Scientific Publications of the University of Toulouse II Le Mirail
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Directional light scattering in Mie-resonant Si particles with ultra-thin plasmonic shells
No full textInternational audienceMetamaterial research has sought to create nanostructures with strong directional optical scattering to control light propagation at the nanoscale. Core-shell architectures comprised of both resonant cores and resonant shells have been suggested as candidate particles in which the spectral overlap of the electric and magnetic dipoles can be controlled to create strong directional scattering. In this study, we present Au-decorated Si core-shell (Si@Au) particles. These were synthesized by first creating Si particles through the thermal disproportionation of hydrogen silsesquioxane (HSQ), which were then decorated with ∼ 4 nm diameter Au nanoparticles. We characterized the resonant behavior of the core-shell particles using electron energy-loss spectroscopy mapping and optical single-particle scatter spectroscopy. These observations were supported by T-matrix simulations and Mie theory calculations of the scattering spectra, which show that compared to Si, Si@Au particles demonstrate a dampened magnetic dipole resonance for smaller Si core diameters (100 -130 nm) and an enhanced magnetic dipole resonance for larger Si core sizes (150 -200 nm). However, we show that to significantly improve forward scattering intensity, continuous plasmonic shells of ~12 nm thickness are needed
Reasoning with Plausibility in Incomplete Argumentation Frameworks
No full textInternational audienceIn the realm of abstract argumentation, Incomplete Argumentation Frameworks (IAFs), i.e. argumentation frameworks such that some arguments and attacks can be uncertain, have received much attention in the last decade. The most classical reasoning approach consists in using completions, which are argumentation frameworks representing all the possible ways to decide about the actual existence of the uncertain elements. Standard decision problems (like verifying whether a set of arguments is acceptable) can be adapted in two variants: verifying whether the property of interest holds for some completion, or for each completion. In this setting, all completions represent equally plausible scenarios for the agent, which is not always a realistic hypothesis in real world situations. In this paper, we propose IAFs with Plausibility (pIAFs), a generalization of the IAF model where the agent is able to reason about the relative plausibility of completions. We study the complexity of the usual decision problems of IAFs, adapted to this new model. We also introduce new decision problems concerning the relative plausibility of extensions and provide complexity upper bounds for these new problems as well
Differential effects of psychological resources on well-being and psychological distress: a one-year longitudinal study during the COVID-19 pandemic
No full textInternational audienceExtensive research evaluated the protective role of psychological resources (PRs, e.g. optimism, hope, gratitude and wisdom). However, few studies have explored their differential contributions when measured together. This study evaluated the longitudinal relationships between (and among) eight psychological resources, psychological distress (depression and anxiety symptomatology) and well-being (hedonic, eudaimonic, social, and inner well-being), over the first year of the COVID pandemic. Participants (N = 481) reported their levels of PRs, psychological distress, and well-being on two occasions (T0: April 2020; T1: June 2021). Cross-lagged panel analysis of the one-year associations revealed that 1) PRs positively, but differentially, predicted well-being and psychological distress; 2) PRs positively reinforced each other; and 3) well-being and low psychological distress also reinforced PRs, but to a lesser degree. In particular, psychological flexibility appeared to be the most predictive variable in all domains. This study highlights the need to include multiple psychological resources in future research
Grayscale evaporation of organic thin-film microstructures
No full textInternational audienceWe demonstrate that the deposition of organic thin films whose thickness is spatially shaped with sub-100-µm lateral resolution can be achieved by evaporation through a reusable flux-controlling micrometric-hole sieve that is separated from the to-be-coated substrate. This approach offers a practical way to grayscale-pattern organic materials without exposing them to detrimental ambient air or chemical solutions. As such, it facilitates the fabrication of long-lasting organic microstructured devices such as the reported spatially-varying absorptive color filters based here on the organic semiconductor (4,4'-Bis[4-(di-p-tolylamino)-styryl]biphenyl (DPAVBi)). Additionally, the ability to readily make multiple thickness-coated samples offers a material-sparing yet convenient way to measure the properties of the evaporated material, a feature exploited hereafter to extract the optical dielectric constants of DPAVBi over the visible and near-infrared range. This work and its extensions to inorganic compounds and freeform shaping pave the way for a new generation of devices that should find applications in light-matter coupling studies, hyperspectral imaging, structural coloring, or optical systems exploiting freeform optics
L'orientation post-troisième des Mineurs non Accompagnés : comment les personnels de l'Éducation Nationale vivent-ils leur fonction ?
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On the Construction of CAD-based Twins of Lattice Structures from Tomographic Images
No full textInternational audienceThe emergence of additive manufacturing has enabled the production of complex structures, notably cellular architected structures, also commonly referred to as lattice structures, which offer exceptional performance characteristics, including high stiffness-to-weight ratios, high stretchability, auxeticity, and more. In practice, lattice structures consist of periodically repeating well-designed unit cells, often composed of struts (or beams) interconnected in various ways via nodes. However, the intricacies of the additive manufacturing process, combined with the geometric complexity of lattice structures, often lead to geometric defects, such as variations in strut thickness, strut waviness, and displacements of lattice nodes, which can significantly influence their mechanical behavior.This study focuses on constructing a mechanical digital twin, i.e., a geometric model that (i) incorporates the specimen-specific geometry for each individual tested sample and (ii) can be easily used for numerical simulations. More precisely, we develop a method to extract an analysis-suitable Computer-Aided Design (CAD)-based geometry from 3D CT scan data of lattice structures. A multipatch B-spline surface model is constructed to represent the boundary of the lattice structure, ensuring a compact yet detailed geometric description. A template- fitting technique is developed to move the control points of the initial as-designed B-spline surface so that it fits the as-manufactured geometry, leveraging active contour methods from computer vision. Key innovations within this framework include utilizing a data fitting metric based on the Virtual Image Correlation (VIC) approach, combined with an image learning component, the integration of the membrane strain energy of the surface for regularization, and the enforcement of higher continuity between the patches where appropriate.The approach has been validated through various experiments, including those on a BCC lattice structure, where sub-voxel measurement accuracy has been achieved. Ultimately, the developed method provides a compact representation of the as-manufactured geometry with the same CAD-based discretization support as the initial as-designed structure, which should facilitate the quantitative assessment of defects and allow for efficient mechanical simulations using IsoGeometric Analysis
Some flocking properties for a model of collective dynamics with topological interactions
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Grand témoin. De la santé par l’alimentation (au plaidoyer) pour une santé globale par l’alimentation: Poser les enjeux sur les liens santé-alimentation-environnement
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Le mode mineur des barks de jeu vidéo
No full textInternational audienceThis paper deals with video game “barks”, the seemingly unimportant lines of discourse produced by non-player characters in specific situations, to which the player has no opportunity to respond. Drawing on theories of character, fiction and immersion, we first build an analytical typology of barks, distinguishing three types of function: a diegetic function, a ludic function and a reflexive function. This poetic analysis then leads to the presentation of a research-creation project that considers the potential of the bark’s marginality to address ethical issues.Cet article s’intéresse aux « barks » vidéoludiques, c’est-à-dire aux lignes de discours en apparence dérisoires que lancent les personnages non-joueurs dans certaines situations et auxquelles le joueur ou la joueuse n’a pas la possibilité de répondre. En s’appuyant sur les théories du personnage, de la fiction et de l’immersion, le travail propose d’abord une typologie analytique des barks en distinguant trois régimes de fonctionnement : un régime ludique, un régime diégétique et un régime réflexif. Cette analyse poétique s’ouvre ensuite à la présentation d’un travail de recherche-création qui envisage le potentiel de la marginalité du bark pour aborder des enjeux éthiques