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We apply boundary integral equations for the first time to the two-dimensional scattering of time-harmonic waves from a smooth obstacle embedded in a continuously-graded unbounded medium. In the case we solve the square of the wavenumber…

Numerical Analysis · Mathematics 2016-05-04 Alex. H. Barnett , Bradley J. Nelson , J. Matthew Mahoney

The domain integral equation method with its FFT-based matrix-vector products is a viable alternative to local methods in free-space scattering problems. However, it often suffers from the extremely slow convergence of iterative methods,…

Numerical Analysis · Mathematics 2015-03-19 Grigorios P. Zouros , Neil V. Budko

Fractional spectral collocation (FSC) method based on fractional Lagrange interpolation has recently been proposed to solve fractional differential equations. Numerical experiments show that the linear systems in FSC become extremely…

Numerical Analysis · Mathematics 2015-10-21 Kui Du

Practical applications of microwave imaging often require the solution of inverse scattering problems with inhomogeneous backgrounds. Towards this end, a novel inversion strategy, which combines the multi-scaling (MS) regularization scheme…

Signal Processing · Electrical Eng. & Systems 2024-01-08 Yu Zhong , Francesco Zardi , Marco Salucci , Giacomo Oliveri , Andrea Massa

Helmholtz decompositions of the elastic fields open up new avenues for the solution of linear elastic scattering problems via boundary integral equations (BIE) [Dong, Lai, Li, Mathematics of Computation,2021]. The main appeal of this…

Numerical Analysis · Mathematics 2024-06-03 V. Dominguez , C. Turc

Surface integral equation (SIE) methods are of great interest for the numerical solution of Maxwell's equations in the presence of homogeneous objects. However, existing SIE algorithms have limitations, either in terms of scalability,…

Computational Physics · Physics 2021-06-14 Shashwat Sharma , Piero Triverio

We consider time-harmonic acoustic scattering by planar sound-soft (Dirichlet) and sound-hard (Neumann) screens embedded in $\mathbb{R}^n$ for $n = 2$ or $3$. In contrast to previous studies in which the screen is assumed to be a bounded…

Analysis of PDEs · Mathematics 2017-09-28 Simon N. Chandler-Wilde , David P. Hewett

Fourier Neural Operators (FNO) have emerged as promising solutions for efficiently solving partial differential equations (PDEs) by learning infinite-dimensional function mappings through frequency domain transformations. However, the…

Machine Learning · Computer Science 2025-05-22 Tianyu Chen , Haoyi Zhou , Ying Li , Hao Wang , Zhenzhe Zhang , Tianchen Zhu , Shanghang Zhang , Jianxin Li

This paper aims to develop and analyze a numerical scheme for solving the backward problem of semilinear subdiffusion equations. We establish the existence, uniqueness, and conditional stability of the solution to the inverse problem by…

Numerical Analysis · Mathematics 2025-05-07 Xu Wu , Jiang Yang , Zhi Zhou

We investigate integral formulations and fast algorithms for the steady-state radiative transfer equation with isotropic and anisotropic scattering. When the scattering term is a smooth convolution on the unit sphere, a model reduction step…

Numerical Analysis · Mathematics 2019-02-20 Yuwei Fan , Jing An , Lexing Ying

The scattering and transmission of harmonic acoustic waves at a penetrable material are commonly modelled by a set of Helmholtz equations. This system of partial differential equations can be rewritten into boundary integral equations…

Numerical Analysis · Mathematics 2022-04-19 Elwin van 't Wout , Seyyed R. Haqshenas , Pierre Gélat , Timo Betcke , Nader Saffari

In this work the Lippmann-Schwinger equation is used to model seismic waves in strongly scattering acoustic media. We consider the Helmholtz equation, which is the scalar wave equation in the frequency domain with constant density and…

Computational Physics · Physics 2021-02-24 Kjersti Solberg Eikrem , Geir Nævdal , Morten Jakobsen

The main goal of this article is to show a new method to solve some Fractional Order Integral Equations (FOIE), more precisely the ones which are linear, have constant coefficients and all the integration orders involved are rational. The…

Classical Analysis and ODEs · Mathematics 2018-02-09 Daniel Cao Labora , Rosana Rodríguez-López

Frequency domain Mie solutions to scattering from spheres have been used for a long time. However, deriving their transient analogue is a challenge as it involves an inverse Fourier transform of the spherical Hankel functions (and their…

Numerical Analysis · Mathematics 2016-10-26 Jie Li , Balasubramaniam Shanker

Generalized impedance boundary conditions are effective, approximate boundary conditions that describe scattering of waves in situations where the wave interaction with the material involves multiple scales. In particular, this includes…

Numerical Analysis · Mathematics 2020-05-29 Lehel Banjai , Christian Lubich , Joerg Nick

In this study, perturbation-iteration algorithm, namely PIA, is applied to solve some types of system of fractional differential equations (FDEs) for the first time. To illustrate the efficiency of the method, numerical solutions are…

Numerical Analysis · Mathematics 2016-07-29 Mehmet Senol , I. T. Dolapci

We present a Calder\'on preconditioning scheme for the symmetric formulation of the forward electroencephalographic (EEG) problem that cures both the dense discretization and the high-contrast breakdown. Unlike existing Calder\'on schemes…

Numerical Analysis · Mathematics 2023-08-16 Viviana Giunzioni , John E. Ortiz G. , Adrien Merlini , Simon B. Adrian , Francesco P. Andriulli

Purpose -- RF circuits often possess a multi-rate behavior. Slow changing baseband signals and fast oscillating carrier signals often occur in the same circuit. Frequency modulated signals pose a particular challenge.…

Numerical Analysis · Mathematics 2016-04-26 Kai Bittner , Hans Georg Brachtendorf

The opacity of FRTE depends on not only the material temperature but also the frequency, whose values may vary several orders of magnitude for different frequencies. The gray radiation diffusion and frequency-dependent diffusion equations…

Numerical Analysis · Mathematics 2023-08-16 Xiaojiang Zhang , Peng Song , Yi Shi , Min Tang

Three types of boundary integral equation (BIE) methods are employed to obtain closed-form solutions of a wave-scattering problem which are compared to the exact, closed-form (reference), solution deriving from the separation-of-variables…

Geophysics · Physics 2020-12-22 Armand Wirgin