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Couplages de sauts d’échelle pour la modélisation du transport réactif
No full textLe transport réactif est la discipline qui cherche à comprendre et prédire le transport de différents éléments (y compris des polluants) au sein de la géosphère. La modélisation du transport réactif s’appuie sur la description des processus chimique - hydraulique et thermique régulant la mobilité de ces éléments dans différents contextes. Cette discipline s’est considérablement élargie pour tenter de décrire davantage de processus pour un panel d’applications en pleine croissance. Au sein de ce manuscrit d’HDR, je décris mes contributions pour étendre l’éventail des possibles pour le transport réactif. Premièrement, les approches proposées pour intégrer des simulations couplées chimie-mécanique sont abordées en décrivant les développements réalisés ainsi que leurs applications à la carbonatation des matériaux cimentaires. Deuxièmement, je décris les développements liés à la collaboration avec Orano sur la thématique de la récupération in situ (ISR) d’uranium, qui ont mené à la description et l’optimisation couplée production - impact environ- nemental. Tout au long du manuscrit, les challenges liés à l’upscaling (spatial & temporel) sont abordés et illustrés
Synthesis of semi-rigid-biobased polyesters from renewable furanic cyclobutane diacid
No full textInternational audienceThe pursuit of novel sustainable materials is driving advancements in polymer science, with the consolidation of furfural and hydroxymethylfurfural derivatives as key renewable building blocks. 3,4-Di(furan-2-yl)cyclobutane-1,2-dicarboxylic acid (CBDA) is a highly promising rigid-structure biobased monomer that is readily synthesized from furfural. In this study, we expanded the scope of CBDA-based polymers by synthesizing this platform molecule and investigating its polymerization with a series of aliphatic diols of varying chain lengths. CBDA was successfully synthesized from furfural-derived 3-(2-furyl)acrylic acid through a green and efficient UV-mediated solid-state dimerization reaction. Subsequent polymerization was carried out in bulk via a two-step method. The success of the polymerization was confirmed through ATR-FTIR, 1H NMR, and 13C CP/MAS NMR spectroscopy. The resulting polymers presented average molecular weights of up to 11 200 g mol−1. Thermogravimetric analysis (TGA) revealed good thermal stability, with a Td10% ranging from 263 to 284 °C and 50% weight retention observed up to 388 °C. Furthermore, DSC analysis indicated that the glass transition temperature of the polymers could be tailored, varying from 6 to 52 °C depending on the chain length of the utilized diol. These results underscore the potential of CBDA as a renewable rigid monomer for the development of sustainable biobased materials
Surface oxidation and oxygen incorporation in ScAlN films grown by molecular beam epitaxy
No full textInternational audienceRecently, there has been much interest in the ScAlN alloy, thanks to its various potential applications in high-frequency high-power, acoustoelectric, and ferroelectric devices. Nonetheless, these applications could be impaired by the presence of oxygen in the alloy and the formation of a surface oxide layer due to the high affinity of scandium with such impurity. A current trend is to increase the Sc content and most of the time it is accompanied by a lowering of the growth temperature. As it probably strongly influences the incorporation of impurities, we have carefully studied the effects of growth temperature and Sc content in the surface oxide and oxygen content of ScAlN films grown by ammonia source molecular beam epitaxy. The oxygen concentration and bonding configuration have been determined by combining normal-incidence, angle resolved, and ion-etching x-ray photoelectron spectroscopy
La mise en dispositif, un cadre d'analyse de l'action collective finalisée : Conceptualisation et méthodologie
No full textInternational audienceAlors que les travaux de Michel Foucault ont été largementmobilisés en sciences de gestion et des organisations dès lesannées 1980, le concept de dispositif, pourtant central dans sonœuvre, est resté jusqu’à récemment peu mobilisé. Cet articlerevient sur la conceptualisation foucaldienne du dispositif,explicite sa transposition récente en sciences de gestionet des organisations à travers « l’analyse dispositionnelle »,présente son intérêt analytique pour l’étude des processusd’action collective finalisés, et propose une clarificationconceptuelle et méthodologique de la notion de « mise endispositif »
Modeling of continuous dynamic recrystallization (CDRX): Application to aluminum alloys
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Molecular dynamics simulations of grain boundary behavior in the presence of particles
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High-fidelity grain growth modeling: Leveraging deep learning for fast computations
No full textInternational audienceGrain growth simulation is crucial for predicting metallic material microstructure evolution during annealing and resulting final mechanical properties, but traditional partial differential equation-based methods are computationally expensive, creating bottlenecks in materials design and manufacturing. In this work, we introduce a machine learning framework that combines a Convolutional Long Short-Term Memory networks with an Autoencoder to efficiently predict grain growth evolution. Our approach captures both spatial and temporal aspects of grain evolution while encoding high-dimensional grain structure data into a compact latent space for pattern learning, enhanced by a novel composite loss function combining Mean Squared Error, Structural Similarity Index Measurement, and Boundary Preservation to maintain structural integrity of grain boundary topology of the prediction. Results demonstrated that our machine learning approach accelerates grain growth prediction by up to 89 × faster, reducing computation time from 10 min to approximately 10 s while maintaining high-fidelity predictions. The best model (S-30-30) achieving a structural similarity score of 86.71 % and mean grain size error of just 0.07 %. All models accurately captured grain boundary topology, morphology, and size distributions. This approach enables rapid microstructural prediction for applications where conventional simulations are prohibitively time-consuming, potentially accelerating innovation in materials science and manufacturing
Learning Physically Consistent Lagrangian Control Models Without Acceleration Measurements
No full textThis article investigates the modeling and control of Lagrangian systems involving nonconservative forces using a hybrid method that does not require acceleration calculations. It focuses in particular on the derivation and identification of physically consistent models, which are essential for model-based control synthesis. Lagrangian or Hamiltonian neural networks provide useful structural guarantees but the learning of such models often leads to inconsistent models, especially on real physical systems where training data are limited, partial and noisy. Motivated by this observation and the objective to exploit these models for model-based nonlinear control, a learning algorithm relying on an original loss function is proposed to improve the physical consistency of Lagrangian systems. A comparative analysis of different learning-based modeling approaches with the proposed solution shows significant improvements in terms of physical consistency of the learned models, on both simulated and experimental systems. The model's consistency is then exploited to demonstrate, on an experimental benchmark, the practical relevance of the proposed methodology for feedback linearization and energy-based control techniques.</div
La gestion, une discipline technique ou technicienne ? Apports de la philosophie de la Technique de Jacques Ellul aux sciences de gestion à l’heure des grands enjeux contemporains
No full textInternational audienceCet article explore l’actualité de la pensée de Jacques Ellul pour les sciences de gestion, en mobilisant sa critique radicale de la Technique — conçue comme une dynamique systémique, autonome, et sacralisée — pour interroger les fondements, les pratiques et les finalités du management contemporain. Alors que les organisations sont de plus en plus gouvernées par des logiques techniciennes, l’œuvre d’Ellul permet de révéler comment les sciences de gestion participent, souvent à leur insu, à la légitimation d’un ordre fondé sur l’efficacité comme valeur suprême. Sa philosophie met en lumière les effets de cette technicisation sur les structures organisationnelles, les outils de gestion, et les imaginaires managériaux. L’article examine cette mise en garde notamment au regard de l’essor de l’intelligence artificielle dans le management. Elle n’implique pas pour autant que la science de gestion soit fatalement technicienne. L’article propose de revisiter la place de l’organisation au regard de la philosophie d’Ellul, en tant que lieu potentiel de résistance ou de reconduction de cette logique. Corolairement, il appelle à une réarticulation entre technique et finalité, et à une revalorisation de l’utopie, de la foi (au sens éthique et existentiel), et du principe de satisfaction comme leviers d’émancipation