27,761 research outputs found
Test results and facility description for a 40-kilowatt stirling engine
A 40 kilowatt Stirling engine, its test support facilities, and the experimental procedures used for these tests are described. Operating experience with the engine is discussed, and some initial test results are presente
Influence of gaseous hydrogen on metals Interim report
Gaseous hydrogen embrittlement in Inconel 718, Inconel 625, AISI 321 stainless steel, Ti-5Al-25Sn ELI, and OFHC coppe
Initial test results with a single-cylinder rhombic-drive Stirling engine
A 6 kW (8 hp), single-cylinder, rhombic-drive Stirling engine was restored to operating condition, and preliminary characterization tests run with hydrogen and helium as the working gases. Initial tests show the engine brake specific fuel consumption (BSFC) with hydrogen working gas to be within the range of BSFC observed by the Army at Fort Belvoir, Virginia, in 1966. The minimum system specific fuel consumption (SFC) observed during the initial tests with hydrogen was 669 g/kW hr (1.1 lb/hpx hr), compared with 620 g/kWx hr (1.02 lb/hpx hr) for the Army tests. However, the engine output power for a given mean compression-space pressure was lower than for the Army tests. The observed output power at a working-space pressure of 5 MPa (725 psig) was 3.27 kW (4.39 hp) for the initial tests and 3.80 kW (5.09 hp) for the Army tests. As expected, the engine power with helium was substantially lower than with hydrogen
NC's Anti-Predatory Lending Law: Doing What It's Supposed To Do: A Reply
We reply to criticisms of our recent study about North Carolina's Anti-Predatory Lending Law reducing predatory loan terms and preserving access to credit (NC's Anti-Predatory Lending Law: Doing What it's Supposed to Do). To examine whether the decline in overall subprime lending in North Carolina, following passage of the predatory lending law, was due to a decline in loans with legitimate terms or to a reduction in loans with abusive terms, we examined specific market segments and market practices using loan level data from the Loan Performance Asset Backed Securities (ABS) database. Our study revealed that, although the total volume of subprime originations in North Carolina declined, the number of home purchase loans was unaffected by the law. Given the robustness of the LP data, we are baffled by the criticism and disappointed by confusion that has arisen over mistaken data interpretation. For reasons discussed in this paper, we stand by our descriptive study and will continue to use LP data in our future work.Technology and Industry, Regulatory Reform
Structure and thermodynamics of a mixture of patchy and spherical colloids: a multi-body association theory with complete reference fluid information
A mixture of solvent particles with short-range, directional interactions and
solute particles with short-range, isotropic interactions that can bond
multiple times is of fundamental interest in understanding liquids and
colloidal mixtures. Because of multi-body correlations predicting the structure
and thermodynamics of such systems remains a challenge. Earlier Marshall and
Chapman developed a theory wherein association effects due to interactions
multiply the partition function for clustering of particles in a reference
hard-sphere system. The multi-body effects are incorporated in the clustering
process, which in their work was obtained in the absence of the bulk medium.
The bulk solvent effects were then modeled approximately within a second order
perturbation approach. However, their approach is inadequate at high densities
and for large association strengths. Based on the idea that the clustering of
solvent in a defined coordination volume around the solute is related to
occupancy statistics in that defined coordination volume, we develop an
approach to incorporate the complete information about hard-sphere clustering
in a bulk solvent at the density of interest. The occupancy probabilities are
obtained from enhanced sampling simulations but we also develop a concise
parametric form to model these probabilities using the quasichemical theory of
solutions. We show that incorporating the complete reference information
results in an approach that can predict the bonding state and thermodynamics of
the colloidal solute for a wide range of system conditions.Comment: arXiv admin note: text overlap with arXiv:1601.0438
Ozone measurements from the NOAA-9 and the Nimbus-7 satellites: Implications of short and long term variabilities
An overview is given of the measurements of total ozne and ozone profiles by the SBUV/2 instrument on the NOAA-9 spacecraft relative to similar measurements from the SBUV and TOMS instruments on Nimbus-7. It is shown that during the three year period from March 14, 1985, to February 28, 1988, when these data sets overlap, there have been significant changes in the calibrations of the three instruments which may be attributed to the drift of the NOSS-9 orbit to later equator crossing times (for SBUV/2). These changes in instrument characteristics have affected the absolute values of the trends derived from the three instruments, but their geophysical characteristics and response to short term variations are accurate and correlate well among the three instruments. For example, the total column ozone measured by the three instruments shows excellent agreement with respect to its day to day, seasonal, and latitudinal variabilities. At high latitudes, the day to day fluctuations in total ozone show a strong positive correlation with temperature in the lower stratosphere, as one might expect from the dynamical coupling of the two parameters at these latitudes
The Enigmatic Radio Afterglow of GRB 991216
We present wide-band radio observations spanning from 1.4 GHz to 350 GHz of
the afterglow of GRB 991216, taken from 1 to 80 days after the burst. The
optical and X-ray afterglow of this burst were fairly typical and are explained
by a jet fireball. In contrast, the radio light curve is unusual in two
respects: (a) the radio light curve does not show the usual rise to maximum
flux on timescales of weeks and instead appears to be declining already on day
1 and (b) the power law indices show significant steepening from the radio
through the X-ray bands. We show that the standard fireball model, in which the
afterglow is from a forward shock, is unable to account for (b) and we conclude
that the bulk of the radio emission must arise from a different source. We
consider two models, neither of which can be ruled out with the existing data.
In the first (conventional) model, the early radio emission is attributed to
emission from the reverse shock as in the case of GRB 990123. We predict that
the prompt optical emission would have been as bright (or brighter) than 8th
magnitude. In the second (exotic) model, the radio emission originates from the
forward shock of an isotropically energetic fireball (10^54 erg) expanding into
a tenuous medium (10^-4 cm^-3). The resulting fireball would remain
relativistic for months and is potentially resolvable with VLBI techniques.
Finally, we note that the near-IR bump of the afterglow is similar to that seen
in GRB 971214 and no fireball model can explain this bump.Comment: ApJ, submitte
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