HAL Portal UPPA (University of Pau and the Pays de l'Adour)
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Une stratégie de Réduction d'Ordre de Modèle pour les EDP Paramétrées : un nouveau paradigme pour l'Imagerie Souterraine efficace.
No full textSubsurface exploration plays a crucial role in many fields, ranging from energy production (oil, gas, geothermal) to civil engineering and environmental issues such as CO storage. This thesis is situated within the framework of subsurface imaging, where the goal is to reconstruct the internal properties of the subsurface from recordings of artificially generated wavefields. This process, known as Full Waveform Inversion (FWI), relies on the repeated solution of wave equations, resulting in high computational costs, particularly in high-resolution and multi-parameter contexts.To address these challenges, this thesis explores model order reduction (MOR) approaches, which aim to reduce the dimensionality of the systems to be solved while preserving their essential dynamics. After presenting the foundations of FWI in the context of acoustic wave propagation, as well as the spectral element method used for discretization, the study focuses on the Proper Orthogonal Decomposition (POD) method and its application to the acoustic wave equation problem. It then introduces a variant using a QR decomposition, designed to mitigate the memory costs of the classical POD approach while maintaining a similar level of accuracy.One of the major challenges of Reduced Order Models (ROMs) lies in their sensitivity to parameter variations. To address this, the thesis proposes a method based on the Fréchet derivatives of the problem, enabling the construction of reduced bases that are more robust to parameter changes. This method is validated on 2D and 3D acoustic problems and then integrated into an FWI framework via the GEOS platform.This work makes an original contribution to the efficient solution of inverse problems in geophysics by combining advanced numerical methods with model reduction, paving the way for large-scale applications with reduced computational costs.L’exploration du sous-sol joue un rôle crucial dans de nombreux domaines, allant de la production d’énergie (pétrole, gaz, géothermie) à l’ingénierie civile, en passant par les enjeux environnementaux comme le stockage du CO2. Cette thèse s’inscrit dans le cadre de l’imagerie souterraine, où l’objectif est de reconstruire les propriétés internes du sous-sol à partir d’enregistrements de champs d’ondes générées artificiellement. Ce processus, connu sous le nom d’inversion de formes d’ondes complètes (FWI), repose sur la résolution répétée d’équations d’ondes, ce qui entraîne un coût computationnel élevé, en particulier dans des contextes à haute résolution et multi-paramètres.Pour répondre à ces défis, cette thèse explore des approches de réduction d’ordre de modèle (MOR), qui permettent de diminuer la dimension des systèmes à résoudre tout en préservant leur dynamique essentielle. Après avoir présenté les fondements de la FWI dans le cadre de la propagation des ondes acoustiques, ainsi que la méthode des éléments spectraux utilisée pour la discrétisation, l’étude se concentre sur la méthode de Décomposition Orthogonale aux Valeurs Propres (POD) et son application au problème de l'équation des ondes acoustique, puis introduit une variante utilisant une décomposition QR, visant à pallier les coûts mémoire de l'approche POD classique tout en maintenant un ordre de précision équivalent.L’une des difficultés majeures des ROMs réside dans leur sensibilité aux variations de paramètres. Pour y remédier, la thèse propose une méthode basée sur les dérivées de Fréchet du problème considéré, qui permet de construire des bases réduites plus robustes face aux changements de paramètres. Cette méthode est validée sur des problèmes acoustiques en 2D et 3D, puis intégrée dans un cadre FWI via la plateforme GEOS.Ce travail apporte une contribution originale à la résolution efficace de problèmes inverses en géophysique, en combinant méthodes numériques avancées et réduction de modèles, ouvrant la voie à des applications à grande échelle avec des coûts réduits
A new cold-active transglutaminase: Discovery, computational insights, and recombinant expression
No full textInternational audienceTransglutaminases (TGases) are versatile enzymes widely applied in food, biomedical, and material sciences, but the cold-active TGases are underexplored despite their significance in low-temperature bioprocessing. This study reports the identification, computational characterization, and recombinant expression of a new transglutaminase (akTGase) derived from the Antarctic krill transcriptome. Bioinformatics analysis revealed that akTGase was estimated of 84.76 kDa, possesses structural traits consistent with cold adaptation, including elevated hydrophilicity, high levels of methionine and aspartic acid but low arginine content, and high proportions of flexible regions. Molecular dynamics simulations at 4 °C and 25 °C showed enhanced surface flexibility and conformational stability at low temperature. Recombinant akTGase was produced in E. coli, recovered from inclusion bodies via stepwise dialysis, and assayed for enzymatic activity. The refolded akTGase displayed significantly higher specific activity at 4 °C than at 25 °C, confirming its cold-active nature. This work highlights a successful strategy combining transcriptomic mining, structural prediction, and experimental validation for the discovery of psychrophilic enzymes, particularly TGase, offering promising potential for sustainable applications in cold-adapted biocatalysis
Instrumentation and experimental hygrothermal investigations of a raw compressed earth brick house in Sense-City equipment: From material to building scale
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A New Method for Isenthalpic Phase Equilibrium Calculations By Direct Maximization of Entropy Using a Combined SSI-Modified Newton Algorithm
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Strongly vs. weakly associating anions: transport–structure relationship in LiTFSI–LiNO3 electrolytes
No full textInternational audienceLiquid battery electrolytes based on mixtures of salts with weakly and strongly associating anions have emerged as a promising route toward high-performance, sustainable battery technologies. Their success is primarily attributed to the unique influence of salt composition on the solvation structure. Here, we employ classical molecular dynamics simulations, corroborated by experimental data, to study mixed lithium bis(trifluoromethanesulfonyl)imide (LiTFSI)/lithium nitrate (LiNO3) in diglyme electrolytes, a formulation of particular interest for lithium–sulfur and lithium–oxygen batteries. We investigate how the ratio of weakly associating anions (TFSI ) to strongly associating anions (NO3) affects ion transport within the electrolyte. Our findings reveal that the anion ratio significantly impacts both the solvation structure and the solvation dynamics, which together contribute to the distinct transport behavior observed in these systems. These findings underscore the tunability of battery electrolyte transport properties through careful mixing of anions
Des matériaux inspirés des coquillages pour du béton à plus faible impact environnemental
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El programa POPSU Eaux-Bonnes y los Heritage Studies. Una investigación al cruce de los campos científicos
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Numerical modeling of multilayer composite pipe with glass fiber‐reinforced polypropylene layer
No full textInternational audienceThis study focuses on the numerical modeling of multilayer composite pipes, specifically those incorporating a glass fiber‐reinforced polypropylene layer. The research investigates the mechanical properties of a high modulus polypropylene grade, BA212E, and a composite material, PP‐GF30, which contains 30 wt.% glass fibers. Various hyperelastic material models are evaluated to accurately represent the mechanical behavior of these materials under different loading conditions. It was found that the Yeoh hyperelastic material model combined with nonlinear isotropic hardening plasticity provides the most suitable representation of the behaviors of these materials. This model was validated through numerical simulations of three‐point bending and pipe compression tests, demonstrating good agreement with experimental data. Highlights Glass fiber‐reinforced multilayer composite pipes for improved stiffness. Comparative evaluation of multiple hyperelastic material models. Yeoh model captures the nonlinear behavior of BA212E and PP‐GF30 accurately. Yeoh model with plasticity offers optimal representation of material behavior. Validated via numerical simulations and experimental data correlation
