Search results for "Statistica"
showing 10 items of 5969 documents
Crystallization of hard spheres revisited. II. Thermodynamic modeling, nucleation work, and the surface of tension
2018
Combining three numerical methods (forward flux sampling, seeding of droplets, and finite-size droplets), we probe the crystallization of hard spheres over the full range from close to coexistence to the spinodal regime. We show that all three methods allow us to sample different regimes and agree perfectly in the ranges where they overlap. By combining the nucleation work calculated from forward flux sampling of small droplets and the nucleation theorem, we show how to compute the nucleation work spanning three orders of magnitude. Using a variation of the nucleation theorem, we show how to extract the pressure difference between the solid droplet and ambient liquid. Moreover, combining th…
Simulation studies of fluid critical behaviour
1997
We review and discuss recent advances in the simulation of bulk critical phenomena in model fluids. In particular we emphasise the extensions to finite-size scaling theory needed to cope with the lack of symmetry between coexisting fluid phases. The consequences of this asymmetry for simulation measurements of quantities such as the particle density and the heat capacity are pointed out and the relationship to experiment is discussed. A general simulation strategy based on the finite-size scaling theory is described and its utility illustrated via Monte-Carlo studies of the Lennard-Jones fluid and a two-dimensional spin fluid model. Recent applications to critical polymer blends and solutio…
Evaluating Thermal Corrections for Adsorption Processes at the Metal/Gas Interface
2019
International audience; Adsorption and desorption steps are key for active catalysts and rely on a subtle balance between enthalpic and entropic terms. While the enthalpic term is becoming ever more accurate through density functional development, the entropic term remains underrated and its precise determination a great challenge. In this work, we have performed extensive first principles thermodynamic integration (TI) simulations for the 1 adsorption of small (e.g., CO) to larger (e.g., phenol) molecules at metallic surfaces and compared their adsorption free energies to the values obtained by vertical, static statistical mechanics approximations to thermal corrections invoking three diff…
Modeling the Spatial Distribution of Xylella fastidiosa: A Nonstationary Approach with Dispersal Barriers
2022
Spatial species distribution models often assume isotropy and stationarity, implying that spatial dependence is direction-invariant and uniform throughout the study area. However, these assumptions are violated when dispersal barriers are present. Despite this, the issue of nonstationarity has been little explored in the context of plant health. The objective of this study was to evaluate the influence of barriers in the distribution of Xylella fastidiosa in the demarcated area in Alicante, Spain. Occurrence data from 2018 were analyzed through spatial Bayesian hierarchical models. The stationary model, illustrating a scenario without control interventions or geographical features, was com…
Methods to Compute Pressure and Wall Tension in Fluids containing Hard Particles
2011
Colloidal systems are often modelled as fluids of hard particles (possibly with an additional soft attraction, e.g. caused by polymers also contained in the suspension). in simulations of such systems, the virial theorem cannot be straightforwardly applied to obtain the components of the pressure tensor. In systems confined by walls, it is hence also not straightforward to extract the excess energy due to the wall (the "wall tension") from the pressure tensor anisotropy. A comparative evaluation of several methods to circumvent this problem is presented, using as examples fluids of hard spheres and the Asakura-Oosawa model of colloid-polymer mixtures with a size ratio $q=0.15$ (for which th…
A cohort perspective of youth poverty in the United States
2014
The aim of this paper is to study the degree of poverty persistence of American young adults and its evolution. Using data from NLSY79 and NLSY97, respectively, we compared two cohorts followed along eight years (in the 1980s and in the 2000s) to asses which socio-economic characteristics preserve them to fall in chronic poverty or determine the duration and severity of this detrimental experience.
Forte baisse de l'embauche des jeunes en Bourgogne
2010
Réalisée en Bourgogne depuis vingt-cinq ans, l'enquête Insertion dans la vie active constitue un outil particulier et unique qui donne la possibilité de suivre l'évolution des conditions d'entrée des jeunes sur le marché du travail. Cette note présente les résultats de la dernière interrogation menée en février 2009, et donne un aperçu de la transition de l'école à l'emploi. En Bourgogne, 7 400 élèves et 4 800 apprentis âgés de 20 ans en moyenne, ont été interrogés sur leur situation professionnelle. Sept mois après la fin des études, 47 % des filles et 55 % des garçons sont salarié-e-s en février 2009. Les jeunes de la région n'échappent pas à la crise économique internationale illustrée p…
De la formation à l'emploi : une transition difficile
2006
Pour connaître le devenir des anciens élèves et apprentis, le ministère de l'Éducation nationale réalise des enquêtes depuis de nombreuses années, avec l'appui des établissements scolaires et des centres de formation d'apprentis. Cette note présente les résultats des dernières enquêtes effectuées en 2005, qui appréhendent les situations des jeunes sept mois après la fin de leurs études en Bourgogne.
L'entrée dans la vie active des jeunes de Bourgogne
2007
Pour connaître le devenir des anciens élèves et apprentis, le ministère de l'Éducation nationale réalise des enquêtes depuis de nombreuses années, avec l'appui des établissements scolaires et des centres de formation. Cette note présente les résultats de la dernière enquête effectuée en 2006, qui appréhende les situations des jeunes sept mois après la fin de leur scolarité en Bourgogne.
Effect of internal noise on the relaxation time of an yttria stabilized zirconia-based memristor
2022
The effects of temperature on the switching kinetics of an yttrium-stabilized zirconia-based memristor from a low-resistance state to a high-resistance state have been experimentally investigated. It was found that the memristor relaxation time depends on the temperature in a non-monotonous way, with a maximum observed at the temperature close to 55 °C. This nonmonotonic behavior is a signature of the noise-enhanced stability phenomenon observed in all physical and complex systems characterized by metastable states.