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Laboratory and numerical investigation on the poro-elasto-visco-plastic behaviour of in-situ heated Callovo-Oxfordian claystone
No full textInternational audienceLaboratory and numerical investigation on the poro-elasto-visco-plastic behaviour of in-situ heated Callovo-Oxfordian clayston
Les centres anciens des villes moyennes françaises. Des quartiers propices à l’accueil des trajectoires résidentielles des ménages en transition(s)
No full textInternational audienceThe present study examines the social and demographic characteristics of residentially immobile households and those undertaking short-distance residential moves in medium-sized cities in France. From a methodological standpoint, it is based on a statistical analysis of census data from nine urban areas. The findings are discussed in light of the concept of peuplement (i.e., the socio-spatial organization of the housing stock and associated residential mobility), in order to analyze the relationship between the structure of the housing stock and the socio-demographic profiles of its occupants. This research highlights the socio-spatial filtering mechanisms at work between city centers and their outskirts, the latter tending to attract households with greater professional and/or marital stability. In particular, it shows the unique nature of the housing stock in historic city centers, which attracts households in transitional phases of their life paths—whether originally from the same urban area or from elsewhere—to settle there for varying lengths of time. Consequently, these neighborhoods exhibit significant socio-residential diversity among their inhabitants, though with notable internal disparities.Cette recherche porte sur la caractérisation sociale et démographique des ménages en immobilité ou en mobilité résidentielle de courte distance dans les villes moyennes françaises. Sur le plan méthodologique, elle se fonde sur une analyse statistique des données du recensement dans neuf aires urbaines correspondant à des villes moyennes. Les résultats sont éclairés par la mobilisation du concept de peuplement, de sorte à analyser les interrelations entre la structure du parc de logements et les caractéristiques sociodémographiques des ménages qui les occupent. Cette recherche met en avant les mécanismes de filtrage sociospatial entre le centre des agglomérations et ses périphéries, qui attirent les ménages les plus stables sur le plan professionnel et/ou matrimonial. En particulier, elle montre la singularité du parc de logements des centres anciens qui conduit les ménages en situation de transition(s) dans leurs parcours de vie – originaires de leurs aires urbaines d’appartenance comme de l’extérieur – à venir s’y implanter pour une durée variable. En résulte une diversité sociorésidentielle importante de ces quartiers, quoiqu’hétérogènes
Coupling LCA And Dynamic MFA: A Literature Analysis
No full textInternational audienceA combined implementation of Life Cycle Assessment (LCA) and Material Flow Analysis (MFA) is needed to represent a system with its flows, stocks and their related transition dynamics and also assess environmental impacts related to system’s flows with a full LC perspective at different scales: production line, company, territory, etc. However, this coupling is subject to several methodological issues that first need to be overcame:LCA of products (which is the traditional LCA, and will be referred as LCA hereafter) and MFA don’t have the same scopes, implying different system boundaries. While MFA has a wide view on a system with all related products implied in the studied territory, LCA focuses on a unique product (i.e. the reference flow) around which the system is built, also taking into account processes that took place outside the studied territory but implied in the LC. As a consequence, links between coproducts have been cut, or substituted, in LCA databases, preventing from considering an industrial process entirely. Based on that assumption, the traditional LCA calculation routine has been built on the basis of matrix inversion (Heijungs and Suh, 2002). The representation of the problem in the form of matrices provides a concise formulation, but restricts to square technological matrices (to be inversible), and so is unable to consider multioutput processes. Taking temporality into consideration is necessary when transition scenarios are considered. The evolution of flows and stocks of material across the time are considered in dynamic MFA, but stocks are completely absent in LCA.As some couplings have already been led (Barkhausen et al., 2023), a bibliographic review will be presented to position those issues in the literature and identify if they are addressed and how to properly couple LCA and MFA in a context of territorial transition.Heijungs, Reinout, et Sangwon Suh. The Computational Structure of Life Cycle Assessment. Vol. 11. Eco-Efficiency in Industry and Science. Dordrecht: Springer Netherlands, 2002. https://doi.org/10.1007/978-94-015-9900-9.Barkhausen, Robin, Leon Rostek, Zoe Chunyu Miao, et Vanessa Zeller. « Combinations of Material Flow Analysis and Life Cycle Assessment and Their Applicability to Assess Circular Economy Requirements in EU Product Regulations. A Systematic Literature Review ». Journal of Cleaner Production 407 (juin 2023): 137017. https://doi.org/10.1016/j.jclepro.2023.137017
Benchmarking raw datasets and collaboratively-evolving processed data for markerless motion capture analysis
No full textInternational audienceWe present a dataset designed for benchmarking markerless motion capture methods (from videos to joint kinematics). The dataset includes both raw and processed data. Two participants performed five tasks - walking, sit-to-stand, manual material handling, handstand hold or Y-pose (depending on the participant), and a jointly performed dance sequence. Movements were captured simultaneously recorded using 10 optoelectronic cameras (Qualisys Miqus M3, 120 Hz) and 9 video cameras (Qualisys Miqus Video, 60 Hz, 1920×1088 pixels). The raw dataset provides 3D marker trajectories and video recordings. The processed dataset includes joint kinematics obtained from both marker-based motion capture and 7 different markerless methods, contributed by multiple research teams as part of a challenge organized during a national biomechanics seminar. Additionally, the openaccess GitHub repository containing processed data enables researchers to contribute new markerless methods estimated and expand the dataset collaboratively. This resource aims to facilitate benchmarking and support the development of robust markerless motion analysis methods
Entre logique et attitudes : une approche sémiotique des outils de gestion
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Multi-physics Modelling of the Influence of Environmental Conditions on the Hardened Properties of 3D-printed Concrete
No full textInternational audienceAs opposed to massive concrete structures, 3D-printed concrete structures have a high surface-to volume ratio, leading to high water loss after printing. This evaporation is known to cause significant plastic shrinkage shortly after printing [1], which often leads to cracks. We demonstrate experimentally that effects of evaporation are also visible at the hardened state, with a significant impact on the compressive strength of printed parts, evaporation being detrimental to the compressive strength.Based on experimental observations indicating a positive correlation between printed wall thickness and compressive strength at the hardened state, and an increase in the compressive strength when preventing evaporation after printing, we propose a fully coupled thermo-poro-mechanical model [2] to describe the evolution of the printed material, from fresh to hardened state. Cement hydration and associated stiffness and strength build-up, as well as water evaporation at the boundaries, water transport within the printed structure and water consumption due to cement hydration are accounted for. Their effects on temperature, strain, stiffness and compressive strength evolution are studied, and compared with experimental data.Comparisons between model predictions and experimental results demonstrate the model’s validity, enabling estimations of both shrinkage and strength development in 3D-printed cementitious structures in given environmental conditions. Indeed, the findings confirm that, in the absence of protective measures to limit water evaporation, thinner walls suffer from greater plastic shrinkage and lower cement hydration, stiffness and compressive strength than thicker walls. Additionally, experimental and numerical investigations confirm that preventing evaporation enhances compressive strength, reaching that of traditionally cast samples.These results highlight the importance of curing strategies in concrete 3D-printing. The model offers a predictive framework to estimate the efficiency of various curing strategies on several parameters, from short- to long-term after printing, and allows to estimate the hardened properties of printed part given the actual environmental conditions
Differentiable constitutive modeling in a machine learning-compatible framework
No full textInternational audienceThe field of computational mechanics is increasingly converging with machine learning, particularly in the area of constitutive modeling. Constitutive models, which are inherently data-driven, share formal similarities with neural network layers. Beyond learning constitutive models from data, there is significant potential in developing implementations of traditional constitutive models that are compatible with machine learning frameworks. Automatic differentiation (AD) has transformed machine learning by enabling complex computations to be composed from simpler operations while automating the calculation of derivatives. In this talk, we will explore the application of AD to constitutive modeling, with a special emphasis on two key areas: efficient tangent operator computation and material parameter sensitivity. First, AD can be used to automatically derive consistent tangent operators, which are essential for the efficient integration of constitutive models in large-scale simulations. We will discuss various strategies for obtaining these operators, including applying AD directly to the unrolled algorithm or using the more efficient method of implicit differentiation. Second, AD can also be leveraged to compute sensitivities of material parameters, enabling more efficient model calibration. Finally, we will delve into how AD and implicit differentiation can be extended to handle more complex constitutive models, such as multi-surface plasticity, which require advanced nonlinear solvers
Optimisation conjointe de la forme d'onde et du circuit de conversion RF-DC pour le transfert d'énergie sans fil
No full textIn wireless power transfer/energy harvesting context, this thesis aims to present an innovative approach to the design of RF rectifier circuits coupled with power-optimized waveforms. The analysis of RF rectifier limitations, particularly in the absence of commercially available rectifying components suitable for low-power conditions, has raised the issue of maximizing RF-to-DC conversion efficiency at low power levels. The use of high PAPR signals, such as OFDM, chaotic signals, multitone, and pulsed RF signals, has demonstrated an enhancement in the RF-to-DC conversion efficiency of the rectifier compared to CW signals. In this framework, the characteristics of multitone and pulsed RF signals are initially investigated, and three numerical tools based on ADS are identified and discussed, aiming to handle the waveform during the synthesis of nonlinear RF circuits process.Following this, a broadband rectifier is characterized under both CW and pulsed regimes. Simulated and measured responses in terms of frequency and power are compared to highlight the improvement in conversion efficiency, as well as the limitations associated with PAPR. The results indicate that, depending on the input power level, conversion efficiency can be enhanced by applying a pulsed RF signal with an “optimal” duty cycle. Through the automated characterization process, maps are generated to identify the optimal duty cycle as a function of frequency, input power level, and output load. Consequently, the power budget of the rectifier is evaluated based on the duty cycle, showing that losses due to impedance mismatch are minimal while output voltage is maximized. This trend is validated by measuring the S11 parameter under pulsed conditions using a suitable measurement setup. Further investigations are conducted on the rectifier by applying different modulation windows to assess the role of the signal envelope in achieving optimal efficiency, and to explore whether optimal efficiency is governed by the presence of an optimal waveform or an optimal PAPR. Finally, a new optimization process for rectifiers is presented, incorporating the PAPR as an additional dimension during the rectifier design phase. Analytical trends are extracted for both CW and pulsed regimes, followed by a presentation of rectifier design rules when optimized for pulsed operation using the previously introduced numerical tool. Four prototypes are fabricated, incorporating various diode models and optimized under both CW and pulsed regimes. A measured maximum efficiency of 53% at -20 dBm and 70% at -10 dBm is achieved. After discussing the performance of the designed rectifiers, their power balances are evaluated to explain the contribution of the joint optimization. Subsequently, various DC-DC converters and a demonstrator are used for the different prototypes to highlight the benefit of using the joint optimized process in the context of low-power wireless energy transferDans le contexte de transfert/récupération d’énergie sans fils, ce travail propose une approche innovante sur la conception de circuits redresseurs RF associés aux formes d’ondes optimisées en puissance. Alors que l’analyse des limitations d’un circuit redresseur RF a permis de soulever, notamment en l'absence d’éléments redresseurs commerciaux adaptés aux faibles puissances, la problématique quant à la maximisation de l'efficacité de conversion RF-dc à faible puissance, l’usage de signaux à fort PAPR tels que l'OFDM, les signaux chaotiques, multitons et RF impulsionnels ont pu établir une amélioration de l'efficacité de conversion RF-dc du redresseur comparé à un signal en CW. Ainsi, les caractéristiques de signaux multitons et RF impulsionnels sont explorés dans un 1er temps et trois outils numériques basés sur ADS sont identifiés et discutés, ceci afin de tenir compte de la forme d’onde lors de la synthèse de circuits RF non-linéaires. Par la suite, un redresseur large bande est caractérisé en régimes CW et impulsionnel. Les réponses simulées et mesurées en fréquence et en puissance sont comparées afin de mettre en évidence l'amélioration de l'efficacité de conversion, ainsi que les limitations liées au PAPR. Les résultats montrent qu'en fonction du niveau de puissance d'entrée, l'efficacité de conversion peut être améliorée en appliquant un signal RF impulsionnel avec un rapport cyclique dit « optimal ». À l’aide du processus de caractérisation automatisé, des cartographies sont extraites et permettent en fonction de la fréquence, du niveau de puissance d'entrée et de la charge de sortie, de localiser le rapport cyclique optimal. Par conséquent, le bilan de puissance du redresseur est évalué en fonction du rapport cyclique et montre que les pertes dues à la désadaptation sont minimales tandis que la tension de sortie est maximale. Cette tendance est validée par la mesure du S11 en régime impulsionnel via l’introduction d’un banc de mesure adapté. Des investigations supplémentaires sont menées sur le redresseur en appliquant différentes fenêtres de modulation afin d'évaluer le rôle que pourrait jouer l’enveloppe du signal pour atteindre l’efficacité optimale et tenter par la même occasion de répondre à la question de savoir si l’efficacité optimale est régie par la présence d’une forme d’onde optimale ou d’un PAPR optimal. Enfin, un nouveau processus d'optimisation pour les redresseurs est présenté afin de tenir compte du PAPR optimal comme dimension supplémentaire et de manière conjointe lors de la phase de conception du redresseur. Les tendances analytiques étant extraites en régimes CW et impulsionnel, cette étude est suivie d’une présentation des règles de conceptions du redresseur lorsqu’optimisé en impulsionnel à l’aide de l’outil numérique introduit au préalable. Quatre prototypes sont alors fabriqués, incluant différents modèles de diodes et optimisés sous régimes CW et impulsionnel. Une efficacité maximale mesurée de 53 % à -20 dBm et 70 % à -10 dBm est mesurée. Après avoir discuté les performances des redresseurs conçus, les bilans de puissance de ces derniers sont évalués afin d’expliquer l’apport de l’optimisation conjointe. Par la suite, divers convertisseurs DC-DC et un démonstrateur sont employés pour les différents prototypes afin de mettre en évidence l’apport d’une structure optimisée en régime impulsionnel dans le contexte du transfert d’énergie sans fil à faible niveau de puissanc
Tiers-lieux : quelles contributions à la santé sur les territoires ?
No full textInternational audienceCet article vise à éclairer le rôle des tiers-lieux en santé dans la redéfinition des relations entre les acteurs de la santé sur les territoires. Une revue de littérature met en évidence l'importance du lien social, du pouvoir d'agir et de l'ancrage territorial pour répondre aux besoins de santé des populations L'analyse des témoignages de douze co-fondateurs et gestionnaires de tiers-lieux spécialisés dans le champ de la santé permet ensuite de montrer comment ils s'emparent de ces concepts pour fédérer des communautés sur les territoires et améliorer l'accès à une santé globale