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Développement d'une méthodologie de conception optimale de liaisons élastiques en prenant en compte les notions de robustesse et de fiabilité.
No full textSpring manufacturers face three major challenges: on one hand, the geometric and mechanical properties of supplied wires vary significantly from one bobbin of wire to another; on the other hand, current spring sizing methods mainly rely on old and rudimentary analytical tools; finally, customer requirements are increasingly demanding. These issues directly affect the reliability of sizing and the stability of production. To address them, manufacturers rely on the expertise of their operators, who are forced to iteratively and empirically adjust the spring geometry to meet the specifications. A thorough literature review has identified two priority research areas.Firstly, we developed new, more accurate analytical models to better predict the mechanical behavior of cylindrical compression springs. The modeled tri-linear stiffness of the spring is evaluated using two scientific advances: the consideration of end coils, and the use of helical finite elements. We also developed a semi-analytical model capable of mapping surface stresses of any curved beam with a circular cross-section. Additional tools were developed to estimate the natural frequency of the spring, its solid length, and its buckling behavior. These tools demonstrated their reliability and robustness through more than 400 experimental tests and 250 numerical simulations on cylindrical compression springs.Then, we developed an optimization algorithm incorporating these more accurate analytical models. The goal of this algorithm was to propose a solution that is both as lightweight as possible and ensures the highest probability of meeting the specifications, while accounting for wire variability, manufacturing uncertainties, and the potential for machine adjustment after wire characterization. The reliability and robustness of this algorithm were successfully validated by comparing it with more than 120 industrial cases.These advances could help researchers, designers, and operators better understand, size, and manufacture cylindrical compression springs with closed ends (ground or not) and constant pitch.Les fabricants de ressorts font face à trois défis majeurs : d’une part, les propriétés géométriques et mécaniques des fils livrés varient sensiblement d’une bobine de fil à l’autre ; d’autre part, les méthodes de dimensionnement actuelles reposent principalement sur des outils analytiques anciens et rudimentaires ; enfin, les exigences des clients sont toujours plus élevées. Ces problématiques affectent directement la fiabilité du dimensionnement et la stabilité de la production. Pour y faire face, les fabricants s’appuient sur le savoir-faire de leurs opérateurs, contraints de corriger itérativement et empiriquement la géométrie des ressorts pour répondre aux exigences du cahier des charges. Une analyse bibliographique approfondie a permis d’identifier deux axes de recherche prioritaires.Premièrement, nous avons développé de nouveaux modèles analytiques plus précis pour mieux prédire le comportement mécanique des ressorts de compression cylindriques. La raideur tri-linéaire modélisée du ressort est évaluée à l'aide de deux avancées scientifiques : la considération des spires d’extrémité, ainsi que l’utilisation d’éléments finis hélicoïdaux. Nous avons également mis au point un modèle semi-analytique permettant de cartographier les contraintes en surface de toute poutre courbe à section circulaire. D’autres outils ont été développés pour estimer la fréquence propre du ressort, sa longueur à spires jointives, ou encore son comportement en flambage. Ces outils ont démontré leur fiabilité et leur robustesse grâce à plus de 400 essais expérimentaux et 250 simulations numériques sur des ressorts de compression cylindriques.Puis, nous avons développé un algorithme d'optimisation intégrant ces modèles analytiques plus précis. L'objectif de cet algorithme était de proposer une solution à la fois la plus légère possible, qui garantit la plus forte probabilité de respecter le cahier des charges, le tout, en considérant les variabilités du fil, les incertitudes de fabrication, ainsi que l'éventuelle possibilité de réglage des machines après caractérisation du fil. La fiabilité et la robustesse de cet algorithme ont été vérifiées avec succès grâce à la confrontation de cet outil avec plus de 120 problématiques industrielles.Ces avancées peuvent aider les chercheurs, concepteurs et opérateurs à mieux comprendre, dimensionner et fabriquer les ressorts de compression cylindriques à extrémités rapprochées (meulées ou non) et à pas constant
Development of Stereo DIC Measurement on thermal energy storage tank: Determination of mechanical response
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A Ground Reaction Forces estimation method to study non-human primate bipedalism out-of-the-lab
No full textInternational audienc
Towards Accurate Gait Instability Assessment: Identifying a Fixed Pelvis Point that Best Matches the Whole-Body Center of Mass
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Opinion Formation in Wikipedia Ising Networks
No full textInternational audienceWe study properties of opinion formation on Wikipedia Ising Networks. Each Wikipedia article is represented as a node and links are formed by citations of one article to another generating a directed network of a given language edition with millions of nodes. Ising spins are placed at each node and their orientation up or down is determined by a majority vote of connected neighbors. At the initial stage there are only a few nodes from two groups with fixed competing opinions up and down while other nodes are assumed to have no initial opinion with no effect on the vote. The competition of two opinions is modeled by an asynchronous Monte Carlo process converging to a spin polarized steady-state phase. This phase remains stable with respect to small fluctuations induced by an effective temperature of the Monte Carlo process. The opinion polarization at the steady-state provides opinion (spin) preferences for each node. In the framework of this Ising Network Opinion Formation model we analyze the influence and competition between political leaders, world countries and social concepts. This approach is also generalized to the competition between three groups of different opinions described by three colors, for example Donald Trump, Vladimir Putin, Xi Jinping or USA, Russia, China within English, Russian and Chinese editions of Wikipedia of March 2025. We argue that this approach provides a generic description of opinion formation in various complex networks
Some invariant classes for parabolic renormalization in the multicritical case
No full textParabolic renormalization associates to a holomorphic map f with a parabolic fixed point another holomorphic map with a parabolic fixed point. This procedure is essential for understanding the phenomenon of parabolic enrichment, which occurs when one perturbs f appropriately.Shishikura defined in [Shi98] (see also [LY14]) a class of maps that is stable under this parabolic renormalization operator.These maps have only one critical point in their immediate basins.We extend here this result to the more general classes of maps conjugated on their immediate basins to finite Blaschke products.For these classes, we introduce an analogue of Milnor's mapping schemes [Mil12] and describe the action of parabolic renormalization on the scheme.This shall be a starting point to the fine study of perturbation of these bigger classes of maps
When the weakest model sees the threat: an explainable ensemble learning system for detecting network attacks
No full textInternational audienceThe growing importance of network security is driven by two major challenges. One is the exponential increase in network traffic, which exceeds human processing capabilities. The other is the rising frequency and sophistication of attacks, which demand advanced, intelligent analysis. To take critical actions-such as blocking suspicious IP addresses-security analysts must understand why intrusion detection systems raise alarms. This highlights the limitations of relying on machine learning models with opaque decision-making processes, often referred to as "black boxes," whose lack of interpretability poses challenges for justifying security actions. Consequently, this paper emphasizes the need for explainable machine learning solutions tailored to network security. To detect new attacks effectively, we adopt a behavioral approach that analyzes short time windows of aggregated traffic to identify abnormal patterns, using various unsupervised machine learning detectors. These detectors often yield complementary results: they may disagree on specific detections, and in some cases, a generally less effective model-the weakest-can uniquely identify an attack. This observation motivates an ensemble approach that integrates the strengths of diverse models. Our approach combines three key contributions: a stacking-based ensemble learning strategy that improves detection by incorporating minority reports, going beyond majority voting; a visual representation technique
Epromoters bind key stress-related transcription factors to regulate clusters of stress response genes
No full textInternational audienceStress insults trigger the rapid and global reprogramming of gene transcription by coordinated recruitment of a limited number of key inducible transcription factors to cis-regulatory elements. Here, we performed a comprehensive analysis of different stress models and observed that co-induced genes are generally located in close genomic proximity. By integrating gene expression and transcription factor binding resources in different stress models, we found an enrichment for clusters whereby only one of the promoters of the cluster recruits the key transcription factors, reminiscent of Epromoters, a type of cis-regulatory elements displaying both promoter and enhancer function. Epromoter-regulated clusters were frequently found irrespectively of the stress or inflammatory response. Predicted Epromoters displayed enhancer activity and regulated clusters of stress-response genes independently of their genomic location. These findings have significant implications for understanding complex gene regulation following the response to acute perturbations.Teaser: When cells face stress, they undergo rapid changes in gene expression, orchestrated by a handful of key transcription factors. But how do these factors coordinate such a complex response? Our study reveals that “Epromoters”—cis-regulatory elements that combine the functions of both promoters and enhancers help organize stress-response genes into tightly regulated clusters. This discovery not only deepens our understanding of gene regulation in the face of stress but also offers exciting implications for studying inflammation and other acute cellular responses
ETSI SmartM2M; oneM2M deployment guidelines and good practices
No full textThe full document is available onhttps://www.etsi.org/deliver/etsi_tr/103800_103899/103843/01.01.01_60/tr_103843v010101p.pdfThe present document describes how to complement the ETSI view by liaising with oneM2M technical bodies for consultation during the definition of the deployment scenarios. From the stakeholder point of view, it can help on the adoption of oneM2M through indicators such as performance evaluation to assess the performance of their proposed products. IoT platforms customers can define their specific deployment scenarios and evaluate the performance of a given IoT platform against their scenarios. Finally, the Open-Source Communities around oneM2M may benefit from these results by taking the output of the development of the TTF PoC into their roadmaps