Este trabalho apresenta o estudo da usinabilidade do carbeto de tungstênio utilizando ferramenta de ponta única de diamante em máquina-ferramenta de ultraprecisão, em função de suas características de dureza e potencial uso para a fabricação de micromoldes. O carbeto de tungstênio foi submetido a testes de usinagem para a determinação dos parâmetros e condições de corte para a obtenção do regime dúctil. Com base nos resultados experimentais, concluiu-se que, para os avanços da ordem de 1 micrômetro/revolução, a profundidade de corte (AP) não influencia significativamente no resultado de rugosidade, e para avanços da ordem de 3 micrômetros, observou-se a formação de trincas na superfície usinada. Além disso, para profundidades de corte maiores que 2 micrômetros as ferramentas começaram a apresentar lascamento. Para avanços da ordem de 3 micrômetro/revolução a profundidade de corte influencia com grande significância no resultado de rugosidade. O torneamento do carbeto de tungstênio usando ferramenta de diamante mostrou-se uma opção viável à produção de superfícies em termos de qualidade óptica, porém, devido à alta dureza deste material (aproximadamente 4000HV) o torneamento mostrou ser um processo com condições limitadas para a produção em série de componentes em função da baixa taxa de remoção de material permitida. É possível que a retificação possa apresentar taxas de remoção maiores, mesmo assim garantindo a qualidade superficial atingida pelo torneamento, ou ainda, a retificação possa ser usada como um processo no desbaste do carbeto de tungstênio seguido do torneamento de ultraprecisão como a opção viável a produção em série de peças. Portanto, para obtenção de uma superfície de carbeto de tungstênio sem danos e com acabamentos da ordem de 10 nm, a profundidade e avanço não devem ser superiores a 2,00 \'mü\'micrômetros e 1,00 \'mü\'micrômetro/revolução, respectivamente, usando uma ferramenta de diamante nova com ângulo de saída 0 ou - 25 graus e uma máquina-ferramenta de alta precisão. / The single point diamond turning of the Tungsten Carbide is presented. The motivation for this study is the material´s high hardness and potential application for micromolds. A Tungsten Carbide sample was subjected to tests for determination of cutting parameters to achieve the ductile regime of material removal. Based on experimental results it was concluded that for the feedrate of the order of 1 \'mü\'m/revolution, the depth of cut did not affect significantly the surface roughness and for federates of the order of 3 \'mü\'m/revolution, the dept of cut influenced results of roughness greatly. Moreover chipping of the cutting edge occurs for depths of cut of 2 \'mü\'m. The diamond machining of tungsten carbide tool using diamond proved to be a viable option for the production of surfaces in terms of optical quality, but due to the high hardness of this material (approximately 4000HV) showed to be limited for the production of components due to the low material removal rate. It is possible that the precision griding may provide higher material removal rates along with the acceptable surface quality. Therefore, to obtain a damage free surface in tungsten carbide with surface finishe in the order of 10 nm, cutting depth and feedrate should be smaller than 2,00 \'mü\'m and 1,00 \'mü\'m/revolution, respectively, using a new diamond tool with rake angle of 0 or - 25 degrees and precision high stiffness machine tool.

Este trabalho apresenta o estudo da usinabilidade do carbeto de tungstênio utilizando ferramenta de ponta única de diamante em máquina-ferramenta de ultraprecisão, em função de suas características de dureza e potencial uso para a fabricação de micromoldes. O carbeto de tungstênio foi submetido a testes de usinagem para a determinação dos parâmetros e condições de corte para a obtenção do regime dúctil. Com base nos resultados experimentais, concluiu-se que, para os avanços da ordem de 1 micrômetro/revolução, a profundidade de corte (AP) não influencia significativamente no resultado de rugosidade, e para avanços da ordem de 3 micrômetros, observou-se a formação de trincas na superfície usinada. Além disso, para profundidades de corte maiores que 2 micrômetros as ferramentas começaram a apresentar lascamento. Para avanços da ordem de 3 micrômetro/revolução a profundidade de corte influencia com grande significância no resultado de rugosidade. O torneamento do carbeto de tungstênio usando ferramenta de diamante mostrou-se uma opção viável à produção de superfícies em termos de qualidade óptica, porém, devido à alta dureza deste material (aproximadamente 4000HV) o torneamento mostrou ser um processo com condições limitadas para a produção em série de componentes em função da baixa taxa de remoção de material permitida. É possível que a retificação possa apresentar taxas de remoção maiores, mesmo assim garantindo a qualidade superficial atingida pelo torneamento, ou ainda, a retificação possa ser usada como um processo no desbaste do carbeto de tungstênio seguido do torneamento de ultraprecisão como a opção viável a produção em série de peças. Portanto, para obtenção de uma superfície de carbeto de tungstênio sem danos e com acabamentos da ordem de 10 nm, a profundidade e avanço não devem ser superiores a 2,00 \'mü\'micrômetros e 1,00 \'mü\'micrômetro/revolução, respectivamente, usando uma ferramenta de diamante nova com ângulo de saída 0 ou - 25 graus e uma máquina-ferramenta de alta precisão. / The single point diamond turning of the Tungsten Carbide is presented. The motivation for this study is the material´s high hardness and potential application for micromolds. A Tungsten Carbide sample was subjected to tests for determination of cutting parameters to achieve the ductile regime of material removal. Based on experimental results it was concluded that for the feedrate of the order of 1 \'mü\'m/revolution, the depth of cut did not affect significantly the surface roughness and for federates of the order of 3 \'mü\'m/revolution, the dept of cut influenced results of roughness greatly. Moreover chipping of the cutting edge occurs for depths of cut of 2 \'mü\'m. The diamond machining of tungsten carbide tool using diamond proved to be a viable option for the production of surfaces in terms of optical quality, but due to the high hardness of this material (approximately 4000HV) showed to be limited for the production of components due to the low material removal rate. It is possible that the precision griding may provide higher material removal rates along with the acceptable surface quality. Therefore, to obtain a damage free surface in tungsten carbide with surface finishe in the order of 10 nm, cutting depth and feedrate should be smaller than 2,00 \'mü\'m and 1,00 \'mü\'m/revolution, respectively, using a new diamond tool with rake angle of 0 or - 25 degrees and precision high stiffness machine tool.

La chaine varisque ouest-européenne est une vaste province métallogénique qui abrite une large diversité de minéralisations. Une grande partie d’entre elles ont fait l'objet d'exploitations historiques, à l'instar de Salau(Pyrénées Centrales), le plus important gisement de tungstène français. Les résultats de terrain combinés aux études minéralogiques et géochimiques convergent pour montrer qu'il existe deux types de minéralisations superposées : (1) un skarn à silicates calciques, rare scheelite fine et sulfures disséminés ; (2) une brèche filonienne à sulfures massifs (pyrrhotite et chalcopyrite dominante), or et abondante scheelite grossière qui a constitué l’essentiel du minerai exploité. Cette brèche se localise dans des zones de cisaillement ductile-fragile(faille Véronique) recoupant la granodiorite. Les datations U/Pb sur zircon, apatite et scheelite situent le skarn contemporain de l'intrusion de la Fourque à 295±2 Ma alors que la brèche à sulfures massifs se forme environ6 Ma après, à 289±2 Ma. Ces minéralisations, issues de deux intrusions successives (granodiorite puis leucogranite), s’inscrivent dans l'évolution d'un modèle Intrusion Related Deposit. La mise en place de labrèche à forte teneur en or-scheelite est initiée par la focalisation progressive de la déformation régionale dans la Zone axiale des Pyrénées au sein de failles E-W dextres inverses. L'origine de l'or à l'échelle des Pyrénées pourrait s'expliquer en partie par une large répartition de ces minéralisations à forte teneur. La carte de paléotempératures RSCM a permis de localiser d’autres intrusions non affleurantes en étendant le district minéralisé sur plus de 7 km jusqu’à l’indice à W-Au d’Aurenère en Espagne. / The Western European variscan belt is a vast metallogenic district which hosts a wide diversity of mineralizations. A large part of them have been historically exploited, such as Salau (Central Pyrenees), the most important French tungsten deposit. The field results combined with the mineralogical and geochemical studies converge to show that it exists two superimposed ore types: (1) a calcic silicates skarn with rare fine grainedscheelite and disseminated sulphides; (2) a mineralized breccia with massive sulphides (pyrrhotiteand chalcopyrite dominant), gold and abundant coarse-grained scheelite which have constituted the main part of the exploited ore. This breccia is localized in ductile-fragile shear-zones (Veronique fault) which crosscut the granodiorite. U/Pb datings on zircon, apatite and scheelite place the skarn, contemporaneous of the LaFourque intrusion at 295±2 Ma while the massive sulphides breccia was formed ca. 6 Ma later at 289±2 Ma.These mineralizations, from two successive intrusions (granodiorite then leucogranite), belong to the evolution of an Intrusion Related Deposit model. The emplacement of the high grade gold and scheelite breccia was initiated by the progressive focalization of the regional deformation in the Axial Zone of the Pyrenees within EWdextral-reverse faults. The source of gold at the Pyrenees scale could be explained in part by this type of high-grade mineralizations. The RSCM paleo-temperature map has made possible to locate other undercover intrusions, extending the mineralized district over more than 7 km until the W-Au Aurenere occurrence in Spain.

Les multiferroïques sont des matériaux dans lesquels plusieurs propriétés ferroïques peuvent coexister, e. g. ferromagnétisme et ferroélectricité. La recherche de tels matériaux fait l'objet d'une activité croissante en raison de l’enjeu majeur qu’ils représentent dans de nombreux domaines (mémoires, spintronique…). Les matériaux qui possèdent les propriétés nécessaires pour des applications futures sont cependant peu nombreux. Des niobates de formule Ba2LnFeNb4O15 (Ln = lanthanide), de structure bronze quadratique (TTB) susceptibles de présenter un ordre ferroélectrique et un ordre magnétique ont été synthétisés. Les propriétés magnétiques des céramiques proviennent d'une phase secondaire, faisant d’eux des composites multiferroïques. Leur souplesse cristallochimique permet de contrôler les propriétés composites par substitutions cationiques dans la matrice TTB. Afin de compléter l'étude cristallochimique, la croissance de monocristaux de TTB a été entreprise avec succès. / Multiferroics are materials which possess several ferroic properties, e.g. ferroelectricity, ferromagnetism. The search for multiferroics arises a growing activity, due to their potential applications in memories, spintronic… Yet the materials displaying the adequate properties for future application are very few. Niobates with the formula Ba2LnFeNb4O15, potentially ferroelectric and ferromagnetic, have been synthesized. The magnetic properties of the ceramics are related to a secondary phase, thus making them composite multiferroics. Their crystal-chemical flexibility allows for the composites properties tuning by cationic substitutions into the TTB framework. To complete the crystal-chemical study, the growth of TTB single-crystals was successfully engaged.

Os Ormosils pertencem aos sistemas nanoestruturados, apresentando uma grande diversidade de estruturas e permitindo o controle das propriedades dos materiais obtidos. Os Ormosils contribuem ao desenvolvimento de materiais multifuncionais pela sua estrutura flexível (matriz hospedeira), que permite a oclusão de diversas espécies (moleculares, iônicas), a qual pode ser ajustada pela mudança dos grupos funcionais dos silanos precursores. Os filmes dos Ormosils têm potencial aplicação em fitas dosimétricas, janelas inteligentes, selos antifraude, dispositivos fotônicos, filmes fotocatalíticos e dispositivos fotocrômicos. Esta Tese abordou a determinação qualitativa, semiquantitativa e quantitativa dos filmes dos Ormosils (contendo nanopartículas de TiO2, ZnO e Fosfotungstatos ([PW12O40]3)) e aqueles constituídos por uma rede interpenetrante de sílica, sesquisiloxano e hidroxiuretana de poli(dimetilsiloxano) contendo Fosfotungstatos, com potencial aplicação em membranas para células combustíveis e na produção de janelas fotocrômicas. Outro dos materiais analisados constituíram Ormosils ocluídos na matriz de Poli(imidas), com potencial aplicação no armazenamento de Hidrogênio, membranas para células combustíveis e revestimentos isolantes e anticorrosivos.<br /><br /> A quantificação e mapeamento dos elementos fotoativos são relevantes para a melhoria no desenvolvimento destes materiais, entretanto, esta não é uma tarefa trivial devido à natureza intrínseca destes materiais híbridos em que a fase orgânica e a inorgânica estão intimamente ligadas e devido à presença de um grande número de elementos químicos que muitas vezes interferem na análise. Desta forma, estes materiais híbridos se constituem em matrizes complexas de análise e há necessidade de se desenvolver e estudar métodos analíticos específicos. A fim de melhor compreender as propriedades fotocrômicas, anticorrosivas e mecânicas destes materiais, é importante conhecer a distribuição dos silicatos e dos fosfotungstatos no interior dos filmes.<br /><br /> Os Estudos de Interferência da Autoabsorção da Fluorescência de Tungstênio pelos demais elementos nos filmes dos Ormosils, nos induziram a abordar a quantificação por XRF, não somente pelo ponto de vista atômico, senão complementar com a abordagem molecular. O Espalhamento Raman Ressonante de RaiosX mostrouse igualmente importante para entender os fenômenos de interferência observados nestes sistemas complexos. <br /><br /> Foi possível identificar e detectar o dopante Ti na faixa de dezenas de mg.Kg1 , mediante análises de Fluorescência de RaiosX em ângulo rasante (GIXRF) assistida por Radiação Síncrotron. De maneira complementar, análises de Microfluorescência de RaiosX (&micro;XRF) assistida por Radiação Síncrotron possibilitaram conhecer a distribuição espacial do Titânio e Zinco nos Ormosils. Nestas análises XRF não se empregaram materiais certificados para validação, contudo fora preparados no nosso laboratório materiais de referência, com procedimento de preparo similar àquele das amostras usando o método de semiquantificação baseado em Parâmetros Fundamentais. Os resultados de Fluorescência de RaiosX foram validados pelos resultados das análises por ICPOES e Ativação por Nêutrons (INAA). Os diferentes métodos de análise empregados (&micro;XRF, GIXRF, EDXRF, ICPOES, AAS) foram efetivos em precisão e em exatidão na quantificação de Tungstênio e Zinco. Entretanto para o caso de Titânio, somente puderam se considerar os resultados de &micro;XRF e ICPOES. Portanto, serão necessários métodos analíticos adicionais para validar os resultados da concentração deste elemento nos Ormosils. ICPOES e INAA demonstraram serem métodos de referência para os resultados XRF (Laboratório, Radiação Síncrotron) nossos materiais.<br /><br /><br /><br /> / Organically modified silicates or Ormosil are nanostructured systems displaying a wide range of structures, which facilitates the control of properties of materials obtained from them. Ormosil contribute to the development of multifunctional materials because of their flexible structure (matrix host), which allow the occlusion of various species (ionic, molecular), can be adjusted by changing functional groups of precursor silanes. Ormosil films have potential for application to dosimetric tapes, smart windows, antifraud sealing, photonic devices, photocatalytic films, and photochromic devices. In this thesis was investigated qualitative, semiquantitative and quantitative determination of ormosil films (containing TiO2 nanoparticles, ZnO, and phosphotungstates ([PW12O40]3))and those composed of an interpenetrating network of silica, sesquisiloxane, and polydimethylsiloxane hydroxyurethane containing phosphotungstate for use in fuel cell membranes, and production of photochromic windows. It also investigated Ormosil containing phosphotungstate occluded in a polyimide matrix with potential application to hydrogen storage, fuel cell membranes, and insulating and anticorrosion coatings.<br /><br /> Quantification and mapping of photoactive elements are important to promote the development of these materials. However, these are not trivial tasks due to the intrinsic nature of these hybrid materials in which organic and inorganic phases are closely linked and the presence of a large number of chemicals elements interferes with the analysis. Since these hybrid materials constitute complex matrices to analyze, it is necessary to develop and examine specific analytical methods. In order to better understand the photochromic, anticorrosive, and mechanical properties of these materials, it is important to identify the distribution of silicates and phosphotungstates inside the films.<br /><br /> Selfabsorption interference studies of Tungsten XRay fluorescence by the others constituents in the Ormosil films led us to approach quantification by XRF, not only from the atomic perspective, but also to supplement with the molecular approach. XRay Resonant Raman Scattering (XRS) was equally important to explain interference phenomena observed in these complex systems. <br /><br /> It was possible to identify and detect Ti dopant in the range of tens of mg.Kg1 by means of Grazing Incidence XRay Fluorescence (GIXRF) analysis assisted by Synchrotron Radiation. In addition, Microscopic Xray Fluorescence analysis (&micro;XRF) assisted by Synchrotron Radiation enabled the identification of spatial distributions of Titanium and Zinc within ormosils. Since these XRF analyses did not employ certified materials for validation, standards were prepared at our laboratory following a similar protocol to that used to prepare the samples. The semiquantification method based on fundamental parameters was also used, which demonstrated be very useful and efficient. Xray fluorescence results were validated by those obtained from Inductively Coupled Plasma Optical Emission Spectrometry (ICPOES) and Instrumental Neutron Activation Analysis (INAA). The different methods of analysis employed (&micro;XRF, GIXRF, EDXRF, ICPOES, AAS) were effective regarding precision and accuracy in Tungsten and Zinc quantification. In the case of Titanium, however, only &micro;XRF and ICPOES results could be taken into account. Therefore, there is the need for additional analytical methods to validate concentration results for this element in ormosils. ICPOES and INAA proved to be reference methods for results obtained through XRF (Laboratory and assisted by Synchrotron Radiation) for our materials.

A determinação direta de arsênio total em águas por espectrometria de absorção atômica com filamentos de tungstênio (150 W) modificados quimicamente com irídio ou ródio, representa uma alternativa para a atomização eletrotérmica de arsênio, que foi avaliada na presente dissertação. A utilização do revestimento com Ir como modificador químico proporcionou um aumento da massa característica de arsênio de 3,5 vezes. As medidas foram feitas com altura de observação selecionada para proporcionar a melhor razão sinal/ruído sem diminuir a sensibilidade do sinal analítico. Avaliaram-se dois programas de aquecimento: com temperatura de secagem constante (com diminuição gradativa da tensão aplicada) e com temperatura de secagem variável (com tensão aplicada de maneira constante). Não houve diferença na sensibilidade entre os dois programas estudados, indicando que a modificação química leva à formação de um precursor atômico com estabilidade térmica elevada. De fato, utilizando-se a modificação química permanente com 1000 müg Ir, e adotando-se programa de aquecimento com temperatura de secagem variável, a temperatura máxima de pirólise foi de aproximadamente 1700 °C ( temperatura de atomização de 2700 °C). Avaliou-se o comportamento eletrotérmico do As na presença dos concomitantes Na, K, Ca e Mg em 0,1% v/v HNO3. Interferências mais severas foram observadas na presença de cálcio acima de 10 \'mü\'g l-1, e acima de 100 \'mü\'g l-1 para os demais concomitantes. As interferências podem estar relacionadas com o elevado gradiente de temperatura entre a superfície do filamento e a fase gasosa do volume de observação, ou mesmo devido à formação de compostos refratários, particularmente para Ca e Mg, na fase condensada, ou seja, na superfície do atomizador. O emprego do método das médias móveis no tratamento dos sinais transientes gerados na atomização do arsênio também foi avaliada. Com o filamento posicionado na altura de observação 2 mm, foram utilizados os fatores 0, 3, 5, 7 e 9, observando-se melhora considerável nos limites de detecção instrumental e do método,utilizando-se média móvel com fator 7. Nestas condições, e depositando-se 20 \'mü\'l de amostra sobre o filamento, o limite de detecção foi de 3,2 \'mü\'g l-1 As e a massa característica de 37,0 pg As. A exatidão foi avaliada analisando-se diferentes amostras de águas provenientes da região do Quadrilátero Ferrífero do Estado de Minas Gerais, por espectrometria de fluorescência atômica com geração de hidretos e por espectrometria de absorção atômica com o filamento de tungstênio modificado com Ir. A comparação dos resultados mostrou que o método proposto pode ser utilizado para o controle de qualidade de águas desta região. Aproximadamente 150 queimas podem ser feitas com um único filamento de tungstênio / The direct determination of arsenic in waters by atomic absorption spectrometry with 150 W tungsten coils, treated with Ir or Rh, was evaluated as a possible alternative for the eletrothermal atomization of As. The use of iridium as a permanent chemical modifier did improve the characteristic mass of arsenic by 3.5 fold. Measurements were made by choosing an appropriate observation height in order to get the best signal to noise ratio. Two heating programs were tested, either by keeping the applied voltage constant or by using an inverted voltage ramp during the drying step. There were no significant differences in the sensitivities between both heating programs, indicating that the permanent modification lead to the formation of an atomic precursor of high thermal stability. Indeed, with the permanent chemical modification with 1000 \'mü\'g Ir, the maximum pyrolysis temperature was approximately 1700 °C (atomization temperature 2700 °C), allowing a heating program with temperature variation during the drying step. Method selectivity was carried out by evaluating the eletrothermal behavior of As in the presence of up to 1000 \'mü\'g l-1 Na, K, Ca and/or Mg in 0,1% v/v HNO3. The most serious interferences were observed with Ca in concentrations higher than 10 \'mü\'g l-1 and when the concentrations were higher than 100 \'mü\'g l-1 for Na, K or Mg, which can be attributed either to the gradient of temperature between the surface of the atomizer and the observation volume or to the formation of refractory compounds in the condensed phase, particularly with Ca and Mg. The absorbance transient signals treatment by the method of moving averages up to factor 9 was also evaluated, with a remarkable improvement in the instrumental and method detection limits. With the center of the observation volume 2 mm above the tungsten coil surface, and a moving average of factor 7, the limit of detection was 3,2 \'müg\' l-1 As and the characteristic mass 37,0 pg As. Accuracy was evaluate by analysing water samples collected in a contaminated area from the Quadrilátero Ferrífero, Minas Gerais State, by hydride generation atomic fluorescence spectrometry and by tungsten coil eletrothermal atomic absorption spectrometry. Results showed that the proposed method fits for the purpose of CONAMA 357 regulation for drinking water quality in the aforementioned contaminated area. Approximately 150 firings can be done with a single tungsten coil atomizer by using 20 \'mü\'l sample volume

[pt] Em mercados onde há competição perfeita não há margem para os agentes maximizarem seus lucros através de comportamento não competitivo. Entretanto, o que se observa em mercados de energia elétrica se aproxima mais de um oligopólio do que de um mercado com competição perfeita. Se a competição não é perfeita, os agentes de geração podem tentar estabelecer estratégias de oferta de preços de forma a maximizar seus lucros. Nesta tese investiga-se a possibilidade de estabeler estratégias ótimas de oferta de preços no mercado de curto prazo em sistemas com predominância hidrelétrica, com ênfase no sistema brasileiro. São avaliados o estabelecimento de estratégias ótimas e o nível de poder de mercado nos dois possíveis esquemas de formação de preço utilizados em sistemas com predominância hidrelétrica. O atualmente utilizado no Brasil, denominado tight pool, em que preços e despachos são determinados centralizadamente através de modelos computacionais de otimização, e onde apenas os geradores termelétricos podem fazer ofertas de preços, e em um possível esquema geral de oferta de preços, onde os geradores hidrelétricos também ofertam preços. O poder de mercado é estudado através de modelos de competição oligopolista baseados na teoria dos jogos, e através de medidas de concentração de mercado. No caso do estabelecimento de estratégias ótimas de oferta de preços, um ponto crucial é a modelagem do comportamento de oferta dos agentes competidores. Em função da inexistência de dados históricos, o comportamento de oferta dos competidores é modelado através de distribuições de probabilidade triangulares, equivalentes a funções de pertinência típicas de uma modelagem fuzzy. Mostra-se para o sistema brasileiro que no tight pool a possibilidade do uso de ofertas estratégicas de preços e conseqüentemente o poder de mercado dos geradores termelétricos são bastante reduzidos. Já para um esquema geral de ofertas, o poder de mercado dos geradores hidrelétricos pode ser significativo, sendo que comportamentos agressivos podem levar o sistema a condições de suprimento críticas, se mecanismos de mitigação de poder mercado não forem estabelecidos. / [en] In perfectly competitive markets, there are no loopholes that can be exploited by agents to maximize profit through non-competitive behavior. However, electricity markets look more like an oligopoly than perfectly competitive markets. If competition is not perfect, generation agents may try to establish optimum price bidding strategies to maximize profits. If an agent is able to increase profits through other means than reducing costs, it is said to have market power. This thesis investigates the possibility of establishing optimum price bidding strategies in the short- term market of systems with hydroelectric predominance, with emphasis in the Brazilian system. The possibility of establishing optimum price bidding strategies and thus market power are evaluated in the two possible price formation schemes used in hydrodominated systems. The one currently used in Brazil, known as tight pool, where price are determined centrally through optimization models, and where only the thermal generators bid prices. Market power is also evaluated in a general price bidding scheme, where hydro generators also bid prices. Market power is evaluated trough an oligopoly model from game theory and through market concentration measures. In establishing optimum price bidding strategies, one crucial issue is modeling competitors`s price bidding behavior. Due to the lack of historical data, the price bidding behavior of the competitors is modeled by triangular probability distributions, equivalent to some membership functions typically used in fuzzy modeling. It is shown for the Brazilian system that in a tight pool scheme the market power and thus the possibility of establishing optimum bidding strategies are very limited. On the other hand, in a general price bidding scheme the market power of hydro generators may be significant and aggressive behavior may lead the system to critical supply conditions, if no market power mitigation mechanism is implemented.

A rapid, mask-less deposition technique for writing metal tracks has been developed. The technique was based on laser-induced chemical vapour deposition. The novelty in the technique was the usage of pulsed ultrafast lasers instead of continuous wave lasers in pyrolytic dissociation of the chemical precursor. The motivation of the study was that (1) ultrafast laser pulses have smaller heat affected zones thus the deposition resolution would be higher, (2) the ultrashort pulses are absorbed in most materials (including those transparent to the continuous wave light at the same wavelength) thus the deposition would be compatible with a large range of materials, and (3) the development of higher frequency repetition rate ultrafast lasers would enable higher deposition rates. A deposition system was set-up for the study to investigate the ultrafast laser deposition of tungsten from tungsten hexacarbonyl chemical vapour precursors. A 405 nm laser diode was used for continuous wave deposition experiments that were optimized to achieve the lowest track resistivity. These results were used for comparison with the ultrafast laser track deposition. The usage of the 405 nm laser diode was itself novel and beneficial due to the low capital and running cost, high wall plug efficiency, high device lifetime, and shallower optical penetration depth in silicon substrates compared to green argon ion lasers which were commonly used by other investigators. The lowest as-deposited track resistivity achieved in the continuous wave laser experiments on silicon dioxide coated silicon was 93±27 µΩ cm (16.6 times bulk tungsten resistivity). This deposition was done with a laser output power of 350 mW, scan speed of 10 µm/s, deposition pressure of 0.5 mBar, substrate temperature of 100 °C and laser spot size of approximately 7 µm. The laser power, scan speed, deposition pressure and substrate temperature were all optimized in this study. By annealing the deposited track with hydrogen at 650 °C for 30 mins, removal of the deposition outside the laser spot was achieved and the overall track resistivity dropped to 66±7 µΩ cm (11.7 times bulk tungsten resistivity). For ultrafast laser deposition of tungsten, spot dwell experiments showed that a thin film of tungsten was first deposited followed by quasi-periodic structures perpendicular to the linear polarization of the laser beam. The wavelength of the periodic structures was approximately half the laser wavelength (λ/2) and was thought to be formed due to interference between the incident laser and scattered surface waves similar to that in laser-induced surface periodic structures. Deposition of the quasi-periodic structures was possible on stainless steel, silicon dioxide coated silicon wafers, borosilicate glass and polyimide films. The thin-films were deposited when the laser was scanned at higher laser speeds such that the number of pulses per spot was lower (η≤11,000) and using a larger focal spot diameter of 33 µm. The lowest track resistivity for the thin-film tracks on silicon dioxide coated silicon wafers was 37±4 µΩ cm (6.7 times bulk tungsten resistivity). This value was achieved without post-deposition annealing and was lower than the annealed track deposited using the continuous wave laser. The ultrafast tungsten thin-film direct write technique was tested for writing metal contacts to single layer graphene on silicon dioxide coated silicon substrates. Without the precursor, the exposure of the graphene to the laser at the deposition parameters damaged the graphene without removing it. This was evidenced by the increase in the Raman D peak of the exposed graphene compared to pristine. The damage threshold was estimated to be 53±7 mJ/cm2 for a scanning speed of 500 µm/s. The deposition threshold of thin-film tungsten on graphene at that speed was lower at 38±8 mJ/cm2. However, no graphene was found when the deposited thin-film tungsten was dissolved in 30 wt% H2O2 that was tested to have no effect on the graphene for the dissolution time of one hour. The graphene likely reacted with the deposited tungsten to form tungsten carbide which was reported to dissolve in H2O2. Tungsten carbide was also found on the tungsten tracks deposited on reduced graphene oxide samples. The contact resistance between tungsten and graphene was measured by both transfer length and four-point probe method with an average value of 4.3±0.4 kΩ µm. This value was higher than reported values using noble metals such as palladium (2.8±0.4 kΩ µm), but lower than reported values using other metals that creates carbides such as nickel (9.3±1.0 kΩ µm). This study opened many potential paths for future work. The main issue to address in the tungsten ultrafast deposition was the deposition outside the laser spot. This prevented uniform deposition in successive tracks close to one another. The ultrafast deposition technique also needs verification using other precursors to understand the precursor requirements for this process. An interesting future study would be a combination with a sulphur source for the direct write of tungsten disulphide, a transition metal dichalcogenide that has a two-dimensional structure similar to graphene. This material has a bandgap and is sought after for applications in high-end electronics, spintronics, optoelectronics, energy harvesting, flexible electronics, DNA sequencing and personalized medicine. Initial tests using sulphur micro-flakes on silicon and stainless-steel substrates exposed to the tungsten precursor and ultrafast laser pulses produced multilayer tungsten disulphide as verified in Raman measurements.

[pt] Aplicação de duas metodologias, para prever e modelar o comportamento de uma serie temporal de carga de energia elétrica, a serie histórica de carga elétrica horária de uma das concessionárias de energia elétrica do sudeste brasileiro, a ESCELSA. Foram aplicadas as metodologias de amortecimento direto, e uma metodologia recente, o método de Holt-Winters com múltiplos ciclos. Ambas as metodologias são utilizadas para fazer previsão horária de carga de energia elétrica, portanto, é feita, previsão 24 passos a frente. / [en] Application of two diferent metodologies, in order to model and forecast the behavior of time series of hourly electrical loads generated by ESCELSA. Was applied to the time series studied the metodology of the direct smoothing, and also a recent metodology, the Holt-Winters with multiple sazonalities. In both of them it has been done the hourly forecast (24 hours load forecasting).

The purpose of this study was to evaluate four different measuring methods as potentialquality control tests for Tungsten Carbide (WC) raw material used in the hard metalmanufacturing at Seco Tools Fagersta. This was warranted as the current quality testcalled the HcK test, is very time consuming and the results provided that are used formilling time calculations cannot be relied on. The four measuring methods chosen wasLaser diffraction, X-Ray diffraction, Brunauer Emmett Teller analysis and Fisher Sub-Sieve Sizer measurement. These measuring techniques were chosen by Seco ToolsThe project followed the general structure of the project cycle modified to fit the projectand involving the steps project planning, present state analysis, goals and requirementdetermination, evaluation elimination of options and final of choice of option. Thealternative methods were evaluated using an evaluation matrix containing therequirements determined to be the most relevant for the quality control process. Therequirements were measurement precision, operator influence, ease of use, time requiredand operator time required. The ability of the measurement method to distinguishbetween all of the different WC powders used a Seco Tools was put as a must requirementas the new method is meant to serve as a verification test as well as a quality test.The analysis methods were evaluated practically through experiments and therefore atesting strategy was established. Initial test on two powder types was performed so thatan early evaluation could be done. During this stage both the Laser diffraction and the XRaydiffraction were eliminated due to poor results. The BET analysis and the Fisher Sub-Sieve Sizer performed better and was therefore tested further. Randomized testing wasthe method chosen when testing with all powders to minimize the environmental impacton the testing as this could affect the results of the study.The testing showed that only the Fisher SSS was able to distinguish between all thedifferent powders making it the only viable option as a new quality test. This was onlypossible when measuring on agglomerated material and the values extracted couldtherefore not be used further in the production. The Fisher SSS also performed the bestwhen ranked against the rest of the requirements, showing a high precision whenmeasuring on deagglomerated material and a combination of the two tests was thereforeconsidered.When compared to the HcK test the Fisher SSS showed a significant reduction in lead timebut also a reduction in information gathered and eventual defects controlled. The FisherSSS provides only an average particle size measurement and since no correlation has yetbeen established between the measured particle size and the required milling times it wasrecommended that the HcK test remains.It was recommended that a study is started aimed at establishing a correlation betweenthe measured particle size and the required milling time is started to investigate if this ispossible.