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https://en.wikipedia.org/wiki/Legion%20%28software%29 | Legion is a computer software system variously classified as a distributed operating system, a peer-to-peer system, metacomputing software, and middleware. It is an object-based system designed to provide secure, transparent access to large numbers of machines, both to computational power and data.
The project was funded by the National Science Foundation and other funding agencies, and was mostly developed at the University of Virginia by a group led by Andrew Grimshaw. The Legion people formed the Avaki Corporation to commercialize the project in 1999, but Avaki eventually abandoned the Legion software base, and finally went bankrupt in 2005, with its intellectual property acquired by Sybase.
Legion is the successor to Hydra, developed to run on the C.mmp hardware system developed at Carnegie Mellon University in the late 1960s.
One of the slogans of the Legion project is "mechanism, not policy!"
References
Distributed data storage
Distributed operating systems
University of Virginia
Carnegie Mellon University |
https://en.wikipedia.org/wiki/Ecash | Ecash was conceived by David Chaum as an anonymous cryptographic electronic money or electronic cash system in 1982. It was realized through his corporation Digicash and used as micropayment system at one US bank from 1995 to 1998.
Design
Chaum published the idea of anonymous electronic money in a 1983 paper; eCash software on the user's local computer stored money in a digital format, cryptographically signed by a bank. The user could spend the digital money at any shop accepting eCash, without having to open an account with the vendor first, or transmitting credit card numbers. Security was ensured by public key digital signature schemes. The RSA blind signatures achieved unlinkability between withdrawal and spend transactions. Depending on the payment transactions, one distinguishes between on-line and off-line electronic cash: If the payee has to contact a third party (e.g., the bank or the credit-card company acting as an acquirer) before accepting a payment, the system is called an on-line system. In 1990, Chaum together with Moni Naor proposed the first off-line e-cash system, which was also based on blind signatures.
History
Chaum started the company DigiCash in 1989 with "ecash" as its trademark. He raised $10 million from David Marquardt and by 1997 Nicholas Negroponte was its chairman. Yet, in the United States, only one bank the Mark Twain bank in Saint Louis, MO implemented ecash, testing it as micropayment system; Similar to credit cards, the system was free to purchasers, while merchants paid a transaction fee. After a three-year trial that signed up merely 5,000 customers, the system was dissolved in 1998, one year after the bank had been purchased by Mercantile Bank, a large issuer of credit cards. David Chaum opined then “As the Web grew, the average level of sophistication of users dropped. It was hard to explain the importance of privacy to them”.
In Europe, with fewer credit cards and more cash transactions, micropayment technologies made |
https://en.wikipedia.org/wiki/Virtual%20PC | Virtual PC is an x86 emulator for PowerPC Mac hosts and a virtualization app for Microsoft Windows hosts. It was created by Connectix in 1997 and acquired by Microsoft in 2003. The Mac version was discontinued in 2006 following the Mac transition to Intel, while the Windows version was discontinued in 2011 in favour of Hyper-V.
Until version 4, Virtual PC only supported Classic Mac OS hosts. Version 4 was released in 2000 for both Mac OS and Windows, and version 5 (2001) added support for Mac OS X hosts. After Microsoft acquired Virtual PC from Connectix in 2003, the program was renamed Microsoft Virtual PC. In July 2006, Microsoft released the Windows version free of charge. In August 2006, Microsoft announced the Mac version would not be ported to Intel-based Macs, effectively discontinuing the product as PowerPC-based Macs would no longer be manufactured.
In 2009, Microsoft released Windows Virtual PC, which is only compatible with Windows 7 hosts, and is the technical foundation for the latter's Windows XP Mode. Windows Virtual PC does not officially support MS-DOS or operating systems older than Windows XP Professional SP3 as guests.
History
Connectix Virtual PC, Microsoft Virtual PC 2004, Microsoft Virtual PC 2007, and Windows Virtual PC are successive versions of the same software. Windows Virtual PC only runs on Windows 7. The earlier Microsoft versions which run on older versions of Windows were still available and support operating systems older than Windows XP. Starting in Windows 8, Microsoft replaced Virtual PC with Hyper-V.
Virtual PC by Connectix
Virtual PC was originally developed as a Macintosh application for System 7.5 and released by Connectix in June 1997. The first version of Virtual PC designed for Windows-based systems, version 4.0, was released in June 2001. Connectix sold versions of Virtual PC bundled with a variety of guest operating systems, including Windows, OS/2, and Red Hat Linux. As virtualization's importance to enterprise u |
https://en.wikipedia.org/wiki/Spontaneous%20process | In thermodynamics, a spontaneous process is a process which occurs without any external input to the system. A more technical definition is the time-evolution of a system in which it releases free energy and it moves to a lower, more thermodynamically stable energy state (closer to thermodynamic equilibrium). The sign convention for free energy change follows the general convention for thermodynamic measurements, in which a release of free energy from the system corresponds to a negative change in the free energy of the system and a positive change in the free energy of the surroundings.
Depending on the nature of the process, the free energy is determined differently. For example, the Gibbs free energy change is used when considering processes that occur under constant pressure and temperature conditions, whereas the Helmholtz free energy change is used when considering processes that occur under constant volume and temperature conditions. The value and even the sign of both free energy changes can depend upon the temperature and pressure or volume.
Because spontaneous processes are characterized by a decrease in the system's free energy, they do not need to be driven by an outside source of energy.
For cases involving an isolated system where no energy is exchanged with the surroundings, spontaneous processes are characterized by an increase in entropy.
A spontaneous reaction is a chemical reaction which is a spontaneous process under the conditions of interest.
Overview
In general, the spontaneity of a process only determines whether or not a process can occur and makes no indication as to whether or not the process will occur. In other words, spontaneity is a necessary, but not sufficient, condition for a process to actually occur. Furthermore, spontaneity makes no implication as to the speed at which as spontaneous may occur.
As an example, the conversion of a diamond into graphite is a spontaneous process at room temperature and pressure. Despite being s |
https://en.wikipedia.org/wiki/Trigram | Trigrams are a special case of the n-gram, where n is 3. They are often used in natural language processing for performing statistical analysis of texts and in cryptography for control and use of ciphers and codes.
Frequency
Context is very important, varying analysis rankings and percentages are easily derived by drawing from different sample sizes, different authors; or different document types: poetry, science-fiction, technology documentation; and writing levels: stories for children versus adults, military orders, and recipes.
Typical cryptanalytic frequency analysis finds that the 16 most common character-level trigrams in English are:
Because encrypted messages sent by telegraph often omit punctuation and spaces, cryptographic frequency analysis of such messages includes trigrams that straddle word boundaries. This causes trigrams such as "edt" to occur frequently, even though it may never occur in any one word of those messages.
Examples
The sentence "the quick red fox jumps over the lazy brown dog" has the following word-level trigrams:
the quick red
quick red fox
red fox jumps
fox jumps over
jumps over the
over the lazy
the lazy brown
lazy brown dog
And the word-level trigram "the quick red" has the following character-level trigrams (where an underscore "_" marks a space):
the
he_
e_q
_qu
qui
uic
ick
ck_
k_r
_re
red
References
Natural language processing
Computational linguistics
Speech recognition |
https://en.wikipedia.org/wiki/Partition%20function%20%28number%20theory%29 | In number theory, the partition function represents the number of possible partitions of a non-negative integer . For instance, because the integer 4 has the five partitions , , , , and .
No closed-form expression for the partition function is known, but it has both asymptotic expansions that accurately approximate it and recurrence relations by which it can be calculated exactly. It grows as an exponential function of the square root of its argument. The multiplicative inverse of its generating function is the Euler function; by Euler's pentagonal number theorem this function is an alternating sum of pentagonal number powers of its argument.
Srinivasa Ramanujan first discovered that the partition function has nontrivial patterns in modular arithmetic, now known as Ramanujan's congruences. For instance, whenever the decimal representation of ends in the digit 4 or 9, the number of partitions of will be divisible by 5.
Definition and examples
For a positive integer , is the number of distinct ways of representing as a sum of positive integers. For the purposes of this definition, the order of the terms in the sum is irrelevant: two sums with the same terms in a different order are not considered to be distinct.
By convention , as there is one way (the empty sum) of representing zero as a sum of positive integers. Furthermore when is negative.
The first few values of the partition function, starting with , are:
Some exact values of for larger values of include:
, the largest known prime number among the values of is , with 40,000 decimal digits. Until March 2022, this was also the largest prime that has been proved using elliptic curve primality proving.
Generating function
The generating function for p(n) is given by
The equality between the products on the first and second lines of this formula
is obtained by expanding each factor into the geometric series
To see that the expanded product equals the sum on the first line,
apply the distributiv |
https://en.wikipedia.org/wiki/Liouville%27s%20theorem%20%28complex%20analysis%29 | In complex analysis, Liouville's theorem, named after Joseph Liouville (although the theorem was first proven by Cauchy in 1844), states that every bounded entire function must be constant. That is, every holomorphic function for which there exists a positive number such that for all is constant. Equivalently, non-constant holomorphic functions on have unbounded images.
The theorem is considerably improved by Picard's little theorem, which says that every entire function whose image omits two or more complex numbers must be constant.
Proof
This important theorem has several proofs.
A standard analytical proof uses the fact that holomorphic functions are analytic.
Another proof uses the mean value property of harmonic functions.
The proof can be adapted to the case where the harmonic function is merely bounded above or below. See Harmonic function#Liouville's theorem.
Corollaries
Fundamental theorem of algebra
There is a short proof of the fundamental theorem of algebra based upon Liouville's theorem.
No entire function dominates another entire function
A consequence of the theorem is that "genuinely different" entire functions cannot dominate each other, i.e. if and are entire, and everywhere, then for some complex number . Consider that for the theorem is trivial so we assume . Consider the function . It is enough to prove that can be extended to an entire function, in which case the result follows by Liouville's theorem. The holomorphy of is clear except at points in . But since is bounded and all the zeroes of are isolated, any singularities must be removable. Thus can be extended to an entire bounded function which by Liouville's theorem implies it is constant.
If f is less than or equal to a scalar times its input, then it is linear
Suppose that is entire and , for . We can apply Cauchy's integral formula; we have that
where is the value of the remaining integral. This shows that is bounded and entire, so it must be constant, by |
https://en.wikipedia.org/wiki/Avalanche%20photodiode | An avalanche photodiode (APD) is a highly sensitive semiconductor photodiode detector that exploits the photoelectric effect to convert light into electricity. From a functional standpoint, they can be regarded as the semiconductor analog of photomultiplier tubes. The avalanche photodiode was invented by Japanese engineer Jun-ichi Nishizawa in 1952. However, study of avalanche breakdown, microplasma defects in silicon and germanium and the investigation of optical detection using p-n junctions predate this patent. Typical applications for APDs are laser rangefinders, long-range fiber-optic telecommunication, and quantum sensing for control algorithms. New applications include positron emission tomography and particle physics.
Principle of operation
By applying a high reverse bias voltage (typically 100–200 V in silicon), APDs show an internal current gain effect (around 100) due to impact ionization (avalanche effect). However, some silicon APDs employ alternative doping and beveling techniques compared to traditional APDs that allow greater voltage to be applied (> 1500 V) before breakdown is reached and hence a greater operating gain (> 1000). In general, the higher the reverse voltage, the higher the gain. Among the various expressions for the APD multiplication factor (M), an instructive expression is given by the formula
where L is the space-charge boundary for electrons, and is the multiplication coefficient for electrons (and holes). This coefficient has a strong dependence on the applied electric field strength, temperature, and doping profile. Since APD gain varies strongly with the applied reverse bias and temperature, it is necessary to control the reverse voltage to keep a stable gain. Avalanche photodiodes therefore are more sensitive compared to other semiconductor photodiodes.
If very high gain is needed (105 to 106), detectors related to APDs called SPADs (single-photon avalanche diodes) can be used and operated with a reverse voltage above a ty |
https://en.wikipedia.org/wiki/Liouville%27s%20theorem%20%28Hamiltonian%29 | In physics, Liouville's theorem, named after the French mathematician Joseph Liouville, is a key theorem in classical statistical and Hamiltonian mechanics. It asserts that the phase-space distribution function is constant along the trajectories of the system—that is that the density of system points in the vicinity of a given system point traveling through phase-space is constant with time. This time-independent density is in statistical mechanics known as the classical a priori probability.
There are related mathematical results in symplectic topology and ergodic theory; systems obeying Liouville's theorem are examples of incompressible dynamical systems.
There are extensions of Liouville's theorem to stochastic systems.
Liouville equation
The Liouville equation describes the time evolution of the phase space distribution function. Although the equation is usually referred to as the "Liouville equation", Josiah Willard Gibbs was the first to recognize the importance of this equation as the fundamental equation of statistical mechanics. It is referred to as the Liouville equation because its derivation for non-canonical systems utilises an identity first derived by Liouville in 1838.
Consider a Hamiltonian dynamical system with canonical coordinates and conjugate momenta , where . Then the phase space distribution determines the probability that the system will be found in the infinitesimal phase space volume . The Liouville equation governs the evolution of in time :
Time derivatives are denoted by dots, and are evaluated according to Hamilton's equations for the system. This equation demonstrates the conservation of density in phase space (which was Gibbs's name for the theorem). Liouville's theorem states that
The distribution function is constant along any trajectory in phase space.
A proof of Liouville's theorem uses the n-dimensional divergence theorem. This proof is based on the fact that the evolution of obeys an 2n-dimensional version of the c |
https://en.wikipedia.org/wiki/Symplectomorphism | In mathematics, a symplectomorphism or symplectic map is an isomorphism in the category of symplectic manifolds. In classical mechanics, a symplectomorphism represents a transformation of phase space that is volume-preserving and preserves the symplectic structure of phase space, and is called a canonical transformation.
Formal definition
A diffeomorphism between two symplectic manifolds is called a symplectomorphism if
where is the pullback of . The symplectic diffeomorphisms from to are a (pseudo-)group, called the symplectomorphism group (see below).
The infinitesimal version of symplectomorphisms gives the symplectic vector fields. A vector field is called symplectic if
Also, is symplectic iff the flow of is a symplectomorphism for every .
These vector fields build a Lie subalgebra of .
Here, is the set of smooth vector fields on , and is the Lie derivative along the vector field
Examples of symplectomorphisms include the canonical transformations of classical mechanics and theoretical physics, the flow associated to any Hamiltonian function, the map on cotangent bundles induced by any diffeomorphism of manifolds, and the coadjoint action of an element of a Lie group on a coadjoint orbit.
Flows
Any smooth function on a symplectic manifold gives rise, by definition, to a Hamiltonian vector field and the set of all such vector fields form a subalgebra of the Lie algebra of symplectic vector fields. The integration of the flow of a symplectic vector field is a symplectomorphism. Since symplectomorphisms preserve the symplectic 2-form and hence the symplectic volume form, Liouville's theorem in Hamiltonian mechanics follows. Symplectomorphisms that arise from Hamiltonian vector fields are known as Hamiltonian symplectomorphisms.
Since the flow of a Hamiltonian vector field also preserves . In physics this is interpreted as the law of conservation of energy.
If the first Betti number of a connected symplectic manifold is zero, symplectic and Ham |
https://en.wikipedia.org/wiki/Gametogenesis | Gametogenesis is a biological process by which diploid or haploid precursor cells undergo cell division and differentiation to form mature haploid gametes. Depending on the biological life cycle of the organism, gametogenesis occurs by meiotic division of diploid gametocytes into various gametes, or by mitosis. For example, plants produce gametes through mitosis in gametophytes. The gametophytes grow from haploid spores after sporic meiosis. The existence of a multicellular, haploid phase in the life cycle between meiosis and gametogenesis is also referred to as alternation of generations.
It is the biological process of gametogenesis; cells that are haploid or diploid divide to create other cells. matured haploid gametes. It can take place either through mitosis or meiotic division of diploid gametocytes into different depending on an organism's biological life cycle, gametes. For instance, gametophytes in plants undergo mitosis to produce gametes. Both male and female have different forms.
In animals
Animals produce gametes directly through meiosis from diploid mother cells in organs called gonads (testis in males and ovaries in females). In mammalian germ cell development, sexually dimorphic gametes differentiates into primordial germ cells from pluripotent cells during initial mammalian development. Males and females of a species that reproduce sexually have different forms of gametogenesis:
spermatogenesis (male): Immature germ cells are produced in a man's testes. To mature into sperms, males' immature germ cells, or spermatogonia, go through spermatogenesis during adolescence. Spermatogonia are diploid cells that become larger as they divide through mitosis. These primary spermatocytes. These diploid cells undergo meiotic division to create secondary spermatocytes. These secondary spermatocytes undergo a second meiotic division to produce immature sperms or spermatids. These spermatids undergo spermiogenesis in order to develop into sperm. LH, FSH, GnRH |
https://en.wikipedia.org/wiki/International%20Birdman | The International Birdman was a series of English competitions held in the West Sussex towns of Bognor Regis, Selsey and Worthing. The competition involved human 'birdmen' attempting to fly off the end of a pier into the sea for prize money. The event began in 1971 and was held on piers in West Sussex, on the south coast of England. First held in Selsey, the event moved to Bognor Regis in 1978. In 2008 and 2009 the competition relocated to Worthing Pier due to renovations of Bognor Regis Pier. From 2010 Bognor Regis and Worthing have both held Birdman competition, forming the International Birdman Series, which ended in 2016. It was the longest running Birdman Rally in the world.
Format
The competition involves running off an elevated ramp of 20 to 35 feet high at the end of a pier and attempting to 'fly' the furthest distance. There was an initial prize of £1,000 for anyone who could travel beyond . Since starting, the prize money and qualifying distance has increased and in 2009 at Worthing it stood at £30,000 for reaching . The competition is divided between serious aviators mainly flying hang-gliders (Condor Class), inventors with home designed and built machines (Leonardo da Vinci Class), and people in fancy dress with little or no actual flying ability (Kingfisher Class), raising money for charity.
History
The event started in 1971 as the International Bird-Man Rally in Selsey on the coast of Sussex. The event was initiated by George Abel, as part of a fund-raising activity for the Selsey branch of the Royal Air Forces Association (RAFA) Club. Abel, a former RAF photographer, emigrated to Australia shortly afterwards, where he also helped to organise Birdman events.
In 1978 organisers were informed they could no longer use the pier at Selsey and the event was moved to Bognor Regis. By 1983 the competition had attracted European teams and the attention of the BBC. In 2008, because of the demolition of an 18 metre (60 ft) length of the end of Bognor pi |
https://en.wikipedia.org/wiki/Autonomous%20system%20%28mathematics%29 | In mathematics, an autonomous system or autonomous differential equation is a system of ordinary differential equations which does not explicitly depend on the independent variable. When the variable is time, they are also called time-invariant systems.
Many laws in physics, where the independent variable is usually assumed to be time, are expressed as autonomous systems because it is assumed the laws of nature which hold now are identical to those for any point in the past or future.
Definition
An autonomous system is a system of ordinary differential equations of the form
where takes values in -dimensional Euclidean space; is often interpreted as time.
It is distinguished from systems of differential equations of the form
in which the law governing the evolution of the system does not depend solely on the system's current state but also the parameter , again often interpreted as time; such systems are by definition not autonomous.
Properties
Solutions are invariant under horizontal translations:
Let be a unique solution of the initial value problem for an autonomous system
Then solves
Denoting gets and , thus
For the initial condition, the verification is trivial,
Example
The equation is autonomous, since the independent variable () does not explicitly appear in the equation.
To plot the slope field and isocline for this equation, one can use the following code in GNU Octave/MATLAB
Ffun = @(X, Y)(2 - Y) .* Y; % function f(x,y)=(2-y)y
[X, Y] = meshgrid(0:.2:6, -1:.2:3); % choose the plot sizes
DY = Ffun(X, Y); DX = ones(size(DY)); % generate the plot values
quiver(X, Y, DX, DY, 'k'); % plot the direction field in black
hold on;
contour(X, Y, DY, [0 1 2], 'g'); % add the isoclines(0 1 2) in green
title('Slope field and isoclines for f(x,y)=(2-y)y')
One can observe from the plot that the function is -invariant, and so is the shape of the solution, i.e. for any shift .
Solving the equation symbolically in MATLAB, by running
syms y(x);
equa |
https://en.wikipedia.org/wiki/Autonomous%20system%20%28Internet%29 | An autonomous system (AS) is a collection of connected Internet Protocol (IP) routing prefixes under the control of one or more network operators on behalf of a single administrative entity or domain, that presents a common and clearly defined routing policy to the Internet. Each AS is assigned an autonomous system number (ASN), for use in Border Gateway Protocol (BGP) routing. Autonomous System Numbers are assigned to Local Internet Registries (LIRs) and end user organizations by their respective Regional Internet Registries (RIRs), which in turn receive blocks of ASNs for reassignment from the Internet Assigned Numbers Authority (IANA). The IANA also maintains a registry of ASNs which are reserved for private use (and should therefore not be announced to the global Internet).
Originally, the definition required control by a single entity, typically an Internet service provider (ISP) or a very large organization with independent connections to multiple networks, that adhered to a single and clearly defined routing policy. In March 1996, the newer definition came into use because multiple organizations can run BGP using private AS numbers to an ISP that connects all those organizations to the Internet. Even though there may be multiple autonomous systems supported by the ISP, the Internet only sees the routing policy of the ISP. That ISP must have an officially registered ASN.
Until 2007, AS numbers were defined as 16-bit integers, which allowed for a maximum of 65,536 assignments. Since then, the IANA has begun to also assign 32-bit AS numbers to regional Internet registries (RIRs). These numbers are written preferably as simple integers, in a notation referred to as "asplain", ranging from 0 to 4,294,967,295 (hexadecimal 0xFFFF FFFF). Or, alternatively, in the form called "asdot+" which looks like x.y, where x and y are 16-bit numbers. Numbers of the form 0.y are exactly the old 16-bit AS numbers. The special 16-bit ASN 23456 ("AS_TRANS") was assigned by IANA as |
https://en.wikipedia.org/wiki/Law%20of%20total%20variance | In probability theory, the law of total variance or variance decomposition formula or conditional variance formulas or law of iterated variances also known as Eve's law, states that if and are random variables on the same probability space, and the variance of is finite, then
In language perhaps better known to statisticians than to probability theorists, the two terms are the "unexplained" and the "explained" components of the variance respectively (cf. fraction of variance unexplained, explained variation). In actuarial science, specifically credibility theory, the first component is called the expected value of the process variance (EVPV) and the second is called the variance of the hypothetical means (VHM). These two components are also the source of the term "Eve's law", from the initials EV VE for "expectation of variance" and "variance of expectation".
Example
Suppose is a coin flip with the probability of heads being . Suppose that when then is drawn from a normal distribution with mean and standard deviation , and that when then is drawn from normal distribution with mean and standard deviation . Then the first, "unexplained" term on the right-hand side of the above formula is the weighted average of the variances, , and the second, "explained" term is the variance of the distribution that gives with probability and gives with probability .
Formulation
There is a general variance decomposition formula for components (see below). For example, with two conditioning random variables:
which follows from the law of total conditional variance:
Note that the conditional expected value is a random variable in its own right, whose value depends on the value of Notice that the conditional expected value of given the is a function of (this is where adherence to the conventional and rigidly case-sensitive notation of probability theory becomes important!). If we write then the random variable is just Similar comments apply to the condit |
https://en.wikipedia.org/wiki/Aspergillus%20niger | Aspergillus niger is a mold classified within the Nigri section of the Aspergillus genus. The Aspergillus genus consists of common molds found throughout the environment within soil and water, on vegetation, in fecal matter, on decomposing matter, and suspended in the air. Species within this genus often grow quickly and can sporulate within a few days of germination. A combination of characteristics unique to A. niger makes the microbe invaluable to the production of many acids, proteins and bioactive compounds. Characteristics including extensive metabolic diversity, high production yield, secretion capability, and the ability to conduct post-translational modifications are responsible for A. niger's robust production of secondary metabolites. A. niger's capability to withstand extremely acidic conditions makes it especially important to the industrial production of citric acid.
A. niger causes a disease known as "black mold" on certain fruits and vegetables such as grapes, apricots, onions, and peanuts, and is a common contaminant of food. It is ubiquitous in soil and is commonly found in indoor environments, where its black colonies can be confused with those of Stachybotrys (species of which have also been called "black mold"). A. niger is classified as Generally Recognized as Safe (GRAS) by the US Food and Drug Administration for use in food production, although the microbe is capable of producing toxins that affect human health.
Taxonomy
Aspergillus niger is included in Aspergillus subgenus Circumdati, section Nigri. The section Nigri includes 15 related black-spored species that may be confused with A. niger, including A. tubingensis, A. foetidus, A. carbonarius, and A. awamori. In 2004, a number of morphologically similar species were described by Samson et al.
In 2007, the strain of ATCC 16404 Aspergillus niger was reclassified as Aspergillus brasiliensis (refer to publication by Varga et al.). This required an update to the U.S. Pharmacopoeia and the |
https://en.wikipedia.org/wiki/10-Yard%20Fight | is an American football sports video game that was developed and published in Japan by Irem for arcades in 1983. It was published overseas by Taito in the Americas, by Electrocoin in Europe, and by ADP Automaten GmbH in West Germany.
Gameplay
10-Yard Fight is viewed in a top-down perspective and is vertical scrolling. The player does not select plays for either offense or defense. On offense, the player simply receives the ball upon the snap and either attempts to run with the quarterback, toss the ball to a running back, or throw the ball to the one long distance receiver – basically the option offense. On defense, the player chooses one of two players to control, and the computer manipulates the others. The ball can also be punted or a field goal can be attempted.
The game has five levels of increasing difficulty: high school, college, professional, playoff, and Super Bowl. If the player wins both halves of an "accelerated real time" 30-minute half at an easier level, the player advances to the next level of difficulty, like a career mode.
A player scores 20,000 points for any kickoff that is returned for a touchdown.
Ports
The arcade game was later ported to the Famicom by Irem first in Japan, and later published in North America and Europe by Nintendo in 1985 for the Nintendo Entertainment System (NES). The arcade game was also ported to the MSX home computer also by Irem, but exclusively in Japan.
While graphically similar, there are some fundamental differences between the arcade and NES versions of the game. The arcade version only seeks to simulate the offense, with the team attempting to score a touchdown, which ultimately leads the player to the next level. The NES version was developed to allow both defense and offense, as well as a simultaneous 2-player mode.
10-Yard Fight was, along with Kung Fu, one of only two NES launch titles not originally developed by Nintendo. Both games were developed initially for arcades by Irem. Although Nintendo deve |
https://en.wikipedia.org/wiki/Mathematical%20morphology | Mathematical morphology (MM) is a theory and technique for the analysis and processing of geometrical structures, based on set theory, lattice theory, topology, and random functions. MM is most commonly applied to digital images, but it can be employed as well on graphs, surface meshes, solids, and many other spatial structures.
Topological and geometrical continuous-space concepts such as size, shape, convexity, connectivity, and geodesic distance, were introduced by MM on both continuous and discrete spaces. MM is also the foundation of morphological image processing, which consists of a set of operators that transform images according to the above characterizations.
The basic morphological operators are erosion, dilation, opening and closing.
MM was originally developed for binary images, and was later extended to grayscale functions and images. The subsequent generalization to complete lattices is widely accepted today as MM's theoretical foundation.
History
Mathematical Morphology was developed in 1964 by the collaborative work of Georges Matheron and Jean Serra, at the École des Mines de Paris, France. Matheron supervised the PhD thesis of Serra, devoted to the quantification of mineral characteristics from thin cross sections, and this work resulted in a novel practical approach, as well as theoretical advancements in integral geometry and topology.
In 1968, the Centre de Morphologie Mathématique was founded by the École des Mines de Paris in Fontainebleau, France, led by Matheron and Serra.
During the rest of the 1960s and most of the 1970s, MM dealt essentially with binary images, treated as sets, and generated a large number of binary operators and techniques: Hit-or-miss transform, dilation, erosion, opening, closing, granulometry, thinning, skeletonization, ultimate erosion, conditional bisector, and others. A random approach was also developed, based on novel image models. Most of the work in that period was developed in Fontainebleau.
From the |
https://en.wikipedia.org/wiki/Dots%20per%20inch | Dots per inch (DPI, or dpi) is a measure of spatial printing, video or image scanner dot density, in particular the number of individual dots that can be placed in a line within the span of . Similarly, dots per centimetre (d/cm or dpcm) refers to the number of individual dots that can be placed within a line of .
DPI measurement in printing
DPI is used to describe the resolution number of dots per inch in a digital print and the printing resolution of a hard copy print dot gain, which is the increase in the size of the halftone dots during printing. This is caused by the spreading of ink on the surface of the media.
Up to a point, printers with higher DPI produce clearer and more detailed output. A printer does not necessarily have a single DPI measurement; it is dependent on print mode, which is usually influenced by driver settings. The range of DPI supported by a printer is most dependent on the print head technology it uses. A dot matrix printer, for example, applies ink via tiny rods striking an ink ribbon, and has a relatively low resolution, typically in the range of . An inkjet printer sprays ink through tiny nozzles, and is typically capable of 300–720 DPI. A laser printer applies toner through a controlled electrostatic charge, and may be in the range of 600 to 2,400 DPI.
The DPI measurement of a printer often needs to be considerably higher than the pixels per inch (PPI) measurement of a video display in order to produce similar-quality output. This is due to the limited range of colours for each dot typically available on a printer. At each dot position, the simplest type of color printer can either print no dot, or print a dot consisting of a fixed volume of ink in each of four color channels (typically CMYK with cyan, magenta, yellow and black ink) or 24 = 16 colours on laser, wax and most inkjet printers, of which only 14 or 15 (or as few as 8 or 9) may be actually discernible depending on the strength of the black component, the strategy used f |
https://en.wikipedia.org/wiki/Cattle%20in%20religion%20and%20mythology | There are varying beliefs about cattle in societies and religions.
Cattle are considered sacred in Indian religions such as Hinduism, Jainism, Buddhism and Sikhism, as well as in African paganism. Cattle played other major roles in many religions, including those of ancient Egypt, ancient Greece, ancient Israel, ancient Rome.
In some regions, especially most states of India, the slaughter of cattle is prohibited and their meat may be taboo.
In Indian religions
Legislation against the slaughter of cattle is in place throughout most states of India except Kerala and parts of the North-East.
Hinduism
Hinduism specifically considers the zebu (Bos indicus) to be sacred. Respect for the lives of animals including cattle, diet in Hinduism and vegetarianism in India are based on the Hindu ethics. The Hindu ethics are driven by the core concept of Ahimsa, i.e. non-violence towards all beings, as mentioned in the Chandogya Upanishad (~ 800 BCE). By mid 1st millennium BCE, all three major religions – Buddhism, Hinduism, and Jainism – were championing non-violence as an ethical value, and something that impacted one's rebirth. According to Harris, by about 200 CE, food and feasting on animal slaughter were widely considered as a form of violence against life forms, and became a religious and social taboo. India, which has 79.80% Hindu population as of (2011 census), had the lowest rate of meat consumption in the world according to the 2007 UN FAO statistics, and India has more vegetarians than the rest of the world put together.
According to Ludwig Alsdorf, "Indian vegetarianism is unequivocally based on ahimsa (non-violence)" as evidenced by ancient smritis and other ancient texts of Hinduism." He adds that the endearment and respect for cattle in Hinduism is more than a commitment to vegetarianism and has become integral to its theology. The respect for cattle is widespread but not universal. According to Christopher Fuller, animal sacrifices have been rare among th |
https://en.wikipedia.org/wiki/Local%20analysis | In mathematics, the term local analysis has at least two meanings, both derived from the idea of looking at a problem relative to each prime number p first, and then later trying to integrate the information gained at each prime into a 'global' picture. These are forms of the localization approach.
Group theory
In group theory, local analysis was started by the Sylow theorems, which contain significant information about the structure of a finite group G for each prime number p dividing the order of G. This area of study was enormously developed in the quest for the classification of finite simple groups, starting with the Feit–Thompson theorem that groups of odd order are solvable.
Number theory
In number theory one may study a Diophantine equation, for example, modulo p for all primes p, looking for constraints on solutions. The next step is to look modulo prime powers, and then for solutions in the p-adic field. This kind of local analysis provides conditions for solution that are necessary. In cases where local analysis (plus the condition that there are real solutions) provides also sufficient conditions, one says that the Hasse principle holds: this is the best possible situation. It does for quadratic forms, but certainly not in general (for example for elliptic curves). The point of view that one would like to understand what extra conditions are needed has been very influential, for example for cubic forms.
Some form of local analysis underlies both the standard applications of the Hardy–Littlewood circle method in analytic number theory, and the use of adele rings, making this one of the unifying principles across number theory.
See also
:Category:Localization (mathematics)
Localization of a category
Localization of a module
Localization of a ring
Localization of a topological space
Hasse principle
Number theory
Finite groups
Localization (mathematics) |
https://en.wikipedia.org/wiki/Jordan%20normal%20form | In linear algebra, a Jordan normal form, also known as a Jordan canonical form (JCF),
is an upper triangular matrix of a particular form called a Jordan matrix representing a linear operator on a finite-dimensional vector space with respect to some basis. Such a matrix has each non-zero off-diagonal entry equal to 1, immediately above the main diagonal (on the superdiagonal), and with identical diagonal entries to the left and below them.
Let V be a vector space over a field K. Then a basis with respect to which the matrix has the required form exists if and only if all eigenvalues of the matrix lie in K, or equivalently if the characteristic polynomial of the operator splits into linear factors over K. This condition is always satisfied if K is algebraically closed (for instance, if it is the field of complex numbers). The diagonal entries of the normal form are the eigenvalues (of the operator), and the number of times each eigenvalue occurs is called the algebraic multiplicity of the eigenvalue.
If the operator is originally given by a square matrix M, then its Jordan normal form is also called the Jordan normal form of M. Any square matrix has a Jordan normal form if the field of coefficients is extended to one containing all the eigenvalues of the matrix. In spite of its name, the normal form for a given M is not entirely unique, as it is a block diagonal matrix formed of Jordan blocks, the order of which is not fixed; it is conventional to group blocks for the same eigenvalue together, but no ordering is imposed among the eigenvalues, nor among the blocks for a given eigenvalue, although the latter could for instance be ordered by weakly decreasing size.
The Jordan–Chevalley decomposition is particularly simple with respect to a basis for which the operator takes its Jordan normal form. The diagonal form for diagonalizable matrices, for instance normal matrices, is a special case of the Jordan normal form.
The Jordan normal form is named after Camille Jord |
https://en.wikipedia.org/wiki/Action%20%28physics%29 | In physics, action is a scalar quantity that describes how the energy of a physical system has changed over time (its dynamics). Action is significant because the equations of motion of a system can be derived through the principle of stationary action.
In the simple case of a single particle moving with a constant velocity (thereby undergoing uniform linear motion), the action is the momentum of the particle times the distance it moves, added up along its path; equivalently, action is twice the particle's kinetic energy times the duration for which it has that amount of energy. For more complicated systems, all such quantities are combined.
More formally, action is a mathematical functional which takes the trajectory (also called path or history) of the system as its argument and has a real number as its result. Generally, the action takes different values for different paths. Action has dimensions of energy × time or momentum × length, and its SI unit is joule-second (like the Planck constant h).
Introduction
Hamilton's principle states that the differential equations of motion for any physical system can be re-formulated as an equivalent integral equation. Thus, there are two distinct approaches for formulating dynamical models.
It applies not only to the classical mechanics of a single particle, but also to classical fields such as the electromagnetic and gravitational fields. Hamilton's principle has also been extended to quantum mechanics and quantum field theory—in particular the path integral formulation of quantum mechanics makes use of the concept—where a physical system randomly follows one of the possible paths, with the phase of the probability amplitude for each path being determined by the action for the path.
Solution of differential equation
Empirical laws are frequently expressed as differential equations, which describe how physical quantities such as position and momentum change continuously with time, space or a generalization thereof. |
https://en.wikipedia.org/wiki/Excavator | Excavators are heavy construction equipment consisting of a boom, dipper (or stick), bucket and cab on a rotating platform known as the "house". The house sits atop an undercarriage with tracks or wheels. They are a natural progression from the steam shovels and often mistakenly called power shovels, as power shovels may have similar looking buckets. All movement and functions of a hydraulic excavator are accomplished through the use of hydraulic fluid, with hydraulic cylinders and hydraulic motors. Due to the linear actuation of hydraulic cylinders, their mode of operation is fundamentally different from cable-operated excavators, which use winches and steel ropes to accomplish the movements.
Terminology
Excavators are also called diggers, JCBs (a proprietary name, in an example of a generic trademark), mechanical shovels, or 360-degree excavators (sometimes abbreviated simply to "360"). Tracked excavators are sometimes called "trackhoes" by analogy to the backhoe. In the UK, wheeled excavators are sometimes known as "rubber ducks".
Usage
Excavators are used in many ways:
Digging of trenches, holes, foundations
Material handling
Brush cutting with hydraulic saw and mower attachments
Forestry work
Forestry mulching
Demolition with hydraulic claw, cutter and breaker attachments
Mining, especially, but not only open-pit mining
River dredging
Hydro excavation to access fragile underground infrastructure using high pressure water
Driving piles, in conjunction with a pile driver
Drilling shafts for footings and rock blasting, by use of an auger or hydraulic drill attachment
Snow removal with snowplow and snow blower attachments
Aircraft recycling
Configurations
Modern hydraulic excavators come in a wide variety of sizes. The smaller ones are called mini or compact excavators. For example, Caterpillar's smallest mini-excavator weighs and has 13 hp; their largest model is the largest excavator available (developed and produced by the Orenstein & Koppel, |
https://en.wikipedia.org/wiki/Fusarium%20oxysporum | Fusarium oxysporum (Schlecht as emended by Snyder and Hansen), an ascomycete fungus, comprises all the species, varieties and forms recognized by Wollenweber and Reinking within an infrageneric grouping called section Elegans. It is part of the family Nectriaceae.
Although their predominant role in native soils may be as harmless or even beneficial plant endophytes or soil saprophytes, many strains within the F. oxysporum complex are soil borne pathogens of plants, especially in agricultural settings.
Taxonomy
While the species, as defined by Snyder and Hansen, has been widely accepted for more than 50 years, more recent work indicates this taxon is actually a genetically heterogeneous polytypic morphospecies, whose strains represent some of the most abundant and widespread microbes of the global soil microflora.
Genome
The family of transposable elements was first discovered by Daboussi et al., 1992 in several formae speciales and Davière et al., 2001 and Langin et al., 2003 have since found them in most strains at copy numbers as high as 100.
Habitat
These diverse and adaptable fungi have been found in soils ranging from the Sonoran Desert, to tropical and temperate forest, grasslands and soils of the tundra. F. oxysporum strains are ubiquitous soil inhabitants that have the ability to exist as saprophytes, and degrade lignin and complex carbohydrates associated with soil debris. They are pervasive plant endophytes that can colonize plant roots and may even protect plants or form the basis of disease suppression.
Because the hosts of a given forma specialis usually are closely related, many have assumed that members of a forma specialis are also closely related and descended from a common ancestor. However, results from research conducted on Fusarium oxysporum f. sp. cubense forced scientists to question these assumptions. Researchers used anonymous, single-copy restriction fragment length polymorphsims (RFLPs) to identify 10 clonal lineages from a collectio |
https://en.wikipedia.org/wiki/Long%20division | In arithmetic, long division is a standard division algorithm suitable for dividing multi-digit Hindu-Arabic numerals (Positional notation) that is simple enough to perform by hand. It breaks down a division problem into a series of easier steps.
As in all division problems, one number, called the dividend, is divided by another, called the divisor, producing a result called the quotient. It enables computations involving arbitrarily large numbers to be performed by following a series of simple steps. The abbreviated form of long division is called short division, which is almost always used instead of long division when the divisor has only one digit. Chunking (also known as the partial quotients method or the hangman method) is a less mechanical form of long division prominent in the UK which contributes to a more holistic understanding of the division process.
While related algorithms have existed since the 12th century, the specific algorithm in modern use was introduced by Henry Briggs 1600.
Education
Inexpensive calculators and computers have become the most common way to solve division problems, eliminating a traditional mathematical exercise, and decreasing the educational opportunity to show how to do so by paper and pencil techniques. (Internally, those devices use one of a variety of division algorithms, the faster ones among which rely on approximations and multiplications to achieve the tasks.) In the United States, long division has been especially targeted for de-emphasis, or even elimination from the school curriculum, by reform mathematics, though traditionally introduced in the 4th or 5th grades.
Method
In English-speaking countries, long division does not use the division slash or division sign symbols but instead constructs a tableau. The divisor is separated from the dividend by a right parenthesis or vertical bar ; the dividend is separated from the quotient by a vinculum (i.e., an overbar). The combination of these two symbols is so |
https://en.wikipedia.org/wiki/Spectrum%20analyzer | A spectrum analyzer measures the magnitude of an input signal versus frequency within the full frequency range of the instrument. The primary use is to measure the power of the spectrum of known and unknown signals. The input signal that most common spectrum analyzers measure is electrical; however, spectral compositions of other signals, such as acoustic pressure waves and optical light waves, can be considered through the use of an appropriate transducer. Spectrum analyzers for other types of signals also exist, such as optical spectrum analyzers which use direct optical techniques such as a monochromator to make measurements.
By analyzing the spectra of electrical signals, dominant frequency, power, distortion, harmonics, bandwidth, and other spectral components of a signal can be observed that are not easily detectable in time domain waveforms. These parameters are useful in the characterization of electronic devices, such as wireless transmitters.
The display of a spectrum analyzer has frequency displayed on the horizontal axis and the amplitude on the vertical axis. To the casual observer, a spectrum analyzer looks like an oscilloscope, which plots amplitude on the vertical axis but time on the horizontal axis. In fact, some lab instruments can function either as an oscilloscope or a spectrum analyzer.
History
The first spectrum analyzers, in the 1960s, were swept-tuned instruments.
Following the discovery of the fast Fourier transform (FFT) in 1965, the first FFT-based analyzers were introduced in 1967.
Today, there are three basic types of analyzer: the swept-tuned spectrum analyzer, the vector signal analyzer, and the real-time spectrum analyzer.
Types
Spectrum analyzer types are distinguished by the methods used to obtain the spectrum of a signal. There are swept-tuned and fast Fourier transform (FFT) based spectrum analyzers:
A swept-tuned analyzer uses a superheterodyne receiver to down-convert a portion of the input signal spectrum to the ce |
https://en.wikipedia.org/wiki/Wah-wah%20pedal | A wah-wah pedal, or simply wah pedal, is a type of electric guitar effects pedal that alters the tone and frequencies of the guitar signal to create a distinctive sound, mimicking the human voice saying the onomatopoeic name "wah-wah". The pedal sweeps the peak response of a frequency filter up and down in frequency to create the sound, a spectral glide, also known as "the wah effect". The wah-wah effect originated in the 1920s, with trumpet or trombone players finding they could produce an expressive crying tone by moving a mute in and out of the instrument's bell. This was later simulated with electronic circuitry for the electric guitar when the wah-wah pedal was invented. It is controlled by movement of the player's foot on a rocking pedal connected to a potentiometer. Wah-wah effects may be used as a fixed-filter to alter an instrument’s timbre (known as a “cocked-wah”); they may be used when a guitarist is soloing; or, classically, they may be used to create a "wacka-wacka" funk-styled rhythm for rhythm guitar playing.
An envelope filter or envelope follower is often referred to as an auto-wah.
History
The first wah pedal was created by Bradley J. Plunkett at Warwick Electronics Inc./Thomas Organ Company in November 1966. This pedal is the original prototype made from a transistorized MRB (mid-range boost) potentiometer bread-boarded circuit and the housing of a Vox Continental Organ volume pedal. The concept, however, was not new. Country guitar virtuoso Chet Atkins had used a similar, self-designed device on his late 1950s recordings of "Hot Toddy" and "Slinkey". Jazz guitarist Peter Van Wood had a modified Hammond organ expression
pedal; he recorded in 1955 a version of George Gershwin's "Summertime" with a "crying" tone, and other recordings including humorous "novelty" effects. A DeArmond Tone and Volume pedal was used in the early 1960s by Big Jim Sullivan, notably in some Krew Cats instrumental tracks, and in Dave Berry's song "The Crying Game".
T |
https://en.wikipedia.org/wiki/Binary%20decoder | In digital electronics, a binary decoder is a combinational logic circuit that converts binary information from the n coded inputs to a maximum of 2n unique outputs. They are used in a wide variety of applications, including instruction decoding, data multiplexing and data demultiplexing, seven segment displays, and as address decoders for memory and port-mapped I/O.
There are several types of binary decoders, but in all cases a decoder is an electronic circuit with multiple input and multiple output signals, which converts every unique combination of input states to a specific combination of output states. In addition to integer data inputs, some decoders also have one or more "enable" inputs. When the enable input is negated (disabled), all decoder outputs are forced to their inactive states.
Depending on its function, a binary decoder will convert binary information from n input signals to as many as 2n unique output signals. Some decoders have less than 2n output lines; in such cases, at least one output pattern may be repeated for different input values.
A binary decoder is usually implemented as either a stand-alone integrated circuit (IC) or as part of a more complex IC. In the latter case the decoder may be synthesized by means of a hardware description language such as VHDL or Verilog. Widely used decoders are often available in the form of standardized ICs.
Types of decoders
1-of-n decoder
A 1-of-n binary decoder has n output bits. This type of decoder asserts exactly one of its n output bits, or none of them, for every integer input value. The "address" (bit number) of the activated output is specified by the integer input value. For example, output bit number 0 is selected when the integer value 0 is applied to the inputs.
Examples of this type of decoder include:
A 3-to-8 line decoder activates one of eight output bits for each input value from 0 to 7 — the range of integer values that can be expressed in three bits. Similarly, a 4-to-16 line dec |
https://en.wikipedia.org/wiki/Vulture%20%28Marvel%20Comics%29 | The Vulture is the alias of several supervillains appearing in American comic books published by Marvel Comics, most of whom are depicted as recurring enemies of the superhero Spider-Man and belong to the collection of adversaries that make up his rogues gallery, typically using special suits which allow them to fly at vast speeds.
The first incarnation of the character, Isidoro Scarlotti, is an Italian scientist and an enemy of the original Human Torch and Toro. The second and most prominent incarnation of the character, Adrian Toomes, is an inventive but maniacal genius who designed his suit and turned to a life of crime, becoming an enemy of Spider-Man and a founding member of the Sinister Six, with later characters to assume the mantle including Blackie Drago, a former cellmate of Toomes, Clifton Shallot and Jimmy Natale, human/bird hybrids of independent origins, and the Vulturions, a gang who use the mantle to commit heists. Toomes is later revealed to be the grandfather of the superhero Starling.
Since his conception, the character has been adapted from into various other forms of Spider-Man media, including television series and video games. In live-action, the character was played by Michael Keaton in the Marvel Cinematic Universe (MCU) film Spider-Man: Homecoming (2017) and the Sony's Spider-Man Universe (SSU) film Morbius (2022).
Publication history
The first Vulture, Italian scientist Isidoro Scarlotti, first appeared in Young Men #26 (December 1953), created by Joe Gill and Carl Burgos and depicted as an enemy of the original Human Torch and Toro.
The second Vulture, Adrian Toomes, first appeared in The Amazing Spider-Man #2 (May 1963), and was created by Stan Lee and Steve Ditko. According to Ditko, Lee wanted the villain to be heavy-set and based on actor Sydney Greenstreet. Ditko designed him to be leaner and more gaunt, feeling he should be swift and fast and also because "The bulkier anything is, the more panel space it has to take up, thereby |
https://en.wikipedia.org/wiki/Block%20%28data%20storage%29 | In computing (specifically data transmission and data storage), a block, sometimes called a physical record, is a sequence of bytes or bits, usually containing some whole number of records, having a maximum length; a block size. Data thus structured are said to be blocked. The process of putting data into blocks is called blocking, while deblocking is the process of extracting data from blocks. Blocked data is normally stored in a data buffer, and read or written a whole block at a time. Blocking reduces the overhead and speeds up the handling of the data stream. For some devices, such as magnetic tape and CKD disk devices, blocking reduces the amount of external storage required for the data. Blocking is almost universally employed when storing data to 9-track magnetic tape, NAND flash memory, and rotating media such as floppy disks, hard disks, and optical discs.
Most file systems are based on a block device, which is a level of abstraction for the hardware responsible for storing and retrieving specified blocks of data, though the block size in file systems may be a multiple of the physical block size. This leads to space inefficiency due to internal fragmentation, since file lengths are often not integer multiples of block size, and thus the last block of a file may remain partially empty. This will create slack space. Some newer file systems, such as Btrfs and FreeBSD UFS2, attempt to solve this through techniques called block suballocation and tail merging. Other file systems such as ZFS support variable block sizes.
Block storage is normally abstracted by a file system or database management system (DBMS) for use by applications and end users. The physical or logical volumes accessed via block I/O may be devices internal to a server, directly attached via SCSI or Fibre Channel, or distant devices accessed via a storage area network (SAN) using a protocol such as iSCSI, or AoE. DBMSes often use their own block I/O for improved performance and recoverability |
https://en.wikipedia.org/wiki/WinGate | WinGate is an integrated multi-protocol proxy server, email server and internet gateway from Qbik New Zealand Limited in Auckland. It was first released in October 1995, and began as a re-write of SocketSet, a product that had been previously released in prototype form by Adrien de Croy.
WinGate proved popular, and by the mid- to late 1990s, WinGate was used in homes and small businesses that needed to share a single Internet connection between multiple networked computers. The introduction of Internet Connection Sharing in Windows 98, combined with increasing availability of cheap NAT-enabled routers, forced WinGate to evolve to provide more than just internet connection sharing features. Today, focus for WinGate is primarily access control, email server, caching, reporting, bandwidth management and content filtering.
WinGate comes in three versions, Standard, Professional and Enterprise. The Enterprise edition also provides an easily configured virtual private network system, which is also available separately as WinGate VPN. Licensing is based on the number of concurrently connected users, and a range of license sizes are available. Multiple licenses can also be aggregated.
The current version of WinGate is version 9.4.5, released in October 2022.
Notoriety
Versions of WinGate prior to 2.1d (1997) shipped with an insecure default configuration that - if not secured by the network administrator - allowed untrusted third parties to proxy network traffic through the WinGate server. This made open WinGate servers common targets of crackers looking for anonymous redirectors through which to attack other systems. While WinGate was by no means the only exploited proxy server, its wide popularity amongst users with little experience administering networks made it almost synonymous with open SOCKS proxies in the late 1990s. Furthermore, since a restricted (two users) version of the product was freely available without registration, contacting all WinGate users t |
https://en.wikipedia.org/wiki/Knot%20polynomial | In the mathematical field of knot theory, a knot polynomial is a knot invariant in the form of a polynomial whose coefficients encode some of the properties of a given knot.
History
The first knot polynomial, the Alexander polynomial, was introduced by James Waddell Alexander II in 1923. Other knot polynomials were not found until almost 60 years later.
In the 1960s, John Conway came up with a skein relation for a version of the Alexander polynomial, usually referred to as the Alexander–Conway polynomial. The significance of this skein relation was not realized until the early 1980s, when Vaughan Jones discovered the Jones polynomial. This led to the discovery of more knot polynomials, such as the so-called HOMFLY polynomial.
Soon after Jones' discovery, Louis Kauffman noticed the Jones polynomial could be computed by means of a partition function (state-sum model), which involved the bracket polynomial, an invariant of framed knots. This opened up avenues of research linking knot theory and statistical mechanics.
In the late 1980s, two related breakthroughs were made. Edward Witten demonstrated that the Jones polynomial, and similar Jones-type invariants, had an interpretation in Chern–Simons theory. Viktor Vasilyev and Mikhail Goussarov started the theory of finite type invariants of knots. The coefficients of the previously named polynomials are known to be of finite type (after perhaps a suitable "change of variables").
In recent years, the Alexander polynomial has been shown to be related to Floer homology. The graded Euler characteristic of the knot Floer homology of Peter Ozsváth and Zoltan Szabó is the Alexander polynomial.
Examples
Alexander–Briggs notation is a notation that simply organizes knots by their crossing number. The order of Alexander–Briggs notation of prime knot is usually sured. (See List of prime knots.)
Alexander polynomials and Conway polynomials can not recognize the difference of left-trefoil knot and right-trefoil knot.
So we |
https://en.wikipedia.org/wiki/3D%20projection | A 3D projection (or graphical projection) is a design technique used to display a three-dimensional (3D) object on a two-dimensional (2D) surface. These projections rely on visual perspective and aspect analysis to project a complex object for viewing capability on a simpler plane.
3D projections use the primary qualities of an object's basic shape to create a map of points, that are then connected to one another to create a visual element. The result is a graphic that contains conceptual properties to interpret the figure or image as not actually flat (2D), but rather, as a solid object (3D) being viewed on a 2D display.
3D objects are largely displayed on two-dimensional mediums (such as paper and computer monitors). As such, graphical projections are a commonly used design element; notably, in engineering drawing, drafting, and computer graphics. Projections can be calculated through employment of mathematical analysis and formulae, or by using various geometric and optical techniques.
Overview
Projection is achieved by the use of imaginary "projectors"; the projected, mental image becomes the technician's vision of the desired, finished picture. Methods provide a uniform imaging procedure among people trained in technical graphics (mechanical drawing, computer aided design, etc.). By following a method, the technician may produce the envisioned picture on a planar surface such as drawing paper.
There are two graphical projection categories, each with its own method:
parallel projection
perspective projection
Parallel projection
In parallel projection, the lines of sight from the object to the projection plane are parallel to each other. Thus, lines that are parallel in three-dimensional space remain parallel in the two-dimensional projected image. Parallel projection also corresponds to a perspective projection with an infinite focal length (the distance from a camera's lens and focal point), or "zoom".
Images drawn in parallel projection rely upon the t |
https://en.wikipedia.org/wiki/Bulldozer | A bulldozer or dozer (also called a crawler) is a large, motorized machine equipped with a metal blade to the front for pushing material: soil, sand, snow, rubble, or rock during construction work. It travels most commonly on continuous tracks, though specialized models riding on large off-road tires are also produced. Its most popular accessory is a ripper, a large hook-like device mounted singly or in multiples in the rear to loosen dense materials.
Bulldozers are used heavily in large and small scale construction, road building, minings and quarrying, on farms, in heavy industry factories, and in military applications in both peace and wartime.
The word "bulldozer" refers only to a motorized unit fitted with a blade designed for pushing. The word is sometimes used inaccurately for other heavy equipment such as a front-end loader designed for carrying rather than pushing material. The term originally referred only to the blade attachment but is now commonly applied to any crawler tractor with a front mounted blade.
Description
Typically, bulldozers are large and powerful tracked heavy equipment. The tracks give them excellent traction and mobility through very rough terrain. Wide tracks also help distribute the vehicle's weight over a large area (decreasing ground pressure), thus preventing it from sinking in sandy or muddy ground. Extra-wide tracks are known as swamp tracks or low ground pressure (lgp) tracks. Bulldozers have transmission systems designed to take advantage of the track system and provide excellent tractive force.
These traits allow bulldozers to excel in road building, construction, mining, forestry, land clearing, infrastructure development, and any other projects requiring highly mobile, powerful, and stable earth-moving equipment.
A variant is the all-wheel-drive wheeled bulldozer, which generally has four large rubber-tired wheels, hydraulically operated articulated steering, and a hydraulically actuated blade mounted forward of the |
https://en.wikipedia.org/wiki/Formal%20concept%20analysis | In information science, formal concept analysis (FCA) is a principled way of deriving a concept hierarchy or formal ontology from a collection of objects and their properties. Each concept in the hierarchy represents the objects sharing some set of properties; and each sub-concept in the hierarchy represents a subset of the objects (as well as a superset of the properties) in the concepts above it. The term was introduced by Rudolf Wille in 1981, and builds on the mathematical theory of lattices and ordered sets that was developed by Garrett Birkhoff and others in the 1930s.
Formal concept analysis finds practical application in fields including data mining, text mining, machine learning, knowledge management, semantic web, software development, chemistry and biology.
Overview and history
The original motivation of formal concept analysis was the search for real-world meaning of mathematical order theory. One such possibility of very general nature is that data tables can be transformed into algebraic structures called complete lattices, and that these can be utilized for data visualization and interpretation. A data table that represents a heterogeneous relation between objects and attributes, tabulating pairs of the form "object g has attribute m", is considered as a basic data type. It is referred to as a formal context. In this theory, a formal concept is defined to be a pair (A, B), where A is a set of objects (called the extent) and B is a set of attributes (the intent) such that
the extent A consists of all objects that share the attributes in B, and dually
the intent B consists of all attributes shared by the objects in A.
In this way, formal concept analysis formalizes the semantic notions of extension and intension.
The formal concepts of any formal context can—as explained below—be ordered in a hierarchy called more formally the context's "concept lattice". The concept lattice can be graphically visualized as a "line diagram", which then may be he |
https://en.wikipedia.org/wiki/RSTS/E | RSTS () is a multi-user time-sharing operating system developed by Digital Equipment Corporation (DEC, now part of Hewlett-Packard) for the PDP-11 series of 16-bit minicomputers. The first version of RSTS (RSTS-11, Version 1) was implemented in 1970 by DEC software engineers that developed the TSS-8 time-sharing operating system for the PDP-8. The last version of RSTS (RSTS/E, Version 10.1) was released in September 1992. RSTS-11 and RSTS/E are usually referred to just as "RSTS" and this article will generally use the shorter form. RSTS-11 supports the BASIC programming language, an extended version called BASIC-PLUS, developed under contract by Evans Griffiths & Hart of Boston. Starting with RSTS/E version 5B, DEC added support for additional programming languages by emulating the execution environment of the RT-11 and RSX-11 operating systems.
Acronyms and abbreviations
BTSS (Basic Time Sharing System – never marketed) – The first name for RSTS.
CCL (Concise Command Language) – equivalent to a command to run a program kept in the Command Line Interpreter.
CIL (Core Image Library) – A container file format used to hold one or more standalone (bootable) programs and operating systems, such as RSTS through version 6A.
CILUS (Core Image Library Update and Save) – DOS-11 program to manipulate a CIL file.
CLI (Command Line Interpreter) – See Command-line interface.
CUSPs (Commonly Used System Programs) – System management applications like Task Manager or Registry Editor on Microsoft Windows. On RSTS-11, CUSPs were written in BASIC-Plus just like user programs.
DCL (Digital Command Language) – See DIGITAL Command Language.
DTR (DATATRIEVE) – programming language
FIP (File Information Processing) – resident area for issuing file requests
FIRQB (File Information Request Queue Block) – A data structure containing information about file requests.
KBM (Keyboard Monitor) – Analogous to Command Line Interpreter.
LAT (Local Area Transport) – Digital's predecessor to TCP/IP
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https://en.wikipedia.org/wiki/Body%20orifice | A body orifice is any opening in the body of an animal.
External
In a typical mammalian body such as the human body, the external body orifices are:
The nostrils, for breathing and the associated sense of smell
The mouth, for eating, drinking, breathing, and vocalizations such as speech
The ear canals, for the sense of hearing
The nasolacrimal ducts, to carry tears from the lacrimal sac into the nasal cavity
The anus, for defecation
In males, the urinary meatus, for urination and ejaculation
In females, the urinary meatus, for urination and female ejaculation
In females, the vagina, for menstruation, sexual intercourse and childbirth
The nipple orifices
Other animals may have some other body orifices:
cloaca, in birds, reptiles, amphibians, and some other animals
siphon in mollusk, arthropods, and some other animals
Internal
Internal orifices include the orifices of the outflow tracts of the heart, between the heart valves.
See also
Internal urethral orifice
Mucosa
Mucocutaneous boundary
Meatus
Body cavity
Anatomy |
https://en.wikipedia.org/wiki/Triptych | A triptych ( ) is a work of art (usually a panel painting) that is divided into three sections, or three carved panels that are hinged together and can be folded shut or displayed open. It is therefore a type of polyptych, the term for all multi-panel works. The middle panel is typically the largest and it is flanked by two smaller related works, although there are triptychs of equal-sized panels. The form can also be used for pendant jewelry.
Beyond its association with art, the term is sometimes used more generally to connote anything with three parts, particularly if integrated into a single unit.
Etymology
The word triptych was formed in English by compounding the prefix tri- with the word diptych. Diptych is borrowed from the Latin , which itself is derived from the Late Greek () . is the neuter plural of () .
In art
The triptych form appears in early Christian art, and was a popular standard format for altar paintings from the Middle Ages onwards. Its geographical range was from the eastern Byzantine churches to the Celtic churches in the west. During the Byzantine period, triptychs were often used for private devotional use, along with other relics such as icons. Renaissance painters such as Hans Memling and Hieronymus Bosch used the form. Sculptors also used it. Triptych forms also allow ease of transport.
From the Gothic period onward, both in Europe and elsewhere, altarpieces in churches and cathedrals were often in triptych form. One such cathedral with an altarpiece triptych is Llandaff Cathedral. The Cathedral of Our Lady in Antwerp, Belgium, contains two examples by Rubens, and Notre Dame de Paris is another example of the use of triptych in architecture. The form is echoed by the structure of many ecclesiastical stained glass windows.
The triptych form's transportability was exploited during World War Two when a private citizens' committee in the United States commissioned painters and sculptors to create portable three-panel hinged altarpie |
https://en.wikipedia.org/wiki/Chemometrics | Chemometrics is the science of extracting information from chemical systems by data-driven means. Chemometrics is inherently interdisciplinary, using methods frequently employed in core data-analytic disciplines such as multivariate statistics, applied mathematics, and computer science, in order to address problems in chemistry, biochemistry, medicine, biology and chemical engineering. In this way, it mirrors other interdisciplinary fields, such as psychometrics and econometrics.
Background
Chemometrics is applied to solve both descriptive and predictive problems in experimental natural sciences, especially in chemistry. In descriptive applications, properties of chemical systems are modeled with the intent of learning the underlying relationships and structure of the system (i.e., model understanding and identification). In predictive applications, properties of chemical systems are modeled with the intent of predicting new properties or behavior of interest. In both cases, the datasets can be small but are often large and complex, involving hundreds to thousands of variables, and hundreds to thousands of cases or observations.
Chemometric techniques are particularly heavily used in analytical chemistry and metabolomics, and the development of improved chemometric methods of analysis also continues to advance the state of the art in analytical instrumentation and methodology. It is an application-driven discipline, and thus while the standard chemometric methodologies are very widely used industrially, academic groups are dedicated to the continued development of chemometric theory, method and application development.
Origins
Although one could argue that even the earliest analytical experiments in chemistry involved a form of chemometrics, the field is generally recognized to have emerged in the 1970s as computers became increasingly exploited for scientific investigation. The term 'chemometrics' was coined by Svante Wold in a 1971 grant application, and |
https://en.wikipedia.org/wiki/Polynomial%20long%20division | In algebra, polynomial long division is an algorithm for dividing a polynomial by another polynomial of the same or lower degree, a generalized version of the familiar arithmetic technique called long division. It can be done easily by hand, because it separates an otherwise complex division problem into smaller ones. Sometimes using a shorthand version called synthetic division is faster, with less writing and fewer calculations. Another abbreviated method is polynomial short division (Blomqvist's method).
Polynomial long division is an algorithm that implements the Euclidean division of polynomials, which starting from two polynomials A (the dividend) and B (the divisor) produces, if B is not zero, a quotient Q and a remainder R such that
A = BQ + R,
and either R = 0 or the degree of R is lower than the degree of B. These conditions uniquely define Q and R, which means that Q and R do not depend on the method used to compute them.
The result R = 0 occurs if and only if the polynomial A has B as a factor. Thus long division is a means for testing whether one polynomial has another as a factor, and, if it does, for factoring it out. For example, if a root r of A is known, it can be factored out by dividing A by (x – r).
Example
Polynomial long division
Find the quotient and the remainder of the division of the dividend, by the divisor.
The dividend is first rewritten like this:
The quotient and remainder can then be determined as follows:
Divide the first term of the dividend by the highest term of the divisor (meaning the one with the highest power of x, which in this case is x). Place the result above the bar (x3 ÷ x = x2).
Multiply the divisor by the result just obtained (the first term of the eventual quotient). Write the result under the first two terms of the dividend ().
Subtract the product just obtained from the appropriate terms of the original dividend (being careful that subtracting something having a minus sign is equivalent to adding someth |
https://en.wikipedia.org/wiki/H-infinity%20methods%20in%20control%20theory | H∞ (i.e. "H-infinity") methods are used in control theory to synthesize controllers to achieve stabilization with guaranteed performance. To use H∞ methods, a control designer expresses the control problem as a mathematical optimization problem and then finds the controller that solves this optimization. H∞ techniques have the advantage over classical control techniques in that H∞ techniques are readily applicable to problems involving multivariate systems with cross-coupling between channels; disadvantages of H∞ techniques include the level of mathematical understanding needed to apply them successfully and the need for a reasonably good model of the system to be controlled. It is important to keep in mind that the resulting controller is only optimal with respect to the prescribed cost function and does not necessarily represent the best controller in terms of the usual performance measures used to evaluate controllers such as settling time, energy expended, etc. Also, non-linear constraints such as saturation are generally not well-handled. These methods were introduced into control theory in the late 1970s-early 1980s
by George Zames (sensitivity minimization), J. William Helton (broadband matching),
and Allen Tannenbaum (gain margin optimization).
The phrase H∞ control comes from the name of the mathematical space over which the optimization takes place: H∞ is the Hardy space of matrix-valued functions that are analytic and bounded in the open right-half of the complex plane defined by Re(s) > 0; the H∞ norm is the supremum singular value of the matrix over that space. In the case of a scalar-valued function, the elements of the Hardy space that extend continuously to the boundary and are continuous at infinity is the disk algebra. For a matrix-valued function, the norm can be interpreted as a maximum gain in any direction and at any frequency; for SISO systems, this is effectively the maximum magnitude of the frequency response.
H∞ techniques can be |
https://en.wikipedia.org/wiki/Barrel%20shifter | A barrel shifter is a digital circuit that can shift a data word by a specified number of bits without the use of any sequential logic, only pure combinational logic, i.e. it inherently provides a binary operation. It can however in theory also be used to implement unary operations, such as logical shift left, in cases where limited by a fixed amount (e.g. for address generation unit). One way to implement a barrel shifter is as a sequence of multiplexers where the output of one multiplexer is connected to the input of the next multiplexer in a way that depends on the shift distance. A barrel shifter is often used to shift and rotate n-bits in modern microprocessors, typically within a single clock cycle.
For example, take a four-bit barrel shifter, with inputs A, B, C and D. The shifter can cycle the order of the bits ABCD as DABC, CDAB, or BCDA; in this case, no bits are lost. That is, it can shift all of the outputs up to three positions to the right (and thus make any cyclic combination of A, B, C and D). The barrel shifter has a variety of applications, including being a useful component in microprocessors (alongside the ALU).
Implementation
The very fastest shifters are implemented as full crossbars, in a manner similar to the 4-bit shifter depicted above, only larger. These incur the least delay, with the output always a single gate delay behind the input to be shifted (after allowing the small time needed for the shift count decoder to settle; this penalty, however, is only incurred when the shift count changes). These crossbar shifters require however n2 gates for n-bit shifts. Because of this, the barrel shifter is often implemented as a cascade of parallel 2×1 multiplexers instead, which allows a large reduction in gate count, now growing only with n x log n; the propagation delay is however larger, growing with log n (instead of being constant as with the crossbar shifter).
For an 8-bit barrel shifter, two intermediate signals are used which shifts |
https://en.wikipedia.org/wiki/M%C3%B6bius%20transformation | In geometry and complex analysis, a Möbius transformation of the complex plane is a rational function of the form
of one complex variable z; here the coefficients a, b, c, d are complex numbers satisfying .
Geometrically, a Möbius transformation can be obtained by first applying the inverse stereographic projection from the plane to the unit sphere, moving and rotating the sphere to a new location and orientation in space, and then applying a stereographic projection to map from the sphere back to the plane. These transformations preserve angles, map every straight line to a line or circle, and map every circle to a line or circle.
The Möbius transformations are the projective transformations of the complex projective line. They form a group called the Möbius group, which is the projective linear group . Together with its subgroups, it has numerous applications in mathematics and physics.
Möbius geometries and their transformations generalize this case to any number of dimensions over other fields.
Möbius transformations are named in honor of August Ferdinand Möbius; they are an example of homographies, linear fractional transformations, bilinear transformations, and spin transformations (in relativity theory).
Overview
Möbius transformations are defined on the extended complex plane (i.e., the complex plane augmented by the point at infinity).
Stereographic projection identifies with a sphere, which is then called the Riemann sphere; alternatively, can be thought of as the complex projective line . The Möbius transformations are exactly the bijective conformal maps from the Riemann sphere to itself, i.e., the automorphisms of the Riemann sphere as a complex manifold; alternatively, they are the automorphisms of as an algebraic variety. Therefore, the set of all Möbius transformations forms a group under composition. This group is called the Möbius group, and is sometimes denoted .
The Möbius group is isomorphic to the group of orientation-preserving |
https://en.wikipedia.org/wiki/Johannes%20Trithemius | Johannes Trithemius (; 1 February 1462 – 13 December 1516), born Johann Heidenberg, was a German Benedictine abbot and a polymath who was active in the German Renaissance as a lexicographer, chronicler, cryptographer, and occultist. He is considered the founder of modern cryptography (a claim shared with Leon Battista Alberti) and steganography, as well as the founder of bibliography and literary studies as branches of knowledge. He had considerable influence on the development of early modern and modern occultism. His students included Heinrich Cornelius Agrippa and Paracelsus.
Early life
The byname Trithemius refers to his native town of Trittenheim on the Moselle River, at the time part of the Electorate of Trier.
When Johannes was still an infant his father, Johann von Heidenburg, died. His stepfather, whom his mother Elisabeth married seven years later, was hostile to education and thus Johannes could only learn in secret and with many difficulties. He learned Greek, Latin, and Hebrew. When he was 17 years old he escaped from his home and wandered around looking for good teachers, travelling to Trier, Cologne, the Netherlands, and Heidelberg. He studied at the University of Heidelberg.
Career
Travelling from the university to his home town in 1482, he was surprised by a snowstorm and took refuge in the Benedictine abbey of Sponheim near Bad Kreuznach. He decided to stay and was elected abbot in 1483, at the age of twenty-one. He often served as featured speaker and chapter secretary at the Bursfelde Congregation's annual chapter from 1492 to 1503, the annual meeting of reform-minded abbots. Trithemius also supervised the visits of the Congregation's abbeys.
Trithemius wrote extensively as a historian, starting with a chronicle of Sponheim and culminating in a two-volume work on the history of Hirsau Abbey. His work was distinguished by mastery of the Latin language and eloquent phrasing, yet it was soon discovered that he inserted several fictional passages |
https://en.wikipedia.org/wiki/Game%20Developer%20%28magazine%29 | Game Developer was a magazine for video game creators, originally started in March 1994 by Miller Freeman, Inc as quarterly, later bimonthly, and finally monthly. In each issue, industry leaders and experts shared technical solutions, reviewed new game development tools, and discussed strategies for creating innovative, successful video games. Monthly postmortems dissected the industry's leading games, from AAA console to social and mobile games and beyond, and columns gave insight into deeper development practices from across all disciplines, from design, to programming, to art, to business, and audio. It was closed in 2013 as part of a restructuring at parent company UBM Tech (part of UBM plc) that included the closing of all print publications owned by that company.
Contents
The magazine contained articles on professional game development topics relating to game programming, art, audio, quality control, design, and production. Monthly columns from industry veterans offered in depth discussion on a variety of topics. It had articles by notable video game industry figures and reviews on game development related books, tools, and software packages. The back page "Soapbox" was also a popular feature but moved to sister site to Gamasutra circa 2004. It was replaced by a splash art page called "Thousand Words" and then replaced again with a regular column "Arrested Development".
Game Developer'''s most popular feature was probably its monthly "Postmortem" column which discusses the recent development of a video game with the top five each of "What Went Right" and "What Went Wrong". It provided a frank, first-hand account of the lessons learned in the development process. The first Postmortem was featured in October 1997 and written by Andre Vrignaud on Dark Sun Online.
Starting in 1998, Game Developer recognized exceptional game development tools with their "Front Line Awards" which were given annually. Winners included software (such as Photoshop and VTune), game |
https://en.wikipedia.org/wiki/Synthetic%20division | In algebra, synthetic division is a method for manually performing Euclidean division of polynomials, with less writing and fewer calculations than long division.
It is mostly taught for division by linear monic polynomials (known as Ruffini's rule), but the method can be generalized to division by any polynomial.
The advantages of synthetic division are that it allows one to calculate without writing variables, it uses few calculations, and it takes significantly less space on paper than long division. Also, the subtractions in long division are converted to additions by switching the signs at the very beginning, helping to prevent sign errors.
Regular synthetic division
The first example is synthetic division with only a monic linear denominator .
The numerator can be written as .
The zero of the denominator is .
The coefficients of are arranged as follows, with the zero of on the left:
The after the bar is "dropped" to the last row.
The is multiplied by the before the bar, and placed in the .
An is performed in the next column.
The previous two steps are repeated and the following is obtained:
Here, the last term (-123) is the remainder while the rest correspond to the coefficients of the quotient.
The terms are written with increasing degree from right to left beginning with degree zero for the remainder and the result.
Hence the quotient and remainder are:
Evaluating polynomials by the remainder theorem
The above form of synthetic division is useful in the context of the polynomial remainder theorem for evaluating univariate polynomials. To summarize, the value of at is equal to the remainder of the division of by
The advantage of calculating the value this way is that it requires just over half as many multiplication steps as naive evaluation. An alternative evaluation strategy is Horner's method.
Expanded synthetic division
This method generalizes to division by any monic polynomial with only a slight modification with chan |
https://en.wikipedia.org/wiki/Monic%20polynomial | In algebra, a monic polynomial is a non-zero univariate polynomial (that is, a polynomial in a single variable) in which the leading coefficient (the nonzero coefficient of highest degree) is equal to 1. That is to say, a monic polynomial is one that can be written as
with
Uses
Monic polynomials are widely used in algebra and number theory, since they produce many simplifications and they avoid divisions and denominators. Here are some examples.
Every polynomial is associated to a unique monic polynomial. In particular, the unique factorization property of polynomials can be stated as: Every polynomial can be uniquely factorized as the product of its leading coefficient and a product of monic irreducible polynomials.
Vieta's formulas are simpler in the case of monic polynomials: The th elementary symmetric function of the roots of a monic polynomial of degree equals where is the coefficient of the th power of the indeterminate.
Euclidean division of a polynomial by a monic polynomial does not introduce divisions of coefficients. Therefore, it is defined for polynomials with coefficients in a commutative ring.
Algebraic integers are defined as the roots of monic polynomials with integer coefficients.
Properties
Every nonzero univariate polynomial (polynomial with a single indeterminate) can be written
where are the coefficients of the polynomial, and the leading coefficient is not zero. By definition, such a polynomial is monic if
A product of monic polynomials is monic. A product of polynomials is monic if and only if the product of the leading coefficients of the factors equals .
This implies that, the monic polynomials in a univariate polynomial ring over a commutative ring form a monoid under polynomial multiplication.
Two monic polynomials are associated if and only if they are equal, since the multiplication of a polynomial by a nonzero constant produces a polynomial with this constant as its leading coefficient.
Divisibility induces a pa |
https://en.wikipedia.org/wiki/Hume%27s%20principle | Hume's principle or HP says that the number of Fs is equal to the number of Gs if and only if there is a one-to-one correspondence (a bijection) between the Fs and the Gs. HP can be stated formally in systems of second-order logic. Hume's principle is named for the Scottish philosopher David Hume and was coined by George Boolos.
HP plays a central role in Gottlob Frege's philosophy of mathematics. Frege shows that HP and suitable definitions of arithmetical notions entail all axioms of what we now call second-order arithmetic. This result is known as Frege's theorem, which is the foundation for a philosophy of mathematics known as neo-logicism.
Origins
Hume's principle appears in Frege's Foundations of Arithmetic (§63), which quotes from Part III of Book I of David Hume's A Treatise of Human Nature (1740). Hume there sets out seven fundamental relations between ideas. Concerning one of these, proportion in quantity or number, Hume argues that our reasoning about proportion in quantity, as represented by geometry, can never achieve "perfect precision and exactness", since its principles are derived from sense-appearance. He contrasts this with reasoning about number or arithmetic, in which such a precision can be attained:
Algebra and arithmetic [are] the only sciences in which we can carry on a chain of reasoning to any degree of intricacy, and yet preserve a perfect exactness and certainty. We are possessed of a precise standard, by which we can judge of the equality and proportion of numbers; and according as they correspond or not to that standard, we determine their relations, without any possibility of error. When two numbers are so combined, as that the one has always a unit answering to every unit of the other, we pronounce them equal; and it is for want of such a standard of equality in [spatial] extension, that geometry can scarce be esteemed a perfect and infallible science. (I. III. I.)
Note Hume's use of the word number in the ancient sense, to mean |
https://en.wikipedia.org/wiki/Reflective%20programming | In computer science, reflective programming or reflection is the ability of a process to examine, introspect, and modify its own structure and behavior.
Historical background
The earliest computers were programmed in their native assembly languages, which were inherently reflective, as these original architectures could be programmed by defining instructions as data and using self-modifying code. As the bulk of programming moved to higher-level compiled languages such as Algol, Cobol, Fortran, Pascal, and C, this reflective ability largely disappeared until new programming languages with reflection built into their type systems appeared.
Brian Cantwell Smith's 1982 doctoral dissertation introduced the notion of computational reflection in procedural programming languages and the notion of the meta-circular interpreter as a component of 3-Lisp.
Uses
Reflection helps programmers make generic software libraries to display data, process different formats of data, perform serialization or deserialization of data for communication, or do bundling and unbundling of data for containers or bursts of communication.
Effective use of reflection almost always requires a plan: A design framework, encoding description, object library, a map of a database or entity relations.
Reflection makes a language more suited to network-oriented code. For example, it assists languages such as Java to operate well in networks by enabling libraries for serialization, bundling and varying data formats. Languages without reflection such as C are required to use auxiliary compilers for tasks like Abstract Syntax Notation to produce code for serialization and bundling.
Reflection can be used for observing and modifying program execution at runtime. A reflection-oriented program component can monitor the execution of an enclosure of code and can modify itself according to a desired goal of that enclosure. This is typically accomplished by dynamically assigning program code at runtime.
In obje |
https://en.wikipedia.org/wiki/Boolean%20prime%20ideal%20theorem | In mathematics, the Boolean prime ideal theorem states that ideals in a Boolean algebra can be extended to prime ideals. A variation of this statement for filters on sets is known as the ultrafilter lemma. Other theorems are obtained by considering different mathematical structures with appropriate notions of ideals, for example, rings and prime ideals (of ring theory), or distributive lattices and maximal ideals (of order theory). This article focuses on prime ideal theorems from order theory.
Although the various prime ideal theorems may appear simple and intuitive, they cannot be deduced in general from the axioms of Zermelo–Fraenkel set theory without the axiom of choice (abbreviated ZF). Instead, some of the statements turn out to be equivalent to the axiom of choice (AC), while others—the Boolean prime ideal theorem, for instance—represent a property that is strictly weaker than AC. It is due to this intermediate status between ZF and ZF + AC (ZFC) that the Boolean prime ideal theorem is often taken as an axiom of set theory. The abbreviations BPI or PIT (for Boolean algebras) are sometimes used to refer to this additional axiom.
Prime ideal theorems
An order ideal is a (non-empty) directed lower set. If the considered partially ordered set (poset) has binary suprema (a.k.a. joins), as do the posets within this article, then this is equivalently characterized as a non-empty lower set I that is closed for binary suprema (that is, implies ). An ideal I is prime if its set-theoretic complement in the poset is a filter (that is, implies or ). Ideals are proper if they are not equal to the whole poset.
Historically, the first statement relating to later prime ideal theorems was in fact referring to filters—subsets that are ideals with respect to the dual order. The ultrafilter lemma states that every filter on a set is contained within some maximal (proper) filter—an ultrafilter. Recall that filters on sets are proper filters of the Boolean algebra of its po |
https://en.wikipedia.org/wiki/Herbert%20Kroemer | Herbert Kroemer (; born August 25, 1928) is a German-American physicist who, along with Zhores Alferov, received the Nobel Prize in Physics in 2000 for "developing semiconductor heterostructures used in high-speed- and opto-electronics". Kroemer is professor emeritus of electrical and computer engineering at the University of California, Santa Barbara, having received his Ph.D. in theoretical physics in 1952 from the University of Göttingen, Germany, with a dissertation on hot electron effects in the then-new transistor. His research into transistors was a stepping stone to the later development of mobile phone technologies.
Career
Kroemer worked in a number of research laboratories in Germany and the United States and taught electrical engineering at the University of Colorado from 1968 to 1976. He joined the UCSB faculty in 1976, focusing its semiconductor research program on the emerging compound semiconductor technology rather than on mainstream silicon technology. Along with Charles Kittel he co-authored the textbook Thermal Physics, first published in 1980, and still used today. He is also the author of the textbook Quantum Mechanics for Engineering, Materials Science and Applied Physics.
Kroemer was elected as a member into the National Academy of Engineering in 1997 for conception of the semiconductor heterostructure transistor and laser, and for leadership in semiconductor materials technology. He was also elected a member of the National Academy of Sciences in 2003.
Kroemer always preferred to work on problems that are ahead of mainstream technology, inventing the drift transistor in the 1950s and being the first to point out that advantages could be gained in various semiconductor devices by incorporating heterojunctions. Most notably, though, in 1963 he proposed the concept of the double-heterostructure laser, which is now a central concept in the field of semiconductor lasers. Kroemer became an early pioneer in molecular beam epitaxy, concentrating o |
https://en.wikipedia.org/wiki/VM%20%28operating%20system%29 | VM (often: VM/CMS) is a family of IBM virtual machine operating systems used on IBM mainframes System/370, System/390, zSeries, System z and compatible systems, including the Hercules emulator for personal computers.
The following versions are known:
Virtual Machine Facility/370
VM/370, released in 1972, is a System/370 reimplementation of earlier CP/CMS operating system.
VM/370 Basic System Extensions Program Product
VM/BSE (BSEPP) is an enhancement to VM/370 that adds support for more devices (such as 3370-type fixed-block-architecture DASD drives), improvements to the CMS environment (such as an improved editor), and some stability enhancements to CP.
VM/370 System Extensions Program Product
VM/SE (SEPP) is an enhancement to VM/370 that includes the facilities of VM/BSE, as well as a few additional fixes and features.
Virtual Machine/System Product
VM/SP, a milestone version, replaces VM/370, VM/BSE and VM/SE. Release 1 added EXEC2 and XEDIT System Product Editor; Release 3 added REXX; Release 6 added the shared filesystem.
Virtual Machine/System Product High Performance Option
VM/SP HPO adds additional device support and functionality to VM/SP, and allows certain S/370 machines that can utilize more than 16 MB of real storage to do so, up to 64 MB. This version was intended for users that would be running multiple S/370 guests at once.
Virtual Machine/Extended Architecture Migration Aid
VM/XA MA is intended to ease the migration from MVS/370 to MVS/XA by allowing both to run concurrently on the same processor complex.
Virtual Machine/Extended Architecture System Facility
VM/XA SF is an upgraded VM/XA MA with improved functionality and performance.
Virtual Machine/Extended Architecture System Product
VM/XA SP is an upgraded VM/XA MA with improved functionality and performance, offered as a replacement for VM/SP HPO on machines supporting S/370-XA. It includes a version of CMS that can run in either S/370 or S/370-XA mode.
Virtual Machine/Enterprise |
https://en.wikipedia.org/wiki/Simultaneous%20multithreading | Simultaneous multithreading (SMT) is a technique for improving the overall efficiency of superscalar CPUs with hardware multithreading. SMT permits multiple independent threads of execution to better use the resources provided by modern processor architectures.
Details
The term multithreading is ambiguous, because not only can multiple threads be executed simultaneously on one CPU core, but also multiple tasks (with different page tables, different task state segments, different protection rings, different I/O permissions, etc.). Although running on the same core, they are completely separated from each other.
Multithreading is similar in concept to preemptive multitasking but is implemented at the thread level of execution in modern superscalar processors.
Simultaneous multithreading (SMT) is one of the two main implementations of multithreading, the other form being temporal multithreading (also known as super-threading). In temporal multithreading, only one thread of instructions can execute in any given pipeline stage at a time. In simultaneous multithreading, instructions from more than one thread can be executed in any given pipeline stage at a time. This is done without great changes to the basic processor architecture: the main additions needed are the ability to fetch instructions from multiple threads in a cycle, and a larger register file to hold data from multiple threads. The number of concurrent threads is decided by the chip designers. Two concurrent threads per CPU core are common, but some processors support up to eight concurrent threads per core.
Because it inevitably increases conflict on shared resources, measuring or agreeing on its effectiveness can be difficult. However, measured energy efficiency of SMT with parallel native and managed workloads on historical 130 nm to 32 nm Intel SMT (hyper-threading) implementations found that in 45 nm and 32 nm implementations, SMT is extremely energy efficient, even with in-order Atom processors. In |
https://en.wikipedia.org/wiki/Monoclonal%20antibody | A monoclonal antibody (mAb, more rarely called moAb) is an antibody produced from a cell lineage made by cloning a unique white blood cell. All subsequent antibodies derived this way trace back to a unique parent cell.
Monoclonal antibodies can have monovalent affinity, binding only to the same epitope (the part of an antigen that is recognized by the antibody). In contrast, polyclonal antibodies bind to multiple epitopes and are usually made by several different antibody-secreting plasma cell lineages. Bispecific monoclonal antibodies can also be engineered, by increasing the therapeutic targets of one monoclonal antibody to two epitopes.
It is possible to produce monoclonal antibodies that specifically bind to almost any suitable substance; they can then serve to detect or purify it. This capability has become an investigative tool in biochemistry, molecular biology, and medicine. Monoclonal antibodies are being used on a clinical level for both the diagnosis and therapy of several diseases. In 2020, the administration of monoclonal antibodies was authorized by several countries for treating moderate symptoms of COVID-19.
History
In the early 1900s, immunologist Paul Ehrlich proposed the idea of a Zauberkugel – "magic bullet", conceived of as a compound which selectively targeted a disease-causing organism, and could deliver a toxin for that organism. This underpinned the concept of monoclonal antibodies and monoclonal drug conjugates. Ehrlich and Élie Metchnikoff received the 1908 Nobel Prize for Physiology or Medicine for providing the theoretical basis for immunology.
By the 1970s, lymphocytes producing a single antibody were known, in the form of multiple myeloma – a cancer affecting B-cells. These abnormal antibodies or paraproteins were used to study the structure of antibodies, but it was not yet possible to produce identical antibodies specific to a given antigen. In 1973, Jerrold Schwaber described the production of monoclonal antibodies using human– |
https://en.wikipedia.org/wiki/Cytotoxicity | Cytotoxicity is the quality of being toxic to cells. Examples of toxic agents are an immune cell or some types of venom, e.g. from the puff adder (Bitis arietans) or brown recluse spider (Loxosceles reclusa).
Cell physiology
Treating cells with the cytotoxic compound can result in a variety of cell fates. The cells may undergo necrosis, in which they lose membrane integrity and die rapidly as a result of cell lysis. The cells can stop actively growing and dividing (a decrease in cell viability), or the cells can activate a genetic program of controlled cell death (apoptosis).
Cells undergoing necrosis typically exhibit rapid swelling, lose membrane integrity, shut down metabolism, and release their contents into the environment. Cells that undergo rapid necrosis in vitro do not have sufficient time or energy to activate apoptotic machinery and will not express apoptotic markers. Apoptosis is characterized by well defined cytological and molecular events including a change in the refractive index of the cell, cytoplasmic shrinkage, nuclear condensation and cleavage of DNA into regularly sized fragments. Cells in culture that are undergoing apoptosis eventually undergo secondary necrosis. They will shut down metabolism, lose membrane integrity and lyse.
Measurement
Cytotoxicity assays are widely used by the pharmaceutical industry to screen for cytotoxicity in compound libraries. Researchers can either look for cytotoxic compounds, if they are interested in developing a therapeutic that targets rapidly dividing cancer cells, for instance; or they can screen "hits" from initial high-throughput drug screens for unwanted cytotoxic effects before investing in their development as a pharmaceutical.
Assessing cell membrane integrity is one of the most common ways to measure cell viability and cytotoxic effects. Compounds that have cytotoxic effects often compromise cell membrane integrity. Vital dyes, such as trypan blue or propidium iodide are normally excluded from t |
https://en.wikipedia.org/wiki/NorthPoint%20Communications | NorthPoint Communications Group, Inc. was a competitive local exchange carrier focused on data transmission via digital subscriber lines. The company had relationships with Microsoft, Tandy Corporation, Intel, Verio, Cable & Wireless, Frontier Corporation, Concentric Network, ICG Communications, Enron, Network Plus, and Netopia. The company had investments from The Carlyle Group, Accel Partners, Benchmark, and Greylock Partners.
History
The company was founded in 1997 by Michael W. Malaga and 5 other former executives of Metropolitan Fiber Systems.
On May 5, 1999, during the dot-com bubble, the company became a public company via an initial public offering in which it sold 15 million shares at $24 per share. Malaga, then 34 years old, was worth $300 million on paper.
In September 2000, Verizon agreed to acquire a 55% interest in the company and merge the companies' DSL businesses.
In November 2000, as its customers failed to pay their bills, NorthPoint restated downwards its financial performance for the third quarter of 2000, lowering revenue from $30 million to $24 million. After the earnings restatement, Verizon terminated its acquisition agreement, claiming that a material adverse change had occurred. Northpoint sued Verizon to force it to complete the transaction. The lawsuit was settled out of court in July 2002, with Verizon agreeing to pay $175 million to Northpoint. NorthPoint stated that "it would cut its workforce by 19%, or 248 jobs, to lower expenses after the collapse of its merger with Verizon."
Bankruptcy
In January 2001, NorthPoint filed bankruptcy. Some internet service providers, which faced a disruption in service, blamed the banks for failing to work out a deal to save the company. In March 2001, AT&T Corporation acquired the assets of NorthPoint for $135 million in a liquidation.
References
1997 establishments in California
1999 initial public offerings
Defunct companies based in the San Francisco Bay Area
Defunct telecommunications comp |
https://en.wikipedia.org/wiki/Bionomics | Bionomics (Greek: bio = life; nomos = law) has two different meanings:
the first is the comprehensive study of an organism and its relation to its environment. As translated from the French word Bionomie, its first use in English was in the period of 1885–1890. Another way of expressing this word is the term currently referred to as "ecology".
the other is an economic discipline which studies economy as a self-organized evolving ecosystem.
An example of studies of the first type is in Richard B. Selander's Bionomics, Systematics and Phylogeny of Lytta, a Genus of Blister Beetles (Coleoptera, Meloidae), Illinois Biological Monographs: number 28, 1960.
When related to the territory Ignegnoli talks about Landscape Bionomics, defining Landscape as the "level of biological organization integrating complex systems of plants, animals and humans in a living Entity recognizable in a territory as characterized by suitable emerging properties in a determined spatial configuration". (Ingegnoli, 2011, 2015; Ingegnoli, Bocchi, Giglio, 2017)
Bionomics as an economic discipline is used by Igor Flor of "Bionomica, the International Bionomics Institute"
References
Benthos - Bionomics
Ingegnoli V, Bocchi S, Giglio E (2017) Landscape Bionomics: a Systemic Approach to Understand and Govern Territorial Development. WSEAS Transactions on Environment and Development, Vol.13, pp. 189–195
Ingegnoli V (2015) Landscape Bionomics. Biological-Integrated Landscape Ecology. Springer, Heidelberg, Milan, New York. Pp. XXIV + 431
Ingegnoli, V. (2011). Bionomia del paesaggio. L’ecologia del paesaggio biologico-integrata per la formazione di un “medico” dei sistemi ecologici. Springer-Verlag, Milano, pp. XX+340.
External links
Website of "Bionomica"
Ecology
zh:生态学 |
https://en.wikipedia.org/wiki/Mount%20Rainier%20%28packet%20writing%29 | Mount Rainier (MRW) is a format for writable optical discs which provides the packet writing and defect management. Its goal is the replacement of the floppy disk. It is named after Mount Rainier, a volcano near Seattle, Washington, United States.
Mount Rainier can be used only with drives that explicitly support it (a part of SCSI/MMC and can work over ATAPI), but works with standard CD-R, CD-RW, DVD+/-R and DVD+/-RW media.
The physical format of MRW on the disk is managed by the drive's firmware, which remaps physical drive blocks into a virtual, defect-free space. Thus, the host computer does not see the physical format of the disk, only a sequence of data blocks capable of holding any filesystem.
Design
The time needed for the disk formatting is shortened to about one minute by the background formatting capabilities of the drive. Formatting allocates some sectors at the end of the disk for defect management. Defective sectors are recorded at a table in the lead-in (an administrative area) and in a copy of the table in the lead-out.
From the host computer's perspective, an MRW disc provides a defect-free block-accessible device, upon which any host supported filesystem may be written. Such filesystems may be FAT32, NTFS, etc., but the preferred format is usually UDF 1.02, as this file format is widely supported. An MRW-formatted CD-RW with a UDF filesystem gives approximately 500 MB free space.
Mt. Rainier allows write access to a disc within seconds after insertion and spin-up, even while a background formatting sequence is taking place. Before this technology, a user would have to wait for the formatting to complete before writing any data to a new disc. It is even possible to read (but not write) MRW disks without an MRW-compatible drive; A "remapper" device driver is needed, an example of which is EasyWrite Reader for Windows.
An alternative to MRW is to physically format a disc in UDF 1.5 or higher using the spared build. This is achieved by the use |
https://en.wikipedia.org/wiki/Endoderm | Endoderm is the innermost of the three primary germ layers in the very early embryo. The other two layers are the ectoderm (outside layer) and mesoderm (middle layer). Cells migrating inward along the archenteron form the inner layer of the gastrula, which develops into the endoderm.
The endoderm consists at first of flattened cells, which subsequently become columnar. It forms the epithelial lining of multiple systems.
In plant biology, endoderm corresponds to the innermost part of the cortex (bark) in young shoots and young roots often consisting of a single cell layer. As the plant becomes older, more endoderm will lignify.
Production
The following chart shows the tissues produced by the endoderm.
The embryonic endoderm develops into the interior linings of two tubes in the body, the digestive and respiratory tube.
Liver and pancreas cells are believed to derive from a common precursor.
In humans, the endoderm can differentiate into distinguishable organs after 5 weeks of embryonic development.
Additional images
See also
Ectoderm
Germ layer
Histogenesis
Mesoderm
Organogenesis
Endodermal sinus tumor
Gastrulation
Cell differentiation
Triploblasty
List of human cell types derived from the germ layers
References
Germ layers
Developmental biology
Embryology
Gastrulation |
https://en.wikipedia.org/wiki/Golden%20angle | In geometry, the golden angle is the smaller of the two angles created by sectioning the circumference of a circle according to the golden ratio; that is, into two arcs such that the ratio of the length of the smaller arc to the length of the larger arc is the same as the ratio of the length of the larger arc to the full circumference of the circle.
Algebraically, let a+b be the circumference of a circle, divided into a longer arc of length a and a smaller arc of length b such that
The golden angle is then the angle subtended by the smaller arc of length b. It measures approximately 137.5077640500378546463487 ...° or in radians 2.39996322972865332 ... .
The name comes from the golden angle's connection to the golden ratio φ; the exact value of the golden angle is
or
where the equivalences follow from well-known algebraic properties of the golden ratio.
As its sine and cosine are transcendental numbers, the golden angle cannot be constructed using a straightedge and compass.
Derivation
The golden ratio is equal to φ = a/b given the conditions above.
Let ƒ be the fraction of the circumference subtended by the golden angle, or equivalently, the golden angle divided by the angular measurement of the circle.
But since
it follows that
This is equivalent to saying that φ 2 golden angles can fit in a circle.
The fraction of a circle occupied by the golden angle is therefore
The golden angle g can therefore be numerically approximated in degrees as:
or in radians as :
Golden angle in nature
The golden angle plays a significant role in the theory of phyllotaxis; for example, the golden angle is the angle separating the florets on a sunflower. Analysis of the pattern shows that it is highly sensitive to the angle separating the individual primordia, with the Fibonacci angle giving the parastichy with optimal packing density.
Mathematical modelling of a plausible physical mechanism for floret development has shown the pattern arising spontaneousl |
https://en.wikipedia.org/wiki/CP-67 | CP-67 is a hypervisor, or Virtual Machine Monitor, from IBM for its System/360 Model 67 computer.
CP-67 is the control program portion of CP/CMS, a virtual machine operating system developed by IBM's Cambridge Scientific Center in Cambridge, Massachusetts. It was a reimplementation of their earlier research system CP-40, which ran on a one-off customized S/360-40. CP-67 was later reimplemented (again) as CP-370, which IBM released as VM/370 in 1972, when virtual memory was added to the System/370 series.
CP and CMS are usually grouped together as a unit, but the "components are independent of each other. CP-67 can be used on an appropriate configuration without CMS, and CMS
can be run on a properly configured System/360 as a single-user system without CP-67."
Minimum hardware configuration
The minimum configuation for CP-67 is:
2067 CPU, model 1 or 2
2365 Processor Storage model 1—262,144 bytes of magnetic core memory with an access time of 750 ns (nanoseconds) per eight bytes.
IBM 1052 printer/keyboard
IBM 1403 printer
IBM 2540 card read/punch
Three IBM 2311 disk storage units, 7.5 MB each, 22.5 MB total
IBM 2400 magnetic tape data storage unit
IBM 270x Transmission Control unit
Installation
Disks to be used by CP have to be formatted by a standalone utility called FORMAT, loaded from tape or punched cards. CP disks are formatted with fixed-length 829 byte records.
Following formatting, a second stand-alone utility, DIRECT, partitions the disk space between permanent (system and user files) and temporary (paging and spooling) space. DIRECT also creates the user directory identifying the virtual machines (users) available in the system. For each user the directory contains identifying information, id and password, and lists the resources (core, devices, etc) that this user can access, Although a user may be allowed access to physical devices it is more common to specify virtual devices, such as a spooled card reader, card punch, and printer. A user can |
https://en.wikipedia.org/wiki/CP/CMS | CP/CMS (Control Program/Cambridge Monitor System) is a discontinued time-sharing operating system of the late 1960s and early 1970s, known for its excellent performance and advanced features. Among its three versions, CP-40/CMS was an important "one-off" research system that established the CP/CMS virtual machine architecture. It was followed by CP-67/CMS, a reimplementation of CP-40/CMS for the IBM System/360-67, and the primary focus of this article. Finally, CP-370/CMS was a reimplementation of CP-67/CMS for the System/370. While it was never released as such, it became the foundation of IBM's VM/370 operating system, announced in 1972.
Each implementation was a substantial redesign of its predecessor and an evolutionary step forward. CP-67/CMS was the first widely available virtual machine architecture. IBM pioneered this idea with its research systems M44/44X (which used partial virtualization) and CP-40 (which used full virtualization).
In addition to its role as the predecessor of the VM family, CP/CMS played an important role in the development of operating system (OS) theory, the design of IBM's System/370, the time-sharing industry, and the creation of a self-supporting user community that anticipated today's free software movement.
History
Fundamental CP/CMS architectural and strategic parameters were established in CP-40, which began production use at IBM's Cambridge Scientific Center in early 1967. This effort occurred in a complex political and technical milieu, discussed at some length and supported by first-hand quotes in the Wikipedia article History of CP/CMS.
In a nutshell:
In the early 1960s, IBM sought to maintain dominance over scientific computing, where time-sharing efforts such as CTSS and MIT's Project MAC gained focus. But IBM had committed to a huge project, the System/360, which took the company in a different direction.
The time-sharing community was disappointed with the S/360's lack of time-sharing capabilities. This led to k |
https://en.wikipedia.org/wiki/Continuous%20Tone-Coded%20Squelch%20System | In telecommunications, Continuous Tone-Coded Squelch System or CTCSS is one type of in-band signaling that is used to reduce the annoyance of listening to other users on a shared two-way radio communication channel. It is sometimes referred to as tone squelch or PL for Private Line, a trademark of Motorola. It does this by adding a low frequency audio tone to the voice. Where more than one group of users is on the same radio frequency (called co-channel users), CTCSS circuitry mutes those users who are using a different CTCSS tone or no CTCSS. It is sometimes referred to as a sub-channel, but this is a misnomer because no additional channels are created. All users with different CTCSS tones on the same channel are still transmitting on the identical radio frequency, and their transmissions interfere with each other; however; the interference is masked under most conditions. The CTCSS feature also does not offer any security.
A receiver with just a carrier or noise squelch does not suppress any sufficiently strong signal; in CTCSS mode it unmutes only when the signal also carries the correct sub-audible audio tone. The tones are not actually below the range of human hearing, but are poorly reproduced by most communications-grade speakers and in any event are usually filtered out before being sent to the speaker or headphone.
Theory of operation
Radio transmitters using CTCSS always transmit their own tone code whenever the transmit button is pressed. The tone is transmitted at a low level simultaneously with the voice. This is called CTCSS encoding. CTCSS tones range from 67 to 257 Hz. The tones are usually referred to as sub-audible tones. In an FM two-way radio system, CTCSS encoder levels are usually set for 15% of system deviation. For example, in a 5 kHz deviation system, the CTCSS tone level would normally be set to 750 Hz deviation. Engineered systems may call for different level settings in the 500 Hz to 1 kHz (10–20%) range.
The ability of a receiver to |
https://en.wikipedia.org/wiki/Airspeed%20indicator | The airspeed indicator (ASI) or airspeed gauge is a flight instrument indicating the airspeed of an aircraft in kilometres per hour (km/h), knots (kn), miles per hour (MPH) and/or metres per second (m/s). The recommendation by ICAO is to use km/h, however knots is currently the most used unit. The ASI measures the pressure differential between static pressure from the static port, and total pressure from the pitot tube. This difference in pressure is registered with the ASI pointer on the face of the instrument.
Colour-coded speeds and ranges
The ASI has standard colour-coded markings to indicate safe operation within the limitations of the aircraft. At a glance, the pilot can determine a recommended speed (V speeds) or if speed adjustments are needed. Single and multi-engine aircraft have common markings. For instance, the green arc indicates the normal operating range of the aircraft, from VS1 to VNO. The white arc indicates the flap operating range, VSO to VFE, used for approaches and landings. The yellow arc cautions that flight should be conducted in this range only in smooth air, while the red line (VNE) at the top of the yellow arc indicates damage or structural failure may result at higher speeds.
The ASI in multi-engine aircraft includes two additional radial markings, one red and one blue, associated with potential engine failure. The radial red line near the bottom of green arc indicates Vmc, the minimum indicated airspeed at which the aircraft can be controlled with the critical engine inoperative. The radial blue line indicates VYSE, the speed for best rate of climb with the critical engine inoperative.
Operation
The ASI is the only flight instrument that uses both the static system and the pitot system. Static pressure enters the ASI case, while total pressure flexes the diaphragm, which is connected to the ASI pointer via mechanical linkage. The pressures are equal when the aircraft is stationary on the ground, and hence shows a reading |
https://en.wikipedia.org/wiki/NetKernel | NetKernel is a British software company and software platform by the same name that is used for High Performance Computing, Enterprise Application Integration, and Energy Efficient Computation.
It allows developers to cleanly separate code from architecture. It can be used as an application server, embedded in a Java container or employed as a cloud computing platform.
As a platform, it is an implementation of the resource-oriented computing (ROC) abstraction. ROC is a logical computing model that resides on top of but is completely isolated from the physical realm of code and objects. In ROC, information and services are identified by logical addresses which are resolved to physical endpoints for the duration of a request and then released. Logical indirect addressing results in flexible systems that can be changed while the system is in operation. In NetKernel, the boundary between the logical and physical layers is intermediated by an operation-system caliber microkernel that can perform various transparent optimization.
The idea of using resources to model abstract information stems from the REST architectural style and the World Wide Web. The idea of using a uniform addressing model stems from the Unix operating system. NetKernel can be considered a unification of the Web and Unix implemented as a
software operating system running on a monolithic microkernel within a single computer.
NetKernel was developed by 1060 Research and is offered under a dual open-source software and commercial software license.
History
NetKernel was started at Hewlett-Packard Labs in 1999. It was conceived by Dr. Russ Perry, Dr. Royston Sellman and Dr. Peter Rodgers as a general purpose XML operating environment that could address the needs of the exploding interest in XML dialects for intra-industry XML messaging.
Rodgers saw the web as an implementation of a general abstraction which he extrapolated as ROC, but whereas the web is limited to publishing information; he set about |
https://en.wikipedia.org/wiki/Partisan%20game | In combinatorial game theory, a game is partisan (sometimes partizan) if it is not impartial. That is, some moves are available to one player and not to the other.
Most games are partisan. For example, in chess, only one player can move the white pieces. More strongly, when analyzed using combinatorial game theory, many chess positions have values that cannot be expressed as the value of an impartial game, for instance when one side has a number of extra tempos that can be used to put the other side into zugzwang.
Partisan games are more difficult to analyze than impartial games, as the Sprague–Grundy theorem does not apply. However, the application of combinatorial game theory to partisan games allows the significance of numbers as games to be seen, in a way that is not possible with impartial games.
References
Combinatorial game theory |
https://en.wikipedia.org/wiki/Icosian%20calculus | The icosian calculus is a non-commutative algebraic structure discovered by the Irish mathematician William Rowan Hamilton in 1856.
In modern terms, he gave a group presentation of the icosahedral rotation group by generators and relations.
Hamilton's discovery derived from his attempts to find an algebra of "triplets" or 3-tuples that he believed would reflect the three Cartesian axes. The symbols of the icosian calculus can be equated to moves between vertices on a dodecahedron. Hamilton's work in this area resulted indirectly in the terms Hamiltonian circuit and Hamiltonian path in graph theory. He also invented the icosian game as a means of illustrating and popularising his discovery.
Informal definition
The algebra is based on three symbols that are each roots of unity, in that repeated application of any of them yields the value 1 after a particular number of steps. They are:
Hamilton also gives one other relation between the symbols:
(In modern terms this is the (2,3,5) triangle group.)
The operation is associative but not commutative. They generate a group of order 60, isomorphic to the group of rotations of a regular icosahedron or dodecahedron, and therefore to the alternating group of degree five.
Although the algebra exists as a purely abstract construction, it can be most easily visualised in terms of operations on the edges and vertices of a dodecahedron. Hamilton himself used a flattened dodecahedron as the basis for his instructional game.
Imagine an insect crawling along a particular edge of Hamilton's labelled dodecahedron in a certain direction, say from to . We can represent this directed edge by .
The icosian symbol equates to changing direction on any edge, so the insect crawls from to (following the directed edge ).
The icosian symbol equates to rotating the insect's current travel anti-clockwise around the end point. In our example this would mean changing the initial direction to become .
The icosian symbol equates to makin |
https://en.wikipedia.org/wiki/Angband%20%28video%20game%29 | Angband is a dungeon-crawling roguelike video game derived from Umoria. It is based on the writings of J. R. R. Tolkien, in which Angband is the fortress of Morgoth. The current version of Angband is available for all major operating systems, including Unix, Windows, Mac OS X, and Android. It is identified as one of the "major roguelikes" by John Harris. Angband is free and open source game under the GNU GPLv2 or the angband license
Gameplay
The goal of Angband is to survive 100 floor levels of the fortress Angband in order to defeat Morgoth. The game is reputed to be extremely difficult.
The player begins in a town where they can buy equipment before beginning the descent. Once in the maze-like fortress, the player encounters traps, monsters, equipment, and hidden doors. With the help of found objects and enchantments, the player's attack and defense power increases, and can even neutralise specific attacks. The player also meets characters and finds artifacts from Tolkien's legendarium.
Angband gameplay emphasises combat and careful resource management. The player has a certain amount of health points. Although Angband records the player's progress to a save file, it does not allow one to resume a saved game in which the player character has already been beaten. The levels are procedurally generated, allowing for a unique game in every play.
Development
The first version of Angband was created by Alex Cutler and Andy Astrand at the University of Warwick in 1990. They wanted to expand the game Umoria by adding items, monsters, and features. After Cutler and Astrand, the source code was maintained at the University of Warwick by Geoff Hill and Sean Marsh. They finally released the game to the public with the version named "2.4.frog_knows" on 11 April 1993. The game, which was previously confided to the University of Warwick, was then enhanced by others and widely ported to non-Unix platforms.
Following their departure, the later principals of Angband have inclu |
https://en.wikipedia.org/wiki/Circular%20error%20probable | In the military science of ballistics, circular error probable (CEP) (also circular error probability or circle of equal probability) is a measure of a weapon system's precision. It is defined as the radius of a circle, centered on the mean, whose perimeter is expected to enclose the landing points of 50% of the rounds; said otherwise, it is the median error radius. That is, if a given munitions design has a CEP of 100 m, when 100 munitions are targeted at the same point, 50 will fall within a circle with a radius of 100 m around their average impact point. (The distance between the target point and the average impact point is referred to as bias.)
There are associated concepts, such as the DRMS (distance root mean square), which is the square root of the average squared distance error, and R95, which is the radius of the circle where 95% of the values would fall in.
The concept of CEP also plays a role when measuring the accuracy of a position obtained by a navigation system, such as GPS or older systems such as LORAN and Loran-C.
Concept
The original concept of CEP was based on a circular bivariate normal distribution (CBN) with CEP as a parameter of the CBN just as μ and σ are parameters of the normal distribution. Munitions with this distribution behavior tend to cluster around the mean impact point, with most reasonably close, progressively fewer and fewer further away, and very few at long distance. That is, if CEP is n metres, 50% of shots land within n metres of the mean impact, 43.7% between n and 2n, and 6.1% between 2n and 3n metres, and the proportion of shots that land farther than three times the CEP from the mean is only 0.2%.
CEP is not a good measure of accuracy when this distribution behavior is not met. Precision-guided munitions generally have more "close misses" and so are not normally distributed. Munitions may also have larger standard deviation of range errors than the standard deviation of azimuth (deflection) errors, resulting in an el |
https://en.wikipedia.org/wiki/Gated%20community | A gated community (or walled community) is a form of residential community or housing estate containing strictly controlled entrances for pedestrians, bicycles, and automobiles, and often characterized by a closed perimeter of walls and fences. Historically, cities have built defensive city walls and controlled gates to protect their inhabitants, and such fortifications have also separated quarters of some cities. Today, gated communities usually consist of small residential streets and include various shared amenities. For smaller communities, these amenities may include only a park or other common area. For larger communities, it may be possible for residents to stay within the community for most daily activities. Gated communities are a type of common interest development, but are distinct from intentional communities.
Given that gated communities are spatially a type of enclave, Setha M. Low, an anthropologist, has argued that they have a negative effect on the net social capital of the broader community outside the gated community. Some gated communities, usually called "guard-gated communities", are staffed by private security guards and are often home to high-value properties, and/or are set up as retirement villages. Some gated communities are secure enough to resemble fortresses and are intended as such.
Features
Besides the services of gatekeepers, many gated communities provide other amenities. These may depend on a number of factors including geographical location, demographic composition, community structure, and community fees collected. When there are sub-associations that belong to master associations, the master association may provide many of the amenities. In general, the larger the association the more amenities that can be provided.
Amenities also depend on the type of housing. For example, single-family-home communities may not have a common-area swimming pool, since individual home-owners have the ability to construct their own private p |
https://en.wikipedia.org/wiki/Fibration | The notion of a fibration generalizes the notion of a fiber bundle and plays an important role in algebraic topology, a branch of mathematics.
Fibrations are used, for example, in Postnikov systems or obstruction theory.
In this article, all mappings are continuous mappings between topological spaces.
Formal definitions
Homotopy lifting property
A mapping satisfies the homotopy lifting property for a space if:
for every homotopy and
for every mapping (also called lift) lifting (i.e. )
there exists a (not necessarily unique) homotopy lifting (i.e. ) with
The following commutative diagram shows the situation:
Fibration
A fibration (also called Hurewicz fibration) is a mapping satisfying the homotopy lifting property for all spaces The space is called base space and the space is called total space. The fiber over is the subspace
Serre fibration
A Serre fibration (also called weak fibration) is a mapping satisfying the homotopy lifting property for all CW-complexes.
Every Hurewicz fibration is a Serre fibration.
Quasifibration
A mapping is called quasifibration, if for every and holds that the induced mapping is an isomorphism.
Every Serre fibration is a quasifibration.
Examples
The projection onto the first factor is a fibration. That is, trivial bundles are fibrations.
Every covering is a fibration. Specifically, for every homotopy and every lift there exists a uniquely defined lift with
Every fiber bundle satisfies the homotopy lifting property for every CW-complex.
A fiber bundle with a paracompact and Hausdorff base space satisfies the homotopy lifting property for all spaces.
An example for a fibration, which is not a fiber bundle, is given by the mapping induced by the inclusion where a topological space and is the space of all continuous mappings with the compact-open topology.
The Hopf fibration is a non trivial fiber bundle and specifically a Serre fibration.
Basic concepts
Fiber homotopy equivalen |
https://en.wikipedia.org/wiki/Ehrhart%20polynomial | In mathematics, an integral polytope has an associated Ehrhart polynomial that encodes the relationship between the volume of a polytope and the number of integer points the polytope contains. The theory of Ehrhart polynomials can be seen as a higher-dimensional generalization of Pick's theorem in the Euclidean plane.
These polynomials are named after Eugène Ehrhart who studied them in the 1960s.
Definition
Informally, if is a polytope, and is the polytope formed by expanding by a factor of in each dimension, then is the number of integer lattice points in .
More formally, consider a lattice in Euclidean space and a -dimensional polytope in with the property that all vertices of the polytope are points of the lattice. (A common example is and a polytope for which all vertices have integer coordinates.) For any positive integer , let be the -fold dilation of (the polytope formed by multiplying each vertex coordinate, in a basis for the lattice, by a factor of ), and let
be the number of lattice points contained in the polytope . Ehrhart showed in 1962 that is a rational polynomial of degree in , i.e. there exist rational numbers such that:
for all positive integers .
The Ehrhart polynomial of the interior of a closed convex polytope can be computed as:
where is the dimension of . This result is known as Ehrhart–Macdonald reciprocity.
Examples
Let be a -dimensional unit hypercube whose vertices are the integer lattice points all of whose coordinates are 0 or 1. In terms of inequalities,
Then the -fold dilation of is a cube with side length , containing integer points. That is, the Ehrhart polynomial of the hypercube is . Additionally, if we evaluate at negative integers, then
as we would expect from Ehrhart–Macdonald reciprocity.
Many other figurate numbers can be expressed as Ehrhart polynomials. For instance, the square pyramidal numbers are given by the Ehrhart polynomials of a square pyramid with an integer unit square as its ba |
https://en.wikipedia.org/wiki/Ecological%20damage | Ecological damage may refer to:
environmental degradation
something adversely affecting ecological health
something adversely affecting ecosystem health
Ecology |
https://en.wikipedia.org/wiki/Quantization%20%28signal%20processing%29 | Quantization, in mathematics and digital signal processing, is the process of mapping input values from a large set (often a continuous set) to output values in a (countable) smaller set, often with a finite number of elements. Rounding and truncation are typical examples of quantization processes. Quantization is involved to some degree in nearly all digital signal processing, as the process of representing a signal in digital form ordinarily involves rounding. Quantization also forms the core of essentially all lossy compression algorithms.
The difference between an input value and its quantized value (such as round-off error) is referred to as quantization error. A device or algorithmic function that performs quantization is called a quantizer. An analog-to-digital converter is an example of a quantizer.
Example
For example, rounding a real number to the nearest integer value forms a very basic type of quantizer – a uniform one. A typical (mid-tread) uniform quantizer with a quantization step size equal to some value can be expressed as
,
where the notation denotes the floor function.
Alternatively, the same quantizer may be expressed in terms of the ceiling function, as
.
(The notation denotes the ceiling function).
The essential property of a quantizer is having a countable-set of possible output-values members smaller than the set of possible input values. The members of the set of output values may have integer, rational, or real values. For simple rounding to the nearest integer, the step size is equal to 1. With or with equal to any other integer value, this quantizer has real-valued inputs and integer-valued outputs.
When the quantization step size (Δ) is small relative to the variation in the signal being quantized, it is relatively simple to show that the mean squared error produced by such a rounding operation will be approximately . Mean squared error is also called the quantization noise power. Adding one bit to the quantizer ha |
https://en.wikipedia.org/wiki/Significant%20figures | Significant figures, also referred to as significant digits or sig figs, are specific digits within a number written in positional notation that carry both reliability and necessity in conveying a particular quantity. When presenting the outcome of a measurement (such as length, pressure, volume, or mass), if the number of digits exceeds what the measurement instrument can resolve, only the number of digits within the resolution's capability are dependable and therefore considered significant.
For instance, if a length measurement yields 114.8 mm, using a ruler with the smallest interval between marks at 1 mm, the first three digits (1, 1, and 4, representing 114 mm) are certain and constitute significant figures. Even digits that are uncertain yet reliable are also included in the significant figures. In this scenario, the last digit (8, contributing 0.8 mm) is likewise considered significant despite its uncertainty. Therefore, this measurement contains four significant figures.
Another example involves a volume measurement of 2.98 L with an uncertainty of ± 0.05 L. The actual volume falls between 2.93 L and 3.03 L. Even if certain digits are not completely known, they are still significant if they are reliable, as they indicate the actual volume within an acceptable range of uncertainty. In this case, the actual volume might be 2.94 L or possibly 3.02 L, so all three digits are considered significant. Thus, there are three significant figures in this example.
The following types of digits are not considered significant:
Leading zeros. For instance, 013 kg has two significant figures—1 and 3—while the leading zero is insignificant since it does not impact the mass indication; 013 kg is equivalent to 13 kg, rendering the zero unnecessary. Similarly, in the case of 0.056 m, there are two insignificant leading zeros since 0.056 m is the same as 56 mm, thus the leading zeros do not contribute to the length indication.
Trailing zeros when they serve as placeholder |
https://en.wikipedia.org/wiki/Quine%E2%80%93McCluskey%20algorithm | The Quine–McCluskey algorithm (QMC), also known as the method of prime implicants, is a method used for minimization of Boolean functions that was developed by Willard V. Quine in 1952 and extended by Edward J. McCluskey in 1956. As a general principle this approach had already been demonstrated by the logician Hugh McColl in 1878, was proved by Archie Blake in 1937, and was rediscovered by Edward W. Samson and Burton E. Mills in 1954 and by Raymond J. Nelson in 1955. Also in 1955, Paul W. Abrahams and John G. Nordahl as well as Albert A. Mullin and Wayne G. Kellner proposed a decimal variant of the method.
The Quine–McCluskey algorithm is functionally identical to Karnaugh mapping, but the tabular form makes it more efficient for use in computer algorithms, and it also gives a deterministic way to check that the minimal form of a Boolean function has been reached. It is sometimes referred to as the tabulation method.
The method involves two steps:
Finding all prime implicants of the function.
Use those prime implicants in a prime implicant chart to find the essential prime implicants of the function, as well as other prime implicants that are necessary to cover the function.
Complexity
Although more practical than Karnaugh mapping when dealing with more than four variables, the Quine–McCluskey algorithm also has a limited range of use since the problem it solves is NP-complete. The running time of the Quine–McCluskey algorithm grows exponentially with the number of variables. For a function of n variables the number of prime implicants can be as large as , e.g. for 32 variables there may be over 534 × 1012 prime implicants. Functions with a large number of variables have to be minimized with potentially non-optimal heuristic methods, of which the Espresso heuristic logic minimizer was the de facto standard in 1995.
Step two of the algorithm amounts to solving the set cover problem; NP-hard instances of this problem may occur in this algorithm step.
Example
|
https://en.wikipedia.org/wiki/Game%20complexity | Combinatorial game theory measures game complexity in several ways:
State-space complexity (the number of legal game positions from the initial position),
Game tree size (total number of possible games),
Decision complexity (number of leaf nodes in the smallest decision tree for initial position),
Game-tree complexity (number of leaf nodes in the smallest full-width decision tree for initial position),
Computational complexity (asymptotic difficulty of a game as it grows arbitrarily large).
These measures involve understanding game positions, possible outcomes, and computation required for various game scenarios.
Measures of game complexity
State-space complexity
The state-space complexity of a game is the number of legal game positions reachable from the initial position of the game.
When this is too hard to calculate, an upper bound can often be computed by also counting (some) illegal positions, meaning positions that can never arise in the course of a game.
Game tree size
The game tree size is the total number of possible games that can be played: the number of leaf nodes in the game tree rooted at the game's initial position.
The game tree is typically vastly larger than the state space because the same positions can occur in many games by making moves in a different order (for example, in a tic-tac-toe game with two X and one O on the board, this position could have been reached in two different ways depending on where the first X was placed). An upper bound for the size of the game tree can sometimes be computed by simplifying the game in a way that only increases the size of the game tree (for example, by allowing illegal moves) until it becomes tractable.
For games where the number of moves is not limited (for example by the size of the board, or by a rule about repetition of position) the game tree is generally infinite.
Decision trees
The next two measures use the idea of a decision tree, which is a subtree of the game tree, with each po |
https://en.wikipedia.org/wiki/Object%20request%20broker | In distributed computing, an object request broker (ORB) is a concept of a middleware, which allows program calls to be made from one computer to another via a computer network, providing location transparency through remote procedure calls. ORBs promote interoperability of distributed object systems, enabling such systems to be built by piecing together objects from different vendors, while different parts communicate with each other via the ORB. Common Object Request Broker Architecture (by Object Management Group) standardizes the way ORB may be implemented.
Overview
ORBs assumed to handle the transformation of in-process data structures to and from the raw byte sequence, which is transmitted over the network. This is called marshalling or serialization. In addition to marshalling data, ORBs often expose many more features, such as distributed transactions, directory services or real-time scheduling. Some ORBs, such as CORBA-compliant systems, use an interface description language to describe the data that is to be transmitted on remote calls.
In object-oriented languages (.e.g. java), an ORB actually provides a framework which enables remote objects to be used over the network, in the same way as if they were local and part of the same process. On the client side, so-called stub objects are created and invoked, serving as the only part visible and used inside the client application. After the stub's methods are invoked, the client-side ORB performs the marshalling of invocation data, and forwards the request to the server-side ORB. On the server side, ORB locates the targeted object, executes the requested operation, and returns the results. Having the results available, the client's ORB performs the demarshalling and passes the results back into the invoked stub, making them available to the client application. The whole process is transparent, resulting in remote objects appearing as if they were local.
Implementations
CORBA - Common Object Reque |
https://en.wikipedia.org/wiki/Cover%20%28topology%29 | In mathematics, and more particularly in set theory, a cover (or covering) of a set is a family of subsets of whose union is all of . More formally, if is an indexed family of subsets (indexed by the set ), then is a cover of if . Thus the collection is a cover of if each element of belongs to at least one of the subsets .
A subcover of a cover of a set is a subset of the cover that also covers the set. A cover is called an open cover if each of its elements is an open set.
Cover in topology
Covers are commonly used in the context of topology. If the set is a topological space, then a cover of is a collection of subsets of whose union is the whole space . In this case we say that covers , or that the sets cover .
Also, if is a (topological) subspace of , then a cover of is a collection of subsets of whose union contains , i.e., is a cover of if
That is, we may cover with either sets in itself or sets in the parent space .
Let C be a cover of a topological space X. A subcover of C is a subset of C that still covers X.
We say that C is an if each of its members is an open set (i.e. each Uα is contained in T, where T is the topology on X).
A cover of X is said to be locally finite if every point of X has a neighborhood that intersects only finitely many sets in the cover. Formally, C = {Uα} is locally finite if for any there exists some neighborhood N(x) of x such that the set
is finite. A cover of X is said to be point finite if every point of X is contained in only finitely many sets in the cover. A cover is point finite if it is locally finite, though the converse is not necessarily true.
Refinement
A refinement of a cover of a topological space is a new cover of such that every set in is contained in some set in . Formally,
is a refinement of if for all there exists such that
In other words, there is a refinement map satisfying for every This map is used, for instance, in the Čech cohomology of .
Every subco |
https://en.wikipedia.org/wiki/UCPH%20Department%20of%20Mathematical%20Sciences | The UCPH Department of Mathematical Sciences () is a department under the Faculty of Science at the University of Copenhagen (UCPH). The department is based at the university's North Campus in Copenhagen.
Location
The department is located in the E building of the Hans Christian Ørsted Institute, on Universitetsparken 5 in Copenhagen, Denmark.
From the founding of the University of Copenhagen in 1479, mathematics had been part of the Faculty of Philosophy. In 1850 it was moved to the new faculty of Mathematics and Natural Sciences. The Institute for Mathematical Sciences was first created in 1934 next to the Niels Bohr Institute building, when Carlsberg Foundation donated money for a building in celebration of the 450th anniversary of the University of Copenhagen in 1929. In 1963 the institute moved to its current location.
Mathematical research
Many different branches of mathematics are being covered by the fields of interest of different researchers at the institute.
Harald Bohr, the brother of physicist Niels Bohr, is one famous alumnus of the department; his research in harmonic analysis and almost periodic functions in the 1930s laid the foundation for a huge drive in analysis. Most notably, since the 1980s the department has been a globally recognized frontrunner in functional analysis, particularly the study of operator algebras and C*-algebras.
Faculty from the department who have contributed to this research include the following:
Bent Fuglede
Søren Eilers
George Elliott
Gert Kjærgaard Pedersen
Ryszard Nest
Richard V. Kadison
Contributing to these efforts, the department houses a center for non-commutative geometry.
Of other major research frontiers are homological algebra, and more recently - grounds have been laid for a boost in the research of algebraic topology.
External links
Department of Mathematical Sciences
Center for Non-commutative Geometry
Topology
University of Copenhagen
Mathematics departments |
https://en.wikipedia.org/wiki/Fibromyalgia | Fibromyalgia is a medical condition defined by the presence of chronic widespread pain, fatigue, waking unrefreshed, cognitive symptoms, lower abdominal pain or cramps, and depression. Other symptoms include insomnia and a general hypersensitivity.
The cause of fibromyalgia is unknown, but is believed to involve a combination of genetic and environmental factors. Environmental factors may include psychological stress, trauma, and certain infections. The pain appears to result from processes in the central nervous system and the condition is referred to as a "central sensitization syndrome".
The treatment of fibromyalgia is symptomatic and multidisciplinary. The European Alliance of Associations for Rheumatology strongly recommends aerobic and strengthening exercise. Weak recommendations are given to mindfulness, psychotherapy, acupuncture, hydrotherapy, and meditative exercise such as qigong, yoga, and tai chi. The use of medication in the treatment of fibromyalgia is debated, although antidepressants can improve quality of life. The medications duloxetine, milnacipran, or pregabalin have been approved by the US Food and Drug Administration (FDA) for the management of fibromyalgia. Other common helpful medications include serotonin-noradrenaline reuptake inhibitors, nonsteroidal anti-inflammatory drugs, and muscle relaxants. Q10 coenzyme and vitamin D supplements may reduce pain and improve quality of life. While fibromyalgia is persistent in nearly all patients, it does not result in death or tissue damage.
Fibromyalgia is estimated to affect 2–4% of the population. Women are affected about twice as often as men. Rates appear similar in different areas of the world and among different cultures. Fibromyalgia was first defined in 1990, with updated criteria in 2011, 2016, and 2019. The term "fibromyalgia" is from Neo-Latin fibro-, meaning "fibrous tissues", Greek μυο- myo-, "muscle", and Greek άλγος algos, "pain"; thus, the term literally means "muscle and fibrous |
https://en.wikipedia.org/wiki/French%20Institute%20for%20Research%20in%20Computer%20Science%20and%20Automation | The National Institute for Research in Digital Science and Technology (Inria) () is a French national research institution focusing on computer science and applied mathematics.
It was created under the name French Institute for Research in Computer Science and Automation (IRIA) () in 1967 at Rocquencourt near Paris, part of Plan Calcul. Its first site was the historical premises of SHAPE (central command of NATO military forces), which is still used as Inria's main headquarters. In 1980, IRIA became INRIA. Since 2011, it has been styled Inria.
Inria is a Public Scientific and Technical Research Establishment (EPST) under the double supervision of the French Ministry of National Education, Advanced Instruction and Research and the Ministry of Economy, Finance and Industry.
Administrative status
Inria has nine research centers distributed across France (in Bordeaux, Grenoble-Inovallée, Lille, Lyon, Nancy, Paris-Rocquencourt, Rennes, Saclay, and Sophia Antipolis) and one center abroad in Santiago de Chile, Chile. It also contributes to academic research teams outside of those centers.
Inria Rennes is part of the joint Institut de recherche en informatique et systèmes aléatoires (IRISA) with several other entities.
Before December 2007, the three centers of Bordeaux, Lille and Saclay formed a single research center called INRIA Futurs.
In October 2010, Inria, with Pierre and Marie Curie University (Now Sorbonne University) and Paris Diderot University started IRILL, a center for innovation and research initiative for free software.
Inria employs 3800 people. Among them are 1300 researchers, 1000 Ph.D. students and 500 postdoctorates.
Research
Inria does both theoretical and applied research in computer science. In the process, it has produced many widely used programs, such as
Bigloo, a Scheme implementation
CADP, a tool box for the verification of asynchronous concurrent systems
Caml, a language from the ML family
Caml Light and OCaml implementations
|
https://en.wikipedia.org/wiki/Cavendish%20experiment | The Cavendish experiment, performed in 1797–1798 by English scientist Henry Cavendish, was the first experiment to measure the force of gravity between masses in the laboratory and the first to yield accurate values for the gravitational constant. Because of the unit conventions then in use, the gravitational constant does not appear explicitly in Cavendish's work. Instead, the result was originally expressed as the specific gravity of Earth, or equivalently the mass of Earth. His experiment gave the first accurate values for these geophysical constants.
The experiment was devised sometime before 1783 by geologist John Michell, who constructed a torsion balance apparatus for it. However, Michell died in 1793 without completing the work. After his death the apparatus passed to Francis John Hyde Wollaston and then to Cavendish, who rebuilt the apparatus but kept close to Michell's original plan. Cavendish then carried out a series of measurements with the equipment and reported his results in the Philosophical Transactions of the Royal Society in 1798.
The experiment
The apparatus consisted of a torsion balance made of a wooden rod horizontally suspended from a wire, with two , lead spheres, one attached to each end. Two massive , lead balls, suspended separately, could be positioned away from or to either side of the smaller balls, away. The experiment measured the faint gravitational attraction between the small and large balls, which deflected the torsion balance rod by about 0.16" (or only 0.03" with a stiffer suspending wire).
The two large balls could be positioned either away from or to either side of the torsion balance rod. Their mutual attraction to the small balls caused the arm to rotate, twisting the suspension wire. The arm rotated until it reached an angle where the twisting force of the wire balanced the combined gravitational force of attraction between the large and small lead spheres. By measuring the angle of the rod and knowing the twisting |
https://en.wikipedia.org/wiki/Paul%20Halmos | Paul Richard Halmos (; March 3, 1916 – October 2, 2006) was a Hungarian-born American mathematician and statistician who made fundamental advances in the areas of mathematical logic, probability theory, statistics, operator theory, ergodic theory, and functional analysis (in particular, Hilbert spaces). He was also recognized as a great mathematical expositor. He has been described as one of The Martians.
Early life and education
Born in Hungary into a Jewish family, Halmos arrived in the U.S. at 13 years of age. He obtained his B.A. from the University of Illinois, majoring in mathematics, but fulfilling the requirements for both a math and philosophy degree. He took only three years to obtain the degree, and was only 19 when he graduated. He then began a Ph.D. in philosophy, still at the Champaign–Urbana campus; but, after failing his masters' oral exams, he shifted to mathematics, graduating in 1938. Joseph L. Doob supervised his dissertation, titled Invariants of Certain Stochastic Transformations: The Mathematical Theory of Gambling Systems.
Career
Shortly after his graduation, Halmos left for the Institute for Advanced Study, lacking both job and grant money. Six months later, he was working under John von Neumann, which proved a decisive experience. While at the Institute, Halmos wrote his first book, Finite Dimensional Vector Spaces, which immediately established his reputation as a fine expositor of mathematics.
From 1967 to 1968 he was the Donegall Lecturer in Mathematics at Trinity College Dublin.
Halmos taught at Syracuse University, the University of Chicago (1946–60), the University of Michigan (~1961–67), the University of Hawaii (1967–68), Indiana University (1969–85), and the University of California at Santa Barbara (1976–78). From his 1985 retirement from Indiana until his death, he was affiliated with the Mathematics department at Santa Clara University (1985–2006).
Accomplishments
In a series of papers reprinted in his 1962 Algebraic Logic, |
https://en.wikipedia.org/wiki/Musica%20universalis | The musica universalis (literally universal music), also called music of the spheres or harmony of the spheres, is a philosophical concept that regards proportions in the movements of celestial bodies – the Sun, Moon, and planets – as a form of music. The theory, originating in ancient Greece, was a tenet of Pythagoreanism, and was later developed by 16th-century astronomer Johannes Kepler. Kepler did not believe this "music" to be audible, but felt that it could nevertheless be heard by the soul. The idea continued to appeal to scholars until the end of the Renaissance, influencing many schools of thought, including humanism.
History
The concept of the "music of the spheres" incorporates the metaphysical principle that mathematical relationships express qualities or "tones" of energy that manifests in numbers, visual angles, shapes and sounds – all connected within a pattern of proportion. Pythagoras first identified that the pitch of a musical note is in inverse proportion to the length of the string that produces it, and that intervals between harmonious sound frequencies form simple numerical ratios. Pythagoras proposed that the Sun, Moon and planets all emit their own unique hum based on their orbital revolution, and that the quality of life on Earth reflects the tenor of celestial sounds which are physically imperceptible to the human ear. Subsequently, Plato described astronomy and music as "twinned" studies of sensual recognition: astronomy for the eyes, music for the ears, and both requiring knowledge of numerical proportions.
Aristotle characterised the theory as follows:
Aristotle rejected the idea, however, as incompatible with his own cosmological model, and on the grounds that "excessive noises ... shatter the solid bodies even of inanimate things", and therefore any sounds made by the planets would necessarily exert a tremendous physical force upon the body.
Boethius, in his influential work De Musica, described three categories of music:
musi |
https://en.wikipedia.org/wiki/Hyperbolic%20space | In mathematics, hyperbolic space of dimension n is the unique simply connected, n-dimensional Riemannian manifold of constant sectional curvature equal to -1. It is homogeneous, and satisfies the stronger property of being a symmetric space. There are many ways to construct it as an open subset of with an explicitly written Riemannian metric; such constructions are referred to as models. Hyperbolic 2-space, H2, which was the first instance studied, is also called the hyperbolic plane.
It is also sometimes referred to as Lobachevsky space or Bolyai–Lobachevsky space after the names of the author who first published on the topic of hyperbolic geometry. Sometimes the qualificative "real" is added to differentiate it from complex hyperbolic spaces, quaternionic hyperbolic spaces and the octononic hyperbolic plane which are the other symmetric spaces of negative curvature.
Hyperbolic space serves as the prototype of a Gromov hyperbolic space which is a far-reaching notion including differential-geometric as well as more combinatorial spaces via a synthetic approach to negative curvature. Another generalisation is the notion of a CAT(-1) space.
Formal definition and models
Definition
The -dimensional hyperbolic space or Hyperbolic -space, usually denoted , is the unique simply connected, -dimensional complete Riemannian manifold with a constant negative sectional curvature equal to -1. The unicity means that any two Riemannian manifolds which satisfy these properties are isometric to each other. It is a consequence of the Killing–Hopf theorem.
Models of hyperbolic space
To prove the existence of such a space as described above one can explicitly construct it, for example as an open subset of with a Riemannian metric given by a simple formula. There are many such constructions or models of hyperbolic space, each suited to different aspects of its study. They are isometric to each other according to the previous paragraph, and in each case an explicit isometry can |
https://en.wikipedia.org/wiki/Embryophyte | The Embryophyta (), or land plants, are the most familiar group of green plants that comprise vegetation on Earth. Embryophytes () have a common ancestor with green algae, having emerged within the Phragmoplastophyta clade of green algae as sister of the Zygnematophyceae. The Embryophyta consist of the bryophytes plus the polysporangiophytes. Living embryophytes therefore include hornworts, liverworts, mosses, lycophytes, ferns, gymnosperms and flowering plants. The land plants have diplobiontic life cycles and it is accepted now that they emerged from freshwater, multi-celled algae.
The embryophytes are informally called land plants because they live primarily in terrestrial habitats (with exceptional members who evolved to live once again in aquatic habitats), while the related green algae are primarily aquatic. Embryophytes are complex multicellular eukaryotes with specialized reproductive organs. The name derives from their innovative characteristic of nurturing the young embryo sporophyte during the early stages of its multicellular development within the tissues of the parent gametophyte. With very few exceptions, embryophytes obtain their energy by photosynthesis, that is by using the energy of sunlight to synthesize their food from carbon dioxide and water.
Description
The Embryophytes emerged a half-billion years ago, at some time in the interval between the mid-Cambrian and early Ordovician, probably from terrestrial multicellular charophytes, a clade of green algae similar to extant Klebsormidiophyceae. The emergence of the Embryophytes depleted atmospheric CO2 (a greenhouse gas), leading to global cooling, and thereby precipitating glaciations. Embryophytes are primarily adapted for life on land, although some are secondarily aquatic. Accordingly, they are often called land plants or terrestrial plants.
On a microscopic level, the cells of charophytes are broadly similar to those of chlorophyte green algae, but differ in that in cell division the d |
https://en.wikipedia.org/wiki/Animalcule | Animalcule (; ) is an archaic term for microscopic organisms that included bacteria, protozoans, and very small animals. The word was invented by 17th-century Dutch scientist Antonie van Leeuwenhoek to refer to the microorganisms he observed in rainwater.
Some better-known types of animalcule include:
Actinophrys, and other heliozoa, termed sun animalcules.
Amoeba, termed Proteus animalcules.
Noctiluca scintillans, commonly termed the sea sparkles.
Paramecium, termed slipper animalcules.
Rotifers, termed wheel animalcules.
Stentor, termed trumpet animalcules.
Vorticella, and other peritrichs, termed bell animalcules.
The concept seems to have been proposed at least as early as about 30 BC, as evidenced by this translation from Marcus Varro's Rerum Rusticarum Libri Tres:
Note also if there be any swampy ground, both for the reasons given above, and because certain minute animals, invisible to the eye, breed there, and, borne by the air, reach the inside of the body by way of the mouth and nose, and cause diseases which are difficult to be rid of.
The term was also used during the 17th century by Henry Oldenburg, the first Secretary of the Royal Society and founding editor of Philosophical Transactions, to translate the Dutch words used by van Leeuwenhoek to describe microorganisms that he discovered.
In Gilbert and Sullivan's The Pirates of Penzance, the word appears in adjectival form in the 'Major-General's Song', in which Major-General Stanley sings, 'I know the scientific names of beings animalculous...'
The term continued to be current at least as late as 1879.
See also
Caminalcule
Infusoria
Van Leeuwenhoek's microscopic discovery of microbial life (microorganisms)
References
Zoology
Antonie van Leeuwenhoek
Biology and natural history in the Dutch Republic |
https://en.wikipedia.org/wiki/Iceland%20spar | Iceland spar, formerly called Iceland crystal ( , ) and also called optical calcite, is a transparent variety of calcite, or crystallized calcium carbonate, originally brought from Iceland, and used in demonstrating the polarization of light.
Characteristics
Iceland spar occurs in large readily cleavable crystals, which are easily divisible into parallelepipeds, and it is remarkable for its birefringence. This means that the refractive index of the crystal is different for light of different polarizations. A ray of unpolarized light passing through the crystal is divided into two rays of mutually perpendicular polarization directed at different angles. This double refraction causes objects seen through the crystal to appear doubled.
Historically, the double-refraction property of this crystal was important to understanding the nature of light as a wave. This was studied at length by Christiaan Huygens and Isaac Newton. Sir George Stokes also studied the phenomenon. Its complete explanation in terms of light polarization was published by Augustin-Jean Fresnel in the 1820s.
Occurrence
Mines producing Iceland spar include many mines producing related calcite and aragonite. As well as those famously in Iceland, there are productive sources in the greater Sonoran Desert region; in Santa Eulalia, Chihuahua, Mexico; and in New Mexico, United States, as well as in China. The clearest specimens, as well as the largest, have been from the Helgustaðir mine in Iceland.
Uses
It has been speculated that the sunstone (, a different mineral from the gem-quality sunstone) mentioned in medieval Icelandic texts such as Rauðúlfs þáttr was Iceland spar, and that Vikings used its light-polarizing property to tell the direction of the sun on cloudy days for navigational purposes. The polarization of sunlight in the Arctic can be detected, and the direction of the sun identified to within a few degrees in both cloudy and twilight conditions using the sunstone and the naked eye. T |
https://en.wikipedia.org/wiki/Dosimetry | Radiation dosimetry in the fields of health physics and radiation protection is the measurement, calculation and assessment of the ionizing radiation dose absorbed by an object, usually the human body. This applies both internally, due to ingested or inhaled radioactive substances, or externally due to irradiation by sources of radiation.
Internal dosimetry assessment relies on a variety of monitoring, bio-assay or radiation imaging techniques, whilst external dosimetry is based on measurements with a dosimeter, or inferred from measurements made by other radiological protection instruments.
Radiation dosimetry is extensively used for radiation protection; routinely applied to monitor occupational radiation workers, where irradiation is expected, or where radiation is unexpected, such as in the contained aftermath of the Three Mile Island, Chernobyl or Fukushima radiological release incidents. The public dose take-up is measured and calculated from a variety of indicators such as ambient measurements of gamma radiation, radioactive particulate monitoring, and the measurement of levels of radioactive contamination.
Other significant radiation dosimetry areas are medical, where the required treatment absorbed dose and any collateral absorbed dose is monitored, and environmental, such as radon monitoring in buildings.
Measuring radiation dose
External dose
There are several ways of measuring absorbed doses from ionizing radiation. People in occupational contact with radioactive substances, or who may be exposed to radiation, routinely carry personal dosimeters. These are specifically designed to record and indicate the dose received. Traditionally, these were lockets fastened to the external clothing of the monitored person, which contained photographic film known as film badge dosimeters. These have been largely replaced with other devices such as Thermoluminescent dosimetry(TLD), optically stimulated luminescence(OSL), or Fluorescent Nuclear Tract Detector(FNTD) |
https://en.wikipedia.org/wiki/Strict%20function | In computer science and computer programming, a function f is said to be strict if, when applied to a non-terminating expression, it also fails to terminate. A strict function in the denotational semantics of programming languages is a function f where . The entity , called bottom, denotes an expression that does not return a normal value, either because it loops endlessly or because it aborts due to an error such as division by zero. A function that is not strict is called non-strict. A strict programming language is one in which user-defined functions are always strict.
Intuitively, non-strict functions correspond to control structures. Operationally, a strict function is one that always evaluates its argument; a non-strict function is one that might not evaluate some of its arguments. Functions having more than one parameter can be strict or non-strict in each parameter independently, as well as jointly strict in several parameters simultaneously.
As an example, the if-then-else expression of many programming languages, called ?: in languages inspired by C, may be thought of as a function of three parameters. This function is strict in its first parameter, since the function must know whether its first argument evaluates to true or to false before it can return; but it is non-strict in its second parameter, because (for example) if(false,,1) = 1, as well as non-strict in its third parameter, because (for example) if(true,2,) = 2. However, it is jointly strict in its second and third parameters, since if(true,,) = and if(false,,) = .
In a non-strict functional programming language, strictness analysis refers to any algorithm used to prove the strictness of a function with respect to one or more of its arguments. Such functions can be compiled to a more efficient calling convention, such as call by value, without changing the meaning of the enclosing program.
See also
Eager evaluation
Lazy evaluation
Short-circuit evaluation
References
Formal methods
D |
https://en.wikipedia.org/wiki/Strict%20programming%20language | A strict programming language is a programming language which employs a strict programming paradigm, allowing only strict functions (functions whose parameters must be evaluated completely before they may be called) to be defined by the user. A non-strict programming language allows the user to define non-strict functions, and hence may allow lazy evaluation.
Examples
Nearly all programming languages in common use today are strict. Examples include C#, Java, Perl (all versions, i.e. through version 5 and version 7), Python, Ruby, Common Lisp, and ML.
Some strict programming languages include features that mimic laziness. Raku, formerly known as Perl 6, has lazy lists. Python has generator functions. Julia provides a macro system to build non-strict functions, as does Scheme.
Examples for non-strict languages are Haskell, R, Miranda, and Clean.
Explanation
In most non-strict languages the non-strictness extends to data constructors. This allows conceptually infinite data structures (such as the list of all prime numbers) to be manipulated in the same way as ordinary finite data structures. It also allows for the use of very large but finite data structures such as the complete game tree of chess.
Non-strictness has several disadvantages which have prevented widespread adoption:
Because of the uncertainty regarding if and when expressions will be evaluated, non-strict languages generally must be purely functional to be useful.
All hardware architectures in common use are optimized for strict languages, so the best compilers for non-strict languages produce slower code than the best compilers for strict languages.
Space complexity of non-strict programs is difficult to understand and predict.
Strict programming languages are often associated with eager evaluation, and non-strict languages with lazy evaluation, but other evaluation strategies are possible in each case. The terms "eager programming language" and "lazy programming language" are often used as syn |
https://en.wikipedia.org/wiki/Microfilament | Microfilaments, also called actin filaments, are protein filaments in the cytoplasm of eukaryotic cells that form part of the cytoskeleton. They are primarily composed of polymers of actin, but are modified by and interact with numerous other proteins in the cell. Microfilaments are usually about 7 nm in diameter and made up of two strands of actin. Microfilament functions include cytokinesis, amoeboid movement, cell motility, changes in cell shape, endocytosis and exocytosis, cell contractility, and mechanical stability. Microfilaments are flexible and relatively strong, resisting buckling by multi-piconewton compressive forces and filament fracture by nanonewton tensile forces. In inducing cell motility, one end of the actin filament elongates while the other end contracts, presumably by myosin II molecular motors. Additionally, they function as part of actomyosin-driven contractile molecular motors, wherein the thin filaments serve as tensile platforms for myosin's ATP-dependent pulling action in muscle contraction and pseudopod advancement. Microfilaments have a tough, flexible framework which helps the cell in movement.
Actin was first discovered in rabbit skeletal muscle in the mid 1940 by F.B. Straub. Almost 20 years later, H.E. Huxley demonstrated that actin is essential for muscle constriction. The mechanism in which actin creates long filaments was first described in the mid 1980. Later studies showed that actin has an important role in cell shape, motility, and cytokinesis.
Organization
Actin filaments are assembled in two general types of structures: bundles and networks. Bundles can be composed of polar filament arrays, in which all barbed ends point to the same end of the bundle, or non-polar arrays, where the barbed ends point towards both ends. A class of actin-binding proteins, called cross-linking proteins, dictate the formation of these structures. Cross-linking proteins determine filament orientation and spacing in the bundles and networks. |
https://en.wikipedia.org/wiki/Rendezvous%20%28Plan%209%29 | Rendezvous is a data synchronization mechanism in Plan 9 from Bell Labs. It is a system call that allows two processes to exchange a single datum while synchronizing.
The rendezvous call takes a tag and a value as its arguments. The tag is typically an address in memory shared by both processes. Calling rendezvous causes a process to sleep until a second rendezvous call with a matching tag occurs. Then, the values are exchanged and both processes are awakened.
More complex synchronization mechanisms can be created from this primitive operation. See also mutual exclusion.
See also
Synchronous rendezvous
Communicating sequential processes
References
External links
Process Sleep and Wakeup on a Shared-memory Multiprocessor by Rob Pike, Dave Presotto, Ken Thompson and Gerard Holzmann.
Plan 9 from Bell Labs
Parallel computing
Inter-process communication |
https://en.wikipedia.org/wiki/Zero-configuration%20networking | Zero-configuration networking (zeroconf) is a set of technologies that automatically creates a usable computer network based on the Internet Protocol Suite (TCP/IP) when computers or network peripherals are interconnected. It does not require manual operator intervention or special configuration servers. Without zeroconf, a network administrator must set up network services, such as Dynamic Host Configuration Protocol (DHCP) and Domain Name System (DNS), or configure each computer's network settings manually.
Zeroconf is built on three core technologies: automatic assignment of numeric network addresses for networked devices, automatic distribution and resolution of computer hostnames, and automatic location of network services, such as printing devices.
Background
Computer networks use numeric network addresses to identify communications endpoints in a network of participating devices. This is similar to the telephone network which assigns a string of digits to identify each telephone. In modern networking protocols, information to be transmitted is divided into a series of network packets. Every packet contains the source and destination addresses for the transmission. Network routers examine these addresses to determine the best network path in forwarding the data packet at each step toward its destination.
Similarly to telephones being labeled with their telephone number, it was a common practice in early networks to attach an address label to networked devices. The dynamic nature of modern networks, especially residential networks in which devices are powered up only when needed, desire dynamic address assignment mechanisms that do not require user involvement for initialization and management. These systems automatically give themselves common names chosen either by the equipment manufacturer, such as a brand and model number or chosen by users for identifying their equipment. The names and addresses are then automatically entered into a directory service.
|
https://en.wikipedia.org/wiki/Law%20of%20tangents | In trigonometry, the law of tangents or tangent rule is a statement about the relationship between the tangents of two angles of a triangle and the lengths of the opposing sides.
In Figure 1, , , and are the lengths of the three sides of the triangle, and , , and are the angles opposite those three respective sides. The law of tangents states that
The law of tangents, although not as commonly known as the law of sines or the law of cosines, is equivalent to the law of sines, and can be used in any case where two sides and the included angle, or two angles and a side, are known.
Proof
To prove the law of tangents one can start with the law of sines:
Let
so that
It follows that
Using the trigonometric identity, the factor formula for sines specifically
we get
As an alternative to using the identity for the sum or difference of two sines, one may cite the trigonometric identity
(see tangent half-angle formula).
Application
The law of tangents can be used to compute the missing side and angles of a triangle in which two sides and and the enclosed angle are given. From
one can compute ; together with this yields and ; the remaining side can then be computed using the law of sines. In the time before electronic calculators were available, this method
was preferable to an application of the law of cosines , as this latter law necessitated an additional lookup in a logarithm table, in order to compute the square root. In modern times the law of tangents may have better numerical properties than the law of cosines: If is small, and and are almost equal, then an application of the law of cosines leads to a subtraction of almost equal values, incurring catastrophic cancellation.
Spherical version
On a sphere of unit radius, the sides of the triangle are arcs of great circles. Accordingly, their lengths can be expressed in radians or any other units of angular measure. Let , , be the angles at the three vertices of the triangl |
https://en.wikipedia.org/wiki/Speculative%20execution | Speculative execution is an optimization technique where a computer system performs some task that may not be needed. Work is done before it is known whether it is actually needed, so as to prevent a delay that would have to be incurred by doing the work after it is known that it is needed. If it turns out the work was not needed after all, most changes made by the work are reverted and the results are ignored.
The objective is to provide more concurrency if extra resources are available. This approach is employed in a variety of areas, including branch prediction in pipelined processors, value prediction for exploiting value locality, prefetching memory and files, and optimistic concurrency control in database systems.
Speculative multithreading is a special case of speculative execution.
Overview
Modern pipelined microprocessors use speculative execution to reduce the cost of conditional branch instructions using schemes that predict the execution path of a program based on the history of branch executions. In order to improve performance and utilization of computer resources, instructions can be scheduled at a time when it has not yet been determined that the instructions will need to be executed, ahead of a branch.
Variants
Speculative computation was a related earlier concept.
Eager execution
Eager execution is a form of speculative execution where both sides of the conditional branch are executed; however, the results are committed only if the predicate is true. With unlimited resources, eager execution (also known as oracle execution) would in theory provide the same performance as perfect branch prediction. With limited resources, eager execution should be employed carefully, since the number of resources needed grows exponentially with each level of branch executed eagerly.
Predictive execution
Predictive execution is a form of speculative execution where some outcome is predicted and execution proceeds along the predicted path until the actual resu |
https://en.wikipedia.org/wiki/Silicon%20controlled%20rectifier | A silicon controlled rectifier or semiconductor controlled rectifier is a four-layer solid-state current-controlling device. The name "silicon controlled rectifier" is General Electric's trade name for a type of thyristor. The principle of four-layer p–n–p–n switching was developed by Moll, Tanenbaum, Goldey, and Holonyak of Bell Laboratories in 1956. The practical demonstration of silicon controlled switching and detailed theoretical behavior of a device in agreement with the experimental results was presented by Dr Ian M. Mackintosh of Bell Laboratories in January 1958. The SCR was developed by a team of power engineers led by Gordon Hall
and commercialized by Frank W. "Bill" Gutzwiller in 1957.
Some sources define silicon-controlled rectifiers and thyristors as synonymous while other sources define silicon-controlled rectifiers as a proper subset of the set of thyristors; the latter being devices with at least four layers of alternating n- and p-type material. According to Bill Gutzwiller, the terms "SCR" and "controlled rectifier" were earlier, and "thyristor" was applied later, as usage of the device spread internationally.
SCRs are unidirectional devices (i.e. can conduct current only in one direction) as opposed to TRIACs, which are bidirectional (i.e. charge carriers can flow through them in either direction). SCRs can be triggered normally only by a positive current going into the gate as opposed to TRIACs, which can be triggered normally by either a positive or a negative current applied to its gate electrode.
Modes of operation
There are three modes of operation for an SCR depending upon the biasing given to it:
Forward blocking mode (off state)
Forward conduction mode (on state)
Reverse blocking mode (off state)
Forward blocking mode
In this mode of operation, the anode (+, p-doped side) is given a positive voltage while the cathode (−, n-doped side) is given a negative voltage, keeping the gate at zero (0) potential i.e. disconnected. In thi |
https://en.wikipedia.org/wiki/7400-series%20integrated%20circuits | The 7400 series is a popular logic family of transistor–transistor logic (TTL) integrated circuits (ICs).
In 1964, Texas Instruments introduced the SN5400 series of logic chips, in a ceramic semiconductor package. A low-cost plastic package SN7400 series was introduced in 1966 which quickly gained over 50% of the logic chip market, and eventually becoming de facto standardized electronic components. Over the decades, many generations of pin-compatible descendant families evolved to include support for low power CMOS technology, lower supply voltages, and surface mount packages.
Overview
The 7400 series contains hundreds of devices that provide everything from basic logic gates, flip-flops, and counters, to special purpose bus transceivers and arithmetic logic units (ALU). Specific functions are described in a list of 7400 series integrated circuits. Some TTL logic parts were made with an extended military-specification temperature range. These parts are prefixed with 54 instead of 74 in the part number. The less-common 64 and 84 prefixes on Texas Instruments parts indicated an industrial temperature range. Since the 1970s, new product families have been released to replace the original 7400 series. More recent TTL logic families were manufactured using CMOS or BiCMOS technology rather than TTL.
Today, surface-mounted CMOS versions of the 7400 series are used in various applications in electronics and for glue logic in computers and industrial electronics. The original through-hole devices in dual in-line packages (DIP/DIL) were the mainstay of the industry for many decades. They are useful for rapid breadboard-prototyping and for education and remain available from most manufacturers. The fastest types and very low voltage versions are typically surface-mount only, however.
The first part number in the series, the 7400, is a 14-pin IC containing four two-input NAND gates. Each gate uses two input pins and one output pin, with the remaining two pins being po |
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