An experimental program was conducted at NASA Langley Research Center, in Hampton Virginia, that included development and evaluation of an operational facility for wall drag measurement and evaluation of the total drag of various wall configurations. The drag of three possible supersonic combustor wall configurations was measured to determine if reduction in skin friction and/or wave drag could be achieved through the use of cavities, vented cavities, and/or mass addition. Data are presented herein as average drag force, wall static pressure distributions and focusing schlieren images. The experimental model consisted of a series of interchangeable aluminum plates attached to an air-bearing suspension system. The system was equipped with load cells that measured forces up to 10 pounds in the drag direction only. The plates were exposed to a Mach 2 air stream at a total pressure of 115 psia. This flow field contained a train of relatively weak, unsteady, reflecting shock waves that were produced by the Mach 2 nozzle and plenum chamber assembly. Mass addition was successfully employed to alter the plate drag in both the transpiration and cavity configurations. Three plate configurations were tested: a flat plate, a plate with air transpiration, and a cavity plate equipped for the introduction of bleed air into the cavity. The resulting data base consists of drag data at Mach 2 for a standard flat plate, and two wall configurations tested with bleed mass flow rates ranging from 0.00 to 0.06 lbm/sec. The experimental wall static pressure distributions and the focusing schlieren images are shown to compare favorably with the CAN-DO computer analysis results. / Master of Science

The accessibility of consumer products is an issue for many people with special needs. This study addresses the usability of non-single-lens reflex (NSLR) cameras for people with limited hand grip strength and finger dexterity, namely people with quadriplegia or people with arthritis. It proposes a three-phase methodology to eliminate or mitigate accessibility barriers on a consumer product. A usability test was conducted with a NSLR camera. Problems were recorded with the Critical Incident technique. Prioritization of the problems reported by the subjects show that the shutter release control and the camera grip are the two major accessibility barriers of the product. Four new camera models were developed: three with gripping aids (rubber pads, a thumbsleeve, or a handle) and one with a remote wired shutter release control. A fifth model was obtained by combining the remote shutter release control and the handle. A designed experiment was conducted with the five models and the standard camera. Performance measurements of framing tilt and camera shake were collected, as well as subjective opinions. Results indicate a recurrent difference between performances of quadriplegics and performances of other subjects. The remote shutter release control was shown to eliminate accessibility barriers. The handle also increased ease of grip and camera stability for disabled subjects. / Master of Science

Data collected with a three-component laser Doppler anemometer system is used to investigate velocity bias. The data is collected in the viscous layer of a fully developed turbulent open water flow at a Reynolds number of 14,766 based on the flow depth. The data collected at a relatively low data rate is analyzed using different correction methods including: straight forward arithmetical averaging, inverse velocity and transit time weighting. The streamwise mean velocity components, the RMS values and the kinematic Reynolds stress are computed using the various weighting methods and are compared to a three-component inverse velocity bias correction model which is taken to represent the "true" values. The three-component inverse velocity bias correction results are in general accordance with the expected behavior in open channel flow and are comparable to the results reported by other researchers employing different experimental techniques. The results of this study show that the bias is sensitive to the correction method used and the theory that the mean streamwise velocity error (without correction) is proportional to the square of the turbulence intensity is confirmed experimentally. Averaging the data without correcting it produced the largest bias while the results from the different inverse velocity techniques were approximately the same although the level of the bias varied with the turbulence variable that was analyzed. As reported in the literature, the transit time weighting method requires accurate determination of the residence time. The relatively poor performance of the transit time method in the present comparison is attributed to the poor accuracy in the measurement of the residence time. / Master of Science

Personal communications has produced a demand for low-Earth orbit satellite (LEOSAT) implementation. A proposed LEOSAT link at VHF would provide paging and radio-location services to subscribers in automobiles. Link performance has traditionally been determined by thermal background noise produced internally as well as externally to the radio receiver. Most recently, however, man-made noise has become the dominant source of link interference at VHF frequencies and below. This thesis examines the statistical behavior of man-made noise through a series of in situ measurements, and implements a statistical-physical mathematical model to provide bit-error rate (BER) predictions for system designers. The model is also applied in an attempt to scale the statistics for bandwidths other than the noise measurement receiver. Man-made noise is inherently impulsive, due to switching processes in the AC power distribution system. Gaussian noise models are therefore inappropriate for the description of man-made noise statistics. A model by Middleton was developed around the Poisson mechanism to accurately predict the amplitude probability distribution (APD) of the received noise. Unlike empirical models, the constants employed by the Middleton model posses physical significance. / Master of Science

This thesis is concerned with the effects of earthquakes on partially-filled water tanks. The analysis is applicable to rectangular water tanks, which have received little attention to date. The analysis is relatively involved and includes the derivation of the equations of motion for the vibration of the whole of tank by means of substructure synthesis, a stochastic analysis relating the random ground motion caused by earthquakes to the random vibration of the tank, a stochastic characterization of the fluid pressure and computation of the probability of failure of the tank. / Master of Science

An analytical treatment of the fatigue performance of a cam-roller followler system as influenced by residual stresses induced by grinding, is developed. An approach based on an extended Hertzian analysis is used to determine the 3-D contact stress fields, which are then combined by elastic superposition with the residual stress fields. These residual stresses were measured previously by the x-ray diffraction technique and represent a range of grinding protocols from mild to abusive. The maximum cyclic component, generally occurring subsurface, is then identified in terms of an effective stress amplitude and mean which are used with a fatigue damage model to predict fatigue crack initiation. Results, pending experimental confirmation, appear reasonable and provide a useful basis for optimizing cam performance in terms of manufacturing and design parameters. / Master of Science

No Virginian was more dedicated to the Confederate cause than Stapleton Crutchfield. Born into a prominent and wealthy family, Crutchfield enjoyed and embraced the southern aristocratic lifestyle. He was a Virginian first and a United States citizen second. When Crutchfield was sixteen, he enrolled at the Virginia Military Institute. The young man had been enamored with the military tradition of his family and the extreme militancy of the South. Graduating at the top of his class in 1855, Crutchfield stayed on at the Institute as a mathematics professor. As Virginia prepared for war in 1861, Crutchfield resigned from his post and joined the Confederate army as an officer. The former mathematician was anxious for a fight. He believed that Virginia and the southern lifestyle was endanger of being destroyed by the North. Crutchfield's military training and family connections helped him receive appointment to the rank of major. In 1862, Gen. Thomas Jackson appointed Crutchfield to chief of artillery of his division. While Crutchfield had received training in artillery at the Institute l the instruction he received would not prepare him for the Civil War. New technology and the massive size of the armies had drastically changed the role of artillery in battle. His experience would come through trial and error on the battlefield. As Jackson's successes catapulted him to the top of the Confederate army's hierarchy, Crutchfield assumed additional commands and responsibilities. He became one of the few men to command artillery corps in the Civil War. During his tenure as artillery chief, the "long arm" of the Army of Northern Virginia experienced its largest growth. Furthermore, it is when Lee's army had its greatest successes on the battlefield. Yet, Stapleton Crutchfield has been overlooked by Civil War historians. They have failed to investigate the complexities of being artillery chief during the army's greatest period of growth and success. Crutchfield played an invaluable role in the shaping of the Army of Northern Virginia's artillery. His actions influenced the artillery corps even after his wound forced him to retire from his post. / Master of Arts

Eye movements are thought to be representative of an observer's attention. Researchers have used eye movements to gain insight to the mental processes of observers while they view pictorial stimuli. The present research was conducted to determine if subjective reports of attention are representative of eye movements, and if there are differences in the subjective reports between novice picture-takers and expert judges. Two studies were performed to answer these questions. The Image Evaluation study employed 24 subjects to examine 20 soft-copy photographic images. The 24 subjects were divided into four nested combinations: Protocol and Group. Two types of protocol were used, concurrent and retrospective, and two expertise groups were used, novice picture-takers and expert judges. The subjects viewed and rated the quality of each image. Subjective reports of attention were then collected by using a mouse to click on the features that influenced the quality rating. The second study, the Eye Tracker study, used six subjects, all novices, to examine and rate each image while eye movements were recorded, after which their subjective reports of attention were collected. Measures of time, frequency, location, and the quality rating were collected for each subject on all images. These measures were then subjected to parametric and nonparametric statistical tests. The two groups, expert and novice, displayed a difference only when rating the quality of the image. The two protocols were not statistically different for any dependent measure, although for this task a retrospective protocol is recommended. The subjective reports of attention did not represent the eye movements. Questions concerning the method employed to collect the reports are addressed. / Master of Science

The concept of quality management is operationalized in an organization through a Quality Management System (QMS) - a complex, coordinated set of activities and behaviors aimed at improving the quality of an organization's processes, goods, and services. Like all systems, a QMS must be planned, monitored, improved, and maintained over time to function at its best. For this, measurement is key. The standard of quality management performance developed by Triantis, et. al. (1991b) is the quality management system definition used in this thesis. The thesis subsequently makes three contributions. First, it provides a methodology for defining generic measures of QMS performance and evolution, and implements this methodology in creating more than 200 prototype measures for 10 out off the 37 component "modules" of a QMS. Second, a methodology is presented for developing a tool to collect the very data called for by the measures. This methodology is implemented and a prototype questionnaire developed to collect measurement data for the Vendor/Contractor Relations (VCR)module of a QMS. Third, given the vast amount of data collected with the various questionnaires that needs to be manipulated in order to manage the QMS, it is important to be able to use automation. Therefore, it becomes necessary to logically organize the data. The entity-relationship (E/R) modeling technique is one approach that can be used to achieve this objective. This E/R approach is used to logically organize data that is generated by the questionnaire for the VCR module. In so doing, one can assess the potential viability of this data modeling approach and begin laying the foundation for a database that will support the measurement requirements of a QMS. / Master of Science

A novel in-situ stress measurement technique to study the formation kinetics of multi component oxide thin films was developed and was applied to PbTiO₃. Single phase PbTi 0₃ thin films were formed from the reaction between films in the deposited PbO ITi0₂ multilayer. The film stoichiometry was accurately controlled by depositing individual layers of the required thickness. Development of film stresses associated with the formation of the product layer at the PbO/Ti0₂ interface of the multilayers was used to monitor growth rate of the PbTiO₃ layer. It was found that growth of the PbTiO₃ phase obeyed the parabolic law and the effective activation energy was estimated to be 108 kJ/mole. It is believed that the mechanism of this reaction was dominated by grain boundary diffusion of the participating cations. / Ph. D.