28,226 research outputs found
Tool provides constant purge during tube welding
Tool provides a constant purge of inert gas during in-place welding of tubular components to prevent contamination and oxidation. It also permits self-jiggings of the tube and sleeve to be welded
Pre-shuttle lidar system research
Included are the results of the initial phase of a simulation study in connection with photomultiplier tubes (PMT) and associated networks and an analytical study of atmospheric physics (including multiscattering) leading to modeling studies in connection with differential absorption lidar (DIAL) observations. This effort was in support of the ER-2 aircraft DIAL projects
Remote Stratigraphic Analysis: Combined TM and AIS Results in the Wind River/bighorn Basin Area, Wyoming
An in-progress study demonstrates the utility of airborne imaging spectrometer (AIS) data for unraveling the stratigraphic evolution of a North American, western interior foreland basin. AIS data are used to determine the stratigraphic distribution of mineralogical facies that are diagnostic of specific depositional environments. After wavelength and amplitude calibration using natural ground targets with known spectral characteristics, AIS data identify calcite, dolomite, gypsum and montmorillonite-bearing strata in the Permian-Cretaceous sequence. Combined AIS and TM results illustrate the feasibility of spectral stratigraphy, remote analysis of stratigraphic sequences
Cleaning the USNO-B Catalog through automatic detection of optical artifacts
The USNO-B Catalog contains spurious entries that are caused by diffraction
spikes and circular reflection halos around bright stars in the original
imaging data. These spurious entries appear in the Catalog as if they were real
stars; they are confusing for some scientific tasks. The spurious entries can
be identified by simple computer vision techniques because they produce
repeatable patterns on the sky. Some techniques employed here are variants of
the Hough transform, one of which is sensitive to (two-dimensional)
overdensities of faint stars in thin right-angle cross patterns centered on
bright (<13 \mag) stars, and one of which is sensitive to thin annular
overdensities centered on very bright (<7 \mag) stars. After enforcing
conservative statistical requirements on spurious-entry identifications, we
find that of the 1,042,618,261 entries in the USNO-B Catalog, 24,148,382 of
them (2.3 \percent) are identified as spurious by diffraction-spike criteria
and 196,133 (0.02 \percent) are identified as spurious by reflection-halo
criteria. The spurious entries are often detected in more than 2 bands and are
not overwhelmingly outliers in any photometric properties; they therefore
cannot be rejected easily on other grounds, i.e., without the use of computer
vision techniques. We demonstrate our method, and return to the community in
electronic form a table of spurious entries in the Catalog.Comment: published in A
Precision CW laser automatic tracking system investigated
Precision laser tracker capable of tracking a low acceleration target to an accuracy of about 20 microradians rms is being constructed and tested. This laser tracking has the advantage of discriminating against other optical sources and the capability of simultaneously measuring range
Discovery of a Non-Thermal Galactic Center Filament (G358.85+0.47) Parallel to the Galactic Plane
We report the discovery of a new non-thermal filament, G358.85+0.47, the
``Pelican'', located ~225 pc in projection from SgrA, and oriented parallel to
the Galactic plane. VLA continuum observations at 20 cm reveal that this 7'
(17.5 pc) structure bends at its northern extension and is comprised of
parallel strands, most apparent at its ends. Observations at 6 and 3.6 cm
reveal that the Pelican is a synchrotron-emitting source and is strongly
linearly polarized over much of its extent. The spectral index of the filament
changes from alpha(20/6)=-0.8 to alpha(6/3.6)=-1.5. The rotation measures
exhibit a smooth gradient, with values ranging from -1000 rad/m2 to +500
rad/m2. The intrinsic magnetic field is well-aligned along the length of the
filament. Based on these properties, we classify the Pelican as one of the
non-thermal filaments unique to the Galactic center. Since these filaments
(most of which are oriented perpendicular to the Galactic plane) are believed
to trace the overall magnetic field in the inner Galaxy, the Pelican is the
first detection of a component of this field parallel to the plane. The Pelican
may thus mark a transition region of the magnetic field orientation in the
inner kiloparsec of the Galaxy.Comment: 6 pages, 4 figures, to appear in ApJ Letters; Figs. 2 & 3 are color
.ps files and best viewed in colo
Determining ethylene group disorder levels in -(BEDT-TTF)Cu[N(CN)]Br
We present a detailed structural investigation of the organic superconductor
-(BEDT-TTF)Cu[N(CN)]Br at temperatures from 9 to 300 K.
Anomalies in the dependence of the lattice parameters are associated with a
glass-like transition previously reported at = 77 K. From structure
refinements at 9, 100 and 300 K, the orthorhombic crystalline symmetry, space
group {\it Pnma}, is established at all temperatures. Further, we extract the
dependence of the occupation factor of the eclipsed conformation of the
terminal ethylene groups of the BEDT-TTF molecule. At 300 K, we find 67(2) %,
with an increase to 97(3) % at 9 K. We conclude that the glass-like transition
is not primarily caused by configurational freezing-out of the ethylene groups
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