Multiscale computational homogenization methods with a gradient enhanced scheme based on the discontinuous Galerkin formulation

in Computer Methods in Applied Mechanics & Engineering (2013), 260

When considering problems of dimensions close to the characteristic length of the material, the size e ects can not be neglected and the classical (so–called first–order) multiscale computational ... [more ▼]

When considering problems of dimensions close to the characteristic length of the material, the size e ects can not be neglected and the classical (so–called first–order) multiscale computational homogenization scheme (FMCH) looses accuracy, motivating the use of a second–order multiscale computational homogenization (SMCH) scheme. This second–order scheme uses the classical continuum at the micro–scale while considering second–order continuum at the macro–scale. Although the theoretical background of the second–order continuum is increasing, the implementation into a finite element code is not straightforward because of the lack of high–order continuity of the shape functions. In this work, we propose a SMCH scheme relying on the discontinuous Galerkin (DG) method at the macro–scale, which simplifies the implementation of the method. Indeed, the DG method is a generalization of weak formulations allowing for inter-element discontinuities either at the C0 level or at the C1 level, and it can thus be used to constrain weakly the C1 continuity at the macro–scale. The C0 continuity can be either weakly constrained by using the DG method or strongly constrained by using usual C0 displacement–based finite elements. Therefore, two formulations can be used at the macro–scale: (i) the full–discontinuous Galerkin formulation (FDG) with weak C0 and C1 continuity enforcements, and (ii) the enriched discontinuous Galerkin formulation (EDG) with high–order term enrichment into the conventional C0 finite element framework. The micro–problem is formulated in terms of standard equilibrium and periodic boundary conditions. A parallel implementation in three dimensions for non–linear finite deformation problems is developed, showing that the proposed method can be integrated into conventional finite element codes in a straightforward and e cient way. [less ▲]

"Rends excellente ta place de l'Occident". Pour une approche intégrée de la décoration des tombes thébaines sous le règne d'Amenhotep II

Doctoral thesis (2013)

Sur l’ensemble des règnes de la XVIIIème dynastie égyptienne, il apparaît, jusqu’assez récemment, que celui d’Amenhotep II a suscité un intérêt moindre de la part des chercheurs, ces derniers lui ayant ... [more ▼]

Sur l’ensemble des règnes de la XVIIIème dynastie égyptienne, il apparaît, jusqu’assez récemment, que celui d’Amenhotep II a suscité un intérêt moindre de la part des chercheurs, ces derniers lui ayant préféré, de manière générale, ceux plus longs ou historiquement plus déterminants de Thoutmosis III, d’Amenhotep III ou encore d’Amenhotep IV – Akhenaton, et ce bien que plusieurs travaux fondamentaux aient déjà permis de mettre en évidence une série de traits spécifiques à cette période. Le règne d’Amenhotep II se caractérise en effet par une nouvelle gestion du gouvernement, où le phénomène d’hérédité qui s’installait progressivement dans certaines fonctions est endigué mais où, dans le même temps, les membres de quelques familles puissantes et particulièrement proches du roi se voient confier les plus hautes charges de l’administration. Aussi, pour la réalisation de leurs « demeures d’éternité », véritables cartes de visite de leurs propriétaires et témoins privilégiés des grandes orientations de l’époque, les principaux officiels du règne d’Amenhotep II ont pour la plupart porté leur choix sur la partie supérieure de la colline de Sheikh Abd el-Gourna, site particulièrement prisé pour sa position surélevée comme pour la proximité qu’il entretient avec les temples funéraires royaux. Les tombes de ces dignitaires se distinguent néanmoins de celles de leurs prédécesseurs, par des dimensions colossales, par l’étendue et la complexité des dispositifs intérieurs ainsi que par le choix de représentations et d’inscriptions qui, placées à des endroits stratégiques, soulignent les relations étroites qu’entretenait le propriétaire avec Pharaon. En outre, le traitement même des scènes figurées est également, à ce moment précis, l’objet de modifications considérables ; l’art pictural, qui se voulait depuis ses origines purement conceptuel et d’apparence hiéroglyphique, s’assouplit à divers égards pour prendre une apparence plus « sensuelle », plus « perceptuelle ». Ces transformations, qui s’amplifieront encore durant les règnes suivants, jettent déjà, en quelque sorte, les bases de ce qui deviendra la « révolution » du règne d’Akhenaton. Dans ce contexte, la présente thèse vise, au moyen d’une analyse pluridisciplinaire et « intégrée » de la décoration des chapelles du règne d’Amenhotep II, à caractériser dans une perspective socioculturelle les changements iconographiques et stylistiques qui affectent cette production artistique en pleine mutation. [less ▲]

Mise au point d’un protocole de multiplication in vitro de Jatropha curcas L. en vue d’une application à grande échelle

Doctoral thesis (2013)

Jatropha curcas L. is a wild plant, that emerged as a source of energy for biodiesel production. It has acquired significant economic potential as it does not compete with the edible oil supplies ... [more ▼]

Jatropha curcas L. is a wild plant, that emerged as a source of energy for biodiesel production. It has acquired significant economic potential as it does not compete with the edible oil supplies. Realizing its importance, in vitro multiplication methods have been established to meet the demand of large scale supply of superior clones. In order to improve the in vitro multiplication rate (number of shoots/explant/subculture/three weeks) of J. curcas, axillary nodes taken from young plants of two accessions (originating from Cameroon and Senegal) have been cultivated for three weeks on a Murashige and Skoog (1962) medium (MS) supplemented with 8.87 µM BAP, 4.92 µM IBA, and 30 g/l sucrose at pH 5.7±0.1, and solidified with 0.7% agar. The shoots obtained from each original explant were then transferred to a multiplication media consisting of MS medium supplemented with 2.21 to 8.9 μM BA or 2.21 to 8.9 μM kinetin in combination with 2.46 μM IBA. Each combination was completed with 12.2 mg.l-1 adenine sulfate and 25 mg.l-1 of glutamine. The best multiplication rate was obtained for the PM medium containing 6.65 μM BA and 2.46 μM IBA. The mean multiplication rate is 8.1 shoots per explant during the 7 following subcultures. Leafy shoots obtained have been rooted in a medium containing half of the major mineral and minor mineral components of MS supplemented with 5.7 μM IBA, then acclimated with a survival rate of 97%. With the aim of finding a more efficient production protocol practicable on a large-scale, an alternative method has been developed to regenerate whole plants of J. curcas from nodes via the induction of buds aggregates. Histological observation shows that bud aggregates are simultaneously formed through axillary budding and adventitious regeneration of buds. These buds are elongated in MS medium supplemented with 2.21 µM BA, 5.70 µM IAA (indole-3-acetic acid) and 15 mg.l-1 L arginine. The leafy stems are then rooted on MS containing 2.46 µM IBA, 2% sucrose, and 0.7% agar. The entire process takes 14 weeks with 98% plants survival after acclimatization. We obtain a multiplication rate of 13 buds per explant per subculture. This protocol is more efficient than previously known protocols. [less ▲]

De la perversion au pervers ; du sexuel à l’adaptatif

Scientific conference (2013, June 08)

Proposition de nouveaux indices de détection de patrons de réponses inappropriés dans le contexte des enquêtes et des épreuves d’évaluation des apprentissages

Conference (2013, June 07)

Il n’est pas rare de voir des étudiants répondre de façon inappropriée à une épreuve d’évaluation comportant des items à réponses choisies. Par exemple, certains individus peuvent tricher alors que ... [more ▼]

Il n’est pas rare de voir des étudiants répondre de façon inappropriée à une épreuve d’évaluation comportant des items à réponses choisies. Par exemple, certains individus peuvent tricher alors que d’autres peuvent tenter de se sous-classer intentionnellement à un examen. Plusieurs approches ont été développées pour faire la détection de ce type d’étudiants. À ce jour, l’approche la plus prometteuse est l’utilisation d’indice de détection de type person‐fit (Meijer et Sijtsma, 2001). L’indice de détection lz (Drasgow, Levine et Williams, 1985) est fort probablement le plus utilisé et le plus connu d’entre tous. Malheureusement, cet indice est fortement affecté par le fait que l’habileté des étudiants est estimée et non pas réelle ; ce qui peut biaiser son calcul (Molenaar et Hoijtink, 1990). Pour pallier ce problème, Snijders (2001) a proposé une correction qui permet de diminuer considérablement le biais associé à la moyenne et à la variance de l’indice lz. Dans le cadre de notre projet doctoral, nous nous inspirerons de la suggestion de Snijders (2001) pour corriger deux autres indices de détection de patrons de réponses inappropriés : l’infit mean square (u) et l’outfit mean square (w). À cette fin, nous utiliserons une approche monte carliste afin d’investiguer plus en détails l’erreur de type 1 et la puissance de ces autres indices. Nos résultats préliminaires, que nous présenterons lors de cette communication, montrent que ces autres indices corrigés semblent eux aussi plus efficaces que leur version traditionnelle sans correction. [less ▲]

Innovative Methodology for the Definition of Design Spaces of Chromatographic Methods

Conference (2013, June 06)

As defined by ICH [1] and FDA, Quality by Design (QbD) stands for “a systematic approach to development that begins with predefined objectives and emphasizes product and process understanding and process ... [more ▼]

As defined by ICH [1] and FDA, Quality by Design (QbD) stands for “a systematic approach to development that begins with predefined objectives and emphasizes product and process understanding and process control, based on sound science and quality risk management”. A risk–based QbD–compliant approach is proposed for the robust development of analytical methods. This methodology based on Design of Experiments (DoE) to study the experimental domain models the retention times at the beginning, the apex and the end of each peak corresponding to the compounds of a mixture and uses the separation criterion (S) rather than the resolution (RS) as a Critical Quality Attribute. Stepwise multiple linear regressions are used to create the models. The estimated error is propagated from the modelled responses to the separation criterion (S) using Monte Carlo simulations in order to estimate the predictive distribution of the separation criterion (S) over the whole experimental domain. This allows finding ranges of operating conditions that will guarantee a satisfactory quality of the method in its future use. These ranges define the Design Space (DS) of the method. In chromatographic terms, the chromatograms processed at operating conditions within the DS will assuredly show high quality, with well separated peaks and short run time, for instance. This Design Space can thus be defined as the subspace, necessarily encompassed in the experimental domain (i.e. the knowledge space), within which the probability for the criterion to be higher than an advisedly selected threshold is higher than a minimum quality level. Precisely, the DS is defined as “the multidimensional combination and interaction of input variables (e.g., material attributes) and process parameters that have been demonstrated to provide assurance of quality” [1]. Therefore, this DS defines a region of operating conditions that provide prediction of assurance of quality rather than only quality as obtained with traditional mean response surface optimisation strategies. For instance, in the liquid chromatography there is a great difference in e.g. predicting a resolution (RS) higher than 1.5 vs. predicting that the probability for RS to be higher than 1.5 (i.e. P(RS> 1.5)) is high. The presentation of this global methodology will be illustrated for the robust optimisation and DS definition of several liquid chromatographic methods dedicated to the separation of different mixtures: pharmaceutical formulations, API and impurities/degradation products, plant extracts, separation of enantiomers, … [less ▲]

L'équilibre sagittal dans la pathologie rachidienne.

Scientific conference (2013, June 05)

Bandgap Measurement by Spectroscopic Ellipsometry for Strained Ge1-xSnx

Conference (2013, June 04)

Ship Manoeuvring Behaviour in Crossing Current Near-by a Lock

in VanTorre, Marc (Ed.) Third International Conference on Ship Manoeuvring in Shallow and Confined Water (2013, June 03)

Ship behaviour in current is one of the classical problems in ship manoeuvrability. However, it is not yet fully investigated. The study is motivated by an assessment study on the ship navigation near by ... [more ▼]

Ship behaviour in current is one of the classical problems in ship manoeuvrability. However, it is not yet fully investigated. The study is motivated by an assessment study on the ship navigation near by a river lock where relatively strong current exists. It is demonstrated how a ship behaves in the current and relatively large drift angle may happen, if the current is comparative to ship speed. In this situation, the hydrodynamic forces and moment acting on a ship is not any more at the range of lift force/moment, and therefore normal mathematical model cannot be applied. Similar situation may occur in case of rapid river stream condition, when a ship losts its power in current. At East Japan Great Earthquake happened in 2011, many ships without their power were drifting in tsunami. It is urgent matter to investigate on the ship behaviour in such situation. [less ▲]

Determination of activation yield curves for fusion escaping particle diagnostics

Conference (2013, June)