32,732 research outputs found
Performance characteristics of the 12 GHz, 200 watt transmitter experiment package for CTS
The experiment package consists of a 200 W output stage tube (OST) powered by a power processing system (PPS). Descriptions of both the PPS and OST are given. The PPS provides the necessary voltages with a measured dc/dc conversion efficiency of 89 percent. The OST, a traveling wave tube with multiple collectors, has a saturated rf output power of 224 W and operates at an overall efficiency exceeding 40 percent over an 85 MHz bandwidth at 12 GHz. OST performance given includes frequency response, saturation characteristics, group delay, AM to PM conversion, inter-modulation distortion, and two channel gain suppression. Single and dual channel FM video performance is presented. It was determined that for 12 MHz peak to peak frequency deviation on each channel, dual channel FM television signals can be transmitted through the TEP at 60 W, each channel, with 40 MHz channel spacing (center to center)
The role of the Public Employment Ser-vices related to ‘Flexicurity’ in the Euro-pean Labour Markets
Evaluation of a ln tan integral arising in quantum field theory
We analytically evaluate a dilogarithmic integral that is prototypical of
volumes of ideal tetrahedra in hyperbolic geometry. We additionally obtain new
representations of the Clausen function Cl_2 and the Catalan constant
G=Cl_2(\pi/2), as well as new relations between sine and Clausen function
values.Comment: 24 pages, no figure
Solution of the Percus-Yevick equation for hard discs
We solve the Percus-Yevick equation in two dimensions by reducing it to a set
of simple integral equations. We numerically obtain both the pair correlation
function and the equation of state for a hard disc fluid and find good
agreement with available Monte-Carlo calculations. The present method of
resolution may be generalized to any even dimension.Comment: 9 pages, 3 figure
Time delay occultation data of the Helios spacecraft for probing the electron density distribution in the solar corona
S-band time delay measurements were collected from the spacecraft Helios A and B during three solar occultations in 1975/76 within heliocentric distances of about 3 and 215 earth radius in terms of range, Doppler frequency shift, and electron content. Characteristic features of measurement and data processing are described. Typical data sets are discussed to probe the electron density distribution near the sun (west and east limb as well) including the outer and extended corona. Steady-state and dynamical aspects of the solar corona are presented and compared with earth-bound-K-coronagraph measurements. Using a weighted least squares estimation, parameters of an average coronal electron density profile are derived in a preliminary analysis to yield electron densities at r = 3, 65, 215 earth radius. Transient phenomena are discussed and a velocity of propagation v is nearly equal to 900 km/s is determined for plasma ejecta from a solar flare observed during an extraordinary set of Helios B electron content measurements
Failure properties of loaded fiber bundles having a lower cutoff in fiber threshold distribution
Presence of lower cutoff in fiber threshold distribution may affect the
failure properties of a bundle of fibers subjected to external load. We
investigate this possibility both in a equal load sharing (ELS) fiber bundle
model and in local load sharing (LLS) one. We show analytically that in ELS
model, the critical strength gets modified due to the presence of lower cutoff
and it becomes bounded by an upper limit. Although the dynamic exponents for
the susceptibility and relaxation time remain unchanged, the avalanche size
distribution shows a permanent deviation from the mean-fiels power law. In the
LLS model, we analytically estimate the upper limit of the lower cutoff above
which the bundle fails at one instant. Also the system size variation of
bundle's strength and the avalanche statistics show strong dependence on the
lower cutoff level.Comment: 7 pages and 7 figure
Mean properties and Free Energy of a few hard spheres confined in a spherical cavity
We use analytical calculations and event-driven molecular dynamics
simulations to study a small number of hard sphere particles in a spherical
cavity. The cavity is taken also as the thermal bath so that the system
thermalizes by collisions with the wall. In that way, these systems of two,
three and four particles, are considered in the canonical ensemble. We
characterize various mean and thermal properties for a wide range of number
densities. We study the density profiles, the components of the local pressure
tensor, the interface tension, and the adsorption at the wall. This spans from
the ideal gas limit at low densities to the high-packing limit in which there
are significant regions of the cavity for which the particles have no access,
due the conjunction of excluded volume and confinement. The contact density and
the pressure on the wall are obtained by simulations and compared to exact
analytical results. We also obtain the excess free energy for N=4, by using a
simulated-assisted approach in which we combine simulation results with the
knowledge of the exact partition function for two and three particles in a
spherical cavity.Comment: 11 pages, 9 figures and two table
Structure of a liquid crystalline fluid around a macroparticle: Density functional theory study
The structure of a molecular liquid, in both the nematic liquid crystalline
and isotropic phases, around a cylindrical macroparticle, is studied using
density functional theory. In the nematic phase the structure of the fluid is
highly anisotropic with respect to the director, in agreement with results from
simulation and phenomenological theories. On going into the isotropic phase the
structure becomes rotationally invariant around the macroparticle with an
oriented layer at the surface.Comment: 10 pages, 6 figues. Submitted to Phys. Rev.
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