Antonio Astillero

Antonio Astillero
Universidad de Extremadura | UNEX · Department of Computers and Communications Technology

Ph. D.

About

23
Publications
1,586
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137
Citations
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January 2001 - present
Universidad de Extremadura
Position
  • Professor (Associate)

Publications

Publications (23)
Preprint
Full-text available
Working in the out of equilibrium regime and using state-of-the-art techniques we have computed the dynamic critical exponent of the three dimensional Heisenberg model. We have run very large lattices ($L\le 250$) in CPUs and GPUs obtaining $z=2.041(16)$ from the growth of the correlation length and $z=2.034(22)$ for the decay of the energy. We com...
Article
Full-text available
Working in and out of equilibrium and using state-of-the-art techniques we have computed the dynamic critical exponent of the three-dimensional Heisenberg model. By computing the integrated autocorrelation time at equilibrium, for lattice sizes L≤64, we have obtained z=2.033(5). In the out-of-equilibrium regime we have run very large lattices (L≤25...
Article
Full-text available
This work considers the problem of finding analytical expressions for the expected values of dis- tributed computing performance metrics when the underlying communication network has a complex structure. Through active probing tests a real distributed computing environment is analysed. From the resulting network, ensembles of synthetic graphs with...
Article
Full-text available
The uniform longitudinal flow is characterized by a linear longitudinal velocity field $u_x(x,t)=a(t)x$, where $a(t)={a_0}/({1+a_0t})$ is the strain rate, a uniform density $n(t)\propto a(t)$, and a uniform granular temperature $T(t)$. Direct simulation Monte Carlo solutions of the Boltzmann equation for inelastic hard spheres are presented for thr...
Article
Full-text available
The temporal evolution of a dilute granular gas, both in a compressible flow (uniform longitudinal flow) and in an incompressible flow (uniform shear flow), is investigated by means of the direct simulation Monte Carlo method to solve the Boltzmann equation. Emphasis is laid on the identification of a first "kinetic" stage (where the physical prope...
Article
Full-text available
Preliminary results for application workflow deployments over a simplified GRID with a complex, non-trivial communications network topology and a homogeneous computing capacity are addressed. Application workflows are mod-eled as Directed Acyclic Graphs (DAG) where communication costs are assumed to depend on the underlying network hopcount. A simp...
Article
Full-text available
The evolution to the steady state of a granular gas subject to simple shear flow is analyzed by means of computer simulations. It is found that, regardless of its initial preparation, the system reaches (after a transient period lasting a few collisions per particle) a non-Newtonian (unsteady) hydrodynamic regime, even at strong dissipation and for...
Conference Paper
Full-text available
Resumen En este trabajo analizamos un caso paradig-mático de sistema complejo como es un flu-ido granular en condiciones de flujo tangen-cial uniforme. Efectuamos simulaciones por or-denador empleando el método de simulación directa de Monte Carlo (DSMC), mostrando que, con independencia de las condiciones ini-ciales, tras unas pocas colisiones por...
Article
En esta tesis se abordará el estudio de las propiedades dinámicas y de transporte en medios granulares en condiciones de flujo rápido. Se utilizará una descripción basada en la mecánica estadística y en la teoría cinética y se emplearán técnicas analíticas, numéricas y de simulación en ordenador.
Article
Full-text available
The prototype model of a fluidized granular system is a gas of inelastic hard spheres (IHS) with a constant coefficient of normal restitution alpha. Using a kinetic theory description we investigate the two basic ingredients that a model of elastic hard spheres (EHS) must have in order to mimic the most relevant transport properties of the underlyi...
Article
Full-text available
In the preceding paper, we have conjectured that the main transport properties of a dilute gas of inelastic hard spheres (IHSs) can be satisfactorily captured by an equivalent gas of elastic hard spheres (EHSs), provided that the latter are under the action of an effective drag force and their collision rate is reduced by a factor (1+alpha)/2 (wher...
Article
Full-text available
The Boltzmann equation for inelastic Maxwell models is used to determine the Navier-Stokes transport coefficients of a granular binary mixture in $d$ dimensions. The Chapman-Enskog method is applied to solve the Boltzmann equation for states near the (local) homogeneous cooling state. The mass, heat, and momentum fluxes are obtained to first order...
Article
Full-text available
We explore the possibility of describing the main transport properties of a granular gas by means of a model consisting of elastic hard spheres under the action of a drag force that mimics the inelastic cooling of the granular gas. Direct Monte Carlo simulations of the Boltzmann equation show a good agreement between the results for a gas of inelas...
Article
Full-text available
In order to determine the atmospheric extinction at Physics Department Astronomical Observatory of the University of Extremadura, located at Badajoz (Spain), several stars were observed during some clear nights of atmospheric stability in the period 1998–2000, at optical wavelengths corresponding to the filters of the Kron-Cousins and Strömgren pho...
Conference Paper
Full-text available
In this work we make a comparative study of the results obtained in the automatic interpretation of the Iberian Peninsula Meteosat images by means of neural networks techniques, in particular, multi-layer perceptrons and self organizing maps. The interpretation of these images implies their segmentation in the classes SEA (S), LAND (L), LOW CLOUDS...

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