Examination of space/volume requirements for US underground coal mine refuge alternatives
ABSTRACT The Mine Safety and Health Administration requires that 1.4 m2 (15 ft2) of floor space is to be provided for each person inside a refuge alternative (RA). However, the amount of floor space needed for a person to reside inside an RA and perform basic tasks is unknown. During testing, participants entered into an RA or a simulated RA of various space/volume configurations and performed several simulated tasks that are representative of the survivability tasks performed within an RA. The results indicate that the floor space requirements were generally adequate for the tasks studied. Certain tasks such as changing scrubber cartridges, using toilets, and moving about the RA were impacted by the minimum height tested (0.6 m). As such, RAs of this height will require critical design consideration as a whole and the supplies provided for use inside of the RA to ensure the ability to use an RA.
The Effects of Ejection Seat Cushion Design on Physical Fatigue and Cognitive Performance
Abstract : The detrimental effects of prolonged sitting during long-duration flights include deep vein thrombosis, pressure sores, and decreased awareness and performance. However, the cushion is often the only component of the ejection seat system that can be modified to mitigate these effects. This study investigated the long-duration effects of sitting in four ejection seat cushions over eight hours. Subjective comfort survey data and cognitive performance data were gathered along with comparative objective data, including seated pressures, muscular fatigue levels, and lower extremity oxygen saturation. Peak seated pressures ranged from 1.22-3.22 psi. Oxygen saturation in the lower extremities decreased over the eight hours. Cognitive performance increased over time regardless of cushion with the exception of the dynamic cushion, which induced a decrease in performance for females. Muscular fatigue increased throughout the eight hours regardless of cushion, with the exception of the dynamic cushion which promoted muscular recovery. Subjective comfort levels declined over the eight hours. Subjective measurements correlated with objective parameters for the static cushions. Trade-offs in performance and fatigue mitigation were apparent in the dynamic cushion which also highlighted the differences between genders. These results will be used to develop cushion design guidelines, both to prevent deep vein thrombosis and to promote performance and comfort for long-duration use.
Recalculation of Mass Defects
THE well-known mass defect curve of the old nuclear scheme calculated with regard to α-particles and protons presented a difficulty with its minimum of binding energy for tin and an increasing portion between tin and lead. On the other hand, the mass defect values against protons give a rather smoothly decreasing curve.1 As has already been pointed out,2 the number of α-particles must be considerably reduced from the point of view of the new scheme, which does not admit any electrons in nuclei, but only neutrons and protons (presumably joined as α-particles). The curve of mass defect against protons and neutrons (perhaps with a single ‘central’ α-particle) is very similar to the old curve against protons, but decreases less rapidly. Clearly the new mass defect values relatively to α-particles, neutrons and protons must lie somewhere between the old values computed relative to protons and α-particles respectively (because the number of α-particles is decreased). We may emphasise that this new mass defect curve shows no increasing portion between tin and lead. For illustration we give two typical values: Old: 50Sn124 = 31α + 12&#38;epsiv;; mass defect = 0.158 (in mass units); 82Pb208 = 52α + 22&#38;epsiv;; mass defect = 0.035. New: 50Sn124= 25α + 24ω (ω = neutron); mass defect = 0.304; 82Pb208 = 41α + 44ω; mass defect = 0.366.