Thesis (Ph. D.)--University of Washington, 2002. / Vita. Includes bibliographical references (leaves 130-134).

Quasicrystal is the term used for a solid that possesses an essentially discrete diffraction pattern without having translational symmetry. Compared to periodic crystals, this difference in structure gives quasicrystals new properties that make them interesting to study -- both from a mathematical and from a physical point of view. In this thesis we review a mathematical description of quasicrystals that aims at generalizing the well-established theory of periodic crystals. We see how this theory can be connected to the cohomology of groups and how we can use this connection to classify quasicrystals. We also review an experimental method, NIXSW (Normal Incidence X-ray Standing Waves), that is ordinarily used for surface structure determination of periodic crystals, and show how it can be used in the study of quasicrystal surfaces. Finally, we define the reduced lattice and show a way to plot lattices in MATLAB. We see that there is a connection between the diffraction pattern and the reduced lattice and we suggest a way to describe this connection.

"RF excited CO2 lasers are widely used in industry. They provide relatively high power discharge levels while maintaining compactness, simplicity, and durability with respect to other competing laser technologies. To attain high power levels in the range of 5-10 KW, lasers with large electrode areas have to be designed. Unfortunately, due to the large electrode length requirements, transmission line effects make the discharge loading nonlinear, adversely affecting the efficiency of the CO2 laser. A standard approach to linearize the discharge loading is to introduce shunt inductors across the length of the electrodes in an effort to counter the capacitive nature of the discharge behavior. This thesis investigates and improves the theoretical models found in the literature in an effort to predict the discharge non-uniformity and allow for multiple shunt inductors installation. Specifically, we discuss the coupling of a CO2 laser discharge model with an electrical circuit solving scheme and how it can be characterized as one dimensional (1-D) and two dimensional (2-D) systems. The 1-D system is modeled using transmission line (TL) theory, where as the 2-D system is modeled using a finite difference time domain (FDTD) scheme. All our models were implemented in standard MATLAB code and the results are compared with those found in the literature with the goal to analyze and ascertain model limitations."

Thesis advisor: Michael J. Naughton / Surface plasmon polaritons (SPPs) are hybridized quasiparticles of photons and electron density waves. They are confined to propagate along metal-dielectric interfaces, and decay exponentially along the direction perpendicular to the interfaces. In the past two decades, SPPs have drawn intensive attention and undergone rapid development due to their potential for application in a vast range of fields, including but not limited to subwavelength imaging, biochemical/biomedical sensing, enhanced light trapping for solar cells, and plasmonic logic gates. These applications utilize the following intrinsic properties of SPPs: (1) the wavelength of SPPs is shorter (and can be much shorter) than that of free photons with the same frequency; (2) the local electric field intensity associated with SPPs can be orders of magnitude larger than that of free photons; and (3) SPPs are bound to metal surfaces, and are thus easily modulated by the geometry of those surfaces. Here, we present studies on SPPs along metal surfaces with novel structures, including the following: (1) SPP standing waves formed along circular metal surfaces that lead to a "plasmonic halo" effect; (2) directional reflectionless conversion between free photons and SPPs in asymmetric metal-insulator-metal arrays; and (3) broadband absorbance enhancement of embedded metallic nanopatterns in a photovoltaic absorber layer. These works may prove useful for new schemes for SPP generation, plasmon-photon modulation, ultrasensitive dielectric/bio sensing, and high efficiency thin film solar cells. / Thesis (PhD) — Boston College, 2014. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Physics.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1980. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Includes bibliographical references. / by Michael E. McClurken. / Ph.D.

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Made available in DSpace on 2016-06-02T20:28:29Z (GMT). No. of bitstreams: 1 6000.pdf: 514563 bytes, checksum: d12f104bdc11c10f2616ada01a16a407 (MD5) Previous issue date: 2014-03-13 / Financiadora de Estudos e Projetos / This work is concerned with the orbital stability of special solutions called "standing waves" for Hamiltonian systems in a real and invariant Hilbert space under the action of a specific group of isometries in such space. The stability investigated is orbital in the usual sense for a dynamical system and is with respect to perturbations of the initial condition. Initially we approach the problem in an abstract manner and then we show an application of the discussed method. / Estudamos, neste trabalho, a estabilidade orbital de soluções especiais do tipo "standing wave" para sistemas hamiltonianos em um espaço de Hilbert real e invariante sob a ação de específico grupo de isometrias em tal espaço. A estabilidade investigada para este perfil de soluções considera perturbações ocorrentes na condição inicial pré-fixada. Inicialmente, abordamos a técnica abstratamente para a obtenção da estabilidade orbital e, posteriormente, apresentamos uma aplicação do método discutido.

Orientadores: João Marcos Bezerra do O, Orlando Francisco Lopes / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Matematica, Estatistica e Computação Cientifica / Made available in DSpace on 2018-08-09T00:03:49Z (GMT). No. of bitstreams: 1 Severo_UberlandioBatista_D.pdf: 985878 bytes, checksum: 9d6e8a161a83e2812687d6ed4364bda1 (MD5) Previous issue date: 2007 / Resumo: Neste trabalho, estudamos questões relacionadas à existência, multiplicidade e comportamento de concentração de soluções do tipo onda estacionária, para uma classe de equações de Schrödinger quase-lineares, as quais modelam fenômenos físicos, por exemplo, na F³sica de Plasmas. Na obtenção de nossos resultados, usamos métodos variacionais, tais como, teoremas do tipo mini-max, bem como, teoria de regularidade de equações elípticas de segunda ordem / Abstract: In this work, we study questions related to existence, multiplicity and concentration behavior of standing waves, for a class of quasilinear Schrödinger equations, arising, for example, in Plasma Physics. To obtain our results, we use variational methods, such as, minimax theorems and also regularity theory of elliptic equations of second order / Doutorado / Analise / Doutor em Matemática

This diploma thesis deals with the determination of the material acoustic absorption in an impedance tube. The aim of the work is to propose a measuring experiment and to design measuring device with the intention of reducing costs. The aim is to carry out a measuring experiment on a manufactured measuring device. The results of the experiment are evaluated in terms of meeting the requirements formeasuring device. The results of the tested materials are compared with the values from the supplier.

We study a system of spatially discrete FitzHugh-Nagumo equations, which are nonlinear differential-difference equations on an infinite one-dimensional lattice. These equations are used as a model of impulse propagation in nerve cells. We employ McKean's caricature of the cubic as our nonlinearity, which allows us to reduce the nonlinear problem into a linear inhomogeneous problem. We find exact solutions for standing waves, which are steady states of the system. We derive formulas for all 1-pulse solutions. We determine the range of parameter values that allow for the existence of standing waves. We use numerical methods to demonstrate the stability of our solutions and to investigate the relationship between the existence of standing waves and propagation failure of traveling waves.