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Weakly asymmetric facilitated exclusion process
No full textInternational audienceWe consider the facilitated exclusion process, an interacting particle system on the integer line where particles hop to one of their left or right neighbouring site only when the other neighbouring site is occupied by a particle. A peculiarity of this system is that, starting from the step initial condition, the density profile develops a downward jump discontinuity around the position of the first particle, unlike other exclusion processes such as the asymmetric simple exclusion process (ASEP). In the weakly asymmetric regime, we show that the field of particle positions around the jump discontinuity converges to the solution of the multiplicative noise stochastic heat equation (i.e. the exponential of a solution to the KPZ equation) on a half-line subject to Dirichlet boundary condition, with initial condition given by the derivative of a Dirac delta function. We prove this result by reformulating the problem in terms of ASEP on a half-line with a boundary reservoir, for which we extend known proofs of convergence to deal with the Dirichlet boundary condition and the very singular type of initial condition that arises in our case
Optimization and decision-making approach for energy storage strategies in a natural gas processing facility with photovoltaic renewable energy supply
No full textInternational audienceThis study offers a thorough examination and enhancement of solar renewable energy systems (RES) for natural gas production facilities (NGPF) in Southern Algeria. The objective is to improve the electrification of the NGPF and decrease their carbon emissions footprint. This research presents a dual-strategy model that integrates photovoltaic (PV) modules, battery-based energy management strategy, and hydrogen-based energy management strategy to address the urgent requirement for sustainable energy solutions in the oil and gas industries. The aim is to establish a robust and eco-friendly energy supply. The primary strategy (battery-based strategy) consists of utilizing battery storage to effectively regulate surplus or insufficient energy generation, with hydrogen storage system serving as a supplementary backup. The second strategy (hydrogen-based strategy) prioritizes hydrogen storage in an inverted manner, use its greater capacity for energy management before turning to battery storage. The Non-dominated Sorting Genetic Algorithm II (NSGA-II) is utilized to optimize the system's setup, which involves determining the appropriate amount of PV modules, battery units, and hydrogen tank capacity. This method simplifies the reduction of the Cost Of Energy (COE) and the Loss of Power Supply Probability (LPSP) while maintaining operational constraints to preserve the sustainability of hydrogen and state of charge (SoC) levels. Subsequently, a decision-making process based on Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) is utilized to decide on the most suitable system configuration. The final optimal design point based on TOPSIS method demonstrates the effectiveness of incorporating solar renewable energy systems (RES) with both strategies can achieve 0 % of LPSP at moderate COE of 0.17 and 0.34 for battery-based strategy and hydrogen-based strategy of storage system respectively. Additionally, results reveal that one month per year (9 % of time) of acceptable LPSP will reduce the COE by 54 % for both storage priorities, if facility operators schedule their maintenance effectively, this cost reduction can be easily achieved. Further, the suggested system will help in mitigating CO2 emissions by 1.76 tons of CO2eq per year generated by current system, offering significant insights for the deployment of renewable energy technologies in the oil and gas sector
Corrected Laplace–Beltrami Operators for Digital Surfaces
No full textInternational audienceDefining consistent calculus frameworks on discrete meshes is useful for processing the geometry of meshes or model numerical simulations and variational problems onto them. However, digital surfaces (boundary of voxels) cannot benefit directly from the classical mesh calculus frameworks, since their vertex and face geometry is too poor to capture the geometry of the underlying smooth Euclidean surface well enough. This paper proposes three new calculus frameworks dedicated to digital surfaces, which exploit a corrected normal field, in a manner similar to the recent digital calculus of Coeurjolly and Lachaud (IAPR second international conference on discrete geometry and mathematical morphology, Springer, Berlin 2022). First, we build a corrected interpolated calculus by defining inner products with position and normal interpolation in the Grassmannian. Second, we present a corrected finite element method which adapts the standard Finite Element Method with a corrected metric per element. Third, we present a corrected virtual refinement method adapting the method of Bunge et al. (Comput Graph Forum 39(2):303-313, 2020, https://doi.org/10.1111/cgf.13931). Experiments show that these digital calculus frameworks seem to converge toward the continuous calculus, offer a valid alternative to classical mesh calculus, and induce effective tools for digital surface processing tasks. We then use these corrected Laplace-Beltrami operators in order to build a regularization method for digital surface, using geometric information given by discrete normal and curvature estimators
Intermittency in fluid and MHD turbulence analyzed through the prism of moment scaling predictions of multifractal models
No full textInternational audienceIn the presence of waves due e.g. to gravity, rotation or a quasi-uniform magnetic field, energy transfer time-scales, spectra and physical structures within turbulent flows differ from the fully developed fluid case, but some features remain such as intermittency or quasi-parabolic behaviors of normalized moments of relevant fields. After reviewing some of the roles intermittency can play in various geophysical flows, we present results of direct numerical simulations at moderate resolution and run for long times. We show that the power-law scaling relations between kurtosis K and skewness S found in multiple and diverse environments can be recovered using existing multifractal intermittency frameworks. In the specific context of the She-Lévêque model (1994) generalized to MHD and developed as a two-parameter system in Politano and Pouquet (1995), we find that a parabolic K (S) law can be recovered for maximal intermittency involving the most extreme dissipative structures
Analyse numérique des mécanismes de couplages entre le frottement aube/disque et le contact aube/carter sur un étage de soufflante de dernière génération ECL5/Catana
No full textInternational audienceFor the first time, the interaction between two contact nonlinearities, blade-tip/casing contact and blade/disk friction, is investigated simultaneously. This contribution addresses the associated complex coupling mechanisms on the state-of-theart industrial fan stage ECL5/Catana open test case. Both contact interfaces are accounted for in nonlinear calculations using the harmonic balance method. First, a static analysis is performed to investigate the coupling mechanism between the friction coefficient and the static blade-tip gap. Then, the dynamics response of the blade is analyzed in forced response for two reference configurations: (1) with blade-tip/casing contacts only and (2) with blade/disk friction only. Particular attention is paid to the contact kinematics of both interfaces and the vibrational motion of the blade. The forced responses are analyzed using different local indicators of the contact interfaces. As the friction coefficient is usually uncertain, the robustness of the numerical strategy is then demonstrated by performing a large number of simulations on different root friction coefficients. In the end, even more computations are performed, as a part of sensitivity studies on first order parameters, in order to map out the different relevant quantities of both interfaces: number of contacting nodes at the tip, tip contact resultant force, energy dissipation. These large scale mappings allow to identify trends and inter-dependences between the kinematics of each interface. The originality of this paper lies in the thorough analysis of this seldom studied nonlinear interaction, that is crucially important for the design of safe and efficient aircraft engines. This work demonstrates that accounting for the blade/disk friction interface in numerical simulations strongly mitigates the dynamics of the blade-tip/casing contacts and can even prevent it for a specific range of friction coefficients.Pour la première fois, l'interaction entre deux non-linéarités de contact, le contact aube/carter et le frottement aube/disque, est étudiée simultanément. Cette contribution aborde les mécanismes de couplage complexes associés sur l'étage de soufflante industriel de dernière génération ECL5/Catana, un cas test ouvert. Les deux interfaces de contact sont prises en compte dans les calculs non linéaires à l'aide de la méthode de l'équilibrage harmonique. Tout d'abord, une analyse statique est réalisée pour étudier le mécanisme de couplage entre le coefficient de frottement en pied de pale et le jeu statique entre la tête de pale et le carter. Ensuite, la réponse dynamique de la pale est analysée en réponse forcée pour deux configurations de référence : (1) avec des contacts entre la tête de pale et le carter uniquement et (2) avec un frottement entre la pale et le disque uniquement. Une attention particulière est accordée à la cinématique de contact des deux interfaces et au mouvement vibratoire de la pale. Les réponses forcées sont analysées à l'aide de différents indicateurs locaux des interfaces de contact. Le coefficient de frottement étant généralement incertain, la robustesse de la stratégie numérique est ensuite démontrée en effectuant un grand nombre de simulations avec différents coefficients de frottement au pied de pale. Enfin, d'autres calculs sont effectués, dans le cadre d'études de sensibilité sur les paramètres de premier ordre, afin de cartographier les différentes quantités pertinentes des deux interfaces : nombre de points de contact au sommet d'aube, force résultante de contact au sommet d'aube et dissipation d'énergie. Ces cartographies à grande échelle permettent d'identifier les tendances et les interdépendances entre les cinématiques de chaque interface. L'originalité de cet article réside dans l'analyse approfondie de cette interaction non linéaire rarement étudiée, qui est d'une importance cruciale pour la conception de moteurs aéronautiques sûrs et efficaces. Ce travail démontre que la prise en compte de l'interface de frottement aube/disque dans les simulations numériques atténue fortement la sévérité des contacts entre l'extrémité de l'aube et le carter et peut même l'empêcher pour une gamme spécifique de coefficients de frottement
Almost automorphic and bijective factors of substitution shifts
No full textInternational audienceIn this article we completely characterise constant length substitution shifts which have a proper almost automorphic factor, or which have a bijective substitution factor such that the factor map is injective on at least one point. Our approach is algebraic: we characterise these dynamical properties in terms of a finite semigroup defined by the substitution. We characterise the existence of almost automorphic factors in terms of Green's R-relation and the existence of bijective factors in terms of Green's L-relation. Our results are constructive.</div
Are stock markets efficient with respect to the Google search volume index? A robustness check of the literature studies
No full textInternational audienceThe Efficient Market Hypothesis (EMH) is still a debated subject in the financial area. Particularly, no conclusions are drawn to date in link with the Google Search Volume Index (GSVI). To conclude on this question, our paper takes up the work of Škrinjarić (2019) by proposing robustness tests, various econometric improvements and the inclusion of additional explanatory variables. On a database of ten emerging European indices studied by Škrinjarić (2019), a dynamic panel model was applied. Unlike Škrinjarić (2019) who modeled the time-series separately and thus neglected any possible dependence or homogeneity between countries, our study operates within the framework of panel data. Drawing from a robust estimation approach, our findings indicate that the GSVI has no impact on market returns. In essence, this suggests that internet search queries fail to provide avenues for investors to seize arbitrage opportunities. Such findings support the EMH in the studied markets and underline the exposure of prior studies to robustness challenges
Modelling drainage-surface exchanges with TELEMAC-SWMM at the scale of a neighbourhood
No full textInternational audienceUrban drainage system failures are becoming more and more common due to the increase in magnitude and frequency of extreme rainfall events and pose significant safety and sanitary risks for urban populations during urban flooding. Practitioners involved in urban planning need comprehensive numerical tools to accurately describe the interplay between flows in the drainage network and floodwaters in the street network during extreme rainfall. EDF R&D, France, and Yuansuan, China, have recently coupled TELEMAC with the stormwater management software SWMM, from the US-EPA, under the git development branch called "swordtail". This branch is available to developers for testing and validation. The coupled system is initially tested against experimental data from a 2×2 street network only (no sewer network), investigated by Mejia-Morales [2021] where numerical parameters are calibrated for the experimental platform, with errors below 3% for flow rates and 5% for flow depths. Building on this calibration, a second case study investigates a surface-todrainage scenario based on experimental observations of a 3×3 street network with 12 drains by Camazzola et al. [2025]. The model is able to reproduce flow rates through the drains, discharge in the main street, and qualitative flow structures such as swirling eddies
What If: Causal Analysis with Graph Databases
No full textInternational audienceGraphs are powerful abstractions for modeling relationships and enabling data science tasks. In causal inference, Directed Acyclic Graphs (DAGs) serve as a key formalism, but they are typically handcrafted by experts and rarely treated as first-class data artifacts in graph data management systems. This paper presents a novel vision to align causal analysis with property graphs—the foundation of modern graph databases—by rethinking graph models to incorporate hypernodes, structural equations, and causality-aware query semantics. By unifying graph databases with causal reasoning, our approach enables the declarative expression of DAG manipulation operations along with interventions and counterfactuals, combining expressiveness with computational efficiency. We validate this vision through a proof-of-concept implementation supporting scalable causal queries over DAGs, ultimately aiming to make graph databases causally aware and support data-driven, personalized decision-making across several scientific domains
Santés en communs.: Éléments pour un récit prospectif de la Biovallée
No full textCe document est la restitution d'un atelier animé en Biovallée en mai 2025 et intitulé "qu'est-ce qui compte en Biovallée". Il se présente sous 4 formes : une description des éléments qui comptent pour les participants, qu'ils soient mesurables ou non ; des indicateurs, sous forme de cartes pour certains, de données, ou d'un livret de plantes indicatrices de l'agroécologie (sur le modèle Botascopia) ; un ensemble d'interdépendances entre les santés environnementale, sociale et humaine ; l'évocation d'un second atelier