33,423 research outputs found
Multi-feed cone Cassegrain antenna Patent
Design and operation of multi-feed cone Cassegrain antenn
Subharmonic gap structure in short ballistic graphene junctions
We present a theoretical analysis of the current-voltage characteristics of a
ballistic superconductor-normal-superconductor (SNS) junction, in which a strip
of graphene is coupled to two superconducting electrodes. We focus in the
short-junction regime, where the length of the strip is much smaller than
superconducting coherence length. We show that the differential conductance
exhibits a very rich subharmonic gap structure which can be modulated by means
of a gate voltage. On approaching the Dirac point the conductance normalized by
the normal-state conductance is identical to that of a short diffusive SNS
junction.Comment: revtex4, 4 pages, 4 figure
Neutron capture production rates of cosmogenic 60Co, 59Ni and 36Cl in stony meteorites
Results for neutron flux calculations in stony meteoroids (of various radii and compositions) and production rates for Cl-36, Ni-59, and Co-60 are reported. The Ni-59/Co-60 ratio is nearly constant with depth in most meteorites: this effect is consistent with the neutron flux and capture cross section properties. The shape of the neutron flux energy spectrum, varies little with depth in a meteorite. The size of the parent meteorite can be determined from one of its fragments, using the Ni-59/Co-60 ratios, if the parent meteorite was less than 75 g/cm(2) in radius. If the parent meteorite was larger, a lower limit on the size of the parent meteorite can be determined from a fragment. In C3 chondrites this is not possible. In stony meteorites with R less than 50 g/cm(2) the calculated Co-60 production rates (mass less than 4 kg), are below 1 atom/min g-Co. The highest Co-60 production rates occur in stony meteorites with radius about 250 g/cm(2) (1.4 m across). In meteorites with radii greater than 400 g/cm(2), the maximum Co-60 production rate occurs at a depth of about 175 g/cm(2) in L-chondrite, 125 g/cm(2) in C3 chrondrite, and 190 g/cm(2) in aubrites
Focusing of Intense Subpicosecond Laser Pulses in Wedge Targets
Two dimensional particle-in-cell simulations characterizing the interaction
of ultraintense short pulse lasers in the range 10^{18} \leq I \leq 10^{20}
W/cm^{2} with converging target geometries are presented. Seeking to examine
intensity amplification in high-power laser systems, where focal spots are
typically non-diffraction limited, we describe key dynamical features as the
injected laser intensity and convergence angle of the target are systematically
varied. We find that laser pulses are focused down to a wavelength with the
peak intensity amplified by an order of magnitude beyond its vacuum value, and
develop a simple model for how the peak location moves back towards the
injection plane over time. This performance is sustained over hundreds of
femtoseconds and scales to laser intensities beyond 10^{20} W/cm^{2} at 1 \mu m
wavelength.Comment: 5 pages, 6 figures, accepted for publication in Physics of Plasma
Head-on collisions of boson stars
We study head-on collisions of boson stars in three dimensions. We consider
evolutions of two boson stars which may differ in their phase or have opposite
frequencies but are otherwise identical. Our studies show that these phase
differences result in different late time behavior and gravitational wave
output
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