Chemnitz, Techn. Univ., Diss., 2005.

Thesis (M.Sc.)--Memorial University of Newfoundland, 2006. / Bibliography: leaves 115-116. Also available online.

Thesis (M. Phil.)--University of Hong Kong, 2005. / Title proper from title frame. Also available in printed format.

Thesis (Ph. D.)--West Virginia University, 2006. / Title from document title page. Document formatted into pages; contains viii, 99 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 93-99).

Universiẗat, Diss., 2000--Kassel. / Lizenzpflichtig.

Thesis (M.S.)--West Virginia University, 2007. / Title from document title page. Document formatted into pages; contains viii, 95 p. : ill. Includes abstract. Includes bibliographical references (p. 79-91).

The Coalition Structure Generation (CSG) problem requires finding an optimal partition of a set of n agents. An optimal partition means one that maximizes global welfare. Computing an optimal coalition structure is computationally hard especially when there are externalities, i.e., when the worth of a coalition is dependent on the organisation of agents outside the coalition. A number of algorithms were previously proposed to solve the CSG problem but most of these methods were designed for systems without externalities. Very little attention has been paid to finding optimal coalition structures in the presence of externalities, although externalities are a key feature of many real world multiagent systems. Moreover, the existing methods, being non-heuristic, have exponential time complexity which means that they are infeasible for any but systems comprised of a small number of agents. The aim of this research is to develop effective heuristic methods for finding optimal coalition structures in systems with externalities, where time taken to find a solution is more important than the quality of the solution. To this end, four different heuristics methods namely tabu search, simulated annealing, ant colony search and particle swarm optimisation are explored. In particular, neighbourhood operators were devised for the effective exploration of the search space and a compact representation method was formulated for storing details about the multiagent system. Using these, the heuristic methods were devised and their performance was evaluated extensively for a wide range of input data.

The thesis work is performed at Norma Precision AB, a company that manufactures ammunition for hunting and competitive shooting. Two types of cases called 300 Winchester Magnum and 308 Winchester are examined on how their hardness were prior to and after the two annealing’s of the neck they experience during the manufacturing. The cases vary in hardness and an investigation will be made to draw connections to the microstructure of the cases in order to understand the variations and possibly avoid the variations in the future. The cases were selected at different days, the 300 Winchester Magnum were chosen at three different days with some properties varying and the 308 Winchester were taken at two different days. At each day twenty cases were selected, five prior to the first neck annealing, five after the first neck annealing, five after the shaping and calibrating of the cases and the final five after the second neck annealing. The selected cases were first measured by a hardness test, where they were measured at 1mm, 3mm and 6mm from the nuzzle and five times around the case at each measurement. After that, the variations were analyzed and the two most varying cases from each day and step were taken into the laboratory at Karlstad University. In the laboratory, the cases were measured by a microhardness tester. The cases were measured at even distances between them all throughout the cases to make a hardness profile. The next step was to etch the cases and examine them in an optical microscope, where the grain size was measured in micrometer and ASTM. The results from the regular hardness measurements and the microhardness tests showed similar tendencies. Variations was found in each step and each day during both hardness measurements the two types of cases behaved similarly. The grain size results showed that after annealing, the grain size increased. Although there was no clear relation between grain size and hardness since the results varied, some cases with higher hardness had a smaller grain size than a case with lower hardness. Using the grain size of the brass could work to get an idea of the hardness, but to get a sincerer perception of the material properties, more properties needs to be investigated. / Examensarbetet är utfört hos Norma Precision, ett företag som tillverkar ammunition för viltjakt och för tävlingsskytte. Två sorters hylsor vid namn 300 Winchester Magnum samt 308 Winchester undersöks hur deras hårdhet är innan respektive efter de två mynningsglödgningar hylsorna genomgår under tillverkningen. Hylsorna varierar i hårdhet och en undersökning kommer göras för att dra kopplingar till hylsornas mikrostruktur för att få en förståelse av variationerna och eventuellt kunna undvika variationer i framtiden. Hylsorna valdes ut vid olika dagar, 300 Winchester Magnum togs vid tre olika tillfällen när olika egenskaper skiljde och 308 Winchester togs vid två tillfällen. Varje dag plockades tjugo hylsor ut, fem innan första mynningsglödgningen, fem efter den första mynningsglödgningen, fem efter formning och kalibrering av hylsorna samt fem efter den andra mynningsglödgningen. På de utplockade hylsorna gjordes först hårdhetstester, då de mättes vid 1mm, 3mm och 6mm ifrån mynningen och fem mätningar runt hylsan vid varje mättillfälle. Efter det analyserades resultaten och de två hylsor som varierade mest från varje dag och varje steg togs med till labbet på Karlstads Universitet. I labbet mättes hylsorna med en mikrohårdhetsmätare. Hylsorna mättes med jämna mellanrum genom hela hylsan för att skapa en hårdhetsprofil. Nästa steg var sedan att etsa hylsorna och undersöka dem i ett ljusmikroskop, där mätningar av kornstorlek i mikrometer och ASTM gjordes. Resultaten från den vanliga hårdhetsmätningen och från mikrohårdhetsmätningen visade liknande tendenser. Det upptäckes variationer i varje steg och varje dag i båda hårdhetsmätningarna och de två sorternas hylsor betedde sig likadant. Resultaten från kornstorleksmätningarna visade att efter glödgning ökade kornstorleken. Det fanns dock inget tydligt mellan kornstorlek och hårdhet då resultaten varierade, i vissa fall hade hylsorna med högre hårdhet en mindre kornstorlek än hylsor med lägre hårdhet. Att använda mässingens kornstorlek kan fungera för att få en övergripande bild av hårdheten, men för att få en bättre förståelse av materialegenskaperna behöver fler egenskaper undersökas.

Ion Implantation of ruthenium ions into a silicon substrate followed by a high temperature anneal (known as Ion Beam Synthesis) has been used for the first time to fabricate three wafers, under the following conditions. 1. 5.67 X 1016 Ru+ cm-2, beam heated 2. 4.25 X 1016 Ru+ cm-2, heated to ~ 600°C 3. 1.27 X 1017 Ru+ cm-2, heated to ~ 600°C All wafers contained precipitates of the orthorhombic semiconducting silicide of ruthenium, Ru2Si3. No other phase was identified. The samples exhibited a complicated microstructure, with 16 different orientation variants identified, and a high degree of disorder (~ +11% strain). The first optical measurements ever carried out on this material are reported here. Absorption measurements in transmittance yielded a direct band gap, in the region of ~ 0.9eV, 0.87eV, and 0.92eV for wafers 1, 2, and 3 respectively. No discernible variation of band gap magnitude with measurement temperature was found. Upon sequential annealing, the direct band gap magnitude remained constant up to ~ 650°C after which it shifted to above that of silicon, possibly due to a change in microstructural disorder as the precipitates increase in size. This observation was confirmed by several single step anneals at various temperatures above 650°C. No photoluminescence was observed in any of the samples.

La evaluación de yacimientos mineros tiene por objetivo estimar, con el menor error posible, la calidad y cantidad de un recurso mineral, que tiene potencial de ser explotado. Una de las principales herramientas utilizadas es la Geoestadística, la cual pone énfasis en el contexto geológico y la relación espacial entre los datos a estudiar. Los métodos de estimación tradicionales, llamados Kriging, calculan el mejor estimador lineal insesgado de una variable en base a los valores de datos vecinos. Para representar de mejor manera la variabilidad espacial de los datos, se recurre a la Simulación Convencional, que consiste en añadir un factor aleatorio a Kriging para obtener una distribución de escenarios, que sirven como medida de la respuesta ante la incerteza. El inconveniente de esta técnica es que no permite correlacionar diversos puntos al mismo tiempo, sólo se pueden correlacionar dos puntos a la vez (se basa en la covarianza de 2 puntos). Este hecho representa una potencial pérdida de información en la construcción del modelo que se utilizará para realizar estimaciones o simulaciones. Al correlacionar dos puntos a la vez, se induce una suavización sobre las estimaciones, lo cual puede entregar resultados sobreestimados o subestimados. Para solucionar el problema anterior, se propone utilizar métodos que contemplan estadísticas de múltiples puntos, representadas por patrones. Se espera que la utilización de patrones junto a un método de simulación no convencional llamado Recocido Simulado (Simulated Annealing) puedan tener un mejor desempeño al evaluar un proceso que la simulación convencional. Los principales problemas del método propuesto son el tiempo de cálculo del Recocido Simulado y el manejo de patrones grandes. Se optó por resolver el primero de ellos y dejar abierta la puerta para posibles trabajos a futuro en la optimización de las estructuras de datos para el manejo de patrones grandes. El tiempo de cálculo del Recocido Simulado aumenta exponencialmente al incrementar el tamaño de los patrones a estudiar. Para solucionar esto, se realizó una implementación utilizando múltiples procesos, configurados según una técnica llamada Computación Especulativa, la cual permite realizar varios pasos de la simulación a la vez. Se estudió el speedup teórico de la paralelización y se realizaron pruebas numéricas, las cuales entregaron resultados satisfactorios en tiempo y en calidad de la imagen simulada.