A high‐frequency approximation of sound propagation in a stratified moving atmosphere above a porous ground surface

1994 ◽  
Vol 95 (4) ◽  
pp. 1840-1852 ◽  
Author(s):  
Kai Ming Li
Keyword(s):  
High Frequency ◽  
Sound Propagation ◽  
Ground Surface ◽  
Frequency Approximation

scholarly journals Study Effect of Objects Orientation in the Mediums On GPR Signal Reflections Using FDTD Simulation

2018 ◽  
Vol 3 (11) ◽  
pp. 73-77
Author(s):  
Aye Mint Mohamed Mostapha ◽  
Gamil Alsharahi ◽  
Abdellah Driouach
Keyword(s):  
Finite Difference ◽  
Time Domain ◽  
Ground Penetrating Radar ◽  
High Frequency ◽  
Electromagnetic Waves ◽  
Ground Surface ◽  
Propagation Path ◽  
Fdtd Simulation ◽  
Ground Penetrating ◽  
Dielectric Objects

Ground penetrating radar (GPR) is a very effective tool for detecting and identifying objects below the ground surface.  based on  the propagation and reflection of high-frequency electromagnetic waves. The GPR reflection can be affected by many things like the type of objects orientation, their shapes ..ect. The purpose of this paper is to  study by simulation the effect of objects orientation in two different mediums (dry and wet sand) on the GPR signal reflection using Reflexw software which is based on a numerical method known as finite difference in time domain (FDTD).  The simulations that have been realized included a conductor  and dielectric objects. The results obtained have led us to find that the propagation path, the reflection strength and the signal form change with the change of object orientation and nature. To confirm the validity of the results, we compared them with experimental results previously published by researchers under the same conditions.

scholarly journals Acoustic Signatures of the Phases and Phase Transitions in the Blume Capel Model with Random Crystal Field

2018 ◽  
Vol 2018 ◽  
pp. 1-13
Author(s):  
Gul Gulpinar
Keyword(s):  
High Frequency ◽  
Sound Propagation ◽  
Ultrasonic Attenuation ◽  
Experimental Studies ◽  
Power Laws ◽  
Sound Attenuation ◽  
Irreversible Processes ◽  
Acoustic Signatures ◽  
Sound Dispersion ◽  
Good Agreement

Sound propagation in the Blume Capel model with quenched diluted single-ion anisotropy is investigated. The sound dispersion relation and an expression for the ultrasonic attenuation are derived with the aid of the method of thermodynamics of irreversible processes. A frequency-dependent dispersion minimum that is shifted to lower temperatures with rising frequency is observed in the ordered region. The thermal and sound frequency (ω) dependencies of the sound attenuation and effect of the Onsager rate coefficient are studied in low- and high-frequency regimes. The results showed that ωτ≪1 and ωτ≫1 are the conditions that describe low- and high-frequency regimes, where τ is the single relaxation time diverging in the vicinity of the critical temperature. In addition, assuming a linear coupling of sound wave with the order parameter fluctuations in the system and ε as the temperature distance from the critical point, we found that the sound attenuation follows the power laws α(ω,ε)~ω2ε-1 and α(ω,ε)~ω0ε1 in the low- and high-frequency regions, while ε→0. Finally, a comparison of the findings of this study with previous theoretical and experimental studies is presented and it is shown that a good agreement is found with our results.

High-frequency approximation for cone-tip backscattering at arbitrary aspects from bodies of revolution

1999 ◽  
Vol 35 (3) ◽  
pp. 1514-1517 ◽  
Author(s):  
M. Martinez-Burdalo ◽  
A. Martin ◽  
R. Villar ◽  
L. Landesa
Keyword(s):  
High Frequency ◽  
Bodies Of Revolution ◽  
Frequency Approximation

High-frequency sound waves in ideal gases with internal dissipation

1968 ◽  
Vol 34 (4) ◽  
pp. 769-782 ◽  
Author(s):  
J. Dunwoody
Keyword(s):  
Asymptotic Analysis ◽  
Vibrational Relaxation ◽  
High Frequency ◽  
Sound Waves ◽  
High Frequency Sound ◽  
Frequency Sound ◽  
Ideal Gases ◽  
Internal Dissipation ◽  
Plane Sound ◽  
Frequency Approximation

High-frequency plane sound waves in ideal gases with internal dissipation are discussed. Particular applications to dissociating diatomic gases and gases displaying vibrational relaxation are considered. A criterion in the form of an inequality is derived for the validity of the high-frequency approximation and an asymptotic analysis is developed.

Stereoscopic Images Enhancement Based on Edge Sharpening of Wavelet Coefficients

2014 ◽  
Vol 511-512 ◽  
pp. 490-494 ◽  
Author(s):  
Yi Min Qiu ◽  
Shi Hong Chen ◽  
Yi Zhou ◽  
Xin Hai Liu
Keyword(s):  
Wavelet Transform ◽  
High Frequency ◽  
Low Frequency ◽  
Subjective Assessment ◽  
Wavelet Coefficients ◽  
Stereoscopic Images ◽  
Multi Scale ◽  
Image Edge ◽  
Frequency Approximation ◽  
Edge Sharpening

This paper proposed a new image enhancement algorithm based on edge sharpening of wavelet coefficients for stereoscopic images. Our scheme uses the multi-scale characteristic of wavelet transform, decomposes the original image into low frequency approximation sub-graph and several high frequency direction. Under the multi-scale, the low frequency approximation sub-graph is processed by edge sharpening method. Then the low frequency sub-graph decomposes in multi-scale again. At last, the low frequency approximation graph after four layers decompose sharpening and the high frequency approximation of the decomposed sub-graph will be refactored to get the new image. Experimental results show that whether PSNR or visual effect, or the subjective assessment of the DMOS value, the proposed method has better enhanced performance than the conventional edge sharpening and wavelet transform. And it has good image edge enhancement, details protection. Meanwhile, the proposed algorithm has the same computational complexity with wavelet transform.

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