HAL Université de Toulouse, et Toulouse INP
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From colloidal nanoparticles in non-polar solvents to 3D microstructures: a new paradigm in Convective Self-Assembly
No full textInternational audienceColloidal nanoparticles (NPs) exhibit unique and tunable physical properties, making them highly attractive for advanced applications in sensing, photonics, flexible electronics, and beyond. Harnessing these properties in functional devices often requires assembling NPs into three-dimensional (3D) microstructures that combine substantial thickness to enhance their functional response, micrometer-scale resolution for precise pattern definition, and high selectivity to minimize material loss. Directed assembly techniques aim to meet these stringent requirements but face significant challenges when NPs are dispersed in non-polar solvents, commonly used for their role in synthesis and colloidal stabilization. Indeed, such solvents hinder NP assembly because of their high wettability and volatility. These limitations are particularly pronounced in Convective Self-Assembly (CSA), which performs efficiently with aqueous dispersions but struggles with non-polar media.In this study, we investigate how the properties of non-polar solvents influence CSA on topographically patterned substrates. To overcome these issues, we propose an upgraded CSA method that combines solvent selection, surface functionalization, and controlled evaporation. This approach enables reproducible and precise assembly of NPs into micrometer-scale 3D structures. The method is versatile, compatible with various nanoparticle types and patterns, and allows sequential co-assembly on a single substrate, offering a scalable route for high-resolution nanomanufacturing of complex multifunctional architectures
Nanoporous alumina-silica nanolaminates grown by mixed thin films processes for selective environmental barrier layers on carbon surfaces
No full textInternational audienc
Inter-comparison of soybean models for simulation of evapotranspiration under rainfed and irrigated conditions
No full textInternational audienceAccurate estimation of evapotranspiration (ET) is crucial for agricultural water management and crop yield prediction. Crop models are frequently used to simulate ET; however, model testing against detailed ET data remains scarce. The objective of this study was to evaluate nine soybean models that incorporated various approaches to estimate ET (n = 19 methods) using high resolution, multi-season eddy flux measurements from rainfed and irrigated soybean at Mead, Nebraska. Field measurements of crop growth, leaf area index (LAI), soil water content, and ET were provided to the modelers sequentially as follows: 1) phenology data for a Blind calibration; 2) irrigated crop growth; 3) irrigated daily ET and soil water; 4) rainfed ET and soil water; and 5) rainfed crop growth. Among models and ET methods, daily ET was simulated with normalized root mean square errors (nRMSE) ranging from 21.5 to 72.8 % after Full calibration, and root mean square errors (RMSE) were 0.7-2.4 mm d-1. The ensemble median across models (E-Median) reduced error in the simulation of daily ET and ranked highly across calibration steps and developmental phases. Furthermore, the E-Median showed reasonable performance under Blind calibration, with a RMSE of 0.90 mm d-1 (nRMSE= 27.7 %) for daily ET and 70.4 mm (16.7 %) for seasonal ET, indicating it can be a valuable approach for model-based ET estimation when data is scarce. This study revealed the major sources of uncertainty in simulating ET and identified opportunities for improving associated model processes, including 1) residue effects on soil evaporation during incomplete canopy cover, 2) potential ET of soybean, particularly during full canopy, and 3) leaf senescence effects on LAI during the late reproductive phase
Chemical hydrogen storage materials – boranes and silanes catalytic solvolysis and dehydrogenation: a mechanistic and regeneration perspective
No full textInternational audienceHydrogen (H 2 ) has gained a lot of interest as an alternative energy vector, to reduce greenhouse gas emission issues caused by the fossil fuel industry. However, to make hydrogen a real energy carrier in a decarbonated economy, a secure and sustainable supply chain is needed. This approach requires notably safe storage and efficient strategies for recycling of raw materials. We discuss in this survey the state-of-the-art in the field of chemical hydrogen storage (CHS) materials, considering two possible vectors: ammonia borane and hydrosilanes. Regardless of the vector, to achieve real use, it is necessary to understand both the performance of the system and its life cycle, which relates to catalysts structure, and the activation of chemical bonds with efficient and complete catalytic cycles. We give herein an overview of hydrolysis and/or alcoholysis from metals, using coordination complexes, molecular supported catalysts or other materials, including nanocatalysts, with a focus on mechanistic information and understanding. Notably, the studies related to these two vectors can be considered somewhat complementary. Thus, the set of bibliographic report on ammonia borane is very documented in efficient catalytic systems, while its recycling remains at a very early stage. In comparison, hydrosilanes have been much less addressed specifically as a vector for hydrogen, while their reactivity at the molecular scale benefits from a relevant understanding from coordination chemistry studies. In addition, both hydrosilane polymerization and solvolysis reaction enables the release of H 2 , and produces by-products of which added value is already established. This opening the way to economical strategies where recycling can be optional. Nevertheless, the reversibility of hydrosilanes chemistry in H 2 uptake remains attractive and is another option to develop
Surface albedo and thermal radiation dynamics under conservation and conventional agriculture in subhumid Zimbabwe
No full textSource Agritrop Cirad (https://agritrop.cirad.fr/614360/) * Autres projets (id;sigle;titre): 101138269;ACCURATE;(EU) Albedo, Conservation agriCUltuRe and climATe bEnefit// FOOD/2021/424–933;RAIZ;(EU) Promoting agroecological intensification for resilience building in Zimbabwe//International audienceWhile conservation agriculture (CA) has been widely evaluated for its biogeochemical effects (e.g soil organic carbon sequestration and greenhouse gas emissions) for climate mitigation, its biogeophysical impacts related to changes in surface albedo remain understudied. This study assessed the biogeophysical effects of CA cropping systems with maize (Zea mays L.) in Zimbabwe. Measurements were conducted continuously over two cropping years at two long-term experiments with contrasting soil characteristics, on an abruptic Lixisol and on a xanthic Ferralsol. The dynamics of surface albedo, longwave radiation, leaf area index, soil moisture and temperature were monitored under three different treatments: conventional tillage (CT, tilled to ~15 cm), no-tillage (NT) and no-tillage with mulch (NTM, 2.5 t DM ha⁻¹). Our results revealed that, on the Ferralsol, NT and NTM significantly (p < 0.05) increased mean annual albedo (0.17) relative to CT (0.16), resulting in a negative instantaneous radiative forcing (iRF) and indicating a net cooling effect. iRF was stronger in 2021/22 (NT: -0.83 ± 0.17 W m-2; NTM: -1.43 ± 0.7 W m-2) than in 2022/23 (NT: -0.43 ± 0.09 W m-2; NTM: -1.03 ± 0.21 W m-2). Conversely, on the Lixisol, while NT increased surface albedo (0.27 vs. CT: 0.24), NTM significantly reduced albedo (0.23), causing positive iRF (warming). iRF was -3.34 ± 0.69 W m-2 and -2.78 ± 0.77 W m-2 for NT in the first and second cropping year, respectively, and increased from 1.14 ± 0.21 W -2 (2021/22) to 2.77 ± 0.41 W m-2 (2022/ 23) under NTM. Overall, our results suggest that the soil background albedo is an important site characteristic that needs to be considered and demonstrates the importance of considering biogeophysical effects when promoting practices of CA for climate change mitigation
Insight into cooling requirements for thermophotovoltaic devices
No full textInternational audiencePerformance of thermophotovoltaic conversion devices depends on the operating temperature of the cell, and thus on how heat generated in the cell is dissipated. The present research examines the cooling requirements that allow the cell to operate at a specified temperature, based on the parameters influencing electrical power generation. A detailed balance approach and a simple thermal model involving an effective heat transfer coefficient are used. Key parameters, such as emitter temperature, view factor, in-band transmission and out-of-band transmission functions, and external radiative efficiency, are systematically varied to evaluate their influence on pairwise efficiency and power density, and on the required effective heat transfer coefficient to ensure that the cell operates at selected temperatures. Although thermophotovoltaic cells are typically presumed to function at close to ambient, our findings indicate that maintaining this operating temperature necessitates a cooling system with a substantially high effective heat transfer coefficient (∼ 10^3 -10^4 Wm -2 K -1 ). The cooling challenge grows when the cell bandgap diminishes, due to the interplay of rising power density and decreasing pairwise efficiency. The cooling requirements increase with the temperature of the emitter and the view factor. Nevertheless, they can be mitigated by reducing both in-band and out-of-band transmission functions. They are underestimated, and the bandgap optimizing pairwise efficiency or power density is inadequately predicted when the cell is assumed to operate in the radiative limit. These insights into cooling requirements imply that they should be considered from the initial stages of thermophotovoltaic device design
Fifty years of research on resource-constrained project scheduling explored from different perspectives
No full textInternational audienceThe resource-constrained project scheduling problem is one of the most investigated problems in the project scheduling literature, and has a rich history. This article provides a perspective on this challenging scheduling problem, without having the ambition to provide a complete overview. Instead, the article does aim to summarize a number of reasons why this problem has been so intensely investigated from different perspectives.It will be shown that this scheduling problem has many faces, and therefore deserves a lot of research time from a computational and theoretical point of view as well as from a practical point of view. An overview of possible extensions to other problems and a detailed overview of the used (both heuristic and exact) solution methods will be given. In addition, the data used will be discussed and interesting avenues for further research will be mentioned throughout the different sections.</div
Low-latency online estimation of human upper-limb pose and kinematics from a single 360 camera
No full textInternational audienceWe present a fully online framework for streaminghuman upper-limb kinematics estimation from a single 360camera. Incoming frames are processed sequentially throughvertical-boundary-aware tracking, pseudo-perspective rendering,and Neural Localizer Fields to estimate a sparse set of 3Danatomical landmarks in real time. These landmarks are mappedto an OpenSim-compatible biomechanical model, with jointangles computed on the fly via an online inverse kinematicssolver. The system achieves end-to-end latencies as low as22.9 ms on a high-performance setup. Evaluated in a single-participant scenario involving an initial T-pose calibration andrepeated object displacement toward the camera, it demonstratesrobust performance under moderate self-occlusion and sphericaldistortion. While tested in a constrained setting, its modular, real-time design makes it a promising candidate for human–robotinteraction and other motion analysis applications, enablingminimal, markerless, and anatomically interpretable upper-limbtracking from omnidirectional vision
Front-surface cooling of infrared thermophotovoltaic cells
No full textInternational audienceThis paper proposes a front-surface cooling method for thermophotovoltaic (TPV) cells utilizing microfluidic channels for efficient heat dissipation. Unlike conventional back-surface cooling, front-surface cooling minimizes thermal resistance by directly cooling the top surface of the cell. The microfluidic channel layer also functions as an antireflection layer through the gradual change in the refractive index. The proposed cooling method was evaluated using a thermo-fluid analysis, considering factors such as the emitter temperature, cell reflectance, thermal resistance, and fluid optical properties. We examined liquids with ideal absorption characteristics and actual liquids whose absorption coefficients were measured. The results showed that front-surface cooling significantly outperformed back-surface cooling in terms of the net power density. This method is particularly advantageous for high emitter temperatures or in cases where the thermal resistance between the cell and backsurface liquid is high. Moreover, this study highlights the potential application of the cooling method in bifacial TPV cells, which can generate electricity from thermal radiation incident on both sides. Bifacial cells offer higher power generation per unit area but face cooling challenges. The proposed cooling technique addresses these challenges, paving the way for innovative TPV system configurations and improved performance
Digital electronics upgrade of the INDRA <math altimg="si2.svg" display="inline" id="d1e354"><mrow><mn>4</mn><mi>π</mi></mrow></math> charged particle detection array and resulting performance improvements
No full textInternational audienceINDRA is a 4π charged particle detection array in use since 1993 for the study of nuclear collisions at bombarding energies from a few 10s to a few 100s of MeV/nucleon. Originally equipped with custom electronics using the VXI standard, the entire acquisition system was recently upgraded to a fully digital system using commercially-available modules supplied by mesytec GmbH & Co. KG. At the same time, both low and high voltage supplies and all cabling and signal routing outside of the reaction chamber have also been replaced. The new electronics were used for the first time in 2022 in an experiment at GANIL coupling INDRA with 12 blocks of FAZIA telescopes placed at forward angles. The full details of the upgraded system, and the resulting improvements in performance, stability, dead time and identification capabilities are presented in this article