6,770 research outputs found
Detector panels-micrometeoroid impact Patent
Development of large area micrometeoroid impact detector panel
Small high-temperature nuclear reactors for space power
Criticality calculations for small, cylindrical, lithium cooled reactors for space power system
Origin of unusual sintering phenomena in compacts of chloride-derived 3Y-TZP nanopowders
After evaluating three alternative possibilities, the present study shows
that seemingly minor amounts (at least as low as 0.06 wt%) of chlorine
impurities are responsible for the poor sintering behavior observed in
chloride-derived 3 mol% yttria stabilized zirconia (3Y-TZP) nanopowders.
Models and quantitative estimates are used to explain the role of evolved HCl
and ZrCl4 gases in such anomalous behaviors as reduced sintered densities for
higher green densities, de-densification, improved sintering in nitrogen over
oxygen, and formation of a dense shell microstructure. Two solutions to
problematic residual chlorides are compared: 1) a thermal treatment composed
of an extended hold at 1000°C to allow HCl gas removal before the onset of
closed porosity, and 2) a chemical treatment performed by washing
bisque-fired samples at room temperature using a concentrated ammonium
hydroxide solution to remove chlorides. The thermal treatment was found to be
superior
Prop-fan data support study
Updated parametric prop-fan data packages are presented and the rationale used in developing the new prop-fan data is detailed. These data represent Hamilton Standard's projections of prop-fan characteristics for aircraft that are expected to be in-service in the 1985 to 1990 time frame. The basic prop-fan configuration was designed for efficient cruise operation at 0.8 Mach number and 10,668M altitude. The design blade tip speed is 244 mps and the design power loading is 301 KW/M squared
International Space Station Utilization: Tracking Investigations from Objectives to Results
Since the first module was assembled on the International Space Station (ISS), on-orbit investigations have been underway across all scientific disciplines. The facilities dedicated to research on ISS have supported over 1100 investigations from over 900 scientists representing over 60 countries. Relatively few of these investigations are tracked through the traditional NASA grants monitoring process and with ISS National Laboratory use growing, the ISS Program Scientist s Office has been tasked with tracking all ISS investigations from objectives to results. Detailed information regarding each investigation is now collected once, at the first point it is proposed for flight, and is kept in an online database that serves as a single source of information on the core objectives of each investigation. Different fields are used to provide the appropriate level of detail for research planning, astronaut training, and public communications. http://www.nasa.gov/iss-science/. With each successive year, publications of ISS scientific results, which are used to measure success of the research program, have shown steady increases in all scientific research areas on the ISS. Accurately identifying, collecting, and assessing the research results publications is a challenge and a priority for the ISS research program, and we will discuss the approaches that the ISS Program Science Office employs to meet this challenge. We will also address the online resources available to support outreach and communication of ISS research to the public. Keywords: International Space Station, Database, Tracking, Method
Field theory of the inverse cascade in two-dimensional turbulence
A two-dimensional fluid, stirred at high wavenumbers and damped by both
viscosity and linear friction, is modeled by a statistical field theory. The
fluid's long-distance behavior is studied using renormalization-group (RG)
methods, as begun by Forster, Nelson, and Stephen [Phys. Rev. A 16, 732
(1977)]. With friction, which dissipates energy at low wavenumbers, one expects
a stationary inverse energy cascade for strong enough stirring. While such
developed turbulence is beyond the quantitative reach of perturbation theory, a
combination of exact and perturbative results suggests a coherent picture of
the inverse cascade. The zero-friction fluctuation-dissipation theorem (FDT) is
derived from a generalized time-reversal symmetry and implies zero anomalous
dimension for the velocity even when friction is present. Thus the Kolmogorov
scaling of the inverse cascade cannot be explained by any RG fixed point. The
beta function for the dimensionless coupling ghat is computed through two
loops; the ghat^3 term is positive, as already known, but the ghat^5 term is
negative. An ideal cascade requires a linear beta function for large ghat,
consistent with a Pad\'e approximant to the Borel transform. The conjecture
that the Kolmogorov spectrum arises from an RG flow through large ghat is
compatible with other results, but the accurate k^{-5/3} scaling is not
explained and the Kolmogorov constant is not estimated. The lack of scale
invariance should produce intermittency in high-order structure functions, as
observed in some but not all numerical simulations of the inverse cascade. When
analogous RG methods are applied to the one-dimensional Burgers equation using
an FDT-preserving dimensional continuation, equipartition is obtained instead
of a cascade--in agreement with simulations.Comment: 16 pages, 3 figures, REVTeX 4. Material added on energy flux,
intermittency, and comparison with Burgers equatio
Molecular and mass spectroscopic analysis of isotopically labeled organic residues
Experimental studies aimed at understanding the evolution of complex organic molecules on interstellar grains were performed. The photolysis of frozen gas mixtures of various compositions containing H2O, CO, NH3, and CH4 was studied. These species were chosen because of their astrophysical importance as deducted from observational as well as theoretical studies of ice mantles on interstellar grains. These ultraviolet photolyzed ices were warmed up in order to produce refractory organic molecules like the ones formed in molecular clouds when the icy mantles are being irradiated and warmed up either by a nearby stellar source or impulsive heating. The laboratory studies give estimates of the efficiency of production of such organic material under interstellar conditions. It is shown that the gradual carbonization of organic mantles in the diffuse cloud phase leads to higher and higher visual absorptivity - yellow residues become brown in the laboratory. The obtained results can be applied to explaining the organic components of comets and their relevance to the origin of life
The Supreme Court as the Grand Mediator in Social Regulation of the Media - De Gustibus Non Disputandum Est: Or Are They
This article presents a study of administrative and statutory schemes designed to regulate various aspects of the media in considering broad questions of indecency, obscenity, and societal and parental controls over content in various forms of media broadcasting. The article then provides an important historical back-drop by referencing Burstyn v. Wilson (a 1950s case involving an alleged secular sacrilege ) and Pacifica Foundation (the George Carlin Filthy Words monologue case). It then turns to a discussion of the litigation and controversy spurred by passage of the Communications Decency Act of 1996 and the Child Online Protection Act of 1998 as the focus of congressional attention turned to regulating the Internet. In this context, the article discusses Reno v. ACLU and American Library Association v. United States, two cases which provided direct challenges to Congressional regulatory responses. This article concludes by noting important international implications of the attempts to place restrictions on the Internet, and offers several tentative conclusions by bringing to the forefront the debate on the use of filtering technology designed to provide controls and supervision over this new media
Model ab initio study of charge carrier solvation and large polaron formation on conjugated carbon chains
Using long C_{N}H_{2} conjugated carbon chains with the polyynic structure as
prototypical examples of one-dimensional (1D) semiconductors, we discuss
self-localization of excess charge carriers into 1D large polarons in the
presence of the interaction with a surrounding polar solvent. The solvation
mechanism of self-trapping is different from the polaron formation due to
coupling with bond-length modulations of the underlying atomic lattice
well-known in conjugated polymers. Model ab initio computations employing the
hybrid B3LYP density functional in conjunction with the polarizable continuum
model are carried out demonstrating the formation of both electron- and
hole-polarons. Polarons can emerge entirely due to solvation but even larger
degrees of charge localization occur when accompanied by atomic displacements
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