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Nonlocal Static Instability
Nonlocal may refer to: * Action at a distance, direct interaction of physical objects that are not in proximity * Conjugated system (or nonlocalized bond), in chemistry, a conjugated system is a system of connected p-orbitals with delocalized electrons in compounds with alternating single and multiple bonds, which in general may lower the overall energy of the molecule and increase stability * Nonlocal goto, an abstract representation of the control state of a computer program * Nonlocal Lagrangian, in field theory, a type of functional \mathcal L\phi(x) which contains terms which are nonlocal in the fields i.e. which are not polynomials or functions of the fields or their derivatives evaluated at a single point in the space of dynamical parameters (e.g. space-time) ** Other nonlocal relationships in physics, such as Pippard's nonlocal generalisation of the Londons' equations for superconductivity * Non-local means, an algorithm in image processing for image denoising * Nonloca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Action At A Distance
Action at a distance is the concept in physics that an object's motion (physics), motion can be affected by another object without the two being in Contact mechanics, physical contact; that is, it is the concept of the non-local interaction of objects that are separated in space. Coulomb's law and Newton's law of universal gravitation are based on action at a distance. Historically, action at a distance was the earliest scientific model for gravity and electricity and it continues to be useful in many practical cases. In the 19th and 20th centuries, field models arose to explain these phenomena with more precision. The discovery of Electron, electrons and of special relativity led to new action at a distance models providing alternative to field theories. Under our modern understanding, the four fundamental interactions (gravity, electromagnetism, the strong interaction and the weak interaction) in all of physics are not described by action at a distance. Categories of action I ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Conjugated System
In physical organic chemistry, a conjugated system is a system of connected p-orbitals with delocalized electrons in a molecule, which in general lowers the overall energy of the molecule and increases Chemical stability, stability. It is Resonance (chemistry), conventionally represented as having alternating single and multiple covalent bond, bonds. Lone pairs, radical (chemistry), radicals or carbenium ions may be part of the system, which may be Cyclic molecule, cyclic, acyclic, Linear molecular geometry, linear or mixed. The term "conjugated" was coined in 1899 by the German chemist Johannes Thiele (chemist), Johannes Thiele. Conjugation is the orbital overlap, overlap of one p-orbital with another across an adjacent Sigma bond, σ bond (in transition metals, d-orbitals can be involved). A conjugated system has a region of overlapping p-orbitals, bridging the interjacent locations that simple diagrams illustrate as not having a π bond. They allow a delocalization of pi el ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Continuation
In computer science, a continuation is an abstract representation of the control state of a computer program. A continuation implements ( reifies) the program control state, i.e. the continuation is a data structure that represents the computational process at a given point in the process's execution; the created data structure can be accessed by the programming language, instead of being hidden in the runtime environment. Continuations are useful for encoding other control mechanisms in programming languages such as exceptions, generators, coroutines, and so on. The "current continuation" or "continuation of the computation step" is the continuation that, from the perspective of running code, would be derived from the current point in a program's execution. The term ''continuations'' can also be used to refer to first-class continuations, which are constructs that give a programming language the ability to save the execution state at any point and return to that point at a l ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nonlocal Lagrangian
In field theory, a nonlocal Lagrangian is a Lagrangian, a type of functional \mathcal phi(x) containing terms that are ''nonlocal'' in the fields \phi(x), i.e. not polynomials or functions of the fields or their derivatives evaluated at a single point in the space of dynamical parameters (e.g. space-time). Examples of such nonlocal Lagrangians might be: * \mathcal = \frac\big(\partial_x \phi(x)\big)^2 - \fracm^2 \phi(x)^2 + \phi(x) \int \frac \,d^ny. * \mathcal = -\frac\mathcal_\left(1 + \frac\right)\mathcal^. * S = \int dt \,d^dx \left psi^*\left(i\hbar \frac + \mu\right)\psi - \frac\nabla \psi^*\cdot \nabla \psi\right- \frac\int dt \,d^dx \,d^dy \, V(\mathbf - \mathbf) \psi^*(\mathbf) \psi(\mathbf) \psi^*(\mathbf) \psi(\mathbf). * The Wess–Zumino–Witten action. Actions obtained from nonlocal Lagrangians are called ''nonlocal actions''. The actions appearing in the fundamental theories of physics, such as the Standard Model The Standard Model of particle physics is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pippard, Brian
Sir Alfred Brian Pippard, FRS (7 September 1920 – 21 September 2008), was a British physicist. He was Cavendish Professor of Physics from 1971 until 1982 and an Honorary Fellow of Clare Hall, Cambridge, of which he was the first President. Biography Pippard was born in London in 1920 and his father was the engineer Alfred Pippard. He was educated at Clifton College and Clare College, Cambridge, where he graduated with MA (Cantab) and PhD degrees. After working as a scientific officer in radar research during the Second World War, he was appointed as a Demonstrator in Physics at the University of Cambridge in 1946, subsequently becoming a Lecturer in the subject in 1950, a Reader in 1959, and the first John Humphrey Plummer Professor of Physics a year later. In 1971 he was elected Cavendish Professor of Physics. Pippard demonstrated the reality, as opposed to the mere abstract concept, of Fermi surfaces in metals by establishing the shape of the Fermi surface of copper ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
London Equations
The London equations, developed by brothers Fritz and Heinz London in 1935, are constitutive relations for a superconductor relating its superconducting current to electromagnetic fields in and around it. Whereas Ohm's law is the simplest constitutive relation for an ordinary conductor, the London equations are the simplest meaningful description of superconducting phenomena, and form the genesis of almost any modern introductory text on the subject. A major triumph of the equations is their ability to explain the Meissner effect, wherein a material exponentially expels all internal magnetic fields as it crosses the superconducting threshold. Description There are two London equations when expressed in terms of measurable fields: :\frac = \frac\mathbf, \qquad \mathbf\times\mathbf_ =-\frac\mathbf. Here _ is the (superconducting) current density, E and B are respectively the electric and magnetic fields within the superconductor, e\, is the charge of an electron or proto ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Non-local Means
Non-local means is an algorithm in image processing for image denoising. Unlike "local mean" filters, which take the mean value of a group of pixels surrounding a target pixel to smooth the image, non-local means filtering takes a mean of all pixels in the image, weighted by how similar these pixels are to the target pixel. This results in much greater post-filtering clarity, and less loss of detail in the image compared with local mean algorithms. If compared with other well-known denoising techniques, non-local means adds "method noise" (i.e. error in the denoising process) which looks more like white noise, which is desirable because it is typically less disturbing in the denoised product. Recently non-local means has been extended to other image processing applications such as deinterlacing, view interpolation, and depth maps regularization. Definition Suppose \Omega is the area of an image, and p and q are two points within the image. Then, the algorithm is: :u(p) = \int_ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nonlocal Operator
In mathematics, a nonlocal operator is a mapping which maps functions on a topological space to functions, in such a way that the value of the output function at a given point cannot be determined solely from the values of the input function in any neighbourhood of any point. An example of a nonlocal operator is the Fourier transform. Formal definition Let X be a topological space, Y a set, F(X) a function space containing functions with domain X, and G(Y) a function space containing functions with domain Y. Two functions u and v in F(X) are called equivalent at x\in X if there exists a neighbourhood N of x such that u(x')=v(x') for all x'\in N. An operator A: F(X) \to G(Y) is said to be local if for every y\in Y there exists an x\in X such that Au(y) = Av(y) for all functions u and v in F(X) which are equivalent at x. A nonlocal operator is an operator which is not local. For a local operator it is possible (in principle) to compute the value Au(y) using only knowledge of the v ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Non-local Variable
In programming language theory, a non-local variable is a variable that is not defined in the local Scope (computer science), scope. While the term can refer to global variables, it is primarily used in the context of nested function, nested and anonymous functions where some variables can be in neither the local scope, local nor the global scope. In Lua (programming language), Lua they are called the ''upvalues'' of the function. Programming in Lua (first edition)'' Examples Nested functions In the Python 3 example that follows there is a nested function inner defined in the scope of another function outer. The variable x is local to outer, but non-local to inner (nor is it global): def outer(): x = 1 def inner(): nonlocal x x += 1 print(x) return inner In JavaScript, the locality of a variable is determined by the closest var statement for this variable. In the following example, x is local to outer as it contains a var x statement, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Python 3
The programming language Python (programming language), Python was conceived in the late 1980s, and its implementation was started in December 1989 by Guido van Rossum at Centrum Wiskunde & Informatica, CWI in the Netherlands as a successor to ABC (programming language), ABC capable of exception handling and interfacing with the Amoeba (operating system), Amoeba operating system. Van Rossum was Python's principal author and had a central role in deciding the direction of Python (as reflected in the title given to him by the Python community, Benevolent dictator for life, ''Benevolent Dictator for Life'' (BDFL)) until stepping down as leader on July 12, 2018. Python was named after the BBC TV show ''Monty Python's Flying Circus''. Python 2.0 was released on October 16, 2000, with many major new features, such as list comprehensions, cycle detection, cycle-detecting garbage collection (computer science), garbage collector, reference counting, memory management and support for ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
