7,560 research outputs found
Improvement of speech recognition by nonlinear noise reduction
The success of nonlinear noise reduction applied to a single channel
recording of human voice is measured in terms of the recognition rate of a
commercial speech recognition program in comparison to the optimal linear
filter. The overall performance of the nonlinear method is shown to be
superior. We hence demonstrate that an algorithm which has its roots in the
theory of nonlinear deterministic dynamics possesses a large potential in a
realistic application.Comment: see urbanowicz.org.p
Excitations of Bose-Einstein condensates in optical lattices
In this paper we examine the excitations observable in atoms confined in an
optical lattice around the superfluid-insulator transition. We use increases in
the number variance of atoms, subsequent to tilting the lattice as the primary
diagnostic of excitations in the lattice. We show that this locally determined
quantity should be a robust indicator of coherence changes in the atoms
observed in recent experiments. This was found to hold for commensurate or
non-commensurate fillings of the lattice, implying our results will hold for a
wide range of physical cases. Our results are in good agreement with the
quantitative factors of recent experiments. We do, howevers, find extra
features in the excitation spectra. The variation of the spectra with the
duration of the perturbation also turns out to be an interesting diagnostic of
atom dynamics.Comment: 6 pages, 7 figures, using Revtex4; changes to version 2: new data and
substantial revision of tex
MegaPipe: the MegaCam image stacking pipeline at the Canadian Astronomical Data Centre
This paper describes the MegaPipe image processing pipeline at the Canadian
Astronomical Data Centre. The pipeline combines multiple images from the
MegaCam mosaic camera on CFHT and combines them into a single output image.
MegaPipe takes as input detrended MegaCam images and does a careful astrometric
and photometric calibration on them. The calibrated images are then resampled
and combined into image stacks. The astrometric calibration of the output
images is accurate to within 0.15 arcseconds relative to external reference
frames and 0.04 arcseconds internally. The photometric calibration is good to
within 0.03 magnitudes. The stacked images and catalogues derived from these
images are available through the CADC website:Comment: Data available at
http://www.cadc-ccda.hia-iha.nrc-cnrc.gc.ca/megapipe/index.htm
The LiAl/FeS2 battery power source for the future
Advanced high power density rechargeable batteries are currently under development. These batteries have the potential of greatly increasing the power and energy densities available for space applications. Depending on whether the system is optimized for high power or high energy, values up to 150 Wh/kg and 2100 W/kg (including hardware) are projected. This is due to the fact that the system uses a high conductivity molten salt electrolyte. The electrolyte also serves as a separator layer with unlimited freeze thaw capabilities. Life of 1000 cycles and ten calendar years is projected. The electrochemistry consists of a lithium aluminum alloy negative electrode, iron disulfide positive electrode, and magnesium oxide powder immobilized molten salt electrolyte. Processed powders are cold compacted into circular discs which are assembled into bipolar cell hardware with peripheral ceramic salts. The culmination of the work will be a high energy battery of 40 kWh and a high power battery of 28 kWh
Dressed Polyakov loop and phase diagram of hot quark matter under magnetic field
We evaluate the dressed Polyakov loop for hot quark matter in strong magnetic
field. To compute the finite temperature effective potential, we use the
Polyakov extended Nambu-Jona Lasinio model with eight-quark interactions taken
into account. The bare quark mass is adjusted in order to reproduce the
physical value of the vacuum pion mass. Our results show that the dressed
Polyakov loop is very sensitive to the strenght of the magnetic field, and it
is capable to capture both the deconfinement crossover and the chiral
crossover. Besides, we compute self-consistently the phase diagram of the
model. We find a tiny split of the two aforementioned crossovers as the
strength of the magnetic field is increased. Concretely, for the largest value
of magnetic field investigated here, , the split is of the order
of . A qualitative comparison with other effective models and recent
Lattice results is also performed.Comment: 10 pages, 3 figures, RevTeX4-1 styl
Mass Shift and Width Broadening of J/psi in hot gluonic plasma from QCD Sum Rules
We investigate possible mass shift and width broadening of J/psi in hot
gluonic matter using QCD sum rule. Input values of gluon condensates at finite
temperature are extracted from lattice QCD data for the energy density and
pressure. Although stability of the moment ratio is achieved only up to T/Tc ~
1.05, the gluon condensates cause a decrease of the moment ratio, which results
in change of spectral properties. Using the Breit-Wigner form for the
phenomenological side, we find that mass shift of J/psi just above Tc can reach
maximally 200 MeV and width can broaden to dozens of MeV.Comment: 4 pages, 5 figures, version to appear in Physical Review Letter
Using Josephson junctions to determine the pairing state of superconductors without crystal inversion symmetry
Theoretical studies of a planar tunnel junction between two superconductors
with antisymmetric spin-orbit coupling are presented. The half-space Green's
function for such a superconductor is determined. This is then used to derive
expressions for the dissipative current and the Josephson current of the
junction. Numerical results are presented in the case of the Rashba spin-orbit
coupling, relevant to the much studied compound CePtSi. Current-voltage
diagrams, differential conductance and the critical Josephson current are
presented for different crystallographic orientations and different weights of
singlet and triplet components of the pairing state. The main conclusion is
that Josephson junctions with different crystallographic orientations may
provide a direct connection between unconventional pairing in superconductors
of this kind and the absence of inversion symmetry in the crystal.Comment: 16 pages, 10 figure
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