7,287 research outputs found

    Engineering calculations for the Delta S method of solving the orbital allotment problem

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    The method of calculating single-entry separation requirements for pairs of satellites is extended to include the interference on the top link as well as on the down link. Several heuristic models for analyzing the effects of shaped-beam antenna designs on required satellite separations are introduced and demonstrated with gain contour plots. The calculation of aggregate interference is extended to include the effects of up-link interference. The relationship between the single-entry C/I requirements, used in determining satellite separation constraints for various optimization procedures, and the aggregate C/I values of the resulting solutions is discussed

    Comparison with excavated and metal-detected finds in the wider region

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    When Roman objects are discovered in rivers they are commonly interpreted as accidental losses or as rubbish deposits revealed by fluvial erosion; this is in contrast to prehistoric assemblages, which are often seen as ritual offerings

    What do stakeholders consider the key issues affecting the quality of foodservice provision for long-stay patients

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    This study aimed to elicit concerns of key stakeholders regarding food service provision to long stay hospital patients. Seventeen focus groups and four individual interviews were conducted involving six stakeholder groups: dietitians, nutrition assistants, patients, nurses, food service assistants and food service managers. Ninety-eight participants (20 male; 78 female) were recruited from public and private hospitals in New South Wales, Australia. Each of the focus groups and individual interviews was conducted in the hospital setting where free and open discussions could be digitally recorded. Transcripts were prepared from the digital recordings and QSR Nvivo 2.0ā„¢ qualitative analysis software was used to code the transcripts prior to content and thematic analysis. Themes were identified by relative frequency in the discussion, number of issues raised within each theme and the importance placed on the issues raised. Five major themes emerged from thirty seven discussion topics: the food service system, menu variety, preparation to eat/feeding assistance, packaging and portion size. Participants were particularly concerned about the increased packaging of food products, perceived lack of meal set up and feeding assistance, limited menu variety especially when considering longer stay hospital inpatients, and the increased use of cook-chill operations. These findings lend themselves well to testing in a wider sphere via quantitative means in a proposed national survey. The results of this survey may produce a position on the main barriers to effective food service provision to long stay patients in the Australian context, and enable identification of practical solutions

    Energy non-equipartition in systems of inelastic, rough spheres

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    We calculate and verify with simulations the ratio between the average translational and rotational energies of systems with rough, inelastic particles, either forced or freely cooling. The ratio shows non-equipartition of energy. In stationary flows, this ratio depends mainly on the particle roughness, but in nonstationary flows, such as freely cooling granular media, it also depends strongly on the normal dissipation. The approach presented here unifies and simplifies different results obtained by more elaborate kinetic theories. We observe that the boundary induced energy flux plays an important role.Comment: 4 pages latex, 4 embedded eps figures, accepted by Phys Rev

    Multiple cyclotron line-forming regions in GX 301-2

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    We present two observations of the high-mass X-ray binary GX 301-2 with NuSTAR, taken at different orbital phases and different luminosities. We find that the continuum is well described by typical phenomenological models, like a very strongly absorbed NPEX model. However, for a statistically acceptable description of the hard X-ray spectrum we require two cyclotron resonant scattering features (CRSF), one at ~35 keV and the other at ~50 keV. Even though both features strongly overlap, the good resolution and sensitivity of NuSTAR allows us to disentangle them at >=99.9% significance. This is the first time that two CRSFs are seen in GX 301-2. We find that the CRSFs are very likely independently formed, as their energies are not harmonically related and, if it were a single line, the deviation from a Gaussian shape would be very large. We compare our results to archival Suzaku data and find that our model also provides a good fit to those data. We study the behavior of the continuum as well as the CRSF parameters as function of pulse phase in seven phase bins. We find that the energy of the 35 keV CRSF varies smoothly as function of phase, between 30-38 keV. To explain this variation, we apply a simple model of the accretion column, taking the altitude of the line-forming region, the velocity of the in-falling material, and the resulting relativistic effects into account. We find that in this model the observed energy variation can be explained simply due to a variation of the projected velocity and beaming factor of the line forming region towards us.Comment: 18 pages, 10 figures, accepted for publication in A&
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