Experiments were performed with naphthalene and a-naphthol to compare the processes involved in the sorption of a polycyclic aromatic hydrocarbon (PAH) and its metabolite, respectively, and to assess the bioavailability of these two compounds adsorbed to two sandy soils with different organic carbon contents. Adsorption conditions were varied to estimate the extent that biologically-mediated and chemically-induced oxidative coupling, and rate-limited diffusive processes contributed to the apparent irreversible adsorption of these compounds. The purposes of this research were to: (1) investigate the processes which cause the irreversible adsorption of organic contaminants to soil~ (2) gauge the impact that these different adsorption processes have on the bioavailability of sorbed contaminants; and, (3) evaluate the environmental significance of these processes in soils and the subsurface. This dissertation has been prepared as three separate articles for publication in peer reviewed journals. The first article serves as a literature review in evaluating the significance of oxidative coupling reactions in soil and subsurface environments. This review concludes that oxidative coupling of organic contaminants may be important in soils and could be stimulated as a viable remediation strategy. For subsurface systems oxidative coupling appears much more limited, however, engineered systems could be developed to enhance this process. The second article presents experimental results used to quantify the individual processes involved in the irreversible adsorption of naphthalene and a-naphthol. This article concludes that both biological and chemical catalysts are important in promoting irreversible adsorption reactions, and that once the partial oxidation of a PAH occurs, oxidative coupling can become a significant process affecting contaminant fate. The third and final article examines the effect of different adsorption processes on the subsequent bioavailability of sorbed naphthalene and anaphthol, and concludes that the biodegradation of naphthalene and α-naphthol adsorbed to both the soils tested was controlled by the rate of desorption and the reversibility of the adsorption process. / Ph. D.

Modern aerospace vehicle design requires the interaction of multiple disciplines, traditionally processed in a sequential order. Multidisciplinary optimization (MDO), a formal methodology for the integration of these disciplines, is evolving toward methods capable of replacing the traditional sequential methodology of aerospace vehicle design by concurrent algorithms, with both an overall gain in product performance and a decrease in design time. A parallel MDO paradigm using variable-complexity modeling and multipoint response surface approximations is presented here for the particular instance of the design of a high speed civil transport (HSCT). This paradigm interleaves the disciplines at one level of complexity, and processes them hierarchically at another level of complexity, achieving parallelism within disciplines, rather than across disciplines. A master-slave paradigm manages a coarse grained parallelism of the analysis and optimization codes required by the disciplines showing reasonable speedups and efficiencies on an Intel Paragon / Master of Science

The experimental parameters controlling the rate and mechanism of the decomposition of compounds and the products formed, in a moving carrier gas stream were investigated. The parameters studied included the effects of pyrolysis temperature, sample size, sample weight, flow rate of the carrier gas, the method of introducing the sample into the pyrolysis unit. An apparatus for pyrolysis-gas chromatography, using tho commonly used boat and furnace technique, was developed. Commercial grade sodium dodecylbenzene sulfonate was chosen for a model compound. The optimum conditions for the pyrolysis-gas chromatographic analysis of this material were established by the careful study of the experimental parameters. The most serious limitations to this method of pyrolysis-gas chromatography appeared to be the strong dependence on the sample size and tho dependence on pyrolysis temperature, i.e., on the rate at which the sample was brought to the pyrolysis temperature. As the size of the sample was increased the amount of residue in the boat also increased. Also, although the majority of the sample was pyrolyzed at 580°C the amount of residue would decrease as the temperature was raised to a maximum of 710°C. A certain amount of residue always remained in the boat. The residue can be explained as the product of secondary reactions occurring between the initial pyrolysis intermediates (free radicals) and the unpyrolyzed portion of the sample. In an attempt to eliminate these effects of secondary reactions a new technique of pyrolysis-gas chromatography by direct injection of solutions was developed. By handling the samples in dilute solution it was shown that a much smaller sample could be pyrolyzed such that the probability or secondary reactions was greatly reduced. Also the very small samples allow an apparent instantaneous heating of the samples to a given pyrolysis temperature. This approach offers a means of obtaining the simplest possible products from the pyrolysis of a compound, therefore offering a more accurate insight into the mechanism of the pyrolysis. These products then offer a means of establishing the structure of the original compound. Using this technique a method was developed for analyzing aqueous solutions containing the alkylbenzene sulfonates. This method provides not only a measure of the total detergent present but also differentiates between the various alkyl groups found in the commercial products. The alkyl groups form the 1-alkenes which can be easily identified chromatographically. The conditions for this analysis along with curves showing the products obtained from the pyrolysis of samples with both straight and branched alkyl groups are given. While the majority of the work done here was with aqueous solutions an attempt was made to determine the stability or some of the common organic solvents under such pyrolysis conditions. Those solvents studied were methylene chloride, chloroform, carbon tetrachloride, methanol, ethanol, and acetone. All of these solvents were round to be stable up to 500°C; however, at temperatures greater than this the decomposition of the solvents limits their use. The technique of pyrolysis-gas chromatography by direct injection or solutions was also applied to certain amino acids in ethanol-water solutions. The results were again much more accurate than those found with the boat technique. This technique was also shown to be useful in determining the structure of organic chelates bound to metal atoms. Solutions of copper II and chromium III acetyl-acetonates in chloroform were pyrolyzed and the product identified as acetylacetone. This offers a means of determining both the number and type of chelates bound to a given metal atom. / Ph. D.

This was a study of middle school students and informal computer usage before entering a forma1 keyboarding course. The purposes of the study were (a) to determine the kinds of informal keyboarding experiences middle school students were exposed to before receiving formal training, (b) to determine if there was a difference in straight copy speed and accuracy among students who had three levels of previous informal keyboarding experience, and (c) to determine if there was a difference in straight copy speed and accuracy among students who had home access to persona1 computers. The students involved in the study were seventh and eighth graders at Blacksburg Middle School and Christiansburg Middle School enrolled in first semester Keyboarding during the 1987-88 school year. These students answered questionnaires that related to their personal experiences with computers and were placed in one of three groups depending upon the amount of time spent using a keyboard before entering a formal keyboarding course. Each student took timed writings and were given a score for speed and accuracy. A one-way analysis of variance was performed to determine if there was a difference between groups on straight copy speed and accuracy scores. The analysis of the data indicated that there was no significant difference in speed or accuracy scores between those students who had very little or no previous informa1 experience and those students who had six months previous informa1 experience. Those students who had a year or more of previous informa1 experience had better speed scores than students who had less than a year of previous informal experience. The data indicated there was no significant difference among any of the groups in accuracy scores. The data also indicated there was a significant difference in speed scores of those students who had access to a home computer and those students who did not. From the study it was concluded that: (a) students who have previous informal keyboarding experiences of one year or more have significantly higher keyboarding straight copy speed than those students who had less than one year of informa1 experiences and (b) previous informal keyboarding experience does not influence straight copy accuracy. / Master of Science

An investigation of the flow field during eject of a cruise missile from the launch tube was undertaken using a "cold" flow simulation. A facility was developed whereby various design changes in the missile ejection apparatus, denoted the vertical support assembly, could be quickly and easily assessed in terms of the relative effects on the flow field. Flow visualization techniques using fluorescent dye allowed for documentation of flow patterns in the baseline configuration, such as backflow, jetting, and recirculation regions, as well as for the location of several potential hot spots. The mixing of the fuel-rich gas generator effulent and the air in the launch tube was assessed by thermocouple measurements; warm water was used to simulate the exhaust while ambient water represented the air initially contained in the launch tube. The results have shown that air is inefficiently mixed in large portions of the vertical support assembly volume. However, strong flameholding zones are established in the region vacated by the accelerating missile, where it is believed that secondary combustion could occur. The flow field characterization has shown that considerable improvements to system performance should be possible through geometrical changes to promote more efficient mixing. / M.S.

This case study focuses on a housing improvement policy in England aimed at low-income neighborhoods, and the participatory process that exists to affect that policy. The research explores factors which affected the participatory process and as a consequence, policy outcomes in two London boroughs (local governments). The recipients of the housing policy in both boroughs are low-income, working-class residents, yet one borough council is controlled by the Labour Party and the other is controlled by the Conservative Party. Based on arguments made in the literature on the prerequisites to participation, it was expected that because Labour decision-makers are supposedly more politically and socially congruent with these residents and their interests than Conservative decision-makers, that there would be greater likelihood for the decision-making process to be open to participation, and thus more responsive to the needs and expectations of the residents within the Labour borough. Findings indicated that the participatory process was generally the same in both boroughs and that decision-makers in the Labour borough were no more tolerant of or responsive to the residents' needs and demands than were those in the Conservative borough. The process of participation yielded similar results in both boroughs. Using a comparative case study method, this research explores reasons why the process and results were more similar than dissimilar. Where different results were achieved by the resident groups, they were mainly due to differences in the existence and quality of resident leadership. / M.U.A.

Twenty six male and two female participants in the Cardiac Therapy Program at Virginia Tech were stratified, based upon level of total cholesterol (TC) and length of time in the Cardiac Program, and then randomly assigned to either experimental or control groups. Participants ranged in age from 43 to 68 years and all had baseline TC levels greater than 200 mg/dl. There were no significant differences between groups in terms of baseline TC (control M : 248 mg/dl; experimental M = 251 mg/dl), blood pressure (BP), weight, predicted percent body fat, dietary fat/cholesterol, age, education, or program attendance. / Master of Science

Master of Science

An analytical formulation for seismic analysis of multiply supported secondary systems is developed. The formulation is based on the random vibration theory of structural systems subjected to correlated inputs at several points. The response of the secondary systems is expressed as a combination of the dynamic, pseudo-static and cross response components. The dynamic part is associated with the inertial effect induced by the support accelerations. The pseudo-static part is due to the relative displacement between supports, and the cross part takes into account the correlation between these two parts of the response. The seismic input in this approach is defined in terms of the auto and cross pseudo-acceleration and relative velocity floor spectra. The information about floor displacements and velocities as well as their correlations is required for calculating the pseudo-static and cross response components. These inputs can be directly obtained from the ground response spectra. The interaction effect between the primary and secondary systems is studied. This effect is specially significant when the modes of the secondary system are tuned or nearly tuned to the modes of the primary system. The floor spectral inputs are appropriately modified to take into account this interaction effect. The design response of the secondary system when computed with these modified floor inputs will incorporate the interaction effect. The applicability of the proposed methods is demonstrated by several numerical examples. / Ph. D. / incomplete_metadata

The development and rapid growth of computer mapping has led to many discussions concerning the accuracy of techniques used to generate these computer representations. The purpose of this study is to analyze the accuracy of thinning methods applied to scanned map data, which is only one in a series of processes used to accomplish digital conversion of conventional maps. In preliminary tests, nine thinning methods based on the successive layer removal process are evaluated. Seven raster images are thinned using these methods. The raster results are compared based on the number of pixels deleted and on the number of retained pixels that fall either on or off the medial axis of the original matrix. The four algorithms that produce the best results are then used for final testing. For the final tests, 25 digital lines are plotted and scanned. The raster images are thinned using the four successive layer removal methods and a line following method developed for this study. The raster output is evaluated using the preliminary testing method. The final vector output is compared to the original input based on line length, anchor line length, and fractal dimension. / Master of Science