no abstract provided by author / Master of Science in Education

There has been increasing interest in the use of Very Small Aperture Terminals (VSATs) in satellite communication links operating in the Ku and Ka bands. Such systems offers the advantage of low signal margins and therefore, low cost. For the same reason, however, VSATs links can be strongly impaired by tropospheric scintillations. The VA Tech OLYMPUS propagation experiment which includes 12, 20, 30 GHz beacon receivers at an elevation angle of 14° provides us with valuable multi-frequency scintillation data. This dissertation focuses on the characterization of tropospheric scintillations on earth-space paths. Tropospheric scintillations are rapid fluctuations of signal caused by multiple scattering from the sma11 scale turbulent refractive index inhomogeneities in the troposphere. Analysis of the scintillation results from the VA Tech OLYMPUS experiment for both short term and long term studies is presented. The results include spectral characteristics, frequency scaling and statistics of the scintillation intensity, statistics of scintillation fading, diurnal and meteorological trends as well as a comparison with the current CCIR predictive model. Sma11 scale spatial diversity is a potential means to counteract tropospheric scintillation fading; it can be cost effective because of the low cost of VSATs. The VA Tech experiment includes 12, 20, 30 GHz beacon receivers and colocated 20 and 30 GHz diversity receivers that allows us to study this restoration technique. In this dissertation the effects of spatial diversity are studied through a cross-correlation analysis. Experimental results are compared to a theoretical model in which the atmosphere is characterized by an "anisotropic" Kolmogorov spectrum. A method to determine minimum vertical spacing between terminals to achieve good diversity performance is introduced. / Ph. D.

Construction of a Ku-band earth station was completed in August 1989 at the teleport in the Corporate Research Center of Virginia Polytechnic Institute and State University. At that time specific applications for the terminal were being determined. Several satellite networks which can use the Ku-band earth station are explored in this thesis. System level designs are presented for each network. The anticipated performance of the network during clear sky conditions and during periods of rain fade conditions are calculated. To aid in these calculations the software package LAMP was developed. detailed system design of a VSAT network is given in later chapters. The development of VSAT networks considers multiple access and data traffic control protocols. VSAT network performance under various traffic conditions also is determined. / Master of Science

The research hypothesis of this study states that when individuals are asked to rank order certain places (environments) in terms of preference, then relationships can be measured between that rank ordering and relevant contextual adjective descriptors that indicate a person's perception of those places. These adjectives include beauty, excitement, distinction, naturalness, security, mystery, tradition, complexity, and familiarity (Canter, 1977; Ganmore, 1975; Ley, 1983; Lynch, 1981; Steele, 1981). After critical sites had been identified in a sketch map study, a sample of community members of the town of Blacksburg, Virginia were asked to respond to the sites along adjective dimensions that represent a sense of place. It was found that positive linear relationships existed in varying degrees of strength between the adjectives and place preference. Statistical significant relationships were found, in descending order of strength, between preference and beauty, excitement, distinction, naturalism, security, and mystery. No linear relationships were found between preference and tradition, complexity and familiarity. It has been concluded that places are perceived on other criteria beside just aesthetic appreciation. Furthermore, this thesis supports the argument that places are experienced on a symbolic and emotional level. Places are not merely a composition of physical elements. This deeper experience is the basis for the concept of a sense of place. / M.L. Arch.

Modern rice (Oryza sativa L.) varieties produce very high yields under high input and favorable environments. Limited work has been done to develop plant types suitable for less than optimal environments at moderate N management levels. The objectives of this study were: 1) to examine the relationship between the uptake of N and different leaf characteristics, sink size, and grain yield of three morphologically distinct rice varieties; 2) to examine the CO2 exchange rates (CER) of rice varieties in relation to light, N management, water use efficiencies (WUE), and N use efficiency (NUE): and 3) to determine characteristics of rice varieties that are associated with productive potentials under low N management levels. A greenhouse experiment was conducted in 1989 at Virginia Polytechnic Institute and State University, Blacksburg, VA and a field experiment was conducted in Sri Lanka at two locations in 1990. In the greenhouse experiment three varieties (a traditional, an intermediate, and a modem variety) were grown under four N management (rate and time) treatments: viz 1) a 0 N control, 2) 200 mg N kg⁻¹ of soil split into two applications, 3) 200 mg N kg⁻¹ of soil split into three applications, and 4) 400 mg N kg⁻¹> of soil split into three applications. Competitive use of fertilizer N for the development of either large leaf area or high leaf N content per unit leaf area (LNLA) varied with the rate and timing of N fertilizer application and rice variety. When N supply was limited and early N applications were restricted, the intermediate variety increased LNLA in the flag leaf with little increase in total leaf area of the plant. Specific leaf weight did not differ with N management except for the low value of the N control treatment. Increased N applications reduced stomatal density. Total stomatal number leaf⁻¹ varied little within cultivars indicating that N fertilization enables the leaf to increase leaf area and thereby disperses the fixed number of stomates. Carbon dioxide exchange rates were higher in the flag leaf than lower leaves and were directly correlated to LNLA. / Ph. D.

The purpose of this study was (a) to investigate the functional use of e-mail in a university setting and the relationship of attitudes toward and self-efficacy with email technology, and (b) to evaluate writing effectiveness in an electronic medium. The study also sought to determine if certain personal characteristics could serve as predictor variables for explaining e-mail use, attitudes toward email, and self-efficacy with e-mail technology. The population of interest was the teaching faculty at Virginia Polytechnic Institute and State University who had a published e-mail address. A random sample of 500 faculty were sent a survey via campus mail. A total of 262 usable responses provided data for statistical treatment which included factor analysis and multiple regression. Additionally, 30 self-selected respondents provided copies of e-mail messages they had written. These messages were rated holistically for writing effectiveness, and the ratings were examined for their relationship with the extent of e-mail use, attitudes toward e-mail, and self-efficacy with e-mail technology. The items on the attitude toward e-mail scale clustered into two factors, "Usefulness," and "Comfort/Anxiety." The items on the e-mail purposes of use scale also clustered into two factors, "Task Use," and "Social Use." These factors were similar to the ones on the instruments from which this study's instrument was adapted. The results of the regression analyses indicated that several of the variables were significant predictors of e-mail use, attitudes toward e-mail, and self-efficacy with e-mail technology. An attitude of e-mail's usefulness and self-efficacy with e-mail technology were significant predictors of the extent of e-mail task and social use. Self-efficacy was a significant predictor of positive attitudes of usefulness and comfort. Age was a significant predictor of social use of e-mail as well as of a positive attitude of e-mail's usefulness. Years e-mail had been used was a significant predictor of the extent of e-mail use and of self-efficacy. Higher ranking teaching faculty had more positive attitudes of e-mail's usefulness. The results of analyses of holistic ratings indicate no significant correlations existed among the variables. Recommendations for instruction and for further research are described. / Ph. D.

This study utilized a longitudinal design, to assess the relationship between measures of problem solving skill, self-appraised problem solving ability, and coping style and measures of adjustment: suicidal ideation, depression, psychological symptomotology, general well-being, and the number of visits to the campus health center. Using multiple regression equations, the direct relationships of the cognitive variables to the measures of adjustment were tested. In addition, interactive effects of the cognitive variables with stress, as predicted by the diathesis-stress hypothesis, originally forwarded by Schotte & Clum (1982) were also examined. Findings demonstrated that the cognitive variables had main effects on the measures of adjustment. Many variables also interacted with stress to account for additional variance in the measures of adjustment. It was also found that the variables accounted for independent variance in predicting adjustment. Problem solving skill, self-appraised problem solving ability, and coping style were separate and distinct predictors of the process of assimilating or accommodating to stressful events. / Ph. D.

Getting old involves a lot of changes in life. Family and social relations change and mobility can decrease. These variations require new settings, and of course special care. A nursing home is a place dedicated to help with this situation. Sometimes nursing homes can be perceived as mere institutions by society, and even by future residents. Inside, senior citizens are suppose to spend the rest of their lives doing the same activities day after day. How can we improve these days? Architecture can help. This project deals with architectural design of a nursing home located in an open green area in Blacksburg, Virginia. The project's focus is in creating a home that is related to its surroundings and the proximity to nature. Also deals with all the complexity of this kind of program, but tries to create a homely feeling, and an architectural environment that can adapt to the resident's physical and mental condition over time. / Master of Architecture

Sixty-two female athletes at Virginia Tech participated in an investigation to compare iron status among those whose primary source of dietary protein was red meat (M), lacto-ovovegetarian (V), or poultry and fish (PF). Subjects' blood was collected three times over the six-month study period and analyzed for hemoglobin, hematocrit, serum iron, transferrin saturation, total iron~binding capacity, serum ferritin, free erythrocyte protoporphyrin, mean corpuscular volume, and red blood cell count. Means for all dietary groups were within normal limits for all blood variables. There were no significant differences among the dietary groups for any of the hematological parameters. Six of the sixty-two subjects were found to be in stage 1 iron deficiency; two from Group M, one from Group V, and three from Group PF. None of the subjects was in stage 2 or 3 iron deficiency. Subjects completed two 3-day dietary recalls which were analyzed for nutrient content. Group M consumed a significantly greater percent of kcals from protein than Group V and significantly more grams of protein than both Groups V and PF. There were no significant differences among the groups for intake of iron; however, only Group H consumed the current RDA for iron for adult women. Three subjects from each dietary group were interviewed to identify factors considered most important in the adoption of their dietary patterns. Primary factors identified were: Group H; habit, taste preference, and health; Group Vi athletic performance and ethical treatment of animals, and Group PF; taste preference and health. Iron status in this population does not appear to be affected by source of dietary protein. / Master of Science

Bulimia has recently emerged as an increasing threat to the health of young women in Western society. Though thought by some to be primarily prompted by psychological and physiological instabilities, this research attempts to explore the association between bulimic symptoms and the external pressures to conform to accepted standards of excessive thinness. It is noted that the bulimia trend primarily appears among the population which is overwhelmingly targeted by messages promoting the ideals of success through excessive beauty and thinness. Therefore, this study explores the relationships among several variables: the level of pressure felt by young, achievement-oriented women to control their weight in order to accomplish their goals; the level of difficulty experienced in achieving weight control; and the presence of bulimic symptoms. The sample for this study was taken from five undergraduate sociology courses at Virginia Polytechnic Institute and State University. The research found that among women who held career, social, and family relationships to be of high priority, the pressure to be thin in order to succeed in these areas, along with the difficulty experienced by the respondent in achieving weight loss, was positively associated with the appearance of bulimic attitudes and behaviors. Analysis of responses of males in the study did not produce significant findings with regard to the relationships between bulimic symptoms, the pressure to lose weight to achieve goals, and the difficulty in controlling one's weight. This study concludes that the unrealistic expectations imposed on young women in Western culture regarding their bodily appearance, and the difficulty in adhering to these expectations, have a direct impact on the appearance of bulimia in young achievement-oriented women. / Master of Science