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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

Electromagnetic Modeling of Induction Tool Responses in Isotropic and Anisotropic Layered Earth Formations

Shakya, Nawayandra 18 September 2015 (has links)
No description available.

Electromagnetically Transparent Feed Networks for Antenna Arrays

Lee, Eugene Y. 11 September 2008 (has links)
No description available.

Imaging of Cancer in Tissues Using an Electromagnetic Probe

Sequin, Emily Katherine January 2009 (has links)
No description available.

Characterization of electromagnetic backscatter from moving tracked vehicles /

Gross, Francis B. January 1982 (has links)
No description available.

Visualization of electromagnetic fields using MATLAB

Burke, Mary Joset 01 January 1998 (has links)
This project entails solving electromagnetic problems and explaining the basic concepts with the use of MATLAB. The aim is to provide several example problems that will help students in the introductory electromagnetics course visualize the abstract concepts associated with electrostatic, magnetostatic and electromagnetic fields. The first part of the project provides examples to explain vector operations and the use of vectors in three coordinate systems. The second part involves examples and problems dealing with the static electric and magnetic fields. Finally problems, explanations, and visuals are shown which will help students visualize the time varying fields and also help them in understanding the propagation of electromagnetic waves. The goal of this project is to provide the students studying introductory electromagnetics with a means of visualizing fields and help them understand the abstract mathematical concepts associated with this study.

An investigation of surface shape effects on near-field radiative transfer

Prussing, Keith F. 07 January 2016 (has links)
It has been shown that the energy exchange between two objects can be greatly enhanced when the separation between the objects is on the order of the wavelength of thermal emission. The earliest theoretical and computational work focused on simple planar and spherical geometries, or they resorted to approximations that separated the object to outside of the thermal wavelength \(\lambda_T = hc/(k_BT)\). Since those original works, the study of near-field energy exchange has expanded to object shapes that can be described by a separable coordinate system using a spectral expansion of the dyadic Green function of the system. The boundary element method has also been used to study arbitrary shapes in thermal equilibrium. Application of these new expansion methods to general shapes out of thermal equilibrium will facilitate in the optimization of nanoscale structures. A three step process is used to investigate the effects of object shape on the total and directionality of the energy exchange between objects. First, a general expression for the energy flux between the objects will be formulated. Second, a computational method to evaluate the expression will be implemented. Finally, the effects of varying the surface geometry will be explored. The computational results demonstrate that the total energy exchange between two bodies is influenced by the surface shape of the objects even when the surface areas are held constant. While the primary increase over the classical blackbody energy exchange \(\sigma T^4 A\) is primarily governed by separation of the surfaces, we show that the view factors from classical far-field radiative transfer can be used to predict the change in the total energy exchange from a reference configuration at the same separation when the surface area of the two objects is comparable. Additionally, we demonstrate that the spatial distribution of the energy exchange can be localized into small spatial region with a peak value increased over \SI{30}{\percent} by using two objects with dramatically different projected areas.

Binary pulsar PSR1913+16 as a laboratory for gravitomagnetism and structure of neutron stars

龔碧平, Gong, Biping. January 2001 (has links)
published_or_final_version / Physics / Doctoral / Doctor of Philosophy

Fourth-order finite difference methods for the time-domain Maxwell equations with applications to scattering by rough surfaces and interfaces

Xie, Zhongqiang January 2001 (has links)
No description available.

Investigations of Nonlinear Optical Phenomenon and Dispersion in Integrated Photonic Devices

McMillan, James Flintoft January 2019 (has links)
Integrated photonics is the field of shrinking and simplifying the fabrication of devices that guide and manipulate light. It not only offers to greatly lower the size and cost of systems used in optical communications it also offers a platform on which new physical phenomenon can be explored by being able to fabricate and manipulate structures on the scale of the wavelength of light. One such platform in integrated photonics is that of two-dimensional slab photonic crystals. These structures exhibit a photonic band-gap, a band of optical frequencies that are prohibited from propagating within the medium, that can be used to guide and confine light. When used to create photonic crystal waveguides these waveguides exhibit unique dispersion properties that demonstrate very low optical group velocities, so called "slow-light". This dissertation begins with the practical realization of design and fabrication of such waveguides using the silicon-on-insulator material system using conventional deep-UV photolithography fabrication techniques. It will detail and demonstrate the effect physical dimensions have on the optical transmission of these devices as well as their optical dispersion. These photonic crystal waveguides will then be used to demonstrate the enhancement of nonlinear optical phenomenon due to the slow-light phenomenon they exhibit. First spontaneous Raman scattering will be theoretically demonstrated to be enhanced by slow-light and then experimentally shown to be enhanced in a practical realization. The process of four-wave mixing will be demonstrated to be enhanced in these devices and be shown to be greatly affected by the unique optical dispersion within these structures. Additionally, we will examine the dispersion that exists in silicon nitride microring resonators and the effect it has on the use of these devices to generate optical frequency combs. This is done by leveraging the dispersion measurement methods used to characterize photonic crystal waveguides. We conclude this work by examining the avenues of future work that can be explored in the area of photonic crystal waveguides.

Lightning return stroke electromagnetics - time domain evaluation and application

McAfee, Carson William Ian January 2016 (has links)
A dissertation submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science in Engineering, 2016 / The work presented extends and contributes to the research of modelling lightning return stroke (RS) electromagnetic (EM) fields in the time domain. Although previous work in this area has focused on individual lightning electromagnetic pulse (LEMP) modelling techniques, there has not been an investigation into the strengths and weaknesses of different methods, as well as the implementation considerations of the models. This work critically compares three unique techniques (Finite Antenna, FDTD, and Single Cell FDTD) under the same ideal simulation parameters. The research presented will evaluate the EM fields in the range of 50m to 500m from the lightning channel. This range, often referred to as the near field distance, has a significant effect on lightning induced overvoltages on distribution lines, which are primarily created by the horizontal EM fields of the RS channel. These close distances have a significant effect on the model implementations, especially with the FDTD method. Each of these modelling methods is explained and tested through examples. The models are implemented in C++ and have been included in the Appendix to aid in future implementation. From the model simulations it is clear that the FDTD method is the most comprehensive model available. It allows for non-ideal ground planes, as well as complex simulation environments. However, FDTD has a number of numerical related errors that the Finite Antenna method does not suffer from. The Single Cell FDTD method is simple to implement and does not suffer from the same numerical errors as a full FDTD implementation, but is limited to simple simulation environments. This work contributes to the research field by comparing and evaluating three techniques and giving consideration to the implementation and the applicability to lightning EM simulations. / MT2017

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