Submitted by Kilvya Braga (kilvyabraga@hotmail.com) on 2018-04-25T13:18:17Z No. of bitstreams: 1 JOSÉ LIRA BRAGA NETO - DISSERTAÇÃO (PPGEM) 2015.pdf: 3214305 bytes, checksum: ec9752a773a381a36000f3a5daa3933a (MD5) / Made available in DSpace on 2018-04-25T13:18:18Z (GMT). No. of bitstreams: 1 JOSÉ LIRA BRAGA NETO - DISSERTAÇÃO (PPGEM) 2015.pdf: 3214305 bytes, checksum: ec9752a773a381a36000f3a5daa3933a (MD5) Previous issue date: 2015-04-30 / Capes / Com o avanço tecnológico as propriedades exigidas aos materiais. Os materiais compósitos, que têm uma ampla aplicação nos mais variados setores. Por outro lado, o desempenho dos compósitos é fortemente dependentes da interface matriz-fibra e consequentemente da distribuição e orientação das fibras. A Mecânica da Fratura é o campo da Mecânica que utiliza métodos analíticos e experimentais para descrever o comportamento de sólidos e estruturas com descontinuidades geométricas frente a solicitações mecânicas. Este trabalho tem por objetivo de analisar e avaliar as propriedades mecânicas em compósitos de fibra de vidro e resina poliéster com descontinuidades geométricas (furo central e com variação da distância entre os furos). A caracterização desses materiais foi realizada através de ensaios de tração uniaxial e tenacidade à fratura. Dessa forma, foram observados os valores da tensão máxima de ruptura para os laminados sem furo, com furo central e furos com variação do espaçamento entre os furos, bem como a característica final da fratura. Para a avaliação da possível influência da presença dos furos centrais e a variação da distância entre os furos, a resistência mecânica foi determinada para cada caso. Verificou-se também que o fator de concentração de tensão, como era de se esperar, variou com a distância entre os furos nos compósitos estudados. Os resultados obtidos comprovam que a presença da descontinuidade geométrica tem efeito danoso nas propriedades mecânicas do material, principalmente quando aumentou o diâmetro do furo central de 6 mm para 12 mm de diâmetro. Quanto ao comportamento à fratura dos compósitos estudados, verificou-se uma fratura final do tipo LGM (Lateral e no Meio do Galgo) para os furos centrais de 6 e 12 mm e com a variação da distância entre os furos de 12 e 48 mm de distância, já para a variação da distância entre os furos de 6,2 mm de distância foi AGM (Angular e no Meio do Galgo). No ensaio de tenacidade à fratura as condições exigidas não foram satisfeitas, portanto os fatores de intensidade de tensão KQ (críticos) determinados não podem ser considerados valores de KIC. Portanto, são dependentes da geometria dos corpos de prova usados. / With technological advancement the properties required of conventional materials have changed leading to the appearance of materials capable of meeting the desired requirements of new technologies. One is composite materials, which have a wide application in various sectors. On the other hand, the performance of the composite is strongly dependent on the matrix-fiber interface and hence the distribution and orientation of fibers. The Fracture Mechanics is the field of mechanics that uses analytical and experimental methods to describe the behavior of solids and structures with geometrical discontinuities in against mechanical stress. This field appears as a solid foundation for analyzing the behavior of the morphology of composites. This paper analyzes and evaluate the mechanical properties of composite of glass and polyester resin with geometrical discontinuities in (center hole and change of distance between the holes). The characterization was carried out by uniaxial tensile tests and fracture toughness. Thus they observed values of maximum stress at break for the laminates without holes, with a central hole and holes with varying spacing between the holes and the final characteristic of the fracture. To evaluate the possible influence of the presence of the central holes and the variation of the distance between the holes, the mechanical strength was determined for each case. There was also the factor of stress concentration, as was to be expected, it varies with the distance between the holes in the studied composites. The results obtained show that the presence of geometric discontinuity has harmful effect on the mechanical properties of the material, especially when the increased diameter of the central hole of 6 mm to 12 mm in diameter. The behavior to fracture of the studied composites, presented the final fracture of the LGM type (Side and Middle Greyhound) for central holes 6 and 12 mm and with the change of distance between holes 12 and 48 mm away, as for the change of distance between the holes of 6.2 mm away was AGM (Angle and Half Greyhound). The fracture toughness of the bulk composite, for two different thicknesses of plates (8 and 10 mm nominal values), was not satisfactory service for predicting the fracture of composites containing the concentrators strain studied.

Made available in DSpace on 2014-12-17T14:57:38Z (GMT). No. of bitstreams: 1 CarlosAlbertoPQLF.pdf: 2273640 bytes, checksum: a4f60a823eb1d55227bb74c387319cef (MD5) Previous issue date: 2007-05-31 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / A model of a solar oven with a reflective surface composed of two mirror segments is presented, constituting a two semi-parabolic surfaces made of fiberglass, applied on a ceramic mold, intended to be used in residential and commercial cooking. The reflective surface of the semi-parable is obtained with the use of multiple plain segments of 2 mm wide mirrors. The semi-parabolic structure has visible movements that are comparable to that of the sun. The technical details of the manufacturing and assembling processes will be presented with an analysis of the viability of thermal, economic, and materials of such prototype. This prototype has important social implications and primordial aspects, which combats the ecological damages caused by the wide-scale use of firewood during cooking. It has been demonstrated that the solar oven has the capacity to cook simultaneous two meals distinct for a family of four / Apresenta-se um modelo de fog?o solar ? concentra??o composto por dois segmentos espelhados, constituindo duas semi-par?bolas, obtidas atrav?s da utiliza??o de fibra de vidro, aplicada sobre um molde cer?mico, destinado ao cozimento de alimentos para fins residenciais, urbanos e rurais. O espelhamento das semi-par?bolas foi obtido atrav?s da utiliza??o de m?ltiplos segmentos planos de espelho de 2 mm de espessura. A estrutura das semi-par?bolas tem mobilidade de movimentos para a corre??o do movimento aparente do sol. Ser?o apresentados detalhes t?cnicos dos processos de fabrica??o e montagem e uma an?lise das viabilidades, t?rmica, econ?mica e de materiais de tal prot?tipo, que tem uma conota??o social importante e um aspecto primordial, que ? o combate a danos ecol?gicos proporcionados pela utiliza??o, ainda em larga escala, da lenha para o cozimento dos alimentos. Comprovou-se que ? poss?vel o cozimento simult?neo de alimentos de duas refei??es distintas para uma fam?lia de quatro pessoas

QDs haben aufgrund ihrer einzigartigen optischen und elektronischen Eigenschaften erhebliche Aufmerksamkeit erregt und sind vielseitige Materialien für verschiedene Anwendungen. T-QDs, wie AIS/ZnS, haben aufgrund ihrer geringeren Toxizität, Umweltverträglichkeit und einstellbaren optischen Eigenschaften an Bedeutung gewonnen. Diese Arbeit konzentriert sich auf die MW-Synthese von AIS/ZnS-QDs und untersucht den Einfluss von Syntheseparametern auf ihre optischen Eigenschaften sowie deren nachfolgende Anwendung in LSCs. Die Synthese kombiniert einen zweistufigen Erhitzungsansatz mit MW, was eine präzise Kontrolle über die QD-Zusammensetzung, Liganden und die chemische Zerfallsreihenfolge ermöglicht. Die Studie untersucht die Variation der Ag:In:S:Zn-Verhältnisse und den Einfluss von vier verschiedenen Liganden auf die optischen Eigenschaften. Die Ergebnisse bestätigen die Vielseitigkeit dieser QDs bei der Herstellung wasserlöslicher, hochphotolumineszierender Materialien. Die AIS/ZnS-QDs werden weiterhin als Materialien für LSCs genutzt, um erneuerbare Energie in BIPV-Systemen zu nutzen. Die Studie erforscht die Integration dieser QDs in eine Polymermatrix für LSCs und betont die Effizienz der Synthese. Zwei Syntheseansätze, ein zweistufiges Erhitzungsverfahren und die MW-Synthese mit Thiol-Liganden, erzeugen QDs, die in Toluol dispergierbar sind. Die resultierenden lumineszierenden Platten, integriert in LSC-Geräte, zeigen eine hohe PL QY (>60%). Die optischen Verluste werden für verschiedene Ligandenkombinationen verglichen, wobei überlegene Ergebnisse für MPA-OLA/OA-capped QDs beobachtet werden. Die LSC-Geräte, gekoppelt mit Si-Solarzellen unter einem Sonnensimulator, zeigen OPE-Werte von 3,8 ± 0,2% und 3,5 ± 0,2% für GSH-OLA/OA bzw. MPA-OLA/OA AIS/ZnS-QDs, und QOE-Werte von 24,1 ± 0,4% und 27,4 ± 0,4%. Die erreichte Leistung, gepaart mit der einfachen, wasserbasierten Synthese und den guten optischen Eigenschaften, unterstreicht das Potenzial von AIS/ZnS-QDs als LSCs. / QDs gained significant attention for their unique optical and electronic properties, making them versatile materials for various applications. t-QDs, such as AIS/ZnS, gained prominence due to their lower toxicity, eco-friendly nature, and tunable optical characteristics. This thesis focuses on the MW-assisted synthesis of AIS/ZnS QDs, exploring the impact of synthesis parameters on their optical properties and subsequent application as LSCs. The synthesis methodology combines a two-step heating approach with MW assistance, allowing for precise control over QD composition, ligands, and chemical decomposition order. The study investigates the variation of Ag:In:S:Zn ratios and the influence of four different ligands on optical properties. The results confirm the versatility of these QDs in producing water-soluble, highly photoluminescent materials with PL QY of 60-65% and long PL decay. The synthesized AIS/ZnS QDs are further utilized as materials for LSCs, aiming to harness renewable energy in building-integrated photovoltaic systems. The study explores the integration of these QDs into a polymer matrix for LSCs, emphasizing the efficiency of the synthesis method. Two synthesis approaches, a two-step heating method and MW-assisted synthesis with thiol ligands, yield QDs dispersible in organic solvents. The resulting luminescent slabs, integrated into LSC devices, exhibit high PLQY (>60%). Optical losses due to reabsorption and matrix effects are compared for different ligand combinations, with superior results observed for MPA-OLA/OA-capped QDs. The LSC devices coupled with Si-solar cells under a solar simulator demonstrate OPE values of 3.8 ± 0.2% and 3.5 ± 0.2% for GSH-OLA/OA and MPA-OLA/OA AIS/ZnS QDs, respectively, and QOE values of 24.1 ± 0.4% and 27.4 ± 0.4%. The achieved device performance, among the highest reported, coupled with the simplicity of the water-based synthesis and the excellent optical properties, underscores the potential of AIS/ZnS QDs as LSCs.

Objective of master’s thesis theoretical part is especially to illustrate influence of operation conditions, such as solar radiation, temperature or pollution of photovoltaic generator active area, on load and power characteristics of photovoltaic generator, or more precisely on photovoltaic conversion efficiency. Possible variants of increasing effectivity of using photovoltaic generator are explored, such as solar radiation concentration, photovoltaic generator active area cooling or aplication of optimalization circuit. Pivotal part of master‘s thesis is focused on experimental device practical realisation, concretely type MSQ36-10 photovoltaic generator with oriented concentrators of solar radiation. Practical realisation includes design of master‘s thesis experimental part construction with subsequent design of photovoltaic generator motion cycle necessary for adequate simulation of configuration variants solved using single testing photovoltaic generator. Description of own experimental device construction with list of measuring places used in task takes up. It is used automatic monitoring system working as independent measurement task for required values measuring and consecutive data collecting. It is done in two phases. First phase is measurement of all required values, in second phase measurement with attached optimalization circuit is made. Optimalization circuit sets best working point of photovoltaic generator according to actual working conditions. Master‘s thesis intention is experimental verification of solar radiation concentrators application convenience, orientation of photovoltaic generator or its mutual combination, namely using type MSQ36-10 photovoltaic generator. Objective is evaluation of reached energetic gain for all experimental device layouts in variable operating conditions.

The aim of this work is informed first about photovoltaics universally, works to inform the photovoltaic panels and complete plants. The work also includes instructions on how to implement PVP in accordance with law. Another part is the rough draft of the photovoltaic power 30 kWp, which can be placed on the house, computation and calculation of investment and them profitable investments to time. Design is made in two separate forms of the Fronius Solar and Sunny Design, their outputs are compared. The practical part of this work cooperates with the company SOLARTEC Ltd. for experimental measurements of the photovoltaic system and develop a methodology for setting the properties of real solar systems in operation from the measured data then stored in a database. These data further evaluate and compare the similar operating conditions. This data will show as the course of production of electricity during the typical day in percentage terms, depending on the incident irradiance, cell temperature, angle of incident radiation, etc. We can compare what it looks like an ideal day in terms of production of photovoltaic power, with the other days. Further are in work mentioned histograms achievement panel behind classical day and behind all - time investigation.