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Classification of complex power quality disturbances under noisy environment using Root-Music and least square techniques
No full textInternational audienc
Eggshell Powder‐Based Eco‐Friendly Cellulose Nanofiber Aerogels With Excellent Thermal Insulation, Superior Flame Retardancy, and Exceptional Mechanical Durability
No full textInternational audienceABSTRACT Green flame‐retardant cellulose nanofiber‐based aerogels were synthesized by the incorporation of eggshell powder (ESP) via a simple mechanical mixing strategy. Various weight percentages of ESP powder (10%, 20%, and 30%) were mixed with 3 wt% of CNF suspension and then freeze‐dried. The ESP‐modified cellulose nanofiber‐based aerogels (ESP‐CNFA) were fabricated by combining 30 wt% ESP with a CNF suspension. The prepared aerogel demonstrated enhanced mechanical strength, outstanding flame retardancy, and extremely low thermal conductivity. The ESP‐modified cellulose nanofiber‐based aerogel (ESP‐CNFA) exhibited a LOI value of 32 and excellent flame‐retardant behavior in the vertical flammability test. The flame retardancy behavior of the ESP‐CNFA was analyzed by cone calorimetry test, which had a low peak heat release rate value of 22.8 kW/m 2 and a total heat release rate value of 5.7 MJ/m 2 . The low smoke production rate value of the ESP‐CNFA was highly desirable for fire safety applications in the current scenario. The low thermal conductivity of 31.7 mW/mK for the ESP‐CNFA demonstrated its effectiveness as an ideal green material for thermal insulation applications. The findings suggest that the ESP‐CNFA finds wide applications such as flame‐retardant materials in the packaging, building, automotive, and aerospace industries, without compromising their thermal insulation behavior
High-velocity laser-driven flyer impact on paraffin gel
No full textInternational audienceThe penetrating ballistic impact of thin 100 micrometers aluminum projectiles, accelerated at high velocities by laser-induced shock wave, on parafin gel is investigated. The laser-driven flyer experiments were conducted at BELENOS laser facility and allow the acceleration of projectile at high velocity ranging from 170 m s to 710 m s. The projectile is monitored during impact and penetration into gel targets using shadowgraphy with ultra-high speed camera. Its velocity is recorded by fast-imaging technics and correlated to Photonic Doppler Velocimeter (PDV) measurements. The ballistic impact phenomena such as the splash ejection on the front face of the gel target and the cavitation effect are analyzed. The strength resistance parameter in the Poncelet model of the gel is obtained from experimental data fit, which predicts the speed of a given fragment from its penetration depth in the target. The cavity dynamics highlights the influence of the strain rate on the mechanical behavior of paraffin gel target under penetrating ballistic impact
Performance Enhancement of Biocomposites Based on Poly (3‐Hydroxybutyrate‐Co‐3‐Hydroxyvalerate)/Polylactide Blend: Synergistic Effect of PHBV ‐ g ‐ MA Compatibilizer and Diss Fibers
No full textInternational audienceABSTRACT This study is focused on investigating the effects of untreated and treated Diss fibers ( Ampelodesmos mauritanicus ) and the PHBV‐ g ‐MA compatibilizer on the properties of biocomposites based on a poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) and poly(lactic acid) (PLA) blend (50/50 wt. %) prepared by melt compounding. Diss fibers and the PHBV‐ g ‐MA compatibilizer were incorporated into the polymer blend at 20 and 5 wt. %, respectively. To examine interfacial adhesion and compatibility between the different components of the system, contact angle measurements, as well as thermal and mechanical properties, of the PHBV/PLA blend and PHBV/PLA/Diss fiber biocomposites with and without the compatibilizer were investigated. The study showed that the addition of alkali‐treated Diss fibers resulted in a slight improvement in impact strength, from 15.4 to 20.7 kJ/m 2 , compared to the untreated biocomposites. Moreover, the addition of PHBV‐ g ‐MA to the alkali‐treated biocomposites led to a more significant improvement in flexural modulus, impact strength, and Shore D hardness, increasing from almost 2200 MPa, 20.0 kJ/m 2 and 74.4 to 3175 MPa, 23.1 kJ/m 2 and 83.4, respectively, compared to the PHBV/PLA blend. Furthermore, the compatibilized PHBV/PLA/Diss fiber biocomposites exhibited enhanced thermal properties and contact angle, indicating good interaction between the components. Overall, this study highlights the synergistic effect of Diss fibers and the PHBV‐ g ‐MA compatibilizer in improving the performance of the PHBV/PLA blend, contributing to the development of fully sustainable materials for rigid food packaging applications
Analysis of the tensile behaviour of flax fibre bundles as a function of the loaded volume
No full textInternational audienceAddressing the mechanical behaviour of flax bundles is a key point when used as reinforcements in composite materials. To determine their mechanical properties, the bundle cross-sectional area must be correctly assessed and has been estimated here using three types of models: elliptical, circular or polygonal. The circular model shows the higher disparity with twice the polygonal standard deviation. Innovatively, 3D rendering of bundles were carried out using microtomographic acquisitions, highlighting their partially cohesive unidirectional composite structure. Then, to analyse the phenomenon involved in the characterisation of bundles, mechanical properties were determined from a threshold value (first damage detected) and expressed as a function of the loaded volume (depends on the bundle cross-section area and the gauge length). To consider the dispersion of the bundles cross-sections, these properties were also weighted using the cross-section distribution curve. The results show their dependence on the volume and morphology of the tested bundles
A space-time hybrid parareal method for kinetic equations in the diffusive scaling
No full textInternational audienceWe present a novel multiscale numerical approach that combines parallel-intime computation with hybrid domain adaptation for linear collisional kinetic equations in the diffusive regime. The method addresses the computational challenges of kinetic simulations by integrating two complementary strategies: a parareal temporal parallelization method and a dynamic spatial domain adaptation based on perturbative analysis. The parallel in time approach employs a coarse fluid solver for efficient temporal propagation coupled with a fine, spatially-hybridized, kinetic solver for accurate resolution. Domain adaptation is governed by two criteria: one measuring the deviation from local velocity equilibrium, and another based on macroscopic quantities available throughout the computational domain. An asymptotic preserving micro-macro decomposition framework handles the stiffness of the original problem. This fully hybrid methodology significantly reduces computational costs compared to full kinetic approaches by exploiting the lower dimensionality of asymptotic fluid models while maintaining accuracy through selective kinetic resolution. The method demonstrates substantial speedup capabilities and efficiency gains across various kinetic regimes
Méthode de dimensionnement d’assemblages collés dans une structure de berceau moteur : Prise en compte des effets de bords dans la méthode par l’utilisation de gradients de propriétés mécaniques dans la modélisation de l’adhésif et évaluation des faciès de rupture par imagerie de transformation par réflectivité
No full textThe achievements of this thesis focus on the analysis of parameters that affect adhesive joints. Firstly, the study focused onthe segmentation of fracture surfaces in order to better understand their behavior under load. Then, the effect of edges and surface treatment on fracture surfaces of adhesive joints was examined to determine their impact on joint performance. The third point addresses the influence of temperature and thickness on fracture surfaces of adhesive joints. Finally, a reduced-time calculation method of bonded assemblies was developed, with a function defining the edge effects. This method was applied to a specific example, a motor cradle. In summary, these achievements aim to improve the understanding of adhesive joints byidentifying the effects of different parameters on their performance, which can be very useful in the industrial sector for designing more reliable and high-performing adhesive joints in the future.Les accomplissements de cette thèse se concentrent sur l’analyse des paramètres qui affectent les joints collés. Tout d’abord, l’étude a porté sur la segmentation des faciès de rupture afin de mieux comprendre leur comportement sous charge. Ensuite, l’effet des bords et du traitement de surface sur les faciès de rupture des joints collés a été examiné pour déterminer leur impact sur la performance du joint. Le troisième point aborde l’influence de la température et de l’épaisseur sur les faciès de rupture des joints collés. Enfin, une méthode de calcul en temps réduit des assemblages collés a été développée, avec une fonction qui définit les effets des bords. Cette méthode a été appliquée sur un exemple concret, un berceau moteur. En résumé, ces résultats visent à améliorer la compréhension des joints collés en identifiant les effets de ces différents paramètres sur leur performance, ce qui peut être très utile dans le secteur industriel pour concevoir des joints collés plus fiables
French perspectives of the genesis of a new international tourism in the Interwar Period
No full textInternational audienc
Anisotropic Shear Metrics for Persistent Homology and Their Application to Convective Systems
No full textVertical wind shear plays a crucial role in the organization and persistence of mesoscale convective systems, yet its geometrical and topological effects remain challenging to quantify.. In this study, we introduce a shear-induced anisotropic metric, denoted d S , which embeds the direction and magnitude of environmental wind shear directly into the framework of persistent homology. The metric deforms the ambient geometry by weighting distances differently along and across the shear direction, enabling topological descriptors to respond dynamically to the flow environment. We establish the analytical properties of d S , and demonstrate its compatibility with Vietoris-Rips filtrations. The method is applied to the Corsican bow-echo event of 18 August 2022, where shear vectors are derived from ERA5 reanalysis data. Two complementary topological analyses are performed : a transport analysis on H 0 using Wasserstein distances, and a structural analysis on H 1 persistent generators under parallel and perpendicular shear metrics. The results reveal distinct topological evolutions associated with different shear orientations, highlighting the sensitivity of persistent homology to shear-induced deformation. Overall, the framework provides a mathematically consistent bridge between dynamical meteorology and topological data analysis, extending persistent homology to anisotropic metric spaces.</div
Intrinsic motivation magnifies the effects of physical activity on perceived cognitive health
No full textPreprint uploaded on SportRχiv, preprint repository dedicated to sport, exercise, performance, and health research.International audienceObjective: Among its health benefits, physical activity improves cognitive health, but the strength of this association remains heterogeneous across studies. While previous research focused on structural factors of physical activity as potential moderating factors (e.g., duration, type), we aimed to examine whether the type of motivation (i.e., intrinsic versus extrinsic forms of motivation) could moderate the strength of the association between physical activity and cognitive health.Methods: Participants were 512 Canadian students (72% female and a mean age = 20 ± 5 years). Seven days after assessing their intrinsic and more extrinsic motivations toward physical activity, moderate-to-vigorous physical activity and perceived cognitive health were measured by questionnaire. Linear regression models were used to examine the moderating effect of motivation on the association between physical activity and cognitive health.Results: Intrinsic motivation moderated the association between moderate-to-vigorous physical activity and self-reported cognitive health (b = .12, = .04; .20, p = .004). As hypothesized, simple slope analyses showed that the association between moderate-to-vigorous physical and cognitive health was positive when intrinsic motivation was high (at sample mean + 1SD, b = .14, 95CI = .03; .25, p& .013), but not significant when intrinsic motivation was low (at sample mean - 1SD, b = -.09, 95CI = -.24; .06, p = .220). However, the moderating effect of extrinsic forms motivation was not significant (ps. > .071).Conclusion: In addition to structural aspects of physical activity, it is important to consider motivation toward physical activity when examining its effect on cognitive health