scholarly journals Passive Detection of Ship-Radiated Acoustic Signal Using Coherent Integration of Cross-Power Spectrum with Doppler and Time Delay Compensations

Sensors ◽  
2020 ◽  
Vol 20 (6) ◽  
pp. 1767
Author(s):  
Wei Guo ◽  
Shengchun Piao ◽  
Junyuan Guo ◽  
Yahui Lei ◽  
Kashif Iqbal
Keyword(s):  
Time Delay ◽  
Power Spectrum ◽  
Target Detection ◽  
Acoustic Signal ◽  
Time Scale ◽  
Power Spectra ◽  
Experimental Data Processing ◽  
Coherent Integration ◽  
Negative Effect ◽  
Cross Power Spectrum

Passive sonar is widely used for target detection, identification and classification based on the target radiated acoustic signal. Under the influence of Doppler, generated by relative motion between the moving target and the sonar array, the received ship-radiated acoustic signals are non-stationary and time-varying, which has a negative effect on target detection and other fields. In order to reduce the influence of Doppler and improve the performance of target detection, a coherent integration method based on cross-power spectrum is proposed in this paper. It can be concluded that the frequency shift and phase change in the cross-power spectrum obtained by each pair of data segments can be corrected with the compensations of time scale (Doppler) factor and time delay. Moreover, the time scale factor and time delay can be estimated from the amplitude and phase of the original cross-power spectrum, respectively. Therefore, coherent integration can be implemented with the compensated cross-power spectra. Simulation and experimental data processing results show that the proposed method can provide sufficient processing gains and effectively extract the discrete spectra for the detection of moving targets.

Stratigraphic filter theory: Combined effects of parallel bedding and random inhomogeneities

Geophysics ◽  
1986 ◽  
Vol 51 (8) ◽  
pp. 1531-1537 ◽  
Author(s):  
I. Lerche
Keyword(s):  
Time Delay ◽  
Power Spectrum ◽  
Layered Medium ◽  
Mean Field ◽  
Power Spectra ◽  
Low Frequencies ◽  
High Frequencies ◽  
Bedding Planes ◽  
Scattering Centers ◽  
The Mean

Mean field renormalization techniques determine the phase distortion (time delay) and effective attenuation as functions of frequency for a plane acoustic wave, normally incident on a layered medium, when the medium also contains a distribution of scattering centers at random sites. The power spectra of impedance fluctuations of both the bedding layers and the random centers contribute to the time delay and mean field effective attenuation. At low frequencies (long wavelengths), the power spectrum of the bedding planes dominates the mean wave response, producing most of the time delay and the effective attenuation. At high frequencies (short wavelengths), the random scattering centers dominate the mean wave behavior. The wave no longer propagates exactly perpendicularly to bedding planes since the random scattering centers cast energy into directions transverse to the normal to the bedding planes. The precise frequency dependence of both the time delay and the effective attenuation of the mean wave are sensitive to the power spectrum of impedance fluctuations of the bedding planes relative to the power spectrum of the random scattering centers.

scholarly journals Power spectrum modelling of galaxy and radio intensity maps including observational effects

2019 ◽  
Vol 489 (1) ◽  
pp. 153-167 ◽  
Author(s):  
Chris Blake
Keyword(s):  
Power Spectrum ◽  
Power Spectra ◽  
Selection Function ◽  
Data Sets ◽  
Significant Information ◽  
Intensity Mapping ◽  
Optimal Weights ◽  
The Cross ◽  
Radio Intensity ◽  
Cross Power Spectrum

ABSTRACT Fluctuations in the large-scale structure of the Universe contain significant information about cosmological physics, but are modulated in survey data sets by various observational effects. Building on existing literature, we provide a general treatment of how fluctuation power spectra are modified by a position-dependent selection function, noise, weighting, smoothing, pixelization, and discretization. Our work has relevance for the spatial power spectrum analysis of galaxy surveys with spectroscopic or accurate photometric redshifts, and radio intensity-mapping surveys of the sky brightness temperature including generic noise, telescope beams, and pixelization. We consider the autopower spectrum of a field, the cross-power spectrum between two fields and the multipoles of these power spectra with respect to a curved sky, deriving the corresponding power spectrum models, estimators, errors, and optimal weights. We note that ‘FKP weights’ for individual tracers do not in general provide the optimal weights when measuring the cross-power spectrum. We validate our models using mock data sets drawn fromN-body simulations.1 Our treatment should be useful for modelling and studying cosmological fluctuation fields in observed and simulated data sets.

The Generalized Cross-Power Spectrum Method for Estimation of Time Delay in Acoustic Pyrometer

2011 ◽  
Vol 88-89 ◽  
pp. 615-620
Author(s):  
Cheng Zhi Li ◽  
Fu Qun Shao ◽  
Zhe Kan ◽  
Hai Xiang Fan
Keyword(s):  
Time Delay ◽  
Power Spectrum ◽  
Experimental Result ◽  
Low Snr ◽  
Correlation Algorithm ◽  
Power Spectrum Method ◽  
Effects Of Radiation ◽  
Estimation Of Time ◽  
Cross Power Spectrum ◽  
Peak Value

The acoustic pyrometer system uses physical properties of the gas and registers the perceivable temperature without the effects of radiation, and the measuring accuracy of acoustic wave flight time is the major factor in its application. The traditional correlation algorithm could not overcome convolution interference and calculate the time delay of acoustic signals accurately, under the low SNR (Signal Noise Ratio) and complex reverberation noise conditions. This paper presents a generalized cross power spectrum algorithm to filter the product and convolution interferences, and improves the performances of anti-noise and anti-convolution by whitening the sample signals and adjusting the weighted value of cross power spectrum algorithm with the variation of SNR. The experimental result and theoretical analysis showed that the new generalized cross power spectrum algorithm compared to the traditional correlation function analytical algorithm, can overcome the convolution interferences from reverberation noise, and sharpen peak value, thereby estimate the time delays of signals accurately.

Log-log scale roughness spectroscopy of surfaces

1993 ◽  
Vol 51 ◽  
pp. 224-225
Author(s):  
P. Fraundorf ◽  
B. Armbruster
Keyword(s):  
Power Spectrum ◽  
Autocorrelation Function ◽  
Power Spectra ◽  
Scanning Force Microscopy ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Force Microscopy ◽  
Scanning Force ◽  
Lateral Structure ◽  
Scale Roughness

Optical interferometry, confocal light microscopy, stereopair scanning electron microscopy, scanning tunneling microscopy, and scanning force microscopy, can produce topographic images of surfaces on size scales reaching from centimeters to Angstroms. Second moment (height variance) statistics of surface topography can be very helpful in quantifying “visually suggested” differences from one surface to the next. The two most common methods for displaying this information are the Fourier power spectrum and its direct space transform, the autocorrelation function or interferogram. Unfortunately, for a surface exhibiting lateral structure over several orders of magnitude in size, both the power spectrum and the autocorrelation function will find most of the information they contain pressed into the plot’s origin. This suggests that we plot power in units of LOG(frequency)≡-LOG(period), but rather than add this logarithmic constraint as another element of abstraction to the analysis of power spectra, we further recommend a shift in paradigm.

scholarly journals The completed SDSS-IV extended Baryon Oscillation Spectroscopic Survey: a multitracer analysis in Fourier space for measuring the cosmic structure growth and expansion rate

2021 ◽  
Vol 504 (1) ◽  
pp. 33-52
Author(s):  
Gong-Bo Zhao ◽  
Yuting Wang ◽  
Atsushi Taruya ◽  
Weibing Zhang ◽  
Héctor Gil-Marín ◽  
...  
Keyword(s):  
Growth Rate ◽  
Power Spectrum ◽  
Confidence Level ◽  
Expansion Rate ◽  
Fourier Space ◽  
Redshift Range ◽  
Significance Level ◽  
Data Product ◽  
New Development ◽  
Cross Power Spectrum

ABSTRACT We perform a joint BAO and RSD analysis using the eBOSS DR16 LRG and ELG samples in the redshift range of z ∈ [0.6, 1.1], and detect an RSD signal from the cross-power spectrum at a ∼4σ confidence level, i.e., fσ8 = 0.317 ± 0.080 at zeff = 0.77. Based on the chained power spectrum, which is a new development in this work to mitigate the angular systematics, we measure the BAO distances and growth rate simultaneously at two effective redshifts, namely, DM/rd (z = 0.70) = 17.96 ± 0.51, DH/rd (z = 0.70) = 21.22 ± 1.20, fσ8 (z = 0.70) = 0.43 ± 0.05, and DM/rd (z = 0.845) = 18.90 ± 0.78, DH/rd (z = 0.845) = 20.91 ± 2.86, fσ8 (z = 0.845) = 0.30 ± 0.08. Combined with BAO measurements including those from the eBOSS DR16 QSO and Lyman-α sample, our measurement has raised the significance level of a non-zero ΩΛ to ∼11σ. The data product of this work is publicly available at https://github.com/icosmology/eBOSS_DR16_LRGxELG and https://www.sdss.org/science/final-bao-and-rsd-measurements/.

scholarly journals Effects of Vector Maturation Time on the Dynamics of Cassava Mosaic Disease

2021 ◽  
Vol 83 (8) ◽  
Author(s):  
F. Al Basir ◽  
Y. N. Kyrychko ◽  
K. B. Blyuss ◽  
S. Ray
Keyword(s):  
Time Delay ◽  
Plant Density ◽  
Plant Viruses ◽  
Mosaic Disease ◽  
Plant Diseases ◽  
Cassava Mosaic Disease ◽  
Maturation Time ◽  
Negative Effect ◽  
Dynamical Regimes

AbstractMany plant diseases are caused by plant viruses that are often transmitted to plants by vectors. For instance, the cassava mosaic disease, which is spread by whiteflies, has a significant negative effect on plant growth and development. Since only mature whiteflies can contribute to the spread of the cassava mosaic virus, and the maturation time is non-negligible compared to whitefly lifetime, it is important to consider the effects this maturation time can have on the dynamics. In this paper, we propose a mathematical model for dynamics of cassava mosaic disease that includes immature and mature vectors and explicitly includes a time delay representing vector maturation time. A special feature of our plant epidemic model is that vector recruitment is negatively related to the delayed ratio between vector density and plant density. We identify conditions of biological feasibility and stability of different steady states in terms of system parameters and the time delay. Numerical stability analyses and simulations are performed to explore the role of various parameters, and to illustrate the behaviour of the model in different dynamical regimes. We show that the maturation delay may stabilise epidemiological dynamics that would otherwise be cyclic.

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