This thesis is to investigate the power quality problems for KMRT system and to derive the optimal strategy to mitigate the harmonic distortion. The mathematical models of dc network which includes the TSS, 3rd track and VVVF Converters will be derived. Based on the power system network configuration, the operation schedule and annual ridership of KMRT system, the ac/dc load flow analysis is executed to find the power demand and current harmonic components for each TSS and each BSS. The harmonic load flow analysis is then performed to solve the voltage harmonic distortion. The optimal planning of harmonic filters will be derived so that the proper locations and years for the harmonic filters to be committed can be determined. The active filters and high pass filters as well as the band pass filters are all considered in the study to achieve the best cost effective for harmonic filter investment. This thesis will also to analyze in the stray current for mass transit system the mathematical models of TSS rectification stations, 3rd rail, running rail, the insulation resistances between running rail, MRT structure and grounding are included in the computer simulation. The variation of stray current for the peak and off peak operation of KMRT system over each study year is derived. The sensitivity analysis of stray current with respect to the insulation level of running rail is executed . The nearby public pipes of the MRT network will be used for the analysis of cathode corrosion due to the stray current. Different strategies to mitigate the stray current are investigated.

This study investigates horizontal water turbine. Firstly, blade element momentum theory is exploited to design blade profiles. Then, CFD software, Fluent, is used to obtain such simulation results as torque, power and efficiency. A shroud outside the water turbine is tested to show the influence on the output power. Detailed parameters, shroud geometry and blade number, are considered too. Additionally, the maximal power generated by the turbine is analyzed under periodic sea current flow in this research. Our studies show that installed shroud can increase the output power more effectively and surely. Various kinds of shroud geometry have influence on the water turbine capability. As for the shroud types, nozzle type is better to achieve the best power. But as the inclined angle increases, the power also rises. The blade number boosts up the output power. Compared with other parameters, shroud length is of minor significance. On condition of periodic current flow, NACA63415 outperforms NACA0009, NACA0011 and Elliptical 10 in terms of airfoil, with its best efficiency and power.

The effect of electromigration on void formation and the failure mechanism of FCBGA packages under a current density of 1*104 A/cm2 and an environmental temperature of 150¢J was investigated. Eight solder/substrate combinations of four lead-free solder systems with two substrates were examined to verify the failure modes. A conservative failure criterion was adopted to define and predict the failure of the package. SEM was employed to observe in situ microstructural changes, IMC growth, and failure modes. All samples exhibited a similar failure, attributed mainly to void occupation along UBM/solder interfaces at the cathode chip side of the bumps with downward electron flow. Voids were initiated at the corner due to current crowding. Two specific void locations were identified at the IMC/solder and UBM/IMC interfaces, and they co-existed in the same specimen but in different bumps. No void coupling mode was found. Since the atom diffusion rate in the solder differs from that in the IMC layer, the voids can be formed between them. A current density of 1*104 A/cm2 was sufficiently high to form a void pattern at the IMC/solder interface. However, the formation of voids at the UBM/IMC interface is generally induced by the consumption of UBM, since the high temperature of 150¢J crucially dominates the void morphology at the UBM/IMC interface. The difference among solder systems did not affect the failure modes nor dominate mechanisms. Two theoretical models based on the experimental results were applied to describe the void formations. They will be more accurate and useful in understanding void formations by further experimental data provided. According to the results of solder bumps with electrons only flowed through Al trace line at die side, it suggested that atoms transport toward the bottom substrate along with the temperature gradient and toward the right corners along with electron flow when electrons flowed through the trace after the resistances of solder joints reaching 120¢H of their initial values. With respect to the differences of substrate surface finishes, more voids appeared at the cathode substrate side of the solders combined with Cu/Ni/Au pad than those combined with Cu-OSP after long-term upward electron stressing. It suggested another possible failure at the substrate side when failure did not occur at the chip side in an EM test.

In recent years, an increasing pursuit of product appearance, so the surface appearance of the product are the main arc, but if we can develop the flexible fuel cells, fuel cells will be able to scratch-type adhesive on the product curved surface, not only for product supply and portable, low pollution have great potential for portable fuel cells. Performance of the experiment found that the decision lies in the amount of carbon fiber bundles, softness and spring pressure on the uniformity imposed by such factors. The experiment that bending radius of curvature of 45.5cm, the battery around the X, Y, XY axis deflection performance and the performance is not the same, and the radius of curvature around the X-axis deflection narrow, performance is not reduced, around the XY axis deflection narrow the radius of curvature, the performance has not decreased significantly, but the radius of curvature around the Y-axis deflection reduced, performance has slightly dropped, from IV Curve that the radius of curvature smaller fiber bundles and electrode contact resistance also increases, but this performance decline in the acceptable range. This will be a torsion-type fuel cell, can be the radius of curvature 45.5 ~ 10.58cm or less within the flexural performance, this battery has the potential of portable fuel cells, advantages of low pollution, high efficiency and easy to carry.

Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, June 2003. / Thesis advisor(s): Robert W. Ashton, John G. Ciezki, Douglas J. Fouts. Includes bibliographical references (p. 125-126). Also available online.

Thesis (M.S. in Physical Oceanography)--Naval Postgraduate School, June 2003. / Thesis advisor(s): Edward B. Thornton, Timothy Stanton. Includes bibliographical references (p. 59-62). Also available online.

Thesis (M.S. in Physical Oceanography)--Naval Postgraduate School, June 2003. / Thesis advisor(s): Curtis A. Collins, Mary L. Batteen. Includes bibliographical references (p. 79-80). Also available online.

M. Tech. Electrical Engineering. / A matrix converter is a direct AC-AC forced commutated converter which uses bidirectional switches to connect two voltage systems of different voltage and frequency. It does not contain any large energy storage elements as it has no DC link between the two systems. The output frequency is theoretically dependant on the switching algorithm and not the input frequency. A combination of bi-directional switches, controlled to obtain any desired output frequencies from a fixed or variable input frequency, will serve as a versatile platform, from which more specific applications could be researched. Most literature uses simulations with ideal switches, or deal with theoretical studies of specific aspects or problems to be solved. A comprehensive study of matrix converters will include the construction of a real converter. The bi-directional switch is the cornerstone of any direct matrix converter. To be able to research matrix converters successfully, it is important to evaluate the bi-directional switch in operation, i.e. in real circuits. This study models, compares and evaluates a basic 3 to 1 matrix converter with various input and output frequencies. This is done for different input and output conditions such as different system frequencies and loads. Practical results with comments and conclusions are included.

published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

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