HAL Arts et Métiers
Not a member yet
14127 research outputs found
Sort by
Agile Laser Wavelength Tuning Using Dynamic Targeting
No full textInternational audienceTunable lasers are essential and versatile tools in photonics, with applications including telecommunications, spectroscopy, and sensing. Advancements have aimed to precisely control the lasing wavelength, expand tuning ranges, suppress mode hopping, and enable photonic integration. In this work, we explore the adaptation of dynamic targeting, a technique originally developed to stabilize lasers under optical feedback, as a method for achieving agile, fast, and continuous wavelength tuning. This technique works by adjusting the feedback rate and phase, enabling a stable and controlled frequency shift. We experimentally demonstrate reliable and reproducible tuning over 2.1 GHz using a free-space optical setup. Simulations further suggest that this approach could extend the tuning range to tens of GHz, with a potential scan speed exceeding 10 17 Hz/s. These results highlight dynamic targeting as a promising route toward agile frequency control in semiconductor lasers for photonic integrated circuits
Data driven prediction of thermal hysteresis in NiTi-based high entropy shape memory alloys
No full textInternational audienceThis study provides a data-driven approach to predict thermal hysteresis in NiTi-based high-entropy shape memory alloys (HESMAs), using a dataset of NiTi-based shape memory alloys that includes the four transformation temperatures (M s , M f , A s , A f ). Machine learning models based on extremely randomized trees were proposed to predict M s and the thermal hysteresis (ΔT = A f -M s ), using 11 physical material descriptors as inputs. M s prediction is dominated by mixing enthalpy, the valence electron ratio, and the difference in electronegativity. In contrast, hysteresis depends equally on 8 additional balanced features such as the melting temperature, electronegativity, atomic radius, and the mixing entropy. The predictions models are highly reliable with mean absolute errors of 31 • C for M s and 11 • C for ΔT. Finally, a design strategy is proposed for (NiCuCo)(TiZrHf) HESMAs that optimises both M s and ΔT with targeted values
Design Optimization of Contra-Rotating Axial Flow Fan Using a SHADE-Based Approach
No full textInternational audienceContra-rotating fans are known to offer an efficient solution for applications requiring high pressure and low energy consumption. This study introduces a novel approach utilizing a metaheuristic algorithm for the optimal design of a contra-rotating axial flow fan. The geometry of the two rotors is obtained using Success-History based Adaptive Differential Evolution (SHADE) optimization algorithm and a 1D inverse design model, aiming to maximize overall hydraulic efficiency. For the optimal design, the blade cross-section between the hub and tip of the two rotors must comply with geometric constraints defined by the limitations of NACA65-type airfoil cascade. To achieve the desired nominal pressure rise, a sequential optimization strategy is proposed. First, the front rotor is optimized, and then the rear rotor is optimized based on the results from the front rotor, including parameters such as hub and tip radius, velocity triangles, and others. The optimal geometry is analyzed over a range of flow rates using loss models and computational fluid dynamics (CFD) software. The results show a high performance for the contra-rotating geometry obtained by the proposed approach, with a wide operating range. At design point, relative to the existing fan in literature, the proposed fan achieves a 5% efficiency improvement and a 4% higher pressure rise than the specification, whereas the reference fan exhibits a 12% deficit
A lateral porous silicon electrokinetic molecular valve
No full textInternational audienceIn this study, we introduce an Electrokinetic Molecular Valve (EMV) based on Lateral Porous Silicon (LPSi) membranes. The LPSi membranes are fabricated and monolithically integrated into silicon microfluidic chips , featuring an average pore size of 25 nm. Upon proper oxidation, LPSi membranes exhibit a relative perm-selectivity of 48% in physiological solution, comparable to that of Nafion. The LPSi chip is able to extract and concentrate 1.5 fmol of fluorescein from 180 nL into 1.3 nL within 10 minutes, and to achieve a concentration factor of more than 120 at voltages less than 4.2 V. A simplified numerical model is developed to describe the electrokinetic behavior of the EMV. The model exibites good qualitative agreement with experimental results. By varying parameters within this framework (the applied voltage, membrane charge density, background ion concentration, and membrane position), the preconcentration performance of the EMV can be reliably predicted. Distinct from conventional electrokinetic concentrators, the EMV architecture mandates that the entire fluid flow through the LPSi nanochannels. This configuration enables high ion selectivity and low voltage operation, while leveraging the Donnan exclusion effect for precise molecular control, concentration, and release. With continued advancements in electrical insulation and membrane charge density, the proposed EMV holds considerable promise for integration into portable µTAS and biosensors
Role of friction on the formation of confined granular structures
No full textInternational audienceAbstract Metastable fluidized granular systems can spontaneously defluidize, forming glass- or crystal-like structures. We performed experiments with polymer spheres of different friction and roughness fluidized in a vertical water pipe flow. Velocity fluctuations were higher for high friction materials. Monodisperse particles form a crystal-like shell on the cylinder wall for a range of flow rates and number of particles. For polytetrafluoroethylene (PTFE) spheres with a friction coefficient near 0.1, structural organization was assessed through nearest-neighbor angle analysis, featuring hexagonal packing with defects. At such low friction, defects decreased, while contact chains became longer and more aligned. These findings highlight the role of surface properties in the emergence of ordered or disordered structures, offering new insights into the mechanisms governing glass- and crystal-like arrangements in fluidized particle systems
EDUCAUSE 2025 Rapport de la délégation française - FR: Visites de Vanderbilt University Arizona State University
No full textDepuis douze ans maintenant, la Délégation Française EDUCAUSE propose à la communauté del’Enseignement Supérieur français une ouverture à l’international sur les enjeux du numérique, en associantdes profils complémentaires à même d’en apprécier les tendances fortes et les perspectives majeures. Cettedémarche s’est ainsi concrétisée par une participation continue aux conférences EDUCAUSE depuis 2013,qui s’est très significativement enrichie au cours des années. D’une philosophie initiale de simpleparticipation, les membres de cette Délégation se sont en effet progressivement impliqués à différentsniveaux d’EDUCAUSE, dans le cadre des conférences et au-delà (voir l’infographie ci-dessous).La Délégation totalise vingt-quatre présentations sélectionnées, sur plusieurs sujets d’actualité. Plusieurs denos membres, par ailleurs, sont mobilisés chaque année en tant que proposal reviewers (relecteurs depropositions d’interventions) pour la conférence EDUCAUSE, mais aussi en tant que membres des comitésde programme respectifs (en 2019, 2023 et 2026). Enfin, certains d’entre nous font partie des panelsd’experts mobilisés dans le cadre du EDUCAUSE Horizon Report et du Top-10 issues annuels, sont actifs ausein de différents Community Groups thématiques (XR et Learning Spaces en particulier), ou s’impliquent entant que rédacteurs d’articles de référence et traducteurs d’outils.Mentionnons également ici les plus de trente visites de sites qui ont été menées depuis 2013 avant ou aprèsles conférences EDUCAUSE et qui, au-delà du remarquable accueil qui nous a toujours été réservé, nous ontapporté une vue de terrain très précieuse au travers d’échanges de grande qualité
Simulation of the Rotational Molding Process of Polyethylene using the Smoothed Particle Hydrodynamics Method
No full textInternational audienceThis work presents the development of a numerical model based on the Smoothed Particle Hydrodynamics (SPH) method to simulate the rotational molding process of powder thermoplastic polymers, used in the manufacture of liners for high-pressure hydrogen tanks. Rotational molding is a complex thermo-mechanical process involving powder heating, melting, flow, and solidification under biaxial rotation. The SPH approach naturally captures free-surface evolution while integrating experimental thermal and rheological properties of LDPE into the model, which has been implemented in the open-source DualSPHysics framework. Numerical simulations make it possible to monitor the progressive process, understand the effect of different parameters on the process, and guide future optimization of rotational molding processes through numerical simulation. Highlights• SPH model simulates rotational molding with powder melting transition.• 2D/3D simulations reproduce melting progression and thickness growth.• SPH model implemented in the open-source DualSPHysics framework.• Experimental LDPE properties are integrated into the model.• Model predictions are validated against experimental observations.</div
Modeling and balancing human-cobot collaboration modes in assembly lines with energy and cost optimization.
No full textInternational audienc
Spatial evolution of mean flow properties in supersonic boundary layers of adiabatic and isothermal curved surfaces including shock interactions
No full textInternational audienceThis study investigates supersonic boundary layers over a turbine cascade under the coupled influence of surface curvature, streamwise pressure gradients, and shock-boundary layer interactions (SBLIs), for both adiabatic and isothermal (cooled, ) wall conditions. Wall-resolved large eddy simulations are performed at an inlet Mach number and Reynolds number . Results show that wall cooling increases near-wall density, reduces temperature and viscosity, and yields fuller streamwise momentum profiles, making the boundary layer more resistant to separation and reducing the scale of the suction-side SBLI. The curvature-induced pressure gradients, favorable on the suction side and adverse on the pressure side, govern the thermodynamic response, causing flow expansion and compression, respectively. A balance analysis reveals that compressibility effects dominate the streamwise evolution of momentum upstream of the SBLIs, while downstream recovery is primarily driven by turbulent transport and mean advection rather than the local pressure gradient
Validation methodology on real data of reversible Kalman Filter for state estimation with Manifold
No full textThis work extends a previous study that introduced an algorithm for state estimation on manifolds within the framework of the Kalman filter. Its objective is to address the limitations of the earlier approach. The reversible Kalman filter was designed to provide a methodology for evaluating the accuracy of existing Kalman filter variants with arbitrary precision on synthetic data. It has favorable numerical properties on synthetic data, achieving arbitrary precision without relying on the small-velocity assumption and depending only on sensor noise. However, its application to real data encountered difficulties related to measurement noise, which was mitigated using a heuristic. In particular, the heuristic involved an event detection step switching between reversible Kalman filter and classical Kalman variant at chosen moments. In the present work, we propose a study of this detection step and propose a methodology to prove at which moment the reversible Kalman approach improves on classical multiplicative variant