abstract: This thesis focuses on the influence of a grounded back electrode on the breakdown characteristics. The back electrode is an electrode which attaches at the back side of solid insulation. Insulation with grounded back electrode is a common type of insulation which is adopted in many high voltage power devices. While most of the power equipment work under AC voltage, most of the research on back electrode is focused on the DC voltage. Therefore, it is necessary to deeply investigate the influence of the back electrode under AC applied voltage. To investigate the influence of back electrode, the research is separated into two phases, which are the experiment phase and the electric field analysis phase. In the experiments, the breakdown voltages for both with and without back electrode are obtained. The experimental results indicate that the grounded back electrode does have impact on the breakdown characteristics. Then with the breakdown voltage, based on real experiment model, the electric field is analyzed using computer software. From the field simulation result, it is found that the back electrode also influences the electric field distribution. The inter relationship between the electric field and breakdown voltage is the key to explain all the results and phenomena observed during the experiment. Additionally, the influence of insulation barrier on breakdown is also investigated. Compared to the case without ground electrode, inserting a barrier into the gap can more significantly improve breakdown voltage. / Dissertation/Thesis / M.S. Electrical Engineering 2014

Em processos de crescimento de cristais pelo método de Czochralski, é observado que um campo elétrico aplicado ao cristal durante o processo de crescimento modifica a quantidade de dopante incorporada ao cristal. É desenvolvido um modelo, baseado na teoria de Burton, Prim e Slichter, levando-se em consideração as duas classes de material envolvidas, os óxidos e os semicondutores, e os efeitos produzidos pelo campo elétrico, eletromigração, subresfriamento constitucional, Efeito Peltier e efeito Seebeck. Resultados experimentais obtidos em crescimentos de LiNbO3:Cr2O3 e Si:Al são usados para aplicações do modelo / In crystal growth processes through the Czochralski method, it is observed that an electrical field applied to the crystal during the growth process modifies the quatity of the dopant incorporated to the crystal. A model is developed based on Burton, Prim and Slichter´s theory, taking into consideration two classes of materials, the oxides and the semiconductors, and the effects produced by the electrical field, electromigration, constitutional supercooling, Peltier Effect, Seebeck Effect. Experimental results obtained from the growth of the LiNbO3:Cr2O3 e Si:Al singlecrystals are used to the model application

Acredita-se que sinais elétricos endógenos afetem remodelamento, metabolismo, reparo e crescimento ósseos. Existe uma ampla literatura que trata do efeito de sinais elétricos externos sobre as respostas de síntese, mitogênese e proliferação em osteoblastos e células ósseas in vitro. Acredita-se que as respostas fisiológicas ao estimulo elétrico sejam devidas a mecanismos celulares que envolvem variações na concentração citosólica de cálcio. No presente estudo esse efeito celular foi observado através da estimulação direta, por campo elétrico de intensidade fisiologicamente significativa de 10mV/cm e frequência 1,5 MHz, de células ósseas em cultura primária obtidas a partir da calota calvária de ratos da raça Sprague-Dawley. Os mecanismos de transdução do campo elétrico são investigados pela mensuração em tempo real do efeito do campo elétrico na concentração citosólica de Ca2+ utilizando-se técnica de fluorescência de Fura-2, em um sistema que permite a medida em células individuais. As estimulações elétricas resultaram em variações significativas na concentração de cálcio citosólico. Mais especificamente, observou-se um aumento na amplitude e na duração das oscilações de cálcio iônico, com tempos de latência variáveis para as células estudadas. / Endogenous electrical signals have been thought to affect bone remodeling, metabolism, healing and growth. Much literature exists concerning the effect of external electrical signals on synthetic, mitogenic, and proliferative responses of osteoblasts or osteoblast-like cells in vitro. Physiological responses to electrical stimulation are thought to be due to cellular mechanisms involving cytosolic calcium concentration changes. In this study this cellular effect was observed by directly stimulating primary culture bone cells from Sprague-Dawley rat calvaria at physiological significant field strength of 10 mV/cm and frequency 1,5 MHz. Electric field transduction mechanisms are investigated by measuring the real-time electric field effect on cytosolic Ca+2 concentrations using Fura-2 fluorescence technology in a system capable of measurement on a cell-by-cell basis. The electrical stimulations resulted in significant changes in cytosolic calcium concentration. More specifically, an increase was noted in calcium oscillation amplitude and duration, and a variable response latency period for the cells studied.

Orientador: Jose Pissolato Filho / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-13T18:17:26Z (GMT). No. of bitstreams: 1 Silva_ValeriaCristiane_M.pdf: 9885573 bytes, checksum: eee5ffee7c0a540498ec7bb5a8436b15 (MD5) Previous issue date: 2009 / Resumo: Este trabalho apresenta a elaboração e a construção de um sensor utilizado na detecçãode intensidade de campo elétrico e consequentemente de descargas atmosféricas. O sensor de diâmetro igual a 10 cm é constituído por uma placa girante composta por quatro aletas, que tem seu movimento de rotação controlado por um mini motor de 12000 rpm, e uma placa fixa, denominada placa de medição, composta por oito aletas que são responsáveis por produzir uma tensão alternada referente ao campo elétrico ao qual o sensor está submetido. Quando o rotor (placa girante) gira sobre o estator (placa de medição), ele expõe a placa de medição ao campo elétrico e isola-o deste campo quando está sobre ele. Dessa forma corta-se o campo elétrico normal estático ou que varia muito lentamente. O medidor de campo elétrico (EFM - do inglês Eletric Field Mill ) cria um campo "variável" que irá induzir uma carga elétrica no estator. A magnitude e polaridade da carga são dependentes da magnitude e polaridade do campo elétrico. A placa de medição gera um sinal da ordem de milivolts, sendo necessário a utilização de amplificadores para torná-lo significante para análise. O sinal amplificado será então digitalizado e enviado à um software para visualização dos dados gerados pelo sensor. Neste trabalho apresenta-se também um estudo sobre origem de cargas nas nuvens, formação de tempestade, assim como formação e classificação dos raios. / Abstract: This paper presents the development and construction of a sensor used to detect intensity of electric field and consequently of lightning. The sensor diameter of 10 cm consists of a plate consisting of four revolving vanes that has its rotation controlled by a small motor to 12000 rpm and a fixed plate, called a measuring board, composed of eight vanes that are responsible for produce a alternating voltage electric field concerning which the sensor is subjected. When the rotor (revolving vanes) turns on the stator (plate measurement), it exposes the plate for measuring the electric field alone, and the field when this is over it. Thus is cut to the normal static electric field or which varies very slowly. The electric field meter (EFM - the English Electric Field Mill) creates a field "variable" that will induce an electric charge in the stator. The magnitude and polarity of the load are dependent on the magnitude and polarity of the electric field. The measurement plate generates a measurement signal of the order of millivolts, requiring the use of amplifiers to make it significant for analysis. The amplified signal is then digitized and sent to a software for visualization of data generated by the sensor. In this work it is also a study of origin of cargoes in the clouds, formation of storm as well as training and classification of rays. / Mestrado / Energia Eletrica / Mestre em Engenharia Elétrica

Orientador: Pedro Xavier de Oliveira / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-25T18:17:39Z (GMT). No. of bitstreams: 1 Zoccoler_Marcelo_M.pdf: 48059333 bytes, checksum: f5fb08bbb5d770ad29791611d11fa8fa (MD5) Previous issue date: 2014 / Resumo: A fibrilação ventricular é uma quadro extremamente grave de ameaça imediata à vida e a única terapia efetiva para sua reversão é a desfibrilação, que consiste na aplicação de campos elétricos (E) de alta intensidade sobre o coração. Este procedimento é capaz de restabelecer o sincronismo do coração, mas ele pode causar lesão em miócitos. A lesão depende da direção de E e é atribuída à eletroporação - formação de poros hidrofílicos na membrana celular - que leva a um aumento expressivo da concentração de íons Ca2+ livres no citosol ([Ca2+]i), resultante de influxo de Ca2+ extracelular pelos poros. Neste trabalho, produzimos um sistema de microfluorimetria capaz de registrar imagens de fluorescência de miócitos cardíacos isolados e estudamos a lesão causada por E de alta intensidade por meio do aumento da fluorescência associada a [Ca2+]i em miócitos orientados longitudinalmente e transversalmente a E. As células foram carregadas com o indicador de fluorescência Fluo-3, estimuladas a 0,5Hz por E de baixa intensidade antes da aplicação de um pulso de E de alta intensidade sub-letal. As imagens de fluorescência foram capturadas por uma câmera EMCCD e processadas por um software específico desenvolvido neste trabalho. O software utilizou dois métodos de análise: média de fluorescência normalizada e razão de uma área que mostrou aumento significativo de fluorescência dividida pela área total da célula. Análise de regiões de interesse (ROIs) voltadas para o ânodo e o cátodo produziu resultados em concordância com a literatura, com maior lesão (inferida por aumento de [Ca2+]i) no lado do ânodo (P<0,05 nos dois os métodos). A comparação entre os grupos longitudinal e transversal apresentou diferença estatística relevante no método da razão de áreas, o que não ocorreu pelo método de média de fluorescência. Imaginamos que a utilização de uma técnica mais direta para medir eletroporação possa solidificar esta correlação entre orientação e lesão. A compreensão dos mecanismos responsáveis pela severidade das lesões é importante para desenvolver terapias mais seguras / Abstract: Ventricular fibrillation is an extremely dangerous immediate life-threatening condition and the only effective therapy to its reversion is defibrillation, which consists in applying high intensity electric fields (E) on the heart. Such procedure is capable of reestablishing heart synchronism, but it may also cause lesion in myocytes. Lesion is associated to E direction and is assigned to electroporation - generation of hydrophilic pores across the membrane caused by high intensity E - which results in an expressive increase in cytosol free Ca2+ concentration ([Ca2+]i), a consequence from extracellular Ca2+ influx through the pores. In this work, we produced a microfluorimetry system capable of recording isolated cardiomyocytes fluorescence images and studied lesion caused by high intensity E by the means of the rise in [Ca2+]i associated fluorescence in myocytes oriented longitudinally and transversally to E. Cells were loaded with fluorescent dye Fluo-3, paced at 0,5Hz with low intensity E before setting one sub-lethal high intensity E pulse. Fluorescence images were recorded by an EMCCD camera and processed by a specific software developed in this work. The software used two analysis methods: normalized fluorescence average and a ratio of an area showing most significant fluorescence increase divided by cell total area. Regions of interest (ROIs) analysis facing the anode and the cathode has produced results in accordance with literature, presenting higher lesion (inferred by [Ca2+]i increase) at anode side (P<0,05 in both methods). Comparison between longitudinal and transversal groups has presented relevant statistic difference when the ratio of areas method was employed, which has no happened when employing the fluorescence average method. We imagine that using a straight-foward technique for assessing electroporation may solidify this correlation between orientation and lesion. The understanding of the mechanisms responsible for lesion severity is important to develop safer therapies / Mestrado / Engenharia Biomedica / Mestre em Engenharia Elétrica

Orientadores: Marco Antonio Robert Alves, Edmundo Silva Braga / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-26T06:17:05Z (GMT). No. of bitstreams: 1 Sant'Anna_GuilhermeMauad_M.pdf: 5334525 bytes, checksum: e4e25f2178b742c06248c80130400b74 (MD5) Previous issue date: 2014 / Resumo: Neste trabalho, foi estudado o comportamento do campo elétrico nas proximidades de uma junção tripla composta de metal, vácuo e dielétrico, utilizando simulações computacionais. Através do modelo bidimensional da junção obtido no software MAXWELL - ANSYS, foi possível analisar as magnitudes dos campos elétricos em função dos ângulos de contato dos materiais. Os resultados mostraram que um enriquecimento de campo ou uma redução de campo podem ocorrer nas regiões próximas a junção tripla para certas razões entre os ângulos de contato. A influência da permissividade relativa do dielétrico no enriquecimento de campo também é estudada, e os resultados mostram que o ganho máximo do campo elétrico devido a este fenômeno é proporcional a permissividade relativa do dielétrico utilizado na junção. Uma saturação no valor de pico do enriquecimento foi manifestada nos resultados desta pesquisa, a medida que a permissividade relativa do dielétrico aumentava a sua magnitude. Esta saturação parece estar relacionada ao fato de que o incremento da tensão aplicada não provoca mudanças substanciais nos valores da permissividade do dielétrico / Abstract: In this work, the electric field behavior in the vicinity of a triple junction, composed by metal, vacuum and dielectric parts, was studied using computational simulations. Through a bi-dimensional model of the junction designed in the software ANSYS MAXWELL, it was possible to analyze the electric field magnitude in function of the contact angles of the materials. The results showed that a field enhancement or a field reduction could happen in the vacuum near the triple junction, for certain values of the vacuum and dielectric contact angles. The influence of the dielectric permittivity in the phenomena was also investigated, and the conclusions showed that the maximum electric field enhancement from the triple junction effect is proportional to the dielectric permittivity of the dielectric portion. Saturation in the peak value of the field enhancment was manifested in the results of this research, as the relative permittivity of the dielectric increased its magnitude. This saturation is related to the fact that the increase of the applied voltage does not cause substantial changes in the values of the dielectric permittivity / Mestrado / Eletrônica, Microeletrônica e Optoeletrônica / Mestre em Engenharia Elétrica

Cell encapsulation is a promising concept in regenerative medicine and stem cell treatment of diseases. Cells encapsulated in hydrogels have shown to yield better therapeutic outcome over cells in suspension. Microfluidic platforms have facilitated the process of cell encapsulation through the controlled mixing of aqueous cell solution and hydrogel with an immiscible liquid to yield a monodispersed population of microcapsules at a high throughput. However, given that the microfluidic process of placing cells in microcapsules is completely random, yielded samples are often riddled with empty microcapsules, raising the need for a post-encapsulation purification step to sort empty microcapsules from cell-laden ones. Sorting of microcapsules can be achieved through several techniques, most desirable of which are electrokinetic such as dielectrophoresis (DEP) and electrophoresis (EP). The advantages of DEP and EP techniques are that they support label-free sorting and yield a high throughput. However to achieve true effective DEP or EP sorting, there is a need to understand how empty microcapsules react to these electrokinetic forces versus occupied microcapsules. This study developed microfluidic devices for characterising the electrokinetic effects on microcapsules using DEP and EP. Results of both characterization techniques showed notable differences in the response of empty microcapsules versus cell-laden ones, reinforcing their potentials for sorting. Furthermore, this study proposed designs for microcapsules sorting devices that leverage EP and DEP.

Malgré le mécanisme de base du transport protonique (PT) dans l'eau ait été proposé en 1806, à ce jour il n'existe pas de théorie complète qui décrive la protolyse. Ce phénomène est à la base du fonctionnement des batteries à hydrogène et de nombreux processus biologiques. Grâce à la technique de dynamique moléculaire Car-Parrinello (CPMD) et à l'aide de l'application d'un champ electrique (EF), une partie de cette thèse a été consacrée à l'étude du PT dans deux phase de la glace: la phase Ih et sa contrepartie ferroélectrique, la glace XI. Certains mécanismes ont été révélés: le rôle joué par les oxygènes lorsque se produit le PT et la contribution du (dés)ordre afin d'assister ce processus [1,2]. Le phénomène du PT est aussi à la base de nombreaux convertisseurs d'énergie constitués par le méthanol tels que le Direct Methanol Fuel Cells et les membranes Nafion. Afin de révéler la nature intime du PT dans le méthanol liquide, une série de simulations CPMD ont été menées sous l'effet d'un EF extérieur. De cette façon il a été possible de comparer le rôle joué par les liasons hydrogène afin d'assister le PT [3]. De plus, quand les intensités du champ sont plus élevées que celles qui donnent lieu au PT, certaines réactions chimiques ont été observées dans le même échantillon "numérique" du méthanol. En exploitant des paramètres typique de la "Théorie de la fonctionnelle de la densité conceptuelle", il a été possible de clarifier les conditions qui donnent lieu à ces réactions chimiques. Enfin, afin de quantifier la contribution du EF à la formation de méthane et de formaldéhyde dans le système, des simulations de métadynamique en conjonction à ceux ab initio ont été menées. / Although the basic mechanism of the proton transfer (PT) phenomenon in water has been envisaged in 1806, nowadays does not exist a detailed theoretical framework that envelop the protolysis process. This phenomenon is at the base of the operation of hydrogen batteries, as well as of many biological processes. Via the Car-Parrinello Molecular Dynamics (CPMD) technique and by means of the application of an electric field (EF), part of this thesis has been devoted to the detailed study of PT in two ice phases: ice Ih and its ferroelectric counterpart, ice XI. Several previously unknown mechanisms have been shown. As an example, the role played by the oxygens when a PT occurs and the contribution due to (dis)order in assisting this process [1,2]. The PT phenomenon is also at the base of the functioning of some methanol-based energy converters such as Nafion membranes. To the aim of disclosing the intimate nature of PT in liquid methanol, a series of CPMD simulations have been carried out by applying an external EF; the role played by the H-bond network have been also compared with the similar PT mechanism in water [3]. At field strengths higher than those leading to PT, several chemical reactions have been observed in this sample. By exploiting the conceptual Density Functional Theory framework, it has been possible to clarify the circumstances under which a given chemical reaction occurs. Moreover, in order to disclose the role played by the EF in assisting chemical reactions, the mechanism leading to the formation of formaldehyde and methane in the sample has been studied with metadynamics approaches in conjuction with the ab initio ones.

An implementation of the Electric Field Approach applied to the simulated RoboCup is presented, together with a demonstration of a learning system. Results are presented from the optimization of the Electric Field parameters in a limited situation, using the learning system. Learning techniques used in contemporary RoboCup research are also described including a brief presentation of their results.

The Electric Field Approach, EFA, is a heuristic for behavior selection for autonomous robot control. This thesis deals with the problem of using the EFA as a heuristics for the perceptive behaviors. The integration is done by extending the EFA with having three electric fields and each having its own probes and charges. The extended EFA was tested in the RoboCup domain.