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Dissertations / Theses on the topic 'Electromagnetics'

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Published: 4 June 2021
Last updated: 7 July 2024

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1

Bekele, Ephrem Teshale. "Innovative Electromagnetic Field Manipulating Devices Based on Transformation Electromagnetics." Doctoral thesis, Università degli studi di Trento, 2015. https://hdl.handle.net/11572/368574.

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Quasiconformal Transformation Optics (QCTO) has been investigated and applied for the design of innovative electromagnetic field manipulating devises. The design is focused on enhancing radiation performance of antenna arrays. Towards this end, the QCTO approach has been utilized for the application of compressing dimension of linear array at the same time keeping its radiation performance equivalent to the original array. The basic QCTO is then generalized to allow an arbitrary physical arrangement coated with a suitable lens to exhibit the same radiating features of an arbitrary reference virtual array in free space. This removed the limitation on the state-of-the-art QCTO method to handle transformation between arbitrarily shaped geometries. A representative numerical example, concerned with a two-dimensional layout, is presented to assess the effectiveness of the proposed method as well as the enhanced features of the resulting metamaterial-coated arrays with respect to standard conformal arrangements. In addition, the capability to achieve significantly simplified structures by means of tile discretization approximation of the synthesized lens is investigated. Selected numerical examples are reported to illustrate the effectiveness of tile-discretized lenses versus ideal QCTO arrangements. The metamaterial lens that resulted from the extended QCTO was found to be significantly anisotropic posing implementation challenge. To address this issue, an innovative approach, based on the System-by-Design (SbD) paradigm, is proposed for the synthesis of isotropic non-magnetic metamaterial lenses. Selected numerical results, concerned with an application of the SbD-QCTO approach, are reported to give some insights on its advantages and current limitations in terms of computational efficiency, effectiveness, and flexibility.
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2

Bekele, Ephrem Teshale. "Innovative Electromagnetic Field Manipulating Devices Based on Transformation Electromagnetics." Doctoral thesis, University of Trento, 2015. http://eprints-phd.biblio.unitn.it/1499/1/Ph.D.Thesis.BEKELE-April.2015.Final.pdf.

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Quasiconformal Transformation Optics (QCTO) has been investigated and applied for the design of innovative electromagnetic field manipulating devises. The design is focused on enhancing radiation performance of antenna arrays. Towards this end, the QCTO approach has been utilized for the application of compressing dimension of linear array at the same time keeping its radiation performance equivalent to the original array. The basic QCTO is then generalized to allow an arbitrary physical arrangement coated with a suitable lens to exhibit the same radiating features of an arbitrary reference virtual array in free space. This removed the limitation on the state-of-the-art QCTO method to handle transformation between arbitrarily shaped geometries. A representative numerical example, concerned with a two-dimensional layout, is presented to assess the effectiveness of the proposed method as well as the enhanced features of the resulting metamaterial-coated arrays with respect to standard conformal arrangements. In addition, the capability to achieve significantly simplified structures by means of tile discretization approximation of the synthesized lens is investigated. Selected numerical examples are reported to illustrate the effectiveness of tile-discretized lenses versus ideal QCTO arrangements. The metamaterial lens that resulted from the extended QCTO was found to be significantly anisotropic posing implementation challenge. To address this issue, an innovative approach, based on the System-by-Design (SbD) paradigm, is proposed for the synthesis of isotropic non-magnetic metamaterial lenses. Selected numerical results, concerned with an application of the SbD-QCTO approach, are reported to give some insights on its advantages and current limitations in terms of computational efficiency, effectiveness, and flexibility.
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3

Fouda, Ahmed Elsayed. "Electromagnetic Time-Reversal Imaging and Tracking Techniques for Inverse Scattering and Wireless Communications." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1366202740.

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4

Alkhateeb, Osama. "Singularity-Free Boundary Methods for Electrostatics and Wave Scattering." University of Akron / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=akron1334816052.

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5

Bau-Hsing, Ann. "Computer-aided electromagnetic analysis of chokes and transformers." The Ohio State University, 1986. http://rave.ohiolink.edu/etdc/view?acc_num=osu1438255468.

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6

Moon, Haksu. "Robust Algorithms for Electromagnetic Field Computation with Conduction Currents and Kinetic Charge-Transport Models." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1440193844.

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7

Abumunshar, Anas Jawad. "Tightly Coupled Dipole Array with Integrated Phase Shifters for Millimeter-Wave Connectivity." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1491172877293751.

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8

Peng, Shaoxin. "Direct Evaluation of Hyper-singularity in Integral Equation with Adaptive Mesh Refinement." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1557107644500354.

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9

Wang, Xiaochuan. "A Domain Decomposition Method for Analysis of Three-Dimensional Large-Scale Electromagnetic Compatibility Problems." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1338376950.

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10

Wu, Bae-Ian 1975. "Electromagnetics in characterizations." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/28269.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2003.
Vita.
Includes bibliographical references (p. 149-159).
(cont.) Characterization of the differential guided mode of a coupled-strip transmission line allows us to understand its behaviors in high frequency circuit applications. S-parameters of the differential mode of a coupled-strip transmission line on a multi-layer silicon substrate extracted from 4-port measurements and simulations are de-embedded by the impedance/admittance subtraction method. By accurately determining the input inductance of the connecting pads, the parameters of the transmission line itself can be de-embedded. For the specific substrate profile considered, it is found that there is a practical upper limit on the value of the differential impedance. Baseline estimation for synthetic aperture radar interferometry is used to refine the height estimation of the resulting digital elevation map. Furthermore, preprocessing is used to reduce the effects of local phase inconsistencies caused by noise. By incorporating the information of the ground control points in the height inversion process, the initial estimation of the baseline parameters based on the satellite state vectors and the commonly used high order polynomial fitting can be improved. In this study, a simulated interferogram of a 2-D terrain is generated, and different levels of phase noise as well as uncertainties in baseline parameters are introduced. Five control points are use in a 60 x 60 km area. The platform height is 500 km and the frequency used is in the L-band ...
A unique negative lateral shift is demonstrated in the study of a Gaussian beam either reflected from a grounded slab or transmitted through a slab with both negative permittivity and permeability, which is distinctly different from the shift caused by a regular slab. The incident beam is modeled as a tapered wave with a Gaussian spectrum. The waves inside and outside the slab are solved analytically from Maxwell's equations by matching the boundary conditions at the interfaces. It is shown that the electric and magnetic fields in all regions can be unambiguously determined. Numerical simulations are presented and the amplitudes of the fields as well as the power densities are computed for all regions. A dramatic negative lateral shift of the beam at the exit interface is observed when both e and are negative. Guided waves in an isotropic dielectric slab are analyzed and it is found that modes with real and imaginary transverse wavenumbers can both exist depending on the constitutive parameters of the slab. The guided modes with both real and imaginary transverse wavenumbers inside in a symmetric dielectric slab with negative permittivity and permeability are solved. It is found that for real transverse wavenumbers, there exist cutoffs for all modes. In addition, a guidance condition of the modes with imaginary transverse wavenumbers in the slab is shown to exist, and a graphical method of determining such imaginary transverse wavenumbers of the guided modes is introduced. Propagation of guided waves inside a less dense negative medium is shown to be possible. Time-averaged Poynting vectors in all regions are derived and it is shown that the direction of power flow inside the slab is opposite to the flow outside the slab.
by Bae-Ian Wu.
Ph.D.
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11

Young, André. "Mesh termination schemes for the finite element method in electromagnetics /." Link to the online version, 2007. http://hdl.handle.net/10019/735.

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12

Almaghrawi, Ahmed Almaamoun. "Collaborative design in electromagnetics." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=103363.

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We present a system architecture and a set of control techniques that allow heterogeneous software design tools to collaborate intelligently and automatically. One of their distinguishing features is the ability to perform concurrent processing. Systems based on this architecture are able to effectively solve large electromagnetic analysis problems, particularly those that involve loose coupling between several areas of physics. The architecture can accept any existing software analysis tool, without requiring any modification or customization of the tool. This characteristic is produced in part by our use of a neutral virtual representation for storing problem data, including geometry and material definitions. We construct a system based on this architecture, using several circuit and finite-element analysis tools, and use it to perform electromagnetic analyses of several different devices. Our results show that our architecture and techniques do allow practical problems to be solved effectively by heterogeneous tools.
On présente une architecture de système et un ensemble de techniquesde contrôle qui permettent aux logiciels d'analyse hétérogènes de collaborerde façon intelligente et automatique. Un de ses traits caractéristiques est sacapacité d'effectuer simultanément plusieurs traitements. Les systèmes baséssur cette architecture sont capables de résoudre de manière efficace des grandsproblèmes dans le domaine de l'analyse électromagnétique, particulièrementceux où existe un accouplement dégagé entre plusieurs domaines de physique.L'architecture peut accepter n'importe quel logiciel d'analyse existant; ellen'exige pas que les logiciels soyent modifiés ou fabriqués sur mesure. Cettecaractéristique est produite en partie par notre utilisation d'une représentationneutre virtuelle pour représenter les données du problème, y inclus sa géométrieet les proprietés de ses matériels. On construit un système basé sur cettearchitecture, comprenant plusieurs logiciels de simulation, et on l'emploie pourexécuter des analyses électromagnétiques de plusieurs appareils différents. Nosrésultats montrent que notre architecture et nos techniques permettent desproblèmes pratiques d'être résolus efficacement par les outils hétérogènes.
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13

Chen, Xudong 1977. "Inverse problems in electromagnetics." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/33933.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2005.
Vita.
Includes bibliographical references (p. 155-164).
Two inverse problems in electromagnetics are investigated in this thesis. The first is the retrieval of the effective constitutive parameters of metamaterials from the measurement of the reflection and the transmission coefficients. A robust method is proposed for the retrieval of metamaterials as isotropic media, and four improvements over the existing methods make the retrieval results more stable. Next, a new scheme is presented for the retrieval of a specific bianisotropic metamaterial that consists of split-ring resonators, which signifies that the cross polarization terms of the metamaterial are quantitatively investigated for the first time. Finally, an optimization approach is designed to achieve the retrieval of general bianisotropic media with 72 unknown parameters. The hybrid algorithm combining the differential evolution (DE) algorithm and the simplex method steadily converges to the exact solution. The second inverse problem deals with the detection and the classification of buried metallic objects using electromagnetic induction (EMI). Both the exciting and the induced magnetic fields are expanded as a linear combination of basic modes in the spheroidal coordinate system. Due to the orthogonality and the completeness of the spheroidal basic modes, the scattering coefficients are uniquely determined and are characteristics of the object.
(cont.) The scattering coefficients are retrieved from the knowledge of the induced fields, where both synthetic and measurement data are used. The ill-conditioning issue is dealt with by mode truncation and Tikhonov regularization technique. Stored in a library, the scattering coefficients can produce fast forward models for use in pattern matching. In addition, they can be used to train support vector machine (SVM) to sort objects into generic classes.
by Xudong Chen.
Ph.D.
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14

Gilbert, Michael Stephen. "A Small-Perturbation Automatic-Differentiation (SPAD) Method for Evaluating Uncertainty in Computational Electromagnetics." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1354742230.

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15

Lei, Feiran. "Homogenization of Heterogeneous Composites by Using Effective Electromagnetic Properties." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1299513068.

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16

Hartman, Gregory. "Monolithically integrated non-reciprocal devices based on magnetic thin films." Wright State University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=wright1369095798.

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17

Evers, Chris. "Novel Techniques for Enhancing SAR Imaging using Spatially Variant Apodization." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1304016482.

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18

Duong, Lawrence. "Computational electromagnetics in microwave hyperthermia." Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=83861.

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Microwave hyperthermia is a cancer treatment used in combination with radiotherapy and/or chemotherapy. Hyperthermia sensitizes cancer cells to the primary treatment by sublethal heat. An antenna array non-invasively launches electromagnetic waves, targeting cancer cells, and produces preferential heating. This thesis discusses the two-arm Archimedean spiral antenna as a possible antenna to deliver such energy.
Simulations are performed on a homogeneous cylindrical numerical phantom using the finite-difference time-domain (FDTD) method. FDTD is well-suited for the analysis of the interaction between electromagnetic waves and complex media.
This thesis explores two types of input signals to the antenna array: a continuous wave and a pulse. By strategically changing the phase of the continuous wave or the delay of the pulse of individual antenna elements, spots of maximal energy deposition within the phantom can be controlled. In the case of pulse-excited antenna array, temperature distribution is also computed.
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19

Kemp, Benjamin. "Evolutionary optimisation for electromagnetics design." Thesis, University of York, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325641.

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20

Venkatasubramanian, Rajiv. "Composite Nanoparticle Materials for Electromagnetics." University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1352993374.

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21

VERNI', FRANCESCO. "Advanced Computational Electromagnetics for Metasurfaces." Doctoral thesis, Politecnico di Torino, 2020. http://hdl.handle.net/11583/2843986.

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22

Zhu, Boyuan. "The Electromagnetic Compatibility Problems of Integrated Circuits." Thesis, Griffith University, 2011. http://hdl.handle.net/10072/365527.

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With the constant speed of growth in semiconductor technology, integrated circuit (IC) has taken a considerable position in an electronic system. The integrated circuit is working in a low supply voltage with high operation frequency. The internal complexity and chip density are also increased dramatically. Modern microelectronic technology in wafer fabrication easily allows component densities to exceed one million transistors per die. So far, integrated circuits are suering from various and complicated electromagnetic environments. Being the heart of an electronic system, stability and reliability of the integrated circuit are of the most important requirement along with the techniques development. The demands of high electromagnetic compatibility (EMC) performance for integrated circuits are therefore broadly spread among semiconductor manufacturers and product users. Traditionally, EMC for IC is only considered at the post-design stage. Once built, it is only then that equipment is tested to see whether or not it conforms to the relevant standards. This can prove very expensive in terms of time, cost, and the potential need for retrot modications. Simulating a piece of equipment is potentially much faster and cheaper than taking a prototype or existing piece of equipment to a test-house. More importantly, it allows the engineer to \look into" the equipment and see where currents and elds are largest; this is almost impossible with physical testing. Recently, computational electromagnetics (CEM) technique has moved from pure mathematical analysis into design in engineering practice. It can provide a much easier, faster and more economical solution of prediction in EMC characteristics than conventional methods. Thus, EMC computer modelling and simulation of IC is going to play an important role in scientic research and industrial applications.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Engineering
Science, Environment, Engineering and Technology
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23

Zeineddin, Rafik Paul. "Numerical electromagnetics codes problems, solutions and applications." Ohio : Ohio University, 1993. http://www.ohiolink.edu/etd/view.cgi?ohiou1176315682.

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24

Esfahani, Pedram. "A Study of the Frequency Dependence of Permittivity and Permeability in Lossless One-Dimensional Composite Right/Left Handed Metamaterials by the Equivalent Circuit Model." University of Akron / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1468524947.

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25

O’Donnell, Andrew Nickerson. "On the Electromagnetic Scattering from Small Grooves in a Conical Surface." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1297889460.

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26

Kolev, Tzanio Valentinov. "Least-squares methods for computational electromagnetics." Texas A&M University, 2004. http://hdl.handle.net/1969.1/1115.

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The modeling of electromagnetic phenomena described by the Maxwell's equations is of critical importance in many practical applications. The numerical simulation of these equations is challenging and much more involved than initially believed. Consequently, many discretization techniques, most of them quite complicated, have been proposed. In this dissertation, we present and analyze a new methodology for approximation of the time-harmonic Maxwell's equations. It is an extension of the negative-norm least-squares finite element approach which has been applied successfully to a variety of other problems. The main advantages of our method are that it uses simple, piecewise polynomial, finite element spaces, while giving quasi-optimal approximation, even for solutions with low regularity (such as the ones found in practical applications). The numerical solution can be efficiently computed using standard and well-known tools, such as iterative methods and eigensolvers for symmetric and positive definite systems (e.g. PCG and LOBPCG) and reconditioners for second-order problems (e.g. Multigrid). Additionally, approximation of varying polynomial degrees is allowed and spurious eigenmodes are provably avoided. We consider the following problems related to the Maxwell's equations in the frequency domain: the magnetostatic problem, the electrostatic problem, the eigenvalue problem and the full time-harmonic system. For each of these problems, we present a natural (very) weak variational formulation assuming minimal regularity of the solution. In each case, we prove error estimates for the approximation with two different discrete least-squares methods. We also show how to deal with problems posed on domains that are multiply connected or have multiple boundary components. Besides the theoretical analysis of the methods, the dissertation provides various numerical results in two and three dimensions that illustrate and support the theory.
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27

Rashid, Kashif. "Optimisation in electromagnetics using computational intelligence." Thesis, Imperial College London, 2000. http://hdl.handle.net/10044/1/8735.

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28

Fernández, Becerra David. "Multicore acceleration of sparse electromagnetics computations." Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=104641.

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Multicore processors have become the dominant industry trend to increase computer systems performance, driving electromagnetics (EM) practitioners to redesign their applications using parallel programming paradigms. This is especially true for computations involving complex data structures such as sparse matrix computations that often arise in EM simulations with the finite element method (FEM). These computations require pointer manipulation that render useless many compiler optimizations and parallel shared memory frameworks (e.g. OpenMP). This work presents new sparse data structures and techniques to efficiently exploit multicore parallelism and short-vector units (the last of which has not been exploited by state of the art sparse matrix libraries) for recurrent computationally intensive kernels in EM simulations, such as the sparse matrix-vector multiplication (SMVM) and the conjugate gradient (CG) algorithms. Up to 14 times performance speedups are demonstrated for the accelerated SMVM kernel and 5.8x for the CG kernel using the proposed methods over conventional approaches for two different multicore architectures. Finally, a new method to solve the FEM for parallel processing is presented and an optimized implementation is realized on two different generations of NVIDIA GPUs (manycore) accelerators with performance increases of up to 27.53 times compared to compiler optimized CPU results.
Les processeurs multicœurs sont devenus la tendance dominante de l'industrie pour accroître la performance des systèmes informatiques, forçant les concepteurs de systèmes électromagnétiques (EM) à reconcevoir leurs applications en utilisant des paradigmes de programmation parallèle. Cela est particulièrement vrai pour les calculs impliquant des structures de données complexes comme les calculs de matrices creuses qui surviennent souvent dans des simulations électromagnétiques (EM) avec la méthode d'analyse par éléments finis (FÉM). Ces calculs nécessitent de manipulation de pointeurs qui rendent inutiles de nombreuses optimisations du compilateur et les bibliothèques de mémoire partagée parallèle (OpenMP, par exemple). Ce travail présente de nouvelles structures de données rares et de nouvelles techniques afin d'exploiter efficacement le parallélisme multicœur et les unités de vecteur court (dont le dernier n'a pas été exploité par des bibliothèques de matrices creuses à la fine pointe de la technologie) pour les noyaux de calcul intensif récurrents dans les simulations EM, tels que les multiplications matrice-vecteur rares (SMVM) et des algorithmes à gradient conjugué (CG). Des performances d'accélérations jusqu'à 14 fois supérieures sont démontrées pour le noyau accéléré par SMVM et jusqu'à 5,8 fois supérieures pour le noyau CG en utilisant les méthodes proposées par rapport aux approches conventionnelles pour deux architectures multicœurs différentes. Enfin, une nouvelle méthode pour résoudre la FÉM pour le traitement parallèle est présentée et une implantation optimisée est réalisée sur deux générations d'accélérateurs de GPU NVIDIA (multicœur) avec des augmentations de performances allant jusqu'à 27,53 fois par rapport aux résultats du CPU optimisé par compilateur.
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29

Meng, Lingling, and 孟玲玲. "Computational electromagnetics methods for IC modeling." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2013. http://hdl.handle.net/10722/195993.

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Two kinds of computational electromagnetics (CEM) methodology are discussed for the challenges in integrated circuit (IC) and printed circuit board (PCB) design. One is an extension of Cagniard-de Hoop method that provides analytic time-domain expressions for the field constituents, making up some drawbacks of numerical techniques that would lose power in super-high frequency simulation or extreme fine structure. A modeling of line-source excited by electromagnetic pulse is analyzed for a thin sheet with high-contrast dielectric and conductive properties. The response of reflection and transmission to the power exponential pulse and the power exponential monocycle pulse are studied using this newly proposed method consequently as a benchmark for practical design. The other method focuses on improving the broadband accuracy of the mixed-form fast multipole algorithm (MF-FMA) by applying rotation techniques. Coordinate system rotation with rotation matrix and pseudo-spectral projection rotation based on fast Fourier transform (FFT) are discussed. Through rotation, translation matrices become very sparse, which enables us to save storage as well as the CPU time. Either of them has certain advantages depending on the number of harmonics used. Hence, increasing the number of multipoles in the low frequency regime to shift up the transition region of MF-FMA can be feasible to improve the overall accuracy significantly. Numerical results of inter connector and sphere with large number of unknowns are given to certify the effectiveness of rotation methods.
published_or_final_version
Electrical and Electronic Engineering
Master
Master of Philosophy
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30

Jin, Nanbo. "Particle swarm optimization in engineering electromagnetics." Diss., Restricted to subscribing institutions, 2007. http://proquest.umi.com/pqdweb?did=1481677311&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.

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31

Viana, Simone A. "Meshless methods applied to computational electromagnetics." Thesis, University of Bath, 2006. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.428380.

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32

Caglayan, Cosan. "Non-Contact Probes: A Novel Approach for On-Wafer Characterization of Millimeter-Wave and Sub-Millimeter-Wave Devices and Integrated Circuits." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1461163685.

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33

Mahaffey, Joshua Vincent. "A Direct Approach at Field Computation Using the FMM Framework." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1330913863.

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34

Hovsepian, Alexander. "Wideband, Scanning Array for Simultaneous Transmit and Receive (STAR)." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1501862593290103.

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35

Cule, Dino. "HPP lattice-gas automata for computational electromagnetics." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0012/MQ32912.pdf.

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36

Aronsson, Jonatan. "Novel tree-based algorithms for computational electromagnetics." IEEE, 2009. http://hdl.handle.net/1993/22086.

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Tree-based methods have wide applications for solving large-scale problems in electromagnetics, astrophysics, quantum chemistry, fluid mechanics, acoustics, and many more areas. This thesis focuses on their applicability for solving large-scale problems in electromagnetics. The Barnes-Hut (BH) algorithm and the Fast Multipole Method (FMM) are introduced along with a survey of important previous work. The required theory for applying those methods to problems in electromagnetics is presented with particular emphasis on the capacitance extraction problem and broadband full-wave scattering. A novel single source approximation is introduced for approximating clusters of electrostatic sources in multi-layered media. The approximation is derived by matching the spectra of the field in the vicinity of the stationary phase point. Combined with the BH algorithm, a new algorithm is shown to be an efficient method for evaluating electrostatic fields in multilayered media. Specifically, the new BH algorithm is well suited for fast capacitance extraction. The BH algorithm is also adapted to the scalar Helmholtz kernel by using the same methodology to derive an accurate single source approximation. The result is a fast algorithm that is suitable for accelerating the solution of the Electric Field Integral Equation (EFIE) for electrically small structures. Finally, a new version of FMM is presented that is stable and efficient from the low frequency regime to mid-range frequencies. By applying analytical derivatives to the field expansions at the observation points, the proposed method can rapidly evaluate vectorial kernels that arise in the FMM-accelerated solution of EFIE, the Magnetic Field Integral Equation (MFIE), and the Combined Field Integral Equation (CFIE).
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37

Knaak, Allison. "3D synthetic aperture for controlled-source electromagnetics." Thesis, Colorado School of Mines, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=3682006.

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Locating hydrocarbon reservoirs has become more challenging with smaller, deeper or shallower targets in complicated environments. Controlled-source electromagnetics (CSEM), is a geophysical electromagnetic method used to detect and derisk hydrocarbon reservoirs in marine settings, but it is limited by the size of the target, low-spatial resolution, and depth of the reservoir. To reduce the impact of complicated settings and improve the detecting capabilities of CSEM, I apply synthetic aperture to CSEM responses, which virtually increases the length and width of the CSEM source by combining the responses from multiple individual sources. Applying a weight to each source steers or focuses the synthetic aperture source array in the inline and crossline directions. To evaluate the benefits of a 2D source distribution, I test steered synthetic aperture on 3D diffusive fields and view the changes with a new visualization technique. Then I apply 2D steered synthetic aperture to 3D noisy synthetic CSEM fields, which increases the detectability of the reservoir significantly. With more general weighting, I develop an optimization method to find the optimal weights for synthetic aperture arrays that adapts to the information in the CSEM data. The application of optimally weighted synthetic aperture to noisy, simulated electromagnetic fields reduces the presence of noise, increases detectability, and better defines the lateral extent of the target. I then modify the optimization method to include a term that minimizes the variance of random, independent noise. With the application of the modified optimization method, the weighted synthetic aperture responses amplifies the anomaly from the reservoir, lowers the noise floor, and reduces noise streaks in noisy CSEM responses from sources offset kilometers from the receivers. Even with changes to the location of the reservoir and perturbations to the physical properties, synthetic aperture is still able to highlight targets correctly, which allows use of the method in locations where the subsurface models are built from only estimates. In addition to the technical work in this thesis, I explore the interface between science, government, and society by examining the controversy over hydraulic fracturing and by suggesting a process to aid the debate and possibly other future controversies.

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38

ECHEVERRI, BAUTISTA MARIO ALBERTO. "Fast solvers for integral equations in electromagnetics." Doctoral thesis, Politecnico di Torino, 2016. http://hdl.handle.net/11583/2643088.

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The purpose of this thesis is the advancement of numerical techniques in computational electromagnetics (CEM), specifically in the area of integral equation formulations in the frequency domain. The research has been focused on the solution of multi-scale, realistic, 3D surface problems using the Method of Moments (MoM). Several state of the art (e.g. with computational costs lower than N2, with N the number of unknowns in the problem) solutions to well-known issues are proposed. The research addresses two important branches in CEM: compression techniques and convergence improvement for iterative solutions. In the compression techniques area, the objective were the so called kernel independent schemes, which work directly on matrix entries (e.g. MoM matrix elements) rather than modifying the computation of these; this kind of schemes is applicable to a broad span of problems (with different kernels) without substantial modifications. The convergence acceleration of iterative solutions was tackled from the low frequency stabilization of kernel independent solvers to a new Domain Decomposition scheme for intermediate and high frequencies.
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39

Viani, Federico. "SVM-based Strategies as applied to Electromagnetics." Doctoral thesis, Università degli studi di Trento, 2010. https://hdl.handle.net/11572/368063.

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In the framework of the electromagnetic approaches based on learning-by-example (LBE) techniques, this thesis focuses on the development of a strategy for the solution of complex problems by means of support vector machine (SVM). The proposed instance-based classification method compared to more traditional optimization techniques solves the arising quadratic optimization problem with constraints in a simple and reliable way leveraging on the statistical learning theory which enables the design of optimal classifiers with a solid theoretical framework. A set of input/output relations representing the training dataset permits to avoid the a-priori knowledge about the system. By exploiting the generalization capabilities, the robustness against noise and the real-time performance, this technique has been proven to be suitable for more than one real-world application. The investigated problems are addressed by integrating the measured electromagnetic field with a suitably defined classifier that is aimed at defining a real-time reconstruction of the observed domain. For each application field a set of numerical results have been reported in order to assess the effectiveness and flexibility of the proposed approach. The real-time capabilities as well as the feasibility when dealing with real data have been also verified by means of an experimental setup for the passive tracking of non-cooperative targets moving throughout the investigated area.
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Viani, Federico. "SVM-based Strategies as applied to Electromagnetics." Doctoral thesis, University of Trento, 2010. http://eprints-phd.biblio.unitn.it/578/1/Ph.D.Thesis.VIANI-December.2010.pdf.

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In the framework of the electromagnetic approaches based on learning-by-example (LBE) techniques, this thesis focuses on the development of a strategy for the solution of complex problems by means of support vector machine (SVM). The proposed instance-based classification method compared to more traditional optimization techniques solves the arising quadratic optimization problem with constraints in a simple and reliable way leveraging on the statistical learning theory which enables the design of optimal classifiers with a solid theoretical framework. A set of input/output relations representing the training dataset permits to avoid the a-priori knowledge about the system. By exploiting the generalization capabilities, the robustness against noise and the real-time performance, this technique has been proven to be suitable for more than one real-world application. The investigated problems are addressed by integrating the measured electromagnetic field with a suitably defined classifier that is aimed at defining a real-time reconstruction of the observed domain. For each application field a set of numerical results have been reported in order to assess the effectiveness and flexibility of the proposed approach. The real-time capabilities as well as the feasibility when dealing with real data have been also verified by means of an experimental setup for the passive tracking of non-cooperative targets moving throughout the investigated area.
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41

Sainath, Kamalesh K. "Robust Numerical Electromagnetic Eigenfunction Expansion Algorithms." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1480340627500682.

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42

Tchorowski, Leo A. "Sparse-Constrained Equivalent Element Distribution Method to Represent Measured Antenna Data in Numerical Electromagnetics Codes." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1582877220383629.

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43

Young, Andre. "Mesh termination schemes for the finite element method in electromagnetics." Thesis, Stellenbosch : Stellenbosch University, 2007. http://hdl.handle.net/10019.1/2831.

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Thesis (MScEng (Electrical and Electronic Engineering))--Stellenbosch University, 2007.
The finite element method is a very efficient numerical tool to solve geometrically complex problems in electromagnetics. Traditionally the method is applied to bounded domain problems, but it can also be forged to solve unbounded domain problems using one of various mesh termination schemes. A scalar finite element solution to a typical unbounded two-dimensional problem is presented and the need for a proper mesh termination scheme is motivated. Different such schemes, specifically absorbing boundary conditions, the finite element boundary integral method and infinite elements, are formulated and implemented. These schemes are directly compared using different criteria, especially solution accuracy and computational efficiency. A vector finite element solution in three dimensions is also discussed and a new type of infinite element compatible with tetrahedral vector finite elements is presented. The performance of this infinite element is compared to that of a first order absorbing boundary condition.
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44

Lu, Jiaqing. "Numerical Modeling and Computation of Radio Frequency Devices." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1543457620064355.

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45

Hellen, Martin Keith. "Near-field and far-field modelling of antennas above half-spaces." Thesis, University of Bristol, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.288290.

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46

Abboudy, Sayed Abboudy Ibrahim Omran. "DC and AC conduction in n-InP and n-InSb in magnetic fields at very low temperatures." Thesis, Royal Holloway, University of London, 1988. http://repository.royalholloway.ac.uk/items/d7aaa129-be57-4fef-b74a-a58f5c697f5e/1/.

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Measurements of the longitudinal and transverse direct current (d.c.) magnetoresistance of n-type InP samples (carrier density from and the alternating current (a.c.) conductivity of n-type InSb samples (carrier density from have been made at temperatures T down to 0.04 K and in magnetic fields H up to 70 kG. For H=0, the InP samples were nonmetallic. At low temperatures, the conductivity is due to nearest neighbour hopping (NNH) which is followed by variable range hopping (VRH) at lower T as described by the first, and second terms in the expression. In the NNH regime, it is necessary to plot In (p/T) against T1 and this yields values of the activation energy much larger than the traditional In p versus T-1 plots In the VRH regime, Mott's law (x = 1/4) is obeyed. Values of To obtained by considering the temperature dependence of the pre-exponential factor are found to be much higher than if the temperature dependence of this factor is ignored. Good agreement between the theory and experiment is achieved in both NNH and VRH regions if an enhanced dielectric constant is used. Magnetoresistance measurements in both the NNH and VRH regimes are analysed using the theories of Shklovskii and Efros (1984) and reasonable agreement is obtained. The anisotropy of the magnetoresistance in the NNH agrees closely with the expected H2 dependence. In the VRH, In(p(H)/p(0)) varies as T-3/4 and H2 as expected for hopping with a constant density of states at the Fermi level. The InSb samples are metallic-like in zero magnetic field. High magnetic fields are applied to shrink the donor wavefunctions (to induce the metal-insulator transition) and to locate the samples on the insulator side where the measurements are carried out. The d.c. resistivity was measured and at low temperatures was of a VRH type with 1/4 x 1/2, and T0 being magnetic field dependent. Reasonable agreement with the theory is found at high fields. The real and imaginary parts of the a.c. conductivity were measured in the frequency range of 110-105 Hz. The real part of conductivity was found to vary as where s is approaching 1 at low temperatures and high fields but decreasing as T increases. At the lowest temperatures was independent of T but at higher T the temperature dependence is stronger than the linear dependence predicted by the simple pair approximation theory. Data are interpreted in terms of multiple hopping of electrons which becomes important at high temperatures and/or low frequencies. The scaling formula; has been applied to discuss the results for the real part of the conductivity, where and are normalized values and f is a universal function obtained by Summerfield (1985). The scaling parameter -log10A is found to be 3.0 +/- 0.2.The relative dielectric constant, due to donors, calculated from the capacitive part was found to be a decreasing function as the frequency is increased and/or the temperature is lowered. At very low temperatures, depending on the magnetic field, however, a temperature-independent, but frequency-dependent behaviour is observed. The lowest temperature value of the dielectric constant was found to diverge as the magnetic field is reduced towards the metal-insulator threshold value.
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47

Li, Liangyu. "Experimental Investigation of Integrated Tunable Passive Microwave Devices." University of Dayton / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1607337154651345.

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48

Sefi, Sandy. "Pay tracing tools for high frequency electromagnetics simulations." Licentiate thesis, KTH, Numerical Analysis and Computer Science, NADA, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-1596.

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Over the past 20 years, the development in ComputationalElectromagnetics has produced a vast choice of methods based onthe large number of existing mathematical formulations of theMaxwell equations. None of them dominate over the others,instead they complement each other and the choice of methoddepends on the frequency range of the electromagnetic waves.This work is focused on the most popular method in the highfrequency scenario, namely the Geometrical Theory ofDiffraction (GTD). The main advantage of GTD is the ability topredict the electromagnetic field asymptotically in the limitof vanishing wavelength, when other methods, such as the Methodof Moments, become computationally too expensive.

The low cost of GTD is due to both the fact that there is noruntime penalty in increasing the frequency and that the raytracing, which GTD is based on, is a geometrical technique. Thecomplexity is then no longer dependent on electrical size ofthe problem but instead on geometrical sub problems which aremanageable. For industrial applications the geometricalstructures, with which the rays interact, are modelled bytrimmed Non-Uniform Rational B-Spline (NURBS) surfaces, themost recent standard used to represent complex free-formgeometries.

Due to the introduction of NURBS, the geometrical subproblems tend to be mathematically and numerically cumbersome,but they can be highly simplified by proper Object Orientedprogramming techniques. This allowed us to create a flexiblesoftware package, MIRA: Modular Implementation of Ray Tracingfor Antenna Applications, with an architecture that separatesmathematical algorithms from their implementation details andmodelling. In addition, its design supports hybridisationtechniques in combination with other methods such as Method ofMoment (MoM) and Physical Optics (PO).

In a first hybrid application, a triangle-based PO solveruses the shadowing information calculated with the ray tracerpart of MIRA. The occlusion is performed between triangles andtheir facing NURBS surfaces rather than between their facingtriangles, thus reducing the complexity. Then the shadowinginformation is used in an iterative MoM-PO process in order tocover higher frequencies, where the contribution of theshadowing effects, in the hybrid formulation, is believed to bemore significant.

Thesis presented at the Royal Institute of Technology ofStockholm in 2003, for the degree of Licentiate in ScientificComputing.

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Wang, Honghou. "Practical adaptive numerical integration for finite element electromagnetics." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0030/MQ64253.pdf.

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Hagdahl, Stefan. "Hybrid Methods for Computational Electromagnetics in Frequency Domain." Doctoral thesis, Stockholm : Numerisk analys och datalogi (NADA) ; Tekniska högsk, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-400.

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