A numerical method has been developed for computing the steady state flow about arbitrary shaped three dimensional bodies on or below the free surface using a Boundary Integral Element Method ( Panel Method). The method uses a singularity distribution over the body surface and the free surface. The method can solve for the potential distribution as well as the source density distribution. In this study a constant source distribution is assumed on each panel. The free surface boundary condition is linearized about the uniform undisturbed flow (Kelvin Free Surface condition). Upstream waves are prevented by the use of an one-sided upstream 4-point finite difference operator for the free surface condition. Wave elevations are computed using the linearized free surface condition. In this study two different bodies were considered: a submerged spheroid and a sphere. The wave resistance was computed for different Froude numbers and compares well with existing results. The study has also analyzed the effect of the number of panels on the body surface, the length of the free surface paneling behind the body and the aspect ratio of the free surface panels. / Master of Science

Job analysis, narrowly defined, refers to the collection of data describing job-related behaviors and the characteristics of the job environment. Job specification refers to the process of inferring required traits or abilities necessary for a desired level of job performance. Differences in the judgmental processes involved in these two functions were explored by (a) investigating the potential schema- or stereotype-based nature of job specification ratings, and (b) assessing the relationship between behavioral specificity and interrater reliability. These concerns were investigated through the use of 3 groups of subject raters: one group possessing extensive job knowledge, one group possessing some degree of job familiarity, and one group possessing little or no job knowledge. All subjects completed a job analysis instrument (the Job Element Inventory) and a job specification instrument (the Threshold Traits Analysis; TTA). Contrary to predictions, little evidence was uncovered to suggest extensive schema-usage on the part of TTA raters. In addition, the 2 instruments achieved similar levels of interrater reliability among the 3 subject groups. However, marginal support was found for the notion that behaviorally specific items generate higher reliability the less-specific items, and in replication of previous findings, job-naive raters were found unable to achieve the reliability of subject matter experts. Suggestions for future research are offered. / Master of Science

This thesis investigates the behavior of two digital communication systems based on Moving-Average Matched Filters (MAMF). In general, matched filters are instrumental in detecting signals corrupted by noise as they are designed to maximize the probability of detection of the transmitted signals. The MAMF represents a subset of the class of matched filters. The two communication systems under investigation are the classical MAMF system and one of its modifications, the proposed MAMF system. In the traditional system the N-dimensional signal vector, which encodes the bit to be communicated, remains fixed throughout the whole communication process ( transmission and reception). In the proposed system the encoding N-dimensional signal vector is composed of K linearly independent basis vectors spanning a signal vector subspace of dimension M (= N /K). By combining these basis vectors in the receiver, any vector in the signal vector subspace can be formed in order to maximize the Output Signal-to-Noise Ratio (OSNR). The relative measure of comparison for the two systems is the Signal-to-Noise Ratio Improvement (SNRI). The SNRI is the ratio of the OSNR, which is measured at the output of the receiver, to the Input Signal-to-Noise Ratio (ISNR), which is measured at the input of the receiver. Since the ISNR is fixed for a particular transmitted signal vector and noise characteristics, an attempt is made to maximize the SNRI by maximizing the OSNR. / Master of Science

Three experiments were conducted to evaluate in vitro and in vivo development of zona pellucid a-intact (ZPI) and zona pellucida-free (ZPF) mouse embryos after encapsulation in either 2% sodium alginate or 0.1% poly-L-Iysine (PLL). In Experiment 1, rate of development of ZPI embryos (n = 150) from morulae to hatched blastocysts was measured after encapsulation in alginate or PLL and as unencapsulated controls. Following encapsulation, developmental stages were recorded every 24 h for 120 h. Percentage of encapsulated embryos completely hatched from the zona pellucid a were not different from each other but were lower than unencapsulated controls at 48, 72, 96 and 120 h. Development of ZPI and ZPF mouse embryos after encapsulation in either alginate or PLL was examined in Experiment 2. Developmental stages and diameters were recorded every 24 h for 72 h. At 72 h, embryos were stained and fixed on slides to examine nuclei. Percentage of ZPI embryos developing to expanded blastocysts, their diameters and nuclear counts were not different from each other or from ZPF embryos. Percentage of ZPI embryos initiating hatching or completely hatched from the zona pellucida, their diameters and nuclear cell numbers were also similar. In the final experiment, ZPI mouse morulae were unencapsulated or encapsulated in either alginate or PLL and transferred into recipients to examine in vivo development. Recipients were allowed to develop fetuses to term. Recipients receiving encapsulated embryos failed to deliver pups. However, five of six recipients of unencapsulated embryos (n = 71) delivered a total of 16 live pups. Additional transfers were performed to examine viable fetuses and resorption sites on day 10 of gestation. Pregnancy rates, diagnosed by the presence of via bIe fetuses or resorption sites, were similar for all treatments: unencapsulated (71.4%), a1ginate (87.5%) and PLL (87.5%). However, the total number of viable fetuses present was higher for unencapsulated embryos (42.1 %) when compared to embryos in alginate microgels (17%) and embryos in PLL microcapsules (14.60/0). Additionally, recipients of alginate and PLL encapsulated embryos had more resorption sites (4 0/0 and 13.4%) when compared to recipients of unencapsulated embryos (0%). These investigations demonstrated that development of encapsulated ZPI mouse morulae is impaired at the hatched blastocyst stage; however, encapsulated ZPI and ZPF mouse morulae develop similarly in size and nuclear counts. In vivo development of ZPI morulae was also impaired due to an asynchronous condition between the uterine environment and the developing embryos. / Master of Science

In order to establish a profile of detoxification via glutathione conjugation, the level of urinary mercapturic acid excreted by a free-living male population and the effect of external environmental and genetic factors, such as consumption of vegetables, fruits, and meat, charbroiled food intake, tobacco, alcohol, caffeinated coffee, and marijuana use, exposure to chemicals and familial cancer incidence, were investigated. A subgroup of 30 subjects was randomly selected from 117 subjects who complied with the collection protocol. Three consecutive 24 hr urine samples of this subgroup were analyzed. The modified method of Seutter-Berlage et al (Chemical Porphyria in Man. Elsevier/North-Holland Biomedical Press, N.Y. 1979:233-236) was used for the quantitation of urinary mercapturic acid. The mean excretion of mercapturic acid was 0.27 mmole mercapturate (-SH)/24 hr and 18.1 umole -SH/mmole creatinine. An analysis of variance showed a large degree of inter- and intraindividual variability. The interindividual coefficients of variation in mmole -SH/24 hr and umole -SH/mmole creatinine were 37.7% and 31.2%, respectively. The intraindividual coefficients of variation in mmole -SH/24 hr and umole - SH/mmole creatinine were 32.4% and 30.1%, respectively. A higher (p≤0.05) excretion of mercapturic acid was observed among subjects with a high frequency of exposure to chemicals. The lack of significance of the other dietary, non-dietary, and genetic factors on the observed mercapturic acid excretion may be due to the large inter- and intravariability, the use of food consumption frequency in food intake analysis, and unequal sample sizes of subgroups. / Master of Science

Custard, cake, beef patties, potatoes, frozen broccoli, and frozen chicken pot pie were cooked or heated at 100% (High), 70% (Medium High) or 50% (Medium) power in a transformer microwave oven or an inverter microwave oven. Separate batches of each food were prepared for instrumental and sensory evaluation. Cooking at 50% (Medium) power produced less smooth custards and broccoli woodier in texture than at other power levels. More moist potatoes, harder in texture, and beef patties more tender at center resulted from cooking at 70% (Medium High) power. Cooking at 100% (High) power produced less set custards and less consistent temperature in pot pie, along with more tender cakes, juicier beef patties, and potatoes whiter in color. Within particular foods, there were also significant differences by oven type. In the inverter oven, at 50% (Medium) power, custards were more set and less tender, while broccoli had a fresher flavor and potatoes a softer texture than the same foods cooked in a transformer microwave. At 70% (Medium High) power, the transformer microwave produced a potato less white than that cooked in the inverter oven. High (100%) power inverter-microwaved custard was less creamy than its transformer-cooked counterpart; broccoli and cake cooked in the inverter microwave at this power level had a fresher flavor and a weaker chocolate flavor, respectively. There were not overall differences in quality in foods cooked at different power levels in the two oven types. However, for certain foods, there were advantages for the selected cooking conditions. / Master of Science

During vibrothermographic experimental testing of damaged composite plates, frequency dependent heat generation phenomena were observed. Local hot spots were formed around imperfection areas especially delaminations. Heat generation was also found to relate to the crack size. In order to explain the above observed phenomena, the dynamic behavior of undamaged and damaged composite plates was studied over a broad frequency range. The analysis was carried out using the finite element method based on the concepts of the three dimensional theory of anisotropic elasticity. Delaminations were modeled, and the local crack resonance’ was justified. Two NDE methods namely, Vibrothermography and SPATE were used to verify the numerical predictions. Experiments performed for both undamaged and damaged specimens, and good correlation between theory and testing was achieved. / Master of Science

A physics-based insulated gate bipolar transistor (IGBT) model has been successfully implemented into a widely available circuit simulation package, IG-Spice. Based on the semiconductor physics, the model accurately predicts the nonlinear junction capacitance variations, recombinations, and conductivity modulation of the power device. The procedure to incorporate the model into IG-Spice and various methods to ensure convergence are described. The IG-Spice IGBT model is presented, including all the physical effects which have been shown to be important in describing the device. Effectiveness of the model is shown by comparing the measured data for single device used in inductive load, and by comparing the static and dynamic current sharing of paralleled IGBTs. The simulated results are verified with experimental results. Accuracy is determined by the accuracy of the required parameters extracted. / Master of Science

The formulation and implementation of a low-order vibration controller using Linear Quadratic (LQ) modern control theory is demonstrated. The controller is implemented to reject persistent disturbances of the fundamental mode of a simply supported plate. The plate is excited by a 60 Hz harmonic excitation, a narrowband excitation centered at 60 Hz, and an impulse excitation caused by an impact hammer. The extraction of the eigen-properties of the first four modes of the plate is presented. The eigen-properties form the basis of the modal model of the plate. Also, a brief discussion of the control law is provided. Simulated and experimental results are presented for the transputer-based, parallel-processing control system. The steady-state fundamental modal amplitude is attenuated by more than an order of magnitude at the disturbance frequency, and the modal damping is doubled. Additionally, the implementation issues of applying the LQG controller are addressed including temporal and spatial aliasing considerations. / Master of Science

Federal law requires hearing protection device (HPD) manufacturers to provide attenuation ratings for use in estimating workers’ protection levels. These ratings, which are laboratory obtained, typically overestimate the actual protection levels achieved in the workplace. This research investigated laboratory protocols for yielding improved estimates of HPD in-field performance. Two experiments were conducted. The first was a pilot study developed by an American National Standards Institute (ANSI) working group. In this experiment, two types of earplugs were tested, a user-molded, malleable foam plug and a pre-molded, multi-sized rubber plug. Attenuation data (obtained using a psychoacoustical real-ear-attenuation-at-threshold measurement procedure) were collected across 10 subjects who entered the study as novice HPD users but were considered experienced HPD users in the latter half of the study. Four testing protocols involving two levels of HPDs, two levels of instruction-insertion techniques, and two levels of user experience were investigated. The same 10 subjects participated in all treatment conditions of the experiment. The second experiment involved similar protocols as the first; however, only one plug type was tested (the pre-molded, multi-sized rubber plug). Four testing protocols involving two levels of instruction-insertion techniques, two levels of user experience, and two levels of auditory feedback [fitting noise] were investigated. Forty subjects participated; each subject was tested in two treatment conditions. The attenuation results of each experiment were analyzed by statistical techniques. Statistical comparisons of results were made between the two experiments as well as between the experiments and selected field data. The major finding of the research was that fitting noise did not help subjects achieve higher attenuation [better protection] when consciously used for that purpose. Other findings indicated that novice subjects using only HPD manufacturer's instructions achieved attenuation that more closely represented the field attenuation than subjects tested under other conditions. However, the results were plug specific, in that no laboratory protocols yielded attenuation similar to the field data for the foam plug. / Master of Science