Publications

2023

• Numerical and experimental studies of two-phase flows interacting with a bundle of tubes
  
  • Bazin Clément
  , 2023. The steam generators (SG) in nuclear power plants are made up of bundles of tubes subjected to two-phase water-steam flows. Vibrations related to this interaction can cause damage (fatigue, wear due to friction and shocks) that can lead to serious consequences for nuclear safety.In the context of preventing vibrational risks in SG tubes, experimental studies are conducted using analytical bundles of straight tubes subjected to transverse two-phase flow. In parallel, it is also important to develop a numerical simulation tool to access data and information that are difficult to measure.The goal of this work is to simulate the interaction between a two-phase fluid and a rigid structure (single tube or bundle of tubes) using the NEPTUNE_CFD code. These simulations aim to reproduce the mechanical loading exerted by the fluid on the tubes. The modeling used in this work is based on a two-fluid - three-field model, including a continuous liquid field, a dispersed gas field made up of slightly deformed bubbles, and a dispersed-continuous hybrid field to account for highly deformed bubbles and gas pockets. The first part of this work focused on the validation of the two-phase liquid-turbulence coupling as well as the modification and adaptation of the modeling to better account for the presence of an immersed structure. New models for turbulent dispersion force, source terms of coalescence and break-up, added mass, and the activation criterion of the continuous field were proposed. In the second part of this work, we simulated the two-phase flow around a fixed single tube to extract underlying physics, and identify its limitations and shortcomings. Finally, in the last part of this work, we simulated the interaction of a two-phase flow with a bundle of rigid tubes. The numerical results were compared to experimental measurements. This approach allowed us to justify the relevance of our modeling, find similarities between numerical and experimental results, while also suggesting areas for improvement.
• Adaptative observers for wave equations and associated discretizations : formulations and analysis.
  
  • Delaunay Tiphaine
  , 2023. The context of this thesis is the study of inverse problems for wave propagation phenomena from a control theory perspective, more specifically using observation theory. Our goal is to formalize, analyze, and discretize strategies called sequential in data assimilation, where measurements are taken into account as they become available. The resulting system, called an observer (or a sequential estimator), stabilizes on the observed trajectory hence reconstructs the state and possibly some unknown parameters of the system. Here we focus in particular on source reconstruction on the right-hand side of our wave equation, an estimation problem intermediate in complexity between state estimation (or initial condition estimation) and the more general problem of parameter identification. In this context, we propose to define in a deterministic framework in infinite dimension a so-called Kalman estimator that sequentially estimates the source term to be identified. Using dynamic programming tools, we show that this sequential estimator is equivalent to the minimization of a functional. This equivalence allows us to propose convergence analysis under observability conditions. We then demonstrate observability inequalities for different source types by combining functional analysis, multiplier methods, and Carleman estimates. In particular, these inequalities inform us about the ill-poseness nature of the inverse reconstruction problems we study and allow us to quantify the degree of ill-posedness hence to propose adapted regularizations. In particular, we compare an invert-and-regularize strategies as opposed to regularize-to-invert. Concerning discretization issues and their analysis, we defend the idea of redefining these observers associated with the minimization of the functional once the direct model has been discretized. This discretize-then-optimize approach is advantageous for the analysis compared to optimize-then-discretize approach. Nevertheless, the observability inequalities need to be extended to discretized systems. In particular, in this context, we extend uniform exponential stabilization results to the discretization for high-order finite element discretizations of the wave equation.
• Study of metallic architected materials under mechanical and electromagnetic loads
  
  • Magda Geoffrey
  , 2023. Recent developments in the fields of meta-materials and magneto-mechanical couplings aim to both enhance existing properties and create new ones. The goal of this thesis is to study the interactions between magnetizable materials, electric currents, and mechanical response. First, we detail the multi-physics model required to address this issue. Whenever possible, an analytical solution is provided. To handle more complex geometries, a variational approach is employed for finite element analyses. Subsequently we examine two practical cases: a partially magnetizable mesh subjected to unidirectional currents and a partially magnetizable, conductive 2D composite. We investigate their behavior under combined magnetic and mechanical loading, as well as their stability.
• Finite Strain Formulation of the Discrete Equilibrium Gap Principle: Application to Mechanically Consistent Regularization for Large Motion Tracking
  
  • Genet Martin
  Comptes Rendus. Mécanique, Académie des sciences (Paris), 2023, 351, pp.429-458. The equilibrium gap principle offers a good trade-off between robustness & accuracy for regularizing motion tracking, as it simply enforces that the tracked motion corresponds to a body deforming under arbitrary loadings. This paper introduces an extension of the equilibrium gap principle in the large deformation setting, a novel regularization term to control surface tractions, both in the context of finite element motion tracking, and an inverse problem consistent reformulation of the tracking problem. Tracking performance of the proposed method, with displacement resolution down to the pixel size, is demonstrated on synthetic images representing various motions with various signal-to-noise ratios. (10.5802/crmeca.228)
  DOI : 10.5802/crmeca.228
• Identification of PCPE-2 as the endogenous specific inhibitor of human BMP-1/tolloid-like proteinases
  
  • Vadon-Le Goff Sandrine
  • Tessier Agnès
  • Napoli Manon
  • Dieryckx Cindy
  • Bauer Julien
  • Dussoyer Mélissa
  • Lagoutte Priscillia
  • Peyronnel Célian
  • Essayan Lucie
  • Kleiser Svenja
  • Tueni Nicole
  • Bettler Emmanuel
  • Mariano Natacha
  • Errazuriz-Cerda Elisabeth
  • Fruchart Gaillard Carole
  • Ruggiero Florence
  • Becker-Pauly Christoph
  • Allain Jean-Marc
  • Bruckner-Tuderman Leena
  • Nyström Alexander
  • Moali Catherine
  Nature Communications, Nature Publishing Group, 2023, 14, pp.8020. Abstract<p>BMP-1/tolloid-like proteinases (BTPs) are major players in tissue morphogenesis, growth and repair. They act by promoting the deposition of structural extracellular matrix proteins and by controlling the activity of matricellular proteins and TGF-β superfamily growth factors. They have also been implicated in several pathological conditions such as fibrosis, cancer, metabolic disorders and bone diseases. Despite this broad range of pathophysiological functions, the putative existence of a specific endogenous inhibitor capable of controlling their activities could never be confirmed. Here, we show that procollagen C-proteinase enhancer-2 (PCPE-2), a protein previously reported to bind fibrillar collagens and to promote their BTP-dependent maturation, is primarily a potent and specific inhibitor of BTPs which can counteract their proteolytic activities through direct binding. PCPE-2 therefore differs from the cognate PCPE-1 protein and extends the possibilities to fine-tune BTP activities, both in physiological conditions and in therapeutic settings.</p> (10.1038/s41467-023-43401-0)
  DOI : 10.1038/s41467-023-43401-0
• On the generalized plane strain assumption for pressurized membranes
  
  • Thbaut Manon
  • Brisard Sébastien
  International Journal of Solids and Structures, Elsevier, 2023, 284, pp.112506. We revisit the problem of translation-invariant pressurized membranes that are squeezed without friction between several planes, all parallel to the axis of translation-invariance (such problem involves material and geometric nonlinearities, including contact). Quite remarkably, it was shown by De Simone and Luongo (2013) that such problems simplify considerably under the plane strain assumption. Indeed, the complex initial boundary-value problem reduces to a simple set of non-linear, algebraic equations. We argue that in many practical cases, the plane strain assumption does not hold. Instead, we introduce the generalized plane strain assumption, that is necessary to account for the longitudinal equilibrium of the membrane. We show how the equations of De Simone and Luongo (2013) are modified, while remaining extremely simple. We thus define an extended class of problems that become (nearly) tractable analytically. (10.1016/j.ijsolstr.2023.112506)
  DOI : 10.1016/j.ijsolstr.2023.112506
• Effect of the scanning strategy and tribological conditions on the wear resistance of IN718 obtained by Laser Metal Deposition
  
  • Zurcher Théo
  • Bouvard Gaëtan
  • Abry Jean-Christophe
  • Charkaluk Eric
  • Fridrici Vincent
  Wear, Elsevier, 2023, 534-535, pp.205152. Since the advent of additive manufacturing processes, new ways of repairing damaged parts emerged. Among those, Laser Metal Deposition offers the possibility of restoration or functionalization of surface properties. In this work, we study the wear properties of an IN718 coating deposited by LMD. IN718 is deposited according to several scanning strategies. Samples are subjected to dry flat-on-flat reciprocating wear tests using the flat surface of a cylindrical pin as a counter body. Then, we investigate the impact of the scanning strategy, the normal load, and the number of cycles on wear. Finally, we compare the wear resistance of the LMD samples with the one of wrought IN718 to evaluate the competitiveness of the wear properties of the material obtained by LMD. Results show that the scanning strategy turns out to not change the wear resistance of the deposited sample despite the highly heterogeneous surface microstructure. As the chosen contact is a flat-on-flat contact, the large area covered by the pin does not perceive the local microstructural heterogeneities. It has been observed as well that the wear volume of the coating increases linearly as the normal load increases, with an evolution of the wear mechanisms. Although oxidized transfer layer is observed at lower load, the main wear mechanisms observed are abrasion and adhesion. Then, by studying the wear evolution with increasing testing time, it has been observed that after a certain amount of cycles, a protective oxide layer appears and prevents IN718 from wear. In similar tribological conditions, wrought IN718 has slightly better wear resistance than its LMD's homolog. This difference in wear between the materials obtained by two processes could certainly be explained by the high initial amount of dislocations in the LMD samples and the presence of detrimental phases in its microstructure, such as Laves phases. Nonetheless, this study highlights the good wear resistance of the IN718 samples obtained by LMD despite their non-optimized as-built properties. (10.1016/j.wear.2023.205152)
  DOI : 10.1016/j.wear.2023.205152
• Reliable fatigue design of personal vehicle chassis parts from multi-input loads and unsupervised statistical analyses
  
  • Baroux Emilien
  • Pamphile Patrick
  • Delattre Benoit
  • Constantinescu Andrei
  • Rota Laurent
  , 2023. A vehicle's chassis plays a critical role in its reliability and durability. To ensure occupant safety and vehicle maneuverability, it is necessary to assess the fatigue strength of chassis components, i.e. their ability to withstand repeated loads during use. This assessment begins at the design stage, with the identification of operating conditions and associated loads. In the case of personal vehicles, various loads must be considered due to diverse road types (e.g., highway, city,. . .) and driving styles (aggressive, sporty,. . .). In this paper we use a multi-dimensional characterization of the damage caused by external multi-input loads on wheels during vehicle use, including load combinations between the left and right wheels of the front and rear axles. Field measurements are used to calculate pseudo-damages for each load and road type, creating multivariate data with hierarchical structure. Unsupervised statistical analyses are used to explore correlations between pseudo-damages and identify driving profiles, providing a multi-dimensional assessment of severity while avoiding overlearning. A multi-dimensional Gaussian mixture model is then fitted to damage-equivalent constraints. This probabilistic model extrapolates damage computing and simulates driving styles, providing design teams with a stress analysis tool for accurate, realistic fatigue design of chassis components in future vehicles.
• Modeling and Data Assimilation for Ultrasonic Guided Waves in Structural Health Monitoring under Operational Loading Conditions
  
  • Dalmora André
  , 2023. The application context of this work is the assessment of the structural health of aircraft, bridges, pipelines, and many others. More specifically, we focus here on methods based on guided ultrasonic wave propagation in the context of Structural Health Monitoring (SHM), where critical parts of the structure are monitored during operation by a distributed system of sensors to detect anomalies. In this context, Environmental and Operational Conditions can lead to misinterpretation of the measured data and must therefore be considered when analyzing the acquired data. In particular, it is known that the mechanical loading of the structure affects ultrasound propagation. As a first contribution, this work proposes a numerical method for modeling efficiently the propagation of guided waves in loaded structures. The effects of mechanical loading on wave propagation are modeled using concepts of acoustoelasticity. The ultrasound waves are assumed to be incremental to the structural deformation caused by the loading. This assumption allows us to define a linearized elastodynamics formulation around the (potentially) large deformation caused by the loading. We then propose adapted finite element methods to solve both formulations. First, the structural deformation is computed using 3D Shell FE, which is then an input of the linearized elastodynamics solver based on the transient High-Order Spectral FE. Such a combination allows a suitable application for SHM systems as it can model arbitrary geometries, loading configurations, and constitutive behavior based on hyperelastic laws. Using this direct model, a second contribution of this dissertation is the development of an original data assimilation strategy to recover the deformation from sensor measurements. The estimation problem is interpreted as a least squares minimization problem, which is then solved by a clever combination of variational and sequential approaches, resulting in an iterative version of the Unscented Kalman Filter. Both the presentation of the direct model and its inversion are complemented by illustrations based on large realistic scenarios to demonstrate the efficiency of the proposed approaches.
• On the accuracy of temperature estimates from in operando X-ray diffraction measurements during additive manufacturing
  
  • Gaudez Steve
  • Weisz-Patrault Daniel
  • Abdesselam Kouider Abdellah
  • Gharbi Hakim
  • Honkimäki Veijo
  • van Petegem Steven
  • Upadhyay Manas Vijay
  , 2023. Lattice strains obtained from in operando synchrotron X-ray diffraction measurements during metal additive manufacturing are being increasingly used to deduce temperature and cooling rates occurring during the process. The underlying assumption behind this deduction is that lattice strain evolution occurs solely due to temperature changes caused by the passage of the heat-source. However, this assumption crucially neglects the role of mechanical constraints on the sample and the evolution of internal stresses generated due to microstructure evolution. The ensuing elastic strains can have a significant contribution to lattice strains and failure to decouple them from the contribution of thermal strains may induce significant errors in temperature and cooling rate estimates. In this study, we quantify these errors using a combined experimental and numerical approach. First, lattice strains are obtained from in operando synchrotron X-ray diffraction measurements during additive manufacturing of a 316L stainless steel thin-wall. Then, the contributions of elastic and thermal strains to the lattice strain are deconvoluted using experimentally validated fast large-scale thermomechanical simulations of the entire AM process. Results reveal that even in the simple case of AM of a single-phase material such as 316L and a thin-wall geometry, significant errors in both temperature amplitudes (up to 30\%) and cooling rates (up to 27\%) occur when the contribution of elastic strains is neglected. Furthermore, mechanical and thermal effects cannot be trivially decoupled from X-ray diffraction data; fast large-scale thermomechanical simulations become necessary to perform this decoupling.
• Tenue à l’usure et réparation de pièces métalliques obtenues par fabrication additive
  
  • Zurcher Théo
  , 2023. La réparation de pièces métalliques usées en service représente un enjeu stratégique de taille pour les industriels. Ces réparations se doivent d’être avantageuses économiquement mais également écologiquement. De nombreux procédés de réparation, dit « conventionnels », sont encore de nos jours utilisés pour répondre à ce besoin. Cependant, ces derniers ne sont pas, pour la grande majorité, adaptés pour la réalisation de réparations fines de géométrie complexe. Un procédé de fabrication additive (FA) appartenant à la famille des procédés Direct Energy Deposition (DED) appelé Laser Metal Deposition (LMD) répond, entre autres, à ce besoin spécifique. Ce procédé, au-delà d’offrir la possibilité de réparer des pièces, peut également fabriquer des pièces métalliques de géométrie simple ou ajouter des fonctions à des pièces métalliques préexistantes. Ce dernier consiste à juxtaposer et empiler des petits joints de soudure appelés « cordons » en faisant fondre de la poudre métallique en la projetant sous le point focal d’un laser. Le faible diamètre du laser et l’assistance du déplacement de la buse par une commande numérique permet de réaliser des réparations de hautes résolutions. L’étude des propriétés mécaniques des pièces/réparations issues de ce procédé FA a déjà été largement traitée dans la littérature cependant très peu d’études se sont intéressées à leur propriété de résistance à l’usure. Cette thèse porte ainsi sur l’étude expérimentale de la tenue à l’usure de pièces réparées par le procédé LMD afin, in fine, de pouvoir proposer des recommandations méthodologiques qui mènent à des réparations avec une bonne tenue à l’usure. Tout d’abord ce manuscrit expose la démarche expérimentale qui a mené à étudier le comportement à l’usure de réparations en IN718 et en 316L dans le cas d’un contact surfacique sec à mouvement linéaire alterné. Puis, une fois les échantillons fabriqués, ce manuscrit propose une caractérisation complète de leurs surfaces de contact (dureté, contraintes résiduelles, microstructure…) et dont notamment une étude métallurgique détaillée de cette face, qui a été très peu étudiée dans la littérature. Puis, le tribomètre est présenté et le contact est modélisé par éléments finis afin d’estimer les contraintes générées dans de telles sollicitations tribologiques. Enfin, le comportement à l’usure de réparations en superalliage base nickel IN718 et en acier 316L est étudié. Ces études ont montré que la stratégie de réparation et la direction de glissement n’impactaient pas leur tenue à l’usure. Des études des contraintes résiduelles en amont et en aval des essais d’usure ont montré que les contraintes résiduelles inhérentes à ce procédé n'impactaient pas significativement l’usure. Ces études ont également permis de démontrer que les résultats d’usure sont extrêmement dépendants du matériau de réparation utilisé et des conditions tribologiques dans lesquelles les réparations évoluent. Il a notamment été constaté que l’acier 316L possède, pour des conditions tribologiques similaires, une meilleure tenue à l’usure. Cependant, il a été démontré que les réparations en IN718 possédaient une tenue à l’usure plus compétitive que celles en acier 316L lorsqu’on les compare à des pièces, composées du même alliage, fabriquées conventionnellement.
• A jump-diffusion stochastic formalism for muscle contraction models at multiple timescales
  
  • Chaintron Louis-Pierre
  • Kimmig François
  • Caruel Matthieu
  • Moireau Philippe
  Journal of Applied Physics, American Institute of Physics, 2023. Muscle contraction at the macro level is a physiological process that is ultimately due to the interaction between myosin and actin proteins at the micro level. The actin-myosin interaction involves slow attachment and detachment responses and a rapid temporal change in protein conformation called power-stroke. Jump-diffusion models that combine jump processes between attachment and detachment with a mechanical description of the power-stroke have been proposed in the literature. However, the current formulations of these models are not fully compatible with the principles of thermodynamics. To solve the problem of coupling continuous mechanisms with discrete chemical transitions, we rely on the mathematical formalism of Poisson random measures. First, we design an efficient stochastic formulation for existing muscle contraction PDE models. Then, we write a new jumpdiffusion model for actin-myosin interaction. This new model describes both the behavior of muscle contraction on multiple time scales and its compatibility with thermodynamic principles. Finally, following a classical calibration procedure, we demonstrate the ability of the model to reproduce experimental data characterizing muscle behavior on fast and slow time scales. (10.1063/5.0158191)
  DOI : 10.1063/5.0158191
• Micro- and macrocirculatory effects of norepinephrine on anaesthesia-induced hypotension: a prospective preliminary study
  
  • Kindermans Manuel
  • Joachim Jona
  • Manquat Elsa
  • Levé Charlotte
  • Hong Alex
  • Mateo Joachim
  • Mebazaa Alexandre
  • Gayat Etienne
  • de Backer Daniel
  • Vallée Fabrice
  BMC Anesthesiology, BioMed Central, 2023, 23 (1), pp.374. Abstract Background Intraoperative arterial hypotension (IOH) leads to increased postoperative morbidity. Norepinephrine is often use to treat IOH. The question regarding the mode of administration in either a bolus or continuous infusion remains unanswered. The aim of the present study was to describe and compare the effects on macrocirculation and microcirculation of a bolus and a continuous infusion of norepinephrine to treat IOH. Methods We conducted a prospective observational study with adult patients who underwent neurosurgery. Patients with invasive arterial blood pressure and cardiac output (CO) monitoring were screened for inclusion. All patients underwent microcirculation monitoring by video-capillaroscopy, laser doppler, near-infrared spectroscopy technology, and tissular CO 2 . In case of IOH, the patient could receive either a bolus of 10 µg or a continuous infusion of 200 µg/h of norepinephrine. Time analysis for comparison between bolus and continuous infusion were at peak of MAP. The primary outcome was MFI by videocapillaroscopy. Results Thirty-five patients were included, with 41 boluses and 33 continuous infusion. Bolus and continuous infusion induced an maximal increase in mean arterial pressure of +30[20-45] and +23[12-34] %, respectively ( P =0,07). For macrocirculatory parameters, continuous infusion was associated with a smaller decrease in CO and stroke volume (p&lt;0.05). For microcirculatory parameters, microvascular flow index (-0,1 vs. + 0,3, p =0,03), perfusion index (-12 vs. +12%, p =0,008), total vessel density (-0,2 vs. +2,3 mm2/mm2, p =0,002), showed significant opposite variations with bolus and continuous infusion, respectively. Conclusions These results on macro and microcirculation enlighten the potential benefits of a continuous infusion of norepinephrine rather than a bolus to treat anaesthesia-induced hypotension. Trial registration (NOR-PHARM: 1-17-42 Clinical Trials: NCT03454204), 05/03/2018 (10.1186/s12871-023-02342-3)
  DOI : 10.1186/s12871-023-02342-3
• cast-post
  
  • Gounand Stephane
  • Courtois Mathieu
  • Bulik Michal
  • Constantinescu Andrei
  , 2023. This shell script customizes a PostScript file produced by Castem 2000/Cast3M.
• Review of "An energy approach to asymptotic, higher-order, linear homogenization
  
  • Audoly Basile
  • Lestringant Claire
  • Seppecher Pierre
  • Pasini Damiano
  • Ganghoffer Jean-Francois
  • Brassart Laurence
  Journal of Theoretical, Computational and Applied Mechanics, INRIA, 2023.
• Development and qualification of clinical grade decellularized and cryopreserved human esophagi
  
  • Godefroy William
  • Faivre Lionel
  • Sansac Caroline
  • Thierry Briac
  • Allain Jean-Marc
  • Bruneval Patrick
  • Agniel Rémy
  • Kellouche Sabrina
  • Monasson Olivier
  • Peroni Elisa
  • Setterblad Niclas
  • Braik Massymissa
  • Even Benjamin
  • Cheverry Sophie
  • Domet Thomas
  • Albanese Patricia
  • Larghero Jérôme
  • Cattan Pierre
  • Arakelian Lousineh
  Scientific Reports, Nature Publishing Group, 2023, 13, pp.18283. Tissue engineering is a promising alternative to current full thickness circumferential esophageal replacement methods. The aim of our study was to develop a clinical grade Decellularized Human Esophagus (DHE) for future clinical applications. After decontamination, human esophagi from deceased donors were placed in a bioreactor and decellularized with sodium dodecyl sulfate (SDS) and ethylendiaminetetraacetic acid (EDTA) for 3 days. The esophagi were then rinsed in sterile water and SDS was eliminated by fltration on an activated charcoal cartridge for 3 days. DNA was removed by a 3-hour incubation with DNase. A cryopreservation protocol was evaluated at the end of the process to create a DHE cryobank. The decellularization was efcient as no cells and nuclei were observed in the DHE. Sterility of the esophagi was obtained at the end of the process. The general structure of the DHE was preserved according to immunohistochemical and scanning electron microscopy images. SDS was efciently removed, confrmed by a colorimetric dosage, lack of cytotoxicity on Balb/3T3 cells and mesenchymal stromal cell long term culture. Furthermore, DHE did not induce lymphocyte proliferation in-vitro. The cryopreservation protocol was safe and did not afect the tissue, preserving the biomechanical properties of the DHE. Our decellularization protocol allowed to develop the frst clinical grade human decellularized and cryopreserved esophagus. (10.1038/s41598-023-45610-5)
  DOI : 10.1038/s41598-023-45610-5
• A micro-poro-mechanical model of the lung parenchyma
  
  • Genet Martin
  • Manoochehrtayebi Mahdi
  • Bel-Brunon Aline
  , 2023.
• Plumes and large scale circulation in turbulent thermal convection with a rough plate
  
  • Sergent Anne
  • Fraigneau Yann
  • Lucor Didier
  , 2023. In a real thermal system, the underlying surfaces have specific topographies or small scale roughness that have a significant effect on heat transfer. In particular, in the case of turbulent convection, the addition of wall roughness leads to a global increase in heat transfer. Three successive heat transfer regimes can be obtained. It is generally accepted that the heat transfer enhancement results from an intensification of the thermal plume emission. In the present study, we consider convection over a regularly roughened plate in a Rayleigh-Bénard cell. The aim of this work is to determine how the roughness alters the interactions between theplumes and the large-scale circulation, as a function of the heat transfer regime. Three-dimensional direct numerical simulations (DNS) have been performed for Rayleigh numbers covering five decades up to Ra = 1010 and for two roughness sizes. However, even though the development of massively parallel DNS solvers now makes it possible to tackle calculations in highly turbulent regimes, it remains difficult to statistically approach all flow scales, store them or easily replay their sequences. Therefore, a first attempt to build a reduced model for 3D flow reconstruction using physically informed neural networks is presented. This work benefits from the French National Research Agency funding (THERMAL project).
• Uterus healing after cesarean: development of a rabbit model
  
  • Debras Elodie
  • Maudot Constance
  • Allain Jean-Marc
  • Pierangelo Angelo
  • Rivière Julie
  • Dahirel Michèle
  • Richard Christophe
  • Gelin Valerie
  • Morin Gwendoline
  • Capmas Perrine
  • Chavatte-Palmer Pascale
  , 2023. Uterine Scar area on C-section horn Normal area on C-section horn Control horn Wilcoxon Mann-Whitney Test *p&lt;0,05 **p&lt;0,01***p&lt;0,001 Mean thickness area Cesarean: Representation and incision of the Csection horn C-section horn with normal scar • Left: Macroscopic view • Right: Section 5µm, haematoxylineosin-safran staining. The objective is to develop an in-vivo model of uterus healing after cesarean in order to analyze histological phenomena controlling scarring tissue development and potential cause of defects.
• Multi-scale analysis of a porous carbonate rock under triaxial conditions
  
  • Doré-Ossipyan Catherine
  • Sulem Jean
  • Bornert Michel
  • Dimanov Alexandre
  • Aimedieu Patrick
  • de Greef Vincent
  • King Andrew
  , 2023, pp.764-769. The formation and evolution of deformation bands in a carbonate rock with high porosity is investigated by performing in situ triaxial experiments with high-resolution synchrotron X-Ray Computed Tomography by placing a specifically designed testing device directly in the tomograph. The processing of images by Digital Volume Correlation techniques provides insight on the deformation modes of the samples for various loading conditions. In more porous specimens with a homogeneous microstructure, many subhorizontal compactant deformation bands sequentially initiate, propagate, widen and fully saturate the volume of the rock sample after a few percent of overall strain, leading to a rather uniform compaction of the sample. In contrast, denser samples with a more heterogeneous microstructure exhibit discrete deformation bands, in limited number. These bands propagate and widen, leading to strong localization of the deformation which remains restricted to certain parts of the sample.
• Mathematical framework for biological tissue perfusion modeling and simulation
  
  • Barré Mathieu
  , 2023. Many biological tissues can be modeled as porous media, namely continuous media composed of a solid skeleton filled by a fluid. In biological tissues, the fluid at stake can be blood, airflows in the lungs or cerebrospinal fluid, all of which can be seen as incompressible fluids. Moreover, in such applications, the porous medium itself can be considered as nearly-incompressible. The goal of this PhD thesis is to analyze a recent partial differential equation model describing the motion of a nearly-incompressible or incompressible porous medium. This model arises from the linearization of a non-linear poromechanics model adapted to soft tissue perfusion, but is also strongly connected to Biot's equations of poroelasticity. In this model, the solid and fluid equations show a hyperbolic/parabolic behavior, and are in addition coupled through the interstitial pressure associated with the incompressibility divergence constraint. The first contribution of this thesis is to show the existence and uniqueness of strong and weak solutions in the nearly-incompressible and incompressible cases. This is achieved by combining semigroup theory, energy estimates and T-coercivity. T-coercivity theory, originally developed for unconstrained problems, is extended here to treat general saddle-point and perturbed saddle-point problems. This concept also appears to be useful for the design of stable finite elements in the incompressible limit and for the numerical analysis of the system. Spatial and temporal convergence analysis are performed for a monolithic scheme, leading to robust error estimates with respect to incompressibility, porosity and permeability. In order to improve computational efficiency, a fractional-step method is proposed and analyzed. In particular, general boundary conditions connecting the fluid and the solid on the boundary are considered and imposed thanks to a Robin-Robin coupling method. Finally, the relevance of the model to biomedical applications is illustrated by comparing microvessels-on-chip simulations with experimental data.
• Biomécanique de la cornée
  
  • Giraudet Chloé
  • Allain Jean-Marc
  , 2023.
• Introduction
  
  • Bansaye Vincent
  • Kuhn Estelle
  • Moireau Philippe
  MathematicS In Action, Société de Mathématiques Appliquées et Industrielles (SMAI), 2023, 12, pp.1-1. At first glance, mathematics and life sciences may appear to be two distant fields. However, history has shown the importance of mathematical modeling in understanding and analyzing biological phenomena. Research has evolved and developed considerably recently, with numerous collaborations between mathematicians and biologists, stimulating both communities. The interface is very active and diversified today, from highly theoretical questions to the most applied aspects. This interface is stimulated by the need for and complexity of models and technological advances and the influx of data. In this special issue of the recent SMAI Math’s in Action open journal, we aim to show the vitality and scientific richness of the work being done today at this interface, where original mathematical results have helped to answer questions raised by biological, ecological or medical applications. Indeed, the reader will find a wide range of applications in this issue, from epidemiology to medical imaging, from subcellular biology to organ physiology. But also a wide range of mathematical tools from probability to statistics, from mathematical analysis of partial differential equations to theoretical computer science using formal methods, from theory to numerics. We would like to dedicate this special issue to Elisabeta Vergu, whose research and scientific leadership have contributed significantly to the development of the interface between mathematics and epidemiology. (10.5802/msia.28)
  DOI : 10.5802/msia.28
• Modeling actin-myosin interaction: beyond the Huxley–Hill framework
  
  • Chaintron Louis-Pierre
  • Caruel Matthieu
  • Kimmig François
  MathematicS In Action, Société de Mathématiques Appliquées et Industrielles (SMAI), 2023, 12 (1), pp.191-226. Contractile force in muscle tissue is produced by the interaction of myosin molecular motors that bind and pull on specific sites located on surrounding actin filaments. The classical framework set by the landmark works of A.F. Huxley and T.L. Hill to model this active system is build on the central assumption that thermal fluctuations of a given myosin motor are sufficiently small so that it cannot interact with more than one binding site at any time. In this paper we present the physiological and mathematical limitations of this approach to motivate a new formulation that circumvent them without resorting to the more complex multi-site model paradigm. The acto-myosin system is now described as a Markov process combining Langevin driftdiffusion and Poisson jumps dynamics. We show that the corresponding system of Stochastic Differential Equation is well-posed and derive its Partial Differential Equation analog in order to obtain the thermodynamic balance laws. We finally show that by applying standard elimination procedures, a modified version of the original Huxley-Hill framework can be obtained as a reduced version of our model. Theoretical results are supported by numerical simulations where the model outputs are compared to benchmark experimental data. (10.5802/msia.38)
  DOI : 10.5802/msia.38
• Metal foam-salt hydrate composites for thermochemical energy storage
  
  • Liu Yutong
  , 2023. Thermochemical heat storage (THS) systems based on the hydration/dehydration reaction between water vapor and hygroscopic salts are considered to be a simple, low-cost and environmentally friendly system. However, hygroscopic salts have drawbacks such as swelling and agglomeration of the crystalline salt particles during hydration/dehydration cycles, which progressively leads to decreasing specific reaction surface, and kinetics of heat and mass transfer, thus resulting in efficiency degradation due to poor cyclic performance and stability.To alleviate the limitations mentioned above, we propose a composite based on open-cell metal foam as host matrix, containing calcium chloride as hygroscopic salt dispersed in the pores. With an adapted microstructure avoiding agglomeration during swelling and shrinking of the salt crystallites related to hydration and dehydration respectively, this composite facilitates the transfers of water vapor and heat and prevents loss of specific reaction surface, thus improving the performance of the THS system.This thesis work focuses first on the mechanical properties of metal foam. The multiscale deformation behavior of different metal foams was studied by compression tests realized in situ with observation by optical microscopy with high-resolution camera (pixel size of 2.75 μm) and scanning electron microscopy (SEM). Laboratory X-ray microtomography technique was also applied. Images were analyzed by 2D and 3D Digital Image Correlation (DIC) for the computation of displacement fields and strain fields. The results show that concerning the mechanical integrity the microstructure of the metal foam is by far more important than the metal itself. Strain localization is limited in metal foams with a comparatively homogeneous microstructure, precluding complete pore collapse, thus preserving the mass transfer properties. In opposition, highly heterogeneous metal foam microstructure leads to the formation of strong localization bands, which might impede the water vapor transfer, thus affecting the performance of the designed composite.The thermochemical properties of the metal foam-salt composites are studied by differential scanning calorimetry (DSC), with respect to the synthesis method and the type of metal foam. In particular, the thermochemical properties of the composites during hydration/dehydration cycles are compared with those of salt hydrate powders of calcium chloride. The evolution of the thermochemical properties is further analyzed, based on in situ observation of the microstructural and morphological evolution during hydration/dehydration cycling in an environmental scanning electron microscope (ESEM). It is demonstrated that the metal foam-salt composites show significant improvement in terms of cyclic stability and quantity of thermal energy released/stored, compared to bulk calcium chloride powder. In situ ESEM observations show that swelling and deliquescence induce moderate redistribution of salt hydrates within the metal foam. However, the open porosity of the composite is essentially preserved. The metal foam efficiently prevents extensive salt agglomeration and loss of specific reaction area, which explains the substantial improvement of the composite’s thermochemical properties and their cyclic stability.In conclusion, the metal foam-salt hydrate composite developed in our work is suitable and promising for thermochemical storage, offering both mechanical and thermochemical advantages. On the one hand, the metallic foam ensures structural integrity allowing for flexible industrial handling of thermochemical storage units. On the other hand, the metal foam ensures the microstructural stability of the reactive material, hence preserving an economically durable life span. At last, the designed composites have a low environmental footprint. The reactive salt hydrates are environmentally friendly. Both the salt hydrate and the metallic foam allow for total recycling.