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The idea of creating a material or barrier that attenuates shock and blast waves has long been investigated. Considerable work has been performed on the interactions of shock and blast waves with various materials. The application of permeable solids, porous materials and textiles for the attenuation and reflection of destructive shock waves have been studied extensively. The studies presented herein examine the interaction of shock waves and porous plates in order to ameliorate the hazardous effects of these waves particularly in ducts or channels leading to protected areas or objects. A number of tests were performed in an automated shock tube to determine the effects that a series of directional porous plates had on the initial peak pressure and impulse amelioration experienced by the end wall. Mild steel test specimens, ranging in porosity values from 6.6 % to 41.1 %, were mounted two at a time in the test section of the shock tube. Each plate had directional properties and since four plates were used in the study, a total of forty eight plate configurations were tested. Six pressure transducers were located along the side of the test section and two pressure transducers were located in the end wall of the shock tube in order to measure initial peak pressure and impulse amelioration values experienced by the end wall and to identify the wave interactions involved in the amelioration process. Schlieren photographs were also taken in order to investigate these wave interactions. Tests were run at three different Mach numbers viz. 1.23, 1.35 and 1.42. The separation distances between the plate specimens were varied between 30 mm and 60 mm; however the distance between the downstream plate and the end wall was kept constant at 140mm for all tests. It was found that significant initial peak pressure and impulse amelioration was achievable. The Back & Back plate arrangement produced the greatest initial peak pressure and impulse amelioration with averages values of 73.7 % and 20.45 % respectively. Both the initial peak pressure and impulse amelioration values were found to be dependant on the plate combination porosity. As the porosity of the combination increased, the amelioration values decreased. Complementary plate combinations produced differing results as different wave interactions occur when plate positions were interchanged. The porosity of the combined plates were found to have an overriding influence on the end wall initial peak pressure and impulse amelioration values when compared to the effect that plate arrangement (i.e. geometrical influences) had. For all tests performed in this study, the time period used for the integration of the end wall pressure traces was 9 250 μs. As an acceptable closing time for a blast valve in a shelter’s ventilation system is approximately 4 000 μs, the impulse amelioration values for certain plate combinations were recalculated. It was found that using this time period greater impulse amelioration values were produced as the rate of pressure rise, dp/dt, was initially lower at the beginning of the end wall pressure trace. Therefore, the lowest impulse amelioration value (7.9 %) achieved in this study, would produce significant impulse amelioration (20.3 %) if it were to be used in a shelter’s ventilation system. Impulse amelioration values were found to increase as the separation distance between v plates were increased. The average impulse amelioration value was found to increase approximately 1 % for a 15mm increase in the distance between plates. The amplitude of the entire end wall pressure trace was found to increase as the incident Mach number was increased. This resulted in greater initial peak pressure and impulse experienced by the end wall. The significant attenuation of the incident shock wave obtained during this study is attributed to the system of multiple reflected and transmitted waves that are produced by the presence of the plate specimens in series. This increases the frequency of shock wave and barrier interactions, when compared to just using a single barrier, creating regions of highly unsteady flow, especially in the air space between the plate specimens. Furthermore, the presence of the series of plates also allows for wave resonance to occur which may further attenuate the strength of the incident shock wave. It is suggested that future studies include numerical techniques in order to further investigate the complex wave processes that occur upon interaction with the plate specimens and confirm the major loss mechanisms of the system.

The purpose of this study is to provide the necessary technical background and data for the development of a suspension system for a recumbent bicycle. For this reason, the customer requirements-design criteria for the development of the suspension system were set, and several static and dynamic tests were conducted on the bicycle's suspension components in order to determine their shock absorption properties. The shock absorption properties of the bicycle's components can be used as means of evaluating the specifications of the suspension system that will satisfy the established design criteria best. In addition, a test machine that can be used for damping coefficient and spring constant measurements was designed to provide further assistance with the analysis of the damping and elastic properties of the recumbent bicycle's suspension components. It was designed so that it can also be used for similar testing of other materials and parts used in the bicycle industry. The subject of this study was BikeE, a recumbent bicycle that was developed by Professor D. G. Ullman and the BikeE Corporation in 1992. / Graduation date: 1995

Both experimental and numerical investigations of converging shock waves have been performed. In the experiments, a shock tube was used to create and study converging shock waves of various geometrical shapes. Two methods were used to create polygonally shaped shocks. In the first method, the geometry of the outer boundary of the test section of the shock tube was varied. Four different exchangeable shapes of the outer boundary were considered: a circle, a smooth pentagon, a heptagon, and an octagon. In the second method, an initially cylindrical shock wave was perturbed by metal cylinders placed in various patterns and positions inside the test section. For three or more regularly spaced cylinders, the resulting diffracted shock fronts formed polygonal shaped patterns near the point of focus. Regular reflection was observed for the case with three cylinders and Mach refection was observed for cases with four or more cylinders. When the shock wave is close to the center of convergence, light emission is observed. An experimental investigation of the light emission was conducted and results show that the shape of the shock wave close to the center of convergence has a large influence on the amount of emitted light. It was found that a symmetrical polygonal shock front produced more light than an asymmetrical shape. The shock wave focusing was also studied numerically using the Euler equations for a gas obeying the ideal gas law with constant specific heats. Two problems were analyzed; an axisymmetric model of the shock tube used in the experiments and a cylindrical shock wave diffracted by cylinders in a two dimensional test section. The results showed good agreement with the experiments. The temperature field from the numerical simulations was investigated and shows that the triple points behind the shock front are hot spots that increase the temperature at the center as they arrive there. As a practical example of shock wave focusing, converging shocks in an electrohydraulic lithotripter were simulated. The maximum radius of a gas bubble subjected to the pressure field obtained from the lithotripter was calculated and compared for various geometrical shapes and materials of the reflector. Results showed that the shape had a large impact while the material did not influence the maximum radius of the gas bubble. / QC 20100706

The primary purpose of the study was to reveal the perceptions of three newlyarrived male Korean students enrolled in Texas A&M University during the 2007 fall semester regarding their experiences with culture shock and the reasons they ascribed for this phenomenon through three in-depth, individualized interviews and weekly L1 journals. The manner in which they responded to the culture shock as well as the influential factors that assisted them in coping was also explored. By using a constant comparative method of analysis, the collected data was scrutinized and analyzed for emerging patterns. To assist in this process, the data was input into computer files and analyzed using the software program NVivo 7. The findings uncovered the existence of some degree of culture shock for each of the three participants at different times throughout the semester. In particular, a comparatively much higher incidence of interpersonal and psychological symptoms of culture shock than of physiological ones was displayed. Strong support for the individual nature of culture shock was also exhibited. In addition, the participants’ perceptions of the experiences as well as their ability to cope or not cope with culture shock revealed a capacity to overcome obstacles and reflect upon differences. Support for the majority of the factors hypothesized to be influential in helping or hindering the participants’ ability to cope with culture shock was exhibited. The noteworthy impact of the participants’ personal outlook, marital status, length of stay in the U.S., religiosity, and previous international experience on lessening the effects of culture shock was found. The influence of English, the university, and social connectedness, however, was important in increasing their adjustment stress. The cultural and ethnic differences between Korea and the U.S. were found to be the source of highly individual challenges faced by the participants during the study. As all the participants were males and their ages were within five years of each other, it was not possible to compare the influence of these variables among them. The only factor expected to have been influential in the participants’ adjustments to culture shock that was not evident was counseling.

Thesis (Ph. D.)--University of Hong Kong, 2001. / Includes bibliographical references.

Thesis (Ed. D.)--West Virginia University, 2002. / Title from document title page. Document formatted into pages; contains viii, 135 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 120-123).

Thesis (M.S. in Mechanical Engineering)--Naval Postgraduate School, June 2004. / Thesis advisor(s): Young S. Shin. Includes bibliographical references (p. 69-70). Also available online.

Thesis (Ph. D.)--University of Texas at Austin, 2001. / Vita. Includes bibliographical references (leaves 118-125). Available also in a digital version from Dissertation Abstracts.

published_or_final_version / Medicine / Master / Master of Medical Sciences