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We study a fully discrete finite element method for variable-order time-fractional diffusion equations with a time-dependent variable order. Optimal convergence estimates are proved with the first-order accuracy in time (and second order…

Numerical Analysis · Mathematics 2019-05-15 Xiangcheng Zheng , Fanhai Zeng , Hong Wang

Kinetic transport equations are notoriously difficult to simulate because of their complex multiscale behaviors and the need to numerically resolve a high dimensional probability density function. Past literature has focused on building…

Numerical Analysis · Mathematics 2022-11-10 Zhichao Peng , Yanlai Chen , Yingda Cheng , Fengyan Li

We present a novel approach that redefines the traditional interpretation of explicit and implicit discretization methods for solving a general class of advection-diffusion equations (ADEs) featuring nonlinear advection, diffusion…

Analysis of PDEs · Mathematics 2025-06-10 Amin Jafarimoghaddam , Manuel Soler , Irene Ortiz

The study of the continuum radiative transfer problem inside circumstellar envelopes is both a theoretical and numerical challenge, especially in the frequency-dependent and multi-dimensional case. While approximate methods are easier to…

Solar and Stellar Astrophysics · Physics 2024-10-14 J. Perdigon , M. Faurobert , G. Niccolini

In the article, new asymptotic approximation of the $n$th order is obtained and proposed to be used in calculations of radiation propagation without scattering in optically thick media; the asymptotic approximation is much simpler and more…

Instrumentation and Methods for Astrophysics · Physics 2020-12-23 S. A. Serov , S. S. Serova

A radiative transfer scheme is presented, based on a moment description of the equation of radiative transfer and the so-called ``M1 closure model'' for the Eddington tensor. This model features a strictly hyperbolic transport step for…

Astrophysics · Physics 2009-11-13 Dominique Aubert , Romain Teyssier

The interpretation of numerical methods, such as finite difference methods for differential equations, as point estimators allows for formal statistical quantification of the error due to discretisation in the numerical context. Competing…

Methodology · Statistics 2018-05-23 Junyang Wang , Jon Cockayne , Chris Oates

As more and more numerical and analytical solutions to the linear neutron transport equation become available, verification of numerical results is increasingly important. This presentation concerns the development of another benchmark for…

Computational Physics · Physics 2024-06-21 Barry Ganapol

The recent implementation of radiative transfer algorithms in numerous hydrodynamics codes has led to a dramatic improvement in studies of feedback in various astrophysical environments. However, because of methodological limitations and…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-04 Jordan Mirocha , Stephen Skory , Jack O. Burns , John H. Wise

In this work, following the discrete de Rham (DDR) approach, we develop a discrete counterpart of a two-dimensional de Rham complex with enhanced regularity. The proposed construction supports general polygonal meshes and arbitrary…

Numerical Analysis · Mathematics 2022-10-28 Daniele A. Di Pietro

The forward model in diffuse optical tomography (DOT) describes how light propagates through a turbid medium. It is often approximated by a diffusion equation (DE) that is numerically discretized by the classical finite element method…

Computational Physics · Physics 2019-06-04 Wenqi Lu , Jinming Duan , Joshua Deepak Veesa , Iain B. Styles

We simulate convection near the solar surface, where the continuum optical depth is of order unity. Hence, to determine the radiative heating and cooling in the energy conservation equation, we must solve the radiative transfer equation…

Astrophysics · Physics 2007-05-23 Robert Stein , Aake Nordlund

We focus on coherent direction of arrival estimation of wideband sources based on spatial sparsity. This area of research is encountered in many applications such as passive radar, sonar, mining, and communication problems, in which an…

Signal Processing · Electrical Eng. & Systems 2024-01-18 Milad Javadzadeh Jirhandeh , Mohammad Hossein Kahaei

In the fields of statistics, machine learning, image science, and related areas, there is an increasing demand for decentralized collection or storage of large-scale datasets, as well as distributed solution methods. To tackle this…

Optimization and Control · Mathematics 2024-01-17 Bowen Li , Bin Shi

In this work, we are concerned with the diffusive optical tomography (DOT) problem in the case when only one or two pairs of Cauchy data is available. We propose a simple and efficient direct sampling method (DSM) to locate inhomogeneities…

Mathematical Physics · Physics 2014-10-07 Yat Tin Chow , Kazufumi Ito , Keji Liu , Jun Zou

A new method for solving non-autonomous ordinary differential equations is proposed, the method achieves spectral accuracy. It is based on a new result which expresses the solution of such ODEs as an element in the so called…

Numerical Analysis · Mathematics 2022-10-03 Stefano Pozza , Niel Van Buggenhout

Aims. The main goal of this paper is to present an accurate and efficient numerical strategy for solving the radiative transfer problem for polarised radiation in strong resonance lines forming out of local thermodynamic equilibrium, taking…

The construction of exact solutions for radiative transfer in a plane-parallel medium has been addressed by Hemsch and Ferziger in 1972 for a partial frequency redistribution model of the formation of spectral lines consisting in a linear…

Solar and Stellar Astrophysics · Physics 2024-10-31 Hélène Frisch

An explicit numerical scheme is proposed for solving the initial-boundary value problem for the radiative transport equation in a rectangular domain with completely absorbing boundary condition. An upwind finite difference approximation is…

Numerical Analysis · Mathematics 2013-03-27 Nobuyuki Higashimori , Hiroshi Fujiwara

We consider the classical integral equation reformulation of the radiative transport equation (RTE) in a heterogeneous medium, assuming isotropic scattering. We prove an estimate for the norm of the integral operator in this formulation…

Numerical Analysis · Mathematics 2019-03-21 J. C. H. Blake , I. G. Graham , F. Scheben , A. Spence
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