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FNOPT: Resolution-Agnostic, Self-Supervised Cloth Simulation using Meta-Optimization with Fourier Neural Operators
No full textInternational audienceWe present FNOPT, a self-supervised cloth simulation framework that formulates time integration as an optimization problem and trains a resolution-agnostic neural optimizer parameterized by a Fourier neural operator (FNO). Prior neural simulators often rely on extensive ground truth data or sacrifice fine-scale detail, and generalize poorly across resolutions and motion patterns. In contrast, FNOPT learns to simulate physically plausible cloth dynamics and achieves stable and accurate rollouts across diverse mesh resolutions and motion patterns without retraining. Trained only on a coarse grid with physics-based losses, FNOPT generalizes to finer resolutions, capturing fine-scale wrinkles and preserving rollout stability. Extensive evaluations on a benchmark cloth simulation dataset demonstrate that FNOPT outperforms prior learning-based approaches in out-ofdistribution settings in both accuracy and robustness. These results position FNO-based meta-optimization as a compelling alternative to previous neural simulators for cloth; thus reducing the need for curated data and improving cross-resolution reliability.</div
System-level monitoring and diagnosis of starvation faults in solid oxide electrolyzers
No full textInternational audienceThis paper presents a model-based methodology for real-time fault detection in Solid Oxide Cells (SOCs), focusing on fuel-side starvation in electrolysis mode. Steam starvation occurs when consumption exceeds supply, while hydrogen starvation arises from an insufficient inlet fraction; both risking electrode degradation. With limited measurements, a lumped model with a square-root Unscented Kalman Filter is adopted to estimate gas partial pressures, stack temperature, and deviations from the nominal inlet fuel flow rate, using stack voltage, outlet air temperature, and outlet hydrogen flow rate measurements. Faults are flagged when the estimated states exceed adaptive thresholds derived from nominal predictions via moving-window filter. For quantification, the observer is augmented with two states capturing deviations in inlet steam and hydrogen flow rates. Furthermore, the total resistance is calculated: it increases under steam starvation and remains nearly unchanged under hydrogen starvation. Experimental validation confirms accurate, real-time detection and identification, helping achieve safer SOEC operatio
3D simulation of residual stresses induced by ElectroMagnetic pulse Peening process
No full textInternational audienceCompression techniques such as shot peening, laser shock peening, and water jet peening are commonly employed to induce residual compressive stresses in mechanical components. These residual stresses play a crucial role in preventing the initiation and propagation of cracks. An innovative method known as the ElectroMagnetic pulse Peening (EMP) process utilizes magnetic forces to introduce residual compressive stresses in mechanical components. The EMP process shares similarities with the ElectroMagnetic Forming (EMF) process, which has been extensively studied through numerical and experimental investigations. Existing numerical studies predominantly feature axisymmetric 2D simulations, with limited availability of 3D simulations due to numerical constraints regarding computing time and resources. Since the EMP process shares similarities with EMF, similar challenges arise with respect to computational resources and time. This paper presents an innovative approach for the 3D simulation of residual stresses induced by the EMP process, based on efficient 2D axisymmetric calculations of the electromagnetic fields. The main objective of this approach is to simulate the mechanical impact of electromagnetic pulses applied by sweeping a surface, in order to analyze the stress distribution in the overlapping regions. First, the 2D model used to simulate electromagnetic phenomena is presented, and the 2D-to-3D transfer technique developed is detailed for computing residual stresses in 3D. Subsequently, the validity of this approach is established through a comparative study between 2D and 3D mechanical results for a single electromagnetic pulse. Finally, a multiple-pulse simulation is conducted to investigate the effect of overlapping treatment regions on an AA6061 aluminum alloy. The outcomes of this study are discussed in terms of the residual stresses at the subsurface
Thermal aging of conductive and dielectric inks for flexible printed electronics: Toward reliable strain gauge application
No full textInternational audiencePrinted electronics (PEs) offer notable advantages in various sectors such as low-cost production, multifunctionality, and flexibility. Technology enables the creation of complex, scalable, and adaptable structures on lightweight substrates, which is particularly valuable for the development of Internet of Things (IoT) devices. These devices facilitate real-time data monitoring, promoting sustainability and cost efficiency for applications in condition monitoring by tracking machinery health to detect failures early. While previous studies have explored printed sensors for such applications, there remains a significant lack of data on the environmental durability of the inks used-particularly under varying temperature and humidity conditions. This study addresses that gap by systematically evaluating the aging behavior of commercially available conductive and dielectric inks used in screen printing. Inks were deposited as multilayer structures on flexible substrates and subjected to various controlled environmental tests. The results provide new insights into the comparative aging stability of ink types: conductive inks demonstrated consistent electrical performance throughout aging, while dielectric inks showed somehow degradation, impacting sensor functionality. These findings contribute to a deeper understanding of material behavior in realistic operational environments and confirm the selection of robust materials for printed sensor systems. Ultimately, this work supports the development of reliable metal strain gauges for integration into reusable space launch platforms
Toward explicability of machine learning models applied to tribology
No full textIssue Section: Friction & WearInternational audienceThis work proposes to use machine learning to predict and interpret the instantaneous coefficient of friction from pin-on-disc tribological tests. A database was constructed from 14 experiments to link third-body morphology to the coefficient of friction. Morphological descriptors were extracted from the SEM image of the friction track, including wear particle and texture descriptors. A random forest algorithm was trained to predict the coefficient of friction with high accuracy. Emphasis is placed on model interpretability using the SHAP tool (SHapley Additive exPlanations) to understand the relative influence of morphological features. This approach aims to provide tribological insights into the structural, mechanical and physical phenomena governing instantaneous friction, opening new perspectives for understanding tribological processes
Data Management Plan of project "Multi-scale APproach for a microscopicunderStanding of thermal transport in nanocomposites" ANR-20-CE05-0046
No full textLPV system identification with unknown scheduling variable
No full textA Linear Parameter Varying (LPV) system is a system whose parameters depend on an exogenous variable, the so-called scheduling variable. LPV systems are generally controlled using LPV controllers i.e., controller whose parameters also depend on the scheduling variable. In order to be able to use an LPV controller for an LPV system, it is generally assumed that the scheduling variable of the LPV system is either fully known or measurable. Here, we consider the case where the scheduling variable has to be identified based on data collected on the system. We do that in the case of LPV systems that are successively operated at different constant values of the scheduling variable. We show how to identify the maximum likelihood estimate of the unknown constant scheduling variable and we derive the statistical properties of this estimate. Moreover, we also develop an optimal experimental design framework in order to optimally design the experimental conditions of the identification experiment yielding the estimate of the scheduling variable
Analyse critique du concept et du terme de désimperméabilisation
No full textInternational audienceSustainable urban management requires us to change our relationship with water and nature. Many initiatives are moving in this direction, notably those aimed at soil unsealing in cities. However, while the term “désimperméabilisation” is increasingly used in France, it is not understood in the same way by all stakeholders. This poses problems in terms of the effectiveness of the actions undertaken in relation to the objectives sought. We’ll start by showing that the French term “désimpermabilisation”, which means moving soil from an impermeable to a permeable state, should not be understood literally. We will then present the various possible meanings and their limits, as well as the links with the related concepts of renaturation or sewer disconnection. We will then analyze the various real benefits that can be expected from unsealing actions in terms of flood control, groundwater recharge, more sustainable urban stormwater management, development of urban amenities and biodiversity, and environmental education. Finally, we explore the means required to effectively implement the concept. This article summarizes the reflections and discussions held within the Eurydice association, on the one hand, and within the Water Department of the Metropolis of Lyon, on the other.La gestion durable des villes nécessite de modifier notre rapport à l’eau et à la nature. De nombreuses initiatives vont dans ce sens et en particulier celles visant à désimperméabiliser les villes. Cependant, si le terme de désimperméabilisation est de plus en plus utilisé, il n’est pas compris de la même façon par tous les interlocuteurs. Cela pose des problèmes vis-à-vis de l’efficacité des actions entreprises au regard des objectifs espérés. Nous commencerons par montrer que ce terme ne peut pas être compris de façon littérale, c’est-à-dire faire passer un sol d’un état imperméable à un état perméable. Nous présenterons ensuite les différents sens possibles avec leurs limites, ainsi que les liens avec les notions voisines de désartificialisation, de renaturation ou de déconnexion. Nous analyserons ensuite les différents bénéfices réels que l’on peut attendre des actions de désimperméabilisation sur le contrôle des inondations, sur la réalimentation des nappes, sur la gestion plus durable des eaux pluviales urbaines, sur le développement des aménités urbaines et de la biodiversité ou sur l’éducation à l’environnement. Enfin nous explorerons les moyens nécessaires à une mise en oeuvre efficace du concept. Cet article synthétise des réflexions et des discussions menées au sein de l’association Eurydice, d’une part, et au sein de la direction de l’Eau de la Métropole du Grand Lyon, d’autre part
Rock-slope failures as a proxy of a paraglacial denudation crisis. Examples in the Icelandic Westfjords (Dýrafjörður and Önundarfjörður areas)
No full textInternational audienc
Post-progressisme et néo-urbaphobie. Le crépuscule de la ville radieuse ?
No full textInternational audienceL’urbaphilie a longtemps constitué l’expression d’un idéal progressiste d’inspiration post-marxiste, tandis que l’urbaphobie était généralement associée à une pensée réactionnaire. Toutefois, ces dernières années — sous l’effet de dynamiques telles que l’écologie radicale, le mouvement des Gilets jaunes ou encore la crise sanitaire — cette opposition a été remise en question : les métropoles se trouvent désormais contestées, voire fuies. Dans ce contexte émerge une forme de néo-urbaphobie, dont le présent chapitre se propose d’examiner les différentes formulations observées dans la presse écrite