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On the validity of two-flux and four-flux models for light scattering in translucent layers: angular distribution of internally reflected light at the interfaces: erratum
No full textInternational audienceThis erratum corrects a mistake in Opt. Express 32 , 9042 ( 2024 ) 10.1364/OE.510888
-structures through quotient by torus actions
No full textWe show that if is a Kähler manifold with an -structure and a Hamiltonian holomorphic action of a compact torus , then the usual symplectic quotient inherits an -structure provided the existence of special 1-forms on X, called twist forms. We then give several applications of our results: on complex projective spaces, on cones over Fano Kähler-Einstein manifold and on toric bundles. We also study the geometry behind these structures in the case of
Acceleration of implicit schemes for large systems of delay differential equations
No full textInternational audienceThe objective is to accelerate numerical implicit schemes for solving large linear or nonlinear delay differential equations. These schemes require solving large linear or nonlinear systems at each integration step, making effective initial guesses critical for rapid convergence. For nonlinear problems, an inexact Newton method is used, whose efficiency depends heavily on the quality of these initial guesses. To generate them, line search or trust-region algorithms are employed -each involving the solution of large linear systems. These linear systems are solved using a Krylov subspace method. Initial guesses are constructed via a Petrov-Galerkin process applied to low-dimensional approximation subspaces derived from previous steps. Error estimates are provided, linking the accuracy of the initial guesses to the timestep size, the scheme's order, and the subspace dimension. Numerical experiments show speedups of up to two orders of magnitude over standard predictor-based methods, when those converge
Respirer avec K. Méthodes et enjeux cartographiques
No full textNational audienceCe texte se propose de mener une discussion avec et autour d’une cartographie , celle de l’itinéraire de K., un homme, asthmatique et allergique. Nous - deux chercheurs et une architecte cartographe - avons expérimenté avec K. un itinéraire en marchant centré sur sa respiration et son expérience ordinaire de l’air, en nous donnant l’objectif suivant : produire une cartographie qui non seulement exprime l’expérience de l’itinéraire, mais aussi constitue un outil réflexif et critique des espaces publics contemporain
Mo-enhanced passivity of stainless steels studied at metal/oxide interfaces by DFT atomistic modeling
No full textInternational audienc
Towards a Smarter Homophone Correction Tool: A Case Study in Khmer Writing
No full textInternational audienceHomophone errors are a common challenge in written communication, affecting both high-resource languages, such as English, and low-resource languages, such as Khmer. These errors are often difficult to detect because they require contextual understanding rather than simple spelling correction. While existing spelling correction tools enhance text accuracy, they do little to improve users’ long-term writing skills, often leading to an over-reliance on automated corrections. This study aims to bridge this gap by investigating the challenges of homophone usage, specifically among Khmer users, and proposing a foundational theoretical blueprint for future solution development. Through a questionnaire-based survey, we analyzed the prevalence of homophone errors and their impact on Khmer speakers. Additionally, we conducted an experimental study using Typing Tracker, where participants transcribed audio-recorded articles to determine their ability to correctly use homophones in context. Based on these insights, we introduce Sor-Ser, an innovative conceptual approach that integrates Natural Language Processing (NLP) with Learning Analytics (LA) techniques. This preliminary framework provides a foundation for addressing homophone errors while enhancing writing proficiency. By addressing both error correction and skill development, Sor-Ser provides a potential pathway for improving Khmer writing accuracy while fostering long-term proficiency and confidence
Hydrophobization of carboxymethyl cellulose by Passerini reaction: towards films with improved water vapor barrier properties
No full textInternational audienceTo address the need for developing sustainable materials with effective barriers to water vapor, this work explores the potential of self-supported films made of carboxymethyl cellulose (CMC) functionalized by the Passerini three-component reaction. Aliphatic aldehydes and tert-butyl isocyanide were grafted onto CMC backbone to yield dually hydrophobized derivatives. These modified polysaccharides were processed into films by solvent casting and their water vapor transfer properties were examined. Small-angle X-ray scattering (SAXS) experiments revealed a nanoscale organization for Passerini-modified films, attributed to the formation of hydrophobic domains characterized by a nanometric interdomain spacing. Dynamic vapor sorption (DVS) analysis demonstrated a significant reduction in moisture content water for modified films, from ≃ 1.1 g g -1 for unmodified CMC to below 0.5 g g -1 for hydrophobized derivatives at a w = 0.95. Guggenheim-Anderson-deBoer (GAB) and Zimm-Lundberg modeling showed a decrease in sorption site availability from 3 to ≃ 1.5 per glucose unit, while the size of water clusters was significantly increased. The Passerini modification also resulted in a substantial decrease of water vapor permeability (WVP) from 44 000 barrer to 2500 barrer at a w = 0.5. These results unequivocally underpin the benefits of the Passerini functionalization which allows to enhance the water vapor barrier performance. The findings highlight the potential of such a reaction for developing next-generation and bio-based packaging materials with tailored water vapor barrier properties.</div
Evaluation of global biotic resource consumption against absolute boundaries
No full textInternational audienceHuman activities rely on biotic natural resources to provide products and services necessary to meet human needs. This instrumental value is captured in life-cycle assessment through the “Natural resources” Area of Protection. Although several absolute boundaries have been proposed to safeguard biotic resources, it remains unclear whether these resources are currently used at a sustainable rate. This study addresses this question by evaluating global biotic resource consumption from 1995 to 2011 against suggested biotic resource boundaries, relying on Exiobase projections to assess the evolution beyond 2011. The assessment couples absolute boundaries with life-cycle impact assessment (LCIA) methods, enabling evaluation using consistent LCIA metrics. Five absolute boundaries and four LCIA methods were adapted to the Exiobase multiregional input-output model. Results show that most of existing boundaries are already transgressed, regardless of whether mass-based or LCIA-based control variables are applied. The wide range and normative nature of existing boundaries emphasize the need for harmonized, science-based boundaries to ensure the sustainable use of biotic resources
Metallic trace elements in wild and farmed fish from the Aveiro Region (Portugal)
No full textInternational audienceThis study assessed the concentrations of 11 metallic trace elements (MTEs: As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Se, Zn) in fish muscle from eight wild and farmed species collected in the Aveiro region of Portugal, an area historically affected by industrial pollution. A total of 66 samples were analyzed by ICP-MS. Mean concentrations (mg/kg ww), arranged in ascending order, were: Ni (0.0001), Cd (0.0015), Co (0.0020), Pb (0.0023), Cr (0.0179), Mn (0.0862), Cu (0.2500), Se (0.2964), Fe (1.9236), As (1.9260, total As), and Zn (3.3701). Significant differences were observed among species and between wild and farmed fish, particularly in Dicentrarchus labrax and Sparus aurata. Although Cd and Pb concentrations remained below current European maximum levels, risk assessment based on safe consumption limits (SCLnc) identified total Se, Cd, and Pb as the most restrictive elements for daily intake, especially in children. For arsenic, only total concentrations were considered, as inorganic As could not be distinguished in this study. No significant non-carcinogenic risks were identified at current national average fish consumption levels; however, the potential cumulative and synergistic effects of multiple metals in chronic exposure warrant further investigation. The Metal Pollution Index (MPI < 1 for all samples) confirmed low overall contamination. These findings underscore the importance of ongoing monitoring of trace elements in fish to ensure food safety and protect vulnerable populations
ALGORITHME PLUG-AND-PLAY AVANT-ARRIÈRE POUR RESTAURER LES IMAGES LANDSAT : UNE ÉTAPE PRÉLIMINAIRE POUR DÉCOUVRIR L'HISTOIRE DES EAUX DE SURFACE
No full textInternational audienceThe temporal and spatial analysis of river dynamics is a key factor for studying and understanding human impacts on floodplains.To assess the changes taking place, it is necessary to have high-resolution images with a large spatial coverage and a high temporal revisit frequency over the long term. Satellite imagery meets several of these criteria. For instance, Sentinel data provide high-resolution images but only after 2015. Therefore, to study water surface evolution prior to this date, it is necessary to rely on other satellite images such as Landsat, which offers longer historical coverage, albeit with lower spatial resolution. In this study, we aim to increase the spatial resolution of Landsat data from 30 to 10 meters (resolution of Sentinel images). To achieve this goal, we develop an innovative single image super-resolution method based on a plug-and-play approach.L'analyse temporelle et spatiale de la dynamique fluviale est un facteur clé pour étudier et comprendre les impacts humains sur les plaines inondables.Pour évaluer les changements qui se produisent, il est nécessaire de disposer d'images haute résolution avec une large couverture spatiale et une fréquence de revisite temporelle élevée sur le long terme. L'imagerie satellite répond à plusieurs de ces critères.Par exemple, les données Sentinel fournissent des images haute résolution, mais uniquement après 2015. Par conséquent, pour étudier l'évolution de la surface de l'eau avant cette date, il est nécessaire de s'appuyer sur d'autres images satellites telles que Landsat, qui offre une couverture historique plus longue, mais avec une résolution spatiale inférieure. Dans cette étude, nous visons à augmenter la résolution spatiale des données Landsat de 30 à 10 mètres (résolution des images Sentinel). Pour atteindre cet objectif, nous développons une méthode innovante de super-résolution d'une seule image basée sur une approche plug-and-play