HAL Portal Cnam (French National Conservatory for Arts and Crafts)
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Experimental and theoretical study of metal combustion in oxygen flows
No full textThe effects of oxygen flow speed and pressure on the iron and mild steel combustion are investigated experimentally and theoretically. The studied specimens are vertical cylindrical rods subjected to an axial oxygen flow and ignited at the upper end by laser irradiation. Three main stages of the combustion process have been identified experimentally: (1) Induction period, during which the rod is heated until an intensive metal oxidation begins at its upper end; (2) Static combustion, during which a laminar liquid "cap" slowly grows on the upper rod end; and, after the liquid cap detachment from the sample, (3) Dynamic combustion, which is characterized by a rapid metal consumption and turbulent liquid motions. An analytical description of these stages is given. In particular, a model of the dynamic combustion is constructed based on the turbulent oxygen transport through the liquid metal-oxide flow. This model yields a simple expression for the fraction of metal burned in the process, and allows one to calculate the normal propagation speed of the solid metal--liquid interface as a function of the oxygen flow speed and pressure. A comparison of the theory with the experimental results is made
Positionnement d'un robot parallèle à câbles avec une précision supérieure à 250 μm à l'aide de systèmes de mesure par multilatération et photogrammétrie
No full textInternational audienceImproving the positioning accuracy of cable-driven parallel robots (CDPRs) is crucial for industrial applications. These robots, operating in large volumes and handling heavy loads, have an accuracy limited by several factors, such as variations in ambient temperature or changes of the load being transported, which affect the mechanical structure of the robot or the tensions in the cables. For instance, CoGiRo is a CDPR of dimensions of 11 m × 15 m × 6 m able to move a platform weighing up to 500 kg. Its resolution is a few tens of micrometres, but its positioning, estimated from the winch encoders, lacks accuracy. To accurately place the CoGiRo mobile platform in the desired position and orientation, this paper proposes to use multilateration and photogrammetric measurement systems in a collaborative way. Photogrammetry continuously measured the poses of the mobile platform with worst-case coordinate uncertainties in the depth direction moving away from the cameras, with 0.2 mm being typical for all lines of sight, dropping to 0.5 mm where lines of sight were blocked by occlusion. The photogrammetric system reported poses at 2 Hz to the multilateration system, enabling it to align its stations on the distant targets and measure static poses of the platform with an estimated uncertainty typically less than 70 µm for the position coordinates and less than 110 µrad for the orientation angles. Multilateration measurements were then used by CoGiRo to reduce its positioning errors to less than 250 µm. The technique was validated using a practical assembly of two square-shaped metallic parts equipped with 10 independent capacitive distance sensors that allowed us to demonstrate part alignment to better than 250 µm
Set-Valued Approaches to Control and Estimation of Uncertain Systems
No full textInternational audienceThis edited book presents recent advances in state estimation, robust control synthesis, system identification, fault detection, localization, and optimization, with a particular emphasis on interval-based methods and set-membership techniques. Covering both theoretical developments and practical applications, the book brings together contributions from recognized experts in these research areas.Topics include set-based state estimation in varied dynamical system settings, sliding-mode predictive and state-feedback control, innovative optimization algorithms, zonotopic fault detection and identification, as well as distributed moving horizon estimation. The proposed methods are illustrated through practical simulation studies in robotics, autonomous vehicles, fuel cell systems, and sensor networks.Intended for researchers, engineers, and graduate students in control systems, applied mathematics, and various engineering disciplines, this book offers both a rigorous foundation and cutting-edge approaches for addressing uncertainty in complex dynamical systems
Engineering MgFe2O4 nanoparticles to enhance magnetic, optical, and dielectric performance
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Static and dynamic Monte Carlo simulations of phonon drag effects on thermoelectric properties in silicon nanostructures
No full textThermoelectric transport in silicon nanofilms is investigated using a self-consistent electro-thermal Monte Carlo simulator that couples electron dynamics to a phonon bath with spatially varying temperature. A key novelty of this work is the explicit inclusion of the phonon-drag contribution, implemented by modifying the electron-phonon momentum exchange based on the local deviation of the phonon distribution from equilibrium. The method is validated against bulk silicon data and extended to incorporate rough boundary scattering for both electrons and phonons, yielding excellent agreement with experimental measurements on nanofilms. We also analyze the transient regime and show that a temperature bias produces a slower current response than a voltage bias, although the phonon-drag effect itself tends to accelerate the response. These results demonstrate that the proposed framework provides a powerful tool for predicting both steady-state and time-dependent thermoelectric behavior in semiconductor nanostructures
L’arrière-pays des ports français : dynamiques et typologie en contexte européen
No full textInternational audienceCet article aborde la problématique des dynamiques et de la typologie de l’arrière-pays des ports français dans le cadre d’une concurrence européenne accrue. En examinant les transformations structurelles subies par le secteur maritime, il est souligné l’importance croissante de l’arrière-pays dans le développement économique des territoires portuaires. L’originalité de l’article réside dans la mobilisation de données douanières, qui permettent une analyse fine des flux de marchandises et dépassent les définitions traditionnelles de l’arrière-pays.En utilisant ces données, l’étude met en lumière la complexité des relations entre ports et hinterlands, révélant que les ports français, confrontés à une forte concurrence de ports européens tels qu’Anvers, peinent à maintenir leur part de marché. Les différentes analyses ont permis d’analyser les hinterlands des ports français à la fois à l’import et à l’export et également de les caractériser. Nous avons réalisé une typologie, présentée sur la carte, à l’échelle départementale, des hinterlands des ports français combinant les données en importations et en exportations
Systematization of Knowledge on Offline-Capable Digital-Currency Protocols
No full textInternational audienceOffline capability is the final element needed to make digital money functionally equivalent to cash. This Systematization of Knowledge (SoK) reviews 12 years of academic and industrial work on offline-capable digital-currency protocols. We contribute: (i) a five-axis taxonomy spanning ledger infrastructure, trust hardware, cryptographic primitives, connectivity levels, and target properties; (ii) a comparative analysis of 34 representative schemes against six security and operational criteria; and (iii) a discussion of cross-cutting challenges: constrained hardware, regulatory UX trade-offs, and interoperability, followed by three forward-looking research agendas: post-quantum security, programmable offline transfers, and self-sovereign identity integration. The resulting design map offers practical guidance for central banks, wallet developers, and standards bodies as they prepare central bank digital currency(CBDC) pilots and hybrid payment deployments for the 2025–2027 horizon
FlowEO: Generative Unsupervised Domain Adaptation for Earth Observation
No full textInternational audienceThe increasing availability of Earth observation data offers unprecedented opportunities for large-scale environmental monitoring and analysis. However, these datasets are inherently heterogeneous, stemming from diverse sensors, geographical regions, acquisition times, and atmospheric conditions. Distribution shifts between training and deployment domains severely limit the generalization of pretrained remote sensing models, making unsupervised domain adaptation (UDA) crucial for real-world applications. We introduce FlowEO, a novel framework that leverages generative models for image-space UDA in Earth observation. We leverage flow matching to learn a semantically preserving mapping that transports from the source to the target image distribution. This allows us to tackle challenging domain adaptation configurations for classification and semantic segmentation of Earth observation images. We conduct extensive experiments across four datasets covering adaptation scenarios such as SAR to optical translation and temporal and semantic shifts caused by natural disasters. Experimental results demonstrate that FlowEO outperforms existing image translation approaches for domain adaptation while achieving on-par or better perceptual image quality, highlighting the potential of flow-matching-based UDA for remote sensing
Accounting for dielectric losses in piezoelectric shunt tuning
No full textInternational audienceEffective vibration reduction of mechanical structures by piezoelectric shunt damping equires a precise design of the electrical shunt circuit. In this context, the influence of dielectric losses on the accuracy of shunt calibration is analyzed. Numerical analysis of an SDOF structure shows that dielectric losses can result in a significantly increased vibration amplitude when not accounted for in the calibration of a resonant shunt. To address this, a new correction method based on impedance matching is proposed, enabling the use of existing tuning expressions not accounting for dielectric losses. It is demonstrated numerically and experimentally that the influence of dielectric losses is more pronounced for low electromechanical coupling factors. The proposed correction method is shown to provide an accurate correction for the influence of dielectric losses on the shunt tuning