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Topic: Cross-correlation

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Correlation - Wikipedia, the free encyclopedia The correlation is 1 in the case of an increasing linear relationship, −1 in the case of a decreasing linear relationship, and some value in between in all other cases, indicating the degree of linear dependence between the variables. However, correlations are not presumed to be acausal, though the causes may not be known. The correlation coefficient defines completely the dependence structure only in very particular cases, for example when elliptic cumulative distribution functions are used (this case includes for example the multivariate normal distribution). en.wikipedia.org /wiki/Correlation   (1003 words)

Cross Correlation Cross correlation is a standard method of estimating the degree to which two series are correlated. The maximum cross correlation for all angles and for each of the two masks is retained for each position. Note that this is a special case of the expression for calculating the cross correlation using Fourier transforms. astronomy.swin.edu.au /~pbourke/analysis/correlate   (1162 words)

LAB717 - Correlation Measurements A major use of cross correlation is the detection of signals buried in noise. The reference is cross correlated with the waveform in Trace 2, as shown in Trace A. This waveform is further enhanced by averaging in Trace B. The existence and location of the return echo is easily determined in the lower trace, even though it was invisible in the original signal. The correlation function for each time delay is plotted vs. the time delay to form the correlation function, as shown in Trace A. While averaging can be used to extract a signal from random noise, correlation can detect a signal in the presence of a deterministic signal such as a sinusoid. www.lecroy.com /tm/Library/labs/LAB717?menuid=2   (554 words)

Correlation: cross-correlation and autocorrelation Cross-correlation is the method which basically underlies implementations of the Fourier transformation: signals of varying frequency and phase are correlated with the input signal, and the degree of correlation in terms of frequency and phase represents the frequency and phase spectrums of the input signal. A function which is related to the correlation function, but arithmetically less complex, is the average magnitude difference function. If the signals are identical, then the correlation coefficient is 1; if they are totally different, the correlation coefficient is 0, and if they are identical except that the phase is shifted by exactly www.csis.ul.ie /ccmcm/cs5611/acoustics/analysis/node18.html   (205 words)

CROSSMOD -- Image Cross Correlation Cross Correlate the 'original' image band with the 'reference' band to produce B0 and B1 coefficient matrices. In the multi-spectral image database ms.pix, cross model channel 3 (the original image) with channel 2 (the reference image), and place the output image into the first channel of b0.pix and b1.pix. Correlation is performed on a window of size (2 * KSIZE + 1) pixels. www.pcigeomatics.com /cgi-bin/pcihlp/CROSSMOD   (510 words)

Research Training Network-Cross Correlation Fortunately, cross correlation effects may lead to line-narrowing, thanks to the mutual cancellation of relaxation mechanisms.This is the basis of the so-called TROSY effect (transverse relaxation optimized spectroscopy),which may be regarded as another manifestation of cross-correlation effects.The presence of a paramagnetic center leads to many additional interactions and thus also introduces additional cross correlation phenomena. Therefore cross correlation can provide valuable structural information that is not accessible by other techniques.In particular, cross correlation rates depend on the motional correlation time, and therefore increase with increasing molecular mass. The objective of this network is a better understanding of cross-correlation effects, the development of the underlying theory and development of new methods to exploit many attractive properties of cross correlation. www.chimie.ens.fr /Resonance/francais/rtn.html   (354 words)

Cross Correlation Rates Cross correlation effects arise from the interference of relaxation mechanisms, which in paramagnetic molecules can be due to the presence of unpaired electron spin density. Cross correlation rates were measured for the Ce substituted derivative as well as for the analog diamagnetic derivative CaLaCb. In the case of isotropic molecular motions and axially isotropic magnetic susceptibility tensors, the cross correlation rate (ccr), expressed in Hertz, due to the interference between Curie spin relaxation and dipolar I-S coupling is given by the following equation, assuming that the molecule is rigid and that the electron spin is localized on the metal: www.cerm.unifi.it /SPECTRO/ccr.html   (193 words)

Cross-site Correlation of DNS Failures To test our assumption, we study the correlation of DNS lookup failures across PlanetLab. From this graph, we can see some minor correlation in failures, shown as downward spikes in the percentage of available nodes, but most of the variation in availability seems largely uncorrelated. If failure across sites is correlated, this assumption is violated, and a cooperative lookup scheme is less feasible. www.cs.princeton.edu /nsg/papers/codns_osdi_04/codns_html/node6.html   (387 words)

Fast Normalized Cross-Correlation Although it is well known that cross correlation can be efficiently implemented in the transform domain, the normalized form of cross correlation preferred for feature matching applications does not have a simple frequency domain expression. This short paper shows that unnormalized cross correlation can be efficiently normalized using precomputing integrals of the image and image 10] for obtaining normalized cross correlation from transform domain convolution. www.idiom.com /~zilla/Work/nvisionInterface/nip.html   (3204 words)

Donoghue Lab The cross-correlation value is related to the ordinary linear correlation coefficient. If you plot the various correlation coefficients at various lag times against the lag times themselves, you obtain a cross-correlogram. Shuffle correction makes a permutation on the order of trials for one of the two data sets, recomputes its correlation function, then subtracts the mean shuffled correlation function from the previously calculated correlation function. donoghue.neuro.brown.edu /crosscorr.php   (318 words)

OhioLINK ETD: Tang, Yuxiao These two estimators are functions of the sample cross correlations computed at each time point. We discuss the problem of estimating the correlation coefficient between two variables observed in a longitudinal study. When some observations are missing with ignorable missing-data mechanism, we propose four estimators: the group weighted mean estimator, the marginal mean estimator, the estimator based on the weighted Fisher's z values, and the weighted marginal mean estimator. rave.ohiolink.edu /etdc/view?acc_num=osu1078857542   (379 words)

Correlation and Cross Sections The correlation and cross section generation capabilities within TerraStation are second to none. Cross sections comprising a variety of data types can also be used for interactive pick editing. Standard cross section displays containing logs, patterns and shading are quickly created and viewed on the screen. www.terrasciences.com /correlat.htm   (636 words)

A simulation study to examine the use of cross-correlation as an estimate of surface EMG cross talk -- Lowery et al. 94 (4): 1324 -- Journal of Applied Physiology In this paper, the relationship between cross talk and the cross-correlation of surface EMG signals is examined by using model A simulation study to examine the use of cross-correlation as an estimate of surface EMG cross talk -- Lowery et al. value of the cross-correlation function, the correlation increased jap.physiology.org /cgi/content/full/94/4/1324   (6029 words)

GPS Cross Correlation Properties The cross correlation for sequences A and B. What this is telling you is that if you are looking for satellite A, you won't get it confused with satellite B. More generally, you will have 8-10 satellites being received at a single time. Note: while the code is a series of 0's and 1's, you use 1's and -1's when computing correlations. Will you get mixed up while looking for satellite A? We now define 4 PRN sequences A, B, C, D. This is A cross-correlate with B+C+D. This is A cross-correlate with A+B+C+D. This means you will be able to extract signal A even if there are other PRN sequences in the same time series. www.colorado.edu /engineering/ASEN/asen5090/correl.html   (238 words)

New Designs for Signal Sets with Low Cross-correlation, Balance Property and Large Linear Span: GF(p) Case (ResearchIndex) Abstract: New designs for families of sequences over GF (p) with low cross correlation, balance property and large linear span are presented. The key idea of the new designs is to use short p-ary sequences of period v with the 2-level auto correlation function to construct a set of long sequences with the designed properties. 5 On mutual correlation of sequences (context) - Sidelnikov - 1978 citeseer.ist.psu.edu /299506.html   (725 words)

The cross-correlation evidence The above operation basically computes the average of all the elements of the matrix and represents the average cross correlation between the various critical band time trajectories at time t. The cross correlation matrix between the time trajectories (length of trajectory The average cross correlation at time t was then computed as: www.clsp.jhu.edu /ws96/ris/update/node3.html   (104 words)

ISS Products: K2T Multifrequency Cross-Correlation Phase and Modulation Fluorometer The K2 is a multifrequency cross-correlation phase and modulation fluorometer for decay times determinations with picosecond resolution; for the measurement of rotational correlation times of molecules; phase and modulation resolved spectra; and for phase and modulation resolved kinetics lifetime. The K2 family of Multifrequency Cross-Correlation Phase and Modulation Fluorometers introduces a new approach to fluorescence and phosphorescence instrumentation for the research laboratory. Alba FCS: Confocal Imaging & Fluorescence Correlation Spectrometer www.iss.com /Products/K2.html   (396 words)

Cross-correlation -- Facts, Info, and Encyclopedia article In (Click link for more info and facts about signal processing) signal processing, cross-correlation or sometimes simply correlation is a measure of similarity of two (Any communication that encodes a message) signals, commonly used to find features in an unknown signal by comparing it to a known one. (A statistical relation between two or more variables such that systematic changes in the value of one variable are accompanied by systematic changes in the other) Correlation www.absoluteastronomy.com /encyclopedia/c/cr/cross-correlation.htm   (181 words)

Improved Cross-Correlation Dynamic-Light-Scattering Method The cross-correlation processing is formulated to exploit the fact that single-scattering speckle arises from inside of the incident laser beam and is correlated over an angular range wider than that of multiple-scattering speckle, which can originate from anywhere within the sample. The outputs of the photodetectors are cross-correlated in such a way as to make it possible to discriminate against the multiple-scattering contribution to the speckle pattern. www.nasatech.com /Briefs/Mar00/LEW16781.html   (820 words)

Cross correlation In the middle window you may wish to type in order numbers that should not be used in the cross correlation. You may also push the toggle button if you want the mean correlation function for each spectrum to be displayed (a good choice for the first time round). You may push the toggle button if you want the correlation function for each order of each spectrum to be displayed. www.saao.ac.za /facilities/giraffe/node33.html   (307 words)

IDENTIFICATION OF PHASE SHIFT USING CROSS CORRELATION Theoretical derivation The similarity in the pattern of two time series x and y, each with N data points, can be calculated by using the coefficient of cross correlation rxy(k), where k is a variable that designates a time (or phase) shift of one series with respect to the other (Chatfield, 1984). In this paper we present an alternative method, which uses the 95% confidence interval of the cross correlation and its corresponding values in the time domain to identify phase shifting in time series data. The low 95% confidence interval of rxy(m) will identify two other correlation values rxy(m-l) and rxy(m+n), which can then be converted to values in the time domain, m-l and m+n (Figure 1). www.asb-biomech.org /onlineabs/NACOB98/177   (828 words)

Cross correlation, and a sequence something like `scross' Cross correlation, and a sequence something like `scross'   Cross correlation, and a sequence something like `scross' The 0.1,0.3 parameters in `cmplxfilt' are quite arbitrary, and the optimum values to use are in fact best determined either by looking at the power spectrum of the data to be filtered, or by consideration of the types of features one wants to emphasise in the determination of the correlation (Hunstead, 1980). star-www.rl.ac.uk /star/dvi/sun86.htx/node89.html   (335 words)

Hypersignal Block Diagram Function Reference - Support The Correlate block is used to cross-correlate two input frames of data to produce one output frame of data. It is important to notice that correlation in general is a time consuming process, and the study of the equation above will reveal the extreme likelihood of the output getting large enough to warrant FLOAT precision; if the correlation yields values in excess of 32767, the INT precision will overflow, yielding incorrect results. The correlation performed is frame-based, and the implementation formula is as follows: R[d] = SUM(x[i]y[i-d]) where d is the lag (or amount of time shift) www.hypersignal.com /support/php/block/FunctionRef.php?block=Correlation   (191 words)

xcorr (Signal Processing Toolbox) In general, the correlation function requires normalization to produce an accurate estimate (see below). See reference [1] for more information on the properties of biased and unbiased correlation estimates. For more information on estimating covariance and correlation functions, see [1] and [2]. www.haystack.edu /computing/matlab5.3.1/help/toolbox/signal/xcorr.html   (577 words)

► » Generalized Cross Correlation Cross correlation is simply a way to measure the amount of You need what has been termed Generalised Cross Correlation. If there are more than two paths, correlating only two www.comp-one.net /Generalized-Cross-Correlation-7892394.html   (562 words)

Cross-Correlation Based Multichannel Blind Equalization (ResearchIndex) We propose a new algorithm which estimates the channels using as basic tool the phase of the cross spectrum of functions of the observations. citeseer.ist.psu.edu /143441.html   (287 words)

Meeting Recorder: PDA cross-correlation What we see from the figure is that there is definitely a visible correlation between the actual speaker and the dominant peak in the cross-correlation. Thus, I plotted just the middle 50 points of the cross correlation function. Moreover, a very simple thresholding scheme goes quite a lot of the way towards usefully discriminating the voices from the separate directions, although it is pretty noisy and not particularly precise. www.icsi.berkeley.edu /~dpwe/research/mtgrcdr/xcorr.html   (438 words)

Cross-Correlation The last equality above follows from the correlation theorem (§7.4.7). www-ccrma.stanford.edu /~jos/mdft/Cross_Correlation.html   (228 words)

Citebase - Cross-correlation of the unresolved X-ray background with faint galaxies In this paper, we present the results of a cross-correlation between the residual, unresolved X-ray photons in a very deep X-ray survey and the positions of faint galaxies, in order to examine the importance of these objects at even fainter flux levels. However, the angular form of the correlation is seen to be qualitatively similar to that expected for clusters of galaxies and the X-ray emission could be associated with hot gas in clusters or with QSOs within galaxy clusters rather than emission from individual faint galaxies. Use the Correlation Generator to explore the correlation between download impact ("hits") and citation impact. citebase.eprints.org /cgi-bin/citations?archiveID=oai:arXiv.org:astro-ph/9906237   (522 words)

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