About 50 synthetic organic chemicals (SOCs), including pesticides and polyaromatic hydrocarbons (PAHs), have been identified as possible contaminants in the Occoquan Watershed. Since 1982, water, sediment, and fish samples have been collected from the streams and reservoirs of the watershed 2-4 times per year. The Occoquan Watershed Monitoring Laboratory (OWML) collected samples and analyzed for a targeted set of compounds. Beginning in 1993, new SOC screening methods consisting of solid-phase extraction (SPE) followed by gas chromatography with mass spectrometric detection (GC/MS) were developed for water and sediment samples. A similar method for fish tissue was developed in this study using methanol extraction with C-18 and alumina SPE cleanup. Method detection limits (MDLs) ranged from 0.03-0.37 mg/kg wet weight and recoveries in matrix spikes ranged from 15-92%. Very few SOCs in OWML's database were found at levels above method detection limits. In water, atrazine was the most commonly detected compound (87 detections out of 610 samples analyzed). It was also found in 8 sediment samples and 1 fish organ sample. Atrazine concentrations were highest in the spring; summer provided the most frequent detections. Detections occurred at multiple locations during the same sampling period; stations furthest west (nearest to agricultural areas) tended to show the highest values. Rainfall events were associated with 23% of atrazine detections. The raw and finished water samples from the two water treatment plants in the basin showed that the average atrazine removal by conventional treatment was 37%. / Master of Science

The problem addressed in this study was: What home modifications are made to residential environments to meet the functional capabilities of the aging in place audience? The study was conducted in two phases. In Phase I 102 Floyd County, Virginia, adults 65 years of age or older were interviewed in order to identify their task capabilities and identify the modifications being made to meet their environmental needs and task capabilities. Phase II consisted of a case study of six females taken from the Phase I sample group. This section of the study focused on the modifications identified in Phase I, the techniques used, and the reasons they were made. The findings indicate that 26% of the adults in the study were experiencing difficulty with at least one Activity of Daily Living, 33% were experiencing difficulty with at least one Instrumental Activity of Daily Living. However, like many older adults, these individuals had a relatively high function level and wanted to stay in their home as long as possible. Modifications are being made in order to equalize the participants' function level and the characteristics of the living environment. Housing education programs should be targeted toward the elderly and their family members and provide more information relating to aging in place. Professionals in housing and related fields should have the knowledge necessary to advise clients on making decisions to help insure their ability to live independently as they age. / Master of Science

Wavelets have received considerable attention in recent general signal processing, image processing, and pattern recognition literature, as a new method of signal analysis. This marks a transition in wavelet study from theoretical investigation to application-driven research. In this paper, wavelets and wavelet transformations are presented in a context intended to be appropriate as a first exposure to the engineer. The wavelet transform, more specifically the discrete wavelet transform, and its relationship to multiresolution analysis is then explored in a framework familiar to those versed in multirate digital signal processing concepts. Elements of the perspective offered by wavelet analysis, in contrast to the features of more conventional Fourier techniques, are examined. General procedures for wavelet-based signal processing applications are discussed and the specific application of reducing noise in audio signals examined. Within the context of this application, considerations unique to wavelet analysis are revealed and trade-offs analyzed. Finally, the results obtained from implementing the noise reduction system are presented and extensions to the technique proposed. / Master of Science

Majority of the world's poor live in marginal areas. In developing countries, about 60 percent of the poorest population live in hilly vulnerable ecological areas which include arid and semi-arid lands with limited soil fertility, hilly upland areas, and steep slopes. Most of the inhabitants of these areas owe their livelihood primarily to the exploitation of the natural resource. However, the natural resources and ecosystems in these areas have continually undergone severe degradation. Governments and development agencies face a major challenge in their efforts to achieve sustainable development in the world's fragile ecological areas. The poor inhabitants of the world's fragile ecological areas are faced with increasing population pressure, lack of protective infrastructure such as transportation and communication systems, investment, and inadequate technology. These conditions continue to affect their social and economical standards of living. The deteriorating living conditions of the world's poorest population inhabiting arid and semi-arid lands result in a cycle of continued economic decline and land resource destruction. Hence the challenge to focus on development strategies which would break the vicious circle of poverty and environmental degradation. This research employs thematic content analysis as a research technique to do a comparative sociological study of two rural development projects, (Turkana rural development project and Lokitaung pastoral rural development project), in arid and semi-arid Turkana district in Kenya. I propose and use COPETT, (culture, organization, population, environment, technology, and time), a human social-ecological framework as a tool for analysis. Specifically, this study presents a descriptive account of the project's history; the formal development objectives of the Turkana rural development project and Lokitaung pastoral development project as set by NORAD and OXF AM. The study also examines the projects management and the interaction effects with the Turkana people, their culture, organization, environment, and technology. The understanding of the two international development agencies of the concept and the effect of time with regard to culture, organization, population, environment, and technology is also examined. I argue that the continued use of the project approach to development particularly in rural areas call for an examination and identification of sociological requirements attached to this framework for development intervention. The use ofCOPETT framework for development planning could provide a holistic human-centered development strategy that engenders mobilization and empowerment of the rural population socially, economically, and politically not only in Kenya but also for the world at large. Further, the analysis adopted in this study could serve as a point of departure for understanding ways through which international development agencies could improve on the strategies needed in designing and implementing development projects in order to achieve sustainable development. / Master of Science

This thesis demonstrates the feasibility of using a medial surface transformation as a tool to rapidly approximate the solidification patterns of convex faceted solid models of castings. The medial surface transformation is used to automate the greatest included sphere approach to solidification pattern approximation. The experimental software of this thesis extracts the medial surface transformation from a convex faceted model by computing the model's Voronoi diagram and uses it to identify casting hot spots and cooling patterns. Comparison with a finite difference method (FDM) solution showed that the locations and shapes of hot spots predicted by FDM converge to the shapes and locations predicted by the experimental software. / Master of Science

The goal to design and build a reliable instrument for the direct measurement of skin friction on the surface of Magnetically Levitated (MagLev) trains was successfully achieved. A wall mounted, cantilevered beam device was used to measure the small tangential flow shear force that passes over the non-intrusive floating element. Piezoresistive strain gage units measure the relatively small strain that is generated by the wall shear. By adapting the geometry of the sensing unit, this design can be adapted for a variety of test flows. Measurements were made on two different vehicle geometries provided by Northrop/Grumman and Lockheed/Martin as well as on a special model designed to study the influence of propulsion rails on the Lockheed/Martin model aerodynamics. The obtained values of the skin friction coefficient C_t are deemed reasonable for the type of flow studied. The estimated uncertainty of the gage is ± 5.2%. The data agreed to within 10% with estimated values from an idealized Couette flow analysis. / Master of Science

Records from treadmill maximal graded exercise tests (GXTs) for 61 patients from the Virginia Tech Intervention Center were screened for changes in systolic blood pressure. These blood pressure responses were standardized according to exercise demand (ΔSBP/MET) between three different levels of the exercise test. Subject records were chosen on the basis that they did not reflect a physician diagnosis of coronary artery disease (CAD) and were not taking antihypertensive medications. The ΔSBP/MET responses were stratified as follows: low to moderate (ΔBP/MET1) = difference between a systolic blood pressure at a moderate intensity stage minus the first stage systolic blood pressure, adjusted for the corresponding changes in metabolic demand (MET); moderate to high (ΔBP/MET2) = difference between systolic blood pressure at the maximal stage minus the moderate-intensity stage per MET change; and low to high (​​ΔBP/METS) = difference between systolic blood pressure at the maximal stage minus the first stage per MET change. Subjects were separated (STΔ and NoSTΔ) according to whether or not they had exercise-induced ST segment shift of 1 mm (≥ 0.1 mV) at maximal exercise. The two groups were similar in physical characteristics, except the NoSTA group had a significantly higher BMI (Body Mass Index), were a few years younger and exhibited a lower RPP at maximal effort. Discriminant Function Analysis was used to predict group classification of individual patients (STA or NoSTA). Based on predictions using physical characteristics alone, (age, BMI, TC), age, BMI and TC (Total Blood Cholesterol) could correctly predicted classification in 66% of the cases. The set of age, BMI, TC and ΔBP/METS3 (low to high) generated a prediction with 77% correct classification. Thus, ΔBP/MET level alone was not the primary variable to explain predictive accuracy for clinically important ST changes in exercise testing. However, in accordance with the Bayesian principle, this hemodynamic exercise response is adjusted for overall metabolic demand in the test and coupled to markers of pre-test coronary risk, the ability to predict ST response is improved. / Master of Science

In spite of the high prevalence of internalizing and externalizing disorders in children, little research has been conducted to directly assess risk factors associated with the development of these disorders. Among other influences, it has been suggested that the expression of childhood psychopathology may be related to family socialization practices. This study uses Olson's circumplex model of marital and family systems to test the relationship between family environment and the internalizing and externalizing domains of childhood psychopathology. It was hypothesized that children with internalizing behavior problems come from families that are high in cohesion (i.e., enmeshed) and low in flexibility (i.e., rigid and structured). Furthermore, it was predicted that these families are low in level of expressed conflict and have poor communication levels within the family. Families o(children with externalizing behavior problems, on the other hand, were hypothesized to be low in cohesion (i.e., disengaged), and to be either high or low in flexibility (i.e., rigid or chaotic). They were predicted to openly express high levels of conflict within the family, but generally have poor communication skills. These hypotheses were tested using Achenbach's Child Behavior Checklist to assign children between the ages of 7 and 11 to internalizing (n = 9) and externalizing (n = 10) groups and using an objective observational measure and several self-report measures to evaluate the families along the dimensions of the circumplex model. Results failed to confirm these hypotheses, however, they were suggestive of a link between family environment and nature and severity of childhood behavior problems. / Master of Science

A series of composite panels were fabricated by resin transfer molding (RTM), varying materials and process conditions. Reinforcements used included a fiberglass woven material, and AS-4 carbon in both sized and unsized plain weave fabrics. Vinyl ester, epoxy, and cyanate ester resins were pressure injected into these fabrics. The epoxy panels were processed with varying injection temperatures and pressures. A density-based technique was used to measure the fiber volume fraction and void content of the composite panels. Optical photomicrographs were used to verify the accuracy of the void calculations. Mechanical tests included compression strength, inplane and interlaminar shear strengths, and impact. Compression after impact tests were performed and compared to undamaged compression strengths. The compression, inplane shear, and interlaminar shear strengths of the epoxy composites were higher than the vinyl ester composites. Similarly, cyanate ester systems with similar reinforcements outperformed the epoxy composites in these tests. In impact testing, the graphite fabric/ epoxy resin composite retained the lowest portion of original strength after impact. The cyante esters retained the most strength, but vinyl ester composites suffered less damage. Vinyl ester composites made with unsized carbon fibers performed better in interlaminar shear, and in impact tests, than those with sized fibers. The variation of injection temperature had little effect on either void content or strength of the epoxy composites. Increases in injection pressure did produce a higher void content in epoxy laminates, but no significant change in strength was observed. / Master of Science

This thesis describes the design of an image interpretation system for the automatic detection of internal hardwood log defects. The goal of the research is that such a system should not only be able to identify and locate internal defects of hardwood logs using computed tomography (CT) imagery, but also should be able to accommodate more than one type of wood, and should show potential for real-time industrial implementation. This thesis describes a new image classification system that utilizes a feed forward artificial neural network as the image classifier. The classifier was trained with back-propagation, using training samples collected from two different types of hardwood logs, red oak and water oak. Pre-processing and post-processing are performed to increase the system classification performance, and to make the system be able to accommodate more than one wood type. It is shown in this thesis that such a neural-net based approach can yield a high classification accuracy, and it shows a high potential for parallelism. Several possible design alternatives and comparisons are also addressed in the thesis. The final image interpretation system has been successfully tested, exhibiting a classification accuracy of 95% with test images from four hardwood logs. / Master of Science