1,318 research outputs found
Range safety signal propagation through the SRM exhaust plume of the space shuttle
Theoretical predictions of plume interference for the space shuttle range safety system by solid rocket booster exhaust plumes are reported. The signal propagation was calculated using a split operator technique based upon the Fresnel-Kirchoff integral, using fast Fourier transforms to evaluate the convolution and treating the plume as a series of absorbing and phase-changing screens. Talanov's lens transformation was applied to reduce aliasing problems caused by ray divergence
Discovery of orbital decay in SMC X-1
The results are reported of three observations of the binary X ray pulsar SMC X-1 with the Ginga satellite. Timing analyses of the 0.71 s X ray pulsations yield Doppler delay curves which, in turn, provide the most accurate determination of the SMC X-1 orbital parameters available to date. The orbital phase of the 3.9 day orbit is determined in May 1987, Aug. 1988, and Aug. 1988 with accuracies of 11, 1, and 3.5 s, respectively. These phases are combined with two previous determinations of the orbital phase to yield the rate of change in the orbital period: P sub orb/P sub orb = (-3.34 + or - 0.023) x 10(exp -6)/yr. An interpretation of this measurement and the known decay rate for the orbit of Cen X-3 is made in the context of tidal evolution. Finally, a discussion is presented of the relation among the stellar evolution, orbital decay, and neutron star spinup time scales for the SMC X-1 system
Stoichiometry, structure, and transport in the quasi-one-dimensional metal, Li(0.9)Mo(6)O(17)
A correlation between lattice parameters, oxygen composition, and the
thermoelectric and Hall coefficients is presented for single-crystal
Li(0.9)Mo(6)O(17), a quasi-one-dimensional (Q1D) metallic compound. The
possibility that this compound is a compensated metal is discussed in light of
a substantial variability observed in the literature for these transport
coefficients.Comment: 5 pages, 4 Figures; Phys. Rev. B (in press
Multiple case-study analysis of quality management practices within UK Six Sigma and non-Six Sigma manufacturing small- and medium-sized enterprises
This paper examines multiple case-study analysis of quality management practices within UK Six Sigma and non-Six Sigma manufacturing small- and medium-sized enterprises
The 2008 Mars Phoenix Lander Thermal and Evolved Gas Analyzer (TEGA) Dataset: Placing Easily Interpretable Evolved Gas Data on the Planetary Data System (PDS)
The Phoenix Scout Lander mission investigated the north polar region of Mars in 2008 with the goal to study the history of water, assess the past/present Martian climate, search for organics, and evaluate the potential for past/present microbial habit-ability on Mars. To accomplish this goal, the Phoenix Landers Thermal and Evolved-Gas Analyzer (TEGA) instrument assessed the gas composition of the Martian atmosphere and evaluated the mineralogy of the Martian regolith. The TEGA instrument consisted of eight small ovens connected to a 4 channel magnetic sector mass spectrometer. The ovens heated soil samples from ambient to 1000C where the gases (e.g., H2O, CO2, etc.) evolved from thermal decomposition of mineral phases were analyzed by the mass spectrometer. Minerals thermally decomposed at characteristic temperatures and the evolving gases indicated the presence of perchlorate, carbonate, and hydrated phases in the Phoenix landing site soils
MITO measurements of the Sunyaev-Zeldovich Effect in the Coma cluster of galaxies
We have measured the Sunyaev-Zeldovich effect towards the Coma cluster
(A1656) with the MITO experiment, a 2.6-m telescope equipped with a 4-channel
17 arcminute (FWHM) photometer. Measurements at frequency bands 143+/-15,
214+/-15, 272+/-16 and 353+/-13 GHz, were made during 120 drift scans of Coma.
We describe the observations and data analysis that involved extraction of the
S-Z signal by employing a spatial and spectral de-correlation scheme to remove
a dominant atmospheric component. The deduced values of the thermal S-Z effect
in the first three bands are DT_{0} = -179+/-38,-33+/-81,170+/-35 microKelvin
in the cluster center. The corresponding optical depth, tau=(4.1+/-0.9)
10^{-3}, is consistent (within errors) with both the value from a previous low
frequency S-Z measurement, and the value predicted from the X-ray deduced gas
parameters.Comment: Ap.J.Letters accepted, 4 pages, 2 figure
Predicting the Starquakes in PSR J0537-6910
We report on more than 7 years of monitoring of PSR J0537-6910, the 16 ms
pulsar in the Large Magellanic Cloud, using data acquired with the RXTE. During
this campaign the pulsar experienced 23 sudden increases in frequency
(``glitches'') amounting to a total gain of over six ppm of rotation frequency
superposed on its gradual spindown of d(nu)/d(t) = -2e-10 Hz/s. The time
interval from one glitch to the next obeys a strong linear correlation to the
amplitude of the first glitch, with a mean slope of about 400 days ppm (6.5
days per uHz), such that these intervals can be predicted to within a few days,
an accuracy which has never before been seen in any other pulsar. There appears
to be an upper limit of ~40 uHz for the size of glitches in_all_ pulsars, with
the 1999 April glitch of J0537 as the largest so far. The change in the
spindown of J0537 across the glitches, Delta(d(nu)/d(t)), appears to have the
same hard lower limit of -1.5e-13 Hz/s, as, again, that observed in all other
pulsars. The spindown continues to increase in the long term,
d(d(nu)/d(t))/d(t) = -1e-21 Hz/s/s, and thus the timing age of J0537 (-0.5 nu
d(nu)/d(t)) continues to decrease at a rate of nearly one year every year,
consistent with movement of its magnetic moment away from its rotational axis
by one radian every 10,000 years, or about one meter per year. J0537 was likely
to have been born as a nearly-aligned rotator spinning at 75-80 Hz, with a
|d(nu)/d(t)| considerably smaller than its current value of 2e-10 Hz/s. The
pulse profile of J0537 consists of a single pulse which is found to be flat at
its peak for at least 0.02 cycles.Comment: 54 pages, 12 figures. Accepted for publication in The Astrophysical
Journal. Cleaner figure 2. V4 -- in line with version accepted by Ap
Pulsar Constraints on Neutron Star Structure and Equation of State
With the aim of constraining the structural properties of neutron stars and
the equation of state of dense matter, we study sudden spin-ups, glitches,
occurring in the Vela pulsar and in six other pulsars. We present evidence that
glitches represent a self-regulating instability for which the star prepares
over a waiting time. The angular momentum requirements of glitches in Vela
indicate that at least 1.4% of the star's moment of inertia drives these
events. If glitches originate in the liquid of the inner crust, Vela's
`radiation radius' must exceed ~12 km for a mass of 1.4 solar masses.
Observational tests of whether other neutron stars obey this constraint will be
possible in the near future.Comment: 5 pages, including figures. To appear in Physical Review Letter
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