For an electromagnetic wave , the coherencetime is the time over which a propagating wave especially a laser or maser beam may be considered coherence physics coherent . In other words, it is the time interval within which its Phase waves phase is, on average, predictable. In long distance telecommunication transmission systems , the coherencetime may be reduced by wave propagation propagation factors such as dispersion optics dispersion , scattering , and diffraction . Coherencetime, , is calculated by dividing the coherence length by the phase velocity of light in a medium approximately given by math tau frac 1 Delta nu approx frac lambda 2 c , Delta lambda math where is the central wavelength of the source, and is the spectral width of the source in units of frequency and wavelength respectively, and c is the speed of light in vacuum. A single mode fiber laser has a linewidth of a few kHz. The Schawlow Townes limit for some cw lasers can be below 1 Hz. Hydrogen masers have linewidth around 1 Hz ref http www.physics.harvard.edu Thesespdfs humphrey.pdf Precision measurements with atomic hydrogen masers ref their coherence length approximately corresponds to the distance from the Earth to the Moon. See also Portal Physics Atomic coherenceCoherencetime communications systems References references FS1037C MS188 DEFAULTSORT CoherenceTime Category Electromagnetic radiation Category Optics Category Radio frequency propagation ar ko ... more details
Context date October 2009 In communications system s, a communication channel may change with time. Coherencetime 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 effect s. Simple model In a simple model, a signal math x t math transmitted at time math t 1 math will be received as math y t 1 t x t t 1 h t 1 t , math where math h t 1 t math is the channel impulse response CIR at time math t 1 math . A signal transmitted at time math t 2 math will be received as math y t 2 t x t t 2 h t 2 t . math Now, if math h t 1 t h t 2 t math is relatively small, the channel may be considered constant within the interval math t 1 math to math t 2 math . Coherencetime math T c math will therefore be given by math T c t 2 t 1. math Relation with Doppler frequency Using Clarke s model , from the maximum Doppler frequency math f d math we can obtain 50 coherencetime ref name shankar2002 Shankar, 2002 ref ref name rappaport2002 Rappaport, 2002 ref math T c frac 67 16 pi f d math Usually, we use the following relation ref name rappaport2002 math T c sqrt frac 9 16 pi frac 1 f d simeq frac 0.423 f d math References references Category Communication ... more details
wiktionary coherence coherency coherent Coherence , coherency , or coherent can refer to In physics Coherence physics Coherencetime In mathematics Mutual coherence linear algebra , sometimes referred to as coherenceCoherence philosophical gambling strategy , a concept in Bayesian statistics Coherence signal processing Coherence statistics Coherence condition Coherent sampling , a relationship used in Fast Fourier Transforms Coherent sheaf In financial economics Coherent risk measure s, a class of risk measures In philosophy Coherentism is an epistemological theory There is also the coherence theory of truth In computational science Cache coherence , a special case of memory coherenceCoherence programming language , an experimental programming language based upon Subtext Memory coherence , a concept in computer architecture As name of IT products Coherence software , a component of Parallels Desktop for Mac, the Windows virtualization software Coherence UPNP , some free DLNA UPnP tools MediaServer MediaRender with a Python framework Coherent operating system , a UNIX clone operating system Oracle Coherence , an in memory data grid product from Oracle Other uses Coherence cognitive science , a property of mental cognitive states Coherence linguistics , what makes a text semantically meaningful Coherence music theory , a synonym for strict Rothenberg propriety in diatonic set theory Coherencetime communications systems , duration when a communication channel can be assumed to be constant Coherent company , a company specializing in equipment to make and measure coherent light See also Cohesion disambiguation Mutual coherence disambiguation disambig cs Koherence de Koh renz it Coerenza he nl Coherentie no Koherens andre betydninger pl Koherencja scn Cuirenza fi Koherenssi sv Koherens uk ... more details
In physics , coherence theory is the study of physical optics optical effects arising from partially coherence physics coherent light and radio sources. Partially coherent sources are sources where the coherencetime or coherence length are limited by Bandwidth signal processing bandwidth , by thermal noise, or by other effect. Many aspects of modern coherence theory are studied in quantum optics . The theory of partial coherence was awoken in the 1930s due to work by P. H. van Cittert and Frits Zernike . Topics in coherence theory Interferometric visibility Visibility Mutual coherence function Degree of coherence Self coherence function Coherence function General interference law Van Cittert Zernike theorem Michelson stellar interferometer Correlation interferometry Hanbury Brown and Twiss effect Phase contrast microscope Pseudothermal light Englert Greenberger duality relation Coherence Collapse See also Nonclassical light Optical coherence tomography Coherence theory of truth References Eugene Hecht and Alfred Zajac, Optics , 1974 Addison Wesley Publishing, Reading, Massachusetts ISBN 978 0 201 02835 5. Chapter 12 provides and undergrad level introduction. Category Interferometry Category Optics optics stub pt Teoria da coer ncia ... more details
repeated after cavity length distances up to this long coherence length. See also Portal Physics Coherencetime References Reflist 2 FS1037C MS188 DEFAULTSORT Coherence Length Category Electromagnetic ...In physics , coherence length is the wave propagation propagation distance from a coherence physics coherent source to a point where a wave e.g. an electromagnetic wave maintains a specified degree of coherence . The significance is that Interference wave propagation interference will be strong within a coherence length of the source, but not beyond it. This concept is also commonly used in telecommunication engineering. This article focuses on the coherence of Classical physics classical electromagnetic fields. In quantum mechanics , there is a mathematically analogous concept of the Coherence physics Quantum coherence quantum coherence length of a wave function . Formulas In radio band systems, the coherence length is approximated by math L c over n , Delta f , math where c is the speed of light in a vacuum, n is the refractive index of the Medium optics medium , and math Delta f math is the Bandwidth signal processing bandwidth of the source. In optical information transfer communications , the coherence length math L math is given by math L 2 ln 2 over pi n lambda 2 over Delta lambda ... Delta lambda math , then a path offset of math L math will reduce the fringe visibility to 50 . Coherence ... definition of coherence length has been suggested The coherence length can be measured using a Michelson ... intensity. In long distance transmission telecommunications transmission systems, the coherence ... , and diffraction . Lasers Multimode helium neon laser s have a typical coherence length of 20 cm, while the coherence length of singlemode ones can exceed 100 m. Semiconductor laser s reach some 100 m. Singlemode fiber laser s with linewidths of a few kHz can have coherence lengths exceeding 100 km. Similar coherence lengths can be reached with optical frequency comb s due to the narrow ... more details
wave delayed by green . The coherencetime of the wave is infinite since it is perfectly ... amount is defined as the coherencetime sub c sub . At 0 the degree of coherence is perfect ... the coherencetime with the time duration of the signal, nor the coherence length with the coherence area see below . The relationship between coherencetime and bandwidth It can be shown that the faster ... whose phase drifts quickly will have a short coherencetime. See Figure 2 Similarly, pulses wave packet s of waves, which naturally have a broad range of frequencies, also have a short coherencetime ... has a very short coherencetime just 10 periods or so , it is often called incoherent. The most ... monochromatic lasers. Holography requires light with a long coherencetime. In contrast, Optical coherence tomography uses light with a short coherencetime. Measurement of temporal coherence Image ... 2 and 3 have different time durations, they have the same coherencetime. In optics, temporal coherence ... for most natural light sources, the coherencetime is much shorter than the time resolution of any ... significantly over a time t equal to sub c sub . In this case, to find the temporal coherence at 2 sub c sub , one would manually time average the intensity. br style clear both Spatial coherence ... , in the extent of a wave to interfere, when averaged over time. More precisely, the spatial coherence ... over the coherencetime math tau c math . Since for a white light source such as a light bulb math ... direction and changes in phase over the coherencetime of the two light waves. An absorbing polarizer ... polarized copy of itself delayed by less than the coherencetime, partially polarized light ...No footnotes date November 2009 In physics , coherence is a property of wave s that enables stationary ..., coherence describes all properties of the Correlation function correlation between physical quantities ... waves are said to be coherent if they have a constant relative phase. The degree of coherence is measured ... more details
Cleanup date December 2007 Unreferenced date May 2009 Coherence bandwidth is a statistical measurement of the range of frequencies over which the channel can be considered flat , or in other words the approximate maximum bandwidth or frequency interval over which two frequencies of a signal are likely to experience comparable or correlated amplitude fading . If the multipath time delay spread equals D second s, then the coherence bandwidth math W c math in rad s is given approximately by the equation math W c approx 2 pi over D math The coherence bandwidth varies over Cellular network cellular or Personal Communications Service PCS communications paths because the multipath spread D varies from path to path. Application Frequencies within a coherence bandwidth of one another tend to all fade in a similar or correlated fashion. One reason for designing the CDMA IS 95 waveform with a bandwidth of approximately 1.25 Megahertz MHz is because in many urban signaling environments the coherence bandwidth W sub c sub is significantly less than 1.25 MHz. Therefore, when fading occurs it occurs only over a relatively small fraction of the total CDMA signal bandwidth. The portion of the signal bandwidth over which fading does not occur typically contains enough signal power to sustain reliable communications.This is the bandwidth over which the channel transfer function remains virtually constant. Example If the delay spread D over a particular cellular communication path in an urban environment is .19 s, then using equation above, the coherence bandwidth is approximately 333 kilohertz kHz , which is only about 27 of the IS 95 bandwidth. See also CoherencetimeCoherence length Category Wave mechanics Category Radio frequency propagation ... more details
In probability theory and statistics , coherence can have two meanings. When dealing with personal probability assessments, or supposed probabilities derived in nonstandard ways, it is a property of self consistency across a whole set of such assessments. One way of expressing such self consistency is in terms of responses to various betting propositions, as described in relation to coherence philosophical gambling strategy . ref name D Dodge, Y. 2003 The Oxford Dictionary of Statistical Terms, OUP. ISBN 0 19 920613 9. ref The coherency principle in Bayesian decision theory is the assumption that personal probabilities follow the ordinary rules for probability calculations where the validity of these rules corresponds to the self consistency just referred to and thus that consistent decisions can be obtained from these probabilities. ref name D In time series analysis , and particularly in spectral analysis , it is used to describe the strength of association between two series where the possible dependence between the two series is not limited to simultaneous values but may include leading, lagged and smoothed relationships. ref name E Everitt, B.S. 2002 The Cambridge Dictionary of Statistics, CUP. ISBN 0 521 81099 x. ref The concepts here are sometimes known as coherency ref name D and are essentially those set out for coherence signal processing . However, note that the quantity coefficient of coherence may sometimes be called the squared coherence . ref name E References references Category Probability assessment Category Statistical theory Category Frequency domain analysis Category Statistical principles de Koh renz Signalanalyse ... more details
Mutual coherence can refer to Mutual coherence physics , sinusoidal waves which exhibit a constant phase relationship Mutual coherence linear algebra , a property of a matrix describing the maximum correlation between its columns See also Coherence disambiguation disambig ... more details
Memory coherence is an issue that affects the design of computer system s in which two or more Central processing unit processor s or Multi core cores share a common area of memory computers memory . ref name censier98 Cite journal first1 L.M. last1 Censier first2 P. last2 Feautrier title A New Solution to Coherence Problems in Multicache Systems journal IEEE Transactions on Computers volume C 27 issue 12 pages 1112 1118 publisher IEEE date December 1978 doi 10.1109 TC.1978.1675013 ref ref name smith82 Cite journal first1 Alan Jay last1 Smith title Cache Memories journal ACM Computing Surveys volume 14 issue 3 pages 473 530 publisher ACM url http doi.acm.org 10.1145 356887.356892 format pdf date September 1982 doi 10.1145 356887.356892 accessdate 2011 02 25 ref ref name li89 Cite journal first1 Kai last1 Li first2 Paul last2 Hudak title Memory coherence in shared virtual memory systems journal Transactions on Computer Systems volume 7 issue 4 pages 321 359 publisher ACM url http doi.acm.org 10.1145 75104.75105 format pdf date November 1989 doi 10.1145 75104.75105 accessdate 2011 02 25 ref ref name stenstrom90 Cite journal first1 Per last1 Stenstrom title A survey of cache coherence schemes for multiprocessors journal IEEE Computer volume 23 issue 6 pages 12 24 publisher IEEE date ..., there are two or more processing elements working at the same time, and so it is possible that they simultaneously ... such a scheme is known as a memory coherence protocol , and if such a protocol is employed the system ... by the consistency model that the coherence protocol implements. In order to write correct concurrent .... When implemented in hardware, the coherency protocol can, e.g., be Directory based coherence ... protocol MOESI . References Reflist See also Bus sniffing Cache coherence Consistency model Directory based coherence protocols Distributed shared memory Race condition Parallel Computing DEFAULTSORT Memory Coherence Category Computer memory Category Parallel computing ja ru ... more details
Unreferenced date September 2007 In physics , atomic coherence is the induced Coherence physics coherence between levels of a multi level atom ic system sometimes observed when it interacts with a coherent electromagnetic field . If a coherent, narrow bandwidth laser is applied to a two level system, the wave function will undergo Rabi flopping Rabi oscillation between the ground and excited states. At some point in time the system will undergo Spontaneous emission spontaneous decay and its wave function will collapse to the ground state wave function. From there on, a new Rabi oscillation will start until the next spontaneous decay. Each spontaneous decay essentially changes the phase of the Rabi oscillation. If instead of single two level system there is a large collection of identical two level systems like a lot of the same species atoms , then all of them will begin Rabi oscillation at the same time, and therefore all of them will be in phase with each other. But due to the spontaneous decay different atoms will collapse to their ground state at different and random times and start a new Rabi oscillation . For this reason fewer and fewer atoms will be in phase as time passes by. This is called Quantum decoherence decoherence meaning individual systems, e.g. atoms, are no longer coherent with each other . Atomic coherence can involve more than two levels and its preparation more than a single laser. An atomic coherence is essential in research on several effects, such as electromagnetically induced transparency EIT , lasing without inversion LWI , enhanced dispersion without absorption , Stimulated Raman Adiabatic Passage STIRAP and nonlinear optical interaction with enhanced efficiency. See also Rabi cycle Category Atomic, molecular, and optical physics Category Photonics atomic physics stub ... more details
In computing , Oracle Coherence a Java based in memory data grid product provides data caching, data replication and distributed computing services. ref http www.oracle.com technetwork middleware coherence overview index.html Oracle Coherence Product Page ref It addresses issues with traditional database centric applications, aiming to improve on reliability, scalability and performance. ref https www.packtpub.com oracle coherence 3 5 book Packt Pub Oracle Coherence 3.5 ref Coherence uses Backing Map to allow further persistence to databases and other storage. Though the product is implemented in Java, .NET and C connectivity is offered though the Coherence Extend component. Some Coherence usage patterns are open source and are listed and supported though the Oracle Coherence incubator. ref http coherence.oracle.com display INCUBATOR Home Coherence Incubator ref These patterns implement features such as messaging, work distribution and data replication across WANs with Coherence. Tangosol Inc. developed the original Coherence product. Oracle Corporation acquired Tangosol in April 2007, when Coherence had about 120 direct customers. ref http www.oracle.com corporate press 2007 mar tangosol.html Oracle acquires Tangosol ref It was also embedded in a few products from companies that included some of Oracle s competitors. ref http www.gartner.com resources 147600 147673 oracle to acquire a lead in 147673.pdf Oracle to Acquire a Lead in Extreme Transaction Processing ref See also Computer cluster Complex event processing Distributed computing Distributed transaction processing Extreme Transaction Processing Grid computing Transaction processing Distributed hash table References Reflist External links http www.oracle.com technetwork middleware coherence overview index.html Oracle Coherence Product page http forums.oracle.com forums forum.jspa?forumID 480 Oracle Coherence User ... Oracle Coherence ... more details
0 math is the central frequency of the light and math tau c math is the coherencetime of the light. Degree of second order coherence Image coherence g2.png thumb Figure 2 This is a plot of g sup 2 sup as a function of the delay normalized to the coherence length sub c sub . The blue curve ... beam , and c bunching chaotic light . sub c sub is the coherencetime the time scale of photon ...In optics , correlation functions are used to characterize the statistical and Coherence physics coherence properties of an electromagnetic field. The degree of coherence is the normalized correlation of electric fields. In its simplest form, termed math g 1 math , it is useful for quantifying the coherence ... to mesons cf. Bose Einstein correlations Degree of first order coherence Image coherence g1.png thumb Figure 1 This is a plot of g sup 1 sup as a function of the delay normalized to the coherence ... pulses. When one deals with stationary states, where the statistical properties do not change with time, one can replace the ensemble average with a time average. If we restrict ourselves to plane parallel ... on math t 1 math , but on the time delay math tau t 1 t 2 math or math tau t 1 t 2 frac z 1 z 2 ... , or Sagnac interferometer , one splits an electric field into two components, time delays one component, and then recombines them. The intensity of resulting field is measured as a function of the time ... by math g 1 tau math . More generally, when combining two space time points from a field visibility ... math Note that this is not a generalization of the first order coherence If the electric fields ... 2 0 math . Nevertheless the second order coherence for an average over fringe of complementary interferometer ... trigger trigger level applied to the signal within the range of coherence . Examples of g sup 2 sup ... ref Degree of nth order coherence A generalization of the first order coherence math g n mathbf ... A generalization of the second order coherence math g n mathbf r 1,t 1 mathbf r 2,t 2 dots mathbf r ... more details
Confusing date March 2011 Expert subject date February 2009 Infobox OS name Coherence family Linux, Windows, Mac OS X, BSD, Open Solaris developer Frank Scholz website http coherence.beebits.net coherence.beebits.net license MIT latest release version 0.6.6.2 latest release date January 2, 2010 support status Current As a stand alone application Coherence acts as a DLNA UPnP MediaServer and exports local and remote media files via its backends to other UPnP clients. And together with a supported client it forms a controllable DLNA UPnP MediaRenderer. Coherence also acts as a Python programming language Python framework to enable applications access to digital living network resources Standalone mode As a stand alone application, Coherence acts as a DLNA UPnP MediaServer. It exports to UPnP DLNA clients local and or remote media via its several back ends. In conjunction up with GStreamer or Rhythmbox , it forms a controllable DLNA UPnP MediaRenderer. Coherence features many back ends as Ampache AmpacheStore Apple Trailers AppleTrailersStore Axis Cam AxisCamStore Elisa ElisaMediaStore Flickr FlickrStore local filesystem FSstore Gallery2 Gallery2Store LastFm LastFMStore LolCats LolcatsStore Youtube YoutubeStore Since release 0.6.0, Coherence features audio transcoding based on Gstreamer ... Coherence provides a framework written in Python, with an emerging DBus API, enabling their application to participate in digital living networks. ref Cite web title Coherence Homepage url http coherence.beebits.net ref at the moment primarily the UPnP universe. The core of Coherence provides an implementation ... Coherence Official Documentation History Coherence has its roots in the work of ref Cite web title Coherence History url http coherence.beebits.net wiki WikiStart History ref http frungy.org ... Coherence Freshmeat coherenceCoherence http pypi.python.org pypi CoherenceCoherence at Python CheeseShop DEFAULTSORT Coherence Upnp Category Cross platform free software Category Free multimedia software ... more details
In mathematics and particularly category theory , a coherence theorem is a tool for proving a coherence condition . Typically a coherence condition requires an infinite number of equalities among compositions of structure maps. A coherence theorem states that, in order to be assured that all these equalities hold, it suffices to check a small number of identities. Examples Consider the case of a monoidal category . Recall that part of the data of a monoidal category is an associator , which is a choice of morphism math alpha A,B,C colon A otimes B otimes C rightarrow A otimes B otimes C math for each triple of objects math A,B,C math . Mac Lane s coherence theorem states that, provided the following diagram commutes for all quadruples of objects math A,B,C, D math , Image monoidal category pentagon.png any pair of morphisms from math cdots A N otimes A N 1 otimes cdots otimes A 2 otimes A 1 math to math A N otimes A N 1 otimes cdots otimes A 2 otimes A 1 cdots math constructed a compositions of various math alpha A,B,C math are equal. References Saunders Mac Lane Mac Lane, Saunders 1971 . Categories for the working mathematician . Graduate texts in mathematics Springer Verlag. Especially Chapter VII. Category Category theory ... more details
cleanup date March 2008 Coherence in linguistics is what makes a text semantics semantically meaningful. It is especially dealt with in text linguistics . Coherence is achieved through syntactical features such as the use of deictic , anaphora linguistics anaphoric and cataphora cataphoric elements or a logical tense structure, as well as presupposition s and implications connected to general world knowledge. The purely linguistic elements that make a text coherent are subsumed under the term Cohesion linguistics 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. But within this textual world the arguments also have to be connected logically so that the reader hearer can produce coherence. Continuity of senses implies a link between cohesion and the theory of Schemata initially proposed by Bartlett in 1932 which creates further implications for the notion of a text . Schemata, subsequently distinguished into Formal and Content Schemata in the field of English as a Foreign or Second Language TESOL by Carrell & Eisterhold in 1983 are the ways in which the world is organized in our .... It can thus be assumed that a text is not always one because the existence of coherence is not always a given. On the contrary, coherence is relevant because of its dependence upon each individual ... A Bibliography of Coherence and Cohesion by Wolfram Bublitz at Universit t Augsburg DEFAULTSORT Coherence Linguistics ling stub Category Syntax Category Semantics ar ca Coher ncia de ... more details
Psychology sidebar Coherence therapy is a system of psychotherapy based in the theory that symptoms of Mood psychology mood , thought and behavior are produced coherently according to the person s current models of reality, most of which are implicit and unconscious. It was founded by Bruce Ecker and Laurel ... Deleted image removed Image ColorCoc4Web.gif thumb Cover of the 1996 book. The basis of coherence therapy is the principle of symptom coherence. This is the view that any response of the brain mind ... of symptom coherence maintains that an individual s seemingly irrational, out of control ... of self and world, rather than a disorder or pathology. Coherence therapy is considered a type of psychological ... coherence is fully explicit and rigorously operationalized, guiding and informing the entire methodology. The process of coherence therapy is experiential rather than analytic, and in this regard ... and Couples location Phoenix, AZ publisher Zieg, Tucker & Theisen isbn ref Symptom coherence Symptom coherence is defined by Ecker and Hulley as follows a A person produces a particular symptom because ... ref There are several forms of symptom coherence. For example, some symptoms are necessary because ..., L. year 2006 title Coherence therapy practice manual and training guide location Oakland, CA publisher ... in shaping experience and behavior. History Coherence therapy was developed in the late 1980s and early ... experiences of the underlying coherence of their symptoms from the first session. In addition to creating ... Brief Therapy DOBT . In 2005 , Ecker and Hulley began calling the system coherence therapy in order ... Toomey present evidence that coherence therapy may be the system of psychotherapy which, according ... and Toomey argue that the mechanism of change in coherence therapy uniquely correlates with the recently ... 722 726 doi 10.1038 35021052 pmid 10963596 ref The indications that coherence therapy achieves implicit ... links http www.coherencetherapy.org CoherenceTherapy.org Coherence Therapy Depth Oriented Brief ... more details
In computing, cache coherence also cache coherency refers to the consistency of data stored in local cache computing caches of a shared resource. Image Cache Coherency Generic.png thumb right 400px Multiple Caches of Shared Resource When clients in a system maintain CPU cache caches of a common memory resource, problems may arise with inconsistent data. This is particularly true of CPUs in a multiprocessing system. Referring to the Multiple Caches of Shared Resource figure, if the top client has a copy of a memory block from a previous read and the bottom client changes that memory block, the top client could be left with an invalid cache of memory without any notification of the change. Cache coherence is intended to manage such conflicts and maintain consistency between cache and memory. Coherency protocol A coherency protocol is a protocol which maintains the consistency between all the caches in a system of distributed shared memory . The protocol maintains memory coherence according to a specific consistency model . Older multiprocessors support the sequential consistency model, while modern shared memory systems typically support the release consistency or weak consistency models. Transitions between states in any specific implementation of these protocols may vary. For example, an implementation may choose different update and invalidation transitions such as update on read, update on write, invalidate on read, or invalidate on write. The choice of transition may affect the amount of inter cache traffic, which in turn may affect the amount of cache bandwidth available ... have been devised for maintaining cache coherence, such as MSI protocol , MESI protocol MESI aka ... MESIF , Write once cache coherence write once , Synapse protocol Synapse , Berkeley protocol Berkeley ... a cache coherent system. Coherence models differ in performance and scalability each must be evaluated ... cache ja ru simple Cache coherence ... more details
Thematic coherence is a term that can be used both in linguistics as a literary technique or in developmental psychology in the last case, it s said to be an organization of a set of meanings in and through an event. ref name BloomeIII David Bloome, Stephanie Power Carter, Beth Morton Christian, Sheila Otto, Discourse analysis & the study of classroom language & literacy events a microethnographic perspective Routledge, 2004 , p.33. ISBN 0805853200, ISBN 9780805853209 ref In education , for example, the thematic coherence happens when a child during a classroom session understands what all the talking is about. ref name BloomeIII This expression was termed by Habermas and Bluck 2000 ref Habermas, T., & Bluck, S. 2000 . Getting a life The development of the life story in adolescence . Psychological Bulletin, 126, 748 769. ref alongside with other terms such as temporal coherence , biographical coherence , and causal coherence to examining the coherence that people during their all process of life since they were a child until adolescence and adulthood , but especially in childhood and adolescence have to narrate their own personal experiences or many different episodes in their life and that needs to be structured within a Context principle context . ref Robyn Fivush, Catherine A. Haden, Autobiographical memory and the construction of a narrative self developmental and cultural perspectives Routledge, 2003 , p.192. ISBN 0805837566, ISBN 9780805837568 ref In conversation although this technique also can be found in literature the thematic coherence is when a person or character is able to derive a general theme or principle about the self based on a narrated sequence of events. ref name McAdams Dan P. McAdams, The redemptive self stories Americans live Oxford University Press ... coherence are rare before adolescence but increase in prominence as a person moves toward emerging ... of coherence in adolescents life narratives. Narrative Inquiry , 11, 35 54. Category Developmental ... more details
Expert subject mathematics date February 2009 In mathematics , and particularly category theory a coherence condition is a collection of conditions requiring that various compositions of elementary morphisms are equal. Typically the elementary morphisms are part of the data of the category. An illustrative example a monoidal category Part of the data of a monoidal category is a chosen morphism math alpha A,B,C math , called the associator math alpha A,B,C colon A otimes B otimes C rightarrow A otimes B otimes C math for each triple of objects math A,B,C math in the category. Using compositions of these math alpha A,B,C math , one can construct a morphism math cdots A N otimes A N 1 otimes A N 2 otimes cdots otimes A 1 rightarrow A N otimes A N 1 otimes cdots otimes A 2 otimes A 1 cdots . math Actually, there are many ways to construct a morphism from math cdots A N otimes A N 1 otimes cdot otimes A 2 otimes A 1 math to math A N otimes A N 1 otimes cdots otimes A 2 otimes A 1 cdots math as a composition of various math alpha A,B,C math . One coherence condition that is typically imposed is that these compositions are all equal. Typically one proves a coherence condition using a coherence theorem , which states that one only needs to check a few equalities of compositions in order to know that the rest also hold. In the above example, one only needs to check that, for all quadruples of objects math A,B,C,D math , the following diagram commutes Image monoidal category pentagon.png Further examples Two simple examples that illustrate the definition are as follows. Both are directly from the definition of a category. Identity Let nowrap f A B be a morphism of a category containing ... the same objects as f . We have, accordingly, the following coherence statement nowrap 1 f small ... coherence statement nowrap 1 h small o small g small o small f h small o small g small o small f . In these two particular examples, the coherence statements are theorems for the case of an abstract ... more details
Context date October 2009 one source date May 2010 Two sinusoidal oscillations of the same frequency are said to be mutually coherent if they exhibit a constant phase relationship during the course of time. See also Coherence physics Energy Phased array External links http www.ccr.jussieu.fr scbs b.htm Z.W.Wolkowski The Concept of Coherence Considered as a Systems Isomorphism physics stub Category Wave mechanics ... more details
. For such signals, the concept of coherence has been extended by using the concept of time frequency distributions to represent the time varying spectral variations of non stationary signals ...Other uses of CoherenceCoherence disambiguation Coherence The Frequency domain spectral coherence is a statistic that can be used to examine the relation between two Signal electrical engineering signals or data sets. It is commonly used to estimate the Power physics power transfer between input and output of a linear system . If the signals are Ergodic process ergodic , and the Transfer function system function Linear system linear , it can be used to estimate the causality between the input and output. Definition and Formulation The coherence sometimes called magnitude squared coherence between ... the restrictions noted above ergodicity, linearity the coherence function estimates the extent to which y t may be predicted from x t by an optimum linear least squares function. br Values of coherence ... input x t and single output y t , the coherence will always be equal to one. To see this, consider ... xx 2 1 math . Thus, analysis of a constant parameter linear system with the coherence statistic offers no useful information. br If x t and y t are completely unrelated the coherence will be zero. If C ... output due to input x t as well as other inputs. br The coherence of a linear system therefore ... the autospectral density of ocean water level over a long period of time. Image Ocean Lake Worth ... at which the groundwater levels are influenced by the ocean surface levels, we compute the coherence ... as the output variable. The computed coherence is shown in figure 4 note that coherence is often denoted as math gamma 2 math . Image Well PBF 5 Ocean Coherence.jpg thumb left Figure 4 Coherence between ... , then values of the coherence can be erroneous. Another common mistake is to assume a causal input ... can contribute to or corrupt the coherence. Extension to non stationary signals If the signals ... more details
longitudinally in time. A property of low coherence interferometry is that interference, i.e. the series ... degree of coherence, i.e. the interference envelope and carrier dependent on reference arm scan or time ...Interventions infobox Name Optical coherence tomography Image Nibib 030207 105309 sarcoma.jpg Caption Optical Coherence Tomography OCT image of a sarcoma ICD10 ICD9 MeshID D041623 OPS301 OPS301 3 300 OtherCodes Optical coherence tomography OCT is an optical signal acquisition and processing method. It captures ... media e.g., biological tissue . Optical coherence tomography is an interferometry interferometric ... have been employed , optical coherence tomography has achieved sub micrometer resolution with very wide spectrum sources emitting over a 100 nm wavelength range . Optical coherence tomography is one ... of optical coherence tomography, frequency domain optical coherence tomography, provides advantages ... coherence tomography systems are employed in diverse applications, including art conservation and diagnostic ... Guagliumi, MD, Andrew M. Rollins, PhD, Daniel I. Simon, MD . Intracoronary Optical Coherence Tomography ... Introduction Image HautFingerspitzeOCT.gif thumb 300px Optical coherence tomography tomogram of a fingertip ... first6 W last7 Hee first7 MR last8 Flotte first8 T last9 Gregory first9 K title Optical coherence ... science.1957169 ref optical coherence tomography OCT with micrometer resolution and cross sectional ... coherence tomography a review of clinical development from bench to bedside. volume 12 issue 5 pages .... K. Hitzenberger, W. Drexler, G. Kamp, and H. Sattmann, In Vivo Optical Coherence Tomography, Am. J ... In vivo retinal imaging by optical coherence tomography pmid 19829430 year 1993 last1 Swanson first1 ... James G. title Ultrahigh resolution ophthalmic optical coherence tomography journal Nature Medicine ... 111 issue 2 pages 396 406 ref OCT bases itself upon Optical interferometry Low coherence interferometry low coherence interferometry . ref cite journal doi 10.1109 51.870229 title Current technical ... more details
Citations missing date October 2008 Coherence theory of truth regards truth as coherence within some specified set of sentences, propositions or beliefs. ref http plato.stanford.edu entries truth coherence ... propositions only derivatively according to their coherence with the whole. While modern coherence ... upon coherence, others, particularly those with strong religious beliefs hold that the such truth ... 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 critical factor in judging its coherence and validity. In other words, the set of base concepts in a universe of discourse must be logically consistent before many theorists consider that the coherence theory of truth is applicable. Varieties of coherence theories Expand section date September 2008 According to one view, the coherence theory of truth is the theory of knowledge which maintains that truth ... Quine & Ullian 1978 . However, coherence theories of truth do not claim merely that coherence ... t exist outside of a system. According to another version of coherence theory, championed especially by H.H. Joachim , truth is a systematic coherence that involves more than logical consistency. In this view ... of truth that is proportionate to how fully they approximate this ideal. Baylis 1962 . Coherence theories in specialized domains Some versions of coherence theory have been claimed to characterize ... R. 1969. Coherence Theory of Truth , Encyclopedia of Philosophy , Vol.2. Macmillan 130 131. ref A claim ... by side, for example, the various noneuclidean geometry alternative geometries . On the whole, coherence ... from the other major theories of truth. ref White, Alan R. 1969. Coherence Theory of Truth , Encyclopedia ... Coherence theories distinguish the thought of continental rationalism rationalist philosophers, especially ... White, Alan R. 1969. Coherence Theory of Truth , Encyclopedia of Philosophy , Vol.2. Macmillan 130 ... more details
Unreferenced date December 2009 Orphan date December 2009 A Superconducting coherence length , usually denoted as math xi math , can be interpreted in two different ways It gives approximate spatial dimension size of the Cooper pair , It sets the length scale on which the superconducting order parameter changes considerably. The superconducting coherence length math xi math , Greek lowercase xi is one of two parameters in a Ginzburg Landau theory of superconductivity. It is given by math xi sqrt frac hbar 2 2 m alpha frac 2 hbar v f pi E g math See also phenomenological Ginzburg Landau theory of superconductivity microscopic BCS theory of superconductivity DEFAULTSORT Superconducting Coherence Length Category Superconductivity uk ... more details
Encyclopedia
top
