28,550 research outputs found
Inorganic glass ceramic slip rings
Prototypes of slip rings have been fabricated from ceramic glass, a material which is highly resistant to deterioration due to high temperature. Slip ring assemblies were not structurally damaged by mechanical tests and performed statisfactorily for 200 hours
Design investigation and development of design improvements for ST124-M stabilized platform slip ring capsules Final report
Eliminating insulating deposits on precious metal contacts in stabilized platform slip ring capsule
Cosmological redshift distortion: deceleration, bias and density parameters from future redshift surveys of galaxies
The observed two-point correlation functions of galaxies in redshift space
become anisotropic due to the geometry of the universe as well as due to the
presence of the peculiar velocity field. On the basis of linear perturbation
theory, we expand the induced anisotropies of the correlation functions with
respect to the redshift , and obtain analytic formulae to infer the
deceleration parameter , the density parameter and the
derivative of the bias parameter at in terms of the
observable statistical quantities. The present method does not require any
assumption of the shape and amplitude of the underlying fluctuation spectrum,
and thus can be applied to future redshift surveys of galaxies including the
Sloan Digital Sky Survey. We also evaluate quantitatively the systematic error
in estimating the value of from a galaxy
redshift survey on the basis of a conventional estimator for which
neglects both the geometrical distortion effect and the time evolution of the
parameter . If the magnitude limit of the survey is as faint as 18.5
(in B-band) as in the case of the Sloan Digital Sky Survey, the systematic
error ranges between -20% and 10% depending on the cosmological parameters.
Although such systematic errors are smaller than the statistical errors in the
current surveys, they will dominate the expected statistical error for future
surveys.Comment: 9 pages, 5 figs, aastex, ApJ in press, replaced version includes
minor correction
Anomalous low temperature specific heat of He-3 inside nanotube bundles
Helium atoms and hydrogen molecules can be strongly bound inside interstitial
channels within bundles of carbon nanotubes. An exploration of the low energy
and low temperature properties of He-3 atoms is presented here. Recent study of
the analogous He-4 system has shown that the effect of heterogeneity is to
yield a density of states N(E) that is qualitatively different from the
one-dimensional (1D) form of N(E) that would occur for an ideal set of
identical channels. In particular, the functional form of N(E) is that of a 4D
gas near the very lowest energies and a 2D gas at somewhat higher energies.
Similar behavior is found here for He-3. The resulting thermodynamic behavior
of this fermi system is computed, yielding an anomalous form of the heat
capacity and its dependence on coverage.Comment: 11 pages, 6 figure
Predictions of entry heating for lower surface of shuttle orbiter
A broad base of thermocouple and phase change paint data was assembled and correlated to the nominal design 14414.1 and proposed STS-1 (first flight of the space transportation system) entry trajectories. Averaged data from phase change paint tests compared favorably with thermocouple data for predicting heating rates. Laminar and turbulent radiation equilibrium heating rates were computed on the lower surface of the Shuttle orbiter for both trajectories, and the lower surface center line results were compared both with aerodynamic heating design data and with flight values from the STS-1 and STS-2 trajectories. The peak laminar heating values from the aerodynamic heating design data book were generally 40 to 60 percent higher than the laminar estimates of this study, except at the 55 percent location of maximum span where the design data book values were less than 10 percent higher. Estimates of both laminar and turbulent heating rates compared favorably with flight data
The upper-branch stability of compressible boundary layer flows
The upper-branch linear and nonlinear stability of compressible boundary layer flows is studied using the approach of Smith and Bodonyi (1982) for a similar incompressible problem. Both pressure gradient boundary layers and Blasius flow are considered with and without heat transfer, and the neutral eigenrelations incorporating compressibility effects are obtained explicitly. The compressible nonlinear viscous critical layer equations are derived and solved numerically and the results indicate some solutions with positive phase shift across the critical layer. Various limiting cases are investigated including the case of much larger disturbance amplitudes and this indicates the structure for the strongly nonlinear critical layer of the Benney-Bergeon (1969) type. It is also shown how a match with the inviscid neutral inflexional modes arising from the generalized inflexion point criterion, is achieved
Coupling of phonons to a helium atom adsorbed on graphite
We compute the self-energy for a ^4He atom adsorbed on graphite to second order in the phonon coupling. The phonon contributions amount to several degrees Kelvin. The imaginary part corresponds to a lifetime of some 10^(-11) s
Bound state of dimers on a spherical surface
The study of particle motion on spherical surfaces is relevant to adsorption
on buckyballs and other solid particles. This paper reports results for the
binding energy of such dimers, consisting of two light particles (He atoms or
hydrogen molecules) constrained to move on a spherical surface. The binding
energy reaches a particularly large value when the radius of the sphere is
about 3/4 of the particles' diameter.Comment: 6 pages, 3 figures, submitted to JLTP, conference proceedings QFS
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