Thesis (M.Ag.Sc.) University of Adelaide, Dept. of Agriculture,1980.

Habilitationsschrift--Universität Fridericiana Karlsruhe. / At head of title: IFO-Institut für Wirtschaftsforschung. Bibliography: p. [133]-137.

Habilitationsschrift--Universität Fridericiana Karlsruhe. / At head of title: IFO-Institut für Wirtschaftsforschung. Bibliography: p. [133]-137.

Thesis (M.S.)--University of Wisconsin--Madison. / Typescript. eContent provider-neutral record in process. Description based on print version record.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1970. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 348-353).

Thesis (M.S.)--West Virginia University, 1999. / Title from document title page. Document formatted into pages; contains viii, 91 p. : ill. (some col.) Includes abstract. Includes bibliographical references (p. 67-69).

The thesis is concerned with static frequency changers, using solid-state switching devices, capable of directly (i.e. without an intermediate dc link) converting polyphase ac power of a given frequency to single or polyphase power of a chosen frequency. The thesis consists of two parts. The first part, comprising five chapters, is devoted to the study of ideal frequency changers operated from ac Sources having zero internal impedance. The second part, comprising two chapters, considers sources with finite internal impedances . Chapter 1 introduces the basic concepts of static frequency conversion, outlines the basic mathematical models representing static frequency changers and defines the output and input performance indicators. Chapter 2 presents a detailed investigation of that class of three-pulse frequency changers which will be studied in the thesis. A large portion of the chapter is devoted to the study of output waveform generation. The mathematical tools of the investigation, existence matrices and modulating functions, are introduced and defined. Analytical expressions for output waveforms corresponding to various practical modulating functions are derived and the related performance indicators are computed. Assuming a given desired output performance, criteria for an optimal modulating function are established. It is proved that only one system can generate an output waveform conforming to the postulated prerequisites. This system is termed the "Unrestricted" Frequency Changer. Expressions for the input current waves are also derived in this chapter and the corresponding input performance indicators are determined . The concept of a new frequency changer having the unique property of providing unity input power factor, regardless of the load, is introduced. This system is termed the "Unity Power Factor" Frequency Changer. In Chapter 3 the previous results are extended to systems having pulse numbers which are integral multiples of three. Chapter 4 is devoted to the study of output voltage control. Three basic methods are analysed and detailed quantitative data for output voltage and input current waves, and the related performance indicators, are presented in graphical form. In Chapter 5 special aspects of static frequency changing are investigated. It is shown that the input displacement factor is variable. The concept of the "Controlled Displacement Factor" Frequency Changer is introduced It is proven that the naturally commutated cycloconvertor is theoretically equivalent to a particular "Controlled Displacement Factor" Frequency Changer. Chapter 6 presents a detailed analysis of the "Unrestricted" Frequency Changer, operated from an ac source with finite internal impedance. The basic conditions are defined and an outline is given of the techniques of symmetrical components used for the analysis. The input current, input terminal voltage and output voltage waveforms are expressed in terms of the input terminal impedance and the positive, negative and zero sequence components of the output currents. The equivalent sequence impedances and the output impedance matrix are derived . The output voltage unbalance is computed under various conditions and presented in graphical form. The relationships between the amplitudes of the unwanted components in the output waveform and the resonant frequency of the input terminal circuit are also graphically presented. The results obtained are verified by computer simulations. In Chapter 7 a similar analysis of the "Unity Power Factor" Frequency Changer is carried out . The computed data are also graphically presented. Again, the results are verified by appropriate computer simulations.

A series of six consecutive input-output tables has been constructed for the economy of West Malaysia for the period from 1960 to 1965. This thesis provides an evaluation of their efficiency when applied in forecasting intermediate output. A brief review of the theoretical structure of the static input-output model developed by Leontief has been presented. Particular attention has been given to the economic assumptions which are necessary to make the prediction procedure tenable. The basic assumption of constant input coefficients was not tested directly, however. Instead, the empirical usefulness of the input-output system has been evaluated in terms of the quality of predictions it yields. Each of the tables from 1960 to 1964 has been used in turn to predict intermediate sectoral outputs for succeeding years to 1965. Input-output prediction errors were calculated by reference to the observed intermediate outputs set forth in the tables. To test the significance of these errors, a comparison was made with the errors that arose when corresponding projections of intermediate output were made from a naive extrapolation model. In addition the overall effect on the input-output predictions of the length of the forecast period was analyzed and the relative performance of individual sectors was examined. Wherever possible, the efficiency of the West Malaysian tables was compared with that of input-output tables for the Netherlands economy. In general the predictive power of the West Malaysian tables was not impressive. On the average the input-output forecasts proved to be superior to the naive extrapolations only when the prediction period did not exceed two years. For individual sectoral forecasts, the input-output model yielded better predictions of intermediate output in only seven of the 15 sectors considered. In every comparison with the efficiency of the Netherlands tables, the inferiority of the West Malaysian tables was demonstrated. Attempts have been made in the thesis to trace the reasons for the poor performance. Some improvements to the tables have been suggested. / Arts, Faculty of / Vancouver School of Economics / Graduate

This thesis is concerned with aspects of a theory of machine perception. It is shown that a comprehensive theory is emerging from research in computer vision, natural language understanding, cognitive psychology, and Artificial Intelligence programming language technology. A number of aspects of machine perception are characterized. Perception is a recognition process which composes new descriptions of sensory experience in terms of stored stereotypical knowledge of the world. Perception requires both a schema-based formalism for the representation of knowledge and a model of the processes necessary for performing search and deduction on that representation. As an approach towards the development of a theory of machine perception, a computational model of recognition is presented. The similarity of the model to formal mechanisms in parsing theory is discussed. The recognition model integrates top-down, hypothesis-driven search with bottom-up, data-driven search in hierarchical schemata representations. Heuristic procedural methods are associated with particular schemata as models to guide their recognition. Multiple methods may be applied concurrently in both top-down and bottom-up search modes. The implementation of the recognition model as an Artificial Intelligence programming language called MAYA is described. MAYA is a multiprocessing dialect of LISP that provides data structures for representing schemata networks and control structures for integrating top-down and bottom-up processing. A characteristic example from scene analysis, written in MAYA, is presented to illustrate the operation of the model and the utility of the programming language. A programming reference manual for MAYA is included. Finally, applications for both the recognition model and MAYA are discussed and some premising directions for future research proposed. / Science, Faculty of / Computer Science, Department of / Graduate

In an ideal world, unwanted or undesirable effects in a system could and would be completely ignored. In fact, this was the case in mid-80s' PC design when an 80286 microprocessor running at a "blazing" 12 MHz was considered leading-edge technology. As technology continued to push the envelope and ever-faster designs were realized, more demanding software packages were developed and utilized efficiently. These increasingly sophisticated software packages in turn allowed designers of all disciplines to test systems of escalating complexity. These more complex models placed a heavier burden on the hardware, prompting a push for better and faster hardware designs. The cycle repeats to this day. As such, we are now in an environment where a 1 GHz microprocessor is considered somewhat dated. More importantly, whereas a small 1 nH (1 billionth of a Henry) inductance in a power delivery path was considered inconsequential a decade ago, it is now a barrier to implementing a design. Similarly, the equivalent series inductance (ESL) of a capacitor plays an increasing (and detrimental) role in the behavior and design of today's VRM (Voltage Regulator Module) design. In fact, it is the ESL of the capacitor that hinders proper voltage regulation at high frequencies by increasing the output impedance beyond a desired level. This dilemma has been recognized and several topologies have been proposed to overcome this problem. One category is improved passive devices, with the latest involving array capacitors to achieve near-zero ESL. As passive devices are almost always preferable to active solutions due to their lower losses, these technologies hold great promise, though they are inherently limited in small-footprint applications. A second category is the addition of active devices, which involves the use of some filtering technique to inject or absorb current during a fast transient by the use of semiconductor switches connected to a power source. These switching-state topologies have been shown to be prone to unstable oscillations, often caused by over-reactions or over-corrections of one transient prompting the opposite switch to engage its power source. The research goal is to develop a methodology to use active filters to more-seamlessly extend the control bandwidth of today's VRM technology. A hybrid active power filter is developed which uses bipolar junction transistors (BJT) in the forward-active region to connect a power supply source to the microprocessor. In this way, the switches are used in a way analogous to a dimmer switch (vs. simply 'on' or 'off'). By proper design of the compensator in the feedback loop, the active power filter can be used to suppress transients in any desired frequency range, limited only by the amplifier's current rating and bandwidth. The compensator design's derivation shows the relationship to the output impedance of the active filter. In essence, we are 'designing' a capacitor with a very low ESL, having more desirable output impedance vs. frequency relationship than either a capacitor, or a more complicated VRM with an extended bandwidth. Using this design, however, at very high frequencies (i.e., approaching 1 GHz, or one trillion cycles per second) requires state-of-the-art packaging designs to limit unwanted impedances, and also an ultra-wide GHz bandwidth, high-current operational amplifier. Both of these barriers are outside the scope of this research. As is often the case in research efforts, we have not '˜solved' the problem, but have shifted it to a frequency range where the effect isn't problematic. Experimental results show the use of a hybrid power filter with a VRM with Adaptive Voltage Positioning (AVP) can significantly suppress voltage undershoot during fast transient load current changes. In addition, the design is modified to reduce and possibly eliminate bulk output capacitors. This provides a promising alternative to a Voltage Regulator Module with a very high control bandwidth. Lastly, simulations give an estimate of the required IC design to use an APF to augment packaging capacitors. / Master of Science