Thesis (M.S.)--University of Texas at El Paso, 2007. / Title from title screen. Vita. CD-ROM. Includes bibliographical references. Also available online.

Thesis (Ph.D.)--Computing, Georgia Institute of Technology, 2008. / Committee Chair: Schwan, Karsten; Committee Member: Cooper, Brian F.; Committee Member: Feamster, Nick; Committee Member: Liu, Ling; Committee Member: Sahai, Akhil.

Thesis (Ph. D.)--Ohio State University, 2007. / Title from first page of PDF file. Includes bibliographical references (p. 108-118).

Orientadores: José Pissolato Filho, Sérgio Kurokawa / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-22T00:02:34Z (GMT). No. of bitstreams: 1 Costa_EduardoCoelhoMarquesda_D.pdf: 1639814 bytes, checksum: 41a5776b46ed850ac50a5bc6db923da7 (MD5) Previous issue date: 2013 / Resumo: Uma metodologia alternativa e aprimorada para modelagem de linhas de transmissão multifásicas é apresentada ao longo do desenvolvimento proposto. O desacoplamento modal das fases e cabos pára-raios dá-se por meio de uma metodologia otimizada no uso das matrizes de transformação modal ao longo das sucessivas transformações entre os domínios dos modos e das fases, eliminando os erros decorrentes da modelagem e representação da linha fazendo uso de análise modal. A representação equivalente de cada modo de propagação é desenvolvida por elementos discretos convencionais com base na teoria fundamental de circuitos elétricos, o que torna a modelagem em questão simplificada, porém não menos precisa. Para modelagem do efeito da frequência nos parâmetros longitudinais da linha, é utilizado vector fitting para sintetizar os parâmetros de forma equivalente e por elementos discretos para cada modo de propagação do sistema multifásico. O sistema de equações diferenciais é representado no espaço de estados e facilmente solucionado por métodos numéricos de integração. No entanto, propõe-se a resolução do sistema de equações de estado por meio de um método de solução analítico, significativamente mais eficaz computacionalmente e mais robusto que o método de integração trapezoidal, amplamente aplicado na simulação de transitórios eletromagnéticos. Ademais, o método analítico possibilita o desenvolvimento de uma metodologia híbrida, adequada tanto na simulação de fenômenos transitórios quanto na simulação fenômenos em regime permanente. O modelo proposto é totalmente desenvolvido no domínio do tempo, sem a utilização de transformadas inversas e convoluções, tornando simples a integração de outros dispositivos e elementos não lineares ao longo da linha. Por fim, um processo utilizando FIR digital filtering integrado à modelagem por matrizes de estado, elimina todas as oscilações espúrias decorrentes da discretização da linha por elementos discretos e erros de truncamento. Em suma, o modelo computacional proposto apresenta uma metodologia aprimorada que se estender desde a modelagem dos parâmetros elétricos da linha à simulação propriamente dita dos transitórios eletromagnéticos, na ordem de poucos milissegundos, e fenômenos transitórios mais lentos, próximos do sinal fundamental em regime permanente / Abstract: An alternative and accurate methodology to model multiphase transmission lines is presented in the proposed development. The modal decoupling of the phases and shield wires is given by an optimized methodology in the use of the modal transformation matrix through the successive transformations between modal and phase domains, correcting the errors associated with the modeling and representation of the line by using analysis modal. Each propagation mode is represented by conventional lumped elements widely approached in the electrical circuit theory, which simplify the equivalent modeling, although a no less accurate procedure. To insert the frequency dependence of the longitudinal parameters in the line model, the vector fitting is applied to synthesize the parameters by an equivalent lumped circuit for each propagation mode of the multiphase system. The system of differential equations, resulting from the differential equations associated with the modal parameters, is represented in the state space and easily solved by numeric integration methods. Although, an analytical solution method is proposed to solve the system of state equations. This solution method is more efficient in computational terms and more robust than the well-known trapezoidal rule, widely used for simulation of electromagnetic transients. Furthermore, the proposed analytical method enables the development of a hybrid methodology, properly adapted to simulate transients as well as steady-state phenomena. The proposed model is completely developed in the time domain, without the use of inverse transforms and convolutions, which means that the proposed modeling is totally compatible with any other power electrical devices and nonlinear elements modeled in the time domain. Finally, a process using FIR digital filtering integrated to the modeling by state matrices eliminates all the spurious oscillations occurred from the line parameters discretization and truncation errors. In short, the proposed computational model presents an improved methodology carried out since the line electrical parameters modeling up to the simulation of electromagnetic transients of a few microseconds up to slow transient phenomena, close of the steady-state fundamental signal / Doutorado / Energia Eletrica / Doutor em Engenharia Elétrica

Orientadores: Luiz Koodi Hotta, Fernando Antônio da Silva Moura / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Matemática, Estatística e Computação Científica / Made available in DSpace on 2018-08-20T15:43:54Z (GMT). No. of bitstreams: 1 LunaHernandez_Angela_M.pdf: 2230052 bytes, checksum: 7cee5005f5f1bd9bbdd565de481db0ad (MD5) Previous issue date: 2012 / Resumo: A dissertação apresenta o processo de estimação em pesquisas repetidas sob o enfoque de séries temporais, empregando Modelos de Espaço de Estados e o filtro dos mínimos quadrados generalizados ou filtro GLS. Este filtro permite o tratamento de modelos com erros de observação autocorrelacionados de forma mais simples do que utilizando o filtro de Kalman e, além disso, possibilita a modelagem conjunta de várias subpopulações ou domínios sob restrições de benchmark obtidas a partir da mesma pesquisa. Isto não só permite manter a coerência entre as estimativas obtidas pelo método, e estimativas agregadas baseadas no planejamento da amostra, como ajuda na proteção contra possíveis erros de especificação dos modelos. Considerando o caso de amostras com rotação, também é abordado o processo de estimação da estrutura de autocorrelação dos erros amostrais empregando o método dos pseudo-erros. Via simulação, é replicado todo o procedimento de estimação, comparando resultados obtidos empregando os filtros GLS e de Kalman. Adicionalmente, é ilustrada a aplicação do filtro sob restrições de benchmark empregando a série de taxa de desemprego da Pesquisa Mensal de Emprego do IBGE, no período de março de 2002 a fevereiro de 2012 / Abstract: This work presents the estimation process in repeated surveys using State Space Models and the generalized linear squares filter, GLS filter, under the time series approach. This filter deals with autocorrelated errors in the observation equation, in a simpler way than the well-known Kalman filter. Additionally, it allows for modeling jointly several domains under benchmark constraints obtained from the same survey. The benchmarking not only achieves coherence between the model-based estimates and the corresponding design-based aggregated estimates, but also provides protection against possible model failures. For the scenario of samples with a rotation scheme, the estimation of the autocorrelation structure of observational errors, using the pseudo-errors method, is also addressed. Simulation are used to compare the GLS and Kalman filter estimators. Moreover, the application of GLS filter under benchmark restrictions is illustrated, using the unemployment rate time serie from the Brazilian monthly labor force survey, from March 2002 to February 2012 / Mestrado / Estatistica / Mestre em Estatística

Yes / A dynamic response analysis model of a Class E2 converter for wireless power transfer applications is presented. The converter operates at 200 kHz and consists of an induction link with its primary coil driven by a class E inverter and the secondary coil with a voltage-driven class E synchronous rectifier. A seventh-order linear time invariant state-space model is used to obtain the eigenvalues of the system for the four modes resulting from the operation of the converter switches. A participation factor for the four modes is used to find the actual operating point dominant poles for the system response. A dynamic analysis is carried out to investigate the effect of changing the separation distance between the two coils, based on converter performance and the changes required of some circuit parameters to achieve optimum efficiency and stability. The results show good performance in terms of efficiency (90–98%) and maintenance of constant output voltage with dynamic change of capacitance in the inverter. An experiment with coils of the dimension of 53 × 43 × 6 mm3 operating at a resonance frequency of 200 kHz, was created to verify the proposed mathematical model and both were found to be in excellent agreement.

How can we evaluate and design integrated photonic circuit performance systematically? Can active photonic circuits be controlled for optimized performance? This work uses control theory to analyze, design, and optimize photonic integrated circuits based on versatile semiconductor optical amplifiers (SOAs). Control theory provides a mathematically robust set of tools for system analysis, design, and control. Although control theory is a rich and well-developed field, its application to the analysis and design of photonic circuits is not widespread. Following control theoretic methods already used for fibreline systems we derive three interrelated state-space models: a core photonic model, a photonic model with gain compression, and a equivalent circuit optoelectronic model. We validate each model and calibrate the gain compression model by pump/probe experiments. We then linearize the state-space models to design and analyze SOA controllers. We apply each linearized model to proof-of-concept SOA control applications such as suppressing interchannel crosstalk and regulating output power. We demonstrate the power of linearized state-space models in controller design and stability analysis. To illustrate the importance of using the complete equivalent circuit model in controller design, we demonstrate an intuitive bias-current controller that fails due to the dynamics of the intervening parasitic circuitry of the SOA. We use the linearized state-space models to map a relationship between feedback delay and controller strength for stable operation, and demonstrate that SOAs pose unusual control difficulties due to their ultrafast dynamics. Finally, we leverage the linearized models to design a novel and successful hybrid controller that uses one SOA to control another via feedback (for reliability) and feedforward (for speed) control. The feedback controller takes full advantage of the equivalent circuit modelling by sampling the voltage of the controlled SOA and using the error to drive the bias current of the controller SOA. Filtering in the feedback path is specified by transfer function analysis. The feedforward design uses a novel application of the linearized models to set the controller bias points correctly. The modelling and design framework we develop is entirely general and opens the way to the robust optoelectronic control of integrated photonic circuits.

How can we evaluate and design integrated photonic circuit performance systematically? Can active photonic circuits be controlled for optimized performance? This work uses control theory to analyze, design, and optimize photonic integrated circuits based on versatile semiconductor optical amplifiers (SOAs). Control theory provides a mathematically robust set of tools for system analysis, design, and control. Although control theory is a rich and well-developed field, its application to the analysis and design of photonic circuits is not widespread. Following control theoretic methods already used for fibreline systems we derive three interrelated state-space models: a core photonic model, a photonic model with gain compression, and a equivalent circuit optoelectronic model. We validate each model and calibrate the gain compression model by pump/probe experiments. We then linearize the state-space models to design and analyze SOA controllers. We apply each linearized model to proof-of-concept SOA control applications such as suppressing interchannel crosstalk and regulating output power. We demonstrate the power of linearized state-space models in controller design and stability analysis. To illustrate the importance of using the complete equivalent circuit model in controller design, we demonstrate an intuitive bias-current controller that fails due to the dynamics of the intervening parasitic circuitry of the SOA. We use the linearized state-space models to map a relationship between feedback delay and controller strength for stable operation, and demonstrate that SOAs pose unusual control difficulties due to their ultrafast dynamics. Finally, we leverage the linearized models to design a novel and successful hybrid controller that uses one SOA to control another via feedback (for reliability) and feedforward (for speed) control. The feedback controller takes full advantage of the equivalent circuit modelling by sampling the voltage of the controlled SOA and using the error to drive the bias current of the controller SOA. Filtering in the feedback path is specified by transfer function analysis. The feedforward design uses a novel application of the linearized models to set the controller bias points correctly. The modelling and design framework we develop is entirely general and opens the way to the robust optoelectronic control of integrated photonic circuits.

We consider a class of queueing systems that consist of server pools in parallel and multiple customer classes. Customer service times are assumed to be exponentially distributed. We study the asymptotic behavior of these queueing systems in a heavy traffic regime that is known as the Halfin and Whitt many-server asymptotic regime. Our main contribution is a general framework for establishing state space collapse results in the Halfin and Whitt many-server asymptotic regime for parallel server systems having multiple customer classes. In our work, state space collapse refers to a decrease in the dimension of the processes tracking the number of customers in each class waiting for service and the number of customers in each class being served by various server pools. We define and introduce a state space collapse function, which governs the exact details of the state space collapse. Our methodology is similar in spirit to that in Bramson (1998); however, Bramson studies an asymptotic regime in which the number of servers is fixed and Bramson does not require a state space collapse function. We illustrate the applications of our results in three different parallel server systems. The first system is a distributed parallel server system under the minimum-expected-delay faster-server-first (MED-FSF) or minimumexpected- delay load-balancing (MED-LB) policies. We prove that the MED-FSF policy minimizes the stationary distribution of total number of customers in the system. However, under the MED-FSF policy all the servers in our distributed system except those with the lowest service rate experience 100% utilization but under the MED-LB policy, on the other hand, the utilizations of all the server pools are equal. The second system we consider is known as the N-model. We show that when the service times only depend on the server pool providing service a static priority rule is asymptotically optimal. Finally, we study two results conjectured in the literature for V-systems. We show for all of these systems that the conditions on the hydrodynamic limits can easily be checked using the standard tools that have been developed in the literature to analyze fluid models.

The study of turbulence has been dominated historically by a bottom-up approach, with a much stronger emphasis on the physical structure of flows than on that of the dynam- ical state space. Turbulence has traditionally been described in terms of various visually recognizable physical features, such as waves and vortices. Thanks to recent theoretical as well as experimental advancements, it is now possible to take a more top-down approach to turbulence. Recent work has uncovered non-trivial equilibria as well as relative periodic orbits in several turbulent systems. Furthermore, it is now possible to verify theoretical results at a high degree of precision, thanks to an experimental technique known as Particle Image Velocimetry. These results squarely frame moderate Reynolds number Re turbulence in boundary shear flows as a tractable dynamical systems problem. In this thesis, I intend to elucidate the finer structure of the state space of moderate Re wall-bounded turbulent flows in hope of providing a more accurate and precise description of this complex phenomenon. Computation of new undiscovered equilibria, relative equilibria, and their heteroclinic connections provide a skeleton upon which a numerically accurate description of turbulence can be framed. The behavior of the equilibria under variation of Reynolds number and cell aspect ratios is also examined. It is hoped that this description of the state space will provide new avenues for research into nonlinear control systems for shear flows as well as quantitative predictions of transport properties of moderate Re fluid flows.