Amsalu Anagaw

Amsalu Anagaw
University of Alberta | UAlberta · Department of Physics

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10
Publications
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180
Citations

Publications

Publications (10)
Article
Full waveform inversion (FWI) is an efficient engine for estimating subsurface model parameters. FWI is often implemented via local optimization methods such as conjugate gradients or steepest descent. In this paper, we examine the effect of model parameterization on the estimation of velocity models obtained via Newton-based optimization FWI metho...
Article
Full-waveform inversion (FWI) can provide accurate estimates of subsurface model parameters. In spite of its success, the application of FWI in areas with high-velocity contrast remains a challenging problem. Quadratic regularization methods are often adopted to stabilize inverse problems. Unfortunately, edges and sharp discontinuities are not adeq...
Article
The computational cost of full-waveform inversion (FWI) is a major obstacle to estimating the velocity model for large-scale problems. One way to reduce the overall cost of waveform inversion is by adopting a simultaneous-source strategy. In other words, multiple sources are simultaneously fired to simulate supershot gathers and thereby reduce the...
Conference Paper
Full waveform inversion (FWI) based upon least-squares is commonly solved through local optimization methods utilizing conjugate gradients or steepest descent. However, gradient optimization methods are generally considered slower and can have difficulties scaling the reconstructed model parameters in comparison to methods that require second-order...
Conference Paper
In multiscale full-waveform inversion strategies, a finite set of discrete frequencies are selected and the inversion is carried out sequentially from low to high frequency data components. First, the long wavelength components of the model parameters are recovered from low frequency data, and then more details and features are extracted as the inv...
Article
Full-text available
Inverse problems are generally mathematically ill-posed and, therefore, regularization methods are required to obtain stable and unique solutions. The total variation (TV) regularization method is used to resolve sharp interfaces and obtain solutions where edges and discontinuities are preserved. TV regularization accomplishes these goals by imposi...
Conference Paper
Full waveform inverse problems based on the least-squares principle are generally ill-posed. Their solution is neither unique nor stable and hence they require regularization. The Total Variation (TV) regularization method is used to resolve sharp interfaces obtaining solutions whose edges and discontinuities are preserved and to address the stabil...
Article
Tuning of the electronic properties of semiconductors can be achieved by surface modification with organic molecules. In this work, we study, by periodic density functional theory, the change in work function that occurs upon the modification of nominally hydrogen-terminated Si(100)-2 × 1 by chemisorption of substituted styrene molecules. Our resul...
Article
Full-text available
Incorporating diversity into structures constructed from the organic modification of silicon surfaces requires the use of molecules that contain multiple substituents of different types. In this work we examine the possible dissociation pathways of diethylhydroxylamine (DEHA, (C(2)H(5))(2)NOH) on the surface of clean silicon(100)-2x1 using cluster...
Article
Full-text available
Waveform inverse problems are mathematically ill-posed and, therefore, regularization methods are required to obtain stable and unique solutions. The Total Variation (TV) regularization method is used to resolve sharp interfaces obtaining solutions where edges and discontinuities are preserved. TV regularization accomplishes these goals by imposing...

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