ED Mathématiques et Informatique
ADER-DG approaches for the nonlinear advection-diffusion : Application to the incompressible Navier-Stokes equations
by Alexis TARDIEU (IMB - Institut de Mathématiques de Bordeaux)
The defense will take place at 14h00 - Salle de conférences (IMB) Institut de Mathématiques de Bordeaux, UMR 5251, 351 cours de la Libération, 33405 TALENCE
in front of the jury composed of
- Angelo IOLLO - Professeur des universités - Université de Bordeaux - Directeur de these
- Vincent PERRIER - Directeur de recherche - UPPA - INRIA - Rapporteur
- Walter BOSCHERI - Chaire de professeur junior - Université Savoie Mont Blanc - Rapporteur
- Raphaël LOUBÈRE - Directeur de recherche - CNRS - Examinateur
- François VILAR - Maître de conférences - Université de Montpellier - Examinateur
- Afaf BOUHARGUANE - Maîtresse de conférences - Université de Bordeaux - CoDirecteur de these
Many applications, such as incompressible multiphase fluid flows or heat conduction in non-homogeneous materials, are characterized by physical parameters that vary significantly across internal interfaces. In conventional approaches, these internal boundaries are handled using fitted meshes. These methods are accurate and can lead to schemes that allow for a simple discretization of interface conditions. However, generating and manipulating such a fitted mesh can be costly and time-consuming, especially when the geometry of the interface changes over time. In addition, calculating the solution on a parallel architecture generally requires partitioning the unknowns on the mesh according to time, which leads to additional computational costs. An alternative consists in developing new schemes based on a discretization of the solution on non-conforming hierarchical meshes, such as quadtrees or octrees. The hierarchical nature of the grid makes its generation and adaptation very efficient, while also facilitating parallelization and controlling memory footprint. Furthermore, local accuracy is achieved through the adaptability of the grid in regions of interest. During the doctoral work of Alice Raeli, Claire Taymans, and Antoine Fondanèche, finite difference and finite volume schemes on quadtrees and octrees were developed for problems involving heat conduction, fluid flows and fluid-structure interaction. These approaches proved to be reliable and effective, but the gain in order of accuracy and parallel efficiency was limited by the need to reconstruct it using polynomials on a larger stencil. More recently, Michele Giuliano Carlino's doctoral thesis extended an ADER approach from conforming grids to chimera meshes. This prediction-correction approach allows for higher-order discretization thanks to a polynomial structure of the solution in the prediction phase, while the correction ensures stability and recombines information between cells through flows at their interfaces. However, the resolution on a chimera mesh led to a loss of accuracy at the interfaces in the overlapping areas between the two meshes. In this context, this thesis work consisted in constructing a discontinuous Galerkin scheme allowing a polynomial representation of the solution to an arbitrary high degree, combined with an ADER approach for the time evolution. The study of penalization and relaxation approaches, tested at different orders of precision and for various simulation parameters, made it possible to establish the best performance compromise for the ADER-DG scheme. The numerical results obtained on the nonlinear advection-diffusion problem were extended to the simulation of incompressible flows by solving the Navier-Stokes equations. Ultimately, this doctoral work contributes to two objectives. On the one hand, it should enable the extension of the developed compact schemes to quadtrees, ensuring both efficient parallelization and maintained accuracy at mesh refinement level jumps. On the other hand, it should facilitate the adaptation to chimera meshes between a background quadtree grid and a fine, possibly anisotropic mesh adapted to internal geometries. The combination of these tools aims to enable realistic, accurate, and efficient simulations of boundary layer phenomena such as flows around aircraft wings or wind turbine blades.
ED Sciences Chimiques
Water droplets in water through the self-coacervation of polyampholytes
by Guillaume GIMENEZ (Institut des Sciences Moléculaires)
The defense will take place at 14h00 - Amphithéâtre 3 ENSMAC, 16 avenue Pey-Berland, 33600 Pessac
in front of the jury composed of
- Adeline PERRO - Maîtresse de conférences - Université de Bordeaux - Directeur de these
- Denis RENARD - Directeur de recherche - INRAE, Nantes Université - Rapporteur
- Nancy DE VIGUERIE - Professeure des universités - Université de Toulouse - Rapporteur
- Emilie POUGET - Directrice de recherche - CNRS, Université de Bordeaux - Examinateur
- Amélie BANC - Maîtresse de conférences - Université de Montpellier - Examinateur
- Nicolas SANSON - Maître de conférences - ESPCI Paris - Examinateur
This PhD project focuses on the formulation of coacervates which would be used in several application areas. Coacervates are present in the solute-rich phase during the liquid-liquid phase separation process of two aqueous phases in the form of micrometric spherical droplets. As part of this project, coacervates will be formed from the solvation loss of one single ampholyte polymer driven by electrostatic interactions into the same polymer chain. This process is called 'self-coacervation'. The main purposes of the PhD project will be to expand research in physical chemistry of 'self-coacervation' and to improve coacervates stability. The versatility of this process is of great interest in different applications such as enantiomeric separation, water clean-up, bio-inspired phenomena reproduction and microreactors elaboration.
ED Droit
The transformations of the principle of indivisibility of the Republic - Towards a new infra-territorial constitutional law
by Pierre BARILLE (CENTRE D'ÉTUDES ET DE RECHERCHES COMPARATIVES SUR LES CONSTITUTIONS, LES LIBERTÉS ET L'ÉTAT)
The defense will take place at 14h00 - 1K Pôle juridique et judiciaire de l'Université de Bordeaux 35, place Pey-Berland 33000 Bordeaux
in front of the jury composed of
- Ferdinand MELIN-SOUCRAMANIEN - Professeur des universités - Université de Bordeaux - Directeur de these
- Laetitia JANICOT - Professeure des universités - Université Paris I Panthéon-Sorbonne - Rapporteur
- Florence CROUZATIER-DURAND - Professeure des universités - Université Côte d'Azur - Rapporteur
- André ROUX - Professeur émérite - I.E.P. d'Aix-en-Provence - Examinateur
- Jean-François BRISSON - Professeur des universités - Université de Bordeaux - Examinateur
The principle of the indivisibility of the French Republic, consecrated in Article 1 of the Constitution of October 4, 1958, was proclaimed during the French Revolution to fulfill a precise function: to transpose into positive law the revolutionary concept of the Republic. This original function of the principle was subsequently consolidated and perpetuated, so that even today the prevailing understanding still strongly echoes the revolutionary ideals of unity and equality. However, since that proclamation, numerous dismantlings of the principle have been carried out, in the overseas territories and more recently within metropolitan territorial collectivities, without the perception of the principle itself evolving. At most, one concedes that compromises with the principle have been made, exceptions tolerated, owing to the “plasticity” of the principle. This gap between an imagined indivisibility and the actual reality of the principle has gradually made its study more complex, leading to the need to enumerate what it no longer prohibits, rather than to define clearly what it means. Today, because the French Republic has evolved and allowed for these dismantlings, without the principle itself evolving, the latter no longer retains a real function or normative utility. From a founding principle of the French Revolution, it has become a principle invoked out of habit, a reassuring incantation. Yet this mutation of the principle of indivisibility of the Republic is by no means inevitable. If the principle has lost its function, it remains possible to conceive a new one. Although Spanish and Italian examples of indivisibility exist, such a renewed function must be compatible with what the French Republic has become today, while potentially opening the way to a new infra-territorial constitutional law.
ED Sciences de la Vie et de la Santé
Wnt signaling and cerebral extra-cellular matrix: role of perivascular fibroblasts
by Romain BOULESTREAU (Biologie des maladies cardiovasculaires)
The defense will take place at 14h00 - Salle de réunion de l'unité Unité INSERM U1034, salle de réunion 1 avenue de Magellan, 33600 Pessac
in front of the jury composed of
- Thierry COUFFINHAL - Professeur des universités - praticien hospitalier - Université de Bordeaux - Directeur de these
- Carine ALI - Professeure des universités - praticienne hospitalière - Université de Caen, UMRS 1237 PHIND - Rapporteur
- Alexandre DUBRAC - Assistant professor - Université de Montréal, CHU de Saintes Justine - Examinateur
- Axel MONTAGNE - Associate Professor - University of Edinburgh - Rapporteur
Vascular and neurodegenerative dementias remain among the most pressing yet unresolved public health challenges, with emerging evidence highlighting the pivotal role of the extracellular matrix (ECM) in their pathogenesis. Perivascular fibroblasts (PVFs), recently identified around meningeal and penetrating arteries, have been implicated in ECM remodeling and neurovascular homeostasis. In this study, we investigate the role of Wnt signaling in PVFs, hypothesizing that its dysregulation contributes to ECM alterations and cognitive impairment. Using fibroblast-reporter mice (Col1a1-GFP), we identified a wave of PVF recruitment along cortical arteries during early postnatal development, coinciding with peak Wnt ligand expression and pathway activation, as confirmed by whole-brain qPCR. Proteomic analysis and immunolabeling revealed a distinct ECM deposition pattern associated with this process. To dissect the influence of Wnt signaling on PVF function and ECM homeostasis, we inhibited either astrocyte-derived Wnt ligands or β-catenin activation in PVFs using astrocyte-Wntless knockout mice (Aldh1L1-CreERT2: Grp177fl/fl) and conditional β-catenin depletion in PVFs (Col1a1-CreERT2: Ctnnb1fl/fl). Postnatal astrocytic Wnt ligand depletion impaired PVF recruitment and altered ECM transcript regulation but had no significant impact on ECM protein deposition or blood-brain barrier (BBB) integrity under physiological conditions or following hypertensive challenge. In contrast, preliminary data on β-catenin deletion in PVFs showed a pronounced ECM dysregulation with significant effects on BBB integrity. These findings underscore the critical role of Wnt signaling in PVF-mediated ECM remodeling and highlight the cerebrovascular matrisome as a key regulator of vascular stability and homeostasis.
ED Sciences Physiques et de l'Ingénieur
Generative approaches for porous media under disentangled physical constraints.
by Pedro CASTRO CÔRTES C COUTINHO (Laboratoire de l'Intégration du Matériau au Système)
The defense will take place at 14h00 - Amphi Jean-Paul Dom UMR 5218 - IMS - Laboratoire de l'Intégration du Matériau au Système 351 Cours de la Libération, 33405 Talence Cedex, France
in front of the jury composed of
- Yannick BERTHOUMIEU - Professeur des universités - Université de Bordeaux - Directeur de these
- Abdourrahmane ATTO - Professeur des universités - Université Savoie Mont Blanc - Rapporteur
- Marc DONIAS - Maître de conférences - Université de Bordeaux - CoDirecteur de these
- Philippe CARRE - Professeur des universités - Université de Poitiers - Rapporteur
- Audrey GIREMUS - Professeure des universités - Université de Bordeaux - Examinateur
- Charles YAACOUB - Professeur - Université Catholique de Lille - Examinateur
Generative models are powerful methods that allow the synthesis of new data by approximating the probability distribution that describes a dataset. During the past decade, several works have demonstrated their utility to a wide range of applications, including in materials science for the design of new structures. In this thesis, we are interested in applying these techniques to the generation of porous media, constrained by different physical properties related to the characterization of lithium-ion batteries. Our research is mainly focused on conditional models, combined with disentanglement approaches, with the objective of independently controlling the different properties of interest. First, we propose a VAE-based method that improves weakly supervised disentanglement methods in a general context. Then, we couple disentanglement to conditional modelling and propose a GAN-based architecture that generates 2D porous media, able to disentangle scalar properties, namely the porosity and the contact surface. Next, we adapt our model to the generation 3D porous media, and propose the disentanglement of more complex and vectorial properties. Finally, we also implement a novel disentanglement metric, focused on the structure of materials, that is more adapted to our data.
Flexible printed piezoelectric transducers for non destructive testing
by Ewen RAOUL (Laboratoire de l'Intégration du Matériau au Système)
The defense will take place at 10h30 - Amphi Jean-Paul Dom, Bâtiment A31, Laboratoire IMS 351 Cours de la Libération, 33405 Talence Cedex, France
in front of the jury composed of
- Anissa MÉZIANE - Professeure des universités - Université de Bordeaux - Directeur de these
- Marc RÉBILLAT - Maître de conférences - Arts et Métiers de Paris - Rapporteur
- Mounsif ECH-CHERIF EL-KETTANI - Professeur des universités - Université Le Havre Normandie - Rapporteur
- Dominique CERTON - Professeur des universités - École Polytechnique de l'Université de Tours - Examinateur
- Romain HODÉ - Docteur - CETIM - Examinateur
- Isabelle DUFOUR - Professeure des universités - Bordeaux INP - Examinateur
Industrial materials and structures require regular inspection and maintenance to ensure integrity throughout manufacturing, assembly, and usage. Existing evaluation methods rely on diverse physical principles and can be either intrusive or non-intrusive. These approaches often remain costly and are limited by restricted access to certain areas and difficulties in pinpointing damage origins. As a result, emerging research is focused on developing embedded devices capable of monitoring structural health over time and in situ, a concept known as Structural HealthMonitoring (SHM). One challenge in SHM ultrasonic imaging lies in adapting transducers to complex geometries. P(VDF-TrFE), a piezoelectric polymer, enables the fabrication of screen-printed ultrasound transducers that are flexible and only a few micrometers thick. These devices can be integrated into curved structures for real-time control and monitoring. Their manufacturing process allows for customized active surface geometries that directly influence the acoustic signals transmitted and received. This thesis begins by presenting the fabrication process and free-vibratio characterization of these transducers. It then investigates their dynamic behavior when bonded to flat surfaces, where piezoelectric actuation generates guided Lamb waves crucial for SHM applications. Given the lower energy conversion efficiency of piezoelectric polymers compared to ceramics, a thorough understanding of the underlying physical mechanisms is required to achieve a satisfactory signal-to-noise ratio. A multiphysics numerical model of the coupled transducerstructure system is developed and compared against analytical formulations and experimental measurements acquired using a 3D Doppler vibrometer. An analysis of geometric parameters (including transducer radii and acoustic wavelengths) is performed to inform future design optimizations for structurally complex environments. Finally, the designed transducers and arrays are being deployed in acoustic emission applications, notably for hydrogen tank surveillance and industrial pipeline monitoring.