M. S.

Virginia Tech has recently developed and constructed seven ground terminals for use in a propagation experiment employing the Advanced Communications Technology Satellite. This satellite was deployed by NASA in September of 1993. The ground terminals are used in the study of propagation effects caused by the atmosphere for 20 and 30 GHz signals. Each of these terminals contains one total power radiometer for each frequency. These radiometers are used to set clear sky attenuation reference levels for satellite beacon calibration. This thesis describes the design, implementation and testing of the radiometers built at Virginia Tech. In addition, a mathematical algorithm used for the prediction of clear sky attenuation along satellite paths is tested for correlation with radiometer predicted clear sky attenuation. Test data is compared to determine if the algorithm might serve as a radiometer replacement in future propagation experiments or other applications. / Master of Science

M. S.

This study suggests that transfer of State forests to the local communities is the least cost policy option to improve prevailing deforestation problem in Nepal. However, there are few problems at operational, institutional, and policy levels, which are restricting community forest (CF) transformation. The critical review of seven representative case studies and modern forest policy of Nepal identifies following important issues in CF transformation in Nepal. They are low marginal flexibility, incomplete and uncertain property rights transfer, equity problem, specific demand adjustment problem, and inconsistent forest policy. This work recommends for amendment of modern CF policy guidelines to reduce CF transformation costs, increase present value of future returns, and reduce present value of enforcement costs. These amendments will be effective to improve prevailing CF work situation in Nepal. Availability / Master of Science

A dynamic pressure measuring system composed of long connecting tube, transducer, D-C amplifier and galvanometer oscillograph were used in a wind study conducted by the Department of Agricultural Engineering, Virginia Polytechnic Institute. The instrumentation was used to measure and record dynamic pressures due to wind velocity. Data recorded in that study indicated velocity head pressure oscillations on some surfaces of the test structure in excess of 100 Hz. This investigation was undertaken to see if the recorded oscillations could have been generated in the measuring system or if they were truly windpressure variations. Components of the pressure measuring system were modeled by transfer functions. From these transfer functions, a system operational transfer function was determined and used to define system frequency response. The frequency analysis indicated the system was severely limited in response by the oscillating air column constrained within the interconnecting tube. The usable frequency range of the system (+ 10% tolerable amplitude error allowable) was found to go from zero to 34.2 Hz. By eliminating the air column this frequency range could have been extended to 99.4 Hz. Phase shifts in these frequency ranges were found to be negligible. Transducers were mounted rigidly to exterior walls of the test structure. The measured fundamental natural frequencies of these walls (transducer mountings) were found to be well within the usable frequency range of the instrumentation; and, therefore, a source of vibration pickup. To improve the measuring system reliability, recommendations were made to eliminate the air column and stiffen the transducer mountings. / Master of Science

The Large Format Camera is a high resolution wide-angle mapping camera. It will be carried into orbit as a payload in the Shuttle Orbiter vehicle's cargo bay. A mapping camera must be calibrated to determine precise values for its elements of interior orientation. The Large Format Camera was calibrated by the stellar method of camera calibration. Descriptions of the procedure used by the National Ocean Service to calibrate the Large Format Camera are included. / Master of Engineering

A noncontact two-color pyrometer, which uses an infrared (IR) transmitting rod and IR lenses to optically measure the temperature of a molten particle as it falls in an evacuated drop tube, has been designed and tested in the laboratory and in the field. The design uses a calcium fluoride (CaF₂) rod which transports optical energy radiated from the molten particle to a beam splitter, where it is split into two signals. Each signal is filtered and focused onto an indium antimonide (InSb) photodetector which is liquid nitrogen (LN₂) cooled. A ratio of the detectors' outputs indicates the temperature of the molten particle. In the laboratory, a blackbody calibrator is used as a source, and a shutter with a speed of 4 ms is used to simulate the particle dropping by the optical sensing port. The pyrometer has been calibrated for a particle temperature range of 650°C - 1200°C. / Master of Science

Le Positionnement Relatif Temporel (ou TRP : Time Relative Positioning, en anglais) est une technique GNSS qui permet de mesurer un déplacement (et non pas une position) avec un seul récepteur en utilisant les différences de mesures de phase entre deux époques. Le but de ce projet de recherche est d’adapter le positionnement TRP pour l’auscultation topographique et pour la mesure des vagues, afin de détecter des déplacements, sur un court intervalle de temps, avec une précision meilleure que 1 cm en horizontal et 2 cm en vertical. Afin d’y parvenir, les algorithmes et le logiciel TRP du Département des sciences géomatiques ont été adaptés pour le traitement des données GNSS à un taux d’échantillonnage élevé (10 Hz) et en utilisant exclusivement les éphémérides transmises qui sont disponibles en temps réel. Les résultats obtenus ont été comparés à ceux de la solution PPK (cinématique relatif en post-traitement) et des solutions de comparaison provenant d’autres sources (graduations, mesures de jauges, …). Les écarts-types obtenus des différences entre la solution TRP et les solutions de comparaison varient entre 0.3 et 0.5 cm en horizontal, et entre 0.5 et 3.1 cm en vertical en utilisant seulement les mesures de phase sur L1 de la constellation GPS. Grâce à l’intégration des observations GLONASS, une amélioration à la précision verticale de plus de 30%, sur des sites obstrués, a permis d’atteindre une précision de 2.1 cm. / Time Relative Positioning (TRP) is a GNSS method that uses phase difference observations between two epochs from a single receiver to determine receiver displacement (or position change). The aim of this research project is to adapt the TRP method for structural health monitoring and wave measurements in order to detect displacements, over short time interval, with an accuracy better than 1 cm for the horizontal and 2 cm for the vertical components. The algorithms and TRP software developed at the Department of Geomatics Sciences at Laval University have been adapted to process GNSS data at high rate of 10 Hz using exclusively broadcast ephemeris that are available in real-time. TRP results were compared to the corresponding Post-Processed Kinematic (PPK) and other control solutions (graduations, gauge measurements, …). Using only GPS L1 frequency data, the standard deviation of the differences between TRP and these comparison solutions ranged from 0.3 to 0.5 cm for the horizontal component and from 0.5 to 3.1 cm for the vertical component. When GLONASS observables were added to the TRP-GPS-L1 solution, for environment where satellite visibility was limited, the standard deviation decreased by 30% to reach 2.1 cm for the vertical component.

An automated luminometer was designed and constructed to facilitate the investigation of reaction conditions and quantitation of the chemiluminescence observed during the oxidation of NADH by horseradish peroxidase in the presence of eosin. The luminometer design incorporates a computer controlled reagent induction system, pulse counting detector and real time display of luminescence profiles. Each of the major reaction conditions was studied individually to determine the most favorable conditions for the analytical application of this reaction. In addition, this chemiluminescent reaction was studied to determine if the luminescing species is recycled. If this were the case it would provide the first essential step necessary for the future design of a chemiluminescent probe that could be reusable or be used for continuous monitoring. During the course of this investigation it was observed that the luminescing species, eosin, was being bleached. A number of experiments were undertaken to determine the nature of the bleaching process. Those steps which suppressed the bleaching process, unfortunately, also suppressed the emission process. Despite the fact that this reaction does not appear to recycle the luminescing species, it does provide a chemiluminescent method for the determination of NADH over the range 5x10⁻⁶ M to 5x10⁻⁴ M. This chemiluminescent reaction has also been coupled to several enzyme systems, which reduce NAD⁺ to NADH, in order to obtain a chemiluminescent signal proportional to the substrate concentration. / Ph. D.

A study was performed to evaluate the effectiveness, efficiency, and strategy associated with three navigation methods: memorized route, conventional paper map, and a moving-map navigational display (the navigator). Thirty-two driver-subjects of both genders, and wide ranges of age (18-73) and driving experience (2,000 to 40,000 miles per year) navigated along public roadways for this research using a specially instrumented automobile. A variety of different roadway conditions were also used for this research including limited access four-lane highways, two-lane state routes, and city streets. In addition, the research was conducted under conditions of both light and moderate traffic densities. Measures taken include eye movement, navigation effectiveness, and driving performance measures. Results showed that the paper map took longer to study at the beginning of a run than the navigator. Even with this handicap, the total time taken when using the paper map was not significantly different from the time taken to use the navigator. Also, there were no differences in the directness or quality of routes selected when using either the paper map or the navigator to navigate. These findings were a result of the strategies adopted in the use of the various methods of navigation. During the initial study phase the paper map was essentially used to plan the entire route from start to finish. After the initial phase, the map was used only as an occasional reference. In contrast, effective use of the navigator could only be accomplished by repetitively glancing at the display to acquire important information as it was updated and presented. As a result, subjects spent more driving time glancing to the navigator than the paper map, and it substantially drew the subjects' gaze away from the driving task relative to the norm established in the memorized route condition, as well as in comparison to the paper map. Still, driving performance did not greatly change as a function of navigation method indicating that the additional visual attentional demand associated with the navigator was drawn primarily from spare driver resources. It is also very likely that the novelty of the navigator was responsible for some portion of the glance time spent on it. / Ph. D.