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We introduce and test a new and highly efficient method for treating the thermal and radiative effects influencing the energy equation in SPH simulations of star formation. The method uses the density, temperature and gravitational…

Astrophysics · Physics 2009-11-13 D. Stamatellos , A. P. Whitworth , T. Bisbas , S. Goodwin

We present a theory of linear optical constants based on a single-particle density matrix and implemented in an extension of the real-space multiple scattering code FEFF. This approach avoids the need to compute wave-functions explicitly,…

Materials Science · Physics 2015-05-13 M. P. Prange , J. J. Rehr , G. Rivas , J. J. Kas , John W. Lawson

Context: Radiative feedback plays a crucial role in the formation of massive stars. The implementation of a fast and accurate description of the proceeding thermodynamics in pre-stellar cores and evolving accretion disks is therefore a main…

Solar and Stellar Astrophysics · Physics 2015-03-13 Rolf Kuiper , Hubert Klahr , Cornelis Dullemond , Wilhelm Kley , Thomas Henning

We present a numerical implementation of radiative transfer based on an explicitly photon-conserving advection scheme, where radiative fluxes over the cell interfaces of a structured or unstructured mesh are calculated with a second-order…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-20 Margarita Petkova , Volker Springel

Radiative transfer modeling of spectral lines including partial redistribution (PRD) effects requires the evaluation of the ratio of the emission to the absorption profile. This quantity requires a large amount of computational work if one…

Solar and Stellar Astrophysics · Physics 2015-06-05 Jorrit Leenaarts , Tiago Pereira , Han Uitenbroek

Inferring brain connectivity and structure \textit{in-vivo} requires accurate estimation of the orientation distribution function (ODF), which encodes key local tissue properties. However, estimating the ODF from diffusion MRI (dMRI)…

Image and Video Processing · Electrical Eng. & Systems 2024-02-07 William Consagra , Lipeng Ning , Yogesh Rathi

We present a new method for computing the Near-To-Far-Field (NTFF) transformation in FDTD simulations which has an overall scaling of $O(N^3)$ instead of the standard $O(N^4)$. By mapping the far field with a cartesian coordinate system the…

Computational Physics · Physics 2013-11-05 Travis Garrett

We demonstrate a three-dimensional (3D) optical diffraction tomographic technique with optimal frequency combination (OFC-ODT) for the 3D quantitative phase imaging of unlabeled specimens. Three sets of through-focus intensity images are…

Optics · Physics 2018-03-06 Jiaji Li , Qian Chen Jiasong Sun , Jialin Zhang , Junyi Ding , Chao Zuo

Modeling the variability of the solar spectral irradiance is a key factor for understanding the solar influence on the climate of the Earth. As a first step to calculating the solar spectral irradiance variations we reproduce the solar…

Astrophysics · Physics 2009-11-13 M. Haberreiter , W. Schmutz , I. Hubeny

Radiation contributes to the acceleration of large-scale flows in various astrophysical environments because of the strong opacity in spectral lines. Quantification of the associated force is crucial to understanding these line-driven…

Solar and Stellar Astrophysics · Physics 2021-03-31 Aylecia S. Lattimer , Steven R. Cranmer

We compare the three-dimensional gas temperature distributions obtained by a dedicated radiative transfer and photoionisation code, MOCASSIN, against those obtained by the recently-developed Smooth Particle Hydrodynamics (SPH) plus…

Astrophysics of Galaxies · Physics 2015-05-20 Barbara Ercolano , Matthias Gritschneder

We study the effects of radiative transfer on the Probability Distribution Functions (PDFs) of simulations of magnetohydrodynamic turbulence in the widely studied $^{13}$CO 2-1 transition. We find that the integrated intensity maps…

Astrophysics of Galaxies · Physics 2015-06-15 Blakesley Burkhart , V. Ossenkopf , A. Lazarian , J. Stutzki

Codes to compute mean opacities and radiative accelerations for arbitrary chemical mixtures using the Opacity Project recently revised data have been restructured in a client--server architecture and transcribed as a subroutine library.…

We demonstrate a strategy for simulating wide-range X-ray scattering patterns, which spans the small- and wide scattering angles as well as the scattering angles typically used for Pair Distribution Function (PDF) analysis. Such simulated…

(abridged) We develop a tool for the automated spectral classification of OB stars according to their sub-types. We use the regular Random Forest (RF) algorithm, the Probabilistic RF (PRF), and we introduce the KDE-RF method which is a…

Solar and Stellar Astrophysics · Physics 2022-01-12 E. Kyritsis , G. Maravelias , A. Zezas , P. Bonfini , K. Kovlakas , P. Reig

Sub-millimetre dust emission is often used to derive the column density N of dense interstellar clouds. The observations consist of data at several wavelengths but of variable resolution. We examine two procedures that been proposed for the…

Astrophysics of Galaxies · Physics 2015-06-15 M. Juvela , J. Malinen , T. Lunttila

We perform three dimensional radiation hydrodynamic simulations of the structure and dynamics of radiation dominated envelopes of massive stars at the location of the iron opacity peak. One dimensional hydrostatic calculations predict an…

Solar and Stellar Astrophysics · Physics 2015-11-04 Yan-Fei Jiang , Matteo Cantiello , Lars Bildsten , Eliot Quataert , Omer Blaes

Today, wide-open, high-resolution Doppler frequency shift (DFS) estimation is essential for radar, microwave/millimeter-wave, and communication systems. Using photonics technology, an effective approach is proposed and experimentally…

Optics · Physics 2014-04-09 Xihua Zou , Wangzhe Li , Bing Lu , Wei Pan , Lianshan Yan , Liyang Shao

The interpretation of the intensity and polarization of the spectral line radiation produced in the atmosphere of the Sun and of other stars requires solving a radiative transfer problem that can be very complex, especially when the main…

Solar and Stellar Astrophysics · Physics 2015-06-16 Jiri Stepan , Javier Trujillo Bueno

The importance of magnetic fields in three-dimensional magnetoconvection models of the Sun's photosphere is investigated in terms of their influence on the continuum intensity at different viewing inclination angles, and on the intensity…

Solar and Stellar Astrophysics · Physics 2015-06-23 D. Fabbian , F. Moreno-Insertis