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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
151

Calculo do equilibrio de fases solido-liquido em misturas binarias por meio de tecnicas de minimização e analise de convexidade

Rocha, Stella Alonso 19 March 2008 (has links)
Orientador: Reginaldo Guirardello / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-10T21:52:58Z (GMT). No. of bitstreams: 1 Rocha_StellaAlonso_M.pdf: 1447122 bytes, checksum: 284050671a884fad6a344a1b77527d60 (MD5) Previous issue date: 2008 / Resumo: Esse trabalho é de caráter teórico e computacional e tem como objetivo o estudo e aplicação de técnicas de otimização para cálculo do equilíbrio sólido-líquido de misturas graxas binárias de origem natural, utilizando dois métodos: um problema de Programação Não-linear, implementado no software GAMS e o outro, uma análise de equações fazendo uso das condições de Kuhn-Tucker. O cálculo do equilíbrio de fases baseia-se na minimização da energia livre de Gibbs do sistema. Para a representação termodinâmica das misturas são utilizados modelos termodinâmicos capazes de representar as fases líquida e sólida. As misturas estudadas são compostas por ácidos graxos e triglicerídeos, as quais foram divididas conforme as características dos compostos utilizados: ácidos graxos saturados, insaturados e triglicerídeos, com diferentes combinações de compostos. A modelagem das fases foi desenvolvida gradativamente, inicialmente consideraram-se as fases ideais, posteriormente a fase líquida foi modelada pela equação de Margules 2-sufixos, com a fase sólida permanacendo ideal, e por fim a fase sólida foi descrita pela equação de SLAUGHTER & DOHERTY e a líquida continou a ser modelada por Margules 2-sufixos. Os modelos desenvolvidos nesse trabalho são classificados como modelos de programação não-linear convexa, o que garante a busca pelo mínimo global. Assim, quando aplicados à linguagem de programação GAMS, utilizando o solver CONOPT, ou quando utilizando as equações encontradas analiticamente, através de microcomputadores, os resultados obtidos garantem que a mínima energia livre de Gibbs foi encontrada e que a mistura está em equilíbrio. Os resultados encontrados foram comparados com os dados medidos por ROLEMBERG (2002), pela técnica DSC, apresentando uma satisfatória proximidade entre eles / Abstract: This work has a theorical and computational character which objective is the study and aplication of optimization technique for the solid-liquid equilibria calculation of binary fat mixtures with natural origin. Two methods was used: One Nonlienar Program problem,an algorithm using the software GAMS and the other, analysis of equations that use the Kuhn-Tucker constrains applied in softwares which can execute conventionals calculation, like Microsoft Excel. The calculation of phasee equilibria is based on the minimization of Gibbs free energy of the sistem. The termodynamic representation of mixtures use models which can represent liquid and solid phases. The mixtures are composed for fat acids and triglycerides which are divided on three characteristics: saturated fatty acids, unsatureted fatty acids and trigycerides with differents combination among themselves. The phases¿ modeling was developed starting for phases on ideal state. In the second step, the solid phase was considered ideal and the liquid phase was modeled using the Margules Model. At the end, it was used the Slaughter & Doherty equation to modeling the solid phase and the Margules Model continued to be used for the liquid phase. The models developed in this work are nonliner programming and convex equations, these characteristics are the proof that the optimal point found is the global optimum. So using the methods propoused in this work, the results, certainly are the minim Gibbs free energy and the compound are in equilibrium. The results founded were compared with experimental data for ROLEMBERG (2002), that were obtained with DSC technique, with satisfactory proximity among them / Mestrado / Desenvolvimento de Processos Químicos / Mestre em Engenharia Química
152

Fracionamento de óleos essenciais por extração líquido-líquido em coluna de discos rotativos perfurados: estudo experimental e simulação do processo / Essential oil fractionation by liquid-liquid extraction: experimental study and process simulation

Cristina Chiyoda Koshima 11 December 2015 (has links)
A fim de possibilitar o emprego industrial dos óleos essenciais como agentes aromatizantes, é interessante que estes sejam submetidos à desterpenação, obtendo-se uma fração mais enriquecida em oxiterpenos, que é mais solúvel em água, estável, além de manter o aroma característico do óleo bruto. Este fracionamento pode ser realizado por extração líquida utilizando etanol como solvente. Neste contexto, o processo de desterpenação de óleo essencial de bergamota em coluna de discos rotativos perfurados (PRDC), utilizando como solventes soluções etanólicas com diferentes teores de água foi estudado por meio da obtenção de dados experimentais e de simulação computacional do processo. Em adição, o equilíbrio de fases, a 25 °C, de sistemas modelo de óleo de eucalipto, cravo e pimenta da Jamaica e de sistemas contendo óleos essenciais brutos de bergamota e lavandim também foram estudados nesta tese. Observou-se que, no estudo do equilíbrio de fases, dentre os sistemas monitorados, o composto oxigenado eugenol e o hidrocarboneto sesquiterpênico cariofileno, presentes nos óleos de cravo e pimenta da Jamaica apresentaram, respectivamente, o maior e menor valores de coeficiente de distribuição. Para os sistemas contendo óleos brutos de bergamota e lavandim verificou-se que os parâmetros binários dos modelos NRTL e UNIQUAC, ajustados previamente para o sistema modelo de óleo de bergamota, são capazes de descrever o equilíbrio de fases dos sistemas mais complexos. Ademais, com relação ao estudo do processo de desterpenação de óleo essencial em PRDC, pode-se inferir que a obtenção de frações enriquecidas nos compostos oxigenados é viável e factível para óleos que apresentem baixos teores de linalol em sua composição. / In order to enable the industrial use of essential oils as flavoring agents, they should be fractionated by means of deterpenation, yielding a fraction enriched in oxiterpenes, which is more soluble in water and more stable, besides keeping the characteristic aroma of the crude oil. This fractionation can be performed by liquid extraction using ethanol as solvent. In this context, the deterpenation process of bergamot essential oil was investigated in a perforated rotating disc column (PRDC) using ethanol solutions with different percentages of water as the solvent. The separation process was studied here by experimental data and computer simulations. Additionally, the phase equilibrium at 25 oC of systems containing eucalyptus, clove, and allspice, and systems containing crude essential oils of bergamot and lavandin were also analyzed. In the phase equilibrium analysis, it was observed that, among the evaluated components, the oxygenated compound eugenol and the terpenic hydrocarbon caryophyllene, found in the clove and allspice oil, showed, respectively, the highest and lowest values of distribution coefficient. For systems containing bergamot and lavandin crude essential oils, it was observed that the NRTL and UNIQUAC binary parameters, previously adjusted to the bergamot essential oil model system, were able to describe the phase equilibrium of more complex systems. Besides, in relation to the study of the deterpenation process of crude essential oils in PRDC, it could be inferred that enriched fractions in oxygenated compounds are viable and feasible to be obtained in oils that show low levels of linalol in their composition.
153

Um ensaio em teoria dos jogos / An essay on game theory

Edgard Almeida Pimentel 16 August 2010 (has links)
Esta dissertação aborda a teoria dos jogos diferenciais em sua estreita relação com a teoria das equações de Hamilton-Jacobi (HJ). Inicialmente, uma revisão da noção de solução em teoria dos jogos é empreendida. Discutem-se nesta ocasião as idéias de equilíbrio de Nash e alguns de seus refinamentos. Em seguida, tem lugar uma introdução à teoria dos jogos diferenciais, onde noções de solução como a função de valor de Isaacs e de Friedman são discutidas. É nesta altura do trabalho que fica evidente a conexão entre este conceito de solução e a teoria das equações de Hamilton-Jacobi. Por ocasião desta conexão, é explorada a noção de solução clássica e é exposta uma demonstração do fato de que se um jogo diferencial possuir uma função de valor pelo menos continuamente diferenciável, esta será uma solução da equação de Hamilton-Jacobi associada ao jogo. Este resultado faz uso do princípio da programação dinâmica, devido a Bellman, e cuja demonstração está presente no texto. No entanto, quando a função de valor do jogo é apenas contínua, então embora esta não seja uma solução clássica da equação HJ associada a jogo, vemos que ela será uma solução viscosa, ou solução no sentido da viscosidade - e a esta altura são discutidos os elementos e propriedades desta classe de soluções, um teorema de existência e unicidade e alguns exemplos. Por fim, retomamos o estudo dos jogos diferenciais à luz das soluções viscosas da equação de Hamilton-Jacobi e, assim, expomos uma demonstração de existência da função de valor e do princípio da programação dinâmica a partir das noções da viscosidade / This dissertation aims to address the topic of Differential Game Theory in its connection with the Hamilton-Jacobi (HJ) equations framework. Firstly we introduce the idea of solution for a game, through the discussion of Nash equilibria and its refinements. Secondly, the solution concept is then translated to the context of Differential Games and the idea of value function is introduced in its Isaacs\'s as well as Friedman\'s version. As the value function is discussed, its relationship with the Hamilton-Jacobi equations theory becomes self-evident. Due to such relation, we investigate the HJ equation from two distinct points of view. First of all, we discuss a statement according to which if a differential game has a continuously differentiable value function, then such function is a classical solution of the HJ equation associated to the game. This result strongly relies on Bellman\'s Dynamic Programming Principle - and this is the reason why we devote an entire chapter to this theme. Furthermore, HJ is still at our sight from the PDE point of view. Our motivation is simple: under some lack of regularity - a value function which is continuous, but not continuously differentiable - a game may still have a value function represented as a solution of the associated HJ equation. In this case such a solution will be called a solution in the viscosity sense. We then discuss the properties of viscosity solutions as well as provide an existence and uniqueness theorem. Finally we turn our attention back to the theory of games and - through the notion of viscosity - establish the existence and uniqueness of value functions for a differential game within viscosity solution theory.
154

Cálculo do equilíbrio sólido-líquido e ajuste de parâmetros para modelos temodinâmicos em misturas binárias e ternárias de ácidos graxos, seus ésteres e triacilgliceróis / Solid-liquid equilibria calculation and parameters determination in thermodynamic models for binary and ternary mixtures of fatty acids, esters and triacylglycerols

Rocha, Stella Alonso 09 September 2011 (has links)
Orientador: Reginaldo Guirardello / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-19T03:13:19Z (GMT). No. of bitstreams: 1 Rocha_StellaAlonso_D.pdf: 2102940 bytes, checksum: d1db5bc412c8ae0218252291126c501e (MD5) Previous issue date: 2011 / Resumo: O trabalho desenvolvido é de caráter teórico e computacional e tem como objetivo o estudo e aplicação de técnicas de otimização juntamente com análise de convexidade para cálculo do equilíbrio sólido-líquido, utilizando um problema de Programação Não-linear, implementado no software GAMS em conjunto com o software Microsoft Excel, aplicado a misturas graxas binárias e ternárias, de origem natural, compostas por ácidos graxos, triacilgliceróis, ésteres de etila e metila, baseando-se na minimização da energia de Gibbs do sistema. A modelagem das fases foi desenvolvida com dois modelos termodinâmicos, em que a fase sólida foi descrita por uma modificação da equação de Slaughter e Doherty e a líquida, modelada por Margules 2-sufixos. Assim esse trabalho trata da utilização de novas aplicações para a fase líquida, com o Modelo de Margules - 2 sufixos, que passa e ser usado e desenvolvido de dois modos: o primeiro, nomeado Margules Assimétrico, em que os parâmetros de interação de Margules são diferentes, e o outro, chamado Margules Simétrico, neste, os parâmetros são considerados equivalentes; e ainda com aplicação do Modelo de Wilson. Para tal desenvolvimento, a proposta é utilizar dados experimentais de equilíbrio, disponíveis da literatura, em caráter comparativo; e fazer o próprio cálculo dos dados da curva de equilíbrio, com os respectivos ajustes dos parâmetros nos modelos utilizados. Os resultados obtidos são apresentados na forma de diagrama de fases e ajustes de parâmetros dos modelos envolvidos, calculados e comparados pela técnica de minimização dos quadrados dos erros, que por sua vez apresentam-se satisfatória proximidade dos dados experimentais. Os resultados ainda foram comparados entre si e puderam apresentar algumas características de comportamento, para algumas classes de compostos / Abstract: This work has theorical and computational character which objectives are the study and application of optimization technique with convexity analysis to calculate solid-liquid equilibrium. This problem was a non-linear program, that was implemented in software GAMS and software Microsoft Excel, which the case studies are binary and ternary mixtures of fatty acids, triglycerides, ethyl and methyl esters using the minimization of Gibbs energy free of the systems. The description of phases was done based in two thermodynamics models, the solid phase was characterized using a modified Slaughter and Doherty model and liquid phase with Margules 2 - suffixes. In this work the on liquid phase, the Margules model assume two forms: Margules Asymmetric, where the Margules parameters are different and Margules Symmetric, with equal Margules parameters, after was used Wilson Model too. Experimental data was used in comparative mode and new equilibrium dates was obtained and the parameters model also was discovery. The results are described in form of phase diagrams, where the equilibrium data and the parameters model was calculated based in the square errors, that are nearly of the experimental data. Comparing the results with each other, in some classes of compounds, there are some similar ways / Doutorado / Desenvolvimento de Processos Químicos / Doutor em Engenharia Química
155

Études thermodynamiques sur les Semi-Clathrate Hydrates de TBAB + gaz contenant du Dioxyde de Carbone / Thermodynamic studies on Semi-Clathrate Hydrates of TBAB + gases containing Carbon Dioxide

Eslamimanesh, Ali 14 August 2012 (has links)
Capturer le CO2 est devenu un domaine de recherche important en raison principalement des forts effets de serre dont il est jugé responsable. La formation d'hydrate de gaz comme technique de séparation montre un potentiel considérable, d'une part pour sa faisabilité physique et d'autre part pour une consommation énergétique réduite. En bref, les hydrates de gaz (clathrates) sont des composés ″cages″ non-stoechiométriques, cristallins comme la glace et formés par une combinaison de molécules d'eau et de molécules hôtes convenables, à basses températures et pressions élevées. Puisque la pression exigée pour la formation d'hydrate de gaz est généralement forte, il est judicieux d'ajouter du bromure tétra-n-butylique d'ammonium (TBAB) comme promoteur de formation d'hydrate de gaz. En effet, le TBAB permet généralement de réduire la pression exigée et/ou d'augmenter la température de formation aussi que de modifier la sélectivité des cages d'hydrates au profit des molécules de CO2. TBAB participe à la formation des cages par liaisons ″hydrogène″. De tels hydrates sont nommés "semi-clathrate hydrates". Évidemment, des données d'équilibres de phase fiables et précises, des modèles thermodynamiques acceptables, et d'autres études thermodynamiques sont requises pour concevoir des procédés de séparation efficaces utilisant la technologie mentionnée ci-dessus. Dans ce but, des équilibres de phase de clathrate/semi-clathrate hydrates de de divers mélanges avec des gaz contenant CO2 (CO2 + CH4/N2/H2) ont été mesurés, ici, en présence d'eau pure et de solutions aqueuses de TBAB. La partie théorique de la thèse présente un modèle thermodynamique développé avec succès sur la base de la théorie des solutions solides de van der Waals et Platteeuw (vdW-P) associée aux équations modifiées de la détermination des constantes de Langmuir des promoteurs d'hydrates pour la représentation/prédiction des équilibres en présence de ″semi-clathrate hydrates″ de CO2, CH4, et N2. Plusieurs tests de cohérence thermodynamique basés soit sur l'équation de Gibbs-Duhem, soit sur une approche statistique ont été appliqués aux données d'équilibre de phase des systèmes de ″clathrate hydrates″ simples/mélanges afin de statuer sur leur qualité. / CO2 capture has become an important area of research mainly due to its drastic green-house effects. Gas hydrate formation as a separation technique shows tremendous potential, both from a physical feasibility as well as an envisaged lower energy utilization criterion. Briefly, gas (clathrate) hydrates are non-stoichiometric, ice-like crystalline compounds formed through a combination of water and suitably sized guest molecule(s) under low-temperatures and elevated pressures. As the pressure required for gas hydrate formation is generally high, therefore, aqueous solution of tetra-n-butyl ammonium bromide (TBAB) is added to the system as a gas hydrate promoter. TBAB generally reduces the required hydrate formation pressure and/or increases the formation temperature as well as modifies the selectivity of hydrate cages to capture CO2 molecules. TBAB also takes part in the hydrogen-bonded cages. Such hydrates are called "semi-clathrate" hydrates. Evidently, reliable and accurate phase equilibrium data, acceptable thermodynamic models, and other thermodynamic studies should be provided to design efficient separation processes using the aforementioned technology. For this purpose, phase equilibria of clathrate/semi-clathrate hydrates of various gas mixtures containing CO2 (CO2 + CH4/N2/H2) in the presence of pure water and aqueous solutions of TBAB have been measured in this thesis. In the theoretical section of the thesis, a thermodynamic model on the basis of the van der Waals and Platteeuw (vdW-P) solid solution theory along with the modified equations for determination of the Langmuir constants of the hydrate formers has been successfully developed to represent/predict equilibrium conditions of semi-clathrate hydrates of CO2, CH4, and N2. Later, several thermodynamic consistency tests on the basis of Gibbs-Duhem equation as well as a statistical approach have been applied on the phase equilibrium data of the systems of mixed/simple clathrate hydrates to conclude about their quality.
156

Recherche de flots stables dans des réseaux de transport multi-agents / Search of stable waves in multi-agent transport networks

Chaabane, Nadia 19 January 2016 (has links)
Nous considérons dans ce travail, des problèmes d’optimisation dans des graphes de flot multi-agent. Trois types d’agents sont considérés : les agents producteurs, transporteurs et usagers et différentes variétés de topologies de réseaux sont abordées. Chaque agent transporteur contrôle la capacité d’un ensemble de routes élémentaires (arcs), ayant chacun une capacité qui peut être augmenté jusqu’à une valeur maximale moyennant un coût fixe. Les autres agents (i.e., usagers/producteurs) sont intéressés par la maximisation du flot qu’ils reçoivent. Dans ce but, ces derniers offrent une récompense aux agents transporteurs, cette récompense est proportionnelle à la valeur du flot reçu. Ce contexte multi-agent particulier est appelé jeu expansion de réseau multi-agent. La stratégie d’un agent transporteur consiste à décider de la capacité de ses arcs sachant qu’un coût supplémentaire est encouru pour toute expansion unitaire de capacité. Il reçoit en contrepartie une part de la récompense. Il est intéressé par la maximisation de son profit et se comporte en conséquence. En outre, la stratégie d’un agent producteur/usager consiste à décider de la politique de partage de sa récompense afin de maximiser le flot qu’il reçoit. Le flot total réalisé dépend finalement des stratégies de tous les agents. Dans ces jeux d’expansion de réseau multi-agent, nous nous intéressons à caractériser des stratégies stables (i.e., Equilibre de Nash) selon diverses hypothèses. En se basant sur cette caractérisation, différents cas sont définis et étudiés. L’analyse de la complexité de quelques problèmes de décision est présentée dans ce manuscrit. Nous nous intéressons particulièrement au problème de recherche d’un équilibre de Nash qui maximise la valeur du flot total circulant dans le réseau. Nous montrons que ce problème est NP-difficile au sens fort et nous montrons comment une telle stratégie peut être caractérisée par des chemins spécifiques dans des graphes résiduels. Nous proposons également un programme linéaire à variables mixtes (PLM) qui résout le problème dans le cas d’un seul agent producteur/usager et un ensemble d’agents transporteurs. Des résultats expérimentaux sont fournis pour prouver l’efficacité de notre approche. / In this work, multi-agent network flow problems are addressed. Three types of agentsare considered, namely the producer, transportation and customer agents and various network topologies are tackled. Every transportation agent controls the capacities of a set of elementary routes (arcs), each one having a capacity that can be increased up to a certain point at a given cost. The other agents (i.e., customers/producers) are interesting in maximizing their flow of products. For that aim, we assume that they offer to the transportation agents a reward that is proportional to the realized flow value. This particular multi-agent framework is referred to as a multi-agent network expansion game. The transportation agent’s strategy consists in deciding upon the capacity of its arcs, an extra-cost being incurred for any capacity expansion. It receives in return a part of the total reward. It is interested in the maximization of its profit and behaves accordingly. Beside that, the producers/customers’ strategies consist in deciding the sharing policy for their reward for maximizing their own flow of products. The total network flow value eventually depends on all agents’ strategies. We take interest in characterizing and finding particular stable strategies (i.e., Nash Equilibria) that are of interest for this game under various assumptions. Based on this characterization, several cases are defined and studied. The analysis of the complexity of some decision problems is made. We particularly focus on the problem of finding a Nash Equilibrium that maximizes the value of the total flow. We prove that this problem is NP-hard in the strong sense and show how such a strategy can be characterized considering paths in specific reduced agent-networks. We also provide a mixed integer linear programming (MILP) formulation that solves the problem in the case of a single producer/customer agent and a set of transportation agents. Computational experiments are provided to prove the effectiveness of our approach
157

Industrialisation and the Big Push in a Global Economy

Kreickemeier, Udo, Wrona, Jens 28 July 2017 (has links) (PDF)
In their famous paper on the "Big Push", Murphy, Shleifer, and Vishny (1989) show how the combination of increasing returns to scale at the firm level and pecuniary externalities can give rise to a poverty trap, thereby formalising an old idea due to Rosenstein-Rodan (1943). We develop in this paper an oligopoly model of the Big Push that is very close in spirit to the Murphy-Shleifer-Vishny (MSV) model, but in contrast to the MSV model it is easily extended to the case of an economy that is open to international trade. Having a workable open-economy framework allows us to address the question whether globalisation makes it easier or harder for a country to escape from a poverty trap. Our model gives a definite answer to this question: Globalisation makes it harder to escape from a poverty trap since the adoption of the modern technology at the firm level is impeded by tougher competition in the open economy.
158

Investigation de la cristallisation hors-équilibre des clathrates hydrates de gaz mixtes : une étude expérimentale comparée à la modélisation thermodynamique avec et sans calculs flash / Investigation of non-equilibrium crystallization of mixed gas clathrates hydrates : an experimental study compared to thermodynamic modeling with and without flash calculations

Le, Quang-Du 09 March 2016 (has links)
L’activité scientifique du sujet porte sur l’acquisition de données expérimentales et la modélisation de la composition des clathrates hydrates de gaz. Les domaines d’application concernent la séparation et le stockage de gaz, la purification de l’eau, et le stockage d’énergie par matériaux à changement de phase.L’équipe a mis en évidence il y a quelques années que la composition des hydrates de gaz était sensible aux conditions de cristallisation, et que le phénomène de formation se produisait en dehors de l’équilibre thermodynamique.Le travail de thèse a permis d’explorer plusieurs modes de cristallisation à partir de solutions de même composition initiale pour observer les différences concernant l’état final, compositions notamment, et les relier à la vitesse de cristallisation. Suivant le mode de cristallisation, lent ou rapide, l’acquisition des données expérimentales peut prendre de quelques jours à plusieurs semaines. Les expériences sont réalisées en réacteur pressurisé dans lequel nous mesurons en ligne la composition de la phase gaz et de la phase liquide, pour calculer par bilan de matière la composition de la phase hydrate.Nous avons bien mis en évidence des variations dans la composition de la phase hydrate suivant le mode de cristallisation. Nous avons dû établir un modèle thermodynamique donnant la composition de la phase hydrate à l’équilibre pour des mélanges de gaz qui n’avaient jamais été traité par la littérature, et qui ont donc nécessité des campagnes de mesure extrêmement lentes et donc longues pour être sûr de l’état thermodynamique à l’équilibre.Nous sommes en cours d’établir un modèle cinétique pour modéliser les écarts à cet état d’équilibre de référence pour nos expériences réalisées à vitesse de cristallisation rapide. / The scientific goal of this thesis is based on the acquisition of experimental data and the modeling of the composition of clathrates gas hydrate. The domains of application concern the gas separation and storage, water purification, and energy storage using change phase materials (PCMs).Our research team has recently demonstrated that the composition of gas hydrates was sensitive to the crystallization conditions, and that the phenomenon of formation was out of thermodynamic equilibrium. During this thesis, we have investigated several types of crystallization, which are based on the same initial states. The goal is to point out the differences between the initial solution composition and the final solution composition, and to establish a link between the final state and the crystallization rate.Depending on the rate of crystallization (slow or fast), the acquisition time of experimental data lasted from a few days to several weeks. The experimental tests were performed inside a stirred batch reactor (autoclave, 2.44 or 2.36 L) cooled with a double jacket. Real-time measurements of the composition of the gas and the liquid phases have been performed, in order to calculate the composition of the hydrate phase using mass balance calculations. Depending on the crystallization mode, we have identified several variations of the composition of the hydrate phase and final hydrate volume.We have established a successful thermodynamic model, which indicates the composition of the hydrate phase and hydrate volume in thermodynamic equilibrium state using a gas mixture which had never been used before in the literature. So this thermodynamic model has required an extremely slow experimental test. These tests were also long in order to be sure of the thermodynamic equilibrium state.We are currently establishing a kinetics model in order to model the deviations from the reference point of equilibrium of our experimental tests which were carried out at a high crystallization rate.
159

Ramp function approximations of Michaelis-Menten functions in biochemical dynamical systems

Dore-Hall, Skye 22 December 2020 (has links)
In 2019, Adams, Ehlting, and Edwards developed a four-variable system of ordinary differential equations modelling phenylalanine metabolism in plants according to Michaelis-Menten kinetics. Analysis of the model suggested that when a series of reactions known as the Shikimate Ester Loop (SEL) is included, phenylalanine flux into primary metabolic pathways is prioritized over flux into secondary metabolic pathways when the availability of shikimate, a phenylalanine precursor, is low. Adams et al. called this mechanism of metabolic regulation the Precursor Shutoff Valve (PSV). Here, we attempt to simplify Adams and colleagues’ model by reducing the system to three variables and replacing the Michaelis-Menten terms with piecewise-defined approximations we call ramp functions. We examine equilibria and stability in this simplified model, and show that PSV-type regulation is still present in the version with the SEL. Then, we define a class of systems structurally similar to the simplified Adams model called biochemical ramp systems. We study the properties of the Jacobian matrices of these systems and then explore equilibria and stability in systems of n ≥ 2 variables. Finally, we make several suggestions regarding future work on biochemical ramp systems. / Graduate
160

Modélisation des équilibres entre phases et simulation de la distillation des eaux-de-vie en vue d’une meilleure compréhension du comportement des composés volatils d’arôme / Modeling of phase equilibria and simulation of spirits distillation for a better understanding of volatile aroma compounds behavior.

Puentes Mancipe, Cristian 13 December 2017 (has links)
La qualité des eaux-de-vie est un paramètre associé à la composition en composés volatils d’arôme. Cette composition résulte de la combinaison de différents facteurs dont la nature et le traitement des matières premières, mais surtout des transformations ayant lieu lors des phases de fermentation, distillation et, dans la plupart de cas, vieillissement.La distillation est une opération de séparation pratiquée depuis des millénaires, avec une technologie assez mature. Cependant, dans le domaine des eaux-de-vie, elle s’appuie essentiellement sur des connaissances empiriques. L’objectif de ce doctorat fut de contribuer à une meilleure compréhension du comportement des composés volatils d’arôme au cours de différents modes de distillation et de fournir des bases scientifiques à la conduite des unités par le biais de modules de simulation. L’attention a été portée sur la distillation d’Armagnac et de Calvados dans des colonnes multiétagées en régime stationnaire.Les modules de simulation ont été construits avec le logiciel ProSimPlus®. La première partie des travaux a été consacrée à l’acquisition de données d’équilibre liquide-vapeur des composés volatils d’arôme en milieu hydroalcoolique pour l’identification du modèle NRTL, en suivant trois approches complémentaires : recherche dans la littérature, détermination expérimentale et prédiction théorique avec les modèles UNIFAC et COSMO. Grâce à la connaissance acquise sur les volatilités relatives par rapport à l’éthanol et à l’eau, les composés volatils d’arôme ont pu être classés en trois groupes : composés légers, composés intermédiaires et composés lourds. La deuxième partie des travaux a porté sur la construction et la validation des modules de simulation, après réconciliation des données issues de la caractérisation expérimentale des unités de distillation. Cette investigation démontre que la simulation est un outil d’ingénierie performant dans le domaine des eaux-de-vie. Les résultats de la simulation ont permis d’affiner la classification des composés intermédiaires en trois catégories supplémentaires selon leur profil de concentration dans la colonne et leur taux de récupération dans le distillat. Enfin, cet outil a mis en évidence que certains paramètres opératoires, notamment l’augmentation de la teneur en éthanol du distillat ainsi que l’extraction de queues, favorisent la séparation préférentielle de certaines espèces de volatilité faible ou intermédiaire par rapport à l’éthanol. / The quality of spirits is a parameter related to the composition of volatile aroma compounds. This composition results from the combined production process of raw material extraction, subsequent fermentation, distillation and, in many cases, ageing.Distillation is a very old and the most important industrial separation technology. However, in spirits production, this operation relies essentially on empirical knowledge. The aim of this PhD was to contribute to a better understanding of the volatile aroma compounds behaviour in spirits distillation and to provide a scientific basis for the process through computer simulation. The study was focused on Armagnac and Calvados production by continuous multistage distillation.The simulation modules were built using the software ProSimPlus®. The first part of this research was dedicated to the acquisition of vapor-liquid equilibrium data of the volatile aroma compounds in ethanol-water solutions, in order to estimate the binary interaction parameters of the NRTL model.Three complementary approaches of data acquisition were used: literature compilation, experimental measurements and predictions with UNIFAC and COSMO models.According to their relative volatilities with respect to ethanol and water, the volatile aroma compounds can be classified in three groups: light compounds, intermediary compounds and heavy compounds. The second part of this research dealt with the creation and validation of simulation modules, by using reconciled experimental data from the distillation units. The results prove that simulation is a powerful tool in spirits distillation. The simulation data enables a more precise classification of the intermediary compounds in three categories, by considering their composition profiles in the distillation column and their recovery ratios from feed to distillate. Finally, the analysis of some operating parameters, including ethanol concentration in the distillate as well as tails extractions, demonstrates that the distillate composition can be modified by virtue of a selective separation of intermediary and heavy compounds with respect to ethanol.

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