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A MIMO system identification approach for the longitudinal control of the filter cavity of the advanced virgo gravitational-wave detector
No full textInternational audienceThe sensitivity of the second generation ground-based gravitational-wave detectors is mostly limited by quantum noise (QN). The injection of frequency-dependent squeezed vacuum states into the output port of the interferometer has been shown to reduce QN across the entire detector bandwidth. Frequency dependent squeezed states are generated by reflecting a frequency independent squeezed states off a detuned optical cavity: the phase response of the cavity rotates the squeeze angle as a function of frequency. The precision of the longitudinal control of the such cavity, known as filter cavity, is one of the key parameters affecting the QN suppression factor. The target longitudinal control precision was achieved by simultaneously acting on both the cavity length and the frequency of the squeezing main laser. In this scenario, the analysis of this system requires a Multiple-Input Multiple-Output (MIMO) system model. In this work, we demonstrate that a MIMO model is required and show that a MIMO system identification technique is effective to characterize the system and improve its robustness. Ultimately we show that these techniques allow the design of robust filters that can keep the cavity residual length fluctuations below 1 pm, allowing for a QN reduction of 4.5 dB at high frequencies and 2 dB at low frequencies in the Advanced Virgo interferometer
Passive hamstring muscles rigidity throughout the menstrual cycle and the effect of oral contraception
No full textInternational audienceObjectives: Female athletes have a lower risk of hamstring strain injuries than males. The variations in oestradiol and progesterone concentrations happening during the menstrual cycle and oral contraceptive use may influence muscle mechanical properties, potentially affecting muscle injury risk. However, to date, no study has combined an assessment of hamstring muscles' mechanical properties spread over the full knee range of motion with rigorous hormonal control of the menstrual cycle, electromyographic monitoring and inclusion of oral contraceptive users. The present study aims to be the first to rigorously evaluate the association between menstrual cycle, oral contraceptive use and hamstring muscles' mechanical properties.Design: Cross-sectional study with repeated measures.Methods: Shear wave elastography measurements were performed at three different times during the menstrual and oral contraceptive cycle. Hormonal assessment and electromyographic monitoring were also carried out.Results: No difference in hamstring muscles' shear wave speed, anatomical cross-sectional area, knee joint musculoarticular stiffness and maximal range of motion were observed along the menstrual cycle despite the presence of the expected variations in ovarian steroid hormones concentrations. No difference in these parameters was also reported throughout the oral contraception use.Conclusions: No differences in the mechanical properties of the hamstring muscles were observed, whether the concentrations of ovarian steroid hormones fluctuate with the menstrual cycle or remain stable with oral contraceptive use, despite the notable effects of these hormones on the muscle composition.Keywords: Contraceptive pill; Hormones; Musculoarticular stiffness; Passive muscle mechanical properties; Shear wave elastography
Stability and fluctuations in granular materials during the critical state regime
No full textInternational audienceReferring to small strain continuum mechanics, a material is unstable if a spontaneous release in kinetic energy can occur following a small perturbation, consistently to the second-order work Hill's instability criterion. Based on a 2-D discrete element method (DEM), this manuscript investigates the stability of granular assemblies in relation with the elastic energy processes along a biaxial loading. The evolution of relevant stability indexes shows that the strong degree of instability very close to the stress peak is linked with the limited capacity of storing elastic energy, resulting in the bifurcation from unstable state to stable state with the formation of one or multiple shear bands. In the post-bifurcation stage, the significant release in net elastic energy within a dense specimen brings the system in a more stable state where a fluctuation regime develops. On the other hand, the loose specimen undergoes stability fluctuation from the very beginning up to the critical state of biaxial loading. From the perspective of configurational mechanisms, the stability fluctuation stems from loops transformations entailing repeated energy storing and release. Such changes in microstructural topology continuously adjust the mesostructures under external loading to approach a stable bifurcated branch in the form of stability fluctuations
Improving fast charging capabilities of graphite electrodes using 6 Li isotope
No full textInternational audienceIn the context of an energy transition, Li-ion batteries (LiBs) are set as one of the main alternatives to fossil fuels. If the 3rd generation of LiBs provides competitive energy densities, it still suffers from poor power densities and this is mainly due to the negative electrode based of graphite. Indeed, graphite displays highly anisotropic properties of lithium intercalation that takes place only on the edge side of the graphene planes [1]. Additionally, the electrode engineering is playing a role, since when the electrodes are highly tortuous, lithium depletions within the electrode porosity can lower the kinetics of intercalation and increase the cell overpotentials. Since the later is very close to the potential of lithium plating, a competition between both processes happens leading to cell performance reduction and potential failure. In this context, this work firstly investigated the characterisation of lithiation heterogeneities at ID31 beamline (ESRF, Grenoble) using z-profiling experiment. Using a calibration curve that was preliminarily acquired on a thin film-like graphite electrode, we were able to quantify the local state of charge of graphite (i.e. x in LixC6) within the electrode depth (see Figure 1). From this, we estimated local kinetics properties of graphite lithiation and observed favoured kinetics near the separator side (electrolyte tank). This observation correlates with a lithiation limited by the diffusion of lithium ions within the electrode porosity, so-called penetration depth model [2].Based on this limitation, we opted for an exotic strategy that is the use of an electrolyte enriched with 6Li isotope. Motivated by the following question: “Does reducing the mass of the diffusing ions can improve the power capabilities?”, we investigated the impact of 6Li on the power capabilities of graphite electrodes. Figure 2 compares the rate capability properties of 6LP30 (6LiPF6 in EC/DMC 1:1) with classical LP30 composition and using the respective Li metal counter electrode (either 6Li or natural Li). We noticed an improvement of power capabilities by using enriched electrolyte in 6Li. To understand this significant gain, ionic conductivity measurements, estimations of diffusion coefficient in graphite phase were realised. Finally, a comparative study on the distribution of local kinetic of lithiation with the results obtained with classical LP30 will be presented
Effectiveness of a Pronoun Interpretation Explicit Teaching on 1st-Graders’ Comprehension
No full textInternational audiencePronoun comprehension is widely recognized as an essential tool for both oral and reading comprehension. For beginning readers, however, interpreting pronominal expressions can be particularly challenging. Explicit training in the comprehension skills needed to interpret pronouns has been shown to be helpful for children in grades 3-5, but has never been shown to be helpful in lower grades. The purpose of this study was to determine whether explicit training in pronoun interpretation could be beneficial for the skill being trained as early as first grade, and whether this positive effect generalized to broader comprehension skills. A pretest-trainingposttest protocol was set up with 153 French first graders who were divided into two groups: an experimental group that received explicit training in pronoun interpretation and an active control group whose training focused on global comprehension of narrative text without a focus on pronoun interpretation. Results show that explicit pronoun interpretation training was more effective than global comprehension training in improving students' ability to interpret pronouns, and that the two types of training produced equivalent gains in overall comprehension. This study demonstrates for the first time that it is possible to train and improve first graders' pronoun interpretation skills using an explicit approach
The impact of global change on the distribution of mountain mammals and birds
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Le bouquet Fluence : 4 applications numériques pédagogiques pour l'apprentissage des fondamentaux, la lecture et l'anglais
No full textNational audienceQuatre applications numériques evidence-based, nommées « le bouquet Fluence », ont été développées et scientifiquement validées pour faciliter l’apprentissage des fondamentaux. Elles sont issues de la recherche et d’un partenariat avec deux entreprises (les Editions Hatier et HumansMatter). Leur développement a été co-financées par les programmes e-FRAN (projet Fluence) et e-FRAN-vague3 (projet Trans3). Ces applications visent l’amélioration des performances en lecture (EVASION, ECRIMO et FLUIDILI) et en compréhension orale de l’anglais (FIREFLY). Des expérimentations en situation réelle de classe et à grande échelle, ont été menées pour mesurer objectivement l’efficacité des 4 applis. Les résultats des dernières expérimentations montrent que s’entrainer avec EVASION en CP améliore les capacités d’attention visuelle impliquées en lecture. ECRIMO permet aux élèves en début d’apprentissage de la lecture, d’améliorer leur capacité d’encodage. Enfin, les élèves de CE1 entrainés avec FLUIDILI améliorent leur compétence en lecture expressive. Quant à FIREFLY, les élèves qui l’ont utilisée ont de meilleures performances en compréhension de l’anglais oral
Incorporating learning and fatigue effects in flowshop scheduling: a case study
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Towards site-specific ground motion estimates in Greece using a partially non-ergodic, mixed-effects, neural network approach
No full textInternational audienceThis study presents a new, data-driven, region-specific ground motion model for Greece. This model utilizes a neural network approach that eliminates the need for any a priori functional form. Due to limitations in the recent Greek dataset, selected records from the RESORCE database have been incorporated. A fully connected multilayer perceptron is employed to predict several ground motion intensity measures (GMIMs), including peak ground velocity (PGV), peak ground acceleration (PGA), and the 5 % damped pseudo-spectral acceleration (PSA) at 18 periods ranging from 0.01 to 4.00 s, for active shallow crustal earthquakes (h 30 km). Given the available dataset information, this GMM is driven by three input parameters; moment magnitude (Mw), Joyner-Boore distance, RJB (km), and the average seismic shear-wave velocity of the uppermost 30 m at the station site, VS30 (m/s). Additional source parameters, such as focal mechanism and depth, were also tested. The linear mixed-effects algorithm of the lme4 package [1] is used to decompose the total ground-motion aleatory variability (GMAV) into inter-event residuals (δBe) and Site-to-Site residuals (δS2S) while analyzing their dependence on the magnitude and distance (heteroscedasticity). The sensitivity of GMIMs predictions to various input parameters is also analyzed. Results indicate that combining the partially non-ergodic assumption (δS2S) with the heteroscedastic model significantly reduces GMAV, while these data-driven predictions exhibit physical trends consistent with classical GMMs. This new GMM enables site-specific predictions throughout Greece, provided sufficient on-site recordings exist to derive the site-specific term δS2Ss
A Comprehensive Analysis of Seismic Site Effects in the Grenoble Basin (French Alps)
No full textInternational audienceThe Grenoble basin, located in the French Alps, is a region of significant interest for seismic hazard assessment due to its thick sedimentary layers and surrounding high massifs, leading to 2D/3D complex wave propagation patterns. With the aim to develop suitable strategies for seismic microzonation in alpine valleys, this study focuses on the seismic response of the basin using state-of- the-art 3D simulations performed with the EFISPEC3D spectral element method code for frequencies up to 5 Hz. These simulations aim to capture the intricate interactions between geological features, including lateral heterogeneity and basin geometry, which are not considered in traditional 1D microzonation approaches.A primary goal of this research is to compare synthetic seismic data derived from 1D and 3D models with observed data to identify the limitations of 1D approach to provide a robust estimation of the site effects. Particular attention is paid to the analysis of fundamental frequencies and seismic wave amplification. While central regions of the basin exhibit consistent fundamental frequencies across 1D and 3D models, discrepancies arise at the edges due to the presence of complex lateral heterogeneities.The study further investigates aggravation factors such as Peak Ground Velocity (PGV), Peak Ground Acceleration (PGA), and Arias Intensity, revealing significant amplification in the central areas of the basin when using 3D models. In contrast, edge zones tend to show neutral or slightly de-amplified responses. These findings underscore the importance of incorporating 3D effects into seismic hazard assessments to improve the accuracy of microzonation strategies.Future work aims to refine seismic hazard maps by leveraging machine learning techniques to automate the classification of zones based on response spectra and frequency-dependent amplification