In this thesis, a PEMFC stack, which can be self-humidification of passive portable hydrogen fuel cell, will be developed. The stack is developed for portable applications, so the structure of the stack is simplified as possible as we can. As the cathode directly exposed under the atmosphere, so in a long time, the membrane easily lead to excessive evaporation of water, so that performance degradation. The traditional humidifier is more complex applications are not suitable for portable, so this thesis stack developed by the use of cotton capillarity, the water from the tanks transferred to the membrane, and then by cotton and a good touch to the membrane humidifier effect, this structure without an increase in large equipment, in line with the principles of portability. The PEMFC stack is made with carbon fiber bunches for current collectors and two 8-cell banded-type MEAs, the stack can develop a high voltage by serially connecting outside of the reaction chamber. 16-cell in series when the current density is greater than 110mA/cm2, use humidification to avoid long time operation, due to water cause a voltage drop. Humidification is not only to help transfer of hydrogen ions, and the role of a cooling stack, the cells temperature is too high will not cause transpiration rate of speed. Current density greater than 250mA/cm2, although humidity can still be effective, but insufficient humidification single cotton, one hour after, the voltage drop of about 20% longer cell performance, such as humidity will be no more have a more significant decline phenomenon, more cotton or additional external humidification humidifier can maintain a long-time stable operation. Therefore, the performance of the cells in order to avoid a recession, should pay attention to in a long time when working conditions and operating range.

The improvement of performance and the maintenance of stability of a portable air-breathing PEMFC are studied in this thesis. The water content within proton exchange membrane affects strongly on the performance and stability of a PEMFC stack, in which water within membrane can form a conduction channel to provide hydrogen ion transferring from anode to cathode. The over-dried condition caused by a long time operation can also be avoided to prevent the membrane from damaging. Thus the proper humidification of a stack is important for a portable air-breathing PEMFC system. The traditional humidifier is too bulky to be suitable for portable fuel cells. A simple humidification system developed in this research is making use of the water stored in the stack bottom and the self-generating heat by chemical reaction to drive the passive humidification system of this stack. The water at the bottom of the tank can be sucked with cotton threads in cathode and a piece of cotton cloth by capillary phenomenon and transfer to the membrane of MEA. The cotton threads humidification in cathode is enough in low and middle current density in this study. It is not enough in high current density due to the large water vapor dissipation in the cathode surface, so a cotton cloth in anode is added to increase the evaporating surface to supply water to membrane. This passive humidification system does not need extra energy, and it only employs the heat generated by the cells. The system follows the simple principle, which is always obeyed in a portable fuel cell system. A 16-cell HFC stack developed in this research adopts carbon fibers as current collectors. Two pieces of 8-cell anodes is placed in the inner sides of the stack, and the 8-cell cathode is located on external sides, which is exposed directly to the ambient air. The 16-cell can connect in series or parallel. The experimental results show that it is helpful to add cotton threads in cathode and cotton cloth in anode to improve the stability of the 16-cell stack during a the long period operation. The 16-cell HFC stack has succeeded in the operation and charging for an IPhone, digital photo frame, and LED light. The experiments have proved that this type of the lightweight humidification system is helpful in the future portable hydrogen fuel cell applications.

Las redes híbridas de fibra óptica y cable coaxial, HFC, fueron implementadas en un principio por operadores de TV Cable, los que posteriormente incluyeron servicios como Video-on-Demand, Pay-Per-View, etc. Con el avance de la tecnología, las redes de TV Cable fueron capaces de ofrecer otros servicios multimedia como telefonía y acceso a Internet de Banda Ancha. Para esto, modificaron las mismas redes existentes, transformándose en Operadores Multi-Servicio, MSO. La red sufrió modificaciones importantes, pasando de ser una red prácticamente unidireccional a ser una red bidireccional desbalanceada. En la discusión actual sobre telecomunicaciones se encuentran habitualmente términos como convergencia IMS (IP Multimedia Subsystem) y Redes de Nueva Generación, NGN (Next Generation Networking). HFC representa un bloque fundamental en la comprensión de estos conceptos. Un factor clave para el éxito de los operadores de cable que pretenden adecuar sus redes para la próxima generación de arquitecturas de comunicaciones, será la capacidad del personal técnico para evaluar las diversas opciones disponibles. Por otro lado, los MSO, se enfrentan a otras consideraciones como el manejo de la compatibilidad de las diversas normas de próxima generación con las arquitecturas existentes y cómo determinar el momento óptimo para realizar este cambio. El objetivo de esta memoria fue diseñar un curso teórico y práctico sobre servicios soportados por redes HFC de nueva generación, basándose en los atributos de escalabilidad y disponibilidad que esta tecnología presenta frente a otras. Para guiar el desarrollo de este proyecto se utilizó una metodología que consiste en la recopilación de información sobre tecnología HFC en la etapa inicial, seguido de un análisis de los datos obtenidos. Con esta información se generó un programa docente y una planificación que permitió desarrollar el curso. En este proyecto de título se diseñó e implementó un curso de servicios teórico y práctico. En lo teórico se cubren temas como: Broadcasting de TV, Internet/Datos, Telefonía, IPTV, eTV, Video-on-Demand, Pay-Per-View, VoIP, videoconferencias y Juegos On Line. En lo práctico, se presenta una propuesta preeliminar de laboratorio docente, que contempla una red HFC a escala y guías prácticas sobre la evaluación de servicio y la vía de retorno. El curso se diseñó para hacer uso de recursos docentes presenciales e interactivos a través de Internet. Este curso representa un aporte, tanto fuera como dentro del Departamento de Ingeniería Eléctrica de la Universidad de Chile, al tratar temáticas actuales con un enfoque orientado a la industria de los servicios ofrecidos por los MSO. El curso diseñado es una propuesta orientada a completar la instrucción de un ingeniero civil electricista.

Des revêtements céramiques sont obtenus par un procédé de dépôt chimique en phase vapeur assisté par injection liquide pulsée (DLICVD) de précurseurs organométalliques. Des dépôts de carbure de chrome (CrCx) sont élaborés dans un réacteur tubulaire à paroi chaude à partir d’une solution de bis(benzène) chrome dans du toluène pour des températures de 475 °C et sous pression partielle d’azote (pression totale 50 Torr). Une couche d’accroche pouvant être nécessaire pour revêtir des pièces métalliques, tels des aciers et alliages, par un revêtement céramique non-oxyde de type CrCx, des couches de chrome métallique (Cr) et des carbures mixtes Cr-Si-C ont également été élaborées par ce procédé DLICVD. Ainsi, l’ajout d’un additif à base de chlore ou de soufre (par exemple l’hexachlorobenzène ou le thiophénol) dans la solution BBC/toluène permet la déposition de films de chrome métallique (Cr) à 475 °C. De plus, l’utilisation d’une solution de précurseur contenant simultanément du Si et du Cr tel que le tetrakis(trimethylsilylmethyl)chromium dans du toluène mène au dépôt d’un carbure mixte Cr-Si-C pouvant jouer le rôle d’interphase dans des assemblage céramique-métal. Des films de carbure de silicium (SiC) sont obtenus à partir de deux précurseurs (1,3 disilabutane et polysilyléthylène) injectés purs ou en solution également dans du toluène. Les dépôts sont faits dans une gamme de température comprise entre 700 et 800 °C, sous pression partielle d’azote (pression totale 50 Torr). Les films obtenus sont des films amorphes de SiC contenant une faible quantité d’hydrogène (provenant du mécanisme de décomposition des précurseurs) : a-SiC:H. Les films sont stœchiométriques dans le cas de l’injection de précurseur pur, et quasi stœchiométrique lorsque les précurseurs sont dilués dans du toluène. Les films amorphes tels que déposés deviennent nanocristallins en présentant la structure cubique du SiC après recuit sous vide à 1000 °C. L’influence du solvant (toluène) sur la composition, la morphologie et la vitesse de croissance des dépôts est discutée en fonction des systèmes chimiques étudiés et des conditions expérimentales, en particulier les conditions locales dans le réacteur DLICVD telles que les gradients de température et de concentration. Des films de carbure de hafnium (HfC) sont également élaborés par le même procédé à partir d’une solution de bis(cyclopentadiényl)diméthyl hafnium dans du toluène après avoir testé plusieurs précurseurs. Une température de 750 °C est utilisée et l’utilité d’une pression partielle de dihydrogène dans le gaz vecteur azote est démontrée (pression totale 50 Torr, 423 sccm de N2 et 77 sccm de H2). Tels que déposés, ces films sont riches en carbone (C-rich HfCx) et ont une structure quasi-amorphe. Ils deviennent nanocristallins après recuit sous vide à 1000 °C. Enfin, la mise en œuvre de films multicouches céramiques par DLICVD à paroi chaude est mise en évidence par l’élaboration de revêtements multicouches HfC/SiC à 750 °C, sous pression partielle d’un mélange de gaz vecteur N2/H2. Le contrôle du procédé permet une nano structuration de ces revêtements multicouches jusqu’à une bi-période de 100 nm (empilement de 100 couches d’environ 50 nm chacune). La stabilité thermique de ces architectures et des tests préliminaires de résistance à l’oxydation à haute température des films de SiC et HfC/SiC sont discutés. / Ceramic coatings are made from metalorganic precursors by a chemical vapour deposition process assisted by pulsed liquid injection (DLICVD). Chromium carbide (CrCx) films are grown in a tubular hot wall reactor from a solution of bis(benzene)chromium in toluene under partial pressure of nitrogen at 475 °C (total pressure set at 50 Torr). Bonding layers are useful on metallic components, such as steels and alloys, with non-oxide ceramic films such as CrCx, to that purpose metallic chromium (Cr) and mixed carbides Cr-Si-C have been made by DLICVD. Furthermore, adding a chlorinated or sulfur based additive (e.g. hexachlorobenzene or thiophenol) in the BBC/toluene solution allows depositing metallic chromium (Cr) at 475 °C. Moreover, using a precursor containing Si and Cr as tetrakis(trimethylsilylmethyl)-chromium in toluene leads to the deposition of Cr-Si-C mixed carbide. Silicon carbide films are made from two precursors (1,3-disilabutane and polysilylethylene) that have been injected either pure or diluted in toluene. A temperature range of 700 to 800 °C has been used under a partial pressure of nitrogen (total pressure of 50 Torr). SiC films are amorphous and contain a small quantity of hydrogen (hydrogen comes from precursor pyrolysis mechanism): a-SiC:H. Films are stoichiometric when pure precursors are injected, and quasi stoichiometric when precursors are diluted in toluene. As deposited coatings are amorphous and become nanocristalline (cubic SiC structure) after annealing at 1000 °C under vacuum. The influences of the solvent (toluene) on the composition, morphology and growth rate are discussed as a function of the chemical system and experimental conditions, in particular reactor gradient conditions such as temperature and precursors concentration in gas phase. Hafnium carbide films are also made using a solution of bis(cyclopentadiényl)diméthyl hafnium in toluene by the same process. Temperature is set to 750 °C and hydrogen partial pressure has been shown useful (total pressure of 50 Torr, 423 sccm of N2 and 77 sccm of H2). As-deposited films are C-rich HfCx and quasi amorphous. They become nanocristalline after annealing at 1000 °C under vacuum. Finally, ceramics multilayer HfC/SiC coatings were deposited by DLICVD at 750 °C under a partial pressure of a mixture of N2/H2. The process allows a good control of the multilayer nanostructure. Thermal stability and high temperature oxidation preliminary tests on SiC and HfC/SiC films are discussed.

Abstract Traditional unipolar/bipolar plates, such as the metal and the graphite unipolar/bipolar plates, are expensive, weight heavy and volume large, so that it is hard to be used in the portable application. A high efficiency, low cost and lightweight portable proton exchange membrane fuel cell (called PEMFC or called HFC when using pure hydrogen fuel), which is made with a new heterogeneous composite carbon fiber bipolar plate and a MEA, is developed in our lab. There are many advantages of the new carbon fiber unipolar/bipolar plates, such as low contact resistance, low cost, lightweight and small volume. We hope that the new unipolar/bipolar plate will be able to replace the conventional metal and graphite unipolar/bipolar plates in the future. The characteristics of a portable PEMFC in different operational conditions are studied in this research. From our experimental result, we find that the factors which affect the HFC performance include the gas temperature, humidity ratio, inlet gas pressure in anode, the geometry of inlet ports, the flow channels within cell, and the oxidant flow rate etc. In addition, the contact resistances between different materials within each cell all strongly influence HFC performance. The ribs of the carbon fiber unipolar/bipolar plates is pored structure, and the gas diffusion layer is no deformation because of only slight compression in stack assembly; therefore, the reactive gas can easily flow into the most of active area. In addition, the contact resistance between the carbon fiber unipolar plate and the gas diffusion layer is lower than that between the traditional unipolar plate and the gas diffusion layer, so that the electrons in active layer is easily to exit or enter this region. The experimental result at 1.15 atm and 40 oC displays that the current density with the new unipolar plate is about twice higher than that with the graphite unipolar plate at overpotential 0.6 V. With air as an oxidizer, we find that increasing the fan rotation speed can avoid output-voltage decay in high current density, but the design with fan is unfavorable for portable application. So a front open unipolar plate and air-breathing design is adopted on the cathode. The power density of this design is slightly lower than that with fan, but it still can reach a value 160 mW/cm2 without any heating and humidification in the anode. Because this design needs little supplement device, the application in portable fuel cells of the new design will be wider than that of a traditional design.

The performance characteristics of pure hydrogen PEMFC (called HFC) stacks made with heterogeneous carbon fiber bipolar plates are studied in this thesis. In addition, the problem that the heterogeneous carbon fiber bipolar plate leaks in the high gas pressure is also solved in this studies so that the new plate can be used to the high current power sources. Because of the gas leakage of the first generation stack at high inlet gas pressure, the fuel supply is insufficient in the high current density. A 4-cell PEMFC stack made with this new bipolar plate is built with weight 370 g and volume 385 cm3 without a fan. The total power out of the 4-cell stack is about 30 W at room temperature. The specific power and volumetric power densities are 81 mW/g and 78 mW/cm3, respectively. The average power density is about 160 mW/cm2, but the power density of a single-cell can reach a value about 220 mW/cm2. The insufficient fuel supply cause that the power density of 4-cell PEMFC stack is lower than single cell, so it is necessary to solve the gas leakage at high pressure. Our experiment found that gas leakage occurs in heterogeneous bipolar plates can be relate to the insufficient or improper hot-pressing temperature, time and pressure while we are making the carbon fiber bunches. So the processes in making new carbon fiber bunches include water expansion, uniform glue adding, high hot-pressing pressure, and using proper temperature and enough solidification time. The airtight of the second generation of heterogeneous carbon fiber bipolar plates improves obviously with the new processes. No leakage occurs for gas pressure under 1atm. We expect that this design can be used to high inlet pressure. It is also quite suitable for various high-power electrical sources.

Inbreeding depression has alarming impacts on threatened species with small population sizes. Assessing inbreeding depression has therefore become an important focus of conservation research. In this study, heterozygosityitness correlations (HFCs) were measured in adult and hatchling Lesser Antillean Iguanas, Iguana delicatissima, from a sampling site at Batali Beach in Dominica to assess the role of inbreeding depression on hatchling fitness and recruitment to the adult population in this endangered species. HFCs in hatchlings revealed no significant correlations and no general effects, suggesting that inbreeding depression may not be affecting hatchling fitness. Further, there were no significant differences in heterozygosity between the adult and hatchling groups suggesting that inbreeding depression may not be an important factor in shaping the population dynamics of I. delicatissima in Dominica. HFCs in the adults, however, revealed a significant negative correlation between heterozygosity and snout-vent length, which is more consistent with outbreeding depression in the population.

[pt] CATV / Gigabit Ethernet / DWDM : Novas Alternativas Técnicas e Econômicas para a Última Milha tem como objetivo descrever a ativação de novas funcionalidades de uma rede de distribuição de CATV associada à distribuição de dados em faixa larga. A utilização da tecnologia DWDM no domínio óptico, associada a novas topologias de distribuição em cabo coaxial e ao padrão Gigabit Ethernet, permite a obtenção de uma nova concepção em rede de telecomunicações, onde os serviços tradicionais de distribuição analógica são inteiramente preservados. As vantagens desta solução residem na obtenção de uma rede de muito alta velocidade, ideal para aplicações Internet de segunda geração e em um dramático aumento do retorno econômico nas redes CATV já instaladas. / [en] CATV / Gigabit Ethernet / DWDM : New Technical and Economic Altermatives to the Last Mile is aiming at describing the activation of a new family of functionalities applicable to a CATV distribution network together with a delivery of broadband data. Optical domain DWDM technology is used, associated with new coaxial cable distribution topologies and the Gigabit Ethernet standard, allowing for a new telecommunications network concept, where the traditional analogical distribution services are totally preserved. The above proposed solution presents two advantages. The first is such that a very high-speed data network becomes available. This last, is an ideal outfit for second generation Internet. The second advantage is that the obtained data network provides for economic revenues by far greater than those of the traditional CATV networks.

Cette thèse présente le devenir atmosphérique de trois alcools saturés CH3(CH2)4OH, CH3CH2CH2CH(OH)CH3 et (C2H5)2CHOH, de trois esters CH3CH2CH2C(O)OC2H5, CH3CH2C(O)OC2H5 et CH3CH2C(O)OCH2CH2CH3 ainsi que d’un HFC insaturé (CF3)2C=CH2 avec OH et Cl. La constante de vitesse de la réaction avec OH de ces composés a été déterminée en fonction de la température (253 – 373 K), en utilisant la technique Photolyse Laser Pulsée couplée à la Fluorescence Induite par Laser (PLP-FIL). La constante de vitesse de la réaction de OH et de Cl avec les alcools, les esters et l’hexafluoroisobutène (HFIB) a été également déterminée à température ambiante en utilisant la chambre de simulation atmosphérique. Pour la réaction du radical OH avec le HFC et de l’atome Cl avec les esters et le HFC, il s’agit d’une première détermination des constantes de vitesse. Les constantes de vitesse obtenues sont comparées à la littérature, la réactivité des alcools et des esters a été discutée. Enfin, le calcul des durées de vie de ces composés ainsi que la recherche de leurs produits éventuels ont permis d’évaluer l’impact atmosphérique de ces composés sur l’environnement. / In this thesis we report the atmospheric fate of three saturated alcohols: CH3(CH2)4OH, CH3CH2CH2CH(OH)CH3 and (C2H5)2CHOH, three esters: CH3CH2CH2C(O)OC2H5, CH3CH2COOC2H5 and CH3CH2COOCH2CH2CH3 and an unsaturated HFC with OH radicals and Cl atoms. The rate coefficients of OH reactions with these compounds have been measured over the temperature range 253 – 373 K, using the Pulsed Laser Photolysis – Laser Induced Fluorescence technique (PLP-LIF). Moreover the rate coefficients of OH and Cl reactions with alcohols, esters and hexafluoroisobutene (HFIB) have been determined at room temperature, using smog chambers. For the reaction of OH radicals with HFIB and Cl atoms with esters and HFIB, the rate coefficients obtained in this study present the first determination. The results have been compared with the literature and the reactivity of the compounds has been discussed. Finally, the atmospheric lifetimes of these compounds have been determined and the OH oxidation products have been identified, which allows us to estimate the atmospheric impact of these compounds.

HCFC-22 is the world�s most widely used refrigerant. It serves in both residential and commercial applications, from small window units to large water chillers, and everything in between. Its particular combination of efficiency, capacity and pressure has made it a popular choice for equipment designers. Nevertheless, it does have some ODP, so international law set forth in the Montreal Protocol and its Copenhagen and Vienna amendments have put HCFC-22 on a phase out schedule. In developed countries, production of HCFC-22 will end no later than the year 2030. Zeotropic blend HFC-407C has been established as a drop-in alternative for HCFC-22 in the industry due to their zero Ozone Depletion Potential (ODP) and similarities in thermodynamic properties and performance. However, when a system is charged with a zeotropic mixture, it raises concerns about temperature glide at two-phase state, differential oil solubility and internal composition shift. Not enough research has been done to cover all aspects of alternative refrigerants applications in the systems. This research intended to explore behavior of this alternative refrigerants compare to HCFC-22 and challenges facing the industry in design, operation service and maintenance of these equipments. The purpose of this research is to investigate behavior of R407C refrigerant in chiller systems. This includes performance and efficiency variations when it replaces R22 in an existing system as well as challenges involved maintaining the system charged with R407C. It is a common practice in the industry these days to evacuate and completely recharge when part of the new refrigerant blend was leaked from the system. This has proved to be extremely costly exercise with grave environmental ramifications. This research is intended to address challenges faced in the real world and practical terms. Theoretical and experimental approaches used as a methodology in this work. The system mathematically modeled to predict detailed system performance and effect of the leak at various conditions. To make this feasible and accurate enough, two separate approaches made, first system performance for pure R22 and R407C, and second system subjected to range of leak fractions. The earlier model was relatively straight forward when compared to the latter. Modeling a system charged with R407C ternary mixture and subjected to range of leaks posed enormous challenges. A sophisticated experimental test apparatus was also designed and built. Comprehensive and detailed tests at various conditions were conducted with special attention on instrumental accuracy and correct methodology. The first part has been successfully modeled and predicted all the factors and performance with excellent accuracy when compared to the test results. In these approaches pure refrigerants R22 and R407C were used and simulated the system behavior at range of conditions. However, the second part was the most challenging ever. Comprehensive leak process simulations produced trends of R32/R125/R134a composition change as function of rate of leak. Starting from this point, equations have been created to represent the composition change as function of percentage of the leak. The system thermodynamic cycle was also modeled to calculate capacity, power input and COP at the range of the conditions. Despite many affecting parameters and complexity of the model, the mathematical model successfully predicted the test outcome with a very reasonable accuracy, averaging around 3% with some times reaching to 5 to 6%. On the experimental stage the system charged with the new HFC-407C was deliberately subjected to refrigerant leak at various leak stages. The aim was to objectively determine to what extend the gas leak can be still acceptable without going through the expensive complete gas charge. The effect of leak was tested and verified at 10% steps, from 10% up to 50% mass fraction for the total charge. It has been observed that at the leaks beyond 30%, the adverse effect on the capacity becomes more significant, from 8 to about 15% decrease. While the power input decreased at slower pace, from 3% up to about 8% depending on the test conditions. This translated to COP decrease ranging from 4 to about 7%. This capacity loss and efficiency decrease are significant figures which suggests that the system, here chiller, can not be allowed to degrade the performance to that extend and still continue operating.