Dissertations / Theses on the topic 'Operator split'

BRAGA, João Philipe Macedo. Técnica split operator em coordenadas generalizadas. 2010. 84 f. Dissertação (Mestrado em Física) - Departamento de Física, Centro de Ciências, Universidade Federal do Ceará, Fortaleza, 2010.
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Quantum mechanics plays a fundamental role in the description and understanding of the natural phenomena. Actually, the phenomena that take place in atomic and subatomic scale can not be well explained without the quantum mechanics approach. Furthermore, there are a lot of phenomena in macroscopic scale that reveals the quantum behavior of nature. In this sense, we can say that quantum mechanics is fundamental for the understanding of all natural phenomena. In Quantum Mechanics the state of a particle is mathematically described by the wave function Ψ(r,t) and its time evolution is governed by time-dependent Schrödinger equation. Thus, we can state that the fundamental problem of quantum mechanics is to solve the Schrödinger Equation in an arbitrary situation. In this work, we study a numerical technique to solve the time-dependent and time-independent Schrödinger Equation known as Split Operator technique. This aproach uses approximations for the exponencial of sum of operators that do not commute in order to implement the time-evolution operator. It makes possible to reduce the solution of the Schrödinger equation to a successive processes of multiplication and solution of tridiagonal system of linear equations. It can be easily performed using a computer. The technique was studied in detail using cartesian coordinates, and we also explained how to use the technique with periodic or finite boundary conditions. We make use this technique to study the behavior of an electron subjected to a random potential. In this situation we face the Anderson Localization phenomena. Furthermore, we developed the Split Operator technique using generalized coordinates, and studied the problem of an electron confined to a cylinder surface. It was verified that the numerical results agree with the analytical ones. So we can conclude that the Split Operator technique using generalized coordinates produce reliable results.
A mecânica quântica desempenha um papel fundamental na descrição e entendimento dos fenômenos naturais. De fato, os fenômenos que ocorrem em uma escala muito pequena (atômica ou sub-atômica) não podem ser corretamente explicados fora do contexto da mecânica quântica. Além disso, existem muitos fenômenos em escala macroscópica que revelam o comportamento quântico da natureza. Nesse sentido, podemos dizer que a mecânica quântica é a base de todo nosso atual conhecimento sobre os fenômenos naturais. O estado de uma partícula em quântica é descrito matematicamente pela sua função de onda Ψ(r,t) e a evolução temporal de Ψ(r,t) é governada pela Equação de Schrödinger dependente do tempo. Dessa forma, podemos enunciar que o problema fundamental da mecânica quântica consiste em solucionar a Equação de Schrödinger numa situação arbitrária. Neste trabalho, estudamos uma técnica numérica de solução da Equação de Schrödinger dependente ou independente do tempo conhecida como Split Operator. Essa técnica utiliza formas aproximadas para a exponencial da soma de operadores que não comutam para implementar o operador evolução temporal, permitindo reduzir o processo de solução da Equação de Schrödinger a sucessivos processos de simples multiplicação e de solução de sistemas de equações lineares tridiagonais, que podem ser facilmente realizados por um computador. O formalismo da técnica em coordenadas cartesianas foi estudado em detalhes, onde mostramos como aplicá-lo para sistemas com condições de com torno periódicas ou com condições de contorno finitas. Utilizamos essa forma da técnica para estudar o comportamento de um elétron confinado numa região de energia potencial aleatória, onde nos deparamos com o fenômeno de Localização de Anderson. Além disso, desenvolvemos a técnica Split Operator em coordenadas generalizadas, aplicando-a para estudar o problema de um elétron confinado na superfície de um cilindro. Os resultados obtidos numericamente concordam muito bem com os resultados obtidos analiticamente, mostrando que a técnica Split Operator em coordenadas generalizadas nos leva a resultados confiáveis.

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico
A mecÃnica quÃntica desempenha um papel fundamental na descriÃÃo e entendimento dos fenÃmenos naturais. De fato, os fenÃmenos que ocorrem em uma escala muito pequena (atÃmica ou sub-atÃmica) nÃo podem ser corretamente explicados fora do contexto da mecÃnica quÃntica. AlÃm disso, existem muitos fenÃmenos em escala macroscÃpica que revelam o comportamento quÃntico da natureza. Nesse sentido, podemos dizer que a mecÃnica quÃntica à a base de todo nosso atual conhecimento sobre os fenÃmenos naturais. O estado de uma partÃcula em quÃntica à descrito matematicamente pela sua funÃÃo de onda Ψ(r,t) e a evoluÃÃo temporal de Ψ(r,t) à governada pela EquaÃÃo de SchrÃdinger dependente do tempo. Dessa forma, podemos enunciar que o problema fundamental da mecÃnica quÃntica consiste em solucionar a EquaÃÃo de SchrÃdinger numa situaÃÃo arbitrÃria. Neste trabalho, estudamos uma tÃcnica numÃrica de soluÃÃo da EquaÃÃo de SchrÃdinger dependente ou independente do tempo conhecida como Split Operator. Essa tÃcnica utiliza formas aproximadas para a exponencial da soma de operadores que nÃo comutam para implementar o operador evoluÃÃo temporal, permitindo reduzir o processo de soluÃÃo da EquaÃÃo de SchrÃdinger a sucessivos processos de simples multiplicaÃÃo e de soluÃÃo de sistemas de equaÃÃes lineares tridiagonais, que podem ser facilmente realizados por um computador. O formalismo da tÃcnica em coordenadas cartesianas foi estudado em detalhes, onde mostramos como aplicÃ-lo para sistemas com condiÃÃes de com torno periÃdicas ou com condiÃÃes de contorno finitas. Utilizamos essa forma da tÃcnica para estudar o comportamento de um elÃtron confinado numa regiÃo de energia potencial aleatÃria, onde nos deparamos com o fenÃmeno de LocalizaÃÃo de Anderson. AlÃm disso, desenvolvemos a tÃcnica Split Operator em coordenadas generalizadas, aplicando-a para estudar o problema de um elÃtron confinado na superfÃcie de um cilindro. Os resultados obtidos numericamente concordam muito bem com os resultados obtidos analiticamente, mostrando que a tÃcnica Split Operator em coordenadas generalizadas nos leva a resultados confiÃveis.
Quantum mechanics plays a fundamental role in the description and understanding of the natural phenomena. Actually, the phenomena that take place in atomic and subatomic scale can not be well explained without the quantum mechanics approach. Furthermore, there are a lot of phenomena in macroscopic scale that reveals the quantum behavior of nature. In this sense, we can say that quantum mechanics is fundamental for the understanding of all natural phenomena. In Quantum Mechanics the state of a particle is mathematically described by the wave function Ψ(r,t) and its time evolution is governed by time-dependent SchrÃdinger equation. Thus, we can state that the fundamental problem of quantum mechanics is to solve the SchrÃdinger Equation in an arbitrary situation. In this work, we study a numerical technique to solve the time-dependent and time-independent SchrÃdinger Equation known as Split Operator technique. This aproach uses approximations for the exponencial of sum of operators that do not commute in order to implement the time-evolution operator. It makes possible to reduce the solution of the SchrÃdinger equation to a successive processes of multiplication and solution of tridiagonal system of linear equations. It can be easily performed using a computer. The technique was studied in detail using cartesian coordinates, and we also explained how to use the technique with periodic or finite boundary conditions. We make use this technique to study the behavior of an electron subjected to a random potential. In this situation we face the Anderson Localization phenomena. Furthermore, we developed the Split Operator technique using generalized coordinates, and studied the problem of an electron confined to a cylinder surface. It was verified that the numerical results agree with the analytical ones. So we can conclude that the Split Operator technique using generalized coordinates produce reliable results.

SILVA, Francisco Wellery Nunes. Transporte eletrônico em semicondutores porosos baseado na equação de Schrodinger dependente do tempo. 2012. 77 f. Dissertação (Mestrado em Física) - Programa de Pós-Graduação em Física, Departamento de Física, Centro de Ciências, Universidade Federal do Ceará, Fortaleza, 2012.
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We propose in this work a theoretical study, of the properties of a electronic pulse, injected under a external bias, on a porous silicon layer, so that we could define fundamentally the shape of T X V and R X V curves, where T is the transmission coefficient and R is the reflection coefficient of the wave packet, trough the porous region. With this, we could make a simple calculation and obtain information about the electrical current in this material, using the very simple model I=Q/t, where we defined the time of transmission, as the time interval necessary for the electronic pulse to be consumed completely. This kind of approach is already known in the literature, propose by Lebedev and co-workers (1998). Using the definition of charge carrier mobility, we obtained information about it, since the principal aim of this work is the electronic transport in this kind of material, that despite a strong research on porous silicon, since the beginning of the nineties, the transport properties still remains a relatively unexplored area. The major incentive for this study is due to the strong possibility of application of this material in new optoelectronic devices such as LEDs. Along the development of this dissertation, we applied well known techniques for the computational modelling such as effective mass theory, for example, associated with methods like the periodic boundary conditions, and the absorbing boundary conditions. Treating of a quantum system, we begin all the work solving the time dependent Schröedinger equation. To do this task, we have used the numerical method known as Split-Operator, in order to obtain the solutions for this equation. Initially, the calculations in this dissertation where based in an isotropic effective mass, in order to optimise the calculation parameters. After this, we made calculations using an anisotropic effective mass for the different valleys of silicon. All these things leads us to believe that this work have a great importance regarding the contribution to the understanding of transport in electronic systems based on porous silicon, to maintain for some time the applications of this kind of material that was so revolutionary in the twentieth.
Neste trabalho, propomos um uma pesquisa teórica onde estudamos as propriedades de um pulso eletrônico em uma camada de silício poroso, injetado sob uma certa voltagem externa V. Desta forma, podemos definir fundamentalmente a forma das curvas T X V e R X V, onde T é o coeficiente de transmissão e R é o coeficiente de reflexão do pacote de onda através da região porosa. Aliado a estes dados, podemos fazer um cálculo simples e obter informações a respeito da corrente elétrica que atravessa o material, utilizando o modelo I=Q/t, onde definimos o tempo como o intervalo necessário para que o pulso seja consumido completamente, como proposto por Lebedev e colaboradores (1998). Utilizando a definição para mobilidade de portadores de carga, obtivemos informações sobre a mesma, pois este trabalho foca-se principalmente no estudo do transporte eletrônico neste tipo de material poroso, que apesar de um estudo intenso em silício poroso desde o início da década de noventa, as propriedades de transporte ainda permanecem um pouco inexploradas. O principal incentivo para que estudemos este material é devido à grande possibilidade da criação de dispositivos em opto-eletrônica tais como LEDs (Light Emissor Diode). Ao longo do desenvolvimento, empregamos técnicas já bem conhecidas para a modelagem de semicondutores, como a teoria da massa efetiva, por exemplo, associadas a técnicas de modelagem computacional, como o emprego de condições periódicas de contorno e condições de contorno absorvente. Por se tratar de um sistema quântico, tudo parte da solução da equação de Schrödinger dependente do tempo, e para executar esta tarefa fizemos uso de um método numérico conhecido como Split-Operator. Assim obtemos as soluções para a equação. Inicialmente, os cálculos realizados neste trabalho foram baseados em uma massa efetiva isotrópica, a fim de otimizar os parâmetros de cálculo, e só em seguida foram feitos cálculos baseando-se em massa efetiva anisotrópica para os diversos vales do silício poroso. Tudo isto nos leva a crer que este trabalho possui uma grande importância no que diz respeito à contribuição para o entendimento do transporte eletrônico em sistemas baseados em silício poroso, de forma a manter por mais algum tempo a aplicação deste tipo de material que foi tão revolucionário no século XX.

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico
Neste trabalho, propomos um uma pesquisa teÃrica onde estudamos as propriedades de um pulso eletrÃnico em uma camada de silÃcio poroso, injetado sob uma certa voltagem externa V. Desta forma, podemos definir fundamentalmente a forma das curvas T X V e R X V, onde T à o coeficiente de transmissÃo e R à o coeficiente de reflexÃo do pacote de onda atravÃs da regiÃo porosa. Aliado a estes dados, podemos fazer um cÃlculo simples e obter informaÃÃes a respeito da corrente elÃtrica que atravessa o material, utilizando o modelo I=Q/t, onde definimos o tempo como o intervalo necessÃrio para que o pulso seja consumido completamente, como proposto por Lebedev e colaboradores (1998). Utilizando a definiÃÃo para mobilidade de portadores de carga, obtivemos informaÃÃes sobre a mesma, pois este trabalho foca-se principalmente no estudo do transporte eletrÃnico neste tipo de material poroso, que apesar de um estudo intenso em silÃcio poroso desde o inÃcio da dÃcada de noventa, as propriedades de transporte ainda permanecem um pouco inexploradas. O principal incentivo para que estudemos este material à devido à grande possibilidade da criaÃÃo de dispositivos em opto-eletrÃnica tais como LEDs (Light Emissor Diode). Ao longo do desenvolvimento, empregamos tÃcnicas jà bem conhecidas para a modelagem de semicondutores, como a teoria da massa efetiva, por exemplo, associadas a tÃcnicas de modelagem computacional, como o emprego de condiÃÃes periÃdicas de contorno e condiÃÃes de contorno absorvente. Por se tratar de um sistema quÃntico, tudo parte da soluÃÃo da equaÃÃo de SchrÃdinger dependente do tempo, e para executar esta tarefa fizemos uso de um mÃtodo numÃrico conhecido como Split-Operator. Assim obtemos as soluÃÃes para a equaÃÃo. Inicialmente, os cÃlculos realizados neste trabalho foram baseados em uma massa efetiva isotrÃpica, a fim de otimizar os parÃmetros de cÃlculo, e sà em seguida foram feitos cÃlculos baseando-se em massa efetiva anisotrÃpica para os diversos vales do silÃcio poroso. Tudo isto nos leva a crer que este trabalho possui uma grande importÃncia no que diz respeito à contribuiÃÃo para o entendimento do transporte eletrÃnico em sistemas baseados em silÃcio poroso, de forma a manter por mais algum tempo a aplicaÃÃo deste tipo de material que foi tÃo revolucionÃrio no sÃculo XX.
We propose in this work a theoretical study, of the properties of a electronic pulse, injected under a external bias, on a porous silicon layer, so that we could define fundamentally the shape of T X V and R X V curves, where T is the transmission coefficient and R is the reflection coefficient of the wave packet, trough the porous region. With this, we could make a simple calculation and obtain information about the electrical current in this material, using the very simple model I=Q/t, where we defined the time of transmission, as the time interval necessary for the electronic pulse to be consumed completely. This kind of approach is already known in the literature, propose by Lebedev and co-workers (1998). Using the definition of charge carrier mobility, we obtained information about it, since the principal aim of this work is the electronic transport in this kind of material, that despite a strong research on porous silicon, since the beginning of the nineties, the transport properties still remains a relatively unexplored area. The major incentive for this study is due to the strong possibility of application of this material in new optoelectronic devices such as LEDs. Along the development of this dissertation, we applied well known techniques for the computational modelling such as effective mass theory, for example, associated with methods like the periodic boundary conditions, and the absorbing boundary conditions. Treating of a quantum system, we begin all the work solving the time dependent SchrÃedinger equation. To do this task, we have used the numerical method known as Split-Operator, in order to obtain the solutions for this equation. Initially, the calculations in this dissertation where based in an isotropic effective mass, in order to optimise the calculation parameters. After this, we made calculations using an anisotropic effective mass for the different valleys of silicon. All these things leads us to believe that this work have a great importance regarding the contribution to the understanding of transport in electronic systems based on porous silicon, to maintain for some time the applications of this kind of material that was so revolutionary in the twentieth.

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Universidade Federal de Sao Carlos
In the present thesis, we realize a computational modeling of semiconductor structures based on multiple quantum wells with filter barriers and on quantum wells with semiconductor diluted magnetic layers. We numerically solve the time-dependent Schrödinger s equation within the effective mass approximation, using the Split Operator method. Through the time evolved wave functions we access the dynamics quantities as the light assisted couplings of the states, in which the light is described by the inclusion of an oscillating electric field in the Hamiltonian. Then we determine the probabilities of absorption, oscillator strengths of the intersubband transitions induced by the light. Moreover we analyze the transmission probabilities and, in special, the system s photocurrent. The eigenstates and the eigenfunctions of the stationary states are also obtained within the method by simply making an imaginary time evolution. In the first work, the photocurrent of a multiple quantum well structure with filter barriers modulating the continuum above the wells was analyzed as a function of the applied bias. We find out an interesting dependence of the photocurrent with the applied field, as a differential negative photoconductance controlled by the field. We attribute this negative conductance to the interaction between the localized and extended states in the continuum, expressed by anticrossings between these states and the enhancement of the photocurrent at the crossings by the Landau-Zener-Stückelberg-Majorama like transitions. In the second work, it was evaluated the spin polarized photocurrent arising from quantum well s structures of GaMnAs, under light, electric and magnetic fields of few teslas. The study shows the existence of spectral domains in the THz ranges for which the proposed structure is strongly spin selective. For such photon frequencies, the photocurrent is spin polarized and the application of the external electric field reverts the polarization s signal. This behavior suggests the possibility of conveniently simple switching mechanisms. The physics underlying these results is studied and understood in terms of the spin-dependent coupling strengths emerging from the particular potential profiles of the heterostructures. We present two additional works related to the main ones. In the first additional one, we evaluated the dark current of the multiple quantum well structure with and without filter barriers. For doing this, we add totally the transmission probability through the structure in the Levine s model for the dark current. We observe that dark current is considerably reduced for the structure with the filter barriers when compared to the structure without these barriers. In the second additional work, we calculate the photocurrent in a ZnMnSe structure. We observe the generation of a spin polarized photocurrent controlled by the external electric field, as in the case of the GaMnAs structures.
Na presente tese, realizamos a modelagem computacional de estruturas semicondutoras baseadas em poços quânticos múltiplos com barreiras de filtro e em poços quânticos com camadas de material semicondutor magnético diluído. Para tanto, resolvemos numericamente a equação de Schrödinger dependente do tempo na aproximação de massa efetiva, por meio da evolução temporal das funções de onda do sistema, utilizando o chamado método do Split- Operator. Com as funções de onda evoluídas no tempo temos acesso às variáveis dinâmicas do sistema, como os acoplamentos entre os estados pela presença de luz, descrita na forma de um campo elétrico oscilante. Determinamos assim as probabilidades de absorção, forças de oscilador das transições intersubbandas geradas por essa excitação com luz, as probabilidades de transmissão através da estrutura e, em especial, o espectro de fotocorrente proveniente desses sistemas semicondutores. As autofunções e as autoenergias dos estados estacionários dos sistemas são obtidas pelo mesmo método realizando a evolução em tempo imaginário. No primeiro trabalho, a fotocorrente da estrutura de poços quânticos múltiplos com barreiras de filtro foi analisada em função do campo elétrico aplicado à estrutura. Foi encontrada uma dependência da fotocorrente com o campo elétrico bastante interessante, na forma de uma fotocondutância negativa controlada pelo campo elétrico aplicado à heteroestrutura. Atribuímos essa condutância negativa à interação entre estados localizados e estendidos no continuo se manifestando na forma de anticrossings e o aumento da fotocorrente para os valores de campo elétrico nos quais ocorrem esses crossings foi associado a transições de dois níveis do tipo Landau-Zener-Stückelberg-Majorama. No segundo trabalho, foi calculada a fotocorrente polarizada em spin de estruturas de poços quânticos de GaMnAs, na presença de um campo elétrico varável e um campo magnético de poucos teslas. O estudo mostrou a existência de domínios espectrais na região de THz do espectro eletromagnético, para os quais as estruturas propostas são altamente seletivas em spin. Para tais frequências, encontramos que a fotocorrente é polarizada em spin e a aplicação do campo elétrico é capaz de reverter forma muito eficiente o sinal da polarização. O comportamento observado sugere a possibilidade de mecanismos simples de controle sobre a fotocorrente e a Física por trás de tais efeitos foi entendida em termos dos acoplamentos dependentes de spin dos estados da estrutura, emergentes do perfil de potencial particular das heteroestruturas. Apresentamos dois trabalhos adicionais diretamente relacionados aos trabalhos principais. No primeiro trabalho, calculamos a corrente de escuro proveniente da estrutura de poços quânticos múltiplos com e sem barreiras de filtro, adicionando de forma integral a probabilidade de transmissão através da estrutura no modelo de Levine que determina essa corrente. Observamos que a presença das barreiras de filtro diminui significativamente a corrente de escuro dessa estrutura no regime de altos valores de campo elétrico. No segundo trabalho adicional, foi calculada a fotocorrente de uma estrutura de PQ com camada DMS, composta por ZnMnSe. Observamos a possibilidade de controle da polarização de spin com o campo elétrico, assim como no caso da estrutura composta de GaMnAs.

Ce travail de thèse consiste à visualiser sur un détecteur sensible en position les oscillations spatiales des électrons lents (~ meV) émis par photoionisation au seuil en présence d’un champ électrique extérieur. La figure d’interférence obtenue représente quantiquement le module carré de la fonction d’onde électronique. Ce travail fondamental nous permet d’avoir accès à la dynamique électronique quelques µm autour de l’atome et donc de mettre en évidence plusieurs mécanismes quantiques (champ coulombien, interaction électron/électron..) se déroulant à l’échelle atomique. Malgré la présence d’un cœur électronique quoique limité dans Li, nous avons réussi, expérimentalement et pour la première fois, à visualiser la fonction d’onde associée aux états Stark quasi-discrets couplés au continuum d’ionisation. En outre, à l’aide des simulations quantiques de propagation du paquet d’ondes, basées sur la méthode de « Split-operator », nous avons réalisé une étude complète sur les atomes H, Li et Cs tout en dévoilant les effets significatifs des résonances Stark. Un très bon accord, sur et hors résonances, a été obtenu entre les résultats simulés et les résultats expérimentaux. Par ailleurs, nous avons développé un modèle analytique généralisable permettant de comprendre profondément le fonctionnement d’un spectromètre de VMI. Ce modèle repose sur l’approximation paraxiale, il est basé sur un calcul d’optique matricielle en faisant une analogie entre la trajectoire électronique et le rayon lumineux. Un excellent accord a été obtenu entre les prédictions du modèle et les résultats expérimentaux
This work of thesis aims to visualize, on a position sensitive detector, the spatial oscillations of slow electrons (~meV) emitted by a threshold photoionization in the presence of an external electric field. The interference figure obtained represents the square magnitude of electronic wavefunction. This fundamental work allows us to have access to the electronic dynamics and thus to highlight several quantum mechanisms that occur at the atomic scale (field Coulomb, electron/electron interaction..). Despite the presence an electronic core in Li atom, we have succeeded, experimentally and for the first time, to visualize the wave function associated with the quasi-discrete Stark states coupled to the ionization continuum. Besides, using simulations of wave packet propagation, based on the "Split-operator” method, we have conducted a comprehensive study of the H, Li and Cs atoms while revealing the significant effects of the Stark resonances. A very good agreement, on and off resonances, was obtained between simulated and experimental results. In addition, we have developed a generalized analytical model to understand deeply the function of VMI spectrometer. This model is based on the paraxial approximation; it is based on matrix optics calculation by making an analogy between the electronic trajectory and the light beam. An excellent agreement was obtained between the model predictions and the experimental results

Ce travail de thèse consiste à visualiser sur un détecteur sensible en position les oscillations spatiales des électrons lents (~ meV) émis par photoionisation au seuil en présence d'un champ électrique extérieur. La figure d'interférence obtenue représente quantiquement le module carré de la fonction d'onde électronique. Ce travail fondamental nous permet d'avoir accès à la dynamique électronique quelques µm autour de l'atome et donc de mettre en évidence plusieurs mécanismes quantiques (champ coulombien, interaction électron/électron..) se déroulant à l'échelle atomique. Malgré la présence d'un cœur électronique quoique limité dans Li, nous avons réussi, expérimentalement et pour la première fois, à visualiser la fonction d'onde associée aux états Stark quasi-discrets couplés au continuum d'ionisation. En outre, à l'aide des simulations quantiques de propagation du paquet d'ondes, basées sur la méthode de " Split-operator ", nous avons réalisé une étude complète sur les atomes H, Li et Cs tout en dévoilant les effets significatifs des résonances Stark. Un très bon accord, sur et hors résonances, a été obtenu entre les résultats simulés et les résultats expérimentaux. Par ailleurs, nous avons développé un modèle analytique généralisable permettant de comprendre profondément le fonctionnement d'un spectromètre de VMI. Ce modèle repose sur l'approximation paraxiale, il est basé sur un calcul d'optique matricielle en faisant une analogie entre la trajectoire électronique et le rayon lumineux. Un excellent accord a été obtenu entre les prédictions du modèle et les résultats expérimentaux.

La microscopie de photoïonisation est une technique qui permet d'obtenir une image macroscopique de la fonction d'onde électronique habituellement confinée autour d'un atome. L'expérience consiste à photoïoniser près du seuil un atome en présence d'un champ électrique statique. Le traitement classique du mouvement d'un électron se déplaçant dans un champ coulombien en présence d'un champ électrique statique, montre qu'une multitude de trajectoires électroniques mènent à un point de l'espace classiquement accessible. Quantiquement, les ondes partielles associées à ces trajectoires interfèrent, et ce phénomène est directement mesurable au moyen d'un détecteur sensible en position. Cette thèse propose une étude classique, semi-classique et quantique de la microscopie de photoïonisation. L'originalité de ce travail est le développement de simulations par propagation de paquets d'ondes grâce un algorithme de type Split-Operator. Nous proposons une étude systématique de l'Hydrogène et montrons qu'il est possible d'observer à l'aide d'un microscope de photoïonisation, la fonction d'onde des états Stark résonants du continuum d'ionisation de l'Hydrogène. Enfin nous décrivons l'effet du cœur électronique sur la microscopie d'atomes non-hydrogénoïdes.

Orientador: Roger William Fernandes Moreira
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba
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Resumo: Objetivos: Avaliar a prevalência, fatores de risco e curso clínico da dor neuropática (DN) após osteotomia sagital dos ramos mandibulares (OSRM) em uma grande amostra de pacientes. Materiais e Métodos: Estudo retrospectivo realizado em dois centros médicos do Hospital Kaiser Permanente da Norte da Califórnia, no período de janeiro de 2007 até setembro de 2012, nos pacientes submetidos à OSRM. Fatores demográficos, clínicos e cirúrgicos foram identificados nos prontuários dos pacientes, bem como comorbidades associadas. A prevalência, sinais e sintomas, características da dor e a resposta ao tratamento nos pacientes afetados foram analisados. Resultados: Os autores identificaram 1.778 pacientes que foram submetidos à OSRM e, destes, 107 foram excluídos de acordo com critérios pré-definidos. A média de idade dos pacientes (1.671) foi de 24 anos (intervalo interquartil de 19 a 35 anos) e 62,4% eram do gênero feminino. Sete pacientes desenvolveram DN após OSRM, cuja prevalência foi de 0,42%. Todos eles eram mulheres, cuja média de idade foi de 48 anos. Os fatores de risco para o desenvolvimento de DN após OSRM incluíram: idade superior a 40 anos (p = 0.0098), depressão (p = 0.0100), e gênero feminino (p = 0.0497). O inicio da DN ocorreu em uma média de 30 dias de pós-operatório (18 a 56 dias), com média de duração de 52 dias (30 a 69,5 dias). Todos os pacientes responderam favoravelmente à medicações anticonvulsivantes (n = 6) ou antidepressivas tricíclicas (n = 1), além de nenhum dos pacientes ter desenvolvido dor crônica pós-cirúrgica. Conclusões: A dor de origem neuropática é uma complicação infrequente após OSRM, acometendo 1 a cada 238 pacientes nesta amostra. A curta duração e a reposta favorável às medicações empregadas reforça esse achado. Os resultados dessa investigação chamam a atenção para a necessidade de futuros estudos prospectivos para melhor compreensão da DN pós-operatória
Abstract: Purpose: To estimate the prevalence of, risk factors for, and clinical course of neuropathic pain (NPP) after sagittal split ramus osteotomy (SSRO) of the mandible in a large cohort of patients. Materials and Methods: A retrospective cohort of all patients who underwent SSRO at 2 medical centers within Kaiser Permanente Northern California from January 2007 through September 2012 was assembled. Demographic, clinical, and surgical factors were collected from medical records and relevant comorbidities were identified. The prevalence of NPP in the cohort was calculated and the clinical signs, symptoms, temporal characteristics and treatment response in affected patients were noted. Results: The authors identified 1.778 patients who underwent SSRO and excluded 107 patients according to predefined criteria. The remaining 1.671 patients had a median age of 24 years (interquartile range from19 to 35 years) and 62.4% were women. Seven patients developed NPP after SSRO, which was an overall prevalence of 0.42%. All patients with NPP in this cohort were women and had a median age of 48 years. The risk factors for developing NPP after this surgery were age over 40 years (p = 0.0098), depression (p = 0.0100), and female gender (p = 0.0497). NPP developed an average of 30 days postoperatively (range, 18 to 56 days) and persisted for a median duration of 52 days (range, 30 to 69.5 days). All patients responded favorably to anticonvulsant (n = 6) or tricyclic (n = 1) medications, and no patients developed chronic postsurgical pain. Conclusions: NPP was an infrequent complication after SSRO, occurring in 1 of 238 patients in this cohort. The short duration and positive response to medication are reassuring findings. The results of this investigation highlight the need for prospective studies to further understand the spectrum of postoperative NPP
Doutorado
Cirurgia e Traumatologia Buco-Maxilo-Faciais
Doutora em Clínica Odontológica

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
The increasing number of users connected to the Internet led it to become a major vehicle for personal and business transactions in the last years. Nevertheless, its unavailability can result in losses, including nancial ones, for its users. Despite of all eorts to keep the network availability nearest to 100% of the time, reasearches have shown that the existing protocols have two algorithmic problems caused by message losses or disruption, named No Brain and Split Brain, which attack the network availability and lead it to crash. Thus, those researches propose that such protocols must be changed considering the possibility of message loss. In this way, this research species and implements the High Availability Router Protocol (HARP), which is a new high availability protocol that operates in stateless environments. Furthermore, a validation system is presented to test high availability protocols for the sake of link failures. The specication concerns to environment assumptions, services, vocabulary, format and procedure rules specied by nite state machine, moreover, the specication is complemented with a TLA+ formal description regarding concurrent systems context intending to ratify the HARP good properties. The HARP implementation consists of its prototyping on FPGA and the validation system based on a System-on-Programmable Chip (SOPC).
O crescente número de usuários conectados à Internet favoreceu que ela se tornasse um dos principais veículos de transações pessoais e empresariais nos últimos anos. Entretanto, sua indisponibilidade pode acarretar perdas, inclusive de caráter nanceiro, aos seus usuários. Apesar dos esforços empenhados para manter a rede 100% do tempo dispon ível, pesquisas apontam que os protocolos de alta disponibilidade apresentam problemas algorítmicos conhecidos como Acéfalo e Cérebro Partido, que são causados por perdas e erros de mensagens e levam à indisponibilidade da rede. Tais pesquisas propõem, então, que alterações sejam feitas nas especicações dos protocolos existentes considerando que mensagens podem não chegar a seus destinos conforme previsto. Em virtude disso, este trabalho especica e implementa um novo protocolo de alta disponibilidade, chamado High Availability Router Protocol (HARP), cuja operação acontece em ambientes sem preservação de estado. Adicionalmente, apresenta-se um sistema de validação para protocolos de alta disponibilidade que os testam segundo falhas nos canais de comunicação. A especicação do HARP concerne ao ambiente de operação, serviços, vocabulário, formato de mensagens e regras de procedimento especicadas através de máquinas de estados - nitos. Ademais, a especicação é complementada pela descrição formal em TLA+ e sua vericação no contexto de sistemas concorrentes para raticar as boas propriedades do protocolo. A implementação do HARP consiste da prototipagem em FPGA e o sistema de validação é baseado em um System on a Programmable Chip.
Mestre em Ciência da Computação

The aim of this work is to show the application of operational research on an example that is put into practise and to show the usabillity of this science field. The problem solved will be the Vehicle routing problem with split delivery. The whole process of solving this issue is described in the text. From the income data and automatised data aquisition from publicly acessible resources for the distance matrix to the created mathemathical model for this issue together with the implementation in SW Lingo. Furthermore, in my work classic distribution problem of linear programming in connection to the solved issue are described. Beside that three mathematical models are shown that are occyupying with this type of delivery. They can not be used for fading the solution to this issue as they include certain requirements or conditions which are not taken into account by the given models.

A nominal setup at Volvo Cars Corporation is the placement determination for two adjacent exterior parts on the car. To place the parts in optimal positions, nominal values for gaps and flushes are determined. When a nominal setup becomes more complex, VSA (Vehicle System Architect) is summoned. These appearing situations regard the involvement of several attributes and the need for a combination of vari- ous contributions. There are static, dynamic (overslam or dynamic movement) and thermal contributions that are combined into nominal values of gap and flush dis- tances. The determination process of a nominal setup contains both calculation for each contribution, as well as the combination method which takes place at the VSA meetings. This Master Thesis project consists of the development of an improved determination process for nominal setups. The current determination process has a low level of transparency within the differ- ent group’s methods. Another issue is the insecurity of the probability estimations made when combining the contributions. Therefore, the focus of the project was to infuse a greater understanding of the contribution derivations, and greater insight into the probability of the taken risks. To achieve that, the project was divided into three parts; mapping of the determination process, individual contribution improve- ments and finally, improvements to the combination method. In contemplation of improving a process, plenty of knowledge needs to be gathered, regarding methods, simulations and possibilities. This was executed by interviewing experts within spe- cific areas at the different groups at VCC. Development of the improvements was done by interviews and various studies. It was shown that the mapping of the determination process increased the trans- parency between the groups as it increased the understanding of individual groups’ work. Contribution improvements lead to more realistic load cases used for dimen- sioning. A performed overslam clinic, where closing velocity data of a tailgate were collected, lead to a greater statistical base for which load case should be used. For dynamic movement, another method is proposed that considers relative movement instead of applied accelerations. For the thermal contribution, the approach of ge- ographically gathered temperature data was proposed. The improved combination method generates combinations with regard to three input values instead of one, from each contribution, to create different combination scenarios. The probabilities of the scenario occurrences are estimated which gave VCC a greater understanding of what risks that are taken. Furthermore, the combination method also educates the VSA meeting attendees by exhibiting the derivations and bases for each contri- bution.

博士
國立交通大學
運輸與物流管理學系
105
The split-delivery vehicle routing problem (SDVRP), in which the demand of a customer can be split and delivered by several vehicles, would result in less cost than the conventional vehicle routing problem. However, split deliveries also incur extra work for logistics operations and undesirable distractions to customers. How to tradeoff cost efficiency and customer service in the split-delivery related problems thus is an important issue. Recently, Gulczynski et al. [29] proposed a variant of the SDVRP called the SDVRP-MDA, in which the customers each require a minimum delivery amount (MDA) every time they are visited. In this dissertation, we propose a new variant of the SDVRP, i.e., the spit-delivery VRP with limited number of deliveries (SDVRP-LND), which considers the number of deliveries for each customer is restrained to kmax. We propose a unified multi-start heuristic method, i.e., SRC+IMP (Split-delivery Route Construction + solution IMProvement), to solve the SDVRP and its variants of the SDVRP-MDA and the SDVRP-LND. The initial-solution generator SRC adaptively applies either node-insertion or route-addition procedures, which were designed specifically for the SDVRP and its variants, to generate an initial solution. The IMP conducts local search with multiple neighborhoods for solution improvement, in which we developed a novel node ejection-chain operator for the split-delivery related problems. The overall SRC+IMP combines the SRC and the IMP modules to implement a multi-start solution procedure with a single parameter to control the restart. The proposed SRC+IMP algorithms are tested with all the related benchmark problems. We conduct the IMP module with two variable neighborhood descent methods, i.e., VND and RVND. It is found that the performance of the SRC+RVND is better than that of the SRC+VND. The results of the SRC+RVND for the SDVRP show that, out of 32 instances tested, the average deviation from the best known solutions (BKS) is 0.36%, which is only second to the ILS algorithm (Silva et al. [44]). For the SDVRP-MDA, out of the 128 instances tested, the results reveal 81 BKS and 36 new best solutions; the average deviation is -0.27%. For the SDVRP-LND, out of the 22 instances tested, we find 5 BKS and 5 new best solutions; the average deviation is 0.07%. We also investigate the impact of kmax to the potential cost saving of the SDVRP-LND. It is found that, for kmax=3, the average cost saving is 4.11%, which is only 0.06% less than that of the SDVRP. This implies that the SDVRP-LND with kmax=3 can provide a valuable and easy-to-implement tool for logistics operations.

The aim of this work is to develop and validate a continuum model for the simulation of the thermomechanical response of a shape memory polymer (SMP). Rather than integral type viscoelastic model, the approach here is based on the idea of two inter-penetrating networks, one which is permanent and the other which is transient together with rate equations for the time evolution of the transient network. We find that the activation stress for network breakage and formation of the material controls the gross features of the response of the model, and exhibits a "thermal Bauschinger effect". The model developed here is similar to a thermoviscoelastic model, and is developed with an eye towards ease of numerical solutions to boundary value problems. The primary hypothesis of this model is that the hysteresis of temperature dependent activation-stress plays a lead role in controlling its main response features. Validation of this hypothesis is carried out for the uniaxial response from the experimental data available in the literature for two different SMP samples: shape memory polyurethane and Veriflex, to show the control of the evolution of the temperature sensitive activation stress on the response. We extend the validated 1D model to a three dimensional small strain continuum SMP model and carry out a systematic parameter optimization method for the identification of the activation stress coefficients, with different weights given to different features of the response to match the parameters with experimental data. A comprehensive parametric study is carried out, that varies each of the model material and loading parameters, and observes their effect on design-relevant response characteristics of the model undergoing a thermomechanical cycle. We develop "response charts" for the response characteristics: shape fixity, shape recovery and maximum stress rise during cooling, to give the designer an idea of how the simultaneous variation of two of the most influential material parameters changes a specific response parameter. To exemplify the efficacy of the model in practical applications, a thermoviscoelastic extension of a beam theory model will be developed. This SMP beam theory will account for activation stress governed inelastic response of a SMP beam. An example of a three point bend test is simulated using the beam theory model. The numerical solution is implemented by using an operator split technique that utilizes an elastic predictor and dissipative corrector. This algorithm is validated by using a three-point bending experiment for three different material cases: elastic, plastic and thermoplastic response. Time step convergence and mesh density convergence studies are carried out for the thermoviscoelastic FEM model. We implement and study this model for a SMP beam undergoing three-point bending strain recovery, stress recovery and cyclic thermomechanical loading. Finally we develop a thermodynamically consistent finite continuum model to simulate the thermomechanical response of SMPs. The SMP is modeled as an isotropic viscoplastic material where thermal changes govern the evolution of the activation stress of the material. The response of the SMP in a thermomechanical cycle is modeled as a combination of a rubbery and a glassy element in series. Using these assumptions, we propose a specific form for the Helmholtz potential and the rate of dissipation. We use the technique of upper triangular decomposition for developing the constitutive equations of the finite strain SMP model. The resulting model is implemented in an ODE solver in MATLAB, and solved for a simple shear problem. We study the response of the SMP model for shear deformation as well as cyclic shear deformation at different initial temperatures. Finally, we implement the thermomechanical cycle under shear deformations and study the behavior of the model.

碩士
國立中興大學
電機工程學系
92
Abstract A memory cell storing more than one bit per cell is termed multilevel memory. Several techniques to implement multilevel flash cells have been proposed. The first category consists of controlling the amounts of charge stored in the single floating gate for multilevel operation, but the peripheral circuit becomes more complicated. The second category consists of the store charges in different locations of a flash cell. We design an asymmetrical split floating gate (ASFG) of multilevel flash memory devices belonged to the second category. The structure of ASFG is like the split gate flash. The ASFG use FN tunneling method to store different amounts of the charge in different floating gates, and to generate different threshold voltage to achieve 4-level operation. It uses FN (tunneling mechanism) for programming and erasure operation in order to low power consumption. In addition, in the reading way, the data can be read from the same electrode. In another way, it does require different electrodes to identify different logic levels. Therefore, the access time of the data from the same electrodes is less. So, we design the structure of ASFG that is reading in the same electrode.

This M.Sc. thesis treats the feasibility of the Radon Split for solving radial integral equation involving radially acting integral operator on the Hardy-Lebesgue Class [Special characters omitted.] of the half-upper plane [Special characters omitted.] . In this process, we take a scrutinizing look at [Special characters omitted.] by means of the conformal map [Special characters omitted.] taking [Special characters omitted.] . We demonstrate that [Special characters omitted.] -functions f always possess a.e. unique boundary values [Special characters omitted.] [Special characters omitted.] as [Special characters omitted.] from within [Special characters omitted.] . These boundary values are also angular limit functions in the [Special characters omitted.] -sense--i.e. [Special characters omitted.] as [Special characters omitted.] from within [Special characters omitted.] . Concomitantly, the [Special characters omitted.] -parameter family of [Special characters omitted.] -kernels [Special characters omitted.] with uniformly bounded double norms, have unique angular limit [Special characters omitted.] -kernels [Special characters omitted.] in the [Special characters omitted.] -sense--i.e. [Special characters omitted.] = [Special characters omitted.] [arrow right] 0 as [Special characters omitted.] from within [Special characters omitted.] . These properties are consequences of the inverse Mellin-Transform, which transformation originates in Fourier-Plancherel Theorem for [Special characters omitted.] and [Special characters omitted.] . Because of this Mellin-Transform representation of [Special characters omitted.] and [Special characters omitted.] we may regard [Special characters omitted.] as the three entities: [Special characters omitted.] and [Special characters omitted.] , where the first two are Hilbert spaces and the third is a dual system with [Special characters omitted.] Consequently, we look upon [Special characters omitted.] as the Banach algebra [Special characters omitted.] and further as the Hilbert space [Special characters omitted.] . We successfully construct for every radial linear integral operator K of finite rank on [Special characters omitted.] , its transpose K T in [Special characters omitted.] as well as its adjoint K * in [Special characters omitted.] , which leans heavily on the interaction of * and T in [Special characters omitted.] . We prove a necessary and sufficient condition as to when an element of [Special characters omitted.] is radially representable. And finally, we construct Fredholm Resolvents not only finite-dimensional [Special characters omitted.] but also, by means of the Radon Split, the Fredholm Resolvents of any [Special characters omitted.] and that of its transpose K T in terms of [Special characters omitted.] . Herein, the Fredholm Alternatives are induced by the derivations.

碩士
國立成功大學
機械工程學系碩博士班
101
The aim of this research is to build up a splint generated program for transferring orthognathic surgical planning to operation. Because of defects of traditional splint including multiple coordiates transformation, time consuming and manual errors. Some researchers employed Boolean different method to generated the digital splint have several pitfalls such as remodeling shape of the pre-build template, undercut and tolerence problems, In this study, we present a new method to solve above problems. Base on the surface modeling operation, we resample the shape of upper and lower crown of teeth to generate the fundamental structure of the splint, then adjusting bite prints to solve the problem of undercut and also expand teeth bite prints. Moreover, we present a new method to automatic adjust bite splint outlook along the arch in order to create smoothness. Finally, the physical splints are genereated by rapid prototype technology. We have verified deviations of the whole process which is 0.500+-0.196mm and, also accuracy of the generated bite splint is 0.269+-0.059mm. In conclusion, the method of designing digital splint can be used by modifying sampling accuracy to solve common undercut problems, which allow the digital bite splint successfully transfer surgical planning to be used in the operation room.

博士
國立成功大學
電機工程學系
88
Combining the outstanding programming efficiency of split-gate structure with the economic advantages of “Flash” erase design, the split-gate Flash memory cell hold the promise to realize the high performance and high reliability Flash EEPROM. In this dissertation, the split-gate Flash memory cell has been intensively investigated. The author has presented new preparation technologies and novel operation techniques to improve performance and reliability of split-gate Flash memory cell. By using the post poly-Si gate N2O annealing, the program efficiency was improved and the program disturbance due to reverse tunneling was suppressed significantly. By utilizing chemical mechanical polishing (CMP) to smooth the poly-Si surface, the tunneling corner profile of floating-gate becomes more uniform and thus a more stable and more reliable erase operation was achieved. In addition, the negative substrate bias (NSB) was first proposed in this dissertation to improve the cell’s performance and to lessen the read-out current degradation in cycling endurance test. The key point is the NSB can effectively enhance the necessary electrical field in both programming and erasing operation. Moreover, a novel operation technique with negative bias on the inhibited word-line has also been utilized to solve the isolation issues resulting from device scaling down and the trade-off between programming speed and programming disturbance. Finally, the impacts of different WSiX polycide gate process on the devices electrical characteristics and polyoxide quality have been investigated in detail. With fluorine incorporation, the CVD WSiX polycide gate devices show lower short channel effects and better ION-IOFF performance. Furthermore, the experimental results indicates that a thin polyoxide with DCS-based CVD WSiX has both good J-E characteristics and high reliability, i.e. low conducted current, high breakdown field and less electron trapping rate, high Qbd due to the moderated fluorine incorporation.

碩士
國立臺灣科技大學
電子工程系
102
The important blocks in the phase locked loop (PLL) are the voltage controlled oscillator (VCO) and the divider circuit. The most power consumption of PLL consumes in VCO and divider. The VCO is requested a low phase-noise to avoid corrupting the mixer-converted signal by close interfering tones for VCO circuit, and the Figure of Merit (FOM) of VCO can be determined by it’s performance. Firstly, this thesis designs complementary Colpitts voltage controlled oscillator, A 0.7GHz Colpitts oscillator is designed and implemented in a 0.18μm CMOS 1P6M process. It consists of a Colpitts negative resistance cell and an open square loop resonator. At the supply voltage of 1.8 V, the output phase noise of the oscillator is -86.28 dBc/Hz at 1MHz offset frequency from the carrier frequency of 0.7 GHz(Using in UHF Band). The FOM(figure of merit) is -135.57dBc/Hz. Total oscillator core power consumption is 5.76 mW. Secondly, a new wide locking range divide-by-3 injection-locked frequency divider (ILFD) using a standard 0.18 μm BiCMOS process is presented. The ILFD uses a cross-coupled nMOSFET oscillator with an HBT tail and it also use two HBT injection SiGe HBTs. The injection HBTs serve as harmonic and nonlinear mixers. The core power consumption of the ILFD core is 8.328 mW. The divider’s free-running frequency is tunable from 4.32 to 3.78 GHz by tuning the varactor’s control bias, and at the incident power of 0 dBm. The maximum locking range is 1.87 GHz (23.71%), The incident frequency from 6.95 to 8.82 GHz. The operation range is 2.85 GHz (36.42%), from 6.4 to 9.25 GHz. In addition, the ILFD uses a cross-coupled nMOSFET oscillator with an HBT tail and it also use two HBT injection SiGe HBTs. The effect of hot-carrier stressed injection HBTs on the performance of the ILFD is studied. The stress induces the shift in oscillation frequency, phase noise and HBT output characteristics. It is found the locking range decreases with stress time at fixed dc injection base-emitter bias. Thirdly , a new wide locking range divide-by-3 injection-locked frequency divider (ILFD) using a standard 0.18 μm CMOS process is presented. The ILFD is based on a class-C capacitive cross-coupled oscillator. By changing the dc gate bias of cross-coupled transistors to below the dc drain voltage, the locking range of ILFD has been improved. At the supply voltage of 1.8 V, the core power consumption of the ILFD core is 10.7 mW. The incident power of 0 dBm the divider’s maximum locking range is 3.3 GHz (24.17%),with the incident frequency from 12 to 15.3 GHz. At incident power of 0 dBm the divider’s operation range is 4.8 GHz (35.2%), from the incident frequency 10.5 to 15.3 GHz. Finally ,a wide locking range divide-by-3 injection-locked frequency dividers (ILFDs) using a standard 0.18 μm CMOS process are presented. The ILFDs are based on a cross-coupled n-core MOS LC-tank oscillator with either injection NMOSFETs or pMOSFETs. The core power consumption of the ILFD core with injection nMOSFETs is 10.8 mW at the supply voltage of 0.9V and with circuit core current of 12mA. At the incident power of 0 dBm the maximum locking range is 4.2 GHz (37.17%), from the incident frequency 9.2 to 13.4 GHz. The core power consumption of the ILFD core with injection pMOSFETs is 13.77 mW at the supply voltage of 0.9V and with circuit core current of 15.3mA. At the incident power of 0 dBm the maximum locking range is 2.4 GHz (25%), from the incident frequency 8.4 to 10.8 GHz.