Free-piston Stirling engine conceptual design and technologies for space power, phase 1

As part of the SP-100 program, a phase 1 effort to design a free-piston Stirling engine (FPSE) for a space dynamic power conversion system was completed. SP-100 is a combined DOD/DOE/NASA program to develop nuclear power for space. This work was completed in the initial phases of the SP-100 program prior to the power conversion concept selection for the Ground Engineering System (GES). Stirling engine technology development as a growth option for SP-100 is continuing after this phase 1 effort. Following a review of various engine concepts, a single-cylinder engine with a linear alternator was selected for the remainder of the study. The relationships of specific mass and efficiency versus temperature ratio were determined for a power output of 25 kWe. This parametric study was done for a temperature ratio range of 1.5 to 2.0 and for hot-end temperatures of 875 K and 1075 K. A conceptual design of a 1080 K FPSE with a linear alternator producing 25 kWe output was completed. This was a single-cylinder engine designed for a 62,000 hour life and a temperature ratio of 2.0. The heat transport systems were pumped liquid-metal loops on both the hot and cold ends. These specifications were selected to match the SP-100 power system designs that were being evaluated at that time. The hot end of the engine used both refractory and superalloy materials; the hot-end pressure vessel featured an insulated design that allowed use of the superalloy material. The design was supported by the hardware demonstration of two of the component concepts - the hydrodynamic gas bearing for the displacer and the dynamic balance system. The hydrodynamic gas bearing was demonstrated on a test rig. The dynamic balance system was tested on the 1 kW RE-1000 engine at NASA Lewis

Self-awareness of driving impairment in patients with cataract or glaucoma

This study compared the driving performance of individuals with the eye diseases cataracts or glaucoma with age-matched controls, as well as the individual’s own perceptions of driving. Participants included drivers over the age of 50 years who had been diagnosed with glaucoma (n=29) or cataracts (n=33) and a control group with no ocular pathology (n=13). Driving performance was measured on a closed road circuit using a range of standardised measures of vehicle control and hazard recognition and avoidance, while visual performance was measured with a battery of tests including visual acuity, contrast sensitivity and visual fields. Perceptions of vision and driving were assessed using the Activities of Daily Vision Scale, Driver Behaviour Questionnaire and a driving exposure questionnaire. Driving performance was significantly poorer (p<0.05) for each of the ocular disease groups compared to the control group. Impaired contrast sensitivity and the higher disease severity scores (for the glaucoma group only) correlated most strongly with poorer driving performance. While participants with cataracts rated their vision significantly more poorly than those in the glaucoma and control groups, there were no significant differences between the participant groups rating of their own driving performance. These findings suggest that there is no direct relationship between self-rated driving ability and actual vision and driving performance. This has serious road safety implications

The Behaviour of Crude Oil Spilled on Snow

Field and laboratory studies of the behavior of isothermal and hot oil spills on snow are described. Alberta crude oil spilled at 0&deg; C is readily absorbed by snow and contaminates an area of about 0.01 square metres per litre. A hot oil spill melts a channel in the snow and flows along the ground under the snow contaminating an area of about 0.024 square metres per litre. There may be considerable spreading of the oil during thaw. The flow regimes by which oil permeates into snow and the clean-up implications are discussed

X-ray photoelectron spectroscopic and Raman microscopic investigation of the variscite group minerals: variscite, strengite, scorodite and mansfieldite

Several structurally related AsO and PO minerals, were studied with Raman microscopy and X-ray Photoelectron Spectroscopy (XPS). XPS revealed only Fe, As and O for scorodite. The Fe 2p, As 3d, and O 1s indicated one position for Fe, while 2 different environments for O and As were observed. The O 1s at 530.3\ua0eV and the As 3d 5/2 at 43.7\ua0eV belonged to AsO, while minor bands for O 1s at 531.3\ua0eV and As 3d 5/2 at 44.8\ua0eV were due to AsO groups exposed on the surface possibly forming OH-groups. Mansfieldite showed, besides Al, As and O, a trace of Co. The PO equivalent of mansfieldite is variscite. The change in crystal structure replacing As with P resulted in an increase in the binding energy (BE) of the Al 2p by 2.9\ua0eV. The substitution of Fe for Al in the structure of strengite resulted in a Fe 2p at 710.8\ua0eV. An increase in the Fe 2p BE of 4.8\ua0eV was found between mansfieldite and strengite. The scorodite Raman OH-stretching region showed a sharp band at 3513\ua0cm and a broad band around 3082\ua0cm. The spectrum of mansfieldite was like that of scorodite with a sharp band at 3536\ua0cm and broader maxima at 3100\ua0cm and 2888\ua0cm. Substituting Al in the arsenate structure instead of Fe resulted in a shift of the metal-OH-stretching mode by 23\ua0cm towards higher wavenumbers due to a slightly longer H-bonding in mansfieldite compared to scorodite. The intense band for scorodite at 805\ua0cm was ascribed to the symmetric stretching mode of the AsO. The medium intensity bands at 890, 869, and 830\ua0cm were ascribed to the internal modes. A significant shift towards higher wavenumbers was observed for mansfieldite. The strengite Raman spectrum in the 900–1150\ua0cm shows a strong band at 981\ua0cm accompanied by a series of less intense bands. The 981\ua0cm band was assigned to the PO symmetric stretching mode, while the weak band at 1116\ua0cm was the corresponding antisymmetric stretching mode. The remaining bands at 1009, 1023 and 1035\ua0cm were assigned to υ(A) internal modes in analogy to the interpretation of the AsO bands for scorodite and mansfieldite. The variscite spectrum showed a shift towards higher wavenumbers in comparison to the strengite spectrum with the strongest band observed at 1030\ua0cm and was assigned to the symmetric stretching mode of the PO, while the corresponding antisymmetric stretching mode was observed at 1080\ua0cm. Due to the band splitting component bands were observed at 1059, 1046, 1013 and 940\ua0cm. The AsO symmetric bending modes for scorodite were observed at 381 and 337\ua0cm, while corresponding antisymmetric bending modes occurred at 424, 449 and 484\ua0cm. Comparison with other arsenate and phosphate minerals showed that both XPS and Raman spectroscopy are fast and non-destructive techniques to identify these minerals based on their differences in chemistry and the arsenate/phosphate vibrational modes due to changes in the symmetry and the unique fingerprint region of the lattice modes

X-ray Photoelectron spectroscopic and Raman spectroscopic study of bayldonite from Wheal Carpenter, Cornwall, UK

Bayldonite [CuPb(AsO)(OH)], Wheal Carpenter (Cornwall, UK) was studied by X-ray Photoelectron Spectroscopy and Raman Microscopy. X-ray Photoelectron Spectroscopy revealed single copper, lead and arsenic positions in the crystal structure. Two oxygen bands with a 1:4 ratio were associated oxygen positions in arsenate- and hydroxyl-groups, excluding the presence of acidic arsenate groups. The relatively large difference in binding energy for the two oxygen bands was interpreted as being due to the dynamic Jahn-Teller distortion of the copper octahedral in the bayldonite crystal structure. Raman microscopy showed bands at 804 and 837\ua0cm assigned to arsenate antisymmetric stretching mode and the symmetric stretching mode. Supported by the X-ray Photoelectron Spectroscopic results the bands at 726, 761, 822 and 886\ua0cm were assigned to copper-hydroxyl modes. Bands around 497\ua0cm were assigned to the arsenate antisymmetric bending modes and around 427\ua0cm to the symmetric bending modes. The 539\ua0cm band was associated with a copper-hydroxyl stretching mode or another υ. The region 250–400\ua0cm showed sharp bands at 313 and 328\ua0cm with weaker bands at 298 and 342\ua0cm assigned to copper-oxygen and/or lead-oxygen stretching modes

Free-Piston Stirling Power Conversion Unit for Fission Surface Power, Phase I Final Report

This report summarizes the design of a 12 kW dual opposed free-piston Stirling convertor and controller for potential future use in space missions. The convertor is heated via a pumped NaK loop and cooling is provided by a pumped water circuit. Convertor efficiency is projected at 27 percent (AC electrical out/heat in). The controller converts the AC electrical output to 120 Vdc and is projected at 91 percent efficiency. A mechanically simple arrangement, based on proven technology, was selected in which the piston is resonated almost entirely by the working space pressure swing, while the displacer is resonated by planar mechanical springs in the bounce space

Intercomparison of field measurements of nitrous acid (HONO) during the SHARP campaign

Because of the importance of HONO as a radical reservoir, consistent and accurate measurements of its concentration are needed. As part of SHARP (Study of Houston Atmospheric Radical Precursors), time series of HONO were obtained by six different measurement techniques on the roof of the Moody Tower at the University of Houston. Techniques used were long path differential optical absorption spectroscopy (DOAS), stripping coil-visible absorption photometry (SC-AP), long path absorption photometry (LOPAP® ), mist chamber/ion chromatography (MC-IC), quantum cascade-tunable infrared laser differential absorption spectroscopy (QC-TILDAS), and ion drift-chemical ionization mass spectrometry (ID-CIMS). Various combinations of techniques were in operation from 15 April through 31 May 2009. All instruments recorded a similar diurnal pattern of HONO concentrations with higher median and mean values during the night than during the day. Highest values were observed in the final 2 weeks of the campaign. Inlets for the MC-IC, SC-AP, and QC-TILDAS were collocated and agreed most closely with each other based on several measures. Largest differences between pairs of measurements were evident during the day for concentrations ~100 parts per trillion (ppt). Above ~ 200 ppt, concentrations from the SC-AP, MC-IC, and QC-TILDAS converged to within about 20%, with slightly larger discrepancies when DOAS was considered. During the first 2 weeks, HONO measured by ID-CIMS agreed with these techniques, but ID-CIMS reported higher values during the afternoon and evening of the final 4 weeks, possibly from interference from unknown sources. A number of factors, including building related sources, likely affected measured concentrations