4,832 research outputs found
Impact of ETO propellants on the aerothermodynamic analyses of propulsion components
The operating conditions and the propellant transport properties used in Earth-to-Orbit (ETO) applications affect the aerothermodynamic design of ETO turbomachinery in a number of ways. Some aerodynamic and heat transfer implications of the low molecular weight fluids and high Reynolds number operating conditions on future ETO turbomachinery are discussed. Using the current SSME high pressure fuel turbine as a baseline, the aerothermodynamic comparisons are made for two alternate fuel turbine geometries. The first is a revised first stage rotor blade designed to reduce peak heat transfer. This alternate design resulted in a 23 percent reduction in peak heat transfer. The second design concept was a single stage rotor to yield the same power output as the baseline two stage rotor. Since the rotor tip speed was held constant, the turbine work factor doubled. In this alternate design, the peak heat transfer remained the same as the baseline. While the efficiency of the single stage design was 3.1 points less than the baseline two stage turbine, the design was aerothermodynamically feasible, and may be structurally desirable
Overview of the solar dynamic ground test demonstration program
The Solar Dynamic (SD) Ground Test Demonstration (GTD) program demonstrates the availability of SD technologies in a simulated space environment at the NASA Lewis Research Center (LeRC) vacuum facility. An aerospace industry/ government team is working together to design, fabricate, build, and test a complete SD system. This paper reviews the goals and status of the SD GTD program. A description of the SD system includes key design features of the system, subsystems, and components as reported at the Critical Design Review (CDR)
Update of the 2 Kw Solar Dynamic Ground Test Demonstration Program
The Solar Dynamic (SD) Ground Test Demonstration (GTD) program demonstrates the operation of a complete 2 kW, SD system in a simulated space environment at a NASA Lewis Research Center (LeRC) thermal-vacuum facility. This paper reviews the goals and status of the SD GTD program. A brief description of the SD system identifying key design features of the system, subsystems, and components is included. An aerospace industry/government team is working together to design, fabricate, assemble, and test a complete SD system
Initial results from the Solar Dynamic (SD) Ground Test Demonstration (GTD) project at NASA Lewis
A government/industry team designed, built, and tested a 2 kWe solar dynamic space power system in a large thermal/vacuum facility with a simulated sun at the NASA Lewis Research Center. The Lewis facility provides an accurate simulation of temperatures, high vacuum, and solar flux as encountered in low earth orbit. This paper reviews the goals and status of the Solar Dynamic (SD) Ground Test Demonstration (GTD) program and describes the initial testing, including both operational and performance data. This SD technology has the potential as a future power source for the International Space Station Alpha
The distance to the young cluster NGC 7129 and its age
The dust cloud TGU H645 P2 and embedded in it young open cluster NGC 7129 are
investigated using the results of medium-band photometry of 159 stars in the
Vilnius seven-colour system down to V = 18.8 mag. The photometric data were
used to classify about 50 percent of the measured stars in spectral and
luminosity classes. The extinction A_V vs. distance diagram for the 20x20
arcmin area is plotted for 155 stars with two-dimensional classification from
the present and the previous catalogues. The extinction values found range
between 0.6 and 3.4 mag. However, some red giants, located in the direction of
the dense parts of the cloud, exhibit the infrared extinction equivalent up to
A_V = 13 mag. The distance to the cloud (and the cluster) is found to be 1.15
kpc (the true distance modulus 10.30 mag). For determining the age of NGC 7129,
a luminosity vs. temperature diagram for six cluster members of spectral
classes B3 to A1 was compared with the Pisa pre-main-sequence evolution tracks
and the Palla birthlines. The cluster can be as old as about 3 Myr, but star
forming continues till now as witnessed by the presence in the cloud of many
younger pre-main-sequence objects identified with photometry from 2MASS,
Spitzer and WISE infrared surveys.Comment: 8 pages, 6 fugures, full Table 1 online. Accepted for publication in
MNRAS on 2013 November 3
A one-sided Prime Ideal Principle for noncommutative rings
Completely prime right ideals are introduced as a one-sided generalization of
the concept of a prime ideal in a commutative ring. Some of their basic
properties are investigated, pointing out both similarities and differences
between these right ideals and their commutative counterparts. We prove the
Completely Prime Ideal Principle, a theorem stating that right ideals that are
maximal in a specific sense must be completely prime. We offer a number of
applications of the Completely Prime Ideal Principle arising from many diverse
concepts in rings and modules. These applications show how completely prime
right ideals control the one-sided structure of a ring, and they recover
earlier theorems stating that certain noncommutative rings are domains (namely,
proper right PCI rings and rings with the right restricted minimum condition
that are not right artinian). In order to provide a deeper understanding of the
set of completely prime right ideals in a general ring, we study the special
subset of comonoform right ideals.Comment: 38 page
The Gravitational Lensing in Redshift-space Correlation Functions of Galaxies and Quasars
The gravitational lensing, as well as the velocity field and the cosmological
light-cone warp, changes the observed correlation function of high-redshift
objects. We present an analytical expression of 3D correlation function,
simultaneously including those three effects. When two objects are separated
over several hundreds Mpc along a line of sight, the observed correlation
function is dominated by the effect of gravitational lensing rather than the
intrinsic clustering. For a canonical lambda-CDM model, the lensing signals in
the galaxy-galaxy and galaxy-QSO correlations are beyond noise levels in
large-scale redshift surveys like the Sloan Digital Sky Survey.Comment: 10 pages, 1 figure, submitted to ApJ
Density Evolution in the New Modified Chaplygin Gas Model
In this paper, we have considered new modified Chaplygin gas (NMCG) model
which interpolates between radiation at early stage and CDM at late
stage. This model is regarded as a unification of dark energy and dark matter
(with general form of matter). We have derived the density parameters from the
equation of motion for the interaction between dark energy and dark matter.
Also we have studied the evolution of the various components of density
parameters.Comment: 6 Latex pages, 4 figures, RevTex styl
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