HAL-Université de Bretagne Occidentale
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Rare earth trace element doping of extrinsic multiferroics for an energy efficient remote control of magnetic properties
No full textInternational audienceDeveloping functional materials for optical remote control of magnetism can lead to faster, more efficient wireless data storage and sensing devices. In terms of desired material properties, this development requires the combined optimization of elastic interactions, low magnetic coercivity, and a narrow linewidth of ferromagnetic resonance to establish low-loss dynamic functionalities. A general pathway to achieve these requirements is still lacking. Here, we demonstrate that rare-earth trace element doping of an extrinsic multiferroic promotes strain mediated energy efficient remote control of static and dynamic magnetic properties induced by non-pulsed visible light. The strain under illumination arises from the photostrictive property of the ferroelectric substrate whereas the magnetism control originates from the enhanced magnetostrictive property of a rare-earth trace element doped ferromagnetic thin film. Combining the light-strain-magnetic interaction in the rareearth doped extrinsic multiferroic provides a general approach for enhanced photo-magnetic elastic control extendable to optically tunable magnetic devices.Combining strain and non-pulsed light for the remote control of magnetism would be of great interest for energy efficient technologies of the digital world. Firstly, strain induced changes of magnetism are recognized to be of great potential for energy efficient issues in the field of materials sciences for digital information technologies such as information storage devices or sensors 1-4 . Secondly, the remote control of magnetism with non-pulsed sources of light such as the Sun, a continuous laser or a light emitting diode (LED), would present an energy saving alternative to the non energy efficient use of a current generated magnetic field 5-8 . Consequently, combining strain and non-pulsed light for the remote control of magnetic properties is of interest for energy savings. The strain and non-pulsed visible light combination for a control of static and dynamic magnetic properties was recently achieved for a family of materials named ferromagnetic/ferroelectric extrinsic multiferoics. Optimizing this energy efficient visible light control of magnetization is now required to develop its full potential, and that relies on materials science. Here, it is demonstrated that rare-earth trace element doping of an extrinsic multiferroic provides a pathway for a combined optimization of static and dynamic magnetic properties and their remote control through strain with continuous light, i.e. a solution to a complex material research paradigm. Results and discussionsThe extrinsic multiferroic considered here consists of a 5 nm magnetostrictive Fe80.9Ga18.9La0.2 (FeGaLa) thin film grown by RF magnetron sputtering on a (011)-Pb(Mg 1/3 Nb 2/3 )O3-Pb(Zr,Ti)O3 (PMN-PZT) piezoelectric substrate. Fe81Ga19 (FeGa) is actually considered as an archetype of a modern magnetostrictive material exhibiting large magnetostriction and good tensile strength 9-12 . Furthermore, previous theoretical and experimental research works have shown that rare-earth trace element doping of Galfenol (Fe1-xGax) alloys may result in anisotropic modifications and magnetostrictive properties' enhancement 13-19 . Among these different studies, an 0.2% La trace element doping of Fe83Ga17 millimeter sized ribbons was shown to result in</div
Unraveling Major Questions in Micronekton Ecology and Their Role in the Biological Carbon Pump Through Integrative Approaches and Autonomous Monitoring
No full textInternational audienceMicronekton consist of crustaceans, cephalopods, gelatinous organisms, and fishes that are 2–20 cm in size (Figure 1). These organisms have unique functional traits that impact their vertical migration patterns and ecosystem processes (Aparecido et al., 2023). Our understanding of their potential carbon transport and sequestration from the epipelagic (upper 200 m) to mesopelagic zones (200–1,000 m) or deeper (e.g., Boyd et al., 2019; Le Moigne, 2019; Cavan et al., 2019) is limited by the tools traditionally used to assess their biomass, diversity, and varied migration patterns (e.g., Annasawmy et al., 2019, 2024; Barbin et al., 2024; Eduardo et al., 2024). These knowledge gaps are notable considering that micronekton are ubiquitous throughout the world ocean
Do Body Mass Index classes define our self-perceptions? Analysis of global, multidimensional, and physical self-esteem in women
No full textInternational audienceConsidered as an indicator of good mental health contributing to positive behaviors, self-esteem is impacted by body perception. Obesity is a risk factor for the development of low self-esteem, particularly among women. Age also plays a protective role in both the healthy population and those living with obesity. Since the relationship between self-esteem and BMI does not appear to evolve linearly, the aims of this study were ( 1) to analyze the link between BMI classes and global, multidimensional, and physical selfesteem, and (2) to identify a potential moderating effect of age. Global, multidimensional, and physical self-esteem were assessed using French versions of RSE, MSE and PSPP scales respectively in 454 women aged 18 to 75 stratified into five BMI groups: healthy weight, overweight, obesity class I, II and III. Global, multidimensional, and physical self-esteem appear to be related to BMI classes. Healthy weight women had significantly higher emotional, professional, physical domains and subdomains self-esteem scores than those in obesity class I, II or III. "Tipping points" associated with reaching a BMI threshold at which scores of self-esteem stabilize have been highlighted. These appeared at obesity class I and II, respectively, for the emotional and physical domains of self-esteem, and at overweight and obesity class II, respectively, for the physical strength and attractive body physical subdomains. Results also revealed a protective moderating effect of age on the relationship between BMI and physical self-esteem, and its subdomains. Obesity intervention programs should consider self-perceptions.</div
Estimation des températures d’air en milieu urbain à l’aide de modèles physiques et de réseaux de neurones
No full textThis thesis is set within the context of climate change and its impacts on urban environments, focusing on the phenomenon of the UHI. The goal is to provide tools for identifying vulnerable areas to implement targeted measures, particularly through neighborhoodscale air temperature maps. This work introduces an innovative methodological framework that combines physical simulations and statistical approaches. The UWG model was employed to construct an urban air temperature database using rural data and surface parameters. A neural network-based model, NUWG-City, was developed. Pre-trained on simulations generated by UWG, it was finetuned using meteorological station data from Toulouse. This city, characterized by its diverse urban fabric and extensive meteorological records, enabled robust training and validation of the model. NUWG-City improves UWG’s performance by 30% and increases simulation speed by 33%, while providing better spatial variability by incorporating the specific characteristics of urban environments.Cette thèse s’inscrit dans le contexte du changement climatique et de l’étude de ses impacts sur les environnements urbains en se concentrant sur le phénomène d’ICU. L’objectif est de fournir des outils permettant d’identifier les zones vulnérables afin de mettre en oeuvre des mesures ciblées, notamment grâce à des cartes de température de l’air à l’échelle des quartiers. Ce travail propose un cadre méthodologique innovant, combinant des simulations physiques et des approches statistiques s’appuyant sur des mesures in-situ. Le modèle Urban UWG a été utilisé pour construire une base de données de températures d’air en milieux urbains en s’appuyant sur des données rurales et des paramètres de surface. Un modèle basé sur les réseaux de neurones, NUWG-City, a été développé. Pré-entraîné sur les simulations issues de UWG, il a été affiné avec des données issues de stations météorologiques de Toulouse. Cette ville, caractérisée par son tissu urbain diversifié et ses riches données météorologiques, a permis un entraînement et une validation robustes du modèle. NUWG-City améliore les performances d’UWG de 30% et offre une rapidité de simulation supérieure de 33%, tout en offrant une meilleure variabilité spatiale grâce à la prise en compte des spécificités des environnements urbains
Energy Efficient Device-To-Device Routing in Three-Tier Symbiotic Radio IoT Networks
No full textInternational audienceThis paper presents a three-tier (3T) symbiotic radio device-to-device (D2D) routing Internet-of-Things network. The primary network (PN) consists of a base station routing data through multiple single antenna decode-and-forward sensor node(s) (DSNs) and to the destination sensor node. The secondary network (SN) consists of single-antenna active sensor tag nodes (ASN) transmitting sensed data to a multi-antenna reader using the backscatter (BC) technique. The tertiary network (TN) consists of single antenna semi-passive energy harvesting sensor tags (SSN) that transmit sensed data using BC to the same multi-antenna reader. The symbiotic nature exists where the ASNs and SSNs utilize the DSNs' radio frequency for data transfer. At the same time, the PN benefits from ASNs and SSNs assistive data transfer in terms of spatial diversity. In this work, we focus on maximizing the EE for the proposed 3T SRN D2D-routing by optimizing the DSN and ASN power allocation and the SSN reflection co-efficient. Based on the optimization problem, a minimum distance-based and a maximum channel gain-based D2D-routing algorithms are proposed. The proposed channel-gain-based 3T SRN D2D-routing algorithm is shown to be superior to the distance-based algorithm.Index Terms-Device-to-device (D2D)-routing, symbiotic radio, energy-efficiency (EE), energy harvesting (EH).</div
La faute policière : une catégorie juridique construite par la police, pour la police
No full textInternational audienceQualifier une faute des forces de l’ordre revient à esquisser un comportement policier idéal, celui que devraient en théorie respecter les agents en toutes circonstances. Comprendre cette faute policière suppose d’étudier les catégories de perception et d’appréciation que les juges utilisent pour modéliser ce comportement policier idéal et ses transgressions. Or ces catégories jurisprudentielles de représentation sont très perméables aux normes professionnelles des forces de l’ordre elles-mêmes
Minières et bas fourneaux de l’âge du Fer dans les Monts d’Arrée : approches archéologiques, archéométriques et paléoenvironnementales
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When Faces Are Masked: Exploring Emotional Expression Through Body Postures in Virtual Reality
No full textInternational audienceAs simulation advances in healthcare training, understanding how body-only signals convey emotions in virtual environments is crucial, particularly with masked virtual agents. This study involved 41 nursing students evaluating 16 faceless fear and surprise postures to assess their realism and the emotion conveyed. While wellrecognized in 2D human representations, only three of 16 postures were correctly identified by more than 50% of participants in a 3D virtual agent. These results highlight the impact of virtual agent design on emotional recognition and the need for rigorous testing and refinement to improve emotional expressiveness and realism