2,314 research outputs found
A unified evaluation of iterative projection algorithms for phase retrieval
Iterative projection algorithms are successfully being used as a substitute
of lenses to recombine, numerically rather than optically, light scattered by
illuminated objects. Images obtained computationally allow aberration-free
diffraction-limited imaging and the possibility of using radiation for which no
lenses exist. The challenge of this imaging technique is transfered from the
lenses to the algorithms. We evaluate these new computational ``instruments''
developed for the phase retrieval problem, and discuss acceleration strategies.Comment: 12 pages, 9 figures, revte
Global Newtonian limit for the Relativistic Boltzmann Equation near Vacuum
We study the Cauchy Problem for the relativistic Boltzmann equation with near
Vacuum initial data. Unique global in time "mild" solutions are obtained
uniformly in the speed of light parameter . We furthermore prove that
solutions to the relativistic Boltzmann equation converge to solutions of the
Newtonian Boltzmann equation in the limit as on arbitrary time
intervals , with convergence rate for any . This may be the first proof of unique global in time validity of the
Newtonian limit for a Kinetic equation.Comment: 35 page
The role of teleworking in Britain: its implications for the transport system and economic evaluation
The probable impacts of teleworking in Britain were assessed through analysis of the National Travel Survey, and interviews with major organisations in the London area. These indicate relatively modest effects overall, but a growing element of part-week teleworking at home
Social inhibition and emotional distress in patients with coronary artery disease:The type D personality construct
We examined the validity of the social inhibition component of Type D, its distinctiveness from negative affectivity, and value regarding emotional distress as measured with the DS14 in 173 coronary artery disease patients. In dimensional analysis, social inhibition and negative affectivity emerged as distinct traits. Analysis of continuous negative affectivity and social inhibition measures showed main effects for several emotional and inhibition markers and an interaction effect for social anxiety. Categorical analysis indicated that Type D patients reported more depression, negative mood, social anxiety, and less positive mood. Social inhibition is not a redundant trait, but has additional conceptual valu
The effects of superconductor-stabilizer interfacial resistance on quench of current-carrying coated conductor
We present the results of numerical analysis of a model of normal zone
propagation in coated conductors. The main emphasis is on the effects of
increased contact resistance between the superconducting film and the
stabilizer on the speed of normal zone propagation, the maximum temperature
rise inside the normal zone, and the stability margins. We show that with
increasing contact resistance the speed of normal zone propagation increases,
the maximum temperature inside the normal zone decreases, and stability margins
shrink. This may have an overall beneficial effect on quench protection quality
of coated conductors. We also briefly discuss the propagation of solitons and
development of the temperature modulation along the wire.Comment: To be published in Superconductor Science and Technology. This
preprint contains one animated figure (Fig. 6(a)). when asked whether you
want to play the content, click "Play". Acrobat Reader (Windows and Mac, but
not Linux) will play embedded flash movies. In the printed copy Fig. 6(b)
will show the temperature profile at gamma t=15
Finite-temperature effects on the superfluid Bose-Einstein condensation of confined ultracold atoms in three-dimensional optical lattices
We discuss the finite-temperature phase diagram in the three-dimensional
Bose-Hubbard (BH) model in the strong correlation regime, relevant for
Bose-Einstein condensates in optical lattices, by employing a quantum rotor
approach. In systems with strong on site repulsive interactions, the rotor U(1)
phase variable dual to the local boson density emerges as an important
collective field. After establishing the connection between the rotor
construction and the the on--site interaction in the BH model the robust
effective action formalism is developed which allows us to study the superfluid
phase transition in various temperature--interaction regimes
The effects of superconductor-stabilizer interfacial resistance on quench of a pancake coil made out of coated conductor
We present the results of numerical analysis of normal zone propagation in a
stack of coated conductors which imitates a pancake coil.
Our main purpose is to determine whether the quench protection quality of such
coils can be substantially improved by increased contact resistance between the
superconducting film and the stabilizer. We show that with increased contact
resistance the speed of normal zone propagation increases, the detection of a
normal zone inside the coil becomes possible earlier, when the peak temperature
inside the normal zone is lower, and stability margins shrink. Thus, increasing
contact resistance may become a viable option for improving the prospects of
coated conductors for high magnets applications.Comment: 9 pages, 4 figure
Force-matched embedded-atom method potential for niobium
Large-scale simulations of plastic deformation and phase transformations in
alloys require reliable classical interatomic potentials. We construct an
embedded-atom method potential for niobium as the first step in alloy potential
development. Optimization of the potential parameters to a well-converged set
of density-functional theory (DFT) forces, energies, and stresses produces a
reliable and transferable potential for molecular dynamics simulations. The
potential accurately describes properties related to the fitting data, and also
produces excellent results for quantities outside the fitting range. Structural
and elastic properties, defect energetics, and thermal behavior compare well
with DFT results and experimental data, e.g., DFT surface energies are
reproduced with less than 4% error, generalized stacking-fault energies differ
from DFT values by less than 15%, and the melting temperature is within 2% of
the experimental value.Comment: 17 pages, 13 figures, 7 table
Resonance phenomena in asymmetric superconducting quantum interference devices
Theory of self induced resonances in asymmetric two-junction interferometer
device is presented. In real devices it is impossible to have an ideal
interferometer free of imperfections. Thus, we extended previous theoretical
approaches introducing a model which contains several asymmetries: Josephson
current , capacitances and dissipation presented in an
equivalent circuit. Moreover, non conventional symmetry of the order parameter
in high temperature superconducting quantum interference devices forced us to
include phase asymmetries. Therefore, the model has been extended to the case
of -shift interferometers, where a phase shift is present in one of the
junctions.Comment: accepted to PRB, low quality figure
Experimental evidence of a fractal dissipative regime in high-T_c superconductors
We report on our experimental evidence of a substantial geometrical
ingredient characterizing the problem of incipient dissipation in high-T_c
superconductors(HTS): high-resolution studies of differential
resistance-current characteristics in absence of magnetic field enabled us to
identify and quantify the fractal dissipative regime inside which the actual
current-carrying medium is an object of fractal geometry. The discovery of a
fractal regime proves the reality and consistency of critical-phenomena
scenario as a model for dissipation in inhomogeneous and disordered HTS, gives
the experimentally-based value of the relevant finite-size scaling exponent and
offers some interesting new guidelines to the problem of pairing mechanisms in
HTS.Comment: 5 pages, 3 figures, RevTex; Accepted for publication in Physical
Review B; (figures enlarged
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