Title from PDF of title page (University of Missouri--Columbia, viewed on March 10, 2010). The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Thesis advisor: Dr. Michael Harmata. Includes bibliographical references.

To optimize the beam angle and fluence map in Intensity Modulated Radiation Therapy (IMRT) planning, we apply Benders decomposition as well as develop a two-stage integer programming-based heuristic. Benders decomposition is first implemented in the traditional manner by iteratively solving the restricted master problem, and then identifying and adding the violated Benders cut. We also implemented Benders decomposition using the “lazy constraint” feature included in CPLEX. In contrast, our two-stage heuristic first seeks to find a good solution by iteratively eliminating the least used angles in the linear programming relaxation solution until the size of the formulation is manageable. In the second stage of the heuristic, the solution is improved by applying local branching. The various methods were tested on real patient data in order to investigate their effectiveness and runtime characteristics. The results indicated that implementing Benders using the lazy constraint usually led to better feasible solutions than the traditional approach. Moreover, the LP rounding heuristic was seen to generate high-quality solutions within a short amount of time, with further improvement obtained with the local branching search. / text

Nearly all studies of gender differences in wages and advancement find that the primary difference between the economic standing of women and men lies in their distribution across occupations and industries. In my dissertation I use micro-econometric techniques to examine different aspects of the evolution and impact of gender-specific occupational structures. The first essay evaluates the capacity of a hierarchical model of discrimination and segregation to explain the gender wage gap within firms for a regional grocery store chain that lost a title VII class action lawsuit for not promoting women into the higher managerial positions. In the process the analysis raises questions about the appropriateness of standard wage model specifications for making inferences about wage determination in a setting where wages for each job are set equal for men and women by precise union rules. The second essay expands the theory of hierarchical segregation to examine changes in the wage and occupational structure over time with panel data. This allows one to analyze the effects of hierarchical segregation over time and observe whether the filing of the lawsuit alone is sufficient to change discriminatory behavior by the firm. The final essay examines how major economic crises, including two World Wars and a Great Depression, led to changes in gender segregation in industrial and clerical jobs.

The use of urea (NH2CONH2) to remove nitric oxide (NO) from exhaust streams was investigated using a laboratory laminar-flow reactor. The experiments used a number of gas compositions to simulate different combustion exhaust gases. The urea was injected into the gases as a urea-water solution. The decomposition processes of the urea-water solutions and urea powder were examined. For both the nitric oxide removal and the urea decomposition experiments, a Fourier transform infrared (FTIR) spectrometer was used to determine the concentrations of the product species. The products from the decomposition were examined every 50 K from 500 K to 800 K. The dominant products were ammonia (NH3), isocyanuric acid (HNCO) and carbon dioxide (CO2). In case of urea-water solution decomposition, for gas temperatures between 550 and 650 K, the highest concentrations were for NH3 and HNCO. On the other hand, the concentrations of CO2 were highest for gas temperatures of about 500 - 550 K. For temperatures above about 650 K, the amount of these three dominant prod-ucts slightly decreased as temperature increased. ivFor the nitric oxide removal (SNCR) experiments, the gas mixture was heated to temperatures between 800 K and 1350 K. Depending on the temperature, gas composition, residence time, and urea feed rate, removal levels of up to 95% were obtained. Other by-products such as N2O were detected and quantified. The effects of the urea/NO (beta) ratio were determined by varying the urea concentration for a constant NO con-centration of 330 ppm. The effects of the levels of oxygen (O2) in the exhaust gases and the residence time also were investigated. Increasing the urea/NO ratio and residence time resulted in higher NO removal and increased the temperature window of the nitric oxide removal.

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The present work used ab initio density functional theory (DFT) to study two different physical phenomena crystallization fouling and clay-based polymer nanocomposites. In the first part, two foulant materials were studied including calcium carbonate, and calcium sulfate. The lattice energy and enthalpy of formations of each crystal system were predicted using DFT methods. The most stable forms of calcium carbonate foul ant, calcite and aragonite, were investigated. For calcium sulfate, both gypsum and anhydrite crystals were investigated. The thermodynamic solubility product of each crystal system, for both foul ants, was predicted from the lattice energy and enthalpy of formations. Comparison of the stability between the different crystal systems for the same foul ant material was carried out to elucidate the effect of crystal atomic configuration and space group on the stability of foulant materials. The effect of temperature on the formation and stability of foulant material was also carried out. The results obtained using DFT methods, for enthalpy of formation and thermodynamic solubility products, were comparable with the experimental data reported in the literature. In the second part, study has been made on the clay-based nylon 6 nanocomposite materials. The purpose was to understand the interfacial interactions between clay and polymer with and without surfactant component. Both sides of the clay were examined with nylon 6. In order to determine specifically the type of interfacial interaction between clay and nylon 6, the electron distribution around the whole system was predicted. The study was carried out at various isomorphic substitutions. The substitutions took place at both octahedral and tetrahedral layers of the clay. The strength between clay and nylon 6 was predicted by calculating the binding energy. The results obtained revealed that, the strength increases with the increase in the degree of isomorphic substitutions. The type of bond between nylon 6 and basal surface of the clay was found to be basically electrostatic interactions, and particularly hydrogen bonds. Whilst, the type of interactions between nylon 6 and clay edge surface was found to include covalent bonds as well as electrostatic interactions. The formation and breakage of covalent bonds between nylon 6 and clay means that, a chemical decomposition of the clay can happen when it is mixed with certain type of polymers. The presence of surfactant can decrease the interfacial interactions between clay and nylon 6.

Thesis (M.S.)--Oregon State University, 1992. / Typescript (photocopy). Includes bibliographical references (leaves 82-85). Also available on the World Wide Web.