HAL Portal Cnam (French National Conservatory for Arts and Crafts)
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In-situ monitoring of µm-sized electrochemically generated corrosion pits using Lamb waves managed by a sparse array of piezoelectric transducers
No full textInternational audienceCorrosion is a major threat in the aeronautic industry, both in terms of safety and cost. Efficient, versatile, and cost affordable solutions for corrosion monitoring are thus needed. Ultrasonic Lamb Waves (LW) appear to be very efficient for corrosion monitoring and can be made cost effective and versatile if emitted and received by a sparse array of piezoelectric elements (PZT). A LW solution relying on a sparse PZT array and allowing to monitor µm-sized corrosion pit growth on stainless 316L grade steel plate is here evaluated. Experimentally, the corrosion pit size is electrochemically controlled by both the imposed electrical potential and the injection of a corrosive NaCl solution through a capillary located at the desired pit location. In parallel, the corrosion pit growth is monitored in-situ every 10 s by sending and measuring LW using a sparse array of 4 PZTs bonded to the back of the steel plate enduring corrosion. As a ground truth information, the corrosion pit volume is estimated as the dissolved volume balancing the electronic charges exchanged during corrosion. The corrosion pit radius is additionally checked post-experiment precisely with an optical measurement. Measured LW signals are then post-processed in order to compute a collection of synthetic damage indexes (DIs). After dimension reduction steps, obtained DI values correlates extremely well with the corrosion pit radius. Using a linear model relating those DI values to corrosion pit radius, it is demonstrated that corrosion pit from 30 µm to 150 µm can be reliably detected, located, and their upcoming size extrapolated. Two independent experiments were achieved in order to ensure the repeatability of the proposed approach. LW managed by a sparse PZT array thus appears to be reliable and efficient to monitor growth of µm-sized corrosion pits on 316L steel plates. If embedded in aeronautical structure, such an approach could be a versatile and cost-effective alternative to actual non-destructive maintenance procedures that are time and manpower consuming
Analyse comparative d'un onduleur à ponts en H cascadé sans MLI et d'onduleurs IGBT/SiC à deux niveaux pour véhicules électriques sur cycles de conduite
No full textInternational audienceElectric Vehicles (EVs) based on Cascaded H Bridge (CHB) promise reduced consumption and improved modularity, repairability, resilience, and versatility. This study focuses on evaluating the efficiency of CHB inverters utilizing low-voltage Si MOSFETs to improve EV performance and range. Through a comprehensive system-level approach and modeling, a simulation of the CHB-based powertrain is developed and experimentally validated. Electrical and mechanical simulations are conducted separately and finally combined to streamline computation times. Subsequently, CHB-based EV is compared with standard twolevel inverters (2LI) across different driving cycles, considering multiple sources of losses from the battery to the road. Despite increased battery losses, CHB proves reduction of consumption during urban driving cycles, making it a compelling choice for sustainable commuter vehicles.Les véhicules électriques (VE) basés sur un onduleur à ponts en H cascadés (CHB) promettent une consommation réduite ainsi qu'une modularité, une réparabilité, une résilience et une polyvalence améliorées. Cette étude se concentre sur l'évaluation de l'efficacité des onduleurs CHB utilisant des MOSFET basse tension en silicium pour améliorer les performances et l'autonomie des VE. Grâce à une approche systémique complète et à la modélisation, une simulation du groupe motopropulseur basé sur CHB est développée et validée expérimentalement. Les simulations électriques et mécaniques sont réalisées séparément puis combinées pour optimiser les temps de calcul. Par la suite, le VE basé sur CHB est comparé aux onduleurs à deux niveaux standard (2LI) sur différents cycles de conduite, en tenant compte de multiples sources de pertes, de la batterie à la route. Malgré des pertes accrues au niveau de la batterie, le CHB démontre une réduction de la consommation lors des cycles de conduite urbains, ce qui en fait un choix convaincant pour les véhicules de transport durable
Structure de graph pour GNN dans les réseaux en détection d'anomalies
No full textInternational audienceThe rise of xG networks has brought unprecedented capabilities in wireless communication, but the complexity of 5G and beyond 5G networks introduces challenges in ensuring reliability and performance. In this article, we propose a new approach to network anomaly detection by leveraging Graph Neural Networks (GNNs) and graph structure learning. GNNs are well-suited for capturing relationships in graph-structured data, making them an effective tool for detecting complex patterns in network behavior. We introduce a novel graph structure extracting feature semantics and demonstrate the effectiveness of GNNs in network anomaly detection. We show we can improve the accuracy up to 4% thanks to the proposed graph structure. The source code is available at https://github.com/Killiancressant/graph4 anomaly detection.</div
La transformation technologique des entreprises s'accompagne-t-elle d'une plus grande maîtrise du temps de travail pour les salariés? Résultats empiriques à l'échelle de l'UE à partir d'un ensemble de données combinées
No full textInternational audienceWe investigate the links between the technological transformation of firms and employee control over working time. We conduct EU-wide analysis at the meso-level by relating information from the European Company Survey 2019 (Eurofound and Cedefop) with the Labour Force Survey ad hoc module 2019 (Eurostat). This dataset allows analysing the technological transformation of firms as a relationship between three types of investments (in R&D, digital technologies and learning capacity of the organisation) that spur innovation outputs. We then study the consequences of the technological transformation on the spread of unfavourable working time arrangements, distinguishing between individual and organisation-oriented arrangements. Our model considers the direct effects of investments in Digital technologies adoption and use and Learning capacity of the organisation and the mediating role of firms’ innovation strategies. Results indicate that the Learning capacity of the organisation is directly associated with more individual-oriented working time flexibility, but entails higher organisation-oriented working time flexibility. The effect of Digital technologies adoption and use depends instead on firms’ innovation strategy: product innovation leads to more employee control over working time, while marketing innovation has the opposite outcome. Process and organisational innovations yield mixed consequences buffering employees from organisation-oriented working time flexibility in more time-constrained work environments
Constructive ergonomics and enabling interventions
No full textInternational audienceThis paper presents a constructive view of Human Factors/Ergonomics (HFE) and its implications regarding work, organisations and HFE interventions.In contrast to a defensive approach to HFE, which would view work mostly as a source of constraints, and the role of HFE as reducing these constraints, the goal of constructive ergonomics is to eliminate obstacles hindering success and development and to maximise opportunities for acting and learning.After having developed the concept and the methods of enabling interventions, as well as their consequences on the role of ergonomists, two enabling interventions are presented to illustrate the implementation of the constructive approach in real work settings.The discussion advocates a conception of development as a fact, a means and a goal of HFE interventions, and emphasises the maieutic role of ergonomists
Is There a Future for Stochastic Modeling in Business and Industry in the Era of Machine Learning and Artificial Intelligence?
No full textInternational audienceThe paper arises from the experience of Applied Stochastic Models in Business and Industry which has seen, over the years, more and more contributions related to Machine Learning rather than to what was intended as a stochastic model. The very notion of a stochastic model (e.g., a Gaussian process or a Dynamic Linear Model) can be subject to change: What is a Deep Neural Network if not a stochastic model? The paper presents the views, supported by examples, of distinguished researchers in the field of business and industrial statistics. They are discussing not only whether there is a future for traditional stochastic models in the era of Machine Learning and Artificial Intelligence, but also how these fields can interact and gain new life for their development
Damage Assessment of Polyamide-Based Woven Composites Using Multi-Directional Lamb Waves After Fatigue or Impact Loading
No full textInternational audienceThis study presents a novel experimental methodology designed to assess damage in woven glass fibers reinforced polyamide 6,6/6 composites, specifically subjected to low-velocity impact and cyclic tensile loading. Conventional ultrasonic testing techniques often fail to detect subtle material degradation, particularly when dealing with barely visible impact damage (BVID), which can go unnoticed but still significantly compromise structural integrity. In contrast, the proposed approach utilizes multi-directional ultrasonic Lamb wave analysis, a more advanced technique that offers greater sensitivity and precision in identifying damage at various stages of the composite’s lifespan. In this work, a damage indicator is defined based on the velocity profile of Lamb waves, which are sensitive to changes in material properties such as stiffness degradation. The Lamb wave-based methodology is rigorously validated through detailed comparisons with X-ray tomography. These comparisons reveal strong correlations between the two techniques, highlighting the effectiveness of the proposed ultrasonic approach in detecting BVID. Moreover, the study demonstrates that this methodology is not only highly sensitive but also scalable, making it suitable for industrial applications where automated inspection of composite components is essential. The proposed method offers a significant advancement in non-destructive testing (NDT) techniques based on Lamb wave diagnostic tools in composite material testing
Réduction de modèle de structures assemblées avec nonlinéarités localisées en dynamique transitoire
No full textNational audienceTime-domain dynamic simulation of assembled structures is generally a challenging task due to the large number of subcomponents and the presence of localized nonlinear interactions at interfaces. The objective of this work is to develop an efficient numerical method to predict the transient response of assembled systems exhibiting local nonlinearities. The model is intended for deployment within a virtual learning environment dedicated to academic training, where interactive-time simulation capability is a key requirement. Computational cost is reduced through the use of simplified physical models (e.g., Iwan elements) and classical model reduction techniques. Different reduction approaches, such as Hurty-Craig-Bampton and Milmann-Chu methods, are compared using both explicit and implicit time integration methods on a simple assembled structure.La simulation dynamique temporelle de structures assemblées présente généralement des difficultés importantes en raison du grand nombre de sous-composants et des interactions non-linéaires au niveau des liaisons. L'objectif de ce travail est de développer une méthode numérique efficace pour prédire la réponse temporelle d'assemblages présentant des non-linéarités locales en régime transitoire. Le modèle est destiné à être intégré dans un environnement virtuel pour la construction d'exercices pédagogiques universitaires où l'obtention de résultats de simulations numériques en temps interactif est critique. Une diminution des temps de calcul est atteinte à l'aide de modèles physiques simplifiés (modèle d'Iwan) et de la réduction de modèle plus classique. Différentes méthodes (Hurty-Craig-Bampton, Milmann-Chu) avec différents schémas numériques (explicite, implicite) sont comparées sur une structure assemblée simple
JC3DHN 2024 - Actes du colloque
No full textInternational audienceCet ouvrage rassemble les actes du colloque du Consortium 3DHN, qui s’est tenu du 26 au 28 novembre 2024 à Nancy. Le Consortium-HN-3DHN est un réseau national, labelisé par l’IR * Huma-Num, qui fédère des équipes de recherche ainsi que des institutions patrimoniales, œuvrant pour le développement, la structuration et la diffusion des bonnes pratiques liées à la production, la gestion, la conservation et la valorisation des données 3D dans le domaine des sciences humaines et sociales.À travers ses actions collectives, le consortium-HN-3DHN poursuit plusieurs objectifs majeurs : accompagner les chercheurs et les acteurs du patrimoine dans l’usage raisonné et critique des technologies 3D. favoriser l’interopérabilité des données 3D, promouvoir les principes FAIR et encourager l’adoption de standards ouverts.Le colloque de Nancy a constitué un moment privilégié d’échange et de réflexion sur ces thématiques et a permis de confronter les expériences, discuter des méthodologies, et d’explorer les perspectives offertes par les approches 3D au sein des Humanités Numériques.L’ensemble des interventions du colloque est consultable sur la chaîne du consortium 3DHN, hébergée sur la plateforme audiovisuelle de l’enseignement supérieur et de la recherche Canal-U (https://www.canal-u.tv/chaines/c3dhn
L'impact des nouvelles technologies sur le leadership
No full textInternational audienceThis paper, presented as part of the second edition of the “2025 Leaders' Meeting,” offers a critical reflection on the impact of new technologies on contemporary leadership. By combining insights from information and communication sciences (ICS) with feedback from leaders, HR managers, and experts in the field, it questions the myth of the “augmented leader” in the digital age. The analysis highlights the tensions between technological performance and ethical discernment, the risks of unregulated automation, and the transformations of the HR function.The theoretical framework draws on concepts from situated action, actor-network theory, and digital mediation to examine the reconfiguration of influence and power networks in organizations. Verbatim quotes collected during the conference illustrate decision-makers' perceptions and concerns about AI, disinformation, and the loss of meaning. The conclusion calls for leadership based on the complementarity of human intelligence and automated systems, integrating responsible governance and hybrid training that combines technology, meaning, and ethics. This contribution is part of an action research approach aimed at supporting digital change in organizations, particularly in emerging African contexts.Cette communication, présentée dans le cadre de la 2ᵉ édition de la "Rencontre des Dirigeants 2025", propose une réflexion critique sur les impacts des nouvelles technologies sur le leadership contemporain. En croisant les apports des sciences de l'information et de la communication (SIC) avec les retours de terrain de dirigeants, DRH et experts, elle interroge le mythe du "leader augmenté" à l’ère numérique. L’analyse met en lumière les tensions entre performance technologique et éthique du discernement, les risques d’automatisation non régulée, ainsi que les transformations de la fonction RH.Le cadre théorique mobilise des notions issues de l’action située, de la théorie de l’acteur-réseau et des médiations numériques pour interroger la recomposition des circuits d’influence et de pouvoir dans les organisations. Des verbatim recueillis durant le colloque illustrent les perceptions et inquiétudes des décideurs face à l'IA, à la désinformation et à la perte de sens. La conclusion plaide pour un leadership fondé sur la complémentarité entre intelligence humaine et systèmes automatisés, intégrant une gouvernance responsable et une formation hybride, alliant technologie, sens, et éthique. Cette contribution s’inscrit dans une démarche de recherche-action visant à accompagner les mutations numériques dans les organisations, notamment dans les contextes africains émergents