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A Space-Time Cartesian Cut-Cell Method for Two-Phase Diffusion Problems using a Two-Fluid Approach
No full textInternational audienceWe present a Cartesian cut-cell finite-volume framework for sharp-interface two-phase diffusion problems in static geometries and prescribed interface motion on a fixed Cartesian grid. Following a two-fluid approach, one scalar field is solved independently in each phase and coupled through embedded interface conditions enforcing conservation together with general jump laws. In the static setting, the governing equations are integrated over phase-restricted control volumes and surfaces, yielding conservative discrete divergence and gradient operators. Interface coupling is achieved by introducing a small set of interfacial unknowns per cut cell on the embedded boundary, so that the resulting algebraic system involves bulk and interfacial averages. A key feature of the method is that all operators are assembled from a reduced geometric description based on low-order moments (volumes, apertures), avoiding explicit construction of cut volumes. For moving interfaces, we extend the discrete balance to phase-restricted space-time control volumes over each time interval; swept volumes and apertures provide the geometric weights that account naturally for cut-cell creation and destruction (fresh/dead-cell events) while preserving strict discrete conservation. The space-time formulation retains the algebraic structure of the static scheme, with motion entering only through local geometric weights and interface coupling operators. We validate the approach in steady and unsteady regimes, including curved embedded boundaries, Dirichlet/Neumann/Robin conditions, general jump laws and strong property and jump contrasts. The results demonstrate a super-linear convergence behavior, sharp enforcement of interfacial laws and excellent conservation properties, providing a robust building block for multiphase transport in evolving geometries and a foundation for future Stefan-type free-boundary extensions
A macro-element for circular shallow foundations on rigid inclusion-reinforced soil
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Gold standard process Markovian poisoning: a semiparametric approach
No full textWe consider in this paper a stochastic process that mixes in time, according to a nonobserved stationary Markov selection process, two separate sources of randomness: i) a stationary process which distribution is accessible (gold standard); ii) a pure i.i.d. sequence which distribution is unknown (poisoning process). In this framework we propose to estimate, with two different approaches, the transition of the hidden Markov selection process along with the distribution, not supposed to belong to any parametric family, of the unknown i.i.d. sequence, under minimal (identifiability, stationarity and dependence in time) conditions. We show that both estimators provide consistent estimations of the Euclidean transition parameter, and also prove that one of them, which is √ n-consistent, allows to establish a functional central limit theorem about the unknown poisoning sequence cumulative distribution function. The numerical performances of our estimators are illustrated through various challenging examples
Incursions upon agricultural land within metropolitan peripheries: Deadlocks and geo-legal trajectories of regularization in Paris and Mexico-city
No full textInternational audienceWithin metropolitan peripheries, irrespective of the national or regional contexts, the clash between rural and urban areas is at the center of metropolitan production. This clash is a twofold movement with urban sprawl, on the one hand, and major environmental injunctions, on the other. By looking at the two contexts of Paris and Mexico City, our research objective is to comprehend peripheries as places magnifying competing land dynamics, leading to scenarios of crises as well as social, political and legal innovations. The methodology is based on the analysis of field observations and surveys, public databases and official documents, using a social geographical approach. The article analyzes how stakeholders within the land system control peripheral land, focusing on public authorities, property market actors, and developers. The goal is to show the limitations of this control and reveal how and why residents and citizen groups build arrangements and regularizations. At the end, this article aims to contribute to the debates on the land rules deadlocks in the urban-rural interface. From different deadlocks observed in each context, the comparison underlines converging geo-legal trajectories of land regulation
The Manchester driving behavior questionnaire (DBQ) integrating health and technology factors: The DBQ 2025 update with translations in 11 languages
No full textInternational audienceThe Manchester Driving Behavior Questionnaire is a widely-used instrument to assess driving behavior but has become outdated, omitting items addressing modern communication technologies and health-related issues that impact today’s drivers. This study updated the original instrument with relevant health and technology items. The instrument updating process involved 5 steps. First, a literature review identified new and relevant items from existing instruments. Second, an international team with expertise in driving behavior, including the original instrument developer, reviewed and suggested revisions, assessed face validity, and recommend changes iteratively. Third, content validity was evaluated via computation of a content validity index (CVI) and content validity ratios (CVR). Fourth, the updated English version was translated into 11 languages by a global team. Finally, reliability of the Persian version was assessed via Cronbach’s alpha and intra-class correlation coefficient. The literature review led to new items addressing topics such as smartphone use and health conditions that may impact safe driving. Experts refined these items iteratively, creating an updated MDBQ with the 27 original items and 12 newly-developed ones. Content validity was assessed, yielding average CVIs of 0.95 and CVRs of 0.87. The questionnaire was then translated into 11 languages (Arabic, Azerbaijani Turkish, Chinese, French, German, Italian, Persian, Spanish, Swedish, Tagalog, and Turkish) according to standardized methods. The updated instrument retained all components of the original MDBQ, preserving comparability with existing data while also assessing contemporary topics. It provides a comprehensive instrument to assess driving behaviors and is recommended for use in research, policy, public health, and intervention development
Negotiating time, space and the body: a Lefebvrian rhythmanalysis of mobile care work in France
No full textInternational audienc
Explaning with trees: interpreting CNNs using hierarchies
No full textInternational audienceChallenges persist in providing interpretable explanations for neural network reasoning in explainable AI (xAI). Existing methods like Integrated Gradients produce noisy maps, and LIME, while intuitive, may deviate from the model’s reasoning. We introduce a framework that uses hierarchical segmentation techniques for faithful and interpretable explanations of Convolutional Neural Networks (CNNs). Our method constructs model-based hierarchical segmentations that maintain the model’s reasoning fidelity and allows both human-centric and model-centric segmentation. This approach offers multiscale explanations, aiding bias identification and enhancing understanding of neural network decision-making. Experiments show that our framework, xAiTrees, delivers highly interpretable and faithful model explanations, not only surpassing traditional xAI methods but shedding new light on a novel approach to enhancing xAI interpretability
Evaluating the Mechanical Performance of Bio-Based Concrete: The Role of Aggregate Type and Orientation in Compression Cyclic Loading
No full textInternational audienceThis study evaluates the effect of the physical aspects of four bio-aggregates (Hemp, bamboo, rapeseed, and reed) on the mechanical properties of bio-based concrete under cyclic compression loading. The bio-based specimens are assessed with respect to two distinct orientations of bio-aggregates: Perpendicular to compaction direction, and parallel to compaction direction. The digital image correlation (DIC) method permits to monitor strain and displacement fields throughout 19 loading–unloading cycles. Beyond conventional mechanical characterization, DIC data were processed to quantify crack density, crack length, and crack opening displacement (COD) as indicators of fatigue damage evolution.Hemp concrete exhibited the highest compressive strength and modulus, while bamboo concrete showed the weakest performance despite its higher density. In perpendicular orientation, specimens demonstrated cyclic hardening up to 4.5 % strain before entering a damage phase, whereas parallel-oriented specimens began degrading around 1.8 % strain.The useable strength of parallel-oriented specimens denotes the particle/binder affinity rather than the actual material's strength. The deformation charts given by the digital image correlation show that specimens tested under perpendicular orientation of bio-aggregates exhibit two horizontal lines of stress concentration whereas specimens tested under parallel orientation show the propagation of a vertical concentration lines.The failure mode of the perpendicular-oriented specimens is characterized by gradual crushing of bio-aggregates whereas the parallel-oriented specimens fail due to buckling that splits the specimen into two different parts on either side of the vertical concentration lines. Crack analysis revealed that hemp, reed, and rapeseed concretes developed limited and slowly propagating cracks (average rate 0.18–0.23 mm/cycle), with maximum crack lengths below 5 mm and narrow CODs (less than 2 mm). In contrast, bamboo concrete displayed rapid crack propagation (dL/dN around 3.66 mm/cycle), high crack density (32), and wide openings (higher than 4 mm), reflecting weak interfacial bonding.Hence, hemp shives oriented perpendicularly provides the ideal optimized configuration of bio-based concretes assessed in this study
Unprecedented polyvinyl polymer loading on SWCNTs in the liquid phase
No full textInternational audienceOutstanding adsorption capacities of three polyvinyl polymers on single-walled carbon nanotubes
Territoria Naturalia. Aménager sans altérer, entre partage et réserve
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