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Numerical simulation of the oblique water impact of double curvature bodies involving suction and cavitation phenomena
No full textInternational audienceThe present study aims to assess the capability of a numerical method to model hydrodynamicimpacts representative of an aircraft ditching. The considered numerical method is based onthe Finite Element explicit solver Radioss and a Coupled Eulerian–Lagrangian approach. Thefluid–structure interaction is dealt with using an immersed contact interface and a penaltycoupling method. The oblique water impacts of three different fuselage sections have beenstudied based on the experimental campaigns carried out during the European project SARAHat the High-Speed Ditching Facility of CNR-INM in Rome, Italy. The results are presented interms of force coefficient, local relative pressure, and free surface elevation. The effect of thecoupling stiffness and size of the fluid elements on the numerical results is analysed to assessthe robustness of the numerical method. The numerical method shows a satisfying capabilityto reproduce most of the experimental results. Particular attention is given to the capabilityof the numerical method to describe the suction and cavitation phenomena. The effect of thespecimens’ transversal cross-section, the specimens’ longitudinal curvature and the developmentof cavitation phenomenon on the hydrodynamic loads are also investigate
Dissemination of Carbapenemases in Gram-negative Bacteria in Brazilian Hospitals: A Review
No full textInternational audienceAntimicrobial resistance in bacteria with carbapenemase activity is a growing public health problem of global proportions. This integrative review synthesizes data from 26 scientific articles published between 2020 and 2024 to analyze the dissemination and genetic diversity of carbapenemases in Brazil. Data were retrieved from the National Library of Medicine (PubMed) and the regional portal of the Virtual Health Library (BVS). The review highlights significant regional variability in carbapenemase prevalence, with the blaKPC gene being the most frequently identified resistance mechanism across multiple Brazilian states. The identification of novel trends, including the simultaneous presence of blaNDM and blaKPC genes in isolates of Proteus mirabilis and Serratia marcescens, in addition to the observation of blaNDM in Klebsiella aerogenes, highlights the intricate nature of antimicrobial resistance patterns. The state of Pernambuco is notable for reporting the first identification of blaVIM-2 in Acinetobacter baumannii and the blaOXA-23-like and blaOXA-143 genes. These findings emphasize the widespread cohabitation of resistance genes, with mobile genetic elements facilitating intra- and interspecies transfer among Gram-negative bacilli. Understanding this genetic diversity is crucial for developing targeted public health interventions. The study underscores the urgent need for enhanced genomic surveillance, robust infection prevention measures, and strengthened antimicrobial stewardship programs to address the growing threat of multidrug-resistant organisms in Brazil and mitigate their impact on global health
How scientific networks can help advancing both scientific knowledge and public policies: the case study of the “Plastics, Environment and Health” network
No full textInternational audienceThe “Plastics, Environment and Health” research network (groupement de recherche, GDR) created in 2019 gathers the French scientific community working on plastic pollution in all environments (soil, air, water) and their impact on ecosystems and human health. The scientific objective is to rapidly increase knowledge on plastic pollution by supporting collaboration of researchers from different fields such as ecotoxicology, chemistry, physics, microbiology, oceanography and social science. Research is carried out at each stage of the plastic life cycle, (from resource extraction all the way to removal and remediation) and across the entire air-soil-water continuum, integrating transfers of both plastic particles (macro, micro- and nanoplastics) and plastic chemicals (e.g., additives) between different environmental compartments. In this context, the GDR supports the development of multi-scale and transdisciplinary approaches across three main axes: Axis 1 - Air-soil-water continuum: contamination levels and transfer between compartments; Axis 2 - Interactions and transformation of plastics in environmental compartments and living organisms; Axis 3. Plastic pollution risk assessment for ecosystems and human health. To do so, the GDR’s actions focus on (1) training and sharing of scientific knowledge, including developments towards innovation, (2) support for collaboration and interdisciplinarity between network members, (3) dissemination, structuring of the community and its national and international influence, and (4) support for public policy and/or decision-making by strengthening the link between scientists, decision-makers and the plastic industry. To date the research network includes more than 50 laboratories spread across France and over 300 scientists in the field of physics, chemistry, biology, ecology and social sciences. Such a network constitutes a powerful tool to build robust science-based knowledge significantly contributing to the international effort, to disseminate state-of-the-art scientific advances and research priorities needed to tackle plastic pollution to Society and to inform policy makers. This talk will present the French taskforce addressing 'Plastic, Environment, and Health' within the national research network, where the entire community works collaboratively to tackle the urgent challenges of plastic pollution, its environmental consequences, and the associated risks to human health. We will also discuss the importance of building a French-speaking community to support multilingualism in international political science interactions
Fatigue crack closure assessment by wavelet transform of infrared thermography signals
No full textInternational audienceThe occurrence of crack closure significantly impacts the fatigue life of materials and structural components. Whether it is induced by the nature of the loading, the fabrication process or the geometry of the structure, its magnitude and effect should be considered to further improve predictive models of fatigue crack propagation. However, the definition of reliable experimental methods for the observation and assessment of fatigue crack closure, and in particular suited to structure testing, remains a challenge. The present study aims to provide a novel approach for the assessment of fatigue crack closure via the continuous wavelet transform of infrared thermography data. The processing of the temperature signal close to the crack in a coherent time-frequency space allows for the identification of crack closing and opening instants associated with high-frequency components. The method is meant to be suited to any testing configuration (conventional compact tension specimen or full-scale structures) with minimum operator-dependent parameters
Bow Echo Alarm System Using Topological Data Analysis
No full textInternational audienceThis study focuses on the extremely severe storm system swept across Corsica early in the morning of August 18, 2022. A derecho refers to thunderstorm episodes that are distinguished by the production of particularly long-lasting, strong and widespread downbursts, generated by an extratropical mesoscale convective system (MCS). The associated radar signatures generally exhibit linear characteristics, with arcuate portions (bow echo).This work studies in particular the life cycle of the bow echo that appeared off the coast of Corsica and caused significant damage on the island as well as victims including five deaths. The bow echo is an exceptional phenomenon that is very difficult to predict because it is very localized. Beyond qualitative observations, methods for detecting the shape of a bow echo from radar images have been studied. We present an alternative method for characterising the bow echo shape using a promising tool based on topological data analysis (TDA) and the measurement of the curvature of the cloud. The use of homological persistence from TDA allows to follow the evolution of the bow echo from its initiation to its maturation just before it hits the Corsican coast. Curvature and persistent homology calculation with the stability property of Wasserstein and Bottleneck distances allows us to detect changes between evolutionary phases. The main idea is to exploit TDA on radar images of this bow echo in order to generate an alert. TDA is one of these new mathematical tools that will help characterize the event.</div
FedShip: Federated Learning for Ship Detection From Multi-Source Satellite Images
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Dissemination of antibiotic-resistant bacteria associated with microplastics collected from Monastir and Mahdia coasts (Tunisia)
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Synchronization of Kuramoto oscillators via HEOL, and a discussion on AI
No full textInternational audienceArtificial neural networks and their applications in deep learning have recently made an incursion into the field of control. Deep learning techniques in control are often related to optimal control, which relies on the Pontryagin maximum principle or the Hamilton-Jacobi-Bellman equation. They imply control schemes that are tedious to implement. We show here that the new HEOL setting, resulting from the fusion of the two established approaches, namely differential flatness and model-free control, provides a solution to control problems that is more sober in terms of computational resources. This communication is devoted to the synchronization of the popular Kuramoto's coupled oscillators, which was already considered via artificial neural networks by L. Bttcher et al. (Nature Commun., 2022), where, contrarily to this communication, only the single control variable case is examined. One establishes the flatness of Kuramotos coupled oscillator model with multiplicative control and develops the resulting HEOL control. Unlike many examples, this system reveals singularities that are avoided by a clever generation of phase angle trajectories. The results obtained, verified in simulations, show that it is not only possible to synchronize these oscillators in finite time, and even to follow angular frequency profiles, but also to exhibit robustness concerning model mismatches. To the best of our knowledge that has never been done before. Concluding remarks advocate a viewpoint, which might be traced back to Wiener's cybernetics: control theory belongs to AI
Etude expérimentale de la cristallisation sous tension dans un caoutchouc naturel chargé
No full textInternational audienceLa modélisation de la cristallisation induite mécaniquement (MIC) est essentielle pour la conception de pièces antivibratoires en caoutchouc, mais le comportement viscoélastique de ces matériaux complique la compréhension des cinétiques de cristallisation. Ces travaux étudient un caoutchouc naturel chargé à travers des essais de traction, à différentes vitesses, et un essai anhystérétique (ANH) combinant des paliers statiques et monotones. Une analyse systématique du triplet {déformation, contrainte, indice de cristallinité}, appuyée par des mesures synchrotron in-situ, met en lumière les cinétiques de cristallisation ainsi que l’influence de l’histoire du chargement sur celle-ci