Dissertations / Theses on the topic 'MOMENTS METHOD'
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Shin, Changmock. "Entropy Based Moment Selection in Generalized Method of Moments." NCSU, 2005. http://www.lib.ncsu.edu/theses/available/etd-06072005-112026/.
Full textLai, Yanzhao. "Generalized method of moments exponential distribution family." View electronic thesis (PDF), 2009. http://dl.uncw.edu/etd/2009-2/laiy/yanzhaolai.pdf.
Full textVirk, Bikram. "Implementing method of moments on a GPGPU using Nvidia CUDA." Thesis, Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/33980.
Full textLi, Tao. "3D Capacitance Extraction With the Method of Moments." Digital WPI, 2010. https://digitalcommons.wpi.edu/etd-theses/86.
Full textLiang, Yitian. "Generalized method of moments : theoretical, econometric and simulation studies." Thesis, University of British Columbia, 2011. http://hdl.handle.net/2429/36866.
Full textMcLeod, James William. "An investigation of the CDF-based method of moments." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0009/MQ34121.pdf.
Full textStrydom, Willem Jacobus. "Recovery based error estimation for the Method of Moments." Thesis, Stellenbosch : Stellenbosch University, 2015. http://hdl.handle.net/10019.1/96881.
Full textENGLISH ABSTRACT: The Method of Moments (MoM) is routinely used for the numerical solution of electromagnetic surface integral equations. Solution errors are inherent to any numerical computational method, and error estimators can be effectively employed to reduce and control these errors. In this thesis, gradient recovery techniques of the Finite Element Method (FEM) are formulated within the MoM context, in order to recover a higher-order charge of a Rao-Wilton-Glisson (RWG) MoM solution. Furthermore, a new recovery procedure, based specifically on the properties of the RWG basis functions, is introduced by the author. These recovered charge distributions are used for a posteriori error estimation of the charge. It was found that the newly proposed charge recovery method has the highest accuracy of the considered recovery methods, and is the most suited for applications within recovery based error estimation. In addition to charge recovery, the possibility of recovery procedures for the MoM solution current are also investigated. A technique is explored whereby a recovered charge is used to find a higher-order divergent current representation. Two newly developed methods for the subsequent recovery of the solenoidal current component, as contained in the RWG solution current, are also introduced by the author. A posteriori error estimation of the MoM current is accomplished through the use of the recovered current distributions. A mixed second-order recovered current, based on a vector recovery procedure, was found to produce the most accurate results. The error estimation techniques developed in this thesis could be incorporated into an adaptive solver scheme to optimise the solution accuracy relative to the computational cost.
AFRIKAANSE OPSOMMING: Die Moment Metode (MoM) vind algemene toepassing in die numeriese oplossing van elektromagnetiese oppervlak integraalvergelykings. Numeriese foute is inherent tot die prosedure: foutberamingstegnieke is dus nodig om die betrokke foute te analiseer en te reduseer. Gradiënt verhalingstegnieke van die Eindige Element Metode word in hierdie tesis in die MoM konteks geformuleer. Hierdie tegnieke word ingespan om die oppervlaklading van 'n Rao-Wilton-Glisson (RWG) MoM oplossing na 'n verbeterde hoër-orde voorstelling te neem. Verder is 'n nuwe lading verhalingstegniek deur die outeur voorgestel wat spesifiek op die eienskappe van die RWG basis funksies gebaseer is. Die verhaalde ladingsverspreidings is geïmplementeer in a posteriori fout beraming van die lading. Die nuut voorgestelde tegniek het die akkuraatste resultate gelewer, uit die groep verhalingstegnieke wat ondersoek is. Addisioneel tot ladingsverhaling, is die moontlikheid van MoM-stroom verhalingstegnieke ook ondersoek. 'n Metode vir die verhaling van 'n hoër-orde divergente stroom komponent, gebaseer op die verhaalde lading, is geïmplementeer. Verder is twee nuwe metodes vir die verhaling van die solenodiale komponent van die RWG stroom deur die outeur voorgestel. A posteriori foutberaming van die MoM-stroom is met behulp van die verhaalde stroom verspreidings gerealiseer, en daar is gevind dat 'n gemengde tweede-orde verhaalde stroom, gebaseer op 'n vektor metode, die beste resultate lewer. Die foutberamingstegnieke wat in hierdie tesis ondersoek is, kan in 'n aanpasbare skema opgeneem word om die akkuraatheid van 'n numeriese oplossing, relatief tot die berekeningskoste, te optimeer.
Arvas, Serhend. "A method of moments analysis of microstructured optical fibers." Related electronic resource: Current Research at SU : database of SU dissertations, recent titles available full text, 2009. http://wwwlib.umi.com/cr/syr/main.
Full textCUNHA, JOAO MARCO BRAGA DA. "ESTIMATING ARTIFICIAL NEURAL NETWORKS WITH GENERALIZED METHOD OF MOMENTS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2015. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=26922@1.
Full textCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
PROGRAMA DE EXCELENCIA ACADEMICA
As Redes Neurais Artificiais (RNAs) começaram a ser desenvolvidas nos anos 1940. Porém, foi a partir dos anos 1980, com a popularização e o aumento de capacidade dos computadores, que as RNAs passaram a ter grande relevância. Também nos anos 1980, houve dois outros acontecimentos acadêmicos relacionados ao presente trabalho: (i) um grande crescimento do interesse de econometristas por modelos não lineares, que culminou nas abordagens econométricas para RNAs, no final desta década; e (ii) a introdução do Método Generalizado dos Momentos (MGM) para estimação de parâmetros, em 1982. Nas abordagens econométricas de RNAs, sempre predominou a estimação por Quasi Máxima Verossimilhança (QMV). Apesar de possuir boas propriedades assintóticas, a QMV é muito suscetível a um problema nas estimações em amostra finita, conhecido como sobreajuste. O presente trabalho estende o estado da arte em abordagens econométricas de RNAs, apresentando uma proposta alternativa à estimação por QMV que preserva as suas boas propriedades assintóticas e é menos suscetível ao sobreajuste. A proposta utiliza a estimação pelo MGM. Como subproduto, a estimação pelo MGM possibilita a utilização do chamado Teste J para verifificar a existência de não linearidade negligenciada. Os estudos de Monte Carlo realizados indicaram que as estimações pelo MGM são mais precisas que as geradas pela QMV em situações com alto ruído, especialmente em pequenas amostras. Este resultado é compatível com a hipótese de que o MGM é menos suscetível ao sobreajuste. Experimentos de previsão de taxas de câmbio reforçaram estes resultados. Um segundo estudo de Monte Carlo apontou boas propriedades em amostra finita para o Teste J aplicado à não linearidade negligenciada, comparado a um teste de referência amplamente conhecido e utilizado. No geral, os resultados apontaram que a estimação pelo MGM é uma alternativa recomendável, em especial no caso de dados com alto nível de ruído.
Artificial Neural Networks (ANN) started being developed in the decade of 1940. However, it was during the 1980 s that the ANNs became relevant, pushed by the popularization and increasing power of computers. Also in the 1980 s, there were two other two other academic events closely related to the present work: (i) a large increase of interest in nonlinear models from econometricians, culminating in the econometric approaches for ANN by the end of that decade; and (ii) the introduction of the Generalized Method of Moments (GMM) for parameter estimation in 1982. In econometric approaches for ANNs, the estimation by Quasi Maximum Likelihood (QML) always prevailed. Despite its good asymptotic properties, QML is very prone to an issue in finite sample estimations, known as overfiting. This thesis expands the state of the art in econometric approaches for ANNs by presenting an alternative to QML estimation that keeps its good asymptotic properties and has reduced leaning to overfiting. The presented approach relies on GMM estimation. As a byproduct, GMM estimation allows the use of the so-called J Test to verify the existence of neglected nonlinearity. The performed Monte Carlo studies indicate that the estimates from GMM are more accurate than those generated by QML in situations with high noise, especially in small samples. This result supports the hypothesis that GMM is susceptible to overfiting. Exchange rate forecasting experiments reinforced these findings. A second Monte Carlo study revealed satisfactory finite sample properties of the J Test applied to the neglected nonlinearity, compared with a reference test widely known and used. Overall, the results indicated that the estimation by GMM is a better alternative, especially for data with high noise level.
Kluskens, Michael S. "Method of moments analysis of scattering by chiral media /." The Ohio State University, 1991. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487688507504775.
Full textKhlifi, Rachid. "Hybrid space discretizing method -method of moments for numerical modeling of transient interference." kostenfrei, 2007. http://mediatum2.ub.tum.de/doc/620327/document.pdf.
Full textChester, David A. III. "Using the method of moments and Robin Hood method to solve electromagnetic scattering problems." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/78502.
Full textCataloged from PDF version of thesis.
Includes bibliographical references (p. 67-69).
This thesis project was to write a program in C++ that solves electromagnetic scattering problems for arbitrarily shaped scatterers. This was implemented by using a surface integral formulation of Maxwell's equations, which discretizes the surface of the scatterer into thousands of triangles. The method of moments (MoM) was applied, which calculates the Green's functions between each triangle element. A matrix equation is obtained and solved using the Robin Hood (RH) method. The solution to this equation gives the scattered electromangetic field. This program is first tested on a sphere, which is compared to the analytic solution known as Mie scattering. Once these results are confirmed, the program can be used for the KATRIN experiment to ensure that no Penning traps occur in the electron spectrometer.
by David A. Chester.
S.B.
Liu, Jianguo, and 劉建國. "Fast computation of moments with applications to transforms." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1996. http://hub.hku.hk/bib/B31235086.
Full textLiu, Jianguo. "Fast computation of moments with applications to transforms /." Hong Kong : University of Hong Kong, 1996. http://sunzi.lib.hku.hk/hkuto/record.jsp?B17664986.
Full textTham, C. Y. "Electromagnetic transient analysis using the frequency domain method of moments." Thesis, Swansea University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.639176.
Full textVered, Nissan. "Method of moments analysis of displaced-axis dual reflector antennas." Thesis, Monterey, Calif. : Naval Postgraduate School, 1992. http://handle.dtic.mil/100.2/ADA247970.
Full textZargar, Amin. "Sequence modeling of raft polymerizations with the method of moments." College Park, Md.: University of Maryland, 2008. http://hdl.handle.net/1903/8782.
Full textThesis research directed by: Dept. of Chemical and Biomolecular Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
SILVA, DENISE FREITAS. "APPLICATION METHOD OF MOMENTS FOR THE ANALYSIS OF CONICAL ANTENNAS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1999. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=7300@1.
Full textNeste estudo faz-se uma análise do desempenho de antenas cônicas compactas para operar em largas bandas de freqüência. Esta análise será feita observando o comportamento da impedância da antena. Serão, primeiramente, consideradas as estruturas convencionais formadas por cones e cones sobrepostos próximos a um plano condutor. Posteriormente, será considerada uma estrutura cônica onde o arredondamento das bordas resulta em um comportamento mais uniforme para a impedância de entrada com variações da freqüência, conferindo um aumento na banda para esta configuração.
The discone antenna is well known as an easy to build multioctave broadband antenna with a omnidirectional radiation pattern in the H-plane, It comprises a plane conductive disc element spaced close to and axially aligned with a conductive cone element. For applications in the UHF and microwave ranges, high performance antennas have been designed to operate from 0.5 to 5 GHz with a VSWR of about 3.5:1 or less. If the length is finite, the impedance still strongly dependent on apex angle as long as the cone is longer than about quarter of wavelength and the apex angle is relatively larger. A problem that is experienced with these antenna designs is the relatively large size required to operate at the low frequencies. In applications where utilization of this antenna. In this work, the analysis and design of these antenna is obtained by employing a rigorous formulation of the electromagnetic scattering problem. As a design tool, we employ Method of Moments for the analysis of rotationally symmetric structures excited by TEM mode. To properly account the variations in driven-point impedance with frequency, the coaxial waveguide used to feed the antenna is also included in the analysis. The excitation is simulated by a distribution of equivalent electric and magnetic currents placed inside the coaxial cable, over a cross-section plane. These currents are defined such that only excite the mode TEM towards the cable-antenna junction. These numerical tool is employed in the shaping the metallic surfaces involved in the discone-type antennas in order to obtain more compact structures. Simple solutions can be easily obtained making the center fed cone and the disc element with radially outer edge portions rolled backwardly and away from each other to form donut-shaped configurations. The ruled edges not only reduce the diameter of the antenna but also permit the current to flow around them smoothly and without reflections that degrade the VSWR at low end of the frequency band.
Koci, Eni. "The stochastic discount factor and the generalized method of moments." Digital WPI, 2006. https://digitalcommons.wpi.edu/etd-theses/873.
Full textMasucci, Antonia Maria. "Moments method for random matrices with applications to wireless communication." Thesis, Supélec, 2011. http://www.theses.fr/2011SUPL0011/document.
Full textIn this thesis, we focus on the analysis of the moments method, showing its importance in the application of random matrices to wireless communication. This study is conducted in the free probability framework. The concept of free convolution/deconvolution can be used to predict the spectrum of sums or products of random matrices which are asymptotically free. In this framework, we show that the moments method is very appealing and powerful in order to derive the moments/asymptotic moments for cases when the property of asymptotic freeness does not hold. In particular, we focus on Gaussian random matrices with finite dimensions and structured matrices as Vandermonde matrices. We derive the explicit series expansion of the eigenvalue distribution of various models, as noncentral Wishart distributions, as well as correlated zero mean Wishart distributions. We describe an inference framework so flexible that it is possible to apply it for repeated combinations of random ma- trices. The results that we present are implemented generating subsets, permutations, and equivalence relations. We developped a Matlab routine code in order to perform convolution or deconvolution numerically in terms of a set of input moments. We apply this inference framework to the study of cognitive networks, as well as to the study of wireless networks with high mobility. We analyze the asymptotic moments of random Vandermonde matrices with entries on the unit circle. We use them and polynomial expansion detectors in order to design a low complexity linear MMSE decoder to recover the signal transmitted by mobile users to a base station or two base stations, represented by uniform linear arrays
Killian, Tyler Norton Rao S. M. "Fast solution of large-body problems using domain decomposition and null-field generation in the method of moments." Auburn, Ala, 2009. http://hdl.handle.net/10415/1881.
Full textOrdonez, Manuel V. "Method of moments analysis of symmetric dual reflector antennas with feeds." Thesis, Monterey, California. Naval Postgraduate School, 1992. http://hdl.handle.net/10945/23953.
Full textNejmeldeen, Ziad H. (Ziad Hassan) 1976. "General method of moments bias and specification tests for quantile regression." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/17628.
Full textIncludes bibliographical references (leaves 74-75).
Chapter 1: This chapter looks at a dynamic panel data model with fixed effects. Estimating the model with GMM is consistent but suffers from small sample bias. We apply Helmert's transformation to the model, assume that error terms and nuisance parameters are homoskedastic and independent across observations and of one another, and utilize the GMM bias calculation of Newey & Smith (2001). This leads to a closed form expression for the GMM bias applied to AR(1) model. Chapter 2: This chapter develops specification tests for quantile regression under various data types. We consider what happens to the quantile regression estimator under local and global misspecification and design specification tests that handle a wide range of data types. We consider how to carry out such tests in practice and present Monte Carlo results to show the effectiveness of such tests. Chapter 3: Through a Taylor expansion, We compute the bias of a general GMM model where the weighting matrix A of the moment conditions g(z, β) is left unspecified, except for some general conditions. Our bias results are compared to those of Newey and West (2003). An important case of GMM estimation with a general weighting matrix A is when A is a function of a vector of parameters with fixed dimension. Arellano's IVE estimator is an example of this type of estimator--we consider the bias properties of Arellano's IVE estimator in the AR(1) setting and compare them to our results from Chapter 1.
by Ziad H. Nejmeldeen.
Ph.D.
Ismatullah. "Analysis of space-borne antennas by higher-order method of moments and inverse equivalent current methods." kostenfrei, 2010. https://mediatum2.ub.tum.de/node?id=977261.
Full textMahachoklertwattana, Pongsak. "A fast full-wave solver for the analysis of large planar finite periodic antenna arrays in grounded multilayered media." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1187152961.
Full textChen, Houfei. "Fast electromagnetic simulation for interconnects on high speed circuits /." Thesis, Connect to this title online; UW restricted, 2002. http://hdl.handle.net/1773/5940.
Full textPfeiffer, Robert. "CONSTRAINED DIVERGENCE-CONFORMING BASIS FUNCTIONS FOR METHOD OF MOMENTS DISCRETIZATIONS IN ELECTROMAGNETICS." UKnowledge, 2015. http://uknowledge.uky.edu/ece_etds/79.
Full textMcDonald, Paul. "Public bodies, private moments : method acting and American cinema in the 1950s." Thesis, University of Warwick, 1997. http://wrap.warwick.ac.uk/34659/.
Full textPRALON, MARIANA GUIMARAES. "APPLICATION OF THE METHOD OF MOMENTS IN THE ANALYSIS OF MICROSTRIP ANTENNAS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2012. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=20556@1.
Full textINSTITUTO MILITAR DE ENGENHARIA
CENTRO TECNOLÓGICO DO EXÉRCITO
Neste trabalho, o Método dos Momentos é aplicado na análise de antenas microfita excitadas por cabo coaxial, utilizando Funções de Green no modelamento dos campos no interior da camada de dielétrico, o que permite considerar as ondas de superfície excitadas no substrato. Para obter a impedância de entrada da antena microfita, foi implementado um algoritmo numérico para a solução do problema. Neste trabalho, atenção especial é dada à análise de singularidades e ao comportamento assintótico dos integrandos envolvidos na solução numérica do problema. A validação do algoritmo é feita através da comparação com resultados apresentados em referências. Os resultados fornecidos pelo Método dos Momentos são comparados com os obtidos na aplicação de outros métodos na solução do problema. Para esta comparação, são utilizados dois programas comerciais de simulação eletromagnética, o Ansoft HFSS e o CST. São feitas simulações com a variação dos parâmetros de entrada do problema, com o objetivo de assegurar a convergência dos resultados e permitir a comparação com os resultados obtidos pelo Método dos Momentos. São apresentadas diferenças entre os resultados obtidos pelos diversos métodos e analisadas as possíveis causas das discrepâncias.
In the present work, the Method of Moments is applied to the analysis of probe fed antennas. The approach uses Green Functions to model the fields within the dielectric layer, which allows to take into account the surface waves excited in the substrate. A numerical algorithm was implemented in order to obtain the microstrip antenna input impedance. The latter is then verified through the comparison with results presented in references. Special attention is given to the analysis of singularities and to the asymptotic behavior of the integrands involved in the numerical solution. A comparison is drawn between the results obtained with the Method of Moments and those obtained with other methods by employing two electromagnetic simulation commercial softwares, Ansoft HFSS and CST. Simulations with different input parameters are performed in order to ensure convergence of the results and allow comparison with results obtained by the Method of Moments. The differences among the results obtained by the several methods addressed in the analysis are presented and the potential causes of them are analyzed.
Peters, Matthew E. "Method of moments analysis of artificial media composed of dielectric wire objects." The Ohio State University, 1994. http://rave.ohiolink.edu/etdc/view?acc_num=osu1300290789.
Full textMenshikova, M. "Uncertainty estimation using the moments method facilitated by automatic differentiation in Matlab." Thesis, Department of Engineering Systems and Management, 2010. http://hdl.handle.net/1826/4328.
Full textObi, Aghogho A. "A Method Of Moments Approach for the Design Of RF Coils for MRI." Digital WPI, 2008. https://digitalcommons.wpi.edu/etd-dissertations/284.
Full textLemdiasov, Rostislav A. "A general purpose computational approach to the design of gradient coils for arbitrary geometries." Worcester, Mass. : Worcester Polytechnic Institute, 2004. http://www.wpi.edu/Pubs/ETD/Available/etd-09214-155502/.
Full textSimmel, Martin. "Numerical solution of the stochastic collection equation: comparison of the linear discrete method and the method of moments." Wissenschaftliche Mitteilungen des Leipziger Instituts für Meteorologie ; 17 = Meteorologische Arbeiten aus Leipzig ; 5 (2000), S. 26-34, 2001. https://ul.qucosa.de/id/qucosa%3A15197.
Full textDie lineare diskrete Methode (LDM; SIMMEL 2000; SIMMEL ET AL. 2000) wird dazu benutzt, die Gleichung für stochastisches Einsammeln (stochastic collection equation, SCE) numerisch zu lösen. Dabei werden Vergleiche gezogen zur Methode der Momente (Method of Moments, MOM; TzIVION ET AL. 1999), die als Referenz für numerische Lösungen der SCE vorgeschlagen wurde. Simulationsrechnungen für beide Methoden werden für die Koaleszenzfunktion nach GoLOVIN (für die eine analytische Lösung existiert) und die hydrodynamische Koaleszenzfunktion nach LONG (1974) wie sie von TZIVION ET AL. (1999) verwendet wird, gezeigt. Verschiedene Klassenauflösungen werden untersucht und die Simulationszeiten verglichen. Zusätzlich werden LDM-Simulationen mit der hydrodynamischen Koaleszenzfunktion nach BÖHM (1992b) gezeigt. Die Ergebnisse für die Koaleszenzfunktion nach GoLOVIN zeigen, daß die LDM der analytischen Lösung etwas näher kommt als MOM. Für die Koaleszenzfunktion nach LONG sind die Ergebnisse von LDM und MOM mit niedriger Auflösung von ähnlicher Qualität verglichen mit der Referenzlösung. Für die Koaleszenzfunktion nach BÖHM wurden nur Simulationen mit der LDM durchgeführt, die eine gute Übereinstimmung der Ergebnisse mit niedriger und hoher Auflösung zeigen.
Ugur, Alper. "Computation of the resonant frequency of a dielectrometer by the method of moments." Related electronic resource: Current Research at SU : database of SU dissertations, recent titles available full text, 2005. http://wwwlib.umi.com/cr/syr/main.
Full textPant, Mohan Dev. "Simulating Univariate and Multivariate Burr Type III and Type XII Distributions Through the Method of L-Moments." OpenSIUC, 2011. https://opensiuc.lib.siu.edu/dissertations/401.
Full textZhuang, Wei. "A 3-d capacitance extraction algorithm based on kernel independent hierarchical method and geometric moments." Thesis, Texas A&M University, 2003. http://hdl.handle.net/1969.1/5794.
Full textImeci, Sehabeddin Taha. "Transmission through an arbitrarily shaped aperture in a conducting plane separating air and a chiral medium." Related electronic resource: Current Research at SU : database of SU dissertations, recent titles available, full text:, 2007. http://wwwlib.umi.com/cr/syr/main.
Full textCaswell, Eric D. "Analysis of a Helix Antenna Using a Moment Method Approach With Curved Basis and Testing Functions." Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/37001.
Full textMaster of Science
Seo, Seung Mo. "A fast IE-FFT algorighm for solving electromagnetic radiation and scattering problems." The Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=osu1149105460.
Full textKent, William J. "Plane wave scattering by thin linear dielectric-coated wires and dielectric strips : a moment method approach with physical basis functions /." The Ohio State University, 1985. http://rave.ohiolink.edu/etdc/view?acc_num=osu148726053195675.
Full textKulkarni, Shashank D. "Development and validation of a Method of Moments approach for modeling planar antenna structures." Worcester, Mass. : Worcester Polytechnic Institute, 2007. http://www.wpi.edu/Pubs/ETD/Available/etd-042007-151741/.
Full textKeywords: patch antennas; volume integral equation (VIE); method of moments (MoM); low order basis functions; convergence. Includes bibliographical references (leaves 169-186 ).
Laskay, Ünige A. "Dynamic collision induced dissociation : a novel fragmentation method in the quadrupole ion trap /." View abstract, 2009. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:3353544.
Full textGamage, Jagath Kumara Halpe. "Efficient Space Domaine Method of Moments for Large Arbitrary Scatterers in Planar Stratified Media." Doctoral thesis, Norwegian University of Science and Technology, Department of Electronics and Telecommunications, 2004. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-398.
Full textKeywords : Conjugate gradient fast Fourier transform (CG-FFT), Discrete complex image method (DCIM), Electric field integral equation (EFIE), Frequency selective surfaces (FSS), Generalized pencil-of-functions (GPOF), Green’s function (GF), Method of moments (MoM), Prony’s method (PM), Sommerfeld integral (SI), Two-dimensional generalized exponential integral (2D-GEI)
As the need for more frequency spectrum drives the design of antennas and other microwave components at higher frequencies, compact but electrically large microwave components are beginning to appear. Since a significant share of these components comprises scatterers etched on planar stratified layers, efficient tools analyzing and optimizing such structures are invaluable. The work carried out here is in fact a continuation of the research performed in the past at the Department of Electronics and Telecommunications at the Norwegian University of Science and Technology in Trondheim, Norway.
The conventional method of moments for analyzing and optimizing scatterers in stratified media is simple in formulation but computationally very intensive. Moreover, the computer memory usage of the software based on conventional MoM is high. Both these factors have so far limited the application of conventional MoM to electrically small and simpler stratified structures. Therefore, the present work focuses on introducing and implementing an improved space domain MoM for large radiating or scattering structures etched on planar stratified media. The space domain method of moments is selected due to its simplicity and potential for further improvements when compared with the spectral domain method of moments.
The major areas of space domain MoM such as finding spectral Green's functions, deriving spatial Green’s functions, matrix formulation and matrix inversion are addressed.
The existing methods are evaluated with respect to their pros and cons. In addition, in order to extract the scattering parameters a few simple de-embedding techniques are introduced. We have attempted to optimize each stage of the conventional space domain MoM such that it can handle electrically large scatterers in planar stratified media. Each method is discussed independently and proved to be performing well compared with the corresponding method applied in conventional space domain MoM. In deriving spectral Green’s functions, a novel formulation of transmission line theory is applied easing the analytical derivation and the software implementation significantly. A robust form of discrete complex image method (DCIM) is used in deriving spatial Green’s functions from the corresponding spectral Green’s functions. DCIM is an accurate and efficient way of evaluating Sommerfeld integrals without resorting to multi-dimensional numerical integration.
The accuracy and efficiency of DCIM are affirmed by applying it to simple scatterers. The outcome of DCIM is a sum of complex exponential functions. These are then used to calculate the impedance matrices of MoM. It is also shown that when using mixed potential integral formulation, the original four-dimensional numerical integration can be simplified to two-dimensional integration with no loss of accuracy, thus reducing the mathematical complexity during matrix filling phase. Nevertheless, some of the complex exponential functions can lead to two-dimensional singular integrals. These singular two- dimensional generalized exponential integrals(2D-GEI) are efficiently handled by generalizing an innovative numerical integration method, thus saving the processing time further. The last but most important operation of MoM, the matrix inversion is achieved by using an iterative algorithm known as conjugate gradient method. It is then combined with fast Fourier transform to exploit the space invariant property present in the impedance matrices of MoM. A new compact formulation of the matrices is also presented to facilitate the programing task. To our knowledge, this is the first time such formulation is presented explicitly. A brief chapter is reserved for de-embedding of scattering parameters from the surface current densities resulting from MoM.
In order to present the thesis as a collection of self-containing and independent chapters, results are included in each chapter whenever it is appropriate. These partial results confirm the accuracy and the efficiency of each method introduced in the corresponding chapter before we move on to the next. The conclusion on the overall method introduced in this work is that the space domain method of moments combined with the discrete complex image method and the conjugate gradient fast Fourier transform presents a very powerful tool for analyzing and optimizing large arbitrary stratified structures. However, to be competitive with commercial products based on either spectral domain method of moments or finite element methods, further improvements in its implementation and methodology are needed. Few improvements such as more efficient implementation of the entire method, inclusion of surface wave contribution in DCIM, integration of non-uniform basis and testing functions and need for better de-embedding techniques are already identified at the end of this work.
Finally we hope that this work clarifies some important issues relating to space domain method of moments when applied to large scatterers etched on planar stratified media and encourages the further research on this particular method.
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