Propagation of sound through the Earth's atmosphere

The data collected at a pressure of one atmosphere for the different temperatures and relative humidities of the air-water vapor mixtures is summarized. The dew point hygrometer used in these measurements did not give reliable results for dew points much above the ambient room temperature. For this reason measurements were not attempted at the higher temperatures and humidities. Viscous wall losses in the resonant tube at 0 C so dominate the molecular relaxation of nitrogen, in the air-water vapor mixture, that reliable data could not be obtained using the free decay method in a resonant tube at one atmosphere. In an effort to obtain viable data at these temperatures, measurements were performed at a pressure of 10 atmospheres. Since the molecular relaxation peak is proportional to the pressure and the viscous losses are proportional to the inverse square root of the pressure the peak height should be measurable at the higher pressure. The tradeoff here is that at 10 atmospheres; the highest relative humidity attainable is 10 percent. The data collected at 10 atmospheres is also summarized

Propagation of sound through the Earth's atmosphere. 1: Measurement of sound absorption in the air: 2: Measurement of ground impedance

Parts were fabricated for the acoustic ground impedance meter and the instrument was tested. A rubber hose was used to connect the resonator neck to the chamber in order to suppress vibration from the volume velocity source which caused chatter. An analog to digital converter was successfully hardwired to the computer detection system. The cooling system for the resonant tube was modified to use liquid nitrogen cooling. This produced the required temperature for the tube, but the temperature gradients within each of the four tube sections reached unacceptable levels. Final measurements of the deexcitation of nitrogen by water vapor indicate that the responsible physical process is not the direct vibration-translation energy transfer, but is a vibration-vibration energy transfer

The contribution of molecular relaxation in nitrogen to the absorption of sound in the atmosphere

Results and statistical analysis are presented for sound absorption in N2-H2O binary mixtures at room temperature. Experimental procedure, temperature effects, and preliminary results are presented for sound absorption in N2-H2O binary mixtures at elevated temperatures

Propagation of sound through the Earth's atmosphere

Progress is reported in the development of hardware and software for an experiment to detect and measure sound transmission through air

Wave Profile for Anti-force Waves with Maximum Possible Currents

In the theoretical investigation of the electrical breakdown of a gas, we apply a one-dimensional, steady state, constant velocity, three component fluid model and consider the electrons to be the main element in propagation of the wave. The electron gas temperature, and therefore the electron gas partial pressure, is considered to be large enough to provide the driving force. The wave is considered to have a shock front, followed by a thin dynamical transition region. Our set of electron fluid-dynamical equations consists of the equations of conservation of mass, momentum, and energy, plus the Poisson\u27s equation. The set of equations is referred to as the electron fluid dynamical equations; and a successful solution therefor must meet a set of acceptable physical conditions at the trailing edge of the wave. For breakdown waves with a significant current behind the shock front, modifications must be made to the set of electron fluid dynamical equations, as well as the shock condition on electron temperature. Considering existence of current behind the shock front, we have derived the shock condition on electron temperature, and for a set of experimentally measured wave speeds, we have been able to find maximum current values for which solutions to our set of electron velocity, electron temperature, and electron number density within the dynamical transition region of the wave

Propagation of sound through the Earth's atmosphere. 1: Measurement of sound absorption in the air. 2: Measurement of ground impedance

The fabrication of parts for the acoustic ground impedance meter was completed, and the instrument tested. Acoustic ground impedance meter, automatic data processing system, cooling system for the resonant tube, and final results of sound absorption in N2-H2O gas mixtures at elevated temperatures are described

Establishing Lean Mass Index Percentiles for Adult Males

Purpose: Lean mass is indicative of an individual’s overall health, as low levels are associated with issues including sarcopenia and increased hospital length of stay. Converting lean mass to a lean mass index (LMI) allows for comparison of individuals of different heights. Four population-based studies have been done to establish fat free mass index (FFMI) percentiles. However, none have had American subjects, with the exception of a small study that utilized an uncommon body composition method. Therefore, the purposes of this study were: 1) to establish a LMI for American adult males, 2) to compare the results to previous studies, and 3) to compare LMI between age categories of this population. Methods: Subjects were 642 men, 18 to 75 yrs of age (x = 29.6 ± 12.4 yrs), who had DXA body composition testing at the Fitness Institute of Texas. LMI was calculated as lean mass/height2. Cumulative relative frequency analysis was performed to create indices for three age categories: 18-22 (G1), 23-39 (G2), and 40+ (G3) yrs of age. LMI values for each age category were compared using ANOVA. To compare the results to those of existing studies, FFMI percentiles were calculated using age groups of 18-34 and 34-59 yrs. Results: Age group LMI percentile graphs were created. Mean LMI was higher in G2 (19.6 ± 2.3 kg/m2) and G3 (19.8 ± 2.3 kg/m2) than in G1 (18.5 ± 2.1 kg/m2) (P\u3c0.05), but there was no difference between G2 and G3 (P\u3e0.05). FFMI percentile results from this study were similar to previous studies, except the FFMI values above the 50th percentile were greater in the 35-59 yr olds in the current study, as shown in Figure 1. Conclusions: The LMI percentile graphs, generated from a large cohort, provide a validated reference for health care professionals and clients. Contrary to expectations, FFMI did not decrease with age for this population. The FFMI percentile values were similar to those of previously published studies