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Typescript, etc. / Digitized by Kansas State University Libraries

The purpose of this research was to develop three real-time adaptive temperature controllers for hyperthermia heating systems. Each scheme is made adaptive by using a transient Gaussian estimation routine to estimate the tissue blood perfusion and by then using these estimated values either in an optimizing routine, or in an observer, or in both. The optimizing routine uses a steady-state Gaussian estimation technique to optimize the power distribution until the best possible match is obtained between the steady-state temperatures predicted by a treatment model and a prespecified ideal temperature distribution. The observer uses a treatment model to control unmeasured locations. The first adaptive control scheme uses the optimizing routine alone, the second uses the observer alone and the third uses both the optimzing routine and observer. The performance of each of the adaptive control schemes is compared to a standard proportional-integral-derivative (PID) control scheme for one-dimensional simulations of typical treatments. Results comparing the deviation of the controlled temperature distribution to the ideal desired temperature distribution for all locations and all times indicate that the adaptive schemes perform better than the PID scheme. It can be concluded that adaptive control yields improved performance if good a priori knowledge of the treated region tissue and perfusion region boundaries is available. While these control schemes were designed for eventual implementation on a scanned focused ultrasound hyperthermia treatment system, the techniques are applicable to any system with the capability to vary specific power with respect to location and with an unknown distributed energy sink proportional to the temperature elevation.

published_or_final_version / abstract / Conservation / Master / Master of Science in Conservation

Cook-Chill Foodservice System was a new alternative foodservice system in the 1960s. Food items in Cook-Chill Foodservice Systems are prepared and chilled in advance of service, stored in inventory, and then rethermalized before consumption. The purpose of this research was to evaluate Cook-Chill Systems from the foodservice manager's view. The objectives of this study were to: (1) identify effects, advantages and disadvantages, and decision making factors for selection Cook-Chill Systems as perceived by managers, and (2) determine if the demographics influence managers' assessment. A survey questionnaire was used to collect current information of Cook-Chill Systems. One hundred thirty-four surveys were mailed nationwide to foodservice managers with 95 (71%) valid responses. Data were analyzed from the 74 respondents who currently used Cook-Chill Systems. The results indicated that the perceived meal quality, quantity control and personnel satisfaction was equal or better, and labor cost was decreased and equipment cost increased were most often reported by managers in comparing Cook-Chill Systems with prior systems. Managers identified seven advantages: good working conditions, high productivity, labor savings, consistent quality food, good quantity control, nutrient retention, and safety. One perceived disadvantage was high capital cost of equipment. The five most often cited factors for selection of Cook-Chill Systems were labor savings, good working conditions, consistent quality food, safety, and high productivity. Factors most often cited for not selecting Cook-Chill Systems were the limited menu and types of products produced, complaints of bad food, and high capital cost. Most Cook-Chill Systems have been installed in the past ten years with previously centralized production flow. Cook-Chill Systems accommodated small to large numbers of meals with both blast chiller and tumbler chiller equipment and many reheating methods. Half of the managers were involved in choosing, designing or implementing Cook-Chill Systems. Four significant outcomes were: (1) microbiological control was the highest of meal quality contributes; (2) manager satisfaction was higher than customer and employee satisfaction; (3) meal quality and personnel satisfaction differed among reheating methods; and (4) management experience for design or implementation influenced managers' willingness in choosing these systems again. Four recommendations were drawn from this research. Recommendations were: (1) studies to identify factors contributing to success of reheating methods, (2) standard models for cost recording, (3) approaches to analyze capital cost, create menu items, and find causes of food quality complaints, and (4) a Cook-Chill Information Center to share knowledge and support the further development of Cook-Chill Systems. / Graduation date: 1991

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Light can be coupled out of a waveguide to a focused point by a focusing grating coupler and has possible applications in optical data storage. The grating can be fabricated with either e-beam techniques or holographic techniques. Two design methods are demonstrated that model the focusing grating coupler with holographic optical elements. Both methods take a geometrical optics approach to designing the holographic optical elements and both methods make use of commercially available ray trace programs. The first method uses complicated non-rotationally symmetric construction optics and requires either a modified ray trace program or special user defined surfaces. The second method involves a much simpler approach which did not require any changes to an existing ray trace program and requires only rotationally symmetric elements to correct the aberrations.

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M.Ing. / During mineral exploration a whole lot of different exploration techniques can be applied. In this thesis the instrumentation used for electromagnetic surveying, which is only one of the prospecting techniques, is inspected. In particular the thesis will be about the transmitter of the single transmitter wide band receiver airborne electromagnetic prospecting system. A new power electronic topology is proposed in order to improve this transmitter. Before this is done a reference is first established. This is done in the form of the exponential transition inverter, which is the inverter that is currently applied as transmitter in South-Africa. Another reason for looking at this circuit topology is because it is the simplest way to realize the transmitter. During the analysis of this inverter topology all the proporties of the transmitter as a whole is also investigated. The main component of the transmitter, namely the transmitter coil is also discussed. This is followed by a summary of the properties of the exponential transition inverter in which the main shortcomings of this transmitter is discussed. The greatest of which is surely that pliable frequency spectra cannot be obtained. Subsequently resonance is viewed as a solution to the shortcomings. The main contribution of this is that the pliability of the frequency spectrum can be increased, because the capasitor in this circuit can easily be changed. It is however shown that a purely resonant circuit on it's own, also is not the solution. This leads to the improved inverter topology for the transmitter, namely the Kwasi resonant inverter. It is shown in detail that the Kwasi resonant inverter is a much beter option as transmitter then the exponential transient inverter. Since this circuit also has a capacitor in it, it is shown that pliable frequency spectra can be obtained. It is futher shown how the pliability of the frequency spectrum can be improved even more by deviating from conventional methods of switch control. Mathematical analysis, as well as an experimental setup, of the different inverter topologies, are used to illustrate all of the above mentioned. As a conclusion the only drawback of the Kwasi resonant inverter, namely high voltage peaks, is addressed. A solution to this problem is proposed in the form of two different voltage clamps. The best one of the two is identified and also implemented.