HAL Portal UPHF (Université Polytechnique Hauts-de-France)
Not a member yet
28473 research outputs found
Sort by
Machine Learning Vulnerabilities in 6G: Adversarial Attacks and Their Impact on Channel Gain Prediction and Resource Allocation in UC-CFmMIMO
No full textInternational audienceMachine learning (ML) models integrated into physical-layer functions in wireless systems are increasingly vulnerable to adversarial attacks. Although prior research has investigated such threats in conventional massive MIMO architectures, the security risks in future 6G topologies, particularly user-centric cell-free massive MIMO (UC-CFmMIMO) deployed in vehicular environments, remain largely unexplored. These architectures depend heavily on frequency-domain channel gain estimation, which opens new attack surfaces. In this work, we present a black-box adversarial framework tailored to UC-CFmMIMO networks operating in dynamic vehicular environments. The attacker passively collects RF data to train a surrogate model and crafts perturbations using the FGSM attack. A local anomaly detector is integrated to assess stealth prior to uplink injection via pilot contamination. Our method significantly disrupts channel gain estimation and subband allocation, while requiring no access to the target model's internals. These results underscore emerging vulnerabilities in ML-enabled wireless systems and highlight the need for robust, context-aware defenses.</div
Multiscale models predicting crack nucleation and propagation under thermal and rate effects
No full textInternational audienceFracture and decohesion phenomena are widely studied across various disciplines dueto their fundamental theoretical significance and broad range of applications. One of themost established and widely employed frameworks in this field is the energetic approach,encapsulated by Griffith’s energy criterion. While analytical and experimental studieshave confirmed the effectiveness of this criterion in describing the propagation of preexistingcracks, it remains inadequate for capturing several critical aspects relevant tostructural design. Notably, it fails to predict crack nucleation and presents significantchallenges in rigorously incorporating temperature effects within an analytical framework.This study investigates the influence of temperature on crack nucleation and propagationin material failure and decohesion. Building upon Griffith’s energy criterion,we propose a simplified model focused on mode I fracture, extending the classical criterionto account for crack nucleation and the role of thermal fluctuations. By leveragingtools from equilibrium statistical mechanics, we integrate entropic contributions into theoverall energy balance. Additionally, we adopt a multiscale approach, simultaneously formulatingboth discrete and continuum (limit) models. This methodology provides deeperinsight into the intricate mechanisms governing fracture and decohesion, elucidating howmicroscopic-scale phenomena influence meso- and macroscopic behavior.Despite the simplicity of the proposed models, they allow for analytical tractabilityand a more profound understanding of the underlying physics. Our energetic approacheffectively captures the competition among external loading, elastic deformation, fractureenergy, and entropic effects. Specifically, our model predicts crack nucleation and quantifiesthe influence of thermal fluctuations on this process. Furthermore, the frameworkaccommodates different fracture and decohesion scenarios, including cases where fracturepropagates from one end or where the damaged region remains confined within the system,such as in the presence of multiple bubbles (e.g., DNA denaturation bubbles). In thelatter case, our model predicts the coalescence of these bubbles prior to complete failure.Interestingly, our approach uncovers a classical critical behavior, wherein the criticalload decreases with increasing temperature following the relation (1 − T/Tc)^(1/2). Consequently,at the critical temperature Tc, the system undergoes a phase transition, leadingto complete rupture even in the absence of an applied mechanical load.In addition to temperature effects, our prototypical model also captures rate-dependentbehavior, i.e., the system’s response under a time-dependent loading rate. Unlike temperatureeffects, which we analyze using equilibrium statistical mechanics, rate effectsnecessitate a departure from equilibrium conditions. Preliminary results indicate that thesystem’s dynamics are significantly influenced by the applied loading rate. Specifically,as the loading rate increases, the fracture propagation velocity also increases, whereas adecrease in the loading rate leads to a softening of the system’s mechanical response.The findings regarding both temperature and rate effects are particularly promising, asthey align with experimentally observed behaviors in materials that have been challengingto describe rigorously through analytical approaches. This study introduces a relativelysimple yet powerful model that captures these complex phenomena without compromisingmathematical tractability and analytical rigor
A unified Eshelbian-like determination of defect driving forces
No full textInternational audienceWithin the framework of Continuum Mechanics, we present a unified theoretical approach todescribe the onset and propagation of defects in solid materials. In this context, the term defectencompasses both changes in the material’s topology—such as fracture propagation, rotation, andvolumetric expansion of inclusions or voids [1]—and material inhomogeneities, referring to spatialvariations in the material properties of the body [2, 3]. We characterize the kinematics of a defect by defining its mode of propagation. Following the principles of Eshelbian Mechanics [2, 3], we compute the associatedenergy release rate or driving force. Furthermore, we distinguish the contributions of thisdriving force by identifying their specific roles in defect propagation—whether purely mechanical,topological, or arising from inhomogeneities in constitutive parameters [2, 3].To illustrate the proposed procedure more clearly, we analyze several prototypical examples fromthe literature, contextualized within our framework [4]. Finally, we compare the obtained resultswith those derived from variational approaches based on conservation laws [1, 5].References[1] Knowles, J. K., Sternberg, E. “On a class of conservation laws in linearized and487finiteelastostatics”. Arch. Rat. Mech. Anal. 44(3):187–211 (1972)[2] Maugin, G. A. “Configurational Forces. Thermomechanics, Physics, Mathematics, and Numerics”CRC Press, 2016.[3] Gurtin, M. E. “Configurational forces as basic concepts of continuum physics”. Vol. 137.493.Springer Science & Business Media, 1999.[4] S. Di Stefano, C. Binetti, G. Puglisi, S. Giordano. “A unified Eshelby-like approach to defectpropagation”. In preparation.[5] Podio-Guidugli, P. “Configurational balances via variational arguments”. Interface FreeBound 3, 323–332. (2001
Edouard Molinaro
No full textRéalisateur, scénariste et dialoguiste français, Édouard Molinaro (*13 mai 1928 à Bordeaux, † 7 décembre 2013 à Paris) s’est distingué par une œuvre télévisuelle et cinématographique d’une grande diversité, conciliant des succès populaires avec une production plus confidentielle, tournée vers des formes narratives exigeantes. Dans les années 1980, il développe un lien privilégié avec l’univers psychologique et la rigueur formelle de Stefan Zweig, dont il adapte La Ruelle au clair de lune, La Pitié dangereuse et L’Ivresse de la métamorphose pour la télévision. Il exprime également son admiration pour Arthur Schnitzler, dont il salue la virtuosité dramaturgique, en particulier dans La Ronde. En 1991, il réalise l’adaptation télévisuelle de L’Amour maudit de Leisenbohg, poursuivant son exploration de l’univers viennois fin de siècle. Cette double référence témoigne d’une orientation esthétique fondée sur l’introspection, la construction maîtrisée du récit et une sensibilité marquée à la littérature autrichienne
Conducting Polymers-Based Microsystems: Mechanical Design Simulation and Fabrication
No full textSeminar in the frame of Weimar TriangleInternational audienceConducting polymer-based microsystems are receiving increasing attention due to their unique electromechanical properties and strong potential for innovative applications. This work presents an integrated approach that spans the fundamental principles of conducting polymer actuators, along with their mechanical design, simulation, and fabrication. Particular emphasis is placed on material selection and microfabrication techniques compatible with flexible and miniaturized systems. The study further explores a range of advanced applications, demonstrating the versatility of these microsystems in smart and multifunctional devices. The work concludes with a forward-looking perspective on the current challenges and future directions in the field of conducting polymer microsystems
Les archives du « sport » : un autre regard sur l’histoire locale
No full textInternational audienceParmi les fonds conservés aux archives municipales, ceux relatifs à la vie sportive permettent à l’historien d’appréhender différents aspects de la culture et des politiques locales : modes de sociabilité, projets sanitaires et sociaux, aménagement du territoire… Par leur variété (dossiers administratifs, lettres, anecdotes, plans, affiches, photos…) les documents constituent de précieux témoignages permettant d’exhumer une quotidienneté, souvent complexe, et parfois oubliée ou maltraitée par la mémoire
Differential Packing of Cs2Mo6Br14 Cluster-Based Halide in Variable Diameter Carbon Nanotubes with Elimination and Polymerization to 1D [Mo2Br6]x Ising Model Structures by Steric Confinement
No full textInternational audienceWe present detailed findings on the imaging, structure, and vibrational properties of novel hybrids of the red-emitting octahedral cluster-based compound Cs2Mo6Br14 encapsulated within single-walled carbon nanotubes (SWCNTs) of varying diameter. We explore the subtle relationship between the SWCNT internal diameter and Cs2Mo6Br14 cluster packing and find a hierarchical relationship between the nature of the cluster packing and a progressive tendency toward formation of one-dimensional (1D) structures as the SWCNT diameter narrows from 24 to 11 Å. As the internal SWCNT van der Waals radius approaches the outside diameter (OD) of the [{Mo6IIBr8i}Br6a]2- (more simplistically, [Mo6IIIBr14]2-) molecular anion species, SWCNT steric confinement causes a compositional elimination and polymerization resulting in the formation of reduced extended [Mo2IIIBr6]x nanoribbons which approximate 1D Ising model structures. Our experimental results, obtained through high-resolution transmission electron microscopy and Raman spectroscopy, are supplemented by density functional theory (DFT) calculations
