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Un apport des géodonnées pour l'analyse de cycle de vie de projets urbains : prise en compte des masques solaires dans les simulations thermiques dynamiques de bâtiments
No full textInternational audienceLife cycle assessment (LCA) can be used to evaluate the environmental impacts of urban projects, but requires a huge amount of data. Geodata currently available can be used as soon as the design phase. Here, we explore the potential contribution of existing geodata to improve the accuracy of building energy modeling (BEM) carried out during the LCA of urban projects. Hence, we have built a model to assess the influence of solar masks on building energy needs and indoor thermal comfort. We use this model to assess the benefits of considering these masks. We then test the use of existing IGN geodata to take into account solar masks formed either by adjacent buildings (BD TOPO), or by buildings and vegetation (LIDAR HD). After the model is validated, we use it on two existing buildings to compare the results of simulations with and without masks. These initial tests confirm the interest of using existing geodatabases. They also encourage us to develop guidelines for BEM and LCA practitioners, and to explore the use of geodata to specify other parameters useful for BEM.L'analyse de cycle de vie (ACV) peut être utilisée pour évaluer les impacts environnementaux d'un projet urbain, mais nécessite un très grand nombre de données. Or, de nombreuses géodonnées aujourd'hui disponibles sont mobilisables dès la phase de conception. Nous explorons ici l'apport possible de référentiels géonumériques existants à l'amélioration de la précision des simulations thermiques dynamiques (STD) réalisées lors d'ACV de projets urbains. Pour cela, nous avons construit un modèle permettant d'évaluer l'influence des masques solaires sur les besoins énergétiques de bâtiments et sur le confort thermique à l'intérieur de ces derniers. Nous utilisons ce modèle pour évaluer l'intérêt de prendre en compte ces masques. Nous testons ensuite l'utilisation de référentiels IGN existants afin de produire des données sur les masques solaires formés soit par les bâtiments seuls (BD TOPO), soit par les bâtiments et la végétation (LIDAR HD). Après avoir validé notre modèle, nous l'utilisons sur deux bâtiments déjà construits, pour comparer les résultats des simulations sans masque et avec les masques issus des référentiels. Ces premiers tests confirment l'intérêt d'utiliser les référentiels existants. Ils nous invitent également à poursuivre vers la formalisation de recommandations pour les développeurs d'outils STD et ACV, et à explorer l'utilisation de géodonnées pour préciser d'autres paramètres utiles aux STD
A twelve-year survey of the HDO and H2O cycles using the Mars Planetary Climate Model from MY26 to MY37
No full textInternational audienceContext : The deuterium/hydrogen isotopic ratio, D/H, is one of the keys to understand the origin of water on terrestrial bodies within the Solar System and its evolution over time in their atmospheres.In the atmosphere of Mars, this D/H ratio is on average 5 to 6 times higher than the Vienna Standard Mean Ocean Water (VSMOW), the Earth’s oceans reference. Although water vapor is present only in very low quantities on Mars (100 ppmv on average), it is rich in deuterium, which points to a wetter past for the Red Planet, a fact corroborated by various geological indicators (valleys, ancient lakes, shorelines). This enrichment is understood as a cumulative effect of differential escape between H and D atoms, the latter being more prone to gravity than its lighter isotopologue. This differential escape is deeply rooted into the seasonal behavior of HDO and H₂O, sole precursors of D and H on Mars, which release H and D at high altitude, when climatic conditions allow photochemistry. [1, 2]Model : The Mars PCM (Planetary Climate Model) simulates the physical, chemical and dynamical processes in the Martian atmosphere, including water ice cloud-related phenomena [3], such as condensation, that fully control the relative behavior of HDO [4, 5]. This model, coupled with observations and data from ACS (Atmospheric Chemistry Suite), has shed light on the HDO cycle recently. However, differences still exist between the model and the observations. This is particularly the case for the vertical distribution of water vapor in the upper atmosphere [5, 6]. Some improvements to the Mars PCM, namely new dust injection scheme and non-orographic gravity waves [7] have been implemented.Results : This study presents a 12-Martian-year simulation, covering Martian Years 26 to 37, with a focus on interannual variations in the HDO and H₂O cycles. The results from the model are compared with multiple observations from instruments such as ACS and SPICAM, capturing a wide range of dust events and revealing key processes to which the HDO and H₂O cycles are particularly sensitive and predicted by the Mars PCM. A third moment is being implemented in the dust particles size distribution to improve its vertical distribution with respect to observations. The first outcomes of this modification will also be addressed.This study is part of a broader effort to better understand the origin and the long-term evolution of the water on Mars. By investigating the processes behind the Mars’ deuterium enrichment, it contributes to unraveling the history of atmospheric escape and climate change on the Red Planet
Les sols comme archives des pratiques humaines et des transformations socio-environnementales
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Inequality and optimal monetary policy in the open economy
No full textInternational audienceWe study optimal monetary policy in a tractable Small Open Economy Heterogeneous-Agent New Keynesian (SOE-HANK) model in which households face uninsured idiosyncratic risk and unequal bond-market access. We derive conditions under which optimal policy in our SOE-HANK economy entails domestic producer price stability, extending the ”open-economy divine coincidence” result of Galí and Monacelli (2005) beyond the Representative-Agent benchmark (SOE-RANK). Away from those conditions, inefficient fluctuations in consumption inequality generate monetary policy tradeoffs. Under plausible calibrations for the trade elasticities, the elasticity of intertemporal substitution, and the cyclicality of income risk, the central bank stabilizes output and the exchange rate more than in SOE-RANK
En magasin, à domicile, en point-relais...: Une exploration des déterminants des pratiques d'achats des Français par catégorie de produits
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Towards Blockchain-Based GDPR-Compliant spontaneous and ephemeral social network
No full textInternational audienceOnline Social Networks (OSNs) have rapidly integrated into our daily lives since their emergence in 2004, primarily serving as platforms for sharing personal information. This paper introduces a novel category of social networks: Spontaneous and Ephemeral Social Networks (SESNs). Unlike traditional OSNs, SESNs are event-centric, facilitating realtime connections and content sharing among participants within specific contexts. The main objective of SESNs is to improve the production, sharing, and consumption of digital content among network members. SESNs operate on a distributed peerto-peer architecture using ad hoc mobile networks, leveraging the capability of mobile devices to communicate directly with each other in peer-to-peer mode. SESNs are ephemeral by nature, dissolving once participants disperse from the event location. However, for future analysis, some content may be retrievable from an external server after the event. A potential concern is that collaborative content creation within SESNs resembles crowdsourcing. However, in SESNs, the service provider may retain control over the data even after the event concludes. This centralized management of user-generated content could pose risks to user anonymity. To address these concerns, we propose a blockchain-based architecture that certifies transactions and ensures data anonymity in a decentralized manner. The proposed architecture demonstrates its robustness through a performance evaluation and a comprehensive security analysis. Our solution guarantees data integrity, confidentiality, privacy, anonymity, and network resilience. Additionally, blockchain technology is employed to ensure SESN compliance with the General Data Protection Regulation (GDPR)
Comment signaler les corrections et les rétractations dans HAL ?
No full textInternational audienceLa correction de la littérature scientifique est un enjeu majeur pour l'avancée scientifique. Cette présentation, préparée pour les journées CasuHAL 2025, aborde la question cruciale du signalement des corrections et des rétractations au sein des archives ouvertes, avec un focus particulier sur la plateforme HAL. En s'appuyant sur une analyse de la manière dont les éditeurs et les bases de données bibliographiques gèrent ces modifications, la présentation met en lumière des lacunes importantes. Une étude de cas sur HAL révèle que la grande majorité (91%) des publications ayant fait l'objet d'une correction ou d'une rétractation n'affichent aucun signalement de cette modification sur la plateforme. De plus, les rares signalements existants ne suivent pas de format standardisé.La présentation se conclut sur une série de propositions concrètes visant à définir des procédures claires et efficaces pour que HAL puisse prendre en charge le signalement des corrections/rétractations. Ces propositions sont plus ou moins difficiles à mettre en oeuvre et ont été débattues à l'occasion de l'atelier. L'objectif est de s'assurer que les archives ouvertes ne restent pas un "angle mort" des initiatives visant à maintenir l'intégrité de la production scientifique
Plastics used in agriculture and for food: uses, properties and impacts. Extended report of the collective scientific assessment
No full textThis document is the report of the collective scientific assessment (CSA) requested and funded by theFrench Agency for ecological transition (ADEME), the French Ministry of agriculture and foodsovereignty, and the French Ministry for the ecological transition, biodiversity, forests, marine affairs andfisheries. The report of the CSA was conducted by a group of scientific experts without prior approvalby the funders, INRAE or the CNRS
Comparative and Interpretative Analysis of CNN and Transformer Models in Predicting Wildfire Spread Using Remote Sensing Data
No full textFacing the escalating threat of global wildfires, numerous computer vision techniques using remote sensing data have been applied in this area. However, the selection of deep learning methods for wildfire prediction remains uncertain due to the lack of comparative analysis in a quantitative and explainable manner, crucial for improving prevention measures and refining models. This study aims to thoroughly compare the performance, efficiency, and explainability of four prevalent deep learning architectures: Autoencoder, ResNet, UNet, and Transformer-based Swin-UNet. Employing a real-world dataset that includes nearly a decade of remote sensing data from California, U.S., these models predict the spread of wildfires for the following day. Through detailed quantitative comparison analysis, we discovered that Transformer-based Swin-UNet and UNet generally outperform Autoencoder and ResNet, particularly due to the advanced attention mechanisms in Transformerbased Swin-UNet and the efficient use of skip connections in both UNet and Transformer-based SwinUNet, which contribute to superior predictive accuracy and model interpretability. Then we applied XAI techniques on all four models, this not only enhances the clarity and trustworthiness of models but also promotes focused improvements in wildfire prediction capabilities. The XAI analysis reveals that UNet and Transformer-based Swin-UNet are able to focus on critical features such as ’Previous Fire Mask’, ’Drought’, and ’Vegetation’ more effectively than the other two models, while also maintaining balanced attention to the remaining features, leading to their superior performance. The insights from our thorough comparative analysis offer substantial implications for future model design and also provide guidance for model selection in different scenarios. The source code for this project is publicly available as open source at https://github.com/Yng314/xai_for_wildfire
Les RER métropolitains comme marqueurs de l’affirmation des Métropoles françaises ? : Enjeux français et éclairages internationaux
No full textAs a new tool of public mobility policies, the suburban railway service (Metropolitan RER) is an instrument on the path to generalization for structuring mobility within France's major metropolitan areas. This work highlights the “French specificity” represented by the absence of this tool in the mobility landscape outside of the capital region, in contrast to Western European countries with both Germanic and Latin traditions. This research then analyzes the observable dynamics in the process of appropriating the Parisian, as well as European framework, with a more in-depth focus on the Lyon Metropolitan RER. This specific case is a significant indicator of the multisectoral and interscalar logics of action (local/national, urban/interurban, technical/decision-making) that constrain the effective implementation of these rail services today. Finally, this work draws on the study of two foreign cases (Barcelona and Montreal), which help to question the effectiveness of metropolitan governance in managing rail services, as well as the need to structure mobility on a new scale, following the metropolitanization process underway for several decadesObjet nouveau des politiques publiques de mobilité, le RER Métropolitain constitue un instrument en voie de généralisation pour structurer les mobilités au sein des principales métropoles françaises. Ce travail étaye la « spécificité française » que représente l’absence de cet outil dans le paysage des mobilités en dehors de la région capitale, et ce en comparaison de l’ensemble des pays ouest européen, de tradition germanique, comme latine. La présente recherche analyse ensuite les dynamiques observables dans le processus d’appropriation du référentiel francilien, comme européen aujourd’hui à l’œuvre, en détaillant de manière plus approfondie le cas du RER lyonnais. Ce cas précis étant un révélateur important des logiques d'action multisectorielles et interscalaires (local/national, urbain/interurbain, technique/décisionnel) contraignant la réalisation effective de ces services ferroviaires aujourd’hui largement plébiscités. Ce travail s’appuie enfin sur l’étude de deux cas étrangers (Barcelone et Montréal) qui permettent d’interroger l’effectivité de la gouvernance métropolitaine des dessertes ferroviaires, comme le besoin de structuration des mobilités à une échelle nouvelle, et ce, suite au processus de métropolisation à l’œuvre depuis plusieurs décennie