22,923 research outputs found
Yamabe-type equations on Carnot groups
This article is concerned with a class of elliptic equations on Carnot groups
depending of one real positive parameter and involving a critical nonlinearity.
As a special case of our results we prove the existence of at least one
nontrivial solution for a subelliptic critical equation defined on a smooth and
bounded domain of the {Heisenberg group} . Our approach is based on pure variational methods and locally
sequentially weakly lower semicontinuous arguments
A Detail Based Method for Linear Full Reference Image Quality Prediction
In this paper, a novel Full Reference method is proposed for image quality
assessment, using the combination of two separate metrics to measure the
perceptually distinct impact of detail losses and of spurious details. To this
purpose, the gradient of the impaired image is locally decomposed as a
predicted version of the original gradient, plus a gradient residual. It is
assumed that the detail attenuation identifies the detail loss, whereas the
gradient residuals describe the spurious details. It turns out that the
perceptual impact of detail losses is roughly linear with the loss of the
positional Fisher information, while the perceptual impact of the spurious
details is roughly proportional to a logarithmic measure of the signal to
residual ratio. The affine combination of these two metrics forms a new index
strongly correlated with the empirical Differential Mean Opinion Score (DMOS)
for a significant class of image impairments, as verified for three independent
popular databases. The method allowed alignment and merging of DMOS data coming
from these different databases to a common DMOS scale by affine
transformations. Unexpectedly, the DMOS scale setting is possible by the
analysis of a single image affected by additive noise.Comment: 15 pages, 9 figures. Copyright notice: The paper has been accepted
for publication on the IEEE Trans. on Image Processing on 19/09/2017 and the
copyright has been transferred to the IEE
Self-Feeding Turbulent Magnetic Reconnection on Macroscopic Scales
Within a MHD approach we find magnetic reconnection to progress in two
entirely different ways. The first is well-known: the laminar Sweet-Parker
process. But a second, completely different and chaotic reconnection process is
possible. This regime has properties of immediate practical relevance: i) it is
much faster, developing on scales of the order of the Alfv\'en time, and ii)
the areas of reconnection become distributed chaotically over a macroscopic
region. The onset of the faster process is the formation of closed circulation
patterns where the jets going out of the reconnection regions turn around and
forces their way back in, carrying along copious amounts of magnetic flux
Jalisco plumipes : new genus and new species of Mexican Aphodiini (Scarabaeoidea: Aphodiidae)
Jalisco plumipes, new genus and new species of Mexican Aphodiini, is described and figured
Systematic revision of the american taxa belonging to the genera Alloblackburneus Bordat, 2009, and Blackburneus Schmidt, 1913, with description of seven new species (Coleoptera: Scarabaeidae: Aphodiinae)
The American species belonging to the genera Alloblackburneus Bordat and Blackburneus Schmidt (Coleoptera: Scarabaeidae: Aphodiinae) are redescribed and figured. Seven new species are described: Alloblackburneus guadalajarae, A. ibanezbernali; Blackburneus amazonicus, B. sanfilippoi, B. surinamensis, B. teposcolulaensis, B. thomasi. The neotype of Scarabaeus rubeolus Palisot de Beauvois, 1809 is designated. The lectotype of Blackburneus argentinensis (Schmidt, 1909) and of Blackburneus laxepunctatus (Schmidt, 1910) are
designated. The following new combinations are proposed: Alloblackburneus aegrotus (Horn, 1870); Alloblackburneus cavidomus (Brown, 1927); Alloblackburneus cynomysi (Brown, 1927); Alloblackburneus fordi (Gordon, 1974); Alloblackburneus geomysi (Cartwright, 1939); Alloblackburneus lentus (Horn, 1870); Alloblackburneus rubeolus (Palisot de Beauvois, 1805); Alloblackburneus saylori (Hinton, 1934); Alloblackburneus tenuistriatus (Horn, 1887); Alloblackburneus troglodytes (Hubbard, 1894)
Systematic errors due to linear congruential random-number generators with the Swendsen-Wang algorithm: A warning
We show that linear congruential pseudo-random-number generators can cause
systematic errors in Monte Carlo simulations using the Swendsen-Wang algorithm,
if the lattice size is a multiple of a very large power of 2 and one random
number is used per bond. These systematic errors arise from correlations within
a single bond-update half-sweep. The errors can be eliminated (or at least
radically reduced) by updating the bonds in a random order or in an aperiodic
manner. It also helps to use a generator of large modulus (e.g. 60 or more
bits).Comment: Revtex4, 4 page
Cephalocyclus majomaensis and Oscarinus cabreroi new species of Mexican Aphodiinae (Coleoptera: Scarabaeidae: Aphodiinae)
The new species Cephalocyclus majomaensis and Oscarinus cabreroi from Mexico are described and figured. While studying specimens from Mexico to complete a systematic revision of the Aphodiinae (Coleoptera: Scarabaeidae) of that region, we found a couple of species new to science. They belong to the genera Cephalocyclus Dellacasa, Gordon and Dellacasa, 1998 and Oscarinus Gordon and Skelley, 2007, and are described here
Systematic revision of the genus Orodaliscoides Schmidt, 1913 (Coleoptera: Scarabaeidae: Aphodiinae)
The species belonging to the genus Orodaliscoides Schmidt (Coleoptera: Scarabaeidae: Aphodiinae) are redescribed and figured. The following new combinations are proposed: Orodaliscoides fimbripes (Brown, 1928) and Orodaliscoides giulianii (Gordon, 1977)
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