Archive ouverte HAL de CY Cergy Paris Université
Not a member yet
38365 research outputs found
Sort by
What is a Fluctuation Theorem?
No full textThis document is the preprint version of Volume 54 of the SpringerBriefs in Mathematical Physics collection. The final authenticated version is available online at https://doi.org/10.1007/978-3-032-02095-6International audienceThis book provides a modern review of Fluctuation Relations and Fluctuation Theorems in nonequilibrium statistical mechanics. It focuses on the pioneering perspectives of Gallavotti and Cohen, according to which a fluctuation theorem describes the statistics of the deviations of entropy production from its expected value. For time-reversal invariant systems, these fluctuations obey a universal (i.e., model-independent) symmetry called the fluctuation relation. The probabilistic framework introduced in the first part of the book allows for a very general formulation of Fluctuation Relations and Theorems for both deterministic and stochastic dynamical systems. We further explore models of physical interest, illustrating this framework by concrete applications. The second part of the book focuses on chaotic dynamics. The formulation of two general Fluctuation Theorems, followed by the detailed study of a concrete example, provides the reader with an understanding of both the theoretical and practical aspects of the subject
Quand la métaphore devient formule : analyse discursive de « submersion migratoire » dans la presse française
No full textInternational audienceThis article examines "submersion migratoire", a metaphorical expression originating from Front National (FN, later Rassemblement National -RN) discourse since the 1980s. Drawing on French Discourse Analysis (ADF), we analyze two French press corpora (2015, 2022) using Sketch Engine. The mixed quantitative-qualitative approach aims to determine if the expression qualifies as a discursive formula by verifying Krieg-Planque's criteria: formal stability, discursive anchoring, social reference status, intrinsic polemic valence. Analysis reveals its role as a metaphorical vector (MIGRANTS ARE WATER FLOWS), which circulates interdiscursively across media, structures polarizing oppositions (us/them), often associates with "grand remplacement" theories, and thus promotes a process of discursive extremization.Cet article interroge « submersion migratoire », expression métaphorique issue du discours du Front National (FN, puis Rassemblement National -RN) dès les années 1980. En nous appuyant sur l'Analyse du Discours Française (ADF), nous analysons deux corpus de pressefrançaise(2015, 2022) via Sketch Engine. L'approche, à la fois quantitative et qualitative, vise à déterminer si l'expression constitue une formule discursive en vérifiant les critères de Krieg-Planque : figement formel, ancrage discursif, statut de référent social, valence polémique intrinsèque. L'analyse révèle son rôle de vecteur métaphorique (LES MIGRANTS SONT DES FLUX D'EAU), qui circule interdiscursivement dans les médias, structure des oppositions polarisantes (nous/eux), s'associe souventaux théories du « grand remplacement » et favorise ainsi un processus d'extrémisation discursive
Alternatives écologiques dans la musique : changer le système, vraiment ?
No full textInternational audienceLes initiatives écologiques dans la musique sont-elles en mesure de transformer le système insoutenable dans lequel est imbriqué le secteur ? Cette conférence avait pour objectif, à partir de la présentation d'une partie des résultats du projet ECOMUSIQ, d'alimenter le débat sur la réalité des transformations du secteur. Le podcast de la conférence est accessible ici : https://soundcloud.com/chez-dd/03e919fb-2146-4f94-b413-d01e1ef402a7 L'article publié sur le sujet est accessible ici : https://cnmlab.fr/recueil/musique-et-territoires/chapitre/8
Inconsistance spatiale : L’influence du lieu sur le tri des déchets ménagers
No full textInternational audienceL’économie circulaire accorde une place centrale au recyclage, qui implique la mise en œuvre généralisée du tri des déchets ménagers dans les espaces privés, semi-publics et publics. La littérature existante a largement étudié les antécédents psychologiques et contextuels du comportement de tri, mais en se focalisant principalement sur un lieu spécifique, sans considérer que le lieu de tri pourrait modérer l’influence de ces antécédents. Pour examiner cette question de recherche, nous développons un modèle dual du comportement de tri des déchets, fondé sur une intégration des cadres TPB (Theory of Planned Behavior) et NAM (Norm Activation Model). Pour le tester, nous avons collecté des données déclaratives sur les pratiques de tri de 296 étudiants français dans trois lieux successifs (domicile, université et trajet vers l’université), que nous avons analysées à l’aide d’équations structurelles (PLS-SEM). Bien que les routes psychologique et contextuelle influencent toutes deux le tri, leur importance relative varie selon les lieux. De plus, à l’université et sur le trajet vers l’université, la route contextuelle influence la route psychologique. Ces résultats éclairent les raisons pour lesquelles le comportement de tri des déchets ménagers peut être inconsistant selon les lieux, et invitent les chercheurs à répliquer les modèles de comportements pro-environnementaux dans tous les contextes pertinents avant de formuler des recommandations de politiques publiques visant à les promouvoir
A Chase-based Approach to Consistent Answers of Analytic Queries in Star Schemas
No full textWe present an approach to computing consistent answers to queries possibly involving an aggregation operator in databases operating under a star schema and possibly containing missing values and inconsistent data. Our approach is based on earlier work concerning consistent query answering for standard queries (with no aggregate operator) in multi-table databases. In that work, we presented polynomial algorithms for computing either the exact consistent answer to a query or bounds of the exact answer, depending on whether the query involves a selection condition or not.In the present work, we consider databases operating under a star schema. Calling data warehouses such databases, we extend our previous work to queries involving aggregate operators, called analytic queries. In this context, we propose specific algorithms for computing exact consistent answers to queries, whether analytic or not, provided that the selection condition in the query satisfies the property of independency (i.e., the condition can be expressed as a conjunction of conditions each involving a single attribute). We show that the overall time complexity of these specific algorithms is in O(W.log(W)), where W is the size of the data warehouse. Moreover, the case of analytic queries involving a having clause associated with a group-by clause is discussed in the context of our approach
On dynamical coherence of partially hyperbolic flows
No full textIn this paper, we introduce the notion of dynamical coherence for a partially hyperbolic flow on a smooth compact manifold , and prove it under the assumption that there exists a compact foliation with trivial holonomy which integrates the subcenter distribution
Railway Track Defects Detection: From a Comprehensive Review of Methods to New Embedded System Modelling Perspectives
No full textInternational audienceThe expansion and increasing complexity of railway infrastructure, combined with a growing demand for higher safety and maintenance standards, has driven important innovation in rail defect detection. This review examines recent methods for railway track defect identification, with a particular focus on their deployment on embedded computing architectures. Detection methods are categorized across multiple sensing modalities—vision, acoustics, vibration, and electromagnetic—while highlighting recent advances in deep learning (DL). This study addresses the critical gap between the performance of algorithms and their potential to be deployed on hardware architectures to design reliable, real-time systems. This review evaluates these approaches in terms of suitability for real-time onboard deployment, identifies their limitations, and proposes a new multisensory, embedded system that will balance performance, energy efficiency, and scalability. A study of detection methods and their in-depth evaluation aims to bridge the gap between complex and high-accuracy detection algorithms and their integration into lighter railway monitoring systems
The influence of the 3D Galactic gas structure on cosmic-ray transport and gamma-ray emission
No full textInternational audienceCosmic rays (CRs) play a major role in the dynamics of the interstellar medium (ISM). Their interactions and transport ionize, heat, and push the ISM thereby coupling different regions of it. The spatial distribution of CRs depends on the distribution of their sources as well as the ISM constituents they interact with, such as gas, starlight, and magnetic fields. Particularly, gas interacts closely with CRs, influencing CR fluxes and gamma -ray emission. We illustrate the influence of 3D gas structures on CR transport and gamma -ray emission. We use the PICARD code and multiple samples of recent 3D reconstructions of the HI and H Galactic gas constituents to investigate the impact on the transport of CRs and emission of gamma -rays. We find the necessary transport parameters to reproduce local measurements of CR fluxes, and see that they depend on the local distribution of gas density and structure. The distribution of CR fluxes exhibits energy-dependent structures that vary for all CR species due to their corresponding loss processes. Regions of enhanced secondary (primary) species are spatially correlated (anti-correlated) with the gas density. We observe a high sensitivity of the gamma -ray emission on the contrast of gas structures, as those determine the 3D spatial distributions of hadronic interactions and bremsstrahlung. We find that corresponding gas-induced structures in the distribution of CR electrons are also visible in Inverse Compton (IC) emission. Due to the aforementioned sensitivity, the analysis of CR data for CR sources and transport parameters requires the usage of accurate 3D gas maps
Static and dynamic Monte Carlo simulations of phonon drag effects on thermoelectric properties in silicon nanostructures
No full textInternational audienceThermoelectric transport in silicon nanofilms is investigated using a self-consistent electro-thermal Monte Carlo simulator that couples electron dynamics to a phonon bath with spatially varying temperature. A key novelty of this work is the explicit inclusion of the phonon-drag contribution, implemented by modifying the electron-phonon momentum exchange based on the local deviation of the phonon distribution from equilibrium. The method is validated against bulk silicon data and extended to incorporate rough boundary scattering for both electrons and phonons, yielding excellent agreement with experimental measurements on nanofilms. We also analyze the transient regime and show that a temperature bias produces a slower current response than a voltage bias, although the phonon-drag effect itself tends to accelerate the response. These results demonstrate that the proposed framework provides a powerful tool for predicting both steady-state and time-dependent thermoelectric behavior in semiconductor nanostructures
