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A new methodology for solving fuzzy systems of equations: Thick fuzzy sets based approach
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Durabilité de connecteurs collés soumis à des sollicitations de fluage pour des applications navales
No full textIn a context of sobriety, it is necessary to extend the lifespan of existing structures to limit energy and resources consumption. They must also be adapted to new constraints unanticipated at their initial design. In these situations, structural reinforcement and fastening solutions are needed. In the case of metallic structures, most of these solutions rely on classic assembly techniques, such as welding, riveting, and drilling. These methods have a wide range of feedbacks but induce damage in the structure and can require hot work. To address this issue, Cold Pad has developed a bonded fastener C-Claw™ whose creates new anchor points on an existing structure. The durability of an assembly must be studied according to several aspects, including environmental (humidity, temperature, …) and mechanics (fatigue, creep, …) effects that can be combined. Regarding this issue, creep seems to be the main phenomena that needs to be considered during the design of the bonded fastener C-Claw™.This thesis work aims at understanding creep of bonded assemblies and to study different design strategies regarding creep phenomenon. A literature review enabled to establish an assessment of knowledge of the creep phenomenon on bonded assemblies. This study justified the followed approach to analyse the behaviour of bonded assemblies. A first design strategy relies on experimental investigations carried out on the bonded fasteners C-Claw™. An inverse identification method was developed to determine the creep parameters of the assembly, then applied to all the tests on bonded fasteners. This approach at the structure scale was compared to a creep analysis on adhesive joints. To perform experimental investigations, specific testing adapted to the Arcan TCS test resources were designed. The influence of several parameters on the creep behaviour of the adhesive joint was studied. This analysis allowed to model the creep behaviour of the adhesive joint considering the more relevant parameters, first with a uniaxial approach,then multiaxial. Then, the different studied strategies of design regarding creep were evaluated. The confrontation of the two strategies highlighted a divergence of the results, raising several prospects.Dans un contexte de sobriété, il est nécessaire de prolonger la durée de vie des structures existantes pour limiter la consommation d’énergie et de ressources. Elles doivent également pouvoir s’adapter à de nouvelles contraintes non prévues lors de leur dimensionnement initial. Dans ces deux situations, les maîtres d’ouvrage ont besoin de solutions de renforcement structurel ou de fixation. Dans le cas des structures métalliques, la plupart de ces solutions reposent sur des techniques d’assemblage classiques, i.e., le soudage, le rivetage ou le perçage. Ces méthodes disposent d’un retour d’expérience conséquent, mais impliquent des travaux invasifs et parfois à chaud. Pour répondre à ce problème, Cold Pad a développé un connecteur C-Claw™ assemblé par collage qui permet de créer de nouveaux points d’ancrage sur une structure. La durabilité d’un assemblage doit être étudiée selon plusieurs aspects, notamment environnemental (humidité, température, …) et mécanique (fatigue, fluage, …) dont les effets peuvent être combinés. Vis-à-vis de cette problématique, le fluage semble être le phénomène principal à étudier lors de la conception du connecteur collé C-Claw™. Les travaux de cette thèse ont pour objectif de mieux appréhender le fluage des assemblages collés et d’étudier différentes stratégies de dimensionnement vis-à-vis de ce phénomène. Une étude bibliographique a permis d’établir un bilan sur les connaissances du fluage des assemblages collés. L’ensemble de cet état de l’art a justifié la démarche à suivre pour analyser le comportement des connecteurs collés. Une première stratégie de dimensionnement repose sur des essais réalisés avec les connecteurs collés C-Claw™. Une méthode d’identification inverse spécifique a été développée pour déterminer les paramètres de fluage de l’assemblage, puis appliquée à l’ensemble des essais sur connecteurs. Cette approche à l’échelle de la structure a été comparée à une analyse en fluage à l’échelle du joint de colle. Pour cela des moyens d’essais spécifiques à l’essai Arcan TCS en fluage ont été conçus. L’influence de plusieurs paramètres sur le comportement en fluage du joint de colle a été étudiée grâce à ces moyens d’essais. Cette analyse a permis de modéliser le comportement en fluage du joint de colle en considérant les paramètres les plus pertinents, d’abord selon une approche uniaxiale, puis multiaxiale. Enfin, les différentes stratégies étudiées de conception vis-à-vis du fluage seront évaluées. La confrontation des deux stratégies a mis en évidence une divergence des résultats, soulevant plusieurs perspectives d’étude
Predict alone, decide together: cardiac abnormality detection based on single lead classifier voting
No full textInternational audienceAbstract Objective . A classifier based on weighted voting of multiple single-lead based models combining deep learning (DL) representation and hand-crafted features was developed to classify 26 cardiac abnormalities from different lead subsets of short-term electrocardiograms (ECG). Approach . A two-stage method was proposed for the multilead prediction. First a lead-agnostic hybrid classifier was trained to predict the pathologies from single-lead ECG signals. The classifier combined fully automated DL features extracted through a convolutional neural network with hand-crafted features through a fully connected layer. Second, a voting of the single-lead based predictions was performed. For the 12-lead subset, voting consisted in an optimised weighting of the output probabilities of all available single lead predictions. For other lead subsets, voting simply consisted in the average of the lead predictions. Main results . This approach achieved a challenge test score of 0.48, 0.47, 0.46, 0.46, 0.45 on the 12, 6, 4, 3, 2-lead subsets respectively on the 2021 Physionet/Computing in Cardiology challenge hidden test set. The use of an hybrid approach and more advanced voting layer improved some individual class classification but did not offer better generalization than our baseline fully DL approach. Significance . The proposed approach showed potential at correctly classifying main cardiac abnormalities and dealt well with reduced lead subsets
Porous Composite Nanomaterials based on MOFs for green Hydrogen Production by Photocatalysis,
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Etat de l’Art du Stockage de l’Hydrogène: du Stockage Liquide au Stockage Solide en passantpar le Stockage Gazeux sous Pression
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Synthesis of Bio-Inspired 1,3-Diarylpropene Derivatives via Heck Cross-Coupling and Cytotoxic Evaluation on Breast Cancer Cells
No full textInternational audienceThe Heck cross-coupling reaction is a well-established chemical tool for the synthesis of unsaturated compounds by formation of a new C-C bond. In this study, 1,3-diarylpropene derivatives, designed as structural analogues of stilbenoids and dihydrostilbenoids, were synthesised by the palladium-catalysed reactions of 2-amidoiodobenzene derivatives with either estragole or eugenol. The products were obtained with high (E) stereoselectivity but as two regioisomers. The ratios of isomers were found to be dependent on the nature of the allylbenzene partner and were rationalised by electronic effects exercising a determining influence in the β-hydride elimination step. In addition, the cytotoxic effects of all the Heck reaction products were evaluated against MCF-7 and MDA-MB-231 human breast cancer cells, with unpromising results. Among all, compound 7d exhibited weak cytotoxic activity towards MCF-7 cell lines with IC50 values of 47.92 µM in comparison with tamoxifen and was considered to have general toxicity (SI value < 2)
Direct observation of relativistic broken plasma waves
No full textInternational audiencePlasma waves contribute to many fundamental phenomena, including astrophysics, thermonuclear fusion and particle acceleration. Such waves can develop in numerous ways, from classic Langmuir oscillations carried by electron thermal motion, to the waves excited by an external force and travelling with a driver. In plasma-based particle accelerators, a strong laser or relativistic particle beam launches plasma waves with field amplitude that follows the driver strength up to the wavebreaking limit, which is the maximum wave amplitude that a plasma can sustain. In this limit, plasma electrons gain sufficient energy from the wave to outrun it and to get trapped inside the wave bucket. Theory and numerical simulations predict multi-dimensional wavebreaking, which is crucial in the electron self-injection process that determines the accelerator performances. Here we present a real-time experimental visualization of the laser-driven nonlinear relativistic plasma waves by probing them with a femtosecond high-energy electron bunch from another laser-plasma accelerator coupled to the same laser system. This single-shot electron deflectometry allows us to characterize nonlinear plasma wakefield with femtosecond temporal and micrometre spatial resolutions revealing features of the plasma waves at the breaking point
Stable and high quality electron beams from staged laser and plasma wakefield accelerators
No full textInternational audienceWe present experimental results on a plasma wakefield accelerator (PWFA) driven by high-current electron beams from a laser wakefield accelerator (LWFA). In this staged setup stable and high quality (low divergence and low energy spread) electron beams are generated at an optically-generated hydrodynamic shock in the PWFA. The energy stability of the beams produced by that arrangement in the PWFA stage is comparable to both single-stage laser accelerators and plasma wakefield accelerators driven by conventional accelerators. Simulations support that the intrinsic insensitivity of PWFAs to driver energy fluctuations can be exploited to overcome stability limitations of state-of-the-art laser wakefield accelerators when adding a PWFA stage. Furthermore, we demonstrate the generation of electron bunches with energy spread and divergence superior to single-stage LW-FAs, resulting in bunches with dense phase space and an angular-spectral charge density beyond the initial drive beam parameters. These results unambiguously show that staged LWFA-PWFA can help to tailor the electron-beam quality for certain applications and to reduce the influence of fluctuating laser drivers on the electron-beam stability. This encourages further development of this new class of staged wakefield acceleration as a viable scheme towards compact, high-quality electron beam sources
Multiple-Photon Resonance Enabled Quantum Interference in Emission Spectroscopy of N_2^+
No full textInternational audienceQuantum interference occurs frequently in the interaction of laser radiation with materials, leading to a series of fascinating effects such as lasing without inversion, electromagnetically induced transparency, Fano resonance, etc. Such quantum interference effects are mostly enabled by single-photon resonance with transitions in the matter, regardless of how many optical frequencies are involved. Here, we demonstrate quantum interference driven by multiple photons in the emission spectroscopy of nitrogen ions that are resonantly pumped by ultrafast infrared laser pulses. In the spectral domain, Fano resonance is observed in the emission spectrum, where a laser-assisted dynamic Stark effect creates the continuum. In the time domain, the fast-evolving emission is measured, revealing the nature of free-induction decay (FID) arising from quantum radiation and molecular cooperativity. These findings clarify the mechanism of coherent emission of nitrogen ions pumped with MIR pump laser and are likely to be universal. The present work opens a route to explore the important role of quantum interference during the interaction of intense laser pulses with materials near multiple photon resonance
Plasma photonic spatiotemporal synchronization of relativistic electron and laser beams
No full textInternational audienceWe present an ultracompact plasma-based method to measure spatial and temporal concurrence of intense electron and laser beams nonintrusively at their interaction point. The electron beam couples with a laser-generated seed plasma in dependence of spatiotemporal overlap, which triggers additional plasma production and manifests as enhanced plasma afterglow. This optical observable is exploited to measure beam concurrence with ∼4 μm spatial and ∼26.7 fs temporal accuracy, supported by auxiliary diagnostics. The afterglow interaction fingerprint is highly sensitive and enables ultraversatile femtosecond-micrometer beam metrology