Thesis (Ph. D.)--Ohio University, March, 1999. / Title from PDF t.p.

Thesis (Ph. D.)--University of Missouri-Columbia, 1997. / Typescript. Vita. Includes bibliographical references (leaves 75-78). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 1997. / Typescript. Vita. Includes bibliographical references (leaves 75-78). Also available on the Internet.

Thesis (Ph. D.)--Industrial and Systems Engineering, Georgia Institute of Technology, 2006. / Dr. Yih-Long Chang, Committee Member ; Dr. Martin Savelsbergh, Committee Member ; Dr. Leon McGinnis, Committee Co-Chair ; Dr. Gunter Sharp, Committee Chair ; Dr. Doug Bodner, Committee Member ; Dr. Joel Sokol, Committee Member.

[pt] O fluxo de potência probabilístico é considerado uma técnica eficiente na obtenção de índices de adequação, tais como: probabilidade do fluxo em uma linha ou em um transformador ser maior do que sua capacidade nominal, probabilidade da magnitude da tensão em um barramento estar fora dos limites usuais de operacio, etc., os quais são medidas extremamente úteis tanto no planejamento como na operação de sistemas de potência. Estes índices são obtidos dada a capacidade de tal algoritmo considerar a natureza probabilística das cargas, geração e da configuração da rede em uma única solução. Vários trabalhos tem sido propostos para resolver probabilisticamente o problema do fluxo de potência. A grande maioria tem considerado somente as incertezas nos dados de carga e geração, modelando a rede elétrica por uma configuração fixa, relativa ao caso base. A influência das incertezas na configuração de uma rede de potência devido à natureza probabilística das contingências de seus elementos foi, até então, muito pouco analisada. Esta tese apresenta um novo método de obtenção para a solução do fluxo de potência probabilístico quando a rede é modelada como uma variável aleatória. O algoritmo proposto é aplicado a um sistema típico e os resultados discutidos / [en] Probabilistic load flow can be considered na efficient tecnnique in order to assess adequacy indices, such as: the probability of a transmission line or transformer flow being greater than its thermal rating, probability of a busbar voltage being outside its operational constraints, etc., which are extremely useful measurements in planning and operation of power systems. These indices are achieved due to the ability of such algorithm in recognising the probabilistic nature of load, generation and network configuration within one solution. Many tecniques have been proposed in order to solve the load flow problem probabilisticaly. The great majorit have aonly accounted for load and generation data uncertainties and therefore the network configuration has been considered fixed. So far, the effects of the configuration uncertainties due to the probabilistic nature of network contingencies have not been deeply analysed. This thesis presents a new method for obtaining a probabilistic load flow solution whe network outages are modelled as a random variable. The proposed technique is applied to a typical power system and the results discussed.

M.Ing. / Mobile adhoc networks (MANETs) are multihop wireless topologies that have rapidly changing node structure and limited connectivity. Since MANETs are not deployed on a wide scale, the research community still depends on the simulators such as the network simulator (Ns2) to evaluate MANET protocols. The topic of how to accurately model an indoor environment in the MANET research community is explored in this dissertation. We take an empirical and simulative approach to model our mobility pattern. Our mobility model is based on activity patterns drawn from the transport science. A comparison with the random way point is made in order to understand the weighty discrepancy between the two models. Our contribution in this research is three fold: 1. We argue that mobility modelling should be based on activities other than stochastic process that have got no realistic backing; 2. We model our network using by putting up an algorithm and take an empirical approach to model the radio frequency propagation. To show the difference of the two mobility models, the behaviour of the signal strength on the two mobility models is drawn; and 3. Finally an implementation of our mobility pattern and RF measurements in ns2 is done.

The influx of new data-intensive applications, such as machine learning and artificial intelligence, in high performance computing (HPC) and data centers (DC), has driven the design of efficient interconnection networks to meet the requisite bandwidth of the growing traffic demand. While the exponentially-growing traffic demand is expected to continue into the future, the free scaling of CMOS-based electrical interconnection networks will eventually taper off due to Moore’s Law. These trends suggest that building all-electrical interconnects to meet the increased demand for low latency, high throughput networking will become increasingly impractical going forward. Integrating optical interconnects capable of supporting high bandwidth links and dynamic network topology reconfiguration offer a potential solution to scaling current networks. However, the insertion of photonic interconnection networks offers a massive design space in terms of network topology and control plane that is currently under-explored. The work in this dissertation is centered around the study and development of control plane challenges to aid in the eventual adoption of optically-enabled reconfigurable networks. We begin by exploring Flexspander, a novel reconfigurable network topology that combines the flexible random expander networks construction with topological-reconfigurability using optical circuit switching (OCS). By incorporating random expander graph construction, as opposed to other more symmetric reconfigurable topologies, Flexspander can be built with a broader range of electrical packet switch (EPS) radix, while retaining high throughput and low latency when coupled with multi-path routing. In addition, we propose a topology-routing co-optimization scheme to improve network robustness under traffic uncertainties. Our proposed scheme employs a two-step strategy: First, we optimize the topology and routing strategy by maximizing throughput and average packet hop count for the expected traffic patterns based on historical traffic patterns. Second, we employ a desensitization step on top of the topology and routing solution to lower performance degradation due to traffic variations. We demonstrate the effectiveness of our approach using production traces from Facebook's Altoona data center, and show that even with infrequent reconfigurations, our solution can attain performances within 15\% of an offline optimal oracle. Next, we study the problem of routing scheme design in reconfigurable networks, which is a more under-studied problem compared to routing design for static networks. We first perform theoretical analyses to first identify the key properties an effective routing protocol for reconfigurable networks should possess. Using findings from these theoretical analyses, we propose a lightweight but effective routing scheme that yields high performance for practical HPC and DC workloads when employed with reconfigurable networks. Finally, we explore two fundamental design problems in the optical reconfigurable network design. First, it investigates how different OCS placement in the physical network topology lead to different tradeoffs in terms of power consumption/cost, network performance, and scalability. Second, we investigate how network performance is affected by different reconfiguration periods to understand how frequency of topology reconfiguration affects application performance. Taken together, the work in this dissertation tackles several key challenges related to efficient control plane for reconfigurable network designs, with the goal of facilitating the eventual adoption of optically-enable reconfigurable networks in high performance systems.

Basic PWM dc-to-dc converter structure is examined wherein a basic substructure of converters, known as a converter cell, is identified. Converter cells can be used in generation and classification of basic PWM dc-to-dc converters. A large number of new converters are generated. Converter analysis, whereby the nonlinear response of the system to perturbations in the control or the input, is determined by two different methods. A classical approach to nonlinear systems analysis is first used wherein the system is represented by a Volterra functional series. The alternative approach presented concentrates on deriving circuit models for the PWM switch. The PWM switch represents the static nonlinear substructure of the vast majority of converter cells. Analysis of converters then proceeds in an analogous fashion to ordinary transistor circuit analysis whereby the nonlinear device is replaced by its circuit model. Topological considerations of single-phase dc-to-ac inverters are discussed. A number of zero-current switching quasi-resonant inverter topologies are derived. Schemes that permit these topologies to handle reactive loads are identified. / Ph. D.

Wireless sensor networks (WSNs) are characterized by limited amount of energy supply at sensor nodes. Hence, energy efficiency is an important issue in system design and operation of WSNs. In this work we focus on solving the energy efficiency problems of data gathering processes in WSNs. We first address this problem on a macroscopic level by investigating the efficiency of data gathering trees when data sent by different sensors are correlated. Such correlation aware data gathering strategies typically shift the aggregation structure from a default shortest-path tree (SPT) to a steiner minimum tree (SMT) in order to achieve the required efficiency. We study the energy efficiency of correlation aware data aggregation trees under various sensor network conditions and the tradeoffs involved in using them. Comprehensive simulation results as well as inferences and theoretical analysis of those results are presented in the thesis. Based on the insights gained through the investigation, we propose a simple, scalable and distributed correlation aware aggregation structure that achieves good energy performance across a wide range of sensor network configurations, and at the same time addresses the practical challenges of establishing a correlation aware data aggregation structure in resource-constrained WSNs. On a microscopic level, we propose a novel communication strategy called Communication through Silence (CtS) to achieve energy-efficient data gathering without significant degradation on overall throughput in WSNs. The proposed scheme primarily uses time, along with a minimal amount of energy to deliver information among sensors. CtS can be used to replace the conventional energy-based transmissions between each pair of sensor nodes during a data gathering process. We analyze in detail the primary energy-throughput tradeoff inherent in this approach as well as other challenges related to the realization of the proposed communication strategy. Finally, we propose a practical realization of CtS strategy that includes radio technology, MAC layer, and higher layer solutions. Performance evaluation results prove that this solution effectively realizes the CtS strategy in a WSN setting, at the same time achieves considerable energy savings compared to conventional communication strategies.

Orientadores: Ernesto Ruppert Filho, Marcelo Gradella Villalva / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-24T10:01:12Z (GMT). No. of bitstreams: 1 Oliveira_LeonardoRuffeilde_M.pdf: 3470428 bytes, checksum: 7972e30772adc6b114e71c8f464265b8 (MD5) Previous issue date: 2013 / Resumo: O objetivo deste trabalho é a construção de um conversor eletrônico de potência monofá-sico completo para conexão à rede elétrica de distribuição de baixa tensão alimentado por painel fotovoltaico Painéis fotovoltaicos comerciais geram uma tensão contínua que varia entre 20 e 50V, dependendo do tipo de painel e da ocorrência ou não de conexão entre os mesmos; sendo necessário, portanto, a adequação dos níveis de tensão gerados pelo painel com o nível de tensão da rede elétrica de distribuição, na qual ele será conectado. O conversor eletrônico de potência utilizado neste trabalho é constituído de dois estágios sendo o primeiro CC ¿ CC e o segundo, um inversor, CC ¿ CA. Ele será controlado de duas maneiras: a primeira será responsável pelo con-trole da tensão de entrada do conversor CC - CC e pela injeção de potência no conversor CC - CA o qual, além de ser o responsável pela transformação da tensão contínua em alternada também é responsável pelo sincronismo do conversor CC - CA com a rede elétrica. São apresentados resultados de simulação do funcionamento do conversor para geração fotovoltaica de energia elétrica, sua malha de controle e o funcionamento do sistema elétrico completo. O projeto com-pleto dos conversores e dos circuitos auxiliares bem como os resultados experimentais obtidos em laboratório são apresentados / Abstract: The objective of this work is the construction of a complete single-phase power electronic converter for grid connection of low voltage distribution powered by photovoltaic panels. Photo-voltaic panels generates a DC voltage that varies between 20 and 50V, depending on the type of panel and presence or absence of connection between them, it is necessary, therefore, the ade-quacy of voltage levels generated by the panel with the voltage level of the electrical distribution network, in which it is connected. The power electronic converter used in this study consists of two stages with the first is a dc ¿ dc converter and the second is a dc-ac converter, frequency inverter. It will be controlled in two ways: the first is responsible for controlling the input voltage of the dc-dc converter and the power injection in the ac-dc converter which, besides being res-ponsible for the transformation into alternating voltage is also responsible by the synchronism of the converter dc-ac with the utility grid. Simulation results of the converter operation connected to the utility grid are presented, its network control and operation of the complete electrical sys-tem. The complete design of converters and auxiliary circuits and the experimental results obtai-ned in the laboratory are presented / Mestrado / Energia Eletrica / Mestre em Engenharia Elétrica