Publications

2019

• Activation-contraction coupling in a multiscale heart model
  
  • Kimmig François
  • Caruel Matthieu
  • Chapelle Dominique
  • Moireau Philippe
  , 2019.
• Model assessment through data assimilation of realistic data in cardiac electrophysiology
  
  • Gérard Antoine
  • Collin Annabelle
  • Bureau Gautier
  • Moireau Philippe
  • Coudière Yves
  , 2019. We consider a model-based estimation procedure-namely a data assimilation algorithm-of the atrial depolarization state of a subject using data corresponding to electro-anatomical maps. Our objective is to evaluate the sensitivity of such a model-based reconstruction with respect to model choices. The followed data assimilation approach is capable of using electrical activation times to adapt a monodomain model simulation, thanks to an ingenious model-data fitting term inspired from image processing. The resulting simulation smoothes and completes the activation maps when they are spatially incomplete. Moreover, conductivity parameters can also be inferred. The model sensitivity assessment is performed based on synthetic data generated with a validated realistic atria model and then inverted using simpler modeling ingredients. In particular, the impact of the muscle fibers definition and corresponding anisotropic conductivity parameters is studied. Finally, an application of the method to real data is presented, showing promising results.
• Minimally-invasive estimation of patient-specific end-systolic elastance using a biomechanical heart model
  
  • Le Gall Arthur
  • Vallée Fabrice
  • Chapelle Dominique
  • Chabiniok Radomir
  , 2019. The end-systolic elastance $(Ees)$-the slope of the end-systolic pressure-volume relationship (ESPVR) at the end of ejection phase-has become a reliable indicator of myocardial functional state. The estimation of $Ees$ by the original multiple-beat method is invasive, which limits its routine usage. By contrast, non-invasive single-beat estimation methods, based on the assumption of the linearity of ESPVR and the uniqueness of the normalised time-varying elastance curve $E N (t)$ across subjects and physiology states, have been applied in a number of clinical studies. It is however known that these two assumptions have a limited validity, as ESPVR can be approximated by a linear function only locally , and $E N (t)$ obtained from a multi-subject experiment includes a confidence interval around the mean function. Using datasets of 3 patients undergoing general anaesthesia (each containing aortic flow and pressure measurements at baseline and after introducing a vasopressor noradrenaline), we first study the sensitivity of two single-beat methods-by Sensaki et al. and by Chen et al.-to the uncertainty of $E N (t)$. Then, we propose a minimally-invasive method based on a patient-specific bio-physical modelling to estimate the whole time-varying elastance curve $E model (t)$. We compare $E model es$ with the two single-beat estimation methods , and the normalised varying elastance curve $E N,model (t)$ with $E N (t)$ from published physiological experiments.
• Validation of Equilibrated Warping-image registration with mechanical regularization-on 3D ultrasound images
  
  • Lee Lik Chuan
  • Genet Martin
  , 2019, 11504, pp.334-341. Image registration plays a very important role in quantifying cardiac motion from medical images, which has significant implications in the diagnosis of cardiac diseases and the development of personalized cardiac computational models. Many approaches have been proposed to solve the image registration problem; however, due to the intrinsic ill-posedness of the image registration problem, all these registration techniques , regardless of their variabilities, require some sort of regularization. An efficient regularization approach was recently proposed based on the equilibrium gap principle, named equilibrated warping. Compared to previous work, it has been formulated at the continuous level within the finite strain hyperelasticity framework and solved using the finite element method. Regularizing the image registration problem using this principle is advantageous as it produces a realistic solution that is close to that of an hyperelastic body in equilibrium with arbitrary boundary tractions, but no body load. The equilibrated warping method has already been extensively validated on both tagged and untagged magnetic resonance images. In this paper, we provide full validation of the method on 3D ultrasound images, based on the 2011 MICCAI Motion Tracking Challenge data. (10.1007/978-3-030-21949-9_36)
  DOI : 10.1007/978-3-030-21949-9_36
• Cardiac displacement tracking with data assimilation combining a biomechanical model and an automatic contour detection
  
  • Chabiniok Radomir
  • Bureau Gautier
  • Groth Alexandra
  • Tintera Jaroslav
  • Weese Jürgen
  • Chapelle Dominique
  • Moireau Philippe
  , 2019, 11504, pp.405-414. Data assimilation in computational models represents an essential step in building patient-specific simulations. This work aims at circumventing one major bottleneck in the practical use of data assimilation strategies in cardiac applications, namely, the difficulty of formulating and effectively computing adequate data-fitting term for cardiac imaging such as cine MRI. We here provide a proof-of-concept study of data assimilation based on automatic contour detection. The tissue motion simulated by the data assimilation framework is then assessed with displacements extracted from tagged MRI in six subjects, and the results illustrate the performance of the proposed method, including for circumferential displacements, which are not well extracted from cine MRI alone.
• Model-based indices of early-stage cardiovascular failure and its therapeutic management in Fontan patients
  
  • Ruijsink Bram
  • Zugaj Konrad
  • Pushparajah Kuberan
  • Chabiniok Radomir
  , 2019, 11504, pp.379-387. Investigating the causes of failure of Fontan circulation in individual patients remains challenging despite detailed combined inva-sive cardiac catheterisation and magnetic resonance (XMR) exams at rest and during stress. In this work, we use a biomechanical model of the heart and Fontan circulation with the components of systemic and pulmonary beds to augment the diagnostic assessment of the patients undergoing the XMR stress exam. We apply our model in 3 Fontan patients and one biventricular "control" case. In all subjects, we obtained important biophysical factors of cardiovascular physiology-contractil-ity, contractile reserve and changes in systemic and pulmonary vascular resistance-which contribute to explaining the mechanism of failure in individual patients. Finally, we used the patient-specific model of one Fontan patient to investigate the impact of changes in pulmonary vas-cular resistance, aiming at in silico testing of pulmonary vasodilation treatments.
• Soft Nucleation of an Elastic Crease
  
  • Ciarletta P.
  • Truskinovsky L.
  Physical Review Letters, American Physical Society, 2019, 122 (24). (10.1103/PhysRevLett.122.248001)
  DOI : 10.1103/PhysRevLett.122.248001
• Investigation of the Relationship Between Microstructural Features and Strain Localization in Polycrystalline 316 L
  
  • Bodelot Laurence
  Experimental Mechanics, Society for Experimental Mechanics, 2019, 59 (5), pp.691-702. In this paper, strains are monitored in-situ at the surface of a polycrystalline 316L sample loaded quasi-statically in uniaxial tension. Initial orientation data collected over thousands of grains is compared with the strain data evolution in order to investigate, with statistical significance, the relationship between the microstructural features and the strain localization patterns emerging at the grain scale. It is shown quantitatively that high values of strain appear early and primarily around grain boundaries, before growing into a network spanning several grains and grain boundaries. Strains are also heterogeneous within a grain, with the heterogeneity tending to be more pronounced in larger grains. Statistical analyses demonstrate that the usual microstructural descriptors-such as Taylor factors, average intragranular misorientation angles or intergranular misorientation angles-do not display any correlation with the localization network. Furthermore, higher Schmid factors, albeit exhibiting some weak correlation with higher strains, fail to systematically identify the grains that experience the largest strains. It is thus proposed to analyze three-dimensional descriptors of orientation expressed in the Rodrigues space and they are shown to help readily identify orientations that exhibit high strains early in the loading. Additionally, the study of the full three-dimensional misorientation information, expressed in the reduced Rodrigues space, clearly highlights the fact that some misorientations oppose localization at certain boundaries in the microstructure at hand. Hence, considering the full three-dimensional orientation (and misorientation) data instead of just scalar descriptors is demonstrated to be of great interest when investigating the relationship between microstructural features and strain localization. (10.1007/s11340-019-00508-0)
  DOI : 10.1007/s11340-019-00508-0
• The High-Resolution Wavevector Analysis for the characterization of the dynamic response of composite plates
  
  • Margerit Pierre
  • Lebée Arthur
  • Caron Jean-François
  • Ege Kerem
  • Boutillon Xavier
  Journal of Sound and Vibration, Elsevier, 2019, 458, pp.177-196. The High Resolution Wavevector Analysis (HRWA) is presented and its application illustrated. Extending the High Resolution Wavenumber Analysis method [1] to 2D signals, it allows the wide-band and local characterization of the linear elastic behavior of anisotropic plates. The method belongs to the family of experimental wavenumber-based characterization methods and uses the high resolution signal processing algorithm ESPRIT (Estimation of Signal Parameters via Rotational Invariance Techniques) and the ESTER criterion (ESTimation of ERror) to overcome some of the limitation of Fourier-based methods. Three experimental applications on composite plate specimens are presented. First (i), from the out-of-plane velocity field of a sandwich plate with a foam core, different wave types (bending, shear and compression) are extracted. The results are compared with numerical predictions. Second (ii), individual layer contributions are separated on a honeycomb sandwich plate by means of the observation of the dependence of the extracted complex wavevectors as a function of wave propagation direction and frequency. Third (iii), a local wavenumber extraction is performed on a 4-layer carbon-epoxy plate made of fiber patches with spatially varying orientations. The local specific bending stiffness of the plate is identified from the extracted wavevectors and compared with theoretical results. (10.1016/j.jsv.2019.06.026)
  DOI : 10.1016/j.jsv.2019.06.026
• Noninvasive continuous detection of arterial hypotension during induction of anaesthesia using a photoplethysmographic signal: proof of concept
  
  • Coutrot Maxime
  • Joachim Jona
  • Dépret François
  • Millasseau Sandrine
  • Nougué Hélène
  • Matéo Joaquim
  • Mebazaa Alexandre
  • Gayat Etienne
  • Vallée Fabrice
  British Journal of Anaesthesia, Oxford University Press (OUP), 2019, 122, pp.605 - 612. (10.1016/j.bja.2019.01.037)
  DOI : 10.1016/j.bja.2019.01.037
• Homogenization approach and Bloch-Floquet theory for band-gap prediction in 2D locally resonant metamaterials
  
  • Comi Claudia
  • Marigo Jean-Jacques
  Journal of Elasticity, Springer Verlag, 2019. This paper provides a detailed comparison of the two-scale homogenization method and of the Bloch-Floquet theory for the determination of band gaps in locally resonant metamaterials. A medium composed by a stiff matrix with soft inclusions with 2D periodicity is considered and the equivalent mass density of the homogenized medium is explicitly obtained both for in-plane and out-of-plane wave propagation through two-scale asymptotic expansion. The intervals of frequency where the effective mass is negative identify the band gaps of the material. The Bloch-Floquet problem is then considered and, through an asymptotic analysis, its is shown that it leads to the same prediction of the band gaps. The results are confirmed by some examples and the limits of the asymptotic approach are explicitly given and numerically verified. (10.1007/s10659-019-09743-x)
  DOI : 10.1007/s10659-019-09743-x
• Mécanique pulmonaire personnalisée : modélisation et estimation - Application à la fibrose pulmonaire
  
  • Patte Cécile
  • Genet Martin
  • Fetita Catalin
  • Brillet Pierre Yves
  • Chapelle Dominique
  , 2019.
• Réduction de modèle viscoplastique par application de la méthode NTFA à un VER de structure
  
  • Pascal Serge
  • Le Tallec Patrick
  • Leturcq Bertrand
  , 2019. Le cœur des réacteurs nucléaires à eau pressurisée est composé de structures répétitives disjointes, appelées assemblages combustibles. Ceux-ci fluent, sous les effets combinés de l'irradiation et des efforts mécaniques et hydrauliques jusqu'à entrer en contact les uns avec les autres. Afin de déterminer les déformations des assemblages en service, on propose de transposer la méthode d'homogénéisation non-linéaire NTFA à un problème de structure, l'assemblage combustible, formant le VER à homogénéiser. L'adoption d'une loi de comportement réduite permet en outre d'alléger significativement la durée des calculs.
• Modélisation du comportement orthotrope viscoplastique de l’alliage aéronautique Ti-6Al-4V sous chargements complexes
  
  • Ruiz de Sotto Miguel
  • Longère Patrice
  • Doquet Véronique
  • Papasidero Jessica
  , 2019. Des chargements complexes entraînant des grandes déformations, des vitesses de déformation élevées et des variations prononcées du taux de triaxialité des contraintes sont considérés dans l’alliage de titane Ti-6Al-4V. On s’intéresse ici à une modélisation unifiée rendant compte des effets combinés d’une dissymétrie importante entre traction et compression, d’un comportement orthotrope induit par le traitement thermomécanique, d’écrouissages isotrope et cinématique et de la viscoplasticité.
• Nonlinear elasticity of incompatible surface growth
  
  • Truskinovsky Lev
  • Zurlo Giuseppe
  Physical Review E, American Physical Society (APS), 2019, 99 (5). Surface growth is a crucial component of many natural and artificial processes, from cell proliferation to additive manufacturing. In elastic systems surface growth is usually accompanied by the development of geometrical incompatibility, leading to residual stresses and triggering various instabilities. In a recent paper [G. Zurlo and L. Truskinovsky, Phys. Rev. Lett. 119, 048001 (2017)] we presented a linearized elasticity theory of incompatible surface growth, which provides a quantitative link between deposition protocols and postgrowth states of stress. Here we extend this analysis to account for both physical and geometrical nonlinearities of an elastic solid. This development reveals the shortcomings of the linearized theory, in particular its inability to describe kinematically confined surface growth and to account for growth-induced elastic instabilities. (10.1103/PhysRevE.99.053001)
  DOI : 10.1103/PhysRevE.99.053001
• State-parameter estimation approach for data-driven wildland fire spread modeling: Application to the 2012 RxCADRE S5 field-scale experiment
  
  • Zhang Cong
  • Collin Annabelle
  • Moireau Philippe
  • Trouvé Arnaud
  • Rochoux Mélanie C.
  Fire Safety Journal, Elsevier, 2019, 105, pp.286 - 299. Data assimilation is an emerging and powerful tool towards real-time flame front monitoring for wildland fire applications. The key idea is to regularly update the state and/or parameters of a fire spread model using observed firelines in order to improve a forecast on future fire locations. The merits of combining state estimation and parameter estimation through a hybrid state-parameter estimation algorithm are demonstrated through the 2012 RxCADRE S5 field-scale controlled burn experiment. For state estimation, we adopt a cost-effective Luenberger observer formulation to reconstruct a complete view of the burning state at a given time. For parameter estimation, we use an ensemble transform Kalman filter to solve the inverse modeling problem consisting of inferring more realistic wind conditions given observations of the actual burning state. The data-driven model relies on a front shape similarity measure derived from image segmentation theory to quantify position errors. We show that the hybrid approach provides an efficient framework to address all sources of model uncertainties and to select burning scenarios that are most likely to occur. Parameter estimation is a key component of the data-driven model by reducing model bias. Using the fire spread model in forecast mode is then an asset to accurately track the flame front dynamics at future lead times. (10.1016/j.firesaf.2019.03.009)
  DOI : 10.1016/j.firesaf.2019.03.009
• Modeling Ovarian Folliculogenesis: Morphogenesis and Population Dynamics
  
  • Bonnet Celine
  • Chahour Keltoum
  • Clement Frederique
  • Postel Marie
  • Robin Frédérique
  • Yvinec Romain
  , 2019.
• Analysis of an observer strategy for initial state reconstruction of wave-like systems in unbounded domains
  
  • Imperiale Sébastien
  • Moireau Philippe
  • Tonnoir A
  ESAIM: Control, Optimisation and Calculus of Variations, EDP Sciences, 2019, 26 (45). We are interested in reconstructing the initial condition of a wave equation in an unbounded domain configuration from measurements available in time on a subdomain. To solve this problem, we adopt an iterative strategy of reconstruction based on observers and time reversal adjoint formulations. We prove the convergence of our reconstruction algorithm with perfect measurements and its robustness to noise. Moreover, we develop a complete strategy to practically solve this problem on a bounded domain using artificial transparent boundary conditions to account for the exterior domain. Our work then demonstrates that the consistency error introduced by the use of approximate transparent boundary conditions is compensated by the stabilization properties obtained from the use of the available measurements, hence allowing to still be able to reconstruct the unknown initial condition. (10.1051/cocv/2019026)
  DOI : 10.1051/cocv/2019026
• Glissement cristallin et glissement aux joints de grains : les deux temps de la partition plastique
  
  • Dimanov Alexandre
  • Bornert Michel
  • Raphanel Jean
  • Héripré Eva
  • Bourcier Mathieu
  • Gaye Ababacar
  • El Sabbagh Alexandre
  • Ludwig W.
  • Andrew King
  , 2019.
• MODULATE: ANR project for the modeling of long period ground motions and the assessment of their effects on large-scale infrastructures
  
  • Meza Fajardo Kristel Carolina
  • Papageorgiou Apostolos S
  • Lopez-Caballero Fernando
  • Chatzigogos Charisis
  • Semblat Jean-François
  • Aochi Hideo
  , 2019. Large-scale infrastructures are increasingly used in urban areas to meet the demands of continuously evolving societies. Recent seismic events showed remarkably that the construction of infrastructures with adequate seismic performance is the main factor in minimizing economic loss and long-term consequences to the communities. The modern design of large-scale structures, through the framework of performance-based earthquake engineering, requires consideration of the unique features of those structures, such as long natural period (> 2 seconds), interaction with the supporting soil, interaction with contained liquid, multi-support excitation, etc. In this project, we are concerned with the analysis, estimation and modeling of long period ground motions and their effects on the response of large-scale infrastructures such as high-rise buildings, liquid-storage tanks and long-span bridges. Intense long-period ground motions are usually generated at large distances from the source by large subduction-zone earthquakes and moderate-to-large crustal earthquakes. Such motions consist primarily of surface waves that arise when seismic waves encounter sedimentary deposits. One of the main objectives of the project is the development of a methodology based on the physics of surface waves, to describe the evolution of the spectral content of the ground motion for a site located in a sedimentary basin, and exposed to potential seismic sources, using relatively easily accessible input data. Furthermore, the stochastic description of ground motion will provide broadband realistic time histories that include basin-generated surface waves and which will be the means for practical assessment of the structural reliability and integrity of the considered large infrastructures. Realistic 3D numerical geological models will be implemented to study the physics of surface wave generation and propagation in sedimentary basins. The project is based on an inter-disciplinary effort with the synergy of Earthquake and Structural Engineers, together with Seismological and Numerical Modelling experts. The ultimate goal of the project is the development of novel, efficient and reliable tools and methods to be used by the earthquake engineering community for more robust and resilient designs of large-scale infrastructures.
• Analyse à l'échelle microstructurale de la fissuration dans une roche argileuse anisotrope par mesure de champs 2D et 3D
  
  • Gharbi H
  • Mezni M
  • Bonnelye A
  • Aimedieu Patrick
  • King A
  • Dimanov A
  • Bornert Michel
  , 2019. Dans cette étude, la fissuration d'un échantillon millimétrique de roche argileuse soumis à un chargement mécanique de compression uni-axiale a été observée dans un premier temps par microscopie optique, donnant accès à une analyse fine de l'initiation et de la propagation. Dans un second temps, des essais similaires sont observés par tomographie RX synchrotron, avec une résolution proche de la microscopie optique, rendant compte ainsi de façon comparable du comportement en volume. L'influence de l'anisotropie du matériau est clairement mise en évidence avec les expériences 2D. L'analyse volumique montre l'évolution du champ de déformation dans l'éprouvette, avec des localisations très caractéristiques de ce type d'essai.
• Analyse 3D du gonflement hydrique transitoire d'une roche argileuse : interaction entre échantillon et imageur
  
  • Bornert Michel
  • Gharbi H
  • Bonnelye A
  • Dimanov A
  • Aimedieu Patrick
  • Keita Emmanuel
  • King A
  , 2019. Les déformations hydriques d'un échantillon millimétrique de roche argileuse soumis à un gradient d'humidité relative sont mesurées par tomographie X synchrotron et corrélation d'images volumiques. On cherche aussi à caractériser l'endommagement induit par les gradients de gonflement. Le suivi de masse de l'échantillon et la complexité des profils de déformation mesurés révèlent que le faisceau synchrotron modifie localement l'équilibre hydrique de l'échantillon pendant l'acquisition d'image, rendant la sollicitation encore plus complexe que celle escomptée. Aucun endommagement macroscopique n'est détecté, malgré l'ampleur des gradients induits, en conséquence probable d'une sélection rigoureuse de l'échantillon qui ne présente pas d'hétérogénéité mésoscopique notable. L'expérience met toutefois en évidence un phénomène totalement inattendu de dissolution préférentielle des inclusions de calcite en périphérie d'échantillon.
• Design of multi-layer materials using inverse homogenization and a level set method
  
  • Nika Grigor
  • Constantinescu Andrei
  Computer Methods in Applied Mechanics and Engineering, Elsevier, 2019, 346, pp.388-409. This work is concerned with the micro-architecture of multi-layer material that globally exhibits desired mechanical properties, for instance a negative apparent Poisson ratio. We use inverse homogenization, the level set method, and the shape derivative in the sense of Hadamard to identify material regions and track boundary changes within the context of the smoothed interface. The level set method and the shape derivative obtained in the smoothed interface context allows to capture, within the unit cell, the optimal micro-geometry. We test the algorithm by computing several multi-layer auxetic micro-structures. The multi-layer approach has the added benefit that contact during movement of adjacent \branches" of the micro-structure can be avoided in order to increase its capacity to withstand larger stresses. (10.1016/j.cma.2018.11.029)
  DOI : 10.1016/j.cma.2018.11.029
• Multiscale modeling of skeletal muscle tissues based on analytical and numerical homogenization
  
  • Spyrou L.A. A
  • Danas K.
  • Brisard Sébastien
  Journal of the mechanical behavior of biomedical materials, Elsevier, 2019. A novel multiscale modeling framework for skeletal muscles based on analytical and numerical homogeniza-tion methods is presented to study the mechanical muscle response at finite strains under three-dimensional loading conditions. First an analytical microstructure-based constitutive model is developed and numerically implemented in a general purpose finite element program. The analytical model takes into account explicitly the volume fractions, the material properties, and the spatial distribution of muscle's constituents by using homogenization techniques to bridge the different length scales of the muscle structure. Next, a numerical homogenization model is developed using periodic eroded Voronoi tessellation to virtually represent skeletal muscle microstructures. The eroded Voronoi unit cells are then resolved by finite element simulations and are used to assess the analytical homogenization model. The material parameters of the analytical model are identified successfully by use of available experimental data. The analytical model is found to be in very good agreement with the numerical model for the full range of loadings, and a wide range of different volume fractions and heterogeneity contrasts between muscle's constituents. A qualitative application of the model on fusiform and pennate muscle structures shows its efficiency to examine the effect of muscle fiber concentration variations in an organ-scale model simulation. (10.1016/j.jmbbm.2018.12.030)
  DOI : 10.1016/j.jmbbm.2018.12.030
• Enhanced resonance of sparse arrays of Helmholtz resonators—Application to perfect absorption
  
  • Maurel Agnès
  • Mercier Jean-François
  • Pham Trung Kien
  • Marigo J.-J
  • Ourir Abdelwaheb
  Journal of the Acoustical Society of America, Acoustical Society of America, 2019, 145 (4), pp.2552-2560. We inspect the influence of the spacing on the resonance of a periodic arrangement of Helmholtz resonators. An effective problem is used which captures accurately the properties of the resonant array within a large range of frequency, and whose simplified version leaves us with an impedance condition. It is shown that the strength of the resonance is enhanced when the array becomes sparser. This degree of freedom on the radiative damping is of particular interest since it does not affect the resonance frequency nor the damping due to losses within each resonator; besides, it does not affect the total thickness of the array. We show that it can be used for the design of a perfect absorbing walls. (10.1121/1.5098948)
  DOI : 10.1121/1.5098948