79,533 research outputs found
Geological applications of LANDSAT-1 imagery to the Great Salt Lake area
The ERTS program has been designed as a research and development tool to demonstrate that remote sensing from orbital altitudes is a feasible and practical approach to efficient management of earth resources. From this synoptic view and repetitive coverage provided by ERTS imagery of the Great Salt Lake area, large geological and structural features, trends, and patterns have been identified and mapped. A comparative analysis of lineaments observed in September and December data was conducted, existing mineral locations were plotted, and areas considered prospective for mineralization based on apparent structure-mineralization relationships were defined. The additional information obtained using ERTS data provides an added source of information to aid in the development of more effective mineral exploration programs
Operation of hydrodynamic journal bearings in sodium at temperatures to 800 deg F and speeds to 12000 rpm
Operation of hydrodynamic journal bearings in liquid sodium at high temperatures and high speed
The O(3P) and N(4S) density measurement at 225 km by ultraviolet absorption and fluorescence in the Apollo-Soyuz test project
The densities of O(3P) and N(4S) at 225 km were determined during the Apollo Soyuz Test Project by a resonance absorption/fluorescence technique in which OI and NI line radiation produced and collimated on board the Apollo was reflected from the Soyuz back to the Apollo for spectral analysis. The two spacecraft maneuvered so that a range of observation angles of plus or minus 15 deg with respect to the normal to the orbital velocity vector was scanned. The measurements were made at night on two consecutive orbits at spacecraft separations of 150 and 500 m. The resulting relative counting rates as function of observation angle were compared to calculated values to determine the oxygen value. This value agrees with mass spectrometric measurements made under similar conditions. The nitrogen value is in good agreement with other measurements and suggests a smaller diurnal variation than is predicted by present models
Multi--hump soliton--like structures in interactions of lasers and Bose--Einstein condensates
An investigation is made of multi-hump and periodic solutions of the
semi-classical coupled equations describing laser radiation copropagating with
a Bose-Einstein condensate. Solutions reminiscent of optical vector solitons
have been found and have been used to gain understanding of the dynamics
observed in the numerical simulations, in particular to shed light on the
phenomenon of jet emission from a condensate interacting with a laser.Comment: 6 pages, 4 figures; submitted to European Physics Letter
The probability density function tail of the Kardar-Parisi-Zhang equation in the strongly non-linear regime
An analytical derivation of the probability density function (PDF) tail
describing the strongly correlated interface growth governed by the nonlinear
Kardar-Parisi-Zhang equation is provided. The PDF tail exactly coincides with a
Tracy-Widom distribution i.e. a PDF tail proportional to , where is the the width of the interface. The PDF tail is
computed by the instanton method in the strongly non-linear regime within the
Martin-Siggia-Rose framework using a careful treatment of the non-linear
interactions. In addition, the effect of spatial dimensions on the PDF tail
scaling is discussed. This gives a novel approach to understand the rightmost
PDF tail of the interface width distribution and the analysis suggests that
there is no upper critical dimension.Comment: 17 pages, 2 figure
Ohmic contacts to GaAs for high-temperature device applications
Ohmic contacts to n-type GaAs were developed for high temperature device applications up to 300 C. Refractory metallizations were used with epitaxial Ge layers to form the contacts: TiW/Ge/GaAs, Ta/Ge/GaAs, Mo/Ge/GaAs, and Ni/Ge/GaAs. Contacts with high dose Si or Se ion implantation of the Ge/GaAs interface were also investigated. The contacts were fabricated on epitaxial GaAs layer grown on N+ or semi-insulating GaAs substrates. Ohmic contact was formed by both thermal annealing (at temperatures up to 700 C) and laser annealing (pulsed Ruby). Examination of the Ge/GaAs interface revealed Ge migration into GaAs to form an N+ doping layer. The specific contact resistances of specimens annealed by both methods are given
Radio Pulse Properties of the Millisecond Pulsar PSR J0437-4715. I. Observations at 20cm
We present a total of 48 minutes of observations of the nearby, bright
millisecond pulsar PSR J0437-4715 taken at the Parkes radio observatory in
Australia. The data were obtained at a central radio frequency of 1380 MHz
using a high-speed tape recorder that permitted coherent Nyquist sampling of 50
MHz of bandwidth in each of two polarizations. Using the high time resolution
available from this voltage recording technique, we have studied a variety of
single-pulse properties, most for the first time in a millisecond pulsar. We
find no evidence for "diffractive" quantization effects in the individual pulse
arrival times or amplitudes as have been reported for this pulsar at lower
radio frequency using coarser time resolution (Ables et al. 1997). Overall, we
find that the single pulse properties of PSR J0437-4715 are similar to those of
the common slow-rotating pulsars, even though this pulsar's magnetosphere and
surface magnetic field are several orders of magnitude smaller than those of
the general population. The pulsar radio emission mechanism must therefore be
insensitive to these fundamental neutron star properties.Comment: 24 Postscript pages, 11 eps figures. Accepted for publication in the
Astrophysical Journal. Abbreviated abstract follow
Superconducting Pairing Symmetries in Anisotropic Triangular Quantum Antiferromagnets
Motivated by the recent discovery of a low temperature spin liquid phase in
layered organic compound -(ET)Cu(CN) which becomes a
superconductor under pressure, we examine the phase transition of Mott
insulating and superconducting (SC) states in a Hubbard-Heisenberg model on an
anisotropic triangular lattice. We use a renormalized mean field theory to
study the Gutzwiller projected BCS wavefucntions. The half filled electron
system is a Mott insulator at large on-site repulsion , and is a
superconductor at a moderate . The symmetry of the SC state depends on the
anisotropy, and is gapful with symmetry near the
isotropic limit and is gapless with symmetry at small anisotropy
ratio.Comment: 6 pages, 5 figure
Streamlines of the Mean Stellar Motions in Elliptical Galaxies
The stellar velocity fields of elliptical galaxies hold clues to their dynamical structure and origin. The construction of velocity field models is greatly simplified by assuming an approximate geometrical form for the streamlines of the mean stellar motions. We test the conjecture that confocal streamlines are a valid approximation for realistic triaxial systems. We numerically integrate orbits in Schwarzschild's logarithmic potential, and fit confocal streamlines to their mean velocity fields by minimizing the RMS magnitude of the cross product between the velocity vectors and the streamlines. We find that most orbits at a given energy can be fitted by nearly identical confocal systems. There are statistically significant differences between the streamline parameters obtained for different orbit families, but the differences are small. The fitted parameters reproduce, to high accuracy, the boundary between short axis and outer long axis tubes, which is a direct measure of the triaxiality of the potential. These results strongly support efforts to obtain accurate statistical measurements of triaxiality from kinematic observations and reasonably simple velocity field models
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