Initial ionization rates in shock-heated Argon, Krypton, and Xenon

The rate of ionization behind strong shock waves in argon, krypton, and xenon, is observed by a transverse microwave probe, over a range of electron densities low enough that atom-atom inelastic collisions are the rate-determining mechanism. Shocks of Mach number 7.0 to 10.0 propagate down a 2-in. sq. aluminum shock tube into ambient gases at pressures of 3.0 to 17.0 mm. Hg., heating them abruptly to atomic temperatures of 5500°K to 9600°K. The subsequent relaxation toward ionization equilibrium is examined in its early stages by the reflection, transmission, and phase shifts of a 24.0 Gc/sec (1.25 cm) transverse microwave beam propagating between two rectangular horns abreast a glass test section. The data yield effective activation energies of 11.9 ± 0.5 eV for argon, 10.4 ± 0.5 eV for krypton, and 8.6 ± 0.5 eV for xenon. These coincide, within experimental error, with the first excitation potentials, rather than the ionization potentials of the gases, indicating that in this range ionization proceeds via a two-step process involving the first excited electronic states of which the excitation step is rate controlling

Space station operating system study

The current phase of the Space Station Operating System study is based on the analysis, evaluation, and comparison of the operating systems implemented on the computer systems and workstations in the software development laboratory. Primary emphasis has been placed on the DEC MicroVMS operating system as implemented on the MicroVax II computer, with comparative analysis of the SUN UNIX system on the SUN 3/260 workstation computer, and to a limited extent, the IBM PC/AT microcomputer running PC-DOS. Some benchmark development and testing was also done for the Motorola MC68010 (VM03 system) before the system was taken from the laboratory. These systems were studied with the objective of determining their capability to support Space Station software development requirements, specifically for multi-tasking and real-time applications. The methodology utilized consisted of development, execution, and analysis of benchmark programs and test software, and the experimentation and analysis of specific features of the system or compilers in the study

Warrior to Civilian: The Impact of Social Identity and Emotional Well-being on the Community Reintegration of US Service Members and Veterans

In this dissertation, the author explores the relationship between the social identity and emotional well-being of military service members and veterans when transitioning to civilian roles following deployment(s) and/or the end of military service. This mixed-methods study uses participant observations, survey measures, and semi-structured interviews to answer the following questions: How does social identity impact the emotional well-being of military service members when transitioning to civilian roles following deployment(s) and/or end of military service? How does participation in formalized or ad hoc community reintegration “rituals” influence the service member’s felt sense of return? By combining Social Identity Theory with Maslow’s Hierarchy of Human Needs, the author hypothesizes that individuals who have participated in communal ceremonies, rituals, or events for reintegration purposes will demonstrate a more secure transition between military and civilian identities; and that individuals who have more integrated, less competing civilian and military identities will demonstrate higher instances of psychosocial well-being. Implications are subsequently drawn from these findings to better inform policy and practice of government and non-governmental organizations that work with the return and reintegration of military service members, as well as public health organizations focused on community well-being in the wake of conflict

Charles E. [Harwell] requesting his discharge papers

https://digitalmaine.com/arc_me_militia/1149/thumbnail.jp

New perspectives in archosaur biology

The respiratory and metabolic biology of dinosaurs is poorly, if at all, reflected in the fossil record. By comparing anatomical features of modern taxa that are functionally linked to specific biology with the remains of theropod dinosaurs (Archosauria: Theropoda) and early birds, we may reasonably infer the physiology of long extinct taxa. This dissertation uses comparative anatomy and experiments with living crocodilians to investigate dinosaur respiratory biology. Modern crocodilians ventilate a relatively unspecialized lung using both costal action as well as fore-aft movement of the transversely oriented liver. During inhalation, the diaphragmaticus muscles, which attach to the pubis and invest the digestive viscera, pull the liver caudally. Interestingly, the unique crocodilian pubis is mobile at its articulation with the pelvic girdle and is capable of dorso-ventral movement. In my experiments, I surgically fixed the pubis and found that this decreased the movement of the liver and tidal volume but did not increase intrabdominal pressure. Thus I infer that theropod dinosaurs with immobile pubes could have utilized a crocodilian-like ventilatory mechanism without suffering excessively high intrabdominal pressure that would limit venous return. Furthermore, the skeleton of theropod dinosaurs strongly suggests the presence of crocodilian-like ventilatory mechanisms. Modern birds ventilate a highly derived lung air-sac system using movements of a specialized thoracic skeleton. Requisite to the proper function of this system are their voluminous, thin-walled abdominal air-sacs that are supported by a specialized synsacrum, pubes and femoral-thigh complex. This lung air-sac system facilitates increased oxygen delivery to serve the demands of highly active tissues characteristic of endothermy. The earliest bird, Archaeopteryx, lacked the skeletal modifications indicative of a modern bird-like lung air-sac system and therefore was likely not endothermic, yet may have been capable of powered flight. Endothermy likely did not evolve in birds until the mid-Cretaceous ornithiurine birds Hesperornis and Ichthyornis

The Effects of Foam Rolling and Static Stretching on Flexibility and Acute Muscle Soreness

Please view abstract in the attached PDF file

Thermal Behavior in the Lens Process

Direct laser metal deposition processing is a promising manufacturing technology which could significantly impact the length oftime between initial concept and finished part. For adoption ofthis technology in the manufacturing environment, further understanding is required to ensure robust components with appropriate properties are routinelyfabricated. This requires a complete understanding ofthe thermal history.during part fabrication and control ofthis behavior. This paper will describe our research to understand the thermal behavior for the Laser Engineered Net Shaping (LENS) process!, where a component is fabricated by focusing a laser beam onto a substrate to create a molten pool in which powder particles are simultaneously injected to build each layer. The substrate is moved beneath the l~ser beam to deposit a thin cross section, thereby creating the desired geometry for each layer. After deposition of each layer, the powder delivery nozzle and focusing lens assembly is incremented in the positive Z-direction, thereby building a three dimensional component layer additively. It is important to control the thermal behavior to reproducibly fabricate parts. The ultimate intent is to monitor the thermal signatures and to incorporate sensors and feedback algorithms to control part fabrication. With appropriate control, the geometric properties (accuracy, surface finish, low warpage) as well as the materials' properties (e.g. strength, ductility) of a component can be dialed into the part through the fabrication parameters. Thermal monitoring techniques will be described, and their particular benefits highlighted. Preliminary details in correlating thermal behavior with processing results will be discussed.Mechanical Engineerin

Hybrid propulsion for launch vehicle boosters: A program status update

Results obtained in studying the origin and suppression of large-amplitude pressure oscillations in a 24 in. diameter hybrid motor using a liquid oxygen/hydroxylterminated polybutadiene/polycyclopentadiene propellant system are discussed. Tests conducted with liquid oxygen flow rates varying from 10 to 40 lbm/sec were designed to gauge the effectiveness of various vaporization chamber flow fields, injector designs, and levels of heat addition in suppressing high-frequency longitudinal mode oscillations. Longitudinal acoustic modes did not arise in any tests. However, initial testing revealed the presence of high-amplitude, sinusoidal, nonacoustic oscillations persisting throughout the burn durations. Analysis showed this to be analogous to chug mode instability in liquid rocket engines brought about by a coupling of motor combustion processes and the liquid oxygen feed system. Analytical models were developed and verified by test data to predict the amplitude and frequency of feed-system-coupled combustion pressure oscillations. Subsequent testing showed that increasing the feed system impedance eliminated the bulk mode instability. This paper documents the work completed to date in performance of the Hybrid Propulsion Technology for Launch Vehicle Boosters Program (NAS8-39942) sponsored by NASA's George C. Marshall Space Flight Center