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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
71

O espaço isolado da vitrine : espaço de autoria / O espaço isolado da vitrine : espaço de autoria

Panek, Bernadette Maria 27 March 2008 (has links)
Esta pesquisa objetiva apresentar uma análise sobre a utilização da vitrine como espaço integrante da obra de arte. Problematiza a necessidade do uso do espaço isolado e intocável da vitrine como área imprescindível para determinadas propostas artísticas contemporâneas. Averigua também as relações entre a área envidraçada da vitrine e o observador. Verifica como a vitrine é tematizada não só no espaço arquitetônico, mas também na pintura e na fotografia. Examina dessa maneira a atitude dos artistas em colecionar, selecionar, organizar, classificar, deslocar e exibir uma série de objetos reunidos no interior de tal dispositivo. Interroga se a presença de artistas que trabalham com a vitrine ou com o espaço, apenas delimitado, não estaria ligada à crise do conceito tradicional de autor. / This research aims to present an analysis of the use of the museums display as an integrating space of the work of art. It gives emphasis on the use of an isolated and untouchable space in the museums display as an essential area to establish contemporary aesthetic proposals. So, it also checks how the display case is given thematically not only in the architectural space, but also in the painting and photograph. It analyses the artists approach of collecting, selecting, arranging, assorting, displacing and displaying a series of united objects in the interior of such device. It is questioned if the presence of the artists who work with the museum display or with demarked space would not be tied to the crisis of the authors traditional concept.
72

Perda de inserção periodontal em uma população isolada brasileira: prevalência, extensão, severidade e indicadores de risco / Periodontal attachment loss in an untreated isolated population of Brazil: prevalence, extent, severity and risk indicators

Corraini, Priscila 08 August 2007 (has links)
Os objetivos deste estudo são avaliar a prevalência, extensão e severidade de perda clínica de inserção (NCI); e investigar as possíveis associações entre variáveis demográficas, socioeconômicas e comportamentais com NCI em uma população isolada brasileira. MATERIAL E MÉTODO: Todos os indivíduos com mais de 12 anos de idade foram identificados por um censo. Eles foram entrevistados por meio de um questionário estruturado e submetidos a um exame clínico completo que consistiu na avaliação de 6 sítios por dente em toda a boca. RESULTADOS: Dentre os 214 indivíduos que foram entrevistados e receberam exame clínico completo, NCI >= 5mm foi observado em 8%, 37%, 70%, 83% e 100% dos indivíduos dentados nas faixas etárias de 12-19, 20-29, 30- 39, 40-49 e 50 ou mais anos de idade; enquanto que a prevalência de NCI >= 7mm foi de 5%, 8%, 20%, 67% e 83% nas faixas anteriormente descritas, respectivamente. Análises de regressão logística multivariável identificaram quantidade de placa visível (OR = 2,8), quantidade de cálculo supra-gengival (20-50%, OR = 2,9; e > 50%, OR= 10,6), idade (OR = 11,4) e tabagismo (OR = 2,4) como indicadores de risco para NCI >= 5mm; e tabagismo (OR = 8,2) para NCI >= 7mm. CONCLUSÃO: Os resultados demonstraram que perda clínica de inserção é altamente prevalente nesta população isolada. A alta prevalência de NCI em faixas etárias jovens e a identificação de indicadores de risco tradicionais para NCI nesta população sugerem que fatores microbiológicos ou a susceptibilidade para a exposição de fatores ambientais possam ser considerados fatores-chave para a alta ocorrência encontrada nesta população. / The aim of this study was to assess the prevalence, extent and severity of clinical attachment loss (CAL); and to investigate the associations between demographic, socioeconomic and behavioral risk indicators with CAL in an untreated isolated population in Brazil. METHODS: All subjects aged 12 years forward were selected by a census. They were submitted to a full-mouth clinical examination of six sites per tooth and were interviewed using a structured written questionnaire. RESULTS: Among the 214 subjects who were interviewed and clinical examined, CAL >= 5mm was observed in 8%, 37%, 70%, 83%, and 100% of the dentate subjects, depending on age; while the age dependent prevalence of CAL >= 7mm was 5%, 8% 20%, 67% and 83%, respectively. Multivariate analysis identified amount of plaque (OR=2.8), thresholds of supragingival calculus (OR=2.9-10.6), age (OR=11.4) and smoking (OR=2.4) as risk indicators for CAL >= 5mm, and smoking (OR=8.2) for CAL >= 7mm. CONCLUSION: The results demonstrate that CAL is highly prevalent in this isolated population. The high prevalence of CAL in young age groups and the observation of traditional risk indicators for CAL in this population suggest microbiological factors or host susceptibility to be key factors explaining the high levels of CAL found in this population.
73

Efeito do hipotiroidismo e da ooforectomia na função cardíaca de ratas. / Effect of hypothyroidism and oophorectomy in the cardiac function of female rats.

Sousa, Severino Denício Gonçalves de 25 September 2017 (has links)
Avaliamos a função cardíaca frente a Isquemia e reperfusão, em corações isolados de ratas intactas, com hipotireoidismo (Hipo), hipotireoidismo subclínico (HTS), redução dos níveis de hormônios ovarianos (OO) e a ambas condições (HTS+OO). Na estabilização, a Pressão Desenvolvida pelo Ventrículo Esquerdo (LVDP), Pressão Diastólica Final (EDP) e Pressão de Perfusão não diferiram. Porém, a Primeira Derivada Positiva das Pressões (+dP/dt), Primeira Derivada Negativa das Pressões (-dP/dt) e frequência cardíaca foram menores no grupo Hipo. Na reperfusão, os corações Hipo tiveram EDP, +dP/dt e -dP/dt semelhantes a estabilização. Assim, sugere-se que o HTS, a OO e o HTS + OO não alteraram a recuperação cardíaca após a isquemia. E que o Hipo é resistente à lesão por isquemia, apesar da função cardíaca deprimida. / We evaluate the cardiac function in relation to an ischemia and reperfusion event in hearts isolated from intact rats, With hypothyroidism (Hypo), subclinical hypothyroidism (HTS), decreased levels of ovarian hormones (OO) and both conditions (HTS + OO). At etabilization the Left Ventricle Developed Pressure (LVDP), Final Diastolic Pressure (EDP) and Perfusion Pressure did not differ. However, the First Positive Pressure Derivative (+ dP / dt), First Negative Pressure Derivative (-dP / dt) and heart rate were lower in the Hypo group. On reperfusion the hypothyroid hearts presented EDP, + dP / dt and -dP / dt Similar to stabilization. Thus, it is suggested that HTS, a OO e o HTS + OO Did not change cardiac recovery after ischemia.Is that hipo is resistant to ischemia injury, despite depressed cardiac function.
74

Spirit of Caprera : an ethnographic analysis of sailing

Galeazzi, Gilberto January 2018 (has links)
The research investigates the Centro Velico Caprera (CVC), a sailing school located in the Mediterrean Sea, whose purpose is to replicate the lifestyle of a ship on land. This ambition creates an isolated environment in which the frequenters are completely immersed and the life is heavily controlled through different spatial and temporal means. The people who attend the school and become part of its community refer to its characteristics and to the collective essence they experience as 'the Spirit of Caprera'. Using an ethnographic approach and in particular participant observation as a primary source of data, and formal semi-structured interviews, the research investigated the internal dynamics of the school and the nature of the 'spirit' by looking at the setting from the insiders' point of view. The investigation aspired to gain a better understanding of the setting as a sailing community and of the relationships that are created that appear to make this environment unique. The research used sociological concepts as 'benchmarks', such as total institution, status and roles, routine and rituals, subculture and power, to guide the data collection and the analysis. Moreover, it made use of key thinkers such as Goffman and Foucault. The analysis has revealed that in the Centro Velico Caprera the 'spirit' can be considered as the consequence and result of more specific dynamics. In particular, the school's organisational and institutional structure, the time management, the role and functioning of authority and finally the rules and norms that derive from the idea of being part of a unique crew. The research engaged also in the analysis of social class and gender discrimination that characterise the school. The study of this school contributes to the study of sport and in particular sailing, which has often been ignored, by adding a new perspective and analysis to its study. The main contributions surround the comparison with other similar sailing subcultures and realities, such as ocean cruising, the development of the concept of the sport panopticon related to authority and its functioning, the notion of spirit, its meaning and significance, and the particular structure of the institution with its consequence for the frequenters. Moreover, the study also aimed to contribute to the narrower debates surrounding the 'benchmark' concepts, their use and their understanding in social theory and for sport studies.
75

Control of wave energy converters using machine learning strategies

Anderlini, Enrico January 2017 (has links)
Wave energy converters are devices that are designed to extract power from ocean waves. Existing wave energy converter technologies are not financially viable yet. Control systems have been identified as one of the areas that can contribute the most towards the increase in energy absorption and reduction of loads acting on the structure, whilst incurring only minimal extra hardware costs. In this thesis, control schemes are developed for wave energy converters, with the focus on single isolated devices. Numerical models of increasing complexity are developed for the simulation of a point absorber, which is a type of wave energy converter with small dimensions with respect to the dominating wave length. After investigating state-of-the-art control schemes, the existing control strategies reported in the literature have been found to rely on the model of the system dynamics to determine the optimal control action. This is despite the fact that modelling errors can negatively affect the performance of the device, particularly in highly energetic waves when non-linear effects become more significant. Furthermore, the controller should be adaptive so that changes in the system dynamics, e.g. due to marine growth or non-critical subsystem failure, are accounted for. Hence, machine learning approaches have been investigated as an alternative, with a focus on neural networks and reinforcement learning for control applications. A time-averaged approach will be employed for the development of the control schemes to enable a practical implementation on WECs based on the standard in the industry at the moment. Neural networks are applied to the active control of a point absorber. They are used mainly for system identification, where the mean power is related to the current sea state and parameters of the power take-off unit. The developed control scheme presents a similar performance to optimal active control for the analysed simulations, which rely on linear hydrodynamics. Reinforcement learning is then applied to the passive and active control of a wave energy converter for the first time. The successful development of different control schemes is described in detail, focusing on the encountered challenges in the selection of states, actions and reward function. The performance of reinforcement learning is assessed against state-of-the-art control strategies. Reinforcement learning is shown to learn the optimal behaviour in a reasonable time frame, whilst recognizing each sea state without reliance on any models of the system dynamics. Additionally, the strategy is able to deal with model non-linearities. Furthermore, it is shown that the control scheme is able to adapt to changes in the device dynamics, as for instance due to marine growth.
76

Alimentation et commande de drivers à très forte isolation galvanique pour des convertisseurs multi-niveaux dédiés à la traction ferroviaire / High isolated drivers order and power supply for multi levels converters applied to railway area

Galaï Dol, Lilia 14 January 2014 (has links)
Ce projet fait l’objet d’une collaboration entre l’équipe EPI du laboratoire SATIE de l’ENS Cachan, le laboratoire LAPLACE et ALSTOM Transport dans le cadre du projet ANR « CONCIGI HT ». Les recherches dans le domaine du ferroviaire visent à réduire toujours plus la taille et le poids de la chaine de traction. Aujourd’hui, la volonté de poursuivre la réduction des temps de parcours est complétée par le souhait de diminuer la puissance consommée, ceci ayant des conséquences importantes sur la conception des chaines de traction. L’objectif de ce projet est de remplacer certaines parties de la chaine de puissance d’une locomotive par des systèmes permettant de diminuer de 30% leur encombrement, donc de diminuer jusqu’à 8,5 % l’énergie électrique consommée et augmenter le nombre de passagers transportés. Le travail présenté dans cette thèse porte sur le dimensionnement et l’étude de l’alimentation des allumeurs de semi-conducteurs SiC HT (pouvant atteindre un transitoire de 10 kV). La particularité de ces semi-conducteurs est leur application : ils constituent des convertisseurs multi-niveaux dont la fonction est de remplacer les transformateurs 25 kV/3 kV-50 Hz actuellement utilisés pour la traction ferroviaire. La principale contrainte porte donc sur la tenue diélectrique qui atteint un maximum de 60 kV liée aux transitoires présents sur la caténaire. Une alimentation à double isolation galvanique (DGIT-Double Galvanic Insulation Transformer) a donc été développée afin de répondre à la nécessité de double tenue diélectrique (10 kV et 60 kV). Dans un premier temps une structure permettant la double isolation galvanique a été développée avec l’objectif de réduire au maximum sa taille et son poids. Sa disposition spatiale et sa géométrique ont également été pris en considération (ainsi que de nombreux paramètre à la fois pertinents et contradictoires). Ceci afin d’obtenir le système optimal et une répartition des capacités de mode commun et différentiel respectant la forte tenue diélectrique. Dans un second temps une étude de l’alimentation adaptée au DGIT a été réalisée et testée. L’association du DGIT qui est un élément très inductif, de la charge qui est un driver à faible puissance et de l’aspect multi-niveau implique un fonctionnement atypique. Pour chacune de ces parties, une étude structurelle, fréquentielle et électrique a été réalisée afin d’obtenir un dispositif optimal du point de vue du volume, du poids et des pertes, tout en respectant la principale contrainte de la tenue à la THT (Très Haute Tension). Enfin, dans un troisième temps nous avons étudié la possibilité de remplacer les fibres optiques utilisées de nos jours pour la commande des allumeurs par un système basé sur la transmission par radio fréquence. / This project is the result of collaboration between the EPI team of the SATIE laboratory at ENS Cachan, the LAPLACE laboratory and ALSTOM Transport in the ANR "CONCIGI HT" project. Research in the railway traction area aims to reduce the increasing size and weight of the power train. Today, the desire to reduce travel time is complemented by the desire to reduce power consumption- it is an important information for the design of traction chains. The objective of this project is to replace parts of the locomotive power supply systems to reduce their size by 30%, thus to reduce the power consumption and increase by 8.5% the number of passengers. The work presented in this thesis focuses on the design and study of the drivers power supply for HV SiC semiconductor (up to a 10 kV transient voltage). The peculiarity of these semiconductors is their application: they are placed in multi-level converters in order to replace the 25 kV / 3 kV, 50 Hz transformers currently used for rail traction. The main constraint is the dielectric strength that reaches a maximum of 60 kV due to transient present on the catenary. So, the Double Galvanic Insulation Transformer (DGIT) has been developed to adapt to the need of holding dual dielectric (10 kV and 60 kV). In a first step, a structure for the dual galvanic insulation has been developed with the objective to minimize its size and weight. Its spatial and geometrical arrangements were also taken into account (as well as many parameters both relevant and contradictory), in order to obtain the optimal system and common and differential mode distributed capacities observing the high dielectric strength. In a second step a study of the DGIT adapted power supply has been completed and tested. The combination of DGIT inductive behavior, the driver low power and the multi-level aspect, involves an atypical work of this power supply converter. For each of these parts, a structural, frequencial and electrical study was performed in order to achieve the maximum optimal device in terms of volume, weight and loss, with respect to the main constraint of VHV (Very High Voltage). Finally, in a third step we studied the possibility of subtituing the optical fibers currently used for the control of lighters with a system based on radio-frequency transmission.
77

A escola isolada à meia-luz (1891/1927) / The school for isolated half-light (1891/1927).

Rosinete Maria dos Reis 27 June 2011 (has links)
A presente tese se insere na Área de História e Historiografia da Educação e objetiva analisar e compreender o processo de constituição das Escolas Isoladas enquanto modalidade escolar no contexto Mato-Grossense no período de 1890-1928. Trata-se de rehistoricizar o objeto escola de (des) naturalizá-la, retratá-la em seus aspectos internos, definindo sua cultura e os processos que configuram a sua modelização e organização. A busca pela compreensão dos aspectos internos da escola isolada, ou seja, como se dava a construção social e cultural das instituições escolares, exigiu o entendimento daquilo que chamamos de cultura escolar. Na medida em que a cultura escolar se constitui numa apropriada ferramenta teórica para explorar o passado e o presente da escola na sua relação com a sociedade e a cultura, e permite explorar o jogo tenso das lutas e tensões que perpassam a escola e expressam as contradições sociais. Como instrumentos de pesquisa, utilizei de documentos oriundos de atividades funcionais e pedagógicas, como: Mensagens governamentais, Relatórios dos inspetores (diretores, após 1880) da instrução; e de Diretores dos Grupos Escolares, alguns números de Jornais, Livros de Matrículas, Ofícios, Circulares, Livros de Notas, Atas de Exames, Mapas de freqüência de alunos e professores, Provas e Exercícios Escolares, Regulamentos, Regimentos e Fotografias. Essas fontes além de oferecerem preciosas informações sobre o funcionamento da escola ainda permitiu-me visualizar as representações dos profissionais envolvidos no processo, a forma pelas quais diretores, inspetores e autoridades do ensino interpretaram e cumpriram as determinações impostas pelas novas concepções pedagógicas. Nessa trilha a educação e a instrução da população estavam sendo amplamente discutidas e reafirmadas como essenciais, a fim de tornar o país, moderno e civilizado. Tais discursos tinham clara intenção em mostrar que, somente através da organização da instrução pública, seria possível elevar o país ao nível das nações civilizadas. Organizar a instrução era, segundo eles, romper com uma estrutura ineficaz, baseada em métodos ultrapassados e dispendiosos e, sobretudo, formar devidamente os professores. A partir de então, os Regulamentos e as Reformas da instrução pública teriam a finalidade de reordenar e restabelecer os critérios para a reorganização da instrução e também para o ingresso e a permanência dos professores no magistério primário. Propósito nosso foi demonstrar que se delineou nas escolas isoladas, a constituição e articulação de uma cultura e de uma forma escolar própria, caracterizada por dispositivos de normatização pedagógica e práticas dos agentes que se apropriaram deles, por meio de estratégias e táticas reveladoras de saberes socialmente acumulados permitindo reconstruir uma identidade escolar e difundir os seus valores e comportamentos específicos. / This thesis falls within the Area of History and Historiography of Education and aims to analyze and understand the constitution of Isolated Schools as a school sport in the context of Mato Grosso in the period 1890-1928. It is the object rehistoricizar school (un) naturalizing it, portray it in its internal aspects, defining its culture and processes that shape modeling and organization. The search for understanding of the internal aspects of the school alone, that is, how was the social and cultural construction of educational institutions, demanded an understanding of what we call school culture. To the extent that the school culture is an appropriate theoretical tool to explore the past and present school in its relationship with society and culture, and the game lets you explore the tense struggles and tensions that pervade the school and express the social contradictions. As research tools, used documents from the functional and educational activities, such as government posts, the inspectors\' reports (directors, after 1880) Education, and Directors of School Groups, some numbers of Journals, Books Enrollment, Crafts, Circulars, Books, Notes, Minutes of Examinations, frequency maps for students and teachers, tests and exercises School, Regulations, Regiments and Photographs. These sources also provide valuable information about the school run has allowed me to see the representations of the professionals involved in the process, the way in which directors, inspectors and education authorities have interpreted and complied with the determinations imposed by the new educational ideas. That track the education and instruction of the population were being widely discussed and reaffirmed as essential in order to make the country, modern and civilized. Such speeches were clearly intent on showing that only through the organization of public instruction; the country could raise the level of civilized nations. Arrange the statement was, according to them, breaking with an ineffective structure, based on outdated methods and expensive and, above all, to properly train teachers. Since then, Regulations and Reforms of public education would have the purpose of reorganizing and re-establish criteria for the reorganization of education and also for entry and retention of teachers in primary teaching. Our purpose was to demonstrate that takes place in isolated schools, the creation and articulation of a culture and a school form itself, characterized by devices pedagogical norms and practices of the agents who took them through strategies and tactics that reveal knowledge socially allowing accumulated rebuild a school identity and spread its values and behaviors.
78

Sistema fotovoltaico para comunidades isoladas utilizando ultracapacitores para armazenamento de energia / Photovoltaic system for isolated communities using ultracapacitors for energy storage

Josà Mascena Dantas 21 December 2012 (has links)
Universidade Federal do Cearà / Este trabalho apresenta a concepÃÃo, projeto e implementaÃÃo de um conversor CC/CC elevador para interligar um painel fotovoltaico a um banco de ultracapacitores para armazenamento de energia em substituiÃÃo Ãs baterias automotivas convencionais. Na saÃda dos ultracapacitores utiliza-se um conversor CC/CC abaixador, que fornece essa energia a um sistema de telecomunicaÃÃo para suprimento de um transceptor monocanal visando ao atendimento do serviÃo de telefonia rural/Internet em comunidades isoladas da rede pÃblica de energia. O sistema pode suprir o serviÃo de comunicaÃÃo para uma comunidade isolada da rede de energia elÃtrica por atà trÃs horas no perÃodo noturno, quando utilizado um equipamento rÃdio com cabos, conectores e antena para transmissÃo e recepÃÃo de sinal de telefonia com potÃncia de consumo de 13 W e com radiaÃÃo solar mÃdia de 5.500 W/m2/dia. Durante o dia, a energia solar à capturada por um painel fotovoltaico e armazenada em ultracapacitores atravÃs de um conversor boost. Este conversor possibilita a carga dos ultracapacitores no ponto de mÃxima potÃncia (MPP) do painel fotovoltaico. O transceptor à ativado quando se tira o fone do gancho e a alimentaÃÃo do sistema vem do painel via ultracapacitores. Caso haja ligaÃÃes durante o dia, o painel fotovoltaico supre as necessidades do equipamento transceptor. à noite, o painel utilizado nÃo gera energia suficiente para alimentar o sistema de telecomunicaÃÃo. No perÃodo noturno, caso ocorra uma chamada telefÃnica para o sistema proposto, o transceptor serà acionado, o assinante deverà retirar o monofone do gancho do aparelho telefÃnico para realizar o atendimento. Durante essa operaÃÃo o transceptor consome aproximadamente 13 W de potÃncia, que à fornecida pelos ultracapacitores, os quais estÃo interligados atravÃs do conversor buck. O sistema proposto à controlado por um microcontrolador e um circuito de controle, que procura o ponto de mÃxima potÃncia (MPP) do painel fotovoltaico, monitora o nÃvel da tensÃo dos ultracapacitores e determina o tempo de funcionamento do conversor CC/CC, que possibilita o fornecimento de energia para o transceptor pelos ultracapacitores. / This work presents the conception, design and implementation of a DC/DC boost converter to connect a photovoltaic panel to a bank of ultracapacitors for energy storage to replace the conventional automotive batteries. In the output of ultracapacitors a DC/DC step-down converter is used. This converter provides power to a telecommunication system for the supply of a single channel transceiver with the purpose of providing the services of rural telephony and Internet in isolated communities from the public energy grid. The system can provide the communication service to a isolated community from the power grid for up to three hours at night when used with radio equipment with cables, connectors and antenna for transmitting and receiving phone signal with consumption power of 13 W and with solar radiation rate of 5.500 W/m2/day. During the day solar energy is captured by a photovoltaic panel and stored in ultracapacitors through a boost converter. This converter enables ultracapacitors to charge at the maximum power point (MPP) of the photovoltaic panel. The transceiver is activated when the phone is taken off the hook and the system power comes from the panel via ultracapacitors. If there are calls during the day, the photovoltaic panel meets the needs of the transceiver. At night, the panel used does not generate enough energy to power the telecommunication system. At night, if there is a phone call to the proposed system, the transceiver will be triggered, and the subscriber should take the handset off the hook to answer an incoming call. During this operation, the transceiver consumes approximately 13 W of power, which is provided by ultracapacitors that are interconnected through the buck converter. The proposed system is controlled by a microcontroller and a control circuit which tracks the maximum power point (MPP) of the photovoltaic panel, monitors the voltage level of ultracapacitors and determines the operating time of the DC/DC converter which enables the provision of power to the transceiver by the ultracapacitors.This work presents the conception, design and implementation of a DC/DC boost converter to connect a photovoltaic panel to a bank of ultracapacitors for energy storage to replace the conventional automotive batteries. In the output of ultracapacitors a DC/DC step-down converter is used. This converter provides power to a telecommunication system for the supply of a single channel transceiver with the purpose of providing the services of rural telephony and Internet in isolated communities from the public energy grid. The system can provide the communication service to a isolated community from the power grid for up to three hours at night when used with radio equipment with cables, connectors and antenna for transmitting and receiving phone signal with consumption power of 13 W and with solar radiation rate of 5.500 W/m2/day. During the day solar energy is captured by a photovoltaic panel and stored in ultracapacitors through a boost converter. This converter enables ultracapacitors to charge at the maximum power point (MPP) of the photovoltaic panel. The transceiver is activated when the phone is taken off the hook and the system power comes from the panel via ultracapacitors. If there are calls during the day, the photovoltaic panel meets the needs of the transceiver. At night, the panel used does not generate enough energy to power the telecommunication system. At night, if there is a phone call to the proposed system, the transceiver will be triggered, and the subscriber should take the handset off the hook to answer an incoming call. During this operation, the transceiver consumes approximately 13 W of power, which is provided by ultracapacitors that are interconnected through the buck converter. The proposed system is controlled by a microcontroller and a control circuit which tracks the maximum power point (MPP) of the photovoltaic panel, monitors the voltage level of ultracapacitors and determines the operating time of the DC/DC converter which enables the provision of power to the transceiver by the ultracapacitors.This work presents the conception, design and implementation of a DC/DC boost converter to connect a photovoltaic panel to a bank of ultracapacitors for energy storage to replace the conventional automotive batteries. In the output of ultracapacitors a DC/DC step-down converter is used. This converter provides power to a telecommunication system for the supply of a single channel transceiver with the purpose of providing the services of rural telephony and Internet in isolated communities from the public energy grid. The system can provide the communication service to a isolated community from the power grid for up to three hours at night when used with radio equipment with cables, connectors and antenna for transmitting and receiving phone signal with consumption power of 13 W and with solar radiation rate of 5.500 W/m2/day. During the day solar energy is captured by a photovoltaic panel and stored in ultracapacitors through a boost converter. This converter enables ultracapacitors to charge at the maximum power point (MPP) of the photovoltaic panel. The transceiver is activated when the phone is taken off the hook and the system power comes from the panel via ultracapacitors. If there are calls during the day, the photovoltaic panel meets the needs of the transceiver. At night, the panel used does not generate enough energy to power the telecommunication system. At night, if there is a phone call to the proposed system, the transceiver will be triggered, and the subscriber should take the handset off the hook to answer an incoming call. During this operation, the transceiver consumes approximately 13 W of power, which is provided by ultracapacitors that are interconnected through the buck converter. The proposed system is controlled by a microcontroller and a control circuit which tracks the maximum power point (MPP) of the photovoltaic panel, monitors the voltage level of ultracapacitors and determines the operating time of the DC/DC converter which enables the provision of power to the transceiver by the ultracapacitors.
79

Conversores DC-DC Dual-Active-Bridge isolados bidirecionais. / Isolated bidirectional dual active bridge DC-DC converter.

Bruno Yukio Enomoto 28 March 2018 (has links)
Este trabalho visa o estudo das regiões de operação de conversores CC/CC isolados bidirecionais do tipo DAB (Dual Active Bridge). É feito um estudo do comportamento do circuito com a variação dos valores das reatâncias de acoplamento, avaliando-se aspectos como eficiência, fator de potência, reativos, entre outros. A seguir é proposta uma estrutura de controle que permite a operação com tensões nos barramentos DC diferentes das nominais, minimizando as correntes absorvidas. Além disso, propõe-se uma estratégia de controle para regular a potência transferida. O trabalho inclui modelagem teórica, implementação em simulação computacional e medidas em protótipo experimental. / This work investigates operation regions of Dual Active Bridge DC-DC isolated bidirectional converters, studying circuit behavior with the variation of the coupling reactance, evaluating parameters like efficiency, power factor, reactive flow etc. A control structure is proposed which allows operating with DC voltages different from nominal voltages, reducing the AC currents. Furthermore, a control strategy to regulate the power transferred is proposed. Methodology includes theoretical modeling, computer simulation and experimental prototype measurements.
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The Paleoindian Chipola: A Site Distribution Analysis and Review of Collector Contributions in the Apalachicola River Valley, Northwest Florida

Tyler, William D 25 March 2008 (has links)
At the end of the Pleistocene and the beginning of the Holocene, between 12,000 and 10,000 years ago, humans began to spread throughout North America and into many areas of Florida. These first Floridians are known as Paleoindians, and their culture is largely defined by their lithic assemblage, which includes the well known Clovis point. As the Pleistocene ice age came to a close glaciers melted, rivers experienced a drastic increase in water volume and the landmass of Florida began to shrink as the sea level in the Gulf of Mexico rose. This event likely submerged many early Paleoindian sites in coastal areas, and the only sites known now are usually found in river valleys. This research will examine the distribution of Paleoindian sites in the Apalachicola River Valley of northwest Florida in terms of environmental characteristics, namely distance to river and site elevation. Using data from known sites and from four artifact collectors, this research will show that Paleoindian sites cluster along the Chipola River, the major tributary of the Apalachicola River, and will also argue that it is far more beneficial for archaeologists to work with artifact collectors and document their vast amounts of data than to shun them and deem their data questionable and their methods unethical.

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