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Development of a finite element strategy for the modeling of thermo-elastic nano-reinforced materials
No full textInternational audienceFor nanoreinforced materials, the inclusion surface/matrix volume ratio is important. Therefore, matrix/reinforcement interface behavior has a major influence on the local and effective material behaviour. Focusing on thermo-elasticity, a numerical approach based on the finite element method is developed for nanomaterials with imperfect coherent interface modeling. For the numerical analysis, a convergence study is performed for multiple homogenization schemes with different boundary conditions
Conférence invitée : Optimisation de structures en acier sûres pour le secteur automobile : le laboratoire commun FuseMetal, un exemple de partenariat académique/industriel
No full textInternational audienceLe récent développement de nuances d’acier à hauterésistance (AHSS) permet d’assurer la sécurité des structuresautomobiles tout en répondant aux préoccupations de leurallègement. L’utilisation de ces matériaux peut être étendue grâce àdes avancées technologiques et scientifiques liées à l’assemblage despièces de la structure des véhicules. Le laboratoire communFuseMetal, issu de la réunion de chercheurs du laboratoire Robervalde l’UTC et du centre Global R&D d’ArcelorMittal France, développedonc des projets autour de l’opportunité que représente l’usage desaciers dits de « 3ème génération », et du potentiel que représentel’utilisation de la technique de fabrication additive pour les aciers etleurs applications
Assessing reliability and validity of different stiffness measurement tools on a multi-layered phantom tissue model
No full textInternational audienceChanges in the mechanical properties (i.e., stiffness) of soft tissues have been linked to musculoskeletal disorders, pain conditions, and cancer biology, leading to a rising demand for diagnostic methods. Despite the general availability of different stiffness assessment tools, it is unclear as to which are best suited for different tissue types and the related measurement depths. The study aimed to compare different stiffness measurement tools' reliability on a multi-layered phantom tissue model (MPTM). A polyurethane MPTM simulated the four layers of the thoracolumbar region: cutis (CUT), subcutaneous connective tissue (SCT), fascia profunda (FPR), and erector spinae (ERS), with varying stiffness parameters. Evaluated stiffness measurement tools included Shore Durometer, Semi-Electronic Tissue Compliance Meter (SCTM), IndentoPRO, MyotonPRO, and ultrasound imaging. Measurements were made by two independent, blinded examiners. Shore Durometer, SCTM, IndentoPRO, and MyotonPRO reliably detected stiffness changes in three of the four MPTM layers, but not in the thin (1 mm thick) layer simulating FPR. With ultrasound imaging, only stiffness changes in layers thicker than 3 mm could be measured reliably. Significant correlations ranging from 0.70 to 0.98 (all p < 0.01) were found. The interrater reliability ranged from good to excellent (ICC(2,2) = 0.75~0.98). The results are encouraging for researchers and clinical practitioners as the investigated stiffness measurement tools are easy-to-use and comparatively affordable
Acute Stress Classification with a Stroop task and in-office biophilic Relaxation in Virtual Reality based on Behavioral and Physiological data
No full textInternational audienceAcute stress in Virtual Reality (VR) requires more experimental inputs to determine how VR affects human psychophysiology, how to alleviate stress, and whether visual fatigue can impact its detection with machine learning. We randomly assigned 93 participants to three experimental conditions: Control, Stressful, and Stereoscopy. Participants fulfilled a rest-baseline period, a Stroop task, an STAI-6 questionnaire, and a relaxation period. We recorded behavioral and physiological data from eye-tracking (ET), electrocardiogram (ECG), and electrodermal activity (EDA). We identified three acute stress levels based on STAI-6 scores and behavioral data. We deployed linear models penalized with L1 constraints to select the most relevant features correlated with stress levels. The EDA sensor provided the most selected features compared to ECG and ET. We compared SVM,Logistic Regression, and Gradient boosting classifiers. The Logistic regression with ElasticNet constraint provides the best feature selection. The Gradient boosting method is the most performant Acute stress classifier, with 89.86% accuracy and an 89.8% F1 score
Plans locaux d’urbanisme et gestion des eaux pluviales : entre volonté politique et incertitude pratique.
No full textInternational audienceLe changement climatique entraîne une altération du cycle naturel de l’eau, notamment en milieu urbain. Pour s’adapter, des solutions de gestion des eaux pluviales (GEP) à la source, de végétalisation ou de désimperméabilisation des sols sont préconisées. Leur déploiement est, toutefois, assujetti aux plans locaux d’urbanisme (PLUi) qui réglementent l’occupation du sol au niveau spatial. Cependant, le fait que la réglementation autorise ces solutions, ne garantit pas leur implémentation, l’effet d’une règle n’étant pas automatique. En effet, les PLUi peuvent établir des règles métriques ou quantitatives, dont les répercussions peuvent être estimées. En même temps, par souci de souplesse, les formulations qualitatives ou appréciatives sont admises. Cela introduit une incertitude quant à l’effet réel des règles d’urbanisme. Ainsi, lorsque les règles encourageant l'implémentation des solutions de GEP sont présentées sous forme qualitative, il n’y a pas de certitude à ce que les porteurs de projets en tiennent compte volontairement. Cette souplesse engendre également une marge de manœuvre dont l’administration disposera lors de l’instruction des autorisations d’urbanisme. La multiplicité des interprétations peut conduire à l’incertitude, surtout si la règle est imprécise. Dans l’objectif de révéler dans quelle mesure le PLUi est déterministe quant aux solutions de GEP, nous analysons un échantillon des permis de construire de Bouguenais, une commune représentative de la métropole française de Nantes. Nous analysons de manière détaillée ce que la réglementation permet en matière de GEP et comment certains projets urbains en ont tenu compte. Les résultats montrent que les pétitionnaires font usage des règles métriques et appréciatives de façon combinatoire. Le seuil minimal demandé par les règles métriques est rarement dépassé par les projets analysés. Il semblerait que le caractère incontournable des dispositions quantitatives soit la clé pour assurer la GEP du territoire. En revanche, la majorité des projets sont volontaristes en termes de traitements paysagers en faisant usage des dispositions qualitatives. Enfin, il ressort que le déterminisme de la règle n’est pas seulement lié à la modalité choisie pour sa rédaction, mais aussi à la manière dont les instructeurs guident les pétitionnaires vers une conception des projets plus adaptée à l’approche de la collectivité
Robust bounded control scheme for quadrotor vehicles under high dynamic disturbances
No full textInternational audienceIn this paper, an optimal bounded robust control algorithm for secure autonomous navigation in quadcopter vehicles is proposed. The controller is developed combining two parts; one dedicated to stabilize the closed-loop system and the second one for dealing and estimating external disturbances as well unknown nonlinearities inherent to the real system's operations. For bounding the energy used by the system during a mission and, without losing its robustness properties, the quadratic problem formulation is used considering the actuators system constraints. The resulting optimal bounded control scheme improves considerably the stability and robustness of the closed-loop system and at the same time bounds the motor control inputs. The controller is validated in real-time flights and in unconventional conditions for high wind-gusts and LoE-Loss of Effectiveness-in two rotors. The experimental results demonstrate the good performance of the proposed controller in both scenarios
Exploring the concept of " mobility hubs " and assessing their impacts in two European cities
No full textInternational audienceMobility hubs bring together, connect and provide users with several modes of transport. Cities adopt them to help reach several objectives, like the reduction of pollution, congestion and car ownership. As part of the Interreg Mobi-Mix, we have taken a close look at mobility hubs (Interreg 2 Seas, 2020). Based on bibliographic research, discussions with experts and city stakeholders, we established a state of the art that will help to better understand the concept. Cities will benefit from recommendations for a better implementation of mobility hubs. A method of estimating the impact on CO2 emissions at each project step has been developed for two partner cities, Norfolk and Valenciennes. It is mainly based on usage surveys and results from other cities as well as multiplicative factors. The first results point a reduction in CO2 emissions that is greater than the targeted objectives
A Method for Quantifying Back Flexion/Extension from Three Inertial Measurement Units Mounted on a Horse’s Withers, Thoracolumbar Region, and Pelvis
No full textInternational audienceBack mobility is a criterion of well-being in a horse. Veterinarians visually assess the mobility of a horse’s back during a locomotor examination. Quantifying it with on-board technology could be a major breakthrough to help them. The aim of this study was to evaluate the accuracy of a method of quantifying the back mobility of horses from inertial measurement units (IMUs) compared to motion capture (MOCAP) as a gold standard. Reflective markers and IMUs were positioned on the withers, eighteenth thoracic vertebra, and pelvis of four sound horses. The horses performed a walk and trot in straight lines and performed a gallop in circles on a soft surface. The developed method, based on the three IMUs, consists of calculating the flexion/extension angle of the thoracolumbar region. The IMU method showed a mean bias of 0.8° (±1.5°) (mean (±SD)) and 0.8° (±1.4°), respectively, for the flexion and extension movements, all gaits combined, compared to the MOCAP method. The results of this study suggest that the developed method has a similar accuracy to that of MOCAP, opening up possibilities for easy measurements under field conditions. Future studies will need to examine the correlations between these biomechanical measures and clinicians’ visual assessment of back mobility defects
Handling Inconsistency in (Numerical) Preferences Using Possibility Theory
No full textInternational audienceGathering the preferences of a user in order to make correct recommendations becomes a difficult task in case of uncertain answers.Using possibility theory as a means of modelling and detecting this uncertainty, we propose methods based on information fusion to make inferences despite observed inconsistencies due to user errors. While the principles of our approach are general, we illustrate its potential benefits on synthetic experiments using weighted averages as preference models
