The development of a power electronic circuitry for a flywheel energy storage system is discussed in the following aspects. First, due to the nature of permanent magnet brushless DC motor/generator, the operation of three-phase voltage source inverter/rectifier can be simplified to that of a bi-directional DC-DC converter, allowing the use of mostly analog control. Second, there is a problem associated with the existing six-step brushless DC motor/generator control in the generator mode. A twelve-step control scheme is proposed to solve this problem. Third, high-switching frequency is necessary for the flywheel charger/discharger in order to reduce the size/weight of the system and to synthesize the high-frequency motor/generator current waveforms. A working prototype demonstrates that a high efficiency can be achieved at 1 ~O-kHz switching frequency by the innovative ZVT soft-switched three-phase inverter/rectifier. / Master of Science

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is well known for its immunotoxic effects particularly on the thymus as well as on T and B lymphocyte functions. Previous studies have suggested that TCDD may induce apoptosis in thymocytes although its demonstration in vivo has met with limited success. TCDD has also been shown to alter the major histocompatibility complex (MHC)-encoded molecules, however, its role in immunotoxicity is not clear. In this study, we investigated the role of Fas (CD95), an important molecule involved in the induction of apoptosis, on TCDD-mediated immunotoxicity using mice bearing homozygous lpr mutation which leads to failure of expression of Fas. When TCDD was administered orally at 0, 0.1, 1.0, or 5.0 pg/kg body weight for 11 days, it was found to be less toxic to the thymocytes from C57BL/6 lpr/lpr mice (Ah-responsive, Fas⁻) when compared to C57BL/6 +/+ mice (Ah-responsive, Fas⁺). Similar results were obtained when peripheral T cell responsiveness to antigenic challenge with conalbumin was studied in these mice. When mice that differed only at the MHC were compared for immunotoxic effects of TCDD, it was noted that B10.D2 (Ah-responsive, H-2ᵈ) were more sensitive to TCDD-mediated thymic atrophy and peripheral T cell dysfunction when compared to B10 mice (Ah-responsive, H-2ᵇ). In all TCDD-sensitive strains tested, the thymic atrophy was accompanied by a uniform depletion of all four subsets of T cells (CD4⁺, CD4⁺CD8⁺, CD4⁻CD8⁻, and CD8⁺). Furthermore, in these strains, TCDD suppressed the antigen-specific peripheral T cell responsiveness but not the responsiveness of naive resting T cells to polyclonal mitogens. Lastly, using cell-mixing experiments, it was demonstrated that TCDD directly affected the T cells responding to conalbumin but not the antigen presenting cells (APCs). Together our studies demonstrate that although Ah locus plays the primary role determining the toxicity of TCDD on the T cells, there are secondary factors such as expression of Fas or the MHC-phenotype which may play an important role in TCDD-mediated immunotoxicity. The role of Fas further suggests that TCDD may induce toxicity in T cells by triggering apotosis. / Master of Science

The advent of the laser has yielded many applications in modern science. One which has recently gained popularity in the area of structural dynamics is the use of a Scanning Laser Doppler Vibrometer (SLDV) to measure the dynamic response of vibrating structures. Essential in the optimal use of such a device is an understanding of the idiosyncrasies and operating parameters which may affect the quality of the experimental data. Specifically, the quality of the data taken with an SLDV system may contain noise which, for the purpose of this investigation, will be defined as "laser noise". It is the purpose of this thesis to characterize the laser noise, and investigate its potential sources. Characterization of laser noise as a function of the range of velocities is presented. An investigation of the speckle pattern motions which correspond to the areas prone to the laser noise and the effect of increased retroreflective surface treatments are explored. Additionally, the effect of three user defined parameters of the SLDV system are examined. In order to quantify the effect of the above on the experimental data, a statistical representation of the quality of the scan data is introduced. The work presented in this thesis provides insight into the physical mechanisms and phenomenon which contribute to the occurrence of laser noise. Additionally, some guidelines which will help the experimentalist use the SLDV system more optimally are presented. Also, some recommendations on future improvements of the SLDV are made, along with proposals for future research. / Master of Science

Fatigue cracks on a steel bridge hanger were monitored for acoustic emission in conjunction with strain gage monitoring. Waveforms of emissions were collected and classified using source location, strain magnitude, position on strain cycle and uniqueness of waveforms as the primary criteria. A vast majority of AE from the cracks were found to be due to crack face rubbing and the crushing of corrosion products between the crack faces while limited crack growth emissions were detected. AE was monitored from A588 compact tension specimens under variable amplitude tension-tension fatigue loading, results of which were used to aid in the interpretation of AE data from the hanger. Crack growth AE were detected only on overload cycles mostly above 92% of maximum load while AE due to crack face rubbing occurred throughout the strain cycle. / Master of Science

Energy recovery from the anaerobic treatment of crab processing wastewater was investigated. Biogas from two laboratory-scale, upflow anaerobic filters (Systems A and B) was collected and analyzed to determine percent by volume composition of methane (CH₄), carbon dioxide (CO₂), and hydrogen sulfide (H₂S). Biogas produced by System A (upflow anaerobic bed filter) produced biogas averaging 68, 28, and 1.5 % CH₄, CO₂, and HS, respectively. System A average gas production ranged from 6.3 to 15.8 liters per day (L/d) (6.6 to 10.0 L gas/L feed) for COD reductions ranging from 11,000 to 27,000 milligrams per day (mg/d) and COD loadings ranging from 16,700 to 43,600 mg/d. System B (upflow anaerobic packed filter) produced biogas averaging 68, 28, and 1.4 % CH₄, CO₂, and H₂S, respectively. System B average gas production ranged from 7.5 to 19.5 L/d (7.1 to 11.9 L gas/L feed) for COD reductions ranging from 11,700 to 28,700 mg/d and COD loadings ranging from 16,100 to 48,500 mg/d. A pilot-scale biogas collection system was constructed to collect, treat (remove H₂S), store, and utilize the biogas produced by an anaerobic/aerobic crab processing wastewater treatment system treating between 15 and 30 gallons per day (gpd). Biogas was produced by a 190 gallon upflow anaerobic bed filter and a 190 gallon anaerobic clarifier operated in series. Preliminary results indicated biogas production rates comparable to maximum average gas production rates of the laboratory-scale systems at approximately 10 L gas/L feed. Biogas was stored in a 120 gallon tank at up to 12 pounds per square inch (psi) following removal of hydrogen sulfide. Biogas was then burned in a modified natural gas hot water heater to produce heated water for maintaining the anaerobic reactors at 35°C. / Master of Science

The purpose of this study was to examine the physiological and affective aspects of the reaction to blood/ injury (B/1) phobia in a normal population with varying levels of B/I fear. From a screening sample (n = 412), ninety subjects (age 18-20) were selected and assigned to groups (n = 30) on the basis of level of fear and avoidance of B/I stimuli as measured by the Fear Questionnaire (Marks & Matthews, 1979). Heart rate (HR) and skin temperature (ST) were measured to establish a baseline and while the subjects watched a graphic surgery video. The subjects also described their emotional state before and after the video by rating affectively laden adjectives from three classes (neutral, fear, disgust). After the video, each subject’s fainting history and experience with B/I stimuli were gathered through use of an interview. The same information was collected from the subjects’ parents through a mailed questionnaire. HR and ST changed significantly across the duration of the procedure, yet no differences were found according to fear group. HR and ST were noted to change in a pattern indicative of fear (Ekman, 1983) after a description of the video was read to the subjects at the end of baseline. Prior to the video, the neutral adjectives were rated highest by all groups, while after the video the high fear group rated the disgust adjectives highest. The primary conclusion of the study is that fear is experienced in anticipation of B/I stimuli, while disgust is experienced during exposure. It was also found that people high in B/I fear as compared to people lower in B/I fear report the following: more anxiety sensitivity; more general anxiety; more social anxiety; more discomfort when others are distressed; more direct, negative experiences, including fainting and feeling faint, with B/I stimuli; and more first degree relatives with similar experiences. / Master of Science

The oxidative addition of E-H bonds to [Ir(1,5-COD)(PMe₃)₃]Cl (1,5-COD = 1,5- cyclooctadiene) has been previously studied (E = B, C, N, O, S). Some of the resulting species have shown activity as catalysts for hydrogenation and the addition of other molecules to unsaturated species. More recently, the addition of amino acids to [Ir(1,5- COD)(PMe₃)₃]Cl was studied in an attempt to create molecules with biological activity as well as species which might be active in asymmetric catalysis. Although inactive as catalysts, one of the these amino acid complexes was shown to be an anti-HIV agent. This finding prompted research into the additions of other molecules of biological importance to [Ir(1,5-COD)(PMe₃)₃]Cl. Since phosphates are an important functional group in biochemistry, the purpose of this research was to study the possible binding modes of the phosphate group to the iridium center and then to react biologically occurring phosphates with [Ir(1,5-COD)(PMe₃)₃]Cl. The reaction of dibenzyl phosphate (DBP) with [Ir(1,5-COD)(PMe₃)₃]Cl has been studied in detail. The resulting complex, Ir(PMe₃)₃(H)(DBP)Cl, is soluble in most common laboratory solvents with the exception of ether and was characterized by infrared, ¹H, ³¹P, and ¹³C NMR spectroscopy and elemental analysis. The dibenzyl phosphate ligand is labile and is easily displaced by nucleophiles. The complex does not undergo reaction with molecular hydrogen at ambient temperatures. Dialkyl phosphate complexes were easily made using the same synthesis as the dibenzyl phosphate. This reaction was unsuccessful for the preparation monoalkyl and diaryl phosphate complexes. The reaction of [Ir(1,5-COD)(PMe₃)₃]Cl with the nucleotides 2'-deoxyadenosine- 5'-monophosphate (d-AMP) and (-)-adenosine-3'-5'-cyclic monophosphate (cyclic-AMP) did not result in the formation of a single product perhaps because the phosphate groups in these compounds are diacids. The reaction of [Ir(1,5-COD)(PMe₃)₃]Cl with 1,2- dihexadecanoyl-rac-glycero-3-phosphoethanolamine (PEA), a dialkyl phosphate, produced only the N-H addition product. / Master of Science

The scarcity of usability studies on computer-aided design (CAD) systems has prompted three questions: (1) Is usability testing different for CAD systems than conventional software? (2) What role does domain expertise play in the use of CAD software since most CAD applications are not simple tasks? (3) How does the design parameters’ presentation affect the user's understanding of the design, the design domain, and the capabilities of the CAD system? This thesis addresses these three questions through the application of human-computer interaction (HCI) techniques in the development of a graphical user interface (GUI) for the metal-ceramic brazing process: First, a GUI for the metal-ceramic brazing process was designed and implemented. Subjects were then invited to test the GUI by performing a set of benchmark tasks. The results of these tests were analyzed, both to characterize design flaws in the interface, and to suggest redesign solutions to observed problems. The GUI was then refined based upon the test results and retested. To further aid in the understanding of the effects of the design parameters’ presentation, a usability evaluation was also performed for a finite element module of a state-of-the-art commercial CAD system (I-DEAS Master Series, version 1.3). This evaluation provided a comparison for the metal-ceramic interface with respect to interaction styles, presentation of domain knowledge, and task performance. This study demonstrated that HCI methodologies can be applied effectively to CAD user interface development. In particular, it encouraged the development of a usability-oriented process for developing usable interfaces. However, it also highlighted the difficulties posed by the complexity of a CAD system and the associated task analysis. It was observed that three distinct sets of knowledge are involved in the use of a CAD system: task knowledge, domain knowledge, and application knowledge. By separating and distinguishing the needs of these sets of knowledge, the CAD system developer is more likely to design a high-quality interface, one that supports the task performance while educating the novice user of the technical background of the application. It was also found that a clearly and intuitively organized interface can provide an invaluable insight for users into the functionality of the system and facilitate users' learning of the system. The subjects who participated in this study were inexperienced in both the application and the application domain and relied greatly upon the organization of the interface to lead them through the benchmark tasks. The organization of the system functions or, in the case of the metal-ceramic brazing interface, the design parameters, was shown to be crucial to the subjects' understanding of the application because it was the only source of guidance the subjects had as to how to perform the benchmark tasks. In particular, it was observed that the subjects had the tendency to align their thought process to that of the interface in their attempts to understand the system. / Master of Science

An experimental study of ceramic lubrication by tribopolymerization at high loads and high speeds is presented. One condensation monomer -- C₃₆ dimer acid/ethylene glycol monoester -- and five addition monomers, i.e., diallyl phthalate, lauryl methacrylate, vinyl acetate, methyl-2-acrylamido-2-methoxy acetate, and vinyl octadecyl ether, were used at 1 wt. % concentrations in hexadecane with alumina on alumina pin-on-disk testing. A two by two matrix of load and speed conditions was used to determine the effects of load and speed on wear reduction. At low speeds, the monomers showed significant wear reductions, from 37 percent up to 98 percent, compared to pure hexadecane lubrication. Changes in load at low speed had mixed effects dependent on the monomer. At high speeds, the monomers did not decrease wear; in some cases wear increased. ESEM surface studies show a relationship between the anti-wear effectiveness and the consistency of a formed wear debris layer on the alumina surface. The surface films of wear debris and the formed polymeric products may reduce wear by providing protection to the sliding surfaces. Proposed wear mechanisms and a discussion of possible speed-wear interactions are presented with recommendations for continued tribological testing. / Master of Science

The purpose of this investigation was to nondestructively characterize a 2-D Nicalon-reinforced, CVI-SiC matrix composite before and after exposure to 1000, 1200, and 1400 °C in oxidizing atmospheres of air. Concurrently, the nondestructive testing methods used to detect thermally induced changes in the SiC/SiC composite were evaluated. All of the NDT techniques, except film X-ray radiography, were sensitive to changes in the ceramic matrix composite (CMC) caused by thermal ageing. Surface and sub-surface scanning acoustic microscope (SAM) micrographs indicated that the CMC specimens were experiencing surface changes. The increase in surface reflectivity of the specimens after heat treatment was attributed to density and elastic property changes related to oxidation of the matrix, formation of silica on the fibers, and increased crystallinity of the Nicalon fibers. Acousto-ultrasonic results indicated that thermal exposure altered the ability of the CMC specimens to transmit ultrasonic energy. The ability to transmit energy was degraded or enhanced depending on ageing temperature and the presence or absence of a refractory coating. C-scans indicated that the heat-treated specimens attenuated/scattered more energy than the as-fabricated specimens. Through-transmission scans indicated that, after thermal exposure, the specimens that had received a refractory coating showed a greater increase in attenuation than the uncoated specimens. Tensile tests performed at room temperature provided strength data and a means for monitoring acoustic emission. Optical micrographs showed void and silica formation around fibers and the development of microcracks within the matrix. Electron microprobe analysis verified that carbon and silicon were being lost and oxygen was being gained within the fiber-matrix interphase. / Master of Science