Contribuições ao método de rastreamento de máxima potência para sistemas fotovoltaicos

The scarcity of natural resources and the search for alternative energy sources promote a rapid change in the energy world. Among the renewable energy sources, solar energy is the most promising, presenting technology of greatest growth rate nowadays. Researchers around the world are seeking ways to facilitate their progress, developing technologies with higher efficiency and lower cost. As a contribution to global progress, this master thesis proposes the development of a strategy of maximum power tracking based on perturbation and observation method for photovoltaic systems. The proposed control strategy is based on active power balance of the system, with a reduced number of sensors. It also allows the PV system to act as a regulator of the power quality at the point of commom coupling (PCC), compensating the harmonic distortion and power factor of the current netw

Estudo da topologia de redes de conexão funcional no córtex sensorial primário e hipocampo durante o sono de ondas lentas

Complex network analysis is a powerful tool into research of complex systems like brain networks. This work aims to describe the topological changes in neural functional connectivity networks of neocortex and hippocampus during slow-wave sleep (SWS) in animals submited to a novel experience exposure. Slow-wave sleep is an important sleep stage where occurs reverberations of electrical activities patterns of wakeness, playing a fundamental role in memory consolidation. Although its importance there s a lack of studies that characterize the topological dynamical of functional connectivity networks during that sleep stage. There s no studies that describe the topological modifications that novel exposure leads to this networks. We have observed that several topological properties have been modified after novel exposure and this modification remains for a long time. Major part of this changes in topological properties by novel exposure are related to fault tolerance

Estratégia de controle robusto para interconexão de sistemas PV trifásicos à rede elétrica

Atualmente há uma grande preocupação em relação a substituição das fontes não renováveis pelas fontes renováveis na geração de energia elétrica. Isto ocorre devido a limitação do modelo tradicional e da crescente demanda. Com o desenvolvimento dos conversores de potência e a eficácia dos esquemas de controle, as fontes renováveis têm sido interligadas na rede elétrica, em um modelo de geração distribuída. Neste sentido, este trabalho apresenta uma estratégia de controle não convencional, com a utilização de um controlador robusto, para a interconexão de sistemas fotovoltaicos com à rede elétrica trifásica. A compensação da qualidade de energia no ponto de acoplamento comum (PAC) é realizada pela estratégia proposta. As técnicas tradicionais utilizam detecção de harmônicos, já neste trabalho o controle das correntes é feita de uma forma indireta sem a necessidade desta detecção. Na estratégia indireta é de grande importância que o controle da tensão do barramento CC seja efetuado de uma forma que não haja grandes flutuações, e que a banda passante do controlador em regime permanente seja baixa para que as correntes da rede não tenham um alto THD. Por este motivo é utilizado um controlador em modo dual DSM-PI, que durante o transitório se comporta como um controlador em modo deslizante SM-PI, e em regime se comporta como um PI convencional. A corrente é alinhada ao ângulo de fase do vetor tensão da rede elétrica, obtido a partir do uso de um PLL. Esta aproximação permite regular o fluxo de potência ativa, juntamente com a compensação dos harmônicos e também promover a correção do fator de potência no ponto de acoplamento comum. Para o controle das correntes é usado um controlador dupla sequencia, que utiliza o princípio do modelo interno. Resultados de simulação são apresentados para demonstrar a eficácia do sistema de controle proposto

Estratégia de conversor para interligação de sistemas de geração eólica à rede elétrica

Currently, there are several power converter topologies applied to wind power generation. The converters allow the use of wind turbines operating at variable speed, enabling better use of wind forces. The high performance of the converters is being increasingly demanded, mainly because of the increase in the power generation capacity by wind turbines, which gave rise to various converter topologies, such as parallel or multilevel converters. The use of converters allow effective control of the power injected into the grid, either partially, for the case using partial converter, or total control for the case of using full converter. The back-to-back converter is one of the most used topologies in the market today, due to its simple structure, with few components, contributing to robust and reliable performance. In this work, is presented the implementation of a wind cogeneration system using a permanent magnet synchronous generator (PMSG) associated with a back-to-back power converter is proposed, in order to inject active power in an electric power system. The control strategy of the active power delivered to the grid by cogeneration is based on the philosophy of indirect control

Análise do efeito do tempo da moagem de alta energia no tamanho de cristalito e microdeformação da rede cristalina do WC-Co

Hard metals are the composite developed in 1923 by Karl Schröter, with wide application because high hardness, wear resistance and toughness. It is compound by a brittle phase WC and a ductile phase Co. Mechanical properties of hardmetals are strongly dependent on the microstructure of the WC Co, and additionally affected by the microstructure of WC powders before sintering. An important feature is that the toughness and the hardness increase simultaneously with the refining of WC. Therefore, development of nanostructured WC Co hardmetal has been extensively studied. There are many methods to manufacture WC-Co hard metals, including spraying conversion process, co-precipitation, displacement reaction process, mechanochemical synthesis and high energy ball milling. High energy ball milling is a simple and efficient way of manufacturing the fine powder with nanostructure. In this process, the continuous impacts on the powders promote pronounced changes and the brittle phase is refined until nanometric scale, bring into ductile matrix, and this ductile phase is deformed, re-welded and hardened. The goal of this work was investigate the effects of highenergy milling time in the micro structural changes in the WC-Co particulate composite, particularly in the refinement of the crystallite size and lattice strain. The starting powders were WC (average particle size D50 0.87 μm) supplied by Wolfram, Berglau-u. Hutten - GMBH and Co (average particle size D50 0.93 μm) supplied by H.C.Starck. Mixing 90% WC and 10% Co in planetary ball milling at 2, 10, 20, 50, 70, 100 and 150 hours, BPR 15:1, 400 rpm. The starting powders and the milled particulate composite samples were characterized by X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) to identify phases and morphology. The crystallite size and lattice strain were measured by Rietveld s method. This procedure allowed obtaining more precise information about the influence of each one in the microstructure. The results show that high energy milling is efficient manufacturing process of WC-Co composite, and the milling time have great influence in the microstructure of the final particles, crushing and dispersing the finely WC nanometric order in the Co particles

Sujeitos e atores sociais nas representações discursivas de docentes da rede estadual de ensino em Sergipe: uma análise crítica em tempos de Ideb

According to the studies in Applied Linguistics, this thesis is based on an interdisciplinary perspective (Critical Discourse Analysis, Sociology towards Social Change, Cultural Studies and Systemic-Functional Linguistics). The overall objective of the research was to analyze the discourses of Elementary School teachers in the state of Sergipe, by means of the discursive representations of the social actors, the processes of subjectivity and their fragmented identities in the context of standardized evaluations before the requirements of globalized pedagogical practices, based on the result-based management. The critical analysis of such discourses was motivated by the rapid pace with which the demands of innovation become part of the classroom, aiming at reaching the target in what concerns the indexes of the rankings which characterize the globalized discourse of the national education management, like Ideb (Basic Education Development Index), which makes teachers change their discourses, become silent or keep resistant. The work was initially endorsed by the theoretical lines of the Critical Discourse Analysis (FAIRCLOUGH, 2001, 2006), and poses a proposal for such purpose: the ASCD Discourse Sociological and Communicative Approach (PEDROSA, 2012, 2013). This is an interpretative-qualitative study of the Critical Discourse Analysis (FAIRCLOUGH, 2001, 2003; RAMALHO ; RESENDE, 2011) and to carry it out, semi-structured interviews were used as instruments of data generation (BAUER; GASKELL, 2011; GILL, 2011). Its corpus is composed of thirteen accounts of teachers from the Elementary school who teach Portuguese and work in the fifteen schools which were chosen to be the universe of the research at the Regional Board of Education (02) in the state of Sergipe. Such narratives are related to their impressions, expectations and actions which favor the management of results to which they have to submit themselves. The analytical overview of sociological and discursive line comes from the pan-semiotic categories (Inclusion and Exclusion) which appear in the theory of Representation of Social Actors (VAN LEEUWEN, 1997, 2008). To present the processes of subjectivity of these teachers, this work is based on the socio-analytical proposal of the classification of the subjects, which stems from the individual s work in the Gestão Relacional de Si , which comes from the Applied Sociology (towards) Social Change (BAJOIT, 2006, 2009). The discursive analyses were guided word for word, in their majority, by having the Systemic Functional Grammar as their theoretical basis, specifically by the processes of the Transitivity System postulated by Halliday, (1985); Halliday and Mathiessen, (2004); Eggins (2004); Cunha and Souza (2011). The work makes the field of Cultural Studies emerge towards the dialogue and the presentation of the fragmented identities of the teachers in the context of late modernity (GIDDENS, 2002; HALL, 2011). The thesis promoted a reflection over the teacher s condition, who is immerse in this context of knowledge construction of the present Brazilian educational system, the standardized evaluations, the indexes of development, the targets and the rankings. The considerations and outcomes of such a research dealt with the teachers emerging social practices and the need of planned initial and continuing teacher education towards the new moment which is foreseeable

A criança e o brinquedo-TV: análise sobre o discurso publicitário direcionado para a infância na Rede Globo de Televisão

Esta investigación es un análisis del contexto actual que rodea a la publicidad brasileña, más concretamente, la publicidad discurso televisivo dirigido a los niños en Brasil. Análisis de los documentos se basa en la revisión retórica (Leach, 2004) (SODRE, 2006) A partir de la primera supuesta inadecuación de algunos de sus contenidos al público para que se comunican. También investiga las posibilidades de regulación y la educación del consumidor y el papel de los medios de comunicación en la sociedad mediante la movilización exigiendo el cumplimiento y la mejora de la legislación vigente, evitando los posibles abusos y distorsiones de las secciones generales de la ley. Hemos llevado a cabo por separado se analiza en los niños y sus conceptualizaciones y la función social, abordando también el juguete y el acto de jugar hoy y su sede histórica en un intento de crear una fundación que apoya el análisis de la relación entre la infancia y la publicidad y el consumo, basado en obras de Roger Silverstone, Kapferer, Leontiev y Walter Benjamin. También se hicieron inferencias basadas en estudios de Pablo Del Río, sobre las posibles consecuencias psicológicas del consumo de medios por los niños, sin embargo, en arvorarmos llevar a cabo investigaciones en el estudio de la recepción. Se enfrentarán, tanto en acciones a favor de la aprobación de la Ley 5.921/2001 N º Suplente sugiere que la prohibición de la publicidad infantil en todo el país, los enfoques ampliamente "integrado" y por lo tanto, favorables a la continuidad de la actividad publicitaria en el país bajo la acción de la CONAR de autorregulación, lo que demuestra sin embargo, la viabilidad de ambas propuestas. Tambien relativa a el CONAR se llevó a cabo un estudio sobre su Consejo Asesor, dando a entender su composición y características. Por último, se estudian las posibilidades y el concepto de la educación para el consumo de los medios de comunicación, a partir de la utilización de los recursos de los propios medios de comunicación, como una propuesta para un cambio de paradigma en el mercado de la publicidad en Brasil. En conclusión, vemos que a partir del análisis de la publicidad comercial de los niños atendidos por la Red Globo de Televisión, en una muestra de 170 inserciones, todavía existen graves lagunas, pero que los desequilibrios se pueden resolver con medidas relativamente sencillas que incluyan campañas de educación y la exigencia de adecuación de los pocos grandes anunciantes que violan la ley. Afortunadamente, una nueva entrega de los anunciantes mostró la responsabilidad social en sus acciones

Estratégias midiáticas na aprendizagem do tema DST/AIDS: ações em rede para reduzir vulnerabilidades de adolescentes e jovens da comunidade de Mãe Luiza, Natal-RN

Youngsters and teenagers are still a very vulnerable group of DST/AIDS. In order to combat this vulnerability the community intervention project being developed in Mãe Luiza neighborhood in the city of Natal-RN, entitled Strengthening Community Action Network for Prevention in HIV/AIDS: knowledge and Intervene emerged, popularly known as Project Viva Mãe Luiza. The project develops workshops of educomunication whose approach involves the DST/AIDS subject with the following media: video, photography, and theater playbook. This research integrates the activities of the project and has as main objective to investigate how strategies and practices of media communication developed in Project Viva Mãe Luiza through workshops of educomunication, assisted learning for the prevention of DST/AIDS and contributed to the reduction of vulnerability to DST/AIDS among adolescents and young participants of the project residents of Mãe Luiza community. The methodological basis was based on intervention research, with the technique of gathering daily field data, literature and documentary, in-depth interviews and ethnographic observation. The qualitative analysis was based on the monitoring of video workshops, photography, theater and primer, respectively, crossed by transverse to the prevention of DST/AIDS, conducted between June 2012 and December 2013 issues. Interviews with eight multipliers, aiming to understand their perceptions of vulnerability, prevention, multiplication and use of media that were part of the project were conducted. The analyzes show that learning workshops educomunication community health repercussions both in the development of individual skills in communication as changing perceptions about the vulnerabilities to which they are exposed, the awareness about prevention at the individual and differentiated actions multiplication in the community

Percolação convencional, percolação correlacionada e percolação por invasão num suporte multifractal

In this work we have studied the problem of percolation in a multifractal geometric support, in its different versions, and we have analysed the conection between this problem and the standard percolation and also the connection with the critical phenomena formalism. The projection of the multifractal structure into the subjacent regular lattice allows to map the problem of random percolation in the multifractal lattice into the problem of correlated percolation in the regular lattice. Also we have investigated the critical behavior of the invasion percolation model in this type of environment. We have discussed get the finite size effects

Modelo de ashkin-teller de três cores na rede ponte de wheatstone

In this work we study the phase transitions of the ferromagnetic three-color Ashkin-Teller Model in the hierarquical lattice generated by the Wheatstone bridge using real space renormalization group approach. With such technique we obtain the phase diagram and its critical points with respective critical exponents v. This model presents four phases: ferromagnetic, paramagnetic and two intermediates. Nine critical points were found, three of which are of Ising model type, three are of four states Potts model type, one is of eight states Potts model type and the last two which do not correspond to any Potts model with integer number of states. iv

Danos e propriedades termodinâmicas no modelo de Ashkin-Teller de n cores

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Teoria semi-clássica para super rede magnética formada por materiais ferromagnético e antiferromagnético

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Fraturas e caminhos ótimos na rede de Barabasi-Albert

Following the study of Andrade et al. (2009) on regular square lattices, here we investigate the problem of optimal path cracks (OPC) in Complex Networks. In this problem we associate to each site a determined energy. The optimum path is defined as the one among all possible paths that crosses the system which has the minimum cost, namely the sum of the energies along the path. Once the optimum path is determined, at each step, one blocks its site with highest energy, and then a new optimal path is calculated. This procedure is repeated until there is a set of blocked sites forming a macroscopic fracture which connects the opposite sides of the system. The method is applied to a lattice of size L and the density of removed sites is computed. As observed in the work by Andrade et al. (2009), the fractured system studied here also presents different behaviors depending on the level of disorder, namely weak, moderated and strong disorder intensities. In the regime of weak and moderated disorder, while the density of removed sites in the system does not depend of the size L in the case of regular lattices, in the regime of high disorder the density becomes substantially dependent on L. We did the same type of study for Complex Networks. In this case, each new site is connected with m previous ones. As in the previous work, we observe that the density of removed sites presents a similar behavior. Moreover, a new result is obtained, i.e., we analyze the dependency of the disorder with the attachment parameter m

Propagação de danos para o modelo Ising em uma rede quadrada totalmente frustrada

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Estudo da transformada rápida wavelet e sua conexão com banco de filtros

In this work we presented an exhibition of the mathematical theory of orthogonal compact support wavelets in the context of multiresoluction analysis. These are particularly attractive wavelets because they lead to a stable and very efficient algorithm, that is Fast Transform Wavelet (FWT). One of our objectives is to develop efficient algorithms for calculating the coefficients wavelet (FWT) through the pyramid algorithm of Mallat and to discuss his connection with filters Banks. We also studied the concept of multiresoluction analysis, that is the context in that wavelets can be understood and built naturally, taking an important step in the change from the Mathematical universe (Continuous Domain) for the Universe of the representation (Discret Domain)