Dissertations / Theses on the topic 'Compaction Energy'

Orientador: Oscar Antonio Braunbeck<br>Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Agricola<br>Made available in DSpace on 2018-08-12T03:37:50Z (GMT). No. of bitstreams: 1 Sidou_NeyBarrosdeAvelino_M.pdf: 3333411 bytes, checksum: 7ee0df98caa4c049f526e9c40d2c553e (MD5) Previous issue date: 2007<br>Resumo: O aumento da capacidade produtiva de energia elétrica por meios renováveis em curto prazo é fundamental para ao desenvolvimento de paises como o Brasil e o uso da fitomassa remanescente da cana-de-açúcar é uma opção viável e abundante em nosso país,entretanto, os métodos de recolhimento do palhiço não estão totalmente estabelecido havendo, então, a necessidade de novas propostas de métodos de recolhimento que atendam as necessidades qualitativas para o uso do palhiço como fonte energética. Uma unidade de testes foi construída para avaliar o comportamento mecânico do palhiço quando submetido ao princípio de adensamento por helicóides cônicos. Com esta unidade teste, foram realizados 16 ensaios combinando duas distâncias entre as helicóides, duas velocidades relativas, dois níveis de pressão de restrição e duas inclinações de taliscas. Os resultados experimentais mostraram relações entre pressão e densidade condizentes com a bibliografia. As pressões aplicadas na direção de carregamento mostraram relação exponencial de variação com as pressões registradas em direção perpendicular à mesma, atingindo valores máximos de 0,3 N.mm.-2. O princípio mecânico de adensamento por helicóides cônico mostrou-se eficaz para o adensamento do palhiço atingindo densidades aparentes entre 188,8 kg.m.-3 e 293,5 kg.m.-3. Os coeficientes de atrito determinados foram elevados, variando entre 3,7 e 1,16, e apresentaram uma tendência de queda com o aumento da pressão a qual o palhiço estava sendo submetido. Os valores experimentais de densidade, pressão normal e coeficientes de atrito gerados por uma talisca com comprimento de 200 mm foram alimentados ao modelo de simulação o qual a simulou valores de densidade para comprimentos de talisca longos o suficiente para atingir a densidade final desejada. Verificou-se que os valores da densidade final próximos de 200 kg.m-3 que puderam ser obtidos com adensadores de altura reduzida, com peso e complexidade construtiva inferiores aos das enfardadoras convencionais.<br>Abstract: This thesis aimed to show that agricultural producers could widen their role as consumers of agricultural lime - in Brazil, 70% of farmable soil is considered to be acid and require liming - and that such consumption would contribute to its sustainability, providing gains in the economic, social and environmental spheres. In addition, the use of agricultural lime is a practice considered important and should include family sized farms, currently on the margins of this market, considering that at the moment the greatest consumers of this corrective are the large and medium sized producers of soybean, corn, sugarcane, citrus products, coffee and cattle. In order to make such a strategy viable, both the potential supply and potential demand of this material were characterized. In Brazil, the productive park already installed consists of more than 300 companies, operating at an average of 57% of their total capacity, and there are reserves of calcareous rocks distributed throughout the Federation in satisfactory quantity and quality. Whilst the annual market potential for consumption of this material was estimated as 75 million tons, current consumption is only 17 million tons, corresponding to 22% of the real need of the Country's soils. The public and private policies developed up to the present time supporting the use of this material, were then analysed, and finally a group of actions were proposed, aiming at constructing a policy directed at the consumption of agricultural lime, with emphasis on family farms.<br>Mestrado<br>Maquinas Agricolas<br>Mestre em Engenharia Agrícola

Ce travail, réalisé en collaboration avec l'usine de recyclage Orano Melox, s'inscrit dans le contexte de l'industrie nucléaire française, qui joue un rôle central dans la production d'électricité du pays. La thèse est centrée sur la fabrication du combustible nucléaire à travers les étapes de compaction et de frittage des poudres nucléaires : les combustibles UOX (Uranium OXide) et MOX (Mixed OXide). La compaction uni-axiale induit un champ de densité hétérogène dans la pastille. Cette hétérogénéité est responsable d’une déformation radiale lors des étapes d’éjection et de frittage (effet diabolo), qui impose au fabricant une étape de rectification de la surface latérale. Le but de la thèse est de développer un outil numérique dédié pour simuler la géométrie des pastilles après compaction et frittage. Il s’agit en particulier d’anticiper l’effet de la composition du MOX.L’outil numérique doit prendre en compte le caractère granulaire des poudres, la composition du mélange, et les conditions industrielles du processus. Pour cela, la méthode des éléments discrets (DEM) est utilisée. Cette méthode de simulation, qui prend explicitement en compte la microstructure granulaire des poudres en modélisant chaque particule individuellement, est explorée en détail dans ce manuscrit. Les lois constitutives pour la compaction et le frittage sont abordées, ainsi que leur application dans le contexte des poudres nucléaires. Nous adaptons un modèle qui permet d’aborder les hautes densités relatives en tenant compte de l’effet de la densité locale (calculée via des cellules de Voronoi) sur l’écrouissage de la poudre.L'approche choisie pour simuler la poudre à l'échelle d'un comprimé entier consiste à représenter la poudre MOX comme étant composée de deux types d'agglomérats poreux : les agglomérats d'UO2 et les agglomérats de mélange primaire (MP, un mélange à haute teneur en plutonium). Cela permet d'optimiser le temps de calcul des simulations, et de rendre compte de la composition des différents mélanges utilisées par l’industriel.Dans un premier temps, l’agglomérat d'UO2 est modélisé. Pour ce faire, une base de données a été générée, comprenant des milliers de simulations dans lesquelles six paramètres matériau ont été variés. Un modèle d'apprentissage machine a été développé et entraîné par apprentissage supervisé, afin de déterminer l'ensemble des paramètres matériau qui correspondent le mieux aux données expérimentales disponibles sur l'UO2.L’agglomérat de MP est modélisé via des hypothèses simplificatrices. Une fois les agglomérats d’UO2 et de MP modélisés, la simulation de la compaction à simple et à double effet sur le UOX et MOX a été réalisée. La cinématique et la géométrie industrielle des pastilles sont prises en compte. En particulier, les phases de décharge élastique et d’éjection sous pression d’accompagnement sont modélisées. A l’issue de l’étape de compaction, un gradient de densité est observé, résultant des mouvements relatifs des parois et du frottement entre les parois et la poudre. Nous obtenons dès cette étape une déformation radiale de la pastille.En fin de manuscrit, le frittage est abordé. Cette partie, servant de preuve de concept, n'aborde pas toute la complexité du frittage, mais permet d'étudier l'influence du gradient de densité sur la géométrie finale du comprimé. Deux modèles sont proposés. Le premier consiste à simuler le frittage via la simulation discrète en prenant en compte les phénomènes de diffusion à l’échelle des contacts. Le second, beaucoup plus simple, prend uniquement en compte la carte de densité dans la pastille compactée<br>This work, conducted in collaboration with the Orano Melox recycling plant, is part of the context of the French nuclear industry, which plays a central role in the country's electricity production. The thesis focuses on the manufacture of nuclear fuel through the stages of compaction and sintering of nuclear powders: UOX (Uranium OXide) and MOX (Mixed OXide) fuels. Uni-axial compaction induces a heterogeneous density field in the pellet. This heterogeneity is responsible for radial deformation during the ejection and sintering stages (diabolo effect), requiring the manufacturer to rectify the lateral surface. The aim of the thesis is to develop a dedicated digital tool to simulate the geometry of pellets after compaction and sintering, particularly anticipating the effect of MOX composition.The digital tool must take into account the granular nature of the powders, the mixture's composition, and the industrial conditions of the process. For this, the discrete element method (DEM) is used. This simulation method, which explicitly considers the granular microstructure of powders by modeling each particle individually, is explored in detail in this manuscript. Constitutive laws for compaction and sintering are discussed, as well as their application in the context of nuclear powders. We adapt a model that addresses high relative densities considering the effect of local density (calculated via Voronoi cells) on powder strain hardening.The chosen approach to simulate the powder at the scale of an entire tablet involves representing MOX powder as consisting of two types of porous agglomerates: UO2 agglomerates and primary mixture (MP, a high-plutonium-content mix) agglomerates. This optimizes the computation time of the simulations and accounts for the composition of different mixes used by the industry.Initially, the UO2 agglomerate is modeled. To do this, a database was generated, including thousands of simulations varying six material parameters. A machine learning model was developed and trained with supervised learning to determine the set of material parameters that best match the available experimental data on UO2.The MP agglomerate is modeled using simplifying assumptions. Once the UO2 and MP agglomerates are modeled, the simulation of single and double-effect compaction on UOX and MOX is carried out. The kinematics and industrial geometry of the pellets are considered. In particular, the phases of elastic unloading and pressure-assisted ejection are modeled. After the compaction stage, a density gradient is observed, resulting from the relative movements of the walls and friction between the walls and the powder. A radial deformation of the pellet is obtained from this stage.At the end of the manuscript, sintering is addressed. This part, serving as a proof of concept, does not cover the entire complexity of sintering but allows for studying the influence of the density gradient on the final geometry of the tablet. Two models are proposed. The first involves simulating sintering via discrete simulation, taking into account diffusion phenomena at the contact scale. The second, much simpler, only considers the density map in the compacted pellet

In this study, the relationship between soil suction and shear strength parameters of compacted METU campus clay were investigated at different moisture contents. Soil samples were tested at optimum moisture content (i.e. w=20.8%), at dry side of optimum moisture content (i.e. w=14.8%, 16.8%, 18.8%) and at wet side of optimum moisture content (i.e. w=22.8%, 24.8%, 26.8%). Direct shear tests were performed to measure shear strength parameters (c&#039<br>, &amp<br>#934<br>&#039<br>) and soil suctions were measured by filter paper method after direct shear tests. These relationships were also investigated on soaked samples. The trends for suction, angle of internal friction and cohesion, which change on the dry side and wet side of optimum moisture content, were analyzed. The compacted METU campus clay gains granular soil fabric at the dry side of optimum moisture content. As moisture content increases, cohesion increases up to optimum moisture content and then decreases. But angle of internal friction decreases as moisture content increases. Soaking affects the samples more which are on the dry side of optimum moisture content. The soil suction (total suction and matric suction) affects the shear strength, and an increase in soil suction increases the shear strength.

Graph processing is an established and prominent domain that is the foundation of new emerging applications in areas such as Data Analytics and Machine Learning, empowering applications such as road navigation, social networks and automatic speech recognition. The large amount of data employed in these domains requires high throughput architectures such as GPGPU. Although the processing of large graph-based workloads exhibits a high degree of parallelism, memory access patterns tend to be highly irregular, leading to poor efficiency due to memory divergence.In order to ameliorate these issues, GPGPU graph applications perform stream compaction operations which process active nodes/edges so subsequent steps work on a compacted dataset. We propose to offload this task to the Stream Compaction Unit (SCU) hardware extension tailored to the requirements of these operations, which additionally performs pre-processing by filtering and reordering elements processed.We show that memory divergence inefficiencies prevail in GPGPU irregular graph-based applications, yet we find that it is possible to relax the strict relationship between thread and processed data to empower new optimizations. As such, we propose the Irregular accesses Reorder Unit (IRU), a novel hardware extension integrated in the GPU pipeline that reorders and filters data processed by the threads on irregular accesses improving memory coalescing.Finally, we leverage the strengths of both previous approaches to achieve synergistic improvements. We do so by proposing the IRU-enhanced SCU (ISCU), which employs the efficient pre-processing mechanisms of the IRU to improve SCU stream compaction efficiency and NoC throughput limitations due to SCU pre-processing operations. We evaluate the ISCU with state-of-the-art graph-based applications achieving a 2.2x performance improvement and 10x energy-efficiency.<br>El processament de grafs és un domini prominent i establert com a la base de noves aplicacions emergents en àrees com l'anàlisi de dades i Machine Learning, que permeten aplicacions com ara navegació per carretera, xarxes socials i reconeixement automàtic de veu. La gran quantitat de dades emprades en aquests dominis requereix d’arquitectures d’alt rendiment, com ara GPGPU. Tot i que el processament de grans càrregues de treball basades en grafs presenta un alt grau de paral·lelisme, els patrons d’accés a la memòria tendeixen a ser irregulars, fet que redueix l’eficiència a causa de la divergència d’accessos a memòria. Per tal de millorar aquests problemes, les aplicacions de grafs per a GPGPU realitzen operacions de stream compaction que processen nodes/arestes per tal que els passos posteriors funcionin en un conjunt de dades compactat. Proposem deslliurar d’aquesta tasca a la extensió hardware Stream Compaction Unit (SCU) adaptada als requisits d’aquestes operacions, que a més realitza un pre-processament filtrant i reordenant els elements processats.Mostrem que les ineficiències de divergència de memòria prevalen en aplicacions GPGPU basades en grafs irregulars, tot i que trobem que és possible relaxar la relació estricta entre threads i les dades processades per obtenir noves optimitzacions. Com a tal, proposem la Irregular accesses Reorder Unit (IRU), una nova extensió de maquinari integrada al pipeline de la GPU que reordena i filtra les dades processades pels threads en accessos irregulars que milloren la convergència d’accessos a memòria. Finalment, aprofitem els punts forts de les propostes anteriors per aconseguir millores sinèrgiques. Ho fem proposant la IRU-enhanced SCU (ISCU), que utilitza els mecanismes de pre-processament eficients de la IRU per millorar l’eficiència de stream compaction de la SCU i les limitacions de rendiment de NoC a causa de les operacions de pre-processament de la SCU.

Este trabalho teve como objetivo principal investigar, do ponto de vista volumétrico, qual seria o número de giros necessário, no Compactador Giratório Superpave (CGS), para produzir corpos de prova com características similares aos produzidos com a energia 50 golpes no compactador Marshall, para misturas tipo Stone Matrix Asphalt (SMA) com volume de vazios igual a 4%. Como complemento, realizaram-se dosagens no CGS com 100 giros, visando avaliar o impacto do aumento da energia de compactação no teor de projeto, também para volume de vazios igual a 4%, em comparação aos CPs compactados com o número de giros equivalente à Marshall determinada anteriormente. Foram utilizadas duas faixas granulométricas de misturas SMA: a com Tamanho Máximo Nominal (TMN) 7,93 mm do DER-SP e a com TMN 12,5 mm da AASHTO. Para todas as misturas foram avaliadas as propriedades mecânicas de corpos de prova com 4% de volume de vazios. Dos resultados dos ensaios concluiu-se que o número de giros no CGS para produzir misturas com volume de vazios igual a 4% nos teores de asfalto de trabalho Marshall são similares para as duas faixas granulométricas utilizadas. Por outro lado, a dosagem com 100 giros no CGS reduziu significativamente o teor de asfalto de trabalho para as duas faixas estudadas em comparação com os teores de trabalho obtidos das dosagens Marshall e no CGS com os números de giros equivalentes. Com relação às propriedades mecânicas, as resistências à tração e os módulos de resiliência dos corpos de prova produzidos com 100 giros no CGS são, de uma maneira geral, um pouco menores que os valores obtidos nos corpos de prova compactados no compactador Marshall, independente da faixa granulométrica, porém maiores que os valores obtidos para a compactação giratória nas energias equivalentes. A vida de fadiga para a faixa mais fina é significativamente maior para os corpos de prova compactados com 100 giros em comparação com a compactação Marshall e para a faixa mais grossa manteve-se na mesma ordem de grandeza da obtida para a compactação Marshall. Para as misturas ensaiadas, não foi constatado influência da compactação no dano causado pela umidade induzida<br>The aim of the work was to investigate, in terms of volumes properties, which would be the number of gyrations required in the Superpave Gyrations Compactor (SGC), to produce samples with characteristics similar to the energy produced with 50 blows in the Marshall Compactor, for Stone Matrix Asphalt (SMA) mixtures with voids content equal to 4%. As a complement, samples designed in the SGC with 100 gyrations, were made to evaluate the impact of increased compaction energy in the binder content, also for voids content equal to 4%, compared to the samples compacted with a number of gyrations equivalent to Marshall, as previously determined. It was used two different aggregates gradations for SMA mixtures: Nominal Maximum Size (NMS) 7,93 mm of the DER and the NMS 12,5 mm of the AASHTO. The mechanical properties of all samples were evaluated with voids content of 4%. The number of gyrations in the SGC to produce mixtures containing voids content equal to 4% for the Marshall`s binder content are similar for both aggregates gradations used. On the other hand, the SMA mixture design with 100 gyrations reduced the binder content for both gradations in comparison with the binder content obtained from Marshall Compaction and SGC with the equivalent number of gyrations. Concerning mechanical properties, the tensile strength and resilient modulus of the samples produced with 100 gyrations in the SGC are, generally, slightly lower than the values obtained with the samples compacted in the Marshall compactor, independent of the aggregate gradations, but higher than the values obtained with the samples compacted with a equivalent energy in the SGC. The fatigue life for the fine gradation (NMS=7,93mm) is significantly higher for the samples compacted in the SGC with 100 gyrations compared with the Marshall compaction, and for the coarse gradation (NMS=12,5 mm) remained in the same order of magnitude that of the Marshall compaction. It was not observed any influence of the compaction method in the induced damage caused by moisture

O objetivo principal desta pesquisa é avaliar a influência que as propriedades estudadas dos agregados exercem sobre propriedades volumétricas e mecânicas de misturas asfálticas densas. Para tanto, foram avaliadas as propriedades de consenso e de origem, especificadas pelo Superpave, de um conjunto de agregados, além de suas densidades, porosidade, absorção e adesividade. Foram estudados agregados de gabro, basalto e areia natural e três tipos de granulometrias, uma denominada AZR, passando acima da zona de restrição da especificação Superpave, e outras duas, obtidas através do sistema de seleção granulométrica Bailey. Também três níveis de energia de compactação foram aplicados às misturas, 75, 110 e 155 golpes por face do corpo-de-prova Marshall. Avaliou-se o comportamento mecânico das misturas através dos ensaios de estabilidade e fluência Marshall, fluência por compressão uniaxial uniforme, fluência por compressão uniaxial dinâmica, resistência à tração, módulo de resiliência e fadiga. Os resultados mostraram que, de uma maneira geral, o agregado de gabro apresentou superioridade em relação ao agregado de basalto e de areia natural, tanto quando analisado isoladamente como quando analisado nas misturas asfálticas. Suas características de forma, angularidade e textura superficial permitiram arranjos entre partículas adequados, formando esqueletos estruturais resistentes à deformação permanente e também à fadiga. As análises das misturas à luz da granulometria mostram que, de uma maneira geral, a granulometria AZR produziu misturas mais estáveis, mais resistentes à deformação permanente e à fadiga. Pôde-se constatar, também, que as propriedades volumétricas são sensíveis às densidades dos agregados e à taxa de absorção destes, além de serem influenciadas diretamente pelas características de superfície dos agregados e pela energia de compactação. Com o aumento da energia de compactação aplicada, as partículas angulosas e rugosas dos agregados de gabro e de basalto arranjaram-se de maneira mais próxima e, por conseqüência, houve a diminuição dos vazios do agregado mineral e elevação da estabilidade e rigidez das misturas, sem, contudo, causar prejuízos à vida de fadiga. Os estudos sobre a absorção de asfalto pelos agregados revelaram que os agregados absorvem mais asfalto quanto mais fina a espessura da película de asfalto que os envolve e, também, que misturas com um mesmo teor de asfalto absorvem quantidades semelhantes de asfalto, sendo o tempo necessário para que a absorção se complete diretamente proporcional à viscosidade (temperatura) do asfalto.<br>The main objective of this research is to evaluate the influence that the studied properties of aggregates have on volumetric and mechanical characteristics of dense asphalt mixtures. It was evaluated origin and consensus properties, specified by the Superpave, for a set of aggregates, besides their densities, porosity, absorption and adhesiveness. Aggregates of gabbro, basalt and natural sand were studied and three types of aggregate gradations, one called AZR, passing above the zone of restriction of the Superpave specification, and two others, obtained through the Bailey method. Three levels of compaction energy were applied, corresponding respectively to 75, 110 and 155 blows of the Marshall hammer per face of the specimen. The mechanical behavior of the hot mix asphalt (HMA) was evaluated through the Marshall stability and flow, static and dynamic creep, indirect tensile strength, resilient modulus and fatigue tests. The results showed that, in general terms, the gabbro aggregate presented a superior behavior compared to the natural sand aggregate and the basalt aggregate, based on both aggregate and asphalt mixture evaluation tests. Its characteristics of form, angularity and surface texture resulted in an adequate arrangement between particles, building a resistant structural skeleton to both permanent deformation and fatigue cracking. Analyses of the HMA mixtures as a function of gradation showed that, in general terms, AZR mixtures were more stable, more resistant to permanent deformation and to fatigue cracking than Bailey mixtures. It could be evidenced that the volumetric properties depends on the specific gravity and the absorption rate of the aggregates, being also directly influenced by aggregate surface characteristics and compaction energy. Increasing the energy applied for specimen compaction resulted, for the angular and rough particles of gabbro and basalt aggregates, in a closer arrangement, with reduction of the voids in mineral aggregate and increase of the stability and stiffness of the mixtures, without, however, causing damages that could conduct to a shorter fatigue life. The studies about absorption of asphalt by aggregates showed that the smaller the asphalt film thickness the greater the asphalt absorption. The results also showed that HMA with the same asphalt content absorb similar amounts of asphalt, although the necessary time to complete the absorption is directly proportional to the asphalt viscosity (temperature).

Although foamed bitumen has been widely applied in pavement construction some of its aspects are still not yet understood. In this study, some of these aspects including: effects of the foaming process on binder chemistry, characterization of foamed bitumen and development of a rational method to optimize foam characteristics, evaluation of aggregate particle coating within foamed bitumen treated materials, and development of a gyratory compaction procedure for laterite gravels treated with foamed bitumen were addressed. The effects of the foaming process on bitumen chemistry were investigated using Fourier transform infrared spectroscopy techniques. Also, foam characteristics of three binders were established and a rational method to optimize foam characteristics proposed. Aggregate particle coating with foamed bitumen was studied using the concepts of surface energy and Rice density. In addition a gyratory laboratory compaction procedure for laterite gravels treated with foamed bitumen was established using the modified locking concept. Infrared techniques have shown that foaming does not cause any changes in the binder chemistry, suggesting that foaming may be a physical process. Further, foam characteristics are greatly influenced by binder viscosity. Also, the equiviscous temperature seems to produce foam with optimum foam characteristics. Rice density results showed that aggregate size fraction, binder expansion ratio and viscosity influenced aggregate particle coating. Surface energy results revealed that foamed bitumen exhibited better coating attributes than neat bitumen. A new compaction procedure for laterite gravels treated with foamed bitumen based on the modified locking point was developed.<br>QC 20110427

O impacto que estruturas algébricas podem exercer em teorias físicas e bem ilustrado pela Mecânica Quântica, onde os números complexos são inquestionavelmente a escolha mais adequada para desenvolver a teoria. A Relatividade Geral pseudo-complexa avalia a possibilidade da interação gravitacional assumir sua descrição mais natural quando construída tendo como base os números pseudo-complexos, que consistem em uma das três possibilidades de números complexos abelianos com uma unica unidade imaginária. Esse conjunto numérico e dotado de elementos não nulos cujo produto e zero, tais números recebem o nome de zeros generalizados ou divisores de zero. A presença de zeros generalizados permite a introdução de um princípio variacional modificado do qual um termo adicional, ausente na Relatividade Geral, emerge nas equações de campo. Esse termo adicional e interpretado como uma energia escura, cuja origem física está relacionada com flutuações no vácuo. A inclusão desse efeito e legítima pois flutuações no vácuo a priori devem gravitar como qualquer outra forma de energia. Das equações de campo podemos resumir a principal ideia conceitual da teoria, na Relatividade Geral pseudo-complexa massa não apenas curva o espaçotempo como também e capaz de alterar a estrutura do espaço-tempo ao redor da massa. As diferenças com relação a Relatividade Geral se manifestam em situações físicas extremas, no regime de campos gravitacionais intensos. Como aplicação analisamos sob o ponto de vista teórico um objeto compacto exótico composto por matéria escura fermiônica.<br>The impact that algebraic structures can exert on physical theories is well illustrated by Quantum Mechanics, where complex numbers are unquestionably the most appropriate choice to develop the theory. Pseudo-complex General Relativity evaluates the possibility that the gravitational interaction acquires its most natural description when constructed upon pseudo-complex numbers, which consist of one of the three possibilities of abelian complex numbers with a single imaginary unit. This numerical set is endowed with nonzero elements whose product is zero, such numbers are called generalized zeros or divisors of zero. The presence of generalized zeros allows the introduction of a modi ed variational principle from which an additional term, absent in General Relativity, emerges in the eld equations. This additional term is interpreted as a dark energy, whose physical origin is related to vacuum uctuations. The inclusion of this e ect is legitimate because a priori vacuum uctuations must gravitate as any other form of energy. From the eld equations we can summarize the main conceptual idea of the theory, in pseudo-complex General Relativity mass not only curves spacetime but also is able to change the structure of the spacetime around the mass. The di erences with respect to General Relativity are manifested in extreme physical situations in the regime of intense gravitational elds. As an application we analyze from the theoretical point of view an exotic compact object composed of fermionic dark matter.

Orientador: Elaine Maria Cardoso<br>Resumo: A energia solar pode ser aproveitada como fonte de energia térmica para aquecimento de água, por exemplo, em coletores solares ou como fonte de energia elétrica usando sistemas de células fotovoltaicas. Entretanto, as células fotovoltaicas, geralmente, de custos relativamente altos, têm algumas restrições relacionadas a altas temperaturas de operação e distribuições de temperatura não homogêneas levando a redução da vida útil e eficiência elétrica de tais sistemas. Essas limitações têm sido o foco de pesquisas, a fim de melhorar as eficiências elétricas, regular as temperaturas de operação e reduzir os materiais necessários para fabricação das células. Assim, este projeto de pesquisa tem como objetivo avaliar o desempenho de um dissipador de calor, baseado em microcanais retangulares paralelos, no resfriamento de uma célula fotovoltaica de alta concentração (HCPV-High Concentration Photovoltaic Cell), utilizando-se de análise teórica (modelo térmico), simulação numérica (usando o software comercial CFD ANSYS® Fluent v15) e de uma bancada experimental. Neste trabalho, foram consideradas as condições de máxima radiação (denominado de pior cenário, quando a célula não gera eletricidade e todo o calor deve ser dissipado) e de radiação média ao longo do período considerado. Os dados climatológicos foram obtidos do site Canal Clima - UNESP, com dados historicos do clima na região noroeste paulista. Foi realizada uma revisão do estado da arte a fim de compreender como os sistemas de... (Resumo completo, clicar acesso eletrônico abaixo)<br>Abstract: Solar energy can be used as a source of thermal energy in solar collectors, for example, or as a source of electricity using photovoltaic cell systems. However, photovoltaic cells requires high investments having some restrictions related to high operating temperatures and nonhomogeneous temperature distributions, leading to a reduction in the useful life and electrical efficiency. These limitations have been the focus of researches in order to improve electrical efficiencies, to regulate operating temperatures, and to reduce required materials in the cells. Thus, this research project aims to evaluate the performance of a heat sink based on parallel rectangular microchannels for cooling of a high concentration photovoltaic cell (HCPV), using theoretical analysis (thermal model), numerical simulation (using commercial software CFD ANSYS® Fluent v15) and an experimental bench. In this work, it was considered the conditions of maximum radiation (named worst scenario, when the cell does not generate electricity and all the heat must be dissipated) and the average radiation over the period considered. These climatological data were obtained from the Canal Clima – UNESP site, in the northwestern region of São Paulo state. A review on the subject was carried out in order to understand how solar photovoltaic systems can be optimized using solar concentrators and more efficient materials (multiple-junction cells). The influence of temperature and cooling systems were analyzed. An exp... (Complete abstract click electronic access below)<br>Mestre

<p>A lot of today’s new developments strive for energy efficiency. This includes the hydraulic side of industry. The Division of Fluid andMechanical Engineering Systems of Linköpings University in collaboration with Volvo Construction Equipment in Eskilstuna has developed a newhydraulic concept when it comes to the control of cylinder loads in a wheel loader. The concept differs from today’s application, where the cylinderload is controlled via a valve, in the way that the load is solely controlled by a pump. To control this system, an electrical feed back of operatorsdemanded signal is needed. These signals have to be correctly interpreted so that valve and the pumps perform the requested operation. The newsystem is going to need a unit that can perform these operations in a way that corresponds to the operating level of today’s hydraulically controlledsystem.The study aims to develop a software platform that solves this. This platform shall, besides performing the operators’ demands, monitor the system.The monitoring of the system is a crucial part because of security issues, but also when analyzing the systems functionality. The implementation ofthis software will be done in a real-time computer with the ability to collect data, interpret it and then control the connected units of the system.Further work that is to be done is an energy consumption study of today’s hydraulic system, and on the basis of this study, theoretically evaluate thenew system.The study has resulted in a great insight of an industrial mechanic machine, this in a level that includes an entire system. The wide range of thistask has brought analysis and development of both hydraul mechanical-, electrical- and software related systems. With an understanding of these,both separate and in interaction with each other, a platform has been designed that shall facilitate the forthcoming development of energy efficienthydraulics, both at VCE and LiTH.</p>

Orientadores: Carlos Alberto Luengo, Jose Luz Silveira<br>Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica<br>Made available in DSpace on 2018-08-03T17:41:57Z (GMT). No. of bitstreams: 1 Santos_FranciscoEulalioAlvesdos_D.pdf: 9554331 bytes, checksum: aa14db7fa4bcdbb3040e87da04137442 (MD5) Previous issue date: 2001<br>Resumo: O emprego de motores alternativos a Diesel para geração apenas de energia elétrica é bastante difundido em todas as regiões do Brasil, principalmente no atendimento de emergência em hospitais, indústrias, shopping centers, serviços de telefonia, campi universitários e supermercados. Além das situações de emergências, encontram-se no país um grande número de sistemas de geração de eletricidade que asseguram o abastecimento de comunidades isoladas, tendo como destaque a região Norte, onde a potência dos parques térmicos vinculados à ELETRONORTE e às Concessionárias Estaduais é da ordem de 980 MW. A ineficiência desses sistemas, em tomo de 2/3, representa o potencial termodinâmico para implementar a tecnologia da cogeração e, através desta, a possibilidade real para recuperar os desperdícios das plantas termelétricas da região. Nesse contexto, com o propósito de assimilar, difundir e elaborar estudos de viabilidade econômica relativos à tecnologia da cogeração é que estamos apresentando o trabalho de desenvolvimento e instalação de um cogerador compacto no campus da Universidade Federal do Acre - UFAC, em Rio Branco, Acre. O cogerador, com capacidade de 355 kV A, tem como finalidade principal atender parte do suprimento de energia elétrica do campus e, simultaneamente, nesta primeira fase, o aproveitamento do calor residual da descarga do motor será utilizado no suprimento de um sistema de absorção para climatização de ambiente<br>Abstract: The use of Diesel engines to generate electricity is an ordinary practice in Brazil, mainly for emergency services in hospitals, industries, shopping centers, telephone centrals, universities, and supermarkets. Besides the emergency uses, there are a large number of thermoelectric systems spread in the country to supply isolated communities. In the North and part of Mid-West Regions in Brazil, the installed thermoelectric capacity is about 980 MW. It is managed by ELETRONORTE and state electric power companies. This system inefficiency is an average of two thirds of the fuel heating value and it represents the thermodynamic potential of the producers. The real possibility to recover the energy waste in those thermoelectric plants throught cogeneration technology is the big motivation in this research. The cogenerated energy will supply the tertiary sector. Here, it is presented a cogeneration study and a pilot plant development. The compact cogeneration is installed at the UF AC (Acre Federal University) in Rio Branco, ACRE. Its capacity is 355 kV A and it aims to recover part of the residual heat from a Diesel engine exhaust. It produces cool air to be used in a air conditioning system. This first step is assessed in terms of its economic viability<br>Doutorado<br>Doutor em Planejamento de Sistemas Energéticos

This work focuses on understanding the impact-initiated combustion of aluminum powder compacts. Aluminum is typically one of the components of intermetallic-forming structural energetic materials (SEMs), which have the desirable combination of rapid release of thermal energy and high yield strength. Aluminum powders of various sizes and different levels of mechanical pre-activation are investigated to determine their reactivity under uniaxial stress rod-on-anvil impact conditions, using a 7.62 mm gas gun. The compacts reveal light emission due to combustion upon impact at velocities greater than 170 m/s. Particle size and mechanical pre-activation influence the initiation of aluminum combustion reaction through particle-level processes such as localized friction, strain, and heating, as well as continuum-scale effects controlling the amount of energy required for compaction and deformation of the powder compact during uniaxial stress loading. Compacts composed of larger diameter aluminum particles (~70µm) are more sensitive to impact initiated combustion than those composed of smaller diameter particles. Additionally, mechanical pre-activation by high energy ball milling (HEBM) increases the propensity for reaction initiation. Direct imaging using high-speed framing and IR cameras reveals light emission and temperature rise during the compaction and deformation processes. Correlations of these images to meso-scale CTH simulations reveal that initiation of combustion reactions in aluminum powder compacts is closely tied to mesoscale processes, such as particle-particle interactions, pore collapse, and particle-level deformation. These particle level processes cannot be measured directly because traditional pressure and velocity sensors provide spatially averaged responses. In order to address this issue, quantum dots (QDs) are investigated as possible meso-scale pressure sensors for probing the shock response of heterogeneous materials directly. Impact experiments were conducted on a QD-polymer film using a laser driven flyer setup at the University of Illinois Urbana-Champaign (UIUC). Time-resolved spectroscopy was used to monitor the energy shift and intensity loss as a function of pressure over nanosecond time scales. Shock compression of a QD-PVA film results in an upward shift in energy (or a blueshift in the emission spectra) and a decrease in emission intensity. The magnitude of the shift in energy and the drop in intensity are a function of the shock pressure and can be used to track the particle scale differences in the shock pressure. The encouraging results illustrate the possible use of quantum dots as mesoscale diagnostics to probe the mechanisms involved in the impact initiation of combustion or intermetallic reactions.

Made available in DSpace on 2014-06-11T19:35:40Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-04Bitstream added on 2014-06-13T18:47:03Z : No. of bitstreams: 1 reis_ja_dr_guara.pdf: 3822491 bytes, checksum: c9fd5a88d775153288d737de07be90be (MD5)<br>Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)<br>Este trabalho desenvolve o projeto, aqui entendido como a seleção das unidades que atendam às exigências de obtenção de eletricidade, calor e frio, e a montagem de um sistema de cogeração que usa um motor de pequeno porte associado a uma máquina de absorção e trocadores de calor que satisfarão tais exigências de uma maneira a mais econômica possível, isto é, otimizado em termos de custos. Aplicando-se um método de obtenção dos custos associados à exergia, cria-se um quadro de custos exergéticos para a obtenção de cada produto, e a soma de cada custo constitui o que chama-se de custo de manufatura exergética. O estudo demonstra que é possível aplicar esse método e identificar os pontos de deficiência de um sistema térmico como o mostrado e ,com isso, tomar medidas que venham a melhorar seu desempenho. Essa otimização física não se utiliza de conhecidos algoritmos de otimização matemática, utilizando-se de dados físicos e termodinâmicos medidos, O método permite identificar a forma operacional (basicamente a rotação do motor) que apresente os menores custos. A compreensão dos aspectos gerais da cogeração, das tecnologias envolvidas, com suas vantagens e desvantagens, torna possível aplicar a avaliação exergética associada a conceitos econômicos,e, com essa análise, tomar-se medidas que melhorem o desempenho do sistema em estudo.<br>This work develop the design of a cogeneration system with a small internal combustion engine coupled with an absorption refrigeration unit utilised in the production of a refrigeration effect, heating effect and electrical power generation with the utilization of exhaust waste heat, in a most possible economic way, i.e., optimized within limits of costs. By developing a method of costs associated to exergy, raises an exergetic costs for each unit, and the total costs is called manufacture exergetic cost. This study demonstrate that the appliance of this method identify the failures in the system and indicate where applies measures that improves its performance. This optimization do not utilizes mathematical algorithms, it is a physical optimization that use thermodynamics and physical data. The objective of this method is to identify the operational form that introduces the smaller cost. This compact cogeneration system have an internal combustion engine coupled with two heat exchangers and an absorption engine. The comprehension of general aspects of cogeneration technologies, its advantages and disadvantages turn possible to apply the exergetic evaluation associated with economic concepts to improve the performance of the system.

Resumo: Este trabalho desenvolve o projeto, aqui entendido como a seleção das unidades que atendam às exigências de obtenção de eletricidade, calor e frio, e a montagem de um sistema de cogeração que usa um motor de pequeno porte associado a uma máquina de absorção e trocadores de calor que satisfarão tais exigências de uma maneira a mais econômica possível, isto é, otimizado em termos de custos. Aplicando-se um método de obtenção dos custos associados à exergia, cria-se um quadro de custos exergéticos para a obtenção de cada produto, e a soma de cada custo constitui o que chama-se de custo de manufatura exergética. O estudo demonstra que é possível aplicar esse método e identificar os pontos de deficiência de um sistema térmico como o mostrado e ,com isso, tomar medidas que venham a melhorar seu desempenho. Essa otimização física não se utiliza de conhecidos algoritmos de otimização matemática, utilizando-se de dados físicos e termodinâmicos medidos, O método permite identificar a forma operacional (basicamente a rotação do motor) que apresente os menores custos. A compreensão dos aspectos gerais da cogeração, das tecnologias envolvidas, com suas vantagens e desvantagens, torna possível aplicar a avaliação exergética associada a conceitos econômicos,e, com essa análise, tomar-se medidas que melhorem o desempenho do sistema em estudo.<br>Abstract: This work develop the design of a cogeneration system with a small internal combustion engine coupled with an absorption refrigeration unit utilised in the production of a refrigeration effect, heating effect and electrical power generation with the utilization of exhaust waste heat, in a most possible economic way, i.e., optimized within limits of costs. By developing a method of costs associated to exergy, raises an exergetic costs for each unit, and the total costs is called manufacture exergetic cost. This study demonstrate that the appliance of this method identify the failures in the system and indicate where applies measures that improves its performance. This optimization do not utilizes mathematical algorithms, it is a physical optimization that use thermodynamics and physical data. The objective of this method is to identify the operational form that introduces the smaller cost. This compact cogeneration system have an internal combustion engine coupled with two heat exchangers and an absorption engine. The comprehension of general aspects of cogeneration technologies, its advantages and disadvantages turn possible to apply the exergetic evaluation associated with economic concepts to improve the performance of the system.<br>Orientador: José Luz Silveira<br>Coorientador: Edson Bazzo<br>Banca: Pedro Magalhães Sobrinho<br>Banca: Julio Santana Antunes<br>Banca: Jose Rui Camargo<br>Banca: Newton Galvão de Campos Leite<br>Doutor

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Engenharia Mecânica.<br>Made available in DSpace on 2012-10-23T13:24:02Z (GMT). No. of bitstreams: 0<br>A energia ocupa uma posição estratégica no mercado nacional, podendo ser considerada como insumo essencial à realização de praticamente todas as atividades humanas e ao desenvolvimento da sociedade. É compreensível a preocupação crescente e a importância de novos projetos de implantação ou ampliação da matriz energética brasileira, tanto em relação a geração como com a distribuição. Tais considerações são oportunas ao se propor também a geração distribuída ou plantas de cogeração como alternativas energéticas, onde se busca melhorar os procedimentos de conversão reduzindo perdas e garantindo uso racional de energia. Este trabalho apresenta um modelo de análise termodinâmica, o projeto, a montagem e o monitoramento de uma planta de cogeração compacta para geração de energia elétrica e água gelada para climatização. A planta é constituída por uma microturbina de 28 kWe e uma máquina de refrigeração por absorção água/amônia de 17 kWT, ambos operando originalmente via queima direta de gás natural. Para aumentar o nível de aproveitamento da energia do combustível utilizado na microturbina, o sistema de queima direta da máquina de refrigeração foi substituído por um sistema de recuperação de calor. Os resultados experimentais comprovam a viabilidade técnica da adaptação da máquina de refrigeração por absorção à microturbina. Operando em carga máxima, a planta de cogeração atinge um índice de utilização de energia primária (CP) em torno de 37 %, o que corresponde a um aumento de 75 % na utilização do combustível quando comparado com a eficiência da microturbina operando em modo simples. Os ensaios realizados mostram ainda que a adaptação da máquina de refrigeração não trouxe prejuízo significativo nos parâmetros de desempenho da microturbina. Em contrapartida, o COP da máquina de refrigeração atinge a 0,26 devido à diminuição da temperatura da fonte quente que alimenta o gerador.

Orientador: Mônica Pinto Barbosa<br>Banca: Cassio Roberto Macedo Maia<br>Banca: Oswaldo Cascudo Matos<br>Resumo: O concreto auto-adensável (CAA) é um material que representa um dos maiores avanços na tecnologia do concreto das últimas décadas. O desenvolvimento do CAA propiciou eficiência e melhora nas condições de trabalho em canteiro de obras e na indústria de pré-moldados. Do ponto de vista reológico, o CAA é uma mistura fluida que proporciona diferenças de comportamento quando comparado ao concreto convencional. Neste contexto, a proposta desta pesquisa foi estudar, num primeiro plano, as características reológicas nas fases de pasta, argamassa e concreto do CAA no estado fresco e seu comportamento no estado endurecido. Para isso, optouse por empregar a metodologia de Repette e Melo (2005), que considera a resistência à compressão como ponto de partida para a composição do traço do CAA e que estuda os aspectos reológicos envolvidos nas diferentes fases de sua dosagem. Os materiais empregados para estudo de dosagem foram o fíler basáltico como adição, areia média, brita 19 mm, aditivo superplastificante e dois tipos de cimento. Foram elaborados dois concretos, com cimentos distintos, ambos com mesma classe de resistência igual a 40 MPa. Num segundo plano, foi realizado um estudo da avaliação da resistência à compressão desses concretos quando submetidos à cura térmica a vapor, variando-se as temperaturas de cura (entre 65oC e 80oC), assim como o patamar isotérmico de cura em 4 h,6 h e 8 h para cada temperatura. A avaliação das propriedades mecânicas dos concretos foi realizada empregando o Método da Maturidade. No emprego da maturidade foram utilizados as funções de Nurse e Saul e a proposta por Freiesleben-Hansen e Pedersen (FHP). As análises comparativas foram realizadas em função do tipo de cimento empregado, temperatura de cura e tempo de patamar isotérmico<br>Abstract: The self-compacting concrete (SCC) is a material that represents one of the greatest advances in concrete technology in recent decades. The development of SCC has resulted in improved efficiency and working conditions at the construction site and the precast industry. Rheological point of view, the SCC is a fluid mix that provides behavior differences when compared to conventional concrete. In this context, the proposal of this research was to study, in the foreground, the rheological phases of paste, mortar and concrete of SCC in the fresh state and its behavior in the hardened state. For this, we chose to employ the methodology Repette e Melo (2005), which considers the compressive strength as a starting point for the composition of the trace of SCC and studying the rheological aspects involved in the different stages of their dosage. The materials used to study the dosage was basalt fillers such as addition, medium sand, gravel 19 mm, superplasticizer additive and two types of cement. We prepared two concretes with different cements, both with the same strength class of 40 MPa. In the background, a study assessing the compressive strength of concrete when subjected to steam curing, varying the curing temperatures (between 65oC and 80oC) as well as the level of isothermal cure at 4 h, 6 h and 8 h for each temperature. The evaluation of mechanical properties of concrete was carried out using the Maturity Method. Employment of maturity was used to Nurse e Saul function, as well as function proposed by Freiesleben-Hansen and Pedersen (FHP). Comparative analysis were performed according to the type of cement used, curing temperature and isothermal plateau<br>Mestre

Made available in DSpace on 2014-06-11T19:27:13Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-04-26Bitstream added on 2014-06-13T20:16:15Z : No. of bitstreams: 1 santos_lf_me_ilha.pdf: 6137370 bytes, checksum: 5de758f11cce6406d87fe87638a96bb5 (MD5)<br>O concreto auto-adensável (CAA) é um material que representa um dos maiores avanços na tecnologia do concreto das últimas décadas. O desenvolvimento do CAA propiciou eficiência e melhora nas condições de trabalho em canteiro de obras e na indústria de pré-moldados. Do ponto de vista reológico, o CAA é uma mistura fluida que proporciona diferenças de comportamento quando comparado ao concreto convencional. Neste contexto, a proposta desta pesquisa foi estudar, num primeiro plano, as características reológicas nas fases de pasta, argamassa e concreto do CAA no estado fresco e seu comportamento no estado endurecido. Para isso, optouse por empregar a metodologia de Repette e Melo (2005), que considera a resistência à compressão como ponto de partida para a composição do traço do CAA e que estuda os aspectos reológicos envolvidos nas diferentes fases de sua dosagem. Os materiais empregados para estudo de dosagem foram o fíler basáltico como adição, areia média, brita 19 mm, aditivo superplastificante e dois tipos de cimento. Foram elaborados dois concretos, com cimentos distintos, ambos com mesma classe de resistência igual a 40 MPa. Num segundo plano, foi realizado um estudo da avaliação da resistência à compressão desses concretos quando submetidos à cura térmica a vapor, variando-se as temperaturas de cura (entre 65oC e 80oC), assim como o patamar isotérmico de cura em 4 h,6 h e 8 h para cada temperatura. A avaliação das propriedades mecânicas dos concretos foi realizada empregando o Método da Maturidade. No emprego da maturidade foram utilizados as funções de Nurse e Saul e a proposta por Freiesleben-Hansen e Pedersen (FHP). As análises comparativas foram realizadas em função do tipo de cimento empregado, temperatura de cura e tempo de patamar isotérmico<br>The self-compacting concrete (SCC) is a material that represents one of the greatest advances in concrete technology in recent decades. The development of SCC has resulted in improved efficiency and working conditions at the construction site and the precast industry. Rheological point of view, the SCC is a fluid mix that provides behavior differences when compared to conventional concrete. In this context, the proposal of this research was to study, in the foreground, the rheological phases of paste, mortar and concrete of SCC in the fresh state and its behavior in the hardened state. For this, we chose to employ the methodology Repette e Melo (2005), which considers the compressive strength as a starting point for the composition of the trace of SCC and studying the rheological aspects involved in the different stages of their dosage. The materials used to study the dosage was basalt fillers such as addition, medium sand, gravel 19 mm, superplasticizer additive and two types of cement. We prepared two concretes with different cements, both with the same strength class of 40 MPa. In the background, a study assessing the compressive strength of concrete when subjected to steam curing, varying the curing temperatures (between 65oC and 80oC) as well as the level of isothermal cure at 4 h, 6 h and 8 h for each temperature. The evaluation of mechanical properties of concrete was carried out using the Maturity Method. Employment of maturity was used to Nurse e Saul function, as well as function proposed by Freiesleben-Hansen and Pedersen (FHP). Comparative analysis were performed according to the type of cement used, curing temperature and isothermal plateau

This thesis presents how experimental results, from wave power research performed offshore at the Lysekil research site, were obtained. The data were used to verify theoretical models as well as evaluate the feasibility of wave power as a future sustainable energy source. The first experiments carried out at the research site was the measurement of the force in a line where one end was connected to a buoy with a diameter of 3 m and the other end to a set of springs with limited stroke length. The system is exposed to high peak forces compared to average forces. The maximum measured force in the line, when the buoy motion is limited by a stiff stopper rope is ten times the average force in that particular sea state. The experiment performed on the first wave energy converter tested at the Lysekil Research Site is described. The infrastructure of the site is presented where the central connection point is the measuring station. The key finding is that it is possible to transform the motions of ocean waves into electrical energy and distribute it to land. Many wave energy converters must be interconnected if large amounts of energy are to be harvested from the waves. The first submerged substation intended for aggregation of energy from wave power converters is described, with focus on the measurement and control system placed inside the substation. During this experiment period the generators were equipped with many different sensors; these measurements are explained in the thesis. The system that aggregates power from the studied wave energy converter is regularly exposed to peak power of up to 20 times the maximum average output from the converter. Vertical and horizontal movement of the buoy has been measured in different ways. The result is that the vertical displacement of the buoy can be measured with a simple accelerometer circuit but it is much more complicated to measure the horizontal displacement. A special method for measuring the horizontal displacement has been implemented by measuring the strain in the enclosure and the force in the line.<br>Den här avhandlingen berättar om hur experimenten vid Lysekils forskningsområde för vågkraft har utförts. Insamlade mätdata har använts för att verifiera teoretiska samband som modulerats vid Elektricitetslära, Uppsala universitet. De teoretiska och praktiska resultaten har visat på att vågkraft har förutsättningarna att implementeras som en hållbar framtida energikälla. Intressanta mätmetoder har utvecklas och påfrestningarna  på utrustningin och dess samband med medel effekten har studerats.<br>Lysekils projektet

Neutron Stars present a wide variety from the observational point of view. The advent of new and powerful detectors and instruments has opened a new era where the classical picture of neutrons stars seen as radio-pulsars has been modified with new classes such as magnetars, X-ray Isolated Neutron Stars (XINSs) or Central Compact Objects (CCOs) in Supernova Remnants . In addition to the more than 2500 sources detected in the radio band, more than two hundred have also been detected as X-ray and gamma-ray sources. This number is expected to increase in the near future. Despite this apparent diversity, some studies demand a theory able to explain the different classes in terms of the same physical scenario (Kaspi, 2010), in which the evolution of the magnetic field appears to play an important role (Viganò et al., 2013). The Population Synthesis of Neutron Stars, which is the central subject of this thesis, is an interesting approach to understand the problem, as both intrinsic properties and observational biases are taken into account. These technique is based on Monte Carlo methods, applied to simulate the whole population of neutron stars. The main objective of the thesis has been to perform a multi-wavelength study of the different populations of Neutron Stars focusing in the effects of magneto-thermal evolution. This report consists of a global summary of the objectives, methods and main results of the thesis. It is structured as follows. The first chapter gives an introduction to Neutron Stars. Chapter two is a description of the method of Population Synthesis of Neutron Stars. In chapter three a global discussion of the main results is presented. Chapter four closes the report with the conclusions. An appendix is also included which constitutes a description of a method based on the pulsar current analysis.

Rolling dynamic compaction (RDC) consists of a non-circular module of 3, 4 or 5 sides, that rotates as it is towed, causing it to fall to the ground and compact it dynamically. There is currently little guidance available for geotechnical practitioners regarding the depths of improvement that are possible in varying soil conditions. Current practice dictates that practitioners rely on personal experiences or available published project case studies that are limited in scope and applicability as they are typically aimed at achieving a project specification. There is a reluctance to adopt RDC as a ground improvement technique as there is uncertainty regarding its limitations and capabilities. The underlying objective of this research is to quantify the ground response of the 8-tonne 4-sided impact roller. This research has used full-scale field trials and bespoke instrumentation to capture the ground response due to dynamic loading in homogeneous soil conditions. It was found that towing speed quantifiably influenced the energy imparted into the ground, with towing speeds of 10-12 km/h found to be optimal. Targeted full-scale field trials were undertaken to quantify the depth of improvement that can be achieved using RDC. Field results were compared to a number of published case studies that have used the 8-tonne 4-sided roller. Significantly, separate equations have been developed to allow practitioners to predict the depths that can be improved for the two major applications of RDC: improving ground in situ and compacting soil in thick layers. Finally, the in-ground response of RDC was measured using buried earth pressure cells (EPCs) and accelerometers. Force was determined from the measured change in stress recorded by EPCs whereas displacement was inferred from the double integration of acceleration-time data to give real-time load-displacement behaviour resulting from a single impact. The energy delivered to the soil by RDC is quantified in terms of the work done, defined as the area under the force versus displacement curve. Quantifying the energy imparted into the ground in terms of the work done is a key difference from past studies. Previous estimates of the energy delivered by impact roller at the ground surface has traditionally been predicted based on either gravitational potential energy (12 kJ) or kinetic energy (30 kJ to 54 kJ for typical towing speeds of 9 to 12 km/h). The two different values have caused confusion amongst practitioners. This research has determined that the maximum energy per impact that the 8-tonne 4-sided impact roller is capable of imparting to the ground is between 22 kJ to 30 kJ for typical towing speeds of 9 to 12 km/h. Quantifying the effectiveness of the 8-tonne 4-sided impact roller in terms of towing speed, depth of influence, and soil response measured via real-time measurements will lead to a greater understanding of the practical applications and limitations of RDC. Significantly, more accurate assessments of RDC will reduce design conservatism and construction costs, reduce instances where the predicted ground improvement does not occur and enable RDC to be used and applied with greater confidence.<br>Thesis (Ph.D.) -- University of Adelaide, School of Civil, Environmental and Mining Engineering, 2020

碩士<br>義守大學<br>土木與生態工程學系碩士班<br>94<br>Compaction is one of the common methods used for soil improvement. The basic concept of compaction is imposing energy onto the soils in order to make the soils densified so that the properties of soils are enhanced. There are two different compaction methods,namely shallow and deep compaction. Shallow compaction is basically using the rolling machines to compact the soils by layers. Usually shallow compaction is widely used in the civil engineering, for examples the road engineering; runway of the airports; retaining walls and clay liners of the waste repository etc. This research is aiming on the study of influence of shallow compaction on the properties of soils. The objects of soil improvement include the increase of shear strength; decrease of the compressibility; control the permeability and reduction of the potential of liquefaction. The factors affecting the compaction consists of soil type; water content; compaction method and compaction energy etc. The way controlling the quality of in-situ compaction depends on the relative compaction, which is determined by the maximum dry density from the compaction experiment in the laboratory and the in-situ dry density in the field after compaction. In order to get higher relative compaction, compaction with high energy is usually adopted in the field. Although compaction with high energy is indeed making soils more densified, the microstructure of the clay soils makes the transition from the random flocculated structure to the aligned dispersed structure, which would therefore reduce the shear strength and increase the compressibility. In other words, compaction with high energy makes the compacted clay soils even worse. This is so called over-compaction. The main objective of this research is to study the influence of compaction energy on the shear strength; compressibility and permeability of clay soils. In this research, different compaction energy will be adopted in the compaction experiments in order to study the properties of clay soils. This research is very helpful on the control of the quality of compaction in the field.

Field compaction of sands usually involves different equipments with the compaction energy varying significantly. The relative density is the better indicator for specifying the compaction of granular soil. If the relative density can be correlated simply by any index property of the granular soil, it can be more useful in the field. The relative density is defined in terms of voids ratio. It is well known that the minimum and maximum voids ratio depend on the mean grain size. However, there is no direct relation available for the voids ratio in terms of grain size. Therefore, in this dissertation, the effect of mean grain size on the relative density of sand has been studied at different compaction energies. In order to arrive at the above, fifty five number of clean sands having D50 ranges from 0.34 to 2.6 mm collected from different river bed of Orissa have been tested in the laboratory. The various index properties like grain specific gravity, grain size distribution of all the samples have been determined. The minimum and maximum voids ratio have been determined. For determining minimum voids ratio; both wet and dry method have been adopted. The voids ratio corresponding to energy level of standard, modified, reduced standard, and reduced modified Proctor tests have been correlated with mean grain size and thus the simple nonlinear empirical relations have been developed. Similarly, the relative densities corresponding to the energy level of above mentioned Proctor tests also have been correlated with mean grain size to arrive at simple empirical equations. The percentage deviation of the relative density estimated by the proposed method is in the range of ± 5 % of the measured value. The above correlations of relative densities will be helpful for the design specifications in the field.

碩士<br>國立海洋大學<br>河海工程學系<br>84<br>Dynamic Consolidation is a fairly simple technique which consists in delivering high energy impacts on to the ground to be compacted in order to densify the compressible soil at depth. It has been carried out on the test area of reclaimed site in Mailiao, and has performed excellent results in all the volume of soil treated. However, the interpretation of the dynamic consolidation method and the availability of the model developed should still be modified. Based on the idea of Boussinesq stress increment together with field data collected from the Mailiao soil improving site under construction, the relationship between the dynamic compaction energy and the degree and depth ofsoil improvement is evaluated. It is found that the results computed from the model developed in this study agree reasonably with field observations and arebetter than those obtained from others proposed. Key Words: soil improvement, dynamic consolidation method, compaction energy, influence depth, influence energy, CPT-qc。

Subband coding schemes have been widely used to encode signals from speech, high quality audio, and image sources. The theory of perfect reconstruction filter banks has also been studied extensively. The purpose of this thesis is to study the properties of the so-called paraunitary systems, and issues pertaining to their applications and implementations. We will begin by proving several properties of paraunitary filter banks. For example, we will prove that all orthonormal discrete-time wavelets can be generated using paraunitary binary trees. We will also extend this result to arbitrary tree-structures and wavelet packets. Next, we will address the two issues involved in the design of a paraunitary subband coding system. 1) the problem of optimal bit allocation among various channels given a fixed bit-rate, and 2) the problem of finding the optimal filter bank (by optimization) to encode a given signal. We will prove several interesting results in this regard. We will then show how generalized polyphase representations can be used to enhance the coding gain of transform coding systems. In practical applications, one often imposes several other conditions on the individual filters in a filter bank. For example, the linear phase property is found to be important for encoding image signals, whereas the 'pairwise mirror-image' property generally yields filters with better responses and, therefore, better frequency selectivity. The final part of the thesis deals with the implementions of paraunitary systems having such additional properties. We will obtain factorizations for such systems which will be proved to be minimal as well as complete. These factorizations yield structures which are robust, i.e., all the desired properties are retained in spite of coefficient quantization.

In the present investigation, elemental powder of Fe–18Cr–13Ni (all in wt. %) composition was used for the preparation of duplex stainless steel (DSS), tungsten dispersed and yttria dispersed duplex stainless steel (WDSS and YDSS) by adding 1 wt. % tungsten and 1 wt. % nano yttria to the composition respectively followed by 10 h milling in a dual drive planetary mill. The WDSS and YDSS milled powder were characterized by X-Ray diffraction, particle size analysis (PSA), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) to study the size, morphology and phase evolution during milling. The gradual transformation from ferrite to austenite is evident from XRD spectra during milling. The crystallite size and lattice strain of yttria dispersed duplex stainless steel after 10 h milling were found to be 7 nm and 1.1% respectively. The crystallite size of tungsten dispersed duplex stainless steel was 5 nm. It has been observed from SEM analysis that particles size has been reduced from 40 to 5 μm in both cases. Annealing of 10 h milled powder was performed at 750°C for 1 h under argon atmosphere to study phase transformation in both tungsten dispersed and yttria dispersed duplex stainless steel. The XRD analysis of annealed stainless steel depicts the phase transformation from α-Fe to γ- Fe with the formation of oxides of Fe and Cr in both cases. The differential scanning calorimetry analysis was conducted by heating the milled powder from room temperature to 1200°C under argon atmosphere to investigate the thermal analysis of both the stainless steel powders. The milled powders were compacted by uni-axial pressing at pressures of 250, 437 and 625 MPa and sintered at 1200 and 1350ºC for 1 h under argon atmosphere to study the effect of compaction pressure and sintering temperature on densification and properties of the consolidated product. It has been found that with increasing compaction pressure and sintering temperature, density and hardness value increases in both cases. In another set of experiment, powder compacts of various heights of 10 mm diameter were prepared by unaxial pressing to study the effect of compact height on densification of the compacts. It has been observed that density increases, whereas hardness value of sintered product decreases with increasing compact height.

Dissertação de mestrado integrado em Engenharia Eletrónica Industrial e Computadores<br>A crescente modernização dos setores económicos e sociais, a par do aumento da qualidade de vida das pessoas, deve-se em larga escala à crescente utilização de equipamentos eletrónicos, capazes de realizar as mais variadas e complexas tarefas. Estes equipamentos absorvem correntes distorcidas, provocando efeitos prejudiciais à qualidade da energia no sistema elétrico, manifestando-se numa sequela de consequências, como aumento das perdas em diferentes dispositivos ou mesmo o mau funcionamento de determinados equipamentos. No sector industrial podem causar uma diminuição da eficiência na produção, e consequentemente reverter em perdas económicas elevadas. No seguimento dos trabalhos de investigação na área da Qualidade de Energia Elétrica desenvolvidos pelo Grupo de Eletrónica de Potência e Energia (GEPE) da Universidade do Minho, esta dissertação descreve o desenvolvimento de um Filtro Ativo Paralelo monofásico, utilizado para mitigar harmónicas na corrente e o baixo fator de potência. Pretende-se que o equipamento desenvolvido seja o mais eficiente e compacto possível, sendo a utilização de MOSFETs no inversor de potência um dos pontos fulcrais para conquistar esse objetivo. Através da utilização de frequências de comutação elevadas é conseguida a diminuição dos componentes constituintes do mesmo, tornando-o mais compacto e leve. Um dos desígnios deste equipamento é a sua utilização em demostrações públicas da tecnologia, para tal foi desenvolvida uma interface gráfica com o utilizador, onde é possível visualizar formas de onda do sistema, bem como outras variáveis importantes para o entendimento do funcionamento do equipamento e da tecnologia envolvida. Ao longo deste documento é realizado um levantamento dos vários componentes constituintes do Filtro Ativo Paralelo, por forma a perceber o seu funcionamento, bem como as diversas topologias de hardware e teorias de controlo exequíveis de implementar. De forma a avaliar o funcionamento do Filtro Ativo Paralelo monofásico, são realizadas simulações computacionais, analisando a sua operação para diferentes condições de carga. Por fim, é apresentada toda a implementação prática deste equipamento, terminando com os resultados experimentais.<br>The growing modernization of economic and social sectors, along with the increase of quality of life, is due in large measure to the growing use of electronics equipment, capable of performing the most varied and complex tasks. These devices absorb distorted currents, causing pernicious effects to the power quality of the electrical system, manifesting itself in several consequences, such as, increased losses on different devices, or even malfunctioning of some equipment. In the industrial sector it may cause a decrease in production efficiency, and consequently revert to high economic losses. Following the research in the area of Power Quality developed by the Group of Energy and Power Electronics (GEPE), of the University of Minho, this dissertation describes the development of a single-phase Shunt Active Power Filter, used to mitigate current harmonics and low power factor. The main goal is that the developed equipment is as efficient and compact as possible, and for that, the use of MOSFETs in the power inverter is of crucial importance in order to achieve this purpose. Through the use of high switching frequencies is achieved a reduction in the size of the components, making it more compact and lightweight. One of the purposes of this equipment is its use in public technology demonstrations, and in this way, an graphical user interface was developed, where is possible to view the waveforms of the system, as well as other important variables, in order to understand the operation of the equipment and the technology involved. Throughout this document the various constituent components of the Shunt Active Power Filter are presented, in order to understand its operation, as well as the various hardware topologies and control theories feasible to be implemented. In order to evaluate the performance of the single-phase Shunt Active Power Filter, computational simulations are performed, and its operation is analyzed for different load conditions. Finally, every practical implementation of this equipment is presented, and this dissertation ends with the experimental results.