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Single atom convolutional matching pursuit: Theoretical framework and application to Lamb waves based structural health monitoring
No full textInternational audienceLamb Waves (LW) based Structural Health Monitoring (SHM) aims to monitor the health state of thin structures. An Initial Wave Packet (IWP) is sent in the structure and interacts with boundaries, discontinuities, and with eventual damages thus generating many wave packets. An issue with LW based SHM is that at least two LW dispersive modes simultaneously exist. Matching Pursuit Method (MPM), which approximates a signal as a sum of delayed and scaled atoms taken from a known dictionary, is limited to nondispersive signals and relies on a priori known dictionary and is thus inappropriate for LW-based SHM. Single Atom Convolutional MPM, which addresses dispersion by decomposing a signal as delayed and dispersed atoms and limits the learning dictionary to only one atom, is alternatively proposed here. Its performances are demonstrated on numerical and experimental signals and it is used for damage monitoring. Beyond LW-based SHM, this method remains very general and applicable to a large class of signal processing problems
La qualité du « vivre et travailler ensemble » comme prédicteur du bien-être et de la satisfaction scolaire des élèves et des enseignants dans une école de la confiance
No full textConférence invitée. Université de Nantes, CREN.Le bien-être à l’école est désormais au programme des politiques éducatives et fait l’actualité de grands évènements scientifiques, mais le projet de refondation de l’École française et la loi d’une école de la confiance de 2019 n’ont été qu’une tentative de réponse aux constats accumulés depuis 2015 sur l’école de la défiance.La promotion d’une école bienveillante et attentive au bien-être de chacun correspond de fait à un changement de paradigme orienté désormais vers des enjeux de qualité, d’exigence et de santé dans le rapport à l’activité de travail. Considérer le travail en termes d’activité revient également à mettre en avant sa dimension psychologique et à reconnaître que, dans le milieu scolaire, « on vit et on travaille ensemble », que l’on soit élève, enseignant, personnel d’éducation ou de direction et qu’un épanouissement réciproque et collectif n’est possible qu’à certaines conditions au-delà des intentions. L’adoption de ce point de vue, en sciences de l’éducation et en psychologie, invite à mobiliser des modèles multidimensionnels, à associer des visées compréhensives et explicatives et à se doter d’indicateurs objectifs et subjectifs adaptés aux différents groupes sociaux et au contexte des établissements scolaires dans lesquels les projets « expérimentaux » qui aspirent au bien-être à l’école sont déployés et évalués. Nous illustrerons notre propos en rapportant une recherche que nous coordonnons depuis 2021-2022 et qui porte sur le «bien-être pour bien apprendre ». Cette recherche (SA3P puis SA3Pnudges) est menée dans un lieu d’éducation associé à l’Institut Français d’Education de Lyon (Ifé) qui promeut les rapprochements entre recherche/enseignement/formation. Elle s’inscrit également depuis 2023 dans le périmètre du PIA3 AMPIRIC. (p.68 référence au projet « bien-être pour bien apprendre », Florin, A, Tricot, A, Chesné, J. F., Piedfer-Quêney, L., & Simonin-Kunerth, M. (2024). Dossier de synthèse. Le bien-être à l’école. Rapport du CNESCO)https://ife.ens-lyon.fr/lea/le-reseau/les-differents-lea/reseau-ecoles-college-a-st-laurent-du-var06https://ampiric.fr/recherche/sa3pnudge
Comptes-rendus de la conférence annuelle CIE France 2025
No full textNational audienceCette conférence rassemble des présentations des équipes de recherche françaises actives dans les différentes divisions de la Commission Internationale de l'Eclairage
Ultrafast dynamics of hot carriers: Theoretical approaches based on real-time propagation of carrier distributions
No full textInternational audienceIn recent years, computational approaches which couple density functional theory (DFT)-based description of the electron–phonon and phonon–phonon scattering rates with the Boltzmann transport equation have been shown to obtain the electron and thermal transport characteristics of many 3D and 2D semiconductors in excellent agreement with experimental measurements. At the same time, progress in the DFT-based description of the electron–phonon scattering has also allowed to describe the non-equilibrium relaxation dynamics of hot or photo-excited electrons in several materials, in very good agreement with time-resolved spectroscopy experiments. In the latter case, as the time-resolved spectroscopy techniques provide the possibility to monitor transient material characteristics evolving on the femtosecond and attosecond time scales, the time evolution of photo-excited, nonthermal carrier distributions has to be described. Similarly, reliable theoretical approaches are needed to describe the transient transport properties of devices involving high energy carriers. In this review, we aim to discuss recent progress in coupling the ab initio description of materials, especially that of the electron–phonon scattering, with the time-dependent approaches describing the time evolution of the out-of-equilibrium carrier distributions, in the context of time-resolved spectroscopy experiments as well as in the context of transport simulations. We point out the computational limitations common to all numerical approaches, which describe time propagation of strongly out-of-equilibrium carrier distributions in 3D materials, and discuss the methods used to overcome them
Innovative Strategie for Eco-Friendly Printed Circuit Board Design
No full textInternational audienceThe growing concern over electronic waste (e-waste) poses significant environmental challenges, particularly in the disposal and recycling of printed circuit boards (PCBs), which are hazardous and difficult to process [1]. Traditional PCB recycling methods often involve complex procedures that are energy-intensive and inefficient [2] . This study introduces a novel multilayer design for PCBs utilizing polylactic acid (PLA) and thermocompression techniques. This study explores the mechanical and thermal properties of three polylactic acid (PLA) variants—PLA0 (as-purchased), PLA1, and PLA2—processed for sustainable multilayer PCB designs. Mechanical testing showed that PLA0 had the best performance with a Young's modulus of 1010 MPa and a breaking point of 45 MPa, while PLA1 (850 MPa) and PLA2 (950 MPa) showed reduced stiffness. Thermal analysis via DSC revealed PLA0's Tg at 62°C and moderate crystallinity. PLA1, thermocompressed with pressure release at 40°C, exhibited a Tg of 41°C and lower crystallinity (11.87%), leading to fragility. PLA2, released at 165°C, showed improved properties with a Tg of 58°C and higher crystallinity (17.58%). Based on these findings, PLA-1 was selected for further development, and a printed circuit was successfully fabricated as a proof of concept using chemical etching. This demonstrates the feasibility of PLA-based materials for PCB manufacturing, offering a sustainable alternative to conventional designs and reducing e-waste
The micro‐foundations of employment systems: An empirical case study of Britain and France
No full textInternational audienceBuilding on existing studies of national employment systems, we undertake a comparative analysis of the micro‐foundations of employment relations in Britain and France. Our analysis utilizes harmonized, linked employer‐employee survey data for the two countries and takes a multi‐dimensional approach in which the national level remains meaningful but within‐country variance is also emphasized. Our analysis contrasts the British model characterized by variability and heterogeneity with a French model characterized by stability and uniformity. We discuss ways in which these systems are shaped by differences in employer and employee networks, the financial and organizational links between firms and macro‐institutions
3DSES: an indoor Lidar point cloud segmentation dataset with real and pseudo-labels from a 3D model
No full textInternational audienceSemantic segmentation of indoor point clouds has found various applications in the creation of digital twins for robotics, navigation and building information modeling (BIM). However, most existing datasets of labeled indoor point clouds have been acquired by photogrammetry. In contrast, Terrestrial Laser Scanning (TLS) can acquire dense sub-centimeter point clouds and has become the standard for surveyors. We present 3DSES (3D Segmentation of ESGT point clouds), a new dataset of indoor dense TLS colorized point clouds covering 427 m 2 of an engineering school. 3DSES has a unique double annotation format: semantic labels annotated at the point level alongside a full 3D CAD model of the building. We introduce a model-to-cloud algorithm for automated labeling of indoor point clouds using an existing 3D CAD model. 3DSES has 3 variants of various semantic and geometrical complexities. We show that our model-to-cloud alignment can produce pseudo-labels on our point clouds with a > 95% accuracy, allowing us to train deep models with significant time savings compared to manual labeling. First baselines on 3DSES show the difficulties encountered by existing models when segmenting objects relevant to BIM, such as light and safety utilities. We show that segmentation accuracy can be improved by leveraging pseudo-labels and Lidar intensity, an information rarely considered in current datasets. Code and data will be open sourced.<div
Towards Inclusive Education: Multimodal Classification of Textbook Images for Accessibility
No full textInternational audienceTo foster inclusive education, accessible educational materials must be tailored to meet the diverse needs of students, especially students with disabilities. Images in educational materials play an important role in understanding textbook exercises but can also distract such students and make them more challenging. Therefore, we need an adaptive system that identifies non-essential images to reduce cognitive load and distractions for students with disabilities. Accordingly, this work proposes a computational framework to categorize textbook exercise images, facilitating their inclusion in accessible textbooks and enhancing learning for visually impaired and neurodevelopmental disorders students. Using three French textbook exercise datasets of 652 (text, image) pairs, we compared monomodal (text-only) and multimodal (text and image) classification approaches. We found that text-based models, particularly CamemBERT, excel in classifying images, achieving an accuracy rate of 85.25% on French text data. We also use Local Interpretable Modelagnostic Explanation for model interpretability and conduct qualitative analyses to deepen insights into model performance. This work is only a very first step towards an automatic translation of inclusive textbooks. Moreover, this paper revealed that this first step is already very challenging. We hope to draw more researchers' attention to this problem
Functional interval estimation for continuous-time linear systems with time-invariant uncertainties
No full textInternational audienceThis paper investigates functional interval estimation for continuous-time linear systems subject to both time-varying and time-invariant uncertainties. Two novel methods are proposed based on peak-to-peak functional observer design and interval analysis. First, we present a splitting-based method that splits the estimation error dynamics into two subsystems to handle the time-invariant disturbances and provide accurate estimation results. Then, to further enhance the estimation accuracy, we present an augmentation-based method that considers the time invariance in both functional observer design and reliable interval estimation. The relationship between a state-of-art method and the proposed methods are analysed theoretically. Finally, simulation results are provided to demonstrate the performances of the proposed methods
Transformer et comprendre. Une introduction à la théorie historico-culturelle de l’activité
No full textInternational audienceIl n’a sans doute jamais été aussi nécessaire d’apprendre à construire collectivement des alternatives au mode d’organisation de nos activités. Cette nécessité implique une théorie forte orientée vers la production d’un avenir possible, réalisable et souhaitable, contenu en germe dans les contradictions de notre présent. La théorie historico-culturelle de l’activité constitue une telle théorie interventionniste.Ce livre en retrace dans une première partie les développements successifs depuis les travaux des psychologues soviétiques du XXe siècle jusqu’aux développements plus récents. Il propose dans une deuxième partie un éclairage sur les concepts clés et leur mobilisation dans la recherche. Il décrit enfin dans une troisième partie les perspectives d’intervention orientée vers la transformation des systèmes d’activité en expliquant les principes méthodologiques des interventions formatives et du laboratoire du changement