Efficient computation of the time-domain scattering from bodies of revolution

2002 ◽  
Author(s):  
A. Wang ◽  
A. Prata ◽  
W.V.T. Rusch
Keyword(s):  
Time Domain ◽  
Efficient Computation ◽  
Bodies Of Revolution ◽  
Time Domain Scattering ◽  
The Time Domain

An efficient multiscale method for time-domain waveform tomography

Geophysics ◽  
2009 ◽  
Vol 74 (6) ◽  
pp. WCC59-WCC68 ◽  
Author(s):  
Chaiwoot Boonyasiriwat ◽  
Paul Valasek ◽  
Partha Routh ◽  
Weiping Cao ◽  
Gerard T. Schuster ◽  
...  
Keyword(s):  
Time Domain ◽  
Multiscale Method ◽  
Staggered Grid ◽  
Multiscale Approach ◽  
Efficient Computation ◽  
Computationally Efficient ◽  
Order Accuracy ◽  
Velocity Models ◽  
Waveform Tomography ◽  
The Time Domain

This efficient multiscale method for time-domain waveform tomography incorporates filters that are more efficient than Hamming-window filters. A strategy for choosing optimal frequency bands is proposed to achieve computational efficiency in the time domain. A staggered-grid, explicit finite-difference method with fourth-order accuracy in space and second-order accuracy in time is used for forward modeling and the adjoint calculation. The adjoint method is utilized in inverting for an efficient computation of the gradient directions. In the multiscale approach, multifrequency data and multiple grid sizes are used to overcome somewhat the severe local minima problem of waveform tomography. The method is applied successfully to 1D and 2D heterogeneous models; it can accurately recover low- and high-wavenumber components of the velocity models. The inversion result for the 2D model demonstrates that the multiscale method is computationally efficient and converges faster than a conventional, single-scale method.

scholarly journals Three-dimensional time-domain scattering of waves in the marginal ice zone

2018 ◽  
Vol 376 (2129) ◽  
pp. 20170334 ◽  
Author(s):  
M. H. Meylan ◽  
L. G. Bennetts
Keyword(s):  
Time Domain ◽  
Fourier Transforms ◽  
Three Dimensional ◽  
Step Method ◽  
Ocean Surface Waves ◽  
Marginal Ice Zone ◽  
Time Domain Scattering ◽  
Universal Structure ◽  
The Time Domain ◽  
Scattering Kernel

Three-dimensional scattering of ocean surface waves in the marginal ice zone (MIZ) is determined in the time domain. The solution is found using spectral analysis of the linear operator for the Boltzmann equation. The method to calculate the scattering kernel that arises in the Boltzmann model from the single-floe solution is also presented along with new identities for the far-field scattering, which can be used to validate the single-floe solution. The spectrum of the operator is computed, and it is shown to have a universal structure under a special non-dimensionalization. This universal structure implies that under a scaling wave scattering in the MIZ has similar properties for a large range of ice types and wave periods. A scattering theory solution using fast Fourier transforms is given to find the solution for directional incident wave packets. A numerical solution method is also given using the split-step method and this is used to validate the spectral solution. Numerical calculations of the evolution of a typical wave field are presented. This article is part of the theme issue ‘Modelling of sea-ice phenomena’.

Apodisation in the time domain

1992 ◽  
Vol 2 (4) ◽  
pp. 615-620
Author(s):  
G. W. Series
Keyword(s):  
Time Domain ◽  
The Time Domain
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