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Journal articles on the topic 'Cross spectral coherency analysis'

Author: Grafiati

Published: 4 June 2021

Last updated: 1 February 2022

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1

Maraun, D., and J. Kurths. "Cross wavelet analysis: significance testing and pitfalls." Nonlinear Processes in Geophysics 11, no. 4 (2004): 505–14. http://dx.doi.org/10.5194/npg-11-505-2004.

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Abstract. In this paper, we present a detailed evaluation of cross wavelet analysis of bivariate time series. We develop a statistical test for zero wavelet coherency based on Monte Carlo simulations. If at least one of the two processes considered is Gaussian white noise, an approximative formula for the critical value can be utilized. In a second part, typical pitfalls of wavelet cross spectra and wavelet coherency are discussed. The wavelet cross spectrum appears to be not suitable for significance testing the interrelation between two processes. Instead, one should rather apply wavelet coh

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Lainscsek, Claudia, Manuel E. Hernandez, Howard Poizner, and Terrence J. Sejnowski. "Delay Differential Analysis of Electroencephalographic Data." Neural Computation 27, no. 3 (2015): 615–27. http://dx.doi.org/10.1162/neco_a_00656.

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We propose a time-domain approach to detect frequencies, frequency couplings, and phases using nonlinear correlation functions. For frequency analysis, this approach is a multivariate extension of discrete Fourier transform, and for higher-order spectra, it is a linear and multivariate alternative to multidimensional fast Fourier transform of multidimensional correlations. This method can be applied to short and sparse time series and can be extended to cross-trial and cross-channel spectra (CTS) for electroencephalography data where multiple short data segments from multiple trials of the sam

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While, James, Andrew Jackson, Dirk Smit, and Ed Biegert. "Spectral analysis of gravity gradiometry profiles." GEOPHYSICS 71, no. 1 (2006): J11—J22. http://dx.doi.org/10.1190/1.2169848.

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The gravity gradient tensor (whose components are the second derivatives of the gravitational potential) is a symmetric tensor that, ignoring the constraint imposed by Laplace's equation, contains only six independent components. When measured on a horizontal plane, these components generate, in the spectral domain, six power spectral densities (PSDs) and fifteen cross-spectra. The cross-spectra can be split into two groups: a real group and a pure imaginary group. If the source distribution is statistically stationary, 1D spectra can be found from the 2D spectra via the slice theorem. The PSD

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Kleeman, Richard. "Spectral Analysis of Multidimensional Stochastic Geophysical Models with an Application to Decadal ENSO Variability." Journal of the Atmospheric Sciences 68, no. 1 (2011): 13–25. http://dx.doi.org/10.1175/2010jas3546.1.

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Abstract Simple linear models with additive stochastic forcing have been rather successful in explaining the observed spectrum of important climate variables. Motivated by this, the authors analyze the spectral character of such a general stochastic system of finite dimension. The spectral matrix is derived in the case that the spectrum is a linear combination of dynamical variables and their stochastic forcings. It is found that the most convenient basis for analysis is provided by the normal modes. In general the spectrum consists of two pieces. The first “diagonal” piece is a symmetric Lore

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Nuzhdina, M. A. "Connection between ENSO phenomena and solar and geomagnetic activity." Natural Hazards and Earth System Sciences 2, no. 1/2 (2002): 83–89. http://dx.doi.org/10.5194/nhess-2-83-2002.

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Abstract. Connections between El Niño – Southern Oscillation (ENSO) phenomena and indices of solar activity and geomagnetic disturbance were investigated. Spectral analysis of the ENSO-data was carried out. Oscillations with periods of about 11–12, 5–6, 2–3 years were found. Correlative and cross-spectral analysis was carried out to estimate connections between ENSO data, and solar and geomagnetic indices. Functions of coherency and phase were calculated.

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Chen, Zhongbiao, Biao Zhang, Vladimir Kudryavtsev, Yijun He, and Xiaoqing Chu. "Estimation of Sea Surface Current from X-Band Marine Radar Images by Cross-Spectrum Analysis." Remote Sensing 11, no. 9 (2019): 1031. http://dx.doi.org/10.3390/rs11091031.

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The cross-spectral correlation approach has been used to estimate the wave spectrum from optical and radar images. This work aims to improve the cross-spectral approach to derive current velocity from the X-band marine radar image sequence, and evaluate the application conditions of the method. To reduce the dependency of gray levels on range and azimuth, radar images are preprocessed by the contrast-limited adaptive histogram equalization. Two-dimensional cross-spectral coherence and phase are derived from neighboring X-band marine radar images, and the phases with large coherences are used t

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Privalsky, V. "On studying relations between time series in climatology." Earth System Dynamics 6, no. 1 (2015): 389–97. http://dx.doi.org/10.5194/esd-6-389-2015.

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Abstract. Relationships between time series are often studied on the basis of cross-correlation coefficients and regression equations. This approach is generally incorrect for time series, irrespective of the cross-correlation coefficient value, because relations between time series are frequency-dependent. Multivariate time series should be analyzed in both time and frequency domains, including fitting a parametric (preferably, autoregressive) stochastic difference equation to the time series and then calculating functions of frequency such as spectra and coherent spectra, coherences, and fre

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Chronis, Themis G., Earle Williams, and Emmanouil N. Anagnostou. "Evidence of Tropical Forcing of the 6.5-Day Wave from Lightning Observations over Africa." Journal of the Atmospheric Sciences 64, no. 10 (2007): 3717–21. http://dx.doi.org/10.1175/jas4021.1.

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Abstract A study employing observations and climatic reanalysis data is concerned with links between convection and the well-documented 6.5-day stratospheric global wave. Observations from a long-range lightning detection network, known as ZEUS, reveal an in-phase behavior between the maximization of daily lightning activity over Africa and the intensification of the wave. To extend the observations on a climatological basis, the authors make use of the outgoing longwave radiation (OLR) as proxy for convection and the surface level pressure (SLP) as an indicator of atmospheric column forcing.

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9

Kriss, A. B., P. A. Paul, and L. V. Madden. "Variability in Fusarium Head Blight Epidemics in Relation to Global Climate Fluctuations as Represented by the El Niño-Southern Oscillation and Other Atmospheric Patterns." Phytopathology® 102, no. 1 (2012): 55–64. http://dx.doi.org/10.1094/phyto-04-11-0125.

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Cross-spectral analysis was used to characterize the relationship between climate variability, represented by atmospheric patterns, and annual fluctuations of Fusarium head blight (FHB) disease intensity in wheat. Time series investigated were the Oceanic Niño Index (ONI), which is a measure of the El Niño-Southern Oscillation (ENSO), the Pacific-North American (PNA) pattern and the North Atlantic Oscillation (NAO), which are known to have strong influences on the Northern Hemisphere climate, and FHB disease intensity observations in Ohio from 1965 to 2010 and in Indiana from 1973 to 2008. For

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Zohar, Sioan, and Chun Hong Yoon. "Bi-cross validation of spectral clustering hyperparameters." Powder Diffraction 35, no. 2 (2020): 112–16. http://dx.doi.org/10.1017/s0885715620000214.

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One challenge impeding the analysis of terabyte scale X-ray scattering data from the Linac Coherent Light Source (LCLS) is determining the number of clusters required for the execution of traditional clustering algorithms. Here, we demonstrate that the previous work using bi-cross validation to determine the number of singular vectors directly maps to the spectral clustering problem of estimating both the number of clusters and hyperparameter values. Applying this method to LCLS X-ray scattering data enables the identification of dropped shots without manually setting boundaries on detector fl

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11

Luo, Hao-Wen, Ting-Yi Chung, Chih-Hao Lee, and Ching-Shiang Hwang. "Numerical analysis of brilliance and coherent photon flux of segmented undulator radiation based on statistical optics." Journal of Synchrotron Radiation 26, no. 1 (2019): 59–73. http://dx.doi.org/10.1107/s1600577518016004.

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A method based on wave optics together with electron tracking is used to analyze synchrotron radiation from a segmented undulator in a double or multi mini-β function lattice storage ring. Radiation brilliance and transverse coherence features are investigated, where the former is calculated with the Wigner distribution function and the latter is evaluated by integrating the photon flux and cross-spectral density to exhibit the coherent flux and overall degree of coherence. To be specific, radiation properties for a single undulator in a typically single mini-β function and a tandem undulator

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12

Hyde, Milo. "Controlling the Spatial Coherence of an Optical Source Using a Spatial Filter." Applied Sciences 8, no. 9 (2018): 1465. http://dx.doi.org/10.3390/app8091465.

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This paper presents the theory for controlling the spectral degree of coherence via spatial filtering. Starting with a quasi-homogeneous partially coherent source, the cross-spectral density function of the field at the output of the spatial filter is found by applying Fourier and statistical optics theory. The key relation obtained from this analysis is a closed-form expression for the filter function in terms of the desired output spectral degree of coherence. This theory is verified with Monte Carlo wave-optics simulations of spatial coherence control and beam shaping for potential use in f

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13

Debeleac, Carmen, Silviu Nastac, and Gina Diana Musca (Anghelache). "Experimental Investigations Regarding the Structural Damage Monitoring of Strands Wire Rope within Mechanical Systems." Materials 13, no. 15 (2020): 3439. http://dx.doi.org/10.3390/ma13153439.

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This paper deals with the area of structural damage monitoring of steel strands wire ropes embedded into various equipment and mechanical systems. Of the currently available techniques and methods for wire ropes health monitoring, the authors focused on the group of techniques based on operational dynamics investigation of such systems. Beyond the capability and efficiency of both occasionally and continuously monitoring application, the dynamics-based methods are able to provide additional information regarding the structural integrity and functional operability of the entire ensemble embeddi

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14

Singer, B. A. "Turbulent Wall-Pressure Fluctuations: A New Model for Off-Axis Cross-Spectral Density." Journal of Fluids Engineering 119, no. 2 (1997): 277–80. http://dx.doi.org/10.1115/1.2819131.

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Models for the distribution of the wall-pressure under a turbulent boundary layer often estimate the coherence of the cross-spectral density in terms of a product of two coherence functions. One such function describes the coherence as a function of separation distance in the mean-flow direction, the other function describes the coherence in the cross-stream direction. Analysis of data from a large-eddy simulation of a turbulent boundary layer reveals that this approximation dramatically underpredicts the coherence for separation directions that are neither aligned with nor perpendicular to th

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15

Shume, E. B., A. J. Mannucci, and R. Caton. "Phase and coherence analysis of VHF scintillation over Christmas Island." Annales Geophysicae 32, no. 3 (2014): 293–300. http://dx.doi.org/10.5194/angeo-32-293-2014.

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Abstract. This short paper presents phase and coherence data from the cross-wavelet transform applied on longitudinally separated very high frequency (VHF) equatorial ionospheric scintillation observations over Christmas Island. The phase and coherence analyses were employed on a pair of scintillation observations, namely, the east-looking and west-looking VHF scintillation monitors at Christmas Island. Our analysis includes 3 years of peak season scintillation data from 2008, 2009 (low solar activity), and 2011 (moderate solar activity). In statistically significant and high spectral coherenc

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Takasaka, Yoichiro, Kazuo Takamatsu, and Minoru Nakagawara. "Anterior-Posterior Relationships of EEG in Photosensitive Subjects: Coherence and Cross-Phase-Spectral Analysis." Psychiatry and Clinical Neurosciences 43, no. 4 (1989): 651–63. http://dx.doi.org/10.1111/j.1440-1819.1989.tb03101.x.

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Liu, Xuan, Jessica C. Ramella-Roman, Yong Huang, Yuan Guo, and Jin U. Kang. "Robust spectral-domain optical coherence tomography speckle model and its cross-correlation coefficient analysis." Journal of the Optical Society of America A 30, no. 1 (2012): 51. http://dx.doi.org/10.1364/josaa.30.000051.

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Afshar-Kaveh, Naghmeh, Mostafa Nazarali, and Charitha Pattiaratchi. "Relationship between the Persian Gulf Sea-Level Fluctuations and Meteorological Forcing." Journal of Marine Science and Engineering 8, no. 4 (2020): 285. http://dx.doi.org/10.3390/jmse8040285.

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Sea-level data from six tide gauge stations along the northern coast of the Persian Gulf were analyzed both in time and frequency domain to evaluate meteorological forcing. Spectral analyses indicated that mixed, predominantly semi-diurnal tides were dominant at all stations, but low-frequency fluctuations correlated well with atmospheric pressure and wind components. Non-tidal sea-level fluctuations up to 0.75 m were observed along the northern coasts of the Gulf due to the combined action of lower atmospheric pressure and cross-shore wind. Coherency between low-frequency sea-level records an

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19

Bai, Ou, Dandan Huang, Peter Lin, Jinglong Wu, Xuedong Chen, and Ding-Yu Fei. "An Event-Related Study for Dynamic Analysis of Corticomuscular Connectivity." Biomedical Engineering and Computational Biology 2 (January 2010): BECB.S5546. http://dx.doi.org/10.4137/becb.s5546.

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Corticomuscular coupling estimated by EEG-EMG coherence may reveal functional cortical driving of peripheral muscular activity. EEG-EMG coherence in the beta band (15–30 Hz) has been extensively studied under isometric muscle contraction tasks. We attempted to study the time-course of corticomuscular connectivity under a dynamic target tracking task. A new device was developed for the real-time measurement of dynamic force created by pinching thumb and index fingers. Four healthy subjects who participated in this study were asked to track visual targets with the feedback forces. Spectral param

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20

Wang, Chien-Ya, Ching-Lun Su, Kang-Hung Wu, and Yen-Hsyang Chu. "Cross Spectral Analysis of CODAR-SeaSonde Echoes from Sea Surface and Ionosphere at Taiwan." International Journal of Antennas and Propagation 2017 (2017): 1–14. http://dx.doi.org/10.1155/2017/1756761.

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It is well known that the primary targets responsible for first-order sea echoes observed by a High-Frequency (HF) radar are the advancing and receding ocean waves with the wavelengths at Bragg scales. However, in light of the fact that the ionospheric sporadic E (Es) and F layers may be present in the viewing range of the HF radar for ocean wave detection, the radar returns reflected from the F and Es layers may significantly contaminate the ocean wave power spectrum. The characteristics of the first-order sea echoes and ionospheric interferences measured by the CODAR-SeaSonde in Taiwan area

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21

Yang, C. C., T. B. Kuo, and S. H. Chan. "Auto- and cross-spectral analysis of cardiovascular fluctuations during pentobarbital anesthesia in the rat." American Journal of Physiology-Heart and Circulatory Physiology 270, no. 2 (1996): H575—H582. http://dx.doi.org/10.1152/ajpheart.1996.270.2.h575.

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We applied auto- and cross-spectral analysis of systemic arterial pressure (SAP) and heart rate (HR) signals to quantify the effects of pentobarbital sodium on short-term cardiovascular fluctuations in adult, male Sprague-Dawley rats. Intravenous administration of pentobarbital, delivered as a bolus injection (5, 10, or 20 mg/kg) or continuous infusion (10, 20, or 40 mg.kg-1.h-1), elicited only mild hypotension and tachycardia. This was accompanied by a dose-related depression of the very low (0-0.25 Hz) and low (0.25-0.8 Hz)-frequency components of both SAP and HR signals and high (0.8-2.4 Hz

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Pavlić, Krešimir, and Jelena Parlov. "Cross-Correlation and Cross-Spectral Analysis of the Hydrographs in the Northern Part of the Dinaric Karst of Croatia." Geosciences 9, no. 2 (2019): 86. http://dx.doi.org/10.3390/geosciences9020086.

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Correlation and cross-spectral analysis of hydrographs was performed on the karst area of the mountainous section of the Kupa River in two time periods. Since there are karst aquifers in this area that is a part of strategic groundwater reserves of potable water, such an analysis could give better insight into the behavior of these aquifers. The functions used to describe karst aquifers are the cross-correlation function, coherence function, gain function, and phase function. The outcomes of the analysis results were very similar in the two analyzed periods, suggesting that differences in inpu

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He, Jun. "Coherence and cross-spectral density matrix analysis of random wind and wave in deep water." Ocean Engineering 197 (February 2020): 106930. http://dx.doi.org/10.1016/j.oceaneng.2020.106930.

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Alonso, Joan Francesc, Jesús Poza, Miguel Ángel Mañanas, Sergio Romero, Alberto Fernández, and Roberto Hornero. "MEG Connectivity Analysis in Patients with Alzheimer’s Disease Using Cross Mutual Information and Spectral Coherence." Annals of Biomedical Engineering 39, no. 1 (2010): 524–36. http://dx.doi.org/10.1007/s10439-010-0155-7.

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25

Ariunbold, Gombojav O., Bryan Semon, Supriya Nagpal, and Prakash Adhikari. "Coherent Anti-Stokes–Stokes Raman Cross-Correlation Spectroscopy: Asymmetric Frequency Shifts in Hydrogen-Bonded Pyridine-Water Complexes." Applied Spectroscopy 73, no. 9 (2019): 1099–106. http://dx.doi.org/10.1177/0003702819857771.

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Hydrogen bonding is a vital molecular interaction for bio-molecular systems, yet deep understanding of its ways of creating various complexes requires extensive empirical testing. A hybrid femtosecond/picosecond coherent Raman spectroscopic technique is applied to study pyridine-water complexes. Both the coherent Stokes and anti-Stokes Raman spectra are recorded simultaneously as the concentration of water in pyridine varied. A 3 ps and 10 cm−1 narrowband probe pulse enables us to observe well-resolved Raman spectra. The hydrogen bonding between pyridine and water forms the complexes that have

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Kosály, George. "Frequency spectra of reactant fluctuations in turbulent flows." Journal of Fluid Mechanics 246 (January 1993): 489–502. http://dx.doi.org/10.1017/s0022112093000230.

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Bilger, Saetran & Krishnamoorthy (1991) give measured values of the variance, cross-correlation coefficient, autospectra, coherence and phase shift of the reactant concentration fluctuations for an irreversible second-order reaction in an incompressible turbulent scalar mixing layer. The present paper approaches the interpretation of the measured data by evaluating the above quantities in the frozen (slow) and equilibrium (fast) chemistry limits. We assume that the limiting values bracket the corresponding intermediate rate data.The analysis leads to values that correspond with the measure

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Aoyagi, Naoko, Kyoko Ohashi, Shinji Tomono, and Yoshiharu Yamamoto. "Temporal contribution of body movement to very long-term heart rate variability in humans." American Journal of Physiology-Heart and Circulatory Physiology 278, no. 4 (2000): H1035—H1041. http://dx.doi.org/10.1152/ajpheart.2000.278.4.h1035.

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A newly developed, very long-term (∼7 days) ambulatory monitoring system for assessing beat-to-beat heart rate variability (HRV) and body movements (BM) was used to study the mechanism(s) responsible for the long-period oscillation in human HRV. Data continuously collected from five healthy subjects were analyzed by 1) standard auto- and cross-spectral techniques, 2) a cross-Wigner distribution (WD; a time-frequency analysis) between BM and HRV for 10-s averaged data, and 3) coarse-graining spectral analysis for 600 successive cardiac cycles. The results showed 1) a clear circadian rhythm in H

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Schmidt, Oliver T., Gianmarco Mengaldo, Gianpaolo Balsamo, and Nils P. Wedi. "Spectral Empirical Orthogonal Function Analysis of Weather and Climate Data." Monthly Weather Review 147, no. 8 (2019): 2979–95. http://dx.doi.org/10.1175/mwr-d-18-0337.1.

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Abstract We apply spectral empirical orthogonal function (SEOF) analysis to educe climate patterns as dominant spatiotemporal modes of variability from reanalysis data. SEOF is a frequency-domain variant of standard empirical orthogonal function (EOF) analysis, and computes modes that represent the statistically most relevant and persistent patterns from an eigendecomposition of the estimated cross-spectral density matrix (CSD). The spectral estimation step distinguishes the approach from other frequency-domain EOF methods based on a single realization of the Fourier transform, and results in

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CAMUSSI, R., G. ROBERT, and M. C. JACOB. "Cross-wavelet analysis of wall pressure fluctuations beneath incompressible turbulent boundary layers." Journal of Fluid Mechanics 617 (December 25, 2008): 11–30. http://dx.doi.org/10.1017/s002211200800373x.

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Pressure fluctuations measured at the wall of a turbulent boundary layer are analysed using a bi-variate continuous wavelet transform. Cross-wavelet analyses of pressure signals obtained from microphone pairs are performed and a novel post-processing technique aimed at selecting events with strong local-in-time coherence is applied. Probability density functions and conditionally averaged equivalents of Fourier spectral quantities, usually introduced for modelling purposes, are computed. The analysis is conducted for signals obtained at low Mach numbers from two different non-equilibrium turbu

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Biswas, A., B. C. Si та F. L. Walley. "Spatial relationship between δ<sup>15</sup>N and elevation in agricultural landscapes". Nonlinear Processes in Geophysics 15, № 3 (2008): 397–407. http://dx.doi.org/10.5194/npg-15-397-2008.

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Abstract. Understanding of the nitrogen (N) cycle and its spatial variability is important for managing ecosystems. Soil δ15N, as an important indicator of different soil nitrogen cycling processes, may provide critical information about the spatial variability in soil N cycling. The objective of this study was to examine the dominant landscape scale variability of δ15N, the location of the variability and its spatial relationship with elevation. Soil δ15N and elevation were measured along two transects (Davidson and Elstow, Saskatchewan, Canada). Each transect had 128 points with 3 m sampling

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Mierzejewski, Mateusz, and Magdalena Lampart. "Analysis of Business Cycles in the Breeding of Pigs, Cattle and Poultry and their Relationship to the Causality of Wheat and Rye Cultivation in Poland." Zeszyty Naukowe SGGW w Warszawie - Problemy Rolnictwa Światowego 18(33), no. 2 (2018): 218–27. http://dx.doi.org/10.22630/prs.2018.18.2.49.

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The article presents a study on the phenomenon of pig gaps in the perspective of pig, cattle, and poultry farming in Poland. The work attempts to define the phenomenon itself as well as to show the reasons for its occurrence and significance for the Polish economy. The study used a cross-spectral analysis, which indicated cyclical relationships and shifts between the studied time series. The methodology of the work was based on a simplified spectral analysis, i.e. the use of the square of coherence, spectral density and phase spectrum. In addition, the article uses a comparative method for sel

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Taggart, Christopher T., and William C. Leggett. "Wind-Forced Hydrodynamics and Their Interaction with Larval Fish and Plankton Abundance: A Time-Series Analysis of Physical–Biological Data." Canadian Journal of Fisheries and Aquatic Sciences 44, no. 2 (1987): 438–51. http://dx.doi.org/10.1139/f87-052.

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We evaluated methods to measure simultaneously biological and physical properties essential for estimating short-term mortality of larval fish. We used the data to test Templeman's watermass exchange hypothesis and the associated safe-site hypothesis. Synoptic estimates of larval capelin (Mallotus villosus) and microzooplankton particle density were obtained simultaneously with a scale resolution of 200 m (horizontal), 2–4 m (vertical) and 6–8 h (temporal) in a 1-km2 coastal embayment in eastern Newfoundland. Statistically significant population estimates were derived from multiple regression

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Kriss, Alissa B., Laurence V. Madden, Pierce A. Paul, and Xiangming Xu. "Heterogeneity of Fusarium Head Blight of Wheat: Multi-scale Distributions and Temporal Variation in Relation to Environment." Plant Health Progress 13, no. 1 (2012): 30. http://dx.doi.org/10.1094/php-2012-0723-01-rs.

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Fusarium head blight (FHB) is a serious disease of wheat, which is highly variable at several spatial and temporal scales. Different statistical approaches were used to either quantify or partially explain this heterogeneity. First, a generalized linear mixed model was fitted to hierarchical survey data for the incidence of FHB in Ohio. Estimated variance terms indicated large and significant spatial heterogeneity among counties and among fields within counties, with substantially lower variation among sites within fields. Second, window-pane analysis was used to investigate the effects of env

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Krishnan, Giri P., Gregory Filatov, and Maxim Bazhenov. "Dynamics of high-frequency synchronization during seizures." Journal of Neurophysiology 109, no. 10 (2013): 2423–37. http://dx.doi.org/10.1152/jn.00761.2012.

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Pathological synchronization of neuronal firing is considered to be an inherent property of epileptic seizures. However, it remains unclear whether the synchrony increases for the high-frequency multiunit activity as well as for the local field potentials (LFPs). We present spatio-temporal analysis of synchronization during epileptiform activity using wide-band (up to 2,000 Hz) spectral analysis of multielectrode array recordings at up to 60 locations throughout the mouse hippocampus in vitro. Our study revealed a prominent structure of LFP profiles during epileptiform discharges, triggered by

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Poulain, Pierre-Marie, Riccardo Gerin, Elena Mauri, and Romain Pennel. "Wind Effects on Drogued and Undrogued Drifters in the Eastern Mediterranean." Journal of Atmospheric and Oceanic Technology 26, no. 6 (2009): 1144–56. http://dx.doi.org/10.1175/2008jtecho618.1.

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Abstract The wind effects on drogued and undrogued drifters are assessed using Coastal Ocean Dynamics Experiment (CODE) and Surface Velocity Program (SVP) drifter datasets and ECMWF wind products in the eastern Mediterranean. Complex and real linear regression models are used to estimate the relative slip of undrogued SVP drifters and to extract the wind-driven currents from the drifter velocities. The frequency response of the wind-driven currents is studied using cross-spectral analysis. By comparing the velocities of cotemporal and nearly collocated undrogued and drogued SVP drifters, it ap

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Sakon, Atsushi, Kunihiro Nakajima, Kazuki Takahashi, et al. "REACTOR NOISE ANALYSIS FOR A GRAPHITE-MODERATED AND -REFLECTED CORE IN KUCA." EPJ Web of Conferences 247 (2021): 09009. http://dx.doi.org/10.1051/epjconf/202124709009.

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In graphite-reflected thermal reactors, even a detector placed far from fuel region may detect a certain degree of the correlation amplitude. This is because mean free path of neutrons in graphite is longer than that in water or polyethylene. The objective of this study is experimentally to confirm a high flexibility of neutron detector placement in graphite reflector for reactor noise analysis. The present reactor noise analysis was carried out in a graphite-moderated and -reflected thermal core in Kyoto University Critical Assembly (KUCA). BF3 proportional neutron counters (1” dia.) were pla

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Dasso, S., C. A. Perazzo, L. Romanelli, et al. "Dynamical analysis of erythrocytes under the assumption of cross-spectral coherence between blood cell counts and the Dst index." Geofísica Internacional 43, no. 2 (2004): 259–64. http://dx.doi.org/10.22201/igeof.00167169p.2004.43.2.177.

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La posible influencia de la actividad solar sobre la salud humana a través de procesos biogeomagnéticos es en la actualidad un tema de gran discusión. Algunos procesos que ocurren en el Sol pueden afectar el entorno terrestre y producir grandes perturbaciones en el campo geomagnético. El índice Dst, el cual mide un promedio de las perturbaciones del campo geomagnético en el ecuador terrestre, es un buen indicador global de estas fluctuaciones. Por otro lado, los eritrocitos, los leucocitos y las plaquetas desempeñan un rol esencial en los sistemas vivos, ya que son responsables del transporte

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Peña, J. C., L. Schulte, A. Badoux, M. Barriendos, and A. Barrera-Escoda. "Influence of solar forcing, climate variability and modes of low-frequency atmospheric variability on summer floods in Switzerland." Hydrology and Earth System Sciences 19, no. 9 (2015): 3807–27. http://dx.doi.org/10.5194/hess-19-3807-2015.

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Abstract. The higher frequency of severe flood events in Switzerland in recent decades has given fresh impetus to the study of flood patterns and their possible forcing mechanisms, particularly in mountain environments. This paper presents a new index of summer flood damage that considers severe and catastrophic summer floods in Switzerland between 1800 and 2009, and explores the influence of external forcings on flood frequencies. In addition, links between floods and low-frequency atmospheric variability patterns are examined. The flood damage index provides evidence that the 1817–1851, 1881

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Peña, J. C., L. Schulte, A. Badoux, M. Barriendos, and A. Barrera-Escoda. "Influence of solar forcing, climate variability and atmospheric circulation patterns on summer floods in Switzerland." Hydrology and Earth System Sciences Discussions 11, no. 12 (2014): 13843–90. http://dx.doi.org/10.5194/hessd-11-13843-2014.

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Abstract. The higher frequency of severe flood events in Switzerland in recent decades has given fresh impetus to the study of flood patterns and their possible forcing mechanisms, particularly in mountain environments. This paper presents an index of summer flood damage that considers severe and catastrophic summer floods in Switzerland between 1800 and 2009, and explores the influence of solar and climate forcings on flood frequencies. In addition, links between floods and low-frequency atmospheric circulation patterns are examined. The flood damage index provides evidence that the 1817–1851

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Badra, Leslie J., William H. Cooke, Jeffrey B. Hoag, et al. "Respiratory modulation of human autonomic rhythms." American Journal of Physiology-Heart and Circulatory Physiology 280, no. 6 (2001): H2674—H2688. http://dx.doi.org/10.1152/ajpheart.2001.280.6.h2674.

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We studied the influence of three types of breathing [spontaneous, frequency controlled (0.25 Hz), and hyperventilation with 100% oxygen] and apnea on R-R interval, photoplethysmographic arterial pressure, and muscle sympathetic rhythms in nine healthy young adults. We integrated fast Fourier transform power spectra over low (0.05–0.15 Hz) and respiratory (0.15–0.3 Hz) frequencies; estimated vagal baroreceptor-cardiac reflex gain at low frequencies with cross-spectral techniques; and used partial coherence analysis to remove the influence of breathing from the R-R interval, systolic pressure,

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Chen, Yuan Ying, Xiao Ling Yin, Dong Lin Bai, and Li Cheng Li. "Spectral Analysis on Sub-Tidal Variability of Salinity in Modaomen Waterway of Pearl River Estuary, China." Advanced Materials Research 518-523 (May 2012): 1982–85. http://dx.doi.org/10.4028/www.scientific.net/amr.518-523.1982.

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Salinity and tidal range time series observed in Modaomen waterway was analyzed in power spectrum method, and both showed the period of half month (14.22d). Moreover, the salinity and tidal range time series were coherent at that period through cross spectrum analysis. Besides, the phase analysis at the period of 14.22d showed that, within the estuary, the salinity time series upstream lagged that of the downstream, and the response time of salinity time series to the tidal range time series was about 9-10d, increasing upstream. But the phase of salinity time series and response time to the ti

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Moss, HeatherE, EricaZ Oltra, ClementC Chow, Thomas Wubben, JenniferI Lim, and FelixY Chau. "Cross-Sectional analysis of neurocognitive function, retinopathy, and retinal thinning by Spectral-Domain optical coherence tomography in sickle cell patients." Middle East African Journal of Ophthalmology 23, no. 1 (2016): 79. http://dx.doi.org/10.4103/0974-9233.150632.

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Daly, Susan M., Christophe Silien, and Martin J. Leahy. "Optimization and extraction of functional information fromin vitroflow models using dual-beam spectral-domain optical coherence tomography cross-correlation analysis." Journal of Biomedical Optics 18, no. 10 (2013): 106003. http://dx.doi.org/10.1117/1.jbo.18.10.106003.

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Yasunaga, Kazuaki, Satoru Yokoi, Kuniaki Inoue, and Brian E. Mapes. "Space–Time Spectral Analysis of the Moist Static Energy Budget Equation." Journal of Climate 32, no. 2 (2018): 501–29. http://dx.doi.org/10.1175/jcli-d-18-0334.1.

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Abstract The budget of column-integrated moist static energy (MSE) is examined in wavenumber–frequency transforms of longitude–time sections over the tropical belt. Cross-spectra with satellite-derived precipitation (TRMM-3B42) are used to emphasize precipitation-coherent signals in reanalysis [ERA-Interim (ERAI)] estimates of each term in the budget equation. Results reveal different budget balances in convectively coupled equatorial waves (CCEWs) as well as in the Madden–Julian oscillation (MJO) and tropical depression (TD)-type disturbances. The real component (expressing amplification or d

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GUO, Y. P., M. C. JOSHI, P. H. BENT, and K. J. YAMAMOTO. "Surface pressure fluctuations on aircraft flaps and their correlation with far-field noise." Journal of Fluid Mechanics 415 (July 25, 2000): 175–202. http://dx.doi.org/10.1017/s0022112000008740.

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This paper discusses unsteady surface pressures on aircraft flaps and their correlation with far-field noise. Analyses are made of data from a 4.7% DC-10 aircraft model test, conducted in the 40 × 80 feet wind tunnel at NASA Ames Research Center. Results for various slat/wing/flap configurations and various flow conditions are discussed in detail to reveal major trends in surface pressure fluctuations. Spectral analysis, including cross-correlation/coherence, both among unsteady surface pressures and between far-field noise and near-field fluctuations, is used to reveal the most coherent motio

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IV, Milo W. Hyde. "Synthesizing General Electromagnetic Partially Coherent Sources from Random, Correlated Complex Screens." Optics 1, no. 1 (2020): 97–113. http://dx.doi.org/10.3390/opt1010008.

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We present a method to generate any genuine electromagnetic partially coherent source (PCS) from correlated, stochastic complex screens. The method described here can be directly implemented on existing spatial-light-modulator-based vector beam generators and can be used in any application which utilizes electromagnetic PCSs. Our method is based on the genuine cross-spectral density matrix criterion. Applying that criterion, we show that stochastic vector field realizations (corresponding to a desired electromagnetic PCS) can be generated by passing correlated Gaussian random numbers through “

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Shusterman, V., K. P. Anderson, and O. Barnea. "Spontaneous skin temperature oscillations in normal human subjects." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 273, no. 3 (1997): R1173—R1181. http://dx.doi.org/10.1152/ajpregu.1997.273.3.r1173.

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A noninvasive method based on high-resolution measurements and bandpass filtering of spontaneous skin temperature oscillations (approximately 4.0 x 10(-2) degrees C) in the low-frequency range (0.01-0.04 Hz) was investigated in normal human subjects. We hypothesized that the oscillations (temperature variability) originate from vasomotor activity of small arteries and arterioles in subcutaneous tissues. To test this hypothesis, continuous blood pressure waveforms were obtained with the use of an external piezoelectric sensor. The peak-to-peak envelope of the pressure signal (pressure variabili

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Guilloteau, Clément, Antonios Mamalakis, Lawrence Vulis, Phong V. V. Le, Tryphon T. Georgiou, and Efi Foufoula-Georgiou. "Rotated Spectral Principal Component Analysis (rsPCA) for Identifying Dynamical Modes of Variability in Climate Systems." Journal of Climate 34, no. 2 (2021): 715–36. http://dx.doi.org/10.1175/jcli-d-20-0266.1.

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AbstractSpectral PCA (sPCA), in contrast to classical PCA, offers the advantage of identifying organized spatiotemporal patterns within specific frequency bands and extracting dynamical modes. However, the unavoidable trade-off between frequency resolution and robustness of the PCs leads to high sensitivity to noise and overfitting, which limits the interpretation of the sPCA results. We propose herein a simple nonparametric implementation of sPCA using the continuous analytic Morlet wavelet as a robust estimator of the cross-spectral matrices with good frequency resolution. To improve the int

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Yasunaga, Kazuaki, and Brian Mapes. "Differences between More Divergent and More Rotational Types of Convectively Coupled Equatorial Waves. Part I: Space–Time Spectral Analyses." Journal of the Atmospheric Sciences 69, no. 1 (2012): 3–16. http://dx.doi.org/10.1175/jas-d-11-033.1.

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Abstract Precipitation-related differences in different types of convectively coupled equatorial waves are examined here and in a companion paper. Here the authors show spectra and cross-spectra among tropical-belt time sections of satellite-derived surface rain, infrared brightness temperature Tb, precipitable water (PW), and Japan Meteorological Agency reanalysis of divergence and PW. Cross-spectra between rain and divergence at 1000- and 200-hPa levels show significant coherence peaks oriented along the dispersion curves of Kelvin, n = 1 equatorial Rossby (ERn1), mixed Rossby–gravity (MRG),

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Schuster, Alexander Karl-Georg, Joachim Ernst Fischer, and Urs Vossmerbaeumer. "Central Corneal Thickness in Spectral-Domain OCT and Associations with Ocular and Systemic Parameters." Journal of Ophthalmology 2016 (2016): 1–6. http://dx.doi.org/10.1155/2016/2596956.

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Background. Optical coherence tomography (OCT) allows quantitative analysis of the anterior segment of the eye with a noncontact examination. The aim of this study is to analyze associations of central corneal thickness (CCT) as measured by OCT with ocular and systemic cardiovascular parameters.Methods. A cross-sectional study of 734 persons was performed in a working age population. Only healthy eyes were included. A comprehensive ophthalmological examination including refraction, noncontact tonometry, and imaging of the anterior segment by SD-OCT was performed. In parallel, a broad range of

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