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The goal of this thesis is to develop a novel polishing tool system, which can be attached to a CNC machine tool and execute a precision polishing job for an axially symmetric free surface. The precision polishing job is to remove the error surface profile, left by the previous machining process, on the work to improve its form precision. The system mainly includes a mechanism of 3 degrees of freedom, a misalignment compensator mounted on the mechanism, and an oscillation-free connector between tool and driver. The mechanism was designed to meet the required motions of tool trajectories. These motions are to assure the tool can play three specific functions. The first one is to keep the tool axis maintain a constant angle with the normal of polished surface. The second one is to control the wear rate distribution of tool to reduce the effect of tool wear on polishing rate. The final one is to achieve the goal of uniform polishing quality at every spot of polished surface. The conceptual design of this mechanism is done based on a strategy of problem decomposition. The misalignment compensator is to reduce the effect of tool misalignment on the variation of polishing rate. The compensator allows a translational motion and is constrained by a spring. When the tool is mounted on the compensator, the study will show that with a proper spring constant the effect of tool misalignment can be significantly reduced. The study will indicate that the smaller the tool mass is the higher the compensation efficiency can be. The oscillation-free connector is to separate the tool and its driver so that the mass of driver is not included in tool, while the driving function retains. It is composed of two parts. One part is connected to tool and the other one is mounted on driver. These two parts are not joined together by any mean. However, the motions of two parts will interfere with each other. Thus, the driving function between tool and drive can be maintained. It is noted that the vibration of driver can be successfully isolated from the tool if a soft material is attached to one part.

Background: Many cancer patients who require external beam radiotherapy such as breast cancer patients, present with irregular surface topographies and tissue inhomogenieties in the treatment field. Such irregularities give rise to unacceptable dose non-uniformity. Standard fields cannot be applied without compensation for missing tissue. 1-D and 2-D missing tissue compensators can be used but they have limitations. 3-D compensators are the most effective but they are normally fabricated using very expensive automated systems. Objectives: To study the variation of linear attenuation coefficients of different materials in megavoltage photon beams, select a tissue equivalent compensating material and commission a local 3-D manual missing tissue compensator cutter. Methods and materials: Linear attenuation coefficients were measured for tin, River sand mix, Lincolnshire bolus and dental modelling wax for different energy megavoltage photon beams. Measurements were done in a water phantom using a cylindrical ionisation chamber at varying depths. The CT numbers and densities of the materials were also measured. Negative plaster of paris moulds of the breast and head and neck areas were made using a RANDOTM Alderson anthropomorphic phantom from typically simulated fields. 3-D missing tissue compensators were then fabricated on the manual cutter and were tested for their effectiveness during treatment delivery. Results: Linear attenuation coefficients were dependent on photon beam energy, the thickness and density of the attenuator, but independent of the depth of measurement for compensator thickness of more than 2 cm. Lincolnshire bolus and dental modelling wax with CT numbers of –78 ± 9 and -88 ± 18 and densities of 1.4 ± 0.0 g/cm3 and 0.9 ± 0.0 g/cm3 respectively can be regarded as tissue equivalent materials. The fabricated 3-D missing tissue compensators were effective in correcting for dose non-uniformities compared to fields with no beam-modifying devices or wedges (1-D compensators). Conclusions: The 3-D missing tissue compensators were effective in correcting for dose non-uniformities in treatment fields involving very irregular surface topographies compared to 1-D and 2-D methods. They can be fabricated cheaply using a 3-D manual missing tissue compensator cutter. Quality control procedures need to be followed during fabrication.

In this thesis, a high-efficient integrated pixel compensator architecture for the H.264/AVC standard has been proposed which can provide both inter and intra prediction functions for luma and chroma components of pixels. By decomposing the algorithms used for both prediction methods into small micro-operation steps, the fundamental arithmetic processing unit architecture capable for performing these operations can be first determined. Next, by considering the possible reference sample transfer issue, the overall compensator architecture will be built by using parallel processing units with some input and intermediate buffers which can be dynamically configured to perform proper computation schedules of different modes suitable for the nature input order of reference samples. The proposed design not only can avoid the additional data transposition buffer, but most importantly the data transfer time spent to fetch the reference samples can be overlapped with the data computation time. Since both arithmetic units and the intermediate data buffer for both inter and intra prediction processes have been shared, our integrated design can achieve more than 30% reduction of gate count compared with the sum of the separate designs. Our design can also lead to more than 38% saving of gate count compared with the previous designs. In addition to the data-path design, this thesis also addresses the memory bandwidth optimization issue which is especially important for the luma interpolation process. A new data-reuse buffer design based on a two-dimensional cache architecture to explore the possible data reuse among the inter and intra partitions will be proposed. The proposed design can be easily integrated with the H.264 interpolator to reduce the enormous demand of memory access. Our experimental results shows that our saving of memory bandwidth can be 20% more than what the best design can achieve by exploring the intra-partition data reuse only. Besides, our compensator can decode the videos up to HDTV resolution, and be applied for the dedicated H.264 hardware codec for various consumer devices.

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Most digital control architectures for power system applications require synchronization with the distribution system voltage. Therefore, a phase-locked loop (PLL), implemented in a DSP, is generally among the digital control blocks of the control system. The PLL analyzes the bus voltage and provides power system information for some of the other blocks to do further calculation. Thus, the performance of the PLL has a broad impact on the system performance. Small-scale power systems, such as naval systems, pose a challenging environment for PLL design due to voltage distortion and variation in the fundamental frequency that is large as compared to large terrestrial systems. Our objective is to improve the accuracy of the PLL digital block and hence enhance the digital control system. This research compares two PLL algorithms, as well as the use of a PI controller or lag controller with respect to their steady state and transient performance.

ABSTRACT With the development of high-tech industry, the power quality has become a critical issue for the industrial customers in science park. The voltage sag and power system stability problems due to fault contingency in Taipower network has caused serious production loss. The manufacturing process platforms, which are driven by power electronics equipments may shutdown when the voltage dip exceeds 30% and it will take long time for the restoration of production. To enhance the service reliability and power quality, the new cogeneration system in Hsin Chu Science Park has been selected for case study to solve the problems of short circuit capacity and voltage sag. The short circuit analysis by both ANSI and IEC is performed to find the magnitudes of fault currents. The transient stability analysis is executed to identify the critical clearing time to support the design of protective relays for tie line tripping. The static var compensator (SVC) is also considered in the simulation to investigate the mitigation of system voltage drop due to fault contingency. It is found that the implementation of cogenerators and SVC can improve the electricity service quality for high-tech customers with proper design of industrial power systems.

This investigates the voltage flicker problem of a large steel plant and presents the mitigation strategy by applying the static var compensator (SVC) and cogenerator. The fluctuation of real power and reactive power consumption by an arc furnace has been measured and recorded during the steel production process. The dynamic load model of the A/C arc furnace is derived based on the actual field data and has been included in the computer simulation by the CYME software package for load flow analysis. The block diagrams of SVC controller and the excitation system of cogenerators are considered to solve the response of reactive power compensation according to the voltage fluctuation of the control bus. To maintain the electric service reliability of arc furnace when an external utility fault occurs, the tie line tripping and load shedding is implemented to prevent the tripping of cogenerator after system disturbance. It is found that the dynamic load behavior of arc furnace in the isolated industrial power system can be well compensated by the cogenerator with adaptive control of exciter and governor to generate proper reactive power and real power according to the fluctuation of bus voltage and system frequency respectively.

[pt] O objetivo do trabalho é, dentro do escopo de estudos dos Sistemas Flexíveis de Transmissão em Corrente Alternada (FACTS), apresenta um estudo preliminar sobre a atuação do Compensador Generalizado, proposto em Gyugyi [1990]. Este trabalho aborda a atuação do equipamento proposto em um sistema duas barras e procura determinar os seus efeitos qualitativos. Dois casos limites foram estudados: sistema radial com carga passiva em uma das barras e sistema com barra infinita simulando o intercâmbio de potência entre sistemas. Este estudo é realizado através da modelagem dos inversores do Compensador Generalizado como fontes de tensão e corrente operando na freqüência fundamental e em regime permanente. A reatância equivalente dos transformadores acoplados não foi considerada. Esta reatância deverá ser considerada em futuros trabalhos. Resultados importantes são obtidos, neste trabalho, em relação aos novos modos de controle do sistema de transmissão, até então impossíveis com os equipamentos de compensação tradicional. / [en] This dissertation presents a preliminary research abouth the Generalized Compensator operation at power systems, proposed in Gyugyi [1990], into the scope of Flexible AC Transmision System studies. This study makes a description of the proposed equipment actuation at a two bus system and explains some of its qualitative effects. Two configurations weree chose: a radial with passive load and a system with infinite bus in order to study power interchange between two systems. The voltage-sourced inverters of Generalized Compensator are modeled by voltage and current contrlolled source. These sources operate at the fundamental frequency and at the steady state. The leakage impendances of the coupking transformers are not considered but they will be considered in future researches. Important results are obtained about the new control modes of the transmission system. These new control modes are impossible with the traditional compensation equipament that have been used up to now.