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La condition au bord de Neumann pour le schéma de Lax-Wendroff bi-dimensionnel. II
No full textInternational audienceWe study the stability of a two-dimensional Lax-Wendroff scheme in a quarter-plane. Following our previous work, we aim here at adapting the energy method in order to study second order extrapolation boundary conditions. We first show on the one-dimensional problem why modifying the energy is a necessity in order to obtain stability estimates. We then study the two-dimensional case and propose a modified energy as well as second order extrapolation boundary and corner conditions in order to maintain second order accuracy and stability of the whole scheme, including near the corner
Enzyme promiscuity in the field of Synthetic Biology applied to White Biotechnology: Opportunities and weaknesses.
No full textInternational audienceWhite biotechnology stands as a major sustainable alternative to address pressing environmental issues arising from our heavy dependence on petrochemical synthesis. However, reaching this goal, both technologically and economically, will take time, resources and money. A major reason is within the biological system itself, as it has evolved into a bow-tie structure in which carbon and energy are converted, via highly regulated, complex and interconnected metabolic networks, into cellular components for growth and homeostasis. This objective is fundamentally at odds with that of biotechnology, which aims to convert carbon and energy into bioproducts. Engineering of microorganism using systems and synthetic biological systems tools has been developed to provide a compromise between these two objectives. However, these genetic and metabolic interventions have revealed often unexpected physiological behaviors, in part due to the fact that a large proportion of metabolic enzymes are catalyzing other reactions than those for which they were evolved. While this promiscuity is the source of an underground metabolism that can prove very advantageous in building high-performance production routes, it is also responsible for loss of yield and production due to metabolic disturbances, negative cross-talks between natural and heterologous pathways as well as it is at the onset of metabolic damages. Identifying these promiscuous enzymes and thus anticipating their opportunities or weaknesses in engineering microbial cell factories for bioproduction is a major challenge in order to improve their performance. It is foreseen that machine learning tools operating on databases continuously fed by genetic, metabolic, enzymatic and fermentation processes data can help to overcome these challenges and provide a better understanding of the physiological functioning of the microbial system
Towards IoT-based Smart Mobility Frameworkfor Proactive Road Stress Detection inIndividuals with ASD
No full textInternational audienc
Differences in growth features between species are driving cereal-legume intercrop yield: A statistical learning approach based on aggregated dataset
No full textInternational audienceIncreasing crop diversification is crucial for developing more sustainable agricultural systems, and cereal-legume intercropping is a promising strategy. This study investigates the factors influencing the yield of cereal-legume intercrops using data from six field experiments in southwestern France, where durum wheat was intercropped with either faba bean or pea. We assessed how differences in plant traits (e.g., height or biomass growth rates) between the associated species were related to the intercrop productivity. Additionally, we developed a novel modeling approach, combining machine learning and mixed-effects models, to identify the key drivers of intercrop performance based on variable importance. Our results showed that interspecific differences in plant traits within intercrops, particularly in biomass accumulation rate, maximum leaf area index, and elongation rates, were the most important factors explaining intercrop yield. These traits and their differences mainly suggest that competitive processes shape the outcome of a mixture and highlight the importance of dynamic measurements in agronomic experiments. The relationship between species yield and trait differences was symmetric for both intercropped species. Furthermore, these relationships were scale-dependent, with trends observed at the aggregate level not always consistent at the level of individual experiments. Our study highlights the importance of considering trade-offs when designing intercropping systems for practical applications and demonstrates the value of combining machine learning with ecological knowledge to gain insights into complex agricultural systems from aggregated datasets
Fast detection of EMC level drifts induced by aging using biased thermal step stress : Application to an AC input EMC filter
No full textThis paper received second prize in the Song-Tsuen Peng Best Student Paper Award competition at APEMC 2025 symposiumInternational audienceThis paper presents the use of step stress accelerated aging tests associated with VNA measurements to efficiently detect the risk of potential EMC level drifts. The method is applied to an AC input EMC filter and a deviation in common mode attenuation is observed. Key points ensuring the validity of the results are discussed. Perspectives and limits are presented
Multichannel Dyson equations for even- and odd-order Green's functions: Application to double excitations
No full textInternational audienceRecently we proposed a multichannel Dyson equation, in which we coupled the one- and the three-body Green's functions, to model photoemission spectra. In this work we extend this concept to higher-order Green's functions and to other spectroscopies. We show the general structure of the equations and how one can systematically approximate the corresponding multichannel self-energy. As a particular case, we focus on the coupling of the two-body and the four-body Green's functions in the electron-hole channel to describe neutral excitations. This formulation allows for the description of important many-body effects, such as biexcitons, in a natural way. We illustrate our approach by applying it to a two-level model system, which, in a one-particle picture, exhibits single and double excitations. Our method can correctly describe both kinds of excitation, unlike standard approaches, and in good agreement with the exact results
Recommendation of TC RILEM TC 274-TCE: 3-point bending test procedure for earthen bricks—quality control of earth bricks for structural masonry by flexural strength
No full textInternational audienceBuilding with unstabilised earth bricks (EB) as units for structural masonry walls offers a sustainable alternative to mitigate resource depletion's negative impact and global warming. Using locally sourced earth for EB production is required to achieve these benefits. This leads to large variations in material composition. Consequently, quality control becomes critical to ensure adequate mechanical performance of the masonry units. In the framework of the RILEM TC 274-TCE, the characterisation of the flexural strength of bricks has been examined. A comprehensive inter-laboratory campaign involving seven laboratories across three countries was conducted, during which flexural tests were performed on 98 bricks. This article details the TC 274-TCE recommendations on the procedure to conduct a 3-point bending test on an EB. Key test parameters such as specimen pre-conditioning, setup boundary conditions, loading rate and determination of material flexural strength are discussed. The calculation of flexural strength was evaluated by comparing results obtained from the beam theory model and a solid mechanics approach, validated through finite element modelling. The findings confirm that the 3-point bending test is a reliable method to assess the mechanical performance of EB and to control their quality
Low-temperature UHV scanning tunneling microscope double sample holder for in situ exchangeable clean room processed samples
No full textInternational audienceA generalization of the double sample holder (DSH) concept is presented for an ultra-high vacuum (UHV) low-temperature (LT) multi-probe scanning tunneling microscope (STM). In UHV, the DSH is carrying, side-by-side, a reference metal sample [Au(111) single crystal for STM tip apex preparation] and an ancillary stand-alone small sample holder (for samples originating from a clean room) that can be mounted in situ in/out of the DSH plate. STM tip navigation on both sample surfaces is performed using a UHV scanning electron microscope positioned above the STM stage. For demonstration, clean room nanofabricated graphene nano-gears (diameter down to 25 nm) on a sapphire sample are characterized using STM. The STM tip apices are cleaned on the atomically precise and UHV cleaned Au(111) reference sample surface. Using our new DSH plate and in situ STM tip apex re-preparation on the reference metallic sample, we demonstrate how a clean room originating sample can be imaged at the atomic resolution using our LT-UHV 4-STM
Decomposition methods for beam-layout optimization
No full textInternational audienceIn the context of payload design for telecommunication satellites, we address the optimization problem of beam layout. The objective is to define the beams emitted by the antennas of a geostationary satellite to cover regions on the Earth’s surface, represented as polygons. The regions must be grouped into beams such that the beam sizes are minimized to favor the link budget. Specifically, our criterion is to minimize the squared radius sum (SRS) of the selected beams. Additionally, each beam layout must be associated with a feasible mapping of beams to reflectors (antenna dishes), typically constrained to NR = 4 reflectors. This mapping must ensure that two beams assigned to the same reflector maintain a minimum separation distance. The mapping and sizing of beams are inherently linked to the arrangement and dimensions of the antenna equipment, which must be physically feasible. Each beam is produced by a single antenna feed, and feeds of beams assigned to the same reflector are grouped into a cluster. The minimum separation distance between beams ensures sufficient space for all feeds within a cluster. The problem of assigning beams to reflectors can be modeled as a graph coloring problem of G, where beams correspond to vertices, and edges represent the minimum distance constraint. To tackle this challenging problem, we propose two decomposition methods: column generation and logic-based Benders decomposition
Aux côtés de Claude, Jacqueline Chevalley
No full textC’est au croisement des innombrables documents d’archives du fonds Alexandre Marc aux Archives de l’Union européenne et des photos inédites dévoilées par les nièces de Jacqueline Chevalley que s’écrit cet article. Nous allons nous immerger dans la période de l’entre-deux-guerres et voyager entre les espoirs du mouvement des non-conformistes des années 1930 et l’effervescence des premiers Bourbaki. Cela nous amènera à découvrir l’histoire de la jeunesse de Jacqueline et Claude Chevalley sous un nouveau jour, suivant le parcours d’émancipation de Jacqueline : femme intelligente et déterminée, elle sut trouver son chemin aux côtés du brillant mathématicien Claude Chevalley, dans un monde où beaucoup de femmes avaient encore peu de prise sur leur destin.Les documents du fonds Alexandre Marc m'ont été généreusement confiés par Norbert Schappacher