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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

The symmetric formulation of the electroencephalography (EEG) forward problem is a well-known and widespread equation thanks to the high level of accuracy that it delivers. However, this equation is first kind in nature and gives rise to…

Medical Physics · Physics 2019-03-21 John E. Ortiz G. , Axelle Pillain , Lyes Rahmouni , Francesco P. Andriulli

We present a Calder\'on preconditioner for the electric field integral equation (EFIE), which does not require a barycentric refinement of the mesh and which yields a Hermitian, positive definite (HPD) system matrix allowing for the usage…

Numerical Analysis · Mathematics 2018-11-07 Simon B. Adrian , Francesco P. Andriulli , Thomas F. Eibert

The Electric Field Integral Equation (EFIE) is notorious for its ill-conditioning both in frequency and h-refinement. Several techniques exist for fixing the equation conditioning problems based on hierarchical strategies, Calderon…

Numerical Analysis · Mathematics 2020-04-28 Lyes Rahmouni , Francesco P. Andriulli

Fast and accurate resolution of electromagnetic problems via the \ac{BEM} is oftentimes challenged by conditioning issues occurring in three distinct regimes: (i) when the frequency decreases and the discretization density remains constant,…

Computational Physics · Physics 2020-04-22 Alexandre Dély , Adrien Merlini , Simon B. Adrian , Francesco P. Andriulli

In this paper we present a new discretization strategy for the boundary element formulation of the Electroencephalography (EEG) forward problem. Boundary integral formulations, classically solved with the Boundary Element Method (BEM), are…

Medical Physics · Physics 2016-03-22 Lyes Rahmouni , Simon Adrian , Kristof Cools , Francesco P. Andriulli

While doing electromagnetic analysis using FEM (Finite element method), if we can implement the underlying symmetric nature of the problem, there will be significant reduction in the computational cost. Symmetric nature of the problem can…

Signal Processing · Electrical Eng. & Systems 2023-03-22 Durgarao Kamireddy , Sreekanth Karanam , Arup Nandy

We propose an unconditionally robust and highly effective preconditioner for general symmetric positive definite (SPD) matrices based on structured incomplete factorization (SIF), called enhanced SIF (eSIF) preconditioner. The original SIF…

Numerical Analysis · Mathematics 2020-07-09 Jianlin Xia

In this paper, we design preconditioners for the matrix-free solution of high-order continuous and discontinuous Galerkin discretizations of elliptic problems based on FEM-SEM equivalence and additive Schwarz methods. The high-order…

Numerical Analysis · Mathematics 2021-03-11 Will Pazner

This paper aims to address two issues of integral equations for the scattering of time-harmonic electromagnetic waves by a perfect electric conductor with Lipschitz continuous boundary: ill-conditioned {boundary element Galerkin matrices}…

Numerical Analysis · Mathematics 2024-10-29 Van Chien Le , Kristof Cools

The relaxed physical factorization (RPF) preconditioner is a recent algorithm allowing for the efficient and robust solution to the block linear systems arising from the three-field displacement-velocity-pressure formulation of coupled…

Numerical Analysis · Mathematics 2021-08-10 Matteo Frigo , Nicola Castelletto , Massimiliano Ferronato

The eXtended Finite Element Method (XFEM) is an approach for solving problems with non-smooth solutions. In the XFEM, the approximate solution is locally enriched to capture discontinuities without requiring a mesh which conforms to the…

Numerical Analysis · Mathematics 2013-12-23 Christapher Lang , David Makhija , Alireza Doostan , Kurt Maute

The CFIE used for solving scattering and radiation problems, although a resonance-free formulation, suffers from an ill-conditioning that strongly depends on the frequency and discretization density, both in the low- and high-frequency…

Computational Physics · Physics 2020-04-22 Tiffany L. Chhim , Simon B. Adrian , Francesco P. Andriulli

We propose a matrix-free solver for the numerical solution of the cardiac electrophysiology model consisting of the monodomain nonlinear reaction-diffusion equation coupled with a system of ordinary differential equations for the ionic…

Numerical Analysis · Mathematics 2023-03-01 Pasquale Claudio Africa , Matteo Salvador , Paola Gervasio , Luca Dede' , Alfio Quarteroni

This paper extends the concept of Laplacian filtered quasi-Helmholtz decompositions we have recently introduced, to the basis-free projector-based setting. This extension allows the discrete analyses of electromagnetic integral operators…

Image and Video Processing · Electrical Eng. & Systems 2022-03-17 Adrien Merlini , Clément Henry , Davide Consoli , Lyes Rahmouni , Francesco P. Andriulli

We present a robust and scalable preconditioner for the solution of large-scale linear systems that arise from the discretization of elliptic PDEs amenable to rank compression. The preconditioner is based on hierarchical low-rank…

Numerical Analysis · Mathematics 2017-12-27 Gustavo Chávez , George Turkiyyah , Stefano Zampini , David Keyes

A new domain decomposition preconditioner is introduced for efficiently solving linear systems Ax = b with a symmetric positive definite matrix A. The particularity of the new preconditioner is that it is not necessary to have access to the…

Numerical Analysis · Mathematics 2021-06-23 Nicole Spillane

We explore a scaled spectral preconditioner for the efficient solution of sequences of symmetric and positive-definite linear systems. We design the scaled preconditioner not only as an approximation of the inverse of the linear system but…

Numerical Analysis · Mathematics 2024-10-04 Youssef Diouane , Selime Gürol , Oussama Mouhtal , Dominique Orban

This work presents a fast direct solver strategy for electromagnetic integral equations in the high-frequency regime. The new scheme relies on a suitably preconditioned combined field formulation and results in a single skeleton form plus…

We introduce a new general purpose multiresolution preconditioner for symmetric linear systems. Most existing multiresolution preconditioners use some standard wavelet basis that relies on knowledge of the geometry of the underlying domain.…

Numerical Analysis · Mathematics 2017-07-10 Pramod Kaushik Mudrakarta , Risi Kondor
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