100 research outputs found
Strict bounding of quantities of interest in computations based on domain decomposition
This paper deals with bounding the error on the estimation of quantities of
interest obtained by finite element and domain decomposition methods. The
proposed bounds are written in order to separate the two errors involved in the
resolution of reference and adjoint problems : on the one hand the
discretization error due to the finite element method and on the other hand the
algebraic error due to the use of the iterative solver. Beside practical
considerations on the parallel computation of the bounds, it is shown that the
interface conformity can be slightly relaxed so that local enrichment or
refinement are possible in the subdomains bearing singularities or quantities
of interest which simplifies the improvement of the estimation. Academic
assessments are given on 2D static linear mechanic problems.Comment: Computer Methods in Applied Mechanics and Engineering, Elsevier,
2015, online previe
A strict error bound with separated contributions of the discretization and of the iterative solver in non-overlapping domain decomposition methods
This paper deals with the estimation of the distance between the solution of
a static linear mechanic problem and its approximation by the finite element
method solved with a non-overlapping domain decomposition method (FETI or BDD).
We propose a new strict upper bound of the error which separates the
contribution of the iterative solver and the contribution of the
discretization. Numerical assessments show that the bound is sharp and enables
us to define an objective stopping criterion for the iterative solverComment: Computer Methods in Applied Mechanics and Engineering (2013) onlin
Strict lower bounds with separation of sources of error in non-overlapping domain decomposition methods
This article deals with the computation of guaranteed lower bounds of the
error in the framework of finite element (FE) and domain decomposition (DD)
methods. In addition to a fully parallel computation, the proposed lower bounds
separate the algebraic error (due to the use of a DD iterative solver) from the
discretization error (due to the FE), which enables the steering of the
iterative solver by the discretization error. These lower bounds are also used
to improve the goal-oriented error estimation in a substructured context.
Assessments on 2D static linear mechanic problems illustrate the relevance of
the separation of sources of error and the lower bounds' independence from the
substructuring. We also steer the iterative solver by an objective of precision
on a quantity of interest. This strategy consists in a sequence of solvings and
takes advantage of adaptive remeshing and recycling of search directions.Comment: International Journal for Numerical Methods in Engineering, Wiley,
201
Improved recovery of admissible stress in domain decomposition methods - application to heterogeneous structures and new error bounds for FETI-DP
This paper investigates the question of the building of admissible stress
field in a substructured context. More precisely we analyze the special role
played by multiple points. This study leads to (1) an improved recovery of the
stress field, (2) an opportunity to minimize the estimator in the case of
heterogeneous structures (in the parallel and sequential case), (3) a procedure
to build admissible fields for FETI-DP and BDDC methods leading to an error
bound which separates the contributions of the solver and of the
discretization
Pilotage de stratĂ©gies de calcul par dĂ©composition de domaine par des objectifs de prĂ©cision sur des quantitĂ©s dâintĂ©rĂȘt
This research work aims at contributing to the development of verification tools in linear mechanical problems within the framework of non-overlapping domain decomposition methods.* We propose to improve the quality of the statically admissible stress field required for the computation of the error estimator thanks to a new methodology of stress reconstruction in sequential context and thanks to optimizations of the computations of nodal reactions in substructured context.* We prove guaranteed upper and lower bounds of the error that separates the algebraic error (due to the iterative solver) from the discretization error (due to the finite element method) for both global error measure mentand goal-oriented error estimation. It enables the definition of a new stopping criterion for the iterative solver which avoids over-resolution.* We benefit the information provided by the error estimator and the Krylov subspaces built during the resolution to set an auto-adaptive strategy. This strategy consists in sequel of resolutions and takes advantage of adaptive remeshing and recycling of search directions .We apply the steering of the iterative solver by objective of precision on two-dimensional mechanical examples.Ces travaux de recherche ont pour objectif de contribuer au dĂ©veloppement et Ă l'exploitation d'outils de vĂ©rification des problĂšmes de mĂ©canique linĂ©aires dans le cadre des mĂ©thodes de dĂ©composition de domaine sans recouvrement. Les apports de cette thĂšse sont multiples : * Nous proposons d'amĂ©liorer la qualitĂ© des champs statiquement admissibles nĂ©cessaires Ă l'Ă©valuation de l'estimateur par une nouvelle mĂ©thodologie de reconstruction des contraintes en sĂ©quentiel et par des optimisations du calcul de l'intereffort en cadre sous-structurĂ©.* Nous dĂ©montrons des bornes infĂ©rieures et supĂ©rieures de l'erreur sĂ©parant l'erreur algĂ©brique (due au solveur itĂ©ratif) de l'erreur de discrĂ©tisation (due Ă la mĂ©thode des Ă©lĂ©ments finis) tant pour une mesure globale que pour une quantitĂ© d'intĂ©rĂȘt. Cette sĂ©paration permet la dĂ©finition d'un critĂšre d'arrĂȘt objectif pour le solveur itĂ©ratif.* Nous exploitons les informations fournies par l'estimateur et les espaces de Krylov gĂ©nĂ©rĂ©s pour mettre en place une stratĂ©gie auto-adaptative de calcul consistant en une chaĂźne de rĂ©solution mettant Ă profit remaillage adaptatif et recyclage des directions de recherche. Nous mettons en application le pilotage du solveur par un objectif de prĂ©cision sur des exemples mĂ©caniques en deux dimensions
The Spatial String Tension, Thermal Phase Transition, and AdS/QCD
We present results of modeling the temperature dependence of the spatial
string tension and thermal phase transition in a five-dimensional framework
nowadays known as AdS/QCD. For temperatures close to the critical one we find a
behaviour remarkably consistent with the lattice results.Comment: 8 pages, 4 figure
Retour d'expérience sur le MOOC pratique du dimensionnement en mécanique
L'objet de cette communication est de proposer un retour d'expérience sur l'un des premiers MOOC dans le domaine de la mécanique proposé sur la plateforme FUN. Nous en présenterons les principales caractéristiques et reviendrons sur les difficultés de la genÚse et de la construction de ce MOOC. Une analyse de la premiÚre mise en ligne de ce MOOC (janvier - avril 2015) sera également proposée.  Conformément à la demande exprimé par les reviewers, nous tenterons (avec le peu d'expérience que nous avons) de donner lors de la présentation orale quelques conseils à suivre pour monter et animer un MOOC
Pour une démocratie socio-environnementale : cadre pour une plate-forme participative « transition écologique »
Contribution publiĂ©e in Penser une dĂ©mocratie alimentaire Volume II â Proposition Lascaux entre ressources naturelles et besoins fondamentaux, F. Collart Dutilleul et T. BrĂ©ger (dir), Inida, San JosĂ©, 2014, pp. 87-111.International audienceLâanthropocĂšne triomphant actuel, avec ses forçages environnementaux et sociaux, est Ă lâorigine de lâaccĂ©lĂ©ration des dĂ©gradations des milieux de vie sur Terre et de lâaccentuation des tensions sociales et gĂ©opolitiques. Passer Ă un anthropocĂšne de gestion Ă©quitable, informĂ© et sobre vis-Ă -vis de toutes les ressources et dans tous les secteurs dâactivitĂ© (slow anthropocene), impose une analyse prĂ©alable sur lâensemble des activitĂ©s et des rapports humains. Cette transition dite « Ă©cologique », mais en rĂ©alitĂ© Ă la fois sociĂ©tale et Ă©cologique, est tout sauf un ajustement technique de secteurs dits prioritaires et technocratiques. Elle est avant tout culturelle, politique et philosophique au sens propre du terme. Elle est un horizon pour des trajectoires de dĂ©veloppement humain, pour des constructions sociales et Ă©conomiques, censĂ©es redĂ©finir socialement richesse, bien-ĂȘtre, travail etc. La dĂ©nomination « transition Ă©cologique » est largement vĂ©hiculĂ©e, mais ses bases conceptuelles ne sont pas entiĂšrement acquises ni mĂȘme Ă©laborĂ©es. Dans ce contexte, les Ă©tudiants en premiĂšre annĂ©e de Master BioSciences Ă lâEcole Normale SupĂ©rieure (ENS) de Lyon ont prĂ©parĂ© une premiĂšre Ă©tude analytique de ce changement radical et global de sociĂ©tĂ© pour mieux comprendre dans quelle sociĂ©tĂ© ils souhaitent vivre, en donnant du sens aux activitĂ©s humaines prĂ©sentes et Ă venir. Une trentaine de dossiers sur divers secteurs dâactivitĂ©s et acteurs de la sociĂ©tĂ© ont Ă©tĂ© produits et ont servis de support Ă cette synthĂšse. Plus largement, le but est de construire un socle conceptuel et une plate-forme de travail sur lesquels les questions de fond, mais aussi opĂ©rationnelles, peuvent ĂȘtre posĂ©es et Ă©tudiĂ©es en permanence. Cette dĂ©marche participative est ouverte Ă la collectivitĂ© sur le site http://institutmichelserres.ens-lyon.fr/
The impact of the Fungus-Host-Microbiota interplay upon Candida albicans infections : current knowledge and new perspectives
ACKNOWLEDGEMENTS: We thank our friends and colleagues in the medical mycology, fungal immunology and microbiota fields for many thought-provoking discussions. FUNDING: We received funding from the European Unionâs Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie action, Innovative Training Network: FunHoMic; grant N° 812969. CdE received funding from the French Government âInvestissement dâAvenirâ program (Laboratoire dâExcellence Integrative Biology of Emerging Infectious Diseases, ANR-10-LABX-62-IBEID), the Agence Nationale de la Recherche (ERA-Net Infect-ERA, FUNCOMPATH, ANR-14-IFEC-0004), the EU Horizon2020 consortium âHost-Directed Medicine in invasive FUNgal infectionsâ - HDM-FUN (Grant Agreement 847507). SLL and CdE received funding from the Swiss National Science Foundation (Sinergia program, #CRSII5_173863). BIOASTER received funding from the French Government âInvestissement dâAvenirâ program (Grant No. ANR-10-AIRT-03). MSG was supported by a Humboldt Research Fellowship for Postdoctoral Researchers by the Alexander von Humboldt-Foundation and the Deutsche Forschungsgemeinschaft (DFG) Emmy Noether Program (project no. 434385622 / GR 5617/1-1). BH was supported by the Deutsche Forschungsgemeinschaft (DFG) project Hu 532/20-1, project C1 within the Collaborative Research Centre (CRC)/Transregio 124 FungiNet and the Balance of the Microverse Cluster under GermanyÂŽs Excellence Strategy â EXC 2051 â Project-ID 390713860, the EU Horizon2020 consortium âHost-Directed Medicine in invasive FUNgal infectionsâ - HDM-FUN (Grant Agreement 847507), the Leibniz Association Campus InfectoOptics SAS-2015-HKI-LWC and the Wellcome Trust (215599/Z/19/Z). IDJ was supported by the Deutsche orschungsgemeinschaft (DFG) project C5 within the Collaborative Research Centre (CRC)/Transregio 124 FungiNet and the Balance of the Microverse Cluster under GermanyÂŽs Excellence Strategy â EXC 2051 â Project-ID 390713860, the Leibniz Association Campus InfectoOptics SAS-2015-HKI-LWC and the Wellcome Trust (Grant 215599/Z/19/Z). CM received funding from the the Instituto de Salud Carlos III/FEDER. MGN was supported by an ERC Advanced Grant (#833247) and a Spinoza grant of the Netherlands Organization for Scientific Research. CAM was supported by EU Horizon2020 consortium âHost-Directed Medicine in invasive FUNgal infectionsâ -HDM-FUN (Grant Agreement 847507) and the Wellcome Trust Strategic Award for Medical Mycology and Fungal Immunology (097377/Z/11/Z). AWW receives core funding support from the Scottish Governmentâs Rural and Environment Science and Analytical Services (RESAS). AJPB was supported by a programme grant from the UK Medical Research Council (MR/M026663/1) and by the Medical Research Council Centre for Medical Mycology at the University of Exeter (MR/N006364/1).Peer reviewedPublisher PD
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