This dissertation is a comparative study of simulation optimization methods. We compare a new technique, genetic search, to two old techniques: the pattern search and the response surface methodology search. The pattern search uses the Hooke and Jeeves algorithm and the response surface method search uses the code of Dennis Smith. The research compares these three algorithms for accuracy and stability. In accuracy we look at how close the algorithm comes to the optimum. The optimum having been previously determined from exhaustive testing. We evaluate stability by using the variance of the response function as determined from 50 searches. The test-bed consists of three simulation models. We took the three simulation models from text books and modified them to make them optimization models if that was required. The first model consists of a big S, little s inventory system with two decision variables: big S and little s. The response is the monthly cost of operating the inventory system. The second model was a university time-sharing computer system with two decision variables: quantum, the amount of time that the computer spends on a job before sending it back to the queue and overhead, that is the time that its takes to execute this routing operation. The response was the cost of operating the system determined from a cost function. The third model was a job-shop with five decision variables: the number of machines at each of the five work stations. The response was the cost of operating the job-shop again determined from a cost function. The decision variables were integer for the inventory system and job-shop, and were real for the computer system. / Ph. D.

This dissertation develops an analytic framework to undertake cell design in a cellular system. The cell is modeled in a broader sense than ever done before. In our analytical model, we incorporated the use of guard channels, queueing of new calls, and hybrid channel allocation. A numerically stable and efficient solution to a queueing system with two arrival streams having reserved and borrowable servers has been developed. This queueing system is used to model the cell behavior. The model provides valuable insights into the behavior of the cell, and this in turn has been used to devise an efficient stochastic optimization algorithm for determining the minimum number of channels required by the cell. Our techniques are stable, easy to implement for practical systems and produce optimized solutions quickly. This is particularly useful because we expect that future designs of cellular systems may execute such algorithms on cell-site processors. / Ph. D.

Fabrication of high-quality composites from thennoplastic prepregs requires careful selection of the processing cycles so that intimate contact at the ply interfaces is achieved resulting in the formation of strong interply bonds and the process-induced residual stress is minimized to ensure superior mechanical performance. The void formation and the consolidation mechanism were studied experimentally. A refined model was developed to relate the processing parameters of pressure, temperature and time to the interply intimate contact of thermoplastic composites. The model was developed by integrating a prepreg surface topology characterization with a resin flow analysis. Both unidirectional and cross-ply lay-ups were modeled. Two-ply unidirectional laminae fabricated from graphite-polysulfone and graphite-PEEK prepregs and [0/90/0]_T laminates were consolidated using different processing cycles. Optical microscopy and scanning acoustic microscopy were used to obtain the degree of intimate contact data. Agreement between the measured and calculated degree of intimate contact was good. A finite element model was developed to analyze residual stresses in thermoplastic composites by combining a plane-strain elasticity analysis and a temperature-dependent matrix properties. The residual stress model takes into account the mismatch of the thermal expansion coefficients and the crystallization shrinkage of the matrix. [O₁₀/90₆]_T graphite-PEEK laminates were manufactured at different cooling rates to verify the model. The induced residual thermal defonnations were measured by a shadow moire system. The model accurately estimated the out-of-plane displacement of the non-symmetrical laminates. / Ph. D.

Let E be an analytic metric space, let X be a separable metric space with a regular Borel probability measure μ and let Π: E → X be a continuous map with μ(X \ Π(E)) =0. Schwartz’s lemma states that there exists a Borel cross-section for Π defined almost everywhere (μ). The equivalence classes of these Borel cross-sections are in one-to-one correspondence with the representations of the form Γ:C_b(E) → L^∞(μ) with Γ(f∘Π) = f for every f ∈ C_b(X). The representations are also in one-to-one correspondence with equivalence classes of the minimal measures on E. Now let E, X, and μ be as above and let Π: E → X be an onto Borel map. There exists a Borel cross-section for Π defined almost everywhere (μ). The equivalence classes of the Borel cross-sections for Π are in one-to-one correspondence with the representations of the form Γ:B(E) → L^∞(μ) with Γ(f∘Π) = f for every f in C_b(X), where B(E) is the C*-algebra of the bounded Borel functions on E. The representations are also in one-to-one correspondence with equivalence classes of the minimal measures on E. / Ph. D.

Supercritical fluids (SF)s have several physicochemical properties that can often make them superior to conventional liquid solvents. These characteristics include relatively high densities, low viscosities, zero surface tension and high diffusivities. This unique combination of properties allows them to have solvating strengths that can approach those of pure liquids while maintaining many of the advantageous transport qualities of gases. In the past decade SFs have seen increased use as solvents for both extraction (SFE) and chromatography (SFC). A particularly exciting area of applications has been in the field of polymeric materials. Since polymers are not discrete molecules, but, rather broad distributions of very similar compounds (oligomers), they can pose interesting challenges for the separation chemist. SFs are uniquely suited to meet these challenges. The goal of the work done in this laboratory over the past few years has been to use SFs to extract and characterize both oligomers and additives from polymeric materials. A method for the post-polymerization fractionation of a low molecular weight, high density polyethylene wax using analytical scale SFE equipment was developed. Supercritical CO₂ was used to separate very narrow molecular weight distributions (MWD)s from the polyethylene feedstock. The resulting MWDs were characterized by SFC and high temperature gel permeation chromatography (GPC) and found to have polydispersities and molecular weights much lower than the parent wax. Supercritical propane was used to fractionate higher MWDs from the feedstock, however its greater solvating strength for the polyethylene oligomers resulted in larger polydispersities. A dual pump SFE system was used to deliver a dynamic mixture of propane in CO₂. The resulting fractions were very similar to those achieved by pure CO₂, but the recoveries were much higher. Increasing the temperature appeared to have both a kinetic and thermodynamic contribution to oligomer extraction. Supercritical CO₂ was also used to extract additives from an insoluble polymeric nitrocellulose (NC). The primary stabilizer additive (diphenylamine) and its nitrated derivatives were extracted from the propellant. The SF extracted stabilizer profile was characterized using liquid chromatography (LC), gas chromatography (GC) and SFC. SFC was shown to provide separations of propellant additives that were superior to the existing LC method while maintaining lower temperatures than GC. Extracts from propellants stored at elevated surveillance temperatures contained more highly nitrated stabilizer derivatives. However, some question was raised as to the actual validity of elevated temperature programs for propellant screening due to potential differences in reaction mechanisms. A LC-thermospray mass spectrometry (MS) interface was modified for use wtih packed column SFC. The system was used as a chemical ionization (CI) source for the high CO₂ flow rates emanating from packed columns. Methane was used as a reagent gas (RG) for positive chemical ionization (PCI). The resulting CO₂ + CH₄ mixed RG was studied at CO₂ pump pressures typical of SFC pressure programming. The background ions varied widely with CO₂ partial pressure and source temperature, however, spectra of a propellant test mixture were relatively unaffected by changing RG. The system was also used to perform negative CI (NCI) using the mobile phase CO₂ as a RG. This method was found to be very useful for nitrated derivatives of diphenylamine. SFC-CH₄-PCI-MS confirmed the intact elution of thermally labile N-nitroso compounds thought to exist in propellants. SFC-CI-MS, both NCI and PCI, was used to characterize the SF extracts of polymeric nitrocellulose and was demonstrated to have potential for the analysis of a wide range of compounds found in the propellant industry. SFC-CH₄-PCI was also determined to be compatible with methanol modified mobile phases. The mobile phases in this case were delivered from premixed cylinders. However, severe limitations regarding the reliability of premixed mobile phases in SFC were shown to exist. / Ph. D.

A numerical and experimental investigation of the bending behavior of six eight-ply graphite-epoxy circular cylinders is presented. Bending is induced by applying a known end-rotation to each end of the cylinder, analogous to a beam in bending. The cylinders have a nominal radius of 6 inches, a length-to-radius ratio of 2 and 5, and a radius-to-thickness ratio of approximately 160. A [±45/0/90]S quasi-isotropic layup and two orthotropic layups, [±45/02]S and [±45/902]s, are studied. A geometrically nonlinear special-purpose analysis, based on Donnell's nonlinear shell equations, is developed to study the prebuckling responses and gain insight into the effects of non-ideal boundary conditions and initial geometric imperfections. A geometrically nonlinear finite element analysis is utilized to compare with the prebuckling solutions of the special-purpose analysis and to study the buckling and postbuckling responses of both geonletrically perfect and imperfect cylinders. The imperfect cylinder geometries are represented by an analytical approximation of the measured shape imperfections. Extensive experimental data are obtained from quasistatic tests of the cylinders using a test fixture specifically designed for the present investigation. A description of the test fixture is included. The experimental data are compared to predictions for both perfect and imperfect cylinder geometries. Prebuckling results are presented in the form of displacement and strain profiles. Buckling end-rotations, moments. and strains are reported, and predicted mode shapes are presented. Observed and predicted moment vs. end-rotation relations, deflection patterns. and strain profiles are illustrated for the postbuckling responses. It is found that a geometrically nonlinear boundary layer behavior characterizes the prebuckling responses. The boundary layer behavior is sensitive to laminate orthotropy, cylinder geometry, initial geometric imperfections, applied end-rotation, and non-ideal boundary conditions. Buckling end-rotations, strains, and moments are influenced by laminate orthotropy and initial geometric imperfections. Measured buckling results correlate well with predictions for the geometrically imperfect specimens. The postbuckling analyses predict equilibrium paths with a number of scallop-shaped branches that correspond to unique deflection patterns. The observed postbuckling deflection patterns and measured strain profiles show striking similarities to the predictions in some cases. Ultimate failure of the cylinders is attributed to an interlaminar shear failure mode along the nodal lines of the postbuckling deflection patterns. / Ph. D.

The design of existing beaded adsorbent materials for column-mode protein purification has emphasized the impact of diffusional transport phenomena upon adsorbent capacity. A design model is presented that optimizes molecular accessibility of proteins relative to the mechanical stability of the material by manipulation of size and solids content for uncross-linked cellulose beads. Cellulose beads of various sizes ranging from about 250 to 1000 pm diameter and having different solids contents were evaluated. Cellulose beads (1.2 mm diameter) gave pressure drops of less than 1 psi per cm of bed at superficial fluid velocities of 100 cm/min in a 1 5 cm bed. Solids content of greater than about 9% cellulose greatly reduced the permeability of large proteins such as thyroglobulin and p-Amylase into the beaded matrix at bead contacting times of 5 and 50 seconds. The amount of permeation in 3% cellulose beads by thyroglobulin at bead contacting times of 5 seconds was about tenfold larger than predicted by diffusion models using the diffusivity of the protein in water. The utility of a low solids content, large bead cellulose support was shown with immobilized IgG (Mr 155 kDa) capturing recombinant human Protein C (M, 62 kDa). The amount of immobilized antibody was varied and immunosorptive capacity of 1 mm cellulose beads was found to be equivalent to that of 0.1 mm cross~linked agarose beads. The immobilization of antibodies to these supports was studied by photomicroscopy of cross-sectioned beads containing immobilized fluorescent labeled antibodies. While 75% of the antibody was immobilized within 0.07 mm of the cellulose bead surface at an antibody density of 1 mg antibody per ml of beads, an appreciable amounts of antibody immobilized deeper into the bead may have been utilized in order to yield capacities equivalent to the smaller agarose beads. The beaded cellulose supports derivatized to form either immunoaffinity or anion exchange matrices exhibited very low non-specific binding. Thus, the particle size, solids content, and extent of derivatization of cellulose matrices can be engineered so as to create matrices that provide high flow rates with low pressure drops while also having desirable adsorptive capacity for proteins. / Ph. D.

A series of experiments was conducted to examine protein and energy utilization in growing and breeding turkeys, and to investigate the impact of body weight restriction on subsequent reproductive performance. In the first experiment, dietary self-selection of energy and protein and feed restriction were studied in growing turkeys. Body weight of males and females was significantly reduced by feed restriction. Protein efficiency was significantly lower in self-selecting males and females. Feed restriction significantly reduced the carcass yield of males, but not females. / Ph. D.

This study focused on the transition process of adult undergraduate students as they progressed from non-student to student status at a large state supported university. This study focused on the factors of transition as described in the Transition Framework developed by Nancy K. Schlossberg. Schlossberg identified three major components of the transition process: the transition, the individual, and the environment. The purpose of this study was to determine the adequacy of the Schlossberg Transition Framework in explaining the actual transition of adults from non-student to student status. A qualitative methodology was utilized for data collection and analysis. Data collected through in-depth personal interviews led to findings which verified those constructs of Schlossberg's model that adult students identified as important to the transition process. The Schlossberg Transition Framework proved to be an adequate tool for explaining this particular transition, although some components of the Framework were of more importance than others. Study findings indicated that the variables characterizing the individual were the most important part of the transition process for the adults in this study. Commitment and values, ego development, outlook, and coping resources all surfaced as critical components to a successful transition. The variables characterizing the transition important to these adults were: stress, role change, trigger event, and previous experience with a transition of a similar nature. All the variables characterizing the environment; support from family, friends, and institutions were found to be important to this transition. The following formula was designed to describe characteristics of the adults in this study who had successfully become undergraduate college students: Determination + Courage + Vision = A Successful Transition. / Ph. D.

Assuming a simple force field involving only short range Non-Coulombic molecular energy terms along with P1 symmetry, a variation of the SQLOO model (Boisen and Gibbs, 1993) successfully generates the structure types of both α and β1 quartz along with at least five alternative structure types of silica not yet observed to our knowledge. These structure types are identified by the existence of symmetry elements represented in the optimized atomic coordinates and cell parameters that define a minimizer in the model. A family of minimizers is discovered through the combined use of Monte Carlo simulated annealing followed by quasi-Newton minimization techniques. The results are in contrast with the assertion made by Tse et al. (1992) that new structure types of SiO₂ can only be arrived at by Molecular Dynamic methods. By varying the parameters used in the minimization process, different families of structure types are discovered. Several structure types were found to have high symmetries. These results are in contrast with the findings by Kramer et aL (1991) that the stability of high symmetry structures of silica are stabilized in part by ionicity. The results reported here are for calculations involving Z = 3 and 6 formula units. This strategy may be useful in the prediction of possible high silica zeolite structure types. An examination of the atomic displacement parameters (ADPs) obtained for TO₄ tetrahedra (T = Si, Al) suggest rigid TO bonds are more common in non-framework than in framework silicates. Correlated motion is found among the ADPs that is consistent with TLS rigid body motion. For these data, the translational motion is represented by the ADPs of the central T atom while both the librational and translational motion is contained in those of the surrounding O atoms. The libration angle for rigid tetrahedra is linearly dependent on the difference between the isotropic equivalent displacement parameter of the T and O atoms, B(T) and B(O), respectively. The value of B(O) is on average twice that of B(T) with a maximum value of ~ 2.0Ų. Variations in the SiO bond lengths of rigid tetrahedra in the silica polymorphs is related only to f_s(O). Rigid TO and OO bonds are a necessary but not sufficient condition for rigid body motion. Nonrigid tetrahedra may represent crystals containing disorder or problems with the refinement. The computer program EXCALIBR (Bloss and Riess, 1973; Bloss, 1981, p. 202) has been rewritten and markedly improved. Like EXCALIBR, EXCALIBR II solves optical extinction data, as determined with a spindle stage, and determines the optic axial angle 2V and the orientation of the crystal’s optical indicatrix. EXCALIBR II uses a modification to Joel’s equation as a means of obtaining the optic axes of a crystal. Furthermore, EXCALIBR II successfully solves extinction data where one optic axis of a biaxial crystal is 90° to the spindle axis, an orientation that had thwarted its predecessor. EXCALIBR II also accurately determines the optical indicatrix orientation for uniaxial crystals. After solving extinction data for several different wavelengths and/or temperatures, EXCALIBR II calculates the angular change of each optic direction with wavelength and/or temperature along with the error on the angle. Using a simple t-test, it then computes a p-value to aid in the decision as to whether the optical direction truly exhibits dispersion. This is a more valid and sensitive procedure than the χ² test used by EXCALIBR, particularly because the covariance in each optic vector’s coefficients are taken into consideration and the results are invariant to the vector’s orientation. / Ph. D.