50,337 research outputs found
Fuzzy audio similarity measures based on spectrum histograms and fluctuation patterns
Spectrum histograms and fluctuation patterns are representations of audio fragments. By comparing these representations, we can determine the similarity between the corresponding fragments. Traditionally, this is done using the Euclidian distance. We propose fuzzy similarity measures as an alternative. First we introduce some well-known fuzzy similarity measures, together with certain properties that can be desirable or useful in practice. In particular we present several forms of restrictability, which allow to reduce the computation time in practical applications. Next, we show that fuzzy similarity measures can be used to compare spectrum histograms and fluctuation patterns. Finally, we describe some experimental observations for this fuzzy approach of constructing audio similarity measures
Evidence for complex order parameter in La_{1.83}Sr_{0.17}CuO_4
The in-plane magnetic field penetration depth (\lambda_{ab}) in
single-crystal La_{1.83}Sr_{0.17}CuO_4 was investigated by means of the
muon-spin rotation (\muSR) technique. The temperature dependence of
\lambda^{-2}_{ab} has an inflection point around 10-15K, suggesting the
presence of two superconducting gaps: a large gap (\Delta_1^d) with d-wave and
a small gap (\Delta_2^s) with s-wave symmetry. The zero-temperature values of
the gaps at \mu_0H=0.02T were found to be \Delta_1^d(0)=8.2(2)meV and
\Delta_2^s(0)=1.57(8)meV.Comment: 5 pages, 3 figure
Supernova Simulations from a 3D Progenitor Model -- Impact of Perturbations and Evolution of Explosion Properties
We study the impact of large-scale perturbations from convective shell
burning on the core-collapse supernova explosion mechanism using
three-dimensional (3D) multi-group neutrino hydrodynamics simulations of an 18
solar mass progenitor. Seed asphericities in the O shell, obtained from a
recent 3D model of O shell burning, help trigger a neutrino-driven explosion
330ms after bounce whereas the shock is not revived in a model based on a
spherically symmetric progenitor for at least another 300ms. We tentatively
infer a reduction of the critical luminosity for shock revival by ~20% due to
pre-collapse perturbations. This indicates that convective seed perturbations
play an important role in the explosion mechanism in some progenitors. We
follow the evolution of the 18 solar mass model into the explosion phase for
more than 2s and find that the cycle of accretion and mass ejection is still
ongoing at this stage. With a preliminary value of 0.77 Bethe for the
diagnostic explosion energy, a baryonic neutron star mass of 1.85 solar masses,
a neutron star kick of ~600km/s and a neutron star spin period of ~20ms at the
end of the simulation, the explosion and remnant properties are slightly
atypical, but still lie comfortably within the observed distribution. Although
more refined simulations and a larger survey of progenitors are still called
for, this suggests that a solution to the problem of shock revival and
explosion energies in the ballpark of observations are within reach for
neutrino-driven explosions in 3D.Comment: 23 pages, 22 figures, accepted for publication in MNRA
Lagrangian Statistics of Navier-Stokes- and MHD-Turbulence
We report on a comparison of high-resolution numerical simulations of
Lagrangian particles advected by incompressible turbulent hydro- and
magnetohydrodynamic (MHD) flows. Numerical simulations were performed with up
to collocation points and 10 million particles in the Navier-Stokes
case and collocation points and 1 million particles in the MHD case. In
the hydrodynamics case our findings compare with recent experiments from
Mordant et al. [1] and Xu et al. [2]. They differ from the simulations of
Biferale et al. [3] due to differences of the ranges choosen for evaluating the
structure functions. In Navier-Stokes turbulence intermittency is stronger than
predicted by a multifractal approach of [3] whereas in MHD turbulence the
predictions from the multifractal approach are more intermittent than observed
in our simulations. In addition, our simulations reveal that Lagrangian
Navier-Stokes turbulence is more intermittent than MHD turbulence, whereas the
situation is reversed in the Eulerian case. Those findings can not consistently
be described by the multifractal modeling. The crucial point is that the
geometry of the dissipative structures have different implications for
Lagrangian and Eulerian intermittency. Application of the multifractal approach
for the modeling of the acceleration PDFs works well for the Navier-Stokes case
but in the MHD case just the tails are well described.Comment: to appear in J. Plasma Phy
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