40,225 research outputs found
Thrust chamber performance using Navier-Stokes solution
The viscous, axisymmetric flow in the thrust chamber of the space shuttle main engine (SSME) was computed on the CRAY 205 computer using the general interpolants method (GIM) code. Results show that the Navier-Stokes codes can be used for these flows to study trends and viscous effects as well as determine flow patterns; but further research and development is needed before they can be used as production tools for nozzle performance calculations. The GIM formulation, numerical scheme, and computer code are described. The actual SSME nozzle computation showing grid points, flow contours, and flow parameter plots is discussed. The computer system and run times/costs are detailed
GALAH Survey: Chemically Tagging the Thick Disk
The GALAH survey targets one million stars in the southern hemisphere down to
a limiting magnitude of V = 14 at the Anglo- Australian Telescope. The project
aims to measure up to 30 elemental abundances and radial velocities (~1 km/s
accuracy) for each star at a resolution of R = 28000. These elements fall into
8 independent groups (e.g. alpha, Fe peak, r-process). For all stars, Gaia will
provide distances to 1% and transverse velocities to 1 km/s or better, giving
us a 14D set of parameters for each star, i.e. 6D phase space and 8D abundance
space. There are many scientic applications but here we focus on the prospect
of chemically tagging the thick disk and making a direct measurement of how
stellar migration evolves with cosmic time.Comment: Barcelona conference (Dec 1-5, 2014): The Milky Way Unravelled by
Gaia, eds. Soubiran, Figueras, Walton; 8 page
Large anisotropy in the optical conductivity of YNi2B2C
The optical properties of YNiBC are studied by using the
first-principles full-potential linearized augmented plane wave (FLAPW) method
within the local density approximation. Anisotropic behavior is obtained in the
optical conductivity, even though the electronic structure shows 3D character.
A large peak in is obtained at 2.4 eV. The anisotropic optical
properties are analyzed in terms of interband transitions between energy levels
and found that the Ni site plays an important role. The electronic energy loss
spectroscopy (EELS) spectra are also calculated to help elucidate the
anisotropic properties in this system.Comment: revtex4, 4 pages, 5 figures, to appear in PR
Quenching of Cross Sections in Nucleon Transfer Reactions
Cross sections for proton knockout observed in (e,e'p) reactions are
apparently quenched by a factor of ~0.5, an effect attributed to short-range
correlations between nucleons. Here we demonstrate that such quenching is not
restricted to proton knockout, but a more general phenomenon associated with
any nucleon transfer. Measurements of absolute cross sections on a number of
targets between 16O and 208Pb were analyzed in a consistent way, with the cross
sections reduced to spectroscopic factors through the distorted-wave Born
approximation with global optical potentials. Across the 124 cases analyzed
here, induced by various proton- and neutron-transfer reactions and with
angular momentum transfer l=0-7, the results are consistent with a quenching
factor of 0.55. This is an apparently uniform quenching of single-particle
motion in the nuclear medium. The effect is seen not only in (d,p) reactions
but also in reactions with A=3 and 4 projectiles, when realistic wave functions
are used for the projectiles.Comment: 5 pages, 3 figures, accepted to Physical Review Letter
Air frame drag balance Patent
Device for measuring drag forces in flight test
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