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li, yiwen. "Predicting Hearing Loss Using Auditory Steady-State Responses." Digital WPI, 2009. https://digitalcommons.wpi.edu/etd-theses/84.
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Auditory Steady-State Response (ASSR) is a promising tool for detecting hearing loss. In this project, we analyzed hearing threshold data obtained from two ASSR methods and a gold standard, pure tone audiometry, applied to both normal and hearing-impaired subjects. We constructed a repeated measures linear model to identify factors that show significant differences in the mean response. The analysis shows that there are significant differences due to hearing status (normal or impaired) and ASSR method, and that there is a significant interaction between hearing status and test signal frequency. The second task of this project was to predict the PTA threshold (gold standard) from the ASSR-A and ASSR-B thresholds separately at each frequency, in order to measure how accurate the ASSR measurements are and to obtain a ¡°correction function¡± to correct the bias in the ASSR measurements. We used two approaches. In the first, we modeled the relation of the PTA responses to the ASSR values for the two hearing status groups as a mixture model and tried two prediction methods. The mixture modeling was successful, but the predictions gave disappointing results. A second approach, using logistic regression to predict group membership based on ASSR value and then using those predictions to obtain a predictor of the PTA value, gave successful results.
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Abdrachimovas, Ruslanas. "Objektinių modelių transformacijų realizavimas." Master's thesis, Lithuanian Academic Libraries Network (LABT), 2004. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2004~D_20040531_150600-88877.
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Presented work covers one of the most important areas of OMG’s model driven architecture (MDA) – problems of object model transformations. Based on research of OMG specifications and other sources, author analyzes transformation process, states importance of modeling and metamodeling for designing of UML like modeling languages. Research work describes designed metamodels of experimental modeling languages: “Entity – process”, Java metamodel and relational metamodel. Author gives a short overview of model editors for these languages, created using EMF framework tools. Based on analysis, author describes very flexible architecture of model transformation implementation, based on filter and pipes architectural pattern. Usage of this architecture gives flexibility to transformation implementation and allows easy and straightforward decomposition of transformation to separate stages. Designed filter and pipes transformation architecture was used for experimental transformation implementation. Research work presents quality and quantity based results of experimental transformations.
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Martinez, Baca Velasco Carlos. "Computational model of a PEM fuel cell." Thesis, Imperial College London, 2007. http://hdl.handle.net/10044/1/11519.
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Bi, Wu. "PEM fuel cell catalyst degradation mechanism and mathematical modeling." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/29756.
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Thesis (Ph.D)--Chemical Engineering, Georgia Institute of Technology, 2008.Committee Chair: Fuller, Thomas; Committee Co-Chair: Deng, Yulin; Committee Member: Gallivan, Martha; Committee Member: Kohl, Paul; Committee Member: Singh, Preet. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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McGrady, Christopher Dwain. "Linking Rheological and Processing Behavior to Molecular Structure in Sparsely-Branched Polyethylenes Using Constitutive Relationships." Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/37924.
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This dissertation works towards the larger objective of identifying and assessing the key features of molecular structure that lead to desired polymer processing performance with an ultimate goal of being able to tailor-make specific macromolecules that yield the desired processing response. A series of eight well-characterized, high-density polyethylene (HDPE) resins, with varying degrees of sparse long chain branching (LCB) content, is used to study the effect of both LCB content and distribution on the rheological and commercial processing response using the Pom-pom constitutive relationship. A flow instability known as ductile failure in extensional flow required the development a novel technique known as encapsulation in order to carry out shear-free rheological characterization.
Ductile failure prevents the rheological measurement of transient stress growth at higher strains for certain strain-hardening materials. This reduces the accuracy of nonlinear parameters for constitutive equations fit from transient stress growth data, as well as their effectiveness in modeling extensionally driven processes such as film casting. An experimental technique to overcome ductile failure called encapsulation in which the material that undergoes ductile failure is surrounded by a resin that readily deforms homogeneously at higher strains is introduced. A simple parallel model is shown to calculate the viscosity of the core material.
The effect of sparse long chain branching, LCB, on the film-casting process is analyzed at various drawdown ratios. A full rheological characterization in both shear and shear-free flows is also presented. At low drawdown ratios, the low-density polyethylenes, LDPE, exhibited the least degree of necking at distances less than the HDPE frostline. The sparsely-branched HDPE resins films had similar final film-widths that were larger than those of the linear HDPE. As the drawdown ratio was increased, film width profiles separated based on branching level. Small amounts of LCB were found to reduce the amount of necking at intermediate drawdown ratios. At higher drawdown ratios, the sparsely-branched HDPE resins of lower LCB had content film-widths that mimicked that of the linear HDPE, while the sparsely-branched HDPE resins of higher LCB content retained a larger film width. Molecular structural analysis via the Pom-pom constitutive model suggested that branching that was distributed across a larger range of backbone lengths serve to improve resistance to necking. As the drawdown ratio increased, the length of the backbones dominating the response decreased, so that the linear chains were controlling the necking behavior of the sparsely-branched resins of lower LCB content while remaining in branched regime for higher LCB content HDPEs. Other processing variables such as shear viscosity magnitude, extrudate swell, and non-isothermal processing conditions were eliminated as contributing factors to the differences in the film width profile.
The effect of sparse long chain branching, LCB, on the shear step-strain relaxation modulus is analyzed using a series of eight well-characterized, high-density polyethylene (HDPE) resins. The motivation for this work is in assessing the ability of step-strain flows to provide specific information about a material's branching architecture. Fundamental to this goal is proving the validity of relaxation moduli data at times shorter than the onset of time-strain separability. Strains of 1% to 1250% are imposed on materials with LCB content ranging from zero to 3.33 LCB per 10,000 carbon atoms. All materials are observed to obey time-strain separation beyond some characteristic time, Ï k. The presence of LCB is observed to increase the value of Ï k relative to the linear resin. Furthermore, the amount of LCB content is seen to correlate positively with increasing Ï k. The behavior of the relaxation modulus at times shorter than Ï k is investigated by an analysis of the enhancement seen in the linear relaxation modulus, G0(t), as a function of strain and LCB content. This enhancement is seen to 1) increase with increasing strain in all resins, 2) be significantly larger in the sparsely-branched HDPE resins relative to the linear HDPE resin, and 3) increase in magnitude with increasing LCB content. The shape and smoothness of the damping function is investigated to rule out the presence of wall-slip and material rupture during testing. The finite rise time to impose the desired strain is carefully monitored and compared to the Rouse relaxation time of the linear HDPE resins studied. Sparse LCB is found to increase the magnitude of the relaxation modulus at short times relative to the linear resin. It is shown that these differences are due to variations in the material architecture, specifically LCB content, and not because of mechanical anomalies.Ph. D.
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Sobral, Júnior Mário Alves. "Proposta de modelo para analisar desempenho do Programa de CCQ de uma empresa de eletroeletrônico do PIM." Universidade Federal do Amazonas, 2013. http://tede.ufam.edu.br/handle/tede/3556.
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Previous issue date: 2013-08-06The Circle of Quality Control consists on a group of employees who volunteer to support a company, whose goal is to identify, analyze and propose improvements to problems detected in work, besides focusing on professional development and improving the work environment. The company studied has increased focus on financial return of the QCC, having no tools to evaluate the attendant performances and the impact on the work environment In this context, this thesis developed a conceptual model to analyze the performance of the QCC program, at an electronic company located in the Industrial Pole of Manaus, by the perspective of the attendant .Therefore, a study was done based in the program used by the company, literature review and existing models. Based by the models and documentary research, an instrument for data collection was developed and applied together at 60 attendents (leaders and secretaries) in September 2012. From the final results, we developed a conceptual model and the main result has achieved good performance of the current program (80.6%), otherwise identifying further development dimensions related to the company and the work environment when compared with the development of the attendents. Were also identified several opportunities for improvement QCC program at the company.
O Círculo de Controle de Qualidade constitui-se de um grupo de colaboradores voluntários que com o suporte da empresa, têm por objetivo identificar, analisar e propor melhorias para problemas detectados no trabalho, além de focar no desenvolvimento profissional dos circulistas e na melhoria do ambiente de trabalho. A empresa em estudo tem maior foco no retorno financeiro do CCQ, não possuindo ferramenta para avaliar o seu desempenho em relação ao desenvolvimento do participante e do impacto na melhoria do ambiente de trabalho. Neste contexto, a presente dissertação desenvolveu uma proposta de modelo conceitual para analisar o desempenho do programa CCQ em uma empresa de eletroeletrônico no Polo Industrial de Manaus, sob a ótica do participante. Para tanto, foi realizado um estudo para levantar as características do programa CCQ utilizado pela empresa, além de revisão bibliográfica e de modelos existentes. Com base nos modelos e na pesquisa documental, um instrumento de coleta de dados foi desenvolvido e aplicado junto a 60 circulistas (líderes e secretários) em setembro de 2012. A partir da análise dos resultados, desenvolvemos o modelo conceitual e o principal resultado alcançado foi o bom desempenho geral do atual programa (80,6%), porém identificando maior desenvolvimento nas dimensões relacionadas à empresa e ao ambiente de trabalho quando comparados com o desenvolvimento dos circulistas. Também foram identificadas junto aos participantes diversas oportunidades de melhorias para o programa de CCQ da empresa.
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Sarmiento, Carnevali Maria Laura. "Modeling and control of PEM fuel cells." Doctoral thesis, Universitat Politècnica de Catalunya, 2017. http://hdl.handle.net/10803/667121.
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In recent years, the PEM fuel cell technology has been incorporated to the R&D plans of many key companies in the automotive, stationary power and portable electronics sectors. However, despite current developments, the technology is not mature enough to be significantly introduced into the energy market. Performance, durability and cost are the key challenges.
The performance and durability of PEM fue! cells significantly depend on variations in the concentrations of hydrogen and oxygen in the gas channels, water activity in the catalyst layers and other backing layers, water content in the polymer electrolyte membrane, as well as temperature, among other variables. Such variables exhibit intemal spatial dependence in the direction of the fuel and air streams of the anode and cathode. Highly non-uniform spatial distributions in PEM fuel cells result in local over-heating, cell flooding, accelerated ageing, and lower power output than expected.
Despite the importance of spatial variations of certain variables in PEM fuel cells, not many works available in the literature target the control of spatial profiles. Most control-oriented designs use lumped-parameter models because of their simplicity and convenience for controller performance. In contrast, this Doctoral Thesis targets the distributed parameter modelling and control of PEM fuel cells.
In the modelling part, the research addresses the detailed development of a non-linear distributed parameter model of a single PEM fuel cell, which incorporates the effects of spatial variations of variables that are relevant to its proper performance. The model is first used to analyse important cell intemal spatial profiles, and it is later simplified in arder to decrease its computational complexity and make it suitable for control purposes. In this task, two different model order reduction techniques are applied and compared.
The purpose of the control part is to tackle water management and supply of reactants, which are two major PEM fuel cell operation challenges with important degradation consequences. In this part of the Thesis, two decentralised control strategies based on distributed parameter model predictive controllers are designed, implemented and analysed via simulation environment State observers are also designed to estímate intemal unmeasurable spatial profiles necessary for the control action.
The aim of the first strategy is to monitor and control observed water activity spatial profiles on both sides of the membrana to appropriate levels. These target values are carefully chosen to combine proper membrane, catalyst layer and gas diffusion layer humídification, whilst the rate of accumulation of excess liquid water is reduced. The key objective of this approach is to decrease the frequency of water removal actions that cause disruption in the power supplied by the cell, increased parasitic losses or degradation of cell efficiency.
The second strategy is a variation of the previous water activity control strategy, which includes the control of spatial distribution of gases in the fuel and air channels. This integrated solution aims to avoid starvation of reactants by controlling corresponding concentration spatial profiles. This approach is intended to prevent PEM fuel cell degradation due to corrosion mechanisms, and thennal stress caused by the consequences of reactant starvation.A pesar de los avances actuales, la tecnología de celdas de hidrógeno tipo PEM no está suficientemente preparada para ser ampliamente introducida en el mercado energético. Rendimiento, durabilidad y costo son los mayores retos. El rendimiento y la durabilidad de las celdas dependen significativamente de las variaciones en las concentraciones de hidrógeno y oxígeno en los canales de alimentación de gases, la humedad relativa en las capas catalizadoras, el contenido de agua de la membrana polimérica, así como la temperatura, entre otras variables. Dichas variables presentan dependencia espacial interna en la dirección del flujo de gases del ánodo y del cátodo. Distribuciones espaciales altamente no uniformes en algunas variables de la celda resultan en sobrecalentamiento local, inundación, degradación acelerada y menor potencia de la requerida. Muy pocos trabajos disponibles en la literatura se ocupan del control de perfiles espaciales. La mayoría de los diseños orientados a control usan modelos de parámetros concentrados que ignoran la dependencia espacial de variables internas de la celda, debido a la complejidad que añaden al funcionamiento de controladores. En contraste, esta Tesis Doctoral trata la modelización y control de parámetros distribuidos en las celdas de hidrógeno tipo PEM. En la parte de modelización, esta tesis presenta el desarrollo detallado de un modelo no lineal de parámetros distribuidos para una sola celda, el cual incorpora las variaciones espaciales de todas las variables que son relevantes para su correcto funcionamiento. El modelo se usa primero para analizar importantes perfiles espaciales internos, y luego se simplifica para reducir su complejidad computacional y adecuarlo a propósitos de control. En esta tarea se usan y se comparan dos técnicas de reducción de orden de modelos. El propósito de la parte de control es abordar la gestión de agua y el suministro de reactantes, que son dos grandes retos en el funcionamiento de las celdas con importantes consecuencias para su vida útil. En esta parte de la tesis, dos estrategias de control descentralizadas, basadas en controladores predictivos de modelos de referencia con parámetros distribuidos, son diseñadas, implementadas y analizadas en un entorno de simulación. Estas tareas incluyen también el diseño de observadores de estado que estiman los perfiles espaciales internos necesarios para la acción de control. El objetivo de la primera estrategia es monitorear y controlar perfiles espaciales observados de la humedad relativa en las capas catalizadoras para mantenerlos en niveles apropiados. Estos niveles son escogidos cuidadosamente para combinar la correcta humidificación de la membrana y las capas catalizadoras, reduciendo la velocidad de acumulación de agua líquida. El objetivo clave de este enfoque es disminuir la frecuencia de las acciones de remoción de agua dentro de la celda, ya que estas acciones causan interrupción en la potencia suministrada, aumento de las cargas parasitarias y disminución de la eficiencia. La segunda estrategia es una variación de la estrategia anterior que considera adicionalmente el control de la distribución espacial de los gases en los canales del ánodo y cátodo. Esta solución integrada tiene como objetivo evitar la ausencia local de reactantes mediante el control de perfiles espaciales de concentración de gases. Este enfoque pretende prevenir la degradación de las celdas debido a mecanismos de corrosión. Los resultados muestran un mayor rendimiento de la celda considerando los enfoques de control de perfiles espaciales propuestos en esta tesis, en comparación con técnicas de control que ignoran dichos perfiles. Además, la característica descentralizada de los esquemas de control, combinada con el uso de modelos reducidos dentro de los controladores predictivos, tiene un impacto positivo importante en el rendimiento general del control.
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Ragb, Omar B. K. "Advanced model based control for PEM fuel cell stacks." Thesis, Liverpool John Moores University, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.590087.
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This thesis investigates the application of three advanced control strategies in oxygen ratio control of fuel cell stacks. The major objective of these control schemes is to maintain the oxygen ratio at the desired value of 2 for variable load current as disturbance and system uncertainty in order to prevent oxygen starvation. These strategies include, feed-forward (FF) plus feedback (FB) control scheme, model predictive control (MPC) scheme and multi variable control. All the developed methods have been assessed using a non-linear simulation of the fuel cell stack (FCS) model. Satisfactory control performances in terms of effective regulation and robustness to disturbance and system component change have been achieved. FF control has been developed based on neural network, fuzzy logic (5 & 9 membership functions) and look-up table. A PID controller is used in the feedback to adjust the difference between the requested and the actual oxygen ratio by compensating the FF controller output. The simulation results show that, the fuzzy logic and neural network FF controllers performed better than the traditional look-up table and proportional FF controllers. An inverse model control that is based on a radial basis function (RBF) model has been developed and is used as feed-forward approach, and is used in combination with feedback control. Furthermore, the RBF model is updated on-line to cope with rapid change of load current, significant parameters uncertainty and stack time-varying dynamics, which leads to the inverse control being adaptive. Simulations show the effectiveness of the method in rejecting the rapid change of the load current and a simulated actuator fault.
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Seay, Christopher Wayne. "The Role of Branching Topology on Rheological Properties and its Effect on Film-Casting Performance." Diss., Virginia Tech, 2008. http://hdl.handle.net/10919/37671.
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With this research, we work towards the overall objective of customizing polymer molecules in terms of their molecular structure to optimize processing performance. The work includes analysis of the rheology in shear and shear-free flows for sparsely long-chain branched, LCB, polyethylene, PE, resins; determination of the consistency of the molecular based constitutive model, the pom-pom model; for these flows, and evaluation of the same PE resins in film-casting. As we progress towards molecular systems with defined molecular structural characteristics, we transition from a linear low density polyethylene, LLDPE, based series of PE resins to a high density polyethylene, HDPE, based series of PE resins, each with materials of varying degrees of sparse LCB.
Evaluation of the shear step-strain rheology for the series of LLDPE-based PE resins allows for the assessment of any inadequacies associated with the step-strain experiments and the ability of the K-BKZ analog of the pom-pom constitutive model to predict step-strain rheological behavior. Finite rise time and wall slip are addressed to ensure the accuracy of the experimental step-strain measurements and eliminated as factors contributing to the stress relaxation moduli response. Analysis of the K-BKZ analog of the pom-pom constitutive model includes comparisons between experimental stress relaxation moduli and predictions from the model using pom-pom model parameters determined from extensional rheology. The results show inconsistencies in the model predictions, where the predictions fail to capture the short time behavior and accurately dampen at larger strains. Pom-pom model parameters are determined using the K-BKZ analog of the pom-pom constitutive model and fitting the stress relaxation moduli. These results are qualitatively consistent indicating that branching occurs on the longest backbone segments, but the values appear to be unrealistic with respect to the molecular theory.
Analysis of film-width reduction or necking during film-casting for the series of LLDPE-based resins determines whether uniaxial extensional rheological characteristics, in particular strain-hardening, that are a result of LCB influence the film-necking properties. At the lowest drawdown ratio necking is observed to be reduced with increasing LCB, and thus strain-hardening characteristics. At the higher drawdown ratios it is observed that LCB no longer reduces necking and the curves merge to the results found for linear PE, except in the case of LDPE, which shows reduced necking at all drawdown ratios. Furthermore, comparisons of film necking are also made to separate the effects of molecular weight distribution, MWD, and LCB. The results indicate that both broadening the MWD and the addition of sparse LCB reduce the degree of necking observed. It is established that film necking is more significantly reduced by LCB than by broadening the MWD. Analysis of the uniaxial extensional and dynamic shear rheology with the pom-pom constitutive model reveals that a distribution of branches along shorter relaxation time modes is important in reducing necking at higher drawdown ratios. Factors such as shear viscosity effects, extrudate swell, and non-isothermal behavior were eliminated as contributing factors because of the similar shear viscosity curves, N1 curves, and activation energies among the sparsely LCB PE resins.
The same experimental concepts have been extended to the series of HDPE-based resins, but the lack of adequate uniaxial extensional data prevents a thorough analysis with respect to uniaxial extensional characteristics. Regardless, in the context of step-strain rheology, the results were found to be similar with those of the LLDPE-based series of resins, where a distinctive shape at short times was observed for any of the PE resins possessing some level of LCB that was not apparent in the linear PE resins. Film-casting revealed similar results to those of the LLDPE-based materials as well, but a broader spectrum of drawdown ratios revealed greater insight into how the distribution of branching controls the film-casting response. At low drawdown ratios all materials exhibit the same necking behavior. At intermediate drawdown ratios separation occurs where the linear PE resins experiences the most drastic necking, the sparsely LCB PE resins show reduced necking, and the LDPE shows an even greater reduction in necking. Progression then to the higher drawdown ratios results in similar necking behavior for the linear and sparsely LCB PE resins and greatly reduced necking for the LDPE. These results support the idea that to reduce necking the backbone segments that dominate the film-casting behavior must contain some level of LCB.Ph. D.
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Boyce, John S. "Linking PPBES and the POM with capabilities." Thesis, Monterey, Calif. : Naval Postgraduate School, 2006. http://bosun.nps.edu/uhtbin/hyperion.exe/06Dec%5FBoyce.pdf.
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Zancul, Eduardo de Senzi. "Gestão do ciclo de vida de produtos: seleção de sistemas PLM com base em modelos de referência." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/18/18140/tde-27052009-132444/.
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A gestão do ciclo de vida de produtos (Product Lifecycle Management) é uma abordagem para a gestão integrada dos processos de negócio e das informações relacionadas aos produtos. Tal abordagem requer a utilização de sistemas de informação (Sistemas PLM) para apoiar a colaboração na empresa estendida, ao longo de todo o ciclo de vida. O problema prático que motiva a realização deste trabalho é a dificuldade enfrentada pelas empresas, atualmente, em avaliar os sistemas PLM existentes no mercado e em selecionar a alternativa mais adequada aos seus processos de negócio. A análise da situação atual da pesquisa na área indica que faltam métodos e instrumentos para apoiar a seleção de sistemas PLM. Visando preencher essa lacuna e propor uma solução para o problema identificado, o trabalho tem como objetivos definir um modelo de referência de sistemas PLM, que represente de forma genérica as funcionalidades que caracterizam esse tipo de sistema, e desenvolver um método para a seleção de sistemas PLM baseado em modelos de referência. A fim de atingir esses objetivos, são gerados quatro resultados principais. O primeiro resultado do trabalho é o framework conceitual de elementos do PLM, que organiza o conhecimento existente sobre PLM de forma estruturada, para que ele possa servir de referência em projetos de implantação da gestão do ciclo de vida de produtos em empresas. O segundo resultado é o modelo de referência de sistemas PLM, que permite estabelecer uma base comum para a comparação entre os diversos sistemas PLM disponíveis comercialmente. O terceiro resultado é o modelo integrado processo-sistemas PLM e a ferramenta para utilização desse modelo integrado na prática. Por fim, o quarto resultado é o método de seleção de sistemas PLM com base em modelos de referência, que utiliza o modelo integrado processo-sistemas PLM para orientar a seleção do sistema mais adequado a uma empresa específica. A avaliação dos resultados indica que os instrumentos e o método propostos neste trabalho contribuem para auxiliar as empresas, especialmente as empresas de médio porte, na identificação de um sistema PLM adequado para atender aos requisitos de seus processos de negócio.Product Lifecycle Management is an approach to the integrated management of business processes and product-related information. This approach requires information systems (PLM Systems) to provide collaboration support throughout the business and across product lifecycle. The practical problem that gave rise to this research was the challenge companies currently face in assessing existing PLM systems and in selecting the best alternative for their business processes. Examining the status of the research carried out in the field to date shows that there is a lack of methods and tools to effectively support companies in choosing their PLM Systems. Aiming at closing this gap and offering a solution for this problem, the goals of this study are: to provide a definition for PLM system reference models that generally represents the functionalities that characterize this kind of system, and to develop a method for choosing PLM systems based on the reference models. In meeting these goals, this research arrived at four main results. Firstly, at a conceptual framework of PLM elements providing an organized structure of the existing knowledge developed so far on PLM. This framework can be used as a reference in projects to implement product lifecycle management in companies. Secondly, at a PLM system reference model that establishes a common basis for comparing the many PLM systems available in the market. Thirdly, at an integrated PLM process-system model and tool for using this integrated model in practice. Lastly, at a method for selecting PLM systems based on the reference model, that uses the integrated PLM process-system model to support and guide users in choosing the best system for a certain company. The assessment of the results shows that the proposed tools and method effectively help companies, specially medium-sized businesses, in identifying the most adequate PLM system to meet their business process requirements.
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Östling, Erik. "Model on degradation of PEM fuel cells in marine applications." Thesis, KTH, Kemiteknik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-299446.
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Sjöfarten står för 3 % av världens totala växthusgaser och är idag högst beroende av fossila bränslen. Ett alternativ för att gå över till en fossilfri flotta är användning av bränsleceller och vätgas som drivmedel. Om vätgasen produceras från elektrolys med förnyelsebara energikällor så är driften utsläppsfri och koldioxidneutral. Bränsleceller kan användas i många olika sammanhang, men har ännu inte slagit igenom med full kraft. En anledning till detta är livslängden som är för kort. För att sjöfarten ska kunna implementera bränslecellsdrift behöver nedbrytningen av bränslecellen bli vidare utforskad och motverkad. Syftet med detta examensarbete var att hitta de mest signifikanta nedbrytningsmekanismerna för sjöfarten samt att bygga en modell för att förutspå livslängden utifrån lastprofiler från fartyg. Rapportens avgränsningar var att enbart studera PEM-bränsleceller tack vare dess höga energitäthet och att teknologin är närmast marknaden för mobila applikationer. En litteraturstudie genomfördes för att fastställa de viktigaste nedbrytningsmekanismerna samt de faktorer som begränsar livslängden. Dessa bestämdes till start/stop cykler samt lastcykler vilka försämrar konduktiviteten i membranet samt minskar den elektrokemiska ytarean. En empirisk modell från experiment från litteraturen etablerades för att hitta relationen mellan parametrarna konduktivitet och elektrokemisk ytarea som funktion av start/stop cykler respektive lastcykler. En Comsol-modell användes för att utvärdera bränslecellens prestanda med dessa försämrade parametrar. Två lastprofiler analyserades och tolkades som antal start/stop cykler samt lastcykler för att utvärdera prestandan som funktion av antal år i drift. Båda fallen var i drift till dess att prestandan minskat med 20 % utvärderat vid strömtätheten 0.6 A/cm2. Båda lastprofilerna var utvärdera med olika körstrategier för att jämföra den modellerade livslängden beroende på ingångsvärden. Den första lastprofilen delades in i Case 1a och Case 1b där antalet start/stop cykler och lastcykler varierade. Resultatet visade att antalet timmar i drift mer än tredubblades i Case 1b där båda ingående indata hade minskats. Case 2 delades upp i tre olika körstrategier där Case 2a var en referens som jämfördes mot Case 2b respektive Case 2c. Skillnaden mot Case 2b var att antalet start/stop cykler per dag multiplicerades med faktor 4. Resultatet från modellen var att livstiden minskade från 6 till 4 år. Vidare utvärderades Case 2c där istället antalet lastcykler dividerades med faktor 4, allt annat identiskt med Case 2a. Utfallet var en ökad livslängd från 6 år till 11 år, med totalt 32 032 timmar i drift. Denna livslängd kan jämföras med kommersialiserade marina produkter från Ballard och Powercell, där livslängden är 30 000 respektive 20 000 timmar i drift. Sammanfattningsvis kan det konstateras att både start/stop cykler och lastcykler bryter ner bränslecellen och därmed minskar dess prestanda. Lastcykler var den faktor som var mest förödande gällande livslängden. Den modellerade livslängden på 32 032 timmar indikerar att den empirisk modellen tillsammans med Comsol-modellen genererade realistiska resultat. Slutligen kan sägas att ett område för framtida forskning inom ämnet innefattar lastcykler eftersom denna hade störst påverkan på modellen. Att särskilja olika typer av lastcykler och koppla till olika degradering skulle skapa än mer förståelse för livslängden. Då denna studie genomfördes på bränslecellsnivå skulle framtida studier kunna inkludera att analysera degradering på systemnivå för att få mer insikt i dessa processer.The shipping industry emits 3 % of the global GHG-emissions and is highly dependent on fossil fuels. One alternative to decarbonise the sector is by utilising hydrogen in fuel cells. The propulsion is free from emissions if hydrogen is produced from renewables. The fuel cell technology can be applied in various applications but have not been fully commercialised. One of the biggest bottlenecks for fuel cell technology is the durability that needs to be improved. In order for marine vessels to implement hydrogen propulsion, the degradation need to be further understood and mitigated. The purpose of this thesis was to assess the most significant degradation mechanisms for marine applications and to build a model to evaluate the lifetime depending on load profiles. The scope of the thesis was to include PEMFCs since they have the highest power density and are closest to commercialisation for transport applications. A literature review was conducted to assess the most important degradation mechanisms and operating conditions that limits the lifetime, which concluded in start/stop cycling and load cycling. These conditions deteriorate the membrane conductivity and the electrochemical surface area. An empirical model based on experimental data from the literature was conducted to find relationships for conductivity and ECSA as function of start/stop cycling and load cycling, respectively. A Comsol model was established to evaluate performance reduction with degraded parameters. Two different load cycles were interpreted as number of start/stop cycles and load cycles in order to simulate the degradation. The output was polarization curves as function of operating years. Each case was operated until a performance reduction of 20 % was obtained at the current density of 0.6 A/cm2. Both load profiles were analysed with different operation strategies to compare the resulting lifetime. The first load curve was divided into Case 1a and Case 1b where start/stop cycles and load cycles were altered. The results showed that the lifetime in operation hours was more than three-folded in Case 1b when the number of start/stop cycles and load cycles was reduced. Case 2 was divided into three operating strategies. For comparison with Case 2a, the number of start/stop cycles per day in Case 2b was increased by a factor of 4. The result was that the lifetime declined from 6 to 4 years. Furthermore, Case 2c evaluated the lifetime if the number of load cycles per day decreased by a factor of 4, all else being equal to Case 2a. The outcome was an increment in lifetime from 6 to 11 years, with a total of 32 032 hours of operation. This lifetime can be compared to commercialised products from Ballard and Powercell with lifetimes of 30 000 and 20 000 operating hours, respectively. Conclusively, the simulations showed that both start/stop cycling and load cycling deteriorates the fuel cell performance. Load cycling is the operating condition that cause the most severe degradation. Moreover, the modelled lifetime of 32 032 hours indicates that the empirical model in combination with the Comsol model generate realistic lifetimes. Finally, since load cycling had the most vital impact on the lifetime, one of the topics for future research would be to distinguish different types of load cycles and connect to separate degradation outcomes. Since the model was on fuel cell level, future work could also include systems effects such as ripple current or distributions within fuel cell stacks.
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Winkler, Markus. "The processmetallurgic reactor model (PRM) an interactive implementation and visualization." Saarbrücken VDM Verlag Dr. Müller, 2007. http://d-nb.info/989496341/04.
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Vadoudi, Kiyan. "Data Model Proposal to Integrate GIS with PLM for DfS." Thesis, Troyes, 2017. http://www.theses.fr/2017TROY0014/document.
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Le déploiement du développement durable passe par des enjeux de transition sociétale et technique auxquels cherche à répondre le Design for Sustainability (DfS). Dans le cadre de la conception des systèmes de production, et en particulier pour les produits manufacturés, les impacts environnementaux que ce soit en termes de consommation de ressources ou de rejets (déchets, émissions) doivent être intégrés comme des paramètres de conception. L’évaluation des impacts environnementaux (par exemple par l’Analyse de Cycle de Vie, ACV) doit donc s’articuler avec la gestion du cycle de vie des produits (PLM). L’inventaire de cycle de vie, ICV est un élément central du lien entre le système de production et son environnement, caractérisé par des informations géographiques et spatiales sur l’écosphère. Le travail de thèse proposé stipule que les impacts environnementaux des systèmes conçus dépendent de cette caractérisation géographique. Les approches d’écoconception et de DFS doivent donc intégrer ces informations géographiques ce qu’elles ne font que très peu, ces informations n’étant pas intégré dans les outils de conception. La thèse propose donc une approche de modélisation pour intégrer les informations relatives au produit et son système de production (via le PLM), l’évaluation de son potentiel d’impact environnemental (via l’ACV et en particulier l’ICV), et les informations géographiques en conception. Pour cela, les informations géographiques à associer sont identifiées et des cas d’études illustratifs sont construits pour montrer l’impact de ces informations sur la définition des produitsThere are different approaches to implement sustainability and Design for Sustainability (DfS) is the one that give more accurate result by considering both global and regional scales. Integration of Life Cycle Assessment (LCA) into Product Lifecycle Management (PLM) is an example of tool integration to support sustainability. In LCA framework, Life Cycle Inventory (LCI) is the quantified and classified list of input and output flow of the LCA model that is a model of the product system, linking the technological system to the ecosphere (Environment system). As each region has a unique environmental system, design characteristics and specifications of technological system should be modified and adopted based on these differences. Implementation of this approach will require geographical information of interacted environmental systems, which is a kind of new strategy in DfS. Therefore, we tested the interest of the integration of Geographical Information Systems (GIS) with PLM to support geographical considerations during product development activities. The main research question of this research work is then how to propose this PLM-GIS integration for DfS. Thus, we conducted that literature review on existing data models about product, environment, geography and their combination is a key to prove the link among them
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Zhang, Sumei. "Product structure modeling for ETO system product considering the product lifecycle : A case study of ABB Mine Hoist." Thesis, Uppsala universitet, Industriell teknik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-385770.
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In order to gain competitive advantages in markets, companies have provided a variety of customized products to satisfy customer-specific requirements, leading to not only a large amount of product data but also high cost, long lead-time and complexity of quality control. Efficient product data management throughout the product lifecycle has become increasingly crucial, of which product structure management is regarded as the most important constituent. The study took ABB Mine Hoist system as a case to investigate how to construct a generic product structure model fit for engineer-to-order system offerings with the consideration of their sales-delivery product lifecycle. The aim of the model is to facilitate the product-related information sharing and reuse across a company, and the integration of different business operations throughout the entire product lifecycle as well. Based on the current situation analysis of product data management on ABB Mine Hoist, three major issues were identified which need to be addressed in the formulation of a generic structure model: namely the integration of requirements of multiple disciplines; the consistency of product information throughout the product lifecycle; and the constant update of product repository. Through illustrating the formulation of ABB Mine Hoist generic structure model, the method of how to construct a generic product structure model for engineer-to-order system product was presented. The model was achieved by applying the framework of the step-based product model and was regarded as a result of integrating domain-specific requirements. The adaptive generic product structure model was then employed to display the role of this generic model in the different phases of a sales-delivery lifecycle. The model could serve as a “master concept” to transfer common product information in the product lifecycle. It’s expected to benefit the business of engineer-to-order system product through improving the integration of different disciplines, enhancing information exchange and reuse. It could also provide an abstract and conceptual basis for potential product repository to reinforce data consistency and completeness.
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Carvalho, Silmara Cardoso de. "Índice da competitividade logística do PIM - modal aéreo." Universidade Federal do Amazonas, 2013. http://tede.ufam.edu.br/handle/tede/3567.
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Previous issue date: 2013-12-27Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Globalization is a reality that affects all sectors of society, economic relations have changed dramatically since the conception of this borderless world. The industries that were established only in their home country , have joined industrial clusters around the world , aiming to make their products more competitive and meet consumer markets scattered to the four corners of the globe . The aspect that emerges in this scenario in which suppliers and customers can be located in the same neighborhood or on different continents, is the efficiency of logistics operations. This activity has become a relevant factor for the competitiveness of a company or a country. Rely on adequate infrastructure to meet local industry, so an efficient management of the supply chain is the expectation of the companies located in the Industrial Pole of Manaus - PIM. Considering the importance of air transportation to the city of Manaus, the study aimed to evaluate the process of release of air cargo passing through the terminals Cargo Logistics Company Brazilian Airport Infrastructure - INFRAERO. This evaluation was done by creating a performance index composed of four variables that formed the basis for the calculation of this index. The methodology was based on literature review, field research for lifting of the variables along the INFRAERO statistical treatment of the data and finally mathematical calculation. The air logistics performance index - IDLAR city of Manaus obtained concept fair and value of 0,58 according to the model proposed. As practical contribution of the work it is proposed that the model be used as a tool for performance evaluation of air logistics Manaus city annually. The result of this research is the development and application of the index that enables the control and management of the process mentioned in order to strengthen the economic potential of the region by improving the agility of services rendered in Terminal Cargo Logistics by the different actors involved.
A globalização é uma realidade que afeta todos os setores da sociedade. As relações econômicas mudaram drasticamente em função da nova concepção do mundo sem fronteiras. As indústrias, que antes eram estabelecidas somente em seu país sede, passaram a integrar aglomerados industriais ao redor do mundo visando tornar seus produtos mais competitivos e atingir mercados consumidores espalhados pelos quatro cantos do globo. O aspecto que desponta neste cenário, em que fornecedores e clientes podem estar situados no mesmo bairro ou em continentes diferentes, é a eficiência das operações logísticas. Essa atividade tornou-se fator relevante para a competitividade de uma empresa ou de um país. Contar com infraestrutura adequada para atender a indústria local, sendo assim um eficiente gerenciamento da cadeia de suprimentos é a expectativa das empresas instaladas no Polo Industrial de Manaus - PIM. Considerando a relevância do modal aéreo para a cidade de Manaus, o trabalho teve como objetivo avaliar o processo de liberação de cargas aéreas que transitam através dos Terminais de Logística de Cargas da Empresa Brasileira de Infraestrutura Aeroportuária INFRAERO. Essa avaliação foi realizada através da criação de um índice de desempenho composto por seis variáveis que serviram de base para o cálculo deste índice. A metodologia foi fundamentada na revisão bibliográfica; pesquisa de campo para levantamento de parte das variáveis junto à INFRAERO; tratamento estatístico dos dados e por fim cálculo matemático. O Índice de Desempenho Logístico Aéreo - IDLAR da cidade de Manaus obteve conceito Regular e valor 0,58 de acordo com a modelo proposto. Como contribuição prática do trabalho propõe-se que o modelo seja usado como instrumento de avaliação de desempenho logístico aéreo da cidade de Manaus anualmente. O resultado desta pesquisa é a elaboração e aplicação do índice que permite o controle e a gestão do processo citado a fim de fortalecer o potencial econômico da região através da melhoria na agilidade de serviços prestados no Terminal de Logística de Cargas pelos diferentes atores envolvidos.
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Keren, Nir. "Model for multi-strata safety performance measurements in the process industry." Texas A&M University, 2003. http://hdl.handle.net/1969.1/319.
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Measuring process safety performance is a challenge, and the wide variations in understanding, compliance, and implementation of process safety programs increase the challenge. Process safety can be measured in three strata: (1) measurement of process safety elements within facilities; (2) benchmarking of process safety elements among facilities; and (3) use of incident data collection from various sources for industrial safety performance assessment.
The methods presently available for measurement of process safety within facilities are deficient because the results are strongly dependent on user judgment. Performance benchmarking among facilities is done within closed groups of organizations. Neither the questionnaires nor the results are available to the public. Many organizations collect data on industrial incidents. These organizations differ from each other in their interests, data collection procedures, definitions, and scope, and each of them analyzes its data to achieve its objectives. However, there have been no attempts to explore the potential of integrating data sources and harnessing these databases for industrial safety performance assessment.
In this study we developed models to pursue the measurement of samples of the strata described above. The measurement methodologies employed herein overcome the disadvantages of existing methodologies and increase their capabilities.
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Annakula, Chandravyas. "Hierarchical and partitioning based hybridized blocking model." Kansas State University, 2017. http://hdl.handle.net/2097/35468.
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Master of ScienceDepartment of Computing and Information Sciences
William H. Hsu
(Higgins, Savje, & Sekhon, 2016) Provides us with a sampling blocking algorithm that enables large and complex experiments to run in polynomial time without sacrificing the precision of estimates on a covariate dataset. The goal of this project is to run the different clustering algorithms on top of clusters formed from above mentioned blocking algorithm and analyze the performance and compatibility of the clustering algorithms. We first start with applying the blocking algorithm on a covariate dataset and once the clusters are formed, we then apply our clustering algorithm HAC (Hierarchical Agglomerative Clustering) or PAM (Partitioning Around Medoids) on the seeds of the clusters. This will help us to generate more similar clusters. We compare our performance and precision of our hybridized clustering techniques with the pure clustering techniques to identify a suitable hybridized blocking model.
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Barsk, Karl-Johan. "Model Predictive Control of a Tricopter." Thesis, Linköpings universitet, Reglerteknik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-79066.
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In this master thesis, a real-time control system that stabilizes the rotational rates of a tri-copter, has been studied. The tricopter is a rotorcraft with three rotors. The tricopter has been modelled and identified, using system identification algorithms. The model has been used in a Kalman filter to estimate the state of the system and for design ofa model based controller. The control approach used in this thesis is a model predictive controller, which is a multi-variable controller that uses a quadratic optimization problem to compute the optimal con-trol signal. The problem is solved subject to a linear model of the system and the physicallimitations of the system. Two different types of algorithms that solves the MPC problem have been studied. These are explicit MPC and the fast gradient method. Explicit MPC is a pre-computed solution to the problem, while the fast gradient method is an online solution. The algorithms have been simulated with the Kalman filter and were implemented on themicrocontroller of the tricopter.
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Lunt, Daniel J., Matthew Huber, Eleni Anagnostou, Michiel L. J. Baatsen, Rodrigo Caballero, Rob DeConto, Henk A. Dijkstra, et al. "The DeepMIP contribution to PMIP4: experimental design for model simulations of the EECO, PETM, and pre-PETM (version 1.0)." COPERNICUS GESELLSCHAFT MBH, 2017. http://hdl.handle.net/10150/623012.
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Past warm periods provide an opportunity to evaluate climate models under extreme forcing scenarios, in particular high ( > 800 ppmv) atmospheric CO2 concentrations. Although a post hoc intercomparison of Eocene ( ∼ 50 Ma) climate model simulations and geological data has been carried out previously, models of past high-CO2 periods have never been evaluated in a consistent framework. Here, we present an experimental design for climate model simulations of three warm periods within the early Eocene and the latest Paleocene (the EECO, PETM, and pre-PETM). Together with the CMIP6 pre-industrial control and abrupt 4 × CO2 simulations, and additional sensitivity studies, these form the first phase of DeepMIP – the Deep-time Model Intercomparison Project, itself a group within the wider Paleoclimate Modelling Intercomparison Project (PMIP). The experimental design specifies and provides guidance on boundary conditions associated with palaeogeography, greenhouse gases, astronomical configuration, solar constant, land surface processes, and aerosols. Initial conditions, simulation length, and output variables are also specified. Finally, we explain how the geological data sets, which will be used to evaluate the simulations, will be developed.
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Schleidt, Bettina. "Personal Resource Management (PRM) in der modernen Produktentwicklung." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-214747.
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Zunächst wird ein Überblick über berufliche Herausforderungen für Menschen in der modernen Produktentwicklung (-> Industrie 4.0) gegeben. Anschließend wird ein allgemeines Rahmenmodell beschrieben, in dem (nicht nur) psychologische Faktoren dargestellt werden, die menschliches Fühlen, Denken und Handeln beeinflussen. Im dritten Abschnitt wird ein Blick über den Tellerrand geworfen: In der Luftfahrt sind sogenannte Crew Resource Management Seminare für Besatzungen von Verkehrsflugzeugen gesetzlich verpflichtender Teil der Personalentwicklung und Weiterbildung. Es wird der Frage nachgegangen, in wieweit Zielsetzung und Inhalte dieser Seminare auf das Setting und die Bedürfnisse eines in der modernen Produktentwicklung tätigen Menschen übertragen werden können. Diese Überlegungen münden in den Ansatz des sogenannten Personal Resource Management, der den in der Produktentwicklung tätigen Menschen dabei unterstützen kann, sich der ihm zur Verfügung stehenden Ressourcen bewusst zu werden und Wege zu finden, diese Ressourcen in einem komplexen Umfeld zielorientiert abzurufen und ntsprechende Leistungen zu erbringen und gesund zu bleiben.
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Garcia, Sergio Leonardo. "A contribution to the understanding of a PEM fuel cell transient model." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/MQ63017.pdf.
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Fortuin, Adrian Charles. "Development of a semi–empirical reaction kinetic model for PEM fuel cells." Master's thesis, University of Cape Town, 2013. http://hdl.handle.net/11427/5334.
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In the drive to more sustainable energy production, polymer electrolyte fuel cells (PEFC) have been at the pinnacle of global research. One of the major drawbacks of PEFCs is therequirement for expensive noble metal catalysts (platinum and ruthenium). Furthermore 75% of the overpotential losses at the cathode are due to the activation of the oxygen reduction reaction (ORR). To reduce the platinum content requirements and understand the cause of the large overpotential of the ORR, a fundamental understanding of the reaction mechanism and the manner in which it proceeds under different operatingconditions is required. Presently, there still remains a large debate in literature around the mechanism followed by the ORR.This study developed a kinetic model from conventional kinetic isotherms and it is proposed that an associative adsorption mechanism occurs at a low overpotential resulting in the dissociation of the hydroperoxyl species determining the rate of the ORR at the cathode of the PEFC. In order to explain the above phenomena a kinetic model was developed, based on the Eley-Rideal mechanism. Furthermore, experiments were conducted at different oxygen partial pressures and low potentials whereby the associative mechanism is believed to dominate. Under these conditions linear sweep voltammograms were recorded. Regression of the derived kinetic model, by using the values for oxygen partial pressure, applied overpotential and kinetic current allowed for the determination of the kinetic constant of a polycrystalline platinum catalyst for ORR.
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Izadpanah, Seyed Hamedreza. "Méthode d'évolution de modèles produits dans les sytèmes PLM." Thesis, Grenoble, 2011. http://www.theses.fr/2011GRENI077/document.
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Le système PLM est l’un des outils stratégiques de l’entreprise. Ces systèmes sont sujets à des changements récurrents dans l’entreprise. Les évolutions organisationnelles, le changement de l’offre produit ou encore le remplacement de logiciels PLM peuvent déclencher l’évolution du système d’information PLM. Une des structures les plus importantes dans les systèmes PLM est le modèle du produit, autour duquel s’articule les informations et processus. C’est autour du modèle produit que se concentrent nos recherches. Les causes d’évolution des modèles produits sont des éléments signifiants qui différencient les étapes de la démarche à suivre. Les méthodes d’IDM sont utilisées afin de formaliser la transformation des modèles. En plus, cette démarche bénéfice d’un cadre de similarité spécialement développé pour la configuration de produit. Un exemple industriel est illustré et résolu en appliquant cette démarche. Il s’agit de l’évolution d’un système gérant les modèles spécifiques de produit vers un système qui est capable de construire et d’utiliser les modèles génériques de produit. Un outil informatique support à nos travaux est développé dans le cadre d'EclipsePLM systems are among the strategic components of enterprise’s information system architecture. These systems undergo frequent evolutions of enterprise. Organizational evolution or product offer variation as well as PLM application replacement may launch PLM systems’ evolution.One of the important structures in PLM systems is the product configuration, which organize and structure all product’s information and processes. Our research activities concern product model evolution. Reasons of product model evolution specify the appropriate methodology and necessary steps in order to handle it. MDE methods are used to formalize the model transformation process.Moreover, our methodology contains a specific similarity framework dedicated to product configuration. An industrial example was illustrated and resolved by this methodology. The problematic of this example is the migration of a system which manage only specific product configuration to a new system that is capable to construct and use generic models of product
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Wahlund, Patrik, and Patrik Sjögren. "Studie av informationsöverföring mellan konstruktion och produktion." Thesis, Linköpings universitet, Maskinkonstruktion, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-129317.
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This master thesis aims to examine how the transfer of product related information is carried out in the manufacturing industry. The study was supposed to give suggestions for improving the CAD courses provided at Linköping University. This thesis is the concluding step for the authors’ master’s degree in mechanical engineering.In the beginning of the project a study of relevant literature was made. The literature was aimed to gain more knowledge of the subject at hand and finding relevant methods for collecting and analyzing data. To examine how the industry deals with product related data a multiple case study was conducted, investigating seven different companies that are working with both product development and production. As data collection method, semi-structured interviews of employees on the different companies were conducted.An adaptation of the “affinity diagram technique” was used when analyzing the collected data. The method divided the answers to questions provided by the different companies into different categories, in the form of statements. These where compared between the companies by the use of tables, showing the results in a clear manner. To give better insight in each company´s methods, a descriptive summary was written for each of the studied companies.To be able to give propositions of improvement for the courses at the University, some of the courses given where analyzed by reviewing the course description and goals, and through informal interviews of the course administrator. This led to better insight in what is included in the courses and what they are supposed to teach the students. The knowledge of what is included in the courses at this time and the results of the study of the companies, were the foundation when determining what could be changed in the courses.The case study showed that it varies greatly how much the companies are adapting new approaches for generating and spreading product related data. This made it difficult to find tangible evidence supporting changes to the courses, however, a few conclusions could be drawn from the results. It was found that 2D-drawings are still used to a great extent for carrying product related information. Only one of the studied companies have transitioned to using the 3D-model as an information carrier. Although it was mentioned on some of the other companies that such an approach seemed interesting.The study also showed that less handling of physical papers seems to be something most companies are interested in, and are also trying to achieve. It was also noted that all the companies studied had implemented some form of digital platform for handling product related documents.A few things that were deemed worth implementing in the mandatory courses were the introduction to PDM/PLM, introduction of 3D-annotations for dimensions and tolerances and increased use of the 3D-model for manufacturing operations.Detta examensarbete ämnar undersöka hur informationsöverföringen av produktrelaterad data sker i industrin för att kunna ge förbättringsförslag för Linköpings Universitets CAD- och ritteknikskurser. Detta för att kurserna bättre ska spegla industrins nuvarande och även framtida behov. Examensarbetet utfördes på avdelningen maskinkonstruktion vid Linköpings Universitet och är det avslutande momentet på författarnas civilingenjörsutbildning i maskinteknik.Till att börja med utfördes en litteraturstudie. Detta för att ge kunskap inom det aktuella området och vilka metoder som kan användas för datainsamling och analys. För att undersöka hur industrins arbetssätt ser ut utfördes en flerfallstudie på sju olika företag som bedriver produktutveckling tillsammans med egen produktion. Som datainsamlingsmetod valdes semistrukturerade intervjuer med anställda på de olika företagen.Analysen utfördes med hjälp av en adaption av ”affinity diagram technique” vilket delade upp företagens svar i kategorier i form av påståenden. Dessa jämfördes mellan företagen med hjälp av tabeller eftersom det var tydligt sätt att representera resultatet. För att ge en inblick i hur varje enskilt företag arbetar utarbetades även en deskriptiv sammanfattning av varje företag.För att kunna ge förbättringsförslag till universitetets CAD- och ritteknikskurser granskades några av de nuvarande kursernas kursplaner. Detta tillsammans med en informell intervju av de kursansvariga ledde till bättre insikt om hur kurserna är uppbyggda och vad målen med dem är. Insikten om vad kurserna innehåller i dagsläget tillsammans med analysen av de studerade företagens arbetssätt bidrog till att ett antal förbättringsförslag kunde föreslås.Det visade sig att graden av användande av modernare arbetssätt varierar kraftigt bland företagen. Detta gjorde det svårt att komma fram till ett enhetligt resultat som gällde för alla de studerade företagen. Däremot kunde ett antal slutsatser dras. Bland annat används fortfarande 2D-ritningar flitigt som ett informationsbärande dokument. En övergång till att enbart använda 3D-modellen som informationsbärare noterades endast på ett utav företagen men nämndes på ett par andra.Papperslöst arbete verkar vara på frammarsch trots att vissa specifika moment fortfarande utförs på papper. Det noterades även att digitala system används för lagring och hantering av produktrelaterad information hos alla de studerade företagen.Det som ansetts värt att implementera i universitets obligatoriska kurser efter genomförd studie är främst ökad användning av PDM/PLM-system, introduktion av 3D-måttsättning samt utnyttjande av 3D-modellen vid tillverkning.
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Denis, Yvan. "Implémentation de PCM (Process Compact Models) pour l’étude et l’amélioration de la variabilité des technologies CMOS FDSOI avancées." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAT045/document.
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Récemment, la course à la miniaturisation a vue sa progression ralentir à cause des défis technologiques qu’elle implique. Parmi ces obstacles, on trouve l’impact croissant de la variabilité local et process émanant de la complexité croissante du processus de fabrication et de la miniaturisation, en plus de la difficulté à réduire la longueur du canal. Afin de relever ces défis, de nouvelles architectures, très différentes de celle traditionnelle (bulk), ont été proposées. Cependant ces nouvelles architectures demandent plus d’efforts pour être industrialisées. L’augmentation de la complexité et du temps de développement requièrent de plus gros investissements financier. De fait il existe un besoin réel d’améliorer le développement et l’optimisation des dispositifs. Ce travail donne quelques pistes dans le but d’atteindre ces objectifs. L’idée, pour répondre au problème, est de réduire le nombre d’essai nécessaire pour trouver le processus de fabrication optimal. Le processus optimal est celui qui conduit à un dispositif dont les performances et leur dispersion atteignent les objectifs prédéfinis. L’idée développée dans cette thèse est de combiner l’outil TCAD et les modèles compacts dans le but de construire et calibrer ce que l’on appelle un PCM (Process Compact Model). Un PCM est un modèle analytique qui établit les liens entre les paramètres process et électriques du MOSFET. Il tire à la fois les bénéfices de la TCAD (puisqu’il relie directement les paramètres process aux paramètres électriques) et du modèle compact (puisque le modèle est analytique et donc rapide à calculer). Un PCM suffisamment prédictif et robuste peut être utilisé pour optimiser les performances et la variabilité globale du transistor grâce à un algorithme d’optimisation approprié. Cette approche est différente des méthodes de développement classiques qui font largement appel à l’expertise scientifique et à des essais successifs dans le but d’améliorer le dispositif. En effet cette approche apporte un cadre mathématique déterministe et robuste au problème.Le concept a été développé, testé et appliqué aux transistors 28 et 14 nm FD-SOI ainsi qu’aux simulations TCAD. Les résultats sont exposés ainsi que les recommandations nécessaires pour implémenter la technique à échelle industrielle. Certaines perspectives et applications sont de même suggéréesRecently, the race for miniaturization has seen its growth slow because of technological challenges it entails. These barriers include the increasing impact of the local variability and processes from the increasing complexity of the manufacturing process and miniaturization, in addition to the difficult of reducing the channel length. To address these challenges, new architectures, very different from the traditional one (bulk), have been proposed. However these new architectures require more effort to be industrialized. Increasing complexity and development time require larger financial investments. In fact there is a real need to improve the development and optimization of devices. This work gives some tips in order to achieve these goals. The idea to address the problem is to reduce the number of trials required to find the optimal manufacturing process. The optimal process is one that results in a device whose performance and dispersion reach the predefined aims. The idea developed in this thesis is to combine TCAD tool and compact models in order to build and calibrate what is called PCM (Process Compact Model). PCM is an analytical model that establishes linkages between process and electrical parameters of the MOSFET. It takes both the benefits of TCAD (since it connects directly to the process parameters electrical parameters) and compact (since the model is analytic and therefore faster to calculate). A sufficiently robust predictive and PCM can be used to optimize performance and overall variability of the transistor through an appropriate optimization algorithm. This approach is different from traditional development methods that rely heavily on scientific expertise and successive tests in order to improve the system. Indeed this approach provides a deterministic and robust mathematical framework to the problem. The concept was developed, tested and applied to transistors 28 and 14 nm FD-SOI and to TCAD simulations. The results are presented and recommendations to implement it at industrial scale are provided. Some perspectives and applications are likewise suggested
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Hassan, Hafiz Muhammad Adeel. "Development and Evaluation of a CFD Model to Simulate Thermal Performance of Phase Change Material (PCM) Based Energy Storage Systems." Thesis, KTH, Kraft- och värmeteknologi, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-150715.
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Waste heat can be recovered and used in different processes to increase energy efficiency and reduce CO2 emissions. It has become an attractive area of research for scientists and several techniques are being investigated and practiced to recover, store and use waste heat. Thermal Energy Storage is one of the modern techniques that is used to store and use waste heat. Energy can be stored in both sensible and latent forms of heat. Latent heat storage is the most efficient way of storing thermal energy as it provides higher storage density and lower temperature differential between storing and releasing heat. The materials that are used for latent energy storage are termed as Phase Change Materials (PCMs). This thesis work investigates the feasibility of a latent heat storage and heat exchanger performance based on phase change material to recover heat at elevated temperatures. The heat transfer study is done by using state of the art commercial CFD tool. Different model geometries of the Thermal Storage equipped with Shell and tube heat exchanger were built with different pipe configurations. The 1st type of model is a set of three 2D models built in COMSOL Multiphysics. These models constitute a cross section of a small portion of heat exchanger having four 10 mm outer diameter pipes immersed in PCM. Fins were mounted on the pipes to enhance the area for heat transfer and hence the heat transfer rate in modified models. Simulations were carried out for melting and solidification of PCM with these 2D models. After analyzing the results, a 3D model of the small block was created to get more realistic results and analyze the effect of pipe diameter on melting and solidification of PCM. The results of 2D models show the effect of fins on heat transfer rates. The model with eight fins on each pipe shows the best results as compared to other two models. The melting and solidification rates are nearly half for eight fin model as compared to the model without fins. The four fin model shows moderate results but better than the model without fins. The comparison of the results for different diameter pipes in 3D model shows that heat transfer rate increases for increasing diameters of the pipe with same flow rate in the case of melting.
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Van, Scoy Bryan Richard. "A Mathematical Model for Hydrogen Production from a Proton Exchange Membrane Photoelectrochemical Cell." University of Akron / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=akron1326217817.
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Rodgers, Steven Francis. "Simulation of PEM fuel cells: validation of model and incorporation of humidity dynamics." Diss., Rolla, Mo. : Missouri University of Science and Technology, 2010. http://scholarsmine.mst.edu/thesis/pdf/Rodgers_09007dcc807d8717.pdf.
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Thesis (M.S.)--Missouri University of Science and Technology, 2010.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed July 29, 2010) Includes bibliographical references (p. 64-67).
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Kim, Yong Sik. "Kinetic and mechanistic studies of polyoxometalate (POM) reaction with lignin and model compounds." Thesis, University of British Columbia, 2007. http://hdl.handle.net/2429/31366.
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Polyoxometalates (POMs) are a rapidly growing class of metal-oxygen-cluster anions. The properties of POMs can be modified by altering the POMs chemical composition and structure. Due to low cost, commercial availability, and synthetic tractability POMs have found application in various fields of chemistry and technology. POMs are reusable and thermally stable to oxidative conditions, making them an attractive alternative to chlorine for the delignification of wood pulp. The research addressed in this dissertation deals with detailed kinetic and mechanistic studies of K₅[SiVW₁₁O₄₀]·12H₂O, a POM used in the delignification of wood pulp, oxidation of phenolic lignin model compounds and milled wood lignin (MWL). Results from lignin model studies suggest an overall second-order reaction rate; first order with respect to both POM and phenolic substrate. It was observed that electron-transfer from neutral phenols was slower than that from the corresponding phenoxide anions. Hammett studies revealed the reaction involved the formation of an electron-deficient radical intermediate where the rate-determining step is electron transfer from a neutral substrate. The structure of the substituted phenol, in terms of its electron donating/withdrawing character, along with the position of the substituent on the aromatic ring heavily influences the reaction rates. Increasing the number of ortho methoxyl groups dramatically increased the reaction rate, e.g. phenol < guaiacyl < syringyl model structures. The ortho methoxyl group(s) resonance stabilizes and delocalizes the forming phenoxyl radical intermediate. Similarly, the reaction rate of para-substituted guaiacyl and syringyl model compounds showed a dependence on the nature of the para-substituent; inductive or resonance conjugated electron withdrawing effects and inductive donating effects. The effect of POM oxidation on the chemical structure of a Lodgepole pine MWL is investigated. ¹³C nuclear magnetic resonance (NMR) spectroscopic data revealed an approximate 28% decrease in β-O-4 inter-unit linkages after POM treatment, the decrease in β-O-4 inter-unit linkages being accompanied by an increase in carbonyl content. These results suggest that POM oxidation involves side-chain (such as α-OH/β-O-4) oxidation. ¹³C NMR spectroscopy along with gel permeation chromatography revealed an increase in the degree of condensation which supports the idea that radical coupling is a major reaction pathway in this process.Forestry, Faculty of
Graduate
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Wang, Guangyao. "An Investigation of Phase Change Material (PCM)-Based Ocean Thermal Energy Harvesting." Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/100989.
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Phase change material (PCM)-based ocean thermal energy harvesting is a relatively new method, which extracts the thermal energy from the temperature gradient in the ocean thermocline. Its basic idea is to utilize the temperature variation along the ocean water depth to cyclically freeze and melt a specific kind of PCM. The volume expansion, which happens in the melting process, is used to do useful work (e.g., drive a turbine generator), thereby converting a fraction of the absorbed thermal energy into mechanical energy or electrical energy. Compared to other ocean energy technologies (e.g., wave energy converters, tidal current turbines, and ocean thermal energy conversion), the proposed PCM-based approach can be easily implemented at a small scale with a relatively simple structural system, which makes it a promising method to extend the range and service life of battery-powered devices, e.g, autonomous underwater vehicles (AUVs). This dissertation presents a combined theoretical and experimental study of the PCM-based ocean thermal energy harvesting approach, which aims at demonstrating the feasibility of the proposed approach and investigating possible methods to improve the overall performance of prototypical systems. First, a solid/liquid phase change thermodynamic model is developed, based on which a specific upperbound of the thermal efficiency is derived for the PCM-based approach. Next, a prototypical PCM-based ocean thermal energy harvesting system is designed, fabricated, and tested. To predict the performance of specific systems, a thermo-mechanical model, which couples the thermodynamic behaviors of the fluid materials and the elastic behavior of the structural system, is developed and validated based on the comparison with the experimental measurement. For the purpose of design optimization, the validated thermo-mechanical model is employed to conduct a parametric study. Based on the results of the parametric study, a new scalable and portable PCM-based ocean thermal energy harvesting system is developed and tested. In addition, the thermo-mechanical model is modified to account for the design changes. However, a combined analysis of the results from both the prototypical system and the model reveals that achieving a good performance requires maintaining a high internal pressure, which will complicate the structural design. To mitigate this issue, the idea of using a hydraulic accumulator to regulate the internal pressure is proposed, and experimentally and theoretically examined. Finally, a spatial-varying Robin transmission condition for fluid-structure coupled problems with strong added-mass effect is proposed and investigated using fluid structure interaction (FSI) model problems. This can be a potential method for the future research on the fluid-structure coupled numerical analysis of AUVs, which are integrated with and powered by the PCM-based thermal energy harvesting devices.Doctor of Philosophy
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Santos, Aline Diorio dos. "Elaboração de modelo conceitual da degradação de poliacrilamidas (PAM) em compostos nitrogenados aplicado a estudo de caso." Universidade Estadual Paulista (UNESP), 2018. http://hdl.handle.net/11449/154196.
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Um dos materiais presentes nos lodos oriundos das estações de tratamento (LETAs) é o polímero denominado Poliacrilamida (PAM). Acredita-se que o mesmo seja inerte no solo, porém sua degradação pode estar associada a presença de compostos nitrogenados no solo, como amônio, nitratos e nitritos. Assim, é essencial avaliar a degradação de polímeros no sistema de tratamento de água que auxiliará na seleção e uso de produtos poliméricos no tratamento de água potável. Através da revisão bibliográfica apresentada neste trabalho, foi elaborado um Modelo Conceitual para a disposição de LETAs em aterro, com enfoque na degradação de poliacrilamidas e sua degradação em compostos nitrogenados, validando-o através de dados observados em estudo de caso. Conforme o Modelo Conceitual elaborado, pela via aeróbia, em que os processos de nitrificação podem ser observados, esperavam-se menores valores de pH (resultado da liberação de íons H+), assim como ambiente oxidante para ocorrência do processo de nitrificação (meio aeróbio necessita de oxigênio disponível), enquanto na área fora da zona de nitrificação, esperava-se maior valores de pH, presença maior de OD e maiores valores de Eh, uma vez que o oxigênio não estará sendo consumido pelas bactérias nitrificantes, podendo ainda haver incremento de OD pela recarga do aquífero através das precipitações. Observa-se outra via de degradação anaeróbia, pela reação anamox, em que amônio é oxidado e nitrito reduzido, liberando gás nitrogênio, em ambiente redutor. Adicionalmente, podem ser observados o íon amônio e óxido de manganês e hidróxido de ferro (abundantes no solo) sendo oxidados a nitrogênio gasoso, consumindo íons H+ no meio. A flutuação do nível de água no aquífero pode influenciar as concentrações observadas, através da recarga do aquífero, devido a precipitação e infiltração da água no solo, a espessura do aquífero livre pode se tornar maior, entrando em contato com camadas superficiais de PAM, ocorrendo maior lixiviação dos íons presentes nestas camadas e aumento das concentrações, havendo incremento de massa. Esse fenômeno pode ocorrer em conjunto com os processos biológicos citados, ocorrendo alternância da dissociação dos compostos nitrogenados por meio aeróbio e anaeróbio, conforme OD disponível no meio. Torna-se, portanto, indispensável a discussão sobre quais tipos de polieletrólitos podem ser utilizados no sistema de tratamento de água, pois conforme dados apresentados neste trabalho, a poliacrilamida presente no LETA pode degradar-se em amônio e por sua vez em nitrato por via aeróbia, contaminando o aquífero local, não se apresentando como resíduo inerte como preconizado pelo mercado e alguns autores.
One of the materials present in the sludge originated from water treatment is the polymer polyacrylamide, which some people believes is inert in the soil however its degradation may be associated with nitrogenous compounds in the soil, such as ammonium, nitrates and nitrites. So, it is essential to evaluate the degradation of polymers in the water treatment system due to it will assist in the selection and use of polymer products in the water treatment. Through the bibliographic review presented, a Conceptual Model for the disposition of sludge from water treatment in soil was developed, with the focus on the degradation of polyacrylamides and their degradation in nitrogenous compounds, validating it through data observed in a case study. According to the Conceptual Model elaborated, considering the aerobic route, where the nitrification processes can be observed, were expected lower pH values and oxidizing environment, while in the area outside the nitrification zone were expected higher pH values, presence of dissolved oxygen and reduction environment, once oxygen will not be consumed by nitrifying bacteria and also oxygen could be increased by water from precipitation which recharges the aquifer. Another anaerobic degradation route is observed, considering the anamox reaction, where ammonia is oxidized and nitrite reduced, releasing nitrogen gas, in a reducing environment. In addition, ammonium ion plus manganese oxide plus iron hydroxide can be oxidized to a vapour nitrogen, consuming hydrogen ions. The water level fluctuation in the aquifer can influence the observed concentrations, through the recharge of the aquifer, due to precipitation and infiltration of the water in the soil, the thickness of the free aquifer can become larger, coming into contact with sludge, occurring higher lixiviation of the ions present in these layers and increasing of the concentrations and mass. This phenomenon can occur together with the biological processes, occurring alternation of dissociation of the nitrogen compounds by aerobic and anaerobic, according to dissolved oxygen available. Therefore, it is essential to discuss what types of polyelectrolytes can be used in the water treatment system, due to according to data presented, the polyacrylamide present in the sludge can degrade in ammonium and in turn in nitrate by aerobic process, contaminating the local aquifer, not presenting as inert residue as recommended by the market and some authors.
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Wang, Lin. "Mass Transfer and GDL Electric Resistance in PEM Fuel Cells." Scholarly Repository, 2010. http://scholarlyrepository.miami.edu/oa_dissertations/486.
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Many modeling studies have been carried out to simulate the current distribution across the channel and shoulder direction in a proton exchange membrane (PEM) fuel cell. However the modeling results do not show agreement on the current density distribution. At the same time, no experimental measurement result of current density distribution across the channel and the shoulder direction is available to testify the modeling studies. Hence in this work, an experiment was conducted to separately measure the current densities under the channel and the shoulder in a PEM fuel cell by using the specially designed membrane electrode assemblies. The experimental results show that the current density under the channel is lower than that under the shoulder except when the fuel cell load is high. Afterwards two more experiments were carried out to find out the reason causing the higher current density under the shoulder. The effects of the electric resistance of gas diffusion layer (GDL) in the lateral and through-plane directions on the current density distribution were studied respectively. The experimental results show that it is the through-plane electric resistance that leads to the higher current density under the shoulder. Moreover, a three-dimensional fuel cell model is developed using FORTRAN. A new method of combining the thin-film model and homogeneous model is utilized to model the catalyst layer. The model is validated by the experimental data. The distribution of current density, oxygen concentration, membrane phase potential, solid phase potential and overpotential in a PEM fuel cell have been studied by the model. The modeling results show that the new modeling method provides better simulations to the actual transport processes and chemical reaction in the catalyst layer of a PEM fuel cell.
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Schwerdtle, Hartwig. "Prozessintegriertes Management - PIM : ein Modell für effizientes Qualitäts-, Umwelt- und Arbeitsschutzmanagement /." Berlin : Springer, 1999. http://aleph.unisg.ch/hsgscan/hm00006710.pdf.
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Yeates, Stuart Andrew. "Text Augmentation: Inserting markup into natural language text with PPM Models." The University of Waikato, 2006. http://hdl.handle.net/10289/2600.
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This thesis describes a new optimisation and new heuristics for automatically marking up XML documents, and CEM, a Java implementation, using PPM models. CEM is significantly more general than previous systems, marking up large numbers of hierarchical tags, using n-gram models for large n and a variety of escape methods. Four corpora are discussed, including the bibliography corpus of 14682 bibliographies laid out in seven standard styles using the BibTeX system and marked up in XML with every field from the original BibTeX. Other corpora include the ROCLING Chinese text segmentation corpus, the Computists' Communique corpus and the Reuters' corpus. A detailed examination is presented of the methods of evaluating mark up algorithms, including computation complexity measures and correctness measures from the fields of information retrieval, string processing, machine learning and information theory. A new taxonomy of markup complexities is established and the properties of each taxon are examined in relation to the complexity of marked up documents. The performance of the new heuristics and optimisation are examined using the four corpora.
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Krima, Sylvère. "Semantic based framework for dynamic customization of PLM-related information models." Phd thesis, Université de Bourgogne, 2013. http://tel.archives-ouvertes.fr/tel-00944190.
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We live in the information age. Data has become an essential asset for most everyday situations and business interactions. The need to share data, to generate information, and create new knowledge from that data is common to all fields of research and all economic activity. Managing data is a critical, and sometimes costly, process. When not properly defined, data might become incomplete, inconsistent or, even worse, unusable. Requirements for data evolve and we must define new data or update existing data over the entire data lifecycle. Evolving data requirements is an important issue and a technological challenge as it is not possible to define, in advance, information structures that meet requirements you do not yet know. Specifying information requirements is particularly challenging in domains such as manufacturing where information exchange involves many actors and sharing across multiple functions and software applications. As a result, it becomes hard to find a common information structure for representing data. The challenge is even bigger when a temporal aspect has to be considered since it requires the ability to extend the information structure dynamically over time. One area within the manufacturing domain that we have identified with these characteristics is Product Lifecycle Management (PLM). PLM involves many global actors using a myriad of software applications that perform a series of product management functions that can last from weeks to decades. Because the mechanism to extend models is static by its nature, requiring numerous updates of the initial information model, this operation is expensive in cost and time, and requires and understanding of the entire initial model to ensure correct extensions are developed. This research presents an alternative based on dynamic customization of information models in the context of PLM, by leveraging existing PLM standards and frameworks, and using emerging semantic web technologies such as OWL, SPARQL and SPIN. Following a state of the art in Chapter 2, Chapter 3 defines technical requirements used to evaluate existing PLM standards and frameworks. Based on the analysis of this evaluation, Chapter 4 presents new framework components for defining dynamically customizable information models for PLM. In chapter 5 these components are integrated together into a framework, and a use case demonstrates the efficiency of the framework. Chapter 6 concludes the research and introduces ideas for future research.
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Forcat, Torras Francesc. "Anàlisi del camp d'ones internes en sistemes limnològics petits. Simulacions amb el POM." Doctoral thesis, Universitat de Girona, 2009. http://hdl.handle.net/10803/7811.
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Aquí hem aplicat el Princeton Ocean Model als embassaments de Sau i Boadella, situats a Catalunya, Espanya. Les simulacions s'han realitzat a l'estació d'estiu, quan la columna d'aigua està estratificada de forma contínua, i sota un règim de brisa amb velocitats de fins a 4 m/s. Basant-nos en aquestes simulacions hem analitzat el camp d'ones internes i comparat els resultats numèrics amb dades experimentals disponibles. El model reprodueix adequadament tots els modes observats en l'espectre de la velocitat i temperatura mesurades i ajuda a identificar els diferents modes. Les simulacions mostren la importància dels modes rotacionals en el camp d'ones internes dels embassaments estratificats. En el període estudiat, el radi de Rossby per l'embassament de Sau és de l'ordre de 100 m, que és varies vegades més petit que la amplitud de l'àrea lacustre de l'embassament, i el número de Rossby és de l'ordre de 0.1, corroborant la importancia de l'efecte de Coriolis.We applied the Princeton Ocean Model to the Sau and Boadella reservoirs, located in Catalonia, Spain. Simulations were done for the summer season, when the water column is continuously stratified, and under a breeze regime with velocities of up to 4 m/s. Based on these simulations we analyzed the internal wave field and compared the numerical results with available field data. The model adequately reproduces all significant modes observed on the spectra of measured velocity and temperature and helps to identify the different modes. The simulations show the importance of rotational modes for the internal wave field of the stratified reservoirs. Under the studied wind regime, the Rossby radius for the Sau Reservoir is of the order of 100 m, that is, several times smaller than the amplitude of the lacustrine zone of the reservoir, and the Rossby number is of order of 0.1, which corroborates the importance of the Coriolis effect.
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Simmler, Urs. "PTC Creo Simulate 3.0." Universitätsbibliothek Chemnitz, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-171761.
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Strahl, Stephan. "Experimental and model-based analysis for performance and durability improvement of PEM fuel cells." Doctoral thesis, Universitat Politècnica de Catalunya, 2014. http://hdl.handle.net/10803/285240.
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Increasing global energy demand, growing carbon emissions and the depletion of fossil fuel sources are some of the most important driving forces for the development of sustainable energy solutions. Proton Exchange Membrane (PEM) fuel cells have been demonstrated to be a potential candidate for clean energy conversion in a wide range of applications reaching from highly dynamic transportation systems to stationary systems. Despite their benefits, such as high efficiency and wide operating range, PEM fuel cells must still meet or exceed the technological advantages, such as durability and cost, of conventional power systems in order to be truly competitive. Thus, current research is focused on improving these aspects.
This doctoral thesis combines experimental and model-based studies in order to improve performance and durability of PEM fuel cells, that work without external humidification, as demanded by recent government-supported research programs. Improved performance and durability can be obtained by proper system control. The key factor for the development of successful control strategies is adequate thermal and water management considering their interconnections. Therefore, this work investigates the important links between performance, efficiency and lifetime with respect to fuel cell temperature and humidification.
The experimental evaluation of temperature-related and purge-related effects shows the great potential of improving the system performance by proper thermal management. In-situ and ex-situ experiments, such as electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), gas chromatography (GC), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and scanning electron microscopy (SEM) were utilized in order to explore short-term and long-term effects of operation modes on performance and durability.
To provide a better understanding of the experimentally observed phenomena and their different dynamics with respect to the development of efficient controllers, mathematical models have been derived. The dynamic models allow for relating electrode structure to the cell voltage transient behavior during changes in fuel cell temperature and humidification, including important phase change and ionomer sorption dynamics of water. The experimentally validated, model-based analysis provides recommendations of proper operating conditions and catalyst structure, such as optimal fuel cell temperature and adequate pore-size-distribution, in order to improve the PEM fuel cell performance.
The modular character and inherent adaptability of the models has been successfully demonstrated in the study of water transport in a high temperature PEM fuel cell stack. It is shown how mathematical modeling can improve the interpretation of experimental results and provide insight into experimentally non-observable interactions.
In conclusion, the presented laboratory and model-based work, including the developed experimental and mathematical tools, contribute to current international research targets for advancing sustainable energy solutions.La creciente demanda mundial de energía, el crecimiento de las emisiones de dióxido de carbono y el agotamiento de las fuentes de combustible fósiles son algunos de los factores más importantes para el desarrollo de soluciones basadas en energies sostenibles. Las pilas de combustible de tipo Proton Exchange Membrane (PEM) han demostrado ser un candidato potencial para la conversión limpia de la energía en una extensa gama de aplicaciones, desde los sistemas de transporte altamente dinámicos hasta sistemas estacionarios. No obstante sus beneficios, tales como una alta eficiencia y un amplio rango de operación, las pilas de combustible PEM todavía deben cumplir o superar las ventajas tecnológicas de los sistemas de energía convencionales, como son su durabilidad y coste, con el fin de ser verdaderamente competitivas. Por lo tanto, la investigación actual se centra en la mejora de estos aspectos. Esta tesis doctoral combina estudios experimentales y estudios basados en modelos físicos con el fin de mejorar el rendimiento y la durabilidad de las pilas de combustible PEM que trabajan sin humidificación externa, tal y como exigen recientes programas de investigación apoyados por los gobiernos. La mejora del rendimiento y de la durabilidad se puede obtener por control apropiado del sistema. El factor clave para el desarrollo de estrategias de control exitosas es la gestión adecuada de la temperatura y del agua y sus interconexiones. Por lo tanto, este trabajo investiga los vínculos importantes entre el rendimiento, la eficiencia y la vida útil con respecto a la temperatura de la pila de combustible y su humidificación. La evaluación experimental de los efectos relacionados con la temperatura y las purgas de hidrógeno muestra el gran potencial para mejorar el rendimiento del sistema pila mediante una gestión térmica adecuada. En esta tesis se emplean experimentos in-situ y ex-situ, tales como la espectroscopía electroquímica de impedancia (EIS), la voltametría cíclica (CV), la cromatografía de gases (CG), la espectroscopia de fotoelectrones emitidos por rayos X (XPS), la difracción de rayos X (XRD) y la microscopía electrónica de barrido (SEM) con el fin de explorar los efectos a corto plazo y a largo plazo de los modos de operación sobre el rendimiento y la durabilidad de una pila PEM. Para proporcionar una mejor comprensión de los fenómenos observados experimentalmente y sus diferentes dinámicas para el correcto desarrollo de controladores eficientes, se derivan modelos matemáticos dinámicos. Los modelos permiten relacionar la estructura de los electrodos con el comportamiento transitorio del voltaje durante los cambios de temperatura y de humidificación de la pila de combustible, incluyendo las dinámicas importantes del cambio de fase y de adsorción y desorción del agua. El análisis basado en modelos validados experimentalmente proporciona recomendaciones de las condiciones de funcionamiento y de la estructura del catalizador, tales como la temperatura óptima y la distribución de tamaño de poros apropiada, con el fin de mejorar el rendimiento de la pila de combustible PEM. El carácter modular y la adaptabilidad inherente de los modelos propuestos se demuestra con éxito en el estudio de transporte de agua en un stack de pilas de combustible PEM de alta temperatura. Se muestra como el modelado matemático puede mejorar la interpretación de los resultados experimentales y proporcionar información sobre las interacciones que experimentalmente no son observables. En conclusión, el trabajo de laboratorio y el basado en modelos que se presenta en esta tesis doctoral, incluyendo las herramientas experimentales y matemáticas desarrolladas, contribuyen a la consecución de los actuales objetivos internacionales de investigación que deben permitir aportar mejoras en las soluciones basadas en energías sostenibles.
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Hattie, Ronald J. "Power assurance for the PT6/T400 engine ghrough the use of a computer model." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ26995.pdf.
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Hattie, Ronald J. (Ronald Joseph) Carleton University Dissertation Engineering Mechanical and Aerospace. "Power assurance for the PT6/T400 engine through the use of a computer model." Ottawa, 1997.
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Beset, Doğan Arda Günaydın Murat. "A model for assesing project management maturity level of architectural design offices (ARCH-PMM)/." [s.l.]: [s.n.], 2007. http://library.iyte.edu.tr/tezlerengelli/doktora/mimarlik/T000666.pdf.
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Caliari, Giuliano Luz Pigatti. "Transformações e mapeamentos da MDA e sua implementação em três ferramentas." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/3/3141/tde-08012008-103612/.
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As transformações de modelos são um ponto vital para os enfoques de desenvolvimento dirigido por modelos, incluindo a MDA. No presente trabalho apresenta-se alguns dos conceitos da MDA relacionados a transformações de modelos. São vistos os conceitos de PIM, PSM, transformações, mapeamentos e marcas. Estes conceitos são analisados no contexto de três ferramentas MDA, a OptimalJ, a AndroMDA e a ArcStyler, para verificar se as ferramentas os implementam de acordo com a MDA. Também é analisado como e quais transformações e mapeamentos de modelos estão sendo implementados pelas ferramentas, através da comparação qualitativa de definições de conceitos e de exemplos do uso destes. Além de verificar os conceitos relacionados às transformações, faz-se um estudo de caso qualitativo para analisar as transformações e mapeamentos providos pelas ferramentas e como as ferramentas trabalham com eles. Mostram-se as dificuldades de se criar um modelo PIM do sistema do estudo de caso e adaptá-lo para cada uma das ferramentas.Model transformations are a vital point for model driven development, including MDA. In the present essay we introduce some of the MDA concepts related with model transformations. We present the concept of PIM, PSM, transformations, mappings and marks. These concepts are analyzed in the context of three MDA tools, OptimalJ, AndroMDA and ArcStyler, to verify if the tools implement the concepts according to MDA. We also analyze how and which model transformations and model mappings are being implemented by the tools, through a qualitative comparison of the definition of these concepts and using some examples of their intended use. In addition to verifying the concepts related to transformations, we create a qualitative case study to analyze the model transformations and model mappings provided by the tools, and how the tools work with them. We show a few of the problems faced when creating a PIM model of the case study\'s system and the adaptations it required for each tool.
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Cook, Shane Stuart. "Effects of headwinds on towing tank resistance and PMM tests for ONR Tumblehome." Thesis, University of Iowa, 2011. https://ir.uiowa.edu/etd/2688.
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Calm water towing tank experiments consisting of resistance tests and static and dynamic planar motion mechanism (PMM) tests are performed for a surface combatant with primary focus on the effects of hurricane scale headwinds. The experiments are designed to gain a better understanding of the physics of ship response to wind and to provide a validation dataset for an unsteady Reynolds-averaged Navier Stokes (RANS)-based computational fluid dynamics (CFD) code used for computing both air and water flow around a ship. Hurricane scale wind speeds are chosen to maximize the measurable effect of wind on ship forces and motions for a more definitive analysis and comparison with CFD. The geometry is the 1/48.9 scale fully appended ONR Tumblehome model 5613, which has length L = 3.147 m and is equipped with a superstructure. Tests are performed in a 3.048 × 3.048 × 100 m towing tank with wind generated by a custom built wind carriage towed ahead of the ship model. Air-stream velocity measurements indicate a maximum relative wind speed magnitude of 9.38 m/s with 6 - 7% uniformity and RMS values of approximately 4.5%. The effects of three wind speeds on static and dynamic forces, moment, and motions are analyzed. Results show that wind contributes significantly to surge force (approximately 46% at Fr = 0.2). Resistance data shows agreement with CFD computations with errors averaging approximately 4%. The drag coefficient above water is approximately 0.3 and generally decreases with increasing ship speed. Sway force and yaw moment are largely affected when the ship experiences oblique orientation to the flow. Forces and moment exhibit quadratic scaling with wind speed. Roll is the most sensitive motion to wind and is counteracted by it up to 1.8° for PMM test conditions. In addition, harmonic amplitudes of forces and moment data from dynamic tests are used to determine hydrodynamic derivatives for all three wind conditions following a mathematical model. The effect of wind on hydrodynamic derivatives is significant with changes on the order of 10 - 100%.
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El, Kadiri Soumaya. "Management des processus collaboratifs dans les systèmes PLM." Thesis, Lyon 2, 2009. http://www.theses.fr/2009LYO22017/document.
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La tendance actuelle des organisations à développer des collaborations avec différentes parties prenantes a pour objectif de répondre à une complexité de plus en plus importante des produits et de favoriser l'innovation ; le tout sous de fortes pressions d'un environnement économique, liées aux exigences du développement durable, de l'accélération des cycles de vie, des normes qualité, etc. Les SIP tendent à garantir une transversalité entre l'ensemble des phases du cycle de vie produit ; répondant ainsi aux besoins d'amélioration de la qualité produit, de maîtrise des processus et de réduction des délais, tout en favorisant la collaboration. La complexité des processus collaboratifs liée à la gestion du cycle de vie du produit ne peut faire l’économie d’une réflexion sur les ressources engagées au regard des objectifs poursuivis, ni même d’une balance économique globale des coûts supportés. Ainsi les critères d’efficacité et d’efficience s’ajoutent aux critères les plus traditionnels du temps imparti et du degré de qualité visé. L'objectif de cette thèse consiste à définir une démarche méthodologique et applicative pour répondre à la question suivante : "Comment instrumenter le SIP pour analyser les activités menées au sein du système et déceler les freins au travail collaboratif ?". Ainsi, nous présentons dans cette thèse un cadre méthodologique et architectural permettant d'assurer un pilotage des processus collaboratifs dans les SIP. Il s'agit entre autre de mettre en place une expérience d'observation basée sur l’ingénierie des traces ; et de mener une réflexion sur la définition d'indicateurs permettant de mettre en place un contrôle de l'activité collaborative. La mise en œuvre effective de ces actions implique la définition d’une architecture complémentaire et générique adaptée à l'environnement du SIP. Finalement, le développement d'un prototype, intégré par la suite au SIP @udros, nous a permis de valider le cadre méthodologique et applicatif de cette thèseThe current trend of organizations to develop partnerships with various stakeholders aims to respond to a rising complexity, of products and to foster innovation; all under great pressures of an economical environment, related to sustainability requirements, lifecycle acceleration, quality standards, etc. PLM systems tend to ensure the transversality within all the stages of product lifecycle; meeting the needs of product quality improvement, process control and delays reduction, while fostering collaboration. The complexity of collaborative processes related to the product lifecycle management cannot lean only on the engaged resources, or on the global balance between costs, budget, and receipts. Then efficacy and efficiency criterions come on top of the traditional ones (quality level, time, etc.). This thesis aims to propose a methodological and applicative approach responding to the following research question: “How can PLM System be « instrumented » in order to analyze the collaborative activities and to reveal the brakes causes?” We present in this thesis a methodological and architectural framework to ensure a collaborative process management in PLM System. The methodological framework leans on observation experiences based on tracks engineering (tracks generated by PLM system) and indicators definition supporting the control of the collaborative activity. The principal objective is to reduce risks by reacting in real time to the incidents or dysfunctions that may occur. The effective implementation of these actions involves the definition of a generic and complementary architecture suitable to the environment of the system. Finally, the development of a prototype, integrated then to the system @udros, allowed us to validate the methodological and architectural framework of this thesis
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Mair, Patrick, and Reinhold Hatzinger. "Extended Rasch Modeling: The eRm Package for the Application of IRT Models in R." Department of Statistics and Mathematics, WU Vienna University of Economics and Business, 2007. http://epub.wu.ac.at/332/1/document.pdf.
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Item response theory models (IRT) are increasingly becoming established in social science research, particularly in the analysis of performance or attitudinal data in psychology, education, medicine, marketing and other fields where testing is relevant. We propose the R package eRm (extended Rasch modeling) for computing Rasch models and several extensions. A main characteristic of some IRT models, the Rasch model being the most prominent, concerns the separation of two kinds of parameters, one that describes qualities of the subject under investigation, and the other relates to qualities of the situation under which the response of a subject is observed. Using conditional maximum likelihood (CML) estimation both types of parameters may be estimated independently from each other. IRT models are well suited to cope with dichotomous and polytomous responses, where the response categories may be unordered as well as ordered. The incorporation of linear structures allows for modeling the effects of covariates and enables the analysis of repeated categorical measurements. The eRm package fits the following models: the Rasch model, the rating scale model (RSM), and the partial credit model (PCM) as well as linear reparameterizations through covariate structures like the linear logistic test model (LLTM), the linear rating scale model (LRSM), and the linear partial credit model (LPCM). We use an unitary, efficient CML approach to estimate the item parameters and their standard errors. Graphical and numeric tools for assessing goodness-of-fit are provided. (author's abstract)Series: Research Report Series / Department of Statistics and Mathematics
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Luna, Pacho Julio Alberto. "Development of control systems and state observers for efficiency and durability improvement in PEM fuel cell based systems." Doctoral thesis, Universitat Politècnica de Catalunya, 2017. http://hdl.handle.net/10803/458885.
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Proton exchange membrane (PEM) fuel cells, which use hydrogen as fuel, provide high power densities while operating at lower temperatures, reducing the cost of materials and maintenance. PEM fuel cells are suitable for a broad range of applications, such as stationary, combined heat and power (CHP), portable systems and automotive. Performance and degradation in PEM fuel cell-based systems is greatly influenced by the internal conditions of the fuel cell.
In this doctoral thesis, an extensive study of modelling, observation and control strategies of a PEM fuel cell-based system is performed. The objective is to obtain advanced control solutions that aid to enhance the durability and improve the efficiency of fuel cells. These control solutions have to take into account the internal conditions of the fuel cell and use this information to operate the system under conditions that guarantee that the degradation rate of the fuel cell is not increased. At the same time, the controllers have to guarantee that the system achieves high efficiencies, considering the parasitic power consumption of the balance of plant (BoP) ancillaries. The observation and control solutions are evaluated using the New European Driving Cycle (NEDC) profile as a case study.
The first part of the thesis introduces the motivation of the present work and the structure of the document. Additionally, the current state of the research regarding modelling, state observers and control strategies for PEM fuel cell-based systems are studied in detail. After the study of the state of the art, the objectives of this doctoral work are presented.
The second part of the thesis is focused on the development, implementation and study in a simulation environment of a PEM fuel cell-based system model. The model considers spatial derivatives for the fuel cell in order to represent the internal dynamic behaviour, which affects the efficiency and degradation rate of the system. In this thesis, a special attention is given to the electrochemically active surface area (ECSA). The ECSA in the cathode catalyst layer (CCL) is modelled using a twophase water model at the cathode side of the fuel cell to better represent its effect on the output voltage. The BoP ancillaries are considered as a parasitic power consumption that has to be delivered by the fuel cell. The most relevant parasitic power consumption is that of the compressor, which is modelled to include its dynamic behaviour in the control strategies.
Once the model equations are presented, model-based nonlinear distributed parameters observers (NDPO) are developed in the third part of the thesis. First, the partial differential equations (PDE) of the PEM fuel cell-based system are discretised and reformulated to obtain the observation model. Using this model, two novel sliding mode control (SMC) approaches for the observation of the internal conditions of the fuel cell are presented and compared, using the NEDC current profile as the case study for the simulations.
The fourth part of the thesis is devoted to model-based predictive control of the PEM fuel cell-based system. In particular, a nonlinear model predictive control (NMPC) strategy is proposed to improve the efficiency and at the same time, enhance the lifetime of the fuel cell. The use of the NDPOs in the control scheme facilitates critical information about the internal conditions of the fuel cell. This allows to design advanced control objectives that would not be achievable if using only the limited measurements that are available in PEM fuel cell-based systems. A multi-objective cost function that can prioritise between the different objectives of the controller during the optimisation procedure is designed. Finally, a discussion of the results obtained comparing different prioritisation between control objectives is provided.
The fifth and last part of the thesis is devoted to extract conclusions.Las pilas de combustible de membrana de intercambio protónico (PEM), las cuales utilizan hidrógeno como combustible, proporcionan altas densidades de potencia operando a bajas temperaturas, reduciéndose el coste de los materiales y el mantenimiento. Las pilas de combustible de tipo PEM son apropiadas para un amplio rango de aplicaciones, tales como estacionarias, de ciclo combinado (CHP), sistemas portátiles y automoción. El rendimiento y la degradación en sistemas basados en pilas de combustible de tipo PEM están importantemente influenciados por las condiciones internas. En la presente tesis doctoral, se realiza un extenso estudio de modelado y estrategias de observación y control en un sistema basado en pila de combustible de tipo PEM. El objetivo es obtener soluciones avanzadas de control que ayuden en la mejora de la durabilidad e incrementar la eficiencia de las pilas de combustible. Dichas soluciones de control tienen que tener en cuenta las condiciones internas de la pila de combustible, y utilizar esta información para operar el sistema bajo condiciones que garanticen que la degradación del sistema no se incrementa. Al mismo tiempo, los controladores deben garantizar que el sistema alcanza altas eficiencias, considerando las pérdidas por consumos parasíticos de los auxiliares del balance de la planta (BoP). Las soluciones de observación y control son evaluadas utilizando el perfil de conducción New European Driving Cycle (NEDC). La primera parte de la tesis introduce la motivación tras el presente trabajo y la estructura del documento. Se estudia en detalle el estado actual de la investigación referente a modelado, observadores de estados y estrategias de control para sistemas basados en pilas de combustible. Tras este estudio del estado del arte, se presentan los objetivos de la tesis. La segunda parte de la tesis está enfocada en el desarrollo, implementación y estudio en un entorno de simulación de un modelo de sistema basado en pila de combustible de tipo PEM. El modelo considera derivadas espaciales para representar el comportamiento de la dinámica interna de la pila. Dicha dinámica interna afecta la eficiencia y el grado de degradación del sistema. En la presente tesis, la degradación de la capa catalizadora se ve reflejada en la pérdida de área de la superficie electroquímicamente activa (ECSA). La ECSA en la capa catalizadora del cátodo (CCL) se modela utilizando un modelo bifásico de agua en el lado catódico de la pila, con el objeto de representar fielmente su efecto en el voltaje de salida. Una vez que las ecuaciones del modelo son presentadas, observadores no-lineales de parámetros distribuidos (NDPO) basados en modelo se desarrollan en la tercera parte del presente trabajo. Primero, las ecuaciones en derivadas parciales (PDE) de la pila de combustible de tipo PEM son discretizadas y reformuladas para obtener el modelo de observación. Utilizando este modelo, se presentan y comparan dos novedosos enfoques de control por modos deslizantes (SMC) para la observación de las condiciones internas de la pila de combustible. La cuarta parte de la presente tesis está dedicada al control predictivo basado en modelos del sistema de pila de combustible de tipo PEM. En particular, se propone una estrategia de controlador predictivo no-lineal basado en modelo (NMPC) para la mejora de la eficiencia y a la vez, la mejora del ciclo de vida de la pila de combustible. El uso de los NDPOs en el esquema de control suministra información crítica acerca de las condiciones internas en la pila de combustible. Este hecho permite el diseño de objetivos de control avanzados que no serían realizables utilizando únicamente las limitadas mediciones que están disponibles en los sistemas basados en pilas de combustible de tipo PEM. La quinta y última parte de la tesis está dedicada a la extracción de conclusiones.
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Bertoco, Juliana. "Solução numérica do modelo constitutivo KBKZ-PSM para escoamentos com superfícies livres." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/55/55134/tde-16012017-162912/.
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Escoamentos viscoelásticos não estacionários com superfícies livres são comuns em muitos processos industriais e diversas técnicas numéricas têm sido empregadas para reproduzir computacionalmente estes processos. A maioria dos modelos empregados utiliza equações diferenciais na definição do tensor de tensões. Porém, para alguns grupos de fluidos complexos, por exemplo, fluidos de Boger, os modelos integrais mostram-se mais capacitados em fornecer uma boa aproximação para os comportamentos não lineares desses fluidos. Este trabalho trata da solução numérica do modelo constitutivo integral KBKZ-PSM para escoamentos transientes bidimensionais com superfícies livres. O método numérico proposto é uma técnica numérica que utiliza diferenças finitas para simular escoamentos com superfícies livres na presença de paredes sólidas. As principais características do método numérico proposto são: solução das equações de conservação de quantidade de movimento e massa utilizando um método semi-implícito; a condição de contorno na superfície livre é acoplada à equação de Poisson, o que garante conservação de massa; a discretização do tempo t é realizada por uma nova técnica numérica; o tensor de Finger é calculado pelo método dos campos de deformação e avançado no tempo pelo método de Euler modificado. Essa nova técnica é verificada em escoamentos cisalhantes e elongacionais. Adicionalmente, uma solução analítica desenvolvida para escoamentos em canais bidimensionais é empregada para verificar e analisar a convergência do método proposto. Com relação a escoamentos com superfícies livres, a convergência é verificada por meio de refinamento de malha nas simulações de um jato incidindo sobre placa rígida e no problema do inchamento do extrudado. Finalmente, o método é aplicado para investigar os problemas jet buckling e inchamento do extrudado de fluidos KBKZ-PSM.Unsteady viscoelastic free surface flows are common in many industrial processes and a variety of numerical techniques have been employed to simulate these flows. The majority of constitutive models employed are based on differential equations to define the extra stress tensor. However, for some complex fluids, for instance, Boger fluids, integral models are more adequate to approximate the nonlinear behaviour of these fluids. This work deals with the numerical solution of the integral constitutive model KBKZ-PSM for two-dimensional unsteady free surface flows. The proposed numerical method is a numerical technique that employs finite differences to simulate moving free surface flows that interact with solid walls. The main features of the method are: numerical solution of the momentum and mass equations by an implicit method; the pressure condition on the free surface is implicitly coupled with the Poisson equation for obtaining the pressure field from mass conservation; a novel scheme for defining the past times t is employed; the Finger tensor is calculated by the deformation fields method and is advanced in time by the modified Euler method. This new technique is verified by solving shear and uniaxial elongational flows. Moreover, an analytic solution for channel flows is obtained that is used in the verification and convergence analysis of the proposed methodology. For free surface flows, the assessment of convergence lies on the mesh refinement on the simulation of a jet impinging on a flat surface and the extrudade swell problem. Finally, the new method is applied to investigate the jet buckling phenomenon and extrudate swell of KBKZ-PSM fluids.
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Paul, Ratnadeep. "A Translator for Converting JT Models to Second Life." University of Cincinnati / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1236966950.
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Christie, Christopher Robert. "Calcium/Phosphate Regulation: A Control Engineering Approach." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/54014.
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Calcium (Ca) homeostasis is the maintenance of a stable plasma Ca concentration in the human body in the presence of Ca variability in the physiological environment (e.g. by ingestion and/or excretion). For normal physiological function, the total plasma Ca concentration must be maintained within a very narrow range (2.2-2.4mM). Meeting such stringent requirements is the task of a regulatory system that employs parathyroid hormone (PTH) and calcitriol (CTL) to regulate Ca flux between the plasma and the kidneys, intestines and bones. On the other hand, plasma phosphate control is less tightly, but simultaneously, regulated via the same hormonal actions. Chronic imbalances in plasma Ca levels are associated with disorders of the regulatory organs, which cause abnormal hormonal secretion and activity. These changes in hormonal activity may lead to long-term problems, such as, osteoporosis (increased loss of bone mineral density), which arises from primary hyperparathyroidism (PHPT) – hyper secretion of PTH.
Existing in silico models of Ca homeostasis in humans are often cast in the form of a single monolithic system of differential equations and are not easily amenable to the sort of tractable quantitative analysis from which one can acquire useful fundamental insight. In this research, the regulatory systems of plasma Ca and plasma phosphate are represented as an engineering control system where the physiological sub-processes are mapped onto corresponding block components (sensor, controller, actuator and process) and underlying mechanisms are represented by differential equations. Following validation of the overall model, Ca-related pathologies are successfully simulated through induced defects in the control system components.
A systematic approach is used to differentiate PHPT from other diseases with similar pathophysiologies based on the unique hormone/ion responses to short-term Ca disturbance in each pathology model. Additionally, based on the changes in intrinsic parameters associated with PTG behavior, the extent of PHPT progression can be predicted and the enlarged gland size estimated a priori.
Finally, process systems engineering methods are used to explore therapeutic intervention in two Ca-related pathologies: Primary (PHPT) and Secondary (SHPT) Hyperparathyroidism. Through parametric sensitivity analysis and parameter space exploration, the calcium-sensing receptor (sensor) is identified as a target site in both diseases and the extent of potential improvement is determined across the spectrum of severity of PHPT. The findings are validated against existing drug therapy, leading to a method of predicting drug dosage for a given stage of PHPT. Model Predictive Control is used in drug therapy in SHPT to customize the drug dosage for individual patients given the desired PTH outcome, and drug administration constraints.Ph. D.