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We investigate the inverse source problem for the wave equation, arising in photo- and thermoacoustic tomography. There exist quite a few theoretically exact inversion formulas explicitly expressing solution of this problem in terms of the…

Analysis of PDEs · Mathematics 2018-08-01 Ngoc Do , Leonid Kunyansky

In transient simulations of particulate Stokes flow, to accurately capture the interaction between the constituent particles and the confining wall, the discretization of the wall often needs to be locally refined in the region approached…

Numerical Analysis · Mathematics 2022-01-10 Yabin Zhang , Adrianna Gillman , Shravan Veerapaneni

Many astrophysical applications require efficient yet reliable forecasts of stellar evolution tracks. One example is population synthesis, which generates forward predictions of models for comparison with observations. The majority of…

Solar and Stellar Astrophysics · Physics 2024-02-16 K. Maltsev , F. R. N. Schneider , F. K. Roepke , A. I. Jordan , G. A. Qadir , W. E. Kerzendorf , K. Riedmiller , P. van der Smagt

We present a new iterative rotation inversion technique based on the Simultaneous Algebraic Reconstruction Technique developed for image reconstruction. We describe in detail our algorithmic implementation and compare it to the classical…

Solar and Stellar Astrophysics · Physics 2024-06-17 Sylvain G. Korzennik , Antonio Eff-Darwich

Two-dimensional Stokes flow through a periodic channel is considered. The channel walls need only be Lipschitz continuous, in other words they are allowed to have corners. Boundary integral methods are an attractive tool for numerically…

Numerical Analysis · Mathematics 2020-05-11 Lukas Bystricky , Sara Pålsson , Anna-Karin Tornberg

This paper describes the inversion procedure being used operationally at the Norwegian Meteorological Institute for estimating ash emission rates from retrieved satellite ash column amounts and a priori knowledge. The overall procedure…

Atmospheric and Oceanic Physics · Physics 2020-05-21 André R. Brodtkorb , Anna Benedictow , Heiko Klein , Arve Kylling , Agnes Nyiri , Alvaro Valdebenito , Espen Sollum

We present two new accurate and efficient method to compute the formal solution of the polarized radiative transfer equation. In this work, the source function and the absorption matrix are approximated using quadratic and cubic Bezier…

Solar and Stellar Astrophysics · Physics 2015-06-12 J. de la Cruz Rodríguez , N. Piskunov

Seismic waves are the most sensitive probe of the Earth's interior we have. With the dense data sets available in exploration, images of subsurface structures can be obtained through processes such as migration. Unfortunately, relating…

Geophysics · Physics 2009-05-05 R. B. Schlottmann

Numerical simulation of atmospheric turbulence is one of the biggest bottlenecks in developing computational techniques for solving the inverse problem in long-range imaging. The classical split-step method is based upon numerical wave…

Image and Video Processing · Electrical Eng. & Systems 2022-10-14 Nicholas Chimitt , Xingguang Zhang , Zhiyuan Mao , Stanley H. Chan

Four Stokes parameters (1852) define the polarisation state of light. Measured changes of the Stokes vector of light traversing an inhomogeneous sample are linked to the local anisotropies of absorption and refraction and are harnessed over…

A new approximation to the Stokes drift velocity profile based on the exact solution for the Phillips spectrum is explored. The profile is compared with the monochromatic profile and the recently proposed exponential integral profile.…

Atmospheric and Oceanic Physics · Physics 2016-02-02 Øyvind Breivik , Jean-Raymond Bidlot , Peter A. E. M. Janssen

We present an automated procedure that derives simultaneously the effective temperature $T_{eff}$, the surface gravity logg, the metallicity [Fe/H], and the equatorial projected rotational velocity vsini for "normal" A and Am stars. The…

Instrumentation and Methods for Astrophysics · Physics 2016-04-20 M. Gebran , W. Farah , F. Paletou , R. Monier , V. Watson

Within the framework of the density matrix theory for the generation and transfer of polarized radiation, velocity density matrix correlations represent an important physical aspect that, however, is often neglected in practical…

Solar and Stellar Astrophysics · Physics 2015-06-15 L. Belluzzi , E. Landi Degl'Innocenti , J. Trujillo Bueno

This paper investigates an inverse source problem for general semilinear stochastic hyperbolic equations. Motivated by the challenges arising from both randomness and nonlinearity, we develop a globally convergent iterative regularization…

Analysis of PDEs · Mathematics 2025-04-25 Qi Lü , Yu Wang

Periodic travelling waves at the free surface of an incompressible inviscid fluid in two dimensions under gravity are numerically computed for an arbitrary vorticity distribution. The fluid domain over one period is conformally mapped from…

Fluid Dynamics · Physics 2025-02-26 Alex Doak , Vera Mikyoung Hur , Jean-Marc Vanden-Broeck

Aims: We simulate the spectra of massive binaries at different phases of the orbital cycle, accounting for the gravitational influence of the companion star on the shape and physical properties of the stellar surface. Methods: We used the…

Solar and Stellar Astrophysics · Physics 2015-06-15 Matthieu Palate , Gregor Rauw , Gloria Koenigsberger , Edmundo Moreno

Real--time and accurate construction of regional sound speed profiles (SSP) is important for building underwater positioning, navigation, and timing (PNT) systems as it greatly affect the signal propagation modes such as trajectory. In this…

Signal Processing · Electrical Eng. & Systems 2025-03-31 Wei Huang , Jixuan Zhou , Fan Gao , Jiajun Lu , Sijia Li , Pengfei Wu , Junting Wang , Hao Zhang , Tianhe Xu

Radiative transfer (RT) modelling is a necessary tool in the interpretation of observations of the thermal emission of interstellar dust. It is also often part of multi-physics modelling. In this context, the efficiency of radiative…

Instrumentation and Methods for Astrophysics · Physics 2024-08-27 Mika Juvela

We propose a scheme for imaging periodic surfaces using a superlens. By employing an inverse scattering model and the transformed field expansion method, we derive an approximate reconstruction formula for the surface profile, assuming…

Numerical Analysis · Mathematics 2024-03-05 Peijun Li , Yuliang Wang

The detection of the state of polarization (SOP) of light is essential for many optical applications. However, it is a challenge for cost-effective SOP measurement due to the complexity of conventional methods and poor transferability of…

Optics · Physics 2024-01-30 Yuxuan Xiong , Ting Jiang , Hao Wu , Zheng Gao , Shaojun Zhou , Zhao Ge , Ming Tang