The rodent navigation system has been the focus of study for over a century. Discoveries made lately have provided insight on the inner workings of this system. Since then, computational approaches have been used to test hypothesis, as well as to improve robotics navigation and learning by taking inspiration on the rodent navigation system. This dissertation focuses on the study of the multi-scale representation of the rat’s current location found in the rat hippocampus. It first introduces a model that uses these different scales in the Morris maze task to show their advantages. The generalization power of larger scales of representation are shown to allow for the learning of more coherent and complete policies faster. Based on this model, a robotics navigation learning system is presented and compared to an existing algorithm on the taxi driver problem. The algorithm outperforms a canonical Q-Learning algorithm, learning the task faster. It is also shown to work in a continuous environment, making it suitable for a real robotics application. A novel task is also introduced and modeled, with the aim of providing further insight to an ongoing discussion over the involvement of the temporal portion of the hippocampus in navigation. The model is able to reproduce the results obtained with real rats and generates a set of empirically verifiable predictions. Finally, a novel multi-query path planning system is introduced, inspired in the way rodents represent location, their way of storing a topological model of the environment and how they use it to plan future routes. The algorithm is able to improve the routes in the second run, without disrupting the robustness of the underlying navigation system.

The objectives of this dissertation were to find a principal domain of promising and technologically feasible reactor physics characteristics for a multi-purpose, modular-sized, lead-cooled, fast neutron spectrum reactor fueled with an advanced uranium-transuranic-nitride fuel and to determine the principal limitations for the design of an autonomous long-term multi-purpose fast reactor (ALM-FR) within the principal reactor physics characteristic domain. The objectives were accomplished by producing a conceptual design for an ALM-FR and by analysis of the potential ALM-FR performance characteristics. The ALM-FR design developed in this dissertation is based on the concept of a secure transportable autonomous reactor for hydrogen production (STAR-H2) and represents further refinement of the STAR-H2 concept towards an economical, proliferation-resistant, sustainable, multi-purpose nuclear energy system. The development of the ALM-FR design has been performed considering this reactor within the frame of the concept of a self-consistent nuclear energy system (SCNES) that satisfies virtually all of the requirements for future nuclear energy systems: efficient energy production, safety, self-feeding, non-proliferation, and radionuclide burning. The analysis takes into consideration a wide range of reactor design aspects including selection of technologically feasible fuels and structural materials, core configuration optimization, dynamics and safety of long-term operation on one fuel loading, and nuclear material non-proliferation. Plutonium and higher actinides are considered as essential components of an advanced fuel that maintains long-term operation. Flexibility of the ALM-FR with respect to fuel compositions is demonstrated acknowledging the principal limitations of the long-term burning of plutonium and higher actinides. To ensure consistency and accuracy, the modeling has been performed using state-of-the-art computer codes developed at Argonne National Laboratory. As a result of the computational analysis performed in this work, the ALM-FR design provides for the possibility of continuous operation during about 40 years on one fuel loading containing mixture of depleted uranium with plutonium and higher actinides. All reactor physics characteristics of the ALM-FR are kept within technological limits ensuring safety of ultra-long autonomous operation. The results obtained provide for identification of physical features of the ALM-FR that significantly influence flexibility of the design and its applications. The special emphasis is given to existing limitations on the utilization of higher actinides as a fuel component.

The objectives of this dissertation were to find a principal domain of promising and technologically feasible reactor physics characteristics for a multi-purpose, modular-sized, lead-cooled, fast neutron spectrum reactor fueled with an advanced uranium-transuranic-nitride fuel and to determine the principal limitations for the design of an autonomous long-term multi-purpose fast reactor (ALM-FR) within the principal reactor physics characteristic domain. The objectives were accomplished by producing a conceptual design for an ALM-FR and by analysis of the potential ALM-FR performance characteristics. The ALM-FR design developed in this dissertation is based on the concept of a secure transportable autonomous reactor for hydrogen production (STAR-H2) and represents further refinement of the STAR-H2 concept towards an economical, proliferation-resistant, sustainable, multi-purpose nuclear energy system. The development of the ALM-FR design has been performed considering this reactor within the frame of the concept of a self-consistent nuclear energy system (SCNES) that satisfies virtually all of the requirements for future nuclear energy systems: efficient energy production, safety, self-feeding, non-proliferation, and radionuclide burning. The analysis takes into consideration a wide range of reactor design aspects including selection of technologically feasible fuels and structural materials, core configuration optimization, dynamics and safety of long-term operation on one fuel loading, and nuclear material non-proliferation. Plutonium and higher actinides are considered as essential components of an advanced fuel that maintains long-term operation. Flexibility of the ALM-FR with respect to fuel compositions is demonstrated acknowledging the principal limitations of the long-term burning of plutonium and higher actinides. To ensure consistency and accuracy, the modeling has been performed using state-of-the-art computer codes developed at Argonne National Laboratory. As a result of the computational analysis performed in this work, the ALM-FR design provides for the possibility of continuous operation during about 40 years on one fuel loading containing mixture of depleted uranium with plutonium and higher actinides. All reactor physics characteristics of the ALM-FR are kept within technological limits ensuring safety of ultra-long autonomous operation. The results obtained provide for identification of physical features of the ALM-FR that significantly influence flexibility of the design and its applications. The special emphasis is given to existing limitations on the utilization of higher actinides as a fuel component.

The aim of the thesis is to analyze the state of preparedness of nuclear power plants (NPP) for long term operation (LTO) based on the IAEA SALTO (Safety Aspects of Long Term Operation) peer review service, analysis of the most significant failures, accidents and operational experience with type reactors PWR/VVER focusing on cases caused by equipment ageing and identification of major structures and components limiting life time of PWR/VVER-type nuclear power plants, and possible measures to ensure their required service life. Based on the results of the IAEA SALTO peer review service, an analysis of the main deficiencies and measures of NPPs in preparation for a safe LTO was performed, focusing on topics whose deeper knowledge is important for the future more precise determination of technical factors limiting the lifetime of NPPs. The main deficiencies and measures in the preparatory phase for LTO and the most important technical measures are summarized in chapter 4.5. The main deficiencies and the most important technical corrective measures in the area of ageing management of structures and components are discussed separately. The history of major failures and operational experience of nuclear power plants with PWR/VVER reactors from the point of view of ageing of structures and components is analyzed in chapter 6.2. The result is a statistic analysis of ageing-related events, an overview of the most significant PWR/VVER reactor failures with an impact on their service life, a statistical overview and discussion of the most important degradation mechanisms, and other important findings from the history of major failures and operational experience. Chapter 6.3 analyzes factors limiting the operation of nuclear power plants with PWR/VVER reactors with focus on structures and components potentially limiting the life of PWR/VVER reactors and possible measures to ensure their required life. In conclusion, the main reasons of permanent shut down of NPPs (actual and potential) for 40, 60 and 80 years of operation and the measures to ensure their required life are summarized.

Submitted by Renata Lopes (renatasil82@gmail.com) on 2016-05-20T17:31:53Z No. of bitstreams: 1 wellingtoncarlosdaconceicao.pdf: 2412660 bytes, checksum: 31c07135427924fe90166a943adbbdd7 (MD5) / Rejected by Adriana Oliveira (adriana.oliveira@ufjf.edu.br), reason: Renata, somente a primeira letra de cada palavra chave é que deve ser em maiúsculo. Não corrigi esta para só para me lembrar de te falar. on 2016-07-02T11:26:49Z (GMT) / Submitted by Renata Lopes (renatasil82@gmail.com) on 2016-07-04T10:15:18Z No. of bitstreams: 1 wellingtoncarlosdaconceicao.pdf: 2412660 bytes, checksum: 31c07135427924fe90166a943adbbdd7 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2016-07-13T16:11:09Z (GMT) No. of bitstreams: 1 wellingtoncarlosdaconceicao.pdf: 2412660 bytes, checksum: 31c07135427924fe90166a943adbbdd7 (MD5) / Made available in DSpace on 2016-07-13T16:11:09Z (GMT). No. of bitstreams: 1 wellingtoncarlosdaconceicao.pdf: 2412660 bytes, checksum: 31c07135427924fe90166a943adbbdd7 (MD5) Previous issue date: 2012-08-02 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O presente trabalho apresenta uma metodologia alternativa para o atendimento da restrição associada à vazão mínima obrigatória no problema de planejamento da operação de médio prazo de sistemas hidrotérmicos interligados. Atualmente, a metodologia oficial adotada no Setor Elétrico Brasileiro consiste na utilização de uma variável de folga associada a esta restrição. Neste trabalho é proposta uma estratégia visando manter os reservatórios operando dentro de níveis seguros associada à utilização de uma variável de folga. Para tanto foi criada uma curva de energia armazenável mínima, que fornece a informação sobre os níveis mínimos de armazenamento dos reservatórios equivalentes, de tal forma que os mesmos sejam capazes de suprir as perdas e a vazão mínima obrigatória. As duas metodologias são comparadas e os resultados das simulações mostraram que a formulação proposta leva a uma diminuição no valor esperado de déficit de vazão mínima obrigatória. / This work presents an alternative methodology to meet the constraint associated with mandatory minimum outflow in the problem of long-term operation planning of hydrothermal interconnected systems. Currently, the official methodology adopted in the Brazilian Electric Sector is the use of a slack variable associated with this restriction. This work proposes a strategy to keep the reservoirs operating within safe levels associated with use of a slack variable. For this, is constructed a storable energy curve minimum, providing information about the minimum levels of storage reservoirs equivalent, so that the reservoirs are able to supply the losses and the mandatory minimum outflow. The two methodologies are compared and the simulation results showed that the proposed formulation leads to a decrease in the expected value of deficit minimum flow.

Submitted by Renata Lopes (renatasil82@gmail.com) on 2016-07-28T12:04:17Z No. of bitstreams: 1 rafaelbrunodasilvabrandi.pdf: 13228407 bytes, checksum: 1e92e8c2fa686ddcaea1c9ed0d33b278 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2016-07-28T12:16:14Z (GMT) No. of bitstreams: 1 rafaelbrunodasilvabrandi.pdf: 13228407 bytes, checksum: 1e92e8c2fa686ddcaea1c9ed0d33b278 (MD5) / Made available in DSpace on 2016-07-28T12:16:14Z (GMT). No. of bitstreams: 1 rafaelbrunodasilvabrandi.pdf: 13228407 bytes, checksum: 1e92e8c2fa686ddcaea1c9ed0d33b278 (MD5) Previous issue date: 2016-02-29 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / CNPq - Conselho Nacional de Desenvolvimento Científico e Tecnológico / O Sistema Elétrico Brasileiro (SEB) apresenta características peculiares devido às grandes dimensões do país e pelo fato da geração elétrica ser proveniente predominantemente de usinas hidráulicas. Como as afluências a estas usinas possuem comportamento estocástico e grandes reservatórios proporcionam ao sistema a capacidade de uma regularização plurianual, a utilização dos recursos hidráulicos deve ser planejada de forma minuciosa em um horizonte de tamanho considerável. Assim, o planejamento da operação de médio prazo compreende um período de 5 a 10 anos com discretização mensal e é realizado por uma cadeia de modelos computacionais tal que o principal modelo desta cadeia é baseado na técnica da Programação Dinâmica Dual Estocástica (PDDE). O objetivo deste trabalho é obter avanços nas metodologias de programação dinâmica atualmente utilizadas. Partindo-se da utilização da inserção iterativa de cortes, implementa-se um modelo computacional para o planejamento da operação de médio prazo baseado na metodologia de Programação Dinâmica Estocástica (PDE) utilizando uma discretização mais eficiente do espaço de estados (PDEE). Além disso, a metodologia proposta de PDE possui um critério de convergência bem definido para o problema, de forma que a inclusão da medida de risco CVaR não altera o processo de avaliação da convergência de forma significante. Dado que a inclusão desta medida de risco à PDDE convencional dificulta a avaliação da convergência do processo pela dificuldade da estimação de um limite superior válido, o critério de convergência proposto na PDEE é, então, base para um novo critério de convergência para a PDDE tal que pode ser aplicado mesmo na consideração do CVaR e não aumenta o custo computacional envolvido. Adicionalmente, obtém-se um critério de convergência mais detalhado em que as séries utilizadas para amostras de afluência podem ser avaliadas individualmente tais que aquelas que, em certo momento, não contribuam de forma determinante para a convergência podem ser descartadas do processo, diminuindo o tempo computacional, ou ainda serem substituídas por novas séries dentro de uma reamostragem mais seletiva dos cenários utilizados na PDDE. As metodologias propostas foram aplicadas para o cálculo do planejamento de médio prazo do SIN baseando-se em subsistemas equivalentes de energia. Observa-se uma melhoria no algoritmo base utilizado para a PDE e que o critério proposto para convergência da PDDE possui validade mesmo quando CVaR é considerado na modelagem. / The Brazilian National Grid (BNG) presents peculiar characteristics due to its huge territory dimensions and hydro-generation predominancy. As the water inflows to these plants are stochastic and a pluriannual regularization for system storage capacity is provided, the use of hydro-generation must be planned in an accurate manner such that it considersalongplanningperiod. So, thelong-termoperationplanning(LTOP)problemis generallysolvedbyachainofcomputationalmodelsthatconsideraperiodof5to10years ahead such that the primary model of this chain is based on Stochastic Dual Dynamic Programming (SDDP) technique. The main contribution of this thesis is to propose some improvements in Stochastic Dynamic Programming techniques usually settled on solving LTOP problems. In the fashion of an iterative cut selection, it is firstly proposed a LTOP problem solution model that uses an ecient state space discretization for Stochastic Dynamic Programming (SDP), called ESDP. The proposed model of SDP has a welldefined convergence criterion such that including CVaR does not hinder convergence analysis. Due to the lack of good upper bound estimators in SDDP when including CVaR, additional issues are encountered on defining a convergence criterion. So, based on ESDP convergence analysis, a new criterion for SDDP convergence is proposed such that it can be used regardless of CVaR representation with no extra computational burden. Moreover, the proposed convergence criterion for SDDP has a more detailed description such that forward paths can be individually assessed and then be accordingly discarded for computational time reduction, or even define paths to be replaced in a more particular resampling scheme in SDDP. Based on aggregate reservoir representation, the proposed methodsofconvergenceofSDDPandtheESDPwereappliedonLTOPproblemsrelatedto BNG. Results show improvements in SDDP based technique and eectiveness of proposed convergence criterion for SDDP when CVaR is used.

This dissertation thesis is concerned with the diagnostics of the main production facilities in Czech power engineering with a focus on its integrating role in the process of gaining, saving and processing information for the purpose of evaluating the technical state of the operated facilities and the plan to manage their lifetime. It is divided into two parts, theoretical and practical. The theoretical part presents the conclusions of examination of the needs of involved workers in the areas of diagnostics, maintenance and expert assessment of technical state of equipment. These conclusions were formulated based on the completed analysis of the current status ("as - is" analysis) of performing diagnostics of systems operated in the technological units of both nuclear and classical power engineering. The monitored equipment involves electrical installations and machinery, steel and building constructions, measuring instruments and vibrodiagnostics. Based on the analysis results, process diagrams are created for the solution of partial tasks. The analysis of the proposed solution for problems in question ("should - be" analysis) includes a design of the fundamental scheme of the data model for a software solution and a design of data flows from the individual data sources. The following part presents an application layer which includes a detailed description of major functionalities. Further, important activities and procedures are described that are necessary to evaluate the technical state of equipment. The practical part deals with the implementation of the LTO suite software product in the environment of power engineering in Czech Republic, specifically within ČEZ, a.s.. The LTO suite functionality is demonstrated in this part of the thesis by screens recorded within the LTO suite individual modules, which work above the actual data. It starts with the initial screen for configuration of displayed data, continues to present examples of the equipment register, planning, processing and saving of information collected through the diagnostic activities over to the module of integration – analytical layer, which is designed for evaluation of the technical state of equipment at the entered date with a reporting output. The thesis also includes the chapters on "Aims of the Study" and "Conclusion". The key chapter presents the "Benefits of the Study", whose overview describes the original results of the research as well as those applicable also outside the power engineering area.

Submitted by Renata Lopes (renatasil82@gmail.com) on 2015-12-16T11:02:24Z No. of bitstreams: 1 talespulinhoramos.pdf: 6134665 bytes, checksum: 349537ae72f568271488022944942fb6 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2015-12-16T11:20:33Z (GMT) No. of bitstreams: 1 talespulinhoramos.pdf: 6134665 bytes, checksum: 349537ae72f568271488022944942fb6 (MD5) / Made available in DSpace on 2015-12-16T11:20:33Z (GMT). No. of bitstreams: 1 talespulinhoramos.pdf: 6134665 bytes, checksum: 349537ae72f568271488022944942fb6 (MD5) Previous issue date: 2015-02-23 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O Sistema Interligado Nacional (SIN) apresenta cerca de 150 usinas hidráulicas e o planejamento de médio prazo contempla entre 5 e 10 anos de estudo, a representação do sistema à usinas individualizadas faz com que a resolução do problema seja muito custoso computacionalmente. Para isso, o sistema é representado a partir de sistemas equivalentes de energia. Existe um trabalho anterior onde foi realizado a flexibilização da modelagem do sistema, denominada modelagem híbrida, em que parte do sistema é representado através de sistemas equivalentes de energia e outra é representada à usinas individualizadas com a produtibilidade constante. Desta forma, consegue-se um maior detalhamento nos estudos de médio prazo mantendo a complexidade do sistema em um nível adequado computacionalmente. Este trabalho apresenta a modelagem híbrida entre sistemas equivalentes de energia e à usinas individualizadas, porém, considerando as não linearidades das usinas hidráulicas. As não linearidades das usinas basicamente se dão em relação a variação do nível do reservatório e da vazão defluente (vazão turbinada acrescida da vazão vertida), o que implica diretamente na geração hidráulica. A proposta consiste em modelar a geração hidráulica das usinas (Função de Produção Hidráulica - FPH), que é uma função analítica não linear e não convexa, por uma função linear por partes convexa que represente adequadamente a função de produção hidráulica analítica. Há um trabalho anterior onde a FPH é aproximada por uma função linear por partes em duas etapas, inicialmente a função é aproximada nas dimensões do armazenamento e do turbinamento e, em uma segunda etapa, é adicionado a contribuição do vertimento. Já neste trabalho, a FPH é aproximada por uma função linear por partes obtida em apenas uma etapa para as três dimensões a partir do algoritmo Convex Hull. Assim, é possível resolver o problema de médio prazo considerando parte do sistema representado de forma equivalente e outra parte de forma individualizada considerando a variação da geração hidráulica em função do volume armazenado, vazão turbinada e vertida (se houver influência no canal de fuga). / The National Interconnected Power System (NIPS) presents around 150 hydraulic plants and the medium term planning contemplates between 5 to 10 years of study, the representation of the system to individualized plants makes the problem impracticable in computing; then the system is represented from equivalent systems of energy. There is an alternative of modeling flexibility of the system named hybrid modeling, in which part of the system is represented through equivalent systems of energy and the other is represented to individualized plants with constant productivity. As a consequence, it is obtained greater detail in the long term studies, maintaining the complexity of the system in an adequate level in computing. This paper presents the hybrid modeling between equivalent systems of energy and individualized plants. However, it considers non-linearities on generation of hydraulic plants. The non-linear characteristic on generation function basically comes from the influence of the reservoir level (head term) and the release term (turbinated outflow added to spilled outflow). The suggestion is to model the hydraulic generation of the plants (Hydraulic Production Function - HPF), which is a non-linear and non-convex analytical function, into a convex piecewise linear function that represents appropriately the function of the analytical hydraulic production. It will be described in detail in this paper the technique used to obtain this piecewise linear function by applying the Convex Hull algorithm to guarantee the convexity of this function. To conclude, it is possible to solve the problem of long term considering part of the system represented by equivalent form and the other part in individualized manner considering the variation of the hydraulic generation in relation to the volume stored, turbaned and spilled outflow.