O trabalho apresenta uma discussão sobre o nível de contratação ótima dos geradores hidroelétricos participantes do Mecanismo de Realocação de Energia (MRE), considerando a influência dos Procedimentos Operativos de Curto Prazo (POCP). O assim denominado POCP é um conjunto de procedimentos realizados pelo Operador Nacional do Sistema (ONS) para proporcionar mais segurança no atendimento à carga do Sistema Interligado, sendo realizado no período de abril a novembro, durante o Programa Mensal de Operação (PMO). O gerador hidráulico, em função do despacho centralizado e normativo adotado no Brasil, dependendo da quantidade de água que aflui aos reservatórios e do consequente despacho das usinas determinado pelo ONS, fica sujeito às exposições no mercado de curto prazo, decorrentes da diferença entre os contratos de venda do gerador e o montante de garantia física (GF) alocada mensalmente após a realização do MRE. Como o POCP não está incorporado nos modelos de despacho das usinas do setor elétrico, uma alternativa de simulação foi construída e, a partir dos seus resultados, pode-se perceber a interferência do mecanismo em tela nas exposições no mercado de curto prazo e no patamar de risco incorrido. A aplicação do POCP traz um efeito líquido de redução da geração hidrelétrica, pois se diminui a possibilidade de utilizar a capacidade de regularização dos reservatórios, evitando riscos de eventual não recuperação dos reservatórios no período chuvoso. Por outro lado, o procedimento conservador hoje utilizado pode gerar um volume muito maior de vertimentos durante o período úmido, limitando a chance de recuperação financeira dos geradores hidrelétricos que tiveram sua geração reduzida no período seco devido ao despacho antecipado de termelétricas, fatalmente com rebatimentos traduzidos por exposições ao PLD. Por conta de todos os fatores de risco citados, os agentes geradores precisam ajustar sua estratégia ótima de contratação, mantendo a função objetivo de maximizar a receita, condicionado a critérios de risco, que ponderem os fatores citados. Nessa perspectiva, foi analisada a aplicação do POCP no ano de 2010 e seus impactos, além de simular a receita esperada e o risco futuro com e sem a aplicação deste mecanismo. Os resultados mostram o quanto o POCP interfere na receita esperada dos agentes, agregando maiores riscos e alterando-se o nível de contratação ótima. Sendo assim, dependendo do risco que cada agente gerador está disposto a assumir, uma revisão de seu nível de contratação torna-se imperiosa. / This work presents a discussion about the optimal level of energy contracting of the Hydroelectric Generators participants of the Energy Reallocation Mechanism, (MRE - Mecanismo de Realocação de Energia), considering the influence of Short Term Operating Procedures (POCP - Procedimentos Operativos de Curto Prazo). The POCP is a set of procedures performed by the National System Operator (ONS - Operador Nacional do Sistema) to provide more security in the Interconnected System, being carried out from April to November, during the Monthly Programme Operation (PMO - Programa Mensal de Operação). Hydro plants are subject to exposure in short-term market due to the centralized dispatch adopted in Brazil, which depends on the amount of water that flows to the reservoir and on the subsequent dispatch of plants determined by the ONS. The exposure in short-term market, arises from the difference between the Generator sales contracts and the amount of assured energy (GF - Garantia Física) monthly allocated after the MRE. As the POCP is not incorporated into the dispatch models of the electricity sector, an alternative simulation was built and, from its results, we can notice the interference of the mechanism displayed in the short-term market and in the incurred risk level. The application of the POCP brings a net reduction in hydropower generation, because it decreases the possibility of using the regularization capacity of the reservoirs, avoiding any risk of non recovery of the reservoirs during the rainy season. On the other hand, the conservative procedure used today can generate a much larger volume of spilling water during the wet season, limiting the chance of financial recovery of hydroelectric dams that had their generation reduced in the dry season due to the anticipated dispatch of thermoelectric plants, inevitably with repercussions represented by exposure to the PLD (SPOT). Considering all risk factors mentioned, the generating agents have to adjust their optimal strategy for contract level, retaining the objective function to maximize revenue, conditional to risk criteria, which consider the factors mentioned. From this perspective, we analyzed the application of the POCP in 2010 and its impacts, as well as simulated the expected revenue and the future risk with and without the application of this procedure. The results show how the POCP interferes in the expected revenue of the agents, adding greater risks and changing the optimal level of energy contracting. Thus, depending on the risk that each generating agent is willing to take, a review of their contracting level becomes imperative.

O trabalho apresenta uma discussão sobre o nível de contratação ótima dos geradores hidroelétricos participantes do Mecanismo de Realocação de Energia (MRE), considerando a influência dos Procedimentos Operativos de Curto Prazo (POCP). O assim denominado POCP é um conjunto de procedimentos realizados pelo Operador Nacional do Sistema (ONS) para proporcionar mais segurança no atendimento à carga do Sistema Interligado, sendo realizado no período de abril a novembro, durante o Programa Mensal de Operação (PMO). O gerador hidráulico, em função do despacho centralizado e normativo adotado no Brasil, dependendo da quantidade de água que aflui aos reservatórios e do consequente despacho das usinas determinado pelo ONS, fica sujeito às exposições no mercado de curto prazo, decorrentes da diferença entre os contratos de venda do gerador e o montante de garantia física (GF) alocada mensalmente após a realização do MRE. Como o POCP não está incorporado nos modelos de despacho das usinas do setor elétrico, uma alternativa de simulação foi construída e, a partir dos seus resultados, pode-se perceber a interferência do mecanismo em tela nas exposições no mercado de curto prazo e no patamar de risco incorrido. A aplicação do POCP traz um efeito líquido de redução da geração hidrelétrica, pois se diminui a possibilidade de utilizar a capacidade de regularização dos reservatórios, evitando riscos de eventual não recuperação dos reservatórios no período chuvoso. Por outro lado, o procedimento conservador hoje utilizado pode gerar um volume muito maior de vertimentos durante o período úmido, limitando a chance de recuperação financeira dos geradores hidrelétricos que tiveram sua geração reduzida no período seco devido ao despacho antecipado de termelétricas, fatalmente com rebatimentos traduzidos por exposições ao PLD. Por conta de todos os fatores de risco citados, os agentes geradores precisam ajustar sua estratégia ótima de contratação, mantendo a função objetivo de maximizar a receita, condicionado a critérios de risco, que ponderem os fatores citados. Nessa perspectiva, foi analisada a aplicação do POCP no ano de 2010 e seus impactos, além de simular a receita esperada e o risco futuro com e sem a aplicação deste mecanismo. Os resultados mostram o quanto o POCP interfere na receita esperada dos agentes, agregando maiores riscos e alterando-se o nível de contratação ótima. Sendo assim, dependendo do risco que cada agente gerador está disposto a assumir, uma revisão de seu nível de contratação torna-se imperiosa. / This work presents a discussion about the optimal level of energy contracting of the Hydroelectric Generators participants of the Energy Reallocation Mechanism, (MRE - Mecanismo de Realocação de Energia), considering the influence of Short Term Operating Procedures (POCP - Procedimentos Operativos de Curto Prazo). The POCP is a set of procedures performed by the National System Operator (ONS - Operador Nacional do Sistema) to provide more security in the Interconnected System, being carried out from April to November, during the Monthly Programme Operation (PMO - Programa Mensal de Operação). Hydro plants are subject to exposure in short-term market due to the centralized dispatch adopted in Brazil, which depends on the amount of water that flows to the reservoir and on the subsequent dispatch of plants determined by the ONS. The exposure in short-term market, arises from the difference between the Generator sales contracts and the amount of assured energy (GF - Garantia Física) monthly allocated after the MRE. As the POCP is not incorporated into the dispatch models of the electricity sector, an alternative simulation was built and, from its results, we can notice the interference of the mechanism displayed in the short-term market and in the incurred risk level. The application of the POCP brings a net reduction in hydropower generation, because it decreases the possibility of using the regularization capacity of the reservoirs, avoiding any risk of non recovery of the reservoirs during the rainy season. On the other hand, the conservative procedure used today can generate a much larger volume of spilling water during the wet season, limiting the chance of financial recovery of hydroelectric dams that had their generation reduced in the dry season due to the anticipated dispatch of thermoelectric plants, inevitably with repercussions represented by exposure to the PLD (SPOT). Considering all risk factors mentioned, the generating agents have to adjust their optimal strategy for contract level, retaining the objective function to maximize revenue, conditional to risk criteria, which consider the factors mentioned. From this perspective, we analyzed the application of the POCP in 2010 and its impacts, as well as simulated the expected revenue and the future risk with and without the application of this procedure. The results show how the POCP interferes in the expected revenue of the agents, adding greater risks and changing the optimal level of energy contracting. Thus, depending on the risk that each generating agent is willing to take, a review of their contracting level becomes imperative.

Magnetic Resonance Elastography is a method of imaging the elasticity of soft tissues through measurement of small motions induced into a sample. It shows great promise in the detection of a wide variety of pathologies, especially tumours. An imaging protocol was developed to acquire MR elastography data for use in a clinical setting. A 3D gradient echo sequence was modified to allow for the detection of harmonic motion and tested on silicone phantoms and ex-vivo muscle and brain samples. The time for acquiring a high resolution, quantitative dataset of 3D motions was about 45 minutes. Our imaging method included motion encoding along all three coordinate axes and at several time points along the motion cycle. This time could be easily be reduced by more than half for future clinical use, while still retaining full quantitative data. A modified EPI sequence shows promise for even faster acquisition. The ability to detect the mechanical anisotropy of brain and muscle tissue in ex-vivo samples was also investigated. Initial results from the muscle data indicate a change in shear wavelength is observed for actuation along orthogonal axes. This is a strong indicator of anisotropy detection. Further work needs to be done to improve results from the brain sample as preliminary results are inconclusive.

The interpretation of heart&#039 / s electrical activity is very important in clinical medicine since contraction of cardiac muscles is initiated by the electrical activity of the heart. The electrocardiogram (ECG) is a diagnostic tool that measures and records the electrical activity of the heart. The conventional 12 lead ECG is a clinical tool that provides information about the heart status. However, it has limited information about functionality of heart due to limited number of recordings. A better alternative approach for understanding cardiac electrical activity is the incorporation of body surface potential measurements with torso geometry and the estimation of the equivalent cardiac sources. The problem of the estimating the cardiac sources from the torso potentials and the body geometry is called the inverse problem of electrocardiography. The aim of this thesis is reconstructing accurate high resolution maps of epicardial potential representing the electrical activity of the heart from the body surface measurements. However, accurate estimation of the epicardial potentials is not an easy problem due to ill-posed nature of the inverse problem. In this thesis, the linear inverse ECG problem is solved using different optimization techniques such as Conic Quadratic Programming, multiple constrained convex optimization, Linearly Constrained Tikhonov Regularization and Minimum Relative Entropy (MRE) method. The prior information used in MRE method is the lower and upper bounds of epicardial potentials and a prior expected value of epicardial potentials. The results are compared with Tikhonov Regularization and with the true potentials.

Magnetic Resonance Elastography is a method of imaging the elasticity of soft tissues through measurement of small motions induced into a sample. It shows great promise in the detection of a wide variety of pathologies, especially tumours. An imaging protocol was developed to acquire MR elastography data for use in a clinical setting. A 3D gradient echo sequence was modified to allow for the detection of harmonic motion and tested on silicone phantoms and ex-vivo muscle and brain samples. The time for acquiring a high resolution, quantitative dataset of 3D motions was about 45 minutes. Our imaging method included motion encoding along all three coordinate axes and at several time points along the motion cycle. This time could be easily be reduced by more than half for future clinical use, while still retaining full quantitative data. A modified EPI sequence shows promise for even faster acquisition. The ability to detect the mechanical anisotropy of brain and muscle tissue in ex-vivo samples was also investigated. Initial results from the muscle data indicate a change in shear wavelength is observed for actuation along orthogonal axes. This is a strong indicator of anisotropy detection. Further work needs to be done to improve results from the brain sample as preliminary results are inconclusive.

Marine Renewable Energy (MRE) is a promising source of energy for the future. However, it is still under development and many challenges need to be overcome to develop competitive solutions. While the design of the station keeping system of traditional offshore oil and gas structures is driven mainly by their low frequency motions, MRE devices are installed at nearshore locations and move dynamically. Because of these criteria, MRE mooring systems require novel mooring systems and associated standards. MRE mooring standards need to take into account the highly dynamic behaviour of these systems, which can lead to large mooring loads. The nature of these loads needs to be investigated to improve the confidence in mooring design and to improve cost-effectiveness. The aim of this thesis is to develop the understanding of peak mooring loads on highly dynamic mooring systems, in particular, the environmental conditions associated with the loads. In addition, preliminary research into the response of the mooring systems to environmental conditions is presented. Both field tests and tank tests have been conducted. Field tests give insight into the behaviour of a dynamic mooring system in real sea conditions. Measuring the mooring loads and the environmental conditions - wave, and current if available – for several months, a methodology has been developed to detect peak mooring loads and identify the associated environmental conditions in order to compare them with the environmental conditions recorded throughout the field tests. The principal finding is that peak mooring loads occur for sea states with large but not always the highest significant wave height HS. The understanding of the effect of tidal conditions on peak mooring loads requires further work. A tank test of a dynamic mooring system in moderate sea states has been conducted to observe the dynamic behaviour of the mooring system. Tank tests enable detailed observations of the dynamic behaviour of a system in a well controlled environment and allow the calibration of a numerical model. The model can be used to investigate separate physical parameters. The results from this thesis will assist in the development of specific standards for MRE mooring systems. These standards are essential for the evolution of the MRE industry.

Le terme élastographie désigne les techniques d'imagerie dédiées à l'étude des propriétés mécaniques des tissus biologiques in vivo. Au cours de cette thèse, nous nous sommes intéressés à deux de ces techniques. La première est l'élastographie quasi-statique par ultrasons permettant de mesurer les déformations locales induites dans un tissu sous l'action d'une contrainte globale. La seconde est l'élastographie par résonance magnétique (ERM) permettant d'accéder localement à une estimation du module de cisaillement. Pour cette dernière technique, une onde de cisaillement est générée au sein du milieu puis imagée a l'aide d'une séquence IRM spécifique. Les images d'ondes acquises permettent la reconstruction du module de cisaillement local. Dans le cadre de ces travaux, une nouvelle technique d'acquisition de l'image d'onde de cisaillement a été proposée, ainsi qu'une méthode de reconstruction du module de cisaillement basée sur l'estimation locale de fréquence par rapport de filtres. Un autre axe de recherche a consisté en l'étude de l'effet d'une précontrainte appliquée à un milieu sur son module de cisaillement mesuré par ERM. Cet effet a tout d'abord été étudié sur des milieux homogènes puis avec des milieux test hétérogènes. Dans ce dernier cas, l'utilisation de l'élastographie quasi-statique par ultrasons s'avère nécessaire pour accéder à la déformation locale du milieu. Cette dernière information a été combinée avec les informations obtenues en ERM pour extraire pour chaque région d'intérêt une courbe déformation/module de cisaillement / The term elastography refers to imaging techniques dedicated to the in vivo investigation of the mechanical properties of biological tissues. During this thesis, we focused on two elastography techniques. The first one is quasi-static ultrasound elastography, able to locally estimate tissue strain induced by a global deformation of a medium. The second one is Magnetic Resonance Elastography (MRE), able to measure the local shear modulus. In MRE, a shear wave is generated within the medium and imaged using a specific MRI sequence. The resulting wave images are then processed to estimate the local shear modulus. A new acquisition scheme of the shear wave images was proposed during this thesis. A method, based on local frequency estimation, was also developed for the estimation of the local shear modulus using the properties of a ratio of filters. Another research axis was the study of the effect of a prestrain application on the measured shear modulus. This effect was first studied with homogeneous media and then with heterogeneous test objects. In this last case, the use of quasi-static ultrasound elastography was necessary to locally access to the medium strain. This information was then combined with the information obtained using MRE to extract, for each region of interest, a strain/shear modulus curve

No description available.

No description available.

O setor elétrico brasileiro é composto, majoritariamente, por usinas hidrelétricas, cuja operação é realizada de forma centralizada pelo Operador Nacional do Sistema (ONS). Devido às características do setor, foi criado durante a década de 1990 o Mecanismo de Realocação de Energia (MRE) com o intuito de compartilhar o risco hidrológico entre as usinas participantes deste mecanismo, o qual é medido pelo Generation Scaling Factor (GSF). Entre os anos de 2014 e 2015, o Brasil enfrentou um período de escassez hídrica que impactou negativamente o caixa dos geradores hídricos. Estes, insatisfeitos com o cenário, articularam-se junto à Agência Nacional de Energia Elétrica (ANEEL) e ao Ministério de Minas e Energia (MME) para que o risco hidrológico fosse transferido para os consumidores. A agência reguladora posicionou-se contrária ao pleito dos geradores na primeira fase da Audiência Pública 32/2015, que tratou do tema em questão, entretanto o governo editou a Medida Provisória 688/2015 que possibilitou a repactuação do risco hidrológico mediante um pagamento de prêmio de risco pelos geradores hídricos. Neste contexto, esta dissertação foi desenvolvida com o objetivo principal de avaliar o processo de repactuação do risco hidrológico, a partir dos estudos sobre a evolução da Teoria da Regulação, com foco na atuação dos grupos de interesse. Os resultados indicam possibilidade em aplicar os pressupostos da Teoria dos Grupos de Interesse, principalmente a abordagem de Pelztman (1976), no processo de repactuação do risco hidrológico, demonstrando que: (i) a regulação surge como demanda dos grupos de interesse; (ii) a regulação tende a beneficiar os grupos de interesse que forem mais ativos politicamente; (iii) os agentes envolvidos no processo de regulação atuam para maximizar sua própria utilidade; e (iv) a regulação tende a beneficiar grupos de interesse cujo benefício per capita seja maior. / The Brazilian Power sector consists of hydroelectric plants, whose operation is performed centrally by the mainly National System Operator. Due to the system characteristics, during the 1990s, was created the Energy Reallocation Mechanism in order to share hydrological risk among mechanism\'s participating, which is measured by the Generation Scaling Factor (GSF). Between 2014 and 2015, Brazil faced a water scarcity period that negatively affected the hydropower generators revenue. The generators unsatisfied with this situation have started seek to influence the electricity regulatory agency and the Ministry of Mines and Energy in order to transferred the hydrologic risk to consumers. The regulatory agency has positioned itself against the claim of the generators in the first phase of the Public Hearing 32/2015, but the government has published Interim Measure 688/2015 which allowed the renegotiation of the hydrological risk through a premium risk payment by hydropower generators. In this context, this work was developed with the main objective of analysing the renegotiation process of hydrological risk, such analysis was based on the evolution of regulation theory studies, focusing on the role of interest groups. The results indicate the possibility of applying the assumptions of Theory of Economics Regulation, mainly the Pelztman (1976) approach, on the renegotiation of the hydrological risk process demonstrating that: (i) regulation is supplied in reponse to the interest groups demand for regulation; (ii) regulation is most likely to benefit the interest groups that are more active politically; (iii) agents involved in the regulatory process act to maximize their own utility; and (iv) regulation trends to benefit interest groups which highest per capita benefit.