Computer simulation modeling is currently the most flexible method of manufacturing system analysis. Unfortunately, current simulation frameworks do not support the modular specification of homogeneous and heterogeneuos models. A Simulation Program Generator (SPG) for prototyping heterogeneuos simulation models is developed. Objects in the model represent elements within a flexible assembly system. These elements are the robot, the conveyor, the part, the schedule plan and the robot program. These objects were modeled using the GIBSS simulation framework. A model base and an user interface is developed to allow the construction and execution of simulation models. Instances of the objects are created and stored into the model base. These are retrieved later to construct a model The user interface is provided with an extensive set of tools for model creation and execution. Icons. representing objects, are selected and placed on the terminal screen and then connected together by interaction lines to create the complete model. The attributes of the objects can be altered and viewed on their respective panes. The SPG is a step forward in the development of computer-aided manufacturing system design environments for prototyping heterogeneous models. It allows the rapid generation and execution of simulation models. / Master of Science

Prior research has shown that frame-of-reference training increases the accuracy of performance appraisals more than rater error training (e.g. Hedge & Kavanaugh, 1988). Frame-of-reference training facilitates the learning of accurate performance standards (e.g. Athey & McIntyre, 1987), while rater error training results in the introduction of biased response sets (e.g. Bernardin & Fence, 1980). Bernardin and Buckley (1981) recommended that individuals who possessed an idiosyncratic rating style or aptitude would benefit especially from frame-of-reference training. However, no research to date has investigated the interaction of rating style and frame-of-reference training effects. The hypothesis of the present study was that rating accuracy and reliability would improve for idiosyncratic raters in frame-of-reference training, while the effective rating style of normative raters would not change. Further, rater error training should impair normative raters’ accuracy and reliability, while it should not affect the ineffective rating style of idiosyncratic raters. However, the results of this study failed to show the rating aptitude-training-time interaction with accuracy. Some support was found for a rating aptitude-training-time interaction with reliability as a result of rater error training. This study replicated previous findings that frame-of-reference training increased rating accuracy and reliability. Frame-of-reference training improved the Cronbach (1955) measures of differential elevation, stereotype accuracy, and differential accuracy. / Master of Science

This research focused on the surface modification and interfacial profile studies of a siloxane modified polyimide, BDS [BTDA (3,3\4.4'~ benzophenonetetracarboxylic dianhydride) ~ DDS (3.3'~diaminodiphenyl sulfone) - PSX (polydimethylsiloxane) copolymer], used as a coating material. The BDS coating surface can be modified by pretreatment in an alkaline solution. This surface pretreatment etched away the top siloxane surface layer, activated the surface by exposing and creating polar functional groups, particularly carboxylic acid groups, and roughened the surface. These changes on the coating surface significantly improved the wettability and the strength of the bond between the coating surface and a polar adhesive. Interfacial composition profiles were obtained from angular dependent X-ray photoelectron spectroscopy and Auger electron spectroscopy. Two kinds of interphases were found near the bond line of the coating/metal substrate. One was a component gradient interphase which was formed by component segregation of the BDS copolymer. The component gradient was different on different metal oxide surfaces with the siloxane interfacial excess in the order of AI > Ti > Zn. The relative acidities of the metal oxide surfaces were characterized by poly(vinyl chloride) adsorption tests which were quantified by XPS measurements. The relative acidities were found in the order of AI > Ti > Zn. Therefore, the cause for the BDS component segregation was suggested to be the influence of acid·base interactions between components of the BDS copolymer and the metal surface oxides. The other kind of interphase was a polymer-metal oxide mixture interphase which formed on penetration of the BDS copolymer solution into porous aluminum surfaces. / Master of Science

High voltage transformers inherently contain undesirable parasitic reactances. A resonant circuit formed by the leakage inductance and parasitic reflected capacitance, makes various resonant technologies practical for high voltage dc applications. The components of a typical high voltage power stage will be investigated in order to identify these parasitics and determine their influence on converter operation. Proto-type high voltage converters will be designed and built using PWM and quasi-resonant techniques and experimental results will be given. Dc analysis will be performed for the PWM and the quasi-resonant designs in order to obtain insight into the actual operation of the two converters. The design of the two proto-type converters will be reviewed and design guidelines will be established. / Master of Science

Clofazimine is a member of the phenazine pigment family which has been successfully used in chemotherapy against a variety of mycobacteria including M. avium. The presence of clofazimine in growth medium resulted in higher carotenoid pigmentation in M. avium cells. Carotenoid pigments have been shown to quench superoxide radicals supporting the hypothesis that pigmentation possibly protected cells against superoxide. Clofazimine caused the generation of superoxide radicals in M. intracellulare strain LR163 represented by cyanide-resistant oxygen consumption. The amount of oxygen consumed was dependant upon the clofazimine concentration. This supports the hypothesis that clofazimine is antibiotic via its ability to generate toxic oxygen metabolites. Higher catalase activity was found in extracts of cells grown in the presence of a low concentration of clofazimine. At a higher concentration, the amount of catalase and superoxide dismutase activities were lower than the basal level. This finding did not agree with the hypothesis. At this point the reason for the drop in the activities (i.e. lower than basal level) is not known. Clofazimine was mildly synergistic with rifampicin. This result supports hypothesis that the defense mechanism of M. intracellulare to clofazimine was enzymatic. Clofazimine-resistant derivatives of M. intracellulare strain LR163 have been isolated. Their characterization will provide a direct approach towards determining the mode of action of clofazimine in cells. / Master of Science

The performance of two-dimensional image processing systems has been well documented. In this thesis we study the performance of three-dimensional imaging systems. Such a study helps in understanding the fundamental restrictions of the propagation of three-dimensional (3-D) wavefields. The knowledge of the obtainable 3-D wave structures are useful for applications such as 3-D data acquisition, material processing, radiation therapy, radiative non-invasive surgery, 3-D microscopy and robotic vision. This thesis primarily deals with some investigations of 3-D optical transfer functions (OTFs). Specific emphasis has been made on the interpretation of 3-D wavefield distributions as an extension of 2-D defocused OTFs and also the interpretations of 3-D diffraction images from convolution relations. / Master of Science

Concrete provides a nearly perfect environment for corrosion protection of steel; However, the use of de-icing salts on the highway system has accelerated the deterioration rate of bridge decks in the snow belt. In 1981, over 100,000 bridges were reported to be structurally deficient, and the estimated cost of repair was placed at $93 billion. Concrete specimens, 1 ft. x 1 ft. x 4 in., containing four pieces of steel reinforcing bars, were prepared. In a first time, five specimens with different rebar networks were cast in order to study the effects of the rebar network on corrosion. Half-cell potential measurements were used to monitor the corrosion behavior of each specimen. In a second time, calcium nitrite, monofluorophosphate and sodium borate were evaluated for their capacity to control corrosion. The various corrosion inhibitors were tested either externally (in the test solution), internally (as a concrete admixture). The specimens were exposed to alternate complete immersion in a 6 wt% sodium chloride solution, plus eventual addition of corrosion inhibitor, for 3 days and 12 hours of drying at 110°F. The effects of corrosion inhibitors were evaluated using half-cell potential measurements and Electrochemical Impedance Spectroscopy (EIS) measurements. The EIS data were analyzed through a computer assisted EIS data analysis system. This allowed for circuit modeling of the corrosion mechanisms and evaluation of polarization resistance values for the different specimens. In both phases of this work, chloride concentration profiles as function of depth were determined. The half-cell potential measurements in complete immersion were found to give an average over the length of bar or electrically connected bars. The corrosion inhibitors applied internally were found to reduce corrosion better than corrosion inhibitors applied externally. It was shown that chloride concentration is not the only parameter controlling corrosion initiation. / Master of Science

Pure, single phase stoichiometric Pb(Fe_0.5Nb_0.5)O₃ (PFN) powders were successfully formed by molten salt synthesis using mixture of NaCl and KCI salts. Lower temperatures and shorter times (0.5 hour at 800°C) were needed for single phase PFN formation from molten salts relative to those required for solid-state methods (4 hours at 1000°C). A systematic study indicating the effects of process parameters, such as temperature, time, and amount of flux with respect to starting oxides, on the PFN formation mechanism and its resulting powder characteristics is reported. The particle size increased with increasing synthesis temperature, the rate of increase is greatest above 900°C which is close to the melting point of lead oxide. PFN powders formed by molten salt synthesis were cuboidal, and were free from agglomerates. The sinterability, microstructure, and dielectric properties of these powders have been studied for the pure form and with the presence of lead oxide or lithium carbonate. The dielectric properties were sensitive to as-sintered density, the type of additive and the amount of additive. For pure PFN, the highest valve of dielectric constant is 12,270 at 1MHz, which is sintered at 1100°C for 13 hours. Ceramics sintered with lead oxide additive exhibited inferior dielectric properties although lead oxide served as a sintering aid to increase the as-sintered density. The dielectric properties of PFN with lithium carbonate sintered at 1000°C were attractive: the dielectric constant was increased to 14,000 at 1MHz and the D.C. conductivity was reduced. This reduction in the D.C. conductivity was interpreted in terms of the substitution of lithium for iron. / Master of Science

A method is developed to predict the critical harmonic excitation of systems undergoing nonlinear oscillations. The method is based on the total energy approach which limits the system responses within a region bounded by a critical total energy in the phase space. Three one-degree-of-freedom nonlinear systems are investigated. Their governing ordinary differential equations are associated with a quadratic nonlinearity and/or a cubic nonlinearity. The study also is extended to a two-degree-of-freedom nonlinear system. The harmonic balance method is the analytical technique used in solving the nonlinear ordinary differential equations. In comparison with the approximate analytical solutions, numerical approaches are implemented. / Master of Science

Robotic manipulators for limited access workspaces, or LAWS robots, must operate in unalterable, confined environments accessed through constrictive portals. The characteristics of these robots distinguish them from the currently accepted classes of industrial robots and field robots and evoke a particular design strategy. Special consideration must be given to the ability of the LAWS manipulator to service a target workspace while constrained within the boundaries of a confined environment. The limited access to the environment also imposes restrictions on the size and shape of the manipulator. This thesis characterizes LAWS robots and develops a strategy for designing them. This strategy is then applied to the design of a LAWS robot for steam generator maintenance in nuclear power plants. The calibration of a LAWS robot is also discussed. Applications for robots that can operate in limited access workspaces exist in the nuclear, construction, mining, and medical industries, among others. This thesis provides, for the first time, a specific set of guidelines to aid in the design of such robots. / Master of Science