HAL Portal Cnam (French National Conservatory for Arts and Crafts)
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Kalman filter for dynamic source power and steering vector estimation based on empirical covariances
No full textInternational audienceInterferometric measurements correspond to sample covariance matrices of signals received by multiple sensors. In dynamic scenarios, such as radio astronomy imaging, the properties of these signals can vary over time, posing a significant challenge for study. This work addresses the issue of estimating the stochastic power and steering vector of signal sources from sample covariance measurements. A novel approach is proposed, introducing a non-standard Kalman filter designed to accommodate any noise and signal distribution, thereby broadening the Kalman filter's applicability to situations with unknown measurement models. The effectiveness of this method is highlighted in the case of joint estimation of source power and direction of arrival through simulations using synthetic data
Comprendre les stratégies d’approvisionnement alimentaire des habitants d’un quartier en politique de la ville. Une enquête qualitative conduite Porte de la Chapelle à Paris
No full textInternational audienceWhere do you shop for food when you live in a disadvantaged neighborhood? Few studies analyze where people purchase their foods and factors, which may influence food store choice. This study explores the food purchasing behaviors and strategies of residents living in Porte de la Chapelle (Paris, France), neighborhood with high proportion of deprived population. The aim is to characterize food purchase places of inhabitant to better understand food purchase location choices based on food stores mapping and 25 interviews. The results confirm that food price is a major determinant, leading all respondents to purchase outside their residential neighborhood as foods in food outlets of the neighborhood are too expensive for their budgets (price). But the other dimensions of accessibility are also present in interviews. Participants declare the lack of food outlets in the neighborhood (spatial dimension), not enough diversified (availability) or unsuited to their eating habits (cultural acceptability, for example). Behaviors and representations vary according to individual characteristics, and according to the area of live. Our results therefore show that a policy of food retail diversification should be developed jointly with inhabitants at local level.Où fait-on ses courses alimentaires quand on habite un quartier en politique de la ville ? Rares sont les recherches sur les lieux d’approvisionnement fréquentés et les raisons de ces choix. Cette étude explore les stratégies d’approvisionnement des habitants du quartier Porte de la Chapelle à Paris, marqué par une forte précarité. Elle vise à caractériser les espaces que les habitants fréquentent et parcourent pour s’approvisionner, et à mieux comprendre leurs choix de lieux de courses alimentaires à partir d’une cartographie de l’offre alimentaire et de 25 entretiens. Les résultats confirment que le prix est un déterminant majeur, qui amène les enquêtés à s’approvisionner à l’extérieur du quartier de résidence car les produits disponibles dans les commerces du quartier sont trop chers. Les autres dimensions de l’accessibilité sont également présentes dans les discours. Les participants regrettent le manque de commerces dans le quartier, pas assez diversifiés ou inadaptés à leurs pratiques alimentaires. Les pratiques et les représentations varient en fonction des individus et des secteurs du quartier. Nos résultats invitent donc à construire une politique de diversification des commerces alimentaires avec les habitants des différents secteurs du quartier
Young Professionals Events at the 2024 European Microwave Week [Young Professionals]
No full textInternational audienceProvides society information that may include news, reviews or technical notes that should be of interest to practitioners and researchers
Online real-time robust framework for non-intrusive load monitoring in constrained edge devices
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Analysis of the Timetable Impact on Energy Consumption of a Subway Line
No full textInternational audienceThis paper analyzes the timetable impact on the energy consumption of a subway line. In most timetable studies, simplified models are used and can lead to misestimation of the braking energy and thus the energy transfer between braking vehicles and accelerating vehicles. In this paper, specific attention is paid to the models of the vehicles, the traction power substation, and the rail supply network to enable an accurate estimation of the energy consumption. The energetic macroscopic representation formalism is used to organize the models of the subsystems so they have the right interactions. The developed model is validated by experimental tests on a real subway line. The error on the global energy consumption is lower than 2.2%. The model is then employed to examine the influence of the vehicle time interval on energy consumption. A 10-second adjustment in this time interval can result in a substantial 22% decrease in energy consumption for the analyzed real subway line
Connaître avec les modèles de langage : une rupture paradigmatique
No full textInternational audienceDepuis la mise en ligne gratuite de ChatGPT, nous assistons à de nombreux débats scientifiques publics et prises à parti passionnées de la part de philosophes de tous bords, d'informaticiens, de linguistes, de biologistes, de statisticiens, d'éthiciens, de juristes, d'artistes, d'investisseurs, d'analystes financiers... Toutes les disciplines scientifiques se sentent concernées, et convoquées, face à l'utilisation d'un outil qui aura réussi à capter 1 million d'utilisateurs en un temps record. Noam Chomsky, qui, depuis longtemps, clame haut et fort ses désaccords avec l'apprentissage automatique, qui domine les techniques en intelligence artificielle aujourd'hui, annonçait dans le New York Times le 8 mars 2023 une prophétie malheureuse : « (machine learning) will degrade our science and debase our ethics by incorporating into our technology a fundamentally flawed conception of language and knowledge ». La faute est lourde, et se retrouve dans d'abondants discours médiatiques venus de différents bords politiques. Ainsi Gaspard Koenig, philosophe chroniqueur pour le journal Les Échos en France, parlait-il en février 2023 de "faille épistémologique de ChatGPT", voyant "la Silicon Valley abolir la norme du vrai". Utiliser ChatGPT, quelle que soit la justification (gagner du temps par exemple), nous amènerait à " renoncer aux principes scientifiques hérités des Lumières pour entrer dans le monde des "ambiguïtés cumulatives", tant redouté par Henry Kissinger". Les informaticiens ne sont, eux non plus, pas indifférents au sujet : ainsi Hugues Bersini, chercheur chevronné en informatique, nous affirme qu'il s'agit [...] "d'un incroyable pas de côté de toute la tradition rationnelle, symbolique et surtout intelligible, qui semblait, par introspection et imitation, la voie royale de l'intelligence logicielle." 1 Cette passion médiatique n'est pas sans rappeler l'engouement généralisé pour l'épidémiologie des confinements de la Covid-19 -pendant lesquels on a vu chacun plonger plus ou moins profondément dans les eaux de la statistique médicale. Face à ChatGPT, sommes-nous donc démunis dans notre rapport à la connaissance comme nous l'étions face au virus SARS-COV-2
Hybrid Silicon Metamaterial combining Microstructured Silicon surface with Silicon/Silicon Dioxide multilayer as a Selective Emitter for Thermophotovoltaic Applications
No full textInternational audienceWe propose a broadband selective emitter for thermophotovoltaic applications, combining a microstructured doped silicon surface with a Si/SiO2 multilayer. This structure enhances emissivity in the above bandgap spectral region (i.e., for wavelengths shorter than λgap) while suppressing emissivity in the below bandgap region (i.e., for wavelengths longer than λgap) over a broad spectral range. The structure composition and properties are optimized using a Particle Swarm Optimization algorith
An AI Security Testbed for the 5G Core
No full textInternational audienceThe 5G core network is the backbone of modern mobile communication, providing high-speed, low-latency, and diverse services for users and industries. Artificial Intelligence (AI) plays an important role in this network by optimizing performance, supporting dynamic resource scaling, and improving security through anomaly detection and threat mitigation. Testing AI in 5G environments is difficult because of the complexity of the network and the many possible attack vectors.In this paper, we present a modular and reproducible testbed for evaluating AI-based security mechanisms in the 5G core. The testbed emulates key 5G components and traffic patterns, enabling systematic experiments under realistic conditions. It also provides reliable measurements of Key Performance Indicators (KPIs) to evaluate the effectiveness, robustness, and operational impact of AI solutions, including their ability to detect and mitigate threats. Our work provides a structured framework for testing AI solutions and supports the development of secure, resilient, and AI-enhanced 5G networks.</div
PROSE+ project: offshore seismic measurements on the seabed to test the ability to assess the spatial variation of the small-strain shear modulus in the subsurface environment
No full textInternational audienceThe increase in the number of offshore wind farm siting projects, combined with the multiplicity of developments in anchoring techniques, means that foundations and anchors need to be optimized for the conditions of the offshore subsurface, requiring precise knowledge of the mechanical characteristics of the medium. According to the recommendations of the CFMS (French committee of Soils Mechanics), detailed geophysical reconnaissance is then necessary during the project phase (design and execution) to obtain the most accurate information possible at the locations of the structures. In this context, the PROSE+ project aims to increase knowledge and provide new methodological and technical elements, based on surface seismic and geoelectrical techniques. This will make possible to approach heterogeneous environments in a quantitative and non-destructive way, thereby reducing the number of costly and invasive geotechnical surveys. To this end, we developed numerically a 2D seismic inversion technique using Surface Seismic Waves based on Particle Swarm optimization methods. In order to validate it on experimental data, we carried out measurements off Concarneau using 70 4-components sensors (GPR -Sercel nodes) placed on the seabed, in an unprecedented manner. 241 seismic shots were fired over this sensor's network using an air gun at variable water depth. Finally, the sensors were left recording on the seafloor for 28 days. The recorded seismic data allow to test the capacity of both active and passive seismic imaging process to assess the shear modulus in a 2D medium under seabed
Young’s modulus of multinanolayer polymer films: the role of the interfaces
No full textInternational audienceThe number of free surfaces in a polymer ultra-thin film has a strong influence on its physical and mechanical properties. In this study, Young’s modulus as well as the glass transition temperature of multinanolayer coextruded polymer films, hence with no free surfaces, have been measured. We observe that contrary to the case of free-standing or supported ultra-thin films, there is no depression of the glass transition temperature or the Young modulus, but an increase for the latter as the layer thickness decreases, whatever the polymer pair (with various compatibilities). It is proposed that this increase is associated with the rise of interphase volume fraction in the films. An interphase modulus of about 25 GPa can be extracted from the empirical model, about 10 times higher than the typical modulus value of a glassy polymer. This value does not appear to depend on the nature of the polymers, meaning that the presence of entanglements at the interfaces is not a key factor to explain the increase in Young’s modulus of multinanolayer films