The drive to find reliable sources of fuel that follow our green concerns and reduce our dependence on foreign sources of fossil fuels has pushed exploration and recovery of natural gas from within the United States to a top priority. Earthquakes generated from the use of hydraulic fracturing techniques and/or use of high pressure injection wells are occurring at an alarming rate due to increases in hydrocarbon exploration and recovery. While the link between earthquakes and hydrocarbon production is still uncertain, earthquake induced changes to groundwater chemistry are clear. Yet it has not been determined if repetitive, smaller earthquakes, i.e. earthquakes with magnitudes less than Mw<4.5, can result in similar disturbances to water chemistry as the more significant events have been proven to cause. Two known earthquake swarms, each having repetitive, small earthquake events, occurred in an intraplate setting in Faulkner County, Arkansas. Testing for groundwater chemical changes related to the timing of earthquake events and total energy released show that small earthquakes indeed create changes to groundwater chemistry most probably due to fluid intrusion from deep, chloride, calcium, and magnesium rich waters. The reduction of the United States dependence on foreign sources or finding green sources of fuel should not be the only mitigating factor for our decisions concerning our natural resources.

A necessidade de redução de emissão de gases de efeito estufa nas atividades humanas, em particular no setor de transporte, tem motivado o uso de combustíveis renováveis em veículos. O etanol se mostra como um dos mais apropriados substituto - total ou parcialmente - aos combustíveis fósseis. Entretanto o uso desse combustível em motores modernos dotados de sistemas de injeção direta de alta pressão impõe desafios como a partida a frio, etapa em que é gerada a grande parte dos poluentes emitidos pelos veículos. O presente trabalho contemplou o estudo experimental da interação do spray de combustível e a formação do núcleo de combustão gerado por uma centelha, fenômenos de extrema importância na condição de partida a frio em motores. O objetivo é elaborar estratégias de injeção/ignição adequadas a cada tipo de combustível - etanol versus hidrocarboneto. Esses experimentos foram realizados em uma câmara de combustão de volume constante, projetada para permitir acessos ópticos e construída especialmente para suportar pressões de até 10 MPa. Uma etapa de caracterização do spray de combustível foi realizada em condições similares às presentes em um motor de combustão interna, variando-se o nível de pressão interna da câmara e o nível de pressão de injeção. Após tal caracterização foram realizados os ensaios de combustão, agora contemplando também variações de intervalo de tempo entre o início da injeção e a ignição. A quantificação da qualidade da formação do núcleo da combustão foi realizada pela integração da luminosidade em uma região próxima aos eletrodos de ignição e pela evolução de pressão no interior da câmara de maneira a permitir comparação entre os casos ensaiados. / The need to reduce the emission of greenhouse gases caused by human activities, especially in the transportation sector, has motivated the use of renewable fuels as energy carriers for vehicles. Ethanol has proven to be one of the most suitable alternatives to a substitute - totally or partially - for fossil fuels. However, the utilization of ethanol in current modern engines which count on high-pressure direct-injection systems imposes challenges like the cold start, stage in which a great amount of total pollutants emitted by the vehicles is generated. The present work focus on the experimental study of fuel spray-ignition interaction and the formation of the combustion kernel by a spark, phenomena present at the cold start condition of internal combustion engines. The experiments were carried out in a constant-volume combustion chamber with optical windows designed and built to withstand pressures of up to 10 MPa. Fuel spray characterization was performed at various environment and injection pressure levels. After such characterization the combustion tests were performed, now also considering the variation of time interval between the start of the injection and the ignition. The quantification of the quality of the combustion kernel formation was carried out by integrating the luminosity in a region close to the ignition electrodes and by the pressure evolution, in a way to allow comparison among the tested cases.

Dans cette thèse, nous avons travaillé sur les différents versants de la technique de dissection sous-muqueuse et les problèmes que pose ce geste quasi chirurgical dans des unités d'endoscopie initialement médicales. Tout d'abord, nous avons travaillé sur la formation à la technique en développant un modèle d'apprentissage sur colon de bovin plus adapté à la situation européenne où les lésions colo-rectales sont les plus fréquentes. Ce modèle de rectum de bovin, simple à trouver et à préparer permet une formation dans des conditions plus proches de la paroi colique humaine que celles offertes par l'estomac de cochon. Un travail à plus grande échelle évaluant les bénéfices d'une aide à l'apprentissage par un logiciel interactif dédié mené sur ce modèle avec 37 étudiants français et japonais est en cours d'analyse et sera publié prochainement. Ensuite, nous avons réfléchi à la stratégie de la procédure pour la rendre plus simple en évaluant précocement la technique du tunnel pour la dissection des lésions œsophagiennes. Cette stratégie permet de maintenir une traction sur les bords lésionnels et nous offrent une sorte de triangulation en élargissant physiquement la zone de travail. Cette stratégie est devenue un standard pour les résections œsophagiennes dans de nombreuses équipes. Enfin, nous avons travaillé conjointement avec la société Nestis® au développement d'un outil permettant d'optimiser la procédure de dissection sous-muqueuse en associant les bénéfices des bistouris bi fonction (injectant et coupant avec le même outil}, de la haute pression pulsée et des solutions macromoléculaires visqueuses. Le système Nestis® permet pour la première fois cette association et a démontré son intérêt en termes de sécurité et de performance par rapport à la méthode classique utilisant l'aiguille et un bistouri électrique conventionnel. Avec cet outil bi fonction, il n'est plus nécessaire de changer d'instrument puisque toutes les étapes de la procédure sont désormais réalisées avec un seul et même outil. D'autres projets sont déjà prévus avec ce matériel pour étudier ses bénéfices et sa sécurité en dissection colique humaine qui est réputée comme la plus difficile compte tenu de la finesse de la paroi. Enfin, ce matériel offre la possibilité d'injecter sous pression des principes actifs qui pourrait dans le futur permettre de prévenir la survenue de sténoses œsophagiennes ou diriger la cicatrisation. Nous avons ainsi travailler avec la pharmacie de l'hôpital Edouard Herriot pour stabiliser la solution macromoléculaires de mélange de glycérol pour permettre son utilisation en pratique quotidienne / First of all, we worked on the training for unexperienced operators by developing a bovine colon model more adapted to the European situation where colo-rectal lesions are the most common. This model of rectum from bovine, easy to find and to prepare allows training in conditions most close to the human colonic wall than those offered by the pig stomach. Furthermore, such models allows to teach the initial skills but avoiding the risk of adverse events for the first procedures in humans. A future work evaluating the benefits of a learning support by a dedicated interactive software on this model with 37 french and Japanese students is now being analyzed and will be reported soon. Then we thought about the strategy of the procedure in order to make it more simple using the tunnel technique to perform ESD for the esophageal lesions. This strategy helps to maintain traction on the edges and offers a sort of triangulation physically expanding the working space. This strategy has become a standard for esophageal resections in many teams and we still work to improve its efficacy. Finally, we worked jointly with Nestis® Company to develop a tool to optimize the submucosal dissection procedure by combining the benefits of the catheters bi function (injecting and cutting with the same tool), but adding high pulsed pressure and capability to inject viscous macromolecular solutions. The Nestis® system allows for the first time this association and demonstrated his interest in terms of security and performance compared with the conventional method using the needle and a conventional electrocautery device. With this bi function tool, it is not necessary to change instrument frequently since all stages of the procedure are now done with a single device. Other projects are already included with this material to explore its benefits and its safety in human colonic dissection that is deemed as the most difficult due to the thinner wall. Finally, this material offers the possibility to inject pressurized active drugs which could be used in the future to prevent the occurrence of esophageal strictures or to direct healing. We also worked with the hospital Edouard Herriot pharmacy to stabilize the solution glycerol mix to allow its use in daily practice in our unit

In the event of hypothetical accident scenarios in PWR, emergency strategies have to be mapped out, in order to guarantee the reliable removal of decay heat from the reactor core, also in case of component breakdown. One essential passive heat removal mechanism is the reflux condensation cooling mode. This mode can appear for instance during a small break loss-of-coolant-accident (LOCA) or because of loss of residual heat removal (RHR) system during mid loop operation at plant outage after the reactor shutdown. In the scenario of a loss-of-coolant-accident (LOCA), which is caused by the leakage at any location in the primary circuit, it is considered that the reactor will be depressurized and vaporization will take place, thereby creating steam in the PWR primary side. Should this lead to ¿reflux condensation¿, which may be a favorable event progression, the generated steam will flow to the steam generator through the hot leg. This steam will condense in the steam generator and the condensate will flow back through the hot leg to the reactor, resulting in counter-current steam/water flow. In some scenarios, the success of core cooling depends on the behaviour of this counter-current flow. Over several decades, a number of experimental and theoretical studies of counter-current gas¿liquid two-phase flow have been carried out to understand the fundamental aspect of the flooding mechanism and to prove practical knowledge for the safety design of nuclear reactors. Starting from the pioneering paper of Wallis (1961), extensive CCFL data have been accumulated from experimental studies dealing with a diverse array of conditions A one-dimensional two field model was developed in order to predict the counter-current steam and liquid flow that results under certain conditions in the cold leg of a PWR when a SBLOCA (small break loss of coolant accident) in the hot leg is produced. The counter-current model that has been developed can predict the pressure, temperature, velocity profiles for both phases, also by taking into account the HPI injection system in the cold leg under a counter-current flow scenario in the cold leg. This computer code predicts this scenario by solving the mass, momentum and energy conservation equations for the liquid and for the steam separately, and linking them by using the interfacial and at the steam wall condensation and heat transfer, and the interfacial friction as the closure relations. The convective terms which appear in the discretization of the mass and energy conservation equations, were evaluated using the ULTIMATE-SOU (second order upwinding) method. For the momentum equation convective terms the ULTIMATE-QUICKEST method was used. The steam-water counter-current developed code has been validated using some experimental data extracted from some previously published articles about the direct condensation phenomenon for stratified two-phase flow and experimental data from the LAOKOON experimental facility at the Technical University of Munich. / Romero Hamers, A. (2014). STUDY OF THE THERMAL STRATIFICATION IN PWR REACTORS AND THE PTS (PRESSURIZED THERMAL SHOCK) PHENOMENON [Tesis doctoral]. Editorial Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/36536