Journal articles: 'Spectral moments analysis'

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KOUSSOULAS, NICK T. "SPECTRAL MOMENTS AND THE ANALYSIS OF CHAOTIC SYSTEMS." International Journal of Bifurcation and Chaos 11, no. 07 (July 2001): 2051–59. http://dx.doi.org/10.1142/s0218127401003140.

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The simplicity of structure of chaotic systems, combined with the richness of their output, inspires their use in modeling efforts. On the other hand, the difficulty of their analysis warrants approximation methods, especially since the absence, by definition, of well-defined limit sets prohibits, in general, a meaningful linearization. In this work we present some results, which can support a methodology founded on spectral analysis for approximating chaotic systems via stochastic linear systems. The main contribution is the use of spectral moments for identifying the location of embedded limit cycles and the spectrum-based validation of approximations.

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Rosenbauer, Kimberly, Kerrie Obert, and Robert Allen Fox. "Spectral moments analysis of stops in tracheoesophageal speakers." Journal of the Acoustical Society of America 111, no. 5 (2002): 2480. http://dx.doi.org/10.1121/1.4778617.

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Tong, Fang, and Zhang Tianshu. "Calculating response spectral moments by complex modal analysis." Acta Mechanica Sinica 5, no. 2 (May 1989): 159–66. http://dx.doi.org/10.1007/bf02489141.

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Jun, Seockhee, and Jun-Bum Park. "Development of Empirical Formulas for Approximate Spectral Moment Based on Rain-Flow Counting Stress-Range Distribution." Journal of Ocean Engineering and Technology 35, no. 4 (August 31, 2021): 257–65. http://dx.doi.org/10.26748/ksoe.2021.014.

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Many studies have been performed to predict a reliable and accurate stress-range distribution and fatigue damage regarding the Gaussian wide-band stress response due to multi-peak waves and multiple dynamic loads. So far, most of the approximation models provide slightly inaccurate results in comparison with the rain-flow counting method as an exact solution. A step-by-step study was carried out to develop new approximate spectral moments that are close to the rain-flow counting moment, which can be used for the development of a fatigue damage model. Using the special parameters and bandwidth parameters, four kinds of parameter-based combinations were constructed and estimated using the R-squared values from regression analysis. Based on the results, four candidate empirical formulas were determined and compared with the rain-flow counting moment, probability density function, and root mean square (RMS) value for relative distance. The new approximate spectral moments were finally decided through comparison studies of eight response spectra. The new spectral moments presented in this study could play an important role in improving the accuracy of fatigue damage model development. The present study shows that the new approximate moment is a very important variable for the enhancement of Gaussian wide-band fatigue damage assessment.

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El-Kader, M. S. A., and G. Maroulis. "Moment analysis in collision-induced absorption: Determination of a single parameter empirical model for the induced dipole moment of He-Ar gas mixtures." Journal of Computational Methods in Sciences and Engineering 21, no. 3 (August 2, 2021): 577–92. http://dx.doi.org/10.3233/jcm-200043.

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We present a method for the construction of a one-adjustable-parameter empirical model for the induced dipole moment. The method is based on classical physics principles and relies on the first three spectral moments of the collision-induced absorption spectra at various temperatures and new interaction potentials. In this work it is applied to the spectra of He-Ar mixtures. Our values are in good agreement with the available ab initio data. The profiles calculated with these models at various temperatures are in excellent agreement with experiment.

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SHEN, JUN, WEI SHEN, and DANFEI SHEN. "ON GEOMETRIC AND ORTHOGONAL MOMENTS." International Journal of Pattern Recognition and Artificial Intelligence 14, no. 07 (November 2000): 875–94. http://dx.doi.org/10.1142/s0218001400000581.

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Moments are widely used in pattern recognition, image processing, computer vision and multiresolution analysis. To clarify and to guide the use of different types of moments, we present in this paper a study on the different moments and compare their behavior. After an introduction to geometric, Legendre, Hermite and Gaussian–Hermite moments and their calculation, we analyze at first their behavior in spatial domain. Our analysis shows orthogonal moment base functions of different orders having different number of zero-crossings and very different shapes, therefore they can better separate image features based on different modes, which is very interesting for pattern analysis and shape classification. Moreover, Gaussian–Hermite moment base functions are much more smoothed, they are thus less sensitive to noise and avoid the artifacts introduced by window function discontinuity. We then analyze the spectral behavior of moments in frequency domain. Theoretical and numerical analyses show that orthogonal Legendre and Gaussian–Hermite moments of different orders separate different frequency bands more effectively. It is also shown that Gaussian–Hermite moments present an approach to construct orthogonal features from the results of wavelet analysis. The orthogonality equivalence theorem is also presented. Our analysis is confirmed by numerical results, which are then reported.

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Tjaden, Kris, and Greg S. Turner. "Spectral Properties of Fricatives in Amyotrophic Lateral Sclerosis." Journal of Speech, Language, and Hearing Research 40, no. 6 (December 1997): 1358–72. http://dx.doi.org/10.1044/jslhr.4006.1358.

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Spectral characteristics of word initial /s/and /∫/produced by individuals with amyotrophic lateral sclerosis (ALS) and healthy controls were quantified using spectral moment analysis. Coefficients of the first four moments were used as descriptive indices of central tendency, spread of energy, shape, and peakedness. The relationship between select moment coefficients and consonant precision ratings was investigated to explore potential perceptual correlates of the acoustic measures. To examine whether spectra for ALS and healthy speakers were influenced similarly by context, first moment coefficients for three occurrences of /s/in “some” were inspected for individual speakers. Select moment coefficients also were compared to hand-derived spectral measures for a subset of speakers. Results suggest articulatory differences in /s/and /∫/for the present group of ALS speakers and healthy controls, as indexed by between-group differences in first moment coefficients. A linear function accounted for a significant proportion of the variance in the relationship between consonant precision ratings and the frequency difference between the first moment for /s/and /∫/. Inspection of first moment coefficients for multiple occurrences of /s/in “some” suggests context influences the first moment in a similar manner for ALS and healthy speakers. The subanalysis comparing moment coefficients and hand-derived spectral measures revealed both similarities and differences in the manner the two measurement techniques reflect spectral shape.

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Osipov, Andrey. "Inverse spectral problem for Jacobi operators and Miura transformation." Concrete Operators 8, no. 1 (January 1, 2021): 77–89. http://dx.doi.org/10.1515/conop-2020-0116.

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Abstract We study a Miura-type transformation between Kac - van Moerbeke (Volterra) and Toda lattices in terms of the inverse spectral problem for Jacobi operators, which appear in the Lax representation for such systems. This inverse problem method, which amounts to reconstruction of the operator from the moments of its Weyl function, can be used in solving initial-boundary value problem for both systems. It is shown that the Miura transformation can be easily described in terms of these moments. Using this description we establish a bijection between the Volterra lattices and the class of Toda lattices which is characterized by positivity of Jacobi operators in their Lax representation. Also, we discuss an implication of the latter result to the spectral theory.

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Viswanathan, A., V. A. Subramanian, and D. Kumar. "Location-based fatigue damage assessment on an FPSO by the spectral analysis method." MATEC Web of Conferences 272 (2019): 01019. http://dx.doi.org/10.1051/matecconf/201927201019.

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Floating production storage and offloading ships (FPSOs) are offshore platforms positioned at a location and operating at different loading conditions and corresponding draughts. Due to their static location, they get subjected to continuous fluctuating loads due to the sea environment. For these reasons the fatigue damage prediction of an FPSO is essential. The emphasis of this study is on the effect of fatigue damage at critical joints of critical structural members under the influence of vertical and horizontal bending in isolation and combination. The method considers an FPSO of 320m length for a case study, selecting a total of fourteen such structural member locations along the periphery at its midship section. The analysis considers two necessary loading conditions namely, fully loaded and ballast condition. The study uses spectral fatigue analysis method wherein the bending moment transfer function generates the stress transfer function, which in turn helps to generate the power spectral density function. Combining the spectral moments with Palmgren-Miner rule gives the cumulative fatigue damage of the FPSO. The results provide an insight into the variation in fatigue damage concerning the location of the structural member under the influence of vertical and horizontal bending moments.

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Galbraith, Gary C., and Eugene H. Wong. "Moment Analysis of Eeg Amplitude Histograms and Spectral Analysis: Relative Classification of Several Behavioral Tasks." Perceptual and Motor Skills 76, no. 3 (June 1993): 859–66. http://dx.doi.org/10.2466/pms.1993.76.3.859.

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Previous studies indicate that EEG amplitude probability density functions are Gaussian (normal) during rest and non-Gaussian during performance of mental tasks. In the present study we compared measures of normality, including higher central moments (e.g., skewness, kurtosis) and relative spectral power, to classify data sampled from several different behavioral tasks (resting eyes closed and mental arithmetic). Analysis shows significant classification in 22 of 25 subjects, based upon a total of 46 EEG variables. However, only two of these variables involved Gaussian properties of the amplitude distribution. Relative spectral power, on the other hand, contributed 33 predictor variables in delta, theta, alpha, and beta frequency bands (alpha was the best single predictor). These results lend support to studies demonstrating the robustness of EEG relative spectra but cast doubt upon the utility of Gaussian patterns in EEG amplitude distributions as predictors of behavioral states.

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Liebmann, Max, Alexander Treffer, Martin Bock, Thomas Seiler, Jürgen Jahns, Thomas Elsaesser, and Ruediger Grunwald. "Spectral meta-moments reveal hidden signatures of vortex pulses." EPJ Web of Conferences 205 (2019): 01005. http://dx.doi.org/10.1051/epjconf/201920501005.

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Ultrashort vortex pulses possess specific spatio-spectral signatures due to Gouy phase shift. Helical movement of anomalies around the phase singularity was found which is referred to as spectral Gouy rotation. The analysis of spectral moments allows for identifying related characteristic patterns even in weakly modulated spectral maps. Radial meta-moments from polar projections deliver information on global spectral gradients and oscillatory behavior. The particular mathematical tools could also be applied to other fields of ultrafast spectroscopy.

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Andriantiana, Eric Ould Dadah, and Stephan Wagner. "Spectral moments of trees with given degree sequence." Linear Algebra and its Applications 439, no. 12 (December 2013): 3980–4002. http://dx.doi.org/10.1016/j.laa.2013.10.019.

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Milbrandt, J. A., and M. K. Yau. "A Multimoment Bulk Microphysics Parameterization. Part I: Analysis of the Role of the Spectral Shape Parameter." Journal of the Atmospheric Sciences 62, no. 9 (September 1, 2005): 3051–64. http://dx.doi.org/10.1175/jas3534.1.

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Abstract With increasing computer power, explicit microphysics schemes are becoming increasingly important in atmospheric models. Many schemes have followed the approach of Kessler in which one moment of the hydrometeor size distribution, proportional to the mass content, is predicted. More recently, the two-moment method has been introduced in which both the mass and the total number concentration of the hydrometeor categories are independently predicted. In bulk schemes, the size spectrum of each hydrometeor category is often described by a three-parameter gamma distribution function, N(D) = N0Dαe−λD. Two-moment schemes generally treat N0 and λ as prognostic parameters while holding α constant. In this paper, the role of the spectral shape parameter, α, is investigated by examining its effects on sedimentation and microphysical growth rates. An approach is introduced for a two-moment scheme where α is allowed to vary diagnostically as a function of the mean-mass diameter. Comparisons are made between calculations using various bulk approaches—a one-moment, a two-moment, and a three-moment method—and an analytic bin model. It is found that the size-sorting mechanism, which exists in a bulk scheme when different fall velocities are applied to advect the different predicted moments, is significantly different amongst the schemes. The shape parameter plays an important role in determining the rate of size sorting. Likewise, instantaneous growth rates related to the moments are shown to be significantly affected by this parameter.

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Standridge, R. K., G. V. Kondraske, V. Mooney, T. W. Carmichael, and T. G. Mayer. "Temporal characterization of myoelectric spectral moments changes: analysis of common parameters." IEEE Transactions on Biomedical Engineering 35, no. 10 (1988): 789–97. http://dx.doi.org/10.1109/10.7285.

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Anandan, V. K., C. J. Pan, T. Rajalakshmi, and G. Ramachandra Reddy. "Multitaper spectral analysis of atmospheric radar signals." Annales Geophysicae 22, no. 11 (November 29, 2004): 3995–4003. http://dx.doi.org/10.5194/angeo-22-3995-2004.

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Abstract. Multitaper spectral analysis using sinusoidal taper has been carried out on the backscattered signals received from the troposphere and lower stratosphere by the Gadanki Mesosphere-Stratosphere-Troposphere (MST) radar under various conditions of the signal-to-noise ratio. Comparison of study is made with sinusoidal taper of the order of three and single tapers of Hanning and rectangular tapers, to understand the relative merits of processing under the scheme. Power spectra plots show that echoes are better identified in the case of multitaper estimation, especially in the region of a weak signal-to-noise ratio. Further analysis is carried out to obtain three lower order moments from three estimation techniques. The results show that multitaper analysis gives a better signal-to-noise ratio or higher detectability. The spectral analysis through multitaper and single tapers is subjected to study of consistency in measurements. Results show that the multitaper estimate is better consistent in Doppler measurements compared to single taper estimates. Doppler width measurements with different approaches were studied and the results show that the estimation was better in the multitaper technique in terms of temporal resolution and estimation accuracy.

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Modi, Chetan K., Ashwin S. Patel, and Bharat T. Thaker. "Synthesis, Spectral, Magnetic and Thermal Studies of the Complexes of CoIIand NiIIWith Some Bidentate and Tridentate Hydrazone Ligands." E-Journal of Chemistry 2, no. 1 (2005): 21–29. http://dx.doi.org/10.1155/2005/608974.

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The reaction of Co(NO3)2.6H2O and Ni(NO3)2.6H2O with hydrazones derived from 1-phenyl-3-methyl-4-acyl-5-pyrazolone (where acyl = acetyl, propionyl, butyryl and benzoyl) with 2-picolinic acid hydrazide have been studied and characterized on the basis of elemental analysis, magnetic moments, molar conductivity measurements, IR and electronic spectral studies and thermogravimetric analysis. Various ligand field parameters have been calculated. Electronic spectral data and the magnetic moment values suggest an octahedral structure for all cobalt(II) and nickel(II) complexes.

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Yu, Tian-You, Ricardo Reinoso Rondinel, and Robert D. Palmer. "Investigation of Non-Gaussian Doppler Spectra Observed by Weather Radar in a Tornadic Supercell." Journal of Atmospheric and Oceanic Technology 26, no. 3 (March 1, 2009): 444–61. http://dx.doi.org/10.1175/2008jtecha1124.1.

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Abstract Radar Doppler spectra that deviate from a Gaussian shape were observed from a tornadic supercell on 10 May 2003, exhibiting features such as a dual peak, flat top, and wide skirt in the nontornadic region. Motivated by these observations, a spectral model of a mixture of two Gaussian components, each defined by its three spectral moments, is introduced to characterize different degrees of deviation from Gaussian shape. In the standard autocovariance method, a Gaussian spectrum is assumed and biases in velocity and spectrum width estimates may result if this assumption is violated. The impact of non-Gaussian weather spectra on these biases is formulated and quantified in theory and, consequently, verified using four experiments of numerical simulations. Those non-Gaussian spectra from the south region of the supercell are further examined and a nonlinear fitting algorithm is proposed to estimate the six spectral moments and compare to those obtained from the autocovariance method. It is shown that the dual-Gaussian model can better represent observed spectra for those cases. The authors’ analysis suggests that vertical shear may be responsible for the flat-top or the dual-peak spectra in the lower elevation of 0.5° and their transition to the single-peak and wide-skirt spectra in the next elevation scan of 1.5°.

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Ribeiro, Victor Barbosa, Gislaine Satyko Kogure, Rafael Costa Silva, Hugo Celso Dutra Souza, Rui Alberto Ferriani, and Rosana Maria dos Reis. "Increased Sympathetic Cardiac Autonomic Modulation after Two Consecutive Tilt Tests in Women with Polycystic Ovary Syndrome." Revista Brasileira de Ginecologia e Obstetrícia / RBGO Gynecology and Obstetrics 42, no. 02 (February 2020): 081–89. http://dx.doi.org/10.1055/s-0040-1701467.

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Abstract Objective The present study aimed to analyze cardiac autonomic modulation via spectral and symbolic analysis of heart rate variability (HRV) in women with polycystic ovary syndrome (PCOS) who were subjected to two consecutive tilt tests. Methods A total of 64 women were selected and divided into 2 groups: control (without PCOS), and PCOS. Concentrations of follicle-stimulating hormone, luteinizing hormone, prolactin, estradiol, homocysteine, sex hormone-binding globulin, thyroid stimulating hormone, fasting insulin, testosterone, androstenedione, and 17-hydroxyprogesterone levels, triglycerides, free androgen index (FAI), and homeostasis assessment model (HOMA-IR) were assessed. Cardiac autonomic modulation was evaluated by spectral and symbolic analyses during two consecutive tilt tests (two moments) and supine moments before, between and after (three moments) the tilt tests. Results Women with PCOS had higher fasting insulin, HOMA-IR indexes, testosterone and FAI. Additionally, we observed that the PCOS group had greater sympathetic autonomic cardiac modulation in supine 2, tilt 1, and supine 3 moments compared with controls. Conclusion Women with PCOS had higher autonomic sympathetic cardiac modulation even after a second tilt test. No adaptation to this provocative test was observed. Spectral analysis was more sensitive for identifying differences between groups than the symbolic analysis.

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ASAITHAMBI, MYTHILI, JOSEPH JESU CHRISTOPHER, and SWAMINATHAN RAMAKRISHNAN. "QUALITATIVE ASSESSMENT OF TENSILE STRENGTH COMPONENTS OF HUMAN FEMUR TRABECULAR BONE USING RADIOGRAPHIC IMAGING AND SPECTRAL ANALYSIS." Journal of Mechanics in Medicine and Biology 09, no. 01 (March 2009): 21–29. http://dx.doi.org/10.1142/s0219519409002869.

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In this work, the primary and secondary tensile strength components of human femur trabecular bone are qualitatively assessed using planar radiographic images and spectral analysis. Normal and abnormal femur trabecular images (N = 40) were recorded using planar radiography following standard image acquisition protocol. From the images, the tensile strength components of the trabeculae are delineated using image processing procedures and are then subjected to Fourier transform. The zero (DC), First (FMOI), and Second Moments of Inertia (SMOI) are the parameters considered and are correlated with presence and absence of mineralization in the image. Results show that the values of moments correlate well with percentage mineralization in normal images when compared to abnormal images for both primary and secondary tensile strength components. Further, no or poor correlations were found for abnormals in all cases. Among all, the values of second moment showed highest correlation in the secondary tensile region. In this paper the objectives, methodology, significance results and the conclusions are presented.

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Mangilli, A., J. Aumont, A. Rotti, F. Boulanger, J. Chluba, T. Ghosh, and L. Montier. "Dust moments: towards a new modeling of the galactic dust emission for CMB B-modes analysis." Astronomy & Astrophysics 647 (March 2021): A52. http://dx.doi.org/10.1051/0004-6361/201937367.

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The characterization of the spectral energy distribution (SED) of dust emission has become a critical issue in the quest for primordial B-modes. The dust SED is often approximated by a modified black body (MBB) emission law but the extent to which this is accurate is unclear. This paper addresses this question, expanding the dust SED at the power spectrum level. The expansion is performed by means of moments around the MBB law, related to derivatives with respect to the dust spectral index. We present the mathematical formalism and apply it to simulations and Planck total intensity data, from 143 to 857 GHz, because no polarized data are yet available that provide the required sensitivity to perform this analysis. With simulations, we demonstrate the ability of high-order moments to account for spatial variations in MBB parameters. Neglecting these moments leads to poor fits and a bias in the recovered dust spectral index. We identify the main moments that are required to fit the Planck data. The comparison with simulations helps us to disentangle the respective contributions from dust and the cosmic infrared background to the high-order moments, but the simulations give an insufficient description of the actual Planck data. Extending our model to cosmic microwave background B-mode analyses within a simplified framework, we find that ignoring the dust SED distortions, or trying to model them with a single decorrelation parameter, could lead to biases that are larger than the targeted sensitivity for the next generation of CMB B-mode experiments.

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Hui, Jian Xin, Lei Wu, Yu Chun Gao, and Jie Zhou. "A Spectral Moment Estimation Method for Wind Profile Radar." Advanced Materials Research 179-180 (January 2011): 740–45. http://dx.doi.org/10.4028/www.scientific.net/amr.179-180.740.

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Spectrum in the wind profile radar data processing, radar detection of low-level spectral data from the library there are usually clutter, intermittent clutter, clutter and atmospheric echoes magnetic mixed overlap situation. In order to effectively restrain and remove clutter and increase the wind profile radar detection range and accuracy, must be on the air back to the effective spectrum of the spectral moments estimation. Based on the wind profile radar Doppler echo power spectral analysis, maximum likelihood method based on estimated spectral data of radar echo spectrum method using MATLAB simulation analysis , compared with the conventional method of analysis to verify the feasibility and effectiveness of the algorithm, also, try the algorithm is applied to the complexity of the weather with a strong interference case of precipitation particles; Data analysis showed that the actual detection, from the library in the lower spectrum moment estimation has been improved significantly.

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Zhou, Jie, Jian Xin Hui, Lei Wu, and Yu Chun Gao. "Based on the Minimum Variance Spectral Estimation of Radar Wind Profile Analysis." Advanced Materials Research 181-182 (January 2011): 82–87. http://dx.doi.org/10.4028/www.scientific.net/amr.181-182.82.

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In this paper, we apply minimum variance method for removing automatically ground and intermittent clutter (airplane echo) from wind profiler radar data. Using the concept of discrete multi-resolution analysis and non-parametric estimation theory, we develop Doppler echo power spectral, which allow us to identify the coefficients relevant for clutter and to suppress them in order to effectively restrain and remove clutter and increase the wind profile radar detection range and accuracy; must be on the air back to the effective spectrum of the spectral moments estimation. Using MATLAB simulation analysis , compared with the conventional method of analysis to verify the feasibility and effectiveness of the algorithm, also, try the algorithm is applied to the complexity of the weather with a strong interference case of precipitation particles; Data analysis showed that the actual detection, from the library in the lower spectrum moment estimation has been improved significantly.

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Norin, L. "A quantitative analysis of the impact of wind turbines on operational Doppler weather radar data." Atmospheric Measurement Techniques 8, no. 2 (February 5, 2015): 593–609. http://dx.doi.org/10.5194/amt-8-593-2015.

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Abstract. In many countries wind turbines are rapidly growing in numbers as the demand for energy from renewable sources increases. The continued deployment of wind turbines can, however, be problematic for many radar systems, which are easily disturbed by turbines located in the radar line of sight. Wind turbines situated in the vicinity of Doppler weather radars can lead to erroneous precipitation estimates as well as to inaccurate wind and turbulence measurements. This paper presents a quantitative analysis of the impact of a wind farm, located in southeastern Sweden, on measurements from a nearby Doppler weather radar. The analysis is based on 6 years of operational radar data. In order to evaluate the impact of the wind farm, average values of all three spectral moments (the radar reflectivity factor, absolute radial velocity, and spectrum width) of the nearby Doppler weather radar were calculated, using data before and after the construction of the wind farm. It is shown that all spectral moments, from a large area at and downrange from the wind farm, were impacted by the wind turbines. It was also found that data from radar cells far above the wind farm (near 3 km altitude) were affected by the wind farm. It is shown that this in part can be explained by detection by the radar sidelobes and by scattering off increased levels of dust and turbulence. In a detailed analysis, using data from a single radar cell, frequency distributions of all spectral moments were used to study the competition between the weather signal and wind turbine clutter. It is shown that, when weather echoes give rise to higher reflectivity values than those of the wind farm, the negative impact of the wind turbines is greatly reduced for all spectral moments.

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Norin, L. "A quantitative analysis of the impact of wind turbines on operational Doppler weather radar data." Atmospheric Measurement Techniques Discussions 7, no. 8 (August 27, 2014): 8743–76. http://dx.doi.org/10.5194/amtd-7-8743-2014.

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Abstract. In many countries wind turbines are rapidly growing in numbers as the demand for energy from renewable sources increases. The continued deployment of wind turbines can, however, be problematic for many radar systems, which are easily disturbed by turbines located in radar line-of-sight. Wind turbines situated in the vicinity of Doppler weather radars can lead to erroneous precipitation estimates as well as to inaccurate wind- and turbulence measurements. This paper presents a quantitative analysis of the impact of a wind farm, located in southeastern Sweden, on measurements from a nearby Doppler weather radar. The analysis is based on six years of operational radar data. In order to evaluate the impact of the wind farm, average values of all three spectral moments (the radar reflectivity factor, absolute radial velocity, and spectrum width) of the nearby Doppler weather radar were calculated, using data before and after the construction of the wind farm. It is shown that all spectral moments, from a large area at and downrange from the wind farm, were impacted by the wind turbines. It was also found that data from radar cells far above the wind farm (near 3 km altitude) were affected by the wind farm. We show that this is partly explained by changes in the atmospheric refractive index, bending the radar beams closer to the ground. In a detailed analysis, using data from a single radar cell, frequency distributions of all spectral moments were used to study the competition between the weather signal and wind turbine clutter. We show that when weather echoes give rise to higher reflectivity values than that of the wind farm, the negative impact of the wind turbines disappears for all spectral moments.

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Minchenko, Marsha, and Ian M. Wanless. "Spectral moments of regular graphs in terms of subgraph counts." Linear Algebra and its Applications 446 (April 2014): 166–76. http://dx.doi.org/10.1016/j.laa.2013.12.028.

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Hora, Akihito. "Central Limit Theorems and Asymptotic Spectral Analysis on Large Graphs." Infinite Dimensional Analysis, Quantum Probability and Related Topics 01, no. 02 (April 1998): 221–46. http://dx.doi.org/10.1142/s0219025798000144.

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Regarding the adjacency matrix of a graph as a random variable in the framework of algebraic or noncommutative probability, we discuss a central limit theorem in which the size of a graph grows in several patterns. Various limit distributions are observed for some Cayley graphs and some distance-regular graphs. To obtain the central limit theorem of this type, we make combinatorial analysis of mixed moments of noncommutative random variables on one hand, and asymptotic analysis of spectral structure of the graph on the other hand.

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Garipov, A. I., and P. A. Pyatkin. "Seismic analysis method of steel structures connections." Вестник гражданских инженеров 17, no. 2 (2020): 51–59. http://dx.doi.org/10.23968/1999-5571-2020-17-2-51-59.

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The article presents a technique of calculating steel structures connections taking into consideration the results of seismic analysis of steel structure carried out by linear spectral method. This technique allows reaching the equilibrium of forces and moments applied to the connection, wherein extreme internal forces’ values received correspond to the internal forces’ values obtained according to the currently valid acting construction codes.

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De Natale, Giuseppe, Raul Madariaga, Roberto Scarpa, and Aldo Zollo. "Source parameter analysis from strong motion records of the Friuli, Italy, earthquake sequence (1976-1977)." Bulletin of the Seismological Society of America 77, no. 4 (August 1, 1987): 1127–46. http://dx.doi.org/10.1785/bssa0770041127.

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Abstract Time and frequency domain analyses are applied to strong motion data recorded in Friuli, Italy, during 1976 to 1977. An inversion procedure to estimate spectral parameters (low frequency level, corner frequency, and high frequency decay) has been applied to displacement spectra using a simple earthquake source model with a single corner frequency. The data were digitized accelerograms from ENEA-ENEL portable and permanent networks. Instrument-corrected SH waves were selected from a set of 138 three-component, hand-digitized records and 28 automatically digitized records. Thirty-eight events with stations having 8 to 32 km epicentral distance were studied. Different stress drop estimates were performed showing high values (200 to 300 bars, on the average) with seismic moments ranging from 2.8 × 1022 to 8.0 × 1024 dyne-cm. The observation of systematic higher values of Brune stress drop (obtained from corner frequencies) with respect to other time and frequency domain estimates of stress release, and the evidence on time series of multiple rupture episodes suggest that the observed corner frequencies are most probably related to subevent ruptures rather than the overall fault size. Seven events recorded at more than one station show a good correlation between rms, Brune, and dynamic stress drops, and a constant scaling of this parameter as a function of the seismic moment. When single station events are also considered, a slight moment dependence of these three stress drop estimates is observed differently. This may be explained by an inadequacy of the ω−2 high-frequency decay of the source model or by high-frequency attenuation due to propagation effects. The high-frequency cutoff of acceleration spectra indicates the presence of an Fmax in the range of 5 to 14 Hz, except for the stations where local site effects produce spectral peaks.

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Wu, Yaping, and Huiqing Liu. "Lexicographical ordering by spectral moments of trees with a prescribed diameter." Linear Algebra and its Applications 433, no. 11-12 (December 2010): 1707–13. http://dx.doi.org/10.1016/j.laa.2010.06.022.

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Han, Xiaoshuang, Weiliang Qiao, and Bo Zhou. "Frequency Domain Response of Jacket Platforms under Random Wave Loads." Journal of Marine Science and Engineering 7, no. 10 (September 21, 2019): 328. http://dx.doi.org/10.3390/jmse7100328.

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This article presents a procedure that simplifies an offshore jacket platform as a non-uniform cantilever beam subjected to an axial force. A Ritz method combined with a pseudo-excitation method is then used to analyze the responses of the jacket platform under random wave loads with the associated power spectral densities, variances and higher spectral moments. The theoretical basis and pertinent governing equations are derived. The proposed procedure not only eases the process of determining the pseudo wave loads, but also requires only the rudimentary structural details that are typically available at the preliminary design stage. Additionally, the merit of the proposed procedure is that the process does not require one to compute the normal modes, which saves time and is particularly convenient for the dynamic-response analysis of a complex structure (such as an offshore platform). An illustrative example based on a three-deck jacket platform is presented to demonstrate the procedure used to obtain the power spectral densities, variances and second spectral moments of jacket-top displacement and the bending moment of the jacket at the mud line. The results obtained are compared with those obtained using a Finite Element Mothed (FEM) model. Based on the findings of the study and good agreement shown in the comparison of results, it is concluded that the proposed method is effective, simple and convenient, and can be a useful tool for the preliminary design analysis of offshore platforms.

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Timkin, Timofei V. "Acoustic Features of the Surgut Khanty Consonants." NSU Vestnik. Series: Linguistics and Intercultural Communication 19, no. 1 (2021): 106–16. http://dx.doi.org/10.25205/1818-7935-2021-19-1-106-116.

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This paper deals with the acoustic features of the Surgut Khanty consonants. The research is based on the data gathered during fieldwork in Kogalym town (2018) and the Ugut village (2019). The audio samples are provided by three native speakers of the Tromjegan, Malyi Yugan, and Bolshoi Yugan idioms. The total size of the sample database numbers more than six thousand isolated consonant pronouncements. The data for the research was obtained using oscillographic and spectrographic methods, formant locus analysis, spectral moment analysis. The analysis was performed via Praat and Emu-SDMS software. Oscillograghy and spectrography methods reveal that voiceless fricative phonemes may be voiced in intervocalic distribution. It is common for the sonants to become devoiced in the final and preconsonantal positions. Moreover, due to devoicing, different phonemes may acquire low-obstruent and obstruent consonant features. For the fricative, lateral-fricative consonants, affricates spectral moment analysis has been carried out. The spectral moments technique gives an opportunity to represent complex noise data as a relatively small set of numbers that can be processed statistically. According to the data on spectral moments, four types of noise have been defined: high-frequency low-dispersion noise resembling /s/, medium-frequency low-dispersion noise resembling /ʃ/, /tʃ/, /cc/, low-frequency medium-dispersed noise for phonemes /ɫ/, / /, low-frequency dispersed noise for phonemes /w/, /γ/. The forman analysis is used o es ima e onsonan resonan frequen ies. As shown by he formant locus analysis, the smallest values of the second formant locus are associated with the labial and velar phonemes. Larger values are associated with the coronal phonemes. The largest ones are specific to the palatal phonemes. At the same time, the acoustic features make it possible to stably distinguish the nasal /n/ - /ɲ/, wherein the opposition of the middle and fron lingual ar i ula ions is observed only in some speakers’ re ordings for the pairs /ɫ/ - / /, /tʃ/ - /cc/.

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Green, Itzhak. "Metrology and numerical characterization of random rough surfaces—Data reduction via an effective filtering solution." Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 234, no. 9 (November 22, 2019): 1452–69. http://dx.doi.org/10.1177/1350650119885281.

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Random rough surfaces appear in measurements as noisy signals varying spatially. Mathematically, there is no theoretical difference between such and time-varying signals. Hence, the extensive array of methods and analysis tools that have been developed for signal processing are available also for rough surfaces characterization. In both, the objective is to reduce the vast amount of data to just a few meaningful parameters that allow the application of other physical concepts. Particularly in contact mechanics, it is well known that the Greenwood–Williamson model requires three parameters for the calculation of the elastic deformation of rough surface asperities. The parameters are the roughness standard deviation, the equivalent asperity radius, and the asperity density. These parameters are byproducts of the spectral moments. The spectral moments have been employed for decades in many fields of engineering and science. For rough surfaces, for example, the work by McCool outlines a mathematical blueprint procedure on how to straightforwardly reduce the entire roughness data into the said three spectral moments. It is commonly claimed, however, that the said procedure inherently suffers from resolution problems, that is, a given surface shall have much different spectral moments depending on the sampling rate (or spacing). To study these issues, synthetic surfaces are generated herein using a harmonic waveform precisely as McCool had done. However, here the signals are contaminated by a white noise process with various magnitudes. A signal-to-noise ratio is defined and used to assess the quality of the signal, and the spectral moments are evaluated for various magnitudes of the noise. Since closed-from solutions are available for the spectral moments of the uncontaminated signal, the contaminated signals are evaluated vis-à-vis the exact anticipated values, and the errors are calculated. It is shown that using the common techniques (such as those outlined by McCool) can lead to enormous and unacceptable errors. Resolution is studied as well; it is shown to have an effect only in the presence of noise, but by itself it has no independent influence on the spectral moments. The venerable Savitzky–Golay smoothing filter is used on the noisy signals, showing some improvements, but the resulting spectral moments predicted still contain objectionable errors. A generalized exponential smoothing filter, G-EXP, is constructed, and it is shown to markedly moderate the errors and reduce them to acceptable levels, while effectively restoring the underlying surface physical characteristics. Moreover, the filtered signals do not suffer from resolution problems, where results, in fact, improve with higher (i.e., finer) resolutions. Fractal-generated signals are likewise discussed.

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Kumar, B., and O. Dikshit. "Texture Based Hyperspectral Image Classification." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XL-8 (November 28, 2014): 793–98. http://dx.doi.org/10.5194/isprsarchives-xl-8-793-2014.

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This research work presents a supervised classification framework for hyperspectral data that takes into account both spectral and spatial information. Texture analysis is performed to model spatial characteristics that provides additional information, which is used along with rich spectral measurements for better classification of hyperspectral imagery. The moment invariants of an image can derive shape characteristics, elongation, and orientation along its axis. In this investigation second order geometric moments within small window around each pixel are computed which are further used to compute texture features. The textural and spectral features of the image are combined to form a joint feature vector that is used for classification. The experiments are performed on different types of hyperspectral images using multi-class one-vs-one support vector machine (SVM) classifier to evaluate the robustness of the proposed methodology. The results demonstrate that integration of texture features produced statistically significantly better results than spectral classification.

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Hysell, D. L., G. Michhue, M. F. Larsen, R. Pfaff, M. Nicolls, C. Heinselman, and H. Bahcivan. "Imaging radar observations of Farley Buneman waves during the JOULE II experiment." Annales Geophysicae 26, no. 7 (July 3, 2008): 1837–50. http://dx.doi.org/10.5194/angeo-26-1837-2008.

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Abstract. Vector electric fields and associated E×B drifts measured by a sounding rocket in the auroral zone during the NASA JOULE II experiment in January 2007, are compared with coherent scatter spectra measured by a 30 MHz radar imager in a common volume. Radar imaging permits precise collocation of the spectra with the background electric field. The Doppler shifts and spectral widths appear to be governed by the cosine and sine of the convection flow angle, respectively, and also proportional to the presumptive ion acoustic speed. The neutral wind also contributes to the Doppler shifts. These findings are consistent with those from the JOULE I experiment and also with recent numerical simulations of Farley Buneman waves and instabilities carried out by Oppenheim et al. (2008). Simple linear analysis of the waves offers some insights into the spectral moments. A formula relating the spectral width to the flow angle, ion acoustic speed, and other ionospheric parameters is derived.

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35

Joslin, C. G. "Collision-induced absorption in the fundamental band of nitrogen gas." Canadian Journal of Physics 65, no. 12 (December 1, 1987): 1629–35. http://dx.doi.org/10.1139/p87-268.

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Compressed nitrogen gas absorbs weakly in the vicinity of its vibrational fundamental frequency (ωvib = 2330 cm−1), with an intensity proportional to the square of the density. This absorption arises through vibrational modulation of the quadrupole-induced collisional dipole moment of a pair of N2 molecules. By neglecting the small anisotropy in the N2 intermolecular potential, we represent the spectral profile as the convolution of a single-molecule vibration–rotation band with a two-molecule translational component. Information theory is used to estimate the "least biased" form for the latter, based on our knowledge of its first four nonvanishing spectral moments. Our theory contains no adjustable parameters, yet yields results in good agreement with experiment. Our analysis shows that the anisotropic component of the molecular polarizability makes a fairly substantial contribution, about 12%, to the spectral intensity.

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Galluzzo, Danilo, Lucia Nardone, Mario La Rocca, Antonietta M. Esposito, Roberto Manzo, and Rosa Di Maio. "Statistical moments of power spectrum: a fast tool for the classification of seismic events recorded on volcanoes." Advances in Geosciences 52 (October 27, 2020): 67–74. http://dx.doi.org/10.5194/adgeo-52-67-2020.

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Abstract. Spectral analysis has been applied to almost thousand seismic events recorded at Vesuvius volcano (Naples, southern Italy) in 2018 with the aim to test a new tool for a fast event classification. We computed two spectral parameters, central frequency and shape factor, from the spectral moments of order 0, 1, and 2, for each event at seven seismic stations taking the mean among the three components of ground motion. The analyzed events consist of volcano-tectonic earthquakes, low frequency events and unclassified events (landslides, rockfall, thunders, quarry blasts, etc.). Most of them are of low magnitude, and/or low maximum signal amplitude, therefore the signal to noise ratio is very different between the low noise summit stations and the higher noise stations installed at low elevation around the volcano. The results of our analysis show that volcano-tectonic earthquakes and low frequency events are easily distinguishable through the spectral moments values, particularly at seismic stations closer to the epicenter. On the contrary, unclassified events show the spectral parameters values distributed in a broad range which overlap both the volcano-tectonic earthquakes and the low frequency events. Since the computation of spectral parameters is extremely easy and fast for a detected event, it may become an effective tool for event classification in observatory practice.

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Gail, H. R., S. L. Hantler, and B. A. Taylor. "Spectral analysis of M/G/1 and G/M/1 type Markov chains." Advances in Applied Probability 28, no. 01 (March 1996): 114–65. http://dx.doi.org/10.1017/s0001867800027300.

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When analyzing the equilibrium behavior of M/G/1 type Markov chains by transform methods, restrictive hypotheses are often made to avoid technical problems that arise in applying results from complex analysis and linear algebra. It is shown that such restrictive assumptions are unnecessary, and an analysis of these chains using generating functions is given under only the natural hypotheses that first moments (or second moments in the null recurrent case) exist. The key to the analysis is the identification of an important subspace of the space of bounded solutions of the system of homogeneous vector-valued Wiener–Hopf equations associated with the chain. In particular, the linear equations in the boundary probabilities obtained from the transform method are shown to correspond to a spectral basis of the shift operator on this subspace. Necessary and sufficient conditions under which the chain is ergodic, null recurrent or transient are derived in terms of properties of the matrix-valued generating functions determined by transitions of the Markov chain. In the transient case, the Martin exit boundary is identified and shown to be associated with certain eigenvalues and vectors of one of these generating functions. An equilibrium analysis of the class of G/M/1 type Markov chains by similar methods is also presented.

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Gail, H. R., S. L. Hantler, and B. A. Taylor. "Spectral analysis of M/G/1 and G/M/1 type Markov chains." Advances in Applied Probability 28, no. 1 (March 1996): 114–65. http://dx.doi.org/10.2307/1427915.

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When analyzing the equilibrium behavior of M/G/1 type Markov chains by transform methods, restrictive hypotheses are often made to avoid technical problems that arise in applying results from complex analysis and linear algebra. It is shown that such restrictive assumptions are unnecessary, and an analysis of these chains using generating functions is given under only the natural hypotheses that first moments (or second moments in the null recurrent case) exist. The key to the analysis is the identification of an important subspace of the space of bounded solutions of the system of homogeneous vector-valued Wiener–Hopf equations associated with the chain. In particular, the linear equations in the boundary probabilities obtained from the transform method are shown to correspond to a spectral basis of the shift operator on this subspace. Necessary and sufficient conditions under which the chain is ergodic, null recurrent or transient are derived in terms of properties of the matrix-valued generating functions determined by transitions of the Markov chain. In the transient case, the Martin exit boundary is identified and shown to be associated with certain eigenvalues and vectors of one of these generating functions. An equilibrium analysis of the class of G/M/1 type Markov chains by similar methods is also presented.

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39

Dehay, Dominique, and Jacek Leśkow. "Functional limit theory for the spectral covariance estimator." Journal of Applied Probability 33, no. 4 (December 1996): 1077–92. http://dx.doi.org/10.2307/3214987.

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Processes that exhibit repeatability in their kth-order moments are frequently studied in signal analysis. Such repeatability can be conveniently expressed with the help of almost periodicity. In particular, almost periodically correlated (APC) processes play an important role in the analysis of repeatable signals. This paper presents a study of asymptotic distributions of the estimator of the spectral covariance function for APC processes. It is demonstrated that, for a large class of APC processes, the functional central limit theorem holds.

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Dehay, Dominique, and Jacek Leśkow. "Functional limit theory for the spectral covariance estimator." Journal of Applied Probability 33, no. 04 (December 1996): 1077–92. http://dx.doi.org/10.1017/s002190020010049x.

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Processes that exhibit repeatability in their kth-order moments are frequently studied in signal analysis. Such repeatability can be conveniently expressed with the help of almost periodicity. In particular, almost periodically correlated (APC) processes play an important role in the analysis of repeatable signals. This paper presents a study of asymptotic distributions of the estimator of the spectral covariance function for APC processes. It is demonstrated that, for a large class of APC processes, the functional central limit theorem holds.

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41

Jakeš, Jaromír. "A Simple Numerical Method for Calculating Gaussian NMR Spectral Line Shapes Partially Narrowed Due to a Motion with the Exponential Spectral Autocorrelation Function." Collection of Czechoslovak Chemical Communications 67, no. 4 (2002): 405–28. http://dx.doi.org/10.1135/cccc20020405.

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A simple numerical method for calculating NMR spectral line shapes resulting from a Gaussian line by a partial narrowing due to a motion with the exponential spectral autocorrelation function of the form exp (-|τ|/τc) was developed. It was found that the partially narrowed line is narrower not only than the parent Gaussian line with the second moment of ωp2 but also than the Lorentzian line with the half-width of 2ωp2τc obtained from the extreme narrowing approximation. The central intensity increase compared with the closer of these two lines is less than 50.2%. Asymptotic developments for large values of ω - ω0 and for large values of ωpτc were derived. Two-term approximation applied to the extreme narrowing case led to a very simple modification of the Lorentzian line having the correct second moment ωp2. Analysis of this modified Lorentzian line showed that attempts to estimate ωp2 from truncated second moments of Lorentzian lines without knowledge of τc are hopeless. The case of the polyexponential spectral autocorrelation function with all but one correlation times fast enough to allow for the extreme narrowing, modelling the case of an anisotropic motion, is also considered.

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Zhu, Ying, and Yuji Tian. "Fatigue Life Evaluation of Linear Structures with Uncertain-But-Bounded Parameters Under Stochastic Excitations." International Journal of Structural Stability and Dynamics 18, no. 03 (February 27, 2018): 1850045. http://dx.doi.org/10.1142/s0219455418500451.

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This study presents two hybrid methods, the full combination method and the simplified expression, for evaluating the fatigue life of linear structures with uncertain-but-bounded parameters subjected to stochastic excitations. First, approximate expressions of the spectral moments and spectral bandwidth parameters are derived based on the improved interval analysis via extra unitary interval and the interval Taylor expansion. Then, the lower and upper bounds of the interval expected fatigue damage rate and fatigue life are evaluated by fully or properly combining the two bounds of the spectral moments and spectral bandwidth parameters by the Tovo–Benasciutti method. Through the numerical study, the full combination method is recommended for the accurate assessment of the interval fatigue life, and the simplified expression is recommended for rapid evaluation of the two bounds of the interval fatigue life using the explicit expression. Finally, three numerical examples are adopted to illustrate the accuracy and efficiency of the proposed methods via comparison of the present results with the exact ones.

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Flipsen, Peter, Lawrence Shriberg, Gary Weismer, Heather Karlsson, and Jane McSweeny. "Acoustic Characteristics of /s/ in Adolescents." Journal of Speech, Language, and Hearing Research 42, no. 3 (June 1999): 663–77. http://dx.doi.org/10.1044/jslhr.4203.663.

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The goal of the current study was to construct a reference database against which misarticulations of /s/ can be compared. Acoustic data for 26 typically speaking 9- to 15-year-olds were examined to resolve measurement issues in acoustic analyses, including alternative sampling points within the /s/ frication; the informativeness of linear versus Bark transformations of each of the 4 spectral moments of /s/ (Forrest, Weismer, Milenkovic, & Dougall, 1988); and measurement effects associated with linguistic context, age, and sex. Analysis of the reference data set indicates that acoustic characterization of /s/ is appropriately and optimally (a) obtained from the midpoint of /s/, (b) represented in linear scale, (c) reflected in summary statistics for the 1st and 3rd spectral moments, (d) referenced to individual linguistic-phonetic contexts, (e) collapsed across the age range studied, and (f) described individually by sex.

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Liu, Z. F., P. S. Kooi, L. W. Li, M. S. Leong, and T. S. Yeo. "A Spectral-Domain Analysis of Microstrip Antenna Array Using Method of Moments: Theory & Experiment." Journal of Electromagnetic Waves and Applications 12, no. 11 (January 1998): 1471–90. http://dx.doi.org/10.1163/156939398x00421.

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GRUSZKA, MARCIN, and ALEKSANDRA BORYSOW. "New analysis of the spectral moments of collision induced absorption in gaseous N2 and CO2." Molecular Physics 88, no. 5 (August 10, 1996): 1173–85. http://dx.doi.org/10.1080/00268979609484502.

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46

Goldmakher, Leo, Cap Khoury, Steven J. Miller, and Kesinee Ninsuwan. "On the spectral distribution of large weighted random regular graphs." Random Matrices: Theory and Applications 03, no. 04 (October 2014): 1450015. http://dx.doi.org/10.1142/s2010326314500154.

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McKay proved the limiting spectral measures of the ensembles of d-regular graphs with N vertices converge to Kesten's measure as N → ∞. Given a large d-regular graph we assign random weights, drawn from some distribution [Formula: see text], to its edges. We study the relationship between [Formula: see text] and the associated limiting spectral distribution obtained by averaging over the weighted graphs. We establish the existence of a unique "eigendistribution" (a weight distribution [Formula: see text] such that the associated limiting spectral distribution is a rescaling of [Formula: see text]). Initial investigations suggested that the eigendistribution was the semi-circle distribution, which by Wigner's Law is the limiting spectral measure for real symmetric matrices. We prove this is not the case, though the deviation between the eigendistribution and the semi-circular density is small (the first seven moments agree, and the difference in each higher moment is O(1/d2)). Our analysis uses combinatorial results about closed acyclic walks in large trees, which may be of independent interest.

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Tuzlukov, V. P. "DIVERSITY SIGNAL PROCESSING OVER WEIBULL FADING CHANNELS." Doklady BGUIR, no. 7-8 (December 29, 2019): 13–21. http://dx.doi.org/10.35596/1729-7648-2019-126-8-13-21.

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We present a moments-based approach to the performance analysis of L-branch equal-gain combining and maximal-ratio combining receivers, operating in independent or correlated, not necessarily identically distributed, Weibull fading. For both equal-gain combining and maximal-ratio combining receivers the moments of the output signal-to-noise ratio are obtained in closed-form. An accurate approximate expression is derived for the moment-generating function of the output signal-to-noise ratio of the equal-gain combining receiver utilizing the Padé approximants theory, while a closed-form expression for the corresponding MGF of the maximal-ratio combining receiver, is obtained. Significant performance criteria, such as average output signal-to-noise ratio, amount of fading and spectral efficiency at the low power regime, are extracted in closed-forms, using the moments of the output signal-to-noise ratio for both independent and correlative fading. Moreover, using the well-known moment-generating function approach, the outage and the average symbol error probability for several coherent, non-coherent, binary, and multilevel modulation schemes, are studied. The average symbol error probability of dual-branch equal-gain combining and maximal-ratio combining receivers is also obtained when correlative fading is considered in the diversity input branches. The proposed mathematical analysis is illustrated by various numerical results and validated by computer simulations.

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Hajj, M. R., R. W. Miksad, and E. J. Powers. "Perspective: Measurements and Analyses of Nonlinear Wave Interactions With Higher-Order Spectral Moments." Journal of Fluids Engineering 119, no. 1 (March 1, 1997): 3–13. http://dx.doi.org/10.1115/1.2819116.

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In fluid flows, fluid-structure interactions and other fluids-related problem, nonlinear dynamics play an important role in determining the development, response or output. Understanding these dynamics is essential for development of analytical models and prediction and control purposes. Higher-order statistical analysis has been shown to be an effective tool that can be applied to identify nonlinear couplings and measure energy transfer rates. These techniques have been applied by our group and others to investigate transition of shear flows, energy cascading in turbulence, oceanographic and geophysical flows, and fluid-structure interactions. The results of these investigations revealed important nonlinear characteristics regarding these problems. In this paper, we review these techniques and explain their usefulness in identification and quantification of nonlinear dynamics.

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Singh, Netra Pal, Anu, and Jagvir Singh. "Magnetic and Spectroscopic Studies of the Synthesized Metal Complexes of Bis(Pyridine-2-carbo) Hydrazide and Their Antimicrobial Studies." E-Journal of Chemistry 9, no. 4 (2012): 1835–42. http://dx.doi.org/10.1155/2012/521345.

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Cobalt(II), Nickel(II), Copper(II) and Manganese(II) complexes, having the general composition {M(L)2X2}, have been synthesized [where L= bis(pyridine-2-carbo) hydrazide(L), and X = Cl–]. All the Metal complexes reported here have been characterized by elemental analysis, molar conductance, magnetic moments, IR, electronic and mass spectral studies. All the complexes were found to have magnetic moments corresponding to unpaired electrons. The possible geometries of the complexes were assigned on the basis of electronic and infrared spectral studies. On the basis of molar conductance values the complexes show 1:2 electrolytic nature. Newly synthesized ligand and its Metal complexes have been screened againstStaphylococcus aureus(ATCC 25923),Staphylococcus aureus(ATCC 3160) bacterial species andCandida albicans(227) and Staphylococcus cereviscae (361) fungal species.

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Patel, R. H., and B. L. Hiran. "Synthesis, Characterizations and Antimicrobial Activity of Metal Complexes of 2-(2-Furanylmethylaminocarbonyl)benzoic Acid." E-Journal of Chemistry 8, no. 1 (2011): 443–48. http://dx.doi.org/10.1155/2011/728069.

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The ligand, 2-(2-furanylmethylaminocarbonyl)benzoic acid (FMBA) and it’s transition metal complexes have been synthesized and characterized by elemental analysis, spectral studies, magnetic moments and thermal studies. The antifungal activity of all the samples was monitored against common fungi.

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Journal articles on the topic 'Spectral moments analysis'

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