The purpose of this research is to examine the significance of a market factor, an industry factor, a company factor and a growth factor in explaining security returns. A secondary objective is to determine if interim financial statements--the balance sheet and the income statement--provide useful information in developing the return model. Market-related and industry-related systematic risks are constructed as surrogate measurements for the market and industry factors. The company factor is composed of one accounting return measure (profitability) and five accounting risk measures (accounting beta, operating leverage, financial leverage, dividend covariability, and cash flow beta). These variables are included as individual regressors in the return model. Also, a company index (the first principal component) is constructed and tested for its significance in the four-factor return model. The compound growth rate in total assets measures the growth of individual companies. Quarterly accounting information is used to measure these company and growth variables, and their significance provides evidence supporting the usefulness of interim financial statements. A multiple regression analysis is employed to develop the return model. In addition to the market factor, an industry factor, components of the company factor (dividend covariability and profitability), and a growth factor are found to contribute significantly to estimation of the return model. The use of a company index in lieu of individual company variables, however, is not recommended for· developing the return model. Additionally, results indicate that the market model provides the best surrogate measure of the market factor, and Line of Business information is recommended for classifying companies into industry groups. Major limitations of the study are (i) a self-selection bias of companies for the sample; (ii) measurement errors in interim financial statement data due to accounting allocations; (iii) seasonality of quarterly accounting information; (iv) use of average regression statistics in determining the best return model; (v) a limited number of regression models examined; and (vi) multicollinearity. These may limit the generalizability of the findings beyond the sample data and the interpretation of relationship between security return and its potential determinants. / Ph. D.

An improved method for designing controllers for nonlinear stochastic systems is developed and analyzed. The resulting controller consists of a nonlinear control law coupled with an adaptive state estimator. The nonlinear control law is developed first. Using Taylor series expansion, linear approximations to the nonlinear systems are generated at selected points in the operating region. Then a control law which will produce the desired response is developed for each linearized configuration using conventional techniques for linear systems. The resulting control law parameters are treated as tabulated values from a set of unknown continuous functions of the nonlinear system parameters. These unknown functions are approximated at all points in the operating region by fitting curves to the tabulated data. The stability and convergence aspects of this nonlinear control law are analyzed in detail, with several derivations given and theorems proved. Two examples are given to illustrate the design procedure and evaluate its performance. The design procedure is extended to stochastic systems by incorporating a suitable state estimator. Two members of the class known as partitioned adaptive estimators (PAE's) are evaluated and their performance compared. The formulation known as the modified semi-Markov PAE is shown to be superior. The design, execution, and analysis of the experiments comprising the evaluation are discussed in detail, with particular attention given to correlating the performance of the estimators with the behavior of the weighting coefficients. Numerous figures and tables which amplify the discussions, along with some suggestions for further research, are also included. / Ph. D.

The viscoelastic response of polymer-based composite laminates, which may take years to develop in service, must be anticipated and accommodated at the design stage. Accelerated testing is therefore required to allow long-term compliance predictions for composite laminates of arbitrary layup, based solely upon short-term tests. In this study, an accelerated viscoelastic characterization scheme is applied to T300/5208 graphiteepoxy laminates. The viscoelastic response of unidirectional specimens is modeled using the theory developed by Schapery. The transient component of the viscoelastic creep compliance is assumed to follow a power law approximation. A recursive relationship is developed, based upon the Schapery single-integral equation, which allows approximation of a continuous time-varying uniaxial load using discrete steps in stress. The viscoelastic response of T300/5208 graphite-epoxy at 149C to transverse normal and shear stresses is determined using 90-deg and 10-deg off-axis tensile specimens, respectively. parameters In each case the seven viscoelastic material required in the analysis are determined experimentally, using a short-term creep/creep recovery testing cycle. A sensitivity analysis is used to select the appropriate short-term test cycle. It is shown that an accurate measure of the power law exponent is crucial for accurate long-term predictions, and that the calculated value of the power law exponent is very sensitive to slight experimental error in recovery data. Based upon this analysis, a 480/120 minute creep/creep recovery test cycle is selected, and the power law exponent is calculated using creep data. A short-term test cycle selection procedure is proposed, which should provide useful guidelines when other viscoelastic materials are being evaluated. Results from the short-term tests on unidirectional specimens are combined using classical lamination theory to provide long-term predictions for symmetric composite laminates. Experimental measurement of the long-term creep compliance at 149C of two distinct T300/5208 laminates is obtained. A reasonable comparison between theory and experiment is observed at time up to 10 5 minutes. Discrepancies which do exist are believed to be due to an insufficient modeling of biaxial stress interactions, to the accumulation of damage in the form of matrix cracks or voids, and/or to interlaminar shear deformations which may occur due to viscoelastic effects or damage accumulation. / Doctor of Philosophy

Small diameter LC columns provide rapid thermal equilibration and are ideal candidates for temperature programmed LC. Special instrumentation requirements are presented and details of column assembly are given to permit the preparation of highly efficient, stable microbore columns. Three LC temperature control systems are described and their individual strengths and weaknesses are discussed. Problems encountered in raising the temperature of an LC column are addressed and solutions are described. Experimental results of column and instrumentation evaluation are given and the effects of temperature on speed, efficiency, stability and retention of a broad range of samples is reported. Temperature and solvent programming are compared directly. / Ph. D.

Three fundamental problems in computer vision are addressed in this dissertation. The first deals with the problem of how to extract and assemble a rich symbolic representation of the gray level intensity changes in an image. Results show that the facet model based feature extraction scheme proposed here is superior to the other existing techniques. The second problem addressed deals with the interpretation of the resulting structures as three-dimensional object surfaces. The three different shape modules described in this dissertation are found to be useful in the recovery of intrinsic scene characteristics. Finally, mechanisms for interaction among different sources of information obtained from different shape modules are studied. It is demonstrated that interactions among shape modules can enhance the data acquired by different means. / Ph. D.

A major thrust for vocational education in the 1980s is the collaboration of schools with industry and other sectors of the community. The Building Our American Communities (BOAC) program was initiated in 1971 by the Future Farmers of America to involve agriculture students in their communities. Considerable financial and human resources have supported BOAC program operations for the past 13 years, yet there is a lack of knowledge as to who has been participating in the program, what resources have been utilized, and what outcomes have resulted. The purpose of the study was to examine the BOAC program by describing community development activities, BOAC projects, and characteristics associated with selected students and advisors who participated in the 1983 BOAC program relative to their FFA chapter, school, and community contextual situations with respect to program inputs and anticipated outcomes. The first four levels of Bennett and Nelson's (1975) evaluation hierarchy used by the Cooperative Extension Service served as a theoretical frame of reference for the study. The population for this descriptive study included the 48 students and 46 advisors who attended the 1983 National Conference on Community Development. Three survey instruments were developed by the researcher. One for students and one for advisors elicited background and participation information. The third instrument was used to gather participants' FFA chapter, school, and community data. BOAC program statistical reports were also used as a data source. The data were analyzed using descriptive techniques. Two major findings of this study were: 1. Benefits to FFA members and vocational agriculture programs represented the major program outcomes. These outcomes were increased citizen participation, increased human relation skills of members, and increased public awareness of the vocational agriculture program. 2. Students and advisors involved numerous individuals and groups in their projects which primarily improved the following community sectors: school/education, civic facilities, agriculture, and recreation. The BOAC program should be viewed as an excellent teaching tool for involving students in their communities. Future studies, using this one as a baseline data source, need to be conducted to determine BOAC program effects on program participants and nonparticipants. / Ed. D.

Mussel studies in the Tennessee River drainage (1973 - 1982) examined ecology and distribution and investigated factors limiting to distribution. This river system presently supports 71 freshwater mussel species, 25% of which are endemic to the Cumberlandian Region. Species have been extirpated from this drainage within the past 60 years, however the number of extant species remains high. The major impact of man's activities has been reduction of available habitat. Past and present distribution records indicate that mussel species assemblages are determined by geologic history and stream size. Although some overlap of species exists among stream size categories, there is no longer a continuous gradation from one category to the next; mussels exist in isolated communities separated by nonproductive river reaches. Productive reaches supporting more than 60 mussel species once existed in habitats spanning the transition from medium to large rivers; reaches now altered by impoundment. The maximum number of species reported in recent collections from any one site in the Tennessee drainage is less than 40, which seems to be the maximum number of species niches available. Quantitative sampling reveals characteristic patterns of species dominance. Changes in species dominance and age class structure provide a better basis for evaluating changes over time than do species composition or diversity alone. Mussel density was found to be more variable than species composition, and was unrelated to species abundance. Experiments on effects of siltation indicated that silt can be a significant limiting factor to mussel distribution. Transplant studies showed that mussels transplanted into heavily silted areas exhibited poor survival over a one year period compared to mussels moved to unsilted habitats. Results indicate that siltation may interfere with reproductive activity. Laboratory experiments testing the effect of suspended silt on the uptake of C-14 tagged algae by freshwater mussels showed that suspended silt can interfere with feeding. Food uptake was reduced to approximately 50% (of control) at silt levels of 211 to 820 mg/l, and to 80% at silt levels over 1000 mg/l. It was concluded that the limiting mechanism is one of dilution of food rather than direct interference with filtration or respiration. / Ph. D.

The effect of moisture stress conditioning on the drought tolerance and performance of three open-pollinated families of loblolly pine (Pinus taeda I.) during water stress were investigated. Seedlings were subjected to prolonged sublethal drought treatments which included a watered control, a moderate stress treatment (MWS, seedlings watered only when needle water potential reached -0.8 MPa) and a severe stress treatment (SWS, seedlings watered only when water potential reached -1.4 MPa). After the conditioning period, numerous physiological and morphological parameters were measured, and performance of seedlings during water stress evaluated. Significant decreases in needle osmotic potential occurred in moisture stress conditioned seedlings. As a result, turgor in conditioned seedlings was equal to or greater than control seedlings even at lower needle water potentials. Photosynthesis vas decreased greatly with reduced needle water potential. However, the MWS and SWS seedlings maintained photosynthesis to water potentials 0.15 and 0.45 MPa lower than control seedlings, respectively. This response is likely the result of both osmotic adjustment, and an acclimation of the photosynthetic process resulting in less non-stomatal inhibition of photosynthesis at low needle water potentials. Initial needle conductance and transpiration, but not photosynthesis, were reduced greatly by the conditioning treatments, and resulted in improved water-use efficiency in conditioned seedlings. The response of stomata to changing vapor pressure deficit was increased through moisture stress conditioning. Boot growth was affected more by moisture stress than shoot growth, causing a decrease in root/shoot ratio. Changes in root morphology as a result of conditioning are not likely to improve the drought tolerance of loblolly pine seedlings. SWS conditioning significantly improved the height growth increment and resulted in slightly greater shoot and root biomass of outplanted, containerized seedlings after the first growing season, despite these seedlings being much smaller at the time of planting. Differences between seed sources did occur in the experiments, with a source from Texas generally showing the least response to moisture stress conditioning. / Ph. D.

Human clinical (n=131) and environmental (n=226) isolates of the Mycobacterium avium-intracellulare and M. scrofulaceum (MAIS) complex were screened for plasmids in an effort to increase knowledge about the genetics and epidemiology of these pathogenic bacteria. Approximately 50% of the clinical MAIS isolates from New York, Maryland, Virginia, South Carolina, and Georgia contained one or more plasmids. On the basis of plasmid content, aerosol MAIS isolates more closely resembled human MAIS isolates than did MAIS isolates from the other environmental sources examined (dust, soil, sediment, and water). Plasmid profiles were remarkably heterogenous, and isolates with identical profiles were rarely encountered. However, a 115 megadalton (Md) plasmid was detected in 15 mercury resistant human and environmental isolates. In one of these isolates (M. scrofulaceum W262) the presence of the 115 Md plasmid was shown to correlate with the presence of an NAD(P)H dependent mercuric reductase. Plasmids with molecular weights of 8.8, 11.2, 14.2, 16.9, 17.9, and 18.3 Md were also common among both human and environmental isolates. On the basis of molecular weight, 36 distinct plasmids were detected; their sizes ranged from 7 to 230 Md. It was concluded that human and environmental MAIS isolates share a number of plasmids with identical molecular weights and that plasmids can serve as useful entities in genetic and epidemiologic studies of this group of extremely slow-growing, poorly understood human and animal pathogens. / Ph. D.

This study developed a general methodology for probabilistic service life prediction of a composite viscoelastic cylindrical structure under random outdoor environment. The analysis emphasized both the statistical variations of environmental thermal loads and of material properties. The daily probability of failure was calculated considering failures due to both the excessive stress and strain. The probabilistic service life was then obtained via the evaluation of cumulative hazard function. Models for the deterministic and random variations of environmental thermal loads- ambient temperature, sky radiation, wind convection, and solar radiation, were developed and were considered in obtaining the structure's surface temperature. The statistical characteristics such as the mean and variance of the induced stresses and-strains were calculated via the uses of complex frequency response functions. Methods for statistical characterization of time and temperature dependent viscoelastic material properties were presented. Five statistical distributions- Normal, Log-Normal, Beta, Gamma, and Weibull, were considered for the goodness of fit. Two forms of material deterioration- time and temperature dependent aging and cumulative damage due to loading were also recognized. Three statistical distributions- Normal, Log-Normal, and Weibull, were used to represent the variations of induced daily maximum stress and strain. The daily probabilities of failure due to the maximum stress and strain were calculated based on the concept of load and resistance interference. The effects of these failure modes were then combined to define daily probability of failure of the structure. / Doctor of Philosophy