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Coherent Noise
Coherence, coherency, or coherent may refer to the following: Physics * Coherence (physics), an ideal property of waves that enables stationary (i.e. temporally and spatially constant) interference * Coherence (units of measurement), a derived unit that, for a given system of quantities and for a chosen set of base units, is a product of powers of base units with no other proportionality factor than one * Coherence time, the time over which a propagating wave (especially a laser or maser beam) may be considered coherent; the time interval within which its phase is, on average, predictable Mathematics * Coherence (philosophical gambling strategy), a concept in Bayesian statistics * Coherence (signal processing), a statistic that can be used to examine the relation between two signals or data sets * Coherence (statistics), a property of self-consistency across a set of assessments, or the strength of association between two series * Coherence condition in category theory ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coherence (physics)
In physics, two wave sources are coherent if their frequency and waveform are identical. Coherence is an ideal property of waves that enables stationary (i.e., temporally or spatially constant) interference. It contains several distinct concepts, which are limiting cases that never quite occur in reality but allow an understanding of the physics of waves, and has become a very important concept in quantum physics. More generally, coherence describes all properties of the correlation between physical quantities of a single wave, or between several waves or wave packets. Interference is the addition, in the mathematical sense, of wave functions. A single wave can interfere with itself, but this is still an addition of two waves (see Young's slits experiment). Constructive or destructive interference are limit cases, and two waves always interfere, even if the result of the addition is complicated or not remarkable. When interfering, two waves can add together to create a wave of g ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cache Coherence
In computer architecture, cache coherence is the uniformity of shared resource data that ends up stored in multiple local caches. When clients in a system maintain caches of a common memory resource, problems may arise with incoherent data, which is particularly the case with CPUs in a multiprocessing system. In the illustration on the right, consider both the clients have a cached copy of a particular memory block from a previous read. Suppose the client on the bottom updates/changes that memory block, the client on the top could be left with an invalid cache of memory without any notification of the change. Cache coherence is intended to manage such conflicts by maintaining a coherent view of the data values in multiple caches. Overview In a shared memory multiprocessor system with a separate cache memory for each processor, it is possible to have many copies of shared data: one copy in the main memory and one in the local cache of each processor that requested it. When on ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coherence (film)
''Coherence'' is a 2013 American surreal science fiction psychological thriller film directed by James Ward Byrkit in his directorial debut. The film had its world debut on September 19, 2013, at Fantastic Fest and stars Emily Foxler as a woman who must deal with strange occurrences following the close passing of a comet. Plot On the night of Miller's Comet's passing, eight friends in Northern California reunite for a dinner party at the home of spouses Mike and Lee. One of the guests, Emily, hesitates over whether to accompany her boyfriend Kevin on an extended business trip to Vietnam. To the party-goers' dismay, their friend Amir has brought Laurie along with him. Laurie is Kevin's ex-girlfriend, who flirts inappropriately and wants Kevin back. During dinner, the conversation becomes strained by the animosity between Emily's close friend Beth and Laurie, compounded when Laurie antagonizes Emily by bringing up a ballet role she lost by waiting too long to decide. As a powe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coherent Risk Measure
In the fields of actuarial science and financial economics there are a number of ways that risk can be defined; to clarify the concept theoreticians have described a number of properties that a risk measure might or might not have. A coherent risk measure is a function that satisfies properties of monotonicity, sub-additivity, homogeneity, and translational invariance. Properties Consider a random outcome X viewed as an element of a linear space \mathcal of measurable functions, defined on an appropriate probability space. A functional \varrho : \mathcal → \R \cup \ is said to be coherent risk measure for \mathcal if it satisfies the following properties: Normalized : \varrho(0) = 0 That is, the risk when holding no assets is zero. Monotonicity : \mathrm\; Z_1,Z_2 \in \mathcal \;\mathrm\; Z_1 \leq Z_2 \; \mathrm ,\; \mathrm \; \varrho(Z_1) \geq \varrho(Z_2) That is, if portfolio Z_2 always has better values than portfolio Z_1 under almost all scenarios then the risk of Z_2 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coherence Time (communications Systems)
In communications systems, a communication channel may change with time. Coherence time is the time duration over which the channel impulse response is considered to be not varying. Such channel variation is much more significant in wireless communications systems, due to Doppler effects. Simple model In a simple model, a signal x(t) transmitted at time t_1 will be received as :y_(t) = x(t-t_1)*h_(t), where h_(t) is the channel impulse response (CIR) at time t_1. A signal transmitted at time t_2 will be received as :y_(t) = x(t-t_2)*h_(t). Now, if h_(t) - h_(t) is relatively small, the channel may be considered constant within the interval t_1 to t_2. Coherence time (T_c) will therefore be given by :T_c = t_2 - t_1. Relation with Doppler frequency Coherence time T_c is the time-domain dual of Doppler spread and is used to characterize the time-varying nature of the frequency dispersiveness of the channel in the time domain. The Maximum Doppler spread and coherence time are inver ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coherent Optical Module
Coherent optical module refers to a typically hot-pluggable coherent optical transceiver that uses coherent modulation (BPSK/QPSK/QAM) rather than amplitude modulation (RZ/ NRZ/ PAM4) and is typically used in high-bandwidth data communications applications. Optical modules typically have an electrical interface on the side that connects to the inside of the system and an optical interface on the side that connects to the outside world through a fiber optic cable. The technical details of coherent optical modules were proprietary for many years, but have recently attracted efforts by multi-source agreement (MSA) groups and a standards development organizations such as the Optical Internetworking Forum. Coherent optical modules can either plug into a front panel socket or an on-board socket. Coherent optical modules form a smaller piece of a much larger optical module industry. Electrical Interface Types There are multiple variants of the electrical interface of coherent optical m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coherence (music Theory)
Coherence, coherency, or coherent may refer to the following: Physics * Coherence (physics), an ideal property of waves that enables stationary (i.e. temporally and spatially constant) interference * Coherence (units of measurement), a derived unit that, for a given system of quantities and for a chosen set of base units, is a product of powers of base units with no other proportionality factor than one * Coherence time, the time over which a propagating wave (especially a laser or maser beam) may be considered coherent; the time interval within which its phase is, on average, predictable Mathematics * Coherence (philosophical gambling strategy), a concept in Bayesian statistics * Coherence (signal processing), a statistic that can be used to examine the relation between two signals or data sets * Coherence (statistics), a property of self-consistency across a set of assessments, or the strength of association between two series * Coherence condition in category theory, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coherence (linguistics)
Coherence in linguistics is what makes a text semantically meaningful. It is especially dealt with in text linguistics. Coherence is achieved through syntactical features such as the use of deictic, anaphoric and cataphoric elements or a logical tense structure, as well as presuppositions and implications connected to general world knowledge. The purely linguistic elements that make a text coherent are subsumed under the term cohesion. However, those text-based features which provide cohesion in a text do not necessarily help achieve coherence, that is, they do not always contribute to the meaningfulness of a text, be it written or spoken. It has been stated that a text coheres only if the world around is also coherent. Robert De Beaugrande and Wolfgang U. Dressler define coherence as a "continuity of senses" and "the mutual access and relevance within a configuration of concepts and relations". Thereby a textual world is created that does not have to comply to the real world. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coherence (cognitive Science)
Coherence theories of truth characterize truth as a property of whole systems of propositions that can be ascribed to individual propositions only derivatively according to their coherence with the whole. While modern coherence theorists hold that there are many possible systems to which the determination of truth may be based upon coherence, others, particularly those with strong religious beliefs, hold that the truth only applies to a single absolute system. In general, truth requires a proper fit of elements within the whole system. Very often, though, coherence is taken to imply something more than simple formal coherence. For example, the coherence of the underlying set of concepts is considered to be a critical factor in judging validity. In other words, the set of base concepts in a universe of discourse must form an intelligible paradigm before many theorists consider that the coherence theory of truth is applicable. History In modern philosophy, the coherence theory of tr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oracle Coherence
In computing, Oracle Coherence (originally Tangosol Coherence) is a Java-based distributed cache and in-memory data grid. It is claimed to be "intended for systems that require high availability, high scalability and low latency, particularly in cases when traditional relational database management systems provide insufficient throughput, or insufficient performance." History Tangosol Coherence was created by Cameron Purdy and Gene Gleyzer, and initially released in December, 2001. Oracle Corporation acquired Tangosol Inc., the original owner of the product, in April 2007, at which point it had more than 100 direct customers. Tangosol Coherence was also embedded in a number of other companies' software products, some of which belonged to Oracle Corporation's competitors. Features Coherence provides a variety of mechanisms to integrate with other services using TopLink, Java Persistence API, Oracle Golden Gate and other platforms using APIs provided by Coherence. Coherenc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coherent (operating System)
Coherent is a clone of the Unix operating system for IBM PC compatibles and other microcomputers, developed and sold by the now-defunct Mark Williams Company (MWC). Historically, the operating system was a proprietary product, but it became open source in 2015, released under the BSD-3-Clause license. Development Coherent was not Unix; the Mark Williams Company had no rights to either the Unix trademark or the AT&T/Bell Labs source code. In the early years of its existence, MWC received a visit from an AT&T delegation looking to determine whether MWC was infringing on AT&T Unix property. The delegation included Dennis Ritchie, who concluded that "it was very hard to believe that Coherent and its basic applications were not created without considerable study of the OS code and details of its applications." However, he also stated that: Much of the operating system was written by alumni from the University of Waterloo: Tom Duff, Dave Conroy, Randall Howard, Johann George, and T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
