Дисертації з теми "Finite Element Method Electromagnetics"
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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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Young, Andre. "Mesh termination schemes for the finite element method in electromagnetics." Thesis, Stellenbosch : Stellenbosch University, 2007. http://hdl.handle.net/10019.1/2831.
Повний текст джерелаАнотація:
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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Lu, Chuan. "Generalized finite element method for electromagnetic analysis." Diss., Connect to online resource - MSU authorized users, 2008.
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Thesis (Ph. D.)--Michigan State University. Electrical and Computer Engineering, 2008.Title from PDF t.p. (viewed on Apr. 8, 2009) Includes bibliographical references (p. 148-153). Also issued in print.
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Vardapetyan, Leon. "Hp-adaptive finite element method for electromagnetics with applications to waveguiding structures /." Digital version accessible at:, 1999. http://wwwlib.umi.com/cr/utexas/main.
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Marais, Neilen. "Higher order hierarchal curvilinear triangular vector elements for the finite element method in computational electromagnetics." Thesis, Stellenbosch : Stellenbosch University, 2003. http://hdl.handle.net/10019.1/53447.
Повний текст джерелаАнотація:
Thesis (MScEng)--Stellenbosch University, 2003.ENGLISH ABSTRACT: The Finite Element Method (FEM) as applied to Computational Electromagnetics (CEM), can be used to solve a large class of Electromagnetics problems with high accuracy, and good computational efficiency. Computational efficiency can be improved by using element basis functions of higher order. If, however, the chosen element type is not able to accurately discretise the computational domain, the converse might be true. This paper investigates the application of elements with curved sides, and higher order basis functions, to computational domains with curved boundaries. It is shown that these elements greatly improve the computational efficiency of the FEM applied to such domains, as compared to using elements with straight sides, and/or low order bases.
AFRIKAANSE OPSOMMING: Die Eindige Element Metode (EEM) kan breedvoerig op Numeriese Elektromagnetika toegepas word, met uitstekende akkuraatheid en 'n hoë doeltreffendheids vlak. Numeriese doeltreffendheid kan verbeter word deur van hoër orde element basisfunksies gebruik te maak. Indien die element egter nie die numeriese domein effektief kan diskretiseer nie, mag die omgekeerde geld. Hierdie tesis ondersoek die toepassing van elemente met geboë sye, en hoër orde basisfunksies, op numeriese domeine met geboë grense. Daar word getoon dat sulke elemente 'n noemenswaardinge verbetering in die numeriese doeltreffendheid van die EEM meebring, vergeleke met reguit- en/of laer-orde elemente.
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Marais, Neilen. "Efficient high-order time domain finite element methods in electromagnetics." Thesis, Stellenbosch : University of Stellenbosch, 2009. http://hdl.handle.net/10019.1/1499.
Повний текст джерелаАнотація:
Thesis (DEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2009.The Finite Element Method (FEM) as applied to Computational Electromagnetics (CEM), can beused to solve a large class of Electromagnetics problems with high accuracy and good computational efficiency. For solving wide-band problems time domain solutions are often preferred; while time domain FEM methods are feasible, the Finite Difference Time Domain (FDTD) method is more commonly applied. The FDTD is popular both for its efficiency and its simplicity. The efficiency of the FDTD stems from the fact that it is both explicit (i.e. no matrices need to be solved) and second order accurate in both time and space. The FDTD has limitations when dealing with certain geometrical shapes and when electrically large structures are analysed. The former limitation is caused by stair-casing in the geometrical modelling, the latter by accumulated dispersion error throughout the mesh. The FEM can be seen as a general mathematical framework describing families of concrete numerical method implementations; in fact the FDTD can be described as a particular FETD (Finite Element Time Domain) method. To date the most commonly described FETD CEM methods make use of unstructured, conforming meshes and implicit time stepping schemes. Such meshes deal well with complex geometries while implicit time stepping is required for practical numerical stability. Compared to the FDTD, these methods have the advantages of computational efficiency when dealing with complex geometries and the conceptually straight forward extension to higher orders of accuracy. On the downside, they are much more complicated to implement and less computationally efficient when dealing with regular geometries. The FDTD and implicit FETD have been combined in an implicit/explicit hybrid. By using the implicit FETD in regions of complex geometry and the FDTD elsewhere the advantages of both are combined. However, previous work only addressed mixed first order (i.e. second order accurate) methods. For electrically large problems or when very accurate solutions are required, higher order methods are attractive. In this thesis a novel higher order implicit/explicit FETD method of arbitrary order in space is presented. A higher order explicit FETD method is implemented using Gauss-Lobatto lumping on regular Cartesian hexahedra with central differencing in time applied to a coupled Maxwell’s equation FEM formulation. This can be seen as a spatially higher order generalisation of the FDTD. A convolution-free perfectly matched layer (PML) method is adapted from the FDTD literature to provide mesh termination. A curl conforming hybrid mesh allowing the interconnection of arbitrary order tetrahedra and hexahedra without using intermediate pyramidal or prismatic elements is presented. An unconditionally stable implicit FETD method is implemented using Newmark-Beta time integration and the standard curl-curl FEM formulation. The implicit/explicit hybrid is constructed on the hybrid hexahedral/tetrahedral mesh using the equivalence between the coupled Maxwell’s formulation with central differences and the Newmark-Beta method with Beta = 0 and the element-wise implicitness method. The accuracy and efficiency of this hybrid is numerically demonstrated using several test-problems.
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Zhao, Kezhong. "A domain decomposition method for solving electrically large electromagnetic problems." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1189694496.
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Wang, Shumin. "Improved-accuracy algorithms for time-domain finite methods in electromagnetics." The Ohio State University, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=osu1061225243.
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Dubcová, Lenka. "Novel self-adaptive higher-order finite elements methods for Maxwell's equations of electromagnetics." To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2008. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.
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Kung, Christopher W. "Development of a time domain hybrid finite difference/finite element method for solutions to Maxwell's equations in anisotropic media." Columbus, Ohio : Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1238024768.
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Watkins, L. R. "Electromagnetic field solutions via the finite element method." Master's thesis, University of Cape Town, 1986. http://hdl.handle.net/11427/21964.
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This thesis examines the application of the finite element method to the solution of two important equations which govern electromagnetic fields, namely, the Poisson equation and the Helmholtz equation. These equations. together with appropriate boundary conditions, describe boundary value and eigenvalue problems respectively. Attention will be restricted to boundary value and eigenvalue problems on domains in R² in which more than one dielectric medium may be present. Weak or variational statements of these problems are derived, comprising the governing partial differential equation and appropriate boundary conditions. The Galerkin method is used to pose the variational statement of the problem in a finite-dimensional subspace and the finite element method employed to generate an appropriate set of basis functions which spans this subspace. A linear matrix or linear matrix eigenvalue problem results and suitable techniques for their numerical solution are presented. Various corrputat ional aspects of the finite element method and the solution techniques are discussed. Finite element programs capable of running on a microcomputer are developed and are used to analyse a number of electromagnetic field problems. The results of these analyses are compared, where possible, with analytic solutions, and elsewhere with results obtained by other methods.
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Park, Gi-Ho. "p-Refinement Techniques for Vector Finite Elements in Electromagnetics." Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/10602.
Повний текст джерелаАнотація:
The vector finite element method has gained great attention since overcoming the deficiencies incurred by the scalar basis functions for the vector Helmholtz equation. Most implementations of vector FEM have been non-adaptive, where a mesh of the domain is generated entirely in advance and used with a constant degree polynomial basis to assign the degrees of freedom. To reduce the dependency on the users' expertise in analyzing problems with complicated boundary structures and material characteristics, and to speed up the FEM tool, the demand for adaptive FEM grows high.
For efficient adaptive FEM, error estimators play an important role in assigning additional degrees of freedom. In this proposal study, hierarchical vector basis functions and four error estimators for p-refinement are investigated for electromagnetic applications.
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Pang, Boluan. "A tetrahedral refinement algorithm for adaptive finite element methods in electromagnetics." Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=86961.
Повний текст джерелаАнотація:
The finite element method (FEM) is a popular method in computational electromagnetics, and tetrahedral meshes are commonly used. However, FEM only provides an approximate solution, and to improve it, adaptive mesh refinement is often used. Bey described a robust refinement algorithm with a good mesh quality in 1995. This thesis implements Bey's method with some extensions: taking into account mesh labelling of boundaries and materials, and providing an interface to an adaptive finite element program. The implementation uses an object-oriented programming language (C++). The quality of the resulting meshes is assessed by means of two geometric indicators and, for the adaptive results, by the number of iterations needed to solve the FE global matrix equation. The results confirm that Bey's method produces meshes of good quality with an acceptable time complexity, suitable for use with FEM.La méthode des éléments finis (MEF) est une méthode populaire de calcul en électromagnétisme, et les maillages tétraédriques sont couramment utilizés. Toutefois, MEF ne fournit qu'une solution approchée, et par l'améliorer, le raffinement adaptatif de maillage est souvent utilizé. Bey a décrit un algorithme de raffinement robuste avec une bonne qualité de maillage en 1995. Cette thèse met en oeuvre la méthode Bey avec quelques extensions: prise en compte de mailles à l'étiquetage des frontières et du matériel et fournissage d'une interface à un programme d'adaptation des éléments finis. La mise en oeuvre utilizé un langage de programmation orienté objet (C++). La qualité des maillages qui en résulte est évaluée au moyen de deux indicateurs géométriques et, pour les résultats d'adaptation, au le nombre d'itérations nécessaires pour résoudre l'équation de la matrice globale FE. Les résultats confirment que la méthode de Bey produit des maillages de bonne qualité avec une complexité de temps acceptable, convenable pour une utilisation avec des éléments finis.
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Kabir, S. M. Raiyan. "Finite element time domain method with a unique coupled mesh system for electromagnetics and photonics." Thesis, City University London, 2015. http://openaccess.city.ac.uk/14523/.
Повний текст джерелаАнотація:
The finite difference time domain (FDTD) method is a popular technique, being used successfully to analyse the electromagnetic properties of many structures, including a range of optical or photonic devices. This method offers several major advantages such as, a minimum level of calculation is required for each of the cells into which the structure is divided, as well as data parallelism and explicit and easy implementation. However, due to the use of the Finite Difference grid, this method suffers from higher numerical dispersion and inaccurate discretisation due to staircasing at slanted and curve edges. The rectangular computational domain in 2D and cuboid computational domain in 3D sometimes makes the method very resource intensive especially for large simulations. Although the finite element (FE) approach is superior for the discretisation of both 2D and 3D structures, most of the FE-based time domain approaches reported so far suffer from limitations due to the implicit or iterative form or the mass matrix formulation, for example. Therefore, the speed of the simulation is much slower than the FDTD method. Time domain analysis of electromagnetic is a very resource intensive numerical technique. Due to the slow performance the FE based techniques are not as popular as the FDTD method. In this research work a new FE based time domain technique has been proposed for both 2D and 3D problems which is similar to the FDTD method explicit and data parallel in nature. The method proposed does not requires any matrix formulation or iteration. It uses minimum possible CPU cycles among any FE-based techniques. The method also utilises a unique meshing scheme to reduce the number of calculation to at least half for 2D and one fifth for 3D compared to any full mesh FE based technique. The method also shows very low numerical dispersion when used with equilateral elements in both 2D and 3D. Thus the proposed method effectively produces results with less numerical dispersion error with lower density mesh compared to the FDTD method. When the advantage in resolution is taken into consideration, calculation of each time-step using the proposed method is significantly faster than the FDTD method.
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Sevilla, Cárdenas Rubén. "NURBS-Enhanced Finite Element Method (NEFEM)." Doctoral thesis, Universitat Politècnica de Catalunya, 2009. http://hdl.handle.net/10803/5857.
Повний текст джерелаАнотація:
Aquesta tesi proposa una millora del clàssic mètode dels elements finits (finite element method, FEM) per a un tractament eficient de dominis amb contorns corbs: el denominat NURBS-enhanced finite element method (NEFEM). Aquesta millora permet descriure de manera exacta la geometría mitjançant la seva representació del contorn CAD amb non-uniform rational B-splines (NURBS), mentre que la solució s'aproxima amb la interpolació polinòmica estàndard. Per tant, en la major part del domini, la interpolació i la integració numèrica són estàndard, retenint les propietats de convergència clàssiques del FEM i facilitant l'acoblament amb els elements interiors. Només es requereixen estratègies específiques per realitzar la interpolació i la integració numèrica en elements afectats per la descripció del contorn mitjançant NURBS.La implementació i aplicació de NEFEM a problemes que requereixen una descripció acurada del contorn són, també, objectius prioritaris d'aquesta tesi. Per exemple, la solució numèrica de les equacions de Maxwell és molt sensible a la descripció geomètrica. Es presenta l'aplicació de NEFEM a problemes d'scattering d'ones electromagnètiques amb una formulació de Galerkin discontinu. S'investiga l'habilitat de NEFEM per obtenir solucions precises amb malles grolleres i aproximacions d'alt ordre, i s'exploren les possibilitats de les anomenades malles NEFEM, amb elements que contenen singularitats dintre d'una cara o aresta d'un element. Utilitzant NEFEM, la mida de la malla no està controlada per la complexitat de la geometria. Això implica una dràstica diferència en la mida dels elements i, per tant, suposa un gran estalvi tant des del punt de vista de requeriments de memòria com de cost computacional. Per tant, NEFEM és una eina poderosa per la simulació de problemes tridimensionals a gran escala amb geometries complexes. D'altra banda, la simulació de problemes d'scattering d'ones electromagnètiques requereix mecanismes per aconseguir una absorció eficient de les ones scattered. En aquesta tesi es discuteixen, optimitzen i comparen dues tècniques en el context de mètodes de Galerkin discontinu amb aproximacions d'alt ordre.
La resolució numèrica de les equacions d'Euler de la dinàmica de gasos és també molt sensible a la representació geomètrica. Quan es considera una formulació de Galerkin discontinu i elements isoparamètrics lineals, una producció espúria d'entropia pot evitar la convergència cap a la solució correcta. Amb NEFEM, l'acurada imposició de la condició de contorn en contorns impenetrables proporciona resultats precisos inclús amb una aproximació lineal de la solució. A més, la representació exacta del contorn permet una imposició adequada de les condicions de contorn amb malles grolleres i graus d'interpolació alts. Una propietat atractiva de la implementació proposada és que moltes de les rutines usuals en un codi d'elements finits poden ser aprofitades, per exemple rutines per realitzar el càlcul de les matrius elementals, assemblatge, etc. Només és necessari implementar noves rutines per calcular les quadratures numèriques en elements corbs i emmagatzemar el valor de les funciones de forma en els punts d'integració. S'han proposat vàries tècniques d'elements finits corbs a la literatura. En aquesta tesi, es compara NEFEM amb altres tècniques populars d'elements finits corbs (isoparamètics, cartesians i p-FEM), des de tres punts de vista diferents: aspectes teòrics, implementació i eficiència numèrica. En els exemples numèrics, NEFEM és, com a mínim, un ordre de magnitud més precís comparat amb altres tècniques. A més, per una precisió desitjada NEFEM és també més eficient: necessita un 50% dels graus de llibertat que fan servir els elements isoparamètrics o p-FEM per aconseguir la mateixa precisió. Per tant, l'ús de NEFEM és altament recomanable en presència de contorns corbs i/o quan el contorn té detalls geomètrics complexes.
This thesis proposes an improvement of the classical finite element method (FEM) for an efficient treatment of curved boundaries: the NURBSenhanced FEM (NEFEM). It is able to exactly represent the geometry by means of the usual CAD boundary representation with non-uniform rational Bsplines (NURBS), while the solution is approximated with a standard piecewise polynomial interpolation. Therefore, in the vast majority of the domain, interpolation and numerical integration are standard, preserving the classical finite element (FE) convergence properties, and allowing a seamless coupling with standard FEs on the domain interior. Specifically designed polynomial interpolation and numerical integration are designed only for those elements affected by the NURBS boundary representation.
The implementation and application of NEFEM to problems demanding an accurate boundary representation are also primary goals of this thesis. For instance, the numerical solution of Maxwell's equations is highly sensitive to geometry description. The application of NEFEM to electromagnetic scattering problems using a discontinuous Galerkin formulation is presented. The ability of NEFEM to compute an accurate solution with coarse meshes and high-order approximations is investigated, and the possibilities of NEFEM meshes, with elements containing edge or corner singularities, are explored. With NEFEM, the mesh size is no longer subsidiary to geometry complexity, and depends only on the accuracy requirements on the solution, whereas standard FEs require mesh refinement to properly capture the geometry. This implies a drastic difference in mesh size that results in drastic memory savings, and also important savings in computational cost. Thus, NEFEM is a powerful tool for large-scale scattering simulations with complex geometries in three dimensions. Another key issue in the numerical solution of electromagnetic scattering problems is using a mechanism to perform the absorption of outgoing waves. Two perfectly matched layers are discussed, optimized and compared in a high-order discontinuous Galerkin framework.
The numerical solution of Euler equations of gas dynamics is also very sensitive to geometry description. Using a discontinuous Galerkin formulation and linear isoparametric elements, a spurious entropy production may prevent convergence to the correct solution. With NEFEM, the exact imposition of the solid wall boundary condition provides accurate results even with a linear approximation of the solution. Furthermore, the exact boundary representation allows using coarse meshes, but ensuring the proper implementation of the solid wall boundary condition. An attractive feature of the proposed implementation is that the usual routines of a standard FE code can be directly used, namely routines for the computation of elemental matrices and vectors, assembly, etc. It is only necessary to implement new routines for the computation of numerical quadratures in curved elements and to store the value of shape functions at integration points.
Several curved FE techniques have been proposed in the literature. In this thesis, NEFEM is compared with some popular curved FE techniques (namely isoparametric FEs, cartesian FEs and p-FEM), from three different perspectives: theoretical aspects, implementation and performance. In every example shown, NEFEM is at least one order of magnitude more accurate compared to other techniques. Moreover, for a desired accuracy NEFEM is also computationally more efficient. In some examples, NEFEM needs only 50% of the number of degrees of freedom required by isoparametric FEs or p-FEM. Thus, the use of NEFEM is strongly recommended in the presence of curved boundaries and/or when the boundary of the domain has complex geometric details.
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Chilton, Ryan Austin. "H-, P- and T-Refinement Strategies for the Finite-Difference-Time-Domain (FDTD) Method Developed via Finite-Element (FE) Principles." The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1219064270.
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Dosopoulos, Stylianos. "Interior Penalty Discontinuous Galerkin Finite Element Method for the Time-Domain Maxwell's Equations." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1337787922.
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Khalaf, Loay D. "Optimization of periodic devices using the finite element method." Diss., Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/13758.
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Pinchuk, Amy Ruth. "Spectrally correct finite element analysis of electromagnetic fields." Thesis, McGill University, 1988. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=75780.
Повний текст джерелаАнотація:
Direct solution for three dimensional electric or magnetic field vectors throughout the frequency spectrum is accomplished by a finite element formulation which includes displacement and conduction currents, and requires no special treatment for material interfaces. Analysis of bus bar and Bath cube eddy current problems demonstrate the capabilities of the method.Spurious components in solutions to vector field problems are shown to corrupt deterministic solutions. These corruptions are identifiable with spurious modes familiar to high frequency modal analysis. Spectrally correct mixed order finite elements are demonstrated to retrieve accuracy in deterministic analyses.
The formulation may be limited by computer round-off at matrix assembly which affects the solenoidality of vector fields. Furthermore, extreme values encountered in low frequency eddy current analysis lead to ill conditioning and unreliable solutions. These numerical instabilities are overcome by parametric adjustment of permittivities. Error estimates are established to monitor inaccuracies introduced by permittivity adjustment.
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Kimn, Edward Sun. "A parametric finite element analysis study of a lab-scale electromagnetic launcher." Thesis, Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/39498.
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The purpose of the study is to better understand the factors that affect melt-wear in the armature-to-rail contact interface of an electromagnetic launcher (EML). In order to investigate the factors, the study uses finite element analysis (FEA) to vary parameters of a lab-scale EML at the Georgia Institute of Technology. FEA is used due to the complex nature of the system, which includes the geometry and various engineering aspects that the EML incorporates. The study focuses on an uncoupled analysis of the structural, electromagnetic (EMAG), thermal, and modal aspects. The reason for the uncoupled analysis was because the system was complex and there were computational limits. Also, by uncoupling the analysis fields, the way the parameters affected melt-wear could be viewed separately. The study varied the geometry of the armature, the stiffness of the rail system (compliance layer), and the material of the armature. The structural analysis was for the initial contact of the rail to the armature and found the von Mises stresses, contact area, and contact pressure. The EMAG analysis found the Lorentz forces in the system based on a current curve used in the lab-scale EML. The thermal analysis consisted of friction heating and Joule heating. The modal analysis was for the unstressed and pre-stressed armature. Based on the study conducted, it was found that aluminum would provide the best speeds due to its lighter mass, but lacked in the thermal resistance area. Tungsten provided the better thermal resistance, but lacked in the potential speed due to its heavier mass.
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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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Yilmaz, Asim Egemen. "Finite Element Modeling Of Electromagnetic Scattering Problems Via Hexahedral Edge Elements." Phd thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12608587/index.pdf.
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In this thesis, quadratic hexahedral edge elements have been applied to the three dimensional for open region electromagnetic scattering problems. For this purpose, a semi-automatic all-hexahedral mesh generation algorithm is developed and implemented. Material properties inside the elements and along the edges are also determined and prescribed during the mesh generation phase in order to be used in the solution phase. Based on the condition number quality metric, the generated mesh is optimized by means of the Particle Swarm Optimization (PSO) technique. A framework implementing hierarchical hexahedral edge elements is implemented to investigate the performance of linear and quadratic hexahedral edge elements. Perfectly Matched Layers (PMLs), which are implemented by using a complex coordinate transformation, have been used for mesh truncation in the software. Sparse storage and relevant efficient matrix ordering are used for the representation of the system of equations. Both direct and indirect sparse matrix solution methods are implemented and used.
Performance of quadratic hexahedral edge elements is deeply investigated over the radar cross-sections of several curved or flat objects with or without patches. Instead of the de-facto standard of 0.1 wavelength linear element size, 0.3-0.4 wavelength quadratic element size was observed to be a new potential criterion for electromagnetic scattering and radiation problems.
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Ren, Da Qi. "Analysis and design development of parallel 3-D mesh refinement algorithms for finite element electromagnetics with tetrahedra." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=103003.
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Optimal partitioning of three-dimensional (3-D) mesh applications necessitates dynamically determining and optimizing for the most time-inhibiting factors, such as load imbalance and communication volume. One challenge is to create an analytical model where the programmer can focus on optimizing load imbalance or communication volume to reduce execution time. Another challenge is the best individual performance of a specific mesh refinement demands precise study and the selection of the suitable computation strategy. Very-large-scale finite element method (FEM) applications require sophisticated capabilities for using the underlying parallel computer's resources in the most efficient way. Thus, classifying these requirements in a manner that conforms to the programmer is crucial.This thesis contributes a simulation-based approach for the algorithm analysis and design of parallel, 3-D FEM mesh refinement that utilizes Petri Nets (PN) as the modeling and simulation tool. PN models are implemented based on detailed software prototypes and system architectures, which imitate the behaviour of the parallel meshing process. Subsequently, estimates for performance measures are derived from discrete event simulations. New communication strategies are contributed in the thesis for parallel mesh refinement that pipeline the computation and communication time by means of the workload prediction approach and task breaking point approach. To examine the performance of these new designs, PN models are created for modeling and simulating each of them and their efficiencies are justified by the simulation results. Also based on the PN modeling approach, the performance of a Random Polling Dynamic Load Balancing protocol has been examined. Finally, the PN models are validated by a MPI benchmarking program running on the real multiprocessor system. The advantages of new pipelined communication designs as well as the benefits of PN approach for evaluating and developing high performance parallel mesh refinement algorithms are demonstrated.
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Wu, Jo-Yu. "Modeling electromagnetic wave problems using tangentially continuous vector finite element method /." The Ohio State University, 1997. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487943610784484.
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Tumonis, Liudas. "Simulation of mechanical behaviour of the electromagnetic railgun by finite element method." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2010. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2010~D_20100303_124423-17934.
Повний текст джерелаАнотація:
The numerical analysis of electromagnetic railgun dynamics under transient load is considered in current PhD thesis. The object of investigation is electro-magnetic accelerator EMA-3 at French-German institute of Sain-Louis (ISL). The aim of work covers the development of the finite element model of the EMA-3 rail gun and its application for investigation of the mechanical behaviour of railgun under differently induced loading regimes.
There are several tasks under consideration. The first one is development of the finite element model. The 2D model consisting of four node plane and elastic springs was suggested and examined. The second one is evaluation of influence particular loading to dynamic behaviour and giving of recommendations.
This thesis contains introduction, four chapters, the summary of results and conclusions, and the list of cited literature and list of publications of the author.
In introductory chapter, the problem is formulated and relevance of the work is discussed. The goals and objectives of the work, research methodology and scientific novelty, practical significance and defended propositions are briefly described. Publications and reports at conferences on the theme of dissertation are presented at the end of introduction.
The first chapter covers the review of the references on the electromagnetic railgun. It contains description of the development history, physical principles and decisive factors. Later, the gun structure is considered with the... [to full text]Disertacijoje baigtinių elementų metodu nagrinėjamas elektromagnetinės šaudyklės (EMŠ) konstrukcinių dalių mechaninis būvis, veikiant dinaminei ap-krovai. Tyrimo objektas yra EMŠ „EMA-3“. Šaudyklės mechaninė dalis sudaryta iš elektrai laidžių bėgių, pritvirtintų prie dielektrinio pagrindo. Tiriama mechani-nio būvio rodiklių priklausomybė nuo apkrovos pobūdžio ir šaudyklės bėgių įtvirtinimo. Šaudyklės mechaninio būvio nustatymas jos darbo metu leistų tiks-liau prognozuoti jos elgseną, pagreitintų projektavimą, tobulinimą ir atpigintų eksploatavimą. Disertacijos tikslas yra skaitiniais metodais aprašyti ir ištirti šau-dyklės mechaninį deformavimą, veikiant dinaminei apkrovai, ištirti mechaninio būvio rodiklių priklausomybes nuo apkrovos parametrų, palyginti skirtingus ap-krovų režimus. Remiantis gautais skaičiavimo rezultatais, siekiama įvertinti šių veiksnių įtaką ir teikti siūlymus režimų patobulinimui. Darbe spręsti keli uždaviniai: sudarytas ir ištirtas „EMA-3“ šaudyklės skaiti-nis baigtinių elementų modelis. Pasiūlytais rodikliais įvertintas šaudyklės mecha-ninis būvis ir palyginta realių apkrovų įtaką bėgių deformavimui. Uždaviniai su-formuluoti atsižvelgiant į esamų modelių ribotumą, į šaudyklės rezonansinę elgseną kritinio greičio aplinkoje ir į tinkamo darbinio režimo parinkimo proble-mą. Disertaciją sudaro įvadas ir keturi skyriai. Įvade apibrėžta tyrimų sritis ir aktualumas, aprašyta mokslo problema, su-formuluotas darbo tikslas ir uždaviniai, paminėti naudoti tyrimo... [toliau žr. visą tekstą]
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Rawat, Vineet. "Finite Element Domain Decomposition with Second Order Transmission Conditions for Time-Harmonic Electromagnetic Problems." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1243360543.
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Bunting, Charles Frederick. "Functionals in electromagnetics: an investigation into methods to eliminate spurious solutions in the application of finite element techniques." Diss., Virginia Tech, 1994. http://hdl.handle.net/10919/40063.
Повний текст джерелаАнотація:
Finite element techniques have been applied to a wide variety of problems in electro magnetics, but have been handicapped by the appearance of spurious solutions. Both weighted residual methods and variational methods are the basic finite element techniques that are examined to establish a framework for the discussion of spurious solutions. A simple waveguide example is used to explore the fundamental problem with these spurious solutions. A method is developed that focuses on the functional form as the fundamental cause underlying the difficulties with spurious solutions. By using analytical rather than numerical means, it is shown that the solution form allows for the existence of
an improper gradient behavior in a general field expansion. A new functional that satisfies Maxwell's equations and eliminates spurious solutions is introduced. This new functional is shown to be self-adjoint and positive definite, thus providing an error minimization. The analytical form as well as the finite element method is applied to demonstrate the robust nature of the functional.Ph. D.
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Franke-Börner, Antje. "Three-dimensional finite element simulation of magnetotelluric fields on unstructured grids." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2013. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-114985.
Повний текст джерелаАнотація:
In der vorliegenden Arbeit werden verschiedene Randwertprobleme zur Beschreibung der Ausbreitung magnetotellurischer Felder mit Hilfe der Finite-Elemente-Methode numerisch gelöst. Die zwei- und dreidimensionalen Randwertprobleme zur Simulation des elektrischen oder des magnetischen Feldes, des magnetischen Vektorpotentials und des elektrischen Skalarpotentials, des magnetischen Vektorpotentials allein oder des anomalen magnetischen Vektorpotentials werden aus den Maxwell-Gleichungen hergeleitet. Auf Grundlage von Anwendung der Konvergenztheorie auf die Finite-Elemente-Lösung werden Konvergenzstudien für zweidimensionale Modelle des homogenen und des geschichteten Halbraums sowie für das dreidimensionale COMMEMI 3-D-2-Modell durchgeführt. Diese werden genutzt, um die Randwertprobleme hinsichtlich ihrer Effizienz zu bewerten. Außerdem liefern Konvergenzstudien eine Abschätzung des lokalen Fehlers der numerischen Lösung für ein realitätsnahes Modell des Vulkans Stromboli und seiner Umgebung, welches digitale Geländedaten enthältThis thesis presents the numerical finite-element solution of different formulations of the magnetotelluric boundary value problem. Based on Maxwell\'s equations, the two-dimensional and three-dimensional boundary value problems are derived in terms of the electric or the magnetic field, the magnetic vector and the electric scalar potential, the magnetic vector potential only, or the anomalous magnetic vector potential. To evaluate their efficiency, convergence studies are performed for the two-dimensional models of the homogeneous and the layered halfspace as well as for the COMMEMI-3-D-2 model. Moreover, convergence studies yield estimates of the local error of the numerical solution for a close-to-reality model of Stromboli volcano incorporating digital terrain data
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Ledfelt, Gunnar. "Hybrid Time-Domain Methods and Wire Models for Computational Electromagnetics." Doctoral thesis, Stockholm : Tekniska högsk, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3115.
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Vouvakis, Marinos N. "A Non-Conformal Domain Decomposition Method for Solving Large Electromagnetic Wave Problems." The Ohio State University, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=osu1125498071.
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Cardoso, Jose Roberto. "Problemas de campos eletromagnéticos estáticos e dinâmicos; Uma abordagem pelo método dos elementos finitos." Universidade de São Paulo, 1986. http://www.teses.usp.br/teses/disponiveis/3/3143/tde-11072017-082059/.
Повний текст джерелаАнотація:
A ideia de realizar este trabalho surgiu durante do curso de pós-graduação, ministrado pelo Prof. M. Drigas, \"Tópicos especiais sobre máquinas elétricas\", realizado no 2º semestre de 1980 na EPUSP, onde foi observada a necessidade do conhecimento das distribuições de campos magnéticos em dispositivos eletromecânicos com o objetivo de se prever seu desempenho na fase de projeto. Nesta época, já havia sido apresentada a tese do Prof. Janiszewski, o primeiro trabalho, de nosso conhecimento realizado no Brasil nesta área, onde foi desenvolvida a técnica de resolução de problemas de Campos Magnéticos em Regime Estacionário, que, evidentemente, não pode ser aplicada na resolução de problemas onde a variável tempo está envolvida; baseado neste tese, em 1982 o Prof. Luiz Lebensztajn, reproduziu o trabalho do Dr. Janiszewski o qual foi aplicado para verificar a consistência dos resultados práticos na tese de Livre Docência do Prof.. Dr. Aurio Gilberto Falcone. As formulações mais frequentes do Método dos Elementos Finitos (MEF), publicada nos periódicos internacionais, são baseadas no Cálculo Variacional, onde o sistema de equações algébricas não linear resultante, é derivado a partir da obtenção do extremo de uma funcional que em algumas situações não pode ser obtida, limitando assim sua aplicação. Em decorrência deste fato, o primeiro objetivo deste trabalho foi organizar os procedimentos para obtenção do sistema de equações de MEF aplicado à resolução de problemas de campo descritos por equações diferenciais não lineares, sem a necessidade. Algumas contribuições interessantes são encontradas no Capítulo II, referente à formulação do MEF para problemas de campo descrito por operadores diferenciais não auto-adjuntos.No Capítulo III são apresentadas as técnicas de montagem das matrizes, bem como aquelas de introdução das condições de contorno, originárias deste método, que muito embora sejam técnicas de aplicação corriqueiras, ajudarão em muito o pesquisador iniciante nesta área, sem a necessidade de recorrer a outro texto. No Capítulo VI são apresentadas as formulações necessárias para a solução de problemas de campos eletromagnéticos estáticos, para elementos de quatro lados retos (e curvos) assim como a técnica utilizada na obtenção da relutividade em meios não lineares. No Capítulo V são tratados os problemas de campo, onde a variável tempo está envolvida, permitindo assim a resolução de uma série enorme de problemas referentes aos campos de natureza eletromagnética, tais como os fenômenos transitórios e o Regime Permanente Senoidal. Os aspectos computacionais ligados ao trabalho estão expostos no Capítulo VI, onde são apresentadas as rotinas de resolução do sistema de equações resultante adaptadas às particularidades do problema, e as rotinas de integração numérica de problemas descrito por equações diferenciais dependentes do tempo de primeira e segunda ordem. Algumas técnicas apresentadas nestes Capítulos, são aplicadas espe3cificamente para a obtenção da distribuição de campo magnético no Capitulo VII deste trabalho, com o objetivo de analisar o desempenho de um transformador em regime transitório, onde é confirmada a consistência do método.The idea of making this work came during a graduation course, \" Special topics on electric machines\", lectured by Prof. Dr. M. Drigas during the 2nd semester of 1980 at EPUSP, when the need of knowing the distribution of magnetic fields in electromechanics devices was notices, in order to foresse its performance during design. At that time, the first work about this subject realized made in Brazil was presented in prof. Janiszewski\'s thesis, where a technique was developed to solve Steady-State Magnetic Fields. However, it is clear that when the time variable is considered, this technique cannot be applied. The usual formulations of the Finite Element Method, published in international journals, was based on Variational Calculations, where the resulting non-linear algebraic equations system is derived from the extreme of a functional, which sometimes cannot be obtained, limiting in this way its application. Consequently, the first aim of this work is to organize procedures to obtain the Finite Method equations system, in order solve non-linear differential equations of fields, without the need of a previous functional for the problem. In Chapter II, one will find some interesting contributions referred to the Finite Element Method formulation, in the description of field problems by the use of non self-adjacent differentials operations.Matrix building techniques are presented in Chapter III, as well as the introduction of boundary conditions in this method. In spite of being an ordinary technique, it will help the beginners a lot, eliminating the need of other sources. Chapter IV presents the necessary formulations, which solve static electromagnetic fields for elements of four square (and curved) sides, and the technique used in the determination of non-linear media reluctivity. In Chapter V, the time variable of electromagnetic fields is treated, making possible the solution of problems of this nature, such as transient phenomena and sinusoidal steady-state. Computer aspects of the work are shown in Chapter VI, presenting resolution routines of the equation system fitted to the problem, and numeric integration routines described by first and second order differential equations, which depend on the time. Some techniques showed in those previous Chapters are specifically used in Chapter VII to obtain the magnetic field distribution, which analyses transformer performance during transients. The coherence of the method is also confirmed.
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Ozgun, Ozlem. "Finite Element Modeling Of Electromagnetic Radiation/scattering Problems By Domain Decomposition." Phd thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/3/12608290/index.pdf.
Повний текст джерелаАнотація:
The Finite Element Method (FEM) is a powerful numerical method to solve wave propagation problems for open-region electromagnetic radiation/scattering problems involving objects with arbitrary geometry and constitutive parameters. In high-frequency applications, the FEM requires an electrically large computational domain, implying a large number of unknowns, such that the numerical solution of the problem is not feasible even on state-of-the-art computers. An appealing way to solve a large FEM problem is to employ a Domain Decomposition Method (DDM) that allows the decomposition of a large problem into several coupled subproblems which can be solved independently, thus reducing considerably the memory storage requirements. In this thesis, two new domain decomposition algorithms (FB-DDM and ILF-DDM) are implemented for the finite element solution of electromagnetic radiation/scattering problems. For this purpose, a nodal FEM code (FEMS2D) employing triangular elements and a vector FEM code (FEMS3D) employing
tetrahedral edge elements have been developed for 2D and 3D problems, respectively. The unbounded domain of the radiation/scattering problem, as well as the boundaries of the subdomains in the DDMs, are truncated by the Perfectly Matched Layer (PML) absorber. The PML is implemented using two new approaches: Locally-conformal PML and Multi-center PML. These approaches are based on a locally-defined complex coordinate transformation which makes possible to handle challenging PML geometries, especially with curvature discontinuities. In order to implement these PML methods, we also introduce the concept of complex space FEM using elements with complex nodal coordinates. The performances of the DDMs and the PML methods are investigated numerically in several applications.
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Tadesse, Yonatan Abebe. "The Electromagnetic Simulation of Birdcage Coils for MRI based on Finite Element Method." Youngstown State University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1484137190762487.
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Pekel, Ümit. "A three-dimensional finite element method approach for the analysis of electromagnetic scattering /." The Ohio State University, 1993. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487841975360022.
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KALARICKEL, RAMAKRISHNAN PRAVEEN. "Reliability of finite element method for time harmonic electromagnetic problems involving moving bodies." Doctoral thesis, Università degli studi di Genova, 2018. http://hdl.handle.net/11567/930777.
Повний текст джерелаАнотація:
This work is mainly concerned about the time-harmonic electromagnetic problems involving moving bodies. Such a formulation is possible when the boundaries between different moving objects are stationary and the sources involved are time-harmonic. Even simple media present bianisotropic properties when they are in motion. This kind of problems find applications in diverse fields. Numerical solution is required for most of the practical problems. We examined the reliability of finite element simulator developed for solving such problems.
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Ati, Modafar K. "Calculation of electromagnetic field problems in large electrical machines using the finite element method." Thesis, University of Newcastle Upon Tyne, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.238937.
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Haider, Shah Ali 1954. "Three-dimensional electromagnetic vector field computation in lossy magnetic media by finite element method." Diss., The University of Arizona, 1996. http://hdl.handle.net/10150/284325.
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A three dimensional finite element method software package has been developed for solving electromagnetic vector fields in conducting, magnetic materials and has been applied in two dimensions to ferromagnetic filaments and in three dimensions to a sphere. The bulk of this dissertation describes the approach to formulating the problem, choosing a solution routine, developing a method of discretization, verifying the accuracy and characterizing the computational efficiency of the package. Spurious vector solutions, which arise in numerical approximations to three dimensional electromagnetic problems, were eliminated by using a node-based formulation, with modified vector wave equation to ensure that divergence free conditions are satisfied. Conjugate gradient, iterative quasi-minimal residual solver (QMR) with a non-zero matrix element storage scheme expedited computation and reduced memory requirements. An automatic mesh generator for hexahedral elements was developed for discretization. The two dimensional study continued earlier analytical and experimental work on induction heating of multi-filament ferromagnetic strands. The present results demonstrate that coupling between filaments does not occur in two dimensions and is, in fact, a three dimensional effect provided the filaments are not in electrical contact. Furthermore, the accuracy of the solution can be established quantitatively by a single parameter, the ratio of one side of the finite element to the electromagnetic skin (or penetration) depth. The three dimensional parametric study investigates the effects on power absorption patterns in the sphere as a function of conductivity and permeability. Primarily, this research demonstrates that these types of problems can be solved accurately. Finally, it is shown that while the discretization must extend completely throughout the sphere for non-magnetic, moderately lossy media (conductivity, σ∼ 1 S/m, relative permeability, μᵣ ∼1), it need only consist of a thin shell of about three skin depths thick for highly conducting magnetic materials. The core of this sphere can be replaced by a field free inner perfectly conducting sphere. While the problem of computing power absorption in ferromagnetic implants for hyperthermia, the motivation for this study, was not solved completely, the foundations have been laid. Dependence of power absorption upon size, shape, permeability and conductivity as well as interactions between filaments of finite length can be addressed with this beginning.
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Wang, Feng. "Development of A Fast Converging Hybrid Method for Analyzing Three-Dimensional Doubly Periodic Structures." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1376923791.
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Khan, Raouf Lawrence. "Finite element method applied to modelling electromagnetic interference and compatibility problems on printed circuit boards." Thesis, University of Ottawa (Canada), 1990. http://hdl.handle.net/10393/5676.
Повний текст джерелаАнотація:
The finite element method is applied to compute the distributed capacitance and inductance matrices for multilayered dielectric, planar transmission media. The analysis involves the solution of the Laplace equation in two dimensions for multiconductor configurations in microstrip, triplate, or TEM Cell configurations of arbitrary cross section and utilizes a unique node allocation algorithm for automatic generation of the finite element mesh. The advantages, disadvantages, and difficulties encountered in application of the FEM for this problem are outlined and discussed. Several programs, based on multiconductor transmission line theory, are developed for application to Electromagnetic Interference and Compatibility (EMI/C) problems for crosstalk and radiated emission analysis. To verify the model experimentally, a simple printed circuit board consisting of five parallel conductors in microstrip configuration was constructed and measured in both time domain and frequency domains. Radiation model results are compared for a multiconductor configuration with numerical results obtained using the Numerical Electromagnetics Code (NEC) moment method program.
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Ladd, Darcy N. "Three dimensional finite element method applied to study the penetration of electromagnetic fields in cavities." Thesis, University of Ottawa (Canada), 1990. http://hdl.handle.net/10393/5924.
Повний текст джерелаАнотація:
A three dimensional formulation of the finite element method was developed to solve the electromagnetic field distribution in an arbitrary region containing conducting and dielectric materials when the tangential magnetic field was known at the boundaries. The formulation was developed using a three component vector magnetic potential and a scalar electric potential. The displacement current as well as the conduction current term was accounted for. The region of interest was discretized using eight node isoparametric hexahedrons and the potential functions were defined using linear first order basis functions. The frequency domain finite element method program was validated by comparison with closed form solutions for simplified geometries. The algorithm proved to have a convergent solution when solving the diffusion of electromagnetic fields into conducting hollow and solid structures without apertures. The penetration of a steady-state electromagnetic field through an aperture into a simple cavity was analyzed with the 3-D FEM program. The diffusion of a step-impulse magnetic filed into a conducting slab was solved directly in the time domain with a time domain finite element program. Conclusions were drawn on the feasibility of using the finite element method as part of an EMI/EMC CAD package.
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Andre, Robert G. "Electromagnetic scattering analysis of a three dimensional inhomogeneous material body using the Finite Element Method /." The Ohio State University, 1993. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487842372897921.
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Anees, Asad [Verfasser], Lutz [Akademischer Betreuer] Angermann, Reza [Akademischer Betreuer] Abedi, and Muhammad Ozair [Akademischer Betreuer] Ahmad. "Time domain finite element method for linear and nonlinear models in electromagnetics and optics / Asad Anees ; Lutz Angermann, Reza Abedi, Muhammad Ozair Ahmad." Clausthal-Zellerfeld : Technische Universität Clausthal, 2020. http://d-nb.info/123136260X/34.
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Bourgeois, Jacqueline M. "A complete three-dimensional electromagnetic simulation of ground-penetrating radars using the finite-difference time-domain method." Diss., Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/14845.
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Morachkovsky, Oleg K., and D. V. Lavinsky. "The Nonlinear Deformation of the Body System Under Electromagnetic Field Action." Thesis, NTU "KhPI", 2016. http://repository.kpi.kharkov.ua/handle/KhPI-Press/23684.
Повний текст джерелаАнотація:
The paper discusses issues concerning the deformation of a system of conductive bodies under the action of the electromagnetic field. Problem of nonlinear deformation of technological system for electromagnetic forming is considered as a practical application. The problem is solved by the finite element method. Spatial-temporal distributions of the main components of the electromagnetic field are obtained. The ability to review the problem of deformation in the quasi-stationary formulation is justified. The distribution of the main component of the stress-strain state is presented. The influence of the current magnitude at the maximum stresses is evaluated.
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Rieben, Robert N. "A novel high order time domain vector finite element method for the simulation of electromagnetic devices /." For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2004. http://uclibs.org/PID/11984.
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Natarajan, Aswani. "Electromagnetic modelling of graphene-based nanophotonic devices : modal and scattering approaches using the finite element method." Thesis, Aix-Marseille, 2021. http://www.theses.fr/2021AIXM0472.
Повний текст джерелаАнотація:
La plasmonique basée sur les matériaux 2D est un domaine en plein essor dans la photonique, avec des implications technologiques potentielles révolutionnaires dans des domaines aussi variés que le diagnostic, l'énergie et la communication. Le graphène, un matériau 2D unique et doté d'excellentes propriétés plasmoniques, est une alternative prometteuse aux métaux nobles conventionnels dans le domaine de la plasmonique, notamment en raison de ses propriétés accordables en fréquence. Le graphène est modélisé dans cette thèse comme une feuille conductrice infiniment mince dans le cadre des éléments finis (vectoriels) de Galerkin, par opposition aux modèles plus conventionnels où la feuille de graphène est considérée comme ayant une épaisseur finie. Une seconde étude 2D rigoureuse du comportement du champ électromagnétique le long de la direction de propagation dans un guide d'ondes ouvert est réalisée en modélisant le graphène comme un diffuseur (1D) qui agit comme une perturbation locale au guide. Enfin, l'important décalage d’indice effectif qui existe entre le mode du guide d'ondes dielectrique et le mode plasmonique du graphène altère le couplage. Pour surmonter ce problème, un coupleur est conçu à l'aide du formalisme direct en champ diffracté développé. Des études approfondies du phénomène de battement observé dans le coupleur sont également réalisées. Plusieurs études impliquant les différents ordres de diffraction du réseau coupleur, l'épaisseur du guide d'ondes, etc. sont menées. Les paramètres du coupleur sont ensuite optimisés pour obtenir un coupleur à réseau compact et intégré à base de graphène dont l'efficacité atteint 80% à dans l’infrarougePlasmonics based on 2D materials is a burgeoning field in photonics with potential groundbreaking technological implications for diagnostics, energy and data communication. Graphene, a unique 2D material with excellent plasmonic properties is a promising alternative to conventional noble metals in plasmonics notably due to its tunable properties. Graphene is modelled in this thesis as an infinitesimally thin current-carrying sheet in a fully vectorial finite element Galerkin framework as opposed to more conventional models where graphene is considered to be of finite thickness. A rigorous study of the behaviour of the electromagnetic field along the propagation direction in an openridge waveguide is carried out by modelling graphene as a 1D conductive scatterer which acts as a local perturbation. The scattering model is verified through a full energy balance in different geometries. The large momentum mismatch that exists between the waveguide mode and the graphene plasmon mode in a graphene-based waveguide severely alters the coupling between these two modes. To overcome this, a coupler is designed using the developed scattering field formalism. Elaborate studies of the beating phenomenon observed in the coupler are performed. The designed waveguide coupler is apt for graphene of lengths equal to or shorter than the order of the wavelength. Several studies involving the various diffraction orders of the grating coupler, waveguide thickness, etc. are conducted. The parameters of the coupler are then optimized to yield a compact and integrated graphene-based grating coupler of efficiency as high as 80% in the infrared region
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Srinivasan, Meera Carleton University Dissertation Engineering Electronics. "A combination of finite element method and complex frequency hopping technique for solution of electromagnetic problems." Ottawa, 1996.
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PETRINI, PAOLO. "Extension of Three-dimensional Electromagnetic Finite Element and Method of Moments Analysis To Include Singular Fields." Doctoral thesis, Politecnico di Torino, 2018. http://hdl.handle.net/11583/2709736.
Повний текст джерелаАнотація:
The Finite Element Method (FEM) and Method of Moments (MoM) are popular numerical methods for solving complex problems encountered in almost any field of engineering. The structure to be studied is divided into small cells (2D or 3D) and the relevant equations can be numerically solved. The modes of the structure are typically obtained by solving a generalized eigenvalue equation (FEM) or performing a matrix inversion (MoM); scattering problems formulated in term of integral equations are typically solved with MoM.
For problems with smooth surfaces or other regular features, high order finite-element techniques based on the use of (hierarchical) curl-conforming for FEM or divergence-conforming vector bases for MoM successfully improve accuracy and efficiency (greatly reducing the dimension of the matrices and minimizing CPU time). High degree polynomial expansion functions often do not improve the solution accuracy, or do not provide as rapid convergence as anticipated, when dealing with geometries containing sharp edges or corners. The slow convergence observed in these cases is a consequence of the non-analytic nature of the solution in the vicinity of the singular point. To improve the accuracy of these problems, special basis functions are being developed that incorporate the singular field behavior.Conversely, by using a $5^{th}$ or $6^{th} $ order base with only four triangles one obtains far better results than with 2748 triangles and order 0 (“classic FEM” implementation).
In the following the reader will be presented with the development of high order polynomial basis for 2D structures (typically waveguide cross sections) in terms of scalar, vector and full-wave analysis; then with especially developed functions which greatly enhance the accuracy of modes that are affected by corner singularities.
Chapters 2 and 3 will show the development of high order polynomial bases for 3D FEM (used to study cavities) founded on tetrahedral or triangular prism based cells.
Chapter 4 will provide the results from the development of divergence-conforming high order hierarchical singular bases for quadrangular cells.
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King, Joshua David. "Using a 3D finite element forward modeling code to analyze resistive structures with controlled-source electromagnetics in a marine environment." Thesis, Texas A&M University, 2004. http://hdl.handle.net/1969.1/1371.
Повний текст джерелаАнотація:
Controlled-Source Electromagnetics (CSEM) is a method that has been used since the 1980s in the marine environment for determining electrical properties of the subsurface. Receivers on the seafloor collect total electric and magnetic fields which are produced as a result of interaction of the transmitter generated primary fields with the seawater and subsurface. Badea et al. (2001) coded an existing algorithm for solving Maxwells equations. This finite element 3D forward modeling algorithm is used to simulate CSEM experiments. The objective of the present study is to model the changes in electromagnetic response for a resistive disk and a more geometrically complex structure, which are rough approximations of hydrocarbon reservoirs. The parameters that are varied in studying these subsurface structures are the disk radius, disk depth, the transmitter frequency, the transmitter location, and the structure orientation.The results showed that a disk of finite radius behaves similar to an infinite disk at short range and grades into double half-space behavior at longer ranges. The frequency of the transmitter must be tuned to the disk depth as certain frequencies will penetrate too shallow or too deep to probe the disk. Moving the transmitter away from the receivers causes a decrease in signal strength, but exhibits a greater capacity to distinguish between the double half-space and infinite disk scenarios. The disk was then replaced by a more complex structure. To determine if the 3D nature of the structure may be located a study was undertaken to probe the structure from different perspectives using different transmitter locations and azimuths. It is determined that the 3D nature of the structure could not be observed until the structures thickness is sufficiently large.The goal of the study is to better understand the effect of subsurface parameters on the total fields and show the usefulness of the 3D forward modeling code. Understanding the relationships between these parameters and the resulting signals is important in terms of setting up a real experiment. Marine CSEM studies are costly and using a valuable tool such as an accurate finite element 3D forward modeling algorithm may save time and money.
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Wilow, Viktor. "Electromagnetical model of an induction motor in COMSOL Multiphysics." Thesis, KTH, Elektrisk energiomvandling, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-160703.
Повний текст джерелаАнотація:
Ansys, Flux or COMSOL are examples of software-tools that can be used to study magnetic noise, caused by magnetic forces in the air-gap, in induction motors. The project team wanted to use COMSOL in this thesis. The electromagnetical domain needs to be coupled to the mechanical domain to complete the study. The air-gap forces, calculated in the electromagnetical model using the Rotating Machinery module, can be exported to the Acoustic-Solid Interaction module in COMSOL to enable the vibro-acoustic analysis. An electromagnetical model of an induction motor is developed in two-dimensions in the finite element method based software-tool COMSOL Multiphysics in this thesis. Simulation results obtained in the frequency domain are compared with results achieved in the software-tool FEMM. Simulation results of the phase inductance, distribution of the flux density and the torque are compared. The simulated torque in COMSOL is validated with the torque derived based on an equivalent lumped model of the induction motor. A time-dependent simulation of the motor is made at 4.7% slip and 1A (peak) supply. The obtained torque is 0.33Nm. The same value is achieved in the frequency study in COMSOL. The corresponding value is 0.003Nm higher in FEMM. The evaluated air-gap forces at 4.7% slip can be used for studying vibro-acoustics in COMSOL.Ansys, Flux eller COMSOL är exempel på datorprogram som kan användas för att studera magnetiskt brus, orsakad av magnetiska krafter i luftgapet, i induktionsmotorer. Projektgruppen ville använda COMSOL i det här examensarbetet. För att kunna utföra studien måste den elektromagnetiska domänen kopplas till den mekaniska domänen. Luftgapskrafterna, beräknade i den elektromagnetiska modellen genom att använda modulen för roterande maskiner, kan exporteras till modulen Acoustic-Solid Interaction för att möjliggöra den vibro-akustiska analysen. En elektromagnetisk modell av en induktionsmotor är utvecklad i två dimensioner i finita elementmetoden-baserade programvaran COMSOL Multiphysics i det här examensarbetet. Simuleringsresultat från frekvensdomänen jämförs med resultat som uppnås med datorprogramvaran FEMM. Simuleringsresultat för fas-induktansen, fördelningen av flödestätheten och momentet jämförs. Det simulerade momentet i COMSOL valideras med momentet som härleds utifrån induktionsmotorns motsvarande ekvivalenta schema. En tidsberoende motor-simulering genomförs vid 4.7% slip, matad med 1A (topp-värde). Det erhållna momentet är 0.33Nm. Samma värde erhålls i frekvensstudien i COMSOL. Värdet är 0.003Nm högre i FEMM. De beräknade luftgapskrafterna vid 4.7% slip kan användas för att göra en vibroakustisk studie i COMSOL.