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A common optimization problem in the areas of magnetized plasmas and fusion energy is the design of magnets to produce a given three-dimensional magnetic field distribution to high precision. When designing arrays of permanent magnets for…

Plasma Physics · Physics 2024-02-20 K. C. Hammond , A. A. Kaptanoglu

Time-of-flight neutron imaging offers complementary attenuation contrast to X-ray computed tomography (CT), coupled with the ability to extract additional information from the variation in attenuation as a function of neutron energy (time…

We introduce a new regularization of the rotational Navier-Stokes equations that we call the Rotational Approximate Deconvolution Model (RADM). We generalize the deconvolution type model, studied by Berselli and Lewandowski [5], to the RADM…

Analysis of PDEs · Mathematics 2012-04-16 Hani Ali

We present a new method for estimating the H2 cooling rate in the optically thick regime in simulations of primordial star formation. Our new approach is based on the TreeCol algorithm, which projects matter distributions onto a spherical…

Solar and Stellar Astrophysics · Physics 2015-05-05 Tilman Hartwig , Paul C. Clark , Simon C. O. Glover , Ralf S. Klessen , Mei Sasaki

We introduce a method to estimate continuum percolation thresholds and illustrate its usefulness by investigating geometric percolation of non-interacting line segments and disks in two spatial dimensions. These examples serve as models for…

The study of accurate methods to estimate the distribution of stellar rotational velocities is important for understanding many aspects of stellar evolution. From such observations we obtain the projected rotational speed v sin(i) in order…

Solar and Stellar Astrophysics · Physics 2019-03-20 Rafael Orellana , Pedro Escarate , Michel Cure , Alejandra Christen , Rodrigo Carvajal , Juan Carlos Agüero

This paper presents a novel non-rigid point set registration method that is inspired by unsupervised clustering analysis. Unlike previous approaches that treat the source and target point sets as separate entities, we develop a holistic…

Computer Vision and Pattern Recognition · Computer Science 2024-06-28 Mingyang Zhao , Jingen Jiang , Lei Ma , Shiqing Xin , Gaofeng Meng , Dong-Ming Yan

Geophysical flows are characterized by rapid rotation. Simulating these flows requires small timesteps to achieve stability and accuracy. Numerical stability can be greatly improved by the implicit integration of the terms that are most…

A simple experimentally accessible realization of current rectification by molecules (molecular films) bridging metal electrodes is described. It is based on the spatial asymmetry of the molecule and requires only one resonant conducting…

Soft Condensed Matter · Physics 2009-11-07 P. E. Kornilovitch , A. M. Bratkovsky , R. S. Williams

Diffusion MRI is a well established imaging modality providing a powerful way to probe the structure of the white matter non-invasively. Despite its potential, the intrinsic long scan times of these sequences have hampered their use in…

Quantitative Methods · Quantitative Biology 2013-12-31 Alessandro Daducci , Dimitri Van De Ville , Jean-Philippe Thiran , Yves Wiaux

This work is motivated by the monitoring of conductive clogging deposits in steam generator at the level of support plates. One would like to use monoaxial coils measurements to obtain estimates on the clogging volume. We propose a 3D shape…

Numerical Analysis · Mathematics 2015-02-25 Houssem Haddar , Mohamed Kamel Riahi , Zixian Jiang

In this paper, we utilize stochastic optimization to reduce the space complexity of convex composite optimization with a nuclear norm regularizer, where the variable is a matrix of size $m \times n$. By constructing a low-rank estimate of…

Machine Learning · Computer Science 2015-12-08 Lijun Zhang , Tianbao Yang , Rong Jin , Zhi-Hua Zhou

To reduce scanning time and/or improve spatial/temporal resolution in some MRI applications, parallel MRI (pMRI) acquisition techniques with multiple coils acquisition have emerged since the early 1990s as powerful 3D imaging methods that…

Optimization and Control · Mathematics 2009-09-03 Lotfi Chaari , Jean-Christophe Pesquet , Philippe Ciuciu , Amel Benazza-Benyahia

In \cite{NRxx}, we proposed a numerical regularized moment method of arbitrary order (abbreviated as NRxx method) for Boltzmann-BGK equation, which makes numerical simulation using very large number of moments possible. In this paper, we…

Mathematical Physics · Physics 2010-11-30 Zhenning Cai , Ruo Li , Yanli Wang

In this article, we propose a strategy for the active manipulation of scalar Helmholtz fields in bounded near field regions of an active source while maintaining desired radiation patterns in prescribed far field directions. This control…

Systems and Control · Electrical Eng. & Systems 2020-06-26 Neil Jerome A. Egarguin , Daniel Onofrei , Chaoxian Qi , Jiefu Chen

Coronagraph instruments on future space telescopes will enable the direct detection and characterization of Earth-like exoplanets around Sun-like stars for the first time. The quest for the optimal optical coronagraph designs has made rapid…

Instrumentation and Methods for Astrophysics · Physics 2018-08-30 G. Ruane , A. Riggs , C. T. Coker , S. B. Shaklan , E. Sidick , D. Mawet , J. Jewell , K. Balasubramanian , C. C. Stark

We present a novel numerical method for solving the elliptic partial differential equation problem for the electrostatic potential with piecewise constant conductivity. We employ an integral equation approach for which we derive a system of…

Numerical Analysis · Mathematics 2022-06-01 Kyle Bower , Kirill Serkh , Spyros Alexakis , Adam R Stinchcombe

We present a comparative computational study of two stabilized Reduced Order Models (ROMs) for the simulation of convection-dominated incompressible flow (Reynolds number of the order of a few thousands). Representative solutions in the…

Fluid Dynamics · Physics 2024-05-01 Pierfrancesco Siena , Michele Girfoglio , Annalisa Quaini , Gianluigi Rozza

We present a new method for recovering the cosmological density, velocity, and potential fields from all-sky redshift catalogues. The method is based on an expansion of the fields in orthogonal radial (Bessel) and angular (spherical…

Astrophysics · Physics 2015-06-24 Karl Fisher , Ofer Lahav , Yehuda Hoffman , Donald Lynden-Bell , Saleem Zaroubi

Dynamic inverse problems are challenging to solve due to the need to identify and incorporate appropriate regularization in both space and time. Moreover, the very large scale nature of such problems in practice presents an enormous…

Numerical Analysis · Mathematics 2025-01-23 Toluwani Okunola , Mirjeta Pasha , Misha Kilmer , Melina Freitag