Elaboration of the magnetically frustrated GeFe2O4 spinel thin films by pulsed laser deposition

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Experimental approach to copper production: towards a better understanding of technical processes

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Techniques de calcul renforçant la vie privée : un enjeu dans l'ère de la société de surveillance

International audienceDans le contexte actuel du capitalisme de surveillance, tel que défini par Shoshana Zuboff dans son livre L'Âge du Capitalisme de Surveillance, les données personnelles sont devenues une ressource</div

A dynamical system approach to the Chandrasekhar-Hamilton-Jacobi equation

48 pagesInternational audienceWe study the local properties of positive solutions of the equation -∆u = e^u -M |∇u|^q in a punctured domain Ω \ {0} of R^N in the range of parameters q&gt; 1 and M&gt;0. We prove a series of a priori estimates near a singular point. In the case of radial solutions we use various techniques inherited from the dynamical systems theory to obtain the precise behaviour of singular solutions. We prove also the existence of singular solutions with these precise behaviours

Déploiement de la géothermie profonde en région Centre-Val de Loire : un argumentaire à destination des acteurs locaux basé sur des analyses sociales, économiques et environnementales

National audienceThe Centre Val-de-Loire region sees deep geothermal energy as a virtuous energy solution for the region, but to date it has not been widely deployed. To encourage its use, the region has financed a research project of regional interest, called "AMIGO". The project is being co-ordinated by BRGM in partnership with LEO (Laboratoire d'Économie d'Orléans), AFPG (Association Française des Professionnels de la Géothermie), AMORCE (Association d'accompagnement des collectivités et des acteurs dans la transition énergétique) and AgreenTech Valley (national cluster dedicated to digital technologies for plant-based industries). Its aim is to draw up a set of arguments to help local authorities and private-sector players in the region to choose between the various possible sources of renewable energy for district heating networks, industrial processes or heating crops in greenhouses. To develop this argument, the phases of the project are: (1) to understand the position of the stakeholders with regard to deep geothermal energy, and (2) to gather the key information in the territorial context (socio-economic and environmental aspects of a deep geothermal energy project, information on the geothermal resource, demand for heat in the territory). This article presents the progress made in the process of constructing the argument, in particular the results of (1) the analysis of the positioning of stakeholders in the region and (2) the economic and environmental analysis of a deep geothermal energy project.La géothermie profonde est vue par la région Centre Val-de-Loire comme une solution énergétique vertueuse pour le territoire, cependant, à ce jour, elle y reste peu déployée. Aussi, pour favoriser sa mise en œuvre, la région a financé un projet de recherche d’intérêt régional, appelé « AMIGO ». Ce projet est coordonné par le BRGM en partenariat avec le LEO (Laboratoire d'Économie d'Orléans), l'AFPG (Association Française des Professionnels de la Géothermie), l’AMORCE (Association d'accompagnement des collectivités et des acteurs dans la transition énergétique) et AgreenTech Valley (Cluster national dédié aux technologies numériques pour les filières végétales). Il a pour objectif d’établir un argumentaire pour aider les collectivités locales et les acteurs privés de la région à choisir entre les différentes sources d'énergie renouvelable possibles pour les réseaux de chauffage urbain, les processus industriels ou le chauffage des cultures sous serres. Pour développer cet argumentaire, les phases du projet sont : (1) comprendre le positionnement des acteurs vis-à-vis de la géothermie profonde, et (2) rassembler les informations clés dans le contexte territorial (aspects socio-économiques et environnementaux d’un projet de géothermie profonde, informations sur la ressource géothermale, demande de chaleur sur le territoire). Cet article présente les avancées dans le processus de construction de l’argumentaire, en particulier les résultats (1) de l’analyse du positionnement des acteurs de la région et (2) de l’analyse économique et environnementale d’un projet de géothermie profonde

Deciphering Degassing Mechanisms of He and H2 H2{\mathbf{H}}_{\mathbf{2}} at the Sedimentary Basin‐Basement Interface by Surface Geophysics and Gas Geochemistry

International audienceWith the increasing importance of the carbon footprint of transport, new sources, closer to consumers, of and He are explored. Within this context, we present a combined near‐surface geophysical imaging, soil gas sampling, and bubbling well gas sampling approach to study fluid and gas pathways near a fault system in the Morvan massif, part of the French Massif Central, in the south‐east of the Paris Basin. Electrical resistivity and seismic refraction tomography profiles allowed identifying a fault network. The co‐located soil gas sampling shows a He hot‐spot clearly linked to a section of one fault, suggesting a preferential pathway via water advection. Very high He concentrations, are also measured in ‐dominated free gas from two bubbling wells very close to the soil He hot‐spot. Evidence for a water reservoir with high ‐He gas bubbles in the very shallow basement‐sediment cover interface is obtained through our geophysical data. In contrast, spreads more widely, pointing to biological production and consumption coupled to soil aeration, as well as a possible geological seep with diffusion processes controlled by clay/marls. The very distinct spatial variability observed for He and results from these different transport processes. A simple geochemical model is proposed to explain the geochemical signature of bubble gas, rich in and He, through exsolution of air dissolved at recharge, where radiogenic He originates from the granitic basement

Numerical Simulations for Optimizing Small Satellite Constellations for TGF Studies

International audienceThe detection of Terrestrial Gamma ray Flashes (TGFs) from space is mostly made by astrophysics satellites, which only provide single-point measurements. Future TGF missions could consist in performing simultaneous detection by a detector array in space. In order to prepare such a scientific objective, we simulate the detection of TGFs by a nanosatellite, or small satellite, constellation. The objective is to quantify the impact of six parameters defining such a constellation, in order to maximize the scientific return of the mission. The parameters characterized in this work are the number of satellites, their relative distance, their altitude, their orbital configuration, the effective detection surface, and their orbital inclination. We use a Monte Carlo simulation code to propagate photons in the atmosphere and simulate the satellite positions and photons hits on satellites. Finally, we quantify the number of TGFs detected by the fleet, multi-detected, the number of photons received, and draw conclusions about the impact of each parameter

Observation of an unmixed particle surface during single-particle experiments of iron combustion

International audienceThis study explores the combustion of single iron particles, emphasizing the phenomenon of an unmixed surface during the liquid-phase combustion regime. While previous single-particle combustion experiments have advanced the understanding of the combustion process, the exact configuration of the liquid phases remains unclear. In addition, insights derived from ex situ microstructure analysis are limited by uncertainties introduced during particle cooling, which can alter the internal structure. To address this, we utilized an electrodynamic levitator and laser ignition to study suspended iron particles heated to a high initial temperature (between 1820 K and 2092 K). The combined use of a high-speed color camera and a luminance acquisition system enables high resolution in situ imaging and luminance tracking. A distinct “unmixed surface period” is observed, during which two immiscible liquid phases – pure iron (L1) and iron oxide (L2) – coexist at the particle surface. Initially, the surface is fully covered with L2, followed by the appearance of moving L1 spots, likely driven by a Marangoni flow. This period concludes with the formation of a core–shell structure. These findings provide new insights into the dynamics of liquid-phase oxidation in iron combustion, as the unmixed surface configuration might influence both the rate-limiting mechanism and evaporation dynamics. Such observations contribute to improving numerical models, particularly in capturing the initial stages of the liquid-state combustion. Moreover, particle size analysis indicates that smaller particles deviate further from a fully external-diffusion-limited regime, underscoring the role of alternative rate-limiting mechanisms in their combustion behavior

Les ateliers monétaires dans le monde celtique : quels vestiges archéologiques ?

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Actes numériques du colloque "La “transition écologique” dans les arts et la culture"

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