2,989 research outputs found
Shuttle orbiter boundary layer transition at flight and wind tunnel conditions
Hypersonic boundary layer transition data obtained on the windward centerline of the Shuttle orbiter during entry for the first five flights are presented and analyzed. Because the orbiter surface is composed of a large number of thermal protection tiles, the transition data include the effects of distributed roughness arising from tile misalignment and gaps. These data are used as a benchmark for assessing and improving the accuracy of boundary layer transition predictions based on correlations of wind tunnel data taken on both aerodynamically rough and smooth orbiter surfaces. By comparing these two data bases, the relative importance of tunnel free stream noise and surface roughness on orbiter boundary layer transition correlation parameters can be assessed. This assessment indicates that accurate predications of transition times can be made for the orbiter at hypersonic flight conditions by using roughness dominated wind tunnel data. Specifically, times of transition onset and completion is accurately predicted using a correlation based on critical and effective values of a roughness Reynolds number previously derived from wind tunnel data
Corn Silage: Influence of Amounts, Feeding Systems and Drought-Damage on Feedlot Performance
This paper will exmaine the influence of silage level systems for feeding corn silage and drought-damaged corn silage on the performance and economic returns of feedlot cattle
Fermi Surface of CrV across the Quantum Critical Point
We have measured de Haas-van Alphen oscillations of CrV, , at high fields for samples on both sides of the quantum critical
point at . For all samples we observe only those oscillations
associated with a single small hole band with magnetic breakdown orbits of the
reconstructed Fermi surface evident for . The absence of oscillations
from Fermi surface sheets most responsible for the spin density wave (SDW) in
Cr for is further evidence for strong fluctuation scattering of these
charge carriers well into the paramagnetic regime. We find no significant mass
enhancement of the carriers in the single observed band at any . An
anomalous field dependence of the dHvA signal for our crystal at
particular orientations of the magnetic field is identified as due to magnetic
breakdown that we speculate results from a field induced SDW transition at high
fields.Comment: 8 pages with 7 figure
Large parallel and perpendicular electric fields on electron spatial scales in the terrestrial bow shock
Large parallel ( 100 mV/m) and perpendicular ( 600 mV/m) electric
fields were measured in the Earth's bow shock by the vector electric field
experiment on the Polar satellite. These are the first reported direct
measurements of parallel electric fields in a collisionless shock. These fields
exist on spatial scales comparable to or less than the electron skin depth (a
few kilometers) and correspond to magnetic field-aligned potentials of tens of
volts and perpendicular potentials up to a kilovolt. The perpendicular fields
are amongst the largest ever measured in space, with energy densities of
of order 10%. The measured parallel electric field
implies that the electrons can be demagnetized, which may result in stochastic
(rather than coherent) electron heating
Space Shuttle orbiter entry heating and TPS response: STS-1 predictions and flight data
Aerothermodynamic development flight test data from the first orbital flight test of the Space Transportation System (STS) transmitted after entry blackout is given. Engineering predictions of boundary layer transition and numerical simulations of the orbiter flow field were confirmed. The data tended to substantiate preflight predictions of surface catalysis phenomena. The thermal response of the thermal protection system was as expected. The only exception is that internal free convection was found to be significant in limiting the peak temperature of the structure in areas which do not have internal insulation
A systematic survey of the fatty acid composition of Neurospora strains
Numerous studies have examined aspects of lipid metabolism in Neurospora crassa, N. tetrasperma and N. sitophila, but little systematic comparison has been done on lipids of the different species. Most obviously missing, however, is comparison of the fatty acid composition of lipids among Neurospora species. Fatty acid composition (especially the production of particular polyunsaturated fatty acids) is often a key factor in genus or species identification, particularly in bacteria, but also in other fungi such as Aspergillus, Penicillium and Mortierella (Kock and Botha 1998 In Frisvad et al. (eds), Chemical Fungal Taxonomy, Marcel Dekker, NY, p. 219-246). Until this study, reports of the fatty acid composition of Neurospora lipids have been limited to a few laboratory strains of N. crassa
Polarization of Broad Absorption Line QSOs I. A Spectropolarimetric Atlas
We present a spectropolarimetric survey of 36 broad absorption line
quasi-stellar objects (BAL QSOs). The continuum, absorption trough, and
emission line polarization of BAL QSOs yield clues about their structure. We
confirm that BAL QSOs are in general more highly polarized than non-BAL QSOs,
consistent with a more equatorial viewing direction for the former than the
latter. We have identified two new highly-polarized QSOs in our sample
(1232+1325 and 1333+2840). The polarization rises weakly to the blue in most
objects, perhaps due to scattering and absorption by dust particles. We find
that a polarization increase in the BAL troughs is a general property of
polarized BAL QSOs, indicating an excess of scattered light relative to direct
light, and consistent with the unification of BAL QSOs and non-BAL QSOs. We
have also discovered evidence of resonantly scattered photons in the red wing
of the C IV broad emission lines of a few objects. In most cases, the broad
emission lines have lower polarization and a different position angle than the
continuum. The polarization characteristics of low-ionization BAL QSOs are
similar to those of high-ionization BAL QSOs, suggesting a similar BAL wind
geometry.Comment: 39 pages, 6 figures (20 .gif files), accepted for publication in The
Astrophysical Journal Supplement
Fermi surface evolution through a heavy fermion superconductor-to-antiferromagnet transition: de Haas-van Alphen effect in Cd-substituted CeCoIn
We report the results of de-Haas-van-Alphen (dHvA) measurements in Cd doped
CeCoIn and LaCoIn. Cd doping is known to induce an antiferromagnetic
order in the heavy fermion superconductor CeCoIn, whose effect can be
reversed with applied pressure. We find a slight but systematic change of the
dHvA frequencies with Cd doping in both compounds, reflecting the chemical
potential shift due to the addition of holes. The frequencies and effective
masses are close to those found in the nominally pure compounds with similar
changes apparent in the Ce and La compounds with Cd substitution. We observe no
abrupt changes to the Fermi surface in the high field paramagnetic state for corresponding to the onset of antiferromagnetic ordering at H=0 in
CeCo(InCd). Our results rule out electron localization as
the mechanism for the tuning of the ground state in CeCoIn with Cd doping
Unusual metamagnetism in CeIrIn
We report a high field investigation (up to 45 T) of the metamagnetic
transition in CeIrIn with resistivity and de-Haas-van-Alphen (dHvA) effect
measurements in the temperature range 0.03-1 K. As the magnetic field is
increased the resistivity increases, reaches a maximum at the metamagnetic
critical field, and falls precipitously for fields just above the transition,
while the amplitude of all measurable dHvA frequencies are significantly
attenuated near the metamagnetic critical field. However, the dHvA frequencies
and cyclotron masses are not substantially altered by the transition. In the
low field state, the resistivity is observed to increase toward low
temperatures in a singular fashion, a behavior that is rapidly suppressed above
the transition. Instead, in the high field state, the resistivity monotonically
increases with temperature with a dependence that is more singular than the
iconic Fermi-liquid, temperature-squared, behavior. Both the damping of the
dHvA amplitudes and the increased resistivity near the metamagnetic critical
field indicate an increased scattering rate for charge carriers consistent with
critical fluctuation scattering in proximity to a phase transition. The dHvA
amplitudes do not uniformly recover above the critical field, with some
hole-like orbits being entirely suppressed at high fields. These changes, taken
as a whole, suggest that the metamagnetic transition in CeIrIn is
associated with the polarization and localization of the heaviest of
quasiparticles on the hole-like Fermi surface.Comment: 29 pages, 9 figure
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