Entity

Time filter

Source Type

Curitiba, Brazil

Fiore C.E.,University Federal Do Paran
Journal of Chemical Physics | Year: 2011

Parallel tempering Monte Carlo simulations have been applied to a variety of systems presenting rugged free-energy landscapes. Despite this, its efficiency depends strongly on the temperature set. With this query in mind, we present a comparative study among different temperature selection schemes in three lattice-gas models. We focus our attention in the constant entropy method (CEM), proposed by Sabo In the CEM, the temperature is chosen by the fixed difference of entropy between adjacent replicas. We consider a method to determine the entropy which avoids numerical integrations of the specific heat and other thermodynamic quantities. Different analyses for first-and second-order phase transitions have been undertaken, revealing that the CEM may be an useful criterion for selecting the temperatures in the parallel tempering. © 2011 American Institute of Physics. Source


Ferreira A.S.,Federal University of Pernambuco | Raposo E.P.,Federal University of Pernambuco | Viswanathan G.M.,Federal University of Rio Grande do Norte | Viswanathan G.M.,Federal University of Alagoas | Da Luz M.G.E.,University Federal Do Paran
Physica A: Statistical Mechanics and its Applications | Year: 2012

An open problem in the field of random searches relates to optimizing the search efficiency in fractal environments. Here we address this issue through a systematic study of Lvy searches in landscapes encompassing several degrees of target aggregation and fractality. For scarce resources, non-destructive searches with unrestricted revisits to targets are shown to present universal optimal behavior irrespective of the general scaling properties of the spatial distribution of targets. In contrast, no such universal behavior occurs in the destructive case with forbidden revisits, in which the optimal strategy strongly depends on the degree of target aggregation. We also investigate how the presence of memory and learning skills of the searcher affect the search efficiency. By considering a limiting model in which the searcher learns through recent experience to recognize food-rich areas, we find that a statistical memory of previous encounters does not necessarily increase the rate of target findings in random searches. Instead, there is an optimal extent of memory, dependent on specific details of the search space and stochastic dynamics, which maximizes the search efficiency. This finding suggests a more general result, namely that in some instances there are actual advantages to ignoring certain pieces of partial information while searching for objects. © 2012 Elsevier B.V. All rights reserved. Source


Fujimotoa M.M.,University Federal Do Paran | Brigg W.J.,University College London | Tennysonb J.,University College London
European Physical Journal D | Year: 2012

Electron collisions with C2H5OH are studied up to impact energies of 10 eV using several theoretical models. Calculated differential cross sections suggest that the extrapolation to low angles used to extend experimental data and hence give integral cross sections significantly underestimates the large, dipole-driven forward scattering cross section. An improved set of values for the rotationally-unresolved elastic cross section is proposed; the corresponding rotationally resolved cross sections are also presented. Static exchange plus polarisation calculations find a very broad shape resonance in each of the 2A' and 2A'' symmetries in the 7 eV collision region however no resonance at lower energies, in qualitative agreement with the interpretation of some but not all dissociative electron attachment measurements. © EDP Sciences, Societ́ Italiana di Fisica, Springer-Verlag 2012. Source


Kremer G.M.,University Federal Do Paran
Physica A: Statistical Mechanics and its Applications | Year: 2010

The aim of this work is to analyze the entropy, entropy flux and entropy rate of granular materials within the frameworks of the Boltzmann equation and continuum thermodynamics. It is shown that the entropy inequality for a granular gas that follows from the Boltzmann equation differs from the one of a simple fluid due to the presence of a term which can be identified as the entropy density rate. From the knowledge of a non-equilibrium distribution functionvalid for processes closed to equilibriumit is obtained that the entropy density rate is proportional to the internal energy density rate divided by the temperature, while the entropy flux is equal to the heat flux vector divided by the temperature. A thermodynamic theory of a granular material is also developed whose objective is the determination of the basic fields of mass density, momentum density and internal energy density. The constitutive laws are restricted by the principle of material frame indifference and by the entropy principle. Through the exploitation of the entropy principle with Lagrange multipliers, it is shown that the results obtained from the kinetic theory for granular gases concerning the entropy density rate and entropy flux are valid in general for processes close to equilibrium of granular materials, where linearized constitutive equations hold. © 2010 Elsevier B.V. All rights reserved. Source


Caddah M.K.,University of Campinas | Goldenberg R.,University Federal Do Paran
Systematic Botany | Year: 2012

During the preparation of a monographic treatment for a group of Miconia from the Atlantic Forest, Brazil, a new species was detected and is presented here. Miconia ruschiana can be recognized among other species of Miconia sect. Glossocentrum by the terete branches, shortly plinerved leaves abaxially covered by non-lepidote stellate trichomes, panicles with glomerulate ending branches, large flowers with the calyx bearing long, caducous, external lobes, and ovaries that are densely covered by trichomes at the apex. The new species is known from the mountains of the state of Espírito Santo in eastearn Brazil. © Copyright 2012 by the American Society of Plant Taxonomists. Source

Discover hidden collaborations