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IntroductionLearning anatomy is fundamental for medical students, but remains complex. It requires the acquisition of a new vocabulary, good visual-spatial skills and mental rotation. This learning was traditionally done through lectures and dissection sessions in the anatomy laboratory. The decrease in the number of teaching hours, the passive aspect of lectures for students and the logistical and economic difficulties of access to anatomical parts have led teachers to develop new teaching methods and to use new technologies, particularly digital technologies, to facilitate this teaching.A new pedagogical concept, called embodied learning, is a concept from cognitive psychology, which refers to thoughts (cognition), feelings (emotions) and behaviours (body), based on sensory experiences and body positions. It is particularly interesting in learning anatomy because the object of learning is also the object of study.Our primary aim was to investigate the pedagogical impact of embodiment on the learning of anatomy. Our secondary aims were to explore the factors influencing and being influenced by such learning, as well as to consider its inclusion in existing educational pathways.Materials and methodsWe conducted two studies with high levels of bodily engagement, incorporating embodiment into the important task.A first ecological study on STAPS students, to investigate the impact of integrating embodied learning within a kinesiology curriculum at the University of Lyon. Then we developed a digital, interactive, 3-dimensional anatomy learning software, and conducted a randomized controlled study on the pedagogical impact of embodiment, on a group of 2nd year medical students at the University of Grenoble-Alpes.ResultsOur first study showed no significant pedagogical impact of embodiment in the short and medium term, but a significant pedagogical impact for the experimental group in the long term. Moreover, this pedagogical modality was simple to set up within a school and inexpensive. Our second study did not show a statistically positive pedagogical impact of the implementation of embodiment compared to the control group, but we did show a better progression of the students with the least visual-spatial abilities thanks to this tool, but not significantly. The overall satisfaction in both cases was high, making it a tool envied by the students and therefore probably stimulating learning.DiscussionOur work describes an improvement in the long-term pedagogical impact of embodiment, as well as high student satisfaction with the use of these tools. These teaching methods do not seem to increase the mental load of the students. The new technologies, especially in digital 3D, seem to bring a learning gain to students with the least visual-spatial abilities (with the lowest scores in the mental rotation test).Our work has some limitations, particularly methodological.ConclusionEmbodied learning appears to be beneficial for learning anatomy, especially functional anatomy, and for long-term retention, without increasing mental workload. It is also a modality that is well adopted by students, stimulating their motivation and interest in their work. Further research and evaluation of these teaching tools is required to ensure that they are fully integrated into the holistic teaching pathway of a comprehensive anatomy programme.; L’apprentissage de l’anatomie est fondamental pour les étudiants en médecine, mais reste complexe. Il nécessite l’acquisition d’un nouveau vocabulaire, de bonnes capacités visuo-spatiales et de rotation mentale. Cet apprentissage se faisait classiquement par des cours magistraux et des séances de dissection au laboratoire d’anatomie. La diminution du nombre d’heure d’enseignement, le coté passif pour les étudiants des cours magistraux et les difficultés logistiques et économiques d’accès aux pièces anatomiques ont conduit les enseignants à développer de nouveaux moyens pédagogiques et à s’aider des nouvelles technologies, notamment numériques pour faciliter cet enseignement.Un nouveau concept pédagogique, appelé apprentissage incarné (ou encorporé) est un concept issu de la psychologie cognitive, qui fait référence aux pensées (cognition), aux sentiments (émotions) et aux comportements (corps), basés sur les expériences sensorielles et sur les positions corporelles. Il est particulièrement intéressant dans l’apprentissage de l’anatomie car l’objet de l’apprentissage est également l’objet d’étude.Notre objectif principal était d’étudier l’impact pédagogique de l’incarnation sur l’apprentissage de l’anatomie. Nos objectifs secondaires étaient d’explorer les facteurs influençant et influencer par un tel apprentissage, ainsi que de réfléchir à son inclusion dans les parcours pédagogiques existants.Matériel et méthodeNous avons conduit deux études à niveaux d’engagement corporel élevé, avec intégration de l’incarnation à la tâche importante.Une première étude écologique sur des étudiants de STAPS, pour étudier l’impact de l’intégration d’un apprentissage incarné, au sein d’un cursus de kinésiologie de l’université de Lyon. Puis nous avons développé un logiciel d’apprentissage de l’anatomie, numérique, interactif en 3 dimensions, et mené une étude randomisée contrôlée sur l’impact pédagogique de l’incarnation, sur un groupe d’étudiants en 2ème année de médecine à l’université de Grenoble-Alpes.RésultatsNotre première étude n’a pas montré d’impact pédagogique significatifs de l’incarnation à court et moyen terme, mais un impact pédagogique significatif pour le groupe expérimental à long terme. De plus, cette modalité pédagogique était simple à mettre en place au sein d’un enseignement, et peu couteuse. Notre seconde étude n’a pas montré d’impact pédagogique statistiquement positif de l’implémentation de l’incarnation par rapport au groupe contrôle, mais nous avons mis en évidence une meilleure progression des étudiants ayant le moins de capacités visuo-spatiales grâce à cet outil, mais de manière non significative. La satisfaction globale dans les deux cas était en revanche élevée, en faisant un outil envié par les étudiants et donc probablement stimulant l’apprentissage.DiscussionNotre travail permet de décrire une amélioration de l’impact pédagogique à long terme de l’incarnation, ainsi qu’une grande satisfaction des étudiants quant à l’utilisation de ces outils. Ces méthodes d’enseignement ne semblent par ailleurs pas augmenter la charge mentale des étudiants. Les nouvelles technologies, notamment en 3D numériques semble apporter un gain d’apprentissage aux étudiants ayant les moins bonnes capacité visuo-spatiales (ayant les moins bons scores aux test de rotation mentale).Notre travail possède quelques limites, notamment méthodologiques.ConclusionL’apprentissage incarné semble bénéfique sur l’apprentissage de l’anatomie, notamment fonctionnelle et sur la rétention à long terme, sans pour autant augmenter la charge mentale. Il s’agit de plus d’une modalité bien adoptée par les étudiants, stimulant leur motivation et leur intérêt au travail. Il convient de poursuivre les recherches et l’évaluation de ces outils pédagogiques pour les intégrer parfaitement au parcours pédagogique holistique d’un programme anatomique complet

Three-dimensional (3D) electrically conductive micro/nanostructures are now a key component in a broad range of research and industry fields. Direct laser writing by two-photon polymerization (TPP) has been established as one of the most promising methods for achieving 3D fabrication in micro/nanoscales, due to its ability to produce arbitrary and complex 3D structures with sub wavelength resolution. However, the lack of TPP-compatible and functional materials represents a significant barrier to realizing the functionality of the fabricated devices, such as high electrical conductivity, high environmental sensitivity, and high mechanical strength, etc. In this work, a novel method was developed to realize metallic 3D micro/nanostructures with silver-thiol-acrylate composites via TPP followed by femtosecond laser nanojoining. Complex 3D micro/nanoscale conductive structures have been successfully fabricated with ~200 nm resolution. The loading of silver nanowires (AgNWs) and joining of junctions successfully enhanced the electrical conductivity of the composites from insulating to 92.9 S m-1 at room temperature. Moreover, for the first time, a reversible switching to a higher conductivity was observed, up to ~103-105 S m-1 at 523 K. The temperature-dependent conductivity of the composite was analyzed using the variable range hopping and thermal activation models. The as-developed nanomaterial assembly and joining method in this study paves a way toward a wide range of device applications, including 3D electronics, sensors, memristors, micro/nanoelectromechanical systems (MEMS/NEMS), and biomedical devices, etc.

International audience; Synostotic anterior plagiocephaly is a rare pathological cranial malformation. Therapeutic options are rarely studied due to the rarity of the malformation and difficulties in diagnosis and care management. The objective of this study was to analyze the results obtained with the Lille protocol based on 62 CT-scans done before and after surgery in 31 patients. A specific analysis was designed for this work. Nine cephalometric measures enabled to evidence on each CT-Scan the corrections made on the fronto-orbital bandeau and the potential impact of surgery on the craniofacial structures. Results show that surgical symmetry of the fronto-orbital bandeau in the transversal plane, according to the symmetrical axis of the semicircular canals, allows a normalization of the skull's growth and morphogenesis for the surgically affected structures but also adjacent ones.

CERVOXY; International audience; Rationale and ObjectivesThis study aimed to assess a novel method of three-dimensional (3D) co-registration of prostate magnetic resonance imaging (MRI) examinations performed before and after prostate cancer focal therapy.Materials and MethodsWe developed a software platform for automatic 3D deformable co-registration of prostate MRI at different time points and applied this method to 10 patients who underwent focal ablative therapy. MRI examinations were performed preoperatively, as well as 1 week and 6 months post treatment. Rigid registration served as reference for assessing co-registration accuracy and precision.ResultsSegmentation of preoperative and postoperative prostate revealed a significant postoperative volume decrease of the gland that averaged 6.49 cc (P = .017). Applying deformable transformation based on mutual information from 120 pairs of MRI slices, we refined by 2.9 mm (max. 6.25 mm) the alignment of the ablation zone, segmented from contrast-enhanced images on the 1-week postoperative examination, to the 6-month postoperative T2-weighted images. This represented a 500% improvement over the rigid approach (P = .001), corrected by volume. The dissimilarity by Dice index of the mapped ablation zone using deformable transformation vs rigid control was significantly (P = .04) higher at the ablation site than in the whole gland.ConclusionsOur findings illustrate our method's ability to correct for deformation at the ablation site. The preliminary analysis suggests that deformable transformation computed from mutual information of preoperative and follow-up MRI is accurate in co-registration of MRI examinations performed before and after focal therapy. The ability to localize the previously ablated tissue in 3D space may improve targeting for image-guided follow-up biopsy within focal therapy protocols.

Ptychography is a coherent diffraction imaging technique which aims in retrieving the lost phase from intensity-only far-field measurements. The versatility of the approach has proved an important asset for 3D mapping of different physical quantities, like the electron density of micrometer-sized specimens with resolution in the 10 - 100nm range. In this work, we explored the possibility to push further the current limits of 3D Bragg ptychography, by addressing the case of an extended InP/InGaAs nanostructured thin film, bonded on a silicon wafer. The experiment was performed at the ID13 beamline at ESRF, with a monochromatic beam focused down to 100nm. 2D intensity patterns were acquired at several incidence angles in the vicinity of the InP (004) Bragg peak, stacking up a three dimensional dataset. Numerical analysis of the given problem was performed beforehand in order to optimize the inversion strategy and study the possibility of introducing additional physical constraints through regularization approaches. Inversions of the dataset were done using a ptychographical gradient-based optimization phase retrieval algorithm. The developed strategy was applied on the experimental data which led to the retrieval of a complex-valued 3D image. The result exhibits the high crystallinity quality of the sample with the expected values of thickness and lattice mismatch, nevertheless, small local lattice tilts have been observed - in the order of 0.02°- and confirmed by numerical modeling. This result demonstrates the high sensitivity of the technique, as well as its exciting perspectives for imaging complex organic and inorganic nanostructured materials., La ptychographie est une technique d’imagerie par diffraction cohérente qui vise à récupérer la phase perdue, uniquement par des mesures d’intensité en champ lointain. Cette technique permet l’imagerie des champs de déformation dans des cristaux périodiques avec des résolutions sous-faisceau. Dans ce travail, la ptychographie de Bragg en 3D est utilisée pour étudier les propriétés d’une couche cristalline nanostructurée de InP/InGaAs collée sur un substrat de silicium. L’expérience a été réalisée sur la ligne ID13 de l’ESRF, avec un faisceau monochromatique concentré à 100nm. Les intensités 2D ont été acquises avec plusieurs angles d’incidence dans le voisinage du pic de Bragg InP (004), empilant un jeu de données tridimensionnelles. L’analyse numérique du problème donné a été effectuée à l’avance afin d’optimiser la stratégie d’inversion et d’étudier la possibilité d’introduire des contraintes physiques supplémentaires basées sur des approches de régularisation. L’inversion de l’ensemble des données a été effectuée en utilisant un algorithme ptychographique de reconstruction de phase. L’image 3D récupérée représente la haute qualité cristalline de l’échantillon, avec les valeurs de l’épaisseur et du désaccord de maille attendus en moyenne. Néanmoins, de petites inclinaisons locales de mailles ont été observées - de l’ordre de 0.02°- et confirmées par modélisation numérique. Les résultats démontrent la sensibilité de la technique, ainsi que ses perspectives passionnantes pour l’imagerie des matériaux organiques et inorganiques nanostructurés complexes.

International audience; Microvascular obstruction (MVO) and transmural infarct size are prognostic factors after acute myocardial infarction (AMI). We assessed the value of myocardial deformation patterns using 3D speckle tracking imaging (3DSTI) in detecting myocardial and microvascular damage after AMI. One hundred patients with first ST-segment elevation MI from the REMI Study were prospectively included. Transthoracic echocardiography with 3DSTI and CMR were performed within 72 h after revascularization therapy. Global (3DG) and segmental (3DS) values of LV longitudinal (LS), circumferential and radial area strain were obtained. Late gadolinium enhancement (LGE) and MVO was quantified as transmural (>50%) or non-transmural ( 75%) was 3DSAS [AUC 0.867 (0.849-0.884), 78.0% sensitivity and 81.1% specificity for 3DSAS = -16.1%]. Importantly, 3DSRS and 3DSAS were associated with an increase in diagnostic accuracy of both transmural LGE and MVO over 3DSLS (all increase in AUC > 0.04, all p < 0.01). The newly developed 3DSTI, especially 3DSAS, is a sensitive and reproducible tool to predict and quantify the transmural extent of scar. This new early imaging strategy improve the prediction of MVO while enabling to assess the success of reperfusion and the risk of late systolic remodeling in STEMI.

cited By 15; International audience; A simple methodology is proposed to quantitatively discuss the quality of the 3D dispersion of grafted silica nanoparticles (NPs) mixed with free chains in nanocomposites. 3D observations of NPs are obtained by transmission electron tomography (TEMT). The NPs are individualized from the tomograms by segmentation and watershed processing. Equivalent dispersions of spherical objects are then generated. By computing 3D Voronoi tessellation from the spheres, the local environment is investigated for each NP through geometrical measurements. Two types of populations of NP can be extracted: either densely packed or isolated. As the length of the free chains decreases, when the length of the free chains are close to the ones of the grafted chains, this second population becomes predominant and the quality of the dispersion gradually increases. The width of the local volume fraction distribution surrounding each NP can be considered as a quantitative parameter indicative of the homogeneity of the microstructure. It becomes narrower as the quality of the dispersion increases. © 2014 American Chemical Society.

International audience; During protein synthesis, many translating ribosomes are bound together with an mRNA molecule to form polysomes (or polyribosomes). While the spatial organization of bacterial polysomes has been well studied in vitro, little is known about how they cluster when cellular conditions are highly constrained. To better understand this, we used electron tomography, template matching, and three-dimensional modeling to analyze the supramolecular network of ribosomes after induction of translational pauses. In Escherichia coli, we overexpressed an mRNA carrying a polyproline motif known to induce pausing during translation. When working with a strain lacking transfer-messenger RNA, the principle actor in the "trans-translation" rescuing system, the cells survived the hijacking of the translation machinery but this resulted in a sharp modification of the ribosomal network. The results of our experiments demonstrate that single ribosomes are replaced with large amounts of compacted polysomes. These polysomes are highly organized, principally forming hairpins and dimers of hairpins that stack together. We propose that these spatial arrangements help maintain translation efficiency when the rescue systems are absent or overwhelmed.

In this paper, we present EETCO: an estimation and exploration tool that provides qualitative assessment of data center design decisions on Total-Cost-of-Ownership (TCO) and environmental impact. It can capture the implications of many parameters including server performance, power, cost, and Mean-Time-To-Failure (MTTF). The tool includes a model for spare estimation needed to account for server failures and performance variability. The paper describes the tool model and its implementation, and presents experiments that explore tradeoffs offered by different server configurations, performance variability, MTTF, 2D vs 3D-stacked processors, and ambient temperature. These experiments reveal, for the data center configurations used in this study, several opportunities for profit and optimization in the datacenter ecosystem: (i) servers with different computing performance and power consumption merit exploration to minimize TCO and the environmental impact, (ii) performance variability is desirable if it comes with a drastic cost reduction, (iii) shorter processor MTTF is beneficial if it comes with a moderate processor cost reduction, (iv) increasing by few degrees the ambient datacenter temperature reduces the environmental impact with a minor increase in the TCO and (v) a higher cost for a 3D-stacked processor with shorter MTTF and higher power consumption can be preferred, over a conventional 2D processor, if it offers a moderate performance increase. © 2013 IEEE. 54 63 Sponsors: IEEE Computer Society intel IBM Research ARM FusionIO Conference code: 98381 Cited By :7

Computational predictions concerning ballooning of multiple fuel pins during a loss of coolant accident (LOCA) with a final reflood phase are now more than ever of interest amongst the design basis accidents in pressurized water reactors (PWR). Difficulties for such studies are twofold. Firstly, modeling has to take into account many coupled phenomena as thermics (heat generation, radiation, convection and conduction), hydraulics (multi-dimensional one-to-three phase flow and shrinkage) and mechanics (thermal expansion, creep and embrittlement) but also chemistry (oxidation, hydriding, etc.). Secondly, there exists only a few experimental investigations to validate the complex coupled modeling enabling such predictions. This paper deals with the new computational 3D tool named DRACCAR which models the deformations of rods within a bundle (from one rod to a full fuel assembly) during LOCA transients including the water reflood phase. © 2012 Elsevier B.V. All rights reserved.

The kinetics of aggregation of non Brownian magnetizable particles in the presence of a magnetic field is studied both theoretically and by means of computer simulations. A theoretical approach is based on a system of Smoluchowski equations for the distribution function of the number of particles in linear chain-like aggregates. Results obtained in the two dimensional (2D) and three dimensional (3D) models are analyzed in relation with the size of the cell, containing the particles, and the particle volume fraction φ . The theoretical model reproduces the change of the aggregation kinetics with the size of the cell and with the particle volume fraction as long as the lateral aggregation of chains is negligible. The simulations show that lateral aggregation takes place when, roughly, φ 2D > 5 % and φ 3D > 1.5 % . Dependence of the average size of the chains with time can be described by a power law; the corresponding exponent decreases with the particle volume fraction in relation with the lateral aggregation. In the 3D simulations, dense labyrinthine-like structures, aligned along the applied field, are observed when the particle concentration is high enough ( φ 3D > 5 % ).

International audience; Chatter stability prediction is widely used to avoid chatter which restricts the machining quality and productivity. A lot of works have been done to predict the stability chart fast and accurately. However, most of them are based on the linear force model, and the chatter stability limits is formulated as independent on the feedrate, which does not conform to the reality well. This paper intends to investigate the chatter stability prediction based on the exponential force model, which is linearized by the Taylor equation when calculating the directional coefficients. Meanwhile, the stability model is extended to the three dimensional, which is especially applicable for the ballend mills, bull-nose end mills and inserted cutter where chatter may be brought up in Z direction. Simulation results show that the exponential force model agrees with the measurements as well as the linear force model in the cutting force prediction, and it is able to demonstrate the effect of the feedrate on the stability limit.

International audience; Rayleigh streaming may hamper the efficiency of thermoacoustic devices through the creation of convective heat transfer between the stack and heat exchangers. A better understanding and characterization of Rayleigh streaming flows is useful to assess their impact on the efficiency of thermoacoustic engines. Streaming flows in idealized configurations such as between infinite parallel plates or in cylindrical waveguides has been investigated in earlier studies. As a first step towards the investigation of streaming in more realistic configurations, streaming flows in a resonator with a square cross-section was investigated. Non-symmetric streaming structures were anticipated. For a horizontal waveguide, velocity fields within the horizontal plane were measured using Particle Image Velocimetry (PIV). These measurements were performed at several vertical positions so that three-dimensional streaming cell structures could be reconstructed from the different planar streaming velocity fields. The acoustic streaming within the boundary layer was also studied by zooming near the wall of the channel. The three dimensional streaming cells reconstructed by combining the data in the different planes reveals the nature of the streaming flow structures in the square cross-section standing wave tube. Streaming amplitudes were quantified and were compared with predictions from theoretical models.

Institut de Radioprotection et de Sûreté Nucléaire (IRSN) performed a study relative to the thermal behaviour of a new TN International package design for transport of spent fuel assemblies called TNH112. The aim of this study is to evaluate the behaviour of the package exposed to fires, with durations and temperatures different from those required in the IAEA regulation TS-R-1 (respectively 30 min and 800°C). Its main objective is to provide quantitative data available for safety assessment in emergency situations involving fires. Moreover it can also be used for a cross comparison with the analysis of the thermal behaviour of the package during the IAEA regulatory fire test presented by the applicant in the package design safety analysis report. This study is based on numerical calculations performed with the code THERMX-PROTEE. The three-dimensional model used represents a quarter of the upper half of the package, where the closure system is located. The thermal behaviour of the neutron-shielding resin located in the cavity plug, the trunnions and the packaging body was modelled to allow simulation of endothermic reactions of vaporisation. During the heating phase of the fire test, the water vapour produced in the heated resin components is transferred and condensed in the nearby colder elements; the associated thermal transfers can rapidly increase the temperature of the colder elements. The part of the vapour which cannot be condensed when most of the nearby resin elements reach a temperature above 100°C is evacuated through the holes that are distributed throughout the external envelope of the packaging and closed by fusible plugs under normal conditions. A specific calculation module has been developed to take into account the corresponding energy transfers. This module was qualified by comparison with the results of experimental fire tests. The calculations performed in the framework of this study cover fire temperatures between 400 and 1000°C. One of the results of those calculations is the time necessary to reach the maximum allowable temperature of the elastomer gaskets. © W. S. Maney & Son Ltd 2012.

Cataloged from PDF version of article. Recent advances in evaluating and measuring the perceived visual quality of three-dimensional (3-D) polygonal models are presented in this article, which analyzes the general process of objective quality assessment metrics and subjective user evaluation methods and presents a taxonomy of existing solutions. Simple geometric error computed directly on the 3-D models does not necessarily reflect the perceived visual quality; therefore, integrating perceptual issues for 3-D quality assessment is of great significance. This article discusses existing metrics, including perceptually based ones, computed either on 3-D data or on two-dimensional (2-D) projections, and evaluates their performance for their correlation with existing subjective studies. © 2011 IEEE.

International audience; In this study, we have attempted to determine the effective hydraulic properties of a highly heterogeneous soil horizon composed of two elementary pedological volumes (EPVs). Our upscaling approach was guided by the “scaleway” approach, in which the properties of a complex system can be estimated by multiple discrete upscaling steps. This approach was tested on a data set from laboratory measurements of hydraulic conductivity at the EPV scale, while an explicit three-dimensional soil structure was considered at the horizon scale. We then formulated a decision tree to guide the choice of the appropriate upscaling method to determine the effective hydraulic conductivity at the horizon scale. In the case of low contrast between hydraulic conductivities at the EPV scale, the effective hydraulic conductivity at the horizon scale can be achieved by calculating the Wiener bounds, which requires only the proportion of the different EPVs. In the case of high contrast between hydraulic conductivities at the EPV scale, we recommend either calculating the Cardwell and Parson bounds, or performing a direct three-dimensional numerical simulation to solve Richards' equation, which requires an explicit representation of the three-dimensional structure of the soil horizon. The Cardwell and Parsons bounds remains a good and easily available approximation. Otherwise, more accurate estimation can be obtained by numerical simulation, although this is time consuming. A decision map is proposed to help choose the best method to estimate the effective hydraulic conductivity.

cited By 13; International audience; This paper presents the development and the application of a new electron tomography technique based on STEM (Scanning Transmission Electron Microscopy) configuration in ESEM (Environmental Scanning Electron Microscopy). This combination provides a new approach for the characterization of the 3D structure of materials, as it optimizes a compromise between the resolution level of a few tens of nm and the large tomogram size due to the high thickness of transparency. The method is well adapted for non-conductive samples, and exhibits good contrast even for materials with low atomic number. The paper describes the development of a dedicated stage for this new tomography technique. Taking advantage of the size of the ESEM chamber, the range of tilt angles is not limited by the space around the sample. The performance of this device is illustrated through the three-dimensional characterization of samples issued from materials science and chosen to illustrate the results in resolution, contrast and thickness. © 2011 Elsevier B.V.

A multi-domain finite element formulation has been applied to determine the semi-solid permeability of an equiaxed granular structure. The granular model was constructed from a Voronoï tessellation algorithm. The liquid-solid interface is represented implicitly by a level set function, and an anisotropic meshing technique is employed for an accurate description of the interface geometry with reasonable computation resources. The liquid phase is considered as an incompressible Newtonian fluid, and permeability is computed based on Darcy's law. A good agreement is found with available literature data and with the Kozeny-Carman prediction. The proposed method, associating the finite element method with a level set framework, is shown to be an effective technique for examining microstructure effects on the semi-solid permeability. This is illustrated by considering the influence of the Gibbs-Thomson effect. © 2010 Elsevier B.V. All rights reserved.

cited By 4; International audience; Among the possible forming processes for structural composite parts, the Liquid Composite Moulding ones are widely used. For such kind of forming process, a resin injection phase occurs after the forming of a dry fibrous reinforcement skeleton. Several parameters can affect the quality of the manufactured part. It has been experimentally proved that the deformation of the fibrous reinforcement has a significant influence on its permeability. In order to evaluate that parameter, it is necessary to have a realistic deformed solid skeleton. During the pre-forming stage, the fibrous reinforcement can be subjected to different kind of loading: yarn tension and in-plane shear to obtain the correct part shape, but also transverse compression. The aim of this paper is to analyze the influence of that last loading mode on the global state of the solid skeleton. For that purpose, two aspects are explored. First, numerical simulations are performed at the mesoscopic scale: a finite element model of the smallest pattern of the woven textile is realized in which each yarn is modelled used 3D elements. The constitutive behaviour of the yarn must exhibit the specificities of a fibrous material. Secondly, experimental characterization of the yarn material is realized. For that, a new experimental setup is used which allow to investigate the relation between longitudinal tension and transverse compression stiffness of the yarn. This allows determining the material parameters used in the yarn constitutive equation. The other material parameters are determined using a tensile test and an in-plane shear test. X-ray tomography gives geometrical validations of the model. © 2010 Springer-Verlag France.

International audience; Procedures for synthesizing digital polycrystalline microstructures are illustrated, either from 2D statistical data or from 3D deterministic data. Finite element meshes representing the digital microstructures are generated using anisotropic and adaptive mesh refinement close to the grain boundaries. Digital mechanical testing based on crystal plasticity theory provides an estimate of the spatial distribution of strain energy within the polycrystalline aggregate. The latter quantity is used as an input for modelling subsequent static recrystallization, grain boundary motion being described within a level set framework. The kinetic law for interface motion accounts for both the stored strain energy and the grain boundary energy. The possibility to include nucleation events within the level set framework is illustrated, as well as the evolving topology of the grain boundary network. The recrystallization model is tested in different configurations and compared to the Johnson-Mehl-Avrami-Kolmogorov (JMAK) theory.

In finite element simulations dedicated to the modelling of microstructure evolution, the mesh has to be fine enough to: (i) accurately describe the geometry of the constituents; (ii) capture local strain gradients stemming from the heterogeneity in material properties. In this paper, 3D polycrystalline aggregates are discretized into unstructured meshes and a level set framework is used to represent the grain boundaries. The crystal plasticity finite element method is used to simulate the plastic deformation of these aggregates. A mesh sensitivity analysis based on the deformation energy distribution shows that the predictions are, on average, more sensitive near grain boundaries. An anisotropic mesh refinement strategy based on the level set description is introduced and it is shown that it offers a good compromise between accuracy requirements on the one hand and computation time on the other hand. As the aggregates deform, mesh distortion inevitably occurs and ultimately causes the breakdown of the simulations. An automatic remeshing tool is used to periodically reconstruct the mesh and appropriate transfer of state variables is performed. It is shown that the diffusion related to data transfer is not significant. Finally, remeshing is performed repeatedly in a highly resolved 500 grains polycrystal subjected to about 90% thickness reduction in rolling. The predicted texture is compared with the experimental data and with the predictions of a standard Taylor model. © 2009 IOP Publishing Ltd.

cited By 5; International audience; The microstructural evolution of an Al-15.8 wt.% Cu slurry held for 80 min at 555 8C has been characterised in-situ by X-ray microtomography. The different parameters measured by segmentation of the 3D images are analysed by reference to a model describing capillary equilibrium in an aggregate of solid particles with uniform solid/liquid interface curvature. Excellent agreement is found between model predictions and experimental data, except for the fact that the solid/liquid interface area predicted by the model is lower by about 12.5% than that measured experimentally. This suggests that, owing to the progressive grain coarsening, the slurry does not achieve uniform interface curvature. The model makes possible the conversion of experimental data into evolutions of the dihedral angle, average surface tensions ratio, and capillary pressure in the liquid. Copyright © Carl Hanser Verlag GmbH & Co. KG.

This paper presents 3D saturated flow and transport calculations performed using numerical methods developed within the MELODIE software in the framework of assessing the performance of a radioactive waste geological repository. This type of computational modeling is a challenging task due to the presence of strong physical, chemical and hydrogeological heterogeneities, as well as the very different geometrical scales (from dm to km) to be handled simultaneously. First, the software is briefly described, with a particular focus on the specific features that help for dealing with such contrasted system, notably the finite volume finite element and the Schwarz domain decomposition methods. IRSN calculations based on the French "spent fuel/iron canister/clay" concept designed by Andra in the framework of its feasibility study of a deep geological repository are then presented. Through sensitivity analyses based on various evolution scenarios, these calculations aim at assessing the possible influence of design features, waste degradation mechanisms or radionuclide transfer properties of repository components on the behavior of the containment system as a whole. The results of the simulation have shown the transport regime in the drifts depends on the efficiency of the seals. When seals are efficient, velocities are low and transfer regime in the drifts is dominated by diffusion, whereas advection is dominant when seals are poorly sealed. However, whatever the dominant transport regime (diffusion or advection) in the drifts, the activity released out from the canisters was shown to be mainly transferred by diffusion to the host rock exits. This transfer through clayey components (bentonite and host rock) highlights the importance of chemical properties of the three types of long-lived radionuclides considered in the present study. The sensitivity analysis has shown that strongly sorbed and/or weakly soluble radionuclides are less influenced by activity release mechanisms and by seal efficiency. Concerning the strongly sorbed radionuclide 94Nb, the activity is hardly transferred beyond the vicinity of the disposal cells: the sorption properties allow limiting and delaying efficiently radionuclide migration. Concerning the weakly soluble radionuclide 79Se, a part of the activity is instantaneously precipitated in the bentonite surrounding the canisters and the activity release in the system is controlled by the dissolution of this precipitated activity. Such radionuclides are thus hardly concerned with canister dissolution mechanisms. On the contrary, the migration and release at the host rock exits of 129I, which is a non-sorbed and soluble radionuclide, is shown to be influenced by the radionuclide source term, i.e. dissolution mechanism and instantaneous released fraction (IRF). The IRF, which corresponds to 8% of the total activity contained in the canisters impacts significantly the activity released out of the host rock when UO2 matrix dissolution controlled by uranium solubility lasts up to several million years, whereas its contribution is far less marked when matrix dissolves rapidly by alpha-radiolysis. © 2008 Elsevier Ltd. All rights reserved.

This letter describes a level set framework for the numerical modelling of primary static recrystallization in a polycrystalline material. The topological evolution of the grain structure is simulated in two and three dimensions, based on a kinetic law relating the velocity of the boundary to the thermodynamic driving force. The adopted finite element approach is described, discussed and tested from simple to more complex configurations. The possibility to accurately describe nucleation and growth is illustrated in three dimensions. © 2008 Acta Materialia Inc.

Published in Russian in Vysokomolekulyarnye Soedineniya, Ser. A, 2008, Vol. 50, No. 5, pp. 827–840.; International audience; The general context of this paper is introduction of a crystallization model into 3D software dedicated to a thermomechanical description of the injection-molding process. From the Kolmogoroff-Avrami-Evans equation for overall kinetics and from additional assumptions on nucleation, a system of differential equations is derived for quiescent crystallization and extended to flow-induced crystallization. The experiments done to identify the relevant crystallization parameters are then described, and the values of these parameters are optimized using the Genetic Algorithm inverse method. To check the validity of the theoretical model and the accuracy of our experimental characterization, the curves calculated for the evolutions of the transformed volume fraction and of the number of spherulites are compared to the experimental ones. Finally, the crystallization model is implemented in the Rem3D® code and some typical calculations are presented.

International audience; Three dimensionally ordered macroporous layered double hydroxides (3-DOM LDH) have been synthesized using sacrificial polystyrene (PS) colloidal crystal templates impregnated by divalent and trivalent metal salts. LDH spatially confined coprecipitation occurs during soaking in NaOH solution, and the PS template is subsequently removed by dissolution to preserve the hydroxyl structure. This synthetic process can be applied to a wide range of LDH compositions (M11: Mg, Ni, Co, Zn and MIII: Al, Cr). On the basis of XRD, SEM, TEM, chemical analysis, nitrogen adsorption, XAS experiments, and TGA, structural, textural, and thermal properties of these new nanostructured LDH particles are described. In particular, the study shows that both macro- and mesoporosity can be present and that the macroporosity is maintained after calcination at temperatures as high as 800 °C, giving rise to the presence of macroporous metal and mixed metal oxides. The photocatalytic activity experiments indicate that decatungstate intercalated into the 3-DOM LDH exhibits a higher photocatalytic activity for the photodegradation of 2,6-dimethylphenol than the decatungstate intercalated into the standard coprecipitated LDH parent material.

International audience; The present paper is devoted to the analysis of the contact/impact problems with Coulomb friction and large deformation between two hyperelastic bodies of Gent model. The total Lagrangian formulation is adopted to describe the geometrically nonlinear behavior. For the finite element implementation, the explicit expression of the incremental law of Gent model is derived. A first order algorithm is applied for the numerical integration of the time-discretized equation of motion. Efficiency and accuracy of the resulting method is illustrated on a three-dimensional dynamic contact problem.

International audience; The present paper is devoted to the analysis of the contact/impact problems with Coulomb friction and large deformation between two hyperelastic bodies of Gent model. The total Lagrangian formulation is adopted to describe the geometrically nonlinear behavior. For the finite element implementation, the explicit expression of the incremental law of Gent model is derived. A first order algorithm is applied for the numerical integration of the time-discretized equation of motion. Efficiency and accuracy of the resulting method is illustrated on a three-dimensional dynamic contact problem.

International audience; The present paper is devoted to the analysis of the contact/impact problems with Coulomb friction and large deformation between two hyperelastic bodies of Gent model. The total Lagrangian formulation is adopted to describe the geometrically nonlinear behavior. For the finite element implementation, the explicit expression of the incremental law of Gent model is derived. A first order algorithm is applied for the numerical integration of the time-discretized equation of motion. Efficiency and accuracy of the resulting method is illustrated on a three-dimensional dynamic contact problem.

Publication Inra prise en compte dans l'analyse bibliométrique des publications scientifiques mondiales sur les Fruits, les Légumes et la Pomme de terre. Période 2000-2012. http://prodinra.inra.fr/record/256699; A physical model simulating the spatio-temporal distribution of temperature in an ellipsoidal fruit has been developed. It is based on the numerical resolution of the three-dimensional (3D) unsteady heat conduction equation with unsteady and non-homogeneous heat fluxes as boundary conditions. The numerical scheme and the physical models have been tested by comparing with an analytical solution for simple configurations. The model quality has been assessed by comparing model outputs to temperature measured with thermocouples at several locations in isolated peach and apple fruits. The root mean square error (RMSE) for temperature simulated at a 1 min time step was about 0.8 °C. A sensitivity analysis showed that accurate estimations of the surface conductance to water vapor diffusion and of the thermal conductivity are necessary. The model has also been used for identifying the main microclimate variables governing temperature dynamics within fruits.

Architectural sites suffers from weathering effects such as liquid sedimentation, lampblack or pollution deposit, moss growing or long-term erosion. Displaying their impact on present buildings could help deciders to plan relevant actions for preserving the architectural heritage. In this paper we present a user-friendly solution for on-line acquiring a semi-physical model from one or few images of a building, immediately followed by real-time simulations. The goal is certainly not to give an accurate prediction of what will happen, but rather to show a plausible state of the site under various possible degradations arising from natural effects. The solution relies on the coupling of two 3-D modelling programs: one dedicated to interactive reconstructions and a second to discreet manipulation for natural phenomena simulations based on a combination of different surface cellular automata. Several experiments were held to estimate the effectiveness of this approach and to identify future works in order to cope with present limitations. A first series applies a lampblack deposit simulation on a large-size 3-D model to demonstrate the solution feasibility and to provide indications about achievable performance. The second series focuses on the solution sensitiveness to both geometrical and semi-physical models granularity through the application of a stone erosion effect on a smaller but less regular-shaped building model. The third series demonstrates the discreet model ability to simulate multiple effects with the example of a vegetation growth simulation. Guidelines for future works are given in the conclusion of this paper.