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The purpose of this research is to describe an efficient iterative method suitable for obtaining high accuracy solutions to high frequency time-harmonic scattering problems. The method allows for both refinement of local polynomial degree…

Computational Physics · Physics 2018-12-26 Ryan Galagusz , Steve McFee

The radiative transfer equation models the interaction of radiation with scattering and absorbing media and has important applications in various fields in science and engineering. It is an integro-differential equation involving time,…

Numerical Analysis · Mathematics 2020-04-20 Min Zhang , Juan Cheng , Weizhang Huang , Jianxian Qiu

Multi-level non-local thermodynamic equilibrium (NLTE) radiation transfer calculations have become standard throughout the stellar atmospheres community and are applied to all types of stars as well as dynamical systems such as novae and…

Solar and Stellar Astrophysics · Physics 2014-07-02 Peter H. Hauschildt , E. Baron

The highly convergent iterative methods developed by Trujillo Bueno and Fabiani Bendicho (1995) for radiative transfer (RT) applications are generalized to spherical symmetry with velocity fields. These RT methods are based on Jacobi,…

Astrophysics · Physics 2007-05-23 A. Asensio Ramos , J. Trujillo Bueno , J. Cernicharo

In this paper, we propose and analyze an additive domain decomposition method (DDM) for solving the high-frequency Helmholtz equation with the Sommerfeld radiation condition. In the proposed method, the computational domain is partitioned…

Numerical Analysis · Mathematics 2020-03-06 Wei Leng , Lili Ju

This work presents efficient solution techniques for radiative transfer in the smoothed particle hydrodynamics discretization. Two choices that impact efficiency are how the material and radiation energy are coupled, which determines the…

Computational Physics · Physics 2021-03-17 Brody R. Bassett , J. Michael Owen , Thomas A. Brunner

The geometric high-order regularization methods such as mean curvature and Gaussian curvature, have been intensively studied during the last decades due to their abilities in preserving geometric properties including image edges, corners,…

Image and Video Processing · Electrical Eng. & Systems 2023-03-22 Zhenwei Zhang , Ke Chen , Ke Tang , Yuping Duan

This study concerns the fast and accurate solution of the line radiation transfer problem, under non-LTE conditions. We propose and evaluate an alternative iterative scheme to the classical ALI-Jacobi method, and to the more recently…

Instrumentation and Methods for Astrophysics · Physics 2015-05-13 F. Paletou , E. Anterrieu

Performing k-space variable density sampling is a popular way of reducing scanning time in Magnetic Resonance Imaging (MRI). Unfortunately, given a sampling trajectory, it is not clear how to traverse it using gradient waveforms. In this…

Optimization and Control · Mathematics 2015-02-25 Nicolas Chauffert , Pierre Weiss , Marianne Boucher , Sébastien Mériaux , Philippe CIUCIU

Direct volume rendering using ray-casting is widely used in practice. By using GPUs and applying acceleration techniques as empty space skipping, high frame rates are possible on modern hardware. This enables performance-critical use-cases…

Graphics · Computer Science 2025-01-09 Michael Rauter , Lukas Zimmermann , Markus Zeilinger

Accreting supermassive black holes are sources of polarized radiation that propagates through highly curved spacetime before reaching the observer. In order to help interpret observations of such polarized emission, accurate and efficient…

High Energy Astrophysical Phenomena · Physics 2020-10-20 Thomas Bronzwaer , Ziri Younsi , Jordy Davelaar , Heino Falcke

We present a general relativistic, ray-tracing radiative transfer code RAIKOU for multi-wavlength studies of spectra and images including the black hole shadows around Kerr black holes. Important radiative processes in hot plasmas around…

High Energy Astrophysical Phenomena · Physics 2023-06-28 Tomohisa Kawashima , Ken Ohsuga , Hiroyuki R. Takahashi

This paper is concerned with the numerical solution of porous-media flow and transport problems , i. e. heterogeneous, advection-diffusion problems. Its aim is to investigate numerical schemes for these problems in which different time…

Numerical Analysis · Mathematics 2016-05-20 Thi-Thao-Phuong Hoang , Caroline Japhet , Michel Kern , Jean E. Roberts

In radio astronomy obtaining a high dynamic range in synthesis imaging of wide fields requires a correction for time and direction-dependent effects. Applying direction-dependent correction can be done by either partitioning the image in…

Instrumentation and Methods for Astrophysics · Physics 2019-09-17 Sebastiaan van der Tol , Bram Veenboer , André R. Offringa

The stationary velocity field (SVF) approach allows to build parametrizations of invertible deformation fields, which is often a desirable property in image registration. Its expressiveness is particularly attractive when used as a block…

Computer Vision and Pattern Recognition · Computer Science 2024-10-16 Johannes Bostelmann , Ole Gildemeister , Jan Lellmann

Many astrophysical phenomena exhibit relativistic radiative flows. While velocities in excess of $v \sim 0.1c$ can occur in these systems, it has been common practice to approximate radiative transfer to $\cO(v/c)$. In the case of neutrino…

Astrophysics · Physics 2007-05-23 Christian Y. Cardall , Eric J. Lentz , Anthony Mezzacappa

A fast method is proposed for solving the high frequency Helmholtz equation. The building block of the new fast method is an overlapping source transfer domain decomposition method for layered medium, which is an extension of the source…

Numerical Analysis · Mathematics 2015-07-10 Wei Leng

In this work, we address the problem of multi-domain image-to-image translation with particular attention paid to computational cost. In particular, current state of the art models require a large and deep model in order to handle the…

Computer Vision and Pattern Recognition · Computer Science 2021-01-12 The-Phuc Nguyen , Stéphane Lathuilière , Elisa Ricci

Deep learning-based methods deliver state-of-the-art performance for solving inverse problems that arise in computational imaging. These methods can be broadly divided into two groups: (1) learn a network to map measurements to the signal…

Image and Video Processing · Electrical Eng. & Systems 2023-10-11 Nebiyou Yismaw , Ulugbek S. Kamilov , M. Salman Asif

Gaussian Processes are widely used for regression tasks. A known limitation in the application of Gaussian Processes to regression tasks is that the computation of the solution requires performing a matrix inversion. The solution also…

Machine Learning · Computer Science 2017-08-22 Sourish Das , Sasanka Roy , Rajiv Sambasivan
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