482 research outputs found
On convergence of solutions of fractal Burgers equation toward rarefaction waves
In the paper, the large time behavior of solutions of the Cauchy problem for
the one dimensional fractal Burgers equation with is studied. It is shown that if the
nondecreasing initial datum approaches the constant states ()
as , respectively, then the corresponding solution converges
toward the rarefaction wave, {\it i.e.} the unique entropy solution of the
Riemann problem for the nonviscous Burgers equation.Comment: 15 page
On the spectrum of a waveguide with periodic cracks
The spectral problem on a periodic domain with cracks is studied. An
asymptotic form of dispersion relations is calculated under assumption that the
opening of the cracks is small
Numerical approximation of a concrete carbonation model: study of the -law of propagation
International audienceIn this paper, we are interested in the long time behavior of approximate solutions to a free boundary model which appears in the modeling of concrete carbonation [1]. In particular, we study the long time regime of the moving interface. The numerical solutions are obtained by an implicit in time and finite volume in space scheme. We show the existence of solutions to the scheme and, following [2, 3], we prove that the approximate free boundary increases in time following a -law. Finally, we supplement the study through numerical experiments
Broadening of hot-spot response spectrum of superconducting NbN nanowire single-photon detector with reduced nitrogen content
The spectral detection efficiency and the dark count rate of superconducting
nanowire single-photon detectors (SNSPD) has been studied systematically on
detectors made from thin NbN films with different chemical compositions.
Reduction of the nitrogen content in the 4 nm thick NbN films results in a more
than two orders of magnitude decrease of the dark count rates and in a red
shift of the cut-off wavelength of the hot-spot SNSPD response. The observed
phenomena are explained by an improvement of uniformity of NbN films that has
been confirmed by a decrease of resistivity and an increase of the ratio of the
measured critical current to the depairing current. The latter factor is
considered as the most crucial for both the cut-off wavelength and the dark
count rates of SNSPD. Based on our results we propose a set of criteria for
material properties to optimize SNSPD in the infrared spectral region.Comment: 15 pages, 6 figure
Probability of the resistive state formation caused by absorption of a single-photon in current-carrying superconducting nano-strips
We have studied supercurrent-assisted formation of the resistive state in
nano-structured Nb and NbN superconducting films after absorption of a single
photon. In amorphous narrow NbN strips the probability of the resistive state
formation has a pronounced spectral cut-off. The corresponding threshold photon
energy decreases with the bias current. Analysis of the experimental data in
the framework of the generalized hot-spot model suggests that the quantum yield
for near-infrared photons increases faster than the photon nergy. Relaxation of
the resistive state depends on the photon energy making the phenomenon feasible
for the development of energy resolving single-photon detectors.Comment: 9 pages, 9 figures, submitted to Eur. Phys. Journa
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