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Modelling P wave reflections on MTZ discontinuities from distant oceanic sources
No full textInternational audienceWe investigate the modelling of P-wave reflections on the mantle transition zone (MTZ) discontinuities (Pv410p* and Pv660p*) using ambient seismic noise generated by distant oceanic sources. Using ray theory and waveform simulations, we assess biases in arrival times and amplitude ratios when interpreting noise correlations as Green’s functions. Our results show that source distribution and the b-caustic effect strongly influence signal recovery. Simulations based on realistic oceanic models (WAVEWATCH III) demonstrate that appropriate source conditions significantly reduce biases. This approach enables reliable imaging of the MTZ, particularly in regions like the greater Alpine area with favourable microseismic source distribution
Modeling the combined influence of maturation and organic matter content on terahertz dielectric properties of oil shales
No full textInternational audienceMaturation and organic matter content are critical factors influencing the hydrocarbon generation potential and economic viability of oil shales. Accurate assessment of these parameters is essential for optimizing extraction techniques and evaluating resource quality. While previous studies have individually linked maturation and organic content to dielectric permittivity in the terahertz (THz) range, their combined influence has not yet been thoroughly investigated. In this study, we explore the interdependence between maturation, organic matter content, and THz dielectric properties. Fifteen oil shale samples from two distinct basins were analyzed using Rock-Eval thermal analysis to quantify organic content, vitrinite reflectance to determine thermal maturity, and THz time-domain spectroscopy to estimate dielectric permittivity. Based on these analyses, we propose an empirical model that links these three parameters through a fitted surface, achieving a 75% accuracy in data representation. These findings provide a more robust framework than previous approaches for characterizing oil shales and enhancing resource evaluation
X-in-the-loop methodology for proton exchange membrane fuel cell systems design: review of advances and challenges
No full textInternational audienceProton Exchange Membrane Fuel Cells (PEMFCs) are seen as an alternative for heavy-duty transportation electrification. Powered by a green hydrogen source, they can provide high efficiency and low carbon emissions compared to traditional fuels. However, to be competitive, these systems require high reliability when operated in real-life conditions, as well as safe and efficient operating management. In order to achieve these goals, the X-in-the-loop (also called model-based design) methodology is well suited. It has been largely adopted for PEMFC system development and optimisation, as they are complex multi-component systems. In this paper, a systematic analysis of the scientific literature is conducted to review the methodology implementation for the design and improvement of the PEMFC systems. It exposes a precise definition of each development step in the methodology. The analysis shows that it can be employed in different ways, depending on the subsystems considered and the objectives sought. Finally, gaps in the literature and technical challenges for fuel cell systems that should be addressed are identified
Phénomènes radiatifs et aérauliques en milieu urbain : comment la géomatique contribue à améliorer leur connaissance et leur prévision ?
No full textInternational audienceThe shape of a city, along with the layout of its streets, buildings, and green spaces, can significantly influence the flow of wind through open spaces and the amount of solar radiation received by various surfaces. Wind patterns and solar radiation directly impact urban overheating and the dispersion of pollutants, thereby affecting the quality of the urban environment and the comfort of its residents. The development of geomatics-based models that directly correlate characteristics of the built environment with wind and sunlight fields can aid in informing political decision-making. The aim of this article is to highlight the relationships between the calculation of specific physical variables and geomatics methods, to describe experiments in modeling the radiative and aeraulic physics of urban areas within the context of GIS, and to identify some of the scientific and technical challenges that remain in this field.La forme de la ville, l’agencement de ses rues, de ses bâtiments et de ses espaces verts peuvent modifier significativement la circulation du vent dans l’espace ouvert et la quantité de rayonnement solaire reçue par les bâtiments et les surfaces. Le vent et le rayonnement affectent directement la surchauffe urbaine et la dispersion des polluants en ville, et par conséquent la qualité de l’environnement urbain et le confort des habitants. Développer, dans le contexte de la géomatique, des modèles qui permettent de relier directement des caractéristiques de l’environnement construit à des champs de vents ou d’ensoleillement permet d’éclairer la décision politique. Cet article vise à mettre en évidence les relations entre le calcul de certaines variables physiques et des méthodes de géomatique, à décrire des expériences de modélisation de la physique radiative et aéraulique de la ville dans le contexte du SIG, et également à relever certains verrous scientifiques ou techniques qui subsistent dans le domaine
Investigation of LiPON and LiSiPON amorphous electrolytes using high-throughput experiments
No full textInternational audienceLiPON is the solid electrolyte material of choice in thin-film lithium batteries (microbatteries), and is increasingly being considered as an interphase material to stabilize electrode/electrolyte interfaces in new battery designs (all-solid-state lithium batteries). In this work, we prepared 76-sample libraries of Li(P,Si)(O,N) thin films by combinatorial synthesis (co-sputtering) that cover extended compositional ranges, to study correlations between chemical composition, local structure and ionic conductivity. They were characterized using automated spatially-resolved techniques to determine dimensions (profilometry), composition (LIBS, EDS, ICP-OES, RBS/NRA), local structure (Raman) and conduction properties (EIS) of each sample. This provided a unified picture of the conduction behavior of amorphous LiPOs and LiPONs for 0.8 < Li/P < 4.0, that revealed similar trends in the evolution of the conductivity in two parts (gradual increase then saturation) and a constant beneficial effect of N introduction on the mobile charge carrier concentration over the whole Li/P range. This suggests that the improvement in conductivity is not specifically related to the presence of [O3P-Nd-PO3] units, but more generally to the presence of bridging nitrogen. Subsequently, the study of the LiSiPON system revealed additional effects of the structure on ionic conductivity
Contribution of post mortem analysis to multiphysics lifetime modeling
No full textInternational audienceMultiphysical lifetime modelling is a way to predict the lifetime of Li-ion batteries, but such a porous electrode theory, pioneered by John Newman, requires many parameters to be identified [1]. Some of them need to be adjusted based on specific characterizations at internal components level. Post-mortem analysis is key to identifying degradation mechanisms and evaluating required model parameters and introduce laws of variation for some of these [2]. A concrete example of post mortem analysis will be presented, using aged negative electrode to illustrate the insights that can be gained from such analysis
Search for the decay
No full textInternational audienceA search for the decay is made using collision data collected with the LHCb detector at centre-of-mass energies of 7, 8 and 13 TeV, corresponding to an integrated luminosity of fb. No significant signal is observed, and an upper limit on the branching fraction of at confidence level is set. This result supersedes the previous LHCb study and improves the upper limit by a factor of two
Weak lensing mass-richness relation of redMaPPer clusters in LSST DESC DC2 simulations
No full textInternational audienceContext. Cluster scaling relations are key ingredients in cluster abundance-based cosmological studies. In optical cluster cosmology, where clusters are detected through their richness, cluster-weak gravitational lensing has proven to be a powerful tool to constrain the cluster mass-richness relation. This work is conducted as part of the Dark Energy Science Collaboration (DESC), which aims to analyze the Legacy Survey of Space and Time (LSST) of the Vera C. Rubin Observatory, starting in 2026.Aims. Cluster properties inferred from weak lensing, such as mass, suffer from several sources of bias. In this paper, we aim to test the impact of modeling choices and observational systematics in cluster lensing on the inference of the mass-richness relation.Methods. We constrained the mass-richness relation of 3600 clusters detected by the redMaPPer algorithm in the cosmoDC2 extragalactic mock catalog of the LSST DESC DC2 simulation, covering 440 deg2, using number count measurements and either stacked weak lensing profiles or mean cluster masses in several intervals of richness (20 ≤ λ ≤ 200) and redshift (0.2 ≤ z ≤ 1).Results. We provide the first constraints on the redMaPPer cluster mass-richness relation detected in cosmoDC2. We find that for an LSST-like source galaxy density, our constraints are robust to changes in the concentration-mass relation, as well as the dark matter density profile modeling choices, when source redshifts and shapes are perfectly known. We find that photometric redshift uncertainties can introduce bias at the 1σ level, which could be mitigated by an overall correction factor fitted jointly with the scaling parameters. We find that including positive shear-richness covariance in the fit shifts the results by up to 0.5σ. Our constraints also offer a fair comparison to a fiducial mass-richness relation, obtained from matching cosmoDC2 halo masses to redMaPPer-detected cluster richness results
Lake SkyWater—A Portable Buoy for Measuring Water-Leaving Radiance in Lakes Under Optimal Geometric Conditions
No full textInternational audienceThis study introduces Lake SkyWater (LSW), a novel radiometric buoy designed for the reliable measurement of remote sensing reflectance (Rrs) in lakes using the Skylight-Blocked Approach (SBA). LSW addresses key challenges in “on-water” field radiometry owing to its motorised rotating system, which maintains the radiance sensor in optimal geometrical conditions (i.e., facing the sun). Our device is easy to transport and deploy and can be controlled with a smartphone over Wi-Fi. Its modular design, which uses standard components and custom 3D-printed parts, facilitates customisation. A field experiment demonstrated excellent performance in the visible spectrum (400–700 nm) and no significant differences compared with handheld SBA measurements when measuring Rrs (coefficient of determination > 0.99 and general accuracy (median symmetric accuracy) of ~2.43%). Areas for potential improvement were identified, such as refinement of orientation control and addressing the occasional rotation of the float. Nonetheless, LSW shortens the acquisition time, reduces the risk of fore-optics contamination, and ensures that the measurements are conducted under optimal geometric conditions. In conclusion, LSW is a promising instrument for the operational collection of high-quality Rrs spectra in lakes, which is important for advancing both research and monitoring applications in aquatic remote sensing