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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

O método de Métivier sobre a distribuição assintótica de autovalores aplicado as equações de Maxwell

Charão, Ruy Coimbra January 1982 (has links)
Aplicando resultados recentes de Métivier sobre os números de aproximação dos espaços clássicos de Sobolev obtemos a distribuição assintÓtica dos autovalores das equações de Maxwell definidas sobre um aberto limitado O de R3 com (coeficientes hBlderianos de expoente s E (0,1] e a hipóteses condição de regularidade de Métivier sobre a fronteira de o) significati vamente mais fracas que as anteriormente pedidas na literatura (em particular a Tese de Mehra), dada pela estimativa. / Applying recent results of Métivier about approximation numbers of classic Sobolev spaces we obtain the asymptotic distribution of the eigenvalues of Maxwell's equations defined over a bounded open set o in R3 with significantly weaker hYpotheses (hölderian coefficients with exponent s E (0,1] and Métivier's regularity condition on the boundary of O) than those asked before in the literature (in particular Mehra's theses) given by the estimate:
22

Maxwell Anderson : Preparation, Methods, and Views in Musical Comedy

Garlington, Donia 01 1900 (has links)
Even before he became a playwright, Maxwell Anderson developed a belief in the right of the individual to determine his own fate, and a hatred for anything that hampered that right. He never faltered in that belief. Thus, most of his plays have themes concerned with the evils of the abuse of governmental power and the social injustice that is the result of such abuse. It is the purpose of this thesis to study those beliefs as they were developed throughout severl preceding plays and as they were finally expressed in both Anderson's musicals, Knickerbocker Holiday (1938) and Lost in the Stars (1949).
23

Non-Reimannian gravitation and its relation with Levi-Civita theories

Scipioni, Roberto January 1998 (has links)
No description available.
24

An approximation to the Heidler Function with an analytical integral for engineering applications using lightning currents

Terespolsky, Brett Ryan January 2015 (has links)
A dissertation submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science in Engineering in the Lightning and EMC Research Group School of Electrical and Information Engineering September 2015 / The work presented contributes to research in lightning protection simulations and focuses on approximating the Heidler function with an analytical integral and hence a frequency domain representation. The integral of lightning current models is required in the analysis of lightning events including the induced effects and frequency analyses of lightning strikes. Previous work in this area has produced very specific forms of the Heidler function that are used to represent lightning current waveshapes. This work however focuses on a generic solution with parameters that can be modified to produce any lightning current waveshape that is required. In the research presented, such an approximation is obtained. This function has an analytical solution to the integral and hence can be completely represented in the frequency domain. This allows for a true representation of Maxwell’s equations for Electromagnetic (EM) fields and for an analytical frequency domain analysis. It has parameters that can be changed to obtain different waveshapes (10/350, 0.25/100, etc.). The characteristics of the approximation are compared with those of the Heidler function to ascertain whether or not the function is applicable for use with the lightning protection standard (IEC 62305-1). It is shown that the approximation does represent the same characteristics as those of the Heidler function and hence can be used in IEC 62305-1 standardised applications. This represents a valuable contribution to engineers working in the field of lightning protection, specifically simulation models. / MT2017
25

Finite volume approximation of the Maxwell's equations in nonhomogeneous media.

January 2000 (has links)
Chung Tsz Shun Eric. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references (leaves 102-104). / Abstracts in English and Chinese. / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Applications of Maxwell's equations --- p.1 / Chapter 1.2 --- Introduction to Maxwell's equations --- p.2 / Chapter 1.3 --- Historical outline of numerical methods --- p.4 / Chapter 1.4 --- A new approach --- p.5 / Chapter 2 --- Mathematical Backgrounds --- p.7 / Chapter 2.1 --- Sobolev spaces --- p.7 / Chapter 2.2 --- Tools from functional analysis --- p.8 / Chapter 3 --- Discretization of Vector Fields --- p.10 / Chapter 3.1 --- Domain triangulation --- p.10 / Chapter 3.2 --- Mesh dependent norms --- p.11 / Chapter 3.3 --- Discrete circulation operators --- p.13 / Chapter 3.4 --- Discrete flux operators --- p.20 / Chapter 4 --- Spatial Discretization of the Maxwell's Equations --- p.23 / Chapter 4.1 --- Derivation --- p.23 / Chapter 4.2 --- Consistency theory --- p.29 / Chapter 4.3 --- Convergence theory --- p.33 / Chapter 4.3.1 --- Polyhedral domain --- p.33 / Chapter 4.3.2 --- Rectangular domain --- p.38 / Chapter 5 --- Fully Discretization of the Maxwell's Equations --- p.63 / Chapter 5.1 --- Derivation --- p.63 / Chapter 5.2 --- Consistency theory --- p.65 / Chapter 5.3 --- Convergence theory --- p.69 / Chapter 5.3.1 --- Polyhedral domain --- p.69 / Chapter 5.3.2 --- Rectangular domain --- p.77 / Chapter 6 --- Numerical Tests --- p.97 / Chapter 6.1 --- Convergence test --- p.97 / Chapter 6.2 --- Electromagnetic scattering --- p.99 / Bibliography --- p.102
26

Eletrodinâmica de Podolsky aplicada à cosmologia / Podolsky’s Electrodynamics applied to cosmology

SOUZA, Clícia Naldoni de 16 May 2016 (has links)
O mesmo procedimento estabelecido em teoria dos campos clássicos que nos leva a deduzir as equações de Maxwell, também conduz à eletrodinâmica de Podolsky, desde que a Lagrangia envolva derivadas do tensor intensidade de campo. A partir das equações de campo para Podolsky, que apresenta uma constante de acoplamento a associada à massa do fóton, é possível deduzir a equação de estado para a radiação de Podolsky. Essa equação é do tipo P=w(a,T)ε, em que P é pressão do gás fotônico; ε, a sua densidade de energia e w é o parâmetro da equação barotrópica que depende da temperatura T, além da massa do fóton. Usando essa equação de estado na expressão de conservação do tensor energia-momento de fluido perfeito e na equação de Friedmann, é possível resolver a dinâmica cósmica para um universo preenchido pela radiação de Podolsky. Mostramos que a dinâmica é pouco afetada pela presença de fótons massivos, uma vez que 0,282<wPodolsky<wMaxwell=1/3 para qualquer valor de T, ou equivalentente, do tempo cosmológico t. A correção de Podolsky para a lei de Stefan-Boltzmann é obtida para qualquer valor de temperatura, descrevendo potencialmente desde o universo primordial até o universo atual. Essa correção é relevante no intervalo 0≲ξ≲8 para o parâmetro adimensional ξ=βm. A máxima influência da massa do fóton acontece em ξref=2,899. Fora do intervalo referido intervalo de ξ, a dinâmica cosmológica de Podolsky tende à de Maxwell: nos limites de universo primordial (ξ≪1) e universo atual/futuro (ξ≫1), wPodolsky → wMaxwell e o fator de escala de Podoslsky vai com √t, de maneira consistente com um gás de fótons não massivos. / The same procedure established by the classical field theory which leads us to Maxwell's equations also leads to Podolsky's electrodynamics provided that the Lagrangian contains derivatives of the field strength. With Podolsky's field equations in hand, which has a coupling constant a associated to the photon mass, it's possible to derive an equation of state for Podolsky's radiation. The equation of state is of the type P=w(a,T)ε, where P is the pressure of the photon gas; ε is its energy density and w is the barotropic parameter depending on the temperature T and the photon mass. If we use the equation of state in the fluid equation and afterwards in Friedmann's equation, it's possible to solve the cosmic dynamics for a universe filled with Podolsky radiation. We show that the cosmic dynamics is not affected in a significant way by the massive photons, once 0,282< wPodolsky<wMaxwell=1/3 for any value of T, or equivalently of the cosmic time t. Podolsky correction to the Stefan-Boltzmann law is obtained for every T; it potentially describes the whole cosmic history. This correction is significant in the interval 0≲ξ≲8 for the dimensionless parameter ξ=βm. The maximum influence of the photon mass takes place at ξref=2,899. Out the above interval for ξ, Podolsky cosmic dynamics tends to the Maxwell's one: the scale factor behaves as √t in the limits corresponding to the primeval universe (ξ≪1) and present-day universe (ξ≫1), when wPodolsky →wMaxwell. / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
27

A survey on numerical methods for Maxwell's equations using staggered meshes / CUHK electronic theses & dissertations collection

January 2014 (has links)
Maxwell’s equations are a set of partial differential equations that describe the classic electromagnetic problems, electrodynamics etc. Effective numerical methods are derived to solve the equations in the past decades, and continued to be of great interest to be developed to its completion. In this thesis, we introduce and propose numerical methods using staggered meshes that deal with both two dimensional and three dimensional space problem in polygonal and general curved domains. / Finite difference method, finite volume method, spectral method and staggered discontinuous Galerkin method are discussed in the thesis. A forth order finite difference method using Taylor expansion technic is proposed. The integral form of the original Maxwell’s equations give rise to methods based on more general domain. For the finite volume method, covolume methods both on the cyclic polygon elements and noncyclic polygon elements are derived. To derive a higher order accurate method, staggered discontinuous Galerkin method based on the same domain decomposition present in the finite volume method use Nedelec elements is derived in two dimensional space, and spectral method using nodal high-order method operate on a general domain in 3D with flexible domain geometry is introduced. Numerical results are shown to show the performance oft he above mentioned approximation methods in 2D case. / 麥克斯韋方程組是一組描述經典電磁問題,電磁力學的偏微分方程。在過去數十年,行之有效的偏微分方程數值解已經被推導出並用於求解該方程,該問題現在仍然吸引著學者極大的興趣,並日臻完善。在這篇論文中,我們介紹並提出一些運用曲域交錯網格數值方法在二維和三維的多面體和更一般幾何體處理麥克斯韋方程組問題。 / 本論文對有限差分法,有限體積法,光譜法和交錯間斷有限元方法進行了討論。利用泰勒展開式這一方法推導出一個二維的四階有限差分方法。基於原來的麥克斯韋方程組的積分形式所得到的數值方法更適用於更普遍的域。對於有限體積法,對循環多邊形元素和非環狀多邊形元素的有限體積方法都將被導出。為了得到一個更高階準確的方法,基於有限體積法中使用的域分解方法,使用Nedelec元素,推導了二維空間的高階有限元方法。基於頂點高階數值方法的光譜法對於三維一般定義域的幾何形態更為靈活適用。在二維的定義域中,數值模擬結果驗證上述數值方法的精確性。 / Jian, Fangqiong. / Thesis M.Phil. Chinese University of Hong Kong 2014. / Includes bibliographical references (leaves 62-65). / Abstracts also in Chinese. / Title from PDF title page (viewed on 07, October, 2016). / Detailed summary in vernacular field only. / Detailed summary in vernacular field only.
28

Complex source point beam expansions for some electromagnetic radiation and scattering problems

Tap, Koray, January 2007 (has links)
Thesis (Ph. D.)--Ohio State University, 2007. / Title from first page of PDF file. Includes bibliographical references (p. 204-208).
29

Examining the application of conway-maxwell-poisson models for analyzing traffic crash data

Geedipally, Srinivas Reddy 15 May 2009 (has links)
Statistical models have been very popular for estimating the performance of highway safety improvement programs which are intended to reduce motor vehicle crashes. The traditional Poisson and Poisson-gamma (negative binomial) models are the most popular probabilistic models used by transportation safety analysts for analyzing traffic crash data. The Poisson-gamma model is usually preferred over traditional Poisson model since crash data usually exhibit over-dispersion. Although the Poisson-gamma model is popular in traffic safety analysis, this model has limitations particularly when crash data are characterized by small sample size and low sample mean values. Also, researchers have found that the Poisson-gamma model has difficulties in handling under-dispersed crash data. The primary objective of this research is to evaluate the performance of the Conway-Maxwell-Poisson (COM-Poisson) model for various situations and to examine its application for analyzing traffic crash datasets exhibiting over- and under-dispersion. This study makes use of various simulated and observed crash datasets for accomplishing the objectives of this research. Using a simulation study, it was found that the COM-Poisson model can handle under-, equi- and over-dispersed datasets with different mean values, although the credible intervals are found to be wider for low sample mean values. The computational burden of its implementation is also not prohibitive. Using intersection crash data collected in Toronto and segment crash data collected in Texas, the results show that COM-Poisson models perform as well as Poisson-gamma models in terms of goodness-of-fit statistics and predictive performance. With the use of crash data collected at railway-highway crossings in South Korea, several COM-Poisson models were estimated and it was found that the COM-Poisson model can handle crash data when the modeling output shows signs of under-dispersion. The results also show that the COM-Poisson model provides better statistical performance than the gamma probability and traditional Poisson models. Furthermore, it was found that the COM-Poisson model has limitations similar to that of the Poisson-gamma model when handling data with low sample mean and small sample size. Despite its limitations for low sample mean values for over-dispersed datasets, the COM-Poisson is still a flexible method for analyzing crash data.
30

Transport Process Between a Plasma and Workpiece

Yeh, Feng-Bin 04 July 2000 (has links)
¡@¡@¡@¡@¡@¡@¡@­^¡@¤å¡@ºK¡@­n¡@¡@¡@¡@¡@¡@¡@ Heat transfer of a molten splat to a thin layer rapidly solidified on a cold substrate and the heat transfer coefficient at the bottom surface of a splat is extensively and self-consistently investigated. Rapid freezing in the splat is governed by a nonequilibrium kinetics at the solidification front in contrast to the melting in the substrate simulated by the traditional phase change problem. Solving one-dimensional unsteady heat conduction equations and accounting for distinct properties between phases and splat and substrate, the results show the effects of dimensionless parameters such as the dimensionless kinetic coefficient, stefan number, latent heat ratio, initial, equilibrium melting, and nucleation temperature, and conductivity, density, and specific heat ratios between solid and liquid and splat and substrate on unsteady temperature fields and freezing and melting rates in the splat and substrate and on unsteady variation of Biot number are presented. The unsteady variation of the heat coefficient or Biot number can be divided by five regimes: liquid splat-solid substrate, liquid splat-liquid substrate, solid splat-solid substrate, solid splat-liquid substrate, and the nucleation of the splat. Appropriate choices of dimensionless parameters to control the time for freezing and melting of the splat and substrate and an understanding and estimation of the heat coefficient at the bottom surface of the splat therefore are presented. The velocity distribution function and transport variables of the positive ions and electrons in the collisionless presheath and sheath of a plasma near a wall partially reflecting ions and electrons are determined from a kinetic analysis. Since velocities of the ions and electrons near the wall are highly non-Maxwell-Boltzmann distributions, accurate predictions of transport variables such as density, fluid velocity, mean pressure, fluidlike viscous stress and conduction require kinetic analysis. The result find that dimensionless transport variables of ions and electrons in the presheath and sheath can be exactly expressed in terms of transcendental functions determined by dimensionless independent parameters of ions and electrons reflectivities of the wall, ion-to-electron mass ratio, charge number and electron-to-ion temperature ratio at the presheath edge. The effects of the parameters on transport variables at the wall are also obtained. The computed transport variables in the presheath and sheath show agreement with available theoretical data for a completely absorbing wall.

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