Uniform high frequency approximation to scattering from infinite strip

1997 ◽  
Vol 38 (5) ◽  
pp. 2308-2331 ◽  
Author(s):  
J. Goldberg ◽  
Thomas Berger ◽  
Roger Dashen
Keyword(s):  
High Frequency ◽  
Infinite Strip ◽  
Frequency Approximation

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.

scholarly journals Opal: An open source ray-tracing propagation simulator for electromagnetic characterization

PLoS ONE ◽  
2021 ◽  
Vol 16 (11) ◽  
pp. e0260060
Author(s):  
Esteban Egea-Lopez ◽  
Jose Maria Molina-Garcia-Pardo ◽  
Martine Lienard ◽  
Pierre Degauque
Keyword(s):  
Ray Tracing ◽  
High Frequency ◽  
Maxwell Equations ◽  
Simulation Tool ◽  
Game Engine ◽  
Electromagnetic Propagation ◽  
Graphical Processing Units ◽  
3D Environments ◽  
Graphical Processing ◽  
Frequency Approximation

Accurate characterization and simulation of electromagnetic propagation can be obtained by ray-tracing methods, which are based on a high frequency approximation to the Maxwell equations and describe the propagating field as a set of propagating rays, reflecting, diffracting and scattering over environment elements. However, this approach has been usually too computationally costly to be used in large and dynamic scenarios, but this situation is changing thanks the increasing availability of efficient ray-tracing libraries for graphical processing units. In this paper we present Opal, an electromagnetic propagation simulation tool implemented with ray-tracing on graphical processing units, which is part of the Veneris framework. Opal can be used as a stand-alone ray-tracing simulator, but its main strength lies in its integration with the game engine, which allows to generate customized 3D environments quickly and intuitively. We describe its most relevant features and provide implementation details, highlighting the different simulation types it supports and its extension possibilites. We provide application examples and validate the simulation on demanding scenarios, such as tunnels, where we compare the results with theoretical solutions and further discuss the tradeoffs between the simulation types and its performance.

Improved applicability of ray tracing in seismic acquisition, imaging, and interpretation

Geophysics ◽  
2007 ◽  
Vol 72 (5) ◽  
pp. SM261-SM271 ◽  
Author(s):  
Håvar Gjøystdal ◽  
Einar Iversen ◽  
Isabelle Lecomte ◽  
Tina Kaschwich ◽  
Åsmund Drottning ◽  
...  
Keyword(s):  
Ray Tracing ◽  
High Frequency ◽  
Numerical Solutions ◽  
Ray Method ◽  
Rapid Changes ◽  
Exploration And Production ◽  
Seismic Acquisition ◽  
Elementary Waves ◽  
Process Elements ◽  
Frequency Approximation

Ray-based seismic modeling methods can be applied at various stages of the exploration and production process. The standard ray method has several advantages, e.g., computational efficiency and the possibility of simulating propagation of elementary waves. As a high-frequency approximation, the method also has a number of limitations, particularly with respect to a lack of amplitude reliability in the presence of rapid changes of the model functions representing elastic parameters and interfaces. Given the objective of improving the applicability of the standard ray method, we present a strategy that does not require specific extension to finite frequencies. Instead, we define each ray-based process as an element of a system that, as a composite process, is able to obtain better results than the ray-based process applied alone. Other elements of the composite process can be finite-difference modeling or numerical solutions for surface and volume integrals, which are basic constituents of Kirchhoff modeling and imaging. We also include among the process elements recently developed techniques for simulating the migration amplitude on a target reflector and in a local volume, e.g., a reservoir zone. The model is decomposed according to its complexity into volume elements, surface elements, or a combination. The composite process consists of a specified interaction between process elements and model elements, which fits well with the philosophy of modern software design. Model elements that will be exposed to ray-tracing algorithms may need appropriate preparation, e.g., smoothing and resampling. We demonstrate specifically, in a tutorial example, that simulating the seismic response from a reflector by ray-based composite processes can yield better results than applying standard ray tracing alone.

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