The ship emission already occupy the eighth position in the world biggest emitters ranking. This happens because the ship operations have a huge demand variation therefore in order to reduce the ship emissions is required an efficient operation of the generators. This work aims at integrating advanced storage systems into the operation of diesel generators. The variation of the operation point has a direct interference on the emissions and on the diesel consumption, this variation is allowed through the frequency and voltage control. The use of lithium batteries for various operation points of the generators is analyzed. The use of an energy storage system allowed the operation of the generators in a better operation point therefore there was a reduction in diesel consumption and in CO2 emissions when the diesel generators. The main result of this work could also shed light in the operation of isolated power systems equipped with advanced storage systems and diesel generators. / As emissões dos navios já ocupam a oitava posição entre os países com maior emissão no mundo. Isso pode ser explicado pelo fato de que as operações dos navios têm uma grande variação de demanda de potência, com isso a operação inteligente dos geradores a diesel é fundamental para a redução das emissões. A abordagem desenvolvida nesse trabalho integra o uso de sistemas de armazenamento avançados na operação dos geradores a diesel. A variação do ponto de operação dos geradores a diesel interfere diretamente no consumo e nas emissões, essa variação só é possível por meio do controle de frequência e tensão providos pelo sistema de armazenamento de energia. Nesse trabalho foram analisados o uso de baterias de lítio para diferentes pontos de operação do gerador a diesel. O uso das baterias possibilitou a operação dos geradores num melhor ponto de carga com isso houve uma redução das emissões e do consumo de combustível. Os resultados encontrados nesse trabalho podem ser extrapolados qualitativamente para outros sistemas de potência offshore, como plataformas de petróleo e de perfuração, que operem com sistemas de baterias avançadas e geradores a diesel.

Submitted by Rosivalda Pereira (mrs.pereira@ufma.br) on 2017-07-19T17:30:37Z No. of bitstreams: 1 PedroLeiteNeto.pdf: 15729023 bytes, checksum: 58efe211075c14c50cf9c297aa235d4f (MD5) / Made available in DSpace on 2017-07-19T17:30:37Z (GMT). No. of bitstreams: 1 PedroLeiteNeto.pdf: 15729023 bytes, checksum: 58efe211075c14c50cf9c297aa235d4f (MD5) Previous issue date: 2017-06-02 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / The development of microgrids was driven by the need to supply consumers with more stable and reliable electricity. The intermittent nature of renewable sources differs from the requirements of consumers - especially in isolated areas - who expect an uninterrupted and quality energy supply. Isolated microstrips may have available one or more renewable sources to be explored, configuring hybrid systems. Although such renewable sources are inexhaustible, energy conversion systems are capacity limited and need to be explored efficiently. Hybrid systems typically include solar photovoltaic and wind, already well studied. In this thesis are introduced the oceanic energies in their gradient and tidal currents forms. This thesis contributes to the efficient exploration of the oceanic sources, both as a single source as well as in a hybrid configuration. In relation to the isolated operation, the storage system is of fundamental importance. Considering the high costs of a battery bank over the total cost of the system, operating strategies that preserve its useful life while maintaining uninterrupted power supply are mandatory. Considering these aspects, in this work is proposed a dual energy storage system composed of two subsystems with diversified functions and submitted to different chage/discharge conditions. The purpose of this new strategy is a more efficient use of the storage system, since this operating regime becomes closer to the recommended by the battery manufacturers. The benefits of this strategy are reflected in the overall cost reduction of the microgrid. In order to achieve optimum operating strategies, a more accurate mathematical model of the batteries is used to reproduce the behavior of the batteries in a more realistic way. In addition, it is investigated the performance of operating strategies that allow maximum benefits to be obtained through the diversification of the microgrid energy matrix, by including hydrokinetic tidal sources. The motivation for including this source lies in its high potential, especially on the northern coast of Brazil. These benefits should be evaluated mainly through the more efficient use of the storage system as well as the reduction of the participation of fossil fuel units in the operation of isolated microgrids. / O desenvolvimento das microrredes foi impulsionado pela necessidade de suprir os consumidores com eletricidade de forma mais estável e confiável. A natureza intermitente das fontes renováveis se contrapõe às exigências dos consumidores - especialmente em áreas isoladas - que esperam por um fornecimento de energia sem interrupções e com qualidade. As microrredes isoladas podem ter disponíveis uma ou mais fontes renováveis para serem exploradas, configurando sistemas híbridos. Embora tais fontes renováveis sejam inesgotáveis, os sistemas de conversão de energia são limitados em capacidade e devem ser explorados com eficiência. Sistemas híbridos normalmente incluem energia solar fotovoltaica e eólica, já bastante estudadas. Nesta tese são introduzidas as energias oceânicas nas suas formas de gradiente e de correntes de marés. Esta tese contribui para a exploração eficiente de fontes oceânicas, tanto na operação como fonte única assim como em configuração híbrida. No que tange a operação isolada, o sistema de armazenamento tem importância fundamental. Considerando os elevados custos de um banco de baterias sobre o custo total do sistema, estratégias de operação que preservem sua vida útil, ao mesmo tempo que mantenham o fornecimento ininterrupto de energia, são mandatórias. Diante destes aspectos, neste trabalho é proposto um sistema dual de armazenamento de energia composto de dois subsistemas com funções diversificadas e submetidos a condições de carga/descarga diferentes. O objetivo desta nova estratégia consiste no uso mais eficiente do sistema de armazenamento, uma vez que esse regime de operação se torna mais próximo daquele recomendado pelos fabricantes de baterias. Os benefícios desta estratégia são refletidos na redução dos custos globais da microrrede. Para conseguir as estratégias de operação ótima, neste trabalho é utilizado um modelo matemático mais acurado das baterias a fim de reproduzir de forma mais realista o comportamento das baterias. Além disso, é investigado o desempenho de estratégias de operação que permitam obter o máximo de benefícios decorrentes da diversificação da matriz energética da microrrede, através da inclusão de fontes hidrocinéticas maremotrizes. A motivação para a inclusão desta fonte está no seu elevado potencial, em especial no litoral norte do Brasil. Estes benefícios devem ser avaliados especialmente quanto ao uso mais eficiente do sistema de armazenamento, assim como a redução da necessidade de participação de unidades baseadas em combustível fóssil na operação de microrredes isoladas.

In this modern rather interconnected era, an organization’s top priority is to protect itself from major security breaches occurring frequently within a communicational environment. But, it seems, as if they quite fail in doing so. Every week there are new headlines relating to information being forged, funds being stolen and corrupt usage of credit card and so on. Personal computers are turned into “zombie machines” by hackers to steal confidential and financial information from sources without disclosing hacker’s true identity. These identity thieves rob private data and ruin the very purpose of privacy. The purpose of this project is to identify suspicious user activity by analyzing a log file which then later can help an investigation agency like FBI to track and monitor anonymous user(s) who seek for weaknesses to attack vulnerable parts of a system to have access of it. The project also emphasizes the potential damage that a malicious activity could have on the system. This project uses Hadoop framework to search and store log files for logging activities and then performs a ‘Map Reduce’ programming code to finally compute and analyze the results.

O aprimoramento de técnicas e dispositivos aplicados à conversão de energia provenientes de fontes alternativas de energia, no contexto da geração distribuída, possui um papel importante para o estabelecimento definitivo de um novo paradigma de despacho e consumo de energia elétrica. Neste contexto, esta tese de doutorado aborda uma proposta de gerenciamento de energia e controle de uma microrede com célula a combustível e painel fotovoltaico como fontes primárias, operando juntamente com elementos armazenadores. Nesta proposta, destaca-se o uso de duas principais técnicas: droop k-sharing e Maximum Power Point Tracking with Saturation Technique (MPPT-ST). A técnica droop k-sharing permite associar uma dinâmica preestabelecida à célula a combustível, de forma que as baterias absorvam o espectro complementar. Adicionalmente, o uso da variável k-sharing com a adição da técnica droop permite o compartilhamento de potência entre as duas fontes sem a necessidade de comunicação entre elas. Já a técnica MPPT-ST, permite a operação de painéis fotovoltaicos no Maximum Power Point (MPP) e fora do MPP utilizando um saturador dinâmico. Por fim, propõe-se uma técnica para o acoplamento dos modelos dinâmicos dos conversores CC-CC por meio do equacionamento da tensão do barramento Corrente Contínua (CC) em espaços de estados, tornando possível analisar a estabilidade da microrede com o método indireto de Lyapunov. Para validar as técnicas propostas, são apresentados resultados de simulação e experimentais. / The improvement of techniques and devices applied to the energy conversion of alternative energy sources, in the distributed generation context, has an important role for the definitive establishment of the new paradigm of energy delivery and consumption. In this context, this PhD thesis addresses a proposal of an energy management strategy for microgrids with fuel cells and photovoltaic panels as primary sources, operating with storage devices. In the proposed control scheme, it is possible to highlight two control techniques: droop k-sharing and MPPT-ST. With the droop k-sharing technique, it is possible to design a specific dynamic behavior for the Fuel Cell, while the battery absorbs the complementary (high frequency) spectrum. Additionally, the use of the k-sharing variable with droop technique makes it possible to share the energy between the two sources without the need of a high-speed communication link. On the other hand, with the MPPT-ST technique, the photovoltaic modules can be operated in the MPP or off-MPP by using a simple dynamic anti-windup strategy. For the stability analysis using the Lyapunov Indirect Method, it is proposed a state space technique to couple the DC-DC converters models using the DC-link capacitor. Finally, to evaluate the proposed theoretical algorithm and analysis, simulations and experimental results are presented.

Secure communication under channel uncertainty is an important and challenging problem in physical-layer security and cryptography. In this dissertation, we take a fundamental information-theoretic view at three concrete settings and use them to shed insight into efficient secure communication techniques for different scenarios under channel uncertainty. First, a multi-input multi-output (MIMO) Gaussian broadcast channel with two receivers and two messages: a common message intended for both receivers (i.e., channel uncertainty for decoding the common message at the receivers) and a confidential message intended for one of the receivers but needing to be kept asymptotically perfectly secret from the other is considered. A matrix characterization of the secrecy capacity region is established via a channel-enhancement argument and an extremal entropy inequality previously established for characterizing the capacity region of a degraded compound MIMO Gaussian broadcast channel. Second, a multilevel security wiretap channel where there is one possible realization for the legitimate receiver channel but multiple possible realizations for the eavesdropper channel (i.e., channel uncertainty at the eavesdropper) is considered. A coding scheme is designed such that the number of secure bits delivered to the legitimate receiver depends on the actual realization of the eavesdropper channel. More specifically, when the eavesdropper channel realization is weak, all bits delivered to the legitimate receiver need to be secure. In addition, when the eavesdropper channel realization is strong, a prescribed part of the bits needs to remain secure. We call such codes security embedding codes, referring to the fact that high-security bits are now embedded into the low-security ones. We show that the key to achieving efficient security embedding is to jointly encode the low-security and high-security bits. In particular, the low-security bits can be used as (part of) the transmitter randomness to protect the high-security ones. Finally, motivated by the recent interest in building secure, robust and efficient distributed information storage systems, the problem of secure symmetrical multilevel diversity coding (S-SMDC) is considered. This is a setting where there are channel uncertainties at both the legitimate receiver and the eavesdropper. The problem of encoding individual sources is first studied. A precise characterization of the entire admissible rate region is established via a connection to the problem of secure coding over a three-layer wiretap network and utilizing some basic polyhedral structure of the admissible rate region. Building on this result, it is then shown that the simple coding strategy of separately encoding individual sources at the encoders can achieve the minimum sum rate for the general S-SMDC problem.

Solving the key issue of sustainability of battery-powered sensors continues to attract significant research attention. The prevailing theme of this research is to address this concern using energy-efficient protocols based on a form of simple cooperative transmission (CT) called the opportunistic large arrays (OLAs), and intelligent exploitation of energy harvesting and hybrid energy storage systems (HESSs). The two key contributions of this research, namely, OLA with transmission threshold (OLA-T) and alternating OLA-T (A-OLA-T), offer an signal-to-noise ratio (SNR) advantage (i.e., benefits of diversity and array (power) gains) in a multi-path fading environment, thereby reducing transmit powers or extending range. Because these protocols do not address nodes individually, the network overhead remains constant for high density networks or nodes with mobility. During broadcasting across energy-constrained networks, while OLA-T saves energy by limiting node participation within a single broadcast, A-OLA-T optimizes over multiple broadcasts and drains the the nodes in an equitable fashion. Another important contribution of this research is the design and analysis of a novel routing metric called communications using HESS (CHESS), which extends the rechargeable battery (RB)-life by relaying exclusively with supercapacitor (SC) energy, and is asymptotically optimal with respect to the number of nodes in the network.

Enterprises today are dealing with extremely large amounts of critical digital information that continues to grow at an astonishing rate. On the other hand, storage software (firmware, middleware) and systems are becoming much more complex and existing failure recovery mechanisms are insufficient to handle the scale of these systems while meeting high availability and service quality expectations. In addition, the concurrent development and quality assurance processes, the large number of test scenarios and the large scale of these systems and services imply that failures will be the norm rather than the exception. Therefore achieving high availability and reliability in storage systems remains a major concern and an open research challenge. Most existing work in the domain of storage system availability addresses failures of the storage media (such as disks) and recoverability from these failures. However, failures at the firmware and middleware layers remain largely unaddressed. This dissertation research addresses these challenges in depth across different storage architectures. Concretely, we make the following contributions: First, we develop a recovery conscious framework for multi-core architectures and a suite of techniques for performing efficient fine-grained recovery (micro-recovery) in storage controller firmware that can be retrofitted into legacy code. The framework includes a task-level recovery mechanism, the Log(Lock) architecture that allows system state restoration during micro-recovery, and recovery-conscious scheduling algorithms that are designed to reduce the ripple effect of failure and improve recovery efficiency and system availability. Our second technical contribution addresses the storage middleware availability. We develop the notion of hierarchical middleware architectures by organizing critical cluster management services into a hierarchical overlay network, which separates persistent application state from global system control state and demonstrate significant improvement in the availability and reliability of enterprise scale storage systems. In addition, we develop the notion of operator reuse and a suite of reuse techniques to improve data availability. The key idea of operator reuse is to efficiently utilize system resources by exploiting reuse opportunities in both operators and persistent state of computing nodes. We demonstrate our design through STREAMREUSE, a reuse-conscious store-forward network of storage nodes, which offers distributed stream query processing services.

Orientador: Prof. Dr. Jorge Tomioka / Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Engenharia Elétrica, 2014. / No contexto energético, as mudanças climáticas e as crescentes crises energéticas aumentaram as preocupações e as pesquisas na área de acumuladores de energia, visando alcançar melhorias no cenário energético e ambiental global. Ao mesmo tempo, a sociedade tornou-se dependente do consumo de energia elétrica, sendo que falhas no fornecimento não são permitidas. Portanto, observa-se a necessidade da energia ofertada ser de boa qualidade e, principalmente, não sofrer interrupções. Atrelado a esses fatores, a bateria de Magnésio ¿ Ar passou a ser considerada uma fonte promissora de energia elétrica, principalmente pela abundância de Magnésio (sétimo elemento mais presente no planeta), por não poluir o meio ambiente, ser barata e possuir energia especifica elevada. Essas características transformam esse acumulador em um potencial substituto para outras tecnologias. No entanto, a bateria demagnésio possui desvantagens que precisam ser vencidas por meio de pesquisas para alavancar o seu uso comercial massivo. Sob essa perspectiva, neste trabalho propõe-se o estudo da liga de magnésio AZ91 para aplicação em baterias de Magnésio ¿ Ar, por meio de ensaios de porosidade e de dureza, como também análise microestrutural e mensuração do potencial de circuito aberto e das curvas de polarização potenciodinâmica, utilizando-se uma célula eletroquímica de três eletrodos e um potenciostato em diferentes tempos de imersão da liga AZ91 na solução eletrolítica de NaCl 0,1 M. A porosidade da peça, observada no microscópio óptico com ampliação de 50 vezes, revelou que em cada fase de solidificação existem poros de tamanhos diferentes, com distribuição específica. Conforme o processo de resfriamento ocorre, nota-se a presença de poros maiores. Relacionado à porosidade, a dureza apresentou valores maiores na fase inicial de solidificação, onde a porosidade é menor. Por meio da análise microestrutural, foi possível verificar a presença de dendritas, com uma complexa dispersão de segunda fase na liga (alumínio), porosidades e inclusões. As medidas de potencial de circuito aberto indicam uma tendência de resistência à corrosão em temposmaiores de contato da amostra com a solução de NaCl. Não foi possível observar passivação aparente na amostra, nem pontos de corrosão localizada (pite) nas curvas de polarização potenciodinâmica. As variações no potencial de corrosão apontaram uma maior resistência à corrosão em tempos de imersão maiores; contudo, os valores estáveis de densidade de corrente de corrosão demonstram que a velocidade de corrosão permaneceu constante, sendo que a camada de óxido formada não contribuiu na proteção do material. Para a aplicação em baterias de magnésio, esses resultados conferem uma limitação da liga AZ91, pois a camada de óxido formada pode prejudicar o funcionamento do dispositivo em processos de descarga intermitente. As principais formas de controlar a eficiência da bateria de Magnésio ¿ Ar são por meio da composição da liga, da oxigenação, do pH, da temperatura e da concentração de sais NaCl no eletrólito. / In the energy sector, weather changes and rising energy crisis raised concerns and research in energy accumulators to achieve improvements in overall environmental and energy scenario. At the same time, society has become dependent on electricity consumption, so failures in supply are not tolerated. Therefore, the energy needs to have a good quality, and not suffer interruptions. Coupled to these factors, the battery Magnesium ¿ Air has been considered a promising source of electricity, mainly by the abundance of magnesium (seventh-most element present on the planet), not to pollute the environment, be cheap and have high specific energy. These characteristics transform this accumulator in a potential substitute for other technologies. However, the magnesium battery has disadvantages that need to be overcome through research to leverage their massive commercial use. From this point of view, this study proposes the characterization of magnesium alloy AZ91 for application in batteries Magnesium ¿ Air, testing the porosity and hardness, as well as microstructural analysis, and the measurement of the open potential circuit and the potentiodynamic polarization, in various immersion times using an electrochemical cell with three electrodes. The porosity of the part, observed in the optical microscope, revealed that at each stage of solidification, the pores have different sizes and distribution. As the cooling process occurs, could observe the presence of larger pores. Associated to the porosity, hardness values were higher in the initial phase of solidification, where the porosity was less. Through microstructural analysis was verified the presence of dendrites, with a complex dispersion of second phase in the alloy (aluminum), porosity and inclusions. The open potential circuit indicated a tendency for corrosion resistance in greater immersion time in the solution of NaCl. In all cases, the potentiodynamic polarization curves did not exhibit apparent passivity, or points of localized corrosion (pitting). The changes in corrosion potential showed greater resistance to corrosion in immersion times larger, however, the steady state values of corrosion current density demonstrated that the corrosion rate remained constant and the oxide layer formed did not protect the material. For use in magnesium batteries, these results provided a limitation of the AZ91 alloy, because the oxide layer can disturb the functioning of the device in cases of intermittent discharge. The main ways to control the battery efficiency Magnesium ¿ Air are through the alloy composition, oxygenation, pH, temperature and salt concentration of NaCl in the electrolyte.

Orientador: Carlos Alberto Mariotoni / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo / Made available in DSpace on 2018-08-12T13:17:33Z (GMT). No. of bitstreams: 1 Borin_FernandoLuders_M.pdf: 5674159 bytes, checksum: 06b685198e7c4437396ce7f2a615662d (MD5) Previous issue date: 2007 / Resumo: Este trabalho tem por objetivo fornecer maiores subsídios tendo em vista a matriz energética brasileira, no que se refere ao planejamento, repotênciação, operação e controle dos sistemas de geração de energia elétrica, de modo a prover meios de otimização mais eficazes, reduzindo os impactos de recursos naturais e econômicos demandados pelo sistema elétrico de geração e transmissão. O uso de técnicas de rotação ajustável já vem sendo empregado com sucesso em vários casos, tanto a nível nacional, quanto a nível internacional. A geração através de sistemas eólicos é o exemplo mais forte neste sentido, superando as expectativas de planejamento em vários casos. Os sistemas eólicos só podem operar por meio de técnicas de rotação ajustável. Contudo, a utilização das técnicas de rotação ajustável, tem muito a contribuir, mediante devidas ponderações, nos mais diversos segmentos de geração de energia. Qualquer que seja o caso, é possível de se obter ganhos consideráveis, no que se refere à otimização dos aproveitamentos energéticos. Dentro deste contexto, o trabalho apresenta um panorama geral das alternativas de geração de energia elétrica, e os possíveis ganhos que o sistema de rotação ajustável pode disponibilizar em cada um destes casos. Inicialmente são abordados aspectos gerais dos sistemas convencionais, de forma a estabelecer parâmetros de comparação. A seguir, aspectos específicos de geração por meios hidráulicos, térmicos, eólicos são abordados. Uma análise referente a sistemas isolados de geração também é apresentada, agregando vantagens adicionais não evidenciadas nos sistemas interligados. Desta forma, espera-se que levando em consideração estas técnicas de rotação ajustável, possam conduzir a investimentos relativos de expansão, reforma e operação do sistema de forma mais racional, minimizando impactos ambientais e sociais, contado ainda com ganhos de eficiência disponibilizados. / Abstract: This work has for objective to supply larger subsidies the head office Brazilian energetics, in what he/she refers to the planning, retrofitting, operation and control of the systems of electric power generation, in way to provide more effective optimization means, reducing the impacts of natural and economical resources disputed by the electric system of generation and transmission. The use of techniques of adjustable speed has already been used with success in several cases, so much at national level, as for international level. The generation through eolic systems is the strongest example in this sense, overcoming the planning expectations in several cases. The eolic systems can only operate through techniques of adjustable rotation. However, the use of the techniques of adjustable speed, has a lot to contribute, by the due considerations in the most several segments of generation of energy. Any that is the case, is possible of obtaining won considerable, in what it refers the optimization of the energy uses. Inside of this context, the work presents a general panorama of the alternatives of electric power generation, and the possible impacts that the system of adjustable speed can make available in each one of these cases. Initially general aspects of the conventional systems are approached, in way to establish comparison parameters. To proceed, specific aspects of generation for means hydraulic, thermal, eolics are approached. An analysis regarding isolated systems of generation is also presented, joining additional advantages no evidenced in the interlinked systems. This way, it is waited that taking into account these techniques of adjustable rotation, they can lead to relative investments of expansion, it reforms and operation of the system in a more rational way, minimizing environmental and social impacts, still counted with won of efficiency made available. / Mestrado / Recursos Hidricos / Mestre em Engenharia Civil

Operating Systems use fast, CPU-addressable main memory to maintain an application’s temporary data as anonymous data and to cache copies of persistent data stored in slower block-based storage devices. However, the use of this faster memory comes at a high cost. Therefore, several techniques have been implemented to use main memory more efficiently in the literature. In this dissertation we introduce three distinct approaches to improve overall system performance by optimizing main memory usage. First, DRAM and host-side caching of file system data are used for speeding up virtual machine performance in today’s virtualized data centers. The clustering of VM images that share identical pages, coupled with data deduplication, has the potential to optimize main memory usage, since it provides more opportunity for sharing resources across processes and across different VMs. In our first approach, we study the use of content and semantic similarity metrics and a new algorithm to cluster VM images and place them in hosts where through deduplication we improve main memory usage. Second, while careful VM placement can improve memory usage by eliminating duplicate data, caches in current systems employ complex machinery to manage the cached data. Writing data to a page not present in the file system page cache causes the operating system to synchronously fetch the page into memory, blocking the writing process. In this thesis, we address this limitation with a new approach to managing page writes involving buffering the written data elsewhere in memory and unblocking the writing process immediately. This buffering allows the system to service file writes faster and with less memory resources. In our last approach, we investigate the use of emerging byte-addressable persistent memory technology to extend main memory as a less costly alternative to exclusively using expensive DRAM. We motivate and build a tiered memory system wherein persistent memory and DRAM co-exist and provide improved application performance at lower cost and power consumption with the goal of placing the right data in the right memory tier at the right time. The proposed approach seamlessly performs page migration across memory tiers as access patterns change and/or to handle tier memory pressure.