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Abstract: Airbag-based methods for crew impact attenuation have been highlighted as a potential simple, lightweight means of enabling safe land-landings for the Orion Crew Exploration Vehicle, and the next generation of ballistic shaped spacecraft. To investigate the feasibility of this concept during a nominal 7.62m/s Orion landing, a full-scale personal airbag system 24% lighter than the Orion baseline has been developed, and subjected to 38 drop tests on land. Through this effort, the system has demonstrated the ability to maintain the risk of injury to an occupant during a 7.85m/s, 0° impact angle land-landing to within the NASA specified limit of 0.5%. In accomplishing this, the personal airbag system concept has been proven to be feasible. Moreover, the obtained test results suggest that by implementing anti-bottoming airbags to prevent direct contact between the system and the landing surface, the system performance during landings with 0° impact angles can be further improved, by at least a factor of two. Additionally, a series of drop tests from the nominal Orion impact angle of 30° indicated that severe injury risk levels would be sustained beyond impact velocities of 5m/s. This is a result of the differential stroking of the airbags within the system causing a shearing effect between the occupant seat structure and the spacecraft floor, removing significant stroke from the airbags. [Copyright &y& Elsevier]

Abstract: We assess the role of septic systems as potential nitrogen (N) sources to coastal open water bodies. To quantify the potential role of septic tanks, we document the distribution pattern and functionality of septic tanks in McIntosh County in Georgia, USA, and examine factors governing the mitigation of septic N loading in coastal groundwater. Employing a field calibrated 2D variable-density reaction-transport model, we focus on the role of setback distance of a leaky septic source from the receiving surface waters, on transport and biogeochemical characteristics of the subsurface environment, and on leachate composition and reactivity. We conclude that the removal of bioavailable nitrogen via denitrification may be increased by increasing the septic system setback distance, in particular in brackish and saline coastal settings where sulfide produced in sulfate reduction can limit N2 production. [Copyright &y& Elsevier]

We estimate the SH-wave velocity and attenuation structures of the western US upper mantle using the dense network of the USArray and new techniques: we observe a multiple-frequency data set of both traveltime and amplitude anomalies, and interpret these with full 3-D finite-frequency sensitivity kernels. Amplitudes show stronger frequency dependence than traveltimes. We perform a joint inversion on the measured traveltime and amplitude anomalies, interpreting them in terms of velocity and attenuation heterogeneities. Aside from the expected clear division between the slow, tectonically active region in the west and the fast craton in the east, several interesting smaller velocity anomalies are observed. The subduction along the Cascades at 100–300 km depths shows lateral discontinuity, with a ‘slab hole’ (absence of fast anomalies) observed around . The delaminated Sierra Nevada Mountains root is observed to have sunk to 200 km depth. The Yellowstone plume seems to have an origin (weak slow velocity anomalies) near 1000 km depth, but the plume conduit seems to be interrupted by a fast anomaly, which is identified as a fragment of the Farallon slab. The S-velocity model shows a trench-perpendicular ‘slab gap’ (absence of fast anomalies) at almost the same location as in the P model recently published by Sigloch et al. (2008) . The methodological improvements described in the first paragraph have several benefits. Amplitude data help to sharpen the edges of narrow velocity heterogeneities in the shallow upper mantle. The focusing effect from velocity heterogeneity dominates over that of attenuation and must be considered when interpreting amplitude anomalies. In general, velocity and attenuation heterogeneities correlate positively, suggesting that temperature plays a major role in forming the anomalies. [ABSTRACT FROM AUTHOR]

The National Institute for Occupational Safety and Health and the Environmental Protection Agency sponsored the completion of an interlaboratory study to compare two fitting protocols specified by ANSI S12.6-1997 (R2002) [(2002). American National Standard Methods for the Measuring Real-Ear Attenuation of Hearing Protectors, American National Standards Institute, New York]. Six hearing protection devices (two earmuffs, foam, premolded, custom-molded earplugs, and canal-caps) were tested in six laboratories using the experimenter-supervised, Method A, and (naïve) subject-fit, Method B, protocols with 24 subjects per laboratory. Within-subject, between-subject, and between-laboratory standard deviations were determined for individual frequencies and A-weighted attenuations. The differences for the within-subject standard deviations were not statistically significant between Methods A and B. Using between-subject standard deviations from Method A, 3–12 subjects would be required to identify 6-dB differences between attenuation distributions. Whereas using between-subject standard deviations from Method B, 5–19 subjects would be required to identify 6-dB differences in attenuation distributions of a product tested within the same laboratory. However, the between-laboratory standard deviations for Method B were -0.1 to 3.0 dB less than the Method A results. These differences resulted in considerably more subjects being required to identify statistically significant differences between laboratories for Method A (12–132 subjects) than for Method B (9–28 subjects). [ABSTRACT FROM AUTHOR]

Ultrawideband (UWB) is defined by the Federal Communications Commission (FCC) for short-range high-capacity wireless communications. We propose and numerically demonstrate a novel scheme of all-optical UWB pulse generation based on parametric processes in cascaded periodically poled lithium niobate (PPLN) waveguides. The commonly used UWB pulses known as derivatives of the Gaussian pulse are considered to be the combination of overshoots and undershoots. As parametric amplification produces overshoots and parametric attenuation creates undershoots, it is expected that UWB pulses can be generated in the optical domain based on parametric processes. By use of sum-frequency generation (SFG) providing parametric attenuation and cascaded second-harmonic generation and difference-frequency generation (SHG + DFG) offering parametric amplification, PPLN-based UWB pulse generation is suggested and implemented. In addition to UWB monocycle and doublet, UWB triplet, quadruplet, and quintuplet are also obtained. The waveforms and radio frequency (RF) spectra of all generated UWB pulses are calculated, with the results showing that all obtained RF spectra meet the UWB definition (FCC, part 15). The operation performance is studied, indicating that the proposed PPLN-based UWB pulse generation has good stability to the UWB pulse wavelength. [ABSTRACT FROM AUTHOR]

The results of a study of the dynamics of an induced attenuation of light in optical fibers exposed to γ radiation are presented. The doses were as high as ∼10 and 100 Mrad at dose rates of ∼10 and ∼100 rad/s. Two types (silica–silica and polymer–silica) of fibers produced by INFOS (Russia), Polymicro (USA), and Hestibel (Turkey) were investigated. [ABSTRACT FROM AUTHOR]