Journal articles: 'Magnitude spectrum'

1

Fukushima, Yoshimitsu. "Scaling relations for strong ground motion prediction models with M2 terms." Bulletin of the Seismological Society of America 86, no. 2 (April 1, 1996): 329–36. http://dx.doi.org/10.1785/bssa0860020329.

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Abstract In most previous studies on the attenuation relation of strong ground motion, the increase in amplitude with earthquake magnitude was expressed by a linear relation. However, if the ω−2 source model is assumed, the corner period of the spectrum varies with the magnitude, and the scaling law of the source spectrum amplitude becomes a complicated function of magnitude. The scaling relation of the spectrum amplitude with MW can be simply approximated as a quadratic function, and the coefficient of the MW2 term should be negative. On the contrary, positive coefficients of the ML2, mbLg2, and MJ2 (MJ: magnitude of Japan Meteorological Agency) terms have been derived by regression analyses of strong ground motions. Based on the ω−2 model, semi-empirical relations between Mo and the magnitudes were derived. Further, the seismological scaling law of the source spectrum obtained from the relation between Mo and the magnitudes was approximated as a quadratic function of the magnitude, and positive coefficients of the squared magnitude terms were obtained. These results stem from the definitions of magnitude derived from amplitudes of seismograms around a specific period of 1.0 sec for ML and mbLg and of 5.0 sec for MJ.

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Rivera, Efraín, Sergio Ruiz, and Raúl Madariaga. "Spectrum of strong-motion records for large magnitude Chilean earthquakes." Geophysical Journal International 226, no. 2 (April 1, 2021): 1045–57. http://dx.doi.org/10.1093/gji/ggab128.

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SUMMARY We studied the broad-band spectra of the eight largest earthquakes that have occurred in Chile in the last 25 yr using strong-motion records and 1-Hz high-rate GNSS (cGNSS) data. To avoid the numerical instability problem with the double integration of the accelerograms, we computed velocity spectra integrating the acceleration time-series in the spectral domain and compared them to time-differentiated the cGNSS displacement records. To compute the velocity spectrum, we used a multitaper algorithm so as to provide stability over the entire spectral band. We found that the velocity spectra of records obtained close to the main rupture of the earthquakes are different from classical Aki and Brune spectra. The velocity spectrum of large events in Chile presents a flat trend at low frequencies produced by the near-field waves. This trend converges at low frequencies to the static displacement as determined from GNSS data. For different magnitude earthquakes, we observe a transition in the ground-velocity spectrum from a decay of ${f^{ - 1}}$ at high frequencies and a flat trend at low frequencies to a more classical model with a peak at the corner frequency. The source-station distance influences the shape of the velocity spectrum at low frequencies, but there is no simple rule for the records available at present. At intermediate frequencies, the spectra are controlled by surface waves and S waves. We found a transition in the velocity spectrum for the 2014 Iquique earthquake, which indicates a change in the decay of the spectrum for stations at distances greater than ∼200 km. Finally, we show that the flat low-frequency trend of the velocity spectra determined from accelerograms, and the peak ground-displacement (PGD) determined from GNSS data scales with the moment to the power 2/3.

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Chen, Pei-Shan, Ke-Zhong Peng, Hai-Tong Chen, and Tong-Xia Bai. "Determination of moment magnitude from acceleration spectrum." Acta Seismologica Sinica 6, no. 2 (May 1993): 379–87. http://dx.doi.org/10.1007/bf02650950.

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Wahls, M. W. C., E. Kenttä, and J. C. Leyte. "Depth Profiles in Coated Paper: Experimental and Simulated FT-IR Photoacoustic Difference Magnitude Spectra." Applied Spectroscopy 54, no. 2 (February 2000): 214–20. http://dx.doi.org/10.1366/0003702001949429.

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Experimental photoacoustic (PA) magnitude spectra of a coated paper and the uncoated basepaper are presented. The normalized and scaled PA magnitude spectra are used to calculate difference magnitude spectra. It was decided to scale all PA magnitude spectra to (low) equal intensity at the approximately optically thin spectral range before subtraction. Then no infrared (IR) bands of identical band shape and height (as needed for common difference spectroscopy) in either PA magnitude spectrum are needed. Contributions of the two individual layers to the IR-PA magnitude spectrum of the coated paper are separated in the difference spectrum by their sign. An increasing relative contribution of the coating layer with an increasing phase modulation frequency is found. On decreasing the thermal length to a value near the coating thickness, the difference spectra increasingly show positive coating bands and negative bulk signals. The extension of the Rosencwaig–Gersho theory to a double-layered system introduced by N. C. Fernelius [J. Opt. Soc. Am. 70, 480 (1980) and J. Appl. Phys. 50, 650 (1980)] applied to synthetic spectra confirms the experimental observation. It is found that photoacoustic difference spectroscopy may provide quantitative depth-resolved spectral information due to the presented scaling procedure, and photoacoustic difference magnitude spectra of any polymeric laminate may therefore be calculated.

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Joo, Young-Bok, Hye-Seung Park, and Kyung-Moo Huh. "Automatic Inspection System for TFT-LCD Cell Defects Using Magnitude Spectrum." Journal of Institute of Control, Robotics and Systems 24, no. 9 (September 30, 2018): 857–60. http://dx.doi.org/10.5302/j.icros.2018.18.0099.

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Gan, Xin Ji, Xing Hua Gao, Yan Chen, and Jing Li. "Design of Single Star Simulator Based on LED Light Source." Applied Mechanics and Materials 397-400 (September 2013): 932–35. http://dx.doi.org/10.4028/www.scientific.net/amm.397-400.932.

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This paper use a single LED light source with wide spectrum to develop a single star simulator of compact structure and high precision. In order to select the spectrum of LED as the light source of star simulators, the spectrum range of simulated star magnitude is researched through Main Star Sequence Diagram. It is found that the spectrum between 2m~7m magnitudes is basically in accordance with the spectrum range of white light. The PWM current control system with 16 bites controller is employed to adjust LED luminescence through changing the duty ratio of PWM, which ensures the error of drive current less than 0.1%. The experiments show that the LED star simulator has the characteristics of compact structure, economical and easily controlled. The simulated precision of star magnitude attains ±0.1m .

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7

Bará, Salvador. "Variations on a classical theme: On the formal relationship between magnitudes per square arcsecond and luminance." International Journal of Sustainable Lighting 19, no. 2 (December 29, 2017): 104. http://dx.doi.org/10.26607/ijsl.v19i2.77.

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The formal link between magnitudes per square arcsecond and luminance is discussed in this paper. Directly related to the human visual system, luminance is defined in terms of the spectral radiance of the source, weighted by the CIE V(l) luminous efficiency function, and scaled by the 683 lm/W luminous efficacy constant. In consequence, any exact and spectrum-independent relationship between luminance and magnitudes per square arcsecond requires that the last ones be measured precisely in the CIE V(l) band. The luminance value corresponding to mVC=0 (zero-point of the CIE V(l) magnitude scale) depends on the reference source chosen for the definition of the magnitude system. Using absolute AB magnitudes, the zero point luminance of the CIE V(l) photometric band is 10.96 x 104 cd·m-2.

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8

Yang, Jichen, Hongji Wang, Rohan Kumar Das, and Yanmin Qian. "Modified Magnitude-Phase Spectrum Information for Spoofing Detection." IEEE/ACM Transactions on Audio, Speech, and Language Processing 29 (2021): 1065–78. http://dx.doi.org/10.1109/taslp.2021.3060810.

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9

Yang, Jichen, and Leian Liu. "Playback speech detection based on magnitude–phase spectrum." Electronics Letters 54, no. 14 (July 2018): 901–3. http://dx.doi.org/10.1049/el.2018.0739.

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10

Herrmann, R. B. "Broadband Lg Magnitude." Seismological Research Letters 58, no. 4 (October 1, 1987): 125–33. http://dx.doi.org/10.1785/gssrl.58.4.125.

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Abstract The application of the Nuttli (1973) definition of mbLg to observations with periods away from 1.0 seconds as suggested by Boore and Atkinson (1987) and Atkinson and Boore (1987) is studied with emphasis on observations in the 1.0 –10.0 second range and on single degree of freedom seismographs. Simulation studies indicate the efficacy of this usage, but also provides insight into the interrelated effects of the instrument, anelastic attenuation and the seismic source on observed amplitudes. In order to relate a broadband Lg magnitude to the source spectrum, a correction term must be applied to the mLg (f) relation of Herrmann and Kijko (1983).

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11

Ruiz-Lara, T., C. Gallart, M. Beasley, M. Monelli, E. J. Bernard, G. Battaglia, P. Sánchez-Blázquez, E. Florido, I. Pérez, and I. Martín-Navarro. "Integrated-light analyses vs. colour-magnitude diagrams." Astronomy & Astrophysics 617 (September 2018): A18. http://dx.doi.org/10.1051/0004-6361/201732398.

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Context. Most of our knowledge of the stellar component of galaxies is based on the analysis of distant systems and comes from integrated light data. It is important to test whether the results of the star formation histories (SFH) obtained with standard full-spectrum fitting methods are in agreement with those obtained through colour-magnitude diagram (CMD) fitting (usually considered the most reliable approach). Aims. We compare SFHs recovered from the two techniques in Leo A, a Local Group dwarf galaxy most of whose stars formed during the last 8 Gyrs. This complements our previous findings in a field in the Large Magellanic Cloud bar, where star formation has been in progress since early epochs at varying rates. Methods. We have used GTC/OSIRIS in long-slit mode to obtain a high-quality integrated light spectrum by scanning a selected region within Leo A, for which a CMD reaching the old main sequence turn-off (oMSTO) is available from HST. We compared the SFH obtained from the two datasets, using state-of-art methods of integrated light (STECKMAP) and resolved stellar population analysis. In the case of the CMD, we computed the SFH both from a deep CMD (observed with HST/ACS) and from a shallower CMD (archival data from HST/WFPC2). Results. The agreement between the SFHs recovered from the oMSTO CMD and from full spectrum fitting is remarkable, particularly regarding the time evolution of the star formation rate. The overall extremely low metallicity of Leo A is recovered up to the last 2 Gyrs when some discrepancies appear. A relatively high metallicity found for the youngest stars from the integrated data is a recurring feature that might indicate that the current models or synthesis codes should be revised, but that can be significantly mitigated using a more restrictive metallicity range. We thoroughly inspect the robustness of both approaches separately, finding that the subtle differences between them are inherent to the methods themselves. The SFH recovered from the shallow CMD also presents differences with the other two. Conclusions. Modern full-spectral fitting codes are able to recover both average constant SFHs (LMC case) and SFHs with a dominant fraction of young stellar populations. The analysis of high S/N spectra seems to provide more reliable SFH estimates than that of CMDs not reaching the oMSTO. The comparison presented in this paper needs to be repeated for predominantly old systems, thus assessing the performance of full-spectrum fitting for a full range of SFHs.

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12

FUKUSHIMA, Yoshimitsu, and Teiji TANAKA. "SCALING RELATIONS FOR EARTHQUAKE SOURCE SPECTRUM AND JMA MAGNITUDE." Journal of Structural and Construction Engineering (Transactions of AIJ) 425 (1991): 19–25. http://dx.doi.org/10.3130/aijsx.425.0_19.

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13

Matson, Charles L. "Weighted-least-squares magnitude-spectrum estimation from the bispectrum." Journal of the Optical Society of America A 8, no. 12 (December 1, 1991): 1914. http://dx.doi.org/10.1364/josaa.8.001914.

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14

Prasad, N., and T. Kishore Kumar. "Speech Bandwidth Extension Aided by Magnitude Spectrum Data Hiding." Circuits, Systems, and Signal Processing 36, no. 11 (March 1, 2017): 4512–40. http://dx.doi.org/10.1007/s00034-017-0526-5.

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15

Hough, S. E., K. Jacob, R. Busby, and P. A. Friberg. "Ground Motion From A Magnitude 3.5 Earthquake Near Massena, New York: Evidence For Poor Resolution of Corner Frequency For Small Events." Seismological Research Letters 60, no. 3 (July 1, 1989): 95–100. http://dx.doi.org/10.1785/gssrl.60.3.95.

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Abstract We present analysis of a magnitude 3.5 event which occurred at 9 km epicentral distance from a digital strong motion instrument operated by the National Center for Earthquake Engineering Research. Although the size of this isolated event is such that it can scarcely be considered to be a significant earthquake, a careful analysis of this high quality recording does yield several interesting results: 1) the S-wave spectra can be interpreted in terms of a simple omega-squared source spectrum and frequency-independent attenuation, 2) there is the suggestion of a poorly-resolved resonance in the P-wave spectrum, and perhaps most importantly, 3) the apparently simple S-wave spectra can be fit almost equally well with a surprisingly wide range of seismic corner frequencies, from roughly 5 to 25 Hz. This uncertainty in corner frequency translates into uncertainties in inferred Q values of almost an order of magnitude, and into uncertainties in stress drop of two orders of magnitude. Given the high quality of the data and the short epicentral distance to the station, we consider it likely that resolution of spectral decay and corner frequency will be at least as poor for any other recording of earthquakes with comparable or smaller magnitudes.

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16

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

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Abstract Simple linear models with additive stochastic forcing have been rather successful in explaining the observed spectrum of important climate variables. Motivated by this, the authors analyze the spectral character of such a general stochastic system of finite dimension. The spectral matrix is derived in the case that the spectrum is a linear combination of dynamical variables and their stochastic forcings. It is found that the most convenient basis for analysis is provided by the normal modes. In general the spectrum consists of two pieces. The first “diagonal” piece is a symmetric Lorentzian curve centered on the normal mode frequencies with breadth and strength determined by the normal mode dissipation. The second cross-spectrum piece derives usually from the coherency of the stochastic forcing of two different normal modes. The cross-spectrum is smaller in magnitude than the corresponding two diagonal pieces. This relative magnitude is controlled by the Wiener coherency, which is equal to the magnitude of the correlation of the stochastic forcings of different normal modes. This new analysis framework is studied in detail for the ENSO case for which a two-dimensional stochastically forced oscillator has been previously suggested as a minimal model. It is found that the observed spectrum is rather easily reproduced given appropriate dissipation. Further, it is found that the cross-spectrum results in a phase-dependent enhancement or suppression of frequencies smaller than the dominant ENSO frequency. This therefore provides a new mechanism for decadal ENSO variability. Since the cross-spectrum is phase dependent, the decadal variability generated has a distinctive spatial character. The significance of the cross-spectrum depends on the Wiener coherency, which in turn depends on the statistics of the stochastic forcing.

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17

Chowdhury, Husne Ara, and Mohammad Shahidur Rahman. "Formant estimation from speech signal using the magnitude spectrum modified with group delay spectrum." Acoustical Science and Technology 42, no. 2 (March 1, 2021): 93–102. http://dx.doi.org/10.1250/ast.42.93.

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Li, Jia, Shi Xue Xu, Ling Fei Xu, and Hai Yan Wang. "Spectrum Changes of Partially Coherent Polychromatic Beams in Laser Resonators." Advanced Materials Research 97-101 (March 2010): 3842–45. http://dx.doi.org/10.4028/www.scientific.net/amr.97-101.3842.

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Spectrum of partially coherent polychromatic beams in laser resonators is studied. Analytical formulae for spectrum of Gaussian Schell-model beams in resonators are derived. Numerical results show that spectral shift generated by unstable resonators is much flat and smaller than that by stable resonators. Spectral switch takes place when mirror spot size increases to a certain order of magnitude. Results also show that dependence of generated spectrum on coherence length of sources is very low. These results may be useful for manufacturing high power laser resonators.

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19

Serreqi, Alessio, and Melvin B. Comisarow. "Frequency Interpolation of Discrete, Apodized, Magnitude Lineshapes." Applied Spectroscopy 41, no. 2 (February 1987): 288–95. http://dx.doi.org/10.1366/000370287774986985.

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All Fourier spectrometers have a residual error in frequency measurement arising from the discrete nature of the experimental Fourier spectrum. This residual error is a systematic error which has a maximum value of half the channel spacing in the discrete spectrum. This systematic error can be reduced by interpolation of values on the discrete lineshape. The residual error remaining after interpolation has not yet been determined for apodized Fourier spectra. In this work, a systematic study of frequency interpolation of discrete, apodized, magnitude-mode lineshapes is reported. Absolute maximum frequency errors as a percentage of the discrete channel spacing are reported in graphical and tabular form as a function of the type of apodization window, the type of function used for three-point frequency interpolation, the number of zero-fillings, and ( T/ r), the ratio of the acquisition time to the relaxation time of the time domain signal. The results allow independent choice of the window function most appropriate for the dynamic range of the spectrum and the interpolating function/zero-filling level which optimizes the accuracy of frequency measurement. General observations are (1) that the interpolation error is reduced by an order of magnitude for each additional level of zero-filling and (2) that the interpolation error is essentially independent of T/r. For the Hanning window, the Hamming window, the three-term Blackman-Harris window, and the Kaiser-Bessel window, the parabola is the interpolating function of choice.

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Yu, Shiwang, Lifeng Zhang, Yuan Wang, and Jun Peng. "Mesoscale Horizontal Kinetic Energy Spectra of an Eastward-Moving Southwest Vortex." Atmosphere 13, no. 5 (April 20, 2022): 653. http://dx.doi.org/10.3390/atmos13050653.

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A high-resolution simulation with the Weather Research and Forecasting (WRF) model is performed to investigate the characteristics of the horizontal kinetic energy (HKE) spectra of an eastward-moving southwest vortex (SWV) generated in Sichuan Province, China, during 16–19 June 2011. The results indicate that the evolution of the SWV can be divided into the development, mature, and decay stages. In the troposphere, the HKE spectrum reproduces the typical atmospheric spectrum, with a slope of approximately −3 for wavelengths greater than 300 km and −5/3 for wavelengths between 300 and 30 km in each stage. The average scale of spectral transition is around 300 km. However, the HKE spectrum in the lower stratosphere shows a −5/3 slope at mesoscales and has no clear spectral transition. During the mature stage of the SWV, the HKE increases prominently for wavelengths between 300 and 30 km. Moreover, the relative contribution of the rotational kinetic energy (RKE) and the divergent kinetic energy (DKE) was investigated. It shows that the RKE spectrum dominates the DKE spectrum for wavelengths greater than 300 km in the lower troposphere, while in the upper troposphere the magnitudes of RKE and DKE are comparable over all scales. However, in the lower stratosphere, the DKE is an order of magnitude larger than the RKE, contributing more to the total HKE spectrum.

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Nizampatnam, Prasad, and Kishore Kumar Tappeta. "Bandwidth extension of telephone speech using magnitude spectrum data hiding." International Journal of Speech Technology 20, no. 1 (January 13, 2017): 151–62. http://dx.doi.org/10.1007/s10772-016-9393-x.

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Paliwal, Kuldip, Belinda Schwerin, and Kamil Wójcicki. "Role of modulation magnitude and phase spectrum towards speech intelligibility." Speech Communication 53, no. 3 (March 2011): 327–39. http://dx.doi.org/10.1016/j.specom.2010.10.004.

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23

Gaubitch, Nikolay D., Mike Brookes, and Patrick A. Naylor. "Blind Channel Magnitude Response Estimation in Speech Using Spectrum Classification." IEEE Transactions on Audio, Speech, and Language Processing 21, no. 10 (October 2013): 2162–71. http://dx.doi.org/10.1109/tasl.2013.2270406.

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Jiang, Wenbin, Peilin Liu, and Fei Wen. "Speech Magnitude Spectrum Reconstruction from MFCCs Using Deep Neural Network." Chinese Journal of Electronics 27, no. 2 (March 1, 2018): 393–98. http://dx.doi.org/10.1049/cje.2017.09.018.

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Verdun, Francis R., Carlo Giancaspro, and Alan G. Marshall. "Effects of Noise, Time-Domain Damping, Zero-Filling and the FFT Algorithm on the “Exact” Interpolation of Fast Fourier Transform Spectra." Applied Spectroscopy 42, no. 5 (July 1988): 715–21. http://dx.doi.org/10.1366/0003702884429094.

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A frequency-domain Lorentzian spectrum can be derived from the Fourier transform of a time-domain exponentially damped sinusoid of infinite duration. Remarkably, it has been shown that even when such a noiseless time-domain signal is truncated to zero amplitude after a finite observation period, one can determine the correct frequency of its corresponding magnitude-mode spectral peak maximum by fitting as few as three spectral data points to a magnitude-mode Lorentzian spectrum. In this paper, we show how the accuracy of such a procedure depends upon the ratio of time-domain acquisition period to exponential damping time constant, number of time-domain data points, computer word length, and number of time-domain zero-fillings. In particular, we show that extended zero-filling (e.g., a “zoom” transform) actually reduces the accuracy with which the spectral peak position can be determined. We also examine the effects of frequency-domain random noise and roundoff errors in the fast Fourier transformation (FFT) of time-domain data of limited discrete data word length (e.g., 20 bit/word at single and double precision). Our main conclusions are: (1) even in the presence of noise, a three-point fit of a magnitude-mode spectrum to a magnitude-mode Lorentzian line shape can offer an accurate estimate of peak position in Fourier transform spectroscopy; (2) the results can be more accurate (by a factor of up to 10) when the FFT processor operates with floating-point (preferably double-precision) rather than fixed-point arithmetic; and (3) FFT roundoff errors can be made negligible by use of sufficiently large (> 16 K) data sets.

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Bhattarai, Shishir, and Prem Nath Maskey. "Effect of Linear Soil Condition on Seismic Inputs." Technical Journal 2, no. 1 (November 10, 2020): 48–55. http://dx.doi.org/10.3126/tj.v2i1.32829.

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Seismic inputs to structures in terms of risk consistent response spectrum and seismic hazard curves are developed at bedrock level considering ten independent seismic source zone in the vicinity of the Kathmandu valley. The seismic hazard curve is derived by assuming temporal occurrence of earthquakes to follow Poisson model. Response spectrum is developed using an empirical relationship of spectral ordinates with magnitude of earthquakes and epicentral distance. The seismic risk factor is introduced in response spectrum using conditional probabilities. Power spectral density function consistent with response spectrum is derived and ground acceleration time histories are derived from power spectral density function using Monte Carlo technique. To obtain free field hazard curves and ground motion parameters, one dimensional wave propagation analysis is used for two different underlying soil conditions.

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Babin, S. A., V. A. Labusov, D. O. Selyunin, and O. V. Pelipasov. "Dynamic-range extension of MAES multichannel analyzers based on BLPP-2000 and BLPP 4000 photodetector arrays." Аналитика и контроль 25, no. 4 (2021): 340–49. http://dx.doi.org/10.15826/analitika.2021.25.4.011.

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One trend in the development of integral atomic emission spectral analysis with low spectral background excitation sources, such as inductively coupled or microwave plasma, is to increase the dynamic range of spectrum recording systems based on photodetector arrays. To achieve low detection limits, it is necessary to use photodetector arrays with low reading noise. The dynamic range of a single readout of such photodetector arrays usually does not exceed four orders of magnitude. The dynamic range increase due to the accumulation of spectra from multiple acquisition leads to a quadratic increase in the measurement time. This method does not allow one to cover the entire dynamic range of spectral line intensities of inductively coupled or microwave plasma (which can reach seven orders of magnitude) while maintaining an acceptable total measurement time of a sample spectrum. As an alternative, it is proposed to increase the dynamic range toward higher line intensities by using two different alternating accumulation times during measurement. The objective of this study is to implement the proposed recording mode in MAES analyzers based on BLPP-2000 and BLPP-4000 photodetector arrays in order to increase the dynamic range of recorded spectral lines. Dependences of the signal-to-noise ratio and the dynamic range of spectral lines recorded in integral atomic emission spectrometry on the accumulation time, the total measurement time, the spectral background level, and the photodetector array parameters are obtained. It is shown theoretically that the use of the recording mode with alternating different accumulation times should increase the dynamic range of BLPP-2000 and BLPP-4000 photodetector arrays by two orders of magnitude. The dynamic range of spectral line intensities of a hollow-cathode lamp is shown experimentally to increase by two orders of magnitude (to five orders of magnitude).

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Keefe, C. Dale, and Melvin B. Comisarow. "Exact Interpolation of Apodized, Magnitude-Mode Fourier Transform Spectra." Applied Spectroscopy 43, no. 4 (May 1989): 605–7. http://dx.doi.org/10.1366/0003702894202418.

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A procedure is developed for the exact interpolation of apodized, magnitude-mode Fourier transform (FT) spectra. The procedure gives the true center frequency, i.e., the location of the continuous peak, from just the largest three discrete intensities in the discrete magnitude spectrum. The procedure is applicable for the peaks in the apodized magnitude spectrum of a time signal of the form f( t) = cos( ωt) exp(– t/τ). There are no restrictions on the value of the damping ratio T/τ. The procedure is demonstrated for the sine-bell and Hanning windows and is generalizable to other windows which consist of a sum of constants and sine/cosine terms. This includes the majority of commonly used windows.

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Wang, Shuhua, Bingchen Han, Xiaomin Lü, Feng Yuan, and Huaisong Zhao. "Doping dependence of unusual electron spectrum in hole-doped cuprate superconductors." Modern Physics Letters B 30, no. 04 (February 10, 2016): 1650032. http://dx.doi.org/10.1142/s0217984916500329.

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Based on the renormalized Hubbard model, the doping dependence of electron spectrum in cuprate superconductors is discussed within the self-consistent mean field theory. It is shown that the renormalization factor [Formula: see text] (then the quasiparticle coherent weight) increases almost linearly with the doping and plays an important role in the unconventional superconductivity for cuprate superconductors. It suppresses the magnitude of the quasiparticle peak in the electron spectrum, especially in underdoped region. By calculation of the energy and doping dependence of the electron spectral function, the main features of the electron spectrum in cuprate superconductors can be described qualitatively. In particular, with the increasing doping concentration, the position of the quasiparticle peak moves to the Fermi energy and the magnitude of the quasiparticle peak increases monotonically. Our results also show that the superconducting order parameter is determined by product of the renormalization factor and the pseudogap.

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Tobin, Nicolas, and Leonardo P. Chamorro. "Turbulence coherence and its impact on wind-farm power fluctuations." Journal of Fluid Mechanics 855 (September 24, 2018): 1116–29. http://dx.doi.org/10.1017/jfm.2018.713.

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Using a physics-based approach, we infer the impact of the coherence of atmospheric turbulence on the power fluctuations of wind farms. Application of the random-sweeping hypothesis reveals correlations characterized by advection and turbulent diffusion of coherent motions. Those contribute to local peaks and troughs in the power spectrum of the combined units at frequencies corresponding to the advection time between turbines, which diminish in magnitude at high frequencies. Experimental inspection supports the results from the random-sweeping hypothesis in predicting spectral characteristics, although the magnitude of the coherence spectrum appears to be over-predicted. This deviation is attributed to the presence of turbine wakes, and appears to be a function of the turbulence approaching the first turbine in a pair.

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Daimiwal, Nivedita, and Revati Shriram. "Power Spectral Density analysis of time series of pixel of functional magnetic resonance image for different motor activity." Biomedical & Pharmacology Journal 12, no. 3 (July 18, 2019): 1193–200. http://dx.doi.org/10.13005/bpj/1748.

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Functional Magnetic Resonance Imaging (fMRI) is a non invasive modality to detect structure and function of the brain. Brain functions for various activities like motor, sensory, speech and memory process are detected using fMRI modality. This paper deals with the analysis of power spectrum of pixel time series for different motor activities. The analysis is to relate the power magnitude of the spike in the power spectrum of the fMRI time series with the activity performed. The fMRI data set consists of a sequence of images with respect to time, when the subject performs a definite task in a given block paradigm. The data set consists of four slices each of size 64×64 pixels. The power spectrum is acquired by taking the Fourier transform of the time series. The shape of the power spectrum is often referred to as 1/f or the inverse frequency function. Low frequency noise is removed by applying discrete cosine transform on time series. Data was originally, collected from General Electric Signa 1.5 T MRI system for 5 male subjects; 3 subjects: Performed lower limb movement (LL) and 2 subjects: Performed upper limb movement (UL). The power magnitude of the spike is recorded for lower limb and upper limb movement. The spike in the power spectrum at f Hz corresponds to the frequency at which the task is performed. The power magnitude amplitude for lower limb activity is around 14.31 dB and upper limb is around 4.0 dB. Power spectral density (PSD) of the time series is used for the detection of activities occurring in the brain.

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Рехвиашвили, С. Ш., А. В. Псху, and З. Ч. Маргушев. "Излучение дробного осциллятора." Письма в журнал технической физики 47, no. 22 (2021): 49. http://dx.doi.org/10.21883/pjtf.2021.22.51728.18964.

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The spectral energy density of the oscillator radiation is calculated in the dipole approximation. The oscillator motion is described by an equation with fractional integro-differentiation. The fractional oscillator model can describe various types of radiation, including those with a nonexponential relaxation law. Found the shape of the spectral line of radiation. The obtained result is compared with the classical Lorentzian spectrum and experimental emission spectra of monochromatic and phosphor LEDs. The order of fractional integro-differentiation in the model sets the magnitude of the broadening of the radiation spectrum.

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Houston, Heidi, and Hiroo Kanamori. "Comparison of strong-motion spectra with teleseismic spectra for three magnitude 8 subduction-zone earthquakes." Bulletin of the Seismological Society of America 80, no. 4 (August 1, 1990): 913–34. http://dx.doi.org/10.1785/bssa0800040913.

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Abstract We studied strong-motion spectra observed for three Mw 7.8 to 8.0 earthquakes (the 1985 Michoacán, Mexico; 1985 Valparaíso, Chile; and 1983 Akita-Oki, Japan earthquakes). We determined the decay of spectral amplitude with distance from the station, considering different measures of distance from a finite fault. We compared strong-motion spectra (Fourier acceleration spectra) observed for these three earthquakes with those estimated from the source spectrum determined from teleseismic P waves. We scaled the teleseismic source spectra to produce reference strong-motion spectra at periods from 1 to 10 sec using a simple physical model of far-field S body waves from a point source recorded at the surface of a homogeneous half-space. For all three earthquakes the reference spectral amplitudes at periods of 1 to 5 sec are about half the observed ones at distances of about 50 km. The difference increases as the distance increases. At distances of 200 to 300 km, the reference spectrum is about 1/10 of the observed one. The difference between the reference and the observed spectrum is attributed to the contribution of phases other than direct S waves and to site response. We applied corrections for the finiteness (spatial extent) of the source using a simple model of rupture propagation on a dipping two-dimensional fault. Including the source finiteness did not improve the estimate substantially at periods from 1 to 20 sec, but it modeled significant changes in the signal duration as a function of azimuth for the 1985 Michoacán earthquake. Our results can be used to establish empirical relations between the observed spectra and the half-space responses, depending on the distance and the site condition. If such empirical relations can be established, source spectra determined from teleseismic records may be used to estimate strong motions.

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Ong, K. C. G., Zengrong Wang, and M. Maalej. "Adaptive magnitude spectrum algorithm for Hilbert–Huang transform based frequency identification." Engineering Structures 30, no. 1 (January 2008): 33–41. http://dx.doi.org/10.1016/j.engstruct.2007.02.018.

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Ekgasit, Sanong, and Hatsuo Ishida. "Quantitative Two-Dimensional Infrared (2D IR) Spectroscopy: Theoretical Development for General and Specific Cases." Applied Spectroscopy 49, no. 9 (September 1995): 1243–53. http://dx.doi.org/10.1366/0003702953965308.

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A quantitative two-dimensional correlation analysis for various spectroscopic techniques is introduced. Normalization of the spectral intensities enables two-dimensional infrared (2D IR) spectroscopy to be used for quantitative purposes. As a result of the normalization, the correlation strengths are characterized by the dynamic parameters of the correlated spectral intensities. Relationships between the chemical species associated with peak positions in 2D IR spectra are characterized by both the magnitude and the sign of the correlation strength. The magnitude describes the degree of harmonization, while the sign shows the relationship between the dynamic behaviors of the correlated spectral intensities. The phase spectrum, which indicates the quantitative relationship among the dynamic behavior of the spectral intensities, is also introduced.

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Doazan, V., A. De La Fuente, M. Barylak, and N. Cramer. "Absolute Magnitude Determination of Be Stars: The Inadequacy of the 2200 Å Bump." International Astronomical Union Colloquium 137 (1993): 787–88. http://dx.doi.org/10.1017/s025292110001887x.

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AbstractWe present fax UV observations of Pleione made with the IUE satellite at two epochs: in 1979, when the star exhibited a strong shell spectrum and, in 1991, when it showed a Be-type spectrum. Between these two epochs, the 2200 Å bump changed dramatically, thus, rendering it inadequate for interstellar extinction/distance determination.

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Popiński, Waldemar. "Statistical View on Phase and Magnitude Information in Signal Processing." Artificial Satellites 47, no. 3 (January 1, 2012): 127–36. http://dx.doi.org/10.2478/v10018-012-0018-6.

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Statistical View on Phase and Magnitude Information in Signal ProcessingIn this work the problem of reconstruction of an original complex-valued signalot,t= 0, 1, …,n- 1, from its Discrete Fourier Transform (DFT) spectrum corrupted by random fluctuations of magnitude and/or phase is investigated. It is assumed that the magnitude and/or phase of discrete spectrum values are distorted by realizations of uncorrelated random variables. The obtained results of analysis of signal reconstruction from such distorted DFT spectra concern derivation of the expected values and bounds on variances of the reconstructed signal at the observation moments. It is shown that the considered random distortions in general entail change in magnitude and/or phase of the reconstructed signal expected values, which together with imposed random deviations with finite variances can blur the similarity to the original signal. The effect of analogous random amplitude and/or phase distortions of a complex valued time domain signal on band pass filtration of distorted signal is also investigated.

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Abraham, B. M., and W. L. Keith. "Wavenumber Spectra of High Magnitude Wall Pressure Events in a Numerically Simulated Turbulent Boundary Layer." Journal of Fluids Engineering 119, no. 2 (June 1, 1997): 281–88. http://dx.doi.org/10.1115/1.2819132.

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A method for conditionally sampling the spatial field of the wall pressure beneath a turbulent boundary layer in order to search for high magnitude events and calculate the corresponding wavenumber spectrum is presented. The high magnitude events are found using a simple peak detection algorithm at a fixed instant in time and the wavenumber spectra are calculated using discrete Fourier transforms. The frequency of occurrence for high magnitude positive events is found to be approximately the same as for high magnitude negative events. The contribution of the high magnitude events to the rms wall pressure for various trigger levels is calculated and compared with results from similar experimental studies performed in the time domain. The high magnitude events are shown to occur infrequently and to contribute significantly to the rms wall pressure. Wavenumber spectra from the high magnitude positive and negative events are calculated and compared with the unconditionally sampled spectra. The high magnitude events contain energy focused around a particular stream-wise wavenumber and have high broadband spectral levels.

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Dodson-Robinson, Sarah E., Victor Ramirez Delgado, Justin Harrell, and Charlotte L. Haley. "Magnitude-squared Coherence: A Powerful Tool for Disentangling Doppler Planet Discoveries from Stellar Activity." Astronomical Journal 163, no. 4 (March 15, 2022): 169. http://dx.doi.org/10.3847/1538-3881/ac52ed.

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Abstract If Doppler searches for Earth-mass, habitable planets are to succeed, observers must be able to identify and model out stellar activity signals. Here we demonstrate how to diagnose activity signals by calculating the magnitude-squared coherence C ˆ xy 2 ( f ) between an activity-indicator time series x t and the radial-velocity (RV) time series y t . Since planets only cause modulation in RV, not in activity indicators, a high value of C ˆ xy 2 ( f ) indicates that the signal at frequency f has a stellar origin. We use Welch’s method to measure coherence between activity indicators and RVs in archival observations of GJ 581, α Cen B, and GJ 3998. High RV-Hα coherence at the frequency of GJ 3998 b and high RV-S index coherence at the frequency of GJ 3998c, indicate that the planets may actually be stellar signals. We also replicate previous results showing that GJ 581 d and g are rotation harmonics and demonstrate that α Cen B has activity signals that are not associated with rotation. Welch’s power spectrum estimates have cleaner spectral windows than Lomb–Scargle periodograms, improving our ability to estimate rotation periods. We find that the rotation period of GJ 581 is 132 days, with no evidence of differential rotation. Welch’s method may yield unacceptably large bias for data sets with N < 75 observations and works best on data sets with N > 100. Tapering the time-domain data can reduce the bias of the Welch’s power spectrum estimator, but observers should not apply tapers to data sets with extremely uneven observing cadence. A software package for calculating magnitude-squared coherence and Welch’s power spectrum estimates is available on github.

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Zhiqiang, Shen, Yan Tingfei, Liu Chuang, Jiao Anchao, and Gu Fei. "Development of a Horizontal Pneumatic Test System for Shock Response Spectrum." Journal of Physics: Conference Series 2239, no. 1 (April 1, 2022): 012011. http://dx.doi.org/10.1088/1742-6596/2239/1/012011.

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Abstract Pendulum impact test equipment cannot meet the high magnitude test demand of large products. This paper designed a pneumatic impact test which can make a high-magnitude impact test, giving the design principle of the pneumatic impact test system, introducing the design methods of the pneumatic test system. The test results show that the technical indexes of the system meet the design requirements. The pneumatic impact test system with a 1.25 m× 1.25 m table based on the shock response spectrum principle can realize the inflection frequency adjustable from 500 to 1500 Hz and the slope adjustable from +6 to +9 dB. And it can realize the shock response spectrum test of 5000g magnitude at full load. The test system can meet the current test magnitude and test requirements of spacecraft products. The method proposed in this paper can serve as a reference for the design of this kind of impact test systems.

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Ferguson, Raechal H., Terry S. Falcomata, Andrea Ramirez-Cristoforo, and Fabiola Vargas Londono. "An Evaluation of the Effects of Varying Magnitudes of Reinforcement on Variable Responding Exhibited by Individuals With Autism." Behavior Modification 43, no. 6 (June 19, 2019): 774–89. http://dx.doi.org/10.1177/0145445519855615.

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Interventions aimed at increasing communicative response variability hold particular importance for individuals with autism spectrum disorders (ASD). Several procedures have been demonstrated in the applied and translational literature to increase response variability. However, little is known about the relationship between reinforcer magnitude and response variability. In the basic literature, Doughty, Giorno, and Miller evaluated the effects of reinforcer magnitude on behavioral variability by manipulating reinforcer magnitude across alternating relative frequency threshold contingencies, with results suggesting that larger reinforcers induced repetitive responding. The purpose of this study was to translate Doughty et al.’s findings to evaluate the relative effects of different magnitudes of reinforcement on communicative response variability in children with ASD. A Lag 1 schedule of reinforcement was in place during each condition within an alternating treatments design. Magnitudes of reinforcement contingent on variable communicative responding were manipulated across the two conditions. Inconsistent with basic findings, the results showed higher levels of variable communicative responding associated with the larger magnitude of reinforcement. These outcomes may have potential implications for interventions aimed at increasing response variability in individuals with ASD, as well as future research in this area.

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Chun, Hye-Yeong, Hyun-Joo Choi, and In-Sun Song. "Effects of Nonlinearity on Convectively Forced Internal Gravity Waves: Application to a Gravity Wave Drag Parameterization." Journal of the Atmospheric Sciences 65, no. 2 (February 1, 2008): 557–75. http://dx.doi.org/10.1175/2007jas2255.1.

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Abstract In the present study, the authors propose a way to include a nonlinear forcing effect on the momentum flux spectrum of convectively forced internal gravity waves using a nondimensional numerical model (NDM) in a two-dimensional framework. In NDM, the nonlinear forcing is represented by nonlinear advection terms multiplied by the nonlinearity factor (NF) of the thermally induced internal gravity waves for a given specified diabatic forcing. It was found that the magnitudes of the waves and resultant momentum flux above the specified forcing decrease with increasing NF due to cancellation between the two forcing mechanisms. Using the momentum flux spectrum obtained by the NDM simulations with various NFs, a scale factor for the momentum flux, normalized by the momentum flux induced by diabatic forcing alone, is formulated as a function of NF. Inclusion of the nonlinear forcing effect into current convective gravity wave drag (GWD) parameterizations, which consider diabatic forcing alone by multiplying the cloud-top momentum flux spectrum by the scale factor, is proposed. An updated convective GWD parameterization using the scale factor is implemented into the NCAR Whole Atmosphere Community Climate Model (WACCM). The 10-yr simulation results, compared with those by the original convective GWD parameterization considering diabatic forcing alone, showed that the magnitude of the zonal-mean cloud-top momentum flux is reduced for wide range of phase speed spectrum by about 10%, except in the middle latitude storm-track regions where the cloud-top momentum flux is amplified. The zonal drag forcing is determined largely by the wave propagation condition under the reduced magnitude of the cloud-top momentum flux, and its magnitude decreases in many regions, but there are several areas of increasing drag forcing, especially in the tropical upper mesosphere and lower thermosphere.

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Zhao, John X., Qingsong Yang, Kaiwei Su, Jiguan Liang, Jun Zhou, Heng Zhang, and Xinge Yang. "Effects of Earthquake Source, Path, and Site Conditions on Damping Modification Factor for the Response Spectrum of the Horizontal Component from Subduction Earthquakes." Bulletin of the Seismological Society of America 109, no. 6 (November 12, 2019): 2594–613. http://dx.doi.org/10.1785/0120190105.

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Abstract Damping modification factors (DMFs) are important for estimating the response spectrum for the design of structures with different damping ratios. This study investigated the effects of earthquake source parameters (magnitude, source depth, and source categories), source distance (the closest distance from a site to a fault plane for large earthquakes and hypocentral distance for the other events), and site conditions on DMFs for the displacement and acceleration response spectra of the horizontal components of the records from Japan. This study used a total of 14,713 strong‐motion records from the KiK‐net and K‐NET to compare the DMFs from three earthquake category groups, namely shallow crustal and upper mantle, subduction interface, and subduction slab earthquakes. Statistical tests were carried out to determine whether the DMFs from these three types of earthquakes differ significantly from each other. The test results show that, between each pair of the three types of earthquakes, the DMFs for both displacement and acceleration response spectra differ significantly in terms of statistical tests and practically for engineering applications at many spectral periods, with the largest difference over 40%. The effects of earthquake category and site conditions for acceleration spectrum are similar to those of the displacement spectrum at short periods up to about 0.3 s but are much larger than those of the displacement spectrum at long spectral periods. The effects of magnitude and earthquake depth are also significant. Therefore, separate DMF models for the response spectrum of the horizontal component should be derived for each type of earthquake and should account for the effects of earthquake source and path parameters and site conditions.

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Werner, Kurt, and François Germain. "Sinusoidal Parameter Estimation Using Quadratic Interpolation around Power-Scaled Magnitude Spectrum Peaks." Applied Sciences 6, no. 10 (October 21, 2016): 306. http://dx.doi.org/10.3390/app6100306.

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Yildirim, Ali Yilmaz, Stefan Couturier, Konstantin Schwalm, Marc Adrat, Christiane Antweiler, and Peter Jax. "Spectrum Monitoring Based on Error Vector Magnitude and Received Signal Strength Indicator." Procedia Computer Science 205 (2022): 10–19. http://dx.doi.org/10.1016/j.procs.2022.09.002.

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Kendall, Gary S., Martin D. Wilde, and William L. Martens. "Apparatus and method for controlling the magnitude spectrum of acoustically combined signals." Journal of the Acoustical Society of America 93, no. 2 (February 1993): 1217. http://dx.doi.org/10.1121/1.406839.

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Loizou, P. C. "Speech enhancement based on perceptually motivated bayesian estimators of the magnitude spectrum." IEEE Transactions on Speech and Audio Processing 13, no. 5 (September 2005): 857–69. http://dx.doi.org/10.1109/tsa.2005.851929.

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Tsai, C. Y., E. J. Rothwell, and K. M. Chen. "Target discrimination using neural networks with time domain or spectrum magnitude response." Journal of Electromagnetic Waves and Applications 10, no. 3 (January 1996): 341–82. http://dx.doi.org/10.1163/156939396x00450.

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Lu, Yang, and Philipos C. Loizou. "Estimators of the Magnitude-Squared Spectrum and Methods for Incorporating SNR Uncertainty." IEEE Transactions on Audio, Speech, and Language Processing 19, no. 5 (July 2011): 1123–37. http://dx.doi.org/10.1109/tasl.2010.2082531.

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Goto, Yutaka. "Highly Accurate Frequency Interpolation of Apodized FFT Magnitude-Mode Spectra." Applied Spectroscopy 52, no. 1 (January 1998): 134–38. http://dx.doi.org/10.1366/0003702981942465.

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“Generalized” interpolation (called GIα here) of fast Fourier transform (FFT) spectra apodized by a family of sinα ( X) windows has previously been proposed. The GIα gives the highly accurate interpolated frequency by calculating the simple formula of frequency determination with the use of two squared ratios between three magnitudes nearest to the peak maximum on the apodized FFT spectrum. Although the value of window parameter α, limited to integer values, has been used for the GIα, we show in the present paper that the GIα with a real α value also gives an extremely good estimate of the true frequency from the sinα ( X)-apodized spectra. Thus, we intend to apply the GIα with the optimal values of α to FFT spectra apodized by any other window functions that are often used in Fourier spectroscopy. Simulation results show that the GIα is easier and more accurate than the KCe interpolation, which uses a family of interpolating functions [ KCe(ω) = ( aω2 + bω + c)e] proposed by Keefe and Comisarow. Finally, in the presence of noise we examine effects of damping and windowing on the frequency interpolation of FFT spectra. Because damping and windowing reduce the signal-to-noise ratio (SNR), we define anew the relative SNR by the ratio of the SNR of the apodized spectrum of a damped sinusoid to the SNR of the unapodized spectrum of an undamped sinusoid. Numerical calculation shows that the relative SNR varies, owing to damping rather than windowing. In fact, the observed frequency error roughly increases as the damping ratio increases for any window functions, as is expected from our previous investigation that the frequency error based upon the GIα is inversely proportional to the SNR. However, no obvious differences between the various window functions are observed in the presence of noise.

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Journal articles on the topic 'Magnitude spectrum'

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