8,878 research outputs found
Development of a computer code for calculating the steady super/hypersonic inviscid flow around real configurations. Volume 2: Code description
A numerical procedure was developed to compute the inviscid super/hypersonic flow field about complex vehicle geometries accurately and efficiently. A second-order accurate finite difference scheme is used to integrate the three-dimensional Euler equations in regions of continuous flow, while all shock waves are computed as discontinuities via the Rankine-Hugoniot jump conditions. Conformal mappings are used to develop a computational grid. The effects of blunt nose entropy layers are computed in detail. Real gas effects for equilibrium air are included using curve fits of Mollier charts. Typical calculated results for shuttle orbiter, hypersonic transport, and supersonic aircraft configurations are included to demonstrate the usefulness of this tool
Growth Kinetics in the N-Component Model. Conserved Order Parameter
We extend the discussion of the growth kinetics of the large-N time-dependent
Ginzburg-Landau model with an order parameter described by a free
energy functional, to the conserved case. Quenches from a high temperature
initial state to a zero temperature state are studied for different selections
of parameters entering the effective potential. In all cases we obtain the
asymptotic form of the structure factor. As expected in analogy with the well
studied model, we find multiscaling behavior whenever stable
equilibrium is reached in the ordering region. On the other hand the present
model also displays a novel feature, namely the occurrence of metastable
relaxation.Comment: 20 pages,Plain Late
Development of a computer code for calculating the steady super/hypersonic inviscid flow around real configurations. Volume 1: Computational technique
A numerical procedure has been developed to compute the inviscid super/hypersonic flow field about complex vehicle geometries accurately and efficiently. A second order accurate finite difference scheme is used to integrate the three dimensional Euler equations in regions of continuous flow, while all shock waves are computed as discontinuities via the Rankine Hugoniot jump conditions. Conformal mappings are used to develop a computational grid. The effects of blunt nose entropy layers are computed in detail. Real gas effects for equilibrium air are included using curve fits of Mollier charts. Typical calculated results for shuttle orbiter, hypersonic transport, and supersonic aircraft configurations are included to demonstrate the usefulness of this tool
Wide-field multi-color photometry of the Galactic globular cluster NGC 1261
(Abriged)This work studies in more detail the stellar population, including
its photometric properties and characteristics, in the rarely studied southern
Galactic globular cluster NGC 1261. We focus on the brighter sequences of the
cluster's color-magnitude diagram (CMD). Like in our previous works, we rely
upon photometry in several passbands to achieve more reliable results and
conclusions. We carried out and analyzed new multi-color photometry of NGC 1261
in UBVI reaching below the turnoff point in all passbands in a fairly extended
cluster field, about 14'x14'. We found several signs of the inhomogeneity
("multiplicity") in the stellar population. The most prominent of them are: (1)
the dependence of the radial distribution of sub-giant branch (SGB) stars in
the cluster on their U magnitude, with brighter stars less centrally
concentrated at the 99.9 \% level than their fainter counterparts; (2) the
dependence of the location of red giant branch (RGB) stars in the U-(U-B) CMD
on their radial distance from the cluster center, with the portion of stars
bluer in the (U-B) color increasing towards the cluster outskirts.
Additionally, the radial variation of the RGB luminosity function in the bump
region is suspected. We assume that both the SGB stars brighter in the U and
the RGB stars bluer in the (U-B) color are probably associated with blue
horizontal branch stars, because of a similarity in their radial distribution
in the cluster. We estimated the metalicity of NGC 1261 from the slope of the
RGB in U-based CMDs and the location of the RGB bump on the branch. These
metallicity indicators give [Fe/H]zw = -1.34 +/- 0.16 dex and [Fe/H]zw = -1.41
+/- 0.10 dex, respectively. We isolated 18 probable blue straggler candidates.
They are more centrally concentrated than the lower red giants of comparable
brightness at the 97.9 \% level.Comment: 8 pages, 9 figures, accepted for publication in A&
Pulsational M_V versus [Fe/H] relation(s) for globular cluster RR Lyrae variables
We use the results from recent computations of updated non-linear convective
pulsating models to constrain the distance modulus of Galactic globular
clusters through the observed periods of first overtone RRc pulsators. The
resulting relation between the mean absolute magnitude of RR Lyrae stars
and the heavy element content [Fe/H] appears well in the range of
several previous empirical calibrations, but with a non linear dependence on
[Fe/H] so that the slope of the relation increases when moving towards larger
metallicities. On this ground, our results suggest that metal-poor
([Fe/H]-1.5) variables follow two different
linear -[Fe/H] relations. Application to RR Lyrae stars in the
metal-poor globular clusters of the Large Magellanic Cloud provides a LMC
distance modulus of the order of 18.6 mag, thus supporting the "long" distance
scale. The comparison with recent predictions based on updated stellar
evolution theory is shortly presented and discussed.Comment: 8 pages, 4 postscript figures, accepted for publication on MNRA
RR Lyrae variables in M5 as a test of pulsational theory
We present B and V CCD photometry for variables in the cluster central
region, adding new data for 32 variables and giving suitable light curves, mean
magnitudes and corrected colors for 17 RR Lyrae. Implementing the data given in
this paper with similar data already appeared in the literature we discuss a
sample of 42 variables, as given by 22 RRab and 20 RRc, to the light of recent
predictions from pulsational theories. We find that the observational evidence
concerning M5 pulsators appears in marginal disagreement with predictions
concerning the color of the First Overtone Blue Edge (FOBE), whereas a clear
disagreement appears between the ZAHB luminosities predicted through
evolutionary or pulsational theories.Comment: 7 pages, 7 postscript figures, accepted for publication on MNRA
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