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We present a simple discretization by radial basis functions for the Poisson equation with Dirichlet boundary condition. A Lagrangian multiplier using piecewise polynomials is used to accommodate the boundary condition. This simplifies…

Numerical Analysis · Mathematics 2013-02-11 Norbert Heuer , Thanh Tran

Nuclear Magnetic Resonance (NMR) is one of the main experimental tools to evaluate the production potential of porous rocks in oil wells. From the relative areas and mean values obtained from relaxation time distribution curves, information…

Applied Physics · Physics 2021-05-25 Ivan S. Oliveira

We describe a technique to analytically compute the multipole moments of a charge distribution confined to a planar triangle, which may be useful in solving the Laplace equation using the fast multipole boundary element method (FMBEM) and…

Computational Physics · Physics 2015-06-22 John P. Barrett , Joseph A. Formaggio , Thomas J. Corona

The purpose of this paper consists in proposing a generalized solution for a porous media type equation on a half-line with Neumann boundary condition and prove a probabilistic representation of this solution in terms of an associated…

Probability · Mathematics 2013-04-16 Ioana Ciotir , Francesco Russo

We present a simple simulation model for analysing magnetic and frictional losses of magnetic nano-particles in viscous fluids subject to alternating magnetic fields. Assuming a particle size below the single-domain limit, we use a…

Atomic and Molecular Clusters · Physics 2023-03-01 Santiago Helbig , Claas Abert , Pedro A. Sánchez , Sofia S. Kantorovich , Dieter Suess

We study the discretization, convergence, and numerical implementation of recent reformulations of the quadratic porous medium equation (multidimensional and anisotropic) and Burgers' equation (one-dimensional, with optional viscosity), as…

Numerical Analysis · Mathematics 2025-11-06 Jean-Marie Mirebeau , Erwan Stampfli

A new method of solution to the local spin density approximation to the electronic Schr\"{o}dinger equation is presented. The method is based on an efficient, parallel, adaptive multigrid eigenvalue solver. It is shown that adaptivity is…

mtrl-th · Physics 2009-09-25 E. Bylaska , S. Khon , S. Baden , A. Edelman , R. Kawai , M. E. G. Ong , J. H. Weare

In this paper we propose and analyse a new formulation and pointwise divergence-free mixed finite element methods for the numerical approximation of Darcy--Brinkman equations in vorticity--velocity--pressure form, coupled with a transport…

Numerical Analysis · Mathematics 2024-07-04 Russel Demos , Rashmi Dubey , Ricardo Ruiz-Baier , Segundo Villa-Fuentes

Rough surface scattering problems are always very challenging both theoretically and numerically. In this paper, we adopt the Bloch transform and the perturbation theory to investigate a special case, i.e., when the rough surface is a…

Analysis of PDEs · Mathematics 2018-12-04 Ruming Zhang

We study the fluid flow through disordered porous media by numerically solving the complete set of the Navier-Stokes equations in a two dimensional lattice with a spatially random distribution of solid obstacles (plaquettes). We simulate…

Disordered Systems and Neural Networks · Physics 2015-06-25 U. M. S. Costa , J. S. Andrade , H. A. Makse , H. E. Stanley

We consider the scattering problem on locally perturbed periodic penetrable dielectric layers, which is formulated in terms of the full vector-valued time-harmonic Maxwell's equations. The right-hand side is not assumed to be periodic. At…

Analysis of PDEs · Mathematics 2019-08-23 Alexander Konschin

We study the influence of diffusion on NMR experiments when the molecules undergo random motion under the influence of a force field, and place special emphasis on parabolic (Hookean) potentials. To this end, the problem is studied using…

Medical Physics · Physics 2016-05-11 Cem Yolcu , Muhammet Memiç , Kadir Şimşek , Carl-Fredrik Westin , Evren Özarslan

In this paper, we consider several possible ways to set up Heterogeneous Multiscale Methods for the Landau-Lifshitz equation with a highly oscillatory diffusion coefficient, which can be seen as a means to modeling rapidly varying…

Numerical Analysis · Mathematics 2021-04-08 Lena Leitenmaier , Olof Runborg

In this paper, we establish the large deviation principles for stochastic porous media equations driven by time-dependent multiplicative noise on $\sigma$-finite measure space $(E,\mathcal{B}(E),\mu)$, and the Laplacian replaced by a…

Probability · Mathematics 2023-04-06 Weina Wu , Jianliang Zhai

We study the properties of an approximation of the Laplace operator with Neumann boundary conditions using volume penalization. For the one-dimensional Poisson equation we compute explicitly the exact solution of the penalized equation and…

Numerical Analysis · Mathematics 2014-03-27 Dmitry Kolomenskiy , Romain Nguyen van yen , Kai Schneider

Nuclear magnetic resonance (NMR) concepts are rooted in quantum mechanics, but MR imaging principles are well described and more easily grasped using classical ideas and formalisms such as Larmor precession and the phenomenological Bloch…

Medical Physics · Physics 2020-09-08 ML Lauzon

We apply the method of slowly-varying amplitudes of the electrical and magnet fields to integro-differential system of nonlinear Maxwell equations. The equations are reduced to system of differential Nonlinear Maxwell amplitude Equations…

Pattern Formation and Solitons · Physics 2007-05-23 Lubomir M. Kovachev

The method of self-consistent expansions is a powerful tool for handling strong coupling problems that might otherwise be beyond the reach of perturbation theory, providing surprisingly accurate approximations even at low order. First…

Statistical Mechanics · Physics 2025-01-15 Minhui Zhu , Nigel Goldenfeld

Efficient numerical methods are required for the design of optimised devices. In magnonics, the primary computational tool is micromagnetic simulations, which solve the Landau-Lifshitz equation discretised in time and space. However, their…

Mesoscale and Nanoscale Physics · Physics 2023-07-26 Wojciech Śmigaj , Krzysztof Sobucki , Paweł Gruszecki , Maciej Krawczyk

We propose a three-dimensional micromagnetic model that dynamically solves the Landau-Lifshitz-Gilbert equation coupled to the full spin-diffusion equation. In contrast to previous methods, we solve for the magnetization dynamics and the…