Groundwater contamination potential by pesticide was evaluated in Albemarle and Louisa counties of the Thomas Jefferson Planning District in Virginia. A qualitative method was developed to perform an assessment of pesticide contamination potential, using an existing pesticide screening model. The Attenuation Factor (AF), was selected for assessment of groundwater vulnerability to pesticide contamination in Albemarle and Louisa counties. Input data availability, consideration of the major transport processes, and ease of its linkage with a suitable geographic information system (GIS) were the main factors considered for selection of the AF model. The input data requirement of the AF model includes soil, hydrogeologic, and pesticide chemical characteristics. An extensive database was developed to perform AF model simulations within a GIS. The database developed for this study included map databases (resolution = 1/9 ha) for landuse, soils, groundwater recharge, and groundwater depth, and non-spatial (relational tables) databases for pesticide chemical characteristics, SCS curve number, and soil properties. A total of 12 landuse categories were identified for Albemarle and Louisa counties. Groundwater recharge, an input to the AF model, was estimated using a water balance model. Runoff and evapotranspiration components of the water balance model were estimated using SCS curve number (CN), and Thornthwaite’s methods, respectively. Forty years of climatological data records were used for estimating groundwater recharge. Two types of groundwater depths, spatially varying and a constant depth of 2 m, were used for computing AF, The groundwater depth was mapped using the information available in groundwater well completion reports. All the data layers were overlaid within a GIS for spatial computation of AF for actual and 2m groundwater depth. This spatial (map) database was categorized into five categories of pollution potential namely, high, medium, low, very low, and unlikely, based on the numerical values of the AF. For evaluating the contamination potential of pesticides, three pesticide leaching potential scenarios were considered in order to facilitate the evaluation of pesticide leaching under maximum, average and minimum cases of degradation and sorption in the soil. A combination of high, average, and low values of half life and sorption coefficient were selected for three leaching scenarios. A total of six simulations were performed (two groundwater depths and three leaching scenarios) for each pesticide. Toxicity of the pesticides was not considered in the contamination potential assessment in this study. A total of 11 relatively mobile pesticides were identified in Albemarle and Louisa counties, based on the results for various leaching scenarios. Groundwater contamination potential maps were produced for mobile pesticides and the results were discussed. Picloram was identified to be the most mobile pesticide in the two counties. Atrazine, carbofuran, metolachlor, simazine and triclopyr were found to have considerable potential to move to the groundwater. Contamination potential of three herbicides, atrazine, simazine and metolachlor, was predicted to be higher than other pesticides in light of the fact that they are often used in combination (tank mixed) for a wide variety of weed control. Dicamba was found to be the most heavily-used pesticide with regard to its area of application. In light of dicamba's moderate contamination potential and its higher usage amount this herbicide was identified to have a considerable potential to move to the groundwater, especially, in Albemarle County. Other pesticides such as fenarimol, lindane, metalaxyl, and metsulfuron methyl were shown to be relatively more mobile than some other pesticides. However, in light of small application areas for these pesticides, the contamination potential of these pesticides was predicted to be relatively small. In addition to 11 mobile pesticides, a few low mobility pesticides were also identified. Among the low mobility pesticides, diazinon was found to have relatively high contamination potential. Comparison between the contamination potential maps and the groundwater recharge map revealed that most of the high contamination potential areas coincided with the higher groundwater recharge regions in the two counties. Soil characteristics such as organic matter and percent sand and clay were also observed to affect the contamination potential of pesticides. The performance of the AF model was evaluated by using six years of groundwater monitoring data from the Nomini Creek watershed study. Two types of rankings were made, one using the AF model simulation results, while the other ranking was based on the frequency of detection of pesticides in the Nomini Creek watershed. A comparison of the rankings revealed that the AF model performed fairly well in identifying the top few mobile pesticides. Sensitivity analysis was performed to identify the important parameters affecting the contamination potential of pesticides. Results of the sensitivity analysis revealed that considerable uncertainty in the model prediction can be invoked due to the variability in the soil and chemical data. To make a better use of results of this study, it was recommended that groundwater monitoring be performed in the two counties to verify the so that results of this study. The results of this study will provide information about the potential threat to groundwater by pesticides to the citizens and policymakers in the two counties. / Master of Science

Finite element analysis of a large structure incorporating material and geometric nonlinearities can be very time-consuming and expensive. For this reason, the purpose of this study is to determine to what degree the finite element model of the dome can be simplified and still yield useful results. The primary objective of this study is to determine if the nonlinear beam-decking connector (BDC) elements can be modeled as constant forces instead of as springs. Modeling the BDC elements in this way could greatly simplify the dome model. Secondary objectives of this thesis include determining if the failure of the beam-decking connectors is such a dominant factor in the dome’s collapse that material and geometric nonlinearities can be neglected and useful results still be obtained. Since many different studies have been carried out on this dome model, this thesis will provide a summary of the major developments in the dome model. It will summarize the main assumptions made, and will state which assumptions have been verified and which are still under investigation. / Master of Science

A new method of representing a second order tensor, the tensor glyph, is used to present the Reynolds stresses found in turbulent flow. Various glyph types discussed in the literature are analyzed, and a glyph suitable for the Reynolds stress tensor is developed. This glyph is constructed so that the degree of anisotropy and the orientation of the principal directions are clearly presented. Using the glyph, the effectiveness of two turbulence model formulations of the Reynolds stress tensor, the Boussinesq approximation and the Algebraic Reynolds Stress Model (ARSM), are studied. Glyphs based upon these two formulations and experimentally measured Reynolds stresses are compared in two flow geometries: fully developed pipe flow and a tip leakage turbine cascade. The glyph representations are compared with traditional presentations of the Reynolds stress tensor to ascertain the strengths and weaknesses of both. / Master of Science

In this thesis, the seismic analysis of base isolated structures is carried out using a base coordinate relative to the inertial space that renders absolute dynamic response, which is fundamental in assessing base isolation. Moreover, the structure is modeled as an Euler-Bernoulli beam cantilevered on a massive basement. The isolation system is modeled as linear. The stochastic analysis is carried out in the frequency domain using a stationary Clough-Penzien spectral representation for the ground excitation. Standard deviations of the structure’s generalized coordinates and their second derivatives are obtained, which characterize the response, including stresses, of the structure. The effectiveness of base isolation can be evaluated by comparing the response of the isolated structure with the nonisolated counterpart. The results show that base isolation is highly effective in reducing the overall response of the structure. Additionally, it is found that the Clough-Penzien representation does not model adequately in the high frequency range. A modification of this model is proposed. / Master of Science

Automated Guided Vehicle Systems (AGVSs) have been widely adopted by many low to medium manufacturing operations, particularly in Flexible Manufacturing Systems (FMS). The high degree of flexibility and control offered in vehicle routing has made AGVS a proven and viable material handling technology in today's manufacturing systems [Bozer91]. An important aspect in maintaining flexibility in an AGVS is its control architecture. A control architecture provides the backbone of the physical and the informational infrastructure of a system. This research has identified three types of control architectures. They are the centralized, hierarchical, and heterarchical control architectures. When designing an AGVS, most designers do not consider control architecture as a design factor, and do not analyze its effect on the system's performance. The objective of this research is to analyze the effect of control architectures on the relative performance of the AGVS. This research uses simulation to study the effect of control architectures on the AGVS. The simulation model for each control architecture contains two parts -- an AGV controller and a shop floor controller. Both models are programmed in C language. The AGV controller consists of three basic components – vehicle scheduling, vehicle routing, and traffic control. Each of these three components is modeled according to the nature and characteristics of the corresponding control architecture. Two different flow path layouts are considered for the shop floor model. The two layouts are different in size and number of work stations. Performance measures chosen for this study are intended to reflect the responsiveness of the system and the overall system performance under the impact of different control architectures. / Master of Science

Two novel techniques, instrumented shear bolts and digital image correlation, were evaluated for studying multiple-bolted wood connection behavior. The instrumented shear bolts output an electronic signal proportional to the shear forces transmitted through the bolt in a double-shear connection during loading. The digital image correlation method combines digital image analysis and image correlation to calculate surface displacements from a set of digitized video images of an object under an applied load. Double-shear connections constructed of clear, straight-grained yellow-poplar were tested in compression parallel to grain. Five different bolt patterns were used to analyze the effect of number of bolts in a vertical row and number of bolts in a horizontal column on load transfer among the bolts. Both techniques were utilized simultaneously during testing of specimens. The shear bolts were found to effectively determine the load distribution among bolts in a multiple-bolted wood connection by providing detailed quantitative data concerning which bolt was the major load carrier throughout the entire test and exactly if and when the load was transmitted between the bolts. The digital image correlation method was found to effectively describe the creation of the surface displacement fields, both parallel and perpendicular to load, below each bolt during loading. The results obtained from this research may be useful to facilitate the understanding of multiple-bolted wood connection behavior and for developing simplified design equations for multi-fastener joints in the future. / Master of Science

This work presents experimental results of a hybrid control technique that blends traditional fixed feedback control with adaptive feedback techniques. The objective is to provide damping for transient disturbances via the fixed controller and rejection of steady disturbances via the adaptive controller. This technique differs from other control techniques in that it does not require a measurement of an external signal coherent with the disturbance, nor does it require knowledge of how the disturbance enters the system. As with all feedback techniques, stability is an issue. The adaptive controller is implemented to minimize stability problems and in the case of perfect system identification, it is guaranteed stability. The experimental results are from a cantilever beam with piezoceramic actuators and sensors. The fixed feedback controller results are compared to the adaptive feedback control results. The comparison will include results from disturbances resulting from a single harmonic, narrowband signal, and broadband signal. / Master of Science

The objective of this thesis is to offer an alternative to the conventional “push and pull” model of transnational labor migration to analyze the sudden inflow of migrant workers to Japan since the mid-1980’s. Michael Piore’s theory of labor market segmentation is used as a framework for the analysis. Piore’s model claims that migrant workers are wanted in the host country to provide their flexible labor in the “secondary sector,” which mostly employs socially disadvantaged groups of citizens, such as women, minorities, and youths. After analyzing the Japanese labor market for segmentation, which has its roots in extensive subcontracting production practices, this thesis argues that the inability of the secondary sector to attract domestic workers during the economic expansion in the mid-1980’s to early 1990’s created the demand for migrant workers, and that some of the measures taken by the Japanese government during the same period are directly responsible for “triggering” the migration. Despite the expectation among employers and some government officials that the influx of migrant workers will alleviate the labor shortage in the secondary sector in the short-term, this thesis postulates that the use of migrant workers as it has been done in Japan will ultimately reinforce the production and employment practices that perpetuate the segmented structure and its labor shortage in the Japanese labor market. In addition, the labor rights and human rights of migrant workers are too often overlooked by their employers and the enforcement authorities. Based on these observations, this thesis recommends that the Japanese government emphasize on improving the remuneration systems and working conditions of the secondary sector, and regain control over immigration of foreign workers, which it did successfully prior to the mid-1980’s. / Master of Arts

Two related areas of research are presented in this thesis. In one area, 106 in-situ wood floor systems were subjectively rated and tested to determine fundamental frequency values. This database of wood floor systems was used to provide further validation of a recently proposed design criterion which uses fundamental frequency to predict acceptability of wood floor systems to vibrations resulting from human footfall impacts. Included in the database are floors tested previously unoccupied which were tested again with occupancy loading. Additional occupied and unoccupied wood floor systems not included in the original study were tested. A second area of research was conducted to quantify the changes in frequency content and modal damping values through construction of six typical wood residences. The data from these floors provided insight into the dynamic behavior of wood floor systems and provided further data to validate the above design criterion. / Master of Science

The concept of countertransference is utilized by many mental health practitioners to denote the emotional response of the therapist to doing therapy. Family therapists do not often use the term "countertransference,” and they have, with some exceptions, avoided exploring the emotional response of therapists in both research and training. The purpose of this study was to describe how the concept of countertransference is approached and utilized by beginning family therapists in their efforts to understand and conduct therapy. The participants in this study were five family therapist interns beginning their practicum placement in one AAMFT-accredited Master’s degree program in the campus clinic in August 1993. They attended five hour-long focus group meetings, and were interviewed about two different taped therapy sessions. The results illustrate aspects of the participants’ countertransference experience: the context, the countertransference reactions themselves, the participants’ responses to those reactions, the effect of those responses on the therapist and the therapy, and the participants’ personal equations which they brought to the therapeutic encounter. In addition, the results document the applicability of the concept of countertransference to the experience of beginning family therapists. / Master of Science