2,845 research outputs found
Cross-diffusion systems for image processing: II. The nonlinear case
In this paper the use of nonlinear cross-diffu\-sion systems to model image
restoration is investigated, theoretically and numerically. In the first case,
well-posedness, scale-space properties and long time behaviour are analyzed.
From a numerical point of view, a computational study of the performance of the
models is carried out, suggesting their diversity and potentialities to treat
image filtering problems. The present paper is a continuation of a previous
work of the same authors, devoted to linear cross-diffusion models.
\keywords{Cross-diffusion \and Complex diffusion \and Image restoration
Identification of the byproducts of the oxygen evolution reaction on rutile-type oxides under dynamic conditions
Peer reviewedPostprin
An optimal transportation approach for assessing almost stochastic order
When stochastic dominance does not hold, we can improve
agreement to stochastic order by suitably trimming both distributions. In this
work we consider the Wasserstein distance, , to stochastic
order of these trimmed versions. Our characterization for that distance
naturally leads to consider a -based index of disagreement with
stochastic order, . We provide asymptotic
results allowing to test vs , that,
under rejection, would give statistical guarantee of almost stochastic
dominance. We include a simulation study showing a good performance of the
index under the normal model
Properties improvement of poly(o-methoxyaniline) based supercapacitors : experimental and theoretical behaviour study of self-doping effect
The support of this research by FAPESP (2011/10897-2, 2013/07296-2), CsF-PVE (99999.007708/2015-07), CAPES and CNPq is gratefully acknowledged. We also thank the University of Aberdeen for providing computational time on MaxwellPeer reviewedPostprin
A white dwarf-neutron star relativistic binary model for soft gamma-ray repeaters
A scenario for SGRs is introduced in which gravitational radiation reaction
effects drive the dynamics of an ultrashort orbital period X-ray binary
embracing a high-mass donor white dwarf (WD) to a rapidly rotating low
magnetised massive neutron star (NS) surrounded by a thick, dense and massive
accretion torus. Driven by GR reaction, sparsely, the binary separation
reduces, the WD overflows its Roche lobe and the mass transfer drives unstable
the accretion disk around the NS. As the binary circular orbital period is a
multiple integer number () of the period of the WD fundamental mode (Pons et
al. 2002), the WD is since long pulsating at its fundamental mode; and most of
its harmonics, due to the tidal interaction with its NS orbital companion.
Hence, when the powerful irradiation glows onto the WD; from the fireball
ejected as part of the disk matter slumps onto the NS, it is partially
absorbed. This huge energy excites other WD radial (-mode) pulsations
(Podsiadlowski 1991,1995). After each mass-transfer episode the binary
separation (and orbital period) is augmented significantly (Deloye & Bildsten
2003; Al\'ecyan & Morsink 2004) due to the binary's angular momentum
redistribution. Thus a new adiabatic inspiral phase driven by GR reaction
starts which brings the binary close again, and the process repeats. This model
allows to explain most of SGRs observational features: their recurrent
activity, energetics of giant superoutbursts and quiescent stages, and
particularly the intriguing subpulses discovered by BeppoSAX (Feroci et al.
1999), which are suggested here to be {\it overtones} of the WD radial
fundamental mode (see the accompanying paper: Mosquera Cuesta 2004b).Comment: This paper was submitted as a "Letter to the Editor" of MNRAS in July
17/2004. Since that time no answer or referee report was provided to the
Author [MNRAS publication policy limits reviewal process no longer than one
month (+/- half more) for the reviewal of this kind of submission). I hope
this contribution is not receiving a similar "peer-reviewing" as given to the
A. Dar and A. De Rujula's "Cannonball model for gamma-ray bursts", or to the
R.K. Williams' "Penrose process for energy extraction from rotating black
holes". The author welcomes criticisms and suggestions on this pape
Mathematical properties and numerical approximation of pseudo-parabolic systems
The paper is concerned with the mathematical theory and numerical
approximation of systems of partial differential equations (pde) of hyperbolic,
pseudo-parabolic type. Some mathematical properties of the
initial-boundary-value problem (ibvp) with Dirichlet boundary conditions are
first studied. They include the weak formulation, well-posedness and existence
of traveling wave solutions connecting two states, when the equations are
considered as a variant of a conservation law. Then, the numerical
approximation consists of a spectral approximation in space based on Legendre
polynomials along with a temporal discretization with strong stability
preserving (SSP) property. The convergence of the semidiscrete approximation is
proved under suitable regularity conditions on the data. The choice of the
temporal discretization is justified in order to guarantee the stability of the
full discretization when dealing with nonsmooth initial conditions. A
computational study explores the performance of the fully discrete scheme with
regular and nonregular data
A theorem on the absence of phase transitions in one-dimensional growth models with onsite periodic potentials
We rigorously prove that a wide class of one-dimensional growth models with
onsite periodic potential, such as the discrete sine-Gordon model, have no
phase transition at any temperature . The proof relies on the spectral
analysis of the transfer operator associated to the models. We show that this
operator is Hilbert-Schmidt and that its maximum eigenvalue is an analytic
function of temperature.Comment: 6 pages, no figures, submitted to J Phys A: Math Ge
Dimensional crossover of the fundamental-measure functional for parallel hard cubes
We present a regularization of the recently proposed fundamental-measure
functional for a mixture of parallel hard cubes. The regularized functional is
shown to have right dimensional crossovers to any smaller dimension, thus
allowing to use it to study highly inhomogeneous phases (such as the solid
phase). Furthermore, it is shown how the functional of the slightly more
general model of parallel hard parallelepipeds can be obtained using the
zero-dimensional functional as a generating functional. The multicomponent
version of the latter system is also given, and it is suggested how to
reformulate it as a restricted-orientation model for liquid crystals. Finally,
the method is further extended to build a functional for a mixture of parallel
hard cylinders.Comment: 4 pages, no figures, uses revtex style files and multicol.sty, for a
PostScript version see http://dulcinea.uc3m.es/users/cuesta/cross.p
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