1,627 research outputs found
Addendum to SSV Generic OFT First Stage Ascent Base Convective Heating Environments
Convective environments for OFT Mission C are presented in graphs for first stage convective heating to the internal surfaces of the OMS nozzle, to the aft facing 8 and 9 RCS nozzles, and to the base (trailing edge) of the vertical tail
Modular space station phase B extension preliminary system design. Volume 2: Operations and crew analyses
All analyses and tradeoffs conducted to establish the MSS operations and crew activities are discussed. The missions and subsystem integrated analyses that were completed to assure compatibility of program elements and consistency with program objectives are presented
SSV Generic OFT first stage ascent base convective heating environments
Space Shuttle Vehicle (SSV) base convective heating environments during the recirculated flow time segment of first stage ascent were determined for the Generic OFT trajectory and performance conditions. These environments are presented in the attachments as cold wall convective heat transfer coefficients for individual or groups of design points for all affected SSV base surfaces. Two gas recovery temperatures applicable to upper and lower base region surfaces are also included. The environments were based upon magnitudes and trends from analysis of data taken during Base Heating Tests IH-39, IH-75, and IH-83. The plume heating trajectory and performance data were supplied by Rockwell International for both the OFT-1 Generic Mission A and Mission C
Vector Casimir effect for a D-dimensional sphere
The Casimir energy or stress due to modes in a D-dimensional volume subject
to TM (mixed) boundary conditions on a bounding spherical surface is
calculated. Both interior and exterior modes are included. Together with
earlier results found for scalar modes (TE modes), this gives the Casimir
effect for fluctuating ``electromagnetic'' (vector) fields inside and outside a
spherical shell. Known results for three dimensions, first found by Boyer, are
reproduced. Qualitatively, the results for TM modes are similar to those for
scalar modes: Poles occur in the stress at positive even dimensions, and cusps
(logarithmic singularities) occur for integer dimensions . Particular
attention is given the interesting case of D=2.Comment: 20 pages, 1 figure, REVTe
Casimir effect for a -dimensional sphere
The Casimir force on a -dimensional sphere due to the confinement of a
massless scalar field is computed as a function of , where is a
continuous variable that ranges from to . The dependence of
the force on the dimension is obtained using a simple and straightforward
Green's function technique. We find that the Casimir force vanishes as ( non-even integer) and also vanishes when is a negative even
integer. The force has simple poles at positive even integer values of .Comment: 22 pages, REVTeX, 4 uuencoded figures, OKHEP-94-0
PT-symetrically regularized Eckart,Poeschl-Teller and Hulthen potentials
Version 1: The well known Eckart's singular s-wave potential is
PT-symmetrically regularized and continued to the whole real line. The new
model remains exactly solvable and its bound states remain proportional to
Jacobi polynomials. Its real and discrete spectrum exhibits several unusual
features.
Version 2: Parity times time-reversal symmetry of complex Hamiltonians with
real spectra is usually interpreted as a weaker mathematical substitute for
Hermiticity. Perhaps an equally important role is played by the related
strengthened analyticity assumptions. In a constructive illustration we
complexify a few potentials solvable only in s-wave. Then we continue their
domain from semi-axis to the whole axis and get the new exactly solvable
models. Their energies come out real as expected. The new one-dimensional
spectra themselves differ quite significantly from their s-wave predecessors.Comment: Original 10-page letter ``PT-symmetrized exact solution of the
singular Eckart oscillator" is extended to a full pape
Evolutionary Status of Dwarf ``Transition'' Galaxies
We present deep B, R and Halpha imaging of 3 dwarf galaxies: NGC3377A,
NGC4286, and IC3475. Based on previous broadband imaging and HI studies, these
mixed-morphology galaxies were proposed by Sandage & Hoffman (1991) to be,
respectively, a gas-rich low surface brightness Im dwarf, a nucleated dwarf
that has lost most of its gas and is in transition from Im to dS0,N, and the
prototypical example of a gas-poor ``huge low surface brightness'' early-type
galaxy. From the combination of our broadband and Halpha imaging with the
published information on the neutral gas content of these three galaxies, we
find that (1) NGC3377A is a dwarf spiral; (2) NGC3377A and NGC4286 have
comparable amounts of ongoing star formation, as indicated by their Halpha
emission, while IC3475 has no detected HII regions to a very low limit; (3) the
global star formation rates are at least a factor of 20 below that of 30
Doradus for NGC3377A and NGC4286; (4) while the amount of star formation is
comparable, the distribution of star forming regions is very different between
NGC3377A and NGC4286; (5) given their current star formation rates and gas
contents, both NGC3377A and NGC4286 can continue to form stars for more than a
Hubble time; (6) both NGC3377A and NGC4286 have integrated total B-R colors
that are redder than the integrated total B-R color for IC3475, and thus it is
unlikely that either galaxy will ever evolve into an IC3475 counterpart; and
(7) IC3475 is too blue to be a dE. We thus conclude that we have not identified
potential precursors to galaxies such as IC3475, and unless signifcant changes
occur in the star formation rates, neither NGC3377A nor NGC4286 will evolve
into a dwarf elliptical or dwarf spheroidal within a Hubble time.Comment: 34 pages, 6 jpg figures, 3 postscript figures, and 4 tables, uses
AASTeX, ApJ, in pres
The Peculiar Motions of Early-Type Galaxies in Two Distant Regions. IV. The Photometric Fitting Procedure
The EFAR project is a study of 736 candidate early-type galaxies in 84
clusters lying in two regions towards Hercules-Corona Borealis and
Perseus-Cetus at distances km/s. In this paper we
describe a new method of galaxy photometry adopted to derive the photometric
parameters of the EFAR galaxies. The algorithm fits the circularized surface
brightness profiles as the sum of two seeing-convolved components, an
and an exponential law. This approach allows us to fit the large variety of
luminosity profiles displayed by the EFAR galaxies homogeneously and to derive
(for at least a subset of these) bulge and disk parameters. Multiple exposures
of the same objects are optimally combined and an optional sky-fitting
procedure has been developed to correct for sky subtraction errors. Extensive
Monte Carlo simulations are analyzed to test the performance of the algorithm
and estimate the size of random and {\it systematic} errors. Random errors are
small, provided that the global signal-to-noise ratio of the fitted profiles is
larger than . Systematic errors can result from 1) errors in the
sky subtraction, 2) the limited radial extent of the fitted profiles, 3) the
lack of resolution due to seeing convolution and pixel sampling, 4) the use of
circularized profiles for very flattened objects seen edge-on and 5) a poor
match of the fitting functions to the object profiles. Large systematic errors
are generated by the widely used simple law to fit luminosity
profiles when a disk component, as small as 20% of the total light, is present.Comment: 47 pages, Latex File, aaspp4.sty, flushrt.sty, 16 Postscript figures,
to appear in ApJ
Casimir Energy for Spherical boundaries
Calculations of the Casimir energy for spherical geometries which are based
on integrations of the stress tensor are critically examined. It is shown that
despite their apparent agreement with numerical results obtained from mode
summation methods, they contain a number of serious errors. Specifically, these
include (1) an improper application of the stress tensor to spherical
boundaries, (2) the neglect of pole terms in contour integrations, and (3) the
imposition of inappropriate boundary conditions upon the relevant propagators.
A calculation which is based on the stress tensor and which avoids such
problems is shown to be possible. It is, however, equivalent to the mode
summation method and does not therefore constitute an independent calculation
of the Casimir energy.Comment: Revtex, 7 pages, Appendix added providing details of failure of
stress tensor metho
Mode-by-mode summation for the zero point electromagnetic energy of an infinite cylinder
Using the mode-by-mode summation technique the zero point energy of the
electromagnetic field is calculated for the boundary conditions given on the
surface of an infinite solid cylinder. It is assumed that the dielectric and
magnetic characteristics of the material which makes up the cylinder
and of that which makes up the surroundings obey the relation . With this
assumption all the divergences cancel. The divergences are regulated by making
use of zeta function techniques. Numerical calculations are carried out for a
dilute dielectric cylinder and for a perfectly conducting cylindrical shell.
The Casimir energy in the first case vanishes, and in the second is in complete
agreement with that obtained by DeRaad and Milton who employed a Green's
function technique with an ultraviolet regulator.Comment: REVTeX, 16 pages, no figures and tables; transcription error in
previous version corrected, giving a zero Casimir energy for a tenuous
cylinde
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