508 research outputs found
An Investigation of a Number of Liquid Propellants and a Study of Scale Effect on Jet Motor Performance
A considerable amount of work has been done at the Air corps Jet Propulsion Research Project with a spontaneously igniting propellant combination consisting of red fuming nitric acid and aniline. (Cf. Ref. 1,2,3,4,5, and 6) Similar studies have been carried out by the Navy Bureau of Aeronautics Projects and by the Aerojet Engineering Corporation. In this report and effort has been made to collect and discuss the results of these investigations and to describe the properties of a number of propellant components
Modern information technologies in high school education
Article is devoted to urgent problems of using modern information technologies in teaching students of universities. New conditions of the development Russian society determine the necessity of using information technologies as a means of accumulation and implementation of innovative potential participants in the educational process. Analyzes the efficiency conditions of using information technologies in improving the quality of educationИсследуются актуальные вопросы использования современных информационных технологий при обучении студентов вузов. Новые условия развития российского общества определяют необходимость использования информационных технологий как средств накопления и реализации инновационного потенциала участников образовательного процесса. Анализируются условия эффективности применения информационных технологий в повышении качества образовани
Large-Amplitude Ultraviolet Variations in the RR Lyrae Star ROTSE-I J143753.84+345924.8
The NASA Galaxy Evolution Explorer (GALEX) satellite has obtained
simultaneous near and far ultraviolet light curves of the ROTSE-I Catalog RR
Lyrae ab-type variable star J143753.84+345924.8. A series of 38 GALEX Deep
Imaging Survey observations well distributed in phase within the star's
0.56432d period shows an AB=4.9mag variation in the far UV (1350-1750A) band
and an AB=1.8mag variation in the near UV (1750-2750A) band, compared with only
a 0.8mag variation in the broad, unfiltered ROTSE-I (4500-10000A) band. These
GALEX UV observations are the first to reveal a large RR Lyrae amplitude
variation at wavelengths below 1800A. We compare the GALEX and ROTSE-I
observations to predictions made by recent Kurucz stellar atmosphere models. We
use published physical parameters for the comparable period (0.57433d),
well-observed RR Lyrae star WY Antliae to compute predicted FUV, NUV, and
ROTSE-I light curves for J143753.84+345924.8. The observed light curves agree
with the Kurucz predictions for [Fe/H]=-1.25 to within AB=0.2mag in the GALEX
NUV and ROTSE-I bands, and within 0.5mag in the FUV. At all metallicities
between solar and one hundredth solar, the Kurucz models predict 6-8mag of
variation at wavelengths between 1000-1700A. Other variable stars with similar
temperature variations, such as Cepheids, should also have large-amplitude FUV
light curves, observable during the ongoing GALEX imaging surveys.Comment: This paper will be published as part of the Galaxy Evolution Explorer
(GALEX) Astrophysical Journal Letters Special Issue. Links to the full set of
papers will be available at http:/www.galex.caltech.edu/PUBLICATIONS after
November 22, 200
GALEX UV Spectroscopy and Deep Imaging of LIRGs in the ELAIS S1 field
The ELAIS S1 field was observed by GALEX in both its Wide Spectroscopic and
Deep Imaging Survey modes. This field was previously observed by the Infrared
Space Observatory and we made use of the catalogue of multi-wavelength data
published by the ELAIS consortium to select galaxies common to the two samples.
Among the 959 objects with GALEX spectroscopy, 88 are present in the ELAIS
catalog and 19 are galaxies with an optical spectroscopic redshift. The
distribution of redshifts covers the range . The selected galaxies
have bolometric IR luminosities (deduced from the flux using ISOCAM) which means that we cover a wide range of galaxies from
normal to Ultra Luminous IR Galaxies. The mean () UV luminosity (not
corrected for extinction) amounts to
L_\sun for the low-z () sample. The UV slope (assuming
) correlates with the GALEX FUV-NUV color if
the sample is restricted to galaxies below . Taking advantage of the
UV and IR data, we estimate the dust attenuation from the IR/UV ratio and
compare it to the UV slope . We find that it is not possible to uniquely
estimate the dust attenuation from for our sample of galaxies. These
galaxies are highly extinguished with a median value .
Once the dust correction applied, the UV- and IR-based SFRs correlate. For the
closest galaxy with the best quality spectrum, we see a feature consistent with
being produced by a bump near 220nm in the attenuation curve.Comment: This paper has been published as part of the GALEX ApJL Special Issue
(ApJ 619, L63
Overview of the Far Ultraviolet Spectroscopic Explorer Mission
The Far Ultraviolet Spectroscopic Explorer satellite observes light in the
far-ultraviolet spectral region, 905 - 1187 A with high spectral resolution.
The instrument consists of four coaligned prime-focus telescopes and Rowland
spectrographs with microchannel plate detectors. Two of the telescope channels
use Al:LiF coatings for optimum reflectivity from approximately 1000 to 1187 A
and the other two use SiC coatings for optimized throughput between 905 and
1105 A. The gratings are holographically ruled to largely correct for
astigmatism and to minimize scattered light. The microchannel plate detectors
have KBr photocathodes and use photon counting to achieve good quantum
efficiency with low background signal. The sensitivity is sufficient to examine
reddened lines of sight within the Milky Way as well as active galactic nuclei
and QSOs for absorption line studies of both Milky Way and extra-galactic gas
clouds. This spectral region contains a number of key scientific diagnostics,
including O VI, H I, D I and the strong electronic transitions of H2 and HD.Comment: To appear in FUSE special issue of the Astrophysical Journal Letters.
6 pages + 4 figure
The Star Formation Rate Function of the Local Universe
We have derived the bivariate luminosity function for the far ultraviolet
(1530Angstroms) and far infrared (60 microns). We used matched GALEX and IRAS
data, and redshifts from NED and PSC-z. We have derived a total star formation
luminosity function phi(L_{tot}), with L_{tot} = L_{FUV}+L_{FIR}. Using these,
we determined the cosmic ``star formation rate'' function and density for the
local universe. The total SFR function is fit very well by a log-normal
distribution over five decades of luminosity. We find that the bivariate
luminosity function phi(L_{FUV},L_{FIR}) shows a bimodal behavior, with L_{FIR}
tracking L_{FUV} for L_{TOT}< 10^10 L_sun, and L_{FUV} saturating at 10^10
L_sun, while L_{TOT} L_{FIR} for higher luminosities. We also calculate the SFR
density and compare it to other measurements.Comment: This paper will be published as part of the Galaxy Evolution Explorer
(GALEX) Astrophysical Journal Letters Special Issue. Links to the full set of
papers will be available at http:/www.galex.caltech.edu/PUBLICATIONS/ after
November 22, 200
Weak Lensing from Space I: Instrumentation and Survey Strategy
A wide field space-based imaging telescope is necessary to fully exploit the
technique of observing dark matter via weak gravitational lensing. This first
paper in a three part series outlines the survey strategies and relevant
instrumental parameters for such a mission. As a concrete example of hardware
design, we consider the proposed Supernova/Acceleration Probe (SNAP). Using
SNAP engineering models, we quantify the major contributions to this
telescope's Point Spread Function (PSF). These PSF contributions are relevant
to any similar wide field space telescope. We further show that the PSF of SNAP
or a similar telescope will be smaller than current ground-based PSFs, and more
isotropic and stable over time than the PSF of the Hubble Space Telescope. We
outline survey strategies for two different regimes - a ``wide'' 300 square
degree survey and a ``deep'' 15 square degree survey that will accomplish
various weak lensing goals including statistical studies and dark matter
mapping.Comment: 25 pages, 8 figures, 1 table, replaced with Published Versio
UV emission and Star Formation in Stephan's Quintet
we present the first GALEX UV images of the well known interacting group of
galaxies, Stephan's Quintet (SQ). We detect widespread UV emission throughout
the group. However, there is no consistent coincidence between UV structure and
emission in the optical, H\alpha, or HI. Excluding the foreground galaxy
NGC7320 (Sd), most of the UV emission is found in regions associated with the
two spiral members of the group, NGC7319 and NGC7318b, and the intragroup
medium starburst SQ-A. The extinction corrected UV data are analyzed to
investigate the overall star formation activity in SQ. It is found that the
total star formation rate (SFR) of SQ is 6.69+-0.65 M_\sun/yr. Among this,
1.34+-0.16 M_sun/yr is due to SQ-A. This is in excellent agreement with that
derived from extinction corrected H\alpha luminosity of SQ-A. The SFR in
regions related to NGC 7319 is 1.98+-0.58 M_\sun/yr, most of which(68%) is
contributed by the disk. The contribution from the 'young tail' is only 15%. In
the UV, the 'young tail' is more extended (~100 kpc) and shows a loop-like
structure, including the optical tail, the extragalactic HII regions recently
discovered in H\alpha, and other UV emission regions discovered for the first
time. The UV and optical colors of the 'old tail' are consistent with a single
stellar population of age t ~10^{8.5+-0.4} yrs. The UV emission associated with
NGC 7318b is found in a very large (~80 kpc) disk, with a net SFR of 3.37+-0.25
M_sun/yr. Several large UV emission regions are 30 -- 40 kpc away from the
nucleus of NGC7318b. Although both NGC7319 and NGC7318b show peculiar UV
morphology, their SFR is consistent with that of normal Sbc galaxies,
indicating that the strength of star formation activity is not enhenced by
interactions.Comment: This paper will be published as part of the Galaxy Evolution
Explorer(GALEX) Astrophysical Journal Letters Special Issue. Links to the
full set of papers will be available at
http:/www.galex.caltech.edu/PUBLICATIONS/ after November 22, 200
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