Finite element model of primary recrystallization in polycrystalline aggregates using a level set framework

International audienceThe paper describes a robust finite element model of interface motion in media with multiple domains and junctions, as is the case in polycrystalline materials. The adopted level set framework describes each domain (grain) with a single level set function, while avoiding the creation of overlap or vacuum between these domains. The finite element mesh provides information on stored energies, calculated from a previous deformation step. Nucleation and growth of new grains are modelled by inserting additional level set functions around chosen nodes of the mesh. The kinetics and topological evolutions induced by primary recrystallization are discussed from simple test cases to more complex configurations and compared with the Johnson-Mehl-Avrami-Kolmogorov theory

Impact of species and antibiotic therapy of enterococcal peritonitis on 30-day mortality in critical care - An analysis of the OUTCOMEREA database

Introduction: Enterococcus species are associated with an increased morbidity in intraabdominal infections (IAI). However, their impact on mortality remains uncertain. Moreover, the influence on outcome of the appropriate or inappropriate status of initial antimicrobial therapy (IAT) is subjected to debate, except in septic shock. The aim of our study was to evaluate whether an IAT that did not cover Enterococcus spp. was associated with 30-day mortality in ICU patients presenting with IAI growing with Enterococcus spp. Material and methods: Retrospective analysis of French database OutcomeRea from 1997 to 2016. We included all patients with IAI with a peritoneal sample growing with Enterococcus. Primary endpoint was 30-day mortality. Results: Of the 1017 patients with IAI, 76 (8%) patients were included. Thirty-day mortality in patients with inadequate IAT against Enterococcus was higher (7/18 (39%) vs 10/58 (17%), p = 0.05); however, the incidence of postoperative complications was similar. Presence of Enterococcus spp. other than E. faecalis alone was associated with a significantly higher mortality, even greater when IAT was inadequate. Main risk factors for having an Enterococcus other than E. faecalis alone were as follows: SAPS score on day 0, ICU-acquired IAI, and antimicrobial therapy within 3 months prior to IAI especially with third-generation cephalosporins. Univariate analysis found a higher hazard ratio of death with an Enterococcus other than E. faecalis alone that had an inadequate IAT (HR = 4.4 [1.3-15.3], p = 0.019) versus an adequate IAT (HR = 3.1 [1.0-10.0], p = 0.053). However, after adjusting for confounders (i.e., SAPS II and septic shock at IAI diagnosis, ICU-acquired peritonitis, and adequacy of IAT for other germs), the impact of the adequacy of IAT was no longer significant in multivariate analysis. Septic shock at diagnosis and ICU-acquired IAI were prognostic factors. Conclusion: An IAT which does not cover Enterococcus is associated with an increased 30-day mortality in ICU patients presenting with an IAI growing with Enterococcus, especially when it is not an E. faecalis alone. It seems reasonable to use an IAT active against Enterococcus in severe postoperative ICU-acquired IAI, especially when a third-generation cephalosporin has been used within 3 months. © 2019 The Author(s)

Eléments Finis anisotropes pour le calcul d'écoulements multiphasiques

Dans ce travail on s'intéresse au calcul d'écoulements de fluides incompressibles (liquide ou gaz à petite vitesse) à faible ou grand Reynolds en utilisant de façon exhaustive l'adaptation de maillage anisotrope. De plus on étend le processus d'adaptation à des écoulements multiphasiques, liquide-air, fluide-solide, fluide-structure en associant à un solveur VMS (éléments finis stabilisés) une approche Level Set, sans traitement spécifique à l'interface autre que l'adaptation. L'adaptation anisotrope est basée sur une analyse de l'erreur d'interpolation le long des arêtes en toute dimension et un processus original de construction des métriques aux noeuds du maillage. On montrera à partir de nombreuses applications de nouvelles possibilités en couches limites, tension de surface, surfaces libres et interfaces

Notation pratique de la quantité vocalique et de la tonalité en rundi et rwanda

info:eu-repo/semantics/publishe

Classification d'un échantillon de langues bantoues d'après la lexicostatistique

Coupez André, Evrard E., Vansina Jan. Classification d'un échantillon de langues bantoues d'après la lexicostatistique. In: Africana Linguistica 6, 1975. pp. 131-158

Level set framework for the finite element modelling of recrystallization and grain growth in polycrystalline materials

International audienceThe paper describes a level set framework for the finite-element modelling of recrystallization in polycrystalline materials, including the nucleation, primary recrystallization and grain growth stages. A set of convection-reinitialization-diffusion equations is implemented within a finite-element formulation to describe boundary motion, according to a kinetic law relating the velocity of the boundary to a thermodynamic driving force. Different theoretical test cases illustrate the potential of the method for simulations of recrystallization and grain growth following large plastic deformation and/or considering complex microstructure

Level Set framework for the numerical modelling of recrystallization

International audienceGeneric model for recrystallization that provides quantitatively correct predictions of crystallographic orientation and grain size distributions has long been sought to fill a critical link to model material processing from start to finish. To date, no such theory exists. Grain growth or recrystallization, like many similar state-altering processes that are driven by thermal energy and internal energy of structural defects are not very well understood. Multiscale models are therefore in principle needed to fully describe recrystallization phenomena in a generic way. Over the last decade, considerable progress has been made in the numerical simulation of primary recrystallization and grain growth. Common approaches include the Monte Carlo (MC) method, the Cellular Automaton (CA) method, the phase field method and the level set method. In this work, a new level set framework is proposed. It is shown that the proposed formulation, associated to adaptive anisotropic automatic remeshing, is an efficient and accurate tool. Nucleation phenomenon can also be described accurately. Some validation test cases will be compared with Monte Carlo recrystallization model. More complexes 2D and 3D simulations, using a realistic computation of the stored energy field within the aggregate, with crystal plasticity based constitutive laws, will be detailed. The advantages and disadvantages of both methods will be discussed

A level set framework for the numerical modelling of primary recrystallization

International audienc