51,825 research outputs found
Television noise reduction device
A noise reduction system that divides the color video signal into its luminance and chrominance components is reported. The luminance component of a given frame is summed with the luminance component of at least one preceding frame which was stored on a disc recorder. The summation is carried out so as to achieve a signal amplitude equivalent to that of the original signal. The averaged luminance signal is then recombined with the chrominance signal to achieve a noise-reduced television signal
Television noise-reduction device
System greatly improves signal-to-noise ratio with little or no loss in picture resolution. By storage of luminance component, which is summed with chrominance component, system performs mathematical integration of basically-repetitive television signals. Integration of signals over interval of their repetition causes little change in original signals and eliminates random noise
Electrolytic hydrogen production: An analysis and review
The thermodynamics of water electrolysis cells is presented, followed by a review of current and future technology of commercial cells. The irreversibilities involved are analyzed and the resulting equations assembled into a computer simulation model of electrolysis cell efficiency. The model is tested by comparing predictions based on the model to actual commercial cell performance, and a parametric investigation of operating conditions is performed. Finally, the simulation model is applied to a study of electrolysis cell dynamics through consideration of an ideal pulsed electrolyzer
Institutional and environmental problems in geothermal resource development
A number of regulatory and institutional impediments to the development of geothermal energy exist. None of these seem likely to prevent the development of this energy source, but in the aggregate they will pace its growth as certainly as the technological issues. The issues are associated with the encouragement of exploration and development, assuring a market for geothermal steam or hot water, and accomplishing the required research and development in a timely manner. The development of geothermal energy in the United States at a high level is apt to cause both favorable and unfavorable, though manageable, impacts in eight major areas, which are discussed
Landau critical velocity in weakly interacting Bose gases
The flow of a uniform Bose gas at speeds greater than the Landau critical
velocity, v_c, does not necessarily destroy superfluidity, but rather need only
lead to a decrease of the superfluid mass density, {\rho}_s. Analyzing a weakly
interacting Bose gas with a finite range interparticle interaction that leads
to a Landau critical velocity at non-zero quasiparticle momentum, we explicitly
construct the (non-uniform) condensate for fluid flow faster than v_c and
calculate the accompanying decrease in {\rho}_s. We briefly comment on the
relation of the physics to other problems in superfluids, e.g., solitons, and
vortices in Bose-Einstein condensates, and critical currents in
superconductors.Comment: 5 pages, 1 figur
Landau levels and the Thomas-Fermi structure of rapidly rotating Bose-Einstein condensates
We show that, within mean-field theory, the density profile of a rapidly
rotating harmonically trapped Bose-Einstein condensate is of the Thomas-Fermi
form as long as the number of vortices is much larger than unity. Two forms of
the condensate wave function are explored: i) the lowest Landau level (LLL)
wave function with a regular lattice of vortices multiplied by a slowly varying
envelope function, which gives rise to components in higher Landau levels; ii)
the LLL wave function with a nonuniform vortex lattice. From variational
calculations we find it most favorable energetically to retain the LLL form of
the wave function but to allow the vortices to deviate slightly from a regular
lattice. The predicted distortions of the lattice are small, but in accord with
recent measurements at lower rates of rotation.Comment: 4 pages, 2 figures, to appear in Phys. Rev. Lett. (extend the
arguments of cond-mat/0402167
Crystallization of classical multi-component plasmas
We develop a method for calculating the equilibrium properties of the
liquid-solid phase transition in a classical, ideal, multi-component plasma.
Our method is a semi-analytic calculation that relies on extending the accurate
fitting formulae available for the one-, two-, and three-component plasmas to
the case of a plasma with an arbitrary number of components. We compare our
results to those of Horowitz, Berry, & Brown (Phys. Rev. E, 75, 066101, 2007),
who use a molecular dynamics simulation to study the chemical properties of a
17-species mixture relevant to the ocean-crust boundary of an accreting neutron
star, at the point where half the mixture has solidified. Given the same
initial composition as Horowitz et al., we are able to reproduce to good
accuracy both the liquid and solid compositions at the half-freezing point; we
find abundances for most species within 10% of the simulation values. Our
method allows the phase diagram of complex mixtures to be explored more
thoroughly than possible with numerical simulations. We briefly discuss the
implications for the nature of the liquid-solid boundary in accreting neutron
stars.Comment: 14 pages, 5 figures, submitted to Phys. Rev.
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