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Towards reconfigurability in aerospace manufacturing systems
No full textNational audienceTowards reconfigurability in aerospace manufacturing system
Integrating electrical wafer sorting and complete-line process control data for optimizing process and equipment performance
No full textInternational audienceIntegrating electrical wafer sorting and complete-line process control data for optimizing process and equipment performanc
Gap-free GNSS-R wind field reconstruction: A neural mapping scheme and initial validation
No full textInternational audienceSpaceborne Global Navigation Satellite System Reflectometry (GNSS-R) has been widely demonstrated as an effective method for ocean wind speed retrieval. This study explores the feasibility of using track-wise GNSS-R wind products to generate gap-free wind fields. A physics-informed neural mapping scheme, 4DVarNet, is adapted to reconstruct wind fields. Results indicate that the root mean square errors (RMSEs) of the 1-hour, 3-hour, and 6-hour 4DVarNet winds are 1.13 m/s, 1.16 m/s, and 1.24 m/s compared to European Center for Medium-Range Weather Forecast (ECMWF) ERA5 wind products, while 1.40 m/s, 1.41 m/s, and 1.48 m/s are referred to Advanced Microwave Scanning Radiometer-2 (AMSR2) all-weather winds. Spatial and temporal error analyses further confirm the robustness of 4DVarNet-derived winds, with daily RMSEs remaining below 1.6 m/s. Error decomposition reveals discrepancies between ECMWF and GNSS-R winds, which may support future recalibration of GNSS-R wind products or enhancements to ECMWF forecasts. A case study of Super Typhoon Surigae proves that 4DVarNet winds closely align with the International Best Track Archive for Climate Stewardship (IBTrACS) track data. The reconstructed winds detect the peak intensity temporally consistent with IBTrACS data, whereas ECMWF forecasts exhibit a two-day lag. Moreover, asymmetries in Tropical Storm Kompasu are observed, with the radius of maximum wind (Rmax) over the Northeast quadrant 38% larger than that over the Northwest quadrant. Despite the absence of background wind field inputs, 4DVarNet effectively learns wind patterns from ECMWF data and integrates GNSS-R observations to generate gap-free wind mappings, exhibiting strong agreement with ECMWF wind fields. The reconstruction performance is degraded at high winds due to the underestimation of referenced ECMWF ERA5 winds and the small quantity of observations. This limitation could be alleviated through denser GNSS-R observations from multiple missions such as Fengyun-3, Tianmu-1, recently launched HydroGNSS, etc., and other training references with more high winds for improving the representation of 4DVarNet at high winds
Sustainable biodiesel production from waste cooking oil: Process design and techno-economic comparison of homogeneous and heterogeneous catalysis
No full textInternational audienceThis study aims to design and model four different semi-continuous process scenarios for biodiesel production, using virgin oil (VO) as a reference feedstock and waste cooking oil (WCO) collected from restaurants in Beirut. Both heterogeneous and homogeneous catalyst configurations were assessed by a thorough techno-economic analysis to identify the most efficient and cost-effective approach. A total collectable quantity of 22,740 kg/week of WCO was processed for the biodiesel production, representing a collection rate of 45 %. The project was developed with a 15 years lifetime and a target payback period (PBP) of 5 years. CaO and Amberlyst 46 were chosen as heterogeneous catalysts for transesterification and esterification, respectively, while KOH and H₂SO₄ were identified as reference homogeneous catalysts. Technical evaluations revealed that heterogeneous configurations were simpler, requiring fewer treatment steps compared to homogeneous ones, which necessitate catalyst neutralization and extensive purification of biodiesel and glycerol. The economic impact of the catalyst regeneration section was analyzed, particularly for the heterogeneous configurations examined without the CaO regeneration section. The economic feasibility of each setup was evaluated with focus on production capacity and how it impacts the PBP, using a 5-year payback as the reference. Among all configurations, the heterogeneous process without CaO regeneration required the lowest feedstock input of 5600 kg/day to achieve the 5-year payback target. However, as production capacity increased, the economic difference between configurations with and without catalyst regeneration decreased, indicating that catalyst regeneration becomes economically advantageous at larger scales
Procédé de pilotage d'un réacteur nucléaire, réacteur nucléaire et procédé de calibration
No full textInternet of Vehicles via Rate-Splitting Multiple Access With Antenna and RIS Partitioning
No full textInternational audienceIntegrating rate-splitting multiple access (RSMA) and reconfigurable intelligent surfaces (RIS) into vehicular communication systems offers significant potential for enhancing quality of service but also introduces challenges in radio resource allocation due to increased system complexity and the heterogeneous mobility patterns of vehicles. In this paper, we propose a vehicle-to-infrastructure (V2I) communication system that leverages a partitioned antenna array and RIS elements for reduced computational complexity, with RSMA serving multiple vehicles and users therein. To mitigate inter-vehicular interference, we employ a zero-forcing technique that decouples precoding at the BS and decoding at the user equipment (UE) into a zero-forcing factor and a precoding factor. For sum-rate maximization, we develop a block coordinate descent (BCD) algorithm, incorporating a dynamic partitioning scheme that divides the BS antenna array and RIS elements into subplanes. Each subplane is dedicated to a single vehicle for transmitting private streams to UEs therein, along with common streams for all UEs across all vehicles. The passive beamforming for each RIS subplane is optimized using the Riemannian conjugate gradient (RCG) method, while precoding at the BS subarray is optimized using a weighted minimum mean square error (WMMSE) approach. Simulation results and comparisons with benchmarks demonstrate that the proposed partitioning scheme achieves robust performance in terms of system sum rate while significantly reducing computational complexity
Hyperspectral imaging for orthopedic surgery: lightweight AI enables real-time bone and cartilage segmentation
No full textInternational audienc
Atmospheric neutrino constraints on Lorentz invariance violation with the first six detection units of KM3NeT/ORCA
No full textInternational audienceLorentz invariance is a fundamental symmetry underlying both the Standard Model of particle physics and General Relativity. Testing its validity provides a direct means of searching for new physics emerging near the Planck scale. A search for isotropic Lorentz invariance violation with 1.4 years of atmospheric neutrino data collected by a partial configuration of the KM3NeT/ORCA detector comprising six detection units is presented. No evidence for such violation is found; thus, competitive limits are set on a subset of isotropic Lorentz invariance violating coefficients, which complement and extend existing experimental constraints
Analog-based ensembles to characterize turbulent dynamics from observed data
No full textInternational audienceWe present a methodology for the study of the dispersion of trajectories of stochastic processes in reconstructed phase spaces from observed data. The methodology allows to find ensembles of analog states, i.e. states that are close in the phase space. Once these states are found, we focus on the characterisation of their dispersion in function of 1) the time and 2) their initial separation. We study an experimental turbulent velocity measurement and two scale-invariant stochastic processes: a regularized fractional Brownian motion and a regularized multifractal random walk. Both stochastic processes are synthesized to have the same covariance structure as the experimental turbulent velocity, but only the regularized multifractal random walk mimics the intermittency of turbulent velocity. We illustrate that while the covariance structure of the processes governs the time dependence of the dispersion of the analog states, the intermittency phenomenon is responsible for the impact of the initial separation of the analogs on their dispersion
The role of tensegrity in the diversity of avian postural stability
No full textInternational audienceAbstract Like humans, all birds adopt a strictly bipedal posture. However, unlike humans, birds have such good balance that they can sleep while standing up, which must require minimal energy. This makes them an interesting model for studying bipedalism in robotics. In this study, we examine balance and postural stability via a tensegrity system (assembly in parallel of rigid bodies and cables). To test this hypothesis, we created mathematical models based on anatomical observations of the legs of various birds (zebra finch, little egret, mallard and military macaw) to investigate different configurations. Building on a previous model, we demonstrate that tensegrity systems can achieve passive stability under simplified loading. Here, we aim to establish whether this model can be generalized, to determine stability, and to identify the impact of certain kinematic, dynamic and material parameters. Our results enabled us to identify the parameters that allow the model to be generalized. We determined that adding two cables corresponding to tendinous and muscular sets generalizes the model to a varied range of configurations and exploits the rear part of the foot when present. These findings offer new insights into avian bipedalism and could inspire the design of bipedal robots with passive stability for greater autonomy