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Multiscale insights into biofilm development on hydrophobic fouling-release coatings
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Defect Suppression and Efficiency Enhancement of Slot-Die-Coated Formamidinium Lead Iodide Solar Devices via Ambient Air Annealing
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Exponential twist of probability measures: drift correction in term of a generalized gradient
No full textIn this paper we study the exponential twist, i.e. a path-integral exponential change of measure, of a Markovian reference probability measure . This type of transformation naturally appears in variational representation formulae originating from the theory of large deviations and can be interpreted in some cases, as the solution of a specific stochastic control problem. Under a very general Markovian assumption on , we fully characterize the exponential twist probability measure as the solution of a martingale problem and prove that it inherits the Markov property of the reference measure. The ''generator'' of the martingale problem shows a drift depending on a {\it generalized gradient} of some suitable {\it value function}
Optimal design of a distributed control system for a power plant using decomposition
No full textInternational audienceOptimal design of a distributed control system for a power plant using decompositio
Détermination expérimentale de l’énergie de fissuration de bétons coquillers par corrélation d’images numériques
No full textInternational audienceDans le cadre de la réduction de l'empreinte environnementale des bétons, de récentes études ont permis de montrer qu'il était possible de substituer 50% des gravillons naturels par des co-produits coquilliers d'huîtres, tout en conservant des propriétés mécaniques suffisantes pour des bétons porteurs et en améliorant leurs propriétés de durabilité. Cependant, l'impact de ces granulats alternatifs sur la fissuration des bétons n'a pas encore été étudié. Le travail présenté ici s'intéresse à la fissuration et plus particulièrement à l'énergie de fissuration de bétons incluant des co-produits coquilliers. Des essais de flexion trois points sur éprouvettes entaillées ont été réalisés. L'utilisation de la corrélation d'images numériques (CIN) a permis de mesurer les champs de déplacement et d'observer la propagation de la fissure au cours de l'essai. En particulier, une méthode utilisant l'identification des séries de Williams par méthode intégrée a été utilisée. Elle permet de déterminer les facteurs d'intensité du matériau et de déduire l'énergie de fissuration pour chaque éprouvette
A theoretical and computational framework for three dimensional inverse medium scattering using the linearized low-rank structure
No full textIn this work we propose a theoretical and computational framework for solving the three dimensional inverse medium scattering problem, based on a set of data-driven basis arising from the linearized problem. This set of data-driven basis consists of generalizations of prolate spheroidal wave functions to three dimensions (3D PSWFs), the main ingredients to explore a low-rank approximation of the inverse solution. We first establish the fundamentals of the inverse scattering analysis, including regularity in a customized Sobolev space and new a priori estimate. This is followed by a computational framework showcasing computing the 3D PSWFs and the low-rank approximation of the inverse solution. These results rely heavily on the fact that the 3D PSWFs are eigenfunctions of both a restricted Fourier integral operator and a Sturm-Liouville differential operator. Furthermore we propose a Tikhonov regularization method with a customized penalty norm and a localized imaging technique to image a targeting object despite the possible presence of its surroundings. Finally various numerical examples are provided to demonstrate the potential of the proposed method
Discrete FEM-BEM coupling with the Generalized Optimized Schwarz Method
No full textThe present contribution aims at developing a non-overlapping Domain Decomposition (DD) approach to the solution of acoustic wave propagation boundary value problems based on the Helmholtz equation, on both bounded and unbounded domains. This DD solver, called Generalized Optimized Schwarz Method (GOSM), is a substructuring method, that is, the unknowns of an iteration are associated with the subdomains interfaces. We extend the analysis presented in a previous paper of one of the author to a fully discrete setting. We do not consider only a specific set of boundary conditions, but a whole class including, e.g., Dirichlet, Neumann, and Robin conditions. Our analysis will also cover interface conditions corresponding to a Finite Element Method - Boundary Element Method (FEM-BEM) coupling. In particular, we shall focus on three classical FEM-BEM couplings, namely the Costabel, Johnson-Nédélec and Bielak-MacCamy couplings. As a remarkable outcome, the present contribution yields well-posed substructured formulations of these classical FEM-BEM couplings for wavenumbers different from classical spurious resonances. We also establish an explicit relation between the dimensions of the kernels of the initial variational formulation, the local problems and the substructured formulation. That relation especially holds for any wavenumber for the substructured formulation of Costabel FEM-BEM coupling, which allows us to prove that the latter formulation is well-posed even at spurious resonances. Besides, we introduce a systematically geometrically convergent iterative method for the Costabel FEM-BEM coupling, with estimates on the convergence speed
Analysis of the interior transmission problem in an unbounded locally perturbed periodic strip
No full textInternational audienceWe analyze the interior transmission problem in a locally perturbed infinite periodic domain, considering the case where the perturbation intersects the periodic background. An equivalent formulation as coupled quasiperiodic problems is obtained by applying the Floquet-Bloch transform. We perform a discretization with respect to the Floquet-Bloch variable and prove the well-posedness of the semi-discretized problem. We then establish some a priori estimates under regularity assumptions that allow us to prove the convergence of the discrete sequence to the solution of the problem
Selecting the best distribution for modeling trends in low, medium, and extreme daily precipitation under climate change
No full textInternational audienceChanges in mean precipitation and the frequency and intensity of extreme precipitation represent one of the most consequential aspects of anthropogenic climate change. This study evaluates a set of statistical distributions for modeling trends across the full precipitation spectrum (low, medium, and extreme daily quantiles). Modeling with a single flexible distribution ensures statistical consistency, thereby avoiding the artificial separation and discontinuity inherent in multi-model approaches. We used time as a covariate for dry-day frequency and sea surface temperature for the wet-day distribution parameters. We applied the methodology to a dense network of over 900 meteorological stations in France, offering a wide variety of climatic regimes, allowing for a robust conclusion. We employed a multi-criterion approach to select the best model, in the first step using the Akaike Information Criterion, and then based on their ability to flexibly capture trends across low, medium, and extreme precipitation quantiles. Our findings highlight that three-parameter distributions (generalized gamma and extended generalized Pareto distribution), particularly with evolving shape parameters, are essential for accurately capturing observed differential changes across the full precipitation spectrum, a flexibility that the two-parameter gamma distribution notably lacked. Although AIC generally favored generalized gamma, both generalized gamma and the extended generalized Pareto distribution demonstrated robust performance. This research underscores the critical need for a multi-criterion model identification framework in nonstationary trend analysis to provide reliable insights essential for hydrological and climate impact assessments
First Paleoseismological Trench in Northwestern France: A Multidisciplinary Study along the South Armorican Shear Zone.
No full textInternational audienceThe South Armorican Southern Shear Zone (SASSZ), located in the northwestern France within the Armorican Massif, represents a major structural feature inherited from the Variscan orogeny. Although this region is now far from active plate boundaries and characterized by very low strain rates (i.e. 10-9 yr-1), it’s characterized by a moderate and diffuse seismicity associated with a few large events (up to M~5), suggesting possible fault reactivations.This study integrates high-resolution mapping, geophysical investigations, and paleoseismic trenching to decipher the SASSZ structure and its possible quaternary activity. Based on high-resolution DEMs (LiDAR, RGEALTI from IGN), the analysis of morphological scarps along the SASSZ shows a wide range of surface trace complexities (bends, secondary splays, step-overs, gaps) associated with initial ductile and more recent brittle deformation. The width of the deformation zone around the SASSZ can reach up to 4 km, alternating between a localized and a distributed shear zone from the Pointe du Raz to Nantes. These measurements are in agreement with slope measurements performed along the SASSZ: the wider the deformation zone (> 0.3 km), the lower the maximum and mean slopes associated with the scarps.Three geophysical surveys were conducted at sites of interest, along the SASSZ, in order to connect observed scarps at the surface with variations in crustal physical properties. They reveal distinct resistivity contrasts consistent with surface scarp locations. At the Moulin Quilly site, two paleoseismic trenches were excavated across two sub-parallel scarps. Trench 1 across the main surface scarp is not associated with a clear lithological contrast. However, the foliated granitoids are affected by several families of fractures oriented from N50°E to N120°E. The main structure is located at the base of the scarp and is made of sub-horizontal goethite deposits filling a N120°E trending open fracture of 10 cm wide, in the same direction as the SASSZ. Trench 2 crosses a secondary scarp and is divided in to three main structural units: (1) a slightly weathered granite unit preserving subvertical foliation and affected by cryogenic processes dated between 20 and 30 ka (from Optically Stimulated Luminescence dates on sand deposits); (2) a narrow transition unit, associated with a high-strain zone showing sub-vertical fabrics filled by sands; and (3) a fine-grained, strongly altered ultramylonite unit dipping 15°–25° northeast. All units are covered by an undeformed modern soil. From the subvertical fabrics in the transition unit, oriented samples were collected for microstructural analysis. Thin sections in the altered fabric show well-oriented minerals, alteration veins, and kinematic indicators that document higher deformation and alteration processes than in the granite. Further analyses will be conducted to quantify the strain distribution, in close comparison with the dating results.Our study highlights a brittle deformation phase of the SASSZ, either linked to a recent tectonic activity, or associated with the Mesozoic regional extension, but the latter raises questions about the preservation of surface morphology through geological times. Future dating results of goethite deposits will help clarify whether the brittle fractures and their subsequent infilling reflect quaternary activity or an older phase of deformation