3,250 research outputs found
HI Observations Towards the Sagittarius Dwarf Spheroidal Galaxy
We have measured the 21-cm line of Galactic HI over more than 50 square
degrees in the direction of the Sagittarius dwarf spheroidal galaxy. The data
show no evidence of HI associated with the dwarf spheroidal which might be
consider analogous to the Magellanic Stream as it is associated in both
position and velocity with the Large Magellanic Cloud. Nor do the HI data show
evidence for any disturbance in the Milky Way disk gas that can be
unambiguously assigned to interaction with the dwarf galaxy. The data shown
here limit the HI mass at the velocity of the Sagittarius dwarf to <7000 solar
masses over some 18 square degrees between Galactic latitudes -13 degrees and
-18 degrees.Comment: 5 pages, 4 figures; accepted for publication in Astronomy &
Astrophysic
Charm Meson Mixing: An Experimental Review
We review current experimental results on charm mixing and CP violation. We
survey experimental techniques, including time-dependent, time-independent, and
quantum-correlated measurements. We review techniques that use a slow pion tag
from D*+ --> pi+ D0 + c.c. decays and those that do not, and cover two-body and
multi-body D0 decay modes. We provide a summary of D-mixing results to date and
comment on future experimental prospects at the LHC and other new or planned
facilities.Comment: 53 pages, 29 figures, 8 table
Global properties of the HI distribution in the outer Milky Way
Aims: We derive the 3-D HI volume density distribution for the Galactic disk
out to R = 60 kpc. Methods: Our analysis is based on parameters for the warp
and rotation curve derived previously. The data are taken from the
Leiden/Argentine/Bonn all sky 21-cm line survey. Results: The Milky Way HI disk
is significantly warped but shows a coherent structure out to R = 35 kpc. The
radial surface density distribution, the densities in the middle of the warped
plane, and the HI scale heights all follow exponential relations. The radial
scale length for the surface density distribution of the HI disk is 3.75 kpc.
Gas at the outskirts for 40 < R < 60 kpc is described best by a distribution
with an exponential radial scale length of 7.5 kpc and a velocity dispersion of
74 km/s. Such a highly turbulent medium fits also well with the average shape
of the high velocity profile wings observed at high latitudes. The turbulent
pressure gradient of such extra-planar gas is on average in balance with the
gravitational forces. About 10% of the Milky Way HI gas is in this state. The
large scale HI distribution is lopsided; for R < 15 kpc there is more gas in
the south. The HI flaring indicates that this asymmetry is caused by a dark
matter wake, located at R = 25 kpc in direction of the Magellanic System.
Conclusions: The HI disk is made up of two major components. Most prominent is
the normal HI disk which can be traced to R = 35 kpc. This is surrounded by a
patchy distribution of highly turbulent gas reaching large scale heights but
also large radial distances. At the position of the Sun the exponential scale
height in the z direction is 3.9 kpc. This component resembles the anomalous
gas discovered previously in some galaxies.Comment: to be published in A&
Fluctuations and massive separation in three-dimensional shock-wave/boundary-layer interactions
Shock-wave unsteadiness was observed in rapidly compressed supersonic turbulent boundary layer flows with significant separation. A Mach 2.85 shock-wave/turbulent boundary layer flow was set up over a series of cylinder-flare bodies in the High Reynolds Number Channel 1. The transition from fully attached to fully separated flow was studied using axisymmetric flares with increasing compression angles. In the second phase, the 30 deg flare was inclined relative to the cylinder axis, so that the effect on a separated flow of increasing 3 dimensionality could be observed. Two 3-D separated cases are examined. A simple conditional sampling technique is applied to the data to group them according to an associated shock position. Mean velocities and turbulent kinetic energies, computed from the conditionally samples data, are compared to those from the unsorted data and to computed values. Three basic questions were addressed: can conditional sampling be used to provide snapshots of the flow; are averaged turbulence quantities dominated by the bimodal nature of the interaction; and is the shock unsteadiness really important to computational accuracy
Heat transfer tests of an 0.006-scale thin-skin space shuttle model (41-OTS) in the Ames 3.5-foot HWT at M equals 5.3 (IH15)
Data obtained from heat transfer tests of an 0.006-scale space shuttle vehicle in a 3.5-foot hypersonic wind tunnel are presented. The purpose of these tests was to parametrically investigate the ascent heating of the integrated vehicle. Configurations tested were complete for integrated vehicle, orbiter alone, external tank alone, and SRB alone. All configurations were tested with and without transition grit. Testing was conducted at a Mach number of 5.3, and at Reynolds numbers of 2 and 5 million per foot. The angle of attack range varied from 0 to minus 5 degress, execpt for SRB alone, which was tested from minus 5 to 90 degrees. Heat transfer data were obtained from 223 iron-constantan thermocouples attached to thin-skin stainless steel inserts
Effects Of Post-Deposition Annealing Temperature And Time On Physical Properties Of Metal-Organic Decomposed Lanthanum Cerium Oxide Thin Film.
Lanthanum cerium oxide (LaxCeyOz) precursor was prepared using metal-organic decomposition method. The effects of post-deposition annealing temperatures (400-1000 °C) and annealing time (15-120 minutes) in argon ambient on physical properties of the deposited film were investigated
Heat transfer test of an 0.006-scale thin-skin thermocouple space shuttle model (50-0, 41-T) in the NASA-Ames Research Center 3.5-foot hypersonic wind tunnel at Mach 5.3 (IH28), volume 1
Data obtained from a heat transfer test conducted on an 0.006-scale space shuttle orbiter and external tank in the NASA-Ames Research Center 3.5-foot Hypersonic Wind Tunnel are presented. The purpose of this test was to obtain data under simulated return-to-launch-site abort conditions. Configurations tested were integrated orbiter and external tank, orbiter alone, and external tank alone at angles of attack of 0, + or - 30, + or - 60, + or - 90, and + or - 120 degrees. Runs were conducted at Mach numbers of 5.2 and 5.3 for Reynolds numbers of 1.0 and 4.0 million per foot, respectively. Heat transfer data were obtained from 75 orbiter and 75 external tank iron-constantan thermocouples
Thermal protection system gap heating rates of the Rockwell International flat plate heat transfer model (OH2A/OH2B)
Heat transfer data for the Rockwell International Flat Plate Thermocouple Model are presented. The model simulated the Space Shuttle Vehicle Thermal Protection System. Data were recorded for locations in and around various size gaps for various gap orientation configurations. The test was conducted at Mach 5.1 for free-stream Reynolds number per foot values from 500,000 to 1,500,000
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