A set of flexible water-blown slab stock polyurethane foams and their respective compression molded plaques as well as a chemically similar polyurea-urethane elastomer, PUUE, were studied to better understand the relaxation behavior and the molecular orientation upon deformation in these systems. The two main experimental techniques used in this investigation were stress relaxation in tension and deformation-IR dichroism. The stress relaxation in the foams and their respective plaques increased with hard segment content. The stress relaxation in the foams also appeared to depend very little on its anisotropic cell geometry and hence, mainly on the material comprising, the cell-wall struts and windows. Segmental orientation was measured as a function of elongation and relaxation, as well as hysteresis behavior for several of the plaques and the PUUE elastomer. The orientation changes upon deformation in the soft segments of both materials were small. Small changes in orientation with time and upon cyclic straining were also observed for the soft segments. The orientation at the interface of the hard and soft segments was influenced more by the soft segments in comparison to the hard segments in the plaques and in the PUUE elastomer. Significant transverse orientation upon deformation was observed in the hard segments of the plaques and up to elongations of 100 percent for the PUUE elastomer. Based on this transverse orientation behavior, the polyurea aggregates in the plaques were thought to possess a lamellar-like structure with the long axis of the aggregates aligning in the stretch direction. Relaxation and hysteresis behavior were observed upon following the orientation of the hard segments of the PUUE elastomer, but were negligible in that of the hard segments of the plaques. / Master of Science

Maintainability must be integrated into software as early in the development life cycle as possible to avoid overwhelming maintenance costs at later stages. This research describes a methodology which assists in the development of maintainable systems and does so without disrupting industry standard development techniques. The process uses software metrics and iterative enhancement concepts to reduce the complexity of high-level language code, making it less error-prone and more maintainable. The experiment uses large-scale system software from a major software producer. / Master of Science

The effect of various growth conditions on the type of superoxide dismutase (SGD) formed anaerobically in three Bacteriodes species was studied. B. fragilis, B. distasonis, and B. thetaiotaomicron were grown in ironâ restricted media with or without manganese supplementation. Iron availability was decreased by treatment of the media with chelex-100, a metal-chelating resin, and addition of desferrioxamine mesylate (desferal, Ciba-Geigy), an iron chelator. Mn-containing (MnSOD) and Fe-containing superoxide dismutase (EeSOD) activities in cell extracts were differentiated by inhibition with azide and inactivation by H₂0₂. The amount of Mn-containing superoxide dismutase was estimated by the fraction of azide- and H₂0₂, -resistant activity. Cells grown in untreated media contained approximately 90% FeSOD and 10% MnSOD. Cells grown in Fe-restricted media supplemented with graded amounts of manganese synthesized a progressively larger fraction of MnSOD. Hemin, added to the Fe-restricted media, did not serve as an iron source for FeSOD formation. Superoxide dismutase specific activities varied (3-6 U/mg) in each extract but not as a function of manganese concentration. / Master of Science

This new form of multiattribute utility optimization is based on ordinal as opposed to cardinal utility and is defined from a corresponding integer programming model in operations research which (1) is solved for ordinal cost factors and (2) serves as the problem's theoretical starting point. It is suggested herein that one start with a mathematical formulation that if solved in an acceptable or — preferably — best manner would yield a satisfactory or possibly best solution to the problem. Then, that mathematical formulation and its solution technique defines the multiattribute utility problem and its solution at issue. This is the reverse of what is usually done; and as will be shown, doing this can be quite fruitful. The illustrative example concerns a mathematical 1 formulation based on operation research's assignment problem. As will be argued, the cost factors must be ordinal, which essentially corresponds to using ordinal utility; hence the technique will be framed in the realm of ordinal utility. The technique for solving the illustrative example's mathematical formulation is to achieve a premium mix of operations research solution properties. From this perspective, some sticky issues in multiattribute utility theory when the attributes involve the preferences of distinct persons are not included in the philosophical base for the multiattribute utility problem and its solution thusly defined. / Master of Arts

The purpose of the research described herein is to prototype a software system that aids a simulationist in developing a general purpose discrete event simulation model. A literature review has shown the need for an integrated visual simulation system that provides for the graphical definition and interactive specification of the model while maintaining application independence. The General Purpose Visual Simulation System (GPVSS) prototyped in this research meets this need by assisting a simulationist to: (1) graphically design the model and its M visualization, (2) interactively specify the model's logic, and (3) automatically generate the executable version of the model, while maintaining domain independence. GPVSS is prototyped on a Sun 3/160C computer workstation using the SunView graphical interface. It consists of over 11,000 lines of documented code. GPVSS has been successfully tested in three different case studies that are described in this work. / Master of Science

It is widely held in the field of adhesion science that the properties of the interfacial region, or interphase, between two bonded surfaces are of critical importance to the performance of an adhesive bond. This thesis describes a study in which a polyimide was modified by the addition of metal compounds in an effort to develop a graded interface between the adhesive and aluminum adherends. The results of mechanical adhesion testing and instrumental analysis of the failed surfaces indicated that the added compounds did in fact preferentially segregate toward the adhered surfaces, but that this segregation decreased the strength of bonds tested in peel. It was concluded that the collection of metal compounds at the metal surfaces did not occur in such a manner as to improve the integrity of adhesive bonds, but the possibility remains that an improved, graded interface might still be formed given a more appropriate adhesive/dopant system and improved specimen preparation and testing techniques. / Master of Science

The design of the VPI plasma torch, which has been used as an ignitor and flameholder in supersonic combustion studies, has been modified in order to decrease the electrode wear and to increase stability. The plasma torch can be used as a source of hydrogen or nitrogen radicals which initiate and stabilize combustion. During previous testing of the unmodified torch, electrode erosion limited operation of the torch to about two hours. The improved torch features a flow swirler in the gas inlet, which adds vortex stabilization to the arc. The vortex stabilization causes the anode attachment point of the arc to be anchored in the low pressure region, downstream of the constrictor. This lowers the heat flux to the anode, so that erosion is decreased. The torch body was redesigned with an emphasis on the alignment of the electrodes. Also, the electrode gap in the improved torch was made continuously adjustable, allowing fine adjustment of the electrode gap during operation of the torch. The operational characteristics of the improved torch were monitored by a microcomputer-based data acquisition system. Stable operation of the improved torch with pure nitrogen was demonstrated, thus eliminating the requirement for argon to stabilize the arc. Operational characteristics of the improved torch running on argon, nitrogen, argon/hydrogen and argon/nitrogen mixtures as feedstocks, are reported. The electrode wear was studied between tests by observation with a microscope, and by measuring the mass change of the electrodes. The electrode erosion of the improved torch was reduced significantly. Anode lifetimes of greater than 20 hours have been demonstrated with operation on mixtures of nitrogen and argon. / Master of Science

Soot volume fractions have been measured using optical techniques in dual mode diffusion flames. A dual mode flame is defined as a diffusion fuel jet that burns in the wake of a premixed flame. The premixed flame combustion products simulate a vitiated-air environment: the air is preheated, rich in radicals, and depleted in oxygen. A two stage burner was used to investigate the effects of vitiation on the soot yield in diffusion flames. In the first stage, a fuel-lean premixed methane flame burned. A diffusion fuel jet was injected in the second stage. The effects of vitiation were simulated by varying the premixed flame stoichiometry, diffusion flame injection height above the premixed flame, and premixed flame temperature. The premixed flame stoichiometry affects the oxygen availability. The oxygen availability was varied from an 18% oxygen index to a 23% oxygen index. Different diluent gases (Ar, N₂, and CO₂) were used to alter the premixed flame temperature. The injection height of the diffusion flame (0.0 to 1.0 cm) affects the radical concentrations and temperature field. The soot yield from dual mode combustion was compared to the yield from similar single mode flames. For the single mode flames, air was injected through the first stage. Experimental results indicate that dual mode combustion increases the soot yield significantly in diffusion flames. Among flames at a 23% oxygen index, the mean increase in soot levels was 84%. Among flames at an 18% oxygen index, mean soot levels increased by 314%. In dual mode flames, the effect of injection height is weak, as is the effect of oxygen availability. The effects of the feed air temperature could not be resolved. In single mode flames, the effect of the injection height was weak, but oxygen availability affects soot yield significantly. Single mode flames show an average increase of 180% in soot yield at the 23% oxygen index with respect to the 18% oxygen index. These conclusions are the same for both ethene and propane as the diffusion flame fuels. / Master of Science

The problem of evaluating new manufacturing technologies, in particular, flexible manufacturing systems (FMS) is a complex one, as its interdisciplinary nature involves multiple variables. These variables are qualitative as well as quantitative, strategic, as well as technological, intangible as well as tangible. This dissertation deals with the problem of the overall evaluation process, in particular, the evaluation of material handling systems within FMS. In particular, automated guided vehicle systems (MVS) are studied from a technical viewpoint, as they are related to strategic and economic considerations. Two main evaluation frameworks are developed. One integrates multiattribute decision models, namely, the analytic hierarchy process or AHP and the displaced ideal model (DIM), and the other integrates analytical techniques with simulation modeling. As a by product, flexibility indices are also developed for MVS and linked to the fundamental aspects of the evaluation of new technologies. This research also shows how analytical techniques can be combined with simulation modeling to form a more extensive evaluation process that includes opportunity costs as well as the usual tangible costs. Finally, a technical analysis of FMS/MVS is done on some typical cell configurations using the flexibility indices developed in this research. / Ph. D.

Soy protein concentrate (SPC) was autoclaved at 121°C and 15 p.s.i for 0, 10, 30 min., 2 and 4 hr. The solubility of the control, 10 and 30 min. autoclaved samples was quite low (about 12%) as compared with the 2 and 4 hr. samples (about 27%) in potassium phosphate buffer (pH 7.6, 0.5 ionic strength). When urea and beta-mercaptoethanol were added in increasing concentration to the buffer, the solubility of control, 10 and 30 min. samples increased dramatically up to 60%; while the solubility of 2 and 4 hr. autoclaved samples changed very little remaining at 25 to 40% throughout. Digestibility of SPC samples was determined by three in vitro methods, all including treatment of SPC with selected proteases, followed by measurement of (1) TCA soluble N production (2) breakdown products via SDS-PAGE and (3) pH drop resulting from enzyme action. In vivo apparent digestibility was determined in a rat feeding study. The digestibility of SPC samples were found to be significantly affected by length of autoclaving. The digestibility of control was higher than autoclaved samples as determined by both in vivo and in vivo assays. The digestibility of 10 and 30 min. autoclaved SPC samples was significantly higher than 2 and 4 hr. autoclaved samples in in vivo assays. While, apparent in vivo digestibility of 10, 30 min. and 2 hr. autoclaved samples was significantly higher than the 4 hr. sample. Correlation coefficients of in vivo digestibility as determined by the TCA soluble N measurement, SDS-PAGE and pH drop method with in vivo apparent digestibility were 0.96, 0.92 and 0.95, respectively. There was no actual destruction of amino acids except cysteine; 10, 30 min., 2 and 4 hr. SPC samples contained 6, 20, 27 and 39% less cysteine respectively than the SPC control. The chemical score of SPC samples indicated that cysteine became the first limiting amino acid in the 2 hr. sample. PERs of the 2 and 4 hr. autoclaved SPC samples were significantly less than control, 10 and 30 min. autoclaved samples. While C-PERs of control, 10 min. samples were higher than 30 min., 2 and 4 hr. samples. Decreased PER values of autoclaved SPC samples were likely due to i) decreased protein digestibility and rate of enzymatic hydrolysis, ii) destruction of essential amino acids, and iii) decreased food intake. / Ph. D.