Journal articles: 'Cross-correlation, cross-power spectral density'

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Alotta, Gioacchino, Mario Di Paola, and Francesco Paolo Pinnola. "Cross-correlation and cross-power spectral density representation by complex spectral moments." International Journal of Non-Linear Mechanics 94 (September 2017): 20–27. http://dx.doi.org/10.1016/j.ijnonlinmec.2017.02.001.

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Nyeina, Oo Kyaw. "MEASUREMENT OF VIBRATION POWER FLOW IN THIN PLATE STRUCTURE WITH CROSS POWER SPECTRAL DENSITY-BASED TECHNIQUE." International Journal of Psychosocial Rehabilitation 24, no. 4 (February 28, 2020): 4703–11. http://dx.doi.org/10.37200/ijpr/v24i4/pr201570.

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Boudraa, Abdel-Ouahab, Thierry Chonavel, and Jean-Christophe Cexus. "-energy operator and cross-power spectral density." Signal Processing 94 (January 2014): 236–40. http://dx.doi.org/10.1016/j.sigpro.2013.05.022.

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Kanazawa, Kenji, and Kazuta Hirata. "Parametric estimation of the cross-power spectral density." Journal of Sound and Vibration 282, no. 1-2 (April 2005): 1–35. http://dx.doi.org/10.1016/j.jsv.2004.02.009.

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Tester, Brian J., and Stewart Glegg. "Phased array transformation methods to estimate non-compact jet noise source characteristics." International Journal of Aeroacoustics 17, no. 4-5 (May 27, 2018): 380–98. http://dx.doi.org/10.1177/1475472x18778267.

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This paper reviews the basis of the beamformer and polar correlation phased array methods and shows that these provide different information about axially distributed, non-compact noise sources, which nevertheless satisfy a simple integral relationship. The conventional beamformer method provides an image of the source power or auto spectral density, whereas the polar correlation method yields a ‘source strength’ which is an image of the axial wavenumber transform of the source cross-spectral density. However, the beamformer method can be generalised to provide an image of the source cross-spectral density. At first sight, the generalised beamformer method is therefore more useful for diagnostic purposes but the results presented here suggest that the combined effects of resolution and source convection place serious limitations on the source cross-spectral density image information. For the same reasons, although the source power or auto spectral density axial shape can be obtained with the conventional beamformer method, it cannot yield its absolute level for this type of source. The polar correlation method yields a source strength axial distribution at each ‘reference’ microphone, which when integrated over the source length, yields the far-field power or auto spectral density at that reference microphone. Therefore, the polar correlation source strength is arguably the more relevant quantity to measure when determining what proportion of the sound at a particular microphone position comes from each region of the jet axis, as a function of radiation angle.

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Zhang, Libin, Le Ma, Rui Chen, Jianfang He, Xiaojing Su, Lisong Dong, Yajuan Su, and Yayi Wei. "Pattern quality and defect evaluation based on cross correlation and power spectral density methods." Journal of Vacuum Science & Technology B 36, no. 5 (September 2018): 052902. http://dx.doi.org/10.1116/1.5040391.

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Li, Jianghui, Yechao Bai, Youwen Zhang, Fengzhong Qu, Yan Wei, and Junfeng Wang. "Cross power spectral density based beamforming for underwater acoustic communications." Ocean Engineering 216 (November 2020): 107786. http://dx.doi.org/10.1016/j.oceaneng.2020.107786.

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Zhang, Dongyu, and Erik A. Johnson. "Substructure identification for shear structures: cross-power spectral density method." Smart Materials and Structures 21, no. 5 (April 24, 2012): 055006. http://dx.doi.org/10.1088/0964-1726/21/5/055006.

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Shuter, W. L. H., R. L. Dickman, and C. Klatt. "21 cm Line Study of Large Scale Density Fluctuations in the Taurus Molecular Complex." Symposium - International Astronomical Union 115 (1987): 67–68. http://dx.doi.org/10.1017/s0074180900094900.

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21-cm spectra on a 41 × 31 grid, centered at 1950: RA 04h30m; DEC 27d00m, at points separated by a true angle of 0.25 degrees, were observed using the Arecibo telescope in October 1985. The identical grid had previously been observed in 13CO by Kleiner and Dickman (1984) with the FCRAO mm wave telescope. In this preliminary analysis we determined autocorrelation functions and power spectra for 21-cm self absorption “intensities”, for a cross passing through the central point. Both arms of the cross, aligned parallel to RA and DEC, show a power spectral peak at a frequency of 0.312 reciprocal degrees, corresponding to a period of 3.2 degrees on the sky. Assuming that the Taurus complex is at a distance of 140 pc, this corresponds to a correlation length of 7.8 pc, which is about a factor of two smaller than the value of 14 pc found by Kleiner and Dickman for 13CO.

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Brondeau, J., D. Canet, C. Millot, H. Nery, and L. Werbelow. "The direct experimental determination of a dipole–dipole cross‐correlation spectral density." Journal of Chemical Physics 82, no. 5 (March 1985): 2212–16. http://dx.doi.org/10.1063/1.448364.

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da Cunha Lima, A. T., I. C. da Cunha Lima, and M. P. de Almeida. "Analysis of turbulence power spectra and velocity correlations in a pipeline with obstructions." International Journal of Modern Physics C 28, no. 02 (February 2017): 1750019. http://dx.doi.org/10.1142/s012918311750019x.

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We calculate the power spectral density and velocity correlations for a turbulent flow of a fluid inside a duct. Turbulence is induced by obstructions placed near the entrance of the flow. The power spectral density is obtained for several points at cross-sections along the duct axis, and an analysis is made on the way the spectra changes according to the distance to the obstruction. We show that the differences on the power spectral density are important in the lower frequency range, while in the higher frequency range, the spectra are very similar to each other. Our results suggest the use of the changes on the low frequency power spectral density to identify the occurrence of obstructions in pipelines. Our results show some frequency regions where the power spectral density behaves according to the Kolmogorov hypothesis. At the same time, the calculation of the power spectral densities at increasing distances from the obstructions indicates an energy cascade where the spectra evolves in frequency space by spreading the frequency amplitude.

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Thammasan, Nattapong, and Makoto Miyakoshi. "Cross-Frequency Power-Power Coupling Analysis: A Useful Cross-Frequency Measure to Classify ICA-Decomposed EEG." Sensors 20, no. 24 (December 9, 2020): 7040. http://dx.doi.org/10.3390/s20247040.

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Magneto-/Electro-encephalography (M/EEG) commonly uses (fast) Fourier transformation to compute power spectral density (PSD). However, the resulting PSD plot lacks temporal information, making interpretation sometimes equivocal. For example, consider two different PSDs: a central parietal EEG PSD with twin peaks at 10 Hz and 20 Hz and a central parietal PSD with twin peaks at 10 Hz and 50 Hz. We can assume the first PSD shows a mu rhythm and the second harmonic; however, the latter PSD likely shows an alpha peak and an independent line noise. Without prior knowledge, however, the PSD alone cannot distinguish between the two cases. To address this limitation of PSD, we propose using cross-frequency power–power coupling (PPC) as a post-processing of independent component (IC) analysis (ICA) to distinguish brain components from muscle and environmental artifact sources. We conclude that post-ICA PPC analysis could serve as a new data-driven EEG classifier in M/EEG studies. For the reader’s convenience, we offer a brief literature overview on the disparate use of PPC. The proposed cross-frequency power–power coupling analysis toolbox (PowPowCAT) is a free, open-source toolbox, which works as an EEGLAB extension.

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Xiao, Tian Yin. "Power Spectral Density Model of Torsional Dynamic Wind Loads on Tall Buildings." Applied Mechanics and Materials 164 (April 2012): 433–36. http://dx.doi.org/10.4028/www.scientific.net/amm.164.433.

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9 models of tall buildings with different rectangular cross-sections are tested in a wind tunnel. After processing and analyzing the measured data of fluctuating pressure on the models, the effects of models’height, aspect ratio, side ratio on the power spectra of torsional wind loads are studied. New formulas of power spectral density of torsional wind loads are proposed by curve fitting method. The applicability of the formulas has been verified by the results from the wind tunnel test.

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Kim, Do-Hwan, Doo Yong Choi, Taeho Choi, and Zong Woo Geem. "In-Depth Investigation of Statistical and Physicochemical Properties on the Field Study of the Intermittent Filling of Large Water Tanks." Mathematical Problems in Engineering 2017 (2017): 1–9. http://dx.doi.org/10.1155/2017/5017428.

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Large-demand customers, generally high-density dwellings and buildings, have dedicated ground or elevated water tanks to consistently supply drinking water to residents. Online field measurement for Nonsan-2 district meter area demonstrated that intermittent replenishment from large-demand customers could disrupt the normal operation of a water distribution system by taking large quantities of water in short times when filling the tanks from distribution mains. Based on the previous results of field measurement for hydraulic and water quality parameters, statistical analysis is performed for measured data in terms of autocorrelation, power spectral density, and cross-correlation. The statistical results show that the intermittent filling interval of 6.7 h and diurnal demand pattern of 23.3 h are detected through autocorrelation analyses, the similarities of the flow-pressure and the turbidity-particle count data are confirmed as a function of frequency through power spectral density analyses, and a strong cross-correlation is observed in the flow-pressure and turbidity-particle count analyses. In addition, physicochemical results show that the intermittent refill of storage tank from large-demand customers induces abnormal flow and pressure fluctuations and results in transient-induced turbid flow mainly composed of fine particles ranging within 2–4 μm and constituting Fe, Si, and Al.

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Li, Chang He, Ya Li Hou, Yu Cheng Ding, and Bing Heng Lu. "Power Spectral Density and Cross Correlation Function Analysis of Finished Surface by Abrasive Jet with Grinding Wheel as Restraint." Key Engineering Materials 416 (September 2009): 300–305. http://dx.doi.org/10.4028/www.scientific.net/kem.416.300.

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The abrasive jet finishing process with wheel as restraint is a kind of compound precision finishing process that combined grinding with abrasive jet machining, in which inject slurry of abrasive and liquid solvent to grinding zone between grinding wheel and work surface under no radial feed condition when workpiece grinding were accomplished. The abrasive particles are driven and energized by the rotating grinding wheel and liquid hydrodynamic pressure and increased slurry speed between grinding wheel and work surface to achieve micro removal finishing.In the paper,the finished surface morphology was studied using Scanning Electron Microscope (SEM) and microscope and microcosmic geometry parameters were measured with TALYSURF5 instrument respectively. According to the metrical results, the surface topographical characteristics were evaluated with correlation function and PSD (Power Spectral Density) of random process about machined surface before and after finishing. The results show that longitudinal geometry parameter values of finishing machining surface were diminished comparing with ground surface,and the mean ripple distance was decreased and, ripple and peak density were increased. Furthermore, the finished surface has little comparability compared to grinding machining surface.The isotropy surface and uniformity veins at parallel and perpendicular machining direction were attained by abrasive jet precision finishing with grinding wheel as restraint and the surface quality is improved obviously.

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Canet, Daniel, Sabine Bouguet-Bonnet, and Pierre Mutzenhardt. "On the calculation of cross-correlation spectral density functions within the model-free approach." Concepts in Magnetic Resonance 19A, no. 2 (2003): 65–70. http://dx.doi.org/10.1002/cmr.a.10085.

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Berry, Richard B., Musa A. Asyali, Michael I. McNellis, and Michael C. K. Khoo. "Within-night variation in respiratory effort preceding apnea termination and EEG delta power in sleep apnea." Journal of Applied Physiology 85, no. 4 (October 1, 1998): 1434–41. http://dx.doi.org/10.1152/jappl.1998.85.4.1434.

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We studied the within-night variability of the maximum esophageal pressure deflection before apnea termination (DPmax) in nine patients with severe obstructive sleep apnea as an index of the arousal threshold and the mean electroencephalogram (EEG) delta power for each 30 s as an index of the timing of sleep cycles. Periodicity in the time variation of delta power and DPmax was analyzed by determining their power spectral density and their relationship determined by cross correlation. DPmax and delta power varied cyclically and in phase with a major periodicity (major peak in power spectral density) of 117.6 ± 8.8 (SE) min. The correlation between the values of DPmax and delta power was significant ( P < 0.001) in each subject (mean r = 0.47 ± 0.03), and the coherence between DPmax and delta power at their dominant frequency was high. Within cycles of non-rapid-eye-movement sleep, DPmax and delta power increased, reaching peak values on average at or after midcycle. These findings suggest that the arousal threshold to airway occlusion in patients with obstructive sleep apnea varies cyclically during the night synchronous to the underlying cycles of sleep.

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Qi, Xiong, Nanhui Chen, and Meisen Pan. "Implementation of the Parallel Algorithm of the Cross Power Spectral Density of Random Signals." International Journal of Signal Processing, Image Processing and Pattern Recognition 8, no. 8 (August 31, 2015): 135–42. http://dx.doi.org/10.14257/ijsip.2015.8.8.15.

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Oparin, Roman D., and Michael G. Kiselev. "Application of Chemometrics Approaches to Analysis of Mid-Infrared Spectra of Ibuprofen Diluted in Supercritical Carbon Dioxide." Applied Spectroscopy 72, no. 10 (July 30, 2018): 1548–60. http://dx.doi.org/10.1177/0003702818775731.

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This work represents a comprehensive analysis of mid-infrared (mid-IR) spectra of ibuprofen diluted in supercritical CO2 (in the temperature range of 40–90 ℃ and at the CO2 density corresponding to 1.3 of its critical value). The study employed mathematical approaches based on data matrix analysis such as two-dimensional cross-correlation analysis (2D-COS) and principal component analysis (PCA). Two-dimensional cross-correlation analysis allowed us to reveal correlations between the spectral contributions constituting the analytical spectral band and assigned to certain ibuprofen conformers, as well as the significance of these correlations. It has been shown that the considerable increase in the total intensity of the analytical spectral band, proportional to the equilibrium ibuprofen concentration in the supercritical CO2 phase, is accompanied by certain redistribution of intensities of the spectral components related to the corresponding conformers. The PCA allowed us to determine the changes of intensities of individual spectral contributions for each thermodynamic point in the considered temperature range. It has been shown that these two complementary methods provide more precise information that may be used as the initial data in the classical analysis of spectral data based on spectral curve deconvolution into individual spectral contributions.

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Krishnan, Anand, Ian Watson, Roger Parton, and James Sharp. "Comparison and Validation of Visual Assessment and Image Processing Algorithms to Quantify Morphology Dynamics of Euglena gracilis." Microscopy and Microanalysis 18, no. 4 (July 30, 2012): 798–807. http://dx.doi.org/10.1017/s1431927612000414.

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AbstractImage processing algorithms were developed and compared with visual assessment from 12 volunteers to quantify the temporal morphological structure of a single Euglena gracilis organism. Representative images of E. gracilis, showing different morphological characteristics from ovate to cylindrical and elongate, were captured with a bright-field video microscopy system. These images were ranked by the volunteers in order from ovate to elongate. The images were analyzed in the spatial and spatial frequency domain, and the order of the images from each analysis was ranked against the visual assessment. The assessment methods agreeing with the volunteer's preferred sequence were an eccentricity measurement (major axis over the sum of the minor axis at three points), the cross correlation of the image without high pass filtering or edge detection, and cross correlation of the power spectral density.

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Alonso, Miguel A., and Emil Wolf. "The cross-spectral density matrix of a planar, electromagnetic stochastic source as a correlation matrix." Optics Communications 281, no. 9 (May 2008): 2393–96. http://dx.doi.org/10.1016/j.optcom.2007.12.054.

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Grądzki, Rafał, Paweł Lindstedt, Zbigniew Kulesza, and Błażej Bartoszewicz. "Rotor Blades Diagnosis Method Based on Differences in Phase Shifts." Shock and Vibration 2018 (October 21, 2018): 1–13. http://dx.doi.org/10.1155/2018/9134607.

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In this work, an innovative diagnosis method of rotor blades is presented. A measurement signal of blade tip displacement is divided into two observation zones, in which two peaks of an additional template signal are introduced. Cross-correlation and power spectral density functions of the measurement and template signals in these two distinct zones are calculated. Next, the phase shift between the two cross-correlation functions is obtained by calculating the ratio of the two power spectral density functions. The changes in parameters of an analytical description of this phase shift are used to determine a distinct and easy-to-analyze image of the technical condition of the tested blade. A graphical portrait indicating the technical condition of all blades in the annulus is developed. Although not directly measured, environmental signals (e.g., external disturbances and sensor’s noise) affecting the diagnostic process are included in the method. It is demonstrated that, by using the proposed signal processing technique, a negative influence of these disturbances is eliminated and the reliability of the machine technical condition indications is improved. The approach is demonstrated using experimental results of turbine engine blade displacements. High effectiveness of the method and measurement equipment has been confirmed in a wide range of analyzed tip-timing results obtained in different periods of the measurement process.

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Caccamo, Maria Teresa, and Salvatore Magazù. "Ethylene Glycol – Polyethylene Glycol (EG-PEG) Mixtures: Infrared Spectra Wavelet Cross-Correlation Analysis." Applied Spectroscopy 71, no. 3 (October 1, 2016): 401–9. http://dx.doi.org/10.1177/0003702816662882.

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Infrared spectra were collected on mixtures of ethylene glycol (EG) and polyethylene glycol 600 (PEG600) as a function of weight fraction from pure EG to pure PEG600. In this paper, it will be shown that while the OH vibrational contribution drastically reduces its center frequency from 3450 cm−1 to 3300 cm−1 in the weight fraction range 0–25%, the displacement of the mixture spectral features of the mixtures from ideal behavior, i.e., in the absence of interaction, shows the presence of a non-ideal mixing process. Furthermore, wavelet cross-correlation analysis of the registered pairs of spectra and of the intramolecular O–H stretching contributions reveals how the addition of a small amount of pure EG to PEG600 dramatically influences the structural properties of the polymeric matrix, owing to an increase the intermolecular connectivity. In particular, the wavelet cross-correlation parameters, evaluated between each pair of the registered data as a function of weight fraction, in a linear–logarithmic plot, reveals an inflection point for a weight fraction of about 25% of EG, which confirms that, within the three-dimensional networks of hydrogen-bonded EG-PEG600 molecules, a key role is played by EG in determining an increase in the hydrogen-bond network density.

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Pistea, Ana Maria, and Hamidreza Saligheh Rad. "On the Cross Correlation Properties of MIMO Wideband Channels under Nonisotropic Propagation Conditions." International Journal of Antennas and Propagation 2015 (2015): 1–13. http://dx.doi.org/10.1155/2015/904153.

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Wideband (WB) and ultrawideband (UWB) systems combined with multiple-input multiple-output (MIMO) technology increase both the systems performances and the complexity of the channel models required to evaluate their capabilities. Because in real scenarios waves propagate nonisotropically, the accuracy of the channel model is increased if nonisotropic propagation is considered. The channel bandwidth is the key term in the evaluation process of these systems because large bandwidths introduce frequency selectivity, a unique phenomenon of WB and UWB systems with more complexity in the latter case. This is due to the fact that, unlike WB technology in which the propagating signal is the only affected parameter by the frequency selectivity, in the UWB case, this phenomenon also affects the antenna propagation pattern (APP). In this paper, we developed a novel channel model based on the statistical analysis of two-dimensional cross correlation functions (CCFs) of WB/UWB MIMO nonisotropic channels. A mathematical solution to assess the frequency selective behavior of the UWB APP is also presented. The CCF reveals how the power spectral density (PSD) of the channel is influenced by bandwidth, nonisotropic propagation, and APP.

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Smallwood, David O. "Generation of Stationary Non-Gaussian Time Histories with a Specified Cross-spectral Density." Shock and Vibration 4, no. 5-6 (1997): 361–77. http://dx.doi.org/10.1155/1997/713593.

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The paper reviews several methods for the generation of stationary realizations of sampled time histories with non-Gaussian distributions and introduces a new method which can be used to control the cross-spectral density matrix and the probability density functions (pdfs) of the multiple input problem. Discussed first are two methods for the specialized case of matching the auto (power) spectrum, the skewness, and kurtosis using generalized shot noise and using polynomial functions. It is then shown that the skewness and kurtosis can also be controlled by the phase of a complex frequency domain description of the random process. The general case of matching a target probability density function using a zero memory nonlinear (ZMNL) function is then covered. Next methods for generating vectors of random variables with a specified covariance matrix for a class of spherically invariant random vectors (SIRV) are discussed. Finally the general case of matching the cross-spectral density matrix of a vector of inputs with non-Gaussian marginal distributions is presented.

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Sakon, Atsushi, Kunihiro Nakajima, Kazuki Takahashi, Shin-ya Hohara, Tadafumi Sano, Yuji Fukaya, and Kengo Hashimoto. "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 placed in graphite reflector region, where the counters were separated by about 35cm and 30cm -thick graphite from the core, respectively. At a critical state and subcritical states, time-sequence signal data from these counters were acquired and analyzed by a fast Fourier transform (FFT) analyzer, to obtain power spectral density in frequency domain. The auto-power spectral density obtained from the counters far from the core contained a significant degree of correlated component. A least-squares fit of a familiar formula to the auto-power spectral density data was made to determine the prompt-neutron decay constant. The decay constant was 63.3±14.5 [1/s] in critical state. The decay constant determined from the cross-power spectral density and coherence function data between the two counters also had a consistent value. It is confirmed that reactor noise analysis is possible using a detector placed at about 35cm far from the core, as we expected.

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Nyein, O. K., B. A. Aminudin, and S. Asnizah. "Experimental and Numerical Investigation of Vibration Power Flow of Thin Plate Using Cross Power Spectral Density Based Technique." IOP Conference Series: Materials Science and Engineering 1051, no. 1 (February 1, 2021): 012043. http://dx.doi.org/10.1088/1757-899x/1051/1/012043.

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Sato, Harumi, Masahiko Shimoyama, Taeko Kamiya, Toru Amari, Slobodan Šašiç, Toshio Ninomiya, Heinz W. Siesler, and Yukihiro Ozaki. "Near Infrared Spectra of Pellets and Thin Films of High-Density, Low-Density and Linear Low-Density Polyethylenes and Prediction of Their Physical Properties by Multivariate Data Analysis." Journal of Near Infrared Spectroscopy 11, no. 4 (August 2003): 309–21. http://dx.doi.org/10.1255/jnirs.376.

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The aim of the present study is to investigate in detail the near infrared (NIR) spectra of the three types of polyethylene, linear low-density polyethylene (LLDPE), low-density polyethylene (LDPE) and high-density polyethylene (HDPE), and to develop calibration models that predict their physical properties such as density, crystallinity and melting point. The effects of spectral resolution on the classification and the prediction of density for the three types of PE have been investigated. Furthermore, the NIR spectral differences among LLDPE, LDPE and HDPE have been explored in more detail using 2 cm−1 resolution. Principal component analysis (PCA) has been performed to differentiate the 18 samples of PE. They are classified into three groups, LLDPE, LDPE and HDPE, by a score plot of the PCA Factor 1 versus 3 based on the NIR spectra pretreated by multiplicative scatter correction (MSC). The 2 cm−1 spectral resolution yields a slightly better result for the classification. Partial least squares (PLS) regression has been applied to the NIR spectra after MSC to propose calibration models that predict the density, crystallinity and melting point of HDPE, LDPE and LLDPE. The correlation coefficient for the density was calculated to be 0.9898, 0.9928, 0.9925 and 0.9872 for the spectra obtained at 2, 4, 8 and 16 cm−1 resolutions, respectively, and the root mean square error of cross validation ( RMSECV) was found to be 0.0021, 0.0018, 0.0018 and 0.0023 g cm−3, respectively. It has been found that the correlation coefficient and RMSECV for the prediction of the density and crystallinity change little with the spectral resolution. However, for the prediction of melting point, the higher resolutions (2 and 4 cm−1 resolution) provide slightly better results than the lower resolutions. NIR transmission spectra of thin films of LLDPE, LDPE and HDPE have also been investigated, and calibration models for predicting their density have been developed for the film spectra.

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Gao, Yu Ling, Qing Huang, Bao Ming Yu, Xiao Tao Kang, and Yao Wu Shi. "False Peaks Suppression based on Cross-High-Order Spectral QR Decomposition Approach." Advanced Materials Research 403-408 (November 2011): 177–81. http://dx.doi.org/10.4028/www.scientific.net/amr.403-408.177.

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In signal processing, a frequently encountered problem is harmonic retrieval in additive colored noise, especially false peaks existence in harmonic signal peaks. The purpose of this paper is to develop an efficient approach to clear the false peaks based on cross-high-order spectral QR decomposition approach. Simulation results indicate that spectral density curve is smooth without false peaks existence. The methods have better in resolving power and performance than previous MUSIC approach. Thus, this approach is ideally suited for harmonic retrieval in additive colored noise and short data conditions, and is also accurate to estimation signal parameter in hybrid colored noises.

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Chen, Dongju, Shuai Zhou, Lihua Dong, and Jinwei Fan. "An Investigation into Error Source Identification of Machine Tools Based on Time-Frequency Feature Extraction." Shock and Vibration 2016 (2016): 1–10. http://dx.doi.org/10.1155/2016/1040942.

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This paper presents a new identification method to identify the main errors of the machine tool in time-frequency domain. The low- and high-frequency signals of the workpiece surface are decomposed based on the Daubechies wavelet transform. With power spectral density analysis, the main features of the high-frequency signal corresponding to the imbalance of the spindle system are extracted from the surface topography of the workpiece in the frequency domain. With the cross-correlation analysis method, the relationship between the guideway error of the machine tool and the low-frequency signal of the surface topography is calculated in the time domain.

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Cui, Bao Zhen, Ze Bing Wang, and Hong Xia Pan. "The Study of Local Wave Noise Reduction Based on the Correlation Analysis." Advanced Materials Research 588-589 (November 2012): 707–10. http://dx.doi.org/10.4028/www.scientific.net/amr.588-589.707.

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The signal can be divided into a number of intrinsic mode components (IMF) through local wave decomposition. The decomposition process is equivalent to the adaptive filter for signal. The frequencies of each IMF have reduced with the decomposition order. This paper established judgment criteria of signal, noise and pseudo component based on the local wave decomposition, used the characteristics of cross-correlation coefficient and autocorrelation sequence, combined with the power spectral density. The dominant mode function was extracted effectively and the final effects are used gear reducer in the JZQ250 of fault rolling bearing inner ring. It provides a new method for non-stationary signal adaptive noise reduction and fault diagnosis of rotating machinery.

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Yang, Zhi Qiang, and C. J. Wu. "The Influence of Non-Uniform Impeller on the Cross Flow Fan Noise." Key Engineering Materials 693 (May 2016): 251–56. http://dx.doi.org/10.4028/www.scientific.net/kem.693.251.

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The aerodynamic noise of a cross flow fan with uneven blade spacing in room air-conditioner was simulated by computational aerodynamic acoustics (CAA) method. It is detailed to analyze the vorticity distribution of the flow field and the power spectral density of measured points’ pressure fluctuations, and the results demonstrate the non-uniform impeller used in this paper can significantly improve internal flow characteristics. Thus the broadband noise got reduced.

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Cui, Song, Enlai Zheng, and Min Kang. "A time-domain procedure for non-Gaussian stationary environmental testing using zero-memory nonlinear transformation." Journal of Vibration and Control 26, no. 15-16 (January 13, 2020): 1197–213. http://dx.doi.org/10.1177/1077546319894853.

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This article proposes a time-domain procedure for a non-Gaussian stationary random vibration test with prescribed power spectral densities. Previous procedures for generating non-Gaussianity suffered from certain defects. For example, zero-memory nonlinear transformation, an algorithm frequently applied to transform Gaussian signals into non-Gaussian signals, often produces changes in both auto-power spectral densities and cross-power spectral densities, which might result in control instability under certain circumstances. In this article, the authors propose a different approach for the zero-memory nonlinear function. First, a time-domain procedure for a non-Gaussian random test is introduced. Second, a rescaling method is applied to correct the magnitude amplification on the auto-power spectral density because of zero-memory nonlinear transformation. We offer experience formulas in this method to adjust the auto-power spectral density of both super-Gaussian and sub-Gaussian responses. Third, a control strategy using a finite impulse response filter is proposed to further improve the auto-power spectral density if the shape of the auto-power spectral density is distorted. The kurtosis loss induced by the filtering process is also analysed and a corresponding solution is put forward to ease the reduction. Numerical test and a biaxial shaker table test are conducted to validate the availability and superiority of the proposed procedure.

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Li, Jinhua, Chunxiang Li, and Shuisheng Chen. "Spline-Interpolation-Based FFT Approach to Fast Simulation of Multivariate Stochastic Processes." Mathematical Problems in Engineering 2011 (2011): 1–24. http://dx.doi.org/10.1155/2011/842183.

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The spline-interpolation-based fast Fourier transform (FFT) algorithm, designated as the SFFT algorithm, is proposed in the present paper to further enhance the computational speed of simulating the multivariate stochastic processes. The proposed SFFT algorithm first introduces the spline interpolation technique to reduce the number of the Cholesky decomposition of a spectral density matrix and subsequently uses the FFT algorithm to further enhance the computational speed. In order to highlight the superiority of the SFFT algorithm, the simulations of the multivariate stationary longitudinal wind velocity fluctuations have been carried out, respectively, with resorting to the SFFT-based and FFT-based spectral representation SR methods, taking into consideration that the elements of cross-power spectral density matrix are the complex values. The numerical simulation results show that though introducing the spline interpolation approximation in decomposing the cross-power spectral density matrix, the SFFT algorithm can achieve the results without a loss of precision with reference to the FFT algorithm. In comparison with the FFT algorithm, the SFFT algorithm provides much higher computational efficiency. Likewise, the superiority of the SFFT algorithm is becoming more remarkable with the dividing number of frequency, the number of samples, and the time length of samples going up.

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Sivathanu, Y. R., and J. P. Gore. "Transient Structure and Radiation Properties of Strongly Radiating Buoyant Flames." Journal of Heat Transfer 114, no. 3 (August 1, 1992): 659–65. http://dx.doi.org/10.1115/1.2911331.

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Measurements of instantaneous temperature and soot volume fractions based on absorption and emission in highly buoyant turbulent acetylene/air and propylene/air flames are reported. These measurements are used to predict mean, rms, probability density functions, and power spectral densities of spectral radiation intensities along a representative horizontal chord in the flame. The results show the presence of large quantities of relatively cold soot in the vicinity of smaller amounts of hot soot particles. The resulting inhomogeneity in the temperature of soot in the flame leads to negative cross correlations between temperature and soot volume fractions. The treatment of such correlations was found necessary for predicting the observed probability density functions and the power spectral densities of spectral radiation intensities.

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Levine, S., J. Gillen, P. Weiser, M. Gillen, and E. Kwatny. "Description and validation of an ECG removal procedure for EMGdi power spectrum analysis." Journal of Applied Physiology 60, no. 3 (March 1, 1986): 1073–81. http://dx.doi.org/10.1152/jappl.1986.60.3.1073.

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We describe a cross-correlation procedure for removing contaminating electrocardiogram (ECG) complexes from the diaphragmatic electromyogram (EMGdi). First, the operator selects ECG templates from the EMGdi signal during expiratory intervals. Second, these templates are used to locate ECG complexes occurring during inspiratory EMGdi activity. Third, at the point of maximum correlation between the template and these ECG complexes, the template is adjusted in size and offset to “match” the ECG complex, and adjustments are determined by the linear regression coefficients. Finally, the modified template is subtracted from the EMGdi signal. To evaluate our method, we compared the power spectral density (PSD) obtained from processing EMGdi signals by our method with those obtained from the EMGdi signal in which ECG complexes had been removed by gating. Our results indicate that PSD obtained by these two different methods shows no statistically significant differences with respect to the following features: centroid frequency, median frequency, total power, standard deviation, skewness, and kurtosis.

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Steidl, Jamison H. "Variation of Site Response at the UCSB Dense Array of Portable Accelerometers." Earthquake Spectra 9, no. 2 (May 1993): 289–302. http://dx.doi.org/10.1193/1.1585716.

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Ten Kinemetrics model SSA-2 Solid State Accelerographs were deployed in two dense arrays following the Landers-Big Bear earthquake sequence. The two arrays were separated by approximately three km, the first at a shallow alluvial soil site and the second at a rock site. We examine the soil and rock sites in terms of spectral ratio and cross-spectrum estimates of the site response. In order to construct an accurate representation of the motion in the horizontal plane, we treat the two horizontal components simultaneously as a complex signal. The Fourier transform of this complex signal represents the true motion in the horizontal plane as expressed in the frequency domain. The spectral ratio estimate is the ratio of this Fourier transform at the soil sites to the rock sites. The cross-spectrum estimate is the ratio of the cross-spectral density between the soil and rock sites to the power spectral density of the rock site. Spectral ratio estimates of site amplification are consistently higher than cross-spectrum estimates. On average the soil sites show amplification factors on the order of 2 to 4 relative to the rock sites between the frequencies of 4 to 15 Hz. There are, however, large variations in the ground motion recorded at sites with separations as small as 80 m. These variations demonstrate that site response studies can be biased by the choice of location of the sensor at distances of 80 m. We conclude that in the analysis of site-specific amplification both cross-spectrum and spectral ratio techniques should be used along with ensemble averages over many events.

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Fleischmann, Patrick, Heinz Mathis, Jakub Kucera, and Stefan Dahinden. "Implementation of a Cross-Spectrum FFT Analyzer for a Phase-Noise Test System in a Low-Cost FPGA." International Journal of Microwave Science and Technology 2015 (September 17, 2015): 1–7. http://dx.doi.org/10.1155/2015/757591.

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The cross-correlation method allows phase-noise measurements of high-quality devices with very low noise levels, using reference sources with higher noise levels than the device under test. To implement this method, a phase-noise analyzer needs to compute the cross-spectral density, that is, the Fourier transform of the cross-correlation, of two time series over a wide frequency range, from fractions of Hz to tens of MHz. Furthermore, the analyzer requires a high dynamic range to accommodate the phase noise of high-quality oscillators that may fall off by more than 100 dB from close-in noise to the noise floor at large frequency offsets. This paper describes the efficient implementation of a cross-spectrum analyzer in a low-cost FPGA, as part of a modern phase-noise analyzer with very fast measurement time.

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Liu, Feng, Ya Dong Gong, Yu Qiao Shan, and Guang Qi Cai. "The Correlation and Spectrum Research on Cylindrical Surface Lapping Machined with Abrasive Jet Finishing Restricted by Grinding Wheel." Key Engineering Materials 389-390 (September 2008): 320–25. http://dx.doi.org/10.4028/www.scientific.net/kem.389-390.320.

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With the correlation in stochastic process applied to the experimental results, the surface during grinding and further lapping with abrasive jet finishing (AJF) restricted by grinding wheel was investigated with respect to auto correlation function (ACF) , cross correlation function (CCF) and power spectral density (PSD) analysis. The results indicated that AJF made the surface contour formed periodicity in a small range and removed fluctuation of the surface contour in low frequency greatly. The average spacing of the surface contour decreased and the machined surfaces changed from continuous parallel micro-groove and plough to randomly distributed discontinuous micro-pit with the increase of machining circles. The surface texture became fine and surface roughness was obviously improved. Furthermore, the isotropy surface and uniformity veins both parallel and perpendicular machining direction was attained by the finishing process to improve greatly the wearable capability of the workpiece.

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Holbert, Keith E., and Nikhil Venkatesh. "Valid Ranges for Using the Cross-Power Spectral Density Phase Angle for Moderator Temperature Coefficient Sign Determination." Nuclear Science and Engineering 119, no. 3 (March 1995): 203–11. http://dx.doi.org/10.13182/nse95-a24086.

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Hurier, G., P. Singh, and C. Hernández-Monteagudo. "First measurement of the cross-correlation between CMB weak lensing and X-ray emission." Astronomy & Astrophysics 625 (May 2019): L4. http://dx.doi.org/10.1051/0004-6361/201732071.

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Since the publication of the results of the Planck satellite mission in 2013, the local and early Universes have been considered to be in tension in respect of the determination of amplitude of the matter density spatial fluctuations (σ8) and the amount of matter present in the Universe (Ωm). This tension can be seen as a lack of massive galaxy clusters in the local Universe compared to the prediction inferred from Planck cosmic microwave background (CMB) best-fitting cosmology. In the present analysis we perform the first detection of the cross-correlation between X-rays and CMB weak lensing at 9.1σ. We next combine thermal Sunyaev–Zel’dovich effect, X-rays, and weak-lensing angular auto- and cross-correlation power spectra to determine the galaxy cluster hydrostatic mass bias. We derive (1 − bH) = 0.71 ± 0.07. Considering these constraints, we observe that estimations of σ8 in the local Universe are consistent with Planck CMB best-fitting cosmology. However, these results are in clear tension with the output of hydrodynamical simulations that favor (1 − bH)> 0.8.

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Gao, C., and M. K. Scullin. "0344 Age-Related Longitudinal Trajectories in NREM and REM Spectral Power." Sleep 43, Supplement_1 (April 2020): A130—A131. http://dx.doi.org/10.1093/sleep/zsaa056.341.

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Abstract Introduction Knowledge of how aging impacts sleep physiology is based almost exclusively on cross-sectional studies. Longitudinal studies, by contrast, can inform how macro- and micro-features of NREM and REM sleep change dynamically across time in individual trajectories. For the current work, we conducted quantitative EEG analyses from a longitudinal polysomnography study to inform age-related trajectories in sleep macro- and micro-architecture. Methods We conducted a secondary data analysis on 2208 participants in the Sleep Heart Health Study (mean age =62.47, SD=10.46, 55.30% females). Participants underwent one night of in-home polysomnography recording during two study visits (M=5.21 years apart, SD=0.53). Spectral power density was calculated for each 0.5 Hz frequency bin for NREM and REM sleep separately. Results In cross-sectional analyses, older chronological age was significantly associated with worse sleep macro-architecture. Plots of the individual trajectories over 5 years, however, revealed considerable inter-individual variability in whether sleep physiology was preserved or declined. Interestingly, there were strong associations between the longitudinal changes in power density in NREM and REM sleep (slow oscillations: r=.53 [.50-.56]; delta: r=.58 [.55-.60]; alpha: r=.69 [.67-.71]; sigma: r=.74 [.73-.76]; beta: r=.82 [.80-.83]; ps<.001). The strongest NREM-REM association was for theta band power (r=.85 [.83-.86]), particularly in the 5.5-6.0 Hz bin (r=.94, [.94, .95]). Conclusion There is substantial inter-individual variability in how aging impacts sleep physiology. Nevertheless, within individuals, power density declines similarly across NREM and REM stages, with nearly perfect convergence for theta activity, indicating a common age-related neurobiological mechanism. Support The National Sleep Research Resource is supported by NIH HL114473.

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Bracco, Andrea, Tuhin Ghosh, François Boulanger, and Jonathan Aumont. "Link between E–B polarization modes and gas column density from interstellar dust emission." Astronomy & Astrophysics 632 (November 21, 2019): A17. http://dx.doi.org/10.1051/0004-6361/201935951.

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Context. The analysis of the Planck polarization E and B mode power spectra of interstellar dust emission at 353 GHz recently raised new questions concerning the impact of Galactic foregrounds on the detection of the polarization of the cosmic microwave background (CMB) and on the physical properties of the interstellar medium (ISM). In the diffuse ISM at high latitude a clear E–B asymmetry is observed that has twice as much power in E modes as in B modes; there is also a positive correlation between the total power, T, and both E and B modes, which is currently interpreted in terms of the link between the structure of interstellar matter and that of the Galactic magnetic field. Aims. In this paper we aim to extend the Planck analysis of the high latitude sky to low Galactic latitudes, investigating the correlation between the T–E–B auto- and cross-correlation power spectra with the gas column density from the diffuse ISM to molecular clouds. Methods. We divided the sky between Galactic latitudes |b| > 5° and |b| < 60° in 552 circular patches, with an area of ~400°2, and we studied the cross-correlations between the T–E–B power spectra and the column density of each patch using the latest release of the Planck polarization data. Results. We find that the B-to-E power ratio (DlBB/DlEE) and the TE correlation ratio (rTE) depend on column density. While the former increases going from the diffuse ISM to molecular clouds in the Gould Belt, the latter decreases. This systematic variation must be related to actual changes in ISM properties. The data show significant scatter about this mean trend. The variations of DlBB/DlEE and rTE are observed to be anticorrelated for all column densities. In the diffuse ISM, the variance of these two ratios is consistent with a stochastic non-Gaussian model in which the values of DlBB/DlEE and rTE are fixed. We finally discuss the dependences of TB and EB with column density, which are however hampered by instrumental noise. Conclusions. For the first time, this work shows significant variations of the T–E–B power spectra of dust polarized emission across a large portion of the Galaxy. Their dependence on multipole and gas column density is key for accurate forecasts of next generation CMB experiments and for constraining present models of ISM physics (i.e., dust properties and interstellar turbulence), which are considered responsible for the observed T–E–B signals.

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Waili, T., Md Gapar Md Johar, K. A. Sidek, N. S. H. Mohd Nor, H. Yaacob, and M. Othman. "EEG Based Biometric Identification Using Correlation and MLPNN Models." International Journal of Online and Biomedical Engineering (iJOE) 15, no. 10 (June 27, 2019): 77. http://dx.doi.org/10.3991/ijoe.v15i10.10880.

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<p class="0abstract">This study investigates the capability of electroencephalogram (EEG) signals to be used for biometric identification. In the context of biometric, recently, researchers have been focusing more on biomedical signals to substitute the biometric modalities that are being used nowadays as the signals obtained from our bodies is considered more secure and privacy-compliant. The EEG signals of 6 subjects were collected where the subjects were required to undergo two baseline experiments which are, eyes open (EO) and eyes closed (EC). The signals were processed using a 2nd order Butterworth filter to eliminate the unwanted noise in the signals. Then, Daubechies (db8) wavelet was applied to the signals in the feature extraction stage and from there, Power Spectral Density (PSD) of alpha and beta waves was computed. Finally, the correlation model and Multilayer Perceptron Neural Network (MLPNN) was applied to classify the EEG signals of each subject. Correlation model has yielded great significant difference of coefficient between autocorrelation and cross-correlation where it gives the coefficient value of 1 for autocorrelation and the coefficient value of less than 0.35 for cross-correlation. On the other hand, the MLPNN model gives an accuracy of 75.8% and 71.5% for classification during EO and EC baseline condition respectively. Therefore, these results support the usability of EEG signals in biometric recognition.</p>

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Luo, Jun Jie, Cheng Su, and Da Jian Han. "A Spectral Representation Model for Simulation of Multivariate Random Processes." Advanced Materials Research 368-373 (October 2011): 1253–58. http://dx.doi.org/10.4028/www.scientific.net/amr.368-373.1253.

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A model is proposed to simulate multivariate weakly stationary Gaussian stochastic processes based on the spectral representation theorem. In this model, the amplitude, phase angle, and frequency involved in the harmonic function are random so that the generated samples are real stochastic processes. Three algorithms are then adopted to improve the simulation efficiency. A uniform cubic B-spline interpolation method is employed to fit the target factorized power spectral density function curves. A recursive algorithm for the Cholesky factorization is utilized to decompose the cross-power spectral density matrices. Some redundant cosine terms are cut off to decrease the computation quantity of superposition. Finally, an example involving simulation of turbulent wind velocity fluctuations is given to validate the capability and accuracy of the proposed model as well as the efficiency of the optimal algorithms.

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Kärnä, Tuomo, Yan Qu, Xiangjun Bi, Qianjin Yue, and Walter Kuehnlein. "A Spectral Model for Forces Due to Ice Crushing." Journal of Offshore Mechanics and Arctic Engineering 129, no. 2 (September 14, 2006): 138–45. http://dx.doi.org/10.1115/1.2426997.

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This paper presents a model of dynamic ice forces on vertical offshore structures. The model concerns a loading scenario where a competent ice sheet is drifting and crushing against the structure. Full scale data obtained on two offshore structures were used in the derivation of a method that applies both to narrow and wide structures. A large amount of events with directly measured local forces was used to derive formulas for spectral density functions of the local ice forces. A nondimensional formula that was derived for the autospectral density is independent of ice thickness. Coherence functions were used to define cross-spectral density functions of the local ice forces. The two kind of spectral density functions were used to obtain the spectral density of the total ice force. The method takes into account both the spatial and time correlation between the local forces. Accordingly, the model provides a tool to consider the nonsimultaneous characteristics of the local ice pressures while assessing the total ice force.

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Podkopayev, A. O., and M. A. Stepanov. "SYNTHESIS OF TWO-POINT PARTIALLY COHERENT MODEL, PROVIDING SPECIFIED CORRELATION CHARACTERISTICS OF ANGULAR NOISE, BASED ON ITS EQUIVALENCE OF THREE-POINT NON-COHERENT MODEL WITH SEPARABILITY OF SPATIAL AND TEMPORAL COORDINATES." Issues of radio electronics, no. 4 (May 10, 2019): 16–21. http://dx.doi.org/10.21778/2218-5453-2019-4-16-21.

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The paper considers approaches developed for the synthesis of a two-point geometric model that emits correlated signals and forms angular noise with given spectral-correlation properties, based on its equivalence of a three-point model that emits noncorrelated signals. Analytical relationships have been obtained that allow us to determine the spectral correlation characteristics of the signals supplied to the emitters of the two-point partially coherent model. The basis for the synthesis of a two-point model, emitting correlated signals, is a three-point model, emitting non-correlated signals. The considered models can replace a one-dimensional object that has the property of separating the spatial and temporal variables in functions that determine the distribution of the density of the auto- and cross-correlation quadrature components of the echo signal over the object. In this case, all points of the object being replaced reflect echoes with the same spectral and correlation properties. The obtained theoretical results are confirmed by digital modeling. The obtained probability density distributions of the angular noise and their correlation functions coincide for the two considered models.

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Li, Peng, Xinhua Zhang, and Wenlong Zhang. "Direction of Arrival Estimation Using Two Hydrophones: Frequency Diversity Technique for Passive Sonar." Sensors 19, no. 9 (April 29, 2019): 2001. http://dx.doi.org/10.3390/s19092001.

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The traditional passive azimuth estimation algorithm using two hydrophones, such as cross-correlation time-delay estimation and cross-spectral phase estimation, requires a high signal-to-noise ratio (SNR) to ensure the clarity of the estimated target trajectory. This paper proposes an algorithm to apply the frequency diversity technique to passive azimuth estimation. The algorithm also uses two hydrophones but can obtain clear trajectories at a lower SNR. Firstly, the initial phase of the signal at different frequencies is removed by calculating the cross-spectral density matrix. Then, phase information between frequencies is used for beamforming. In this way, the frequency dimension information is used to improve the signal processing gain. This paper theoretically analyzes the resolution and processing gain of the algorithm. The simulation results show that the proposed algorithm can estimate the target azimuth robustly under the conditions of a single target (SNR = −16 dB) and multiple targets (SNR = −10 dB), while the cross-correlation algorithm cannot. Finally, the algorithm is tested by the swell96 data and the South Sea experimental data. When dealing with rich frequency signals, the performance of the algorithm using two hydrophones is even better than that of the conventional broadband beamforming of the 64-element array. This further validates the effectiveness and advantages of the algorithm.

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Xu, Lang, Paolo Pennacchi, and Steven Chatterton. "A new method for the estimation of bearing health state and remaining useful life based on the moving average cross-correlation of power spectral density." Mechanical Systems and Signal Processing 139 (May 2020): 106617. http://dx.doi.org/10.1016/j.ymssp.2020.106617.

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Fleming, Andrew J., Brett Ninness, and Adrian Wills. "Recovering the spectrum of a low level signal from two noisy measurements using the cross power spectral density." Review of Scientific Instruments 84, no. 8 (August 2013): 085112. http://dx.doi.org/10.1063/1.4815982.

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Journal articles on the topic 'Cross-correlation, cross-power spectral density'

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