HAL Université de Savoie
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Interfaces électroniques pour la récupération d'énergie vibratoire par des générateurs piézoélectriques bistables
No full textAs part of an ambitious PSPC project (Structuring Projects for Competitiveness), involving 3 academic and 4 industrial partners, this thesis aims to develop electronics for extracting the electrical energy produced by non-linear vibratory energy harvesting devices. The use of wireless sensors in industrial applications enables gains in productivity, reliability and energy efficiency. Wireless measurement and communication technologies are available, while energy autonomy remains a major barrier to the deployment of sensor networks. The scientific background to this thesis is the development of devices for harvesting ambient vibratory energy, to be used as an energy source to power autonomous wireless sensors, as an alternative to electrochemical batteries, which are polluting and costly to replace. The power delivered must be of the order of a few hundred μW to a few mW. Current devices generally use linear mechanical resonance, which limits the range of ambient vibration frequencies that can be exploited to a few Hz on either side of the resonance frequency. This is a major barrier to the use of such devices in real environments, where ambient vibratory energy is often distributed over a wide frequency band. The approach adopted by the SYMME laboratory is based on the use of bistable (non-linear) mechanical structures combined with piezoelectric transducers. The devices developed in recent years within this framework, notably in collaboration with Cedrat Technologies, a partner in the project, exhibit the special feature of converting energy over a wide frequency band. However, these devices require the development of specific electronics to extract the electrical energy produced. These electronics can also be used to adjust the non-linear dynamics of the harvester to improve its bandwidth. However, due to their non-linear nature, the dynamics of these systems is particularly complex to predict, presenting new challenges in terms of modeling and studying the influence of the energy extraction electronics. This work has led to the development of analytical models to predict the influence of electronics on the non-linear dynamics of the harvester, and to develop a physical interpretation. The models developed have been validated experimentally, and allowed to set up comparison tools to assess the performance of different extraction electronics, and to select the electronics that maximizes the extracted power and the energy conversion frequency band. Finally, an original, self-controlled and self-powered implementation of extraction electronics has been proposed. Its performance were studied experimentally and then compared with standard electronics, highlighting a power gain between 2 and 10 over a wide frequency band, as well as the ability to extract sufficient amount of energy to power wireless sensors.Dans le cadre d'un ambitieux projet PSPC (Projets Structurants pour la Compétitivité), impliquant 3 partenaires académiques et 4 partenaires industriels, cette thèse vise à développer une électronique d'extraction de l'énergie électrique produite par des dispositifs non-linéaires de récupération d'énergie vibratoire. La mise en œuvre de capteurs communicants dans des applications industrielles permet d'obtenir des gains de productivité, de fiabilité et de performance énergétique. Les technologies de mesure et de communication sans fil sont disponibles tandis que l'autonomie énergétique demeure un des verrous majeurs au déploiement de réseaux de capteurs. Le contexte scientifique de cette thèse est le développement de dispositifs de récupération de l'énergie vibratoire ambiante, utilisés comme source d'énergie pour l'alimentation de capteurs autonomes communicants, en alternative aux piles électrochimiques, polluantes et couteuses à remplacer. La puissance délivrée doit être de l'ordre de quelques centaines de μW à quelques mW. Les dispositifs actuels utilisent généralement une résonance mécanique linéaire, ce qui limite la plage de fréquences des vibrations ambiantes pouvant être exploitée à quelques Hz de part et d'autre de la fréquence de résonance. Ceci est un obstacle majeur à l'utilisation de tels dispositifs dans des environnements réels, où l'énergie vibratoire ambiante est souvent répartie sur une large bande de fréquence. L'approche adoptée au laboratoire SYMME repose sur l'utilisation de structures mécaniques bistables (non-linéaires) combinées à des transducteurs piézoélectriques. Les dispositifs réalisés ces dernières années dans ce cadre, notamment en collaboration avec l'entreprise Cedrat Technologies, partenaire du projet, présentent la particularité de convertir de l'énergie sur une large bande de fréquence. Ces dispositifs nécessitent cependant le développement d'une électronique spécifique pour l'extraction de l'énergie électrique produite. Cette électronique peut aussi être utilisée afin d'ajuster la dynamique non-linéaire du récupérateur en vue d'améliorer sa bande passante. Cependant, en raison de leur caractère non-linéaire, la dynamique de ces systèmes est particulièrement complexe à prévoir, faisant ainsi apparaître des nouveaux défis quant à la modélisation et à l'étude de l'influence de l'électronique d'extraction de l'énergie. Ces travaux ont ainsi mené au développement de modèles analytiques permettant de prédire l'influence de l'électronique sur la dynamique non-linéaire du récupérateur et d'en développer une interprétation physique. Les modèles développés ont été validés expérimentalement et ont permis la mise en place d'outils de comparaison permettant d'évaluer les performances de différentes électroniques d'extraction et de sélectionner l'électronique permettant de maximiser la puissance extraite et la bande de fréquence de conversion de l'énergie. Enfin, une implémentation originale, auto-pilotée et auto-alimentée d'une électronique d'extraction a été proposée. Ses performances ont été étudiés expérimentalement puis comparées avec une électronique standard, mettant ainsi en lumière un gain de puissance compris entre 2 et 10 sur une large bande de fréquence, ainsi que la possibilité d'extraire une quantité d'énergie suffisante pour l'alimentation de capteurs communicants
The Longitudinal and Transverse Piezoelectric Effects of the Ferroelectric Polymer P(VDF‐TrFE)
No full textInternational audiencePolyvinylidene fluoride‐trifluoroethylene (P(VDF‐TrFE)) exhibits outstanding electromechanical properties and is a material of choice for non‐volatile memories, energy‐harvesting systems, multifunctional actuators, and sensors. However, this polymer remains one of the least understood materials among ferroelectric materials due to its semi‐crystalline structure with chains folding in elongated grains through the lamellae and amorphous regions. Here, operando high‐resolution X‐ray diffraction is exploited to unravel the P(VDF‐TrFE) structural evolution upon the first electric field application, called poling. This X‐ray technique allows revealing drastic changes in the lamellae with the ordered amorphous (OA) emergence between crystalline nanodomains. The discovery of this OA emergence is critical because it significantly affects the structure, as well as the mechanical, ferroelectric, and piezoelectric properties of the polymer. After poling, even small nanostructural changes lead to measurable effects yielding the piezoelectric coefficients. The longitudinal and transverse piezoelectric effects can be explained by the complex P(VDF‐TrFE) structure. The elongated grains consist of lamellae separated by isotropic amorphous (IA) regions. This study not only sheds light on the fundamental mechanisms occurring in P(VDF‐TrFE), but also offers guidance for new ferroelectric organic materials for flexible, biocompatible sensor and energy applications
Femoral Malpositioning of Anterolateral Ligament Reconstruction Is a Significant Risk Factor for Anterior Cruciate Ligament Graft Failure
No full textInternational audienceBackground: The femoral attachment of the anterolateral ligament (ALL) reported by anatomic studies is posterior and proximal to the lateral femoral epicondyle. Purpose: To assess the femoral positioning of the ALL graft while performing a percutaneous technique and evaluate the correlation between this positioning and the graft rupture rate, as well as clinical and functional outcomes. Study Design: Cohort study; Level of evidence, 3. Methods: A total of 211 patients undergoing combined anterior cruciate ligament (ACL) and ALL reconstruction were included. Radiological measurements, Knee injury and Osteoarthritis Outcome Score (KOOS), International Knee Documentation Committee (IKDC) score, and graft failure rate were collected at 24 months after surgery. Results: The rate of anatomic positioning of ALL femoral anchors was 79.1% (n = 167). The mean proximal and posterior distances relative to the ALL anatomic femoral position were 1.4 ± 2.8 mm and 0.2 ± 0.2 mm, respectively. The rate of outliers, defined as >5 mm from the anatomic position, was 20.85% (n = 44). The mean KOOS and IKDC score were 84 ± 10.9 and 80.1 ± 11.3, respectively. No statistically significant difference in KOOS and IKDC score was observed between the group of patients with anatomic positioning and the group of outliers ( P = .1). The rate of ACL rerupture for all patients was 3.79% (n = 8). Of these, 87.5% (n = 7) were outliers. The correlation between ALL femoral malpositioning and ACL rerupture was statistically significant ( P < .00001). Conclusion: Independent ALL reconstruction while performing a percutaneous technique enabled anatomic positioning of the ALL graft in 79% of cases. The femoral malpositioning was correlated with a higher ACL graft rerupture rate but not with a decrease in the functional outcomes
Search for gravitational waves emitted from SN 2023ixf
No full textInternational audienceWe present the results of a search for gravitational-wave transients associated with core-collapse supernova SN 2023ixf, which was observed in the galaxy Messier 101 via optical emission on 2023 May 19th, during the LIGO-Virgo-KAGRA 15th Engineering Run. We define a five-day on-source window during which an accompanying gravitational-wave signal may have occurred. No gravitational waves have been identified in data when at least two gravitational-wave observatories were operating, which covered of this five-day window. We report the search detection efficiency for various possible gravitational-wave emission models. Considering the distance to M101 (6.7 Mpc), we derive constraints on the gravitational-wave emission mechanism of core-collapse supernovae across a broad frequency spectrum, ranging from 50 Hz to 2 kHz where we assume the GW emission occurred when coincident data are available in the on-source window. Considering an ellipsoid model for a rotating proto-neutron star, our search is sensitive to gravitational-wave energy and luminosity for a source emitting at 50 Hz. These constraints are around an order of magnitude more stringent than those obtained so far with gravitational-wave data. The constraint on the ellipticity of the proto-neutron star that is formed is as low as , at frequencies above Hz, surpassing results from SN 2019ejj
First evidence for direct CP violation in beauty to charmonium decays
No full textInternational audienceThe asymmetry and branching fraction of the CKM-suppressed decay are precisely measured relative to the favoured decay , using a sample of proton-proton collision data corresponding to an integrated luminosity of recorded at center-of-mass energy of during 2016--2018. The results of the asymmetry difference and branching fraction ratio are \begin{align*} \Delta\mathcal{A}^{C\!P} &\equiv \mathcal{A}^{C\!P}(B^+ \to J\mskip -3mu/\mskip -2mu\psi\,\pi^+) - \mathcal{A}^{C\!P}(B^+ \to J\mskip -3mu/\mskip -2mu\psi\,K^+) = (1.29 \pm 0.49 \pm 0.08) \times 10^{-2}, \end{align*}\begin{equation*} \mathcal{R}_{\pi/K} \equiv \frac{\mathcal{B}(B^+ \!\to J\mskip -3mu/\mskip -2mu\psi\,\pi^+)}{\mathcal{B}(B^+ \!\to J\mskip -3mu/\mskip -2mu\psi\,K^+)} = (3.852 \pm 0.022 \pm 0.018) \times 10^{-2}. \end{equation*} where the first uncertainties are statistical and the second systematic. A combination with previous LHCb results based on data collected at and in 2011 and 2012 yields and . The combined value deviates from zero by 3.2 standard deviations, providing the first evidence for direct violation in the amplitudes of beauty decays to charmonium final states
Study of in decays
No full textInternational audienceAn amplitude analysis of the transition is performed simultaneously in , , and decays. The study is based on a data sample of proton-proton collisions recorded with the LHCb detector at centre-of-mass energies of and TeV, corresponding to a total integrated luminosity of . A clear double-peak structure is observed in the spectrum of the decay. The data can be described either with a model including , and resonances, in which the contributions of and are unexpectedly large, or with a model including , a doubly charged open-charm tetraquark state and its isospin partner . If the former is considered implausible, the states are observed with high significance, and the data are consistent with isospin symmetry. When imposing isospin constraints between the two states, their mass and width are determined to be MeV and MeV, respectively, where the first uncertainty is statistical and the second is systematic. The mass is slightly below the threshold, and a spin-parity of is favoured with high significance
Visual attention matters during word recognition: A Bayesian modeling approach
No full textInternational audienceIt is striking that visual attention, the process by which attentional resources are allocated in the visual field so as to locally enhance visual perception, is a pervasive component of models of eye movements in reading, but is seldom considered in models of isolated word recognition. We describe BRAID, a new Bayesian word Recognition model with Attention, Interference and Dynamics. As most of its predecessors, BRAID incorporates three sensory, perceptual and orthographic knowledge layers together with a lexical membership submodel. Its originality resides in also including three mechanisms that modulate letter identification within strings: an acuity gradient, lateral interference and visual attention. We calibrated the model such that its temporal scale was consistent with behavioral data, and then explored the model's capacity to generalize to other, independent effects. We evaluated the model's capacity to account for the word length effect in lexical decision, for the optimal viewing position effect and for the interaction of crowding and frequency effects in word recognition. We further examined how these effects were modulated by variations in the visual attention distribution. We show that visual attention modulates all three effects and that a narrow distribution of visual attention results in performance patterns that mimic those reported in impaired readers. Overall, the BRAID model could be conceived as a core building block, towards the development of integrated models of reading aloud and eye movement control, or of visual recognition of impaired readers, or any context in which visual attention does matter
« That Sound » La voix d’un attracteur en méthodes visuelles
No full textInternational audienceAN DOMHAN was presented in a live performance. A user is immersed in the virtual reality headset, while sound artist Tommy Lawson composes a live sound creation following the user's movements. An intrinsic relationship, an attraction, is created between the inside of the VR headset and the outside of the sound installation, as well as between the inside of the sound machine and the outside of the user's immersive experience. There is also a "That Sound" narrator giving rhythm to the experience between the bodies, just as there is a "That Person" in Matt Mullican's performances and installations. Isn't sound, in this immersive, narrative framework/landscape, above all a trace and sign of a voice, resonating and allowing us to map the modes and relationships at work between body/machine through an artistic, performative protocol in place? For us, sonification, as developed by Philippe Zarka, is a process with strong artistic, narrative and phenomenological potential for exploring this sonic cartography, and perhaps even redesigning the sonic face of experience.L’expérience en réalité mixte AN DOMHAN a été présenté dans une performance « live ». Un utilisateur est immergé dans le casque en réalité virtuelle pendant que Tommy Lawson (artiste sonore) compose une création sonore en directe suivant les mouvements de l’utilisateur. Une relation intrinsèque, une attraction, se crée entre le dedans du casque VR et l’extérieur de l’installation sonore ainsi que l’intérieur de la machine sonore et le dehors de l’expérience immersive vécue par l’utilisateur. Aussi, existe-t-il un « That Sound » narrateur rythmant l’expérience entre les corps, comme il y a un « That Person » dans les performances et installation de Matt Mullican. Le son dans ce cadre/paysage narratif et immersif n’est-il pas avant tout trace et signe d’une voix, qui résonne et nous permet de cartographier les modes et les relations à l’oeuvre entre corps/machine par le biais d’un protocole artistique, performatif en place ? La sonification, développée par Philippe Zarka devient alors pour nous un procédé méthodologique au fort potentiel artistique, narratif et phénoménologique pour creuser cette cartographie sonore et peut être même redessiner un visage sonore de l’expérience
Mapping potential environmental impacts of alien species in the face of climate change
No full textInternational audienceRisk maps are a useful tool to prioritise sites for management and allocate resources where they are most needed as they can show us where impacts of biological invasions are most likely to happen or expected to be largest. Given the pace of global changes, we need to understand not only the risks under current conditions, but future risks taking these changes into account. In this study, we use Australian acacias alien to South Africa as a case study to model their potential distribution under future climate change to map their potential impacts at the middle and end of the century and the uncertainty related to three socio-economic pathways and five climatic models. The resulting risk maps across South Africa are a pioneering attempt to combine impacts of alien species with potential future distributions. We found that although climatic suitability and therefore the risk is predicted to decrease under climate change in 51,4% of the country’s area, the opposite is predicted for 26% of the area and the highly vulnerable fynbos biome remains an area with high projected impacts. Such risk maps can help us prioritise management actions and aid the development of suitable plans to protect biodiversity under current and future climate conditions. However, they have to be interpreted with caution and we highlight some shortcomings around species distribution models in general, vulnerability of ecosystems to the potential impacts, data gaps on impacts, as well as currently benign or unknown invaders, which are not included in the projections