7,478 research outputs found
Turbopump thermodynamic cooling
System for cooling turbopumps used in cryogenic fluid storage facilities is described. Technique uses thermodynamic propellant vent to intercept pump heat at desired conditions. Cooling system uses hydrogen from outside source or residual hydrogen from cryogenic storage tank
The GPRIME approach to finite element modeling
GPRIME, an interactive modeling system, runs on the CDC 6000 computers and the DEC VAX 11/780 minicomputer. This system includes three components: (1) GPRIME, a user friendly geometric language and a processor to translate that language into geometric entities, (2) GGEN, an interactive data generator for 2-D models; and (3) SOLIDGEN, a 3-D solid modeling program. Each component has a computer user interface of an extensive command set. All of these programs make use of a comprehensive B-spline mathematics subroutine library, which can be used for a wide variety of interpolation problems and other geometric calculations. Many other user aids, such as automatic saving of the geometric and finite element data bases and hidden line removal, are available. This interactive finite element modeling capability can produce a complete finite element model, producing an output file of grid and element data
The Atomic to Molecular Transition in Galaxies. I: An Analytic Approximation for Photodissociation Fronts in Finite Clouds
In this series of papers we study the structure of the atomic to molecular
transition in the giant atomic-molecular complexes that are the repositories of
most molecular gas in galaxies, with the ultimate goal of attaining a better
understanding of what determines galaxies' molecular content. Here we derive an
approximate analytic solution for the structure of a photodissociation region
(PDR) in a cloud of finite size that is bathed in an external dissociating
radiation field. Our solution extends previous work, which with few exceptions
has been restricted to a one-dimensional treatment of the radiation field. We
show that our analytic results compare favorably to exact numerical
calculations in the one-dimensional limit. However, our more general geometry
provides a more realistic representation than a semi-infinite slab for
atomic-molecular complexes exposed to the interstellar radiation field,
particularly in environments such as low-metallicity dwarf galaxies where the
curvature and finite size of the atomic envelope cannot be neglected. For
clouds that are at least 20% molecular we obtain analytic expressions for the
molecular fraction in terms of properties of the gas and radiation field that
are accurate to tens of percent, while for clouds of lower molecular content we
obtain upper limits. As a side benefit, our analysis helps clarify when
self-shielding is the dominant process in H_2 formation, and under what
circumstances shielding by dust makes a significant contribution.Comment: 19 pages, 11 figures, emulateapj style, accepted to ApJ. Discussion
slightly changed from previous version, and some new analytic approximations
added. Underlying results unchange
Health needs of the Roma population in the Czech and Slovak Republics.
In the growing literature on the human rights of Roma people in Central Europe, their relatively poor health status is often mentioned. However, little concrete information exists about the contemporary health status of the Roma in this region. We sought information on the health of the Roma in two of countries with significant Roma minorities, the Czech and Slovak Republics, by means of systematic searches for literature on the health of Roma people published in Czech or Slovak or by authors from the two countries. Published research on health of the Roma population is sparse. The topics that have received attention suggest a focus on concepts of contagion or social Darwinism, indicating a greater concern with the health needs of the majority populations with which they live. What limited evidence exists indicates that the health needs of the Roma population are considerable. With very few exceptions, the health status of Roma is worse than that of non-Roma population in both countries. The burden of communicable disease among Roma is high and diseases associated with poor hygiene seem to be particularly important. Evidence on health care suggests poor communication between Roma and health workers and low uptake of preventative care. The health needs of Roma lack visibility, not only because of the absence of research but also the absence of advocacy on their behalf. Since 1989, Czech and Slovak researchers have largely turned away from health research on particular ethnic groups. This probably reflects a growing sensitivity about stigmatising Roma, but it also makes it difficult to know how their circumstances might be improved. There is a need for further research into the health of Roma people with particular emphasis on non-communicable disease and for interventions that would improve their health
Active management of multi-service networks.
Future multiservice networks will be extremely large and complex. Novel management solutions will be required to keep the management costs reasonable. Active networking enables management to be delegated to network users as a large set of independent small scale management systems. A novel architecture for an active network based management solution for multiservice networking is presented
Study of volatile contaminants in reclaimed water
Different methods were evaluated for reducing the volatile contaminants found in water recovered from urine by distillation. The use of activated carbon, addition of potassium permanganate, and the use of oxidation catalyst are described along with laboratory tests. It is concluded that catalytic decomposition appears to be feasible, and further investigation is recommended
Similarities and contrasts in tectonic and volcanic style and history along the Colorado plateaus-to-basin and range transition zone in Western Arizona: Geologic framework for tertiary extensional tectonics
The overall temporal and spatial relations between middle Tertiary volcanism and tectonism from the Basin and Range province onto the edge of the Colorado Plateaus province suggest that a single magnetic-tectonic episode affected the entire region more or less simultaneously during this period. The episode followed a post-Laramide (late Eocene through Oligocene) period of 25 million years of relative stability. Middle Tertiary volcanism did not migrate gradually eastward in a simple fashion onto the Colorado Plateau. In fact, late Oligocene volcanism appears to be more voluminous near the Aquarius Mountains than throughout the adjacent Basin and Range province westward to the Colorado River. Any model proposed to explain the cause of extension and detachment faulting in the eastern part of the Basin and Range province must consider that the onset of volcanism appears to have been approximately synchronous from the Colorado River region of the Basin and Range across the transition zone and onto the edge of the Colorado Plateaus
Far-Infrared Spectral Energy Distributions and Photometric Redshifts of Dusty Galaxies
We infer the large-scale source parameters of dusty galaxies from their
observed spectral energy distributions (SEDs) using the analytic radiative
transfer methodology presented in Chakrabarti & McKee (2005). For local
ultra-luminous infrared galaxies (ULIRGs), we show that the millimeter to
far-infrared (FIR) SEDs can be well fit using the standard dust opacity index
of 2 when self-consistent radiative transfer solutions are employed, indicating
that the cold dust in local ULIRGs can be described by a single grain model. We
develop a method for determining photometric redshifts of ULIRGs and sub-mm
galaxies from the millimeter-FIR SED; the resulting value of is typically
accurate to about 10%. As such, it is comparable to the accuracy of near-IR
photometric redshifts and provides a complementary means of deriving redshifts
from far-IR data, such as that from the upcoming . Since our analytic radiative transfer solution is developed for
homogeneous, spherically symmetric, centrally heated, dusty sources, it is
relevant for infrared bright galaxies that are primarily powered by compact
sources of luminosity that are embedded in a dusty envelope. We discuss how
deviations from spherical symmetry may affect the applicability of our
solution, and we contrast our self-consistent analytic solution with standard
approximations to demonstrate the main differences.Comment: 37 pages, 14 Figures, 3 Tables, submitted to ApJ. submitted to Ap
The Spaceborne Global Climate Observing Center (SGCOC): Executive summary
Conceptual planning of the Spaceborne portion of the Global Climate Observing Systems (SGCOS) is reviewed. Fundamentals of the SGCOS are summarized
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