54,642 research outputs found
Green's functions for dislocations in bonded strips and related crack problems
Green's functions are derived for the plane elastostatics problem of a dislocation in a bimaterial strip. Using these fundamental solutions as kernels, various problems involving cracks in a bimaterial strip are analyzed using singular integral equations. For each problem considered, stress intensity factors are calculated for several combinations of the parameters which describe loading, geometry and material mismatch
Constricted channel flow with different cross-section shapes
Pressure driven steady flow through a uniform circular channel containing a constricted portion is a common problem considering physiological flows such as underlying human speech sound production. The influence of the constriction’s cross-section shape (circle, ellipse, circular sector) on the flow within and downstream from the constriction is experimentally quantified. An analytical boundary layer flow model is proposed which takes into account the hydraulic diameter of the cross-section shape. Comparison of the model outcome with experimental and three-dimensional numerically simulated flow data shows that the pressure distribution within the constriction can be modeled accurately so that the model is of interest for analytical models of fluid–structure interaction without the assumption of two-dimensional flow
The millimeter-wave properties of superconducting microstrip lines
We have developed a novel technique for making high quality measurements of the millimeter-wave properties of superconducting thin-film microstrip transmission lines. Our experimental technique currently covers the 75-100 GHz band. The method is based on standing wave resonances in an open ended transmission line. We obtain information on the phase velocity and loss of the microstrip. Our data for Nb/SiO/Nb lines, taken at 4.2 K and 1.6 K, can be explained by a single set of physical parameters. Our preliminary conclusion is that the loss is dominated by the SiO dielectric, with a temperature-independent loss tangent of 5.3 ± 0.5 x 10^(-3) for our samples
Improved lattice QCD with quarks: the 2 dimensional case
QCD in two dimensions is investigated using the improved fermionic lattice
Hamiltonian proposed by Luo, Chen, Xu, and Jiang. We show that the improved
theory leads to a significant reduction of the finite lattice spacing errors.
The quark condensate and the mass of lightest quark and anti-quark bound state
in the strong coupling phase (different from t'Hooft phase) are computed. We
find agreement between our results and the analytical ones in the continuum.Comment: LaTeX file (including text + 10 figures
Leading-Order Actions of Goldstino Fields
This paper starts with a self-contained discussion of the so-called
Akulov-Volkov action S_AV, which is traditionally taken to be the leading-order
action of Goldstino field. Explicit expressions for S_AV and its chiral version
S_AV^ch are presented. We then turn to the issue on how these actions are
related to the leading-order action S_NL proposed in the newly proposed
constrained superfield formalism. We show that S_NL may yield S_AV/S_AV^ch or a
totally different action S_KS, depending on how the auxiliary field in the
former is integrated out. However, S_KS and S_AV/S_AV^ch always yield the same
S-matrix elements, as one would have expected from general considerations in
quantum field theory.Comment: Minor changes, version to appear in European Physical Journal
Metric adjusted skew information: Convexity and restricted forms of superadditivity
We give a truly elementary proof of the convexity of metric adjusted skew
information following an idea of Effros. We extend earlier results of weak
forms of superadditivity to general metric adjusted skew informations.
Recently, Luo and Zhang introduced the notion of semi-quantum states on a
bipartite system and proved superadditivity of the Wigner-Yanase-Dyson skew
informations for such states. We extend this result to general metric adjusted
skew informations. We finally show that a recently introduced extension to
parameter values of the WYD-information is a special case of
(unbounded) metric adjusted skew information.Comment: An error in the literature is pointed ou
Theoretical modeling of spatial and temperature dependent exciton energy in coupled quantum wells
Motivated by a recent experiment of spatial and temperature dependent average
exciton energy distribution in coupled quantum wells [S. Yang \textit{et al.},
Phys. Rev. B \textbf{75}, 033311 (2007)], we investigate the nature of the
interactions in indirect excitons. Based on the uncertainty principle, along
with a temperature and energy dependent distribution which includes both
population and recombination effects, we show that the interplay between an
attractive two-body interaction and a repulsive three-body interaction can lead
to a natural and good account for the nonmonotonic temperature dependence of
the average exciton energy. Moreover, exciton energy maxima are shown to locate
at the brightest regions, in agreement with the recent experiments. Our results
provide an alternative way for understanding the underlying physics of the
exciton dynamics in coupled quantum wells.Comment: 8 pages, 5 figure
A polarized beam splitter using an anisotropic medium slab
The propagation of electromagnetic waves in the anisotropic medium with a
single-sheeted hyperboloid dispersion relation is investigated. It is found
that in such an anisotropic medium E- and H-polarized waves have the same
dispersion relation, while E- and H-polarized waves exhibit opposite amphoteric
refraction characteristics. E- (or H-) polarized waves are positively refracted
whereas H- (or E-) polarized waves are negatively refracted at the interface
associated with the anisotropic medium. By suitably using the properties of
anomalous refraction in the anisotropic medium it is possible to realize a very
simple and very efficient beam splitter to route the light. It is shown that
the splitting angle and the splitting distance between E- and H- polarized beam
is the function of anisotropic parameters, incident angle and slab thickness.Comment: 14 pages, 6 figure
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