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International audience; Comme toute technologie le radar évolue et fait face à de nombreuses problématiques (management de spectre, traitement du clutter, amélioration de la résolution, ...). Cela conduit à la création et l'optimisation de nouvelles formes d'ondes conjointement à leur traitement. Pour y parvenir, nous avons orienté notre étude sur des signaux bio-inspirés de ceux des chauvessouris et observé les avantages potentiels à utiliser de telles formes d'ondes. Cet article présente une comparaison entre des formes d'ondes dites classiques en radar et une autre bio-inspirée en analysant notamment leurs réponses à un traitement usuel. La modélisation de cette forme d'onde bio-inspirée permet de comparer plusieurs stratégies de modulation fréquentielle au sein d'une impulsion. Les bornes de Cramér-Rao sont calculées afin de quantifier les capacités d'estimation en retard et Doppler de chaque forme d'onde.

It is well known that acoustical factors explain only partly the human perception of aircraft noise. In order to truly understand annoyance ratings, acoustical and non-acoustical factors have to be taken into consideration, making it often complex to analyze studies that treat only one side of the issue. While field studies give a good insight of long-term annoyance in realistic living conditions, laboratory tests are commonly used as means to understand the impact of acoustic factors on noise annoyance and unpleasantness while usually smoothing inter individual differences. A French project (CIGALE) has set a goal of creating a frame of reference making it possible to include non-acoustical factors into laboratory studies. After an extensive field study and focus groups in the first part of the project resulting in six different profiles of residents, the second part comprises a vast laboratory test campaign in Toulouse and Paris region aiming at evaluating the impact of these profiles on the perception of two common acoustical factors in an ecological experimental setup. Overall more than 300 residents of the Toulouse Blagnac airport area and the Roissy Charles de Gaulle airport area participated in the CIGALE listening test. Participants were asked to read novels while seated in a listening room with a 3D audio simulation of an everyday soundscape. They were asked to rate their perception of four 15 minutes sequences randomly presented in which the number of aircraft flyovers and the maximum A-weighted sound level of each flyover were varied. Four different scales were used: task interference, mental effort, annoyance and comfort. The results support the hypothesis that profile type and noise sensitivity have an impact on annoyance ratings. The collected data also highlighted different response strategies regarding acoustical factors that need to be further investigated., Il est bien connu que les facteurs acoustiques n'expliquent qu'en partie la perception humaine du bruit des avions. Afin de bien comprendre une évaluation de gêne, les facteurs acoustiques et non acoustiques doivent être pris en compte, ce qui rend souvent complexe l'analyse d'études qui ne traitent qu'un aspect du problème. Alors que les études sur le terrain donnent un bon aperçu de la gêne à long terme dans des conditions de vie réalistes, les tests en laboratoire sont couramment utilisés pour comprendre l'impact des facteurs acoustiques sur la gêne et le désagrément liés au bruit, tout en atténuant généralement les différences interindividuelles. Un projet français (CIGALE) s'est fixé pour objectif de créer un référentiel permettant d'intégrer des facteurs non acoustiques dans les études en laboratoire. Après une vaste étude de terrain et des ateliers participatifs dans une première partie du projet aboutissant à six profils d'habitants différents, la seconde partie comprend une vaste campagne de tests en laboratoire à Toulouse et en région Parisienne visant à évaluer l'impact de ces profils sur la perception de deux facteurs acoustiques communs dans un montage expérimental écologique. Au total plus de 300 habitants de la région aéroportuaire de Toulouse Blagnac et de celle de Roissy Charles de Gaulle ont participé au test d'écoute CIGALE. Les participants ont été invités à lire des romans assis dans une salle d'écoute avec une simulation audio 3D d'un paysage sonore représentant une situation sonore rencontrée au quotidien. On leur a demandé d'évaluer leur perception de quatre séquences sonores de 15 minutes présentées au hasard dans lesquelles le nombre de survols d'aéronefs et le niveau sonore maximal de chaque survol étaient modifiés. Quatre échelles différentes ont été utilisées : l'interférence sur la tâche, l'effort mental, la gêne et le confort. Les résultats soutiennent l'hypothèse selon laquelle le type de profil et la sensibilité au bruit ont un impact sur les notations de gêne. Les données collectées ont également mis en évidence différentes stratégies de réponse concernant les facteurs acoustiques qui doivent être étudiées plus en détail.

International audience; The present work studies the mechanism of tonal slat noise generation in high-lift devices. Peaks in the emitted noise spectrum are observed for small-scale geometries with various slat configurations. They are attributed to a feedback mechanism in the slat cove similar to that in cavity flows. The objective of this study is to characterize the flow structures which are at the origin of this tonal noise, and future work may focus on investigating the effect of the flow parameters (Reynolds number, Mach number, angle of attack) on its generation. To this end, a 2-element airfoil composed of a slat and a main body is considered. This geometry is designed to isolate slat noise from other possible sources while providing a flow representative of a realistic 3-element airfoil near the slat. The coherent structures involved in the tonal noise are then identified from high-fidelity unsteady CFD data using Spectral Proper Orthogonal Decomposition (SPOD). The present work reveals that the obtained structures show good agreement with the recent paper of Himeno et al. (JFM 2021). In addition to the midrange frequencies, which are classically associated with the loop feedback mechanism, the analysis also reveals a high-frequency mode whose structure is concentrated in the wake of the upper slat trailing edge.; La présente activité étudie le mécanisme de génération de bruit de bec tonales dans les dispositifs hypersustentateurs. Des pics dans le spectre de bruit émis sont observés pour des géométries à petite échelle avec diverses configurations de becs. Ils sont attribués à un mécanisme de rétroaction dans la cavité similaire à celui des écoulements en cavité ouverte. L'objectif de cette étude est de caractériser les structures d'écoulement qui sont à l'origine de ce bruit tonal, et des travaux futurs pourraient se concentrer sur l'étude de l'effet des paramètres d'écoulement (nombre de Reynolds, nombre de Mach, angle d'attaque) sur sa génération. A cet effet, une voilure à 2 éléments composée d'un bec et d'un corps principal est considérée. Cette géométrie est conçue pour isoler le bruit du bec des autres sources possibles tout en fournissant un écoulement représentatif d'un profil aérodynamique réaliste à 3 éléments près du bec. Les structures cohérentes impliquées dans le bruit tonal sont ensuite identifiées à partir de données CFD instationnaires haute fidélité à l'aide de la décomposition spectrale en mode propre (SPOD). Les pics observées dans le spectre champ lointain sont également identifiées dans le spectre SPOD. Les structures de mode SPOD aux fréquences des raies montrent un bon accord avec le mécanisme de génération de bruit de bec identifié dans la littérature.

International audience; In the context of airplane structures monitoring, the performance of an embedded SHM system for composite material components is studied. The present article focuses on the influence of the PZT transducers integration on the Lamb waves it generates. First the article presents finite element modeling of Lamb waves generation in a carbon/epoxy plate, either with surface mounted or with embedded PZT transducer. Ultrasonic wavefield simulated in both configurations are compared. Experiments are also performed on composite laminates with embedded or surface mounted PZT. The out-of-plane displacement induced by PZT excitation on the plate surface is measured by Laser Doppler Vibrometry in both configurations. Out-of-plane displacements are compared together.

International audience; This work presents an actuator disk-like body force method designed for propeller modeling, which is based on a full coupling between Computational Fluid Dynamics (CFD) and Blade Element Theory (BET). An analysis is conducted on the model to identify best practices for source term distribution. It is found that the source term volume shape has no impact on propeller loads and flow field, and that the velocities used for the BET analysis at each radial section should be evaluated exactly where half the source terms have been distributed in the CFD domain. Four tip-loss corrections, including two from literature, are also analyzed and compared to lifting-line and CFD blade-resolved computations. The best practices and the most effective tip-loss correction lead to a final model that is evaluated for different pitch angles and incidence angles, on ONERA's HAD-1 three-bladed light propeller. The RANS/BET body force model predicts thrust within 3% for axial flow and 8% for cases with incidence. The same accuracy is obtained for wake prediction.; Ce travail présente une méthode de modélisation d’hélices par termes sources appelée RANS/BET. Elle est basée sur un couplage complet entre CFD et Blade Element Theory. Une analyse est menée sur le modèle afin d'identifier les meilleures pratiques pour la distribution des termes source. Les résultats montrent que la forme du volume dans lequel les termes sources sont répartis n’a pas d'impact sur les charges de l'hélice et sur les champs de vitesse dans le sillage, et que les vitesses utilisées pour l'analyse BET doivent être évaluées exactement là où la moitié des termes sources ont été distribués dans le domaine CFD. Quatre corrections de bout de pale, dont deux provenant de la littérature, sont également analysées et les résultats sont comparés à des calculs ligne-portante et CFD pales maillées. Le modèle est évalué pour différents angles de calage et d'incidence, sur l'hélice légère tripale ONERA HAD-1. Le modèle RANS/BET prédit la poussée hélice avec un écart de 3 % pour l'écoulement axial et de 8 % pour les cas avec incidence. La même précision est obtenue pour la prédiction des champs de vitesse du sillage.

International audience; Useful parameterisations of shapes for engineering models often climb from many tens to a few hundreds design variables, potentially jeopardising usual optimisation techniques. Surrogate models are intractable when parameter numbers exceed a few tens, and gradient descent through adjoint computation in high-dimension is threatened by potential multimodality. Dimension reduction addresses these problems nicely. This paper aims to improve upon the Active Subspaces dimension reduction method by applying a combination of active subspaces in subregions of the design space, where their use of the objective function’s gradients will exploit useful local information to discover specific trends instead of trying to identify global trends over an entire design space. The partitioning of the input space is done through Gaussian Mixture Model clustering, where the authors assume the distribution of the joint inputs/outputs to be a mixture of Gaussians. This GMM clustering is used to drive a Support Vector Machines (SVM) based supervised classifier. The SVC classifier’s margin (the maximal separation distance between points of different clusters) is chosen using cross validation in order to set an optimal width for the overlapping zones. The use of overlapping increases prediction accuracy at the boundaries between clusters, an improvement over recombination methods typically found in the literature. The local expert of choice is Kriging, in part due to its built-in variance prediction.

International audience; This paper presents a comparison among efficient techniques for uncertainty quantification on the RAE2822 airfoil whose shape is affected by uncertain geometrical parameters. Transonic conditions are considered with focus on estimating the statistics of the aerodynamic coefficients predicted by RANS simulations and using a far-field drag analysis of the computed flow field. Generalized polynomial chaos expansion with least-square approximation is employed for stochastic surrogate modelling. Two different kind of approaches enabling the high-dimensionality of the uncertainty space are investigated: 'compressed sensing' through Least Angle Regression and Basis Pursuit Denoising methods, and the 'gradient enhanced' formulation of the least-square approach exploiting the adjoint capabilities of modern CFD solvers.; Cet article presente une comparaison de différentes techniques efficaces de quantification d'incertitudes sur le profil RAE2822 en condition transsonique, dont la forme est affectée par des incertitudes géométriques. Le focus porte sur l'estimation des moments statistiques des coefficients aérodynamiques par simulation RANS suivie d'une décomposition de trainée champ lointain. Une expansion basée sur les polynomes du chaos construite par la méthode des moindres carrés est ensuite utilisée pour construire un meta-modèle. Deux approches differentes permettant de traiter la grande dimension de l'espace des paramètres incertains sont étudiées : 'compress sensing' avec les méhodes Least Angle Regression et Basis Pursuit Denoising, et une formulation 'gradient augmentée' de l'approche moindres carrés qui exploite les capacités adjointes des solveurs CFD modernes.

International audience; Flow control consists in modifying a flow natural state in order to converge towards another state which is considered as favorable, as drag or noise radiation might be reduced. In this paper, open-loop flow control experiments are carried out on a subsonic open-cavity flow. In the case of unstable flow control, the control focus is brought onto the flow fluctuations modifications rather than modification of the mean flow properties. Therefore, the forcing flexibility using arbitrary signals and the forcing linearity are essential for such flow control cases. In that sense, a linear array of Micro Magneto-Electro-Mechanical Systems actuators has been implemented to perform open-loop flow control experiments on an open-cavity. The actuators are able to generate both quasi-steady and pulsed jets with linear behavior. We proved the microvalves efficiency to damp the cavity oscillations. The quasi-steady jets reached a reduction of 20 dB in the cavity fundamental amplitude sound pressure level. Pulsed jets enabled an additional cavity tone amplitude reduction, which depends on the pulsating frequency and on the forcing amplitude. These results are a first step towards the implementation of the closed-loop control of the open-cavity flow.

International audience; The tip gap region of an axial compressor rotor is the source of complex flows inducing losses and stability issues. Recent works have proven the ability of blowing high-speed jets in the tip region to improve the surge margin of an axial compressor stage with a narrow tip gap configuration. Nevertheless, the tip gap size can evolve during the compressor lifetime, possibly affecting its performance and operability. The objective is to evaluate the performance of an active flow control system on a compressor with different tip gap sizes. The present work is based on the single stage compressor CME2 located at the Laboratory of Fluid Mechanics of Lille and equipped with actuators blowing at the rotor tip leading edge. Configurations with two different values of the tip gap to chord ratio (0.6% and 2.4%) have been experimentally tested. RANS simulations have also been performed. The effect of tip gap sizes and of the tip-blowing is evaluated on the flow topology and compressor performance.; La région du jeu en extrémité d'aubes de rotor de compresseur est la source d'écoulements complexes à l'origine de pertes et d'instabilités. De récents travaux ont montré la capacité de jet fluidiques haute-vitesse à améliorer la marge au pompage d'un compresseur axial monoétagé, avec un jeu réduit. Néanmoins, la taille de jeu évolue au cours de la vie du compresseur. ce qui affecte ses performances et son domaine d'opérabilité. L'objectif est d'évaluer la performance d'un dispositif de contrôle actif pour différentes tailles de jeu, sur le compresseur CME2. Ce travail est basé sur le banc d'essais localisé au Laboratoire de Mécanique des Fluides de Lille, et équipé d'actionneurs soufflant à l'amont du bord d'attaque, en tête de rotor. Deux tailles de jeu ont été évaluées expérimentalement (0,6% et 2,4%) ainsi que numériquement à l'aide de simulations RANS. L'effet de la taille de jeu et de l'injection est évalué en termes de topologie d'écoulement et de performances du compresseur.

International audience; For high dimensional spaces, a randomized Gram-Schmidt (RGS) algorithm is beneficial in computational costs as well as numerical stability. We apply this dimension reduction technique by random sketching to Krylov subspace methods, e.g. to the generalized minimal residual method (GMRES). We propose a flexible variant of GMRES with the randomized Gram-Schmidt based Arnoldi iteration to produce a set of basis vectors of the Krylov subspace. Even though the Krylov basis is no longer l2 orthonormal, its random projection onto the low dimensional space shows l 2 orthogonality. As a result, it is observed the numerical stability which turns out to be independent of the dimension of the problem even in extreme scale problems. On the other hand, as the Harmonic Ritz values are commonly used in GMRES with deflated restarting to improve convergence, we consider another deflation strategy, for instance disregarding the singular vectors associated with the smallest singular values. We thus introduce a new algorithm of the randomized flexible GMRES with singular value decomposition (SVD) based deflated restarting. At the end, we carry out numerical experiments in the context of compressible turbulent flow simulations. Our proposed approach exhibits a quite competitive numerical behaviour to existing methods while reducing computational costs.

International audience; This study presents simulations and experiments on the effect of porous bleed systems on a supersonic turbulent boundary layer at a Mach number of M=1.6. The results indicate a good fit between the RANS simulations and the experiments based on LDV, BOS, and pressure measurements. The numerical simulations well capture the overall flow topology. Both approaches show the same trend of fuller profiles with higher suction rates. The findings suggest that RANS simulations can be used to investigate the effect of bleed systems for different bleed parameters to improve bleed models. Overall, this study provides valuable insights into the working principle of bleed systems, which are crucial for designing and optimizing supersonic air intakes.

International audience; The International Civil Aviation Organization (ICAO) needs to define standards for the advent of this new generation of supersonic aircrafts. In this context, the SENECA EU H2020 project aims at quantifying the NO x , H 2 O and contrails climate effects from supersonic aviation. 3D RANS contrails simulations are performed during the jet phase with a realistic supersonic aircraft configuration. A crucial step of the contrail simulation process related to the grid mesh optimization is described and analysed in this paper.

International audience; This paper presents the aerodynamic performance study of an isolated ultra-high bypass ratio turbofan engine. The performance assessment methodology relies on an exergy balance, computed using the ONERA FFX software on the basis of RANS CFD solutions. The study first investigates aspects associated with the computational strategy used to simulate engines of this type. This concerns in particular a grid convergence study and a comparison of different types of modelisation methods for the fan and OGV, in terms of the exergy balance. At a second step, an exergy-balance-based analysis of the engine is carried out at different operating conditions. This analysis allows the evaluation of the system's overall performance, while at the same time providing a phenomenological decomposition of mechanical/thermocompressible exergy outflows and the characterization of exergy losses due to irreversible effects.; Ce papier présente l'étude de la performance aérodynamique d'un moteur de type turbofan à très haut taux de dilution (UHBR = ultra-high bypass ratio). La méthodologie d'évaluation de la performance repose sur un bilan d'exergie, calculé en utilisant le logiciel FFX de l'ONERA sur la base de solutions CFD RANS. L'analyse concerne tout d'abord des aspects associés à la stratégie numérique utilisée pour la simulation de ce type de moteurs. Cela concerne en particulier une étude de convergence en maillage et une comparaison de différents types de méthodes de modélisation pour le fan et l'OGV, en termes du bilan d'exergie. Dans un deuxième temps, une analyse du moteur par bilan d'exergie est effectuée à différents points de fonctionnement. Cette analyse permet l'évaluation de la performance globale du système, tout en fournissant une décomposition phénoménologique des flux sortants d'exergie mécanique/thermocompressible et la caractérisation des pertes d'exergie à cause des effets irréversibles.

International audience; The MICROSCOPE mission tested the Weak Equivalence Principle (WEP) with an unprecedented precision of order 10−15, two orders of magnitude better than the previous best lab experiments. While the WEP, the cornerstone of General Relativity (GR), does not sway, the decade-long problems faced by fundamental physics stay still: how can we unify GR with the Standard Model, and how can we explain the acceleration of the cosmological expansion? As most beyond-GR models predict a violation of the WEP, albeit at an unknown level, it remains critical to even better test the WEP. In this paper, we review the MICROSCOPE mission, give its final constraint on the WEP, and build on its experimental limitations to show how we could improve them by a further two-order of magnitude in the precision of the test of the WEP.

International audience; This article presents a data-based methodology to build Reynolds-Averaged Navier-Stokes (RANS) wall models for aerodynamic simulations at low Mach numbers. Like classical approaches, the model is based on nondimensional local quantities derived from the wall friction velocity u τ , the wall viscosity µ w , and the wall density ρ w. A fully-connected neural network approximates the relation u + = f (y + , p +). We consider reference data (obtained with RANS simulations based on fine meshes up to the wall) of attached turbulent flows at various Reynolds numbers over different geometries of bumps, covering a range of wall pressure gradients. After training the neural networks on a subset of the reference data, the paper assesses their ability to accurately recover data for unseen conditions on meshes that have been trimmed from the wall up to an interface height where the learned wall law is applied. The network's interpolation and extrapolation capabilities are quantified and carefully examined. Overall, when tested within its interpolation and extrapolation capabilities, the neural network model shows good robustness and accuracy. The global error on the skin friction coefficient is a few percent and behaves consistently over all the considered test cases.

International audience; Context. Adaptive optics (AO) is a technique allowing for ground-based telescopes' angular resolution to be improved drastically. The wavefront sensor (WFS) is one of the key components of such systems, driving the fundamental performance limitations.Aims. In this paper, we focus on a specific class of WFS: the Fourier-filtering wavefront sensors (FFWFSs). This class is known for its extremely high sensitivity. However, a clear and comprehensive noise propagation model for any kind of FFWFS is lacking. Methods. Considering read-out noise and photon noise, we derived a simple and comprehensive model allowing us to understand how these noises propagate in the phase reconstruction in the linear framework.Results. This new noise propagation model works for any kind of FFWFS, and it allows one to revisit the fundamental sensitivity limit of these sensors. Furthermore, a new comparison between widely used FFWFSs is held. We focus on the two main FFWFS classes used: the Zernike WFS (ZWFS) and the pyramid WFS (PWFS), bringing new understanding of their behavior.; Contexte: L'optique adaptative (OA) est une technique permettant d'améliorer de façon drastique la résolution angulaire des télescopes terrestres. L'analyseur de surface d'onde (WFS pour WaveFront Sensing en anglais) est l'un des composants clés de ces systèmes, ce qui entraîne des limitations de performance fondamentales.Objectifs: Dans cet article, nous nous concentrons sur une classe spécifique de de WFS : les capteurs de front d'onde à filtrage de Fourier (FFWFS). Cette classe est connue pour sa sensibilité extrêmement élevée. Cependant, un modèle clair et complet de propagation du bruit pour tout type de FFWFS fait défaut.Méthodes: En considérant le bruit de lecture et le bruit photonique, nous dérivons un modèle simple et complet permettant de comprendre comment ces bruits se propagent dans la reconstruction de phase dans le cadre linéaire.Résultats: Ce nouveau modèle de propagation du bruit fonctionne pour tout type de FFWFS, et permet de revisiter la limite de sensibilité fondamentale de ces capteurs. De plus, une nouvelle comparaison entre les FFWFS les plus utilisés est effectuée. Nous nous concentrons sur les deux principales classes de FFWFS utilisées : le Zernike WFS (ZWFS) et le pyramid WFS (PWFS), apportant une nouvelle compréhension de leur comportement.

In this paper, we present the MESSII Dataset (Manipulator Experimental SyStem Identification and Interaction Dataset). This novel dataset aims at providing numerous sequences of movements of the KUKA iiwa manipulator, in order to evaluate methods for identification and estimation of the robot's dynamic parameters and signals, respectively. Different movements of the manipulator are provided, including trajectories moving one or multiple joints at the same time, trajectories that are specially designed for parameter identification, and trajectories including a payload attached at the end-effector of the manipulator. The information obtained from the propioceptive sensors of position and torque is presented. Furthermore, as physical Human-Robot Interaction (pHRI) is the main application of this robot, sequences with interaction with a person are provided to estimate the forces applied, where a force-torque sensor acts as the ground truth. The dataset can also be used in ROS to evaluate real-time methods as information is presented in rosbags files. Possible applications are given, highlighting the advantage of the dataset to help with state-of-the-art challenges, without the need of the real robot nor doing new and complex experiments. The dataset, as well as more information and tools, are publicly available in https://messii-dataset.enit.fr.

International audience; This work presents a study of the microstructure and mechanical properties of a TNM+ alloy (Ti-43.5Al-4Nb-1Mo-0.1B-0.3C-0.3Si, in at.%) densified by Spark Plasma Sintering (SPS), in comparison to the as-SPSed TNM alloy, which contains neither carbon nor silicon. Tensile tests at room temperature and 800 °C, as well as creep tests at 800 °C and 200 MPa, were performed. The microstructures and the fracture surfaces of deformed samples were studied by scanning and transmission electron microscopies, as well as by X-ray diffraction. The deformation mechanisms were investigated by means of in situ straining experiments and post-mortem analyses of deformed samples, both performed by transmission electron microscopy. Contrary to the TNM alloy, the as-SPSed microstructure of the TNM+ alloy does not contain β/βo phase due to the incorporation of carbon. At room temperature, the TNM+ alloy exhibits a yield stress of 520 MPa but a poor ductility of less than 0.1% of plastic strain. The incorporation of carbon and silicon leads to an increase in the creep resistance of the alloy at 800 °C. Despite the fact that iron inclusions are responsible for the premature failure of some samples during tensile tests, the TNM+ alloy is found to be able to deform plastically at room temperature by the glide of ordinary dislocations and by twinning.; Ce travail présente une étude de la microstructure et des propriétés mécaniques d'un alliage TNM+ (Ti-43.5Al-4Nb-1Mo-0.1B-0.3C-0.3Si, en at.%) densifié par Spark Plasma Sintering (SPS), en comparaison avec l'alliage TNM brut de SPS qui ne contient ni carbone ni silicium. Des essais de traction à température ambiante et 800°C ainsi que des essais de fluage à 800°C et 200 MPa ont été réalisés. Les microstructures et les surfaces de rupture des échantillons déformés ont été étudiées par microscopie électronique à balayage et à transmission, ainsi que par diffraction des rayons X. Les mécanismes de déformation ont été étudiés au moyen d'expériences de déformation in situ et d'analyses post-mortem d'échantillons déformés, toutes deux réalisées par microscopie électronique à transmission. Contrairement à l'alliage TNM, la microstructure brute de SPS de l'alliage TNM+ ne contient pas de phase bêta/bêta0 en raison de l'incorporation de carbone. Malgré le fait que les inclusions de fer soient responsables de la rupture prématurée de certains échantillons lors des essais de traction, l'alliage TNM+ est capable de se déformer plastiquement à température ambiante. L'incorporation de carbone et de silicium conduit à une augmentation de la résistance au fluage de l'alliage à 800°C.

International audience; With the approach of next generation supersonic transport entry into service, new research activities were initiated to support updates on ICAO regulations and certification processes for supersonic transport vehicles. Within this context, the EU Horizon 2020 SENECA project has been launched to investigate the levels of noise and gaseous emissions in the vicinity of airports as well as the global climate impact of next generation supersonic civil aircraft. This paper introduces some of the preliminary outcomes of this investigation. It presents the preliminary design and performance analysis of a Mach 1.6 business jet, following an integrated aircraft-engine design approach. The preliminary design was performed accounting for the limitations posed by future environmental restrictions on respective subsonic vehicles. The market space and mission route definition exercise assumed only "over-sea" supersonic operations, while for "over-land", only subsonic operations where allowed. Parametric studies on engine integrated design demonstrated modest core temperatures while cruising and the significant impact of engine installation on performance. At this first design iteration, assuming current state of the art technology, the Mach 1.6 business jet showed good potential to satisfy the predicted mission requirements while respecting the environmental constraints in terms of Landing & Take-Off (LTO) noise and emissions.; Avec la mise en service prochaine d’avions de transport supersoniques de nouvelle génération, de nouvelles activités de recherches ont été démarrées pour aider à la mise à jour des procédures de régulation et de certification de l’OACI pour les avions de transport supersoniques. Dans ce contexte, le projet européen Horizon 2020 SENECA a été lancé pour étudier les niveaux ce bruit et les émissions de polluants à proximité des aéroports, ainsi que l’impact global sur le climat des avions supersoniques civils de nouvelle génération. Ce papier illustre certains résultats préliminaires de cette étude. Il présente la conception préliminaire et l’analyse de performances d’un avion d’affaire supersonique à Mach 1.6, selon une approche intégrée de conception avion-moteur. La conception préliminaire a été réalisée en prenant en compte les limitations posées par les futures restrictions environnementales sur les aéronefs subsoniques. L’exercice de définition de l’espace de marché et de la mission considère le vol supersonique uniquement au-dessus des océans, tandis que le vol reste subsonique au-dessus des terres. Des études paramétriques sur des concepts avec moteur ont démontré une température interne modeste pendant le vol de croisière et l’impact significatif de l’installation du moteur sur les performances. Pour cette première itération, en considérant l’état de l’art actuel des technologies, l’avion d’affaire à Mach 1.6 montre un bon potentiel pour satisfaire les exigences attendues de la mission tout en respectant les contraintes environnementales en terme de bruit au décollage et à l’atterrissage (bruit LTO) et les émissions.

International audience; The EU-funded project ALTERNATE aims to explore the possibility of broader use of sustainable aviation fuels (SAFs). Part of the project assesses the effect of SAFs on soot production using experimental results and model predictions. In this regard, the combustion of two fuels was investigated under high-pressure conditions on the MICADO test rig at ONERA. This combustor allows a detailed analysis of soot formation based on advanced laser diagnostics. During the experimental campaign, the effect of Jet A-1 and Alcohol to Jet (ATJ) on soot levels was studied for three operating conditions in which the pressure of the combustion chamber varied from 4.5 to 9 bar, while maintaining almost constant the fuel-to-air ratio. An investigation of spray formation, flame shape and combustion dynamics is carried out to shed light on the impact of fuel composition on soot formation. In addition, the sooting behavior of the two fuels is compared, and it is observed that ATJ has a lower sooting capacity than Jet A-1 for the studied conditions. In parallel, Safran Tech and CERFACS worked jointly to perform Large Eddy Simulation (LES) for the case 4.5 bar fueled with Jet A-1. Semi-detailed chemistry for fuel oxidation and gaseous soot precursors together with the Lagrangian Soot Tracking model, both developed by CERFACS, is applied, and a first comparison against the available experimental data in terms of spray evolution and flame shape is obtained. The present work gives an overview of the experimental data collected during ALTERNATE, of SAF effects on soot generation and a first comparison obtained with LES for the Jet A-1 case at 4.5 bar.

International audience; Different additive manufacturing (AM) technologies such as L-PBF and DED do become really attractive for both repair and 3D part manufacturing. In particular, extensive work is in progress for the non-weldable nickel-based superalloys which tend to exhibit cracks due to residual stresses build-up during AM thermal cycles. Within the framework of the project FAPS conducted at Université Paris-Saclay, the present investigation will highlight the processing conditions and build-up strategy that produce crack-free specimens for alloy AD730®. The latter was developed by Aubert & Duval for cast&wrought gas turbine applications. In this work, a comparison between such conventional processing and AM will be provided in terms of mechanical performance. The results clearly show an anisotropic behaviour related to the sharp crystallographic texture induced by the epitaxial grain growth. The results will be discussed, with a perspective analysis of maturity for this AM processedmaterial, the process robustness, the potential technological developments and application prospects.; Différentes technologies FA telles que L-PBF et DED deviennent réellement attractives pour à la fois de la réparation et de la fabrication de pièces 3D. En particulier, un travail important est en cours pour les superalliages base Ni non soudables qui tendent à se fissurer en raison d’une augmentation des contraintes résiduelles lors des cycles thermiques FA. Dans le cadre du projet FAPS mené à Paris-Saclay, ces travaux vont mettre en exergue les conditions de process et de stratégie de construction qui produisent des échantillons sans fissures pour l’alliage AD730. Ce dernier a été développé par Aubert&Duval pour des applications coulé+forgé dans les turbines aéronautiques. Dans ce travail, on présentera une comparaison entre un tel procédé conventionnel et la FA en termes de performance mécanique. Les résultats montrent clairement un comportement anisotrope relié à la forte texture cristallographique induite par la croissance épitaxiale des grains. On discutera des résultats, avec en perspective l’analyse de la maturité de ce matériau issu de FA, la robustesse du procédé, les développements technologiques potentiels et les applications prospectives.

International audience; Space lidar instruments for missions like AEOLUS or MERLIN require advanced high-power laser systems with according technical and financial effort. In order to increase the impact of such missions, it is advantageous to expand the versatility of their instruments. In the case of trace gas sensing, the ability to detect multiple trace gas species with the same instrument greatly enhances their value. Multi-species trace gas differential absorption lidar (DIAL) systems require absolute frequency referencing across large spectral bandwidths. While absorption cell based references need individual lasers at online and offline wavelengths for each species, a broadband mode locked laseroffering a frequency combcan provide the required frequency accuracy over the complete spectral range of the lidar instrument. In the frame of the LEMON project, we developed a combined design for an absolute frequency reference based on a wavemeter for coarse frequency determination (

International audience; The MICROSCOPE satellite ended its mission in October 2018. Aiming at testing the Equivalence Principle (EP), the funding hypothesis of the General Relativity with unprecedented precision, a first publication in 2017 showed no evidence of a violation at 10−14 level. Since then; 3 years of analysis made it possible to improve the accuracy by one order of magnitude, placing this test as a reference for the test of General Relativity (GR). This presentation will focus on the most challenging topic of the data analysis: estimating errors and ensuring the best accurate test. The final result will be discussed and its impact on alternative theories to GR will be given.

International audience; In the context of lightning strike impacting aeronautical fasteners, we investigate the in situ behaviour of fasteners subject to a current level of a few kA by using high-speed Xray phase-contrast imaging in a synchrotron facility. It reveals that the fastener erosion occurs in two time scales. On a microsecond timescale, hot particles are ejected from cavity walls of the Carbon fibre reinforced polymer due to sparking/arcing phenomena, whereas on a sub-millisecond time scale, the fastener wall is vaporized due to the electrical energy deposited in the arc-fastener interface. The experimental observations have been used as input for an electro-thermal model of electric contact. The estimated vaporised depth is in good agreement with the measured one. The nature of the internal damages has been confirmed by using X-ray phase tomography.

National audience; L'apprentissage de distance propose d'optimiser la distance de Mahalanobis pour des problèmes de classification. Plusieurs algorithmes associés à ce problème s'interprètent comme des estimateurs d'une matrice de covariance. Partant de ce constat, nous proposons un nouveau problème d'estimation appelé Robust Geometric Metric Learning (RGML) qui vise à estimer une matrice de covariance par classe et leur barycentre riemannien. Deux algorithmes associés à ce problème d'estimation sont développés : RGML gaussien et RGML Tyler. Ces algorithmes optimisent deux fonctions de coût sur la variété riemannienne des matrices symétriques définies positives et sa sous-variété à déterminant unitaire. Enfin, les algorithmes proposés sont appliqués sur des jeux de données réels. De bonnes performances ainsi qu'une robustesse aux données mal étiquetées sont obtenues.

National audience; Cet article a pour but de présenter un nouvel algorithme pour améliorer l'estimation des phases SAR interférométriques (InSAR) dans le contexte de séries temporelles. Basée sur l'estimateur du maximum de vraisemblance d'un modèle gaussien multivarié, l'estimation des phases InSAR est résolue en utilisant une approche de Descente en Bloc de Coordonnées (DBC). Par rapport aux approches classiques, l'amélioration principale réside dans l'estimation conjointe de la cohérence interférométrique et des phases InSAR au lieu de l'utilisation d'un estimateur annexe de cohérence, obtenue

This paper proposes new algorithms for the metric learning problem. We start by noticing that several classical metric learning formulations from the literature can be viewed as modified covariance matrix estimation problems. Leveraging this point of view, a general approach, called Robust Geometric Metric Learning (RGML), is then studied. This method aims at simultaneously estimating the covariance matrix of each class while shrinking them towards their (unknown) barycenter. We focus on two specific costs functions: one associated with the Gaussian likelihood (RGML Gaussian), and one with Tyler's M -estimator (RGML Tyler). In both, the barycenter is defined with the Riemannian distance, which enjoys nice properties of geodesic convexity and affine invariance. The optimization is performed using the Riemannian geometry of symmetric positive definite matrices and its submanifold of unit determinant. Finally, the performance of RGML is asserted on real datasets. Strong performance is exhibited while being robust to mislabeled data., Published in EUSIPCO 2022. Best student paper award

International audience; This paper presents a new sequential method to calibrate a material model in the presence of significant material variability. Material variability is handled in the mixed-effects framework. In this approach, material variability is described by a probability distribution calibrated by maximizing a likelihood. Yet, when the number of model parameters or the computational time of a single run of the models increases (for multiaxial models for instance), the maximization of the likelihood of mixed-effects is more difficult to perform. Furthermore, the parameters do not have the same influence on the material model depending on the nature of the test. The proposed procedure enables to calibrate the model on multiple experiments. It relies on the definition of a sequence of calibration subproblems. Associated to the relevant experimental data, each subproblem allows to calibrate the joint distribution of a subset of the model parameters. The maximization of the attached likelihood is eased as the number of unknown parameters is reduced compared to full problem. The subproblems are solved sequentially. To ensure consistency of the global process, the research space for the distribution parameters already estimated with a previous calibration is restricted to a trust region. The proposed calibration process is applied to an orthotropic elastic model with laminates made from T700GC/M21 base ply material. The ability of the procedure to sequentially estimate the model parameters distribution is investigated. Its capability to ensure consistency throughout the calibration process is discussed. Results show that the proposed procedure is a promising methodology to handle the calibration of complex material models in the mixed-effects framework.

International audience; Wind tunnel generation of flows representative of the Atmospheric Boundary Layer (ABL) still requires trial-and-error based design process for both passive and active devices. To address this issue, a new type of passive grids – Multiscale Inhomogeneous Grids (MIGs) — is presented. It takes advantage of obstruction variations and interacting wakes to tailor both mean flow profile and turbulent intensity profiles downstream of the grid.The present work derives theoretical models in order to predict the MIG-generated flows characteristics (mean velocity, turbulence intensities, integral length scales profiles), especially for applications to neutral atmospheric boundary layer. These prediction models are investigated experimentally downstream of MIGs using Hot-Wire Anemometry within the SCL-PIV subsonic wind tunnel at ONERA Lille (Section H×W = 290mm ×300mm, velocities up to 30 m/s).First, the mean velocity profile prediction, based on McCarthy (1954), is validated and applied successfully with MIGs to generate logarithmic mean profiles for two equivalent roughness length h0 (up to h0⁄H=0.001).A theoretical turbulence model is then derived based on the Turbulent Kinetic Energy (TKE) equation in the turbulence decaying region. Empirical models are suggested to close the main model, enabling a turbulence-based grid design.; La génération en soufflerie d'écoulements représentatifs de la Couche Limite Atmosphérique (CLA) requiert encore aujourd'hui l'utilisation de méthodes de design par essai-erreur, à reproduire pour toutes nouvelles installations et toutes nouvelles configurations souhaitées. Pour tenter de réduire cette difficulté, un nouveau type de grilles passives – les grilles multi-échelles inhomogènes (MIGs) – est proposé. Elles tirent parti d'une variation d'obstruction locale et d'interactions entre sillages pour controler à la fois le champs moyens et l'intensité turbulente en aval de grille.Le travail actuel décrit plusieurs modèles théoriques permettant une prédiction des caractéristiques des écoulements en aval de MIGs (profil de champs moyen, d'intensité turbulente et d'échelles intégrales), en vue d'une application à la génération de conditions atmosphèriques (CLA neutre). Ces modèles sont comparés à des mesures réalisés en soufflerie par Hot-Wire Anemometry (HWA) dans la soufflerie SCL-PIV de l'ONERA Lille (Section H×W = 290mm ×300mm, velocities up to 30 m/s).Tout d'abord, les prédictions de champs moyens, basées sur le modèle de McCarthy (1954), sont bien validés et appliqués avec succès pour permettre la génération de profil logarithmique pour deux longueurs de rugosités h0 différentes (jusqu'à h0/H=0.001).Un modèle d'évolution aval de la turbulence générée est ensuite développé, basé sur l'équation de l'énergie cinétique turbulente, pour décrire la région de déclin de turbulence. Des modèles empiriques sont enfin suggérés pour clore le modèle principale et ainsi permettre un design de grille pour un profil de turbulence souhaité.

International audience; The transformation process in sooting flames leading to the formation of nanoparticles in the condensed phase from molecular precursors in the gas phase (soot nucleation) is not yet fully understood [1]. Information on the physical chemical properties of the nascent particles is difficult to accessexperimentally but also essential for the validation of the hypotheses on soot nucleation currently being examined by the scientific community. In this work, we characterize the molecular precursors and the soot particles formed in a laminar diffusion methane flame by combining several in situ and ex situ diagnostics (fluorescence, incandescence, secondary ion mass spectrometry and Raman spectroscopy) with the goal of inferring the chemical composition and the structure of the nascent particles. The presented work highlights that several of the investigated physical chemical properties suddenly change within a narrow flame region that acquires the character of a discontinuity point correlated to the soot nucleation process. Notably, the obtained data shows evidences of the transition from flat to curved molecular structures, and the progressive apparition of finite size, sandwiched graphene like layers. Furthermore, the fraction of atomic hydrogen features a local maximum immediately upstream the detection of nascent soot particles consistent with the increasing in flame rate of C-C covalent bonds formation postulated by the major hypotheses explaining the nucleation of soot particles.References[1] J.W. Martin, M. Salamanca, M. Kraft, Soot inception: Carbonaceous nanoparticle formation in flames, Progress in Energy and Combustion Science. 88 (2022) 100956.https://doi.org/10.1016/j.pecs.2021.100956.

International audience; To provide for an ever-increasing need for camouflage, experts in stealth have been envisioning for a few years to use metasurfaces and their unconventional electromagnetic properties to serve as efficient cloaking devices. To prepare for the use of surface-mounted electronic components, useful for frequency-selecting purposes, we take interest in an equivalent circuit analysis of metasurfaces. Indeed, metasurfaces using electronic components invite one to combine the passive behavior of the host structure with that of the lumped elements. The equivalent circuit analysis of the hosting surface deprived of electronic components has so far been dedicated to the case of metasurfaces constituted by rectangular or square unit cells. This work, therefore, aims at extending the former study on Cartesian unit cells to the coaxial geometry of interest. The validity of such a method is then assessed by comparison with the numerical simulation results obtained using a finite-element method.

Ordinary Differential Equations are derived for the adjoint Euler equations firstly using the method of characteristics in 2D. For this system of partial-differential equations, the characteristic curves appear to be the streamtraces and the well-known C+ and C- curves of the theory applied to the flow. The differential equations satisfied along the streamtraces in 2D are then extended and demonstrated in 3D by linear combinations of the original adjoint equations. These findings extend their well-known counterparts for the direct system, and should serve analytical and possibly numerical studies of the perfect-flow model with respect to adjoint fields or sensitivity questions. Beside the analytical theory, the results are demonstrated by the numerical integration of the compatibility relationships for discrete 2D flow-fields and dual-consistent adjoint fields over a very fine grid about an airfoil., 22 pages, 7 figures

This work deals with recursive dynamic parameter identification in robotics and presents a new method applied to industrial manipulators based on the recursive instrumental variable. We construct the instrumental matrix by filtering the reference trajectory and its derivatives with the position closed-loop transfer function previously identified with standard today’s toolboxes, such as CAPTAIN. This implies that we no longer need to simulate the direct dynamic model and, therefore, to know the controller, and that we can build the instrumental matrix beforehand. Besides the closed-loop transfer function acting as a unitary gain at low frequencies, we can use the references directly if only low frequencies are excited. This approach, called Inverse Dynamic Identification Model Recursive Instrumental Variable (IDIM-RIV), is evaluated offline on the 7 degrees of freedom KUKA LBR iiwa R820 manipulator. The experimental validation suggests that IDIM-RIV is computationally cheaper than its en-bloc version, can identify 64 dynamic parameters, and presents good robustness against noise and algorithm initialization.

International audience; Infrared focal plane arrays are widely used for astronomical observations and are constantly optimized to provide higher-quality images. The knowledge of the pixel spatial response becomes critical to extract ever more data from scientific missions. A specific cryogenic spot scan objective with an f-number of 1.2 has been developed in order to finely characterize 15 µm (or smaller) pixel pitch cooled infrared focal plane arrays in the spectral band between 3-5 µm. It will be operated in the MIRCOS test bench with different narrow-band filters. We present the first optical characterization of this objective obtained with a cryogenic wavefront analyzer-a quadrilateral shearing interferometer. The measured wavefront indicates a peak-to-valley amplitude of 2 µm, which corresponds to an optical quality of about λ/2 at 3.75 µm working wavelength. This value higher than expected might be due to a non-uniform cooling of the objective.; Les détecteurs infrarouges sont largement utilisées pour les observations astronomiques et sont constamment optimisées pour fournir des images de meilleure qualité. La connaissance de la réponse spatiale des pixels devient primordiale pour extraire toujours plus de données provenant des missions scientifiques. Un objectif spot scan cryogénique spécifique avec un nombre d'ouverture de 1,2 a été développé afin de caractériser finement les détecteurs infrarouges refroidies avec un pas de 15 μm (ou moins) dans la bande spectrale entre 3-5 μm. Elle sera exploitée dans le banc d'essai MIRCOS avec différents filtres à bande étroite. Nous présentons la première caractérisation optique de cet objectif obtenue avec un analyseur de front d'onde cryogénique - un interféromètre à décalage quadrilatéral. Le front d'onde mesuré indique une amplitude peak-to-valley de 2 μm, ce qui correspond à une qualité optique d'environ λ/2 à une longueur d'onde de travail de 3,75 μm. Cette valeur supérieure à celle attendue pourrait être due à un refroidissement non uniforme de l'objectif.

International audience; In this paper, we present the design and prototyping of the HARMONI Adaptive Optics Calibration Unit (AOCU). The AOCU consists of a set of on-axis sources (covering 0.5-2.4 µm) with a controllable wavefront shape. It will deploy into the instrument focal plane to inject calibration light into the rest of the system. The AOCU supports all-natural guide-star wavefront sensors for SCAO, HCAO, and LTAO. The AOCU will be used to calibrate the WFSs, the internal interaction matrices of HARMONI, measure and compensate NCPAs between AO dichroics and the science detectors, and calibrate the pointing model zero position. The illumination assembly of the AOCU will consist of six diffraction-limited sources and a resolved source coupled into fibres. Because of the wide range of wavelengths and the spatial separations requirements, we use two endlessly single-mode fibres and a multimode fibre. In addition, several LED sources need to be coupled efficiently into the single-mode fibres. In this paper, we present the general AOCU design using off-the-shelf with a focus on the illumination and source module.

International audience; In low-Earth-orbit satellite tracking applications, the apparent wind component due to relative motion between the telescope and the different atmospheric turbulence layers leads to faster turbulence temporal dynamics, and thus increases the servo-lag error of adaptive optics systems. Nevertheless, this apparent wind component can be known a priori, since it only depends on the satellite's orbit. We propose a model-based predictive controller that incorporates a priori wind layer velocity information. The controller uses an autoregressive model computed from layer wind speeds and a C 2 n (z) profile. This approach derives from the spatio-angular linear quadratic Gaussian controller, and benefits from an analytical formulation. We present performance simulation results for two applications: optical communications and satellite observation; we analyse the impact of prediction in terms of relevant performance criteria for each application.

International audience; Today, the combination of high angular resolution and high revisit rate is not readily available from space, at least not at a reasonable cost. Many applications in the science, civil or defense domains would benefit from having access to detailed images of the ground as often as possible, in order to study temporal evolutions of specific events. The high angular resolution requires large optics hence large platforms, whereas the revisit rate requires constellations of multiple satellites and therefore small and affordable platforms. We proposed the concept of a deployable telescope onboard a CubeSat, called AZIMOV [1, 3, 5], to address this specific gap. Reaching a diameter of 30 cm once deployed, this concept gives access to a meter resolution on the ground from a Low Earth Orbit, or to a 70 cm resolution on Mars surface from a 400 km polar orbit. We study in this paper the performance of such a telescope in the aggressive thermal environment of space, with respect to the tight optical requirements of the system.

International audience; HARMONI is the first light visible and near-IR integral field spectrograph for the ELT. It covers a large spectral range from 450nm to 2450nm with resolving powers from 3500 to 18000 and spatial sampling from 60mas to 4mas. It can operate in two Adaptive Optics modes-SCAO (including a High Contrast capability) and LTAO-or with NOAO. The project is preparing for Final Design Reviews. The SCAO Sensors subsystem (SCAOS) is located within the Natural Guide Star Sensors (NGSS) system which includes several wavefront sensors (WFS) to cover the needs of the different HARMONI observing modes and operates in a cold, thermally stabilized (+2°C) and dry gas environment for thermal background limitation. To reach the required performance, the SCAOS will use different modules and mechanisms among which, two particularly critical devices have been prototyped and are tested: The SCAOS Pyramid Modulator Unit (SPMU) and the SCAOS Object Selection Mechanism (SOSM). Both devices are tip-tilt mirrors but have very different specifications (amplitude and speed). In this work, we will present and discuss the design, the assembly and the full test (performance, control) of the two systems, in both ambient and cold environments.

International audience; HARMONI is the first light visible and near-IR integral field spectrograph for the ELT. It covers a large spectral range from 450nm to 2450nm with resolving powers from 3500 to 18000 and spatial sampling from 60mas to 4mas. It can operate in two Adaptive Optics (AO) modes - SCAO (including a High Contrast capability) and LTAO - or with NOAO. The project is preparing for Final Design Reviews.The SCAO system for HARMONI is based on a pyramid wavefront sensor (PWFS) operating in the visible (700 – 1000 nm). Previous implementations on very large telescopes have demonstrated the challenges associated with optimising PWFS performance on-sky, particularly when operated at visible wavelengths. ELT operation will pose further challenges for AO systems, particularly related to the segmentation of the telescope and the control of badly seen ‘petal modes’. In this paper we investigate these challenges in the context of the HARMONI SCAO system. We present the results of end-to-end simulations of our baseline approach, using a coupled control basis to avoid the runaway development of petal modes in the control loop. The impact of key parameters are investigated and methods for optical gain compensation and optimisation of the control basis are presented. We discuss recent updates to the control algorithms and demonstrate the possibility of improving performance using a form of super resolution. Finally, we report on the expected performance across a range of conditions.

International audience; HARMONI is the first light visible and near-IR integral field spectrograph for the ELT covering a large spectral range from 450nm to 2450nm with resolving powers from 3500 to 18000 and spatial sampling from 60mas to 4mas. It can operate in two Adaptive Optics modes-SCAO and LTAO-or with no AO. The project is preparing for Final Design Reviews. The laser Tomographic AO (LTAO) system provides AO correction with very high sky-coverage thanks to two systems: the Laser Guide Star Sensors (LGSS) and the Natural Guide Star Sensors (NGSS). LGSS is dedicated to the analysis of the wavefront coming from 6 laser guide stars created by the ELT. It is made of 6 independent wavefront sensor (WFS) modules mounted on a rotator of 600mm diameter to stabilise the pupil onto the microlens array in front of the detector. The optical design accepts elongated spots of up to 16 arcsec with no truncation using a CMOS detector from SONY. We will present the final optical and mechanical design of the LGSS based on freeform lenses to minimize the numbers of optical components and to accommodate for the diversity of sodium layer configurations. We will focus on rotator design, illustrating how we will move 1 tons with 90" accuracy in restrictive environment. Finally, we will present the strategy to verify the system in HARMONI context. The main challenge for the verification being how to test an AO system without access to the deformable mirror, part of the ELT.

International audience; We present recent laboratory results demonstrating high-contrast coronagraphy for the future space-based large IR/Optical/Ultraviolet telescope recommended by the Decadal Survey. The High-contrast Imager for Complex Aperture Telescopes (HiCAT) testbed aims to implement a system-level hardware demonstration for segmented aperture coronagraphs with wavefront control. The telescope hardware simulator employs a segmented deformable mirror with 37 hexagonal segments that can be controlled in piston, tip, and tilt. In addition, two continuous deformable mirrors are used for high-order wavefront sensing and control. The low-order sensing subsystem includes a dedicated tip-tilt stage, a coronagraphic target acquisition camera, and a Zernike wavefront sensor that is used to measure and correct low-order aberration drifts. We explore the performance of a segmented aperture coronagraph both in "static" operations (limited by natural drifts and instabilities) and in "dynamic" operations (in the presence of artificial wavefront drifts added to the deformable mirrors), and discuss the estimation and control strategies used to reach and maintain the dark-zone contrast using our low-order wavefront sensing and control. We summarize experimental results that quantify the performance of the testbed in terms of contrast, inner/outer working angle and bandpass, and analyze limiting factors.

International audience; PISTIL is an interferometric metrology tool dedicated to the analysis of regular segmented wavefront surfaces. Its ease of use and the quality of its measurements make it an ideal and independent analyzer for the diagnosis of the phasing of coherent combined lasers. The results presented here were obtained on the XCAN laser, a digital laser composed of 61 CBC laser fibers.; PISTIL est un moyen de métrologie interférométrique dédié à l'analyse des surfaces d'onde segmentées régulières. Sa facilité de mise en oeuvre et la qualité de ses mesures en font un analyseur idéal et indépendant pour le diagnostic de la mise en phase des lasers à combinaison cohérente. Les résultats présentés ici ont été obtenus sur le laser XCAN, laser digital composé de 61 fibres laser CBC.

International audience; The proposition of innovative and competitive designs of aeronautical structures manufactured with composite materials made of carbon fibres and thermoplastic matrix, presenting high potential for recyclability and interesting welding capabilities, cannot be performed without a deep understanding of the different sources of non-linearities specific to those high performance materials. The objective of the present study consists therefore in understanding the underlying physical phenomena leading to transverse cracking in a new generation of composite material with carbon fibres and thermoplastic matrix and in highlighting their specificities compared to a UD ply made of the same carbon fibres but associated with an epoxy matrix.; La proposition de méthodes de dimensionnement innovantes et compétitives de structures aéronautiques fabriquées avec des matériaux composites à base de fibres de carbone et de matrice thermoplastique, présentant un fort potentiel de recyclabilité et des capacités de soudage intéressantes, ne peut être effectuée sans une compréhension approfondie des différentes sources de non-linéarités spécifiques à ces matériaux hautes performances. L'objectif de cette étude consiste donc à comprendre les phénomènes physiques sous-jacents conduisant à la fissuration transverse dans une nouvelle génération de matériau composite à fibres de carbone et matrice thermoplastique et à mettre en évidence leurs spécificités par rapport aux plis UD constitués des mêmes fibres de carbone mais associés à une matrice époxy.

International audience; In May 2021, a measurement campaign was carried out several miles off the west coast of France as part of the preparedness for the response to pollution at sea. This campaign, under the command of the French Navy, involved CEDRE, CEPPOL and ONERA and aimed to test different LWIR systems on board ships or aircraft. During this campaign, various chemicals, legally called HNS for Hazardous Noxiuous Substances (HNS), were released on the sea surface: acetone, butyl acetate, methanol, heptane, xylene and styrene.; En mai 2021, une campagne de mesure a été menée à plusieurs milles au large de la côte ouest de la France dans le cadre de la préparation à la lutte contre la pollution en mer. Cette campagne, sous le commandement de la Marine nationale, a impliqué le CEDRE, le CEPPOL et l'ONERA et visait à tester différents systèmes LWIR à bord de navires ou d'aéronefs. Au cours de cette campagne, divers produits chimiques, légalement appelés HNS pour Hazardous Noxiuous Substances (HNS), ont été rejetés à la surface de la mer : acétone, acétate de butyle, méthanol, heptane, xylène et styrène.

International audience; This paper examines the role of emotion annotations to characterize extremist content released on social platforms. The analysis of extremist content is important to identify user emotions towards some extremist ideas and to highlight the root cause of where emotions and extremist attitudes merge together. To address these issues our methodology combines knowledge from sociological and linguistic annotations to explore French extremist content collected online. For emotion linguistic analysis, the solution presented in this paper relies on a complex linguistic annotation scheme. The scheme was used to annotate extremist text corpora in French. Data sets were collected online by following semi-automatic procedures for content selection and validation. The paper describes the integrated annotation scheme, the annotation protocol that was setup for French corpora annotation and the results, e.g. agreement measures and remarks on annotation disagreements. The aim of this work is twofold: first, to provide a characterization of extremist contents; second, to validate the annotation scheme and to test its capacity to capture and describe various aspects of emotions.

X-ray imaging is widely used in non-destructive testing dedicated to industry, medical or security domain. Classically, its use is based on the measurement of X-ray attenuation, well suited for imaging dense materials (metals, bones, weapons,etc.) because they strongly attenuate the Xray beam and bring contrast to the image. However, there is a wide range of materials of interest, which are not very attenuating (composites, carbon fibers, soft tissues, explosives, etc.) and therefore difficult to image using conventional techniques. Furthermore, in addition to their attenuation, phase shifting happens, in particular for low-attenuating material. The measurement of the phase shift by a grating interferometer allows to estimate the geometry of the observed object. The imaging associated with this measurement is called phase imaging by Multi-Lateral Shearing Interferometer (MLSI) and allows to restore a strong contrast for sparse materials, where conventional imaging techniques is limited. Since the phase measurement is not direct to the measurement, it requires specific extraction algorithms that can lead to estimation errors also called extraction artifacts. A first goal of my thesis was to develop a tool for mapping these artefacts to the phase image that allows a direct feedback of the phase extraction quality. On the other hand, my work consisted in correcting these estimation errors by developing two image processing methods. The first method applies to aliasing errors induced by the sampling constraints of wave-fronts with abrupt transition by MLSI and has already been deployed for Non Destructive Testing (NDT) applications that I will present. The second method seeks to minimize the noise by exploiting the redundancy of the phase measurement and allowed me to improve, with the support of a simulation model I developed, new geometries of MLSI that maximizes signal-to-noise gains in phase images.; L’imagerie par rayons X est fortement développée dans de nombreux domaines de notre société, notamment dans les milieux industriels, médicaux ou sécuritaires. Classiquement son utilisation repose sur la mesure d’atténuation des rayons X, bien adaptée pour imager des matériaux denses (métaux, os, armes…) car fortement atténuants et amenant du contraste à l’image. Toutefois, il existe un large panel de matériaux d’intérêt peu atténuants (composites, fibres carbonées, tissus mous, explosifs…) donc difficiles à imager par les techniques classiques. Les rayons X, en plus de leur atténuation, subissent un déphasage qui est d’autant plus important que le matériau traversé est peu atténuant. La mesure de ce déphasage, notamment à travers l’ajout d’un réseau de diffraction sur le trajet du faisceau, permet de remonter à la géométrie de l’objet observé. L’imagerie associée à cette mesure est appelée imagerie de phase par interférométrie à décalage multi-latéral (IDML) et permet de restituer un fort contraste pour les matériaux peu denses. Par ailleurs, la mesure de phase n’est pas directe à la mesure et nécessite des algorithmes spécifiques d’extraction pouvant amener des erreurs d’estimation. Un premier volet de ma thèse a ainsi consisté à développer un outil de cartographie des erreurs de l’image de phase servant de retour direct de la qualité d’estimation de phase. D’autre part, mon travail a consisté à corriger ces erreurs d’estimation à travers le développement de deux méthodes traitement d’image. La première méthode s’applique aux erreurs liées au sous-échantillonnage du signal par l’IDML et son déploiement a été démontré expérimentalement pour des applications en contrôle non-destructif (CND). La deuxième méthode cherche à minimiser le bruit de mesure par l’exploitation de la redondance accessible par l’IDML. Avec l’appui d’un modèle de simulation que j’ai développé, de nouvelles géométries de réseau de diffraction ont été étudiées permettant de maximiser les performances de cette méthode.

An earlier version of this paper was presented at the IEEE Sensors 2020 conference and was published in its Proceedings with the title “Aerodynamic wall pressure measurement using a high temperature gradient Pirani micro-sensor” (DOI: 10.1109/SENSORS47125.2020.9278842); International audience; This paper presents and discusses the first demonstration of aerodynamic wall pressure measurement using a thermal Pirani effect based micro-sensor. The thermal micro-sensor is designed as a suspended micro-hot-wire separated from the substrate by a nanoscale gap, and mechanically supported by perpendicular micro-bridges. The micro-sensor was calibrated for pressure measurement from 10 kPa to 800 kPa. It was then used as aerodynamic wall pressure sensor in a turbulent boundary layer wind tunnel and successfully measured the 1.1 kPa depression occurring in the wind tunnel when the flow velocity goes up to 40 m/s.

Context.The combination of large segmented space telescopes, coronagraphy, and wavefront control methods is a promising solution for producing a dark hole (DH) region in the coronagraphic image of an observed star in order to study planetary companions. The thermal and mechanical evolution of such a high-contrast instrumental setup leads to wavefront drifts that degrade the DH contrast during the observing time, thus limiting the ability to retrieve planetary signals.Aims.Lyot-style coronagraphs are starlight-suppression systems that remove the central part of the image for an unresolved observed star, that is, the point spread function, with an opaque focal plane mask (FPM). When implemented with a flat mirror containing an etched pinhole, the mask rejects part of the starlight through the pinhole which can be used to retrieve information about low-order aberrations.Methods.We propose an active control scheme using a Zernike wavefront sensor (ZWFS) to analyze the light rejected by the FPM, control low-order aberrations, and stabilize the DH contrast. We first present the concept formalism and then describe how we characterized the sensor behavior in simulations and in the laboratory. We performed experimental tests to validate a wavefront control loop using a ZWFS on the HiCAT testbed.Results.By controlling the first 11 Zernike modes, we show a decrease in the standard deviation of the wavefront error by a factor of up to 9 between open- and closed-loop operations using the ZWFS. In the presence of wavefront perturbations, we show the ability of this control loop to stabilize a DH contrast around 7 × 10−8with a standard deviation of 7 × 10−9.Conclusions.Active control with a ZWFS proves to be a promising solution in Lyot coronagraphs with an FPM-filtered beam for controlling and stabilizing low-order wavefront aberrations and DH contrast for exoplanet imaging with future space missions.

The impact of a temperature mesosphere inversion on the vertical propagation of gravity waves has been investigated using OH airglow images and ground-based Rayleigh lidar measurements carried out on December 2017 at the Haute-Provence Observatory (OHP, France, 44N). These measurements provide complementary information that allows the vertical propagation of gravity waves to be followed. An intense Mesospheric Inversion Layer (MIL) observed near 60 km with the lidar disappeared in the middle of the night offering a unique opportunity to evaluate its impact on gravity wave (GW) propagation observed above the inversion with airglow cameras. With these two instruments, a wave with 150 min period has been observed, and was also identified in meteorological analyses. The gravity waves potential energy vertical profile shows clearly the GW energy lost below the inversion altitude and a large increase of gravity waves energy above the inversion in OH airglow images with waves exhibiting higher frequency. The MIL are known to causes instabilities at its top part and this is probably the reason of enhanced gravity waves observed above., L'impact d'une inversion de température mésosphérique sur la propagation verticale des ondes de gravité a été étudié à l'aide d'images airglow et de mesures au sol par lidar Rayleigh effectuées en décembre 2017 à l'Observatoire de Haute-Provence (OHP, France, 44N). Ces mesures fournissent des informations complémentaires qui permettent de suivre la propagation verticale des ondes de gravité. Une intense couche d'inversion mésosphérique (MIL) située au voisinage de 60 km observée avec le lidar a disparu au milieu de la nuit offrant une opportunité unique d'évaluer son impact sur la propagation des ondes de gravité (GW) observées au-dessus de l'inversion avec les caméras airglow. Avec ces deux instruments, une onde avec une période de 150 min a été observée, et a également été identifiée dans les analyses météorologiques. Le profil vertical de l'énergie potentielle des ondes de gravité montre clairement la perte d'énergie des ondes de gravité en dessous de l'altitude de l'inversion et une forte augmentation de l'énergie des ondes de gravité au-dessus de l'inversion dans les images airglow avec des ondes de fréquence plus élevée. L'inversion mésosphérique est connue pour provoquer des instabilités dans sa partie supérieure et c'est probablement la raison de l'augmentation des ondes de gravité observées au-dessus.

In this article, we present a cryogenic spot scan bench in the 3-5 µm band currently under development in the ONERA MIRCOS platform. Initial tests have been carried out on a HgCdTe detector with a 30 µm pitch and improvements are underway to characterise smaller pixels., Dans cet article, nous présentons un banc de spot scan cryogénique dans la bande 3-5 µm actuellement en développement dans la plateforme MIRCOS de l'ONERA. Des premiers tests ont été réalisés sur un détecteur HgCdTe au pas de 30 µm et des améliorations sont en cours pour pouvoir caractériser de plus petits pixels.