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Magnetic Resonance Imaging can produce detailed images of the anatomy and physiology of the human body that can assist doctors in diagnosing and treating pathologies such as tumours. However, MRI suffers from very long acquisition times…

Image and Video Processing · Electrical Eng. & Systems 2022-03-30 George Yiasemis , Jan-Jakob Sonke , Clarisa Sánchez , Jonas Teuwen

The tearing mode instability is a key process for magnetic energy conversion in magnetohydrodynamics, once anti-parallel components are allowed to reconnect, leading to the formation of magnetic islands. It has been employed to explain…

Solar and Stellar Astrophysics · Physics 2024-07-16 Grzegorz Kowal , Diego A. Falceta-Gonçalves

Accurate estimates of the horizontal electric field on the Sun's visible surface are important not only for estimating the Poynting flux of magnetic energy into the corona but also for driving time-dependent magnetohydrodynamic models of…

Solar and Stellar Astrophysics · Physics 2017-02-22 A. R. Yeates

A multilayered particle is illuminated by plane acoustic or electromagnetic waves of one or several frequencies. We consider the inverse scattering problem for the identification of the layers and of the refraction coefficients of the…

Mathematical Physics · Physics 2016-09-07 Semion Gutman

Geophysical inversion attempts to estimate the distribution of physical properties in the Earth's interior from observations collected at or above the surface. Inverse problems are commonly posed as least-squares optimization problems in…

Geophysics · Physics 2019-05-22 Vladimir Puzyrev

Modeling strong gravitational lenses in order to quantify the distortions in the images of background sources and to reconstruct the mass density in the foreground lenses has been a difficult computational challenge. As the quality of…

Instrumentation and Methods for Astrophysics · Physics 2023-07-05 Alexandre Adam , Laurence Perreault-Levasseur , Yashar Hezaveh , Max Welling

A particular instance of the inverse magnetisation problem is considered. It is assumed that the support of a magnetic sample (a source term in the Poisson equation in $\mathbb{R}^3$) is contained in a bounded planar set parallel to the…

Analysis of PDEs · Mathematics 2024-11-15 Dmitry Ponomarev

We have developed new methods to calculate dispersion curves (analytically in the simpler cases) from which we are able to derive the spatial distribution of electron and current densities. We investigate the case where the magnetic field…

Condensed Matter · Physics 2009-10-28 E. Hofstetter , J. M. C. Taylor , A. MacKinnon

Undersampling the k-space during MR acquisitions saves time, however results in an ill-posed inversion problem, leading to an infinite set of images as possible solutions. Traditionally, this is tackled as a reconstruction problem by…

Image and Video Processing · Electrical Eng. & Systems 2022-02-10 Kerem C. Tezcan , Neerav Karani , Christian F. Baumgartner , Ender Konukoglu

We study stability of reconstruction in current density impedance imaging (CDII), that is, the inverse problem of recovering the conductivity of a body from the measurement of the magnitude of the current density vector field in the…

Analysis of PDEs · Mathematics 2020-08-04 Robert Lopez , Amir Moradifam

We calculate the local density of states of a two-dimensional electron system under strong crossed magnetic and electric fields. We assume a strong perpendicular magnetic field which, in the absence of in-plane electric fields and collision…

Mesoscale and Nanoscale Physics · Physics 2011-05-11 S. Erden Gulebaglan , I. Sokmen , A. Siddiki , R. R. Gerhardts

The control of charges in a circuit due to an external electric field is ubiquitous to the exchange, storage and manipulation of information in a wide range of applications, from electronic circuits to synapses in neural cells. Conversely,…

Applied Physics · Physics 2018-04-26 Adolfo De Sanctis , Iddo Amit , Steven P. Hepplestone , Monica F. Craciun , Saverio Russo

We consider a bilevel optimatisation method for inverse linear atmospheric dispersion problems where both linear and non-linear model parameters are to be determined. We propose that a smooth weighted Mahalanobis distance function is used…

Atmospheric and Oceanic Physics · Physics 2016-07-19 Niklas Brännström , Leif Å Persson

In this paper we present a two-dimensional, time dependent, numerical simulation of a reconnection current layer in incompressible resistive magnetohydrodynamics with uniform resistivity in the limit of very large Lundquist numbers. We use…

Astrophysics · Physics 2009-10-31 Dmitri A. Uzdensky , Russell M. Kulsrud

There is growing evidence that when magnetic reconnection occurs in high Lundquist number plasmas such as in the Solar Corona or the Earth's Magnetosphere it does so within a fragmented, rather than a smooth current layer. Within the extent…

Solar and Stellar Astrophysics · Physics 2016-07-12 Peter F. Wyper , Michael Hesse

The infuence of the conduction-electron spin magnetization density, induced in a two-dimensional electron layer by a microwave electromagnetic field, on the rejection and transmission of the field is considered. Because of the induced…

Mesoscale and Nanoscale Physics · Physics 2016-06-29 Victor M. Edelstein

We consider the imaging of anisotropic conductivity tensors $\gamma=(\gamma_{ij})_{1\leq i,j\leq 2}$ from knowledge of several internal current densities $\mathcal{J}=\gamma\nabla u$ where $u$ satisfies a second order elliptic equation…

Analysis of PDEs · Mathematics 2014-03-21 Guillaume Bal , Chenxi Guo , François Monard

Strongly correlated electron systems are challenging to calculate, and entanglement in such systems is not widely analyzed. We present an approach that can be used as a post-processing step for calculating the two-site reduced density…

Strongly Correlated Electrons · Physics 2024-05-29 Gergő Roósz , Anna Kauch , Frederic Bippus , Daniel Wieser , Karsten Held

The simulation of nanophotonic structures relies on electromagnetic solvers, which play a crucial role in understanding their behavior. However, these solvers often come with a significant computational cost, making their application in…

Machine Learning · Computer Science 2024-05-22 Liang Cheng , Prashant Singh , Francesco Ferranti

This paper concerns the reconstruction of a scalar coefficient of a second-order elliptic equation in divergence form posed on a bounded domain from internal data. This theory finds applications in multi-wave imaging, greedy methods to…

Analysis of PDEs · Mathematics 2020-05-19 Faouzi Triki , Tao Yin