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An Overview and Classification of Machine Learning Approaches for Radar Signal Deinterleaving
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Impact of Convectively Coupled Tropical Waves on the composition and vertical structure of the atmosphere above Cabo Verde in September 2021 during the CADDIWA campaign
No full textInternational audienceIn summer, Mixed Rossby Gravity Waves/Tropical Disturbances (MRG-TD) are known to drive intraseasonal humidity variability in the northeastern Atlantic troposphere, modulated by Equatorial Rossby (ER) and Kelvin waves. However, their impact on dust remains poorly understood, and MRG-TD tracks are often mingled in the literature. During the Clouds-Atmosphere Dynamics-Dust Interaction in West Africa (CADDIWA) campaign in September 2021, in-situ and remote sensing data (dropsondes, radiosondes, GNSS, and IASI) were used to investigate the 3D impact of tropical waves on dust and thermodynamics over Cape Verde. The distinct contributions of Kelvin waves, ER, and MRG-TD were isolated using frequency-wave number filtering of Total Column Water Vapor (TCWV). The latter was efficiently split into southern and northern-track African Easterly Waves using distinct frequency windows (respectively MRG-TD1 and MRG-TD2) and enabled us to demonstrate their distinct horizontal structures and impacts. ER waves mainly impacted thermodynamics above 750 hPa, MRG-TD1 affected jet-level thermodynamics, and MRG-TD2 modulated moisture in the lower troposphere. MRG-TD2 was identified as the main driver of dust events over Cape Verde in September 2021. Tropical cyclogenesis was linked to interactions among multiple tropical waves. Notably, a delay of up to 2 days was observed between Kelvin wave interactions with MRG-TD1 and cyclone formation, consistent with previous findings. These results highlight the critical role of tropical wave interactions in cyclogenesis and underscore their potential for improving forecasting
Workshop: Development of an Analytical Framework for FOGOS
No full textInternational audienceThis workshop set out to sketch the basic topology of the problem of future oriented space governance. It established the basic parameters of the problem which will later be put into play in the other work done by the FOGOS project
Enhancing Epoxy Nanocomposites for High‐Impact Applications: Dynamic Performance of Carbon Black‐Reinforced DGEBA Under SHPB Testing
No full textInternational audienceABSTRACT This study presents a novel investigation into the dynamic mechanical behavior of epoxy nanocomposites reinforced with carbon black (CB) nanoparticles. While the static mechanical enhancement of DGEBA epoxy by CB has been widely reported, its performance under high strain rate loading remains insufficiently explored. To address this gap, epoxy nanocomposites containing 1, 2, and 5 wt.% CB were fabricated and tested using a Split Hopkinson Pressure Bar (SHPB) at impact pressures of 1.5, 2, and 4 bar. The results demonstrate that a 1 wt.% CB concentration provides the best balance of stiffness, strength, and toughness without compromising elasticity. At this level, the material exhibited a 60% increase in maximum stress and a 50.8% increase in toughness compared to neat epoxy at 1.5 bar. In contrast, 5 wt.% CB led to nanoparticle agglomeration, reducing energy absorption and elastic recovery. Scanning Electron Microscopy (SEM) and numerical simulations confirmed the influence of CB dispersion on mechanical performance. This work contributes a comprehensive understanding of CB‐reinforced epoxy systems under dynamic loading, offering new insights for advanced structural applications requiring impact resistance
Prediction of compatibility and chemical structure influencing plasticization of poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3HB4HB)
No full textInternational audienceThis study aims to predict the plasticization of poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3HB4HB) using two theoretical approaches: polymer-plasticizer compatibility via Hansen solubility parameters, and the chemical structure of polymers through the prediction of the entanglement molecular weight (M e ) based on Van Krevelen's method. Hansen solubility parameters were calculated for three P3HB4HB copolymers with varying 4HB molar contents (10 %, 15 % and 30 %), allowing for the identification of potentially compatible plasticizers. In parallel, M e was theoretically predicted and compared to experimental rheological measurements. The discrepancies observed highlight the significant influence of crystallinity, particularly the size and distribution of spherulites, on the viscoelastic behavior of the materials. The transition to the rubbery plateau, analyzed through oscillatory rheology, confirmed the decisive role of the semi-crystalline structure in governing polymer chain mobility. This dual approach, combining chemical modeling and experimental validation, provides a deeper understanding of the plasticization mechanisms of P3HB4HB. It represents a valuable tool for guiding the formulation of more efficient bio-based materials tailored to industrial requirements
Solutions analytiques pour le flambement élastoplastique de réservoirs cylindriques sous pression externe en présence de défauts
No full textInternational audienceSolutions analytiques pour le flambement élastoplastique de réservoirs cylindriques sous pression externe en présence de défaut
Radar Cross Section and Micro-Doppler Simulation of Offshore Wind Turbines in X-Band
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3D Diver Positioning in Water Column Using Mills Cross Sonar
No full textInternational audienceIn typical configurations, 2D forward-looking sonars (FLS) use a wide vertical beam that compresses elevation into a single plane, providing only a horizontal slice of the scene. This limits 3D localization accuracy, especially for stealthy underwater targets moving in depth, such as divers and Autonomous Underwater Vehicles (AUVs). This paper presents a novel framework for 3D localization of underwater targets using the Seapix-L sonar system configured in a dual-view from a Mills Cross antennas arrangement. The proposed system incorporates ping-to-ping time-averaging to improve the signal-to-noise ratio (SNR), a Constant False Alarm Rate (CFAR) detector to ensure consistent detection thresholds, and DBSCAN clustering to aggregate detections into coherent targets. A 3D Kalman filter fuses information from both sonar views, yielding robust and precise target localization. Experimental validation in real-world underwater scenarios confirms the effectiveness of the proposed method, demonstrating its potential to enhance situational awareness and security in maritime environments. The implications of this research extend to applications such as maritime infrastructure protection and environmental monitoring
Optimization and Multi-Model Approaches for Maximizing Ship Decarbonization
No full textInternational audienceAligned with the International Maritime Organization's (IMO) aim to lower greenhouse gas emissions, the use of Wind-Assisted Ship Propulsion (WASP) in maritime transport is gaining increased attention. The study and optimization of WASP remain challenging due to complex physics and the high number of parameters involved. This includes interactions between aerodynamics, hydrodynamics, and structural dynamics, which require advanced multi-physics modeling. Additionally, numerous factors must be optimized, from design and control parameters to route selection, all within the variable maritime environment. Addressing these challenges demands multi-model approaches and multi-criteria optimization methods to maximize energy efficiency effectively. In this context, the laboratories of Ecole Navale, IFREMER, ENSM, and ENSTA Bretagne are collaborating on several research projects, with a selection of two thematic studies presented here.The first study is carried out as part of the SHIVA and SAWASP projects, jointly led by Ecole Navale, IFREMER and ENSTA Bretagne. The goal of these projects is to optimize the hydrodynamic performance of innovative, fully electric, Vertical-Axis Propellers (VAPs) and their optimal use in conjunction with a wind-assisted ships. To achieve this, the SHIVA project implements a multi-criteria optimization of the propeller blade-pitching laws, utilizing multi-fidelity numerical and experimental surrogate models. These optimizations enable the determination of a set of optimal pitch laws for different operating points of the propeller. In the SAWASP project, a 6-meter wind-assisted ship equipped with VAPs is developed to study the optimal aerodynamic-hydrodynamic coupling. In particular, the energy gains from using VAPs as the main propulsion system, generating a lateral anti-drift force, are studied. The use of Reinforcement Learning (RL) methods to maintain optimal ship operation performance at sea, as an uncertain environment, is also part of this project.The second study is conducted within the framework of the SOMOS project, jointly managed by ENSM and ENSTA Bretagne. The project's goal is to create and validate a set of numerical tools, that allow for rapid and precise assessment of the energy efficiency of wind-assisted ships. For the purposes of this study, a modular and comprehensive ship motion solver is formulated as an optimal control optimization problem, to evaluate, compare, and optimize energy performance. Such an approach is very complex to implement and, depending on the fidelity-level used, may require very high modeling costs. This is why most research efforts focus on specific aspects of the broader problem, often overlooking the coupling of maritime routing, ship motion analysis, and the optimization of control parameters along the planned sea route. The present work provides an innovative approach for the calculation of optimized trajectories for wind-assisted ship, by both considering the ship's maneuvering capabilities and the optimization of ship control and/or design parameters. In contrast to conventional routing methods, the proposed approach achieves high computational efficiency and relies on direct multiple shooting methods to determine optimal ship control parameters (RPM, rudder angle, etc.) and design variables (rotor Flettner or sail positioning, rudder area, etc.) along the sea route, satisfying the constraints of complying with the ship's equations of motion
