15,834 research outputs found
Solar cell radiation flight experiment Quarterly progress report, 2 Dec. 1968 - 14 Mar. 1969
Design and test data of solar cells selected for flight on ATS-E for radiation effect
QCD: Challenges for the Future
Despite many experimental verifications of the correctness of our basic
understanding of QCD, there remain numerous open questions in strong
interaction physics and we focus on the role of future colliders in addressing
these questions. We discuss possible advances in the measurement of ,
in the study of parton distribution functions, and in the understanding of low
physics at present colliders and potential new facilities. We also touch
briefly on the role of spin physics in advancing our understanding of QCD.Comment: 12 pages, LATEX2e with snow2e, epsfig and 2 figures. Also available
at http://penguin.phy.bnl.gov/~dawson/qcdsnow.ps . QCD working group summary
at DPF/DPB Summer Study on New Directions for High Energy Physics, Snowmass,
CO, June 25- July 12, 199
Solar cell radiation flight experiment Quarterly progress report, 14 Aug. - 2 Dec. 1968
Design, specifications, and test of solar cells for ATS-E spacecraf
Mechanism of enhanced light output in InGaN-based microlight emitting diodes
Micro-light emitting diode (LED) arrays with diameters of 4 to 20 mum have been fabricated and were found to be much more efficient light emitters compared to their broad-area counterparts, with up to five times enhancement in optical power densities. The possible mechanisms responsible for the improvement in performance were investigated. Strain relaxation in the microstructures as measured by Raman spectroscopy was not observed, arguing against theories of an increase in internal quantum efficiency due to a reduction of the piezoelectric field put forward by other groups. Optical microscope images show intense light emission at the periphery of the devices, as a result of light scattering off the etched sidewalls. This increases the extraction efficiency relative to broad area devices and boosts the forward optical output. In addition, spectra of the forward emitted light reveal the presence of resonant cavity modes [whispering gallery (WG) modes in particular] which appear to play a role in enhancing the optical output
Systematic characterization of thermodynamic and dynamical phase behavior in systems with short-ranged attraction
In this paper we demonstrate the feasibility and utility of an augmented
version of the Gibbs ensemble Monte Carlo method for computing the phase
behavior of systems with strong, extremely short-ranged attractions. For
generic potential shapes, this approach allows for the investigation of
narrower attractive widths than those previously reported. Direct comparison to
previous self-consistent Ornstein-Zernike approximation calculations are made.
A preliminary investigation of out-of-equilibrium behavior is also performed.
Our results suggest that the recent observations of stable cluster phases in
systems without long-ranged repulsions are intimately related to gas-crystal
and metastable gas-liquid phase separation.Comment: 10 pages, 8 figure
Sensitivity of arrest in mode-coupling glasses to low-q structure
We quantify, within mode coupling theory, how changes in the liquid structure
affect that of the glass. Apart from the known sensitivity to the structure
factor at wavevectors around the first sharp diffraction peak , we
find a strong (and inverted) response to structure at wavevectors \emph{below}
this peak: an increase in {\em lowers} the degree of arrest over a
wide -range. This strong sensitivity to `caged cage' packing effects, on
length scales of order 2d, is much weaker in attractive glasses where
short-range bonding dominates the steric caging effect.Comment: 4 pages, 5 figures. v2: 3 figures replaced; text rewritte
Fault-tolerant quantum computation with high threshold in two dimensions
We present a scheme of fault-tolerant quantum computation for a local
architecture in two spatial dimensions. The error threshold is 0.75% for each
source in an error model with preparation, gate, storage and measurement
errors.Comment: 4 pages, 4 figures; v2: A single 2D layer of qubits (simple square
lattice) with nearest-neighbor translation-invariant Ising interaction
suffices. Slightly improved threshol
InGaN nano-ring structures for high-efficiency light emitting diodes
A technique based on the Fresnel diffraction effect for the fabrication of nano-scale site-controlled ring structures in InGaN/GaN multi-quantum well structures has been demonstrated. The ring structures have an internal diameter of 500 nm and a wall width of 300 nm. A 1 cm-1 Raman shift has been measured, signifying substantial strain relaxation from the fabricated structure. The 9 nm blueshift observed in the cathodoluminescence spectra can be attributed to band filling and/or screening of the piezoelectric field. A light emitting diode based on this geometry has been demonstrated
Star polymers: A study of the structural arrest in presence of attractive interactions
Simulations and Mode-Coupling Theory calculations, for a large range of the
arm number and packing fraction have shown that the structural
arrest and the dynamics of star polymers in a good solvent are extremely rich:
the systems show a reentrant melting of the disordered glass nested between two
stable fluid phases that strongly resemble the equilibrium phase diagram.
Starting from a simple model potential we investigate the effect of the
interplay between attractive interactions of different range and ultrasoft core
repulsion, on the dynamics and on the occurrence of the ideal glass transition
line. In the two cases considered so far, we observed some significant
differences with respect to the purely repulsive pair interaction. We also
discuss the interplay between equilibrium and non equilibrium phase behavior.
The accuracy of the theoretical tools we utilized in our investigation has been
checked by comparing the results with molecular dynamics simulations.Comment: 24 pages, 14 figures, accepted for publication in Physical Review
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