Orientador: Vivaldo Fernando da Costa / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-04T02:38:10Z (GMT). No. of bitstreams: 1 Castro_MarceloSilva_M.pdf: 2888180 bytes, checksum: c1ada4e17a5c4cf84afc7096d84a2d50 (MD5) Previous issue date: 2005 / Resumo: Essa dissertação de mestrado apresenta um estudo que avalia o desempenho dos controladores FACTS (Flexible AC Transmission Systems) para a melhoria da estabilidade de ângulo a pequenas perturbações de sistemas elétricos de potência. O potencial do Modelo de Sensibilidade de Potência (MSP), uma alternativa ao clássico modelo Heffron-Phillips (MHP) para o estudo e análise do problema de oscilações eletromecânicas de baixa frequência fracamente amortecidas, é explorado. A análise da estabilidade e o projeto de estabilizadores POD (Power Oscillation Damping) para controladores FACTS são baseados em análise modal, bifurcações de Hopf, gráficos do lugar das raízes, e técnicas de resposta em frequência e no tempo. O desempenho de diferentes sinais de entrada para estabilizadores POD é investigado. Os resultados das simulações revelam que tanto os controladores FACTS série quanto os controladores em derivação possuem um grande potencial para a manutenção da estabilidade angular do sistema / Abstract: This master¿s dissertation presents an assessment of Flexible AC Transmission Systems (FACTS) controllers performance on power system small-signal angle stability improvement. The potential of the Power Sensitivity Model (PSM), an alternative approach to the classical Heffron-Phillips model (HPM) for study and analysis of poorly damped low frequency electromechanical oscillations problem, is explored. The stability analysis and design of FACTS Power Oscillation Damping (POD) controllers are based on modal analysis, Hopf bifurcations, root locus plots, and time and frequency response techniques. The performance of different input signals to the POD controllers is investigated. Simulation results reveal that both shunt FACTS controllers and series ones are very effective on keeping system angle stability / Mestrado / Energia Eletrica / Mestre em Engenharia Elétrica

Orientadores: Stefano De Leo, Marcelo Moraes Guzzo / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-04T03:16:44Z (GMT). No. of bitstreams: 1 Bernardini_AlexEduardode_D.pdf: 11144393 bytes, checksum: e30aa87333dab96117370f24e37b259b (MD5) Previous issue date: 2005 / Resumo: Na primeira parte deste trabalho, nós introduzimos um esquema de aproximações para perfazer um estudo do fenômeno quântico de oscilação de sabores de maneira pedagógica e compreensiva. Com a utilização de pacotes de ondas gaussianos, nós demonstramos que a probabilidade de oscilação é delimitada por uma função de amortecimento dependente do tempo, a qual caracteriza o fenômeno de slippage ( escorregamento ) entre dois pacotes de ondas associados aos autoestados de massa. Nós também demonstramos que o spreading (alargamento) do pacote de ondas representa um efeito secundário o qual tem um papel relevante somente no limite não-relativístico. Em nossa análise, notamos a presença de uma nova fase de oscilação dependente do tempo e calculamos como este termo adicional modifica o caráter de oscilação na fórmula de conversão de sabores. Na segunda parte, consideramos que, no tratamento standard de oscilações quânticas, assume-se implicitamente que os autoestados de massa são escalares e, consequentemente, a forma spinorial das funções de ondas que venham a caracterizar uma partícula fermiônica, como por exemplo um neutrino, não são incluídas nos cálculos efetuados até tal ponto. Para analisar este efeito adicional, nós discutimos a fórmula de oscilação de probabilidades obtida com o uso da equação de Dirac como a equação de movimento para os autoestados de massa de neutrinos. A localização inicial do estado espinorial também faz com que apareça uma interferência entre componentes de energia positiva e negativa dos pacotes de ondas de cada autoestado de massa que leva a descrição de um fenômeno de oscilações ultra-rápidas o qual pode alterar a probabilidade de oscilação standard. Finalmente, nós investigamos como a inclusão dos efeitos de oscilação quiral podem modificar a fórmula de conversão desabores. Nosso estudo leva à conclusão de que a natureza fermiônica das partículas, onde oscilaçÕes de quiralidade e a interferência entre componentes de frequência positiva e negativa de pacotes de ondas associados a autoestados de massa são implicitamente consideradas, modifica o perfil das oscilações de sabores. Contudo, para partículas ultra-relativísticas e distribuições de momentos altamente centradas, é possível demonstrar analiticamente que estas modificações introduzem fatores de correção proporcionais a m2 1,2 /P2 0 , os quais são, praticamentes indetectáveis por meio de análise experimental / Abstract: In the first part of this work, we introduce an approximation scheme to perform an analytic study of quantum fiavor oscillation phenomena in a pedagogical and comprehensive way. By using gaussian wave packets, we show that the oscillation probability is bounded by a time-dependent vanishing function which characterizes the slippage between the mass-eigenstate wave packets. We also demonstrate that the wave packet spreading represents a secondary effect which play a significant role only in the non-relativistic limit. In our analysis, we note the presence of a new time-dependent phase and calcu1ate how this additional term modifies the oscillating character of the fiavor conversion formu1a. At second, we consider that in the standard treatment of particle oscillations the mass eigenstates are implicitly assumed to be scalars and, consequently, the spinorial form of a fermionic wave function, like the neutrino one, is not included in the calcu1ations. To analyze this additional effect, we discuss the oscillation probability formu1a obtained by using the Dirac equation as evolution equation for the neutrino mass eigenstates. The initial localization of the spinor state also implies an interference between positive and negative energy components of mass eigenstate wave packets which modifies the standard oscillation probability. Finally, we investigate how the inclusion of chiral oscillation effects can modify the flavor conversion probability formula. Our study leads to the conclusion that the fermionic nature of the particles, where chiral oscillations and the interference between positive and negative frequency components of mass-eigenstate wave packets are implicitly assumed, modifies the standard oscillation probability. Nevertheless, for ultra-relativistic particles and sharply peaked momentum distributions, we can analytically demonstrate that these modifications introduce correction factors proportional to m 2 1/2 /P2 0 which are practically un-detectable by any experimental analysis / Doutorado / Física das Particulas Elementares e Campos / Doutor em Ciências

Nous étudions l’influence d’une rétroaction optique à conjugaison de phase dans une diode laser. Ce type de rétroaction a été peu étudié et nous montrons ici qu’il donne des résultats intéressants, permettant de débloquer du contenu à haute fréquence. Cela pourrait mener à de meilleures performances dans des systèmes de génération de nombres aléatoires utilisant du chaos optique. / We study the influence of phase-conjugate feedback in a laser diode. This type of feedback has not been studied a lot and yet we show here that it can give interesting results. It unlocks oscillations at high frequencies. This could lead to an improvement in the performance of random number generators based on optical chaos.

Three-dimensional basic problems of statics, pseudo-oscillations, general dynamics and steady state oscillations of the thermoelasticity of isotropic bodies have been completely investigated by many authors. In particular, exterior steady state oscillation problems have been studied on the basis of Sommerfeld-Kupradze radiation conditions in the thermoelasticity, and the uniqueness theorems were proved with the help of the well-known Rellich's lemma, since the components of the displacement vector and the temperature in the isotropic case can be represented as a sum of metaharmonic functions . Unfortunately, the methods of investigation of thermoelastic steady state oscillation problems developed for the isotropic case are not applicable in the case of general anisotropy. This is stipulated by a very complicated form of the corresponding characteristic equation which plays a significant role in the study of far field behaviour of solutions to the oscillation equa- tions. We note that the basic and crack type boundary value problems (BVPs) for the pseudo-oscillation equations of the thermoelasticity theory in the anisotropic case are considered in [3,14]. To the best of the authors' knowledge the problems of thermoelastic steady oscillations for anisotropic bodies have not been treated in the scientific literature. In the present paper we will consider a wide class of basic and mixed type BVPs for the equations of thermoelastic steady state oscillations. We will formulate thermoelastic radiation conditions for an anisotropic medium (the generalized Sommerfeld-Kupradze type radiation conditions) and prove the uniqueness theorems in corresponding spaces. To derive these conditions we have essentially applied results of Vainberg. Further, using the potential method and the theory of pseudodifferential equations on manifolds we will prove existence theorems in various functional spaces and establish the smoothness properties of solutions.

Geomagnetic pulsations are ultra-low frequency (ULF) oscillations of the geomagnetic field that have been observed in the magnetosphere and on the Earth since the 1800’s. In the 1960’s in situ observations of the solar wind suggested that the source of pulsation activity must lie beyond the magnetosphere. In this work the influence of several solar wind plasma and interplanetary magnetic field (IMF) parameters on Pc3 pulsations are studied. Pc3 pulsations are a class of geomagnetic pulsations with frequency ranging between 22 and 100 mHz. A large dataset of solar wind and pulsation measurements is employed to develop two empirical models capable of predicting the Pc3 index (an indication of Pc3 intensity) at one hour and five minute time resolution, respectively. The models are based on artificial neural networks, due to their ability to model highly non-linear interactions between dependent and independent variables. A robust, iterative process is followed to find and rank the set of solar wind input parameters that optimally predict Pc3 activity. According to the parameter selection process the input parameters to the low resolution model (1 hour data) are, in order of importance, solar wind speed, a pair of time-based parameters, dynamic solar wind pressure, and the IMF orientation with respect to the Sun-Earth line (i.e. the cone angle). Input parameters to the high resolution model (5 minute data) are solar wind speed, cone angle, solar wind density and a pair of time-based parameters. Both models accurately predict Pc3 intensity from unseen solar wind data. It is observed that Pc3 activity ceases when the density in the solar wind is very low, even while other conditions are favourable for the generation and propagation of ULF waves. The influence that solar wind density has on Pc3 activity is studied by analysing six years of solar wind and Pc3 measurements at one minute resolution. It is suggested that the pause in Pc3 activity occurs due to two reasons: Firstly, the ULF waves that are generated in the region upstream of the bow shock does not grow efficiently if the solar wind density is very low; and secondly, waves that are generated cannot be convected into the magnetosphere because of the low Mach number of the solar wind plasma due to the decreased density.

The orbital parameters of binaries at intermediate periods (10(2)-10(3) d) are difficult to measure with conventional methods and are very incomplete. We have undertaken a new survey, applying our pulsation timing method to Kepler light curves of 2224 main-sequence A/F stars and found 341 non-eclipsing binaries. We calculate the orbital parameters for 317 PB1 systems (single-pulsator binaries) and 24 PB2s (double-pulsators), tripling the number of intermediate-mass binaries with full orbital solutions. The method reaches down to small mass ratios q approximate to 0.02 and yields a highly homogeneous sample. We parametrize the mass-ratio distribution using both inversion and Markov-Chain Monte Carlo forward-modelling techniques, and find it to be skewed towards low-mass companions, peaking at q approximate to 0.2. While solar-type primaries exhibit a brown dwarf desert across short and intermediate periods, we find a small but statistically significant (2.6 sigma) population of extreme-mass-ratio companions (q < 0.1) to our intermediate-mass primaries. Across periods of 100-1500 d and at q > 0.1, we measure the binary fraction of current A/F primaries to be 15.4 per cent +/- 1.4 per cent, though we find that a large fraction of the companions (21 per cent +/- 6 per cent) are white dwarfs in post-mass-transfer systems with primaries that are now blue stragglers, some of which are the progenitors of Type Ia supernovae, barium stars, symbiotics, and related phenomena. Excluding these white dwarfs, we determine the binary fraction of original A/F primaries to be 13.9 per cent +/- 2.1 per cent over the same parameter space. Combining our measurements with those in the literature, we find the binary fraction across these periods is a constant 5 per cent for primaries M-1 < 0.8 M-circle dot, but then increases linearly with log M-1, demonstrating that natal discs around more massive protostars M-1 greater than or similar to M-1(circle dot) become increasingly more prone to fragmentation. Finally, we find the eccentricity distribution of the main-sequence pairs to be much less eccentric than the thermal distribution.

Le projet de recherche, initié en automne 2014 par le Centre des Technologies Avancées de Sherbrooke, partenariat entre Bombardier Recreational Products (BRP) et l’Université de Sherbrooke, se focalise sur le système de transmission d’un véhicule de sport-tourisme à trois roues dans le but de réduire, d’une part la consommation énergétique de ce dernier et d’autre part le niveau de vibration de ce dernier. La première partie du projet de recherche vise à imaginer, modéliser, dimensionner, optimiser, concevoir et contrôler (end-to-end) un nouvel actionneur d’embrayage électrique innovant et moins énergivore que l’actuel actionneur d’embrayage électrohydraulique utilisé dans la transmission manuelle automatisée (AMT) du véhicule. Grâce à une stratégie de commande avancée, cette rupture technologique doit permettre d’être écoénergétique tout en ayant un niveau de performance élevé et pour un coût acceptable. La deuxième partie du projet de recherche vise à investiguer le sens physique et mathématique d’un phénomène d’oscillations transverses de la courroie de transmission – transmettant le couple du bloc moteur à la roue arrière – observé sur le véhicule pour certains régimes moteurs. Puis, proposer une solution mécatronique innovante, basée sur une stratégie de contrôle spécifique de l’actionneur d’embrayage du véhicule, afin de supprimer ces oscillations de courroie sans altérer l’expérience de conduite. Ce document regroupe l’ensemble des travaux effectués et les résultats obtenus pour les deux projets de recherche. Dans un premier temps, la revue de l’état de l’art sur les embrayages, leurs actionnements et leurs stratégies de contrôle sont présentés. Puis, le nouveau dispositif d’actionnement d’embrayage dimensionné et optimisé et sa stratégie de contrôle sont développés. Ensuite, une nouvelle méthode agile et faible coût pour évaluer expérimentalement la consommation d’énergie d’un dispositif d’actionnement virtuellement intégré à un véhicule sur un cycle normalisé est exposée et appliquée à notre cas d’étude. Par la suite, les travaux réalisés pour comprendre le phénomène d’oscillations de courroie et la solution mécatronique proposée pour supprimer celui-ci sont présentés. Puis, la stratégie de contrôle spécifique de l’actionneur d’embrayage conçue, dans notre cas, pour supprimer les oscillations de courroie est développée en détail. Pour finir, les travaux effectués pour ces deux projets de recherche sont conclus en fin de document.

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[pt] O objetivo desta tese é estudar os mecanismos de escape em sistemas estruturais sensíveis a imperfeições quando submetidos a certas classes de carregamentos dinâmicos, identificar os parâmetros que controlam o escape e criar critérios capazes de prever a fronteira de escape e a perda de estabilidade da estrutura no espaço dos parâmetros de controle. Isto permitirá um melhor entendimento dos processos de perda de estabilidade e servirá de base para o cálculo e controle da integridade dessas estruturas. Após a descrição dos fenômenos que podem ocorrer na dinâmica dessa classe de estruturas, são testados e adaptados alguns critérios existentes na literatura, que verificam a estabilidade de uma estrutura a partir do conhecimento dos parâmetros de controle. Em seguida estuda-se a evolução da estabilidade global do conjunto das soluções medida pela área da bacia de atração, e pelas características de sua fronteira. Desenvolvem-se expressões gerais para o critério de Melnikov, e mostra-se, a partir de perturbações aleatórias nos parâmetros de controle e na força externa, que essas expressões podem ser tomadas como um limite inferior para o carregamento de escape e conseqüentemente como uma contribuição para o desenvolvimento de critérios de projeto. Verifica-se também que os valores obtidos pelos critérios de escape podem ser tomados como limites superiores para o valor da força de escape. / [en] The purpose of this thesis is to study the escape mechanisms in imperfection sensitive structural systems under certain dynamical loading conditions. Other objectives are to identify the parameters that control the escape phenomenon and to create some criteria capable of predicting the escape boundary and the structures stability in the control parameters space. This will allow a better understanding of the stability loss process and can serve as a basis to the integrity control and design of these structures. After a description of the phenomena that can occur in the dynamics of this class of structures, some predictive criteria, found in literature, that verify the structure stability based on the control parameters knowledge, are adapted and tested. Following is a study of the evolution of the global stability of the set of solutions measured by the basin of attraction area, and by the characteristics of its boundary. Some general expressions for the Melnikov criterion are developed, and it is shown by randomly perturbing the control parameters and the external force, that these expressions can be taken as a lower bound for the escape load, and consequently as a contribution to the development of design criteria. It is also observed that the values obtained by the escape criteria can be taken as an upper bound for the values of the escape force. / [es] EL objetivo de esta tesis es estudiar los mecanismos de escape en sistemas extructurales que son sensibles a imperfecciones cuando son sometidos a ciertas clases de cargas dinámicas. Outro objetivo es identificar los parámetros que controlan el escape y crear criterios capaces de preveer la frontera de escape y la pérdida de estabilidad de la extructura en el espacio de los parámetros de control. Esto permitirá una mejor comprensión de los procesos de pérdida de estabilidad y servirá de base para el cálculo y control de la integridad de esas extructuras. Después de describir los fenómenos que pueden ocurrir en la dinámica de esta clase de extructuras, se prueban y adaptan algunos criterios existentes en la literatura, que verifican la estabilidad de una extructura a partir del conocimiento de los parámetros de control. Seguidamente, se estudia la evolución de la estabilidad global del conjunto de las soluciones, se dearrollan expresiones generales para el criterio de Melnikov, y se muestra, a partir de perturbaciones aleatorias en los parámetros de control y en la fuerza externa, que esas expresiones pueden ser tomadas como límite inferior para la carga de escape y conseqüentemente como una contribución para el desarrollo de criterios de proyecto. Se verifica también que los valores obtenidos por los criterios de escape pueden ser tomados como límites superiores para el valor de la fuerza de escape.

Schizophrenia is a neuropsychiatric disorder lying at the extreme of a spectrum of disorders that possibly share a common abnormality in neural connectivity. Efforts to reverse the core cognitive manifestations of schizophrenia using drug treatments have so far been unsuccessful. This thesis investigates the cognitive abnormalities and their electrophysiological correlates across the schizophrenia spectrum in order to identify and validate biomarkers for proof of concept studies of cognitive enhancers. Such studies in milder disorders of the schizophrenia spectrum such as schizotypal personality trait may be a crucial method in identifying new effective compounds, as reviewed in Chapter 3, and tested in Chapter 4. The latter features the results of a large three-centre study which probed the sensitivity of several neuropsychological measures to the schizotypy phenotype, as well as to the effects of amisulpride, risperidone and nicotine. Schizotypal volunteers showed impaired performance only on the more difficult tasks. The most consistent pharmacological finding was that amisulpride tended to improve performance in the high schizotypy group but to impair it in the average schizotypy controls. One interpretation is that the ability of low dose amisulpride to enhance dopamine function in frontal cortex reversed an impairment of dopamine function present in the high schizotypes which is thought to occur in schizophrenia. Chapter 5 explored the methodological question of whether low or average schizotypy individuals should be used as controls in cognitive comparisons versus high schizotypy. The results suggest that low schizotypes have the most intact cognitive performance and are therefore the control group of choice. Chapters 6, 7 and 8 tested the hypothesis that cognitive deficits are part of a larger information processing abnormality in the schizophrenia spectrum. In accordance, both high schizotypy and schizophrenia patients exhibited reduced amplitude of an early visual evoked potential P1 (Chapters 6 and 8, respectively) and disruptions of the underlying evoked neural oscillations (Chapters 7 and 8). The pattern of abnormalities suggested an inefficient top-down modulation of perception in the schizophrenia spectrum. These data argue that cognitive abnormalities and their electrophysiological correlate may be sensitive biomarkers of the core dysconnectivity deficit in schizophrenia. This thesis supports their use in proof of concept studies to foster the development of cognitive enhancers.