish computer scientist who advanced the idea that Fibonacci numbers in nature can be in part understood as the expression of certain algebraic constraints on free groups, specifically as certain Lindenmayer grammars. Prusinkiewicz's main work is on the modeling of plant growth through such grammars.
Early life and education
in 1978 Prusinkiewicz received his PhD from Warsaw University of Technology .
Career
As of 2008 he was a professor of Computer Science at the University of Calgary.
Awards
Prusinkiewicz received the 1997 SIGGRAPH Computer Graphics Achievement Award for his work.
Influences
In 2006, Michael Hensel examined the work of Prusinkiewicz and his collaborators - the Calgary team - in an article published in Architectural Design. Hensel argued that the Calgary team's computational plant models or "virtual plants" which culminated in software they developed capable of modeling various plant characteristics, could provide important lessons for architectural design. Architects would learn from "the self-organisation processes underlying the growth of living organisms" and the Calgary team's work uncovered some of that potential. Their computational models allowed for a "quantitative understanding of developmental mechanisms" and had the potential to "lead to a synthetic understanding of the interplay between various aspects of development."
Prusinkiewicz's work was informed by that of the Hungarian biologist Aristid Lindenmayer who developed the theory of L-systems in 1968. Lindenmayer used L-systems to describe the behaviour of plant cells and to model the growth processes, plant development and the branching architecture of plant development.
Publications
References
External links
Biography of Przemysław Prusinkiewicz from the University of Calgary
Laboratory website at the University of Calgary
Warsaw University of Technology alumni
Polish mathematicians
Living people
Computer graphics professionals
Com
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https://en.wikipedia.org/wiki/Equivariant%20cohomology
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In mathematics, equivariant cohomology (or Borel cohomology) is a cohomology theory from algebraic topology which applies to topological spaces with a group action. It can be viewed as a common generalization of group cohomology and an ordinary cohomology theory. Specifically, the equivariant cohomology ring of a space with action of a topological group is defined as the ordinary cohomology ring with coefficient ring of the homotopy quotient :
If is the trivial group, this is the ordinary cohomology ring of , whereas if is contractible, it reduces to the cohomology ring of the classifying space (that is, the group cohomology of when G is finite.) If G acts freely on X, then the canonical map is a homotopy equivalence and so one gets:
Definitions
It is also possible to define the equivariant cohomology
of with coefficients in a
-module A; these are abelian groups.
This construction is the analogue of cohomology with local coefficients.
If X is a manifold, G a compact Lie group and is the field of real numbers or the field of complex numbers (the most typical situation), then the above cohomology may be computed using the so-called Cartan model (see equivariant differential forms.)
The construction should not be confused with other cohomology theories,
such as Bredon cohomology or the cohomology of invariant differential forms: if G is a compact Lie group, then, by the averaging argument, any form may be made invariant; thus, cohomology of invariant differential forms does not yield new information.
Koszul duality is known to hold between equivariant cohomology and ordinary cohomology.
Relation with groupoid cohomology
For a Lie groupoid equivariant cohomology of a smooth manifold is a special example of the groupoid cohomology of a Lie groupoid. This is because given a -space for a compact Lie group , there is an associated groupoidwhose equivariant cohomology groups can be computed using the Cartan complex which is the totalization of the d
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https://en.wikipedia.org/wiki/Hartogs%20number
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In mathematics, specifically in axiomatic set theory, a Hartogs number is an ordinal number associated with a set. In particular, if X is any set, then the Hartogs number of X is the least ordinal α such that there is no injection from α into X. If X can be well-ordered then the cardinal number of α is a minimal cardinal greater than that of X. If X cannot be well-ordered then there cannot be an injection from X to α. However, the cardinal number of α is still a minimal cardinal not less than or equal to the cardinality of X. (If we restrict to cardinal numbers of well-orderable sets then that of α is the smallest that is not not less than or equal to that of X.) The map taking X to α is sometimes called Hartogs's function. This mapping is used to construct the aleph numbers, which are all the cardinal numbers of infinite well-orderable sets.
The existence of the Hartogs number was proved by Friedrich Hartogs in 1915, using Zermelo–Fraenkel set theory alone (that is, without using the axiom of choice).
Hartogs's theorem
Hartogs's theorem states that for any set X, there exists an ordinal α such that ; that is, such that there is no injection from α to X. As ordinals are well-ordered, this immediately implies the existence of a Hartogs number for any set X. Furthermore, the proof is constructive and yields the Hartogs number of X.
Proof
See .
Let be the class of all ordinal numbers β for which an injective function exists from β into X.
First, we verify that α is a set.
X × X is a set, as can be seen in Axiom of power set.
The power set of X × X is a set, by the axiom of power set.
The class W of all reflexive well-orderings of subsets of X is a definable subclass of the preceding set, so it is a set by the axiom schema of separation.
The class of all order types of well-orderings in W is a set by the axiom schema of replacement, as
(Domain(w), w) (β, ≤)
can be described by a simple formula.
But this last set is exactly α. Now, because a transitive set
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https://en.wikipedia.org/wiki/Conjugation%20of%20isometries%20in%20Euclidean%20space
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In a group, the conjugate by g of h is ghg−1.
Translation
If h is a translation, then its conjugation by an isometry can be described as applying the isometry to the translation:
the conjugation of a translation by a translation is the first translation
the conjugation of a translation by a rotation is a translation by a rotated translation vector
the conjugation of a translation by a reflection is a translation by a reflected translation vector
Thus the conjugacy class within the Euclidean group E(n) of a translation is the set of all translations by the same distance.
The smallest subgroup of the Euclidean group containing all translations by a given distance is the set of all translations. So, this is the conjugate closure of a singleton containing a translation.
Thus E(n) is a direct product of the orthogonal group O(n) and the subgroup of translations T, and O(n) is isomorphic with the quotient group of E(n) by T:
O(n) E(n) / T
Thus there is a partition of the Euclidean group with in each subset one isometries that keeps the origins fixed, and its combination with all translations.
Each isometry is given by an orthogonal matrix A in O(n) and a vector b:
and each subset in the quotient group is given by the matrix A only.
Similarly, for the special orthogonal group SO(n) we have
SO(n) E+(n) / T
Inversion
The conjugate of the inversion in a point by a translation is the inversion in the translated point, etc.
Thus the conjugacy class within the Euclidean group E(n) of inversion in a point is the set of inversions in all points.
Since a combination of two inversions is a translation, the conjugate closure of a singleton containing inversion in a point is the set of all translations and the inversions in all points. This is the generalized dihedral group dih (Rn).
Similarly { I, −I } is a normal subgroup of O(n), and we have:
E(n) / dih (Rn) O(n) / { I, −I }
For odd n we also have:
O(n) SO(n) × { I, −I }
and hence not only
O(n) / SO(n) { I, −I
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https://en.wikipedia.org/wiki/N-skeleton
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In mathematics, particularly in algebraic topology, the of a topological space presented as a simplicial complex (resp. CW complex) refers to the subspace that is the union of the simplices of (resp. cells of ) of dimensions In other words, given an inductive definition of a complex, the is obtained by stopping at the .
These subspaces increase with . The is a discrete space, and the a topological graph. The skeletons of a space are used in obstruction theory, to construct spectral sequences by means of filtrations, and generally to make inductive arguments. They are particularly important when has infinite dimension, in the sense that the do not become constant as
In geometry
In geometry, a of P (functionally represented as skelk(P)) consists of all elements of dimension up to k.
For example:
skel0(cube) = 8 vertices
skel1(cube) = 8 vertices, 12 edges
skel2(cube) = 8 vertices, 12 edges, 6 square faces
For simplicial sets
The above definition of the skeleton of a simplicial complex is a particular case of the notion of skeleton of a simplicial set. Briefly speaking, a simplicial set can be described by a collection of sets , together with face and degeneracy maps between them satisfying a number of equations. The idea of the n-skeleton is to first discard the sets with and then to complete the collection of the with to the "smallest possible" simplicial set so that the resulting simplicial set contains no non-degenerate simplices in degrees .
More precisely, the restriction functor
has a left adjoint, denoted . (The notations are comparable with the one of image functors for sheaves.) The n-skeleton of some simplicial set is defined as
Coskeleton
Moreover, has a right adjoint . The n-coskeleton is defined as
For example, the 0-skeleton of K is the constant simplicial set defined by . The 0-coskeleton is given by the Cech nerve
(The boundary and degeneracy morphisms are given by various projections and diagonal embeddings, respec
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https://en.wikipedia.org/wiki/Cytochemistry
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Cytochemistry is the branch of cell biology dealing with the detection of cell constituents by means of biochemical analysis and visualization techniques. This is the study of the localization of cellular components through the use of staining methods. The term is also used to describe a process of identification of the biochemical content of cells. Cytochemistry is a science of localizing chemical components of cells and cell organelles on thin histological sections by using several techniques like enzyme localization, micro-incineration, micro-spectrophotometry, radioautography, cryo-electron microscopy, X-ray microanalysis by energy-dispersive X-ray spectroscopy, immunohistochemistry and cytochemistry, etc.
Freeze Fracture Enzyme Cytochemistry
Freeze fracture enzyme cytochemistry was initially mentioned in the study of Pinto de silva in 1987. It is a technique that allows the introduction of cytochemistry into a freeze fracture cell membrane. immunocytochemistry is used in this technique to label and visualize the cell membrane's molecules. This technique could be useful in analyzing the ultrastructure of cell membranes. The combination of immunocytochemistry and freeze fracture enzyme technique, research can identify and have a better understanding of the structure and distribution of a cell membrane.
Origin
Jean Brachet's research in Brussel demonstrated the localization and relative abundance between RNA and DNA in the cells of both animals and plants opened up the door into the research of cytochemistry. The work by Moller and Holter in 1976 about endocytosis which discussed the relationship between a cell's structure and function had established the needs of cytochemical research.
Aims
Cytochemical research aims to study individual cells that may contain several cell types within a tissue. It takes a nondestructive approach to study the localization of the cell. By remaining the cell components intact, researcher are able to study the intact cell activ
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https://en.wikipedia.org/wiki/ISO%207001
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ISO 7001 ("public information symbols") is a standard published by the International Organization for Standardization that defines a set of pictograms and symbols for public information. The latest version, ISO 7001:2023, was published in February 2023.
The set is the result of extensive testing in several countries and different cultures and have met the criteria for comprehensibility set up by the ISO. The design process and testing of ISO 7001 symbols is governed by ISO 22727:2007, Graphical symbols — Creation and design of public information symbols — Requirements. Common examples of public information symbols include those representing toilets, car parking, and information, and the International Symbol of Access.
History
ISO 7001 was first released in October 1980, with a single amendment in 1985. The second edition was released in February 1990, with one amendment in 1993. The third edition, the latest edition was released in November 2007, and has received four amendments in 2013, 2015, 2016 and 2017. The use of the symbols of ISO 7001 is recommended by the European standard EN 17210.
Implementation
ISO 7001 sets out some general guidelines for how symbols should be utilized, though large aspects are left up to the decision of the individual or entity designing signage for their facility.
Symbols were created with the goal of being able to stand alone, without any accompanying text. However, text can be used to further aid in communicating the message, particularly in a situation where a custom symbol has been designed for a unique situation not covered by standard ISO 7001 symbols. Specific sizes for symbols are not provided in ISO 7001, though symbols are designed with the goal of being clearly understood regardless placed on something as small as a floor plan of a building or as a large as a giant sign hanging from a ceiling in a large open space.
While symbols are intended and recommended to be reproduced as presented in ISO 7001, the ISO acknowled
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https://en.wikipedia.org/wiki/Cathodic%20arc%20deposition
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Cathodic arc deposition or Arc-PVD is a physical vapor deposition technique in which an electric arc is used to vaporize material from a cathode target. The vaporized material then condenses on a substrate, forming a thin film. The technique can be used to deposit metallic, ceramic, and composite films.
History
Industrial use of modern cathodic arc deposition technology originated in Soviet Union around 1960–1970.
By the late 70's Soviet government released the use of this technology to the West.
Among many designs in USSR at that time the design by L. P. Sablev, et al., was allowed to be used outside the USSR.
Process
The arc evaporation process begins with the striking of a high current, low voltage arc on the surface of a cathode (known as the target) that gives rise to a small (usually a few micrometres wide), highly energetic emitting area known as a cathode spot. The localised temperature at the cathode spot is extremely high (around 15000 °C), which results in a high velocity (10 km/s) jet of vapourised cathode material, leaving a crater behind on the cathode surface. The cathode spot is only active for a short period of time, then it self-extinguishes and re-ignites in a new area close to the previous crater. This behaviour causes the apparent motion of the arc.
As the arc is basically a current carrying conductor it can be influenced by the application of an electromagnetic field, which in practice is used to rapidly move the arc over the entire surface of the target, so that the total surface is eroded over time.
The arc has an extremely high power density resulting in a high level of ionization (30-100%), multiple charged ions, neutral particles, clusters and macro-particles (droplets). If a reactive gas is introduced during the evaporation process, dissociation, ionization and excitation can occur during interaction with the ion flux and a compound film will be deposited.
One downside of the arc evaporation process is that if the cathode spot stay
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https://en.wikipedia.org/wiki/Terayon
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Terayon Communication Systems, Inc. was a company that vended equipment to broadband service providers for delivering broadband voice, video and data services to residential and business subscribers.
History
Terayon was founded by Israeli brothers Zaki Rakib and Shlomo Rakib in 1993; both brothers graduated from high school at age 16 and went on to university. Shlomo studied electrical engineering, and Zaki did a PhD in mechanical engineering and post-doctorate studies in applied mathematics. He taught for a while at Tel Aviv University’s computer science faculty, and then joined Helios. After Helios was sold to Cadence Design Systems, Zaki moved to the US, and urged his brother to join him and set up the company. Terayon held an IPO on NASDAQ in August 1998.
In 1999, the company initiated a strategy to expand its offerings to the telecommunication and satellite industries but later refocused its business on the cable industry in 2000. During 1999 and 2000 the company acquired seven other companies, including: Imedia, a video processing startup founded by Efi Arazi (founder of Scitex) for $100m; Radwiz for $64m from the Rad Group, Teledata Networks (which was later sold) and Ultracom Communications for $32m in March 2000.
In 2004, Terayon recentered its strategy on digital video solutions, marketing to television broadcasters, telecom carriers and satellite television providers. Terayon also decided to phase out equipment for home access, such as cable modems and home networking devices.
In April 2006, Terayon was delisted from NASDAQ due to outstanding financial reports. Motorola Inc. acquired Terayon for $140 million in June 2007.
See also
Motorola Inc.
References
Companies formerly listed on the Nasdaq
Companies based in Santa Clara, California
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https://en.wikipedia.org/wiki/MuseWeb
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MuseWeb (formerly Museums and the Web) is an annual international conference in the field of museums and their websites. It was founded and organized by Archives & Museum Informatics and has taken place each spring since 1997 in North America, along with events in other countries.
Since 2011 it has been organized by Museums and the Web LLC and Co-Chaired by Nancy Proctor and Rich Cherry, who also co-edit the proceedings.
Overview
The conference includes the GLAMi awards(The Galleries, Libraries, Archives, and Museums Innovation awards) which recognizes the best GLAM work in the sector. Projects are nominated by GLAM professionals from around the world and reviewed by a committee of peers. The conference previously included annual "Best of the Web awards" for museum-related websites in a number of different categories, as well as an overall winner.
Individual conferences
The following events have been held or are planned:
MW1997, March 16–19, 1997 — Los Angeles, California, US
MW1998, April 22–25, 1998 — Toronto, Ontario, Canada
MW1999, March 11–14, 1999 — New Orleans, Louisiana, US
MW2000, April 16–19, 2000 — Minneapolis, Minnesota, US
MW2001, March 14–17, 2001 — Seattle, Washington, US
MW2002, April 17–20, 2002 — Boston, Massachusetts, US
MW2003, March 19–22, 2003 — Charlotte, North Carolina, US
MW2004, March 31 – April 3, 2004 — Arlington, Virginia / Washington DC, US
MW2005, April 13–17, 2005 — Vancouver, British Columbia, Canada
MW2006, March 22–25, 2006 — Albuquerque, New Mexico, US
MW2007, April 11–14, 2007 — San Francisco, California, US
MW2008, April 8–12, 2008 — Montreal, Quebec, Canada
MW2009, April 14–18, 2009 — Indianapolis, Indiana, US
MW2010, April 13–17, 2010 — Denver, Colorado, US
MW2011, April 6–9, 2011 — Philadelphia, Pennsylvania, US
MW2012, April 11–14, 2012 — San Diego, California, US
MW2013, April 17–20, 2013 — Portland, Oregon, US
MWA2013, December 9–12, 2013 — Hong Kong
MWF2014, February 19–21, 2014 — Florence, Italy
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https://en.wikipedia.org/wiki/Orange%20oil
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Orange oil is an essential oil produced by cells within the rind of an orange fruit (Citrus sinensis fruit). In contrast to most essential oils, it is extracted as a by-product of orange juice production by centrifugation, producing a cold-pressed oil. It is composed of mostly (greater than 90%) d-limonene, and is often used in place of pure d-limonene. D-limonene can be extracted from the oil by distillation.
Composition
The compounds inside an orange oil vary with each different oil extraction. Composition varies as a result of regional and seasonal changes as well as the method used for extraction. Several hundred compounds have been identified with gas chromatograph-mass spectrometry. Most of the substances in the oil belong to the terpene group with limonene being the dominant one. Long chain aliphatic hydrocarbon alcohols and aldehydes like 1-octanol and octanal are second important group of substances. The presence of sinensetin, a flavone, explains the orange color.
Uses
Structural pest control
California has authorized and registered d-Limonene (Orange Oil) as an active ingredient with the EPA. and Florida for the extermination of drywood termites, Formosan termites, and other structural pests. It is the active ingredient of the popular structural termiticide XT-2000. Regarded an alternative to traditional fumigation, d-Limonene orange oil is increasing in popularity as approximately 70% of modern consumers in California prefer local structural chemical injections over traditional "tenting" or fumigation.
Biological pest control
Orange oil can be used in green pesticides for biological pest control. It can exterminate or control ants and other insects by erasing their scent-pheromone trail indicators, or dissolving their exoskeleton, eliminating the infestation or disrupting re-infestation.
Orange oil is also known to be useful to control, but not exterminate, drywood termites (Incisitermes), killing only those who come into direct contact with it.
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https://en.wikipedia.org/wiki/Delta%20neutral
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In finance, delta neutral describes a portfolio of related financial securities, in which the portfolio value remains unchanged when small changes occur in the value of the underlying security. Such a portfolio typically contains options and their corresponding underlying securities such that positive and negative delta components offset, resulting in the portfolio's value being relatively insensitive to changes in the value of the underlying security.
A related term, delta hedging is the process of setting or keeping the delta of a portfolio as close to zero as possible. In practice, maintaining a zero delta is very complex because there are risks associated with re-hedging on large movements in the underlying stock's price, and research indicates portfolios tend to have lower cash flows if re-hedged too frequently.
Mathematical interpretation
Delta measures the sensitivity of the value of an option to changes in the price of the underlying stock assuming all other variables remain unchanged.
Mathematically, delta is represented as partial derivative
of the option's fair value with respect to the price of the underlying security.
Delta is clearly a function of S, however Delta is also a function of strike price and time to expiry.
Therefore, if a position is delta neutral (or, instantaneously delta-hedged) its instantaneous change in value, for an infinitesimal change in the value of the underlying security, will be zero; see Hedge (finance). Since delta measures the exposure of a derivative to changes in the value of the underlying, a portfolio that is delta neutral is effectively hedged. That is, its overall value will not change for small changes in the price of its underlying instrument.
Creating the position
Delta hedging - i.e. establishing the required hedge - may be accomplished by buying or selling an amount of the underlier that corresponds to the delta of the portfolio. By adjusting the amount bought or sold on new positions, the portfolio de
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https://en.wikipedia.org/wiki/Gyricon
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Gyricon is a type of electronic paper developed at the Xerox PARC (Palo Alto Research Center). It has many of the same properties as paper: it is flexible, contains an image, and is viewable from a wide angle, but it can be erased and written thousands of times.
A Gyricon sheet is a thin layer of transparent plastic, in which millions of small beads, somewhat like toner particles, are randomly dispersed. The beads, each contained in an oil-filled cavity, are free to rotate within those cavities. The beads are "bichromal", with hemispheres of two contrasting colors (e.g. black and white, red and white), and charged, so they exhibit an electrical dipole. When voltage is applied to the surface of the sheet, the beads rotate to present one colored side to the viewer. Voltages can be applied to the surface to create images such as text and pictures. The image will persist until new voltage patterns are applied
As of December, 2005, Xerox closed down the direct subsidiary Gyricon LLC, their Gyricon e-paper display business, and is focusing on licensing the technology.
The company have said that the reason for their closure has been their inability to source backplane technology for their Gyricon frontplane at a price of less than $10 per square foot (US$100/m2). Being able to achieve a price of under $10 was said to be critical to the success of marketing their e-paper-based electronic signage products. Although the company will stop direct manufacture and sale of Gyricon e-paper display products, it will, however, still be licensing their frontplane technology to other users.
References
Display technology
Synthetic paper
Electronic paper technology
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https://en.wikipedia.org/wiki/Minkowski%E2%80%93Hlawka%20theorem
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In mathematics, the Minkowski–Hlawka theorem is a result on the lattice packing of hyperspheres in dimension n > 1. It states that there is a lattice in Euclidean space of dimension n, such that the corresponding best packing of hyperspheres with centres at the lattice points has density Δ satisfying
with ζ the Riemann zeta function. Here as n → ∞, ζ(n) → 1. The proof of this theorem is indirect and does not give an explicit example, however, and there is still no known simple and explicit way to construct lattices with packing densities exceeding this bound for arbitrary n. In principle one can find explicit examples: for example, even just picking a few "random" lattices will work with high probability. The problem is that testing these lattices to see if they are solutions requires finding their shortest vectors, and the number of cases to check grows very fast with the dimension, so this could take a very long time.
This result was stated without proof by and proved by . The result is related to a linear lower bound for the Hermite constant.
Siegel's theorem
proved the following generalization of the Minkowski–Hlawka theorem. If S is a bounded set in Rn with Jordan volume vol(S) then the average number of nonzero lattice vectors in S is vol(S)/D, where the average is taken over all lattices with a fundamental domain of volume D, and similarly the average number of primitive lattice vectors in S is vol(S)/Dζ(n).
The Minkowski–Hlawka theorem follows easily from this, using the fact that if S is a star-shaped centrally symmetric body (such as a ball) containing less than 2 primitive lattice vectors then it contains no nonzero lattice vectors.
See also
Kepler conjecture
References
Geometry of numbers
Theorems in geometry
Hermann Minkowski
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https://en.wikipedia.org/wiki/Cryptographic%20key%20types
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A cryptographic key is a string of data that is used to lock or unlock cryptographic functions, including authentication, authorization and encryption. Cryptographic keys are grouped into cryptographic key types according to the functions they perform.
Description
Consider a keyring that contains a variety of keys. These keys might be various shapes and sizes, but one thing is certain, each will generally serve a separate purpose. One key might be used to start an automobile, while another might be used to open a safe deposit box. The automobile key will not work to open the safe deposit box and vice versa. This analogy provides some insight on how cryptographic key types work. These keys are categorized in respect to how they are used and what properties they possess.
A cryptographic key is categorized according to how it will be used and what properties it has. For example, a key might have one of the following properties: Symmetric, Public or Private. Keys may also be grouped into pairs that have one private and one public key, which is referred to as an Asymmetric key pair.
Asymmetric versus symmetric keys
Asymmetric keys differ from symmetric keys in that the algorithms use separate keys for encryption and decryption, while a symmetric key’s algorithm uses a single key for both processes. Because multiple keys are used with an asymmetric algorithm, the process takes longer to produce than a symmetric key algorithm would. However, the benefits lay in the fact that an asymmetric algorithm is much more secure than a symmetric key algorithm is.
With a symmetric key, the key needs to be transmitted to the receiver, where there is always the possibility that the key could be intercepted or tampered with. With an asymmetric key, the message and/or accompanying data can be sent or received by using a public key; however, the receiver or sender would use his or her personal private key to access the message and/or accompanying data. Thus, asymmetric keys are suit
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https://en.wikipedia.org/wiki/South%20African%20Computer%20Olympiad
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The South African Computing Olympiad (SACO) is an annual computer programming competition for secondary school students (although at least one primary school student has participated) in South Africa. The South African team for the International Olympiad in Informatics is selected through it.
Competition rounds
The competition consists of three rounds. The first is a pen-and-paper aptitude examination at the entrant's school, testing a combination of general knowledge, computer knowledge, problem-solving and basic programming. (Entrants are often required to program an imaginary robot in a fictional Logo-like language.) Although the first round is not compulsory, it is accessible to those who do not have access to, or knowledge of, computers. 31,926 students entered it in 2006.
In the second round, actual programs must be written and executed. There are five questions, each requiring a different program to be written. Most entrants answer only a single question. The tasks usually include one basic shape-drawing program—for example, the 2004 question "TriSquare" required output such as:
*
* *
* *
*****
* *
* *
* *
*****
The top performers—those who have answered four or five questions in the second round—are invited to the final round. In prior years, between 10 and 15 students were chosen; but the introduction of a new language, and increased funding from the Shuttleworth Foundation in 2005, has increased it to between 20 and 30 students. The final round is held at the University of Cape Town, where finalists stay over a weekend. It consists of two five-hour rounds, the first on Saturday and second on Sunday. The problems are similar to those in the USACO, though somewhat easier. A prize ceremony is held that Monday.
Prizes
The top six entrants are awarded medals (one gold, two silver and three bronze). There are cash prizes, both for the winners and their schools. There were bonus prizes totalling R100,000 for using Python, due to Shuttlewor
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https://en.wikipedia.org/wiki/Focused%20ion%20beam
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Focused ion beam, also known as FIB, is a technique used particularly in the semiconductor industry, materials science and increasingly in the biological field for site-specific analysis, deposition, and ablation of materials. A FIB setup is a scientific instrument that resembles a scanning electron microscope (SEM). However, while the SEM uses a focused beam of electrons to image the sample in the chamber, a FIB setup uses a focused beam of ions instead. FIB can also be incorporated in a system with both electron and ion beam columns, allowing the same feature to be investigated using either of the beams. FIB should not be confused with using a beam of focused ions for direct write lithography (such as in proton beam writing). These are generally quite different systems where the material is modified by other mechanisms.
Ion beam source
Most widespread instruments are using liquid metal ion sources (LMIS), especially gallium ion sources. Ion sources based on elemental gold and iridium are also available. In a gallium LMIS, gallium metal is placed in contact with a tungsten needle, and heated gallium wets the tungsten and flows to the tip of the needle, where the opposing forces of surface tension and electric field form the gallium into a cusp shaped tip called a Taylor cone. The tip radius of this cone is extremely small (~2 nm). The huge electric field at this small tip (greater than volts per centimeter) causes ionization and field emission of the gallium atoms.
Source ions are then generally accelerated to an energy of , and focused onto the sample by electrostatic lenses. LMIS produce high current density ion beams with very small energy spread. A modern FIB can deliver tens of nanoamperes of current to a sample, or can image the sample with a spot size on the order of a few nanometers.
More recently, instruments using plasma beams of noble gas ions, such as xenon, have become available more widely.
Principle
Focused ion beam (FIB) systems have been prod
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https://en.wikipedia.org/wiki/Petriscript
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PetriScript is a modeling language for Petri nets, designed by Alexandre Hamez and Xavier Renault. The CPN-AMI platform provides many tools to work on Petri nets, such as verifying and model-checking tools.
Originally, simple Petri nets were created through graphic design, but research conducted internally at LIP6 revealed that it was needed to automate such tasks. PetriScript was designed to provide some facilities in modeling places-transition and coloured Petri nets within the CPN-AMI platform. Petriscript's main purpose is to automate modeling operations on Petri nets by merging, creating, and connecting nodes. It supports almost everything needed, such as macros, loops control, lists, and string and arithmetic expressions, and blocks intervention of the user as much as possible. Its syntax is Ada-like.
The following script produces a FIFO with three sections:
define(FIFO_SIZE,3)
define(FIFO_BASE_X,100)
define(FIFO_BASE_Y,100)
define(FIFO_STEP,120)
int $wave := 0;
for $wave in 1..FIFO_SIZE loop
create place "Slot_" & '$wave' (x FIFO_BASE_X + FIFO_STEP * $wave,
y FIFO_BASE_Y);
create place "Empty_" & '$wave' (x FIFO_BASE_X + FIFO_STEP * $wave,
y FIFO_BASE_Y + 100, marking "1");
end loop;
for $wave in 1..FIFO_SIZE+1 loop
create transition "t" & '$wave -1' & "_to_" & '$wave' (x FIFO_BASE_X + FIFO_STEP * $wave - FIFO_STEP / 2,
y FIFO_BASE_Y + 50);
if $wave < FIFO_SIZE+1 then
connect "1" transition "t" &'$wave -1' & "_to_" & '$wave' to place "Slot_" & '$wave';
connect "1" place "Empty_" & '$wave' to transition "t" &'$wave -1' & "_to_" & '$wave';
end if;
if $wave > 1 then
connect "1" transition "t" &'$wave -1' & "_to_" & '$wave' to place "Empty_" & '$wave - 1';
connect "1" place "Slot_" & '$wave - 1' to transition "t" &'$wave -1' & "_to_" & '$wave';
end if;
end loop;
set transition "t0_to_1" to (name "FIFO_Start");
set transition "t" & 'FIFO_SIZE' & "_to_" & 'FIFO_SIZE + 1' to (name "FIFO_End");
Which produces the fol
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https://en.wikipedia.org/wiki/ITU-R%20468%20noise%20weighting
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ITU-R 468 (originally defined in CCIR recommendation 468-4, therefore formerly also known as CCIR weighting; sometimes referred to as CCIR-1k) is a standard relating to noise measurement, widely used when measuring noise in audio systems. The standard, now referred to as ITU-R BS.468-4, defines a weighting filter curve, together with a quasi-peak rectifier having special characteristics as defined by specified tone-burst tests. It is currently maintained by the International Telecommunication Union who took it over from the CCIR.
It is used especially in the UK, Europe, and former countries of the British Empire such as Australia and South Africa. It is less well known in the USA where A-weighting has always been used.
M-weighting is a closely related filter, an offset version of the same curve, without the quasi-peak detector.
Explanation
The A-weighting curve was based on the 40 phon equal-loudness contour derived initially by Fletcher and Munson (1933). Originally incorporated into an ANSI standard for sound level meters, A-weighting was intended for measurement of the audibility of sounds by themselves. It was never specifically intended for the measurement of the more random (near-white or pink) noise in electronic equipment, though has been used for this purpose by most microphone manufacturers since the 1970s. The human ear responds quite differently to clicks and bursts of random noise, and it is this difference that gave rise to the CCIR-468 weighting curve (now supported as an ITU standard), which together with quasi-peak measurement (rather than the rms measurement used with A-weighting) became widely used by broadcasters throughout Britain, Europe, and former British Commonwealth countries, where engineers were heavily influenced by BBC test methods. Telephone companies worldwide have also used methods similar to 468 weighting with quasi-peak measurement to describe objectionable interference induced in one telephone circuit by switching transients
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https://en.wikipedia.org/wiki/Shoring
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Shoring is the process of temporarily supporting a building, vessel, structure, or trench with shores (props) when in danger of collapse or during repairs or alterations. Shoring comes from shore, a timber or metal prop. Shoring may be vertical, angled, or horizontal.
Methods
Buildings
Raking shores
In this method, inclined members called rakers are used to give temporary lateral support to an unsafe wall. One or more timbers slope between the face of the structure to be supported and the ground. The most effective support is given if the raker meets the wall at an angle of 60 to 70 degrees. A wall-plate is typically used to increase the area of support.
Foundations
Shoring is commonly used when installing the foundation of a building. A shoring system such as piles and lagging or shotcrete will support the surrounding loads until the underground levels of the building are constructed. Commonly used shoring equipment includes post shores, shoring beams, and timber jacks.
Trenches
During excavation, shoring systems speed up excavation and provide safety for workers since trenches can be prone to collapse. In this case, shoring should not be confused with shielding. Shoring is designed to prevent collapse where shielding is only designed to protect workers when collapses occur.
Concrete-structure and stone-building shoring, in these cases also referred to as falsework, provides temporary support until the concrete becomes hard and achieves the desired strength to support loads.
Hydraulic shoring
Hydraulic shoring is the use of hydraulic pistons that can be pumped outward until they press up against the trench walls. They are typically combined with steel plate or plywood, either being 1-1/8" thick plywood, or special heavy Finlyjutyj
Beam and plate
Beam and plate steel I-beams are driven into the ground and steel plates are slid in amongst them. A similar method that uses wood planks is called soldier boarding. Hydraulics tend to be faster and easier; the
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https://en.wikipedia.org/wiki/Collision%20resistance
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In cryptography, collision resistance is a property of cryptographic hash functions: a hash function H is collision-resistant if it is hard to find two inputs that hash to the same output; that is, two inputs a and b where a ≠ b but H(a) = H(b). The pigeonhole principle means that any hash function with more inputs than outputs will necessarily have such collisions; the harder they are to find, the more cryptographically secure the hash function is.
The "birthday paradox" places an upper bound on collision resistance: if a hash function produces N bits of output, an attacker who computes only 2N/2 (or ) hash operations on random input is likely to find two matching outputs. If there is an easier method to do this than brute-force attack, it is typically considered a flaw in the hash function.
Cryptographic hash functions are usually designed to be collision resistant. However, many hash functions that were once thought to be collision resistant were later broken. MD5 and SHA-1 in particular both have published techniques more efficient than brute force for finding collisions. However, some hash functions have a proof that finding collisions is at least as difficult as some hard mathematical problem (such as integer factorization or discrete logarithm). Those functions are called provably secure.
Definition
A family of functions {hk : {0, 1}m(k) → {0, 1}l(k)} generated by some algorithm G is a family of collision-resistant hash functions, if |m(k)| > |l(k)| for any k, i.e., hk compresses the input string, and every hk can be computed within polynomial time given k, but for any probabilistic polynomial algorithm A, we have
Pr [k ← G(1n), (x1, x2) ← A(k, 1n) s.t. x1 ≠ x2 but hk(x1) = hk(x2)] < negl(n),
where negl(·) denotes some negligible function, and n is the security parameter.
Weak and strong collision resistance
There are two different types of collision resistance.
A hash function has weak collision resistance when, given a hashing function H and an x, n
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https://en.wikipedia.org/wiki/Bred%20vector
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In applied mathematics, bred vectors are perturbations related to Lyapunov vectors, that capture fast-growing dynamical instabilities of the solution of a numerical model. They are used, for example, as initial perturbations for ensemble forecasting in numerical weather prediction. They were introduced by Zoltan Toth and Eugenia Kalnay.
Method
Bred vectors are created by adding initially random perturbations to a nonlinear model. The control (unperturbed) and the perturbed models are integrated in time, and periodically the control solution is subtracted from the perturbed solution. This difference is the bred vector. The vector is scaled to be the same size as the initial perturbation and is then added back to the control to create the new perturbed initial condition. After a short transient period, this "breeding" process creates bred vectors dominated by the naturally fastest-growing instabilities of the evolving control solution.
References
Functional analysis
Mathematical physics
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https://en.wikipedia.org/wiki/Builders%27%20rites
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Builders' rites are ceremonies attendant on the laying of foundation stones, including ecclesiastical, masonic or other traditions connected with foundations or other aspects of construction.
One such custom is that of placing a few coins, newspapers, etc. within a cavity beneath the stone. Should the stone later be removed, the relics may be found. Though this tradition is still practiced, such memorials are deposited in the hope that they will never be disturbed.
History
Living victims were once entombed as a sacrifice to the gods and to ensure the stability of the building. Throughout the ancient world, it was common to sacrifice children, who were buried as good luck charms for building occupants.
Grimm remarked "It was often thought necessary to entomb live animals and even men in the foundation, on which the structure was to be raised, to secure immovable stability." This gruesome practice is well evidenced, in multiple cultures. "The old pagan laid the foundation of his house and fortress in blood." Under the walls of two round towers in Ireland (the only ones examined) human skeletons were discovered. In the 15th century, the wall of Holsworthy church was built over a living human being, and when this became unlawful, images of living beings were substituted.
References to this practice can be found in Greek folk culture in a poem about "Arta's bridge". According to the poem, the wife of the chief builder was sacrificed to establish a good foundation for a bridge that was of grave importance to the secluded city of Arta. The actual bridge was constructed in 1602. A similar legend appears in the Romanian folk poem Meșterul Manole, about the building of the church in the earliest Wallachian capital city.
See also
Bay Bridge Troll
Builder's signature
Cornerstone
Foundation deposit
Hitobashira
Masonic manuscripts
Ship naming and launching
Time capsule
Topping out
Votive offering
References
Further reading
Alan Dundes' The Walled-up Wife. U.of Wisconsin
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https://en.wikipedia.org/wiki/Fixed-satellite%20service
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Fixed-satellite service (short: FSS | also: fixed-satellite radiocommunication service) is – according to article 1.21 of the International Telecommunication Union's (ITU) Radio Regulations (RR) – defined as A radiocommunication service between earth stations at given positions, when one or more satellites are used; the given position may be a specified fixed point or any fixed point within specified areas; in some cases this service includes satellite-to-satellite links, which may also be operated in the inter-satellite service; the fixed-satellite service may also include feeder links for other space radiocommunication services.
Classification
This radiocommunication service is classified in accordance with ITU Radio Regulations (article 1) as follows:
Fixed service (article 1.20)
Fixed-satellite service (article 1.21)
Inter-satellite service (article 1.22)
Earth exploration-satellite service (article 1.51)
Meteorological-satellite service (article 1.52)
Frequency allocation
The allocation of radio frequencies is provided according to Article 5 of the ITU Radio Regulations (most recent version, Edition of 2020).
In order to improve harmonisation in spectrum utilisation, the majority of service-allocations stipulated in this document were incorporated in national Tables of Frequency Allocations and Utilisations which is within the responsibility of the appropriate national administration. The allocation might be primary, secondary, exclusive, and shared.
primary allocation: is indicated by writing in capital letters (see example below)
secondary allocation: is indicated by small letters
exclusive or shared utilization: is within the responsibility of administrations
Example of frequency allocation
Use in North America
FSS – is as well the official classification (used chiefly in North America) for geostationary communications satellites that provide broadcast feeds to television stations, radio stations and broadcast networks. FSSs also transmit informatio
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https://en.wikipedia.org/wiki/DFI
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DFI (Diamond Flower Inc) is a Taiwanese industrial computer company with headquarters in Taipei. It designs, develops, manufactures, and sells industrial motherboard, industrial PCs, System-on-Module, industrial displays, and ODM/OEM services.
DFI was founded by Y.C Lu on July 14, 1981, developing and selling electronics components and add-on cards in the beginning. However, DFI switched to the production of motherboards after searching for potential markets and deciding to focus on the strengths of DFI. Targeting the new growing market in motherboard products, DFI announced the Patent License Agreement with Intel Corporation to build partnership with Intel in 1990 and has been developing and manufacturing motherboard products since 1992. With continuous dedication, DFI quickly gained a reputation in Asia-Pacific region after five years and was awarded Top 10 Motherboard Manufacturer in CRN Magazine from the year 1997 to 1999. Starting from 1998, DFI began to follow the strategies of Intel by releasing Intel 440BX series motherboards, 810 motherboards, and 810e motherboards to worldwide markets. Since its growing advances in manufacturing motherboards, DFI was awarded the Intel Global Demo Board manufacturer award in 1998 and 1999 respectively.
Catering to the growing market of high-end motherboards, DFI developed advanced overclocking motherboards, the LanParty series, which has proven to be a valuable segment for small powerful computers that meet the requirements of end users in the 2000s. DFI introduced the junior lineup (“JR”) with two products, p45 and 790gx, in the beginning, which has since been extended with Nvidia and X58 chipsets. There are other LanParty series like LT, DK(Dark), and Lanparty UT.
With blossoming business in the market, DFI went public and launched its initial public offering (IPO) on January 15, 2000. DFI has already gained a reputation from its motherboard products and hot-selling lineup, LanParty, at that time. And aside from develo
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https://en.wikipedia.org/wiki/251%20%28number%29
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251 (two hundred [and] fifty-one) is the natural number between 250 and 252. It is also a prime number.
In mathematics
251 is:
a Sophie Germain prime.
the sum of three consecutive primes (79 + 83 + 89) and seven consecutive primes (23 + 29 + 31 + 37 + 41 + 43 + 47).
a Chen prime.
an Eisenstein prime with no imaginary part.
a de Polignac number, meaning that it is odd and cannot be formed by adding a power of two to a prime number.
the smallest number that can be formed in more than one way by summing three positive cubes:
Every 5 × 5 matrix has exactly 251 square submatrices.
References
Integers
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https://en.wikipedia.org/wiki/257%20%28number%29
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257 (two hundred [and] fifty-seven) is the natural number following 256 and preceding 258.
257 is a prime number of the form specifically with n = 3, and therefore a Fermat prime. Thus a regular polygon with 257 sides is constructible with compass and unmarked straightedge. It is currently the second largest known Fermat prime.
Analogously, 257 is the third Sierpinski prime of the first kind, of the form ➜ .
It is also
a balanced prime,
an irregular prime,
a prime that is one more than a square,
and a Jacobsthal–Lucas number.
There are exactly 257 combinatorially distinct convex polyhedra with eight vertices (or polyhedral graphs with eight nodes).
References
Integers
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https://en.wikipedia.org/wiki/SageTV
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SageTV Media Center, now open source, was a proprietary, commercial DVR (Digital Video Recording) and HTPC (Home theater PC) software for Mac OS X, Windows and Linux. It requires that the host computer have a hardware-based TV tuner card. The SageTV software has an integrated Electronic Programming Guide (EPG) that is updated via the Internet. The program provides a television interface for DVR, music, and photos on Windows and Linux. SageTV Media Center typically records in standard MPEG2, making it possible to transfer recordings to laptops or other devices. It also has a built-in conversion feature to transcode files into other formats compatible with iPod, PSP, cell phones and other portable devices.
A "lite" version is commonly shipped as part of an OEM software bundle. Both the lite and regular versions offer a Java API.
SageTV Placeshifter allows the user to watch TV from any high speed internet connection, similar to the Slingbox. As of Version 6, the SageTV Placeshifter is available for Windows, Linux and Macintosh platforms. The SageTV Media Extender set-top allows other TVs to connect to SageTV over a home network. There is also the ability to use the Hauppauge MediaMVP with SageTV by purchasing a MediaMVP Client License.
On June 18, 2011, Jeffrey Kardatzke, CTO and founder of the company, announced in a SageTV forum post that his company had been acquired by Google. An official press release followed later the same day, and since then the SageTV products have no longer been available for purchase.
On March 9, 2015, Jeffrey Kardatzke announced that SageTV would be open-sourced "in the near future (i.e. months, not years)". Then a few months later, SageTV became open source, hosted on GitHub.
Google Fiber
After the acquisition of SageTV, LLC by Google, they began modifying and updating it to work with Google's upcoming Google Fiber TV service. SageTV v8 was the initial platform used for the Google Fiber Storage Box (DVR) and TV Box (Client). It has s
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https://en.wikipedia.org/wiki/1-Click
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1-Click, also called one-click or one-click buying, is the technique of allowing customers to make purchases with the payment information needed to complete the purchase having been entered by the user previously. More particularly, it allows an online shopper using an Internet marketplace to purchase an item without having to use shopping cart software. Instead of manually inputting billing and shipping information for a purchase, a user can use one-click buying to use a predefined address and credit card number to purchase one or more items. Since the expiration of Amazon's patent, there has been an advent of checkout experience platforms, such as ShopPay, Simpler, PeachPay, Zplit, and Bolt which offer similar one-click checkout flows.
Patent
The United States Patent and Trademark Office (USPTO) issued a patent for this technique to Amazon.com in September 1999. Amazon.com also owns the "1-Click" trademark.
On May 12, 2006, the USPTO ordered a reexamination of the "One-Click" patent, based on a request filed by Peter Calveley. Calveley cited as prior art an earlier e-commerce patent and the Digicash electronic cash system.
On October 9, 2007, the USPTO issued an office action in the reexamination which confirmed the patentability of claims 6 to 10 of the patent. The patent examiner, however, rejected claims 1 to 5 and 11 to 26. In November 2007, Amazon responded by amending the broadest claims (1 and 11) to restrict them to a shopping cart model of commerce. They have also submitted several hundred references for the examiner to consider. In March 2010, the reexamined and amended patent was allowed.
Amazon's U.S. patent expired on September 11, 2017.
In Europe, a patent application on 1-Click ordering was filed with the European Patent Office (EPO) but was rejected by the EPO in 2007 due to obviousness; the decision was upheld in 2011.
A related gift-ordering patent was granted in 2003, but revoked in 2007 following an opposition.
In Canada, the Federal Co
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https://en.wikipedia.org/wiki/Square-free%20element
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In mathematics, a square-free element is an element r of a unique factorization domain R that is not divisible by a non-trivial square. This means that every s such that is a unit of R.
Alternate characterizations
Square-free elements may be also characterized using their prime decomposition. The unique factorization property means that a non-zero non-unit r can be represented as a product of prime elements
Then r is square-free if and only if the primes pi are pairwise non-associated (i.e. that it doesn't have two of the same prime as factors, which would make it divisible by a square number).
Examples
Common examples of square-free elements include square-free integers and square-free polynomials.
See also
Prime number
References
David Darling (2004) The Universal Book of Mathematics: From Abracadabra to Zeno's Paradoxes John Wiley & Sons
Baker, R. C. "The square-free divisor problem." The Quarterly Journal of Mathematics 45.3 (1994): 269-277.
Ring theory
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https://en.wikipedia.org/wiki/Signed%20measure
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In mathematics, signed measure is a generalization of the concept of (positive) measure by allowing the set function to take negative values, i.e., to acquire sign.
Definition
There are two slightly different concepts of a signed measure, depending on whether or not one allows it to take infinite values. Signed measures are usually only allowed to take finite real values, while some textbooks allow them to take infinite values. To avoid confusion, this article will call these two cases "finite signed measures" and "extended signed measures".
Given a measurable space (that is, a set with a σ-algebra on it), an extended signed measure is a set function
such that and is σ-additive – that is, it satisfies the equality
for any sequence of disjoint sets in
The series on the right must converge absolutely when the value of the left-hand side is finite. One consequence is that an extended signed measure can take or as a value, but not both. The expression is undefined and must be avoided.
A finite signed measure (a.k.a. real measure) is defined in the same way, except that it is only allowed to take real values. That is, it cannot take or
Finite signed measures form a real vector space, while extended signed measures do not because they are not closed under addition. On the other hand, measures are extended signed measures, but are not in general finite signed measures.
Examples
Consider a non-negative measure on the space (X, Σ) and a measurable function f: X → R such that
Then, a finite signed measure is given by
for all A in Σ.
This signed measure takes only finite values. To allow it to take +∞ as a value, one needs to replace the assumption about f being absolutely integrable with the more relaxed condition
where f−(x) = max(−f(x), 0) is the negative part of f.
Properties
What follows are two results which will imply that an extended signed measure is the difference of two non-negative measures, and a finite signed measure is the difference
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https://en.wikipedia.org/wiki/Hahn%20decomposition%20theorem
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In mathematics, the Hahn decomposition theorem, named after the Austrian mathematician Hans Hahn, states that for any measurable space and any signed measure defined on the -algebra , there exist two -measurable sets, and , of such that:
and .
For every such that , one has , i.e., is a positive set for .
For every such that , one has , i.e., is a negative set for .
Moreover, this decomposition is essentially unique, meaning that for any other pair of -measurable subsets of fulfilling the three conditions above, the symmetric differences and are -null sets in the strong sense that every -measurable subset of them has zero measure. The pair is then called a Hahn decomposition of the signed measure .
Jordan measure decomposition
A consequence of the Hahn decomposition theorem is the , which states that every signed measure defined on has a unique decomposition into a difference of two positive measures, and , at least one of which is finite, such that for every -measurable subset and for every -measurable subset , for any Hahn decomposition of . We call and the positive and negative part of , respectively. The pair is called a Jordan decomposition (or sometimes Hahn–Jordan decomposition) of . The two measures can be defined as
for every and any Hahn decomposition of .
Note that the Jordan decomposition is unique, while the Hahn decomposition is only essentially unique.
The Jordan decomposition has the following corollary: Given a Jordan decomposition of a finite signed measure , one has
for any in . Furthermore, if for a pair of finite non-negative measures on , then
The last expression means that the Jordan decomposition is the minimal decomposition of into a difference of non-negative measures. This is the minimality property of the Jordan decomposition.
Proof of the Jordan decomposition: For an elementary proof of the existence, uniqueness, and minimality of the Jordan measure decomposition see Fischer (2012).
Proof of
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https://en.wikipedia.org/wiki/Keyfile
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A keyfile (or key-file) is a file on a computer which contains encryption or license keys.
A common use is web server software running secure socket layer (SSL) protocols. Server-specific keys issued by trusted authorities are merged into the keyfile along with the trusted root certificates. By this method keys can be updated without recompiling software or rebooting the server.
A keyfile is often part of a public key infrastructure (PKI).
Some applications use a keyfile to hold licensing information, which is periodically reviewed to ensure currency and compliance. Other applications allow users to merge multiple service-specific security settings into a single common store (for example, Apple Computer's Keychain in later Mac OS X versions, GNOME Keyring and KWallet in the GNOME and KDE environments in Linux, respectively).
See also
License manager
List of license managers
Passphrase
Encryption software
Product activation
Digital rights management
.KEY extension - Keynote (Apple presentation software)
Key management
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https://en.wikipedia.org/wiki/Alfred%20Young%20%28mathematician%29
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Alfred Young, FRS (16 April 1873 – 15 December 1940) was a British mathematician.
He was born in Widnes, Lancashire, England, and educated at Monkton Combe School in Somerset and Clare College, Cambridge, graduating BA as 10th Wrangler in 1895. He is known for his work in the area of group theory. Both Young diagrams and Young tableaux (which he introduced in 1900) are named after him.
Young was appointed to the position of lecturer at Selwyn College, Cambridge, in 1901, transferring to Clare College in 1905. In 1902 he collaborated with John Hilton Grace on the book The Algebra of Invariants.
In 1907 he married Edith Clara née Wilson. In 1908 he became an ordained clergyman, and in 1910 became parish priest at Birdbrook in Essex, a village 25 miles east of Cambridge. He lived there for the rest of his life, but in 1926 began lecturing once again at Cambridge.
Most of his long series of papers on invariant theory and the symmetric group were written while he was a clergyman.
See also
Hyperoctahedral group
Young's lattice
Young–Fibonacci lattice
Young symmetrizer
Representation theory of the symmetric group
References
Bibliography
19th-century English mathematicians
20th-century English mathematicians
1873 births
1940 deaths
People educated at Monkton Combe School
People from Widnes
Group theorists
Combinatorialists
Alumni of Clare College, Cambridge
Fellows of the Royal Society
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https://en.wikipedia.org/wiki/Soft%20goal
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In connection with modeling languages and especially with goal-oriented modeling, a soft goal is an objective without clear-cut criteria. Soft goals can represent:
Non-functional requirements
Relations between non-functional requirements
Non-functional requirements (or quality attributes, qualities, or more colloquially "-ilities") are global qualities of a software system, such as flexibility, maintainability, usability, and so forth. Such requirements are usually stated only informally; and they are often controversial (i.e. management wants a secure system but staff desires user-friendliness). They are also often difficult to validate.
Why soft?
Normally a goal is a very strict and clear logical criterion. It is satisfied when all sub-goals are satisfied. But in non-functional requirements you often need more loosely defined criteria, like satisficeable or unsatisficeable. The term satisficing was first coined by Herbert Simon. Soft goals are goals that do not have a clear-cut criterion for their satisfaction: they are satisficed when there is sufficient positive and little negative evidence for this claim, while they are unsatisficeable in the opposite case.
Relations between soft goals
Decompositions
AND
OR
Contributions
Helps (+)
Hurts (-)
Makes (++)
Breaks (--)
Unknown
References
Further reading
From Object-Oriented to Goal-Oriented Requirements Analysis, Mylopoulos John, Chung Lawrence, Yu Eric
Software requirements
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https://en.wikipedia.org/wiki/Product%20measure
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In mathematics, given two measurable spaces and measures on them, one can obtain a product measurable space and a product measure on that space. Conceptually, this is similar to defining the Cartesian product of sets and the product topology of two topological spaces, except that there can be many natural choices for the product measure.
Let and be two measurable spaces, that is, and are sigma algebras on and respectively, and let and be measures on these spaces. Denote by the sigma algebra on the Cartesian product generated by subsets of the form , where and This sigma algebra is called the tensor-product σ-algebra on the product space.
A product measure
(also denoted by by many authors)
is defined to be a measure on the measurable space satisfying the property
for all
.
(In multiplying measures, some of which are infinite, we define the product to be zero if any factor is zero.)
In fact, when the spaces are -finite, the product measure is uniquely defined, and for every measurable set E,
where and , which are both measurable sets.
The existence of this measure is guaranteed by the Hahn–Kolmogorov theorem. The uniqueness of product measure is guaranteed only in the case that both and are σ-finite.
The Borel measures on the Euclidean space Rn can be obtained as the product of n copies of Borel measures on the real line R.
Even if the two factors of the product space are complete measure spaces, the product space may not be. Consequently, the completion procedure is needed to extend the Borel measure into the Lebesgue measure, or to extend the product of two Lebesgue measures to give the Lebesgue measure on the product space.
The opposite construction to the formation of the product of two measures is disintegration, which in some sense "splits" a given measure into a family of measures that can be integrated to give the original measure.
Examples
Given two measure spaces, there is always a unique maximal product measure μmax
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https://en.wikipedia.org/wiki/Non-functional%20requirements%20framework
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NFR (Non-Functional Requirements) need a framework for compaction. The analysis begins with softgoals that represent NFR which stakeholders agree upon. Softgoals are goals that are hard to express, but tend to be global qualities of a software system. These could be usability, performance, security and flexibility in a given system. If the team starts collecting them it often finds a great many of them. In order to reduce the number to a manageable quantity, structuring is a valuable approach. There are several frameworks available that are useful as structure.
Structuring Non-functional requirements
The following frameworks are useful to serve as structure for NFRs:
1. Goal Modelling
The finalised softgoals are then usually decomposed and refined to uncover a tree structure of goals and subgoals for e.g. the flexibility softgoal. Once uncovering tree structures, one is bound to find interfering softgoals in different trees, e.g. security goals generally interferes with usability. These softgoal trees now form a softgoal graph structure. The final step in this analysis is to pick some particular leaf softgoals, so that all the root softgoals are satisfied.[1]
2. IVENA - Integrated Approach to Acquisition of NFR
The method has integrated a requirement tree. [2]
3. Context of an Organization
There are several models to describe the context of an organization such as Business Model Canvas, OrgManle [3], or others [4]. Those models are also a good framework to assign NFRs.
Measuring the Non-functional requirements
SNAP is the Software Non-functional Assessment Process. While Function Points measure the functional requirements by sizing the data flow through a software application, IFPUG's SNAP measures the non-functional requirements.
The SNAP model consists of four categories and fourteen sub-categories to measure the non-functional requirements. Non-functional requirement are mapped to the relevant sub-categories. Each sub-category is sized, and the size of
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https://en.wikipedia.org/wiki/Goal-oriented%20Requirements%20Language
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Goal-oriented Requirements Language (GRL), an i*-based modeling language used in systems development, is designed to support goal-oriented modeling and reasoning about requirements especially the non-functional requirements
GRL topics
Concepts
Goal-oriented Requirements Language (GRL) allows to express conflict between goals and helps to make decisions that resolve conflicts. There are three main categories of concepts in GRL:
intentional elements,
intentional relationships and
actors.
They are called for intentional because they are used in models that primarily concerned with answering "why" question of requirements (for ex. why certain choices for behavior or structure were made, what alternatives exist and what is the reason for choosing of certain alternative.)
Intentional elements
Intentional elements are: goal, soft goal, task, belief and resource.
Goal is condition or situation that can be achieved or not. Goal is used to define the functional requirements of the system. In GRL notation goal is represented by a rounded rectangle with the goal name inside.
Task is used to represent different ways of how to accomplish goal. In GRL notation task is represented by hexagon with the task name inside.
Softgoal is used to define non-functional requirements. It’s usually a quality attribute of one of the intentional elements. In GRL notation softgoal is represented by irregular curvilinear shape with the softgoal name inside.
Resource is a physical or informational object that is available for use in the task. Resource is represented in GRL as a rectangle.
Belief is used to represent assumptions and relevant conditions. This construct is represented as ellipse in GRL notation.
Relationships
Intentional relationships are: means-ends, decomposition, contribution, correlation and dependency.
Means-ends relationship shows how the goal can be achieved. For example, it can be used to connect task to a goal.
Decomposition relationship is used to show the sub
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https://en.wikipedia.org/wiki/Direct-conversion%20receiver
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A direct-conversion receiver (DCR), also known as homodyne, synchrodyne, or zero-IF receiver, is a radio receiver design that demodulates the incoming radio signal using synchronous detection driven by a local oscillator whose frequency is identical to, or very close to the carrier frequency of the intended signal. This is in contrast to the standard superheterodyne receiver where this is accomplished only after an initial conversion to an intermediate frequency.
The simplification of performing only a single frequency conversion reduces the basic circuit complexity but other issues arise, for instance, regarding dynamic range. In its original form it was unsuited to receiving AM and FM signals without implementing an elaborate phase locked loop. Although these and other technical challenges made this technique rather impractical around the time of its invention (1930s), current technology, and software radio in particular, have revived its use in certain areas including some consumer products.
Principle of operation
The conversion of the modulated signal to baseband is done in a single frequency conversion. This avoids the complexity of the superheterodyne's two (or more) frequency conversions, IF stage(s), and image rejection issues.
The received radio frequency signal is fed directly into a frequency mixer, just as in a superheterodyne receiver. However unlike the superheterodyne, the frequency of the local oscillator is not offset from, but identical to, the received signal's frequency. The result is a demodulated output just as would be obtained from a superheterodyne receiver using synchronous detection (a product detector) following an intermediate frequency (IF) stage.
Technical issues
To match the performance of the superheterodyne receiver, a number of the functions normally addressed by the IF stage must be accomplished at baseband. Since there is no high gain IF amplifier utilizing automatic gain control (AGC), the baseband output level may vary ove
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https://en.wikipedia.org/wiki/TRIX%20%28operating%20system%29
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TRIX is a network-oriented research operating system developed in the late 1970s at MIT's Laboratory for Computer Science (LCS) by Professor Steve Ward and his research group. It ran on the NuMachine and had remote procedure call functionality built into its kernel, but was otherwise a Version 7 Unix workalike.
Design and implementation
On startup, the NuMachine would load the same program on each CPU in the system, passing each instance the numeric ID of the CPU it was running on. TRIX relied on this design to have the first CPU set up global data structures and then set a flag to signal that initialization was complete. After that, each instance of the kernel was able to access global data. The system also supported data private to each CPU. Access to the filesystem was provided by a program in user space.
The kernel supported unnamed threads running in domains. A domain was the equivalent of a Unix process without a stack pointer (each thread in a domain had a stack pointer). A thread could change domains, and the system scheduler would migrate threads between CPUs in order to keep all processors busy. Threads had access to a single kind of mutual exclusion primitive, and one of seven priorities. The scheduler was designed to avoid priority inversion. User space programs could create threads through a spawn system call.
A garbage collector would periodically identify and free unused domains.
The shared memory model used to coordinate work between the various CPUs caused memory bus contention and was known to be a source of inefficiency. The designers were aware of designs that would have alleviated the contention. Indeed, TRIX's original design used a nonblocking message passing mechanism, but "this implementation was found to have deficiencies often overlooked in the literature," including poor performance.
Although the TRIX operating system was first implemented on the NuMachine, this was due to the availability of the NuMachine at MIT, not becau
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https://en.wikipedia.org/wiki/Floquet%20theory
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Floquet theory is a branch of the theory of ordinary differential equations relating to the class of solutions to periodic linear differential equations of the form
with a piecewise continuous periodic function with period and defines the state of the stability of solutions.
The main theorem of Floquet theory, Floquet's theorem, due to , gives a canonical form for each fundamental matrix solution of this common linear system. It gives a coordinate change with that transforms the periodic system to a traditional linear system with constant, real coefficients.
When applied to physical systems with periodic potentials, such as crystals in condensed matter physics, the result is known as Bloch's theorem.
Note that the solutions of the linear differential equation form a vector space. A matrix is called a fundamental matrix solution if all columns are linearly independent solutions. A matrix is called a principal fundamental matrix solution if all columns are linearly independent solutions and there exists such that is the identity. A principal fundamental matrix can be constructed from a fundamental matrix using . The solution of the linear differential equation with the initial condition is where is any fundamental matrix solution.
Floquet's theorem
Let be a linear first order differential equation,
where is a column vector of length and an periodic matrix with period (that is for all real values of ). Let be a fundamental matrix solution of this differential equation. Then, for all ,
Here
is known as the monodromy matrix.
In addition, for each matrix (possibly complex) such that
there is a periodic (period ) matrix function such that
Also, there is a real matrix and a real periodic (period-) matrix function such that
In the above , , and are matrices.
Consequences and applications
This mapping gives rise to a time-dependent change of coordinates (), under which our original system becomes a linear system with real constant coe
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https://en.wikipedia.org/wiki/Global%20Biodiversity%20Information%20Facility
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The Global Biodiversity Information Facility (GBIF) is an international organisation that focuses on making scientific data on biodiversity available via the Internet using web services. The data are provided by many institutions from around the world; GBIF's information architecture makes these data accessible and searchable through a single portal. Data available through the GBIF portal are primarily distribution data on plants, animals, fungi, and microbes for the world, and scientific names data.
The mission of the GBIF is to facilitate free and open access to biodiversity data worldwide to underpin sustainable development. Priorities, with an emphasis on promoting participation and working through partners, include mobilising biodiversity data, developing protocols and standards to ensure scientific integrity and interoperability, building an informatics architecture to allow the interlinking of diverse data types from disparate sources, promoting capacity building and catalysing development of analytical tools for improved decision-making.
GBIF strives to form informatics linkages among digital data resources from across the spectrum of biological organisation, from genes to ecosystems, and to connect these to issues important to science, society and sustainability by using georeferencing and GIS tools. It works in partnership with other international organisations such as the Catalogue of Life partnership, Biodiversity Information Standards, the Consortium for the Barcode of Life (CBOL), the Encyclopedia of Life (EOL), and GEOSS. The biodiversity data available through the GBIF has increased by more than 1,150% in the past decade, partially due to the participation of citizen scientists.
From 2002 to 2014, GBIF awarded a prestigious annual global award in the area of biodiversity informatics, the Ebbe Nielsen Prize, valued at €30,000. , the GBIF Secretariat presents two annual prizes: the GBIF Ebbe Nielsen Challenge and the Young Researchers Award.
See al
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https://en.wikipedia.org/wiki/Duffing%20equation
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The Duffing equation (or Duffing oscillator), named after Georg Duffing (1861–1944), is a non-linear second-order differential equation used to model certain damped and driven oscillators. The equation is given by
where the (unknown) function is the displacement at time , is the first derivative of with respect to time, i.e. velocity, and is the second time-derivative of i.e. acceleration. The numbers and are given constants.
The equation describes the motion of a damped oscillator with a more complex potential than in simple harmonic motion (which corresponds to the case ); in physical terms, it models, for example, an elastic pendulum whose spring's stiffness does not exactly obey Hooke's law.
The Duffing equation is an example of a dynamical system that exhibits chaotic behavior. Moreover, the Duffing system presents in the frequency response the jump resonance phenomenon that is a sort of frequency hysteresis behaviour.
Parameters
The parameters in the above equation are:
controls the amount of damping,
controls the linear stiffness,
controls the amount of non-linearity in the restoring force; if the Duffing equation describes a damped and driven simple harmonic oscillator,
is the amplitude of the periodic driving force; if the system is without a driving force, and
is the angular frequency of the periodic driving force.
The Duffing equation can be seen as describing the oscillations of a mass attached to a nonlinear spring and a linear damper. The restoring force provided by the nonlinear spring is then
When and the spring is called a hardening spring. Conversely, for it is a softening spring (still with ). Consequently, the adjectives hardening and softening are used with respect to the Duffing equation in general, dependent on the values of (and ).
The number of parameters in the Duffing equation can be reduced by two through scaling (in accord with the Buckingham π theorem), e.g. the excursion and time can be scaled as: and a
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https://en.wikipedia.org/wiki/List%20of%20Apple%20II%20application%20software
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Following is a List of Apple II applications including utilities and development tools.
0–9
3D Art Graphics - 3D computer graphics software, a set of 3D computer graphics effects, written by Kazumasa Mitazawa and released in June 1978
A
A2Command - Norton Commander style file manager
ADTPro - telecom
Apple Writer - word processor
AppleWorks - integrated word processor, spreadsheet, and database suite (II & GS)
ASCII Express - telecom
B
Bank Street Writer - word processor
C
CatFur - file transfer / chat software for the APPLE-CAT modem
Cattlecar Galactica - Super Hi-Res Chess in its later, expanded version
Contiki - 8-bit text web browser
Copy II+ - copy and disk utilities
Crossword Magic - Given clues and answers, software automatically arranges the answers into a crossword grid.
D
Dalton Disk Desintegrator - disk archiver
Davex - Unix type shell
Dazzle Draw - bitmap graphics editor
Design Your Own Home - home design (GS)
Disk Muncher - disk copy
Diversi Copy - disk copy (GS)
DOS.MASTER - DOS 3.3 -> ProDOS utility
E
Edisoft - text editor
EasyMailer
EasyWriter
F
Fantavision - vector graphics animation package
G
GEOS - integrated office suite
GNO/ME - Unix type shell (GS)
GraphicEdge - business graphics for AppleWorks spreadsheets (II & GS & Mac)
Great American Probability Machine - first full-screen Apple II animations
L
Lock Smith - copy and disk utilities
Logo - easy educational graphic programming language
M
Magic Window - one of the most popular Apple II word processors by Artsci
Merlin 8 & 16 - assembler (II & GS)
Micro-DYNAMO - simulation software to build system dynamics models
MouseWrite and MouseWrite II - first mouse based word processor for Apple II (II & GS)
O
Omnis I,II, and III - database/file manager (II & GS)
ORCA - program language suite (II & GS)
P
Point2Point - computer to computer communications program for chat and file transmission (II)
PrintShop - sign, banner, and card maker (II & GS)
ProSel - disk and file utilities (II & GS)
Pro
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https://en.wikipedia.org/wiki/Philopatry
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Philopatry is the tendency of an organism to stay in or habitually return to a particular area. The causes of philopatry are numerous, but natal philopatry, where animals return to their birthplace to breed, may be the most common. The term derives from the Greek roots philo, "liking, loving" and patra, "fatherland", although in recent years the term has been applied to more than just the animal's birthplace. Recent usage refers to animals returning to the same area to breed despite not being born there, and migratory species that demonstrate site fidelity: reusing stopovers, staging points, and wintering grounds.
Some of the known reasons for organisms to be philopatric would be for mating (reproduction), survival, migration, parental care, resources, etc.. In most species of animals, individuals will benefit from living in groups, because depending on the species, individuals are more vulnerable to predation and more likely to have difficulty finding resources and food. Therefore, living in groups increases a species' chances of survival, which correlates to finding resources and reproducing. Again, depending on the species, returning to their birthplace where that particular species occupies that territory is the more favorable option. The birthplaces for these animals serve as a territory for them to return for feeding and refuge, like fish from a coral reef. In an animal behavior study conducted by Paul Greenwood, overall female mammals are more likely to be philopatric, while male mammals are more likely to disperse. Male birds are more likely to be philopatric, while females are more likely to disperse. Philopatry will favor the evolution of cooperative traits because the direction of sex has consequences from the particular mating system.
Breeding-site philopatry
One type of philopatry is breeding philopatry, or breeding-site fidelity, and involves an individual, pair, or colony returning to the same location to breed, year after year . The animal can liv
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https://en.wikipedia.org/wiki/Bus%20analyzer
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A bus analyzer is a type of a protocol analysis tool, used for capturing and analyzing communication data across a specific interface bus, usually embedded in a hardware system. The bus analyzer functionality helps design, test and validation engineers to check, test, debug and validate their designs throughout the design cycles of a hardware-based product. It also helps in later phases of a product life cycle, in examining communication interoperability between systems and between components, and clarifying hardware support concerns.
A bus analyzer is designed for use with specific parallel or serial bus architectures. Though the term bus analyzer implies a physical communication and interface that is being analyzed, it is sometimes used interchangeably with the term protocol analyzer or Packet Analyzer, and may be used also for analysis tools for Wireless interfaces like wireless LAN (like Wi-Fi), PAN (like Bluetooth, Wireless USB), and other, though these technologies do not have a “Wired” Bus.
The bus analyzer monitors and captures the bus communication data, decodes and analyses it and displays the data and analysis reports to the user. It is essentially a logic analyzer with some additional knowledge of the underlying bus traffic characteristics. One of the key differences between a bus analyzer and a logic analyzer is notably its ability to filter and extract only relevant traffic that occurs on the analyzed bus. Some advanced logic analyzers present data storage qualification options that also allow to filter bus traffic, enabling bus analyzer-like features.
Some key differentiators between bus and logic analyzers are:
1. Cost: Logic analyzers usually carry higher prices than bus analyzers. The converse of this fact is that a logic analyzer can be used with a variety of bus architectures, whereas a bus analyzer is only good with one architecture.
2. Targeted Capabilities and Preformatting of data: A bus analyzer can be designed to provide very specific
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https://en.wikipedia.org/wiki/Northbound%20interface
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In computer networking and computer architecture, a northbound interface of a component is an interface that allows the component to communicate with a higher level component, using the latter component's southbound interface. The northbound interface conceptualizes the lower level details (e.g., data or functions) used by, or in, the component, allowing the component to interface with higher level layers.
In architectural overviews, the northbound interface is normally drawn at the top of the component it is defined in; hence the name northbound interface. A southbound interface decomposes concepts in the technical details, mostly specific to a single component of the architecture. Southbound interfaces are drawn at the bottom of an architectural overview.
Typical use
A northbound interface is typically an output-only interface (as opposed to one that accepts user input) found in carrier-grade network and telecommunications network elements. The languages or protocols commonly used include SNMP and TL1. For example, a device that is capable of sending out syslog messages but that is not configurable by the user is said to implement a northbound interface. Other examples include SMASH, IPMI, WSMAN, and SOAP.
The term is also important for software-defined networking (SDN), to facilitate communication between the physical devices, the SDN software and applications running on the network.
References
Network architecture
Computer networking
Computer architecture
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https://en.wikipedia.org/wiki/Butyl%20acetate
|
n-Butyl acetate is an organic compound with the formula . A colorless, flammable liquid, it is the ester derived from n-butanol and acetic acid. It is found in many types of fruit, where it imparts characteristic flavors and has a sweet smell of banana or apple. It is used as an industrial solvent.
The other three isomers (four, including stereoisomers) of butyl acetate are isobutyl acetate, tert-butyl acetate, and sec-butyl acetate (two enantiomers).
Production and use
Butyl acetate is commonly manufactured by the Fischer esterification of butanol (or its isomer to make an isomer of butyl acetate) and acetic acid with the presence of sulfuric acid:
Butyl acetate is mainly used as a solvent for coatings and inks. It is a component of fingernail polish.
Occurrence in nature
Apples, especially of the 'Red Delicious' variety, are flavored in part by this chemical. The alarm pheromones emitted by the Koschevnikov gland of honey bees contain butyl acetate.
References
External links
Ethylene and other chemicals in fruit
Material Safety Data Sheet
CDC - NIOSH Pocket Guide to Chemical Hazards
Ester solvents
Flavors
Acetate esters
Commodity chemicals
Sweet-smelling chemicals
Butyl compounds
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https://en.wikipedia.org/wiki/DBc
|
dBc (decibels relative to the carrier) is the power ratio of a signal to a carrier signal, expressed in decibels. For example, phase noise is expressed in dBc/Hz at a given frequency offset from the carrier. dBc can also be used as a measurement of Spurious-Free Dynamic Range (SFDR) between the desired signal and unwanted spurious outputs resulting from the use of signal converters such as a digital-to-analog converter or a frequency mixer.
If the dBc figure is positive, then the relative signal strength is greater than the carrier signal strength. If the dBc figure is negative, then the relative signal strength is less than carrier signal strength.
Although the decibel (dB) is permitted for use alongside SI units, the dBc is not.
Example
If a carrier (reference signal) has a power of , and noise signal has power of .
Power of reference signal expressed in decibel is :
Power of noise expressed in decibel is :
The calculation of dBc difference between noise signal and reference signal is then as follows:
It is also possible to compute the dBc power of noise signal with respect to reference signal directly as logarithm of their ratio as follows:
.
References
External links
Encyclopedia of Laser Physics and Technology
Units of measurement
Radio frequency propagation
Telecommunications engineering
Logarithmic scales of measurement
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https://en.wikipedia.org/wiki/Key%20whitening
|
In cryptography, key whitening is a technique intended to increase the security of an iterated block cipher. It consists of steps that combine the data with portions of the key.
Details
The most common form of key whitening is xor-encrypt-xor -- using a simple XOR before the first round and after the last round of encryption.
The first block cipher to use a form of key whitening is DES-X, which simply uses two extra 64-bit keys for whitening, beyond the normal 56-bit key of DES. This is intended to increase the complexity of a brute force attack, increasing the effective size of the key without major changes in the algorithm. DES-X's inventor, Ron Rivest, named the technique whitening.
The cipher FEAL (followed by Khufu and Khafre) introduced the practice of key whitening using portions of the same key used in the rest of the cipher. This offers no additional protection from brute force attacks, but it can make other attacks more difficult. In a Feistel cipher or similar algorithm, key whitening can increase security by concealing the specific inputs to the first and last round functions. In particular, it is not susceptible to a meet-in-the-middle attack. This form of key whitening has been adopted as a feature of many later block ciphers, including AES, MARS, RC6, and Twofish.
See also
Whitening transformation
References
Key management
Block ciphers
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https://en.wikipedia.org/wiki/Nested%20Context%20Language
|
In the field of digital and interactive television, Nested Context Language (NCL) is a declarative authoring language for hypermedia documents. NCL documents do not contain multimedia elements such as audio or video content; rather they function as a "glue" language that specifies how multimedia components are related. In particular, NCL documents specify how these components are synchronized relative to each other and how the components are composed together into a unified document. Among its main facilities, it treats hypermedia relations as first-class entities through the definition of hypermedia connectors, and it can specify arbitrary semantics for a hypermedia composition using the concept of composite templates.
NCL is an XML application language that is an extension of XHTML, with XML elements and attributes specified by a modular approach. NCL modules can be added to standard web languages, such as XLink and SMIL.
NCL was initially designed for the Web environment, but a major application of NCL is use as the declarative language of the Japanese-Brazilian ISDB-Tb (International Standard for Digital Broadcasting) terrestrial DTV digital television middleware (named Ginga). It is also the first standardized technology of the ITU-T multimedia application framework series of specifications for IPTV (internet protocol television) services. In both cases it is used to develop interactive applications to digital television.
Structure of an NCL document
NCL was designed to be modular to allow for use of subsets of modules according to the needs of the particular application. The 3.1 version of the standard is split into 14 areas with each module assigned to an area. Each module in turn defines one or more XML elements. The areas and associated modules are
Structure
Structure Module
Components
Media Module
Context Module
Interfaces
MediaContentAnchor Module
CompositeNodeInterface Module
PropertyAnchor Module
SwitchInterface Module
Layout
Layout Module
Present
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https://en.wikipedia.org/wiki/Modeling%20perspective
|
A modeling perspective in information systems is a particular way to represent pre-selected aspects of a system. Any perspective has a different focus, conceptualization, dedication and visualization of what the model is representing.
The traditional way to distinguish between modeling perspectives is structural, functional and behavioral/processual perspectives. This together with rule, object, communication and actor and role perspectives is one way of classifying modeling approaches.
Types of perspectives
Structural modeling perspective
This approach concentrates on describing the static structure. The main concept in this modeling perspective is the entity, this could be an object, phenomena, concept, thing etc.
The data modeling languages have traditionally handled this perspective, examples of such being:
The ER-language (Entity-Relationship)
Generic Semantic Modeling language (GSM)
Other approaches including:
The NIAM language (Binary relationship language)
Conceptual graphs (Sowa)
Looking at the ER-language we have the basic components:
Entities: Distinctively identifiable phenomenon.
Relationships: An association among the entities.
Attributes: Used to give value to a property of an entity/relationship.
Looking at the generic semantic modeling language we have the basic components:
Constructed types built by abstraction: Aggregation, generalization, and association.
Attributes.
Primitive types: Data types in GSM are classified into printable and abstract types.
Printable: Used to specify visible values.
Abstract: Representing entities.
Functional modeling perspective
The functional modeling approach concentrates on describing the dynamic process. The main concept in this modeling perspective is the process, this could be a function, transformation, activity, action, task etc. A well-known example of a modeling language employing this perspective is data flow diagrams.
The perspective uses four symbols to describe a process, these being:
Process:
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https://en.wikipedia.org/wiki/Hodgkin%E2%80%93Huxley%20model
|
The Hodgkin–Huxley model, or conductance-based model, is a mathematical model that describes how action potentials in neurons are initiated and propagated. It is a set of nonlinear differential equations that approximates the electrical engineering characteristics of excitable cells such as neurons and muscle cells. It is a continuous-time dynamical system.
Alan Hodgkin and Andrew Huxley described the model in 1952 to explain the ionic mechanisms underlying the initiation and propagation of action potentials in the squid giant axon. They received the 1963 Nobel Prize in Physiology or Medicine for this work.
Basic components
The typical Hodgkin–Huxley model treats each component of an excitable cell as an electrical element (as shown in the figure). The lipid bilayer is represented as a capacitance (Cm). Voltage-gated ion channels are represented by electrical conductances (gn, where n is the specific ion channel) that depend on both voltage and time. Leak channels are represented by linear conductances (gL). The electrochemical gradients driving the flow of ions are represented by voltage sources (En) whose voltages are determined by the ratio of the intra- and extracellular concentrations of the ionic species of interest. Finally, ion pumps are represented by current sources (Ip). The membrane potential is denoted by Vm.
Mathematically, the current flowing through the lipid bilayer is written as
and the current through a given ion channel is the product of that channel's conductance and the driving potential for the specific ion
where is the reversal potential of the specific ion channel.
Thus, for a cell with sodium and potassium channels, the total current through the membrane is given by:
where I is the total membrane current per unit area, Cm is the membrane capacitance per unit area, gK and gNa are the potassium and sodium conductances per unit area, respectively, VK and VNa are the potassium and sodium reversal potentials, respectively,
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https://en.wikipedia.org/wiki/Parenthesome
|
Within the cells of some members of basidiomycetes fungi are found microscopic structures called parenthesomes or septal pore caps. They are shaped like parentheses and found on either side of pores in the dolipore septum which separates cells within a hypha. Their function has not been established, and their composition has not been fully elucidated. The variations in their appearance are useful in distinguishing individual species.
Generally, they are barrel shaped, with an endoplasmic reticulum covering.
See also
Pit connection
References
Organelles
Mycology
Fungal morphology and anatomy
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https://en.wikipedia.org/wiki/Synapsis
|
Synapsis is the pairing of two chromosomes that occurs during meiosis. It allows matching-up of homologous pairs prior to their segregation, and possible chromosomal crossover between them. Synapsis takes place during prophase I of meiosis. When homologous chromosomes synapse, their ends are first attached to the nuclear envelope. These end-membrane complexes then migrate, assisted by the extranuclear cytoskeleton, until matching ends have been paired. Then the intervening regions of the chromosome are brought together, and may be connected by a protein-RNA complex called the synaptonemal complex. During synapsis, autosomes are held together by the synaptonemal complex along their whole length, whereas for sex chromosomes, this only takes place at one end of each chromosome.
This is not to be confused with mitosis. Mitosis also has prophase, but does not ordinarily do pairing of two homologous chromosomes.
When the non-sister chromatids intertwine, segments of chromatids with similar sequence may break apart and be exchanged in a process known as genetic recombination or "crossing-over". This exchange produces a chiasma, a region that is shaped like an X, where the two chromosomes are physically joined. At least one chiasma per chromosome often appears to be necessary to stabilise bivalents along the metaphase plate during separation. The crossover of genetic material also provides a possible defences against 'chromosome killer' mechanisms, by removing the distinction between 'self' and 'non-self' through which such a mechanism could operate. A further consequence of recombinant synapsis is to increase genetic variability within the offspring. Repeated recombination also has the general effect of allowing genes to move independently of each other through the generations, allowing for the independent concentration of beneficial genes and the purging of the detrimental.
Following synapsis, a type of recombination referred to as synthesis dependent strand annealing
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https://en.wikipedia.org/wiki/Neutrodyne
|
The Neutrodyne radio receiver, invented in 1922 by Louis Hazeltine, was a particular type of tuned radio frequency (TRF) receiver, in which the instability-causing inter-electrode capacitance of the triode RF tubes is cancelled out or "neutralized" to prevent parasitic oscillations which caused "squealing" or "howling" noises in the speakers of early radio sets. In most designs, a small extra winding on each of the RF amplifiers' tuned anode coils was used to generate a small antiphase signal, which could be adjusted by special variable trim capacitors to cancel out the stray signal coupled to the grid via plate-to-grid capacitance. The Neutrodyne circuit was popular in radio receivers until the 1930s, when it was superseded by the superheterodyne receiver.
History
The circuit was developed about 1922 by Harold Wheeler who worked in Louis Hazeltine's laboratory at Stevens Institute of Technology, so Hazeltine is usually given the credit. The tuned radio frequency (TRF) receiver, one of the most popular radio receiver designs of the time, consisted of several tuned radio frequency (RF) amplifier stages, followed by a detector and several audio amplifier stages. A major defect of the TRF receiver was that, due to the high interelectrode capacitance of early triode vacuum tubes, feedback within the RF amplifier stages gave them a tendency to oscillate, creating unwanted radio frequency alternating currents. These parasitic oscillations mixed with the carrier wave in the detector, creating heterodynes (beat notes) in the audio frequency range, which were heard as annoying whistles and howls from the speaker.
Hazeltine's innovation was to add a circuit to each radio frequency amplifier stage which fed back a small amount of energy from the plate (output) circuit to the grid (input) circuit with opposite phase to cancel ("neutralize") the feedback which was causing the oscillation. This effectively prevented the high-pitched squeals that had plagued early radi
|
https://en.wikipedia.org/wiki/Area%20compatibility%20factor
|
In survival analysis, the area compatibility factor, F, is used in indirect standardisation of population mortality rates.
where:
is the standardised central exposed-to risk from age x to x + t for the standard population,
is the central exposed-to risk from age x to x + t for the population under study and
is the mortality rate in the standard population for ages x to x + t.
The expression can be thought of as the crude mortality rate for the standard population divided by what the crude mortality rate is for the region being studied, assuming the mortality rates are the same as for the standard population.
F is then multiplied by the crude mortality rate to arrive at the indirectly standardised mortality rate.
References
Actuarial science
Demography
Epidemiology
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https://en.wikipedia.org/wiki/263%20%28number%29
|
263 is the natural number between 262 and 264. It is also a prime number.
In mathematics
263 is
a balanced prime,
an irregular prime,
a Ramanujan prime, a Chen prime, and
a safe prime.
It is also a strictly non-palindromic number and a happy number.
References
Integers
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https://en.wikipedia.org/wiki/269%20%28number%29
|
269 (two hundred [and] sixty-nine) is the natural number between 268 and 270. It is also a prime number.
In mathematics
269 is a twin prime,
and a Ramanujan prime.
It is the largest prime factor of 9! + 1 = 362881,
and the smallest natural number that cannot be represented as the determinant of a 10 × 10 (0,1)-matrix.
References
Integers
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https://en.wikipedia.org/wiki/Difference%20set
|
In combinatorics, a difference set is a subset of size of a group of order such that every non-identity element of can be expressed as a product of elements of in exactly ways. A difference set is said to be cyclic, abelian, non-abelian, etc., if the group has the corresponding property. A difference set with is sometimes called planar or simple. If is an abelian group written in additive notation, the defining condition is that every non-zero element of can be written as a difference of elements of in exactly ways. The term "difference set" arises in this way.
Basic facts
A simple counting argument shows that there are exactly pairs of elements from that will yield nonidentity elements, so every difference set must satisfy the equation
If is a difference set and then is also a difference set, and is called a translate of ( in additive notation).
The complement of a -difference set is a -difference set.
The set of all translates of a difference set forms a symmetric block design, called the development of and denoted by In such a design there are elements (usually called points) and blocks (subsets). Each block of the design consists of points, each point is contained in blocks. Any two blocks have exactly elements in common and any two points are simultaneously contained in exactly blocks. The group acts as an automorphism group of the design. It is sharply transitive on both points and blocks.
In particular, if , then the difference set gives rise to a projective plane. An example of a (7,3,1) difference set in the group is the subset . The translates of this difference set form the Fano plane.
Since every difference set gives a symmetric design, the parameter set must satisfy the Bruck–Ryser–Chowla theorem.
Not every symmetric design gives a difference set.
Equivalent and isomorphic difference sets
Two difference sets in group and in group are equivalent if there is a group isomorphism between and such that for
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https://en.wikipedia.org/wiki/Jena%20Observatory
|
Astrophysikalisches Institut und Universitäts-Sternwarte Jena (AIU Jena, Astrophysical Institute and University Observatory Jena, or simply Jena Observatory) is an astronomical observatory owned and operated by Friedrich Schiller University of Jena. It is located in Großschwabhausen close to Jena, Germany.
WASP-3c & TTV
Transit Timing Variation (TTV), a variation on the transit method, was used to discover an exoplanet WASP-3c by Rozhen Observatory, Jena Observatory, and Toruń Centre for Astronomy.
See also
List of astronomical observatories
References
External links
Jena Observatory
Universitäts-Sternwarte Jena
Astronomical observatories in Germany
Buildings and structures in Jena
Glass engineering and science
|
https://en.wikipedia.org/wiki/Rhodamine%20B
|
Rhodamine B is a chemical compound and a dye. It is often used as a tracer dye within water to determine the rate and direction of flow and transport. Rhodamine dyes fluoresce and can thus be detected easily and inexpensively with fluorometers.
Rhodamine B is used in biology as a staining fluorescent dye, sometimes in combination with auramine O, as the auramine-rhodamine stain to demonstrate acid-fast organisms, notably Mycobacterium. Rhodamine dyes are also used extensively in biotechnology applications such as fluorescence microscopy, flow cytometry, fluorescence correlation spectroscopy and ELISA.
Other uses
Rhodamine B is often mixed with herbicides to show where they have been used.
It is also being tested for use as a biomarker in oral rabies vaccines for wildlife, such as raccoons, to identify animals that have eaten a vaccine bait. The rhodamine is incorporated into the animal's whiskers and teeth. Rhodamine B is an important hydrophilic xanthene dye well known for its stability and is widely used in the textile industry, leather, paper printing, paint, coloured glass and plastic industries.
Rhodamine B (BV10) is mixed with quinacridone magenta (PR122) to make the bright pink watercolor known as Opera Rose.
Properties
Rhodamine B can exist in equilibrium between two forms: an "open"/fluorescent form and a "closed"/nonfluorescent spirolactone form. The "open" form dominates in acidic condition while the "closed" form is colorless in basic condition.
The fluorescence intensity of rhodamine B will decrease as temperature increases.
The solubility of rhodamine B in water varies by manufacturer, and has been reported as 8 g/L and ~15 g/L, while solubility in alcohol (presumably ethanol) has been reported as 15 g/L. Chlorinated tap water decomposes rhodamine B. Rhodamine B solutions adsorb to plastics and should be kept in glass.
Rhodamine B is tunable around 610 nm when used as a laser dye. Its luminescence quantum yield is 0.65 in basic ethanol, 0.49
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https://en.wikipedia.org/wiki/SigmaTel
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SigmaTel, Inc., was an American system-on-a-chip (SoC), electronics and software company headquartered in Austin, Texas, that designed AV media player/recorder SoCs, reference circuit boards, SoC software development kits built around a custom cooperative kernel and all SoC device drivers including USB mass storage and AV decoder DSP, media player/recorder apps, and controller chips for multifunction peripherals. SigmaTel became Austin's largest IPO as of 2003 when it became publicly traded on NASDAQ. The company was driven by a talented mix of electrical and computer engineers plus other professionals with semiconductor industry experience in Silicon Hills, the number two IC design region in the United States, after Silicon Valley.
SigmaTel (trading symbol SGTL) was acquired by Freescale Semiconductor in 2008 and delisted from NASDAQ.
History
In the 90's and early 2000's SigmaTel produced audio codecs which went into the majority of PC sound cards. Creative's Sound Blaster used mainly SigmaTel and ADI codecs. This expanded to on board audio for computer motherboards and MP3 players.
In 2004, SigmaTel SoCs were found in over 70% of all flash memory based MP3 devices sold in the global market. However, SigmaTel lost its last iPod socket in 2006 when it was not found in the next-generation iPod Shuffle. PortalPlayer was the largest competitor, but were bought by Nvidia after PortalPlayer's chips lost their socket in the iPod. SigmaTel was voted "Best Place to Work in Austin 2005" by the Austin Chronicle.
In July 2005, SigmaTel acquired the rights to different software technologies sold by Digital Networks North America (a subsidiary of D&M Holdings, and owner of Rio Audio).
On July 25, 2006, Integrated Device Technology, Inc. (IDT) announced its acquisition of SigmaTel, Inc.'s AC'97 and High Definition Audio (HD-Audio) PC and Notebook audio codec product lines for approximately $72 million in cash, and the acquisition of SigmaTel's intellectual property and e
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https://en.wikipedia.org/wiki/Immunostimulant
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Immunostimulants, also known as immunostimulators, are substances (drugs and nutrients) that stimulate the immune system usually in a non-specific manner by inducing activation or increasing activity of any of its components. One notable example is the granulocyte macrophage colony-stimulating factor. The goal of this stimulated immune response is usually to help the body have a stronger immune system response in order to improve outcomes in the case of an infection or cancer malignancy. There is also some evidence that immunostimulants may be useful to help decrease severe acute illness related to chronic obstructive pulmonary disease or acute infections in the lungs.
Classification
There are two main categories of immunostimulants:
Specific immunostimulants provide antigenic specificity in immune response, such as vaccines or any antigen.
Non-specific immunostimulants act irrespective of antigenic specificity to augment immune response of other antigen or stimulate components of the immune system without antigenic specificity, such as adjuvants and non-specific immunostimulators.
Non-specific
Many endogenous substances are non-specific immunostimulators. For example, female sex hormones are known to stimulate both adaptive and innate immune responses. Some autoimmune diseases such as lupus erythematosus strike women preferentially, and their onset often coincides with puberty. Other hormones appear to regulate the immune system as well, most notably prolactin, growth hormone and vitamin D.
Some publications point towards the effect of deoxycholic acid (DCA) as an immunostimulant of the non-specific immune system, activating its main actors, the macrophages. According to these publications, a sufficient amount of DCA in the human body corresponds to a good immune reaction of the non-specific immune system.
Claims made by marketers of various products and alternative health providers, such as chiropractors, homeopaths, and acupuncturists to be able to stimulate
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https://en.wikipedia.org/wiki/Bugonia
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In the ancient Mediterranean region, bugonia or bougonia was a ritual based on the belief that bees were spontaneously (equivocally) generated from a cow's carcass, although it is possible that the ritual had more currency as a poetic and learned trope than as an actual practice.
Description
A detailed description of the bugonia process can be found in Byzantine Geoponica:
Build a house, ten cubits high, with all the sides of equal dimensions, with one door, and four windows, one on each side; put an ox into it, thirty months old, very fat and fleshy; let a number of young men kill him by beating him violently with clubs, so as to mangle both flesh and bones, but taking care not to shed any blood; let all the orifices, mouth, eyes, nose etc. be stopped up with clean and fine linen, impregnated with pitch; let a quantity of thyme be strewed under the reclining animal, and then let windows and doors be closed and covered with a thick coating of clay, to prevent the access of air or wind. After three weeks have passed, let the house be opened, and let light and fresh air get access to it, except from the side from which the wind blows strongest. Eleven days afterwards, you will find the house full of bees, hanging together in clusters, and nothing left of the ox but horns, bones and hair.
The story of Aristaeus was an archetype of this ritual, serving to instruct bee keepers on how to recover from the loss of their bees. By extension, it was thought that fumigation with cow dung was beneficial to the health of the hive.
Variations
The idea that wasps are born of the corpses of horses was often described alongside bugonia. And given that European wasps bear a passing resemblance to European bees, it may be possible that the myth arose out of a mis-reported or misunderstood observation of a natural event.
Different variations are attested, such as simply burying the cow, or covering the corpse with mud or dung. Another variation states that use of the rumen alone is
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https://en.wikipedia.org/wiki/Tensor%20product%20of%20modules
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In mathematics, the tensor product of modules is a construction that allows arguments about bilinear maps (e.g. multiplication) to be carried out in terms of linear maps. The module construction is analogous to the construction of the tensor product of vector spaces, but can be carried out for a pair of modules over a commutative ring resulting in a third module, and also for a pair of a right-module and a left-module over any ring, with result an abelian group. Tensor products are important in areas of abstract algebra, homological algebra, algebraic topology, algebraic geometry, operator algebras and noncommutative geometry. The universal property of the tensor product of vector spaces extends to more general situations in abstract algebra. The tensor product of an algebra and a module can be used for extension of scalars. For a commutative ring, the tensor product of modules can be iterated to form the tensor algebra of a module, allowing one to define multiplication in the module in a universal way.
Balanced product
For a ring R, a right R-module M, a left R-module N, and an abelian group G, a map is said to be R-balanced, R-middle-linear or an R-balanced product if for all m, m′ in M, n, n′ in N, and r in R the following hold:
The set of all such balanced products over R from to G is denoted by .
If φ, ψ are balanced products, then each of the operations and −φ defined pointwise is a balanced product. This turns the set into an abelian group.
For M and N fixed, the map is a functor from the category of abelian groups to itself. The morphism part is given by mapping a group homomorphism to the function , which goes from to .
Remarks
Properties (Dl) and (Dr) express biadditivity of φ, which may be regarded as distributivity of φ over addition.
Property (A) resembles some associative property of φ.
Every ring R is an R-bimodule. So the ring multiplication in R is an R-balanced product .
Definition
For a ring R, a right R-module M, a left R-module N,
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https://en.wikipedia.org/wiki/Marek%20Karpinski
|
Marek Karpinski is a computer scientist and mathematician known for his research in the theory of algorithms and their applications, combinatorial optimization, computational complexity, and mathematical foundations. He is a recipient of several research prizes in the above areas.
He is currently a Professor of Computer Science, and the Head of the Algorithms Group at the University of Bonn. He is also a member of Bonn International Graduate School in Mathematics BIGS and the Hausdorff Center for Mathematics.
See also
List of computer scientists
List of mathematicians
References
Theoretical computer scientists
Mathematical logicians
Graph theorists
Academic staff of the University of Bonn
American computer scientists
20th-century Polish mathematicians
21st-century Polish mathematicians
Members of Academia Europaea
Polish computer scientists
Living people
Year of birth missing (living people)
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https://en.wikipedia.org/wiki/Thue%27s%20lemma
|
In modular arithmetic, Thue's lemma roughly states that every modular integer may be represented by a "modular fraction" such that the numerator and the denominator have absolute values not greater than the square root of the modulus.
More precisely, for every pair of integers with , given two positive integers and such that , there are two integers and such that
and
Usually, one takes and equal to the smallest integer greater than the square root of , but the general form is sometimes useful, and makes the uniqueness theorem (below) easier to state.
The first known proof is attributed to who used a pigeonhole argument. It can be used to prove Fermat's theorem on sums of two squares by taking m to be a prime p that is congruent to 1 modulo 4 and taking a to satisfy a2 + 1 = 0 mod p. (Such an "a" is guaranteed for "p" by Wilson's theorem.)
Uniqueness
In general, the solution whose existence is asserted by Thue's lemma is not unique. For example, when there are usually several solutions , provided that and are not too small. Therefore, one may only hope for uniqueness for the rational number , to which is congruent modulo if y and m are coprime. Nevertheless, this rational number need not be unique; for example, if , and , one has the two solutions
.
However, for and small enough, if a solution exists, it is unique. More precisely, with above notation, if
and
,
with
and
then
This result is the basis for rational reconstruction, which allows using modular arithmetic for computing rational numbers for which one knows bounds for numerators and denominators.
The proof is rather easy: by multiplying each congruence by the other and subtracting, one gets
The hypotheses imply that each term has an absolute value lower than , and thus that the absolute value of their difference is lower than . This implies that , hence the result.
Computing solutions
The original proof of Thue's lemma is not efficient, in the sense that it does not provi
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