A TDM synchronization system for multiple access satellite communication

Time Division Multiple Access /TDMA/ system for satellite communication with ground station syste

Electro-Mechanical Characterization of Carbon Nanotube Sheets in Simulated Space Environments: The Dawn of “Carbon Spacecraft”

Carbon nanotube (CNT) materials are exciting candidates for spacecraft by virtue of their unprecedented specific mechanical and electrical properties. Analysis in this thesis identifies 14 types of CNT-sheets with distinct variables, and discovers the mechanisms controlling macroscopic properties. Specimen variables include acid treatment, polymer coatings, production method, and combinations. Mechanical testing includes tensile-tests and investigation with scanning electron microscopy and energy-dispersive x-ray spectroscopy. Physical properties testing include electromagnetic interference (EMI) shielding effectiveness (SE) and electrical conductivity. This research also highlights the resilience of CNT-sheets to atomic oxygen and thermal fatigue qualifying them for performance in space. EP CNT-sheets have decreased mechanical and electrical properties from a large composition of impurities. Acid treatment increases both mechanical and electrical properties. The acid treated sheets are better consolidated and have reduced impurities which lead to superior properties. This investigation found that strength and EMI SE are unaffected by atomic oxygen and thermal fatigue. Young’s modulus increases in both environments while strain decreases. Electrical conductivity decreases from atomic oxygen for both specimens as a result of reduced conductive area. Thermal fatigue only diminishes electrical conductivity in the more compact acid treated sheets

Occupational Therapy\u27s Role in Upper Extremity Posture, Ergonomics, and Injury Prevention in Esports

Electronic sports, also known as esports, is organized competitive gaming. Esports athletes routinely sustain injury to the upper extremity (UE) and are forced into early retirement due to pain and limitation. Employing ergonomic principles through education has a significant impact in assisting with pain reduction and prevention of disability. This program sought to decrease the prevalence of upper extremity injury seen in the esports athlete population, and decrease the intensity of pain if it was already present. Twelve total participants were included in the program, as determined by the inclusion and exclusion criteria. Data was gathered through the use of pain scales, the Rapid Upper Limb Assessment (RULA), and surveys so inclusion and exclusion criteria could be upheld and the program could be improved for future use. The program was implemented through five informative presentations regarding instruction of anatomy and ergonomic strategy implementation, and six surveys monitoring pain levels and feedback from participants. The program was determined to be somewhat effective at maintaining and reducing pain levels in athletes whose pain was already present, and also reducing ergonomic risk exhibited by participants.https://soar.usa.edu/otdcapstones-spring2022/1000/thumbnail.jp

Space law information system design, phase 2

Design alternatives were defined for the implementation of a Space Law Information System for the Office of the General Counsel, NASA. A thesaurus of space law terms was developed and a selected document sample indexed on the basis of that thesaurus. Abstracts were also prepared for the sample document set

The Symbiotic Efficiency of Some Peanut Cultivars and Their Interaction with Strains of Rhizobium Spp.

A series of greenhouse and growth room tests were conducted to investigate the interactions between strains of Rhizobium spp. and cultivars of peanut (Arachis hypogea (L.)). Two preliminary greenhouse studies. Experiments 1 and 2, involved testing five and seven strains of rhizobia respectively on two cultivars of peanut. Experiment 1 identified a strain (TAL 236) which was significantly better than other effective strains on both cultivars (Florida Giant and Starr). Data from the effective strains (those which reduced acetylene) indicated that cultivar Florida Giant fixed more nitrogen in early growth than Starr. Both cultivars had similar growth potential when provided NH4N03. Experiment 2 showed significant strain by cultivar interactions among effective strains. Burpee Spanish yielded significantly more than Florunner when inoculated with strain AH8 but significantly less than Florunner when both were inoculated with strain T-1. This interaction emphasized the danger in assuming that strains selected for high efficiency on one cultivar of peanut will perform in a similar fashion on another. Strain TAL 1000 proved to be better than the other effective strains when data from both cultivars were considered. Observations of plants during Experiments 1 and 2 indicated that plants inoculated with strains TAL 236 and TAL 1000 underwent greening of foliage earlier than those plants inoculated with less effective strains. A growth room experiment (Experiment 3) was undertaken to determine whether the earlier greening of foliage by the more effective host-strain combinations were related to the time required for nodule formation. Experiment 3 revealed a significant relation between host seed size and the time to nodule formation. However, the time to nodule formation could not be related to the degree of symbiotic effectiveness of host-strain combinations as determined in Experiments 1 and 2. Effective strains TAL 1000, TAL 236, and TAL 309 were selected to test the symbiotic effectiveness of 1 2 cultivars of peanut in Experiment 4. Differences between cultivars and significant strain by cultivar interactions were revealed. The yields of the cultivars were more uniform when provided NH4N03 than when relying on the symbiosis as a nitrogen source. Some cultivars' average symbiotic yields were over 80% of their respective yields when supplied with mineral N. Other less efficient cultivars yielded only 50% of their mineral N controls. Cultivars inoculated with TAL 1000 generally had greater yields than those inoculated with strains TAL 309 or TAL 236. These tests demonstrated the specific host by strain interactions involved in the peanut-Rhizobium symbiosis. An effective symbiosis is both host and strain determined. Strains which had been shown to be highly effective on more than one cultivar in preliminary tests did not always result in a highly effective symbiosis with other cultivars

The Effect of Salinity on Rhizobium Survival, Nodule Function and Nodule Fomation in the Soybean-Rhizobiurn Japonicum

Symbiotic nitrogen fixation may be adversely affected by saline environments. This dissertation describes experiments that assess the salt sensitivity of: 1) Rhizobium as free living organisms; 2) soybean nodule function; and 3) soybean nodule formation. In addition, a split-root plant growth system is described which can be used to separate the effects of salinity stress on host yield potential from the effects of salinity on nodule processes. The growth rate of Rhizobium in culture media is slowed by the addition of NaCl. Some strains were incapable of growth at the highest level of salt used (120 mM NaCl). However, all withstood substantial osmotic shock and most survived for extended periods in saline solutions equivalent to the concentration of sea water. The results show that the effects of increasing moisture tension and salinity on Rhizobium survival in soil are additive. By independently subjecting nodules and shoots to salinity stress it was possible to show that the soybean-Rhizobium japonicum nodule system was not greatly affected by exposure to 120 mM NaCl. The main reduction in nitrogen fixation was the indirect effect of salinity on leaf expansion, shoot yield potential and the sink for nitrogen. The early processes of nodule formation were extremely sensitive to NaCl in the rooting medium. When only 26.3 mM NaCl was added to the nutrient solution two hours prior to inoculation, nodule number and mass were reduced by 50% and 79.9 mM NaCl reduced nodule number, mass and nitrogen fixation to less than 10% of the controls. Rhlzobium japonicum, reisolated from nodules from the high salt treatment did not form more nodules under saline conditions than isolates from controls. By independently subjecting the various processes of the symbiosis to salinity stress it was determined that the early steps in nodule formation are the most sensitive to salinity. This sensitivity indicates that high quality irrigation water must be used during the establishment of symbiotic legumes

The steps in the development of an atmospheric vorticity meter

Submitted in partial fulfillment of the requirements for the degree of Master of Science at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 1995This thesis describes the steps necessary to develop an acoustic vorticity meter for the atmosphere. The analysis is based on Benthic Acoustic Stress Sensor (BASS) technology that is currently used for similar acoustic measurements in the ocean. Compared to sonic anemometer measurements, the BASS measurements of velocity are not only made in a different fluid but in a different way. Due to these differences, the physical make up of BASS needed to be altered, and the validity of the measurement technique had to be explored. The alterations to the BASS hardware occurred for several reasons. Because attenuation of sound is much higher in air than in water for the same frequencies, it was necessary to change the transducers. The generally faster and unidirectional mean flows that are present in the air encourage open measurement volumes which the BASS vorticity meters do not have. The difference in group speed of sound is different for water and air, and this forced a change to the timing and burst generation board of the BASS vorticity meter. The measurement technique used by the BASS instrumentation is validated by the error analysis in the text. Because the BASS instrumentation actually provides a time difference, the equation used by the BASS instrumentation to compute velocity was assumed throughout the error analysis. The error analysis shows that the combination of BASS measurement techniques with a temperature sensor will provide errors that are less than 2% of the velocity. The types of measurements that an atmospheric vorticity meter would provide to a researcher are described in the text to show the meter's potential. If deployed on a buoy, a vorticity meter could measure shearing of the wind close to the surface of the waves. If deployed at heights much greater than its path lengths, an atmospheric vorticity meter could provide three-dimensional vorticity measurements which would provide a unique measurement of a fundamental characteristic of turbulent flows