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We present the results of a series of calculations studying the collapse of molecular cloud cores performed using a three-dimensional smoothed particle hydr odynamics code with radiative transfer in the flux-limited diffusion approximation.…

Astrophysics · Physics 2009-11-13 Stuart C. Whitehouse , Matthew R. Bate

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

In an ultrasonic array system, increasing the aperture size to achieve a high resolution requires more transmit and receive channels, thus making it essential to have an analysis technique that can reconstruct the shape and physical…

Optics · Physics 2025-08-21 Kai Yabumoto , Takayoshi Yumii , Kenjiro Kimura

The problem of radio wave reflection from an optically thick plane monotonous layer of magnetized plasma is considered at present work. The plasma electron density irregularities are described by spatial spectrum of an arbitrary form. The…

Plasma Physics · Physics 2009-10-31 N. A. Zabotin , A. G. Bronin , G. A. Zhbankov

We provide the construction of a set of square matrices whose translates and rotates provide a Parseval frame that is optimal for approximating a given dataset of images. Our approach is based on abstract harmonic analysis techniques.…

Image and Video Processing · Electrical Eng. & Systems 2019-09-05 Davide Barbieri , Carlos Cabrelli , Eugenio Hernández , Ursula Molter

A new numerical method to solve an inverse source problem for the radiative transfer equation involving the absorption and scattering terms, with incomplete data, is proposed. No restrictive assumption on those absorption and scattering…

Numerical Analysis · Mathematics 2019-04-02 Alexey V. Smirnov , Michael V. Klibanov , Loc H. Nguyen

This paper presents an efficient parallel radiative transfer-based inverse-problem solver for time-domain optical tomography. The radiative transfer equation provides a physically accurate model for the transport of photons in biological…

Medical Physics · Physics 2022-08-31 E. L. Gaggioli , O. P. Bruno

This paper addresses the problem of synchronizing orthogonal matrices over directed graphs. For synchronized transformations (or matrices), composite transformations over loops equal the identity. We formulate the synchronization problem as…

Optimization and Control · Mathematics 2017-04-10 Johan Thunberg , Florian Bernard , Jorge Goncalves

Understanding the orientation of geological structures is crucial for analyzing the complexity of the Earths' subsurface. For instance, information about geological structure orientation can be incorporated into local anisotropic…

Geophysics · Physics 2024-09-10 Ali Gholami , Silvia Gazzola

Large-scale simulations of the wave equation in electromagnetism, seismology, and acoustics, can be solved efficiently by finite difference methods. The accuracy of these numerical solutions usually depends on the minimization of…

Medical Physics · Physics 2021-06-23 Gianmarco Pinton

New exact solutions of the steady and incompressible 2D MHD equations in polar coordinates are presented. The solutions describe the process of reconnective magnetic annihilation in a curved current layer. They are particularly interesting…

Plasma Physics · Physics 2009-11-07 E. Tassi , V. S. Titov , G. Hornig

We present angular-resolved correlation measurements between photons after propagation through a three-dimensional disordered medium. The multiple scattering process induces photon correlations that are directly measured for light sources…

Optics · Physics 2011-06-30 Stephan Smolka , Otto L. Muskens , Ad Lagendijk , Peter Lodahl

Context: Radio astronomical receivers are now expanding their frequency range to cover large (octave) fractional bandwidths for sensitivity and spectral flexibility, which makes the design of good analogue circular polarizers challenging.…

Instrumentation and Methods for Astrophysics · Physics 2015-05-27 Koyel Das , A. L. Roy , R. Keller , G. Tuccari

We consider the numerical approximation of the radiative transfer equation using discontinuous angular and continuous spatial approximations for the even parts of the solution. The even-parity equations are solved using a diffusion…

Numerical Analysis · Mathematics 2019-09-19 Olena Palii , Matthias Schlottbom

Matching problems on 3D shapes and images are challenging as they are frequently formulated as combinatorial quadratic assignment problems (QAPs) with permutation matrix constraints, which are NP-hard. In this work, we address such problems…

Computer Vision and Pattern Recognition · Computer Science 2021-07-09 Marcel Seelbach Benkner , Vladislav Golyanik , Christian Theobalt , Michael Moeller

We study the spectral approximation of a second-order elliptic differential eigenvalue problem that arises from structural vibration problems using isogeometric analysis. In this paper, we generalize recent work in this direction. We…

Numerical Analysis · Mathematics 2018-02-05 Quanling Deng , Vladimir Puzyrev , Victor Calo

We derive a nonlinear moment model for radiative transfer equation in 3D space, using the method to derive the nonlinear moment model for the radiative transfer equation in slab geometry. The resulted 3D HMPN model enjoys a list of…

Computational Physics · Physics 2020-05-28 Ruo Li , Peng Song , Lingchao Zheng

Fundamental antenna limits of the gain-bandwidth product are derived from polarizability calculations. This electrostatic technique has significant value in many antenna evaluations. Polarizability is not available in closed form for most…

Optics · Physics 2014-02-18 Morteza Shahpari , David V. Thiel , Andrew Lewis

Context. Three-dimensional non-local thermodynamical equilibrium (NLTE) radiative transfer calculations are a fundamental tool for a detailed spectral analysis in stellar atmospheres, but require vast amounts of computer power. This…

Solar and Stellar Astrophysics · Physics 2023-07-12 Elias R. Udnæs , Tiago M. D. Pereira

In many time-harmonic electromagnetic wave problems, the considered geometry exhibits an axial symmetry. In this case, by exploiting a Fourier expansion along the azimuthal direction, fully three-dimensional (3D) calculations can be carried…

Numerical Analysis · Mathematics 2022-11-22 Erik Schnaubelt , Nicolas Marsic , Herbert De Gersem