5,656 research outputs found
Solid propellant rocket motor
The characteristics of a solid propellant rocket engine with a controlled rate of thrust buildup to a desired thrust level are discussed. The engine uses a regressive burning controlled flow solid propellant igniter and a progressive burning main solid propellant charge. The igniter is capable of operating in a vacuum and sustains the burning of the propellant below its normal combustion limit until the burning propellant surface and combustion chamber pressure have increased sufficiently to provide a stable chamber pressure
CC125 Chemical Drying Sprays as an Aid for Seed Production
Extension Circular CC125 This circular is about using chemical drying sprays as an aid for seed production
CC125 Chemical Drying Sprays as an Aid for Seed Production
Extension Circular CC125 This circular is about using chemical drying sprays as an aid for seed production
Comparison of the COBE FIRAS and DIRBE Calibrations
We compare the independent FIRAS and DIRBE observations from the COBE in the
wavelength range 100-300 microns. This cross calibration provides checks of
both data sets. The results show that the data sets are consistent within the
estimated gain and offset uncertainties of the two instruments. They show the
possibility of improving the gain and offset determination of DIRBE at 140 and
240 microns.Comment: Accepted for publication in the Astrophysical Journal 11 pages, plus
3 figures in separate postscript files. Figure 3 has three part
Measuring Molecular, Neutral Atomic, and Warm Ionized Galactic Gas Through X-Ray Absorption
We study the column densities of neutral atomic, molecular, and warm ionized
Galactic gas through their continuous absorption of extragalactic X-ray spectra
at |b| > 25 degrees. For N(H,21cm) < 5x10^20 cm^-2 there is an extremely tight
relationship between N(H,21cm) and the X-ray absorption column, N(xray), with a
mean ratio along 26 lines of sight of N(xray)/N(H,21cm) = 0.972 +- 0.022. This
is significantly less than the anticpated ratio of 1.23, which would occur if
He were half He I and half He II in the warm ionized component. We suggest that
the ionized component out of the plane is highly ionized, with He being mainly
He II and He III. In the limiting case that H is entirely HI, we place an upper
limit on the He abundance in the ISM of He/H <= 0.103.
At column densities N(xray) > 5x10^20 cm^-2, which occurs at our lower
latitudes, the X-ray absorption column N(xray) is nearly double N(H,21cm). This
excess column cannot be due to the warm ionized component, even if He were
entirely He I, so it must be due to a molecular component. This result implies
that for lines of sight out of the plane with |b| ~ 30 degrees, molecular gas
is common and with a column density comprable to N(H,21cm).
This work bears upon the far infrared background, since a warm ionized
component, anticorrelated with N(H,21cm), might produce such a background. Not
only is such an anticorrelation absent, but if the dust is destroyed in the
warm ionized gas, the far infrared background may be slightly larger than that
deduced by Puget et al. (1996).Comment: 1 AASTeX file, 14 PostScript figure files which are linked within the
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Synthesis and electronic properties of Ruddlesden-Popper strontium iridate epitaxial thin films stabilized by control of growth kinetics
We report on the selective fabrication of high-quality SrIrO and
SrIrO epitaxial thin films from a single polycrystalline SrIrO
target by pulsed laser deposition. Using a combination of X-ray diffraction and
photoemission spectroscopy characterizations, we discover that within a
relatively narrow range of substrate temperature, the oxygen partial pressure
plays a critical role in the cation stoichiometric ratio of the films, and
triggers the stabilization of different Ruddlesden-Popper (RP) phases. Resonant
X-ray absorption spectroscopy measurements taken at the Ir -edge and the O
-edge demonstrate the presence of strong spin-orbit coupling, and reveal the
electronic and orbital structures of both compounds. These results suggest that
in addition to the conventional thermodynamics consideration, higher members of
the SrIrO series can possibly be achieved by kinetic
control away from the thermodynamic limit. These findings offer a new approach
to the synthesis of ultra-thin films of the RP series of iridates and can be
extended to other complex oxides with layered structure.Comment: 7 pages, 6 figure
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