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 Texas at Austin, 2004. / Supervisor: Greg Plaxton. Vita. Includes bibliographical references. Also available from UMI.

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.

The Induction Linac System Experiment (ILSE) is a heavy-ion fusion (HIF) device that is being designed at Lawrence Berkeley Laboratory (LBL). The machine will be capable of accelerating 16 carbon ion beams, which are subsequently merged into 4 beams, to energies in the neighborhood of 10 MeV (10 million electron- volts). The purpose of the experiment will be to demonstrate the process of simultaneous acceleration and current amplification for a multiple beam accelerator configuration. If this process can be mastered, the beams produced by a machine such as ILSE would be used to implode and heat a deuterium-tritium (D-T) fuel pellet and produce a thermonuclear inertial confinement fusion (ICF) burn. This technology of achieving a fusion reaction using ion beams is referred to as Heavy-Ion Fusion (HIF) [1].

No description available.

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.

A modularized three-dimensional power electronics environment will become increasingly necessary as power converters are more intertwined with the dynamic desires of modern society. This is driven by ever-changing requirements, combined with the desire for quick design cycles, and then further compounded by the increased penetration of electrified technologies. The high demand for various power converters presents a design, manufacturing, and validation burden which can be lessened with a three-dimensional power electronics environment, where power converters of any arbitrary set of voltage, current, or quantity of independent input/outpt requirements can be assembled from a grouping of pre-existing converter modules. This, however, has drawbacks when compared with bespoke power converter designs. Modularization can be complex, lossy, and large, and the resulting converter's overall efficiency and power density will then suffer. To compensate for these costs of modularization, the individual modules must be first be power dense and efficient, and then the framework for grouping modules together must be simple. This dissertation first proposes a high performance Power Conversion Unit (PCU) which is achieved through a unique combination of techniques. The first of these techniques is modification to the ubiqutioius buck converter topology in a form of an adjustment to its output filter. This topological modification results in decreased current ripple handling requirements of the filter, which can be used to reduce its volume. The second topological technique is an additional capacitance placed across the drain-source terminals of each FET, which is used to reduce their turn-off switching energy at the expense of their turn-on switching energy. A variable frequency soft-switching scheme is utitlized to prevent the converter from incurring turn-on losses, and a duty cycle compensation scheme is developed to mitigate the distortions caused by this increased drain-source capacitance. Finally, a process for balancing the PCU design parameters that results in a Pareto frontier of efficiency-power density optimal points is defined, one selected, and a protoype PCU constructed and tested in a three-phase inverter configuration. A framework for the vertical stacking of PCUs is then shown. This framework, named the Manhattan Topology, is a multilevel power converter topology which is defined by a set of series stacked capacitances where there exists a method to transfer power between capacitances. This framework has linear complexity and switching device stress scaling with the number of levels, which yields a simple methodology for grouping modules together in the vertical dimension. Furthermore, it exhibits Partial Power Processing (PPP) characteristics as the power processed internally to the overall converter is less than its output power. This framework is validated for both DC/DC and AC/DC applications and control and conversion of voltages greater than the rating of any individual component within the converter is experimentally demonstrated. Lastly, another three-phase inverter is built using this topological framework and the performance of this vertically-modularized inverter is compared with the non-modularized inverter. It is shown that the three-dimensional modular power electronics environment with optimized PCUs, despite the costs of modularization, is still performance-competitive with the non-modular power electronics environment.