HAL Portal Cnam (French National Conservatory for Arts and Crafts)
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Dynamic modeling of a liquid piston compressor system including conjugate heat transfer
No full textInternational audienceEfficient and cost-effective hydrogen storage necessitatesquick compression across significant pressure ranges (usu-ally up to 700 bar), while keeping heat generation toa minimum during the process. This can be achievedby improved understanding of gas-to-wall heat transferenhancement in hydrogen compression systems, carefuldesign and operational optimisation.In this context,the present paper introduces a 0D/1D lumped numericalmodel of a liquid piston compressor for hydrogen applica-tions. Heat transfer is considered as (i) convective at theliquid-gas interface, (ii) conductive within the gas volumebased on a 1D approach accounting for thermal stratifica-tion, and (iii) as conjugate at the gas-to-wall interface. Toachieve a pressure ratio of 30 (from 15 to 450) bar, at apower density of approximately 65kW/m3, the compres-sion energy cost reaches 1.85kW h/kg. Further, variousstandard pressure vessels materials with different thermaland mechanical properties are considered, highlighting thepotential compromise between lightweight and thermal ef-ficiency
Review of Autonomous Racing Competitions and Technologies
No full textInternational audienceThis work comprehensively analyzes autonomous racing competitions and their technologies, addressing a gap in current literature. We evaluate these platforms through five key metrics: cost, system modularity, speed performance, technical complexity, and academic impact. Using bibliometric analysis of scientific literature, we identify dominant technologies, including Model Predictive Control and reinforcement learning. Our comparative framework reveals clear trade-offs: Formula Student Driverless offers accessibility and academic involvement but features lower speeds. At the same time, full-scale competitions like Indy Autonomous Challenge provide high-velocity testing but at increased cost. Reduced-scale platforms serve as valuable precursors to full-scale projects, offering cost-effective insights into perception, control, and system integration. The study demonstrates how competitions complement each other in advancing autonomous driving technologies and identifies patterns in simulator usage for algorithm development and validation. This comparison provides researchers with guidance for selecting appropriate platforms based on research objectives and available resources
Essai de prospective sur l’évolution de la complexité des organisations à l’horizon 2035
No full textInternational audienceIntituler ce texte « essai de prospective » est un aveu d’humilité. C’est à ce titrequ’il sera fait usage de deux des catégories du champ : la référence à des signauxfaibles et la construction de scénarii. Le texte va développer une argumentationautour de la bureaucratie post-weberienne, du management post-moderne et del’hypermodernité comme éléments fondateurs de la complexité organisationnelle.La prospective de cette complexité organisationnelle sera construite à partir d’unetypologie des liens entre « économie » et « développement durable » afin de fonderles « modèles » d’entreprises associés, la question de la smart governance et lesapports de la référence au care
Cognitive Biases in Sailor-AI Interaction : Exploratory Insights and Experimental Perspectives
No full textInternational audienceIn 2024, the French Naval Action Force reviewed the ten most significant maritime incidents of 2023. Once again, human factors were identified as the primary cause. According to the report, these incidents often stemmed from “misjudgments in communication, decision-making, or seamanship,” potentially worsened by “the increasing use of modern tools, which can foster overconfidence.”In this context, the rapid integration of artificial intelligence (AI) into naval operations, particularly in mine warfare and maritime patrol radar detection (Knocton et al., 2021), raises questions about how sailors interact with these technologies, and the human risks that may emerge (Tangredi & Galdorisi, 2021). While AI brings clear operational benefits, it also introduces new challenges in terms of human-machine cooperation, trust, and cognitive workload.Through field investigations focused on sailor-AI interactions, we have identified several cognitive biases that may impair effective use of AI systems (e.g., overtrust in technology, halo effects, availability heuristics, base rate neglect). However, the likelihood and impact of these biases likely depend on variables such as, for example, the AI's role, its level of autonomy, and the nature of the interface.In this presentation, we will examine how these biases manifest in operational settings and explore their potential consequences for decision-making and team performance. We will also present the empirical protocols we are currently developing to test these effects experimentally, using high-fidelity ship simulators. By better understanding how cognitive biases influence sailor-AI interactions, we hope to inform the design of more resilient systems and training strategies ultimately supporting safer, more effective decision-making in complex, high-stakes maritime environments
Solutions fondées sur la nature et risques liés à l’eau : quels apports des Sciences humaines et sociales ?
No full textNational audienceNature-based solutions (NbS) are designed to meet the challenges of climate change and biodiversity erosion. The concept, developed at the end of the 2000s, is becoming increasingly institutionalized at all levels of public policies, and in many policy sectors. Perceptions of this multi-faceted concept differ according to the actors and institutions involved. This productive ambiguity can also be a source of tension between actors and conflicting interests. A conference organized in Strasbourg in June 2024 aimed to create a space for dialogue between human and social science research on SfN for water-related risks. This article summarizes the work and discussions that took place at the conference, which dealt respectively with: governance (1); social representations (2); territorialization; (3) a dialogue between France and the United States within the framework of two round-table discussions involving administrations and managers from both countries (4); future research avenues for developing knowledge around NbS (5).Les Solutions fondées sur la Nature (SfN) sont des aménagements promus pour répondre aux enjeux du changement climatique et de l’érosion de la biodiversité. Le concept, développé à la fin de la décennie 2000, suit une institutionnalisation croissante à toutes les échelles d’action publique, et dans de nombreux secteurs de politiques publiques. Les appréhensions de ce concept, aux contours multiples, diffèrent selon les acteurs et les institutions qui s’en saisissent. Cette ambiguïté productive peut aussi être source de tensions entre acteurs et intérêts contradictoires. Une conférence organisée à Strasbourg en juin 2024 visait à créer un espace d’échange pour faire dialoguer les travaux en sciences humaines et sociales autour des SfN pour les risques liés à l’eau. Cet article représente la synthèse des travaux et des échanges ayant eu lieu lors de cette conférence
Méthode et approche de conception d'alliages fonctionnel dans le cadre d'alliages à haute entropie et composition complexe.
No full textInternational audienceMéthode et approche de conception d'alliages fonctionnel dans le cadre d'alliages à haute entropie et composition complexe
Hybrid simulation of non-linear soil-structure interaction under earthquake using subdomain-coupling method
No full textInternational audienceHybrid simulation of non-linear soil-structure interaction under earthquake using subdomain-coupling metho
Handgrip strength reference values and determinants of muscle weakness in French adults: results from the NutriNet-Santé study
No full textInternational audienceThe aim of this study was to determine sex-and age-specific handgrip strength percentiles in French adults and investigate sociodemographic and anthropometric variables associated with lower upper arm strength.Methods: A sample of 18,532 French adults (5,262 men, 13,090 women), aged 18-91, from the NutriNet-Santé cohort (2011-2014) was assessed for handgrip strength. For each hand, the maximum grip strength in kilograms was recorded. Grip strength was analyzed in absolute terms and relative units (relative to body weight and BMI). Percentiles (5th to 95th) were established by age and sex. Sociodemographic, lifestyle, and anthropometric factors associated with low handgrip strength (<20 th percentile) were evaluated using logistic regression, considering age, education, income, smoking status, BMI, physical activity, and sitting time.Results: Low BMI was linked to low handgrip strength in both sexes, whereas overweight was protective in men (OR 0.77). In women, lower education correlated with higher odds of low strength (OR 0.78-0.84). Male former or current smokers had higher odds of low grip strength (OR 1.20-1.35), while women showed an inverse association (OR 0.86). Physical activity reduced risk in both sexes, particularly at high activity levels (men OR 0.74; women OR 0.73). Age was a key factor in women, with increased odds in the 45-49 and 55-59 age groups (OR 1.27 and 1.32). Conclusions:The reference values provide reference data for French adults, and these data should be useful in identifying populations at risk of low muscle strength and sarcopenia
Bow Echo Alarm System Using Topological Data Analysis
No full textInternational audienceThis study focuses on the extremely severe storm system swept across Corsica early in the morning of August 18, 2022. A derecho refers to thunderstorm episodes that are distinguished by the production of particularly long-lasting, strong and widespread downbursts, generated by an extratropical mesoscale convective system (MCS). The associated radar signatures generally exhibit linear characteristics, with arcuate portions (bow echo).This work studies in particular the life cycle of the bow echo that appeared off the coast of Corsica and caused significant damage on the island as well as victims including five deaths. The bow echo is an exceptional phenomenon that is very difficult to predict because it is very localized. Beyond qualitative observations, methods for detecting the shape of a bow echo from radar images have been studied. We present an alternative method for characterising the bow echo shape using a promising tool based on topological data analysis (TDA) and the measurement of the curvature of the cloud. The use of homological persistence from TDA allows to follow the evolution of the bow echo from its initiation to its maturation just before it hits the Corsican coast. Curvature and persistent homology calculation with the stability property of Wasserstein and Bottleneck distances allows us to detect changes between evolutionary phases. The main idea is to exploit TDA on radar images of this bow echo in order to generate an alert. TDA is one of these new mathematical tools that will help characterize the event.</div
