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Balasubramanian, Karthik. "Smart bulk modulus sensor". [Gainesville, Fla.] : University of Florida, 2003. http://purl.fcla.edu/fcla/etd/UFE0002824.
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Loveday, J. S. "Skin effect measurements of the bulk modulus of potassium". Thesis, University of Bristol, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233723.
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Huang, Shu. "Influence of Chemical Composition and Water on the Bulk Modulus of Pyrope". FIU Digital Commons, 2014. http://digitalcommons.fiu.edu/etd/1185.
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Garnets are major silicates from the upper mantle to the transition zone. Elastic properties of garnets are essential to interpret the variation of seismic velocities at different depths and construct a model of the Earth’s composition. Due to the chemical flexibility at octahedron sites of the crystal structures, garnets usually exist with multiple components and have many composition variations. Pyrope is an important member in the garnet group. Fe2+-Mg2+ substitution in pyrope is one of the common solid solutions. We have synthesized and measured three synthetic solid solutions samples (Py83Alm17, Py54Alm46 and Py30Alm70). Equations of state yielded their isothermal bulk moduli K0 to be 172(4)GPa, 174(2)GPa, and 183(2)GPa, respectively, which confirmed that almandine content (Fe2+ substitution) increased the bulk modulus of the garnet. A relation between the bulk modulus and the almandine mole fraction (n) was derived to be K0 = 170 + 15 n, showing it is a nearly ideal mixing model.
Another factor that also significantly influences the elasticity of pyrope is water. Water is transported to the deep Earth by subduction slabs and mainly exists in nominally anhydrous minerals (NAM) as hydroxyl (OH-). Its content in minerals varies as depth increases. We therefore investigated pressure influence on water solubility in pyrope. A suite of pyrope single crystals was synthesized in a water-saturated environment at 6, 7, 9 and 12GPa and water was characterized by FTIR. IR spectra showed a typical peak at 3630 cm-1. At 9 and 12GPa, new peaks at 3572 cm-1 and 3504 cm-1 appeared and indicated that a new substitution mechanism, other than hydrogarnet substitution SiO4=(OH)4, was adopted in the pyrope crystal structure. Water solubility in pyrope reached 0.2wt% at 7GPa. From 4-7GPa, water solubility increased. At 9GPa, water content dropped to 0.07wt% and increased to 0.3wt% at 12GPa, where a cubic to tetragonal phase transition was observed. Water showed a weakening effect on the bulk moduli of hydrous pyrope. Their bulk moduli were 166GPa, 173GPa and 161GPa with water contents of 0.07wt%, 0.1wt% and 0.2wt%, respectively. An approximate linear relationship was proposed about the bulk modulus as a function of water content.
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Rusia, Devendra Kumar. "A modified viscoplastic formulation for large deformations using a bulk modulus approach". Ohio : Ohio University, 1987. http://www.ohiolink.edu/etd/view.cgi?ohiou1183058011.
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Common, David N. "Development of a system for the measurement of the static bulk modulus of fluids". Thesis, Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/17579.
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Michael, Paul W., i Shreya Mettakadapa. "Bulk Modulus and Traction Effects in an Axial Piston Pump and a Radial Piston Motor". Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-200173.
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This paper describes an investigation into the effects of fluid bulk modulus and traction coefficient properties on piston pump flow losses and radial pison motor torque losses through experimentation, modelling and simulation. Synthetic ester, high bulk modulus, multi-grade, and single grade mineral oils were evaluated. The high bulk modulus fluid exhibited 20% lower pump case and compensator flow losses than a conventional mineral oil of the same viscosity grade. Low traction coefficient fluids reduced the lowspeed torque losses of the radial piston motor by 50%. Physical models for pump case flow and motor torque losses were derived from the experimental data. Field data was collected from a hydraulically propelled agricultural machine. This data was used to model fluid performance in the machine. The simulation results predict that at an operating temperature of 80⁰C, optimizing the bulk modulus and traction coefficients of the fluid could reduce flow losses by 18% and torque losses by 5%. These findings demonstrate the potential of combining comprehensive fluid analysis with modeling and simulation to optimize fluids for the efficient transmission of power.
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Njane, Stephen Njehia. "Precise Fish Volume Estimation Using Underwater Helmholtz Resonance". Kyoto University, 2019. http://hdl.handle.net/2433/244557.
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Kyoto University (京都大学)0048
新制・課程博士
博士(農学)
甲第22076号
農博第2368号
新制||農||1072(附属図書館)
学位論文||R1||N5230(農学部図書室)
京都大学大学院農学研究科地域環境科学専攻
(主査)教授 近藤 直, 准教授 小川 雄一, 教授 飯田 訓久
学位規則第4条第1項該当
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Yang, Shudong, Aihua Tao, Yulin Luo, Junxiang Zhang, Peng Zhou i Lin Zhou. "Experimental measurements of bulk modulus for two types of hydraulic oil at pressures to 140MPa and temperatures to 180°C". Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-199503.
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Bulk modulus of hydraulic oil represents the resistance of hydraulic oil to compression and is the reciprocal of compressibility. The bulk modulus is a basic thermodynamic property of hydraulic oil that has a very important influence on work efficiency and dynamic characteristics of hydraulic systems, especially for the hydraulic systems at ultra-high pressure or ultra-high temperature. In this study, a bulk modulus experimental equipment for hydraulic oil was designed and manufactured, two types of hydraulic oil were selected and its isothermal secant bulk modulus were measured at pressures to 140MPa and temperatures of 20~180°C. Compared the experimental results with the calculated results from the prediction equations of liquid bulk modulus that proposed by Klaus, Hayward, and Song, it is found that the experimental results are not completely identical with the calculated results.
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Lombardo, Nick, i e56481@ems rmit edu au. "Properties of Composites Containing Spherical Inclusions Surrounded by an Inhomogeneous Interphase Region". RMIT University. Mathematical and Geospatial Sciences, 2007. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20080408.143315.
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The properties of composite materials in which spherical inclusions are embedded in a matrix of some kind, have been studied for many decades and many analytical models have been developed which measure these properties. There has been a steady progression in the complexity of models over the years, providing greater insight into the nature of these materials and improving the accuracy in the measurement of their properties. Some of the properties with which this thesis is concerned are, the elastic, thermal and electrical properties of such composites. The size of the spherical inclusion which acts as the reinforcing phase, has a major effect on the overall properties of composite materials. Once an inclusion is embedded into a matrix, a third region of different properties between the inclusion and matrix is known to develop which is called the interphase. It is well known in the composite community that the smaller the inclusion is, the larger the interphase region which develops around it. Therefore, with the introduction of nanoparticles as the preferred reinforcing phase for some composites, the interphase has a major effect on its properties. It is the aim of this thesis to consider the role of the interphase on the properties of composites by modeling it as an inhomogeneous region. There is much scientific evidence to support the fact that the interphase has an inhomogeneous nature and many papers throughout the thesis are cited which highlight this. By modeling the inhomogeneous properties by arbitrary mathematical functions, results are obtained for the various properties in terms of these general functions. Some specific profiles for the inhomogeneous region are considered for each property in order to demonstrate and test the models against some established results.
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Pereira, Amanda Cavalcante. "Influência da profundidade e de um processo de envelhecimento acelerado em propriedades de resinas bulk fill". Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/23/23140/tde-15022018-101701/.
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O presente estudo teve como objetivo avaliar o desempenho de quatro resinas bulk fill (Filtek Bulk Fill (FBF), Opus Bulk Fill (OBF), Sonicfill (SF) e Tetric N-Ceram Bulk Fill (TNBF)) e uma resina convencional (Charisma Diamond (CD)) quanto às seguintes propriedades: resistência à flexão (RF), módulo de elasticidade (ME) e dureza Knoop (KHN) em função da profundidade e após a realização de um envelhecimento acelerado. Corpos de prova em formato de barra foram confeccionados simultaneamente em diferentes profundidades (1, 2, 3, 4 e 5 mm) para realização dos testes de resistência à flexão (n=10), módulo de elasticidade (n=10) e dureza Knoop (n=3). Os testes foram realizados em dois momentos, previamente e após a realização de um envelhecimento acelerado, que consistiu na realização de uma termociclagem com banhos alternados em água a 5 e 55ºC, com 1 min de imersão em cada, por 2000 ciclos. Os resultados para o teste de RF e ME mostraram que os valores para estas duas propriedades diminuíram em função da profundidade e após a realização da termociclagem para todas as resinas estudadas. Apenas a resina TNBF não apresentou diferença estatística para valores de ME após o envelhecimento acelerado. Quanto à dureza, os valores também diminuíram em função da profundidade, porém aumentaram após a realização do envelhecimento acelerado. Apenas a resina SF não apresentou diferença estatística entre os valores de dureza antes e após o envelhecimento. A resina convencional CD após a ciclagem térmica foi a única que apresentou relação base/topo (2 mm) acima de 80%. Nenhuma das resinas do tipo bulk fill apresentou uma relação base/topo acima de 80% para a dureza quando avaliadas na espessura máxima recomendada. Com base nos resultados obtidos, pode-se afirmar que, quando fotoativadas na espessura máxima recomendada, apenas a resina convencional CD apresentou resultados condizentes com a homogeneidade esperada em todas as condições deste estudo. Entretanto, para as resinas do tipo bulk fill, pode-se observar que as propriedades estudadas, de modo geral, sofreram uma diminuição significativa em função da profundidade. Para o envelhecimento, a dureza, diferentemente dos outros parâmetros, mostrou uma tendência de aumento.The purpose of this study was to evaluate the performance of four bulk fill resins (Filtek Bulk Fill (FBF), Opus Bulk Fill (OBF), Sonicfill (SF) and Tetric N-Ceram Bulk Fill (TNBF)) and a conventional resin (Charisma Diamond (CD)) for the following properties: flexural strength (FS), flexural modulus (FM) and Knoop hardness (KHN) as a function of depth and after accelerated aging. Specimens were made simultaneously with different depths (1, 2, 3, 4 and 5 mm) for flexural strength tests (n = 10), flexural modulus (n = 10) and Knoop hardness (n = 3). The tests were carried out in two moments, before and after the accelerated aging process, which consisted of thermocycling with alternating baths in water at 5 and 55ºC, with 1 min immersion in each, for 2000 cycles. The results for the FS and FM tests showed that the values for these two properties decreased as a function of depth and after the thermocycling for all the studied resins. Only TNBF resin showed no statistical significant differences in FM values after accelerated aging. For the hardness test, values also decreased as a function of depth, but increased after accelerated aging. SF resin was the only one that showed no statistical significant differences between hardness values before and after aging. CD, after thermal cycling, was the exclusive resin to show a bottom/top ratio above 80%. None of the bulk fill resins had a bottom/top ratio above 80% for hardness when evaluated at the maximum recommended thickness. Based on the results obtained, it can be stated that, when photoactivated at the maximum recommended thickness, only the conventional resin CD presented results consistent with the expected homogeneity in all the conditions of this study. However, for bulk fill resins, it can be observed that the studied properties, in general, suffered a significant decrease as a function of depth. For aging, the hardness, unlike the other parameters, showed a tendency to increase.
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Freitas, Iberê Cruz. "A influência da etapa de fixação do processo de texturização por falsa torção no volume do fio de poliéster texturizado". Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/100/100133/tde-16092014-213609/.
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A propriedade volume do fio texturizado é importante por questões estéticas e funcionais. O volume do fio pode garantir que um produto tenha bom desempenho mecânico tanto na produção dos artigos (como na tecelagem, malharia e acabamento) quanto para as aplicações finais dos produtos (produtos com alto fator de cobertura, com elasticidade, isolamento térmico etc.). A texturização por falsa torção fixada é um importante processo industrial que possui dentre os principais objetivos o aumento de volume. A etapa de fixação consiste em um tratamento térmico do fio ao final do processo, por meio da passagem do fio texturizado em um forno, conhecido como forno de fixação ou segundo forno. No presente estudo foi analisada a interação entre as variáveis temperatura do forno de fixação e sobrealimentação do fio dentro do forno de fixação. A propriedade volume dos fios texturizados é comumente tratada nas literaturas como encrespamento, termo que será utilizado no presente trabalho. Para a análise do volume do fio definiu-se três propriedades mecânicas: contração do encrespamento, módulo do encrespamento e estabilidade do encrespamento. Com a utilização da ferramenta estatística planejamento do desenvolvimento definiu-se que o estudo seria realizado com dois fatores (temperatura do forno e sobre alimentação do fio); dois diferentes níveis (mínimo e máximo para cada fator) e um ponto central. Para cada proposta de teste foram feitas 10 replicações e 50 ensaios foram realizados. Com as amostras dos fios texturizados foram realizados os ensaios para a determinação das propriedades: contração, módulo e estabilidade do encrespamento; com o equipamento Texturmat da Textechno. Com os dados, realizou-se a análise fatorial para a determinação da importância deles e a regressão linear, para a compreensão do comportamento desses dados em função dos ensaios realizados. As análises possibilitaram observar que a etapa de fixação é muito importante nas propriedades de volume do fio, sendo que a sobrealimentação do fio dentro do forno de fiação apresentou-se como a variável mais relevante para a definição desse parâmetro.Crimp properties are important by functional and aesthetics issues. The crimp of a yarn can provide a good mechanical performance in the production (weaving, knitting and finishing) and also a good result in the final application (products with high covering factor, elasticity, thermal insulation etc). The False Twist texturing is an important industrial process that has the objective of apply bulk on the yarn. The heat setting stage consists of a thermal treatment on the yarn at the end of the process, by the passage of yarn thru a heater that is known as heat setting heater or second heater only. At this paper was analyzed the interaction between second heater temperature and yarn overfeed inside second heater. For crimp analysis were considered three mechanical properties: crimp contraction, crimp module and crimp stability. Using the statistical tool, Design of Experiments, it was defined that would be used two factors (second heater temperature and yarn overfeed inside second heater); two different levels (minimum and maximum for each factor) and a center point. For each test proposal were realized 10 replications, resulting on 50 trials. With Texturmat, from Textechno, tests were realized on the samples (textured yarn) to verify the crimp properties (contraction, modulus and stability). A factor analysis was realized with data from Texturmat to verify the importance of each factor. A linear regression for each property was calculated to better understand the data in terms of the tests. In general it was possible to see the importance of heating set stage on crimp properties of textured yarns and the yarn overfeed inside second heater is the most important variable to define this parameter.
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Arias, Evelyn Patricia Santos. "Avaliação do grau de conversão, dureza e módulo de elasticidade de resinas compostas Bulk Fill". Universidade Estadual de Ponta Grossa, 2018. http://tede2.uepg.br/jspui/handle/prefix/2622.
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O objetivo deste estudo foi avaliar o grau de conversão, dureza e o módulo de elasticidade de três resinas Bulk Fill e duas resinas convencionais. Foram testadas as resinas Bulk Fill: Filtek™ Bulk Fill (FBP), Tetric N-Ceram Bulk Fill (TBF), Filtek™ Bulk Fill Flow (FBF); e adicionalmente duas resinas compostas convencionais: Empress Direct (ED) e Filtek™ Z350XT (Z350). Quarenta e cinco amostras cilíndricas (5 × 4 mm) foram confeccionadas a partir de cada um dos materiais por meio de uma matriz metálica. As matrizes foram preenchidas em incremento único para as resinas compostas Bulk Fill e em dois incrementos para as resinas compostas incrementais. As amostras foram armazenadas à seco no escuro à temperatura ambiente por 24 h antes da realização dos testes. O grau de conversão (GC) foi determinado utilizando a Espectroscopia de Infravermelho com Transformada de Fourier (FTIR). O teste de nanoindentação foi realizado nas superfícies de cada espécime, para obtenção da dureza (H) e módulo de elasticidade (E). Os dados foram submetidos a ANOVA 1 fator e teste de Tukey (α=0.05). Quanto o GC%, o maior foi obtido pelo grupo Z350 (69,92 3,5), e o grupo FBF (60,68 2,1) apresentou o valor significativamente inferior quando comparado com os outros grupos. Quanto os valores da nanodureza (GPa), os grupos FBF (0,3 0,02) e ED (0,3 0,01) apresentaram os menores valores de nanodureza e os grupos Z350 (0,9 0,04 ) e FBP (0,8 0,05 ) apresentaram os maiores valores de nanodureza. Quanto os valores do módulo de elasticidade (GPa), o grupo FBP apresentou os maiores valores de módulo de elasticidade (17,7 0,5) e o grupo FBF apresentou os menores valores de módulo de elasticidade (8,6 0,4). Conclui-se assim, que o compósito incremental (Filtek™ Z350XT) apresentou o maior desempenho do GC e o compósito Bulk Fill (Filtek™ Bulk Fill Flow) exibiu os menores valores de módulo de elasticidade e nanodureza.
The aim of this study was to evaluate the degree of conversion, hardness and elastic modulus of three Bulk Fill composites and two incremental-fill composites. The resin-composites: Filtek™ Bulk Fill (FBP), Tetric N-Ceram Bulk Fill (TBF), Filtek™ Bulk Fill Flow (FBF); and two incremental-fill composites: Empress Direct (ED), Filtek ™ Z350XT (Z350) were tested. Forty-five cylindrical specimens (5 × 4 mm) were made from each material in a metallic mold. Mold was filled in one increment for the Bulk Fill composites and in two increments for the incremental-fill composites. Specimens were stored dry in dark at room temperature for 24 h before testing. Degree of conversion (DC) was determined using Fourier transform infrared spectroscopy (FTIR). Nanoindentation was performed on the surfaces of each specimen, to obtain the hardness (H) and elastic modulus (E). Data for DC and H and E were analyzed by one-way ANOVA, Tukey's test (all at p<0,05). Z350 group (69.92 3.5) showed the highest DC% and FBF group (60,68 2,1) showed the lowest values when compared with the other groups. FBF (0.3 0.02) and ED (0,3 0,01) groups showed the lowest values for nanohardness (GPa) and Z350 (0,9 0,04 ) and FBP (0,8 0,05) groups showed the highest values for nanohardness. FBP group (17,7 0,5) showed the highest values for elastic modulus and FBF group (8.6 0.4) showed the lowest values for elastic modulus (GPa). It was concluded that incremental-fill composite (Filtek™ Z350XT) showed the highest performance DC and Bulk Fill composite (Filtek™ Bulk Fill Flow) showed the lowest values for elastic modulus and nanohardness.
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Lu, Li Rong. "Topology optimization of acoustic metamaterials". 京都大学 (Kyoto University), 2014. http://hdl.handle.net/2433/189362.
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Johnson, Eleda. "The Elastic Behavior of Plagioclase Feldspar at High Pressure". Thesis, Virginia Tech, 2007. http://hdl.handle.net/10919/36450.
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Feldspars are one of the archetypical families of framework silicates. They not only comprise around 60% volumetrically of the Earthâ s crust, but are among some of the most structurally complicated minerals. Investigation into the structural behavior of various intermediate plagioclases at pressure has been undertaken with the intent of categorizing the elastic behavior with pressure across the solid solution series and establishing a conceptual model to characterize feldspar compression.
Complex behavior has been observed in the Equation of State for plagioclase feldspars in excess of 3 GPa, including an anomalous softening of ordered albite in excess of 8.4 GPa (Benusa et al 2005: Am Min 90:1115-1120). This softening was not observed in the EoS for the more intermediate plagioclase compositions containing between 20 and 40 mol% of end-member anorthite. The calculated elastic compliance tensor sums at room pressure show a general stiffening with increasing anorthite component, small elastic changes at the C-1 to I-1 transition, and a dominantly first-order response at the P-1 to I-1 transition near end-member anorthite.
The crystal structure of An37 plagioclase was determined by single-crystal X-ray diffraction. The compression mechanisms in An37 are similar to those in albite at lower pressures. The softening in albite at higher pressures is therefore attributed to the structural shearing in albite that is absent in An37 plagioclase up to 9.5 GPa.Master of Science
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Thornton, Ben Johnston. "Parameter Evaluation and Sensitivity Analysis for an Automotive Damper Model". The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1354115794.
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Hirsch, Sebastian. "Compression-sensitive Magnetic Resonance Elastography". Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät, 2015. http://dx.doi.org/10.18452/17205.
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Diese Arbeit stellt das Konzept der kompressionssensitiven Magnetresonanzelastographie vor. Kompressionssensitive MRE analysiert die Ausbreitung von Kompressionswellen und liefert dadurch Erkenntnisse über die Kompressionseigenschaften eines Mediums auf Grundlage eines poroelastischen Modells. Anomalien bei der Regulation des Gewebedrucks stehen in Zusammenhang mit verschiedenen Krankheitsbildern, wie Normaldruck-Hydrozephalus und Pfortader-Hypertonie. Statischer Druck spielt als Porendruck eine zentrale Rolle in den poroelastischen Wellengleichungen; die kompressionssensitive MRE könnte daher ein nichtinvasives Diagnoseinstrument darstellen, das die durch konventionelle Scherwellen-Elastographie gewonnenen Informationen um weitere Aspekte ergänzt. Diese Arbeit beschreibt die Entwicklung einer schnellen Singleshot-EPI-Bildgebungssequenz, mit deren Hilfe die durch propagierende Druckwellen hervorgerufene volumetrische Verzerrung quantifiziert werden kann. Die Validierung der kompressionssensitiven MRE erfolgte an verschiedenen Systemen: an porösen Gelphantomen, an der menschlichen Lunge in zwei Atemzuständen, in einer ex-vivo Schafsleber bei unterschiedlichen hydrostatischen Drücken und schließlich am menschlichen Gehirn. Die Ergebnisse belegen, dass die Stärke der induzierten volumetrischen Verzerrung sensitiv gegenüber Druckänderungen ist, wohingegen die Scherverzerrung keine derartige Abhängigkeit aufweist. In einer weiteren Studie wurde intrinsische Pulsation des menschlichen Hirns anstelle einer externen Vibrationsquelle ausgenutzt. Dabei erzeugte die arterielle Pulswelle eine kurze lokale Expansion des Hirnparenchyms; in der sich anschließenden diastolischen Phase erfolgte eine langsame Rückkehr zum Ausgangszustand. Aus den gemessenen volumetrischen Verzerrungen wurden durch Inversion der Druckwellengleichung numerische Werte für den Druckwellenmodul M berechnet; Rauschen wurde als primäre Ursache für die systematische Unterschätzung von M identifiziert.This thesis introduces the concept of compression-sensitive Magnetic Resonance Elastography. Compression-sensitive MRE detects the propagation of pressure waves, providing insight into the compressibility of a material based on a poroelastic tissue model. Poroelastic models incorporate compressibility through interaction of compartments, even as each individual compartment remains incompressible. Hydrostatic tissue pressure abnormalities are associated with a number of diseases, such as normal pressure hydrocephalus or hepatic portal hypertension. Since pore pressure plays a central role in the poroelastic wave equations, compression-sensitive MRE could potentially serve as a diagnostic tool, providing information complimentary to shear-wave MRE data. This thesis describes the development of a fast single-shot EPI MR sequence capable of quantifying volumetric strain induced by external vibrations. Compression-sensitive MRE was validated in porous gel phantoms, in the human lung at two different respiratory states, in an ex vivo sheep liver at varying levels of hydrostatic pressure, and finally in human liver and brain. Results illustrate that compression-sensitive MRE is capable of quantifying volumetric strain in phantoms and in human organs. It was found that volumetric strain was sensitive toward pressure changes associated with different physiological states, whereas shear strain remained constant. In an additional study, pulsation of the human brain, driven by the heart cycle, was used as the actuation source instead of the external vibration generator. Results indicate local expansion of brain parenchyma upon the arrival of the arterial pulse wave, followed by a slow return to the initial state during the diastolic phase. Numerical values for the pressure wave modulus M were calculated from measured volumetric strain through inversion of the pressure wave equation. Measurement noise was identified as the primary effect causing a severe underestimation of M.
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Kriuchevskyi, Ivan. "Mechanical and viscoelastic properties of glass-forming polymers in the bulk and thin films : molecular dynamics study of model systems". Thesis, Strasbourg, 2017. http://www.theses.fr/2017STRAE044/document.
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En nous concentrant sur les valeurs du module de cisaillement l’équilibre Geq pour le modèle bien connu des polymères vitrifiables (echantillionné par le biais de la MD), nous avons adressé la question générale de en quoi les propriétées méchaniques des couches mince diffères de la phase volumique. Il a été démontrè que dans les deux cas Geq de manière non ambigus sèpare l’état fluide (Geq = 0) de l’état vitreux (Geq > 0). Nous avons aussi insisté sur le fait que Geq pour la couche mince dépend de lépaisseur du film h mais aussi de de la pression tangentielle qui est un résultante de la procédure de préparation de la couche minceFocusing on the equilibrium shear modulus Geq of well-known glass-forming polymer model system (sampled by means of MD), we have addressed the general question of how the mechanical properties of the thin polymer films differs from the bulk. Using ”stress fluctuation” formalism we obtained Geq(T) for the bulk and films. It has been demonstrated that in both cases Geq unambiguously separates the fluid state (Geq = 0) from the glass (Geq > 0). We also stressed that Geq for the film does not only depend on film thickness h, but also on tangential pressure that is a consequence of the film preparation procedure
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Milani, Sula. "Compressibility and thermal expansion of garnets with compositions typical of inclusions in diamonds". Doctoral thesis, Università degli studi di Padova, 2015. http://hdl.handle.net/11577/3424306.
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Most of the diamonds formed in the sub-cratonic lithospheric mantle, in the so called ‘diamond window’, but only 1% of these diamonds have mineral phases trapped as inclusions. Although inclusion-bearing diamonds are so rare, they are geologically important, because they are the only direct and unaltered samples that we have from the Earth’s mantle. For this reason, the determination of their pressure of formation (i.e. depth of provenance) is fundamental to better constrain the chemico-physical environment in which they formed.
The pressure of formation can be typically estimated by classical geobarometry methods that are based on the cation partitioning between mantle minerals. However, these methods can only be applied to rare cases (e.g. only when the appropriate set of mineral assemblages is present in the same inclusion within a diamond). Recently, analternative method has been developed, the ‘elastic method’. This method is based on the residual pressure (Pinc) of the inclusion still trapped in the diamond while at room conditions (i.e. room temperature and pressure). This Pinc arises from the contrast in elastic properties (expansivity and compressibility) between the diamond host and the trapped inclusion regardless the P-T-t path taken during the exhumation. In principle thismethod can be applied to any diamond-mineral inclusion pair, but requires accurate knowledge of the thermoelastic parameters of the diamond host and inclusion and an accurate determination of Pinc.
Given that in literature reliable thermo-elastic parameters for diamond already exist, in this thesis I focused on the determination of the bulk modulus and thermal expansion of a series of garnets, which, together with olivines, are the most abundant phase included in diamonds. Garnet inclusions show a broad chemical variability and therefore the key point is to understand the compositional dependence of garnet elastic coefficients. This can be done by determining the elastic properties of the relevant garnet end-members (pyrope, almandine, grossular, and uvarovite) thus retrieving their variation within the solid solutions. This PhD project provides new values of the compressibility and thermal expansion for pyrope (Mg3Al2Si3O12), almandine II" "(Fe3Al2Si3O12), grossular (Ca3Al2Si3O12), and uvarovite (Ca3Cr2Si3O12) garnet end members,determined by in-situ high-pressure and high-temperature single-crystal X-ray diffraction experiments. As a simple proof of concept the elastic properties of a synthetic single crystal with eclogitic-like composition (i.e. Py51Al22Gr27) have been determined. In order to test if the compositional dependence of garnet elasticity can be reliably modeled assuming an ideal mixing model the measured elastic coefficients for this complex solid solution (Py51Al22Gr27) have been compared to those calculated from the end-member properties. Two sets of entrapment pressures at temperatures typical for subcratoniclithosphericregions for the eclogitic-like garnet were therefore calculated with the ‘elastic method’, using both the observed and the extrapolated elastic parameters.
The results show that the differences between the calculated and measured values produced discrepancies in the entrapment pressures of about 0.03 GPa along the entire temperature range considered (e.g. 1000 – 1800 K). Such difference in entrapment pressures cause shifts of less than 1 km in estimation of the depth of formation for the pair. Despite other minor uncertainties that may arise applying the elastic method to garnets still trapped in diamonds (e.g. more complex garnet solid solutions, presence of fractures of the host around the inclusion), these results clearly indicate that the elastic method allows retrieving the pressure of formation for garnet inclusion in diamonds with uncertainties one order of magnitude lower than classical geobarometry.La maggior parte dei diamanti si sono formati nel mantello litosferico subcratonico, e più precisamente nella porzione di mantello definita in inglese come ‘diamond window’. Solo l’1% di questi diamanti contiene altre fasi minerlai incluse. Nonostate la loro rara ricorrenza sono molto importanti nelle Scienze della Terra, in quanto rappresentano gli unici campioni che contengono al loro interno le fasi minerali del mantello terrestre più profonde e non alterate che vengono studiate oggigiorno. Per questo motivo la determinazione della loro pressione di formazione, e quindi della loro profondità di provenienza, è di rilevante importanza per determinare le condizioni chimico-fisiche dell’ambiente in cui si sono formati. Nella maggior parte dei casi la pressione di provenienza di tali campioni viene determinata applicando la geobarometria classica, che si basa sul partizionamento degli elementi chimici tra i minerali costituenti il mantello. Questo metodo però può venir utilizzato soltanto in rari casi, ovvero quando all’interno dello stesso diamante sono presenti le fasi minerali adatte. Per questo motivo negli ultimi decenni è stato sviluppato un metodo alternativo, definito come metodo elastico. Questo metodo permette la determinazione della pressione di formazione considerando la pressione residua, definita come Pinc, alla quale è soggetto il minerale incluso in condizioni superficiali, ovvero a pressione e temperatura ambiente. La Pinc è dovuta alle differenze nelle propietà termoelastiche (compressibilità ed espansività) del diamante e dell’incluso. In linea di principio il metodo elastico può essere applicato a qualsiasi diamante contenente una o più fasi minerali incluse, ma è necessaria l’accurata conoscienza dei parametri termoelastici sia del diamante che del minerale incluso. Dal momento che in passato i parametri termoelastici del diamante sono già stati determinati con accuratezza, nel presente lavoro di tesi mi sono focalizzata sulla determinazione del bulk modulus ed espansione termica dei granati, che assieme alle olivine sono le fasi minerali più abbondanti incluse nei diamanti. A causa della complessa variabilità composizionale dei granati è molto importante studiare come le proprietà termoelastiche dei granati variano con la composizione chimica. Questo può IV" " essere determinato solamente studiando le proprietà elastiche dei termini estremi, quali il piropo, l’almandino, la grossularia e l’uvarovite. Per questo motivo durante il lavoro della presente tesi sono stati determinati dei nuovi valori del bulk modulus e dell’espansione termica di piropo (Mg3Al2Si3O12), almandino (Fe3Al2Si3O12), grossularia (Ca3Al2Si3O12) e uvarovite (Ca3Cr2Si3O12). Questi parametri sono stati determinati tramite esperimenti di diffrazione a raggi-X ad alta pressione e temperatura in-situ. In conclusione sono state determinate le proprietà elastiche di un cristallo singolo sintetico di composizione eclogitica (i.e. Py51Al22Gr27). Per verificare se la variazione del bulk modulus misurata può essere calcolata considerando una soluzione solida ideale, è stato fatto un semplice calcolo di media pesata. A questo punto le pressioni di intrappolamento di un granato eclogitico sono state calcolate con il metodo elastico in condizioni di mantello litosferico subcratonico considerando i valori termoelastici calcolati e misurati. I risulatati ottenuti evidenziano la minima differenza tra la pressione di intrappolamento calcolata con il coefficiente misurato e calcolato, che è di soli 0.03 GPa, nell’intera regione termica considerata (1000-1800 K). Tale differenza nel calcolo della pressione corrisponde a una differenza nella profonditá di formazione di solo 1 km. Nonostante le ulteriori complicazioni che potrebbero comparire con l’applicazione del metodo elastico, come per esempio la presenza di soluzioni solide più complesse e la presenza di fratture, questo risultato dimostra chiaramente la potenzialità del metodo elastico nel calcolare le pressioni di intrappolamento con incertezze di un’ordine di grandezza inferiori a quelle calcolate con la geobarometria classica.
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Lindroth, Emma. "Acoustic Characterization of the Cellulose-coated Perfluorocarbon Droplets based on Phase Velocity Measurements". Thesis, KTH, Skolan för kemi, bioteknologi och hälsa (CBH), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-276837.
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Today, microbubbles are one of the most commonly used ultrasound contrast agents, since their high compressibility results in a strongly scattered signal. Despite this advantage, microbubbles experience limitations by the decreased stability and large diameter. The cellulose nanofiber (CNF) stabilized perfluoropentane (PFC5) droplets have the possibility of eliminating these drawbacks. In order to examine the droplet behavior and scattering ability when exposed to ultrasound, the acoustic response of the droplets is studied and compared with that of microbubbles (MBs). Therefore, this thesis aims to design an experimental set-up and a processing method to determine the phase velocity, bulk modulus and compressibility of the CNF-coated PFC5 droplets. The experimental study of the acoustic characterization uses pulse-echo spectroscopy with an aluminum reflector and seven flat transducers covering the frequency range 0.7 to 14.1 MHz. By using fast Fourier transform, while accounting for the 2πn ambiguity, the phase velocity profiles are obtained. The dispersions within this frequency spectrum are 1391-1487 m/s and 1387-1488 m/s for the concentrations 10 ∙ 106 and 50 ∙ 106 droplets/ml, respectively. These profiles display an increasing phase velocity with frequency and a slight increase in dispersion with concentration. These results agree with theory and studies examining the phase velocity of MBs. The bulk modulus presents values between 3-4 GPa, while the compressibility is 2.7 − 3.2 ∙ 10-10 𝑃𝑎-1 within the frequency range studied. Compared to water and certain MBs, both possessing a lower bulk modulus, the droplets are less compressible. To conclude, the droplets have similar phase velocity profiles with the same dependencies on frequency and concentration as MBs, resulting in similar behavior of these droplets when exposed to ultrasound. Hence, affecting the wave similarly to MBs in terms of spreading. The droplet are, however, not as compressible. This most likely affects their oscillation and they, hence, might not have equally beneficial scattering ability. This could reduce their utilization as contrast agents. Some of the potential error sources present during the laboratory work and the development of the post-processing code were not achieving perfect optimization of the transducer alignment, vaporization of the droplets resulting in reduced concentration, possible diffraction, not optimal processing of data and inadequate correction for 2πn ambiguity.
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Pasquini, Enrico, Hubertus Murrenhoff i Katharina Schmitz. "On the thermodynamic consistency of experimentally determined fluid properties". Technische Universität Dresden, 2020. https://tud.qucosa.de/id/qucosa%3A71160.
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In the field of fluid power, accurate knowledge of fluid properties is vital for reasonable prediction of component behaviour and system performance. In general, these properties depend on the pressure and temperature levels that the respective medium is exposed to. The properties and their respective dependencies are not publicly accessible for many fluids commonly used in fluid power. If measured values – typically published in the form of mathematical fluid property models – are available at all, their quality is typically unknown. The paper aims to provide tools to objectively ascertain the quality of measured fluid properties. For this purpose, an equation is derived which establishes a relationship between the thermodynamic parameters of density, bulk modulus, heat capacity and thermal expansion coefficient. The presented equation is always satisfied by liquids as well as gases as long as they can be treated as a continuum. Based on this relationship, the degree of thermodynamic consistency of measured properties is evaluated: The less the equation is fulfilled by experimentally determined fluid properties, the more the measured values violate physical laws. The procedure of assessing the thermodynamic consistency is demonstrated by evaluating published fluid property models with the method outlined above. To aid engineers in judging which degree of thermodynamic inconsistency is acceptable, a cut-off value is suggested.
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Valilou, Shirin. "Nonlinear Model and Control of Electro Hydraulic Servo-Systems". Doctoral thesis, Università degli studi di Bergamo, 2018. http://hdl.handle.net/10446/104971.
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In many applications, the use of hydraulic drives is still preferable to other driving powers. For instance, in shaking table systems for simulating earthquake signal, hydraulic actuators are still widely applied, because the technology of electrical actuators does not(yet) provide the superior performance of hydraulic actuators in generating high power to weight ratio. However, with increasing demands on the performance of complex motion systems, the limits of performance of hydraulic servo-systems, due to the nonlinear and dynamic characteristics of these systems, come into the picture. Most nonlinearities of these systems arise from compressibility of the hydraulic fluid, the complex flow properties of the servo-valve, valve overlap and friction in the hydraulic cylinder. Aside from the nonlinear nature of the hydraulic dynamics, there are many considerable model uncertainties, such as internal and external leakages and external disturbances which cannot be modeled exactly. Therefore, in order to design a high performance controller for simulating the earthquake signal which is the goal of a servo-hydraulic shaking table, a suitable dynamical model of the system needs to be formulated.
In this thesis beside a specific application of hydraulic actuator, a shaking table servo system, an integrated approach to the modeling and control of a hydraulic servo system is presented. The application of servo-hydraulic shaking table shows that the dynamics and nonlinearities of the servo-valve and the compressibility of hydraulic oil which basically constitute the limits of the performance of the controlled servo-system. Especially, in case of acceleration model and control of a hydraulic servo-system. In the shaking table application, for modeling and identification of the system, in contrary of the previous works which in them position and pressure sensors are used, only the position and acceleration sensor are available.
In order to obtain structural insight in the way that the performance is limited by the
properties of (the subsystems of) the hydraulic servo-system, the modeling of this system
has been treated thoroughly in this thesis. At the one hand, this has opened the way to
model-based control design, so that unavoidable limits of performance can be narrowly
approached. At the other hand, the obtained insight appears to be useful in the system
design stage, such that potential control problems may be avoided by proper system design.
Because of the twofold purpose of the modeling, with control design requiring quantitatively accurate models and simulating the behavior of the system precisely which requiring qualitative insight in the system behavior, the so-called grey-box modeling approach has been applied. This approach
comprises physical modeling including model analysis by means of simulation, and subsequent identification and validation of the obtained physical models, using experimental
data.
In the physical modeling stage, a consistent integration of the nonlinear dynamic modeling of the different subsystems of the hydraulic servo-system, namely servo-valve and actuator are presented. In this model, the most nonlinearities of the system which arise from compressibility of the hydraulic fluid, the complex flow properties of the servo-valve, valve overlap and friction in the hydraulic cylinder are simulated. Four different kinds of friction model are considered and the accuracy of these models for simulating the behavior of the system are compared experimentally. However, due to the limitation of these models in high velocity and bandwidth, it has been shown that for simulating the behavior of the system, nonlinear modeling of the friction is not enough. Then, by gathering some position and acceleration information of the real system, the sensitivity of the model to different nonlinearity of the system are investigated. This led to the insight, that only some of the modeled nonlinear effects are really relevant, such as the nonlinear flow characteristic of the servo-valve spool due to non-ideal port geometries and the compressibility of hydraulic oil, and the position dependence of the actuator dynamics.
Based on the experimental results, two new nonlinear dynamic models for simulating the behavior of the servo-hydraulic shaking table are proposed. First, with defining 6
main parameters of the model and identifying them for different sinusoidal
inputs, a neural network model is proposed. Second, a new empirical nonlinear model
for effective bulk modulus of hydraulic oil is proposed which increase the accuracy of the model to predict the behavior of the position and acceleration output of the system.
In this approach, the link between the physical and the system theoretic interpretation of the properties of the hydraulic servo system are strongly emphasized. This makes, that the presented models are not only useful for shaking table design, but also for the design of the hydraulic servo-system.
Based on the task specification of the shaking table which is tracking the position and velocity reference signals with considering uncertain load conditions, different kinds of robust controller design are presented. For control designing purpose, the full order dynamic model of the system is simplified in a new approach and then due to the availability of only the position sensor on the experimental setup, a robust sliding mode observer is designed which can estimate the velocity and acceleration states of the system from the position sensor. Finally, experiments with a hydraulic actuator in a single degree-of-freedom setup have shown the validity of the approach for control design. The experimental results of the closed loop system controlling by three different controllers (feed forward PI controller, sliding mode and super twisting controller) with considering different load condition and reference signals are presented. An analysis of different control strategies for this setup led to the conclusion, that super twisting sliding mode controller shows a smaller error and smother response for position and velocity trajectory tracking with respect to sliding mode and feedforward PI controller.
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Liu, Wei. "Investigations of the atomic order and molar volume in the binary sigma phase by DFT and CALPHAD approaches". Thesis, Aix-Marseille, 2017. http://www.theses.fr/2017AIXM0471/document.
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La phase sigma peut servir de prototype de phases topologiquement compactes, car la phase sigma possède une large gamme d'homogénéité et il existe de nombreuses données expérimentales disponibles pour la phase sigma. Dans le présent travail, les propriétés physiques, comprenant l'ordre atomique, le volume molaire, l'enthalpie de formation et le module d’élasticité isostatique, de la phase sigma binaire ont été étudiées en utilisant les calculs de premiers principes et la méthode CALPHAD combinée aux données expérimentales de la littérature.Tout d'abord, nous avons constaté que l'ordre atomique (c'est-à-dire la distribution du constituant atomique ou la préférence d'occupation du site sur les sites non équivalents d'une structure cristalline) de la phase sigma est affecté par le facteur de taille et la configuration électronique des éléments constitutifs. En outre, nous avons dissocié les effets de ces facteurs d'influence sur l'ordre atomique. Ensuite, nous avons mis en évidence un effet de l'ordre atomique sur l'enthalpie de formation, le module d’élasticité isostatique et le volume molaire. A l'état ordonné à 0K, la phase sigma a une faible enthalpie de formation et un grand module d’élasticité isostatique. L'influence de l'ordre atomique sur le volume molaire de la phase sigma dépend de la configuration électronique des deux éléments constitutifs. Par ailleurs, la base de données des volumes molaires des phases sigma binaires a été construite, ce qui devrait grandement faciliter la conception du matériau. Enfin, nous avons discuté de la prédiction de l'occupation du site de la phase sigma en utilisant la méthode CALPHAD combinée aux calculs de premiers principesThe sigma phase can serve as a prototype of topologically close-packed (TCP) phases, as the sigma phase bears a broad homogeneity range and there are numerous experimental data available for the sigma phase. In the present work, physical properties, including atomic order, molar volume, enthalpy of formation and bulk modulus, of the binary sigma phase were investigated by using first principles calculations and CALPHAD method combining with the experimental data from the literature. Firstly, we found that the atomic order (i.e. atomic constituent distribution or site occupancy preference on nonequivalent sites of a crystal structure) of the sigma phase is affected by the size factor and electron configuration of the constituent elements. Furthermore, we have dissociated the effect of the individual influencing factor on atomic order. Secondly, the atomic order is found affecting physical properties, such as enthalpy of formation, bulk modulus and molar volume. When in the ordered state at 0K, the sigma phase shows a low enthalpy of formation and a large bulk modulus. The influence of atomic order on the molar volume of the sigma phase depends on the electron configuration of the two constituent elements. Thirdly, the molar volume database of the binary sigma phase has been built up within the CALPHAD framework, which can greatly facilitate material design. Finally, we tentatively discussed the site occupancy prediction of the sigma phase by using the CALPHAD method combined with first-principles calculations
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Lee, Wayne Yeung. "Numerical Modeling of Blast-Induced Liquefaction". BYU ScholarsArchive, 2006. https://scholarsarchive.byu.edu/etd/524.
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A research study has been conducted to simulate liquefaction in saturated sandy soil induced by nearby controlled blasts. The purpose of the study is to help quantify soil characteristics under multiple and consecutive high-magnitude shock environments similar to those produced by large earthquakes. The simulation procedure involved the modeling of a three-dimensional half-space soil region with pre-defined, embedded, and strategically located explosive charges to be detonated at specific time intervals. LS-DYNA, a commercially available finite element hydrocode, was the solver used to simulate the event. A new geo-material model developed under the direction of the U.S. Federal Highway Administration was applied to evaluate the liquefaction potential of saturated sandy soil subjected to sequential blast environments. Additional procedural enhancements were integrated into the analysis process to represent volumetric effects of the saturated soil's transition from solid to liquid during the liquefaction process. Explosive charge detonation and pressure development characteristics were modeled using proven and accepted modeling techniques. As explosive charges were detonated in a pre-defined order, development of pore water pressure, volumetric (compressive) strains, shear strains, and particle accelerations were carefully computed and monitored using custom developed MathCad and C/C++ routines. Results of the study were compared against blast-test data gathered at the Fraser River Delta region of Vancouver, British Columbia in May of 2005 to validate and verify the modeling procedure's ability to simulate and predict blast-induced liquefaction events. Reasonable correlations between predicted and measured data were observed from the study.
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Wei, Jia. "Investigation of High-Input-Voltage Non-Isolated Voltage Regulator Modules Topology Candidates". Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/32482.
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Since the early 80s, the computer industry has undergone great expansion. Processors are becoming faster and more powerful. Power management issues in computing systems are becoming more complex and challenging. An evolution began when the high-performance Pentium processor was driven by a non-standard, less-than-5V power supply, instead of drawing its power from the 5V plane on the system board. A so-called Voltage Regulator Module (VRM), is put close to the processor in order to provide the power as quickly as possible. Nowadays, for desktop and workstation applications, VRM input voltage has moved to the 12V output of the silver box. In the meantime, microprocessors will run at very low voltage (below 1V), will consume up to 100A of current, and will have dynamics of about 400A/us.
This work presents an investigation of three 12V VRM topologies: the synchronous buck converter, the tapped-inductor buck converter and the active-clamp couple-buck converter. The limitations of today¡¯s synchronous buck approach are identified. The extreme duty cycle of the current topology makes it difficult to design an efficient VRM with decent transient response.
The tapped-inductor buck and the active-clamp couple-buck converters are discussed as solutions. The transient response and efficiency of each type of converter are compared. Ripple cancellation is also addressed. The analytical and experimental results are presented: The tapped-inductor buck can improve the efficiency, but suffers a voltage spike, which nullifies its candidacy; the active-clamp couple-buck converter can improve the efficiency while maintaining good transient response, and it is therefore a good candidate for 12V VRMs.Master of Science
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McCarthy, Andrew C. "Behavior of Sodium Clinopyroxenes Under Compression". Diss., The University of Arizona, 2007. http://hdl.handle.net/10150/194006.
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Three end-member clinopyroxenes from the NaM13+Si2O6 series (M1 = Al, Fe and Ga) have been examined by single-crystal X-ray diffraction at pressures up to 11 GPa. NaGaSi2O6 was also examined with Raman spectroscopy to 16.5 GPa. NaAlSi2O6 (jadeite) and NaFeSi2O6 (aegirine) are naturally occurring minerals. NaGaSi2O6 is synthetic. Various characteristics of each of the three clinopyroxenes as a function of pressure are reported, including bulk moduli (K0), unit cell volumes, atomic positions, and bond lengths.The compressibilities of a selection of clino- and orthopyroxenes from the literature were examined and considered in terms of M2-O3 bonding and unit cell volumes. As predicted by previous workers, pyroxene compressibilities generally correlate with unit cell volumes at ambient conditions. Compressibilities are also found, however, to be significantly affected by the relationship of M2-O3 bonds with the sense of rotation of silica tetrahedra upon compression. Two such relationships are observed: sympathetic, where the corner of the SiO4 tetrahedron tilts toward M2, and antipathetic, where the corner of the tetrahedron tilts away from M2. All interatomic separations in pyroxenes decrease with pressure, but sympathetic-type separations decrease more than expected based on isotropic scaling of the unit cell. Pyroxene structures may have one of several M2-O3 bond configurations: none, one, two or four bonds, and none, only sympathetic, only antipathetic, or a mixture of both types of bonds. Structures with antipathetic bonds are significantly stiffer than structures without, all else constant. The sympathetic/antipathetic bond hypothesis represents a new, previously unrecognized, first-order control on pyroxene compressibility.M1 size controls ambient unit cell volumes of clinopyroxenes. However, M1 size does not correlate well with pyroxene bulk moduli. Applying the idea of sympathetic and antipathetic M2-O3 bonding, much of the dispersion in a plot of M1 cation size versus bulk modulus can be explained. The three NaM13+Si2O6 clinopyroxenes examined in this study exhibit very similar behavior under compression. All show signs of approaching a C2/c -> C2/c phase transition at ~20 GPa. All exhibit unit strain ellipsoids with similar orientations and dimensions. All have identical bond topologies and bulk moduli that correlate with their ambient unit cell volumes.
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Morrison, Luke. "Feedback controller design for power pole electronics laboratory buck converter module". Thesis, Morrison, Luke (2012) Feedback controller design for power pole electronics laboratory buck converter module. Other thesis, Murdoch University, 2012. https://researchrepository.murdoch.edu.au/id/eprint/14811/.
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This thesis paper details the design of a feedback control compensator device to suit a Buck converter. The apparatus that was used is a configurable experimental laboratory device made by the University of Minnesota. The author had aims to provide a fast and stable response to both input voltage disturbances and change in load resistance type disturbances. The voltage output was required to remain constant or return to steady state as fast as possible, without oscillation, after one of these types of disturbances. The design was found to work quite well but there is definitely scope for future students to improve the design or approach the project from an embedded systems perspective.
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XU, PENG. "HYBRID X-BAND POWER AMPLIFIER DEVELOPMENT FOR 3D-IC PHASED ARRAY MODULE". University of Cincinnati / OhioLINK, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1049977754.
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Stone, Thomas Shannon. "A numerical/experimental method for evaluating the bulk and shear complex dynamic moduli of viscoelastic polymers in the kilohertz range". Thesis, Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/17038.
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Tell, Erik. "Inte en glödlampa LED-armatur 35000 timmar till, Not a lightbulb LED luminaire 35000 hours more". Thesis, Malmö högskola, Fakulteten för teknik och samhälle (TS), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:mau:diva-20088.
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Uppsatsen behandlar belysningsarmaturer inom LED-segmentet. Uppsatsen behandlar isynnerhet varför ljuskällan i LED-belysningsarmaturer oftast konstrueras så att ljuskällorna inteär utbytbara.Metoder som har använts i förstudien har varit; informationssökning, kvalitativa intervjuer,teknisk LED-modulsinventering samt konstruktionsundersökningar. Metoder som använts iproduktutvecklingsfasen har varit; tekniska informationsstudier, Idéinventering genom visuellidégenerering, imageboards och skissprocess (att tänka med en penna).Syftet med projektet har varit att utveckla en LED-armatur med utbytbar ljuskälla. Projektetsresultat blev en LED-golvarmatur med utbytbar ljuskälla. Ljuskällan som används i armaturenär enligt den unga branschfrivilliga standarden för LED-moduler, Zhaga.The essay deals with luminaries in the LED segment. The essay deals in particular with why thelight sources in LED lighting fixtures usually is designed so that the light sources are notreplaceble.Methods used in this work has been; information searching, qualitative interviews, technicalLED module inventory and construction surveys. Methods used in the product developmentphase have been; technical information studies, Idea inventory by visual idea generation, imageboards and sketching process (thinking with a pen).The aim of the project was to develop an LED fixture with a replaceable light source. The resultof the project became an LED floor fixture with replaceable light source. The light source usedin the luminarie is of the young voluntary industry standard for LED modules, Zhaga.
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Siryabe, Emmanuel. "Evaluation non destructive par ultrasons de l'adhésion aux interfaces de joints collés". Thesis, Bordeaux, 2016. http://www.theses.fr/2016BORD0427/document.
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Cette thèse a pour objectif de développer des méthodes ultrasonores pour l’END de l’adhésion de joints collés. Pour aborder ce problème, les assemblages sont réalisés avec des substrats en aluminium (isotrope, élastique) et un adhésif de type époxy(isotrope, viscoélastique). Selon la géométrie des assemblages, deux méthodes sont proposées pour obtenir une information quantitative sur le niveau d’adhésion. La première est adaptée à des échantillons de type tri-couches avec recouvrement total.Elle consiste à analyser la transmission d’ondes ultrasonores planes de volume à travers l’assemblage immergé dans l'eau.Les conséquences d'un mauvais traitement de surface des substrats sur la mesure des modules de viscoélasticité du joint adhésif sont étudiées. Il a été montré que des interphases dégradées provoquent une anisotropie apparente des modules mesurés pour le joint de colle. Cette anisotropie a été quantifiée à l'aide de deux paramètres β1 et β2 dont les valeurs permettent de révéler la qualité des interphases. Ensuite, les modules élastiques (ou raideurs kL et kT) des interphases ont été estimés, en supposant les propriétés de l'adhésif connues. On montre que leurs valeurs sont maximales lorsque l'adhésion est nominale, et qu’elles diminuent franchement lorsque l'adhésion est dégradée, mais dans des proportions différentes. Des mesures de la contrainte à rupture, réalisées sur des échantillons préparés dans les mêmes conditions, corroborent la chute des modules des interphases. La seconde méthode est adaptée à des échantillons collés avec un recouvrement partiel. Elle es tbasée sur la mesure du coefficient de transmission d'ondes de Lamb se propageant d'un substrat à l'autre, à travers la zone de recouvrement. Une étude de sensibilité numérique (par éléments finis) des coefficients de transmission des modes de Lamb a montré que les propriétés mécaniques des interphases (modélisées par des raideurs surfaciques) peuvent être évaluées si les autres caractéristiques de l’assemblage sont connues. Des mesures expérimentales de ces coefficients de transmission ont ensuite été réalisées avec deux échantillons. L’un d’eux possède des interphases à adhésion nominale et l’autre des interphases dégradées. Une confrontation entre les résultats des mesures obtenus pour les différents modes et les simulations numériques permet de déterminer les valeurs des raideurs d’interfaces pour chaque échantillon. Là encore, il est observé qu’une mauvaise adhésion se traduit par des valeurs faibles des raideurs d’interfaces, qui peuvent être quantifiées, cette fois,grâce aux ondes ultrasonores guidéesThe aim of this thesis is to develop NDT ultrasonic methods for the evaluation of the adhesion at interfaces in bonded joints.To address this problem, the assemblies are made of aluminum substrates (isotropic, elastic) and epoxy adhesive (isotropic,viscoelastic). Depending on the geometry of the studied assemblies, two methods are proposed to obtain quantitativeinformation on the adhesion level. The first method is suitable for three-layered plate-like samples. It consists in analyzingthe transmission of bulk ultrasonic plane waves through the assembly immersed in water. The consequences of a inapropriatesurface treatment of the substrates on the measurement of viscoelastic moduli of the joint are studied. It has been shown thatdegraded interphases cause an apparent anisotropy of the measured elastic moduli of the joint. This anisotropy was quantifiedusing two parameters β1 and β2 whose values can reveal the quality of the interphases. Then, the elastic moduli (or stiffnesseskL and kT) of the interphases were estimated, assuming that the adhesive layer properties are known. It was shown that theirvalues are higher when the adhesion is nominal, and are strongly decreased when the adhesion is degraded. Measurements ofthe mechanical strength, on samples prepared under the same conditions, confirmed the drops in these elastic moduli. Thesecond method is more suitable for lap joint samples. It is based on the Lamb wave transmission coefficient measured fromone substrate to the other, across the overlap zone. A numerical sensitivity analysis (finite element model) of the transmissioncoefficients of Lamb waves showed that the mechanical properties of the interphases (modeled by interfacial stiffnesses) canbe evaluated if the other characteristics of the assembly are well known. Experimental measurements of the transmissioncoefficients were then performed on two samples. One of them has interphases with nominal adhesion and the other hasdegraded interphases. A comparison between the measured results obtained for the different modes and numericalsimulations was used to determine the values of the interfacial stiffnesses for each sample. Again, it was observed that pooradhesion leads to low values of the interfacial stiffnesses of the interphases, that can be quantified using guided ultrasonicwaves
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Gallardo, Angelo Miguel Asuncion. "Design and Construction of 1800W Modular Multiple Input Single Output Non-Isolated DC-DC Converters". DigitalCommons@CalPoly, 2017. https://digitalcommons.calpoly.edu/theses/1739.
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This thesis report details the design and construction of non-isolated DC-DC converters to create a Multiple Input Single Output (MISO) converter for combining multiple renewable energy sources into one single output. This MISO uses the four-switch buck-boost topology to output a single 48V from multiple nominal 24V inputs. The MISO converter implements a modular approach to deliver 1800W output power. Each module in the MISO is rated at 600W and they share the output power equally. Hardware results show that the converter produces 1800W of output power from three sources with 96.4% efficiency. Each module also demonstrates equal sharing feature of the MISO converter.
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Makarynska, Dina. "Theoretical and numerical modelling of the effect of viscous and viscoelastic fluids on elastic properties of saturated rocks". Thesis, Curtin University, 2010. http://hdl.handle.net/20.500.11937/289.
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Rock physics is an essential link connecting seismic data to the properties of rocks and fluids in the subsurface. One of the most fundamental questions of rock physics is how to model the effects of pore fluids on rock velocity and density. Contemporary scientific computing allows geophysicists to conduct extremely complex virtual (computational) experiments on realistic digital representations of complex porous media, and thus directly relate the measurable properties of the media to their microstructure and saturation. Computational (digital) rock physics can also serve as an effective tool in examining new and existing rock physics models. The finite element method (FEM) has been proved effective in simulations of the linear elastic properties of porous rock under static conditions. In this thesis, FEM is used to study the effect of patchy saturation on elastic velocities of digital images of rocks. However, FEM belongs to a group of grid methods, and its accuracy is limited by discretization errors. This can cause errors in rock property predictions and needs to be thoroughly examined. In this thesis, a test scenario based on rigorous theories for grid-based methods such as FEM is developed, which allows establishing optimal computational parameters in terms of accuracy of the results and time cost of computations.Gassmann’s equations are the most widely used relations to predict velocity changes resulting from different pore fluid saturations. This problem is also known as fluid substitution. Despite the popularity of Gassmann’s equations and their incorporation in most software packages for seismic reservoir interpretation, important aspects of these equations such as sensitivity to microheterogeneity has not been thoroughly examined. In this thesis, the sensitivity of Gassmann’s equations to microheterogeneity is estimated for different quartz/clay porous mixtures using computational (FEM) simulations. The results of this study suggest that the accuracy of Gassmann’s fluid substitution remains adequate for a wide variety of highly porous rocks even if the contrast between the elastic properties of mineral constituents is large.While Gassmann’s fluid substitution is robust for rocks saturated with Newtonian fluids (brine, gas, light oil), it breaks down for viscoelastic fluids such as heavy oils. An alternative fluid substitution scheme for rocks saturated with viscoelastic fluids based on self-consistent effective medium theory is proposed in this thesis. Comparison with laboratory measurements shows that the scheme realistically estimates the frequency- and temperature dependent properties of heavyoil rocks and can be used for practical applications.A useful tool for modelling and estimation of properties of rocks with arbitrary or unknown microstructure are rigorous bounds on elastic moduli. The common elastic bounding methods such as Hashin-Shtrikman bounds are not applicable for heavy-oil rocks because of viscoelastic rheology of heavy oils. In this work, it is demonstrated that the viscoelastic bounding method of Milton and Berryman for the effective shear modulus of a two phase three-dimensional isotropic composite provides rigorous bounds for dispersion and attenuation of elastic waves in heavy-oil rocks. In particular, computation of these bounds shows that dispersion and attenuation in a rock saturated with a fluid (viscous or viscoelastic) can be much stronger than in the free fluid. This phenomenon is caused by wave-induced fluid flow relative to the solid. At sonic and ultrasonic frequencies, dispersion and attenuation appears to be dominated by the local (pore-scale) flow between pores of different shapes and orientations. The Mavko and Jizba expressions for the so-called unrelaxed frame bulk and shear moduli are one of the most popular quantitative models of squirt dispersion. However, these expressions are limited to liquidsaturated rocks and high frequency. In this thesis, The Mavko-Jizba relations are generalized to gas-saturated rocks. Furthermore, dispersion and attenuation is computed using a new squirt flow model, presented in this thesis. All the parameters in this model can be independently measured or estimated from measurements. The model gives complex frequency- and pressure-dependent effective bulk and shear moduli of a rock consistent with laboratory measurements.Variation of elastic properties of rocks with pressure is often modelled using penny-shaped or spheroidal cracks as idealization of real crack/pore geometry. In this doctorate, the validity of this approach is analysed by extracting the ratios of shear to bulk stress sensitivity coefficients, and normal to tangential compliances from ultrasonic measurements on a number of dry sandstone samples. The ratios show large scatter and, for a large number of dry sandstone samples, are not consistent with spheroidal crack theory. This inconsistency results in significantly different estimates of crack density from bulk and shear moduli, and in deviation of predicted pressure variation of Poisson’s ratio from the measured data.
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Vokatý, Vojtěch. "Mechanické vlastnosti lamelového materiálu". Master's thesis, Česká zemědělská univerzita v Praze, 2016. http://www.nusl.cz/ntk/nusl-256876.
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This thesis evaluated experimental research on the influence of selected factors (species, thickness, density, number of stress cycles) on the specified material characteristics (modulus of elasticity, modulus of rupture, limit of proportionality, bendability coefficient). The measured values were statistically evaluated and expressed in tables and graphs. Beech (Fagus Sylvatica L.) was selected to represent hardwood and aspen (Populus Tremula L.) softwood.
Tree species affects all observed characteristics. The results show that the modulus of elasticity increases with increasing densification of the material, but decreases with the increasing thickness of the material. A similar dependence is observed even with the modulus of rupture and limit of proportionality, which is also dependent on the number of cycles. The bendability coefficient is affected by material thickness.
It is expected that based on the evaluation of the results it will be possible to design materials with tailored properties.
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Mandrioli, Riccardo. "A modular interleaved converter for output current ripple minimization in dc fast chargers for electric vehicles". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amslaurea.unibo.it/18995/.
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In this work, a DC off-board fast battery charger topology is presented, designed, and tested. It is expected to be able to fight the range anxiety by significantly diminish the EVs' charging times up to 15-20 minutes, meanwhile keeping low manufacturing, Operation and Maintenance (O&M) costs.
The charger is made out of two main power stages the AC/DC and DC/DC converters. In order to keep the costs lower as possible, both parts are designed using interleaved topologies organized by using the same two-level three-phase modules coupled through reactors. This architecture allows to use the already well-known industrial three-phase modules taking advantage of the benefits guaranteed by mass production and at the same time permitting an effortless expansion thanks to its modularity. Thanks to the interleaved connections, it is possible to reach a high efficiency by distributing current and power evenly among the legs. Furthermore, this topology can handle bidirectional power flows, and it might be used for operating in both Grid to Vehicle (G2V) and Vehicle to Grid (V2G) modalities. In order to reduce the dimensions, and the costs of the filters, a control strategy able to keep a zero current ripple at any operative condition is developed. The proposed charger architecture uses an AC input BUS followed by an active rectifier stage. A ripple-free strategy acts on the variable DC BUS voltage according to the chopper duty cycle keeping the current ripple null. Meanwhile, DC/DC provides the requested output current. This strategy involves the AC/DC with the tasks to regulate the DC BUS voltage level and correcting the input power factor.
A model-based control system ensures that every leg’s current follows an average current reference signal. Legs’ currents are actively rebalanced throughout a current rebalancing network.
Finally, the simulation results are carried out trough MATLAB Simulink and validated with laboratory measurements on an adequately scaled prototype.
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Hussein, Hussein. "Contribution to digital microrobotics : modeling, design and fabrication of curved beams, U-shaped actuators and multistable microrobots". Thesis, Besançon, 2015. http://www.theses.fr/2015BESA2048/document.
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Un nombre de sujets concernant la microrobotique numérique ont été abordés dans le cadre de cette the` se. Une nouvelle génération du microrobot numérique ”DiMiBot” a e´ te´ proposé ce qui rend le DiMiBot plus précis, plus contrôlable et plus petit. La nouvelle structure est formée de deux modules multistables seulement, ce qui ajoute des fonctionnalités´ s importantes comme l’augmentation du nombre de positions avec une taille plus réduite et la capacité´ de réaliser des trajectoires complexes dans l’espace de travail. Le principe du nouveau module multistable combine les avantages des microactionneurs pas à pas en termes du principe et du concept numérique en termes de la répétabilité et la robustesse en boucle ouverte. Un mécanisme de positionnement précis, capable de compenser les incertitudes de fabrication a e´ te´ développé et utilise´ pour assurer un positionnement précis. En parallèle, des modèles analytiques ont e´ te´ développés pour les principaux composants dans le DiMiBot: poutres flambées préformées et actionneurs e´ électrothermiques en U. Des méthodes de conception ont été développées par la suite qui permettent de choisir les dimensions optimales garantissant les performances requises en respectant les spécifications et limites de design. Des prototypes de modules multistables, fabrique´ s dans la salle Blanche MIMENTO, ont montré´ un bon Fonctionnement dans les expériencesA number of topics concerning digital microrobotics were addressed in this thesis. A new generation of the digital microrobot ”DiMiBot” was proposed with several advantages making the DiMiBot more accurate, more controllable and smaller. The new structure consists of only two multistable modules which adds some important features such as increasing the number of positions with smaller size and the ability to realize complex trajectories in the workspace. The principle of the new multistable module combines the advantages of the stepping microactuators in terms of the principle and of the digital concept in terms of the repeatability and robustness without feedback. The accuracy is ensured with an accurate positioning mechanism that compensate the fabrication tolerances. In parallel, analytical models was developed for the main components in the DiMiBot: preshaped curved beams and U-shaped electrothermal actuators. Subsequently, design methods were developed that allow choosing the optimal dimensions that ensure the desired outputs and respecting the design specifications and limitations. Multistable module prototypes, fabricated in the clean room MIMENTO, showed a proper functioning in the experiments
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Malou, Amokrane. "A study on an integrated 4-Switch Buck-Boost DC-DC converter with high efficiency for portable applications". Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEI027.
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L’augmentation des performances des produits portables requièrent une exploitation la plus efficace possible de la batterie afin de permettre à ces produits d’être utilisés le plus longtemps possible avant d’être rechargés. Les circuits en aval ont besoin d’une source de tension stable qui peut varier pour chacun d’entre eux entre 1.0 V et 5.5 V à partir d’une tension d’entrée pouvant varier entre 2.5V et 5V. Un convertisseur DC-DC à 4 interrupteurs de type dévolteur-survolteur apparait comme une solution intéressante permettant des opérations de diminutions et d’augmentations de tension d’une part, et d’autres part le meilleur compromis entre rendement, performances dynamiques et coûts (en termes de place occupée sur le Silicium et sur la carte). ON Semiconductor a développé et produit un prototype en technologie CMOS 0.25 µm (procédé propriétaire) d’un tel convertisseur qui sert d’étude de cas pour la thèse. Le convertisseur opère selon plusieurs modes de fonctionnement (mode dévolteur, mode survolteur et mode dévolteur-survolteur) à cause d’un impératif de fonctionnement en fréquence de commutation fixe. Le mode dévolteur-survolteur est le sujet principal traité dans la thèse. Le mode dévolteur-survolteur, aussi appelé mode de transition, peut être implémenté via plusieurs Séquences de Topologie (SdT) possibles. Trois SdTs sont comparées en termes de rendement parmi lesquelles figure la SdT implémentée par le prototype. Les performances dynamiques du convertisseur dans ses différents mode de fonctionnement sont ensuite étudiées en dérivant les expressions analytiques des fonctions de transfert qui les caractérisent. Les modèles dérivés dans Matlab et Mathcad pour évaluer le rendement et les performances dynamiques du convertisseur sont ensuite utilisés pour développer un outil servant à obtenir un dimensionnement rapide de la boucle de contrôle du convertisseur. À partir de cette étape, la stabilité du convertisseur dans ses différents modes de fonctionnement est analysée en utilisant la théorie de Floquet et un modèle échantillonné-linéarisé du convertisseur permettant l’établissement d’une méthodologie de conception d’un tel convertisseur. Enfin, pour améliorer le rendement en mode de transition pour tous les points de fonctionnement, un algorithme contrôlant la valeur de l’hystérésis du comparateur utilisé dans la boucle de contrôle a été développé en Verilog, simulé dans l’environnement CADENCE et implémenté en FPGA. Cet algorithme peut améliorer le rendement de près de 3% en mode de transition comparé au réglage initial de la valeur d’hystérésisThe increase in the performances of the portable devices calls for an energy conversion from the battery that is the most efficient as possible in order to make the devices last as long as possible. The downstream circuits need a steady voltage supply which can vary for each one of them from 1.0 V to 5.5 V from an input voltage varying between 2.5 V and 5 V. A 4-Switch Buck-Boost (4SBB) DC-DC converter appears to be the solution which can perform step-up and step-down voltage perations and get the best trade-off between fficiency, dynamic performances and costs (in terms of Silicium and Board area). ON Semiconductor has developed and taped out in CMOS 0.25 µm (ON Semiconductor process) a 4SBB converter which serves as the case study of the thesis. The converter operates in multiple modes (namely Buck mode, Boost mode and Buck-Boost mode) due to fixed frequency operations. The Buck-Boost mode is the main topic dealt with in the thesis. The Buck-Boost mode, also called "transition mode", can be implemented using several possible Sequences of Topologies (SoT). Three SoTs are compared in terms of efficiency among which the one implemented in the converter. Then the dynamical performances of the converter are studied for the different modes of operations by deriving the analytical expressions of the relevant transfer functions. The models derived in Matlab and Mathcad to evaluate efficiency and dynamical performances are then used to develop a tool to get a rapid sizing of the converter’s control loop components. From this step, the stability of the converter is analyzed using Floquet’s theory and Sampled-Data modeling enabling the building of a design methodology to design such a converter. Finally, to enhance efficiency in Buck-Boost mode whatever the working conditions, an algorithm controlling the hysteresis value of the control loop’s comparator has been developed in Verilog, simulated in CADENCE and implemented in FPGA. This algorithm can improve efficiency by almost 3% in Buck-Boost mode compared to its default setting
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Akinyemi, Segun Ajayi. "Geochemical and mineralogical evaluation of toxic contaminants mobility in weathered coal fly ash: as a case study, Tutuka dump site, South Africa". Thesis, University of the Western Cape, 2011. http://etd.uwc.ac.za/index.php?module=etd&action=viewtitle&id=gen8Srv25Nme4_1226_1360593017.
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The management and disposal of huge volumes of coal combustion by products such as fly ash has constituted a major challenge to the environment. In most cases due to the inadequate alternative use of coal fly ash, the discarded waste is stored in holding ponds, slag heaps, or stock piled in ash dumps. This practice has raised concerns on the prospect of inorganic metals release to the surface and groundwater in the vicinity of the ash dump. Acceptable scientific studies are lacking to determine the best ash disposal practices. Moreover, knowledge about the mobility patterns of inorganic species as a function of mineralogical association or pH susceptibility of the dry disposed ash dump under natural weathering conditions are scarce in the literature. Fundamental understanding of chemical interactions of dry disposed ash with ingressed CO2 from atmosphere, percolating rain water and brine irrigation within ash disposal sites were seen as key areas requiring investigation. The mineralogical association of inorganic species in the dry disposed ash cores can be identified and quantified. This would provide a basis for understanding of chemical weathering, mineralogical transformations or mobility patterns of these inorganic species in the dry ash disposal scenario. The current study therefore aims to provide a comprehensive characterisation of weathered dry disposed ash cores, to reveal mobility patterns of chemical species as a function of depth and age of ash, with a view to assessing the potential environmental impacts. Fifty-nine samples were taken from 3 drilled cores obtained respectively from the 1 year, 8 year and 20-year-old sections of sequentially dumped,
weathered, dry disposed ash in an ash dump site at Tutuka - a South African coal burning power station. The core samples were characterized using standard analytical procedures viz: X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier transforms infrared (FTIR) techniques, Scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) and Acid neutralisation capacity (ANC) test. A modified sequential extraction (SE) method was used in this study. The chemical partitioning, mobility and weathering patterns in 1 year, 8 year and 20-year-old sections of the ash dump were respectively investigated using this modified sequential extraction scheme. The sequence of the extractions was as follows: (1) water soluble, (2) exchangeable, (3) carbonate, (4) iron and manganese and (5) residual. The results obtained from the 5 steps sequential extraction scheme were validated with the total metal content of the original sample using mass balance method. The distribution of major and trace elements in the different liquid fractions obtained after each step of sequential extraction of the 59 drilled core samples was determined by inductively coupled plasma mass spectrometry (ICPMS). The data generated for various ash core samples were explored for the systematic analysis of mineralogical transformation and change in ash chemistry with ageing of the ash. Furthermore, the data was analyzed to reveal the impact of ingressed CO2 from atmosphere, infiltrating rain water and brine irrigation on the chemistry of ash core samples. Major mineral phases in original ash core samples prior to extraction are quartz (SiO2) and mullite (3Al2O3·
2SiO2). Other minor mineral phases identified were hematite (Fe2O3), calcite (CaCO3), lime (CaO), anorthite (CaAl2Si2O8), mica (Ca (Mg, Al)3 (Al3Si) O10 (OH)2), and enstatite (Mg2Si2O6). X-ray diffraction results show significant loss of crystallinity in the older ash cores. The presence of minor phases of calcite and mica in dry disposed ash cores are attributed to reduction in the pore water pH due to hydration, carbonation and pozzolanic reactions. The X-ray diffraction technique was unable to detect Fe-oxyhydroxide phase and morealuminosilicate phases in ash core samples due to their low abundance and amorphous character. X-ray fluorescence results of the original ash core samples showed the presence of major oxides, such as SiO2, Al2O3, Fe2O3, while CaO, K2O, TiO2, Na2O, MnO, MgO, P2O5, and SO3 occur in minor concentrations. The ratio of SiO2/Al2O3 classified the original core samples prior to extraction as a silico-aluminate class F fly ash. The ternary plot of major elements in 1-year-old ash core samples was both sialic and ferrocalsialic but 8 year and 20-year-old ash core samples were sialic in chemical composition. It is noteworthy that the mass % of SiO2 varies through the depth of the core with an increase of nearly 3 %, to 58 mass % of SiO2 at a depth of 6 m in the 1-year-old core whereas in the case of the 8-year-old core a 2 % increase of SiO2 to a level of 57.5 mass % can be observed at levels between 4-8 m, showing dissolution of major components in the matrix of older ash cores.. The Na2O content of the Tutuka ash cores was low and varied between 0.6-1.1 mass % for 1-year-old ash cores to around 0.6-0.8 mass % for 8-year-old ash cores. Sodium levels were higher in 1-year-old ash cores compared to 8 year and 20-year-old ashcores. Observed trends indicate that quick weathering of the ash (within a year) leached out Na+ from the ash dump. No evidence of Na+ encapsulation even though the ash dump was brine irrigated. Thus the dry disposal ash placement method does not result in a sustainable salt sink for Na-containing species over time. The total content of each of the elements in 1 year and 20-year-old ash cores was normalised with their total content in fresh ash from same power station to show enrichment and depletion factor. Major elements such as K+, Mn showed enrichment in 1-year-old ash cores whereas Al, Si, Na+, Ti, Ca, Mg, S and Fe showed depletion due to over time erosion. Trace elements such as Cr, Sr, P, Ba, Pb, V and Zn showed enrichment but Ni, Y, Zr showed depletion attributed to over time erosion. In 20-year-old ash cores, major elements such as Al, Na+ and Mn showed enrichment while Si, K+, Fe, Mg and Ca showed depletion highlighting their mobility. Trends indicated intensive flushing of major soluble components such as buffering constituents (CaO) by percolating rain water. The 1-year-old and 20-year-old coal ash cores showed a lower pH and greater loss/depletion of the soluble buffering constituents than the 2-week-old placed ash, indicating significant chemical weathering within a year. Based
on ANC results the leaching behaviours of Ca, Mg, Na+, K+, Se, Cr, and Sr were found to be controlled by the pH of the leachant indicating high mobility of major soluble species in the ash cores when in contact with slightly acid rain water. Other investigated toxic metals such as As, Mo and Pb showed amphoteric behaviour with respect to the pH of the leachant. Chemical alterations and formation of transient minor secondary mineral phases was found to have a significant effect on the acid susceptibility and depletion pattern of chemical species in the core ash samples when compared to fresh ash. These ANC results correlated well with the data generated from the sequential extraction scheme. Based on sequential extraction results elements, showed noticeable mobility in the water soluble, exchangeable and carbonate fractions due to adsorption and desorption caused by variations in the pore water pH. In contrast, slight mobility of elements in the Fe and Mn, and residual fractions of dry disposed fly ashes are attributed to the co-precipitation and dissolution of minor amount of less soluble secondary phase overtime. The 1-year-old dry disposed ash cores were the least weathered among the 3 drilled ash cores. Therefore low concentration of toxic metals in older ash cores were ascribed to extensive weathering with slower release from residual mineral phases over time. Elements were found to associate with different mineral phases depending on the age or depth of the core samples showing greater heterogeneity in dispersion. For instance the average amount of total calcium in different mineral associations of 1-year-old ash cores is as follows
water soluble (10.2 %), exchangeable (37.04 %), carbonate (37.9 %), Fe and Mn (7.1 %) and residual (2.97 %). The amount of total Na+ in different mineral phases of 1-year-old ash cores followed this trend: water soluble (21 %), exchangeable (11.26 %), carbonate (2.6 %), Fe and Mn (4.7 %) and residual (53.9 %). The non-leachable portion of the total Na+ content (namely that contained in the residual fraction) in the 1-year-old ash core samples under conditions found in nature ranged between 5-91 %. This non-leachable portion of the Na+ showed the metastability of the mineral phases with which residual Na+ associates. Results showed older ash cores are enriched in toxic elements. Toxic elements such as As, B, Cr, Mo and Pb are enriched in the residual fraction of older ash cores. For instance As concentration in the residual fraction varied between 0.0003- 0.00043 mg kg-1 for 1-year-old ash cores to around 0.0003-0.0015 mg kg-1 for 20-year-old ash cores. This suggests that the older ash is enriched in toxic elements hence dust from the ash dump would be toxic to human health. The knowledge of mobility and ecotoxicological significance of coal fly ash is needed when considering its disposal or reuse in the environment. The mobility and ecotoxicology of inorganic metals in coal fly ash are determined by (i) mineralogical associations of inorganic species (ii) in-homogeneity in the ash dumps (iii) long and short term exposure to ingress CO2 and percolating rain water. Management issues such as inconsistent placement of ash in the dumps, poor choice of ash dump site, in-homogeneity in brine irrigation, no record of salt load put on the ash dumps and lack of proper monitoring requires improvement. The thesis provides justification for the use of the modified sequential extraction scheme as a predictive tool and could be employed in a similar research work. This thesis also proved that the dry ash disposal method was not environmental friendly in terms of overall leaching potential after significant chemical weathering. Moreover the study proved that the practice of brine co-disposal or irrigation on ash dumps is not sustainable as the ash dump did not act as a salt sink.
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Müller, Max [Verfasser], i Veronica [Akademischer Betreuer] Egger. "Dendritic integration in olfactory bulb granule cells: Thresholds for lateral inhibition and role of active conductances upon 3D multi-site photostimulation of spines using a holographic projector module / Max Müller ; Betreuer: Veronica Egger". Regensburg : Universitätsbibliothek Regensburg, 2020. http://d-nb.info/1211556727/34.
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Freitas, Pedro Augusto Ramos de. "Proposta de um compensador sériie de tensão de elevada dinâmica para a correção da tensão instantânea da carga diante de afundamentos ou elevações da tensão da rede elétrica". Universidade Federal de Uberlândia, 2014. https://repositorio.ufu.br/handle/123456789/14580.
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This paper proposes two new topological arrangements consisting in connecting the AC power supply in series with two DC converters, one operating during the positive half-cycle and the other during the negative half cycle. It is noteworthy that these DC converters in series in a case are Buck EIE converters and on the other a buck. The results obtained with both arrangements are analyzed and compared. The control strategy is developed with the goal of imposing an AC voltage output within the limits imposed by the rules in order to mitigate the problems associated with Sags and Swells from the AC power supply . The principles of operation as well as the experimental and simulation results obtained in both steady and transient state are presented and validated for a 1kVA experimental prototype. Finally, some works still on progress related to this dissertation are presented, like the multilevel compensation and the three phase compensation.Este trabalho propõe dois novos arranjos topológicos que consistem em se conectar a alimentação CA em série com dois conversores CC, um para operar durante o semiciclo positivo e o outro durante o semiciclo negativo. Vale ressaltar que estes conversores CC em série, em um caso são conversores Buck EIE e no outro um conversor Buck. Os resultados obtidos com ambos os arranjos são analisados e comparados. A estratégia de controle é desenvolvida com o intuito de impor uma tensão de saída CA dentro dos limites impostos pelas normas de forma a mitigar os problemas associados com Sags e Swells da rede de alimentação CA. Os princípios de operação, os resultados experimentais e de simulação obtidos, tanto em regime permanente quanto em condições transitórias de operação, são apresentados e validados para um protótipo experimental de 1kVA. Por fim apresentam-se os trabalhos relacionados a esta dissertação que ainda estão em desenvolvimento, que são a compensação em multinível e a compensação trifásica.
Mestre em Ciências
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Elamalayil, Soman Deepak. "Multilevel Power Converters with Smart Control for Wave Energy Conversion". Doctoral thesis, Uppsala universitet, Elektricitetslära, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-332730.
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The main focus of this thesis is on the power electronic converter system challenges associated with the grid integration of variable-renewable-energy (VRE) sources like wave, marine current, tidal, wind, solar etc. Wave energy conversion with grid integration is used as the key reference, considering its high energy potential to support the future clean energy requirements and due the availability of a test facility at Uppsala University. The emphasis is on the DC-link power conditioning and grid coupling of direct driven wave energy converters (DDWECs). The DDWEC reflects the random nature of its input energy to its output voltage wave shape. Thereby, it demands for intelligent power conversion techniques to facilitate the grid connection. One option is to improve and adapt an already existing, simple and reliable multilevel power converter technology, using smart control strategies. The proposed WECs to grid interconnection system consists of uncontrolled three-phase rectifiers, three-level boost converter(TLBC) or three-level buck-boost converter (TLBBC) and a three-level neutral point clamped (TLNPC) inverter. A new method for pulse delay control for the active balancing of DC-link capacitor voltages by using TLBC/TLBBC is presented. Duty-ratio and pulse delay control methods are combined for obtaining better voltage regulation at the DC-link and for achieving higher controllability range. The classic voltage balancing problem of the NPC inverter input, is solved efficiently using the above technique. A synchronous current compensator is used for the NPC inverter based grid coupling. Various results from both simulation and hardware testing show that the required power conditioning and power flow control can be obtained from the proposed multilevel multistage converter system. The entire control strategies are implemented in Xilinx Virtex 5 FPGA, inside National Instruments’ CompactRIO system using LabVIEW. A contour based dead-time harmonic analysis method for TLNPC and the possibilities of having various interconnection strategies of WEC-rectifier units to complement the power converter efforts for stabilizing the DC-link, are also presented. An advanced future AC2AC direct power converter system based on Modular multilevel converter (MMC) structure developed at Siemens AG is presented briefly to demonstrate the future trends in this area.
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Osiowy, Kimber B. P. "The bulk modulus, shear modulus, and Poisson's ratio of isotropic ice tested in creep". 1989. http://hdl.handle.net/1993/16977.
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huang, ji-jie, i 黃基杰. "Numerical modelling of the effective plane strain bulk modulus of composite materials". Thesis, 1996. http://ndltd.ncl.edu.tw/handle/54004370888153062688.
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SINGH, UTKARSH. "SOME STUDIES ON SURFACE TENSION, VISCOSITY AND BULK MODULUS OF COMPRESSIBILITY OF BIODIESELS BY DEVELOPING MATLAB MATHEMATICAL MODELS". Thesis, 2019. http://dspace.dtu.ac.in:8080/jspui/handle/repository/16773.
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The future for biodiesels relies heavily on the optimization of the thermo-physical properties such as the surface tension, viscosity and bulk modulus of compressibility of biodiesels. These three properties play a crucial role in the atomization of fuel, pre – combustion of fuel, knocking tendency and ignition timing of the fuel respectively. Estimation of the properties could give a good insight about these properties and also about what can be done further to alter those values to be in the ASTM range defined. Hence a proper understanding of these parameters with their values is essential. The values of surface tension, viscosity and bulk modulus of compressibility can be predicted by developing mathematical models which function on the values of properties of the biodiesel such as density, FAMEs composition of biodiesel in mass fraction, temperature, speed if sound in biodiesel, individual values of surface tension and viscosity of FAMEs of the biodiesel etc. For prediction of surface tension, three models in MATLAB have been developed, a single model in MATLAB for prediction of viscosity of biodiesels and a single model in MATLAB for prediction of bulk modulus of compressibility of biodiesels. The values of the properties were estimated and then made to compare with the values of those properties found experimentally using various equipments mentioned in this thesis. The biodiesels taken into consideration for value prediction of properties on MATLAB models are: karanja, jatropha, soybean, palm, sunflower and rapeseed. The FAMEs composition of biodiesels, individual values of surface tension and viscosity of FAMEs have been taken from literature survey.
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Bakhorji, Aiman M. "Laboratory measurements of static and dynamic elastic properties in carbonate". Phd thesis, 2010. http://hdl.handle.net/10048/908.
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Thesis (Ph. D.)--University of Alberta, 2010.Title from pdf file main screen (viewed on Mar. 18, 2010). A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Geophysics, Department of Physics, University of Alberta. Includes bibliographical references.
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"Modeling and experimental evaluation of the effective bulk modulus for a mixture of hydraulic oil and air". Thesis, 2013. http://hdl.handle.net/10388/ETD-2013-09-1225.
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The bulk modulus of pure hydraulic oil and its dependency on pressure and temperature has been studied extensively over the past years. A comprehensive review of some of the more common definitions of fluid bulk modulus is conducted and comments on some of the confusion over definitions and different methods of measuring the fluid bulk modulus are presented in this thesis.
In practice, it is known that there is always some form of air present in hydraulic systems which substantially decreases the oil bulk modulus. The term effective bulk modulus is used to account for the effect of air and/or the compliance of transmission lines. A summary from the literature of the effective bulk modulus models for a mixture of hydraulic oil and air is presented. Based on the reviews, these models are divided into two groups: “compression only” models and “compression and dissolve” models.
A comparison of various “compression only” models, where only the volumetric compression of air is considered, shows that the models do not match each other at the same operating conditions. The reason for this difference is explained and after applying some modifications to the models, a theoretical model of the “compression only” model is suggested.
The “compression and dissolve” models, obtained from the literature review, include the effects of the volumetric compression of air and the volumetric reduction of air due to the dissolving of air into the oil. It is found that the existing “compression and dissolve” models have a discontinuity at some critical pressure and as a result do not match the experimental results very well. The reason for the discontinuity is discussed and a new “compression and dissolve” model is proposed by introducing some new parameters to the theoretical model.
A new critical pressure (PC) definition is presented based on the saturation limit of oil. In the new definition, the air stops dissolving into the oil after this critical pressure is reached and any remaining air will be only compressed afterwards.
An experimental procedure is successfully designed and fabricated to verify the new proposed models and to reproduce the operating conditions that underlie the model assumptions. The pressure range is 0 to 6.9 MPa and the temperature is kept constant at °C. Air is added to the oil in different forms and the amount of air varies from about 1 to 5%. Experiments are conducted in three different phases: baseline (without adding air to the oil), lumped air (air added as a pocket of air to the top of the oil column) and distributed air (air is distributed in the oil in the form of small air bubbles). The effect of different forms and amounts of air and various volume change rates are investigated experimentally and it is shown that the value of PC is strongly affected by the volume change rate, the form, and the amount of air. It is also shown that the new model can represent the experimental data with great accuracy.
The new proposed “compression and dissolve” model can be considered as a general model of the effective bulk modulus of a mixture of oil and air where it is applicable to any form of a mixture of hydraulic oil and air. However, it is required to identify model parameters using experimental measurements. A method of identifying the model parameters is introduced and the modeling errors are evaluated. An attempt is also made to verify independently the value of some of the parameters.
The new proposed model can be used in analyzing pressure variations and improving the accuracy of the simulations in low pressure hydraulic systems. The new method of modeling the air dissolving into the oil can be also used to improve the modeling of cavitation phenomena in hydraulic systems.
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Motamed, Arash. "Constitutive modeling of viscoelastic behavior of bituminous materials". Thesis, 2012. http://hdl.handle.net/2152/23464.
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Asphalt mixtures are complex composites that comprise aggregate, asphalt binder, and air. Several research studies have shown that the mechanical behavior of the asphalt mixture is strongly influenced by the matrix, i.e. the asphalt binder. Therefore, accurate constitutive models for the asphalt binders are critical to ensure accurate performance predictions at a material and structural level. However, researchers who use computational methods to model the micromechanics of asphalt mixtures typically assume that (i) asphalt binders behave linearly in shear, and (ii) either bulk modulus or Poisson’s ratio of asphalt binders is not time dependent. This research develops an approach to measure and model the shear and bulk behavior of asphalt binders at intermediate temperatures. First, this research presents the findings from a systematic investigation into the nature of the linear and nonlinear response of asphalt binders subjected to shear using a Dynamic Shear Rheometer (DSR). The DSR test results showed that under certain conditions a compressive normal force was generated in an axially constrained specimen subjected to cyclic torque histories. This normal force could not be solely attributed to the Poynting effect and was also related to the tendency of the asphalt binder to dilate when subjected to shear loads. The generated normal force changed the state of stress and interacted with the shear behavior of asphalt binder. This effect was considered to be an “interaction nonlinearity” or “three dimensional effect”. A constitutive model was identified to accommodate this effect. The model was successfully validated for several different loading histories. Finally, this study investigated the time-dependence of the bulk modulus of asphalt binders. To this end, poker-chip geometries with high aspect ratios were used. The boundary value problem for the poker-chip geometry under step displacement loading was solved to determine the bulk modulus and Poisson’s ratio of asphalt binders as a function of time. The findings from this research not only improve the understanding of asphaltic materials behavior, but also provide tools required to accurately predict pavement performance.text
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Luchini, Bruno. "Processing and properties of bulk and cellular carbon-bonded refractory materials". 2019. https://tubaf.qucosa.de/id/qucosa%3A35080.
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In this manuscript, distinct problems concerning carbon-bonded materials processing and characterization were analyzed, from bulk to cellular samples. The main motivation was to address central topics that would enhance the comprehension of the material’s behavior, as well as trigger targeted improvements. Some of the topics this thesis covers are: Non-linear Young’s modulus behavior of carbon-bonded alumina at high temperatures; Influence of the processing route on the cold crushing strength of carbon-bonded alumina foam filters; Geometric characterization of ceramic foam filters as a tool to understand processing parameters; Use of advanced techniques such as computer tomography and finite element modelling to correlate processing parameters and mechanical behavior. In most of the analyses, non-standard computational strategies were adopted. In those cases, algorithms were written to facilitate the evaluations, or even enable it in the first place. All the algorithms’ concepts are described in this thesis and their codes are available in the Appendices. The current work was carried out within the framework of the Collaborative Research Center 920 (CRC 920) “Multifunctional filters for metal melt filtration - a contribution to zero defect materials” at the Technische Universität Bergakademie Freiberg funded by the German Research Foundation (DFG).
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Miranda, Caetano R., i Toshifumi Matsuoka. "FIRST-PRINCIPLES STUDY ON MECHANICAL PROPERTIES OF CH4 HYDRATE". 2008. http://hdl.handle.net/2429/1068.
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The structural and mechanical properties of s-I methane hydrate have been investigated by first
principles calculations. For the first time, the fully elastic constant tensor of s-I methane hydrate
is obtained entirely ab-initio. The calculated lattice parameter, bulk modulus, and elastic
constants were found to be in good agreement with experimental data at ambient pressure. The
Young modulus, Poisson ratio and bulk sound velocities are estimated from the calculated
elastic constants and compared with wave speed measurements available.
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Locht, Inka Laura Marie. "Cohesive and Spectroscopic properties of the Lanthanides within the Hubbard I Approximation". Licentiate thesis, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-267285.
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We describe the rare-earth elements using the Hubbard I approximation. We show that the theory reproduces the cohesive properties, like the volume and bulk modulus, and we find an excellent agreement between theory and experiment for the (inverse) photo emission spectra of the valence band. In addition we reproduce the spin and orbital moments of these elements. This licentiate thesis contains an introduction to the cohesive, magnetic and spectral properties of the rare-earth elements, to density functional theory and to density functional theory in combination with dynamical mean-field theory within the Hubbard I approximation. We also focus on some technical details, e.g. the optimal basis used in the electronic structure code and the role of charge self-consistency in properly describing the valence electrons.
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Jian, Jhen-Yu, i 簡振宇. "Charging Scenario for Serial Buck-Boost Type Battery Power Modules". Thesis, 2013. http://ndltd.ncl.edu.tw/handle/57629112434006299081.
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碩士國立中山大學
電機工程學系研究所
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Battery power modules (BPMs) with bidirectional buck-boost converters, which are connected in series, are operated interactively but substantially can be controlled individually for either charging or discharging. During the charging process, the battery currents can be scheduled by adjusting the duty-ratios of the associated buck-boost converters. To fully utilize the charger’s capacity, several charging scenarios are proposed according to the state of charges (SOCs) of the batteries under the limitations of the charger’s power and current. To demonstrate the feasibility and capability of the charging scenarios, a battery power system formed by 4 serial buck-boost type BPMs is built and tested. A microcontroller is used for estimating the battery SOCs, and then scheduling the battery currents accordingly. Experimental results show the effectiveness of the charging scenarios.