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International audience; The preparation and characterization of pure fluorite-type phases allowed exploring the CeO2–ZrO2–PrOx (CZP) phase diagram. On the basis of magnetic susceptibility measurements, the Pr4+/Pr3+ molar ratio of several oxides annealed at T = 700 °C under air was determined; the higher the Zr content, the lower the Pr4+ concentration. Thermogravimetric analysis and temperature-programmed reduction measurements showed various Pr and Ce reduction steps. The Pr4+ reduction starts at T = 250 °C and is maximum around T = 400 °C. For the most reducible compositions, which exhibit the lowest Zr content and the highest Pr rate, the reduction phenomena strongly depend on the Pr/Ce molar ratio. As a remarkable result, Pr and Ce reductions can simultaneously take place at lower temperature (T > 430 °C) than for oxides of the CeO2–ZrO2 solid solution evidencing that the increase of Pr content also allows enhancing the reducibility of Ce4+ at low temperature. On the basis of a discussion taking into account the probability of oxygen surroundings in disordered fluorite networks and the rate of oxygen released in materials after the first reduction step performed at T < 500 °C, a mapping of the most probable labile oxygen sites in the CZP phase diagram is proposed. In particular, it is shown that for the oxides containing 10 atom % Zr, the most labile oxygen site should be systematically coordinated with one Zr atom, one Ce, and two Pr atoms. In the same series (10 atom % Zr), the electronic transport properties allowed showing semiconducting behavior with a strong increase of the total conductivity as the Pr content increases. On the basis of the thermal variation of the Seebeck coefficient, these phenomena are associated with hopping of electrons and holes, involving intra-atomic charge transfers, which depend on the reduction temperature of Pr4+ ions under air. Finally, the oxygen mobility strongly increases with the Pr content in this series. The oxygen tracer self-diffusion coefficient D* has been estimated by two independent measurements, and the best value is around 10–8 cm2/s at T = 400 °C for the Ce0.45Zr0.1Pr0.45O2–x composition, which is quite high in this temperature range. These fundamental properties of CZP phases design very promising new materials like automotive exhaust catalysts, gas sensors, electrolytes, or oxygen electrodes for solid oxide fuel cells.

International audience; Stirling machine as auxiliary power unit for range extender hybrid electric vehicles

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International audience; Nonlinearities effects at the crack tip, due to the elastic-plastic material behavior , impact the crack growth rate and path. This paper is devoted to the study of the plastic zone evolution in the crack tip region. The methodology relies on coupling an elastic-plastic Finite Elements Method (FEM) model and experimental displacements measured by Digital Image Correlation (DIC). These latter are introduced as Dirichlet boundary conditions in the finite elements analysis. The considered FEM domain is constant, i.e. the same mesh with a centered crack is moved to each new crack tip position deduced from DIC. The new boundary conditions are updated and the residual stresses and plastic strains of the former computation are interpolated and actualized on the mesh shifted to the new crack tip position in order to incorporate them in the numerical model. The coupling method allowed applying experimental boundary conditions in order to be as close as possible to real experimental conditions and to observe the plasticity evolution from small to large scale yielding conditions. A fatigue test was conducted to validate the proposed approach. The identification residues are proved to be lower than those obtained with an experimental displacements projection onto Williams' series basis, which is a method commonly used with DIC. The coupling results present an attractive similarity with Irwin's model regardless of the crack length. Thus, the definition of the mask needed for the displacements fields projection on Williams' model can be deduced with a reliable estimate of Irwin's plastic radius.

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International audience; Bayesian algorithms (e.g., EGO, GPareto) are a popular approach to the mono and multi-objective optimization of costly functions. Despite the gains provided by the Gaussian models, convergence to the problem solutions remains out of reach when the number of variables and / or the number of objective functions increase.In this presentation, we show how with Gaussian processes it is possible to restrict ambitions in order to recover problems that can be solved.With strong restrictions on the number of objective function evaluations, it is often only feasible to target a specific point of the Pareto front. We describe the mEI criterion to do so. When no such point is known a priori, we propose to target the Pareto front center. Thus, we define this center, explain how to estimate it and how to detect convergence to it.Once the center of the Pareto front has been found, we propose to enlarge the search for Pareto optimal solutions around it in a manner that is compatible with the remaining computational budget. To achieve this, virtual Bayesian optimizations are carried out on the Gaussian processes.Finally, we discuss how to parallelize the resulting multi-objective Bayesian optimization algorithm.

This paper presents the design of a fractional order based controller for a high-speed electromagnetic actuator developed for a camless engine valvetrain. For rapid prototyping and flexibility, the controller is digital and it is particularly shown that it can be designed while taking into account all sampling issues even if a high closed-loop bandwidth is required. Simulations and experimental results shows that the design of the innovative actuator and of its controller provides very good dynamic performance.

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This article aims to propose a real-time compatible strategy for the energy management of a compression-ignition Hybrid Electric Vehicle (HEV), under pollutants emissions constraints. First, an offline method is applied in order to obtain a performance reference. Then, an online-oriented approach based on Model Predictive Control (MPC) is described, and a projected gradient algorithm used to solve the successive optimal control problems is explicitly presented. Both approaches are compared through simulation and the results are validated through experimentation.

Microbuckling is an important failure mode for fibre reinforced composites loaded under compression and the topic has received substantial attention of the research community. This effort led to a good understanding of the basic mechanisms behind the microbuckling phenomenon. However in spite of the well-developed theory, the ability to accurately predict failure loads and other related properties based on available data has not been attained yet. This may be attributed to a number of factors, arising at different scales. Consequently, numerous computational models and methods were put forward in the literature to approach this objective and this survey attempts to provide an overview of these developments. A concise reminder of the phenomenology and theoretical basis is also included to make the present survey self-contained.

International audience; One of the major curb to electric vehicles (EV) acceptability is their constraints when performing long distance trips. Even if improvements made on fast charging technology enable to recover up to 400 km range in 20 minutes, the low density of this kind of infrastructure and the variability in their availability can lead to significant waiting times for users. Many articles develop communication scenario between vehicles in order to coordinate users charging places choices, permitting a better distribution that minimize waiting queue. The authors compare their approaches performances with theoretical resolution of the relaxed problem. In this article, the authors deal with a situation where many electric vehicles run along a highway with few charging stations, representing a usual daily traffic flow. It provides an approach that permits to find an optimal charging schedule for all users, minimizing their waiting and charging time at charging stations, using an all-knowing point of view. A differential evolution algorithm is used, with some improvements to better adapt it to this problem and speed the convergence.

International audience; The major priority of the carmakers is to reduce the energy consumption and the emissions of the future passenger cars and to deliver an efficient mobility service for the customers. The number of electrified vehicles increases in the mobility market. The range and the energy storage of the vehicle on board are important. The recharging of the vehicles and their connection to the energy grid became an important question. In this article, the energy system is extended and includes the energy storage and conversion of vehicles and their connection to the grid. The extended energy system is modelled on vehicles flows on the highway and a single objective optimization is performed to define the optimal energy storage capacity of the vehicles and the optimal number of recharges of from the grid. The time and the occupation rates of the chargers are as well evaluated. The optimality is researched for long way drives on electric mode. The results illustrate a method to rethink the usage and the energy management on the vehicle during the driving. As well it is researched how to adapt the recharging capacities and their location on the grid, by using a holistic approach. The target is to propose a high quality service for the electric mobility for long way drives.

International audience; Today manufacturing systems face a volatile demand with varying customer needs in terms of both volume and product mix ratio. The highly automated dedicated production lines can not fulfil the demand diversity which needs quick adaptation of the production system. Market fluctuations for the next years are unknown and products have shorter lifecycles. In order to specify precisely needs of factories regarding flexibility, this paper presents a methodology using a qualitative analysis and its application to a use case company. The aim is identification of current needs regarding reconfigurability of production systems and following research directions. To do so, decision makers from various fields and decision levels are identified and interviewed individually using a questionnaire. An Analytic Hierarchy Process (AHP) is also applied to identify weights of the six characteristics of reconfigurability: modularity, integrability, customization, convertibility, scalability and diagnosability; based on the experience of the interviewed decision-makers. Indeed, there is no standardized reconfigurability indicator for the assessment of a production system regarding its changeability capacity. Weighting of these characteristics is the first step before computing numerical values for each characteristic based on a mathematical model proposed in literature.

Trija Vaidya,1,2 Claire de Bisschop,2 Marc Beaumont,3,4 Hakima Ouksel,5 Véronique Jean,6 François Dessables,7 Arnaud Chambellan,1,8 On behalf of IRSR RéhaEffort cohort group 1Explorations Fonctionnelles Respiratoires, l’institut du thorax, CHU de Nantes, 2Université de Poitiers, Laboratoire MOVE EA 6314, F-86000 Poitiers, 3Pulmonary Rehabilitation Unit, Morlaix Hospital Centre, 4European University of Occidental Brittany, EA3878, Brest, 5Service de Pneumologie, CHU d’Angers, Angers, 6Service de Réhabilitation Respiratoire, Soins de Suite et Rééducation, CHU de Nantes, 7Service de Réhabilitation Respiratoire, la Tourmaline, UGECAM, 8Université de Nantes, Laboratory EA 4334 “Mouvement, Interactions, Performance,” Nantes, France Background: The 1-minute sit-to-stand (STS) test could be valuable to assess the level of exercise tolerance in chronic obstructive pulmonary disease (COPD). There is a need to provide the minimal important difference (MID) of this test in pulmonary rehabilitation (PR).Methods: COPD patients undergoing the 1-minute STS test before PR were included. The test was performed at baseline and the end of PR, as well as the 6-minute walk test, and the quadriceps maximum voluntary contraction (QMVC). Home and community-based programs were conducted as recommended. Responsiveness to PR was determined by the difference in the 1-minute STS test between baseline and the end of PR. The MID was evaluated using distribution and anchor-based methods.Results: Forty-eight COPD patients were included. At baseline, the significant predictors of the number of 1-minute STS repetitions were the 6-minute walk distance (6MWD) (r=0.574; P

To C. Bathias memory Many components in several industries are loaded in VHCF regime, either at high frequencies (wheels of high speed trains, blades in aircraft turbojet engines, etc.) or at lower frequencies during decades (artificial heart, mooring chains for off-shore petroleum platforms, etc.). Testing specimens up to 1E9 or 1E10 cycles in a realistic time requires to use a very high loading frequency (20 or 30 kHz). Several devices using the ultrasonic testing technique are described in [1]. Specimens can be tested under tension (R=-1 or R>0), torsion (R=-1 or R>0) or bending (R>0), either at room, low or high temperature (up to 600°C), in air or in liquid environment, but there is no machine for testing specimens under multiaxial loading. That is the reason why a new fatigue testing device has been developed to test specimens under biaxial loading at 20 kHz. This new machine is able to test flat smooth specimens under biaxial bending. The specimen, with a disc geometry, is placed on a circumferential frame. The load is applied at the center of the upper face, so that the stress state on the opposite face is a biaxial proportional stress state. Several positive loading ratios can be applied. This machine is interesting - for instance - to test under biaxial loading a cast aluminum alloy (used to produce cylinder heads) in order to determine its fatigue strength at high hydrostatic pressure. The principle of this machine and the first results obtained in VHCF regime on such aluminum alloy are presented and compared with those obtained in literature under a similar stress state in HCF regime [2, 3]. The crack initiation is investigated, as two competing parameters play a role: the biaxial stress state which is maximal on the surface, and the possible presence of subsurface defects. [1] Bathias C, Paris PC. (2005) Gigacycle Fatigue in Mechanical Practice. New York USA: Marcel Dekker Publisher Co. [2] Koutiri I, Bellett D, Morel F, Augustins L. and Adrien J. (2013) High cycle fatigue damage mechanisms in cast aluminium subject to complex loads. International Journal of Fatigue, Vol. 47: 44–57. [3] Koutiri I., Morel F., Bellett D. and Augustins L. (2009) Effect of high hdrostatic stress on the fatigue behaviour of metallic materials,12th International Conference on Fracture ICF-12, Vol. 5: 3694-3703

Introduction Nowadays, air pollution is becoming more and more critical in huge overcrowded towns with large industrial activities. This is a societal problem causing more than 3 million deaths/year according to WHO [1]. As a result, monitoring of the concentration of gases or Particulate Matter (PM) is more and more expected in polluted areas. Large equipment is usually installed for this purpose, but increasingly sophisticated research is being conducted to use sensitive and reliable sensors of low cost and small size with reduced power. Among the existing sensors, resonant MEMS sensors are known for their high sensitivities to gas and PM [2]. Previous work already showed that printed self-actuated and self-readout piezoelectric cantilevers using longitudinal vibration mode are good candidates for mass detection [3]. In this work, feasibility of piezoelectric transducers for PM detection, more precisely cigarette smoke particles, is shown. Transducer processing and experimental set-up The cantilever-based piezoelectric transducers are fabricated using screen-printing technology associated with sacrificial layer technique. In this process, all the layers are successively printed before a co-firing at 900°C, leading to free-standing microcantilevers. The final transducers are made of a PZT active layer sandwiched between to Au electrodes, the clamping part being attached to an alumina ceramic substrate. Details on the process can be found in [3]. Figure 1 shows the design of all layers and photographs of dried and fired cantilevers. After polarization of the PZT, determination of the resonant frequency f0 of the in-plane longitudinal axial first resonant mode is led using an Agilent Impedance analyzer. This frequency f0 is the maximum of the conductance curve extracted using a polynomial fit [3]. High quality factor (highest 1700), low noises (lowest 0.5Hz) and theoretical sensitivities between 50 and 740Hz/µg are obtained for resonators of dimensions 4x1x0.1mm3 to 1x1x0.1mm3, respectively. The smallest resonator 1×1×0.1mm3is finally placed in the test bench shown Fig. 2 allowing PM deposition on the surface of the PZT cantilever. The PM are either calibrated silica powders generated by stirring (in the container with a magnetic agitator) or cigarette particles produced by a cigarette burning (Fig. 3). During PM particle deposition, temperature (T) and humidity (RH) are measured thanks to sensors placed as close as possible to the resonator. These values are stabilized before the PM generation thanks to a 20 min N2 flow. Last, a Fidas Frog optical particle analyzer placed at the end of the gas line gives information on the PM generation. Results and Conclusions Feasibility of silica powder detection with the experimental bench was demonstrated in a previous work [4] with estimated mass of 23ng. As expected, the PM particles are detected by the analyzer when cigarette smoke is released (Fig. 4c). Resonant frequency curve is a function of T, RH and PM variations (Fig. 4a). Indeed, previous humidity tests showed that the resonant frequency of the microcantilever decreased with both temperature and humidity [4]. Here, three distinct behaviors can be discussed. In fact, the overshoot (labeled 1 in Fig 4a) may be attributed to an important RH change as seen Fig. 4b. The corresponding calculated sensitivity (~7Hz/%RH) proves that the second frequency shift (~200Hz ) is too high to be only due to RH variation (5%). This clearly illustrates that other contributions have to be taken into account such as T variations and/or PM deposition. Once this transitory state is achieved, signal stabilization indicates that the cigarette particles are immobilized on the cantilever top electrode. SEM analysis (Fig. 4d, 4e and 4f) confirm the PM cigarette deposition. The corresponding frequency shift is estimated to 110Hz. Considering the theoretical sensitivity of 740Hz/µg estimated for this device, deposited cigarette particle mass can be estimated to 0,46µg. Then, using values given by the PM analyzer and the cell volume (2cm3) 128 µg is considered to be flowing around the sensor. Hence, a collection efficiency of 0.36% can be deduced. With this first bench test, it has been shown that printed microcantilevers can be used as fine particle sensors. Temperature and relative humidity are interfering on the measurement, clearly showing the necessity of temperature compensation and humidity detection. Knowing the complex composition of the cigarette, other pollutants may affect the resonance behavior. Also, collection efficiency appears to be an improvement route, as well as considering sensor cleaning after several trials [5] . References [1] WHO, Ambient air pollution A global assessment of exposure and burden of disease. Switzerland: World Health Organization, 2016. [2] Piezoelectric MEMS Resonators for Cigarette Particle Detection, Javier Toledo, Víctor Ruiz-Díez , Maik Bertke, Hutomo Suryo Wasisto, Erwin Peiner and José Luis Sánchez-Rojas, Micromachines 2019, 10, 145; doi:10.3390/mi10020145 [3] Fabrication and characterisation of piezoelectric screen-printed in plane resonant microcantilevers used as gravimetric sensors, Simon Grall, Isabelle Dufour, Vincent Aubry and Hélène Debéda, 2019, Smart Material and structures Volume 28, Number 10 [4] Screen-Printed Microcantilevers for Environmental Sensing, Simon Grall, Hélène Debéda Isabelle Dufour and Vincent Aubry MDPI Proceedings 2018, 2, 722; doi:10.3390/proceedings2130722 [5] Aerosol mass concentration measurements: Recent advancements of real-time nano/micro systems U.Soysal, E. Géhin,, E. Algré, B. Berthelot, G. Da, E. Robine, Journal of Aerosol Science 114 (2017) 42–54 Figure 1

International audience; The present paper focuses on the fatigue life of a Compacted Graphite cast Iron (CGI) as compared to a Spheroidal Graphite cast Iron (SGI). Fatigue crack growth laws have been determined with digital image correlation. Main difference between the materials is that cracks propagate faster in the CGI than in the SGI. X-ray tomography was also used in order to assess graphite morphologies and crack shapes. A complex morphology was observed for the vermicular graphite with rounded edges that limit notch effects. The crack spreads easily in CGI via a quasi cleavage mechanism and by propagating through graphite mainly by breaking the vermicules.

The technology of cylinder of deactivation has been developed in order to reduce gas consumption and CO2 emissions. Two strategies were studied at groupe PSA called fixed and rotating deactivations depending on the number of cylinders deactivated per engine cycle. This implies non neglecting modifications of sound and vibrations transmitted to the car cabin depredating the global comfort of the car.This research work focused on how driver’s comfort was altered by these engine configurations and how it would be possible to improve this comfort. Among the solutions possible, appears the principle of real-time sonification of the engine noise.To answer these questions, five perceptual experiments have been conducted. First, the aim was to evaluate global comfort with different engine configurations and validate the use of a vibro-acoustic simulator. This showed that one deactivation strategy was significantly reducing the comfort evaluation. Then, we focused on the second strategy which was also considered as not comfortable. On the third experiment, we were interested in finding an acceptable threshold between the vibrations and sounds with the deactivation and with the usual engine configuration. This led to a target of signal to reach in order to provide acceptable situations in terms of sound and vibrations. In the last two experiments, we were interested in the simulation of two solutions about the deactivation settings that would reduce the annoyance: the modification of the engine speed range in which the deactivation occurs and the softening of horizontal suspensions part in order to reduce vibrations resonances at low engine speed., La technologie de désactivation des cylindres a été développée dans le but de réduire la consommation de carburant et les émissions de CO2. Deux stratégies ont été étudiées au sein du groupe PSA, les désactivations fixes et rotatives, en fonction du nombre de cylindres désactivés par cycle moteur. Ceci implique des modifications non négligeables des sons et des vibrations transmis à l'habitacle de la voiture, ce qui nuit au confort global de la voiture.Ce travail de recherche s'est intéressé à la manière dont le confort du conducteur était modifié par ces configurations moteur et comment il serait possible d'améliorer ce confort. Parmi les solutions possibles, apparaît le principe de la sonification en temps réel du bruit du moteur.Pour répondre à ces questions, cinq expériences perceptives ont été menées. Tout d'abord, il s'agissait d'évaluer le confort global avec différentes configurations du moteur et de valider l'utilisation d'un simulateur vibro-acoustique. Ces expériences ont montré qu'une stratégie de désactivation réduisait de manière significative l'évaluation du confort. Ensuite, nous nous sommes concentrés sur la deuxième stratégie qui était également considérée comme peu confortable. Lors de la troisième expérience, nous avons cherché à trouver un seuil acceptable entre les vibrations et les sons avec la désactivation et avec la configuration habituelle du moteur. Ceci a conduit à une cible de signal à atteindre afin de fournir des situations acceptables en termes de sons et de vibrations. Dans les deux dernières expériences, nous nous sommes intéressés à la simulation de deux solutions concernant les paramètres de désactivation qui réduiraient la gêne : la modification de la plage de régime moteur dans laquelle la désactivation se produit et l'assouplissement de la partie horizontale des suspensions afin de réduire les résonances des vibrations à bas régime.

International audience; The present manuscript deals with experimental investigations on thermal effects of air leakage zones at the boundaries of the vehicle hood. Measurements are carried out on a Peugeot 207 (Front Wheel Drive) in wind tunnel. The front wheels are activated by the car's engine and rolling on controlling rollers built in the wind tunnel. In parallel, the wind velocity is well controlled in order to simulate real conditions of driving. The underhood compartment is equipped with 80 thermocouples distributed on different components. Three operating conditions are studied according to the engine's rpm, to the wind and wheels velocities. The leakage zones are purposely clogged with five different configurations. The effect of the leakage zones has shown significant impact on the temperature field and has been physically analyzed.

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International audience; A new hybrid meta-modeling approach is proposed and developed for the propagating and quantifying of uncertainties in friction-induced instabilities. According to the available knowledge about design parameters, the associated uncertainty can be described by using different models. Hence, hybrid meta-models prove to be necessary to simultaneously treat different uncertainty models. So, this study presents a novel hybrid meta-model issued from the associating of the kriging formalism together with the generalized polynomial chaos for the prediction of friction-induced instabilities submitted to interval and probabilistic uncertainties. Its assessing through the considering of a friction system, reveals suitable accuracy about the estimating of the dispersion of the occurrences of instabilities. Moreover, it offers a promising alternative to the prohibitive Monte-Carlo/scanning based methods that are usually used for the same task.

International audience; We consider multi-objective optimization problems, min x∈Rd(f1(x), . . . , fm(x)), where the functionsare expensive to evaluate. In such a context, Bayesian methods relying on Gaussian Processes(GP) [1], adapted to multi-objective problems [2] have allowed to approximate Pareto fronts ina limited number of iterations.In the current work, we assume that the Pareto front center has already been attained (typicallywith the approach described in [3]) and that a computational budget remains. The goal is touncover of a broader central part of the Pareto front: the intersection of it with some regionto target, IR(see Fig. 1). IRhas however to be defined carefully: choosing it too wide, i.e.too ambitious with regard to the remaining budget, will lead to a non converged approximationfront. Conversely, a suboptimal diversity of Pareto optimal solutions will be obtained if choosinga too narrow area.The GPs allow to forecast the future behavior of the algorithm: they are used in lieu of thetrue functions to anticipate which inputs/outputs will be obtained when targeting growingparts of the Pareto front. Virtual final Pareto fronts corresponding to a possible version of theapproximation front at the depletion of the budget are produced for each IR. A measure ofuncertainty is defined and applied to all of them to determine the optimal improvement region IR∗, balancing the size of the approximation front and the convergence to the Pareto front.

International audience; The design phase of a car development is a long and tedious process that requires a lot of trial and error. In this article we introduce a new concept aiming to make this process easier and more interactive. Our solution consist in using a modular robot together with a shape memory polymer in order to create an interactive model of a car piece. We came up with an algorithm to approximate the surface of a piece using NURBS to describe the shape and the resulting molded polymer is simulated on our simulator VisibleSim, proving the accuracy of our system.

Optimizing nonlinear systems involving expensive computer experiments with regard to conflicting objectives is a common challenge. When the number of experiments is severely restricted and/or when the number of objectives increases, uncovering the whole set of Pareto optimal solutions is out of reach, even for surrogate-based approaches: the proposed solutions are sub-optimal or do not cover the front well. As non-compromising optimal solutions have usually little point in applications, this work restricts the search to solutions that are close to the Pareto front center. The article starts by characterizing this center, which is defined for any type of front. Next, a Bayesian multi-objective optimization method for directing the search towards it is proposed. Targeting a subset of the Pareto front allows an improved optimality of the solutions and a better coverage of this zone, which is our main concern. A criterion for detecting convergence to the center is described. If the criterion is triggered, a widened central part of the Pareto front is targeted such that sufficiently accurate convergence to it is forecasted within the remaining budget. Numerical experiments show how the resulting algorithm, C-EHI, better locates the central part of the Pareto front when compared to state-of-the-art Bayesian algorithms., Submission pre-print, extended version

Driving is a high demanding task, in terms of cognitive resources and in its proneness to generate stress in the driver. As it is interacting with personality and environmental factors, stress might influence our abilities to drive properly, and thus have dramatic consequences. Our purpose is to study the multiple interactions between vulnerability to stress and individual characteristics. An online survey has been set up to collect data about daily life, personality traits, mood, coping strategies and driving behaviors. Results are then processed to find correlations between these dimensions., La conduite automobile demande un effort cognitif et un niveau d'attention importants. Sous l'emprise du stress, les fonctions cognitives engagées peuvent se détériorer et avoir un impact sur les performances en conduite. Le stress peut se définir comme le processus cognitif d'évaluation et de prise en compte des menaces et des défis de son environnement et a des impacts psycho-physiologiques souvent négatifs. La vulnérabilité au stress ou la capacité individuelle d'adaptation pourrait moduler la disposition du conducteur à maintenir un niveau de performance suffisant pour avoir une conduite sûre. Cette étude préliminaire vise à révéler des grandes tendances dans les relations entre les différentes dimensions caractérisant les conducteurs, afin de comprendre les différences interindividuelles de la vulnérabilité au stress. Une enquête en ligne, constituée de questionnaires validés évaluant le stress de la vie quotidienne, l'humeur, les stratégies d'adaptation, le type de personnalité et le style de conduite, est diffusée à un public de conducteurs tout venant. Les données sont collectées puis traitées par analyse multidimensionnelle. L'objectif est de mettre en évidence des relations entre profils psychologiques d'individus, notamment vis-à-vis de la vulnérabilité au stress, et les styles de conduite. Les résultats sont discutés en termes de typologie, de classification d'individus et de facteurs prédominants.

Driving is a high demanding task, in terms of cognitive resources and in its proneness to generate stress in the driver. As it is interacting with personality and environmental factors, stress might influence our abilities to drive properly, and thus have dramatic consequences. Our purpose is to study the multiple interactions between vulnerability to stress and individual characteristics. An online survey has been set up to collect data about daily life, personality traits, mood, coping strategies and driving behaviors. Results are then processed to find correlations between these dimensions.

Connected and Automated Vehicle is the next goal for car manufacturers towards traffic safety and efficiency. To ensure safety, automotive applications rely on data acquired through vehicular communication and locally embedded sensors. Among these data, classification data permit the autonomous vehicle to decide to pass another vehicle according to not only its dynamic but also its length and width. Unlike sensors which are prone to measurement errors, vehicular communication allows others connected vehicles to provide their exact dimension values based on car manufacturer specification. However, this fact assumes that other road users may not lie. Currently, researchers focus on malicious mobility data but none focus on classification data within V2X message. Therefore, this paper proposes a misbehavior classifier related to classification data for multiple types of road users. Thus, we compare four methods that include a threshold classifier (MinMax) and three machine learning algorithms.

International audience; Improvement of vibroacoustic models prediction capabilities in a probabilistic context requires a adapted metric to compare experimental results with stochasitic computations. The likelihood appears as the natural tool to compare experiments with probabilistic computations as soon as the probability of a given result may be computed. Since vibroacoustic analysis mainly rely on complex Frequency Response Functions ([FRF] = {ω → [FRF(ω)]}) matrices that can be easily measured and computed, the likelihood of such complex and frequency dependent matrices is investigated. A two stage statistical reduction, based on Indepen-dant Components Analysis, is proposed in order to separate statisticaly independent components with complex amplitudes which probability may be computed independently one from each others. Bi-dimensional probability density fonctions of the complex components amplitudes are deduced from a Monte-Carlo simulation of a non-parametric stochastic model, using MSC/NASTRAN. The proposed statistical reduction presents many interesting properties regarding the physical understanding of FRF matrices as well as a numerical aspects.

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This work investigates different geometries for fully screen-printed self-actuated self-readout microcantilevers made using a sacrificial layer process. The microcantilevers are made of PZT sandwiched between two gold electrodes. Q-factors as high as 1300 are reported. Promising theoretical sensitivities are reported (1000 Hz/µg at 620 kHz) and applications as humidity, temperature and particles sensor are explored in this work.

International audience; An investigation of a polyamide 6.6/6 composite reinforced with woven glass fibers is described with a focus on its response to fatigue solicitations. The main purpose is to elaborate a quantitative and a qualitative study of the induced damage as well as its detectability. To do so, several nondestructive testing methods were used. The different damage mechanisms, relative to fatigue loading, were identified using X-Ray tomography as a reference for the ultrasonic investigations. As a result, each damage mechanism is visualized and a measure of the induced void is established for comparison. An ultrasonic investigation based on C-scans and guided waves is performed under different signal analysis approaches in an attempt to extract as much information as possible. The discoveries and experiences are important in the framework of a collaboration with the automotive industry en for biomechanical applications.

International audience; Deep Neural Networks are achieving great success in various fields. However, their use remains limited to non critical applications because their behavior is unpredictable and unsafe. In this paper we propose some fault tolerant approaches based on diversifying learning in order to improve DNNs dependability and particularly safety. Our main goal is to increase trust in the outcome of deep learning mechanisms by recognizing the unlearned inputs and preventing misclassification.

International audience; The HVAC system represents the main auxiliary load in electric vehicles (EVs) and requires efficient control approaches that balance energy saving and thermal comfort. In fact, passengers always demand more comfort, but on the other hand the HVAC system consumption strongly impacts the vehicle driving range, which constitutes the major concern in EVs. In this paper, dynamic programming is applied to develop an HVAC system supervisor that optimizes the thermal comfort on a given journey, for given climatic conditions and energy available. The electric vehicle model and the optimization approach are presented. Two test- cases, corresponding to hot climate, are simulated. In the first one, the energetic cost of improved comfort is quantified, while in the second one the trade-off between driving speed and thermal comfort is analyzed.

International audience; Garantir le confort thermique de l'habitacle tout en minimisant la consommation énergétique du véhicule est un enjeu clef pour la conception de la supervision du système de climatisation (HVAC) des véhicules électriques (VE). En effet, la consommation énergétique du HVAC et son comportement dynamique influencent considérablement l'autonomie du VE. La gestion énergétique proposée dans ce travail optimise le confort thermique sur un trajet donné en utilisant la programmation dynamique. Des simulations ont été réalisées pour des conditions météorologiques données sur un trajet afin de calculer le confort thermique pour différents niveaux d'énergie disponible. Les résultats montrent l'intérêt de l'approche proposée pour déterminer le meilleur compromis entre consommation énergétique et confort thermique.

International audience; Multi-objective optimization aims at finding the Pareto set composed of all the best trade-off solutions between several objectives. When dealing with expensive-to-evaluate black box functions, surrogate-based approaches, in the vein of EGO have proven their effectiveness. However, for extremely narrow budgets, and/or when the number of objectives is large, uncovering the entire Pareto set becomes out of reach even for these approaches. In this work, we restrict our search to well-chosen targeted parts of the Pareto set. This accelerates the search as only a subset of the objective space is considered. As an end-user would typically choose solutions with equilibrated trade-offs between objectives rather than ones favoring a single objective over the others, we will focus on the central part of the Pareto Front, which corresponds to the most well-balanced solutions. First, we discuss how to define and estimate the center of the Pareto Front. That estimated point has to fairly represent the topology of the front, in spite of the parsimonious knowledge of the objective space. Then, three infill criteria which will guide the optimization, includiing the Expected Hypervolume Improvement are studied and tailored through some of their hyperparameters to enable them to target.To assess performance, a benchmark built from real-world airfoil aerodynamic data, with variable dimension and number of objectives is used. Compared with standard techniques, the proposed methodology leads to a faster and a more precise convergence towards the Pareto Frontin the targeted region.

International audience

International audience; This paper describes a Stirling Engine used as an Auxiliary Power Unit in a Series Hybrid Vehicle. Integration of the Stirling engine in the vehicle power train is described. Using a vehicle model, fuel consumption is compared between Stirling Engines and Spark ignition Engines. The results show that Stirling engines present good performances compared to internal combustion engines in the same configuration. Finally, the prototype design and first experimental results are presented.

Relations between existing spot-weld finite element models and the mechanical behaviour of spot-weld are investigated for fatigue design application. Specifically, the different zones that constitute the numerical model are interrogated with respect to physical observation. In order to identify the Mechanical Influence Area of the Spot-Weld here designated as “MIASW” we propose a methodology to determine numerically its size. Hence, we develop a finite element coupon representing a spot-weld under a basis of four unit load cases. The coupon provides mechanical quantities of interest that allows us to characterize the spot-weld response that shell element are unable to represent. This response is crucial to be captured for further fatigue analysis.

Plasmonic resonators are excellent candidates to control reflectance of functionalized substrates. Because of their subwavelength characteristic dimensions, they can even be used to modify the color of transparent glass plates without altering the transparency quality. Their spatial arrangement must be carefully chosen so that the plates do not produce nonspecular diffraction, whatever their spatial density. We compare here the response of silver nanoparticles (NPs) arrays with different NPs sizes, spatial densities, and arrangements (periodic and correlated disordered). The effects of these geometrical parameters are analyzed in detail by measuring the reflectance and transmittance spectra in visible wavelength. We show that correlated disordered gratings attenuate diffraction effects appearing at lower spatial densities while keeping similar reflectance and transmittance responses and maintaining clear transparency of the glass plate. Promising configurations for head-up displays and applications in aug...

International audience; La présente étude se place dans le cadre général du développement de machines à absorption eau/bromure de lithium compactes pour la climatisation automobile, permettant de réduire les émissions de CO 2 en valorisant les rejets thermiques des moteurs. Elle porte plus particulièrement sur la caractérisation du comportement d'un désorbeur à plaques, développé par la société Mahle pour le compte du constructeur automobile PSA Group. Les performances du désorbeur, traduites en termes d'efficacité massique, sont étudiées pour différentes conditions de fonctionnement, en dissociant les parts de puissances transmises à la solution sous forme de chaleurs sensible et latente.

National audience; Ce travail s’inscrit dans le cadre de l’amélioration de l’intelligibilité des signaux de parole en contexte bruité automobile. Contrairement aux approches de rehaussement il s’agit ici de réallouer l’énergie de la parole pour améliorer sa compréhension, mais sans modifier le RSB (Rapport Signal sur Bruit) global. L’approche étudiée consiste à effectuer cette réallocation en maximisant une fonction objectif basée sur le SII (Speech Intelligibility Index). Ce critère est calculé à partir d'une somme pondérée de RSB sur différents canaux fréquentiels et il est alors possible d’appliquer un égaliseur dynamique aux signaux de parole sous la contrainte donnée. À la différence d’autres méthodes, nous proposons une résolution exacte du problème d'optimisation du SII avec adaptation dynamique aux signaux (parole et bruit). Elle prend en compte la sensibilité acoustique de l’utilisateur et utilise une échelle de puissance adaptée au contexte de manière à ne pas augmenter l’intensité perçue. Des résultats préliminaires montrent une nette amélioration de l’intelligibilité et des tests d’écoute subjectifs viendront valider la méthode. L’influence des différents paramètres d'ajustement de la méthode sera détaillée pour d'une part, mettre en évidence des aspects importants liés à l’égalisation et d'autre part, relever certaines limitations d'une approche basée sur le SII.

International audience; This paper presents an ongoing work aimed at evaluating Extended Reality training for the interaction of general public with mobile robots, with a particular focus on semi-autonomous cars.

International audience

This article presents a gesture sonification system for blind interface manipulation based on interaction with a virtual object (VO). Commands are given through gestures, and sounds carry the feedback on how the VO was affected. The sound feedback allows the user to manipulate the interface without vision. Here, we chose to focus on a swipe gesture. In the first part of the article, we study different curves that relate the VO parameters to sound parameters to create the most natural association between the two.

International audience; Many stages of the industry workflow have been benefiting from CAD software applications and real-time computer graphics for decades allowing manufacturers to perform team project reviews and assessments while decreasing the need for expensive physical mockups. However, when it comes to the perceived quality of the final product, more sophisticated physically based engines are often preferred though involving huge computation times. In this context, our work aims at reducing this gap by providing a predictive rendering solution leveraging the computing resources offered by modern multi-GPU supercomputers. To that end, we propose a simple static load balancing approach leveraging the stochastic nature of Monte Carlo rendering. Our solution efficiently exploits the available computing resources and addresses the industry collaboration needs by providing a real-time multiuser web access to the virtual mockup.