Dissertations / Theses on the topic 'GAS5'

The formation of Saccharomyces cerevisiae cell wall requires the coordinated activity of enzymes involved in the biosynthesis and modification of its components, such as glucans. The β-(1,3)-glucan synthase complexes, that have Fks proteins as putative catalytic subunits, use UDP-glucose as a substrate and catalyse the synthesis and vectorial extrusion of glucan chains into the outer space. Then, β-(1,3)-glucan chains are branched, elongated and remodelled in order to create a robust texture capable of counteracting the high internal pressure and determining cell morphology. β-(1,3)-glucan is the main component of the vegetative cell wall and one of the most abundant polymers of the spore wall. Several enzymes belonging to the family GH72 of glycosyl hydrolases have been identified in fungi. These enzymes are responsible of the lateral elongation of β-(1,3)-glucan, thus contributing to the assembly and organization of the glucan layer. The multigene GAS family of S. cerevisiae is composed of five members, GAS1-5, involved in cell wall maintenance. They share significant similarity with Aspergillus fumigatus GEL1 and GEL2, and with Candida albicans PHR1 and PHR2. Similar to the most extensively characterized member, Gas1p, the remaining Gas proteins are β-(1,3)-glucanosyltransferases involved in cell wall assembly and maintenance. Based on their expression patterns, they appear to play partially overlapping roles throughout the yeast life cycle: GAS1 and GAS5 are expressed during vegetative growth, whereas GAS2 and GAS4 are expressed exclusively during sporulation and required for normal spore wall formation, finally GAS3 is a weakly expressed gene. Thus these enzymes could satisfy the cellular needs to remodel β-(1,3)-glucan in different physiological conditions and in different conformations along the yeast life cell cycle. Moreover, considering its role in yeast cell biology, the GAS enzyme family represents a very promising molecular target for new antifungal drugs. During my PhD thesis I focused my interest on the functional characterization of GAS1, 2, 3 and 4 in various stages of the yeast life cycle: vegetative growth, meiosis, sporulation and spore germination. This study is aimed to understand the biological significance of the developmentally regulated requirement of the specific members of the GAS redundant family in the morphological stages of yeast life cycle. GAS2 and GAS4 genes are specifically induced during sporulation and encode for glycoproteins. The effects of the loss of Gas2 and Gas4 proteins on spore wall morphogenesis are dramatic. Synthesis of all the layers of the spore cell wall occurs, but the accumulation and organization of wall material is abnormal. The lack of the elongase activity of Gas2 and Gas4 proteins in the double mutant might cause the formation of shorter or less branched β(1,3)-glucan chains in the inner layer of the spore wall. Thus, the connection of the outermost layers to a less compact glucan network could make the spore wall more fragile and easily stripped under harsh conditions. These defects cause an increase in spore permeability to exogenous substances, a decrease in refractivity, and a marked decrease in spore viability. The possible execution point for GAS2 and GAS4 could be between the synthesis and organization of β(1,3)-glucan and, more specifically, in the elongation of the β(1,3)-glucan chains. Consistently with their role, during sporulation Gas2 and Gas4 proteins localize at the newly assembling prospore membrane during the meiotic divisions and in mature ascospore the proteins decorate the spore periphery. A slight difference in the protein patterns of fluorescence on the spore suggests that Gas2p and Gas4p final localization could be respectively the spore wall and the prospore membrane. In this work, an extensive study of the localization of the Gas1 protein during the yeast life cycle was performed, taking advantage of a GFP-tagged version of the protein. During vegetative growth Gas1p has a dual localization: in the plasma membrane and at the site of bud emergence, particularly in the neck, in the chitin ring that surrounds the neck region and in the bud scars where Gas1p remains after cytokinesis. At the neck region Gas1p appears to absolve important functions in yeast as a part of the mechanisms that ensure the resistance of the neck region and the morphogenesis of the septum. The size and morphology of the neck region is severely affected both in the gas1Δ and gas1Δ chs3Δ mutant, suggesting an involvement of the protein in the maintenance of the integrity of the mother-bud neck region. The presence of Gas1p in the chitin ring could be part of the mechanism necessary to prevent new incorporation of glucan chains into the neck region or alternatively the protein could be required for a particular type of remodelling necessary for the septum region in preparation to cell division. Additionally, Gas1p could act as landmark protein for the choice of the site of bud emergencee. As to Gas1p localization at the plasma membrane, our study supports the validity of Gas1p-GFP as a marker to follow the dynamics of lipid raft. At the induction of sporulation, GAS1 mRNA levels steadily decrease and by 10h it is completely declined. Surprisingly, Gas1p levels are roughly constant during the entire sporulation processs and the protein is very stable, being detectable also at 43h after the induction of sporulation. During spore development, a translocation event occurs through which at the completion of meiosis II, Gas1p, synthesized during vegetative growth, is removed from the plasma membrane and internalized. Later, Gas1p is detected associated to the nascent prospore membrane surrounding the nuclear lobes and finally in mature spores it localizes at the spore periphery. This translocation event suggests that Gas1p delivery to the spore surface is not part of the developmentally reprogramming of the secretory pathway from the trans Golgi to the prospore membrane, whereas it involves at least in part the endocytic pathway. We demonstrated that END3-mediated endocytosis is one of the mechanisms required for the removal of the Gas1p from the plasma membrane and its efficient re-localization at the prospore membrane. Moreover in a sps1Δ mutant, Gas1p remains localized at the plasma membrane and fails to reach the spore surface. Sps1p is a member of the Ste20 protein kinase family and regulates the trafficking to the prospore membrane of enzymes involved in spore wall synthesis, such as the glucan synthase Fks2p and chitin synthase Chs3p. Thus Sps1p could regulate the traffic of Gas1p most likely in an indirect way by interacting and modifying the components of the intracellular trafficking machinery. Gas1p translocation during sporulation To test a possible involvement of Gas1p in spore wall formation, in this study we tried to characterize the sporulation phenotype of a gas1Δ mutant. Unfortunately our analysis was complicated by the mutant reduced cell viability when grown in presence of a poor carbon source such as acetate. gas1Δ sporulation defect could rely in a unsatisfied energetic request as the cell wall perturbations, typical of a gas1Δ mutant, enhance carbon and energy mobilization to efficiently combat cell wall weakening and the metabolism of acetate as the sole carbon source could be not sufficient to satisfy this energetic request. Moreover the addition of sorbitol to the sporulation medium only partially rescues gas1Δ defective phenotype during spore development. Even though sorbitol can mitigate the gas1Δ cell wall damages, it has no buffering effect on the gas1Δ energetic request, thus the mutant cells remained substantially unable to sporulate. Consequently, gas1Δ sporulation defective phenotype appears to be reminiscent of the mutant defects during vegetative growth, even worsened in a poor carbon source. Even though we cannot exclude a role for Gas1p during spore morphogenesis, it is our consumption that the protein translocation to the spore represents a “storage”mechanisms to ensure the presence of the Gas1p during spore germination. At 3h after the shift to a rich medium, Gas1p exhibits a highly polarized distribution, decorating exclusively half of the germinating spore in its growing pole. The protein localization is consistent with its role in glucan layer remodelling of the cell wall at the growing portion of the germinating cell. Besides gas1Δ germinating spore inability to support the elongation during the polarized growth of the cell suggests that Gas1p is required for a very early step in germination. Besides the protein is involved in a post-germination stage to support the polarized growth of the newly emerging bud. Finally, in this study we reported the preliminary results about the functional characterization of GAS3. The gene is expressed at a very low level during the vegetative growth in glucose and acetate. Consistently with the GAS3 expression pattern, Gas3p appears as a highly polydispersed glycoprotein of high molecular weight that is present in vegetative growing cells and along the sporulation process. EndoH treatment reduces the size and the aspect of the protein to a sharp band, suggesting that Gas3p is a heavily N-glycosylated protein. The experiments indicated that neither the overexpression nor the deletion of the GAS3 gene, alone or in combination with GAS2 and GAS4, lead to relevant differences in sporulation with respect toh the wild type or with the defective phenotype of the gas2 gas4 null mutant strain . The construction of a tagged version of the Gas3 protein to determine its localization will be a useful tool to understand the function ofl Gas3p during yeast life cycle.

This work addresses the mobile robot navigation problem. More specifically, we propose a novel approach, in the robotics context, for constructing navigation functions based on the Laplaces equation solution. This approach is based on Finite Elements Methods, which allows for complex shaped obstacles and robots. Also, we propose rules for attaching boundary conditions to the boundary domain, in order to solve the Laplaces Equation, thus guaranteeing completeness for the proposed methodology, i.e., if a path exists the robot always reach the goal in a finite time, independently of its initial position and orientation. A new boundary condition, called Periodic Condition, is proposed and used to take into account the robots orientation. Additionally, we propose an algorithm for constructing configurations spaces in R3, useful when three degrees of freedom, planar robots are considered. Our methodology is validated in actual, holonomic mobile robots
Este trabalho aborda o problema de navegação de robôs móveis. Mais especificamente, é proposta uma nova abordagem, no contexto de robótica, para a solução da equação Laplace visando a construção de funções de navegação. Esta nova abordagem consiste na aplicação do Método de Elementos Finitos, o que permite o tratamento de obstáculos e robôs de formatos complexos. O trabalho ainda propõe regras para a definição de condições de contorno para a solução da equação de Laplace, as quais tornam a metodologia proposta completa, isto é, caso exista um caminho possível, o robô sempre atinge o alvo num tempo finito, independentemente da posição e orientação iniciais. Uma nova condição de contorno, dentro do contexto de robótica, chamada Condição de Contorno Periódica, também é proposta neste trabalho, permitindo um tratamento fechado da orientação do robô. O tratamento da orientação do robô passa também pela construção de espaços de configurações em R3, utilizados quando a orientação de robôs navegando no plano é considerada. Esta dissertação propõe um novo algoritmo para uma construção aproximada desses espaços. Os resultados do trabalho são validados numa plataforma constituída de robôs holonômicos reais

This work addresses the computer vision use in siderurgical (steel mill)process, from raw material extraction in the mines, passing for the reduction stages, stell plants, rolling, until finished products inspection. It shows a large survey where it describes the typical problems found by the researchers in the steel mill plants and the adopted solutions to solve them. This work still comments the development process of four computer vision aplications for the Ouro Branco mills siderurgical process and describes other solutions that can contribute in process quality increase.
Este trabalho busca discutir a utilização de visão computacional nos processos siderúrgicos, desde a extração da matéria-prima nas minas, passando pelas etapas de redução, aciaria, laminação até a inspeção dos produtos finais. O trabalho apresenta uma extensa revisão bibliográfica na qual se descreve os principais problemas encontrados pelos pesquisadores em ambientes siderúrgicos e as respectivas soluções adotadas para contorná-los. O trabalho comenta ainda o desenvolvimento de quatro protótipos de aplicações paraos processos siderúrgicos da usina de Ouro Branco, além de descrever o levantamento de outras soluções que podem contribuir para a melhoria dos processos.

This thesis addresses the problem of controlling very large groups of robots, refereed as swarms. Scalable solutions in which there is no need for labelling the robots are proposed. All the robots run the same software and the success of the task execution does not depend on specific members of the group. Robustness to dynamic addition and deletion of agents is also an advantage of our approaches. In the first methodology, we model the swarm as a fluid immersed in a region where a field of external forces, which is free of local minima, is defined. In this case, the Smoothed Particle Hydrodynamics (SPH) method is applied to model the robotic fluid', more specifically, to model the interactions among the robots of the group. The Finite Element Method (FEM) is also used in this work to compute the fields that determine external forces. This approach is instantiated in a pattern generation task and also in a coverage task. In the second methodology, a problem of optimal environment coverage using robots equipped with sensors is addressed by means of tools from the Locational Optimization theory. Three important extensions of well-known results in the literature are presented: (i) sensors with different footprints, (ii) disk-shaped robots, and (iii) nonconvex polygonal environments. Both approaches are verified in simulations. The first technique is also implemented and tested in actual robots.
Esta tese aborda o problema de controle de grandes grupos de robôs, referidos como enxames. São propostas soluções escaláveis as quais não necessitam da identificação única dos robôs. Todos os robôs executam o mesmo código e o sucesso na execução de uma tarefa não depende de membros específicos do grupo. Robustez à adição e remoção dinâmica de agentes também é uma vantagem das abordagens propostas. Na primeira metodologia, o enxame é modelado como um fluido imerso numa região onde um campo de forças externas livre de mínimos locais é definido. Neste caso, utiliza-se o método de Hidrodinâmica de Partículas Suavizadas (HPS) para modelar o fluido robótico'', mais especificamente, para modelar as interações entre robôs do grupo. O Método de Elementos Finitos (MEF) também é utilizado neste trabalho para calcular os campos vetoriais que determinam as forças externas. Esta abordagem é instanciada num problema de geração de padrões e também num problema de cobertura de ambientes. Na segunda metodologia, um problema de cobertura ótima de ambientes utilizando robôs equipados com sensores é tratado por meio de ferramentas provenientes da teoria de Otimização Locacional. São apresentadas três extensões importantes de resultados já conhecidos na literatura: (i) sensores com diferentes campos de visão, (ii) robôs com formato circular e (iii) ambientes poligonais não-convexos. Ambas metodologias são verificadas em simulações. A primeira metodologia é também implementada e testada em robôs reais.

Finding the shortest path between two points in thematic maps is a common problem. However, this planning can be slightly complex, taking into account the large number of variables and constraints of the problem. This thesis proposes the use of map overlay and optimization techniques to find the optimal route approximation, considering all necessary topological information and constraints. Furthermore, a post-processing technique to refine the solution is shown. The problem can be modeled by a set of thematic maps without loss of generality. Cost functions are assigned to each region in order to estimate the difficulty to transpose that region. The map overlay technique is used to couple all the thematic map information. This technique produces a combined map which contains all the information of each map. A triangle discretization has been used to decompose the map in convex regions. After the discretization, the vertices of the triangles are the nodes of the search graph. The graph is constructed taking into account the distance between nodes. This distance is defined as the minimal number of edges between the nodes. One can assure the best solution only considering all possible connections. However, this addresses the worst case and the computational cost is prohibitive in most cases. A post-processing technique has been proposed to find good solutions without a significative increasing of considered connections. To achieve the initial solution path, the Dijkstra algorithm has been used. Two route planning problems are addressed in this work, the robot motion planning in outdoor environments and the design of routes for transmission lines. In both cases, practical systems have been used to test the developed method.
Encontrar o caminho de menor custo entre dois pontos em um mapa temático é um problema comum. Entretanto, esse planejamento pode se tornar complexo levando-se em conta o elevado número de variáveis e restrições do problema. Essa dissertação propõe o uso de técnicas de sobreposição de mapas e de otimização para encontrar uma aproximação da rota ótima, considerando todas as informações topológicas e restrições necessárias. Além disso, uma técnica de pós-processamento para refinar a solução é apresentada. O problema pode ser modelado, sem perda de generalidade, por um conjunto de mapas temáticos aos quais funções de custo são associadas a cada região, com o objetivo de estimar sua dificuldade de transposição. A técnica de sobreposição de mapas é usada para combinar as informações dos mapas temáticos. Essa técnica produz um mapa combinado contendo as informações de cada mapa e o mapa resultante é então decomposto em regiões convexas utilizando uma triangulação. Após a discretização, os vértices dos triângulos correspondem aos nós do grafo. O grafo é construído levando em conta o custo de transposição entre os nós e a distância topológica entre eles. Esta distância é definida como o número mínimo de arestas entre os nós. Pode-se assegurar a melhor solução somente quando o grafo completo é considerado. Entretanto, o custo computacional para este caso é proibitivo. Uma técnica de pós-processamento é proposta para encontrar boas soluções sem considerar um número elevado de conexões. O algoritmo de Dijkstra é utilizado para calcular o caminho inicial. Como aplicação, dois problemas de planejamento de rotas são considerados: navegação de robôs em ambientes externos e o projeto de rotas de linhas de transmissão. Em ambos os casos, exemplos práticos foram usados para a validação do método desenvolvido.

The localization task of a mobile robot is one of the most important steps towards its autonomous locomotion, since a vehicle must know its geographic position must be able to avoid known obstacles and to arrive at desired places. The fulfillment of this task requires the use of noisy information provided by many types of sensors. In this work the objective is the study of sensor fusion techniques applied to the development of a localization system for an automobile. This automobile will be used later as a mobile robotic platform in UFMG. The developed system not only provides information concerning the geographic position of the vehicle, but also estimates speed and orientation. This is accomplished by the use of position, speed and acceleration sensors, which are adequately installed and calibrated. The sensors measurements are processed using estimation algorithms based on Kalman Filter. As example of application of the localization system proposed in this work, an onboard electronic guide was developed, which, based on maps stored previously on a computer, can display geographical information to the vehicle driver.
A tarefa de localização de um robô móvel constitui-se como uma das etapas fundamentais para se atingir o objetivo de locomoção autônoma do mesmo, tendo em vista que um veículo deve conhecer sua posição geográfica, em relação a um determinado referencial, para conseguir se desviar de obstáculos conhecidos e alcançar lugares desejados. O cumprimento desta tarefa demanda a utilização de informações ruidosas provenientes de diversos tipos de sensores. Neste trabalho tem-se como objetivo o estudo de técnicas de fusão sensorial aplicadas ao desenvolvimento de um sistema de localização para um automóvel de passeio, o qual será futuramente usado como plataforma robótica móvel. O sistema desenvolvido provê não apenas informações acerca da posição geográfica do veículo, mas também fornece estimativas de velocidade e orientação ao longo do trajeto, graças à utilização de sensores de posição, velocidade e aceleração, adequadamente instalados e calibrados, cujas medições são processadas por algoritmos de estimação baseados no Filtro de Kalman. Como exemplo de aplicação do sistema de localização proposto neste trabalho, foi desenvolvido um guia eletrônico embarcado que, em conjunto com mapas fornecidos previamente, pode apresentar informações ao motorista que trafega com o veículo em um dado instante.

Safe navigation is fundamental for autonomous vehicles. That requires a complete interaction with its surroundings. Self localization, motion planning, environment perception and obstacle avoidance, are important steps that must be realized by the vehicle. This work presents a safe navigation approach for a car-like robot. It uses a path planning algorithm based on Velocity Vector Fields combined together with a Dynamic Window Approach for unmodeled obstacle avoidance. Basically, the vector field is associated to a controller whose outputs are validated by the Dynamic Window Approach and applied as control inputs for the car. To assist the navigation, some known technics have been incorporated to the final solution, such as a sensor fusion system for localization and a local occupancy grid for environment perception. The methodology of this work was validated in a simulation system, where lasers and visual sensors were evaluated, and posteriorly applied to CADU (a car-like robot developed in the Federal University of Minas Gerais) that uses a stereo vision camera for obstacles detection. The results, for both cases, controlled the vehicle in an unstructured environment. The vehicle was able to track the vector field and avoid obstacles in its way. It is expected that more sensors and a better localization system would allow the car to navigate around more complex places using the methodology presented in this work.
A navegação segura é uma tarefa fundamental para os veículos autônomos, os quais necessitam de uma interação completa com o meio em que estão inseridos. Saber se localizar no mundo, planejar seu movimento, perceber o ambiente e desviar de possíveis obstáculos, são apenas algumas das etapas que devem ser realizadas pelo veículo. Este trabalho aborda o problema de navegação segura de um carro autônomo. Para tanto, é utilizado um planejamento de movimento por meio de campos vetoriais de velocidade aliado ao Método da Janela Dinâmica para o desvio de obstáculos não modelados. Basicamente, o campo vetorial é associado a um controlador cujas saídas são validadas pelo Método da Janela Dinâmica e aplicadas como entradas de controle do carro. Para auxiliar na navegação, técnicas de localização por fusão sensorial e percepção do ambiente por uma grade ocupação local foram incorporadas à solução. A validação da metodologia apresentada foi realizada em um ambiente de simulação, onde sensores a laser e visuais foram avaliados, e posteriormente implementada no CADU (Carro autônomo desenvolvido na Universidade Federal de Minas Gerias) que utiliza visão estéreo para a percepção dos obstáculos. Os resultados, para ambos os casos, controlaram o veículo em um ambiente não estruturado. Neles, o veículo foi capaz de se guiar pelo campo vetorial e desviar de obstáculos em seu caminho. Espera-se que a incorporação de mais sensores e um sistema localização mais preciso permita que o carro navegue por ambientes mais complexos utilizando a metodologia proposta neste trabalho.

The increasing use of guns in crimes has been a constant worrying to the law enforcemen and the need of capable information in order to get a solution for those crimes is evident. The detection of correlative previous crimes becomes a powerful tool that can be decisive to the solution of a criminal action. The creation of a proper system that is able to detect the use of the same gun on diferent crimes becomes a huge need for the techno-scientific policy institutes and it opens a wide range of information that wasn't possible before due to de complexity in ballistic comparishion processes, that envolves the ballistics examiner to indivualy analyze each speciment. This work introduces a beginning in the development of equipment with national technology for automatic ballistic projects comparison. It is introduced the mechanism of image acquisition of the projectile, a methodology of the set up of this image and the comparisons among the micro striation marks, and determining the similarity level among picked samples using Cross Correlation Function (CCF)The most important results were the capture and the set up of the lateralarea image of a three-dimensional object as well the comparison of acquired sample images. These comparisons allowed to determine what samples were produced by the same gun. It is expected, with the future development of the present work, it can be produced national solutions for the automatic ballistic comparisons, by searching related facts in appropriated databases.
O crescente uso de armas de fogo na prática de crimes tem sido umapreocupação constante dos órgãos de investigação policial. A detecção de crimes relacionados entre si é uma ferramenta poderosa que pode ser decisiva no desvendamento de uma ação delitiva. O desenvolvimento de um sistema capaz de detectar o uso de uma mesma arma em crimes diferentes torna-se uma necessidade para os órgãos de polícia técnico-científica, pois abre um novo leque de informações que antes não era possível, dada a complexidadee demora nos processos de confronto balístico. Este trabalho apresenta-se como o indício do desenvolvimento de um equipamento com tecnologia nacional para a microcomparação balística automáticade projéteis. Nele é apresentado o mecanismo de aquisição da imagem do projetil, uma metodologia de montagem desta imagem e também de comparação entre os microestriamentos, determinando o grau de semelhançaa entre as amostras colhidas utilizando a Função de Correlação Cruzada (FCC). Os principais resultados alcançados foram a captura e a montagem da imagem da área lateral de um objeto tridimensional e comparação das imagens das amostras adquiridas. Estas comparações permitiram determinar quais amostras foram produzidas pela mesma arma. Espera-se, com o desenvolvimento futuro deste trabalho, que possa ser produzida uma solução brasileira para a microcomparação balística automática e busca de casos relacionados em um banco de dados.

This work addresses the robotization problem of a small-scale commercial helicopter. The problem solution involves three subtasks: design and implementation of algorithms for localization, development of the helicopter mathematical model and design and implementation of control laws. For localization, the combination of a stereo vision system and inertial sensors information via Kalman Filtering is proposed. The estimated states, which are linear and angular positions and velocities, along with the pilot commands are used to estimate, through system identification methods, the parameters of a gray box model. Once the helicopter model is identified, the controllers are designed. The first tests were performed in a platform that restricted the helicopter movements to variations in the attitude angles. In the following tests, the helicopter was controlled without any device to restrict its movements, using traditional PID cascade control. Experimental results show stabilization of all the helicopter degrees of freedom.
Este trabalho aborda o problema de robotização de um helimodelo comercial de pequeno porte para operação em ambientes internos. A solução para o problema ´e dividida em três sub-tarefas: projeto e implementação de algoritmos de localização, desenvolvimento da modelagem matemática do helimodelo e projeto e implementação de leis de controle. Para localização, propõe-se a combinação de informações provenientes de um sistema de visão estéreo e de sensores inerciais via Filtragem de Kalman. Os estados estimados, que compreendem posições e velocidades lineares e angulares, são usados em conjunto com os sinais de comando do piloto para estimar, por meio de métodos de identificação, os parâmetros de um modelo caixa-cinza. De posse do modelo dinâmico do helimodelo, são projetados os controladores. Inicialmente, são feitos testes numa plataforma que restringe o movimento do helimodelo a variações nos ângulos de atitude. Em seguida, o controle é feito sem qualquer mecanismo de restrição de movimentos, utilizando-se controladores PID clássicos em cascata. Resultados experimentais mostram a estabilização de todos os graus de liberdade do helimodelo.

Lo scopo di questa Tesi di Dottorato consiste nell'investigare la distribuzione di metallicità del gas ionizzato nelle galassie a disco nell'universo locale, esplorando le relazioni con le proprietà galattiche e dell'ambiente. La metallicità del gas è il risultato della storia cumulativa della formazione stellare, degli episodi che influenzano la componente gassosa, e dell'ambiente. Quindi è un tracciante fondamentale per studiare la formazione ed evoluzione delle galassie. In questa Tesi, mi avvalgo dei dati di spettroscopia a campo integrale dello strumento MUSE della survey GASP (Poggianti et al., 2017), che ha collezionato osservazioni di alta qualità di galassie a disco in ambienti diversi, comprese galassie di ammasso caratterizzate da code di gas extraplanare dovute a ram pressure stripping. Per ogni galassia del campione, derivo la mappa spazialmente risolta della metallicità del gas usando il codice PYQZ, l'inclinazione del disco, l'angolo di posizione, e il raggio efficace. Inizialmente, esploro la metallicità del gas al raggio efficace di un campione di 29 galassie di ammasso di GASP sottoposte a ram pressure stripping, comparandolo con un campione di riferimento 32 galassie di ammasso e di campo senza segni di disturbo del gas. Queste galassie mostrano una ben definita relazione tra la massa stellare e la metallicità del gas nell'intervallo di massa stellare 10^9.25 < M < 10^11.5 Msun. Ad ogni data massa, le galassie di ammasso di riferimento e le galassie sottoposte a stripping hanno metallicità simili, mentre le galassie di campo con M < 10^10.25 Msun mostrano in media metallicità del gas più basse delle galassie di ammasso. I risultati indicano che il ram pressure stripping non sta significativamente influenzando la metallicità del gas, almeno al raggio efficace. Piuttosto, segni di un'anticorrelazione tra metallicità e tasso di formazione stellare sono osservati, in accordo con studi precedenti. Poi, indago la distribuzione dei gradienti di metallicità del gas in funzione della massa stellare, sfruttando un campione più ampio di 85 galassie di GASP e un campione di ~1800 galassie a disco di MaNGA (Bundy et al., 2015), divise in galassie di campo e di ammasso. In generale, i profili di metallicità diventano più ripidi all'aumentare della massa stellare fino a 10^10.3 Msun e si appiattiscono alle masse più alte. Le galassie di ammasso hanno profili sistematicamente più piatti rispetto alle loro controparti di campo. Combinando i risultati ottenuti dai profili di metallicità e i gradienti di densità superficiale di massa stellare, le pendenze osservate posso essere interpretate come conseguenza del locale arricchimento di metalli dovuto alla formazione stellare in-situ durante la formazione inside-out delle galassie a disco. La relazione gradienti di metallicità-massa stellare è caratterizzata da un'ampia dispersione, specialmente a 10^9.8 < M < 10^10.5 Msun. Inoltre, i gradienti di metallicità anti-correlano con la frazione di gas nelle galassie, giustificando la differenza dei profili di metallicità tra galassie in ambienti differenti. Infine, conduco un'analisi dettagliata della metallicità del gas delle regioni di formazione stellare nelle code di quattro galassie sottoposte ad un intenso ram pressure stripping. L'abbondanza di ossigeno nel gas situato nelle code diminuisce in funzione della distanza dal disco galattico. I profili di metallicità osservati indicano che più del 50% delle regioni più povere di metalli è costituito da mezzo interammasso raffreddato. Questa è la prima volta che un tale processo è osservato grazie alla metallicità del gas, ed è qualitativamente in accordo con le simulazioni che predicono il mescolamento tra il mezzo interstellare ricco di metalli e il mezzo interammasso povero di metalli. Allo stesso tempo, questi risultati forniscono punti chiave per i modelli teorici che indagano questo fenomeno.
The aim of this Ph.D. Thesis is to investigate the distribution of the ionized gas metallicity in local disk galaxies, probing the relations with galaxy properties and the environment. The metals are the products of the stellar nucleosynthesis, therefore the gas metallicity is the result of the cumulative history of star formation, but also encodes the episodes affecting the gas component, which, in turn, are strictly connected to the environment. In other words, the gas metallicity is a fundamental tracer to study galaxy formation and evolution. In this Thesis I exploit the integral-field spectroscopic data from the GAs Stripping Phenomena in galaxies with MUSE (GASP; Poggianti et al., 2017) survey, which collected high quality observations of galaxies in different environments, including cluster galaxies with extraplanar gas tails as a consequence of ram pressure stripping. These data allow me to explore in detail the spatially resolved distribution of the ionized gas emission not only within the galaxy disk but also along the gas stripped beyond the stellar extent. For each galaxy in the sample I derive the gas metallicity map using the PYQZ code, the disk inclination, the position angle, and the effective radius. Initially, I explore the gas metallicity at the effective radius of a sub-sample of GASP, constituted of 29 cluster galaxies undergoing ram pressure stripping, and 32 cluster and field galaxies with no signs of gas disturbance for a reference comparison. These galaxies show a well-defined stellar mass-gas metallicity relation in the stellar mass range 10^9.25 < M < 10^11.5 Msun. At any given mass, reference cluster and stripping galaxies have similar metallicities, while the field galaxies with M < 10^10.25 Msun show on average lower gas metallicity than galaxies in clusters. The results indicate that ram pressure stripping is not significantly affecting the gas metallicity, at least at the effective radius. Rather, signs of an anticorrelation between the metallicity and the star formation rate are observed, in agreement with previous studies. Then, I investigate the distribution of gas metallicity gradients as a function of stellar mass, exploiting a larger sample of 85 GASP galaxies and a sample of ~1800 disk galaxies from MaNGA (Mapping Nearby Galaxies at Apache Point Observatory; Bundy et al., 2015), divided in field and cluster galaxies. Overall, metallicity profiles steepen with increasing stellar mass up to 10^10.3 Msun and flatten out at higher masses. Cluster galaxies have systematically flatter metallicity profiles than their field counterparts. Combining the results from the metallicity profiles and the stellar mass surface density gradients, the observed steepening can be interpreted as a consequence of local metal enrichment due to in-situ star formation during the inside-out formation of disk galaxies. The metallicity gradient-stellar mass relation is characterized by a rather large scatter, especially for 10^9.8 < M < 10^10.5 Msun. In addition, metallicity gradients anti-correlate with the galaxy gas fraction, justifying the differences of metallicity profiles between galaxies in different environments. Finally, I carry out a detailed analysis of the gas metallicity of star-forming clumps in the tails of four extreme ram pressure stripping galaxies. The oxygen abundance of the stripped gas decreases as a function of the distance from the parent galaxy disk. The observed metallicity profiles indicate that more than 50% of the most metal-poor stripped clouds are constituted by cooled intracluster medium. This is the first time that such a process is observed using the gas metallicity, and finds qualitative agreement with simulations that predict mixing between the metal-rich interstellar medium and the metal-poor intracluster medium. At the same time these results provide key constraints to theoretical models investigating this phenomenon.

Well integrity is an important topic in oil and gas well operations. The intention is to control the reservoir fluids and well pressures, by technical, operational and organizational barriers. Inadequate barriers can lead to unwanted influx and cause a kick, which can escalate further into a blowout. The Deepwater Horizon accident in the Gulf of Mexico in 2010 raised concerns about the safety of offshore deepwater drilling. This rig was considered to be an efficient and safe drilling unit, until the fatal blowout occurred leading to the loss of eleven lives, and the worst environmental disaster in US history.The main objective of a well barrier is to prevent leakage from the wellbore to the external environment during the various well operations. Well barriers are classified as primary or secondary barriers. The primary barriers are the barriers closest to the hydrocarbons and are the first obstacle to unwanted flow of formation fluid. The secondary barrier acts as a backup barrier. Barriers can further be classified as static or dynamic. The static barriers apply for the production phase, meaning that they are present over a longer period of time. Dynamic barriers occur during drilling and well intervention, and these are the once that are most difficult to assess because of the constantly changing parameters involved.Various drilling types such as overbalanced (conventional) and underbalanced drilling are used in the search for oil and gas. The main difference between these types, is how the pressure in the wellbore is maintained, and for this different barriers are needed.Laws and regulations dictate the requirements the industry has to follow. The Petroleum Safety Authority governs the regulations in Norway, and gives requirements to well barriers. In their regulations, they also refer to other guidelines and standards for more detailed requirements. NORSOK D-010 from 2013, “Well integrity in drilling and well operations”, is a widely used standard which defines requirements and guidelines relating to well integrity in drilling and well activities. Ways to regulate is found to vary between countries, such as for Norway and the US. During drilling, a dynamic barrier situation applies, where the activation of the barrier depends on the current situation, and there is no pre-made sequence of barrier activation. Overall, this makes the assessment a difficult task. Various approaches have been suggested for the assessment of dynamic barriers over the years, with contributions to the topic from oil-companies, standards and research papers. Most of what has been suggested has some kind of weaknesses, and no common approach has been accepted and put into use by the industry. As a contribution a new approach has been suggested in this thesis. An overbalanced drilling operation in deep waters initiated by a kick is selected as case study. The approach is based on using two different types of analysis, in combination. An event tree is used to illustrate the dynamics of the event, and various fault trees are used to analyze the barriers involved. To understand what can cause a kick, the possibility of avoiding it, and what to do if it happens are given attention. From the suggested approach, it emerges that the human factor plays an important role in the kick evaluation and to maintain the well integrity. If the primary barrier is lost, there will be a kick. For this to escalate into a blowout, the secondary barrier must also be lost. If the control equipment functions as intended, lack of detection and understanding, together with insufficient training and competence of personnel can make this happen.To prevent major accidents and hazardous events in the future, it is important to learn and gain experience from previous incidents and learn from each other, and the ability to work together, also between companies, on these difficult topics.

U okviru doktorske disertacije izvedena su eksperimentalna istraživanja osnovnih hidrodinamičkih i maseno-prenosnih karakteristika airlift reaktora sa spoljnom recirkulacijom sa ugrađenom višekanalnom cevnom membranom u silaznu cev (ALSRM). ALSRM je radio na dva načina rada: bez mehurova u silaznoj cevi (način rada A) i sa mehurovima u silaznoj cevi (način rada B) u zavisnosti od nivoa tečnosti u gasnom separatoru. Ispitivani su uticaji prividne brzine gasa, površinskih osobina tečne faze, tipa distributora gasa i prisustva mehurova gasa u silaznoj cevi na sadržaj gasa, brzinu tečnosti u silaznoj cevi i zapreminski koeficijent prenosa mase u tečnoj fazi u ALSRM. Rezultati su poređeni sa vrednostima dobijenim u istom reaktoru ali bez membrane (ALSR). Sadržaj gasa u uzlaznoj i silaznoj cevi određivan je pomoću piezometarskih cevi merenjem hidrostatičkog pritiska na dnu i vrhu uzlazne i silazne cevi. Brzina tečnosti merena je pomoću konduktometrijskih elektroda dok je zapreminski koeficijent prenosa mase dobijen primenom dinamičke metode merenjem promene koncentracije kiseonika u vremenu optičkom elektrodom. Eksperimentalni rezultati pokazuju da sadržaj gasa, brzina tečnosti i zapreminski koeficijent prenosa mase zavise od prividne brzine gasa, vrste alkohola i tipa distributora gasa kod oba reaktora. Višekanalna cevna membrana u silaznoj cevi uzrokovala je povećanje ukupnog koeficijenta trenja za 90% i time dovela do smanjenja brzine tečnosti u silaznoj cevi do 50%. Smanjena brzina tečnosti u silaznoj cevi povećala je sadržaj gasa do 16%. Predložene neuronske mreže i empirijske korelacije odlično predviđaju vrednosti za sadržaj gasa, brzinu tečnosti i zapreminski koeficijent prenosa mase.
An objective of this study was to investigate the hydrodynamics and the gas-liquid mass transfer coefficient of an external-loop airlift membrane reactor (ELAMR). The ELAMR was operated in two modes: without (mode A), and with bubbles in the downcomer (mode B), depending on the liquid level in the gas separator. The influence of superficial gas velocity, gas distributor’s geometry and various diluted alcohol solutions on hydrodynamics and gas-liquid mass transfer coefficient of the ELAMR was studied. Results are commented with respect to the external loop airlift reactor of the same geometry but without membrane in the downcomer (ELAR). The gas holdup values in the riser and the downcomer were obtained by measuring the pressures at the bottom and the top of the riser and downcomer using piezometric tubes. The liquid velocity in the downcomer was determined by the tracer response method by two conductivity probes in the downcomer. The volumetric mass transfer coefficient was obtained by using the dynamic oxygenation method by dissolved oxygen probe. According to experimental results gas holdup, liquid velocity and gas-liquid mass transfer coefficient depend on superficial gas velocity, type of alcohol solution and gas distributor for both reactors. Due to the presence of the multichannel membrane in the downcomer, the overall hydrodynamic resistance increased up to 90%, the liquid velocity in the downcomer decreased up to 50%, while the gas holdup in the riser of the ELAMR increased maximally by 16%. The values of the gas holdup, the liquid velocity and the gas-liquid mass transfer coefficient predicted by the application of empirical power law correlations and feed forward back propagation neural network (ANN) are in very good agreement with experimental values.

A gradient-independent model of gas fluxes was formulated and tested. The model is built on the relationship between gas flux and the time history of surface gas concentration, known as half-order derivative (HOD), when the transport of the gas in the boundary layer is described by a diffusion equation. The eddy-diffusivity of gas is parameterized based on the similarity theory of boundary layer turbulence combined with the MEP model of surface heat fluxes. Test of the new model using in-situ data of CO2 concentration and fluxes at several locations with diverse vegetation cover, geographic and climatic conditions confirms its usefulness and potential for monitoring and modeling greenhouse gases. The proposed model may also be used for estimating other GHGS fluxes such as methane (CH4) and Water vapor flux. This proof-of-concept study justifies the proposed model as a practical solution for monitoring and modeling global GHGS budget over remote areas and oceans where ground observations of GHGS fluxes are limited or non-existent. One focus of the on-going research is to investigate its application to producing regional and global distributions of carbon fluxes for identifying sinks and sources of carbon and re-evaluating the regional and global carbon budget at monthly and annual time scales.

Currently, almost all new vehicles are equipped with airbags. A common type of airbag inflator is the Heated Gas Inflator (HGI). These inflators are cylindrical shaped canisters that are filled to very high pressures with a gaseous mixture of fuel and air. The mixture is ignited from one or both ends of the cylinder. The resulting high temperatures from combustion heats the excess air, which is then used to inflate the airbag. Once the mixture is ignited, large pressure waves form, traveling along the length of the tube. These waves, inherent to the design of the inflator, do not allow the use of a volume averaged assumption for the combustion chamber. Therefore, it is necessary to use a Computational Fluid Dynamics (CFD) code to model the dynamic nature of the inflator. Commercial CFD codes are readily available that could be used to model the HGI. These codes use the Ideal Gas Law to calculate the properties of the mixture. The high pressures in an HGI do allow for the use of an ideal gas assumption. Instead, a Real Gas equation of state must be used. An existing Airbag Inflator Model that was capable of Real Gas equation of state calculations had been previously created to simulate solid propellant inflators. In order to properly model the wave dynamics in an HGI and include Real Gas calculations, a CFD model has been added to the Airbag Inflator Model. The CFD model must be capable of handling multiple species of gases and be able to properly model the sharp gradients associated with large pressure waves and changes in chemical species. Therefore, a high-resolution shock capturing technique is used to handle the homogeneous part of the governing equations. The non-homogeneous terms of the governing equations are solved using an ordinary differential equations solver. In order to combine the solutions, a time splitting technique is used to combine the solutions from the homogeneous and non-homogeneous parts of the governing equations. The addition of the CFD model to an Airbag Inflator Model with Real Gas equation of state capabilities provides a very useful tool in the design of HGIs. The model can be used to ensure that a design does not produce unexpected large magnitude pressure waves that could possibly cause dangerous mechanical failures. Later models of HGIs have ignitors at each end of the cylinder. The secondary ignitor can be delayed to vary the production rate of the exhaust gasses, depending on the severity of the crash. This time delay is an additional parameter that can have an effect on the wave dynamics in the HGI. The addition of the CFD model to the Airbag Inflator Model provides a fast and economical way to predict the outcome of any change in the design parameters of an HGI.

Gas lift is one of the most common forms of artificial lift, particularly for offshore wells. This is due to its relative downhole simplicity, flexibility, reliability, and ability in operating over a wide range of flow rates with the limited well head space. Generally, Gas lift optimization can reduce the operating cost with increase in the Net Present Value (NPV) and maximization of the recovery from the asset. All of the previous researches have reported that conventional gas lift technologies’ designs have limitations on gas lift valve. Nonetheless, traditional gas lift technologies that were designed and developed in 1950’s do not have resistance when subjected to high temperature and high pressure in subsea wells. This therefore unable the flows of the gas lift to be coherently controlled. Moreover, gas-lifted oil wells can lead to failure unless a smart gas lift valve unit is used in the controlling the amount of the gas inside the tubing string. In this study, an automation gas lift valve unit with the corresponding control line was experimentally simulated on a dedicated apparatus. This enables real-time data on the gas lift valve to the surface to be demonstrated and accordingly analyzed. Under the conventional method of practice the injection pressure of the gas is normally used in operation of the valve. Whereas in this investigation the port size of the gas lift valve was remotely adjusted from the assumed surface using the apparatus. A devoted computer program LabVIEW was also used in determination of the gas passage through the smart gas lift valve, thus distilling the real time data. The results have shown those optimizations are achievable at high gas injection pressure when 87 psi is used and when the valve is 15% open (or 0.95mm port size diameter). Also, the wellhead pressure reaches to the minimum value of 0.9 psi in which high-pressure drop between the reservoir pressure and the top surface will occur. Throughout this investigation, water was used as a working fluid since the column of corresponding water in petroleum production tubing has the highest hydrostatic pressure of 2.8 psig compared with crude oil. Hence, during the gas lift process crude oil will be less cumbersome to produce than water. The results present the maximum production rate of 18.3 lit/min (with 83% improvement on production) could be achieved. The results obtained experimentally were also used in constructing an economic analysis from the use of smart gas lift valve for different scenarios namely: (i) in gas lift natural flow and (ii) the gas lift wells. It was demonstrated that the flow rate can be enhanced from 91bbl/day to 166.5 bbl/day for the gas lift natural flow, and from ‘Zero’ (or non-production) to165.6 bbl/day for the gas lift well. Based on these results, the NPV of the gas lift natural flow will be approximately $2793 on $37 per barrel and for the gas lift well will be about $6127.2.

In the last decade, shale reservoirs emerged as one of the fast growing hydrocarbon resources in the world unlocking vast reserves and reshaping the landscape of the oil and gas global market. Gas-condensate reservoirs represent an important part of these resources. The key feature of these reservoirs is the condensate banking which reduces significantly the well deliverability when the condensate forms in the reservoir below the dew point pressure. Although the condensate banking is a well-known problem in conventional reservoirs, the very low permeability of shale matrix and unavailability of proven pressure maintenance techniques make it more challenging in shale reservoirs. The nanoscale range of the pore size in the shale matrix affects the gas flow which deviates from laminar Darcy flow to Knudsen flow resulting in enhanced gas permeability. Furthermore, the phase behaviour of gas-condensate fluids is affected by the high capillary pressure in the matrix causing higher condensate saturation than in bulk conditions. A good understanding and an accurate evaluation of how the condensate builds up in the reservoir and how it affects the gas flow is very important to manage successfully the development of these high-cost hydrocarbon resources. This work investigates the gas Knudsen flow under condensate saturation effect and phase behaviour deviation under capillary pressure of gas-condensate fluids in shale matrix with pore size distribution; and evaluates their effect on well productivity. Supplementary MATLAB codes are provided elsewhere on OpenAIR: http://hdl.handle.net/10059/2145.

The research on Determination of Residual Gas Saturation and Gas-Water Relative Permeability in Water-Driven Gas Reservoirs is divided into four stages: literature research, core-flooding experiments, development and application of a new technique for reservoir simulation. Overall, all stages have been completed successfully with several breakthroughs in the areas of Special Core Analysis (SCAL), reservoir engineering and reservoir simulation technology.Initially, a literature research was conducted to survey all available core analysis techniques and their individual characteristics. The survey revealed that there are several core analysis techniques for measuring residual gas saturation (Sgr) and hence, the lack of a commonly agreed method for measuring Sgr. The often-used core analysis techniques are steady-state displacement, co-current imbibition, centrifuge and counter-current imbibition. In this research, all centrifuge tests were performed with a decane-brine system to investigate the possibility of replacing gas with a 'model fluid' to minimise errors due to gas compressibility. Furthermore, Sgr is a function of testing temperature and pressure, types of fluid, wettability, viscosity, flow rate and overburden pressure. Consequently, large uncertainties are associated with measured Sgr and the recoverable gas reserves for water-driven gas reservoirs.Due to the lack of a common method for measuring Sgr, the first important step is to clarify which is the most representative core analysis technique for measuring Sgr. In Stage 2 of the research, core analysis experiments were performed with uniform fluids and ambient temperature. In the core flooding experiments, four different sets of core plugs from various gas reservoirs were selected to cover a wide range of permeability and porosity. Finally, all measured Sgr from the various common core analysis techniques were compared.The evidence suggested that steady-state displacement and co-current imbibition tests are the most representative techniques for reservoir application. Steady-state displacement also yields the complete relative permeability (RP) data but it requires long stabilisation times and is costly.In the third stage, a new technique was successfully developed for determining both Sgr and gas-water RP data. The new method consists of an initial co-current imbibition experiment followed by the newly developed correlation (Mulyadi, Amin and Kennaird correlation). Co-current imbibition is used to measure the end-point data, for example, initial water saturation (Swi) and Sgr. The MAK correlation was developed to extend the co-current imbibition test by generating gas-water relative permeability data. Unlike previous correlations, MAK correlation is unique because it incorporates and exhibits the formation properties, reservoir conditions and fluid properties (for example, permeability, porosity, interfacial tension and gas density) to generate the RP curves. The accuracy and applicability of MAK correlations were investigated with several sets of gas-water RP data measured by steady-state displacement tests for various gas reservoirs in Australia, New Zealand, South-East Asia and U.S.A. The MAK correlation proved superior to previously developed correlations to demonstrate its robustness.The purpose of the final stage was to aggressively pursue the possibility of advancing the application of the new technique beyond special core analysis (SCAL). As MAK correlation is successful in describing gas water RP in a core plug scale, it is possible to extend its application to describe the overall reservoir flow behaviour. This investigation was achieved by implementing MAK correlation into a 3-D reservoir simulator (MoReS) and performing simulations on a producing field.The simulation studies were divided into two categories: pre and post upscaled application.The case studies were performed on two X gas-condensate fields: X1 (post upscaled) and X2 (pre upscaled) fields. Since MAK correlation was developed for gas-water systems, several modifications were required to account for the effect of the additional phase (oil) on gas and water RP in gas-condensate systems. In this case, oil RP data was generated by Corey's equations. Five different case studies were performed to investigate the individual and combination effect of implementing MAK correlation, alternative Swi and Sgr correlations and refining porosity and permeability clustering. Moreover, MAK correlation has proven to be effective as an approximation technique for cell by cell simulation to advance reservoir simulation technology.

The research on Determination of Residual Gas Saturation and Gas-Water Relative Permeability in Water-Driven Gas Reservoirs is divided into four stages: literature research, core-flooding experiments, development and application of a new technique for reservoir simulation. Overall, all stages have been completed successfully with several breakthroughs in the areas of Special Core Analysis (SCAL), reservoir engineering and reservoir simulation technology.Initially, a literature research was conducted to survey all available core analysis techniques and their individual characteristics. The survey revealed that there are several core analysis techniques for measuring residual gas saturation (Sgr) and hence, the lack of a commonly agreed method for measuring Sgr. The often-used core analysis techniques are steady-state displacement, co-current imbibition, centrifuge and counter-current imbibition. In this research, all centrifuge tests were performed with a decane-brine system to investigate the possibility of replacing gas with a 'model fluid' to minimise errors due to gas compressibility. Furthermore, Sgr is a function of testing temperature and pressure, types of fluid, wettability, viscosity, flow rate and overburden pressure. Consequently, large uncertainties are associated with measured Sgr and the recoverable gas reserves for water-driven gas reservoirs.Due to the lack of a common method for measuring Sgr, the first important step is to clarify which is the most representative core analysis technique for measuring Sgr. In Stage 2 of the research, core analysis experiments were performed with uniform fluids and ambient temperature. In the core flooding experiments, four different sets of core plugs from various gas reservoirs were selected to cover a wide range of permeability and porosity. Finally, all measured Sgr from the various common core analysis techniques ++
were compared.The evidence suggested that steady-state displacement and co-current imbibition tests are the most representative techniques for reservoir application. Steady-state displacement also yields the complete relative permeability (RP) data but it requires long stabilisation times and is costly.In the third stage, a new technique was successfully developed for determining both Sgr and gas-water RP data. The new method consists of an initial co-current imbibition experiment followed by the newly developed correlation (Mulyadi, Amin and Kennaird correlation). Co-current imbibition is used to measure the end-point data, for example, initial water saturation (Swi) and Sgr. The MAK correlation was developed to extend the co-current imbibition test by generating gas-water relative permeability data. Unlike previous correlations, MAK correlation is unique because it incorporates and exhibits the formation properties, reservoir conditions and fluid properties (for example, permeability, porosity, interfacial tension and gas density) to generate the RP curves. The accuracy and applicability of MAK correlations were investigated with several sets of gas-water RP data measured by steady-state displacement tests for various gas reservoirs in Australia, New Zealand, South-East Asia and U.S.A. The MAK correlation proved superior to previously developed correlations to demonstrate its robustness.The purpose of the final stage was to aggressively pursue the possibility of advancing the application of the new technique beyond special core analysis (SCAL). As MAK correlation is successful in describing gas water RP in a core plug scale, it is possible to extend its application to describe the overall reservoir flow behaviour. This investigation was achieved by implementing MAK correlation into a 3-D reservoir simulator (MoReS) and performing simulations on a producing ++
field.The simulation studies were divided into two categories: pre and post upscaled application.The case studies were performed on two X gas-condensate fields: X1 (post upscaled) and X2 (pre upscaled) fields. Since MAK correlation was developed for gas-water systems, several modifications were required to account for the effect of the additional phase (oil) on gas and water RP in gas-condensate systems. In this case, oil RP data was generated by Corey's equations. Five different case studies were performed to investigate the individual and combination effect of implementing MAK correlation, alternative Swi and Sgr correlations and refining porosity and permeability clustering. Moreover, MAK correlation has proven to be effective as an approximation technique for cell by cell simulation to advance reservoir simulation technology.

For a natural gas importing country, &ldquo
take or pay&rdquo
approach creates problems since the demand for natural gas varies during the year and the excess amount of natural gas should be stored. In this study, an underground gas storage project is evaluated in a depleted gas Field M. After gathering all necessary reservoir, fluid, production and pressure data, the data were adapted to computer language, which was used in a commercial simulator software (IMEX) that is the CMG&rsquo
s (Computer Modelling Group) new generation adoptive simulator, to reach the history matching. The history matching which consists of the 4 year of production of the gas reservoir is the first step of this study. The simulation program was able to accomplish a good history match with the given parameters of the reservoir. Using the history match as a base, five different scenarios were created and forecast the injection and withdrawal performance of the reservoir. These scenarios includes 5 newly drilled horizontal wells which were used in combinations with the existing wells. With a predetermined injection rate of 13 MMcf/D was set for all the wells and among the 5 scenarios, 5 horizontal &ndash
6 vertical injectors &
5 horizontal - 6 vertical producers is the most successful in handling the gas inventory and the time it takes for a gas injection and production period. After the determination of the well configuration, the optimum injection rate for the entire field was obtained and found to be 130 MMcf/D by running different injection rates for all wells and then for only horizontal wells different injection rates were applied with a constant injection rate of 130 MMcf/d for vertical wells. Then it has been found that it is better to apply the 5th scenario which includes 5 horizontal &ndash
6 vertical injectors &
5 horizontal - 6 vertical producers having an injection rate of 130 MMcf/d for horizontal and vertical wells. Since within the 5th scenario, changing the injection rate to 1.3 Bcf/d and 13 Bcf/d, did not effect and change the average reservoir pressure significantly, it is best to carry out the project with the optimum injection rate which is 130 MMcf/d. The total gas produced untill 2012 is 394 BCF and the gas injected is 340 BCF where the maximum average reservoir pressure was recovered and set into a new value of 1881 psi by injection and cushion gas pressure as 1371 psi by withdrawal. If 5th scenario is compared with the others, there is an increase in injection and production performance about 90%.

The reliabilities of the gas-path components (compressor, burners and turbines) of a gas turbine (GT) are usually high when compared with those of other GT systems such as fuel supply and control. However, in the event of forced outage, downtimes are normally high, giving a relatively low availability. The purpose of condition monitoring and fault diagnostics is to detect, isolate and assess (i.e. estimate quantitatively the magnitude of) the faults within a system, which in this case is the gas turbine. An effective technique would provide a significant improvement in economic performance, reduce operational and maintenance costs, increase availability and improve the level of safety achieved. However, conventional analytical techniques such as gas-path analysis and its variants are limited in their applications to engine diagnostics due to several reasons that include their inability to:- operate effectively in the presence of noisy measurements; distinguish effectively sensor bias from component faults; preserve the nonlinearity in the gas-turbine parameter relationships; and the requirement for more sensors for achieving accurate diagnostics. The novelty of this research stems from its objective of overcoming most of these limitations and much more. In this thesis, we present the approach adopted in developing a diagnostic framework for the detection of faults in the gas-path of a gas turbine. The framework involves a large-scale integration of artificial neural networks (ANNs) designed and trained to detect, isolate and assess the faults in the gas-path components of the engine. Input to the diagnostic framework are engine measurements such as spool speeds, pressures, temperatures and fuel flow while outputs are either levels of changes in sensor(s) for the case of sensor fault(s) or the level of changes in efficiencies and flow capacities for the case of faulty components. The diagnostic framework has the capacity to assess both multiple component and multiple sensor faults over a range of operating points. In the case of component faults, the diagnostic system provides changes in efficiencies and flow capacities from which interpretations can be sought for the nature of the physical problem. The implication of this is that the diagnostic system covers a wide range of problems - both likely and unlikely-. The technique has been applied to several developed test cases, which are not only thermodynamically similar to operational engines, but also covers a range of engine configurations and operating conditions. The results obtained from the developed approach has been compared against those obtained from linear and nonlinear (recursive linear) gas-path analysis, as well as from the use of fuzzy logic. Analysis of the results demonstrates the promise of ANN applied to engine gas-path fault diagnostic activities. Finally, the limitations of this research and direction for future work are presented.

A study into potential gas shales is conducted to define the controlling factors of gas adsorption and evaluate gas adsorption capacity in shale gas reservoirs. The results from high-pressure adsorption experiment show that temperature, moisture and composition affect the gas adsorption in shale. In this study, a tool is introduced to predict gas adsorption capacity. This study helps to understand the mechanism of gas adsorption and evaluate gas storage in shale gas reservoirs.

Die Dynamik anfänglich aus dem Gleichgewicht gebrachter wechselwirkender Quantenvielteilchensysteme wirft aktuell noch spannende Fragen auf. In Bezug auf die Thermalisierung ist z.B. nach wie vor ungeklärt, in welcher Form sie überhaupt stattfindet und in welchen Observablen bzw. auf welcher Zeitskala sie zu beobachten ist. Eine ideale Grundlage zur Erforschung von Relaxationsdynamiken in wechselwirkenden Vielteilchensystemen bieten ultrakalte Quantengase aufgrund ihrer guten Kontrollier- und Variierbarkeit. Ein allgemeiner theoretischer Rahmen, auf dessen Basis solche Prozesse zu untersuchen sind, steht jedoch infolge der großen Anzahl der beteiligten Freiheitsgrade bisher nicht zur Verfügung. Für ultrakalte bosonische Gase stellt die Gross-Pitaevskii-Gleichung eines der wichtigsten theoretischen Werkzeuge dar, eine klassische Feldgleichung für die Kondensatwellenfunktion in Molekularfeldnäherung. Die ihr zugrunde liegende Näherung erlaubt jedoch keine nicht-trivialen Aussagen über den vollen N-Teilchenzustand, dessen Kenntnis für die Untersuchung einer möglichen Relaxationsdynamik unabdingbar ist. Um der theoretischen Beschreibung des vollen bosonischen Feldes einen Schritt näher zu kommen, untersucht die vorliegende Arbeit die Anwendung semiklassischer Methoden auf ultrakalte Bosegase. Diese sind in der Regel dann sehr genau, wenn die beteiligten Wirkungen groß gegenüber dem Planckschen Wirkungsquantum sind. Für bosonische Felder wird dieser Grenzfall durch die Bedingung einer großen Teilchenzahl ersetzt. Die immense Anzahl an Teilchen in den hier behandelten Vielteilchensystemen macht die Anwendung semiklassischer Methoden auf diesem Gebiet also vielversprechend. Als zentrales Modellsystem wird ein anfänglich aus dem Gleichgewicht gebrachtes ultrakaltes bosonisches Doppelmuldensystem betrachtet, das eine hochinteressante Dynamik aufweist, die auf das Wechselspiel der Tunneldynamik einerseits und der Wechselwirkung der Teilchen untereinander andererseits zurückzuführen ist. Als Referenz lassen sich aufgrund der speziellen Fallengeometrie im Rahmen der Zwei-Moden-Näherung die Ergebnisse einer numerisch exakten Untersuchung heranziehen. Durch den Einsatz der namhaften WKB-Quantisierung und des besonders aus der Molekülphysik bekannten Reflexionsprinzips wird hier ein geschlossener analytischer Ausdruck für die sogenannte Populationsdifferenz im Doppelminimum hergeleitet, der ausschließlich von den wenigen relevanten Systemparametern abhängt. Diese mächtige Formel erlaubt es nun zum ersten Mal, in quantitativer Weise die charakteristische Sequenz aus Oszillationen, Kollapsen und Revivals in Abhängigkeit der vorausgesetzten Parameter zu untersuchen. Nach dieser ersten erfolgreichen Anwendung semiklassischer Methoden im Modellsystem wird über die reduzierte Dynamik der Populationsdifferenz hinausgegangen. Mithilfe des semiklassischen Herman-Kluk-Propagators lässt sich selbst der volle N-Teilchenzustand untersuchen. Da es letztlich um die Beschreibung ultrakalter Bosonen in beliebigen Potentialen gehen soll, wird zunächst der Herman-Kluk-Propagator für eine Feldtheorie vorgestellt. Im Doppelmuldensystem zeigt sich dann in der Anwendung die semiklassische Propagation in der Lage, für alle untersuchten Parameterregime gute Übereinstimmung mit den numerisch exakten Ergebnissen zu liefern. Zusätzlich findet ein Abgleich der Resultate mit der Truncated Wigner Approximation statt, auf die im Forschungsgebiet ultrakalter Bosonen häufig zurück gegriffen wird. Diese beschreibt die Zeitentwicklung einer Wignerverteilung unter Aussparung der Quanteninterferenzen. In der vorliegenden Arbeit wird gezeigt, dass die Herman-Kluk-Propagation unter Berücksichtigung der Phasen weit über die Truncated Wigner Approximation hinausgeht: Sie gibt alle wichtigen Charakteristika der Dynamik im Doppelmuldensystem wieder. Um die Semiklassik auf ihre Aussagefähigkeit in Bezug auf eine noch komplexere Dynamik zu untersuchen, wird zum Abschluss das Drei-Topf-System betrachtet, das zusätzlich chaotische Regionen im Phasenraum aufweist. Auch hier zeigt sich, dass die semiklassische Berücksichtigung der Phasen die Truncated Wigner Approximation in den Schatten stellt. Allerdings ergeben sich durch die Instabilität der Trajektorien für stark chaotische Regime numerische Probleme, die es in der Zukunft zu lösen gilt
The dynamics of initially non equilibrium interacting quantum many body systems is an ongoing and interesting field of research. It is still an open question in which form relaxation occurs in such systems, and in which observables and on which timescales a possible thermalization might appear. A perfect playground for the investigations of relaxation dynamics in interacting many body schemes is provided by ultracold quantum gases, which are easily to be controlled and varied in experiments. However, a general theoretical framework for the investigation of such processes is still missing, due to the huge amount of involved degrees of freedom. One of the main theoretical tools in the field of ultracold bosonic gases represents the famous Gross-Pitaevskii equation, a field equation for the Bose-Einstein condensate wave function in terms of a mean-field approximation. However, the underlying approximation prevents the possibility to draw non-trivial conclusions about the full N-particle state, the information of which is necessary for the analysis of relaxation processes. To gain the theoretical description of the full bosonic field, the present thesis deals with the application of semiclassical methods to ultracold boson gases. Those techniques become in general exact, as long as the involved actions are large compared to Planck's constant. For many body systems it turns out that semiclassics are expected to give good results also for the condition of high particle numbers, which is precisely fulfilled in these schemes, making the semiclassical approaches promising. As an essential model system an initially out of equilibrium ultracold bosonic double-well system is investigated. This configuration provides highly interesting dynamics due to the interplay of the tunneling dynamics on the one hand and the interaction amongst the particles on the other. The special trap geometry makes exact numerical calculations in the framework of the two-mode approximation available, which serve in the following as reference data. By applying the common semiclassical WKB approximation and the reflection principle known from molecule physics, a closed analytical expression for the so-called population imbalance of the bosons in the double-well is derived, depending only on the few relevant system parameters. This mighty formula allows for the first time the quantitative investigation of the characteristic sequence consisting of oscillations, collapse and revivals in dependence on the parameters of the system. Since the semiclassical approaches succeeded for the double-well model so far the so-called Herman-Kluk propagator is adopted, to go beyond the reduced dynamics of the population imbalance. The propagator provides the possibility to treat the full N-particle state theoretically and is introduced for the most general case of a bosonic quantum field. Its application to the double-well system yields for all investigated parameter regimes very good agreement with the numerical exact results. Furthermore the outcomes are compared to the Truncated Wigner approximation, which is frequently used in the research field of ultracold bosons. This approach pictures the time evolution of a Wigner distribution, without taking into account the quantum interferences. In the present thesis it is shown that the Herman-Kluk propagation goes clearly beyond the truncated Wigner approach by considering in addition the quantum phases: The propagator is able to reproduce all of the distinctive features of the double-well dynamics. In order to test the performance of semiclassical methods in matters of even more complex systems, the ultracold bosonic triple-well model is finally considered, which exhibits unlike the double-well scheme chaotic regions in phase space. It turns out that the semiclassical propagation outplays again the truncated Wigner approximation. On the other hand the instability of the highly chaotic trajectories causes numerical problems, which have to be solved in the future

Auf der diesjährigen Leipziger Buchmesse präsentierte sich die Schweiz bei ihrem Länderauftritt mit einem literarisch opulenten Programm, das über 80 Autorinnen und Autoren und mehr als 70 Verlage versammelte. „Helvetia zu Gast in Sachsen“ hieß es auch in Annaberg-Buchholz. Im Rahmen dieses Programms, getragen vom Landesverband Sachsen im Deutschen Bibliotheksverband e.V. und dem Sächsischen Staatsministerium für Wissenschaft und Kunst, konnte am Vorabend der Leipziger Buchmesse der renommierte Schweizer Autor Adolf Muschg zusammen mit seiner Frau Atsuko in der Stadtbibliothek begrüßt werden. Der Veranstaltungsraum war bis zum letzten Platz gefüllt. Viele hatten Bücher von Adolf Muschg noch aus DDR-Zeiten zum Signieren mitgebracht und waren glücklich, den Autor einmal persönlich erleben zu können. Im Gepäck hatte er seinen 2012 erschienenen Roman „Löwenstern“, der die Geschichte von Hermann Ludwig von Löwensterns abenteuerlicher Japanreise zu Beginn des 19. Jahrhunderts erzählt.

The reaction of Water Gas Shift (WGS) plays a key role in the production of H2 or syngas, widely employed in the chemical industry. More than 90% of the H2 is currently produced by Steam Reforming (SR) of the natural gas or low molecular weight hydrocarbons, with an increasing role of its production from alternative sources such as the clean biogas (CBG), mixture of CH4 and CO2 obtained by elimination of S- and N-containing compounds from the gas mixture obtained by anaerobic fermentation of biomass. Compared to the mixture obtained in the SR of the natural gas, that obtained from CBG shows more hard conditions related to a higher CO concentration and a lower Steam/Dry Gas (S/DG) ratio. By hypothesizing a 2 steps process, the tests at high temperature (HTS, 350-450 °C) performed feeding the mixture obtained from CBG showed that Cu/Zn/Al catalysts (Cu 4 wt%) doped with small amount of Ga (Al/Ga = 50) can be usefully employed considering the higher activity and stability in comparison to a reference un-doped catalyst. The H2/CO ratio depended on the amount of the CO in the feed mixture and amount of steam fed. The best performances of the catalyst doped by Ga can be attributed to a higher dispersion and stability of the active phase, such as evidenced by a study of model catalysts and by the DRIFTS analysis in the adsorption/desorption of CO. An alternative to the two steps process is a single step process operating at medium temperature (MTS, 250-350 °C) using only one reactor. On the basis of previous studies, Cu/Zn/Al catalysts (Cu 20 wt%) have been investigated doped with small amounts of promoters (Al/Ce or Al/Zr 50), using a S/DG = 0,55 ratio. At 350°C Ce and Zr improve the catalityc activity, with a deactivation in presence of Zr only of 4%. On the contrary the catalyst containing Ce was stable at increasing reaction temperature.

Lo studio delle miscele di gas è un tema che oggigiorno risponde alle necessità di vari campi di ricerca, come l'ingegneria aerospaziale, gli studi climatici, le industrie energetiche, ecc. Per questo motivo la costruzione di modelli matematici che simulino il comportamento di gas reali si rivela estremamente utile. Tra tutti gli approcci possibili, quello cinetico, che si basa sulle equazioni di Boltzmann per le funzioni di distribuzione dei gas, rappresenta uno degli strumenti più validi. Esso permette, infatti, di descrivere miscele a partire dall'interazione tra particelle, per poi derivare modelli per le quantità osservabili. Il lavoro contenuto in questa tesi è volto a riprendere i risultati presenti in letteratura per miscele di gas e a estenderli considerando casi più realistici, come miscele di specie monoatomiche e poliatomiche, che interagiscono in modo inelastico o chimico. Per prima cosa, nell'introduzione vengono presentati i concetti basilari e i risultati più rilevanti per lo studio cinetico dei gas, insieme a una sintesi più dettagliata dei contenuti della tesi. Nel Capitolo 1 proponiamo lo studio di una miscela reattiva costituita da quattro gas utilizzando la classica teoria cinetica di Boltzmann. Questo problema è già stato analizzato nell’ipotesi in cui i gas hanno lo stesso numero di livelli di energia interna, lo affrontiamo nel caso più generale supponendo che ciascuna delle specie coinvolte abbia un diverso numero di livelli energetici. Nei due capitoli successivi vengono studiate miscele di gas utilizzando un approccio cinetico di tipo BGK. In particolare, nel Capitolo 2 forniamo un modello BGK per una miscela inerte di gas monoatomici e poliatomici. Dimostriamo la consistenza del modello e analizziamo la stabilità degli equilibri; deriviamo poi opportune equazioni macroscopiche ed eseguiamo alcune simulazioni numeriche ispirandoci ai gas reali. Nel Capitolo 3, invece, proponiamo due modelli BGK per miscele di gas reagenti. Nel primo consideriamo quattro specie di gas coinvolte in una reazione chimica reversibile, nel secondo otto gas che partecipano a due reazioni disgiunte. La procedura precedente viene applicata in entrambi i casi, la principale differenza risiede nel dimostrare la consistenza del modello, poiché si ottengono equazioni trascendenti più complicate per la determinazione di tutti i parametri. Anche in questo contesto vengono eseguite simulazioni numeriche che modellino il comportamento di miscele reattive reali. Nella parte restante della tesi, studiamo miscele di gas mediante tecniche ulteriori. Nel Capitolo 4 consideriamo una miscela di cinque specie di gas, di cui tre costituiscono il mezzo ospite in cui interagiscono le altre due. Gli urti tra le particelle possono essere di tipo elastico, inelastico o chimico e ipotizziamo che questi avvengano su scale temporali diverse. Successivamente, scriviamo le equazioni di Boltzmann classiche per le funzioni di distribuzione delle varie componenti. Dopo opportune integrazioni delle equazioni e tramite un passaggio al limite otteniamo equazioni di reazione-diffusione per le densità di specie. Nello specifico, applichiamo questo procedimento in tre diversi regimi idrodinamici, ottenendo per ciascuno di essi un diverso sistema di reazione-diffusione. Le proprietà di stabilità di tali sistemi vengono discusse nel Capitolo 5. Ci concentriamo in particolare sul verificarsi del fenomeno dell’instabilità di Turing per scelte opportune dei valori energetici e delle frequenze di collisione. Attraverso simulazioni numeriche, verifichiamo poi la formazione di pattern nell’evoluzione delle densità, come previsto dall'analisi di Turing. Concludiamo con alcune ulteriori osservazioni e prospettive per futuri sviluppi del presente lavoro di ricerca.
The study of gas flows is an issue that nowadays responds to the necessities of various fields of research, as aerospace engineering, climate studies, energy industries, etc. For this reason, the construction of mathematical models simulating the behavior of real gas mixtures is extremely useful. Among all possible approaches, the kinetic one, based on Boltzmann equations for species distribution functions, seems to be a very powerful tool. It allows, in fact, to describe mixtures starting from interaction among particles, with the possibility of deriving models for the behavior of the global system at observable level. The work of this thesis is devoted to considering results obtained so far for mixtures of gases and extending them considering more real-like cases, such as mixtures of monoatomic and polyatomic gas species, that may also interact inelastically or chemically. As first, we provide an introduction in which the basic concepts and the most relevant results for kinetic description of gases are presented, along with a more detailed summary of the work carried out in the thesis. In Chapter 1, we propose the study of a reacting mixture of four gases using the classical Boltzmann kinetic theory. This case was already analyzed when the four gases are considered to have the same number of internal energy levels. We generalize it allowing each of the gas species to have a different number of energetic levels. Chapter 2 and Chapter 3 are devoted to the study of gas mixtures using a kinetic approach of BGK type. In particular, in Chapter 2 we provide a BGK model for an inert mixture of monatomic and polyatomic gases. We prove the consistency of the model and analyze the stability of equilibria, then we derive macroscopic equations and perform some numerical simulations being inspired by real gases. In Chapter 3, instead, we propose two BGK models for mixtures of reacting gases. In the first one we have four gas species involved in a reversible chemical reaction, in the second case eight gases react through two disjoint reactions. The previous strategy is applied to both cases, the main differences are in proving the consistency of the model, since we face more complicate transcendental equations to determine all the parameters. Also in these cases, numerical simulations are performed to reproduce the behavior of real reacting mixtures. In the remaining part of the thesis, we study gas mixtures using different techniques. In Chapter 4 we consider a mixture of five gas species, three of them constituting a background medium in which the other two interact. Encounters among particles can be elastic, inelastic, or chemical and we suppose that they occur at different time scales. We write classical Boltzmann equations for the interacting components, we pass to the asymptotic diffusive limit and, by means of suitable integrations of the kinetic equations, we obtain reaction-diffusion equations for densities of the species. Specifically, we apply this procedure in three different hydrodynamic regimes, obtaining in each case a proper reaction-diffusion system. The stability properties of these systems are then studied in Chapter 5. We consider the possibility of having Turing instability for a suitable choice of internal energy amounts and of collision frequencies. Through numerical simulations, we verify the formation of spatial patterns in the evolution of the number densities of reactants, as predicted by Turing analysis. We conclude with some further observations and perspectives for a future development of the present research work.

Проведені вимірювання спектрів пропускання в області екситонного поглинання 2,095-2,14 еВ монокристалічних зразків GaSe та (KOH)GaSe (зразки селеніду галію витримувались в розчині KOH). Вимірювання спектрів пропускання GaSe та (KOH)GaSe проводились при температурах 293 К і 77 К.

Les composants iii-v a base gasb ont de nombreuses applications dans le moyen infrarouge comme les liaisons optiques par fibres a verres fluores, les transmissions radar a travers les fenetres atmospheriques ou la detection et l'analyse spectroscopique des gaz. La premiere partie de ce memoire est consacree a l'epitaxie en phase liquide des alliages quaternaires gainassb et gaalassb accordes sur substrat de gasb et a leur caracterisation physique (dopage, photoluminescence, electroreflexion). Dans une autre partie les proprietes electrique et optique des heterointerfaces de type i gaalassb/gasb et de type ii gainassb/gasb sont etudies. Les discontinuites de bandes de conduction et de valence sont evaluees et, dans le cas des heterojonctions de type ii gainassb/gasb, des transitions indirectes dans l'espace reel sont mises en evidence par photoluminescence. La partie finale traite de la realisation et de la caracterisation de doubles heterostructures lasers gainassb/gaalassb emettant vers 2. 38 micrometres a temperature ambiante et de photodiodes a heterojonction gasb/gainassb a longueur d'onde de coupure 2. 5 micrometres. En conclusion de ce travail, une transition directe elementaire source-detecteur a ete demontree a 2. 1 micrometres

Natural gas hydrates are solid crystalline substances found in the subsurface. Since gas hydrates are stable at low temperatures and moderate pressures, gas hydrates are found either near the surface in arctic regions or in deep water marine environments where the ambient seafloor temperature is less than 10°C. This work addresses the important issue of geomechanical stability in hydrate bearing sediments during different perturbations. I analyzed extensive data collected from the literature on the types of sediments where hydrates have been found during various offshore expeditions. To better understand the hydrate bearing sediments in offshore environments, I divided these data into different sections. The data included water depths, pore water salinity, gas compositions, geothermal gradients, and sedimentary properties such as sediment type, sediment mineralogy, and sediment physical properties. I used the database to determine the types of sediments that should be evaluated in laboratory tests at the Lawrence Berkeley National Laboratory. The TOUGH+Hydrate reservoir simulator was used to simulate the gas production behavior from hydrate bearing sediments. To address some important gas production issues from gas hydrates, I first simulated the production performance from the Messsoyakha Gas Field in Siberia. The field has been described as a free gas reservoir overlain by a gas hydrate layer and underlain by an aquifer of unknown strength. From a parametric study conducted to delineate important parameters that affect gas production at the Messoyakha, I found effective gas permeability in the hydrate layer, the location of perforations and the gas hydrate saturation to be important parameters for gas production at the Messoyakha. Second, I simulated the gas production using a hydraulic fracture in hydrate bearing sediments. The simulation results showed that the hydraulic fracture gets plugged by the formation of secondary hydrates during gas production. I used the coupled fluid flow and geomechanical model "TOUGH+Hydrate- FLAC3D" to model geomechanical performance during gas production from hydrates in an offshore hydrate deposit. I modeled geomechanical failures associated with gas production using a horizontal well and a vertical well for two different types of sediments, sand and clay. The simulation results showed that the sediment and failures can be a serious issue during the gas production from weaker sediments such as clays.

Gas sensitive semiconductors have been known for many years and applied in static gas alarm systems for the monitoring of hazardous gases, however, their application has been limited by a lack of selectivity. In this work a semiconducting gas sensor has been configured for use as a gas chromatographic detector thus combining the sensitivity of semiconductor sensors with the selectivity of gas chromatography. The study has been confined to tin oxide devices, more specifically the Taguchi gas sensor (TGS) . The majority of this work has concentrated on the TGS 813 although the use of other TGS is described. The development of suitable instrumentation is described and rigorous optimisation of the operating parameters e.g. heater voltage and column temperature has been performed using the variable step size simplex technique. Attention was concentrated on the response of the TGS 813 to hydrogen which was used as a test gas. A novel figure of merit, response multiplied by retention time and divided by skew factor was designed so that optimum response was obtained whilst maintaining adequate chromatographic separation. Optimum conditions were verified by univariate searches and the response was observed to be most dependant upon heater voltage. A limit of detection of 20 ppb v/v of hydrogen in a 1 ml sample was obtained at optimal conditions. Illustrative analyses of hydrogen were performed in human breath and laboratory air with results found to be in close agreement with literature values. Calibration was found to be linear over at least three orders of magnitude. The response of the TGS 813 to low molecular weight alkanes has also been investigated. It was observed that different heater voltage optima existed for each of the C1-C5 alkanes and that the sensor was relatively more sensitive to the higher molecular weight compounds. As with hydrogen linear response was obtained over at least three orders of magnitude and an illustrative analysis of natural gas showed excellent agreement with known levels. A compromise optimum heater voltage was used to study the response of the TGS 813 to alcohols, aldehydes, ketones and some Cs hydrocarbons. Capillary columns were used in this investigation and it was noted that they had potentially wider application than packed columns due to the use of an inert carrier with an air make-up flow to the detector. This replaced the air carrier gas used previously which might degrade certain stationary phases. Three different types of TGS: the 813; 822 and 831 were used in a study of the response and skew factor for the detection of halogen-containing compounds. Very high skew factors were often observed, although, for some compounds it appeared that symmetrical peaks could be obtained within narrow heater voltage ranges. Skewed response was observed to be dependant upon sensor type, heater voltage and halogen proportion and type. Analysis of the three sensor types was performed and differences in potential surface area and tin oxide additives observed. The presence of additives was observed to adversely affect sensor recovery.

Thesis: S.M. in Technology and Policy, Massachusetts Institute of Technology, School of Engineering, Institute for Data, Systems, and Society, Technology and Policy Program, 2016.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 69-72).
Climate change is a major factor reforming the world's energy landscape today, and as electricity consumes 40% of total energy, huge efforts are being undertaken to reduce the carbon footprint within the electricity sector. The electric sector has been taking steps to reform the grid, retiring carbon-intensive coal plants, increasing renewable penetration, and introducing cyber elements end-to-end for monitoring, estimating, and controlling devices, systems, and markets. Due to retirements of coal plants, discovery of shale gas leading to low natural gas prices, and geopolitical motives to reduce dependence on foreign oil, natural gas is becoming a major fuel source for electricity around the United States. In addition, with increasingly intermittent renewable sources in the grid, there is a need for a readily available, clean, and flexible back-up fuel; natural gas is sought after in New England to serve this purpose as a reliable and guaranteed fuel in times when wind turbines and solar panels cannot produce. While research has been conducted advocating natural gas pipeline expansion projects to ensure this reliability, not enough attention has been paid to the overall market structure in the natural gas and electricity infrastructures which can also impact reliable delivery of gas and therefore efficient interdependency between the two infrastructures. This thesis explores the market structures in natural gas and electricity, the interdependence of natural gas and electricity prices with increasing reliance on natural gas as the penetration of renewable energy resources (RER) increases in order to complement their intermittencies, possible volatilities in these prices with varying penetration rates in RER, and alternatives to existing market structures that improve reliability and reduce volatility in electricity and gas prices. In particular, the thesis will attempt to answer the following two questions: What will the generation mix look like in 2030 and how will this impact gas and electricity prices? How do Gas-Fired Generator (GFG) bids for gas change between 2015 and 2030? In order to answer these questions, a computational model is determined using regression analysis tools and an auction model. Data from the New England region in terms of prices, generation, and demand is used to determine these models.
by Neha Nandakumar.
S.M. in Technology and Policy

An inter-laboratory study of high-pressure gas sorption measurements on two carbonaceous shales has been conducted to assess the reproducibility of sorption isotherms on shale and identify possible sources of error. The measurements were carried out by 7 different international research laboratories on either in-house or commercial sorption equipment using manometric as well as gravimetric methods. Excess sorption isotherms for methane, carbon dioxide and ethane were measured at 65°C and at pressures up to 25 MPa on two organic-rich shales at dry conditions. The inter-laboratory reproducibility of the methane excess sorption isotherms was better for the high-maturity shale (within 0.02 – 0.03 mmol g-1) than for the low-maturity sample (up to 0.1 mmol g-1), which is in agreement with results of earlier studies on coals. The procedures for sample conditioning prior to the measurement, the measurement procedures and the data reduction approach must be optimized to achieve higher accuracy. Unknown systematic errors in the measured quantities must be minimized first by applying standard calibration methods. Furthermore, the adsorption of methane on a dry, organic-rich, high-maturity Alum shale sample was studied at a wide temperature range (300 – 473 K) and pressures up to 14 MPa. These conditions are relevant to gas storage under geological conditions. Maximum methane excess uptake is 0.176 – 0.042 mmol g-1 (125 - 30 scf t-1) at 300 - 473 K. Supercritical adsorption was parameterized using the modified Dubinin-Radushkevich and the Langmuir equations. Gas in shales is stored in three different states: adsorbed, compressed (free) and dissolved; quantifying each underpins calculations of gas storage capacity and also the mechanisms by which gas must be transported from pore (surfaces), to fracture, to the well. While compressed gas dominates in meso- and macropores, it is often assumed that (a) sorbed gas occurs mainly in micropores (< 2nm) and (b) micropores are mainly associated with organic matter. In the third part of this thesis, those ideas are tested by characterising the porous structure of six shales and isolated kerogens from the Posidonia Formation in combination with high pressure methane sorption isotherms at 45, 65 and 85°C. Together, these data help us to understand the extent to which (a) small pores control CH4 sorption and (b) whether “sorption” pores are associated with the organic and inorganic phases within shales. Samples were selected with vitrinite reflectance of 0.6, 0.9 and 1.45%. Pore volumes – named sorption pore volumes here - were determined on dry shales and isolated kerogens by CO2 isotherms measured at -78°C and up to 0.1 MPa. These volumes include micropores (pore II width < 2nm) and narrow mesopores; according to the Gurvitch Rule this is the volume available for sorption of most gases. Sorption pore volumes of Posidoniashales range from 0.008 to 0.016 cm3 g-1, accounting for 21 - 66% of total porosity. Whilst sorption pore volumes of isolated kerogen are much higher, between 0.095 – 0.147 cm3 g-1, normalization by TOC shows that only half the sorption pore volume of the shales is located within the kerogen. Excess uptakes on dry Posidonia shales at 65°C and 11.5MPa range from 0.056−0.110 mmol g-1 (40−78 scf t-1) on dry shale, and from 0.36−0.70 mmol g-1 (253−499 scf t-1) on dry kerogen. Enthalpies of adsorption show no variation with TOC and maturity, respectively. The correlation between maximum CH4 sorption and CO2 sorption pore volume at 195 K is very strong and goes through the origin, suggesting that the vast majority of sorbed CH4 occurs in pores smaller than 6 nm. Approximately half the sorption pore volume and thus CH4 sorption potential of these dry shales is in organic matter, with the rest likely to be associated with clay minerals. Sorption mass balances using isotherms for kerogen and clay minerals do not always account for the total measured sorbed CH4 on dry shales, suggesting that some sorption may occur at interfaces between minerals and organic matter.

Elevated concentrations of ground-gases (CH4 and CO2) and VOCs in contaminated soil and water around the world pose significant risk both to human health and the environment. There is, therefore, a requirement to monitor them for effective risk assessment and remediation. Current ground-gas monitoring is often ineffective for determining their representative concentrations and fluxes – the two most important parameters necessary for ground-gas risk assessment. These failures of current monitoring may arise from its low temporal resolution. The recent ability to monitor at high temporal resolution – using Gasclam - makes it possible to determine whether this is the case and whether high resolution monitoring can be more effective. CH4 and CO2 were monitored at several sites using Gasclam. This showed that in many cases concentrations were sufficiently variable that current sampling practices would be ineffective at detecting worst case concentrations. Furthermore, the time-series data produced by Gasclam allowed the predictive power of the established relationships between atmospheric pressure and gas concentration to be improved. The failures in the relationship could also be understood as hysteresis which gave an index of ground permeability and/or gas generation. These improvements in understanding could be used to improve the conceptual site models on which risk assessments are based. Similarly, high temporal resolution VOC measurement demonstrated the need for such measurement. The factors controlling VOC concentration were shown to be same to those controlling ground-gases; again this understanding of process would also improve the conceptual site model. A monitoring method that incorporated parallel non-specific real time measurement with a time integrated VOC measurement that identified specific VOC’s was tested. The method was an improvement on the separate methods as it could be used to reasonably infer the concentrations of specific VOC’s at high temporal resolution. The ability to monitor gas concentrations at high temporal resolution gave the potential for the rate of gas concentration recovery subsequent to purging of the borehole to be used as an index of gas flux. These tests proved to be practical, generally taking less than the time of a site visit, and reproducible. Variability in these recovery profiles was assessed at different sites, times and for different gases.

Title from PDF of title page (University of Missouri--Columbia, viewed on Feb 24, 2010). The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Dissertation advisor: Dr. Jerry L. Atwood. Vita. Includes bibliographical references.

In this study, gas sensing systems that are based on piezoelectric smart material and structures are proposed, designed, developed, and tested, which are mainly aimed to address the temperature dependent CO2 gas sensing in a real environment. The state-of-the-art of gas sensing technologies are firstly reviewed and discussed for their pros and cons. The adsorption mechanisms including physisorption and chemisorption are subsequently investigated to characterize and provide solutions to various gas sensors. Particularly, a QCM based gas sensor and a C-axis inclined zigzag ZnO FBAR gas sensor are designed and analyzed for their performance on room temperature CO2 gas sensing, which fall into the scope of physisorption. In contrast, a Langasite (LGS) surface acoustic wave (SAW) based acetone vapor sensor is designed, developed, and tested, which is based on the chemisorption analysis of the LGS substrate. Moreover, solid state gas sensors are characterized and analyzed for chemisorption-based sensitive sensing thin film development, which can be further applied to piezoelectric-based gas sensors (i.e. Ca doped ZnO LGS SAW gas sensors) for performance enhanced CO2 gas sensing. Additionally, an innovative MEMS micro cantilever beam is proposed based on the LGS nanofabrication, which can be potentially applied for gas sensing, when combined with ZnO nanorods deposition. Principal component analysis (PCA) is employed for cross-sensitivity analysis, by which high temperature gas sensing in a real environment can be achieved. The proposed gas sensing systems are designated to work in a high temperature environment by taking advantage of the high temperature stability of the piezoelectric substrates.

Descripción: El consumo del vino se ha globalizado y el interés por conocer más sobre esta bebida viene alcanzando mayor importancia a nivel mundial; no solo para apreciar sus cualidades sensoriales, sino también para encontrar un valor agregado en la alianza armoniosa de un maridaje con las preparaciones culinarias y expresiones culturales de un lugar. Es así que este conocimiento debe ser parte de la formación integral del profesional de gastronomía quien tendrá la capacidad de brindar al consumidor una oferta eno-gastronómica especializada que logre satisfacer sus mayores expectativas. Propósito: El curso Elaboración y cata de Vinos es de especialidad en la carrera de Gastronomía y Gestión Culinaria, de carácter teórico-práctico dirigido a los estudiantes del quinto ciclo, que busca desarrollar las competencias específicas de Director de Alimentos y Bebidas en el nivel 2.

Wet Gas Metering is becoming increasingly important to the Oil and Gas Industry. In this research a wet gas flow is defined as a liquid / gas two-phase flow that has a gas mass content greater then 50 %. The Venturi Meter is a favoured wet gas meter in the Oil and Gas Industry. However, industry's understanding of wet gas flow phenomena in such a meter is limited and is therefore forced to accept large metering errors when existing correlations are used to take account of the liquid presence. Furthermore, these correlations all require an input value for the liquid flowrate. This information is not readily available to natural gas production engineers. This research extensively discusses the current wet gas metering situation and then uses new independent data from the NEL Wet Gas Loop to compare the performance of existing correlations when used with a Venturi Meter. This new data is examined to determine parameters that effect the meter reading and then new correlations are presented. One new correlation offered uses the additional information from a downstream pressure tapping in conjunction with the traditional upstream pressure reading and the Venturi pressure differential to predict the gas flowrate without knowledge of the liquid flowrate.