3,728 research outputs found
Evaluation of dissociated and steam-reformed methanol as automotive engine fuels
Dissociated and steam reformed methanol were evaluated as automotive engine fuels. Advantages and disadvantages in using methanol in the reformed rather than liquid state were discussed. Engine dynamometer tests were conducted with a four cylinder, 2.3 liter, spark ignition automotive engine to determine performance and emission characteristics operating on simulated dissociated and steam reformed methanol (2H2 + CO and 3H2 + CO2 respectively), and liquid methanol. Results are presented for engine performance and emissions as functions of equivalence ratio, at various throttle settings and engine speeds. Operation on dissociated and steam reformed methanol was characterized by flashback (violent propagation of a flame into the intake manifold) which limited operation to lower power output than was obtainable using liquid methanol. It was concluded that: an automobile could not be operated solely on dissociated or steam reformed methanol over the entire required power range - a supplementary fuel system or power source would be necessary to attain higher powers; the use of reformed mechanol, compared to liquid methanol, may result in a small improvement in thermal efficiency in the low power range; dissociated methanol is a better fuel than steam reformed methanol for use in a spark ignition engine; and use of dissociated or steam reformed methanol may result in lower exhaust emissions compared to liquid methanol
Long-life mission reliability for outer planet atmospheric entry probes
The results of a literature analysis on the effects of prolonged exposure to deep space environment on the properties of outer planet atmospheric entry probe components are presented. Materials considered included elastomers and plastics, pyrotechnic devices, thermal control components, metal springs and electronic components. The rates of degradation of each component were determined and extrapolation techniques were used to predict the effects of exposure for up to eight years to deep space. Pyrotechnic devices were aged under accelerated conditions to an equivalent of eight years in space and functionally tested. Results of the literature analysis of the selected components and testing of the devices indicated that no severe degradation should be expected during an eight year space mission
Absorption Line Survey of H3+ toward the Galactic Center Sources III. Extent of the Warm and Diffuse Clouds
We present follow-up observations to those of Geballe & Oka (2010), who found
high column densities of H3+ ~100 pc off of the Galactic center (GC) on the
lines of sight to 2MASS J17432173-2951430 (J1743) and 2MASS J17470898-2829561
(J1747). The wavelength coverages on these sightlines have been extended in
order to observe two key transitions of H3+, R(3,3)l and R(2,2)l, that
constrain the temperatures and densities of the environments. The profiles of
the H3+ R(3,3)l line, which is due only to gas in the GC, closely matches the
differences between the H3+ R(1,1)l and CO line profiles, just as it does for
previously studied sightlines in the GC. Absorption in the R(2,2)l line of H3+
is present in J1747 at velocities between -60 and +100 km/s. This is the second
clear detection of this line in the interstellar medium after GCIRS 3 in the
Central Cluster. The temperature of the absorbing gas in this velocity range is
350 K, significantly warmer than in the diffuse clouds in other parts of the
Central Molecular Zone. This indicates that the absorbing gas is local to Sgr B
molecular cloud complex. The warm and diffuse gas revealed by Oka et al. (2005)
apparently extends to ~100 pc, but there is a hint that its temperature is
somewhat lower in the line of sight to J1743 than elsewhere in the GC. The
observation of H3+ toward J1747 is compared with the recent Herschel
observation of H2O+ toward Sgr B2 and their chemical relationship and
remarkably similar velocity profiles are discussed.Comment: 6 pages, 3 figures, 2 tables, Accepted for publication in
Publications of the Astronomical Society of Japa
The Interstellar Medium of IRAS 08572+3915 NW: H3+ and Warm High Velocity CO
We confirm the first detection of the molecular ion H3+ in an extragalactic
object, the highly obscured ultraluminous galaxy IRAS 08572+3915 NW. We also
have detected absorption lines of the fundamental band of CO in this galaxy.
The CO absorption consists of a cold component close to the systemic velocity
and warm, highly blueshifted and redshifted components. The warm blueshifted
component is remarkably strong and broad and extends at least to -350 km/s.
Some analogies can be drawn between the H3+ and cold CO in IRAS08572+3915 NW
and the same species seen toward the Galactic center. The profiles of the warm
CO components are not those expected from a dusty torus of the type thought to
obscure active galactic nuclei. They are probably formed close to the dust
continuum surface near the buried and active nucleus and are probably
associated with an unusual and energetic event there.Comment: 21 pages, 4 postscript figures, accepted by Ap
Polarimetry of the Type Ia Supernova SN 1996X
We present broad-band and spectropolarimetry of the Type Ia SN 1996X obtained
on April 14, 1996 (UT), and broad-band polarimetry of SN 1996X on May 22,1996,
when the supernova was about a week before and 4 weeks after optical maximum,
respectively. The Stokes parameters derived from the broad-band polarimetry are
consistent with zero polarization. The spectropolarimetry, however, shows broad
spectral features which are due intrinsically to an asymmetric SN atmosphere.
The spectral features in the flux spectrum and the polarization spectrum show
correlations in the wavelength range from 4900 AA up to 5500 AA. The degree of
this intrinsic component is low (<0.3 %). Theoretical polarization spectra have
been calculated. It is shown that the polarization spectra are governed by line
blending. Consequently, for similar geometrical distortions, the residual
polarization is smaller by about a factor of 2 to 3 compared to the less
blended Type II atmosphere, making it intrinsically harder to detect
asphericities in SNIa. Comparison with theoretical model polarization spectra
shows a resemblance to the observations. Taken literally, this implies an
asphericity of about 11 % in the chemical distribution in the region of partial
burning. This may not imperil the use of Type Ia supernovae as standard candles
for distance determination, but nontheless poses a source of uncertainty. SN
1996X is the first Type Ia supernova for which spectropolarimetry revealed a
polarized component intrinsic to the supernova and the first Type Ia with
spectropolarimetry well prior to optical maximum.Comment: 7 pages, 5 figures, macros 'aas2pp4.sty,psfig.tex'. LaTeX Style.
Astrophysical Journal Letters, submitted September 199
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