1,269 research outputs found
Telecommunications and data acquisition systems support for Voyager missions to Jupiter and Saturn, 1972-1981, prelaunch through Saturn encounter
The Deep Space Network has supported the Voyager Project for approximately nine years, during which time implementation, testing, and operational support was provided. Four years of this time involved testing prior to launch; the final five years included network operations support and additional network implementation. Intensive and critical support intervals included launch and four planetary encounters. The telecommunications and data acquisition support for the Voyager Missions to Jupiter and Saturn are summarized
Tracking and data system support for the Viking 1975 mission to Mars. Volume 1: Prelaunch planning, implementation, and testing
The tracking and data acquisition support for the 1975 Viking Missions to Mars is described. The history of the effort from its inception in late 1968 through the launches of Vikings 1 and 2 from Cape Kennedy in August and September 1975 is given. The Viking mission requirements for tracking and data acquisition support in both the near earth and deep space phases involved multiple radar tracking and telemetry stations, and communications networks together with the global network of tracking stations, communications, and control center. The planning, implementation, testing and management of the program are presented
Relating Habitat Use to Survival of Oncorhynchus in Rock Creek and the Clark Fork River
Westslope Cutthroat Trout Oncorhynchus clarkii lewisi (WCT) is a native trout species of conservation concern in Montana. Both migratory and resident life histories can be found in cutthroat from the same natal stream. Habitat degradation and hybridization with rainbow trout O. mykiss (RBT) have resulted in few genetically pure, migratory WCT populations persisting in large river systems. These WCT conservation populations are occurring more and more as isolated, resident populations in headwater streams. Rock Creek in Western MT has retained a unique population of migratory, non-hybridized WCT, and is of special conservation and ecological interest. As we work to protect WCT and migratory life histories, we need to better understand how these fish use habitats and how that habitat use may relate to subsequent survival. From 2018 to 2021, 80 of these WCT, along with 81 hybrids and 29 RBT had radio telemetry tags implanted to be tracked primarily for spawning migrations and habitat use. I used locations and mortality indicators from radio telemetry data collected over the course of the three-year study to examine how survival differed between fish with varied genetic ancestry and then examined whether there was a relationship between survival and habitat use. There was no significant difference in annual survival between different ancestries of Oncorhynchus spp. I combined all 190 fish in the study to examine the association between survival and habitat use. Fish spending the summer (June, July, and August) in Rock Creek showed much higher survival rates than those spending the summer in the Clark Fork River. I found major differences in the habitats in question, with substantially higher temperatures in the Clark Fork River versus Rock Creek, but are also correlated with lower flow and higher contaminant levels. Results of this study build a better understanding of how survival relates to habitat use and can be useful to help protect and prioritize habitats
Winners and Losers: Formula versus Competitive Funding of Agricultural Research
Research and Development/Tech Change/Emerging Technologies, O3, O4, Q16,
Tracking and data system support for the Viking 1975 mission to Mars. Volume 2: Launch through landing of Viking 1
Problems inherent in the deployment and management of a worldwide tracking and data acquisition network to support the two Viking Orbiters and two Viking Landers simultaneously over 320 million kilometers (200 million miles) of deep space are discussed. Activities described include tracking coverage of the launch phase, the deep space operations during the long cruise phase that occupied approximately 11 months, and the implementation of the a vast worldwide network of tracking sttions and global communications systems. The performance of the personnel, hardware, and software involved in this vast undertaking are evaluated
Assigning channels via the meet-in-the-middle approach
We study the complexity of the Channel Assignment problem. By applying the
meet-in-the-middle approach we get an algorithm for the -bounded Channel
Assignment (when the edge weights are bounded by ) running in time
. This is the first algorithm which breaks the
barrier. We extend this algorithm to the counting variant, at the
cost of slightly higher polynomial factor.
A major open problem asks whether Channel Assignment admits a -time
algorithm, for a constant independent of . We consider a similar
question for Generalized T-Coloring, a CSP problem that generalizes \CA. We
show that Generalized T-Coloring does not admit a
-time algorithm, where is the
size of the instance.Comment: SWAT 2014: 282-29
PGS4 ESOMEPRAZOLE AS MAINTENANCE THERAPY IN EROSIVE ESOPHAGITIS: A QUANTITATIVE ASSESSMENT OF EFFICACY USING AN EVIDENCE-BASED APPROACH
Effect of baryon density on parton production, chemical equilibration and thermal photon emission from quark gluon plasma
The effect of baryon density on parton production processes of
and is studied
using full phase space distribution function and also with inclusion of quantum
statistics i.e. Pauli blocking and Bose enhancement factors, in the case of
both saturated and unsaturated quark gluon plasma. The rate for the process is found to be much less as compared to the most
commonly used factorized result obtained on the basis of classical
approximation. This discrepancy, which is found both at zero as well as at
finite baryon densities, however, is not due to the lack of quantum statistics
in the classical approximation, rather due to the use of Fermi-Dirac and
Bose-Einstein distribution functions for partons instead of Boltzmann
distribution which is appropriate under such approximation. Interestingly, the
rates of parton production are found to be insensitive to the baryo-chemical
potential particularly when the plasma is unsaturated although the process of
chemical equilibration strongly depends on it. The thermal photon yields, have
been calculated specifically from unsaturated plasma at finite baryon density.
The exact results obtained numerically are found to be in close agreement with
the analytic expression derived using factorized distribution functions
appropriate for unsaturated plasma. Further, it is shown that in the case of
unsaturated plasma, the thermal photon production is enhanced with increasing
baryon density both at fixed temperature and fixed energy density of the quark
gluon plasma.Comment: Latex, 24 pages, 6 postscript figures. Submitted to Phys. Rev.
Hard Thermal Photon Production in Relativistic Heavy Ion Collisions
The recent status of hard thermal photon production in relativistic heavy ion
collisions is reviewed and the current rates are presented with emphasis on
corrected bremsstrahlung processes in the quark-gluon plasma (QGP) and
quark-hadron duality. Employing Bjorken hydrodynamics with an EOS supporting
the phase transition from QGP to hot hadron gas (HHG), thermal photon spectra
are computed. For SPS 158 GeV Pb+Pb collisions, comparison with other
theoretical results and the WA98 direct photon data indicates significant
contributions due to prompt photons. Extrapolating the presented approach to
RHIC and LHC experiments, predictions of the thermal photon spectrum show a QGP
outshining the HHG in the high-pT-region.Comment: 20 pages with 8 figures. v3: Erratum to [Phys. Lett. B 510 (2001) 98]
with correctly labeled Figs. 2, 4, and 5 adde
In-medium Yang-Mills equations: a derivation and canonical quantization
The equations for Yang-Mills field in a medium are derived in a linear
approximation with respect to the gauge coupling parameter and the external
field. The obtained equations closely resemble the macroscopic Maxwell
equations. A canonical quantization is performed for a family of Fermi-like
gauges in the case of constant and diagonal (in the group indices) tensors of
electric permittivity and magnetic permeability. The physical subspace is
defined and the gauge field propagator is evaluated for a particular choice of
the gauge. The propagator is applied for evaluation of the cross-section of
ellastic quark scattering in the Born approximation. Possible applications to
Cherenkov-type gluon radiation are commented briefly.Comment: 27 pages, references added, version extended with emphasis on
non-Abelian gauge group impact on medium characteristics. To appear in J.
Phys.
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