This study was designed to examine various aspects of information use a selected sample of Brazilian mechanical engineers (BMEs) working in academic institutions in Brazil and to relate these findings to the influence of their personal, work and environmental factors. A survey questionnaire was administered to groups of mechanical engineers working in four academic institutions (Federal and State) located in the central-south regions of Brazil. Data were gathered on the following aspects of information use: frequency of use of information sources and channels; number of hours spent reading and communicating; categories of locations consulted; categories of people consulted; problems encountered in information use; attitudes taken by engineers when information is needed but is not available; types of information used and the engineers perception of the availability and pertinence of various information services offered by the engineer's information system. Hypotheses on the interplay between information use and educational level, productivity, reading language ability, seniority, interinstitutional involvement, project type, accessibility of the source; problems on information use and institutional restrictions on the use of information were tested.

All across the world, attention is turning to renewable energies to serve at least as a partial substitute to fossil fuels in the global energy mix, braking the latter’s depletion and providing a greener solution for a more sustainable future. However, the intermittent nature of most renewable energy sources, wind and solar in particular, raises major concerns over the integration of these technologies, on a large scale, to grid systems. This thesis focuses on large-scale renewable energy storage systems, primarily compressed air energy storage (CAES) systems, which are particularly well suited for renewable energy applications. CAES can play a major role in shaping the future of renewable energy systems for not only can it bring load levelling to the system, but it can also add substantial value by providing ancillary services to the grid. The main focus of this research is adiabatic CAES which endeavours to minimize the use of natural gas by using recuperators and thermal energy storage systems, where the heat from the air during the compression stages is absorbed by a heat transfer fluid, stored, and then supplied back during the expansion process. This project aimed to explore the potential of CAES systems as an energy storage technology for large-scale grid integrated renewable energy system. A computer model was developed to size the different components in the CAES system and also to predict the operational performance of the CAES system for different conditions using MATLAB programming. The thermal energy storage of an adiabatic CAES system was optimized using CFD analysis and experimental testing of the thermal energy storage system was carried out to validate the models. Also, an economic study was performed to assess the feasibility of the CAES system based on a case study of the Egyptian grid. The dynamic simulation of a novel configuration of an adiabatic CAES system showed that the system can achieve improved performance compared to existing CAES plants, while the economic study showed that CAES can improve the economics of a wind farm, at least by the standards of our chosen case study location.

Made available in DSpace on 2014-06-11T19:29:05Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-02-17Bitstream added on 2014-06-13T20:18:51Z : No. of bitstreams: 1 ballottin_dpm_me_araiq.pdf: 2551243 bytes, checksum: 6bc5b0d91a3b15a3677e5d02307c45c8 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A alta demanda de energia no mundo atual, bem como o grande número de problemas ambientais existentes, resultam em uma crescente necessidade por novas fontes de energia, estimulando assim o interesse por fontes alternativas para os combustíveis de origem fóssil. Surge então o Biodiesel, combustível biodegradável derivado de fontes renováveis. No entanto, este biocombustível apresenta certos contaminantes que podem causar sérios danos ao motor e ao ambiente dependente de seus teores. Dentre estes, estão os acilgliceróis, remanescentes da matéria prima para a produção do biodiesel. Por exemplo, a alta concentração destes compostos aumenta a viscosidade do biocombustível, provocando depósitos nos cilindros e nas válvulas diminuindo assim a vida útil do motor. Assim, foi avaliado neste trabalho o comportamento voltamétrico do mono, di e trilinoleato de glicerina através da técnica de Redissolução Adsortiva com Voltametria AC. As curvas analíticas para o mono e trilinoleato de glicerina apresentaram linearidade de 4,0 x 10-8 a 1,6 x 10-6 mol L-1, com limites de detecção da ordem de 10-8 mol L-1. A curva analítica do dilinoleato de glicerina mostrou-se linear de 4,0 x 10-9 a 4,0 x 10-7 mol L-1, com limite de detecção da ordem de 10-9 mol L-1. Os limites de quantificação foram da ordem de 10-8 mol L-1 para o mono e o dilinoleato de glicerina e 10-7 mol L-1 para o trilinoleato de glicerina. Porém, estes não puderam ser determinados simultaneamente e, por isso, utilizou-se um método cromatográfico com detecção eletroquímica para a separação e posterior detecção destes compostos. Os acilgliceróis foram separados em coluna de fase reversa (C-18) operando em modo isocrático com fase móvel tampão fosfato pH 3,0/MeOH 60:40 (v/v) com adição de ácido ascórbico / Currently, the high energy demand in today's world, as well as the environmental problems result in an increased need for developing renewable energy sources, thereby stimulating interest in alternative sources to fossil fuels. Then, Biodiesel comes as a biodegradable fuel derived from renewable sources. However, this biofuel has certain contaminants that can cause serious damage to the engine and the environment if they are present in inadequate amounts. Among these contaminants are the glycerides, remnants of the raw material for biodiesel production. For example, the high concentration of these compounds increases the viscosity of the biofuel causing deposits in the cylinders and valves reducing the engine lifetime. Thus, it was evaluated in this study the voltammetric behavior of glyceryl mono, di and trilinoleate by Adsorptive Stripping technique with AC voltammetry. The analytical curves for mono and tri showed linearity from 4.0 x 10-8 to 1.6 x 10-6 mol L-1, with detection limits of about 10-8 mol L-1. The analytical curve of glyceryl dilinoleate was linear from 4.0 x 10-9 to 4.0 x 10-7 mol L-1, with a detection limit of about 10-9 mol L-1. The quantification limits were in the order of 10-8 mol L-1 for mono and dilinoleate and 10-7 mol L-1 for trilinoleate. However, these could not be determined simultaneously and therefore it was developed a chromatographic method with electrochemical detection for separation and detection of these compounds. The glycerides were separated on a reversed phase column (C-18) operating in isocratic mode with mobile phase pH 3.0 phosphate buffer / MeOH 60:40 (v/v) with addition of ascorbic acid

Made available in DSpace on 2014-06-11T19:30:09Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-05Bitstream added on 2014-06-13T20:00:01Z : No. of bitstreams: 1 rodriguez_cjc_me_guara.pdf: 4550695 bytes, checksum: 39fdcc0a3d1ecf7ac3bdba90c51c9d49 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Após as crises do petróleo de 1973 e de 1979, notou-se um efeito nocivo dos elevados custos e contínuo aumento dos preços do petróleo, razão pela qual aumentou o interesse pelas fontes de energias renováveis, amplamente disponíveis nos países em desenvolvimento. Em todo o mundo, tornaram-se objetivos prioritários de se economizar energia e buscar tecnologias racionais, levando-se sempre em consideração os efeitos relacionados ao meio ambiente. Por outro lado, a escassez iminente dos combustíveis fósseis tem exigido da humanidade o uso racional de energia primária e como conseqüência, novas plantas em versões tecnológicas mais desenvolvidas têm sido concebidas visando sempre o aumento da eficiência energética. Neste contexto, destacam-se as tecnologias de gaseificação de madeira, que consistem em técnicas de conversão da biomassa em gás combustível. O objetivo principal deste trabalho é o desenvolvimento e a demonstração de uma metodologia de dimensionamento de um gaseificador de leito fixo tipo Downdraft para uma alimentação de 100 kg/h de biomassa lignocelulósica. Avalia-se e escolhe-se os diversos equipamentos e acessórios necessários para a limpeza e acondicionamento do gás combustível para a alimentação de um motor de combustão interna. A análise técnica inclui além dos parâmetros construtivos específicos do gaseificador, o balanço de massa, de energia, e a determinação das eficiências, tanto para a eficiência a frio como para a eficiência a quente do gaseificador. A análise econômica inclui uma avaliação e obtenção dos custos tanto do gaseificador como do Motor de Combustão Interna acoplado, os custos dos equipamentos e acessórios da zona de gaseificação, os custos operacionais e os custos da instalação e amortização do projeto. / After the oil crisis of 1973 and 1979, an effect of the increase costs and continuously increment of the oil prices was noted. For this reason, the interest for renewable energies sources widely available in developing countries was increased. The governments have formulated main objectives for energy savings and search for friendly technologies, taking into account the effects related with the environment. The new plants with improved technology have been conceived always taking into account energy savings and efficiency improvement. In this context, biomass gasification technologies are important, since they consist in techniques of parallel production of electricity and heat from just one fuel. The main objective of this work is to develop and to demonstrate a scale up methodology for the construction of a bed fix downdraft gasifier with a 100 kg/h supply using as raw material lignocelulosic biomass. It will be evaluated and analytically chosen the necessary accessories and equipments for the cleaning and preparation of the biomass fuel gas, then this gas will be used in a internal combustion engine. The technical analysis includes in addition to the constructive specifics parameters, the balance of mass, balance of energy and determination of the efficiencies for thermal generation and power generation (hot efficiencies or cold efficiencies, respectively. The economic analysis includes cost evaluation of the gasifier, internal combustion engine, equipment and accessories of the gasification zone, operational and installation and amortization of the project.

La localisation de sources (en champ lointain ou en champ proche) et l'estimation des temps de retard ont de nombreuses applications pratiques. Pour localiser une source en champ lointain à partir d'un réseau de capteur, seule la direction d'arrivée (DDA) de la source est nécessaire. Quand les sources se situent dans une situation de champ proche, le front d'onde du signal est sphérique et deux paramètres sont nécessaires pour localiser les sources : la direction d'arrivée et la distance entre la source et le réseau de capteurs. Dans cette thèse, on se focalise sur la localisation de sources (en champ lointain et en champ proche) ainsi sur l'estimation des temps de retard dans le contexte où les signaux sont cohérents, mélangés et avec un faible nombre de réalisation. Tout d'abord, nous proposons de combiner la théorie de la méthode SVR (Support vector regression qui est une méthode de régression à base d'apprentissage supervisée) avec la théorie de la prédiction linéaire avant-arrière. La méthode proposée, appelée FBLP-SVR, est développée pour deux applications : la localisation de sources en champ lointain et l'estimation des temps de retard des échos radar en champ lointain. La méthode développée est évaluée par des simulations et des expérimentations. Nous proposons également une méthode de localisation de sources en champ proche dans le contexte où les signaux sont cohérents et mélangés. La méthode proposée est basée sur une technique de focalisation, de moyennage en sous-bande et sur une méthode à sous-espaces pour l'estimation des DDAs. Ensuite, les distances entre les sources et le réseau de capteur sont estimées avec la méthode du maximum de vraisemblance. / Source localization (in far-field or in nearfield) and time-delay estimation have many practical applications. To locate a far-field source from a sensor array, only the direction of arrival (DOA) of the source is necessary. When the sources are in a nearfield situation, the wavefront of the signal is spherical and two parameters are needed to locate the sources: the direction of arrival and the distance between the source and the sensors. In this thesis, we focus on the localization of sources (both in far-field and nearfield) as well as the estimation of time-delay in the context where the signals are coherent, overlapped and with a small number of snapshots. First, we propose to combine the theory of the SVR method (support vector regression, which is a supervised learning-based regression method) with the theory of forward-backward linear prediction (FBLP). The proposed method, called FBLP-SVR, is developed for two applications: far-field source localization and time-delay estimation by using ground penetrating radar. The proposed method is evaluated by simulations and experiments. We also propose a near-field source localization method in the context where the signals are coherent and overlapped. The proposed method is based on a focusing technique, a spatial smoothing preprocessing, and a subspace method in the estimation of DOA. Then, the distances between the sources and sensors are estimated with the maximum likelihood method.

Storage ring light sources are in use around the world operating as high brightness photon sources from the infrared to the X-ray photon regimes. Whilst modern light source designs achieve horizontal emittances in the few-nm range, they are only diffraction limited in the vertical plane with emittances as low as 10~pm-rad. To achieve fully diffraction limited light sources in the X-ray regime requires a fundamental change in the design of such machines. Many such designs have been proposed based on the multi-bend achromat (MBA) lattice, which have been shown to achieve the required emittance reduction. However MBA lattices typically have a reduced dynamic acceptance, and consequently shorter beam lifetimes. Whilst this can be ameliorated somewhat through the use of top-up injection schemes, many issues still remain. In this thesis we explore one possible alternative to the multi-bend achromat (MBA) paradigm: the stacked storage ring. We propose a storage ring consisting of two synchrotrons joined via a static magnetic vertical transfer line. One of the rings has a reduced emittance through the use of high field damping wigglers, whilst the other is used for standard user experiments. The cumulative emittance of the combined ring structure is a function of the emittances of the two rings. The stacked ring approach allows for a reduction in the beam emittance without a consequent increase in the machine footprint, as in the case of the MBA lattice. Additionally, we may use the more relaxed lattice structures popular in currently operating 3rd generation light sources to maintain a reasonable dynamic acceptance even with the reduced emittance. We apply the stacked storage ring concept to the design of a low emittance 700~MeV compact light source for low energy vacuum ultraviolet photon output. The desirability of such a low energy photon source for UK science has previously been explored in depth. We examine the design of such a light source based around a strong damping stacked storage ring in the presence of Touschek and Intra-Beam scattering whilst analysing the effects on the dynamic properties of the lattice. We also apply the stacked ring concept to two lattices designed to operate in the high energy X-ray region of the photon spectrum and investigate the potential advantages in this regime, including as an adjunct to further improve proposed MBA concepts.

Lorsque l'on manipule un signal audio, il est généralement utile d'opérer un isolement du ou des éléments sonores que l'on cherche à traiter. Cette étape est couramment appelée séparation de sources audio. Il existe de nombreuses techniques pour estimer ces sources et plus on prend en compte d'informations à leur sujet plus la séparation a des chances d'être réussie. Une façon d'incorporer des informations sur une source est l'utilisation d'un signal de référence qui va donner une première approximation de cette source. Cette thèse s'attache à explorer les aspects théoriques et appliqués de la séparation de sources audio guidée par signal de référence. La nouvelle approche proposée appelée SPOtted REference based Separation (SPORES) examine le cas particulier où les références sont obtenues automatiquement par détection de motif, c'est-à-dire par une recherche de contenu similaire. Pour qu'une telle approche soit utile, le contenu traité doit comporter une certaine redondance ou bien une large base de données doit être disponible. Heureusement, le contexte actuel nous permet bien souvent d'être dans une des deux situations et ainsi de retrouver ailleurs des motifs similaires. L'objectif premier de ce travail est de fournir un cadre théorique large qui une fois établi facilitera la mise au point efficace d'outils de traitement de contenus audio variés. Le second objectif est l'utilisation spécifique de cette approche au traitement de bandes-son de films avec par exemple comme application leur conversion en format surround 5.1 adapté aux systèmes home cinéma. / In audio signal processing, source separation consists in recovering the different audio sources that compose a given observed audio mixture. They are many techniques to estimate these sources and the more information are taken into account about them the more the separation is likely to be successful. One way to incorporate information on sources is the use of a reference signal which will give a first approximation of this source. This thesis aims to explore the theoretical and applied aspects of reference guided source separation. The proposed approach called SPOtted REference based Separation (SPORES) explore the particular case where the references are obtained automatically by motif spotting, i.e., by a search of similar content. Such an approach is useful for contents with a certain redundancy or if a large database is be available. Fortunately, the current context often puts us in one of these two situations and finding elsewhere similar motifs is possible. The primary objective of this study is to provide a broad theoretical framework that once established will facilitate the efficient development of processing tools for various audio content. The second objective is the specific use of this approach to the processing of movie soundtracks with application in 5.1 upmixing for instance.

Organic Rankine cycles (ORC) have unique properties that are well suited to power generation from low grade heat sources. It is envisaged that a domestic scale ORC Heat Engine can be developed that will be able to run off heat stored in a solar charged rock thermal battery. The use of a thermal battery as the heat source for the ORC system will provide the user with electricity during the day and for a number of hours into the night. The concept presented consists of four key components: rock thermal battery, 1 kW scroll expander, condenser and working fluid pump.

Economies aim to expand over time, which always implies the need for increased energy availability in support of this growth. Governments can use their procurement of energy generation to further enhance the benefit to their economies via certain policy tools. One such tool is Local Content Requirements (LCR) where procurement of a good dictates that a certain value has to be sourced locally. The argument for this tool is that spend is localised and manufacturing, as well as job creation, can be stimulated due to industry establishing in the host economy. However, this practice is distortionary in effect and it does not create a fair playing field for global trade. Furthermore, if the local content definition is weak, or open to manipulation, the goals of such a policy may not be achieved at all. This study looked into the local content requirements of South Africa’s Renewable Energy Independent Power Producer Procurement Programme (REIPPPP) and measured the impact of this policy on the renewable energy sector in general. It was found that, in order to implement a policy such as local content, the host economy had to have certain pre-existing conditions in order to avoid any negative welfare effects. Due to SA not holding all supportive pre-conditions for supporting local content policy, the impact and effect of LCRs has not been optimal and it has not been found to be a sustainable mechanism to continue using into the future indefinitely. The pricing of renewable energy was also found to be higher due to local content and such pricing is passed on to the energy consumer. Therefore, the net welfare impact created for South Africa is diminished in exchange for the creation of jobs and manufacturing, but due to the unsustainability and potential manipulation of the system the country is not maximising the welfare potential from the REIPPPP as it should. It was found that SA renewable energy resources do exist and the logistics infrastructure is strong, providing good potential for investment into renewable energy projects. The demand created by the REIPPPP provided a good market, but there was uncertainty in the long term planning and stability. So, from a market perspective this could be further enhanced. Government had created a sufficient platform for investment, but areas of development such as clusters, R&D and skills training would create a better support environment for LCR policy and strict monitoring of this would also be required to prevent any manipulation. The use of LCRs increases project costs and risk, which is passed onto the energy consumers, but this could be reduced if local goods were more readily available at the right price and at the right quality and quantity. Focus on clusters would once again assist in this regard as independent power producers (IPPs) and engineering procurement and construction (EPC) entities would be able to source components and goods locally in a more cost-effective manner. As the LCRs currently stand in the REIPPPP, it would seem that South Africa is making renewable energy more expensive and although it is argued that this is done for the benefit of creating a new industry and jobs, these are not sustainable and so the current LCR policy will only create short term benefits.

Operational characteristics and performance of two mass spectrometers incorporating improved versions of the Very High Yield Electron Impact (VHY-EI) ion source are described. The ionizers are designed around a large volume, low pressure, hot cathode Penning geometry and operate at source pressures of 10⁻⁵ torr and below. In combination with low spherical aberration focusing optics, mass analyzed ion currents 100 to 1000 times more intense than those produced by conventional ionizers operated under identical or comparable conditions of resolution, analyzer type, sample pressure, and electron impact energy are obtained. In addition, high ionization-mass analysis efficiencies have been demonstrated for a variety of organic compounds with sample mass flow rates approaching 1 mg/min. Typical electron impact spectra are obtained with no evidence of pyrolysis or ion molecule reactions. Unusually intense spectra can be produced with low energy electrons.