In this dissertation, two nonlinear regressive models, the forward model and the inverse model, have been developed to determine the pose (position and orientation) of the scanning laser Doppler vibrometer (SLDV) with respect to a structural coordinate system. The parameters in the forward model include the pose and the ranges. The parameters in the inverse model include the pose only. The parameters of those models are obtained by using the least squares technique. A geometrical method is developed to get an estimation of the pose and the ranges. This estimation is used as an initial solution in the iterative procedure for determining the parameters in the nonlinear regressive models. The statistical inferences are made about the inverse model by the linear approximation. The nonlinearity of the inverse modal is measured in order to verify the validity of the linear approximation. Included along with the development of the models, are the implementation of the algorithm (geometrical method and inverse model), the assessment of the inverse model, the calibration of the scanner, and the accuracy evaluation of the algorithm. / Ph. D.

Two control schemes for PWM converters, average current-mode (ACM) control and charge control, are studied in this dissertation. The small-signal models are derived for continuous-conduction mode PWM converters employing these two controls. Sampled-data modeling is applied to the current loop modeling, and the obtained models are accurate up to half the switching frequency. The relationships between current loop instability and converter operating conditions for both controls are found for the first time. The derived models are verified by both time-domain simulations and experiments. The models can be used for both voltage loop and current loop analysis and designs. Comprehensive design guidelines for PWM converters with both controls are also provided. The small-signal characteristics of these two controls are compared with those of peak current-mode control. The applications of ACM control and charge control to power factor correction (PFC) circuits are studied. Charge control is applied to continuous-conduction mode flyback converter to achieve a single-stage PFC. The current loop instability in PFC circuit and its effect on the input EMI filter design are investigated. The trade-off between the current loop stability nlargin and line current distortion is also discussed. / Ph. D.

This dissertation presents a design of a robust, automatic speaker recognition (ASR) system. The ASR system is designed to work with both text-independent and text-dependent speaker recognition. Several speaker spectral features are studied to determine their contribution in term of accuracy to the system. A new algorithm is designed to label a speaker voice as either male-type voice or female-type voice. Following this division, the processing time of the speaker identification for the ASR system will be reduced by about half. Rectangular window, Hamming window, first order preemphasis filter, and many proposed spectral distances are also investigated. The principal components analysis is used to achieve high degree of female-type and male-type separation as well as the speaker recognition accuracy. Spectral features are combined to improve the recognition performance of the system. In addition, many other system components such as speech endpoint detection, automatic noise thresholds, etc. are required to build correctly in order to achieve high speaker recognition accuracy. Multi-stage decision process is used both to improve and to speed up the decision if certain criteria are met. Finally, TIMIT acoustic continuous speech corpus is used to evaluate the speaker recognition performance and the robustness of the system. / Ph. D.

This work is a contribution to the minimization of some of the selectivity and detection limitations in capillary electrophoresis. A more practical design of an electrochemical detector is introduced with simultaneous on-line UV detection¹, for the selective detection of a number of pungent and neurological compounds, the piperines and the capsacinoids. Commercially available microelectrodes together with large 25 μm id fused silica capillary columns are used for the first time in the presence of an auxiliary electrode. Minimum detectable quantities and efficiencies are sample dependent and were found to be comparable to the earlier more laborious electrochemical cell designs. To exploit the benefits of common additives that enhance the selectivity of electrolyte systems, various additives including α, β and γ Cyclodextrins, organic modifiers, as well as a series of cationic surfactants are explored for the separation of a number of industrially important isomeric aromatic carboXylic acids². The separation was found to depend largely on the analyte1s geometry, degree of ionization as well as on the buffer pH and composition. The resultant separations were compared for best efficiency, resolution and ruggedness. In addition, to add to the arsenal of CE selectors, a number of new micellar systems are investigated. Oligomeric sodium 10-undecylenate, a recently introduced oligomeric surfactant³ is structurally investigated through the separation of vitamins and the resultant selectivity and resolution is compared to the more commonly used surfactant sodium dodecyl sulfate⁴. Additionally, a number of phospholipids and Iysophospholipids, common constituents of cell membranes, are investigated not only as possible MECC surfactants but also as highly hydrophobic analytes needing themselves separation⁵. Finally, as a contribution to methods development, the effect of variations in systemparameter conditions is examined in a successful separation of a number of enzymes. / Ph. D.

Research was conducted that culminated in the merging of the objectives of two tools: predetermined motion time systems and posture recording. This dissertation reports the development and testing of a computerized tool-the Work and Posture Analysis Sequence Technique (WAPAST)-used to collect methods, postural, and work measurement data. From the data collected, one can determine the method used to complete an activity by task identification, the time it takes to complete each task, as well as the time to complete an entire activity, and the postural considerations for each task and for the overall activity. The tool is based on the Maynard Operations Sequence Technique (MOST) with some characteristics of the Ovako Working Posture Analysis System (OWAS). Criteria established were speed of completion, accuracy, and reliability. A validation study was conducted to assess the data collected with WAPAST against data collected with known, validated tools. The study was an experiment that had several subjects use WAPAST to analyze videotaped work activities while several other subjects used MOST or OW AS to analyze the same videotaped activities. The data collected with WAPAST were compared with the data collected with MOST and OWAS. The work measurement data collected with WAPAST were found to be both accurate and reliable, but the postural data were not. Times to cornplete applications were extensive. Recommendations are given for improving the tool, which include a different way of recording postural data and expanding the limitations of the tool. / Ph. D.

Much of accounting research is predicated on the fact that the capital markets operate well because disclosures of annual earnings are verified. It is generally observed, however, that market responses to the unverified management forecasts may be as strong as responses to similar l verified information disclosures. This dissertation is concerned with the credibility of such unverified information. Three hypotheses are investigated in the study. The data includes managements' annual earnings forecasts gathered from the 1986 to 1992 editions of the Wall Street Journal. The first hypothesis concerns the timing of the disclosure of the forecasts by management. It is tested by comparing liquidity and leverage ratios at the event date to prior same-firm ratios. Evidence is found that supports the conclusion that the firm is preparing the market for a possible capital offering. The second hypothesis concerns the asymmetry of information between the firm and investors. This asymmetry affects the stock market reaction. It is tested using OLS regressions with the market reaction as the dependent variable and various asymmetry surrogates as independent variables. Evidence is found that supports the conclusion that as more investors follow the firm, there is less new information associated with the management forecast disclosure. Further, as fewer investors follow the firm, there is a lower tendency to disclose forecasts. The third hypothesis concerns the ability of the firm to provide credible communication. It is tested using OLS regressions with the market reaction as the dependent variable and various proprietary information surrogates as independent variables. Weak support is found for the conclusion that those firms releasing proprietary information through the forecast disclosure provide more credible communication. The support is restricted to the negative forecasts. For positive forecasts, it may be that reputation is most important to investor response. / Ph. D.

Aqueous dispersion prepregging, a relatively new method for forming graphite reinforced, polymer matrix composites, was investigated. This methodology could circumvent many of the environmental and processing problems prominent in the current state of the art. Aqueous dispersion prepregging requires that the matrix resin be in the form of a stable colIoidal dispersion, preferably of small uniform particles. Formation of submicron particles from poly(ether ether ketone) (PEEK) for use in aqueous dispersion prepregging was demonstrated. The procedure involved synthesis 4,4'-difluoro (N-benzohydroxylidene aniline) followed by the step polymerization of this monomer and hydroquinone via aromatic nucleophilic substitution to 'form an amorphous PEEK derivative, poly(ether ether ketimine). This monomer can also be statistically copolymerized with 4,4'-difluorobenzophenone to afford a semicrystalline, soluble PEEK derivative. Acid catalyzed hydrolysis of these derivatives to insoluble PEEK can be used to generate submicron particles. A high performance stabilizer, which was used for suspending PEEK particles in water, has also been developed. This facilitated the development of processes for aqueous dispersion prepregging. The stabilizer is a poly(arylene ether) copolymer formed from 4,4'-difluoro- (N-benzohydroxylidene aniline), 2,6-dichloropyridine, and hydroquinone. Poly{ ether ether ketone) has excellent mechanical properties as well as solvent resistance. However, it has been reported that under the recommended high temperature melt processing conditions the material may degrade via branching and crosslinking. An alternative to melt processing PEEK is to apply the powder metallurgy technique of sintering. This involves cold (room temperature) compaction of the polymeric powder, followed by pressure free sintering of the resultant green body. Sintering occurs due to a reduc1tion of surface free energy, and in this regard small particles (large surface area) have a large driving force for sintering. Pressure free sintering of PEEK par1icles with emphasis on the development of mechanical properties such as stiffness and strength as a function of sintering time, temperature, and particle size was examined. The data was analyzed using the two particle model developed by Frenkel and the crack healing theory developed by Wool. The latter is based on the reptation theory of de Gennes and Doi and Edwards. Sintering conditions were established which allowed for the attainment of comparable mechanical behavior to conventional processes. / Ph. D.

A spatial linear stability analysis of circular and elliptical jets has been carried out. For the circular jet, the Michalke's shooting method has been extended to the case with a swirling basic flow. For the elliptical jet, an algebraic eigenvalue problem has been formulated by applying the Chebyshev and Fourier spectral collocation method to the disturbance equations of the flow expressed in a generalized cylindrical coordinate system. The resulting algebraic eigenvalue problem was solved using the inverse power method. The approach developed is capable of handling the influences of different distributions of the momentum thickness, swirl, and heat release. In addition to studying the stability properties of the elliptical jet in comparison with those of a circular jet, the linear stability analysis has been used to obtain the insight into the entrainment process. A possible way to enhance the entrainment of elliptical jets has been suggested. / Ph. D.

Semiconductor device simulators have generally been based on either classical or semi-classical approaches. In these approaches, the Poisson's equation is solved with either the current continuity equation or the Boltzmann transport equation. Methods based on quantum mechanics have been generally very computer intensive, and thus until recently not much favored. However, with the availability of faster and more powerful computers this picture is changing. As the physical dimensions of the semiconductor devices are reduced, the assumptions made in the classical and the semi-classical approaches become invalid and the simulation results become inaccurate. For such cases, quantum mechanical concepts must be introduced to provide accurate simulation results. This dissertation presents the proof of concept of a semiconductor device simulator based on the quantum mechanical principals. The simulation technique is based on the self consistent solution of the Poisson's and time independent Schrodinger wave equation for a 1-D finite differenced grid. The applicability of the technique to a 2-D finite differenced grid is also presented. The simulation is performed by first solving for the Fermi energy distribution inside the simulation domain. The initial estimates about the carrier concentrations are developed from the Fermi energy distribution. Based on the carrier concentrations, the potential distribution inside the device is updated using the Poisson's equation. The updated potential distribution is then used in the time independent Schrodinger's equation and the carrier wave vectors are thus determined. The carrier wave vectors, along with appropriate density of state function and distribution function are used to update the carrier concentrations. For the 1-D case, the density of state function is based on a single dimension of a three dimensional volume with the assumption that the density of states is the same for all the three dimensions. The distribution function used is the Fermi-Dirac distribution function. The new carrier concentrations thus computed are then substituted back into the Poisson's equation, and self consistency is obtained when minimum error criteria has been met. The device simulator has the capability of simulating heterojunctions semiconductor devices fabricated from elemental semiconductors such as Si and Ge, as well as binary and tertiary compound semiconductors. / Ph. D.

The objective of this work is to solve a model one dimensional duct design problem using a particular optimization method. The design problem is formulated as an equality constrained optimization, called All at once method, so that the analysis problem is not solved until the optimal design is reached. Furthermore, the block structure in the Jacobian of the linearized constraints is exploited by decomposing the variables into the design and flow parts. To achieve this, Sequential quadratic programming with BFGS update for the reduced Hessian of the Lagrangian function is used with Variable reduction method which preserves the structure of the Jacobian in representing the null space basis matrix. By updating the reduced Hessians only of which the dimension is the number of design variables, the storage requirement for Hessians is reduced by a large amount. In addition, the flow part of the Jacobian can be computed analytically. The algorithm with a line search globalization is described. A global and local analysis is provided with a modification of the paper by Byrd and Nocedal [Mathematical Programming 49(1991) pp 285-323] in which they analyzed the similar algorithm with the Orthogonal factorization method which assumes the orthogonality of the null space basis matrix. Numerical results are obtained and compared favorably with results from the Black box method - unconstrained optimization formulation. / Ph. D.