Seed priming is a controlled hydration process, followed by dehydration, that allows pregerminative metabolic activity to proceed without germination. The objective of this research was to investigate the effects of priming on intrinsic characteristics of seed germination including temperature, water, and development, in order to understand how priming affects the germination of broccoli (<i>Brassica oleracea var. italica</i> Plenck) seeds. Priming of broccoli seeds consistently improved germination and emergence rate in the laboratory and field and was related to the accumulation of a specific level of hydropriming units expressed in MPa*h. Priming reduced the sensitivity of seed germination to temperature and increased the temperature range of germination but did not lower the minimum temperature for germination. Primed seeds leaked less electrolytes at supraoptimal temperatures (≥ 35°C) compared to nonprimed seeds. In the field, primed seeds produced a greater plant stand and yield under stressful emergence conditions. Under optimal conditions in the field for stand establishment, the advancement in emergence of primed seeds did not carry over to earlier, greater yields. Matric priming, using calcium silicate as the carrier in the ratio 1.0:0.8:1.8 (seed:carrier:water; by weight) for 7 d at 20°C, was superior to osmotic priming using polyethylene glycol (pEG 8000) at -1.2 :MPa in nearly all variables examined. This may be attributed to reduced respiration during priming of seeds in PEG or nutrient uptake by seeds in calcium silicate. The testa was observed to be a barrier to broccoli seed germination. Priming-induced changes to the physical characteristics of broccoli seeds included increased volume (32%) and an irreversibly expanded, and weakened testa with some minute cracking near the area where the radicle emerges. Primed seeds germinated faster, in part by maintaining a lower hydrotime constant, and thus exhibited a greater progression towards germination per unit water potential at a constant temperature compared with nonprimed seeds. It was hypothesized that, since the testa threshold was reduced after priming by expansion and formation of free spaces, the reversibly expanded embryo of primed seeds does not become immediately appressed to the testa upon rehydration. Thus the yield threshold component controlling the rate of germination of primed seeds is lower by the amount of the testa threshold. The priming effect is more than just reducing the yield threshold as indicated by a significant invigoration of seeds with split testae. Despite the increased volume as a result of the formation of free spaces, primed broccoli seeds did not imbibe more water or have a greater turgor at full hydration. Priming did not lower the minimum water potential allowing germination, and primed seeds did not plateau in water uptake but, instead, moved immediately from imbibition to expansive growth. Priming improved the germination rate of broccoli seeds at all stages of maturity with the most significant effects at stages before attainment of maximum dry weight. Dry storage of broccoli seeds at harvest able maturity (≥ 56 days after pollination) did not improve germination, indicating a lack of post harvest dormancy. / Ph. D.

This research shows that a model that concurrently determines product, production, and capacity can provide better results than a model that makes these decisions sequentially. Three versions of a life-cycle complete concurrent model and corresponding sequential model that solve product, production, and capacity planning problems are mathematically formulated and compared through an hypothetical example. All versions of the concurrent and sequential models consider three types of work centers and corresponding types of capital budgeting projects. Each version of the concurrent and sequential models considers a specific type of capital budgeting project. These are: (1) projects that may be partially accepted with no upper limit, (2) projects that may be partially accepted with an upper limit of one, and (3) projects restricted to values of zero and one. An hypothetical example spanning twelve fiscal periods that included five products, two product sub-groups, one pre-production/post-support project, three production projects, and one support project was developed to enable comparison of the models. Nine comparisons between each of the three versions of the concurrent and sequential models were conducted resulting in a total of 27 comparisons. Comparisons of the models required the development of five computer programs. Four of these programs provided Mathematical Programming System (MPS) formatted mixed integer linear programs (MIP) that were solved using the LINDO/386 optimization program. The fifth program read output from LINDO/386 and provided the future worth of the sequential model. Results obtained from tests of the concurrent and sequential models were compared based upon future worth, capital budgeting projects funded, products funded, production and inventory quantities, and regular and overtime labor levels. For every combination of product sub-group demand and capital budgeting constraint type, the concurrent model always provided the highest future worth. In addition, while both models funded the same set of products, the concurrent model provided more level labor, production and inventory quantities, and support for products. Following these comparisons, it was concluded that, for any capital budgeting constraint type and product sub-group demand, a concurrent model can provide better planning results than a sequential model. / Ph. D.

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.