97,216 research outputs found
Nuclear reactor descriptions for space power systems analysis
For the small, high performance reactors required for space electric applications, adequate neutronic analysis is of crucial importance, but in terms of computational time consumed, nuclear calculations probably yield the least amount of detail for mission analysis study. It has been found possible, after generation of only a few designs of a reactor family in elaborate thermomechanical and nuclear detail to use simple curve fitting techniques to assure desired neutronic performance while still performing the thermomechanical analysis in explicit detail. The resulting speed-up in computation time permits a broad detailed examination of constraints by the mission analyst
Life Science Payloads Planning Study Integration Facility Survey: Executive Summary
Analyses of proposed life science shuttle era payload operations are discussed. A summary of results from a survey conducted to: (1) examine facility and equipment resources needed for life science payload integration, checkout, test and mission support activities; (2) identify presently available resources; and (3) determine methods by which operational era status may be implemented based on currently available resources, is presented
Off-Line, Multi-Detector Intensity Interferometers II: Implications and Applications
Intensity interferometry removes the stringent requirements on mechanical
precision and atmospheric corrections that plague all amplitude interferometry
techniques at the cost of severely limited sensitivity. A new idea we recently
introduced, very high redundancy, alleviates this problem. It enables the
relatively simple construction (~1cm mechanical precision) of a ground-based
astronomical facility able to transform a two-dimensional field of point-like
sources to a three-dimensional distribution of micro-arcsec resolved systems,
each imaged in several optical bands. Each system will also have its high
resolution residual timing, high quality (inside each band) spectra and light
curve, emergent flux, effective temperature, polarization effects and perhaps
some thermodynamic properties, all directly measured. All the above attributes
can be measured in a single observation run of such a dedicated facility. We
conclude that after three decades of abandonment optical intensity
interferometry deserves another review, also as a ground-based alternative to
the science goals of space interferometers.Comment: The article has been accepted for publication in MNRA
Life science payloads planning study integration facility survey results
The integration facility survey effort described is structured to examine the facility resources needed to conduct life science payload (LSP) integration checkout activities at NASA-JSC. The LSP integration facility operations and functions are defined along with the LSP requirements for facility design. A description of available JSC life science facilities is presented and a comparison of accommodations versus requirements is reported
An X-ray-UV correlation in Cen X-4 during quiescence
Quiescent emission from the neutron star low-mass X-ray binary Cen X-4 is
seen to be variable on timescales from hundreds of seconds to years, suggesting
that at least in this object, low-level accretion is important during
quiescence. Here we present results from recent XMM-Newton and Swift
observations of Cen X-4, where the X-ray flux (0.5 - 10 keV) varies by a factor
of 6.5 between the brightest and faintest states. We find a positive
correlation between the X-ray flux and the simultaneous near-UV flux, where as
there is no significant correlation between the X-ray and simultaneous optical
(V, B) fluxes. This suggests that while the X-ray and UV emitting regions are
somehow linked, the optical region originates elsewhere. Comparing the
luminosities, it is plausible that the UV emission originates due to
reprocessing of the X-ray flux by the accretion disk, with the hot inner region
of the disk being a possible location for the UV emitting region. The optical
emission, however, could be dominated by the donor star. The X-ray/UV
correlation does not favour the accretion stream-impact point as the source of
the UV emission.Comment: 8 pages, 3 figures, accepted for publication in MNRA
Studies related to ocean dynamics. Task 3.2: Aircraft Field Test Program to investigate the ability of remote sensing methods to measure current/wind-wave interactions
The feasibility of remote sensing of current flows in the ocean and the remote sensing of ocean currents by backscattering cross section techniques was studied. It was established that for capillary waves, small scale currents could be accurately measured through observation of wave kinematics. Drastic modifications of waves by changing currents were noted. The development of new methods for the measurement of capillary waves are discussed. Improvement methods to resolve data processing problems are suggested
Interquark Potential in Schrodinger Representation
Static charges are introduced in Yang-Mills theory via coupling to heavy
fermions. The states containing static color charges are constructed using
integration over gauge transformations. A functional representation for
interquark potential is obtained. This representation provides a simple
criterion for confinement.Comment: 9pp., Late
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