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A generic tomography-based conforming finite elements model
No full textInternational audienceThis study presents a novel, automated pipeline to transform Micro-computed tomography (µCT) images into conformal Finite element analysis (FEA) models with high-quality tetrahedral elements. The proposed methodology uses image separation techniques and levelset methods to isolate distinct material components while avoiding overlaps and voids. A graph-based algorithm further optimizes the separation by grouping components into minimal non-overlapping level sets, enhancing computational efficiency and ensuring geometric fidelity. Subsequent mesh adaptation and remeshing procedures produce conformal meshes that accurately represent complex geometries and boundaries. The framework is validated through three case studies: woven composites, polycrystals, and dental implants, demonstrating its applicability across diverse material systems. This approach provides a robust solution for bridging tomographic imaging and high fidelity simulations, enabling more precise predictions of mechanical behavior and material performance
Anticipating potential environmental risks of offshore hydrogen production powered by offshore wind farm
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Ophthalmotoxicology of polyhalogenated compounds
No full textInternational audiencePolyhalogenated compounds (PHCs), including polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), polychlorinated dibenzodioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and per- and polyfluoroalkyl substances (PFAS), are persistent organic pollutants that bioaccumulate in tissues and are increasingly recognized as threats to human health. While their neurotoxic and endocrine-disrupting effects are often described, their potential impact on the ocular system remains underexplored. However, recent evidence suggests that chronic PHC exposure may contribute to a spectrum of ocular pathologies, such as retinal degeneration, cataracts and retinoblastoma. To clarify these emerging risks, this review synthesizes findings at the intersection of toxicology, ophthalmology, and environmental health, highlighting mechanistic insights into how PHCs impair ocular function. Epidemiological studies linking environmental contaminant exposure to visual deficits are discussed alongside experimental data from animal models and in vitro systems, with a particular focus on oxidative stress, mitochondrial dysfunction, endocrine disruption, and altered retinoid signaling as plausible pathways mediating PHC-induced visual toxicity. Given the widespread nature of PHC exposure and the increasing global burden of visual impairment, further research and regulatory oversight are urgently needed to bridge the gap between environmental toxicology and ocular health, ultimately aiming to better understand and mitigate the visual risks posed by these persistent pollutants
Deformation band patterns and dislocation structures in finite strain crystal viscoplasticity
No full textInternational audienceDeformation band patterning in single crystals is investigated using a finite strain crystal viscoplasticity model based on the evolution of dislocation densities. In the presence of strong latent hardening and weak rate dependence, the deformation organizes into laminate microstructures consisting of single-slip regions separated by dislocation walls. The influence of material and numerical parameters on the nucleation and morphology of these patterns is analyzed in 2D single crystals under plane strain compression. Pattern formation is also observed in 3D single-crystal cylinders subjected to tension, where the characteristic size of deformation microstructures is found to depend on mesh size and boundary conditions in the absence of an intrinsic material length scale. To address this limitation, strain gradient plasticity is introduced, providing a length scale that governs the size of the patterns. Finally, we demonstrate that deformation patterns and dislocation structures also emerge in 2D and 3D polycrystals, highlighting the generality of the phenomenon
Platform competition and strategic trade-offs for complementors: Heterogeneous reactions to the entry of a new platform
No full textInternational audienceWe study how the entry of a rival platform affects the strategies of the incumbent's complementors. The latter face a trade-off: While the entry threatens their benefits from indirect network effects, it also allows them to escape intense within-platform competition. Studying Epic Games' entry into the PC video game market - until then dominated by Steam - we show that this trade-off does not resolve uniformly, driving heterogeneity in strategic reactions. Complementors with weaker strategic resources (independent developers) were more likely to multihome and became less responsive to the incumbent's attempts to orchestrate collective action through platform-wide sales promotions. In contrast, complementors more reliant on indirect network effects (multiplayer developers) were less likely to multihome and became more responsive to orchestration attempts
Experimental insights into early cement development in carbonate aquifers: from diffusion to surface-controlled calcite growth
No full textInternational audienceDespite their geological significance, the thermochemical processes leading to the formation of early carbonate cements remain elusive. To bridge this knowledge gap, we carried out here laboratory-simulated diagenesis on aragonite ooids. They were placed in autoclaves, filled with distilled water, and subjected to varying temperatures and durations. Our results focus on the transformation from aragonite to calcite with temperaturedependent kinetics. At the grain scale, considered as a thermodynamic system on its own, two distinct stages of microstructural evolution were observed. In the first stage, diffusion processes predominate: the ooids experience progressive dissolution while a fringe of calcite cement forms around their periphery. In a second stage, radial diffusion stops and transformations are dominated by surface-controlled processes, characterized by calcite crystal growth within the ooids. The end-result is generally referred to as "neomorphism" in natural analogues. The transition from the diffusion-dominated to the surface-controlled stage is temperature-dependent and does not occur below 150°C. This behaviour can be explained by the progressive growth of the calcite fringe, which isolates the ooid from the surrounding pore water, while internal aragonite dissolution continues within the grain. These experiments show that early calcite cements, similar to those observed in meteoric phreatic environments, can grow without any external CaCO 3 input. They also show that neomorphism in ooids requires the closure of the ooid system, a condition that can occur at any stage of diagenesis. Finally, our experiments support the presence of a diffusive boundary layer, offering a process-based refinement of the traditional 'thin film' concept
Abstract VCG: Tie-breaking rules in VCG mechanism design
No full textInternational audienceWe present computer-checked solutions to the tie-breaking problem in Vickrey-Clarke-Groves (VCG) auctions for Sponsored Search, addressing scenarios involving equal bids. We formally prove that our solution preserves the incentive compatibility property. Both the specification and verification of this theorem are carried out using mech.v, a formal framework for mechanism design built on top of the MathComp library within the Rocq proof assistant. As mech.v and its applications continue to evolve, we aim to contribute not only provably correct algorithms but also reusable tactics for the development of machine-checked proofs in mechanism design
Design creativity for transitions: C-K/Topos, an advanced design theory for creative preservation
No full textInternational audienceAbstract In recent decades, design creativity and design theory have made great progress in terms of understanding and supporting the logic of engineering design for breakthrough and disruptive innovation. Design for transition relies on these new methods, but it also requires the capacity to be creative to facilitate more effective preservation – whether in terms of natural resources, biodiversity, energy, ways of life or other factors. Design for transition calls for a type of engineering design that is not Schumpeterian, not a ‘creative destruction’, but rather a design that manages creative preservation, creativity for better preservation and preservation for improved creativity. In the first section, we clarify the notion of creative preservation for transition; in the second section, we show how creative preservation can be addressed by recent advances in design theory, namely, C-K/Topos. Finally, in the conclusion, we demonstrate the implications of C-K/Topos for the management of the unknowns of transitions and the underlying logic of creative preservation
Signal Injection for Systems with Direct Feedthrough - Application to Water Content Estimation in Fuel Cells
No full textInternational audienceProton exchange membrane fuel cells (PEMFCs) suffer from water-management issues that can lead to drying or flooding, thereby reducing performance and durability. Accurate estimation of water content is therefore essential for Fuel Cell Management Systems design. In this work, we investigate how the introduction of a known high-frequency excitation into the system input enhance estimation capabilities. This paper extends signal-injection techniques to nonlinear feedthrough dynamical systems, such as the ones used to model PEMFCs. It proposes a signal injection procedure tailored for systems with nonlinear input dependencies in both state and output equations. The approach is applied to an open-cathode PEMFC model to recover temperature, liquid water saturation in the cathode catalyst layer and ohmic resistance from the sole voltage measurement. Numerical simulations confirm the interest of the proposed method and show that estimation precision improves as the excitation frequency increases
Dislocation density evolution in hot‑compressed dual‑phase titanium alloys: A phase‑resolved EBSD–Taylor framework
No full textInternational audienceThis study proposes a generic phase-resolved framework to quantify dislocation density evolution during hot compression of dual-phase titanium alloys by integrating electron backscatter diffraction (EBSD) analysis with Taylor-based flow-stress modeling. Comparative tests were conducted on Ti–6Al–4V (α+β) and Ti–10V–2Fe–3Al (metastable β) in equiaxed and lamellar microstructures. Initial differences in dislocation density and flow stress, driven by morphology, diminish with strain as phase-resolved restoration mechanisms and α-texture development converge, underscoring the intrinsic contribution of both phases to flow softening. EBSD and Taylor approaches exhibit divergent dislocation density estimations with strain but provide complementary insights, as these trends are explained by phase-specific mechanisms. In the α phase, texture evolution involves c-axis rotation toward a soft configuration and increased low-angle grain boundary (LAGB) density, accommodating strain through progressive LAGB formation with limited high-angle grain boundary (HAGB) development near interfaces. Conversely, the β phase undergoes extensive continuous dynamic recrystallization (CDRX), stabilizing flow via new grain formation. Despite alloy-specific differences, phase-level mechanisms remain consistent under subtransus conditions, confirming the transferability of the framework. These findings advance understanding of microstructural restoration and texture evolution, offering a robust basis for predictive modeling and forging process optimization