Couplage non-intrusif: réanalyse locale et calcul haute performance

Le couplage non-intrusif permet de prendre en compte efficacement des modifications locales (non-linéarités, conditions limites, géométrie) dans un modèle initial linéaire pré-existant sans que ce dernier ne soit affecté. Ce concept est étendu au cas des non-linéarités apparaissant de manière généralisée à l’échelle globale. Dans ce cas un ensemble de patchs recouvre l’intégralité du domaine, et le couplage peut être assimilé à une méthode de décomposition de domaine non-linéaire s’appuyant sur un logiciel industriel séquentiel

Non-Intrusive model coupling: A flexible way to handle local geometric and mechanical details in FEA

Computer Aided Engineering (CAE) often involves structural mechanics analysis (most of the time using the finite element method). When dealing with nonlinear complex models on large 3D structures, the computational cost becomes prohibitive. In this paper, we present the recent developments linked to an innovative computing method: non-intrusive coupling. Such a method allows to efficiently taking into account local modifications on an initial existing model in a non-intrusive way: the previously computed analysis is left unchanged. Large scale linear models can thus be easily computed, then localised nonlinear complex models can be used to pinpoint the analysis where required on the structure. After a presentation of the scientific context and a description of non-intrusive coupling methods, we will present its application to crack growth simulation and parallel structure analysis

Local/global non-intrusive parallel coupling for large scale mechanical analysis

The permanent increase in available computing resources can achieve more and more ambitious numerical simulations (most of the time using the finite element method). When dealing with non-linear complex models on large 3D structures, the computational cost becomes prohibitive. In this paper, we present the recent developments linked to an innovative computing method: non-intrusive coupling. Such a method allows to efficiently take into account local modifiations on an initial existing model in a non-intrusive way: the previously computed analysis is left unchanged. Large scale linear models can thus be easily computed, then localised non-linear complex models can be used to pinpoint the analysis where required on the structure. After a presentation of the scientific context and a description of non-intrusive coupling methods, we will present its application to crack growth simulation and parallel structure analysis

Residual error based adaptive mesh refinement with the non-intrusive patch algorithm

This paper deals with the introduction of mesh refinement techniques within the non-intrusive patch process. For this, an ad hoc residual based explicit error estimator is built, which is adapted to a multi-scale solution, associated with those non-intrusive mesh refinement technique. Moreover, to reduce the global cost of the process, one introduces an estimate of the convergence error of the non-intrusive algorithm, which allows to reduce the number of iterations. This method is discussed and illustrated in various numerical examples

Non-intrusive Coupling: Recent Advances and Scalable Nonlinear Domain Decomposition

This paper provides a detailed review of the global/local non-intrusive coupling algorithm. Such method allows to alter a global finite element model, without actually modifying its corresponding numerical operator. We also look into improvements of the initial algorithm (Quasi- Newton and dynamic relaxation), and provide comparisons based on several relevant test cases. Innovative examples and advanced applications of the non-intrusive coupling algorithm are provided, granting a handy framework for both researchers and engineers willing to make use of such process. Finally, a novel nonlinear domain decomposition method is derived from the global/local non-intrusive cou- pling strategy, without the need to use a parallel code or software. Such method being intended to large scale analysis, we show its scalability. Jointly, an efficient high level Message Passing Interface coupling framework is also proposed, granting an universal and flexible way for easy software coupling. A sample code is also given

Serum vitamin D and cingulate cortex thickness in older adults: quantitative MRI of the brain

International audienceBACKGROUND: Vitamin D insufficiency is associated with brain changes, and cognitive and mobility declines in older adults.OBJECTIVE: Our objective was to investigate in older adults whether vitamin D insufficiency<50nmol/L was associated with thinner cingulate cortex, a brain area related to cognitive functions influenced by vitamin D.METHODS: Two hundred and fifteen Caucasian older community-dwellers (mean±SD, 72.1±5.5years; 40% female) received a blood test and brain MRI. The thickness of perigenual anterior cingulate cortex, midcingulate cortex and posterior cingulate cortex was measured using FreeSurfer from T1-weighted MR images. Age, gender, education, BMI, mean arterial pressure, comorbidities, use of vitamin D supplements or anti-vascular drugs, MMSE, GDS, IADL, serum calcium and vitamin B9 concentrations, creatinine clearance were used as covariables.RESULTS: Participants with vitamin D insufficiency (n=80) had thinner total cingulate thickness than the others (24.6±1.9mm versus 25.3±1.4mm, P=0.001); a significant difference found for all 3 regions. Vitamin D insufficiency was cross-sectionally associated with a decreased total cingulate thickness (β=- 0.49, P=0.028). Serum 25OHD concentration correlated positively with the thickness of perigenual anterior (P=0.011), midcingulate (P=0.013) and posterior cingulate cortex (P=0.021).CONCLUSION: Vitamin D insufficiency was associated with thinner cingulate cortex in the studied sample of older adults. These findings provide insight into the pathophysiology of cognitive and mobility declines in older adults with vitamin D insufficiency.Copyright© Bentham Science Publishers; For any queries, please email at [email protected]

Vitamin D and the mechanisms, circumstances and consequences of falls in older adults: A case-control study

To determine i) whether cases of elderly fallers had lower serum 25-hydroxyvitamin D (25OHD) concentration than controls without history of falls; and ii) whether serum 25OHD concentration was associated with specific mechanisms, circumstances and consequences of falls.Case-control study with a 1:2 ratio.Geriatric ward of the University Hospital of Angers, France, between February 2012 and March 2014.216 inpatients (72 cases and 144 age- and gender-matched controls).Falls were defined as involuntary events causing the person to the ground or other lower level. The main mechanisms, circumstances and consequences of falls were identified using standardized questionnaires. Vitamin D deficiency was defined as serum 25OHD concentration 25nmol/L. Age, gender, body mass index, polypharmacy, use antihypertensive drugs, use psychoactive drugs, disability, cognitive performance, serum concentrations of parathyroid hormone, creatinine and albumin, and season of evaluation were used as potential confounders.216 participants (72 cases and 144 controls) were included in the study. There was no between-group difference in the prevalence of vitamin D deficiency (P=0.176). After adjusting for confounding factors, vitamin D deficiency was positively associated with falls (OR=4.03, P=0.014). Finally, the fallers with vitamin D deficiency exhibited more often orthostatic hypotension (68.8% against 33.3%, P=0.039) and a history of recurrent falls (85% against 50%, P=0.002) than those without vitamin D deficiency.This casecontrol study reported that vitamin D deficiency was associated with falls in older inpatients. There was a greater prevalence of orthostatic hypotension and of the reccurrence of falls among fallers with vitamin D deficiency, suggesting that vitamin D may influence the conditions predisposing to falls rather than the fall by itself

Circulating vitamin D concentration and age-related macular degeneration: Systematic review and meta-analysis

International audienceVitamin D may be involved in ocular function in older adults, but there is no current consensus on a possible association between circulating concentrations of 25-hydroxyvitamin D (25OHD) and the occurrence of age-related macular degeneration (AMD). Our objective was to systematically review and quantitatively assess the association of circulating 25OHD concentration with AMD. A Medline search was conducted in November 2015, with no date limit, using the MeSH terms "Vitamin D" OR "Vitamin D deficiency" OR "Ergocalciferols" OR 'Cholecalciferol' combined with "Age-related macular degeneration" OR "Macular degeneration" OR "Retinal degeneration" OR "Macula lutea" OR "Retina". Fixed and random-effects meta-analyses were performed to compute (i) standard mean difference in 25OHD concentration between AMD and non-AMD patients; (ii) AMD risk according to circulating 25OHD concentration. Of the 243 retrieved studies, 11 observational studies-10 cross-sectional studies and 1 cohort study-met the selection criteria. The number of participants ranged from 65 to 17,045 (52-100% women), and the number with AMD ranged from 31 to 1440. Circulating 25OHD concentration was 15% lower in AMD compared with non-AMD on average. AMD was inversely associated with the highest 25OHD quintile compared with the lowest (summary odds ratio (OR)=0.83 [95%CI:0.71-0.97]), notably late AMD (summary OR=0.47 [95%CI:0.28-0.79]). Circulating 25OHD<50nmol/L was also associated with late-stage AMD (summary OR=2.18 [95%CI:1.34-3.56]), an association that did not persist when all categories of AMD were considered (summary OR=1.26 [95%CI:0.90-1.76]). In conclusion, this meta-analysis provides evidence that high 25OHD concentrations may be protective against AMD, and that 25OHD concentrations below 50nmol/L are associated with late AMD.Copyright © 2016 Elsevier Ireland Ltd. All rights reserved

Contributions académiques à l'ANR ICARE

Présentation au nom des partenaires universitaires du projet ANR ICARE (U. Toulouse, GeM Nantes, LMT-Cachan)National audienceCette présentation a pour but de présenter les contributions deséquipes universitaires impliquées dans le projet ICARE : l'institutClément Ader de l'université de Toulouse, le GeM de l'école centrale deNantes, et le LMT-Cachan de l'école normale de Cachan.Le projet a pour but de proposer des méthodes non-intrusives quipermettent l'amélioration des modèles de calcul et de leurs solveurstout en préservant autant que possible l'environnement de travail desindustriels. Nos travaux ont permis d'une part de perfectionner la technique decouplage en la reliant à de grandes familles de méthodes (méthodes dedécomposition de domaine, méthodes multigrille, techniques d'operator-splitting) et en proposant diverses techniques d'accélération pourlimiter les coûts de calcul, et en améliorant les techniques deraccord. D'autre part d'étendre le domaine d'application de la méthode. i) Enpermettant le couplage entres modèles simplifiés globaux (plaques,coques + connecteurs 1D) et modèles raffinés 3D là où ceci sontnécessaires (prise en compte de boulons dans toutes leur complexité etutilisation d'un logiciel dédié à leur simulation). ii) En permettantd'évaluer les effets structuraux d'incertitudes locales. iii) Enpermettant l'introduction d'une hiérarchie de modèles (analytique puisXFEM) au sein d'un calcul standard, conduisant à des calculs efficacesde la fissuration de pièces industrielles. iv) En évaluant lespossibilités d'utiliser le calcul non-intrusif pour la parallélisationcomplète d'un calcul non-linéaire

Contributions académiques à l'ANR ICARE

Présentation au nom des partenaires universitaires du projet ANR ICARE (U. Toulouse, GeM Nantes, LMT-Cachan)National audienceCette présentation a pour but de présenter les contributions deséquipes universitaires impliquées dans le projet ICARE : l'institutClément Ader de l'université de Toulouse, le GeM de l'école centrale deNantes, et le LMT-Cachan de l'école normale de Cachan.Le projet a pour but de proposer des méthodes non-intrusives quipermettent l'amélioration des modèles de calcul et de leurs solveurstout en préservant autant que possible l'environnement de travail desindustriels. Nos travaux ont permis d'une part de perfectionner la technique decouplage en la reliant à de grandes familles de méthodes (méthodes dedécomposition de domaine, méthodes multigrille, techniques d'operator-splitting) et en proposant diverses techniques d'accélération pourlimiter les coûts de calcul, et en améliorant les techniques deraccord. D'autre part d'étendre le domaine d'application de la méthode. i) Enpermettant le couplage entres modèles simplifiés globaux (plaques,coques + connecteurs 1D) et modèles raffinés 3D là où ceci sontnécessaires (prise en compte de boulons dans toutes leur complexité etutilisation d'un logiciel dédié à leur simulation). ii) En permettantd'évaluer les effets structuraux d'incertitudes locales. iii) Enpermettant l'introduction d'une hiérarchie de modèles (analytique puisXFEM) au sein d'un calcul standard, conduisant à des calculs efficacesde la fissuration de pièces industrielles. iv) En évaluant lespossibilités d'utiliser le calcul non-intrusif pour la parallélisationcomplète d'un calcul non-linéaire