The effect of surface pretreatment on the adhesive bonding and bond durability of carbon fiber/epoxy and carbon fiber/bismaleimide matrix composites was studied. Methyl ethyl ketone (MEK) wipe, peel ply, grit blast and gas plasma treatments were the pretreatments of interest. Chemical and physical changes which occurred in the cured composite surfaces following pretreatment were characterized with x-ray photoelectron spectroscopy (XPS), ion scattering spectroscopy (ISS), contact angle analysis, diffuse reflection infrared spectroscopy (DRIFT), profilometry and scanning electron microscopy (SEM). Double lap shear and Boeing wedge configurations were used to evaluate the strength as well as the durability of the composites bonded with an epoxy film adhesive. Fluoropolymer residues which were found on the composite surfaces were fully removed by grit blasting and oxygen plasma treatments, but not by an MEK wipe. The use of a peel ply prevented fabrication contamination from depositing on the bonding surfaces. In addition to its cleaning effect, oxygen plasma was also capable of incorporating additional polar functionality into the composite surface. The presence of the fluoropolymer contamination on the MEK-wiped surface resulted in low surface energy and wettability, whereas peel ply, grit blast and oxygen plasma improved both the surface energy and the wettability of the composite surfaces. The grit blasted and peel ply surfaces were observed to have a significant degree of roughness, as measured by profilometry and seen by SEM. A rubber-toughened epoxy film adhesive was used for the bonding studies. Lap shear strengths were evaluated under ambient conditions as well as at 82°C, both dry and following a 30 day/71°C water exposure. Wedge durability testing was carried out in a dry 75°C oven, 75°C water, 100°C water and aircraft de-icing fluid. Relative to the MEK-wiped controls, lap shear strength as well as hot/wet durability was improved by the peel ply and oxygen plasma treatments for both epoxy and bismaleimide composites. Grit blasting was seen to have some utility for the epoxy composites at room temperature, but was generally observed to be detrimental to strength and durability, particularly in the case of the bismaleimide composites. In order to separate the effect of surface chemistry from the effect of surface roughness on composite bond strength, a study was carried out in which surface functionality was varied while the topography remained constant. For this purpose, peel ply surfaces, which have a consistent and reproducible degree of roughness, were treated with fluoropolymer compounds and gas plasmas, as well as left untreated. It was found that the removal of fluoropolymer contamination was the main contributor to the observed bond strength improvement following plasma treatment; however, highly functionalized oxygen plasma-treated surfaces showed evidence of improved durability in a hot aqueous environment. The effect of elapsed time following oxygen plasma treatment of epoxy composites was also studied. XPS atomic concentration, wettability by water and a liquid epoxy resin, and lap shear strengths were plotted as a function of time following removal from the plasma reactor. Changes which occurred in the chemistry and wettability of an oxygen plasma-treated surface had a subsequent negative effect on the lap shear strengths of the bonded specimens. A study was carried out using model epoxy and bismaleimide compounds in thin film form, for the purpose of studying surface chemistry and interfacial reactions following an oxygen plasma treatment. XFS and infrared reflection-absorption spectroscopy (IR-RAS) were used to probe the reactions which occurred. Close correspondence was found between the XPS and IR-RAS analysis of functional groups incorporated into the surface of the films by the plasma treatment. IR-RAS analysis of the model surfaces following exposure to a neat, liquid epoxy resin revealed that, while adsorption of the liquid epoxy occurred on both plasma-treated and nonplasma-treated surfaces, the oxygen plasma treated surface alone was capable of initiating ring-opening reactions in the epoxy. However, this effect was not observed unless immediate contact was made between the plasma-treated surface and the liquid epoxy resin. / Ph. D.

An investigation of shear response for various composite material systems is presented. The uniformity of the strain fields is studied experimentally and numerically for different specimen configurations. Conventional strain gage measurements and the moiré interferometry technique are employed to obtain information of actual deformation of the specimen. Based on the contour maps of displacement obtained from moiré tests, the localized hybrid method is used to quantify the magnitude and scale of the nonuniform deformation in the real strain fields. The finite element analysis is also performed for predicting the global nonuniformity of the strain fields. It is shown that the significant nonuniformity in shear deformation observed in experimental results can not be predicted by the existing analytical and numerical models. It is considered that the nonuniformity is primarily at a local level, which is associated with the material inhomogeneity. The implication of the local non-uniform deformation fields on the material property evaluation and failure prediction are discussed. The nonlinearity of shear response is investigated experimentally by performing strain gage and moiré tests. Curve fitting techniques proved to be a convenient and effective tool for characterizing the nonlinear shear response of composites. It is suggested that not only the initial shear modulus but also other coefficients of the fitting function be used for the evaluation of nonlinear shear behavior of a composite. The experimental results show that the nonlinearity has no significant effect on the shear strain distribution, verifying the validity of correction factors in the nonlinear range. Shear stress at a selected shear strain level is suggested as an engineering definition for shear strength of composites. The shear response of some novel composites is also investigated, the test results of which are presented. / Ph. D.

A new methodology is proposed to investigate the large-signal stability of interconnected power electronics systems. The approach consists of decoupling the system into a source subsystem and a load subsystem, and stability of the entire system can be analyzed based on investigating the feedback loop formed by the interconnected source/load system. The proposed methodology requires two stages: (1) since the source and the load are unknown nonlinear subsystems, system identification, which consists of isolating each subsystem into a series combination of a linear part and a nonlinear part, must be performed, and (2) stability analysis of the interconnected system is conducted thereafter based on a developed stability criterion suitable for the nonlinear interconnected-block-structure model. Applicability of the methodology is verified through stability analysis of PWM converters and a typical power electronics system. / Ph. D.

The goals of the present study were to determine whether any or all scales of the Myers-Briggs Type Indicator (MBTI) are susceptible to response distortion, and whether certain personality types are more proficient at distorting these scales. A 4 (temperament type) X 3 (level of information) X 3 (intelligence group) factorial design was used to examine the experimental hypotheses. Subjects were asked to respond to the MBTI twice, once reporting their honest preferences, and once faking a role polar opposite to their own preferences. Results indicated all MBTI scales’ are susceptible to response distortion to varying degrees. Subjects were able to create accurate faking profiles on the MBTI with relatively little information on the role to be faked. Certain temperaments, particularly NFs, are better at distorting their responses to these scales than others. Intelligence may also play a role in subjects’ ability to fake their responses. Level of information given on the MBTI scales did not affect subjects’ ability to distort their responses to the individual scales. Because of its susceptibility to response distortion, it was suggested that the MBTI not be used as part of the organizational selection process. Implications for these results on other organizational applications of the MBTI and suggestions for future research are also discussed. / Ph. D.

The goal of this research project was to determine optimal breeding strategies for improving important traits of Marone species hybrids reared in recirculating aquaculture systems (RAS). Effects of hybridization and backcrossing among striped bass (Marone saxatilis), white bass (M chrysops) and yellow bass (M mississippiensis) on important traits were determined. This dissertation is described in four studies. In the first study, performance of striped bass female x white bass male (SBxWB) and striped bass female x yellow bass male (SBxYB) fingerlings reared in RAS was evaluated. SBxWB were superior to SBxYB for overall mean growth rate and feed conversion. Survival was higher for SBxYB than for SBxWB. Time x hybrid interactions for growth rate indicated that growth rate of SBxYB improved through time relative to that of SBxWB. Time x hybrid interactions for growth may have been due to differential responses ofSBxYB and SBxWB to deterioration of water quality. The slow growth of SBxYB limits its use for aquaculture. In the second study, relationships among total weight, body shape, visceral components and fillet yield were examined in SBxWB and SBxYB in order to evaluate strategies for improving fillet yield. Fillets were heavier (5g per fish) for SBxYB than for SBxWB. Relative increase of fillet weight was slightly greater than total weight in both hybrids indicating that small increases in fillet yield can be achieved by rearing fish to a larger size. Low variation in fillet weight (SD ± 9.6 to 11.3g) and poor predictability of fillet weight from body shape (models with r2s of .27 to .43) in both hybrids indicated that potential for improving fillet yield within hybrids is limited. Identification of superior species or strain crosses appears to be the best strategy for improving fillet yield of Morone hybrids. / Ph. D.

The extended describing function method is proposed as a systematic small-signal modeling approach to nonlinear switching circuits. This method offers significant simplification upon the previous work on using the multi-variable describing functions to treat the circuit nonlinearities. As an extension to the statespace averaging method, this modeling technique can incorporate any Fourier components for good model accuracy and provides continuous-time small-signal models for PWM topologies and various soft-switching resonant topologies. The proposed method is demonstrated using four resonant topologies and two multi-resonant topologies. These circuits are strongly oscillatory, and thus they cannot be modeled by means of traditional averaging techniques. By employing the proposed modeling method, the dynamics of the resonant converters are analyzed with emphasis on the nonlinear interaction between the switching frequency and the circuit natural resonant frequency. Equivalent circuit models are provided for more convenience of practical designs. Small-signal analysis is also performed for two challenging multi-resonant topologies with complex structure and operation. All of the theoretical models are verified experimentally and the predictions are well supported by the measurement data up to the Nyquist frequency. / Ph. D.

A user-centered approach to interactive system development requires a way to represent the behavior of a user interacting with an interface. While a number of behavioral representation techniques exist, not all provide the capabilities necessary to support the interaction development process. The original goal of this research was to modify and extend the User Action Notation (UAN), a user- and task-centered behavioral representation technique. In order to facilitate and evaluate the improvement in the UAN, we developed and evaluated a taxonomic model of behavioral representation techniques. The development and evaluation of our model followed the epistemological cycle of observation, theorization, and evaluation. The model provides a framework for discussing, analyzing, extending, and comparing existing behavioral representation techniques, as well as being a springboard for developing and evaluating new techniques. / Ph. D.

Prediction of body composition was assessed in thirty-eight female and thirty-seven male random source dogs using in vivo methods of deuterium oxide dilution, subjective and objective morphometry, bioelectrical impedance and ultrasound, either separately or in various combinations. Carcass composition determined by chemical analyses of carcass homogenates served as criterion measures of body composition. Dogs were selected based on gender, body weight and body condition score. Body weight ranged from 7.3 to 34.5 kilograms (kg), subdivided into 4.5 kg increments with 6 female and 6 male dogs per increment. Body condition was categorized as thin, optimum or obese using a defined criteria, body condition scoring system (subjective morphometry) with 12 female and 12 male dogs per body condition category. Selection criteria produced 18 body weight condition groups with 2 female and 2 male dogs per group. One additional male and 2 female dogs were included for economic and ethical reasons. Equations to predict carcass composition from in vivo measurements were derived using standard regression techniques. Influence diagnostics, residual analysis and data splitting were used to validate predictive equations. Predictions from deuterium oxide dilution produced the most precise estimates of body composition. Average standard errors of estimation (SEE) from deuterium equations were 1.3, 1.8, 1.0, and 0.4 percent for percentages of body moisture, fat, protein and ash, respectively, and 0.39, 0.57,0.21 and 0.08 kg for absolute quantities of moisture, fat, protein and ash, respectively. Morphometry produced the most imprecise, but economical, estimates. Average SEE from morphometry equations for proportions were 3.0, 4.0, 1.3, and 0.4 percent, and 0.9, 0.9, 0.3 and 0.07 kg for absolute quantities of moisture, fat, protein and ash, respectively. Subjective morphometry could estimate body fat with an average SEE of 3.4 percent and correctly categorized 75 percent of the dogs. Bioelectrical impedance and ultrasound produced predictions with average SEE intermediate to deuterium and morphometry. Bioelectrical impedance was equivalent to deuterium dilution on the basis of cost per unit improvement in SEE, but ultrasound was not cost effective. / Ph. D.

There is a growing literature in the filed of accounting that addresses the issue of the ideological manure of accounting. This literature does not address the distinctive are of public organizations. This literature does not acknowledge that development of the new technioques of textual analysis generally called deconstruction. This dissertation focuses on the ideology of accounting theory and practices and addresses this issue through deconstructivist methodology as applied to a case study of accounting for a community college / Ph. D.

This dissertation presents a new, highly robust algorithm for electric power system state estimation. A graph theory-based system decomposition scheme is coupled with a high breakdown point estimator to allow reliable identification of multiple interacting bad data even in cases of conforming errors. The algorithm is inherently resistant to bad measurements in positions of leverage, makes no a priori measurement error probability distribution assumptions, and is applicable in a real-time environment. In addition to presenting a new state estimation algorithm, the weaknesses of two prominent state determination methods are explored. The comparative advantages of high breakdown point estimators are then summarized. New theorems quantifying the previously unexamined effect system sparsity has on the exact fit point of some members of this estimator family are presented. These results serve as the catalyst for the overall state estimation algorithm presented. Numerous practical implementation issues are addressed with efficient implementation techniques described at each step. / Ph. D.