Archive Ouverte INSA Lyon
Not a member yet
75807 research outputs found
Sort by
A parametric study of the turbulent energy transfer in three-dimensional Lattice-Boltzmann Hall-MHD plasma simulations
No full textInternational audienceObservations from heliospheric missions have deepened our understanding of the solar wind. However, the complexity arising from its quasi-collisionless and multiscale nature leaves open several key questions on how energy is transferred and dissipated in the interplanetary plasma. In this parametric study, we investigate turbulent energy transfer and intermittent plasma processes in three-dimensional direct numerical simulations, in the Hall-MHD framework, performed with the Fast Lattice-Boltzmann Algorithm for Magnetohydrodynamics Experiments (FLAME) . We analyze properties of the global and pseudo-local energy transfer, to characterize the scale-dependent behavior of the energy cascade in Hall-MHD plasmas by means of the so called local energy transfer proxy (or LET), the analysis of the probability distribution functions of the macroscopic fields, and the flatness of their increments. Our results indicate that scale-dependent structures, small-scale intermittency, and statistical properties in the plasma flow are sensitive to variations of the Hall term, providing insights that are potentially useful for the interpretation of space plasma dynamics
Brittle Crack Initiation Seen as a Dynamic Crack Propagation Phenomenon
No full textInternational audienceWhile dynamic propagation of long cracks is well established, the early stage of brittle crack initiation remains to be clarified. We address the identification of the crack velocity profile during initiation under quasi-static loading conditions within the coupled criterion framework. Based on stress and energy conditions, the load level and crack length at initiation are obtained. An additional dynamic crack propagation condition is proposed to ensure the crack length and velocity continuity between the end of the initiation stage and the beginning of subsequent crack propagation. This defines a minimum admissible initiation crack length, only attained for quasi-static crack initiation followed by stable crack growth. If inertial effects are not negligible, the fulfillment of the energy equilibrium during initiation constrains the crack to reach a minimum velocity at the end of initiation and a larger initiation crack length. The proposed approach thus makes it possible to estimate the validity of the quasi-static application of the coupled criterion. It enables determining the crack velocity profile during initiation, which is found to be similar to the crack velocity profiles measured experimentally in unnotched and notched specimens
Où implanter des Solutions fondées sur la Nature pour répondre à la surchauffe urbaine et à la fragmentation des réseaux écologiques des insectes pollinisateurs : cas d'étude sur la Ville de Lyon
No full textInternational audienceEn France, chaque année, environ 31000 ha passent du statut d'Espace Naturel, Agricole ou Forestier à celui d'artificialisé (Fosse, 2021). Dans la ville de Lyon, 56% de l'occupation du sol est composée de bâtiments et de leurs espaces artificialisés associés ce qui engendre localement de la surchauffe urbaine, et globalement, le phénomène d'îlot de chaleur urbain (Elliot et al., 2020). Parallèlement, l'homogénéisation des modes de cultures et l'utilisation massive de produits phytosanitaires conduisent les insectes pollinisateurs à délaisser les espaces agricoles environnants pour trouver refuge dans les zones urbaines (Baldock et al., 2015; Hall et al., 2017). Les Solutions fondées sur la Nature (SfN), actions visant à améliorer les conditions de la biodiversité tout en répondant à des questions sociétales, ont été récemment développées sur le territoire lyonnais afin de répondre de la meilleure manière aux deux problématiques.Ce travail cherche à tester où des SfN peuvent être implantées dans la ville de Lyon pour permettre de favoriser la connectivité écologique des insectes pollinisateurs tout en tentant de réduire la surchauffe urbaine.À partir d'une cartographie d'occupation des sols modifiée depuis la base CosIA de l'IGN (ajout de hauteur de bâtiments, des routes et des surfaces enherbées sous les canopées), un premier graphe paysager est réalisé pour un groupe d'insectes pollinisateurs. Ce graphe permet d'identifier les ruptures de continuités écologiques à Lyon et de vérifier leur corrélation avec les zones de surchauffe urbaine. De nouveaux nœuds sont ensuite ajoutés dans les secteurs précédemment identifiés. Ils représentent d'hypothétiques SFN (toits verts, murs végétalisés) pensée pour répondre à la fois aux problématiques humaines et animales. Plusieurs scénarios sont étudiés en fonction des spécificités écologiques des pollinisateurs, en termes de ressources nécessaires à leur implantation, leur distance de déplacement (quotidien, dispersion) et des hauteurs atteignables en déplacement vertical par les individus
La guerre de l’énergie a déjà commencé en Ukraine : pourquoi l’Europe a tout intérêt à développer le stockage thermique
No full textInternational audienc
MITIGATION OF NON-SYNCHRONOUS VIBRATION WITH GEOMETRIC MISTUNING: EXPERIMENTAL INVESTIGATION OF LEADING-EDGE MODIFICATION ON THE OPEN TEST CASE ECL5
No full textThe mitigation of Non-Synchronous Vibration (NSV) is essential to extend the operational range of fans and compressors in aircraft engines. Near the stability limit at part-speed conditions, increased tip blockage enables circumferential convection of aerodynamic disturbances, leading to coupled blade vibrations known as lock-in. Previous studies have shown that local variations in blade geometry influence the propagation of these disturbances. In particular, asymmetric tip clearance affects their speed and intensity, potentially altering the dominant flow wave numbers and the corresponding structural nodal diameters involved in lock-in.In earlier work, non-uniform tip clearance was found to significantly influence disturbance formation, though it did not provide sufficient NSV suppression. To enhance the local aerodynamic effect, this study investigates geometric modifications of the blade leading edge.A numerical investigation using unsteady RANS simulations is conducted on the open test case geometry ECL5 to assess the influence of leading-edge modifications on disturbance propagation. The study also examines variations in the mistuning pattern, defined by the circumferential distribution of cut blades. Selected geometrically mistuned configurations were experimentally tested at Centrale Lyon. This paper presents both numerical and experimental results, providing a detailed characterization of the effects of geometric modifications on local aerodynamics and fluid-structure interactions relevant to NSV behavior
Analysis of mode I fracture propagation in wood using high-resolution full-field measurements and imaging
No full textInternational audienceExperimental characterization of wood fracture properties raises a number of challenges: crack tip location or the application of equivalent linear elastic fracture mechanics theory to a heterogeneous and anisotropic material. This article presents the application of the Localized Spectrum Analysis, a full-field measurement method, to obtain high-resolution strain maps for the analysis of three mode I crack propagation tests on TDCB silver fir wood specimens. The strain maps presented enabled us to identify annual rings through stiffness variations, to observe internal cracks through abnormal compression zones, and to determine the material's resistance-curves, therefore its critical energy release rate. This work opens up interesting prospects for the use of new measurement methods in the characterization of wood fracture properties
Diffusion-Based Authentication of Copy Detection Patterns: A Multimodal Framework with Printer Signature Conditioning
No full textInternational audienceCounterfeiting affects diverse industries, including pharmaceuticals, electronics, and food, posing serious health and economic risks. Printable unclonable codes, such as Copy Detection Patterns (CDPs), are widely used as an anti-counterfeiting measure and are applied to products and packaging. However, the increasing availability of high-resolution printing and scanning devices, along with advances in generative deep learning, undermines traditional authentication systems, which often fail to distinguish high-quality counterfeits from genuine prints. In this work, we propose a diffusion-based authentication framework that jointly leverages the original binary template, the printed CDP, and a representation of printer identity that captures relevant semantic information. Formulating authentication as multi-class printer classification over printer signatures lets our model capture fine-grained, device-specific features via spatial and textual conditioning. We extend ControlNet by repurposing the denoising process for class-conditioned noise prediction, enabling effective printer classification. On the Indigo 1 × 1 Base dataset, our method outperforms traditional similarity metrics and prior deep learning approaches. Results show the framework generalizes to counterfeit types unseen during training
For the use of exterior form in daily physics, an introduction without coordinate frame
No full textThis is a short introduction of the exterior form formalism focus on its appli-cations in physics and then mostly aimed to physics students. If exterior formsare more than a century old they are unfortunately still seen (and teached) asa high level mathematics object and then little used outside theorical physics.We then focus here on simple examples which occure in daily phiysics. Thereexists already a lot of very good mathematical textbooks and courses on thesubject but the originality of these notes, the physical applications aside, is thatwe keep a completely geometrical approach. As a rule of a game played here wenever use a coordinate frame neither in the definitions nor in the proofs but onlyat the end in order to recover the classical physics equations
Experimental study on gravity currents flowing on heated walls
No full textWe present an experimental study on steady gravity currents advancing along a heated wall. The current is generated by a mixture of air and carbon dioxide continuously supplied at the channel inlet. To have a complete point-wise characterization of the flow, simultaneous high-frequency measurements of two velocity components, CO_2 concentration, and temperature are performed. An experimental protocol is presented to reconstruct the local fluid density and to estimate turbulent vertical and horizontal fluxes of CO_2, temperature, and buoyancy. The reliability of both the flow measurements and of the estimate of convective heat flux exchanged at the wall is assessed through integral balances of \textnormal{CO} mass, enthalpy, and buoyancy, performed at different distances from the source. Three wall-heating conditions are considered: an adiabatic case, a moderately heated case, and a strongly heated case. In the heated experiments, a convectively unstable boundary layer forms near the wall, capped by a stably stratified region. The influence of this condition on the first- and second-order flow statistics profiles is examined. Although wall heating influences the vertical shear, the Brunt-Vaisala frequency, and both shear and buoyancy production of turbulent kinetic energy within the stably-stratified region characterized by an almost constant vertical gradient of streamwise velocity, neither the gradient Richardson number nor the flux Richardson number exhibits a clear trend in this region with the imposed wall heat flux
Gender differences in audience participation at infectious disease and microbiology conferences: a prospective observational study
No full textInternational audienceObjectivesIn medicine, women constitute a large proportion of the workforce but remain underrepresented in senior positions. Scientific conferences, critical for career advancement, reflect these inequities, with prior studies documenting gender gaps in invited speakers. However, less attention has been given to audience engagement, such as asking questions or making comments, which also enhances professional visibility. This study investigates gender differences in audience participation at infectious disease and clinical microbiology conferences, examining their prevalence, contextual variation, and potential structural drivers.MethodsThis prospective observational study recorded audience participations during national and international infectious disease and clinical microbiology conferences (October 2023–October 2024). Consortium members documented eligible sessions with traditional presentation–discussion formats, noting gender, role, and type of participation. Statistical analyses compared observed gender proportions with attendee distributions and examined factors associated with women's participation.ResultsA total of 298 sessions from 24 conferences were analysed, comprising 1873 audience participations. Women delivered 47.8% of presentations (n = 487/1018; 95% CI, 44.8–50.9%) but accounted for only 36.4% of participations (n = 681/1873; 95% CI, 34.2–38.5%), significantly fewer than men both in absolute terms and relative to their representation among attendees (p < 0.001). Multivariable analysis showed women were more likely to intervene when at least one moderator was female (OR = 1.44; 95% CI, 1.02–2.04%; p 0.037), with a stronger effect when all moderators were women (OR = 2.12; 95% CI, 1.40–3.24%; p < 0.001), and when the first question was asked by a woman (OR = 1.35; 95% CI, 1.00–1.81%; p 0.046).ConclusionOur findings highlight actionable levers to advance equity. Addressing participation gaps and raising awareness of gender disparities are essential to foster inclusive visibility, empower women, and strengthen scientific innovation