HAL Portal Cnam (French National Conservatory for Arts and Crafts)
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How to Achieve the Best Trade-off Between Robustness and Performance
No full textThe work presents an innovative approach to addressing the trade-off between robustness and performance, known as the optimality criterion. Moreover, the procedure relies on well-established methods that effectively support the search for the best trade-off, namely multi-criteria optimization problem. Thus, by separating the robustness and performance problems, it becomes possible to achieve the best trade-off between these two criteria. In this search for a trade-off, two complementary approaches are combined: robust control for the closed-loop system by minimizing Hinf-norm, and performance optimization in open-loop by minimizing l2-norm. This combination is made possible by the Youla-Kučera parameterization. However, to implement this parameterization in the presence of model errors, a new approach is used: estimating the Youla-Kučera parameterization.</div
Doctrine - L'action de groupe 2.0 est (presque) opérationnelle
No full textInternational audienceLes décrets d’application de l’article 16 concernant l’action de groupe dont le dernier est entré en vigueur le 1er janvier 2026, viennent préciser les règles procédurales de cette nouvelle action de groupe unifiée ainsi que les conditions d'agrément des entités pour la conduite des actions de groupe nationales et transfrontières. Ils précisent également les différentes mesures de publicité s’y rattachant. Pour éviter tout dévoiement du dispositif, notamment le risque que l'action soit instrumentalisée par un concurrent, le respect de l'indépendance constitue une condition fondamentale d'octroi de l'agrément. Cette préoccupation se retrouve tant dans la procédure d’agrément que dans l’examen des modalités de financement des entités exerçant une action de groupe
En quoi le cas du Louvre questionne-t-il la sécurité des musées ?
No full textThe conversation https://theconversation.com/en-quoi-le-cas-du-louvre-questionne-t-il-la-securite-des-musees-272835This article examines contemporary challenges in museum security through the lens of the dramatic 2025 heist at the Louvre Museum. It highlights structural and human vulnerabilities in protective systems, the tensions between public accessibility and safety, and the limitations of technological surveillance. The author discusses how these issues call into question prevailing governance and security models in cultural institutions.Cet article analyse les enjeux contemporains de la sécurité des musées à partir du cambriolage spectaculaire survenu au Musée du Louvre en octobre 2025. Il met en lumière les vulnérabilités structurelles et humaines des dispositifs de protection, les tensions entre ouverture au public et sûreté, ainsi que les limites des approches technologiques en matière de surveillance. L’auteur discute comment ces défis remettent en question les modèles de gouvernance et de sécurité des institutions patrimoniales
New directions for interconnector research: drawing from social sciences and humanities perspectives to explore the Celtic Interconnector
No full textInternational audienceThe current discourse on interconnectors primarily centers on the technical and economic aspects necessary for delivering a stable grid infrastructure powered by renewable sources and for integrating energy markets. This article, therefore, explores opportunities to broaden definitions of energy grid interconnectivity beyond the techno-economic sphere. It considers multidisciplinary perspectives and presents novel exploratory viewpoints from the social sciences and humanities. It examines ideas of interconnection by drawing on the Celtic Interconnector, an Irish-French initiative, to explore the cultural, historical, political, and geographical dimensions of interconnectivity. Insights are derived from two workshops with academics in Ireland and France, encouraging a more contextual understanding of energy interconnections beyond their physical and economic dimensions. The article builds on these insights to set out an agenda for future research and reflect on frames of reference for describing, analysing, and engaging with emerging interconnector processes and the multiple stakeholders involved
Optical force balance for measurement in the nanonewton range
No full textInternational audienceThe redefinition of the kilogram in 2019, based on the Planck constant, has led to new opportunities for innovation in metrology, particularly in the field of mass and related quantities. Responding to growing industrial and academic needs for the measurement of small forces and masses, several projects have been launched at LNE-CNAM. Among them, the 2023 project “Laser Power Measurement” (pPyC) led to the development of a traceable measurement system capable of generating an optical force with a relative standard uncertainty of 1 % in the nanonewton range. Building on the expertise gained, a prototype of the first optical force balance has been developed in 2022, aimed at measuring very small forces (1 nN–100 nN). This prototype is based on the diamagnetic properties of pyrolytic graphite to create the conditions necessary for the levitation of a balance beam around a fixed axis. The creation of a contactless pivot enables very high sensitivity. The experimental results showed the balance’s sensitivity to be 13.5 μrad/nN, with a repeatability of 0.2 μrad/nN
The impact of mine ownership on trade of metal ores
No full textInternational audienceMetals are essential to the global economy, yet traditional criticality assessments, often based solely on the geographic concentration of mining production, overlook the corporate control dimension of risk. Here, we analyzed whether ownership structures affect trade patterns in critical minerals and examined how production and corporate control diverged from 2000 to 2022. We developed a comprehensive country-level dataset using S&P Capital IQ Pro for 12 key metals and metal ores, calculated Herfindahl-Hirschman indices (HHI) for production and ownership, and statistically tested the relationship between foreign mine ownership and international trade flows using logistic and fixed-effects regressions. Finally, we built scenarios for production and ownership in 2030 to match demand estimates from the International Energy Agency (IEA). Results showed only 2%-14% of global ore trade value overlaping with existing foreign ownership ties and no statistically significant relationship between foreign mine ownership and trade flows. Additionally, clear divergences emerged between ownership and production concentration: cobalt production was highly geographically concentrated (HHI of 4602 in 2022) but had dispersed corporate ownership (HHI of 1985), and high-income countries frequently held substantial ownership stakes despite declining shares of actual production. Projected scenarios indicated continued shifts, notably reduced cobalt and lithium production shares in traditional producer countries, offset by growing Canadian and Australian ownership. Although market dynamics do not appear to be influenced by ownership structures today, corporate control remains a potential lever for supply chain disruption. This underscores the need to incorporate ownership into criticality assessments for a more comprehensive understanding of supply risks.</div
Decentralized multi-agent multi-armed bandits for smart electric vehicles charging
No full textInternational audienceSmart charging of electrical vehicles can help in avoiding congestion and peak load demands in an electrical distribution network. On the consumer's side, the advantage lies in minimizing the daily charging cost. He may also benefit from cheap photovoltaic electricity from local sources and therefore reduce his environmental impact. However, this cheaper electricity is variable and uncertain. In many research works, this has been formulated and solved as a centralized or hierarchical optimization problem. However, such systems may suffer from lack of scalability, single point of failures, and privacy breaches. We propose a fully decentralized and fair multi-agent system combined with reinforcement learning called "Decentralised multi-armed bandit (2-armed bandit) based on Thompson sampling"(D-MAB2AB-TS) to control the charging of electrical vehicles under uncertainties. The problem under consideration is formulated as a two-armed bandit (charging or not) for each instant. The proposed algorithm, based on Thompson Sampling, takes into account the uncertainties in the choice of arms combination of other players. The proposed algorithm finds the best combination of arms to play with a computational complexity O(m) linear with the number of arms. The suggested system is also model-free, as it does not assume the model of the environment to be perfectly known, which is a common assumption in many of the existing centralized optimization strategies for smart charging.</div
Interval Estimation for Linear Switched Systems Using Observer and Zonotopic Analysis
No full textInternational audienc
Ciels de Paris: Mutations d'un ciel urbain, de 1870 aux années 2000
No full textInternational audienceThis book analyzes major reconfigurations of the Parisian skyscape and the urban environment, emphasizing the central role played by infrastructures and the knowledge and techniques of scientists and engineers.Cet ouvrage analyse plusieurs reconfigurations mutuelles majeures du paysage céleste parisien et de l’environnement urbain, en insistant sur le rôle central joué par les infrastructures et les savoirs et techniques des scientifiques et ingénieurs
A Python/Fortran Implementation of the Lattice‐Boltzmann Kernel on Multiple GPU Using the OpenACC Framework
No full textInternational audienceABSTRACT The increasing availability of GPU accelerated architectures for high‐performance computing presents new opportunities for scientific software but also challenges due to the complexity of porting legacy codes to accelerator platforms. Directive‐based programming models such as OpenACC offer a minimally intrusive pathway to exploit GPU acceleration without requiring extensive rewriting of existing codes. The current work presents a comprehensive performance and portability study of a LatticeBoltzmann Method solver (PyLB) originally written in Python, Mpi4Py, and Fortran for CPU architectures, which is ported to GPUs using OpenACC directives applied to the Fortran routines. The performance of the solver is evaluated on NVIDIA V100, A100, and H100 GPUs available on the Jean Zay supercomputer from Institute for Development and Resources in Intensive Scientific Computing (IDRIS) in France. Roofline analysis and extensive strong and weak scalability tests are conducted, showing that the GPU‐enabled version of PyLB scales efficiently across multiple GPUs. The solver achieves performance on the H100 GPU equivalent to thousands of CPU cores and shows strong energy and carbon efficiency advantages over traditional CPU‐based simulations. The implementation is validated using classical benchmarks, including the decaying Taylor‐Green vortex and the flow over a 3‐D sphere. The results confirm the physical accuracy of the GPU port while highlighting its computational and environmental advantages