Simulation of the Scattered EM Field of a Rotating Conducting Cylinder Using Static Data

The effect of the rotation of a very good conducting cylinder on the backscattered field will be investigated where the incident wave is considered as a plane wave in both polarizations (E-wave and H-wave). Previous work has explained that rotation or vibration of the object may induce phase changes of the scattered signal. Modulation during rotation or vibration is referred to as micro-Doppler effect. Also, the effect of the rotation of a conducting cylinder was investigated by many researchers in the past using the Galilean transformation. These analyses conclude that the effect of rotation does not exist in the case of a perfectly conducting cylinder in both polarizations. In this work, the Franklin transformation is used instead of the Galilean transformation to analyze scattering of both types of electromagnetic waves (H-wave and E-wave) by rotating a very good circular conducting cylinder. This work shows that the scattered field is affected by the rotation of a very good conducting cylinder, especially in the case of H-wave (TE-mode). Finally, the model that will be presented is used to simulate rotation using static backscattered field data of an arbitrary object

Optical antennas and plasmonics

Optical antenna is a nanoscale miniaturization of radio or microwave antennas that is also governed by the rule of plasmonics. We introduce various types of optical antenna and make an overview of recent developments in optical antenna research. The role of local and surface plasmons in optical antenna is explained through antenna resonance and resonance conditions for specific metal structures are explicitly obtained. Strong electric field is shown to exist within a highly localized region of optical antennas such as antenna feed gap or apertures. We describe physical properties of field enhancement in apertures(circular and rectangular holes) and gaps(infinite slit and feed gap), as well as experimental techniques measuring enhanced electric vector field. We discuss about analogies and differences between conventional and optical antennas with a projection of future developments.Comment: To be published in Contemporary Physic

A model for calculating EM field in layered medium with application to biological implants

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.Modern wireless telecommunication devices (GSM Mobile system) (cellular telephones and wireless modems on laptop computers) have the potential to interfere with implantable medical devices/prostheses and cause possible malfunction. An implant of resonant dimensions within a homogeneous dielectric lossy sphere can enhance local values of SAR (the specific absorption rate). Also antenna radiation pattern and other characteristics are significantly altered by the presence of the composite dielectric entities such as the human body. Besides, the current safety limits do not take into account the possible effect of hot spots arising from metallic implants resonant at mobile phone frequencies. Although considerable attention has been given to study and measurement of scattering from a dielectric sphere, no rigorous treatment using electromagnetic theory has been given to the implanted dielectric spherical head/cylindrical body. This thesis aims to deal with the scattering of a plane electromagnetic wave from a perfectly conducting or dielectric spherical/cylindrical implant of electrically small radius (of resonant length), embedded eccentrically into a dielectric spherical head model. The method of dyadic Green's function (DGF) for spherical vector wave functions is used. Analytical expressions for the scattered fields of both cylindrical and spherical implants as well as layered spherical head and cylindrical torso models are obtained separately in different chapters. The whole structure is assumed to be uniform along the propagation direction. To further check the accuracy of the proposed solution, the numerical results from the analytical expressions computed for the problem of implanted head/body are compared with the numerical results from the Finite-Difference Time-Domain (FDTD) method using the EMU-FDTD Electromagnetic simulator. Good agreement is observed between the numerical results based on the proposed method and the FDTD numerical technique. This research presents a new approach, away from simulation work, to the study of exact computation of EM fields in biological systems. Its salient characteristics are its simplicity, the saving in memory and CPU computational time and speed.Cochlear UK Limited and EPSR

Fluctuation-induced phenomena in non-equilibrium systems

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2013.Cataloged from PDF version of thesis.Includes bibliographical references (pages 128-134).In this thesis, we investigate the implications of fluctuations in systems away, possibly even far, from equilibrium due to their motion either in or out of thermal equilibrium. This subject encompasses several topics in physics including the dynamical Casimir effect in the presence of moving boundaries, and non-contact friction between objects in relative motion. In both cases, photons are created due to the coupling of the motion and zero-point fluctuations in the vacuum, resulting in dissipation and radiative loss. We introduce a general formalism, equally applicable to lossy and ideal objects, to compute the quantum radiation and dissipation effects solely in terms of the classical scattering matrices. We obtain trace formulas which are general and independent of any approximation scheme where numerous examples, many novel, are discussed in great detail. Specifically, we give an exact treatment of quantum fluctuations in the context of a neutral rotating object, and show that it spontaneously emits photons and drags objects nearby, and compute the associated photon statistics and entropy generation. In the context of non-contact friction, we find a quantum analog of the classical Cherenkov effect for two neutral plates in relative motion, purely due to quantum fluctuations. We present a number of arguments and exact proofs, including a method introduced in the context of quantum field theory in curved space, as well as the scattering approach, to show that a friction force between two plates appears at a threshold velocity set by the speed of light in their medium.by Mohammad F. Maghrebi.Ph.D

Numerical methods for computing Casimir interactions

We review several different approaches for computing Casimir forces and related fluctuation-induced interactions between bodies of arbitrary shapes and materials. The relationships between this problem and well known computational techniques from classical electromagnetism are emphasized. We also review the basic principles of standard computational methods, categorizing them according to three criteria---choice of problem, basis, and solution technique---that can be used to classify proposals for the Casimir problem as well. In this way, mature classical methods can be exploited to model Casimir physics, with a few important modifications.Comment: 46 pages, 142 references, 5 figures. To appear in upcoming Lecture Notes in Physics book on Casimir Physic

Superradiance -- the 2020 Edition

Superradiance is a radiation enhancement process that involves dissipative systems. With a 60 year-old history, superradiance has played a prominent role in optics, quantum mechanics and especially in relativity and astrophysics. In General Relativity, black-hole superradiance is permitted by the ergoregion, that allows for energy, charge and angular momentum extraction from the vacuum, even at the classical level. Stability of the spacetime is enforced by the event horizon, where negative energy-states are dumped. Black-hole superradiance is intimately connected to the black-hole area theorem, Penrose process, tidal forces, and even Hawking radiation, which can be interpreted as a quantum version of black-hole superradiance. Various mechanisms (as diverse as massive fields, magnetic fields, anti-de Sitter boundaries, nonlinear interactions, etc...) can confine the amplified radiation and give rise to strong instabilities. These "black-hole bombs" have applications in searches of dark matter and of physics beyond the Standard Model, are associated to the threshold of formation of new black hole solutions that evade the no-hair theorems, can be studied in the laboratory by devising analog models of gravity, and might even provide a holographic description of spontaneous symmetry breaking and superfluidity through the gauge-gravity duality. This work is meant to provide a unified picture of this multifaceted subject. We focus on the recent developments in the field, and work out a number of novel examples and applications, ranging from fundamental physics to astrophysics.Comment: 279 pages. Second Edition of the "Lecture Notes in Physics" book by Springer-Verlag. Overall improvement, typos and incorrect statements of Edition 1 are now corrected; new sections were added, reflecting activity in the field. Bounds on ultralight fields are summarized in Table 4, and updated online regularly at https://centra.tecnico.ulisboa.pt/network/grit/ and https://web.uniroma1.it/gmunu

Nanofotónica de estructuras dieléctricas de alto índice de refracción: resonancias ópticas en metasuperficies y nanohilos semiconductores

Tesis doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Física de la Materia. Fecha de lectura: 15-12-202

Two Dimensional Scattering Analysis of Data-Linked Support Strings for Bistatic Measurement Systems

Use of data-linked strings to support a bistatic antenna is being considered as a possible improvement to indoor bistatic radar cross section measurement systems. Analysis of candidate data-linked strings is required to understand the potential clutter contribution posed by such a system. The main objective of this research is to determine the scattering properties of four data-linked support string samples. An- other goal is to determine the material properties of the string material through nondestructive means if possible. The final goal is to model the samples as a single wire coated with a dielectric material and determine the validity of the model. To meet these goals, the two dimensional radar cross section of each sample is measured with a focused beam system. The resulting measurements are used in conjunction with an analytic model of a dielectric-coated wire to estimate the material proper- ties of the string material. Finally, a dielectric-coated wire model for each sample is analyzed using COMSOL Multiphysics software, and the results are compared with the measured two dimensional radar cross section. As a result of this study, the two dimensional radar cross section of each sample is presented for both vertical and horizontal polarizations. Also, the effective relative permittivity of each string sample is found and used in the COMSOL model. The COMSOL models are shown to be relatively accurate representations of the string samples

Electromagnetic properties and macroscopic characterization of composite materials

Ph.DNUS-SUPELEC JOINT PH.D. PROGRAMM