Portail HAL edf
Not a member yet
11029 research outputs found
Sort by
A Bayesian update of Kotha et al. (2020) ground-motion model using Résif dataset
No full textInternational audienc
Numerical Modelling of the Behaviour over 60 Years of a Nuclear Power Plant Containment Vessel Submitted to an Internal Swelling Reaction
No full textInternational audienceIn France, the extending of nuclear power plant service life from 40 to 60 years is an actual issue. Due to the number of nonlinear and concomitant concrete phenomena, such structure needs a reliable tool to ensure and predict their behavioural evolution. In this work, a thermo-hydro-chemo-mechanical model considering passive reinforcements in a distributed manner is applied to the calculation of a containment vessel with ISR. Shrinkage, creep, ISR swelling and induced damage are strongly coupled to each other, and all depend on thermal and humidity environmental conditions. The calculation is based on the available basic mechanical characteristics, the passive reinforcement ratios, the tensioning kinetic data of the prestressing cables and the structure’s geometry. The results show a good correlation with the multiaxial strains of the structure on the in-situ data. The model is used to make predictions over the next 30 years. Two scenarios of maximum swelling are considered. Cracking, which is an essential information for these containment structures, is compared between 30 years and 60 years. The prediction at 60 years shows that the pathology, with a hypothesis of rapid evolution, does not have a deleterious effect on the structure
The Potential of Wacapou (Vouacapoua americana) Extracts to Develop New Biobased Protective Solutions for Low-Durability Wood Species
No full textInternational audienceThe valorization of Amazonian wood residues into active chemical compounds could be an eco-friendly, costeffective and valuable way to develop wood preservative formulations to enhance the decay and termite resistance of low-durable wood species. Wacapou (Vouacapoua americana., Fabaceae) is a well-known Guianese wood species commonly used in local wood construction due to its outstanding natural durability, which results from the presence of a large panel of extractives compounds. In addition, its industrial processing generates large amounts of residues. Wacapou residues were extracted by maceration using four different solvents (water/ethanol, ethyl acetate, hexane and dichloromethane/methanol), separately and successively. The yield of each extractive fraction was determined, and their chemical compositions were analyzed by Liquid Chromatography-Mass Spectrometry (LC-MS). Ethyl acetate led to the highest extraction yield, and the active compounds were identified in the obtained extractive fraction. In this sense, the fungicidal and termite-repellent properties of these extractives were then tested using a screening laboratory (with temperate and tropical microorganisms), according to the solution concentration (1%, 2.5%, 5%, 8% and 10%). Finally, Virola michelii Heckel wood samples (low durable species) were impregnated with the 8% concentration solution. The impregnated wood samples were then exposed to a soil bed test. The results highlighted that the nature of the solvent used during wood maceration affects the content of the obtained extractive fractions. Ultra-Performance Liquid Chromatography-High-Resolution Mass Spectrometry (UHPLC-HRMS) analyses showed the influence of extraction parameters on the nature of the extracted molecules. Wacapou extracts (from ethyl acetate maceration) showed good anti-fungal and anti-termite activities. Additionally, the concentration in extractives had an impact on the anti-termite activity level for Reticulitermes flavipes and Cryptotermes sp. Formulations based on Wacapou extractives showed a good potential for valorization in eco-friendly preservatives, aiming to confer better durability to local low-durability wood species
Développement d’outils pour la quantification des incertitudes des données hydrométriques
No full textInternational audienceQuantifying the uncertainty of hydrometric data (river discharge measurements) is recognised as essential, but in practice it requires a set of tools adapted to the processing of measurements throughout a complex workflow ranging from field measurements (streamgaugings, stage records) to rating curves and discharge time series. We present several methods and software tools that have been developed over the last twenty years and integrated into the practices of field hydrologists in France. The greater uncertainty of flood discharges is one of the current challenges. In addition to continuing methodological developments, there is a need to consider how to best communicate and archive the uncertainties
Adaptive Importance Sampling Based on Fault Tree Analysis for Piecewise Deterministic Markov Process
No full textInternational audiencePiecewise deterministic Markov processes (PDMPs) can be used to model complex dynamical industrial systems. The counterpart of this modeling capability is their simulation cost, which makes reliability assessment untractable with standard Monte Carlo methods. A significant variance reduction can be obtained with an adaptive importance sampling method based on a cross-entropy procedure. The success of this method relies on the selection of a good family of approximations of the committor function of the PDMP. In this paper original families are proposed. Their forms are based on reliability concepts related to fault tree analysis: minimal path sets and minimal cut sets. They are well adapted to high-dimensional industrial systems. The proposed method is discussed in detail and applied to academic systems and to a realistic system from the nuclear industry
Presencia de residuos antibióticos en carnes comercializadas en el área transfronteriza España‑Francia: un enfoque novedoso en los métodos de vigilancia
No full textInternational audienceAlthough antimicrobials are valuable allies in animal production, their extended use has led to the emergence of antimicrobial resistance. Moreover, when withdrawal periods in food-producing animals are not observed, antimicrobial residues can access the food chain, causing direct toxicity, allergies, and/or intestinal microbiota dysbiosis in consumers. Given that Spain and France are the largest meat producers in the EU and are among the top consumers, our study’s aim was to investigate the presence of antimicrobials in commercialized meat purchased in the Spain-France cross-border area (POCTEFA region). 5,357 meat samples were collected from different animal species and a variety of different retailer types in Spain (Zaragoza, Bilbao, and Logroño) as well as in France (Toulouse and Perpignan). Meat samples were analysed by a screening method (Explorer®+QuinoScan®), yielding 194 positive samples, which were further evaluated by UPLC-QTOF (Ultra Performance Liquid Chromatography-Quadrupole Time of Flight) for confirmation. Chromatographic analyses found antimicrobial residues in 30 samples, although only 5 of them (0.093 % of initial samples) were non-compliant according to the current legislation. Further studies suggested that this mismatch between screening and confirmatory analyses might be due to the presence of biologically active metabolites derived from antimicrobials unidentified by the targeted UPLC-QTOF method, causing inhibition of the biological Explorer ® test. Although chromatographic techniques detect the marker compounds determined by legislation and are the methods selected for official control of antimicrobials in food, metabolites might escape their monitoring. This thus suggests that biological tests are the most adequate ones in terms of ideal consumer health protection.Aunque los antimicrobianos son grandes aliados en producción animal, su uso masivo ha contribuido a la aparición de antibiorresistencias. Además, cuando los periodos de supresión no se respetan, sus residuos pueden llegar a la cadena alimentaria, provocando toxicidad directa, alergias y/o disbiosis en la microbiota intestinal de los consumidores.Puesto que España y Francia son los mayores productores de carne en la UE y están entre los principales consumidores a nivel mundial, el objetivo de nuestro estudio fue investigar la presencia de antimicrobianos en carne comercializada en el área transfronteriza España‑Francia. Se recogieron 5.357 muestras de carne de diferentes especies animales en España (Zaragoza, Bilbao y Logroño) y Francia (Toulouse y Perpignan), que se analizaron por un método de cribado (Explorer®+QuinoScan®, Zeulab S.L., Zaragoza, España), obteniendo 194 muestras positivas, que se analizaron por cromatografía UPLC‑QTOF para su confirmación. Los análisis cromatográficos revelaron presencia de residuos en 30 muestras, aunque solo 5 de ellas (0,093 % de las muestras iniciales) fueron no‑conformes de acuerdo a la legislación. Análisis posteriores sugirieron que esta divergencia entre el cribado y la confirmación se debe a la presencia de metabolitos biológicamente activos derivados de los antimicrobianos originales, no identificados por el método dirigido UPLC‑QTOF, generando la inhibición del test Explorer®. Así, aunque las técnicas cromatográficas detectan el compuesto marcador indicado por la legislación y son los métodos de elección para control oficial de antibióticos en alimentos, sus metabolitos pueden escapar al monitoreo, lo que sugiere que los test biológicos son más adecuados para proteger la salud de los consumidores
Capacité portante sismique des fondations sur sol renforcé par inclusions rigides
No full textInternational audienceThe kinematic exterior approach, in the framework of the yield design theory, is widely utilised for assessing foundation bearing capacity. This study aims at extending this approach to shallow foundations on reinforced soil by rigid inclusions. The interaction diagram in the (V, H, M) space is obtained by combining the interaction curves derived from different failure mechanisms. The resisting forces provided by the rigid inclusions are evaluated using a multicriterion approach and are considered at the intersection of the inclusions with the failure surface. Furthermore, the soil inertia due to the horizontal seismic excitation is also considered in the analysis. The results reveal that the bearing capacity under seismic load is unaffected in the zone of interest for foundations with a sufficient safety factor under static loading.L’approche cinématique par l’extérieur, dans le cadre de la théorie de calcul à la rupture, est largement utilisée pour évaluer la capacité portante des fondations. Cette étude vise à étendre cette approche aux fondations renforcées par inclusions rigides. Pour ce faire, le diagramme d’interaction dans l’espace (H, V, M) est obtenu en combinant les diagrammes d’interaction issus de différents mécanismes de rupture. L’effet de renforcement apporté par les inclusions rigides est pris en compte au moyen des forces résistantes développées à l’intersection de l’inclusion avec la surface de rupture, et sont évaluées à l’aide d’un multicritère. De plus, cette étude prend en compte les effets d’inertie du. Les résultats révèlent que la capacité portante sous charge sismique n'est pas impactée dans la zone d'intérêt pour les fondations présentant un facteur de sécurité suffisant sous charge statique
Characterization of the Performance of Perovskite Solar Cells by Operando X-Ray Photoemission Spectroscopy
No full textInternational audienc
An algorithmic framework for the optimization of deep neural networks architectures and hyperparameters
No full textInternational audienceIn this paper, we propose an algorithmic framework to automatically generate efficient deep neural networks and optimize their associated hyperparameters. The framework is based on evolving directed acyclic graphs (DAGs), defining a more flexible search space than the existing ones in the literature. It allows mixtures of different classical operations: convolutions, recurrences and dense layers, but also more newfangled operations such as self-attention. Based on this search space we propose neighbourhood and evolution search operators to optimize both the architecture and hyper-parameters of our networks. These search operators can be used with any metaheuristic capable of handling mixed search spaces. We tested our algorithmic framework with an evolutionary algorithm on a time series prediction benchmark. The results demonstrate that our framework was able to find models outperforming the established baseline on numerous datasets
Phase-field simulation and coupled criterion link echelon cracks to internal length in antiplane shear
No full textInternational audienceThis paper provides a comprehensive numerical analysis of daughter crack localization in pure antiplane shear. Although antiplane shear fracture is important in various industrial applications, understanding the morphology of the resulting fragmentation remains challenging. The paper develops innovative phase-field models to induce the facets using a small spatial variation in the toughness field and examines the impact of numerical and material parameters on the newly formed daughter cracks’ shape and spacing. Through meticulous comparison to the coupled criterion, the paper reveals a compelling connection between the internal length-scale of damage regularization, Irwin’s length and the facet crack spacing. Furthermore, the effect of Poisson’s ratio on the crack form and spacing is investigated: the results reveal a significant influence and showcase comparable initiation distances between the numerical simulations and experimental measurements in pure antiplane loading