906 resultados para porosità, PME, termodinamica del non equilibrio, modello iperbolico e propagazione ondosa, secondo suono


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This Final Project Grade, whose title is “Analysis of the non-lucrative entities of the Basque Country dedicated to animal protection”, has as main purpose the study of the historical, theoretical and legal context in which these institutions develop their activity, focusing in those which occur in the Basque Country.

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Homenaje a Georges Laplace, realizado en Vitoria-Gasteiz el 13, 14 y 15 de noviembre de 2012. Edición a cargo de Aitor Calvo, Aitor Sánchez, Maite García-Rojas y Mónica Alonso-Eguíluz.

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Jornada “Educación Intercultural, La Óptica Del Norte. Organiza: Mundubat, Bilbao, 22 de noviembre de 2003

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[EN] This PhD work started in March 2010 with the support of the University of the Basque Country (UPV/EHU) under the program named “Formación de Personal Investigador” at the Chemical and Environmental Engineering Department in the Faculty of Engineering of Bilbao. The major part of the Thesis work was carried out in the mentioned department, as a member of the Sustainable Process Engineering (SuPrEn) research group. In addition, this PhD Thesis includes the research work developed during a period of 6 months at the Institut für Mikrotechnik Mainz GmbH, IMM, in Germany. During the four years of the Thesis, conventional and microreactor systems were tested for several feedstocks renewable and non-renewable, gases and liquids through several reforming processes in order to produce hydrogen. For this purpose, new catalytic formulations which showed high activity, selectivity and stability were design. As a consequence, the PhD work performed allowed the publication of seven scientific articles in peer-reviewed journals. This PhD Thesis is divided into the following six chapters described below. The opportunity of this work is established on the basis of the transition period needed for moving from a petroleum based energy system to a renewable based new one. Consequently, the present global energy scenario was detailed in Chapter 1, and the role of hydrogen as a real alternative in the future energy system was justified based on several outlooks. Therefore, renewable and non-renewable hydrogen production routes were presented, explaining the corresponding benefits and drawbacks. Then, the raw materials used in this Thesis work were described and the most important issues regarding the processes and the characteristics of the catalytic formulations were explained. The introduction chapter finishes by introducing the concepts of decentralized production and process intensification with the use of microreactors. In addition, a small description of these innovative reaction systems and the benefits that entailed their use were also mentioned. In Chapter 2 the main objectives of this Thesis work are summarized. The development of advanced reaction systems for hydrogen rich mixtures production is the main objective. In addition, the use and comparison between two different reaction systems, (fixed bed reactor (FBR) and microreactor), the processing of renewable raw materials, the development of new, active, selective and stable catalytic formulations, and the optimization of the operating conditions were also established as additional partial objectives. Methane and natural gas (NG) steam reforming experimental results obtained when operated with microreactor and FBR systems are presented in Chapter 3. For these experiments nickel-based (Ni/Al2O3 and Ni/MgO) and noble metal-based (Pd/Al2O3 and Pt/Al2O3) catalysts were prepared by wet impregnation and their catalytic activity was measured at several temperatures, from 973 to 1073 K, different S/C ratios, from 1.0 to 2.0, and atmospheric pressure. The Weight Hourly Space Velocity (WHSV) was maintained constant in order to compare the catalytic activity in both reaction systems. The results obtained showed a better performance of the catalysts operating in microreactors. The Ni/MgO catalyst reached the highest hydrogen production yield at 1073 K and steam-to-carbon ratio (S/C) of 1.5 under Steam methane Reforming (SMR) conditions. In addition, this catalyst also showed good activity and stability under NG reforming at S/C=1.0 and 2.0. The Ni/Al2O3 catalyst also showed high activity and good stability and it was the catalyst reaching the highest methane conversion (72.9 %) and H2out/CH4in ratio (2.4) under SMR conditions at 1073 K and S/C=1.0. However, this catalyst suffered from deactivation when it was tested under NG reforming conditions. Regarding the activity measurements carried out with the noble metal-based catalysts in the microreactor systems, they suffered a very quick deactivation, probably because of the effects attributed to carbon deposition, which was detected by Scanning Electron Microscope (SEM). When the FBR was used no catalytic activity was measured with the catalysts under investigation, probably because they were operated at the same WHSV than the microreactors and these WHSVs were too high for FBR system. In Chapter 4 biogas reforming processes were studied. This chapter starts with an introduction explaining the properties of the biogas and the main production routes. Then, the experimental procedure carried out is detailed giving concrete information about the experimental set-up, defining the parameters measured, specifying the characteristics of the reactors used and describing the characterization techniques utilized. Each following section describes the results obtained from activity testing with the different catalysts prepared, which is subsequently summarized: Section 4.3: Biogas reforming processes using γ-Al2O3 based catalysts The activity results obtained by several Ni-based catalysts and a bimetallic Rh-Ni catalyst supported on magnesia or alumina modified with oxides like CeO2 and ZrO2 are presented in this section. In addition, an alumina-based commercial catalyst was tested in order to compare the activity results measured. Four different biogas reforming processes were studied using a FBR: dry reforming (DR), biogas steam reforming (BSR), biogas oxidative reforming (BOR) and tri-reforming (TR). For the BSR process different steam to carbon ratios (S/C) from 1.0 to 3.0, were tested. In the case of BOR process the oxygen-to-methane (O2/CH4) ratio was varied from 0.125 to 0.50. Finally, for TR processes different S/C ratios from 1.0 to 3.0, and O2/CH4 ratios of 0.25 and 0.50 were studied. Then, the catalysts which achieved high activity and stability were impregnated in a microreactor to explore the viability of process intensification. The operation with microreactors was carried out under the best experimental conditions measured in the FBR. In addition, the physicochemical characterization of the fresh and spent catalysts was carried out by Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES), N2 physisorption, H2 chemisorption, Temperature Programmed Reduction (TPR), SEM, X-ray Photoelectron Spectroscopy (XPS) and X-ray powder Diffraction (XRD). Operating with the FBR, conversions close to the ones predicted by thermodynamic calculations were obtained by most of the catalysts tested. The Rh-Ni/Ce-Al2O3 catalyst obtained the highest hydrogen production yield in DR. In BSR process, the Ni/Ce-Al2O3 catalyst achieved the best activity results operating at S/C=1.0. In the case of BOR process, the Ni/Ce-Zr-Al2O3 catalyst showed the highest reactants conversion values operating at O2/CH4=0.25. Finally, in the TR process the Rh-Ni/Ce-Al2O3 catalyst obtained the best results operating at S/C=1.0 and O2/CH4=0.25. Therefore, these three catalysts were selected to be coated onto microchannels in order to test its performance under BOR and TR processes conditions. Although the operation using microreactors was carried out under considerably higher WHSV, similar conversions and yields as the ones measured in FBR were measured. Furthermore, attending to other measurements like Turnover Frequency (TOF) and Hydrogen Productivity (PROD), the values calculated for the catalysts tested in microreactors were one order of magnitude higher. Thus, due to the low dispersion degree measured by H2-chemisorption, the Ni/Ce-Al2O3 catalyst reached the highest TOF and PROD values. Section 4.4: Biogas reforming processes using Zeolites L based catalysts In this section three type of L zeolites, with different morphology and size, were synthesized and used as catalyst support. Then, for each type of L zeolite three nickel monometallic and their homologous Rh-Ni bimetallic catalysts were prepared by the wetness impregnation method. These catalysts were tested using the FBR under DR process and different conditions of BSR (S/C ratio of 1.0 and 2.0), BOR (O2/CH4 ratio of 0.25 and 0.50) and TR processes (at S/C=1.0 and O2/CH4=0.25). The characterization of these catalysts was also carried out by using the same techniques mentioned in the previous section. Very high methane and carbon dioxide conversion values were measured for almost all the catalysts under investigation. The experimental results evidenced the better catalytic behavior of the bimetallic catalysts as compared to the monometallic ones. Comparing the catalysts behavior with regards to their morphology, for the BSR process the Disc catalysts were the most active ones at the lowest S/C ratio tested. On the contrary, the Cylindrical (30–60 nm) catalysts were more active under BOR conditions at O2/CH4=0.25 and TR processes. By the contrary, the Cylindrical (1–3 µm) catalysts showed the worst activity results for both processes. Section 4.5: Biogas reforming processes using Na+ and Cs+ doped Zeolites LTL based catalysts A method for the synthesis of Linde Type L (LTL) zeolite under microwave-assisted hydrothermal conditions and its behavior as a support for heterogeneously catalyzed hydrogen production is described in this section. Then, rhodium and nickel-based bimetallic catalysts were prepared in order to be tested by DR process and BOR process at O2/CH4=0.25. Moreover, the characterization of the catalysts under investigation was also carried out. Higher activities were achieved by the catalysts prepared from the non-doped zeolites, Rh-Ni/D and Rh-Ni/N, as compared to the ones supported on Na+ and Cs+ exchanged supports. However, the differences between them were not very significant. In addition, the Na+ and Cs+ incorporation affected mainly to the Disc catalysts. Comparing the results obtained by these catalysts with the ones studied in the section 4.4, in general worst results were achieved under DR conditions and almost the same results when operated under BOR conditions. In Chapter 5 the ethylene glycol (EG) as feed for syngas production by steam reforming (SR) and oxidative steam reforming (OSR) was studied by using microchannel reactors. The product composition was determined at a S/C of 4.0, reaction temperatures between 625°C and 725°C, atmospheric pressure and Volume Hourly Space Velocities (VHSV) between 100 and 300 NL/(gcath). This work was divided in two sections. The first one corresponds to the introduction of the main and most promising EG production routes. Then, the new experimental procedure is detailed and the information about the experimental set-up and the measured parameters is described. The characterization was carried out using the same techniques as for the previous chapter. Then, the next sections correspond to the catalytic activity and catalysts characterization results. Section 5.3: xRh-cm and xRh-np catalysts for ethylene glycol reforming Initially, catalysts with different rhodium loading, from 1.0 to 5.0 wt. %, and supported on α-Al2O3 were prepared by two different preparation methods (conventional impregnation and separate nanoparticle synthesis). Then, the catalysts were compared regarding their measured activity and selectivity, as well as the characterization results obtained before and after the activity tests carried out. The samples prepared by a conventional impregnation method showed generally higher activity compared to catalysts prepared from Rh nanoparticles. By-product formation of species such as acetaldehyde, ethane and ethylene was detected, regardless if oxygen was added to the feed or not. Among the catalysts tested, the 2.5Rh-cm catalyst was considered the best one. Section 5.4: 2.5Rh-cm catalyst support modification with CeO2 and La2O3 In this part of the Chapter 5, the catalyst showing the best performance in the previous section, the 2.5Rh-Al2O3 catalyst, was selected in order to be improved. Therefore, new Rh based catalysts were designed using α-Al2O3 and being modified this support with different contents of CeO2 or La2O3 oxides. All the catalysts containing additives showed complete conversion and selectivities close to the equilibrium in both SR and OSR processes. In addition, for these catalysts the concentrations measured for the C2H4, CH4, CH3CHO and C2H6 by-products were very low. Finally, the 2.5Rh-20Ce catalyst was selected according to its catalytic activity and characterization results in order to run a stability test, which lasted more than 115 hours under stable operation. The last chapter, Chapter 6, summarizes the main conclusions achieved throughout this Thesis work. Although very high reactant conversions and rich hydrogen mixtures were obtained using a fixed bed reaction system, the use of microreactors improves the key issues, heat and mass transfer limitations, through which the reforming reactions are intensified. Therefore, they seem to be a very interesting and promising alternative for process intensification and decentralized production for remote application.

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The individuals studied came from commercial catches on the coastal area off Mar del Plata. The monthly distribution of sizes shows that the juvenile stay in coastal waters, while the adult individuals leave those waters during winter season to return there in the spring during the season of sexual maturation and spawning, when the water reaches temperature of 10-11°C. The jack mackerel is a relatively small fish, compared with other species of its genus, and has a total length of scarcely 25 cm. The comparison of indexes and mesurements does not reveal any marked difference between sexes, except for the total length, which is greater in the females. Sexually nature individuals at a lenth of 13 cm have been found. Spawning takes place in coastal waters. A great part of the population spawns from December to January. There are oscillations ranging from November to March. On this latter month mature individuals of smaller size have veen found. The jack mackerel feeds usually on copepods and other planktonic organims, but it can feed also on juveniles of other fishes. This fish is caught throghout the whole year. The catches show their greater peak during winter; one other non-constant peak occurs during the spring (October-November) and declines shoraply during the summer months. It follows from this that the time of greates catch does not coincide with spawning season, or with the appearence of the greatest mean sizes. This happens because the interests of the fishermen are attracted during those months by others species of greater commercial value.

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Este proyecto se centra en el control de un robot con estabilidad dinámica más concretamente en un robot que responde al conocido modelo del péndulo invertido. Una de las aplicaciones más famosas del péndulo invertido es el Segway. El péndulo invertido del Segway se define solo en un eje, al tener dos ruedas paralelas como soporte. El proyecto general consta de tres partes, poner el robot en equilibrio, el control remoto del robot vía Bluetooth y el uso de los encoders de los motores para manejar el robot. Poner el robot en equilibrio: Esta parte consiste en la lectura e interpretación de los datos que nos ofrece la Unidad de Medición Inercial (IMU) para conseguir que el robot se mantenga horizontalmente en todo momento utilizando un control PID y se ha desarrollado junto al compañero, Anartz Recalde. Las otras dos partes están pensadas con el objetivo de darle más personalidad al proyecto individual de cada uno. Control remoto vía Bluetooth: Con esta parte lo que se pretende es controlar el robot remotamente mediante el Bluetooth y ha sido desarrollada únicamente por mí. Uso de los encoders de los motores para manejar el robot: Esta parte ha sido totalmente desarrollada por Anartz Recalde, y consiste en hacer uso de los encoders de los motores e interpretar los datos que proporcionan para sacar distintos datos como la distancia recorrida o la velocidad. De esta manera, intentará conseguir que el robot en todo momento se mantenga en la misma posición, es decir si alguna fuerza externa al robot hace que el robot se mueva, éste se tiene que situar en la misma posición en la que estaba antes de que se le hubiera ejercido dicha fuerza externa. Por lo tanto, este proyecto consiste en construir un robot balancín, bastante similar a un Segway pero en una escala más pequeña, conseguir que se mantenga en equilibrio y manejarlo por control remoto mediante uso del Bluetooth.

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En este proyecto presentamos el diseño e implementación de un móvil de dos ruedas, en concreto un robot balancín. En él se estudiarán las teorías necesarias para que un móvil de dos ruedas se mantenga en equilibrio y poner dichas teorías en práctica.

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Introducción y objetivo: El collarín cervical es un dispositivo que tiene como objetivo disminuir el movimiento del cuello para evitar lesiones secundarias en el manejo del paciente traumático en el ámbito prehospitalario. Mediante la realización de esta revisión sistemática se ha pretendido evaluar si la colocación del collarín cervical disminuye la movilidad del cuello en el paciente traumático, así como determinar si puede producir o evitar lesiones durante su manejo. Metodología: Revisión sistemática en base a las disposiciones PRISMA. Se elaboró un protocolo de búsqueda que se utilizó en cuatro bases de datos (Medline, Scopus, CINAHL y Web of Science) y se incluyeron ensayos clínicos y estudios observacionales publicados entre enero de 1995 y diciembre de 2014. Resultados: La revisión se realizó a partir de 10 ensayos clínicos no aleatorizados de modesta calidad metodológica: en 6 se utilizaron cadáveres con lesión cervical y en los otros 4 voluntarios sanos sin lesión cervical y un ensayo clínico aleatorizado de muestra pequeña realizado sobre cadáveres con lesión cervical. En los estudios realizados en pacientes sanos sin lesión cervical se observó que el collarín disminuía de forma significativa la movilidad del cuello frente a la no inmovilización. Por el contrario, en los estudios en los que participaban cadáveres con lesión cervical se determinó que el collarín cervical no disminuía la movilidad del cuello. Además en tres estudios se detectó un aumento de la separación intervertebral y en uno, un aumento de la presión venosa yugular. Conclusiones: Si bien la inmovilización cervical reduce la movilidad del cuello en pacientes sin lesión, este efecto no se produce en quienes presentan lesiones cervicales.

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[ES]En el siguiente trabajo se ha realizado una revisión bibliográfica en la que se muestran los resultados obtenidos al llevar a cabo la purificación del biogás y/o la eliminación del metano, en los casos en los que su valorización no sea posible, mediante métodos biológicos (biofiltración). Se recogen asimismo las diversas fuentes desde las que se genera el biogás (generación incontrolada o producción controlada) junto con las concentraciones típicas de todos los compuestos que pueden formar su composición. En la purificación del biogás se ha estudiado la eliminación de compuestos perjudiciales para el aprovechamiento energético del biogás, como son el sulfuro de hidrógeno (H2S), los mercaptanos y los siloxanos. Para el estudio de los compuestos a eliminar se ha diferenciado entre distintas configuraciones de biorreactores (biofiltros, biofiltros percoladores y biolavadores) y para cada una de ellas se han recogido datos representativos como la temperatura óptima de operación, las diferencias entre operar a pH ácido o básico (teniendo en cuenta que el pH natural de operación es ácido pero que en estas condiciones la solubilidad del H2S es menor y el relleno se deteriora con mayor rapidez). También se ha analizado la influencia de la cantidad de oxígeno necesario para garantizar la degradación total de los contaminantes y evitar la acumulación de depósitos de azufre, llegando incluso a necesitarse proporciones de O2/H2S de 49.2 para la oxidación completa del H2S. Se ha estudiado también la cantidad necesaria de nitrógeno (nutriente) en los procesos llevados a cabo en condiciones anaerobias (cercana a 200 mgN-NO3 -/L), así como el efecto que tienen los compuestos producidos en la oxidación parcial (azufre elemental (S0), metanol, formaldehido, etc.) en el funcionamiento del sistema.

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[ES]En este trabajo de fin de grado se realiza el cálculo de bases de pilares metálicos en sus diferentes configuraciones dependiendo del esfuerzo axil, cortante y momento flector aplicados en base a la normativa actual. Tras esto, se desarrolla un software donde, de una forma sencilla e intuitiva, se puede evaluar si el predimensionamiento de las bases es correcto o no.

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[ES]Este trabajo trata sobre el diseño del blindaje de una sala de rayos X. Concretamente se ha centrado en el procedimiento para diseñar el blindaje de una sala de radiografías del tórax. Para ello, se ha tomado como punto de partida una posible sala de radiografía de un centro sanitario y se le han aplicado a este caso las pautas que se deben seguir a la hora de hacer estos cálculos con el objetivo de reducir las dosis de radiación recibidas por el personal de operación y asegurar el bienestar del paciente y de los trabajadores Primero y todo para situar en el tema expuesto se ha descrito el contexto, donde se hace un breve resumen del desarrollo que han tenido los rayos X en el ámbito de la medicina. A continuación en el apartado de alcance se han explicado los campos que se van a abarcar en este proyecto. Por último y para acabar la introducción se han escrito lo beneficios del proyecto y su importancia. Para empezar el proyecto se ha presentado la sala de radiografía torácica tomada como ejemplo y se le han hecho los cálculos pertinentes a sus paredes, puertas y ventanas. A continuación se ha expuesto el aspecto económico y de la distribución y para ello se ha realizado un presupuesto y el diagrama de Gantt. Por último se han escrito unas conclusiones generales sobre todo el proyecto.

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[ES] Durante pruebas cíclicas de larga duración ha sido probada que las estrategias para gestionar la fatiga pueden ser un factor determinante. A pesar de ello, este mismo fenómeno no está del todo probado que pueda darse en esfuerzos máximos de corta duración. Es por eso, que el objetivo de este trabajo ha sido analizar si variando el grado de conocimiento de los atletas durante este tipo de pruebas puede darse alguna alteración en su rendimiento. METODO: Siete deportistas varones completaron durante tres diferentes días un mismo protocolo (8 repeticiones máximas de 30 metros con un minuto de recuperación) en el que se varió la información que se les deba. Así, el primer día se les señaló que realizarían 4 repeticiones, pero cuando finalizaron se les indicó que realizarían 4 más (Prueba decepción). El segundo día, no se les informó del número de repeticiones a realizar (Prueba Suspense) y se les mandó parar al realizar la octava. Y por último, el tercer día se les señaló que realizarían 8 repeticiones (Prueba Control). RESULTADOS: Diferencias significativas (p>0.05) se encontraron en los tiempos de las cuatro primeras repeticiones entre la Prueba Suspense y Prueba Decepción. CONCLUSIÓN: Los resultados muestran como en pruebas máximas de corta duración las estrategias de gestión de la fatiga se pueden dar de manera anticipatoria al número de repeticiones a realizar.

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[ES]En la actualidad, el modelo de transporte apenas ha avanzado en el intento de frenar el Cambio Climático o en el cuidado del medio ambiente. Además, el gran negocio que existe detrás del petróleo hace que este tipo de transporte sea poco sostenible. Es por eso que se está desarrollando, a nivel nacional e internacional, una solución a dicho problema que es el uso del vehiculó eléctrico (VE). La introducción masiva del VE permitirá el uso extensivo de fuentes de energía no contaminantes e intermitentes, como son las energías renovables. Sin embargo, los VEs están lejos de ser una tecnología probada. Existen aún muchos problemas en torno a él que deben ser resueltos, entre ellos se encuentra el desarrollo de las baterías, su modelo de negocio y coste o la influencia de la conexión del VE sobre la red eléctrica. Este último problema, estará muy influenciado por el comportamiento social del futuro conductor, lo cual es el eje central del proyecto.