Bibliography: pages 168-174. / The Emergency Electric Power Supply Systems at Pressurized Water Reactor Nuclear Power Plants are reviewed, problem areas are identified, and recommendations are made for existing and future Nuclear Power Plants. A simplified introduction to a typical Pressurized Water Nuclear Reactor is given and the problems associated with the commercial use of nuclear power are discussed. An overview of the Nuclear industry's solutions is presented and covers the Reliability of equipment and the American Regulatory requirements. The alternating and direct current power supply systems are examined in terms of plant operational state and equipment type (Diesel generators, Grid network, Lead-acid batteries, Battery chargers, Inverters, and Power Distribution networks). The trends in the design of Emergency Electric Power supply systems at Nuclear Power Plants are presented. The loss of all alternating current power, known as Station Blackout, is discussed and the American and European response to this. problem is presented. Problems experienced in the direct current systems are discussed and solutions are presented. The experience at Koeberg Nuclear Power station with Lead-acid batteries is included in the discussion. The thesis concludes with recommendations for designers and operators of the Electric Power Supply Systems at Nuclear Power Stations.

The main aim of diploma thesis "China - real threat for American hegemony?" is to answer the question whether China is trying to threaten American position of world hegemon. After the dissolution of USSR and the fall of Iron Curtain USA became the only world superpower. Balance of power theory assumes that the occurrence of leading actor in the system will invoke attempts of others to balance the power of the leader, or to weaken him. In current world political system there are powers whose power potential is growing. One of them is China, mainly because its fast growing and prospering economy. Author of the thesis works with the concept of hegemony based on hard and soft power and three types of exercising of power - three faces of power - as means of achieving its goals. Author analyses Chinese use of hard and soft power resources, that can be classified under three types of use of power. All policies are then examined from "balance of power" theory view. Author tries to find out which one of behavior "balancing" attempts to balance, weaken USA or "bandwagoning" - support of USA is prevailing in Chinese policies. According to the prevailing tendency of Chinese behavior towards USA the author is capable to state whether China can be considered as a threat for US hegemony.

This study examined the impact of load on lower body performance variables during the hang power clean. Fourteen men performed the hang power clean at loads of 30%, 45%, 65%, and 80% 1RM. Peak force, velocity, power, force at peak power, velocity at peak power, and rate of force development were compared at each load. The greatest peak force occurred at 80% 1RM. Peak force at 30% 1RM was statistically lower than peak force at 45% (p = 0.022), 65% (p = 0.010), and 80% 1RM (p = 0.018). Force at peak power at 65% and 80% 1RM was statistically greater than force at peak power at 30% (p < 0.01) and 45% 1RM (p < 0.01). The greatest rate of force development occurred at 30% 1RM, but was not statistically different from the rate of force development at 45%, 65%, and 80% 1RM. The rate of force development at 65% 1RM was statistically greater than the rate of force development at 80% 1RM (p = 0.035). No other statistical differences existed in any variable existed. Changes in load affected the peak force, force at peak power, and rate of force development, but not the peak velocity, power, or velocity at peak power.

This Ph.D. thesis carries out extensive and in-depth research on the packaging technology of silicon carbide (SiC) power modules, including new packaging structures, multi-physics modeling and optimal design methods for half-bridge power modules, manufacturing processes, and experimental validations. A new packaging scheme, the Silver-Sintered Molybdenum (SSM) packaging, is proposed in this thesis. It contains a molybdenum (Mo) -based insulated-metal-substrate (IMS) structure, nano-silver sintering die-attachments, and planar interconnections. This technology has the potential to increase the operating temperature of SiC power modules to above 200 degrees, and can greatly improve their lifetime. These advantages are verified by active power cycling and passive temperature cycling simulations. Analytical modeling methods for half-bridge power modules with the SSM packaging are also studied. A decoupled Fourier-based thermal model is introduced. This model considers the decoupling effect between different heat source regions and can give a three-dimensional analytical solution for the temperature field of a simplified half-bridge power module structure. In addition, based on the partial inductance model for rectangular busbars, an analytical stray inductance model for half-bridge power modules is also proposed. The accuracy of these two models is estimated by both numerical simulations and experiments. With the proposed analytical models, an optimal design method for half-bridge power modules with the SSM packaging is proposed in this study, which uses the particle swarm optimization algorithm. This method is successfully applied in the design of a prototype power module and is able to minimize the stray inductance and volume while maintaining desired junction temperatures. This thesis also introduces the manufacturing process of the prototype power module. Several new processes are proposed and validated, including a pressure-less nano-silver sintering process to bond SiC dies on Mo substrates, the formation of the Mo-based IMS structure, and the re-metallization of SiC dies. / Thesis / Doctor of Philosophy (PhD)

Future all-electric warships with an integrated power system (IPS) are capable of unlocking large amounts of power dedicated to propulsion and redirecting this power for service loads, weapon loads, and other loads. The IPS for all-electric ships combines the power generation system, electric propulsion system, power distribution system, and power control and management system all together. The move to IPS design will significantly improve efficiency, effectiveness, and survivability. To meet the needs of the US Navy, enhancing survivability by reducing susceptibility to damage, a IPS prefers decentralized reconfiguration system is preferred for IPS instead of traditional reconfiguration techniques used for terrestrial power grids. A multi-agent system (MAS) is a loosely coupled network composed of several agents. These agents interact with their environments and communicate with each other to solve problems that are beyond the individual capabilities or knowledge of each single agent. Because of its decentralized feature and lack of a global control feature, MAS appears to be the best candidate for IPS reconfiguration. This research work proposes a new model of an IPS, based on the Naval Combat Survivability, DC Distribution Test-bed (NCS DCDT). The new model combines the electric power generation system, electric propulsion system, and AC-DC zonal distribution system. To decrease the probability of distribution zones losing power, the new model modifies original design of the zonal distribution system in NCS DCDT. Another main endeavor of this research work is to design a MAS for reconfiguration of an IPS with AC-DC zonal distribution system. The MAS consists of three sub-MAS, named power generation MAS, propulsion MAS, and distribution MAS, and includes forty-one different agents which are instances of nineteen different abstract agent classes. The MAS is implemented with JAVA/JADE software and simulated on a platform of JADE 3.4.1 and JAVA jdk 1.5.0_08. Simulation results show that the MAS can execute reconfiguration functions such as fault area isolation, automatic switching, and load shedding.

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No description available.

No description available.

The IEEE 802.11 standard has been widely adopted as a Wireless LAN (WLAN) technology. This widespread proliferation of the technology has lead to an increase in the number of users taking advantage of so-called "hot-spots" which leads to an increased demand on bandwidth provided by Access Points (APs) in the hot-spot. The logical solution is to deploy more overlapping access points in the same coverage area, thus increasing the capacity of the system by providing load balancing services. However, when a hot-spot is located in an outdoor environment, it becomes difficult to provide the AP with power which is traditionally carried over wired links thus causing the service provider to incur additional costs, not to mention the impossibility in some cases of delivering power to the AP. This problem can be overcome by using solar-panel powered APs which we will refer to as solar nodes (SNs). In this thesis we examine the load-balancing problem that arises when two or more SNs are co-located in the same coverage area. We propose and evaluate two algorithms for efficiently distributing the load among them (transferring stations (STAs) from SN to neighboring SNs) and increasing their lifetime by using power saving schemes that co-ordinate the wake/sleep patterns of the SNs based on traffic load. Finally, a Connection Admission Control (CAC) function is proposed that the SN should use in order to provide controlled access to services. We demonstrate through simulations that our proposals can significantly reduce the hardware requirements and cost of SNs and improve the service perceived by STAs in terms of transmission delay. / Thesis / Master of Applied Science (MASc)

The growing demand for high voltage, compact pulsed power supplies has gained great attention. It requires power supplies with high power density, low profile and high efficiency. In this thesis, topologies and techniques are investigated to meet and exceed these challenges. Non-isolation type topologies have been used for this application. Due to the high voltage stress of the output, non-isolation topologies will suffer severe loss problems. Extremely low switching frequency will lead to massive magnetic volume. For non-isolation topologies, PWM converters can achieve soft switching to increase switching frequency. However, for this application, due to the large voltage regulation range and high voltage transformer nonidealities, it is difficult to optimize PWM converters. Secondary diode reverse recovery is another significant issue for PWM techniques. Resonant converters can achieve ZCS or ZVS and result in very low switching loss, thus enabling power supplies to operate at high switching frequency. Furthermore, the PRC and LCC resonant converter can fully absorb the leakage inductance and parasitic capacitance. With a capacitive output filter, the secondary diode will achieve natural turn-off and overcome reverse recovery problems. With a three-level structure, low voltage MOSFETs can be applied for this application. Switching frequency is increased to 200 kHz. In this paper, the power factor concept for resonant converters is proposed and analyzed. Based on this concept, a new methodology to measure the performance of resonant converters is presented. The optimal design guideline is provided. A novel constant power factor control is proposed and studied. Based on this control scheme, the performance of the resonant converter will be improved significantly. Design trade-offs are analyzed and studied. The optimal design aiming to increase the power density is investigated. The parallel resonant converter is proven to be the optimum topology for this application. The power density of 31 W/inch3 can be achieved by using the PRC topology with the constant power factor control. / Master of Science