arXiv subjects

Amer Rasheed

Publications and source records attributed to Amer Rasheed.

4 recordsLinked to original sources

arXiv2018

Error and stability analysis of an anisotropic phase-field model for binary-fluid mixtures in the presence of magnetic-field

In this article, we study the error and stability of the proposed numerical scheme in order to solve a two dimensional anisotropic phase-field model with convection and externally applied magnetic field in an isothermal solidification of binary alloys. The proposed numerical scheme is based on mixed finite element method satisfying the CFL condition. A particular application with real physical parameters of Nickel-Copper(Ni-Cu) is considered in order to validate the numerical scheme employed. The results of stability and error analysis substantiates complete accordance with the postulated theoretical error estimates which demonstrates the efficiency of the presented method.

math.NA↗

arXiv2018

Fractional calculus approach for the phase dynamics of Josephson junction under the influence of magnetic field

This article presents the phase dynamics of an inline long Josephson junction in voltage state under the influence of constant external magnetic field. Fractional calculus approach is used to model the evolution of the phase difference between the macroscopic wave functions of the two superconductors across the junction. The governing non-linear partial differential equation is then solved using finite difference-finite element schemes. Other quantities of interest like Josephson current density and voltage across the junction are also computed. The effects of various parameters in the model on phase difference, Josephson current density and voltage are analyzed graphically with the help of numerical simulations.

math.NA↗

arXiv2014

Electromagnetic source localization with finite set of frequency measurements

A phase conjugation algorithm for localizing an extended radiating electromagnetic source from boundary measurements of the electric field is presented. Measurements are taken over a finite number of frequencies. The artifacts related to the finite frequency data are tackled with $l_1-$regularization blended with the fast iterative shrinkage-thresholding algorithm with backtracking of Beck & Teboulle.

math-ph↗

arXiv2014

Electromagnetic time reversal algorithms and source localization in lossy dielectric media

The problem of reconstructing the spatial support of an extended radiating electric current source density in a lossy dielectric medium from transient boundary measurements of the electric fields is studied. A time reversal algorithm is proposed to localize a source density from loss-less wave-field measurements. Further, in order to recover source densities in a lossy medium, we first build attenuation operators thereby relating loss-less waves with lossy ones. Then based on asymptotic expansions of attenuation operators with respect to attenuation parameter, we propose two time reversal strategies for localization. The losses in electromagnetic wave propagation are incorporated using the Debye's complex permittivity, which is well-adopted for low frequencies (radio and microwave) associated with polarization in dielectrics.

math-ph↗