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Réduction du rayonnement acoustique de plaques et de coques à l’aide de microperforations
No full textVibro-acoustique : session générale; GVB - Vibro acoustique et Contrôle du BruitNational audienceLa réduction des vibrations et du bruit basse fréquence (BF) est un enjeu industriel, particulièrement pour les structures légères de faible épaisseur. Ainsi, les vibrations de plaques microperforées chargées par un fluide ont été étudiées théoriquement et expérimentalement. Ces structures dissipent de l’énergie grâce aux pertes thermo-visqueuses qui se produisent dans les couches thermo-visqueuses au niveau de la paroi solide des perforations. Cependant, l’impact des microperforations sur l’amortissement ajouté et les propriétés de rayonnement acoustique des plaques et des coques cylindriques reste peu étudié. Cette étude propose d’appliquer la théorie classique du rayonnement acoustique des plaques flexibles à des structures microperforées, en tenant compte du couplage fluide-structure et des dissipations visqueuses dans les couches limites des perforations. Le modèle vibratoire analytique des plaques microperforées, précédemment développé par les auteurs, est : i) utilisé pour déterminer le champ vibratoire des plaques microperforées ; ii) adapté pour obtenir le champ vibratoire des coques cylindriques microperforées. Les champs vibratoires ainsi obtenus permettent d'analyser le rayonnement acoustique des structures microperforées soumises à des excitations mécaniques et/ou acoustiques. Les résultats montrent une réduction significative du rayonnement acoustique des structures microperforées par rapport à leurs homologues non perforés. Les études numériques et expérimentales menées sur ces structures permettent de valider ces résultats. Ainsi, les microperforations apparaissent comme une solution prometteuse pour atténuer les vibrations BF et réduire le bruit associé
Review on the removal and degradation methods of chloridazon and its metabolites
No full textInternational audienceDue to their excessive use, pesticides are considered emerging micropollutants in water. The risk induced comes not only from their presence in surface and groundwater and the inability of conventional water treatments to fully eliminate them, but also from their transformation products in the environment. The latter are reported to be more persistent and more difficult to treat than their parent compounds. In addition to this, potentially more toxic degradation products can be formed following treatments. Given the pollution of drinking water, as recently highlighted in the Hauts-de-France region by the metabolites of the herbicide chloridazon, and the risk they induce on human health and the environment, this review was written in order to summarize all the methods of remediation with regard to chloridazon and its metabolites, whether they are removal or degradation methods, and to compare the effectiveness of the treatments. In addition, the degradation products known in the literature are reported and a brief overlook on their toxicological properties is discussed, shedding light on the lack of data for these compounds
Cybersecurity Risk Assessment of Wheel Slide Protection System in Railways
No full textInternational audienceThe Wheel Slide Protection (WSP) system plays a critical safety role in railway braking by preventing wheel lock and maintaining adhesion control under low-friction conditions. While traditionally seen as isolated and secure, the growing sophistication of cyber threats and the rail sector's rising profile as a target reveal the need to reassess its cybersecurity posture. Even non-networked, safety-critical subsystems like WSP can be exposed to cyber-physical risks. This paper presents a structured methodology for conducting a cybersecurity risk assessment of the Wheel Slide Protection (WSP) system, in alignment with the TS 50701:2023 cybersecurity standard for the railway sector. To the best of our knowledge, this is the first study to assess the WSP subsystem from a cybersecurity standpoint using a formal, standards-based approach. Our contributions are threefold: (1) we perform a functional and architectural decomposition of the WSP system to identify its key functions and critical interfaces; (2) we apply a lifecycle-based methodology to generate traceable cybersecurity artefacts; and (3) we evaluate the effectiveness of structured security activities in supporting the risk assessment and protection of such safety-critical railway subsystems
Wavelet Estimation of Partial Derivatives in Multivariate Regression Under Discrete-Time Stationary Ergodic Processes
No full textInternational audienceThis study introduces a wavelet-based framework for estimating derivatives of a general regression function within discrete-time, stationary ergodic processes. The analysis focuses on deriving the integrated mean squared error (IMSE) over compact subsets of Rd, while also establishing rates of uniform convergence and the asymptotic normality of the proposed estimators. To investigate their asymptotic behavior, we adopt a martingale-based approach specifically adapted to the ergodic nature of the data-generating process. Importantly, the framework imposes no structural assumptions beyond ergodicity, thereby circumventing restrictive dependence conditions. By establishing the limiting behavior of the wavelet estimators under these minimal assumptions, the results extend existing findings for independent data and highlight the flexibility of wavelet methods in more general stochastic settings
Ecodesign and life cycle assessment of piezoelectric energy harvesters
No full textInternational audiencePiezoelectric energy harvesting has gained significant attention in various engineering fields due to its efficient electromechanical conversion, particularly in the context of sustainability and self-powered systems. While energy harvesters help reduce reliance on batteries, their environmental impact throughout their life cycle remains a concern. Despite extensive research focusing on the modeling, prototyping, and performance enhancement of harvesters, few studies have addressed their environmental footprint. This study conducts a life cycle assessment (LCA) to evaluate the environmental impacts of piezoelectric energy harvesters manufactured via the screen-printing process by considering two piezoelectric materials. A comparative analysis is performed, taking lead zirconate titanate Pb(Zr,Ti) (PZT) as the reference material according to lead-free material potassium sodium niobate (K,Na) (KNN). The impact assessment is performed using ILCD 2011 method by examining multiple impact categories and identifying the most environmentally burdensome components based on unique scores calculated at the Midpoint. The results indicate that PZT exhibits an overall environmental impact approximately four times greater than that of KNN. Environmental burdens are largely driven by the electrodes, with additional significant contributions from the PZT layer and the stainless-steel substrate. In terms of performance, trade-offs arise: while PZT excels in displacement and short-circuit power, certain KNN variants surpass PZT in open-circuit power generation due to more favorable charge transfer mechanisms. The findings emphasize the critical role of LCA in assessing the sustainability of piezoelectric harvesters and highlight key technical insights and recommendations for ecodesign improvements
Développement d'un nouveau procédé hydrométallurgique pour la récupération du zinc à partir de plantes hyperaccumulatrices
No full textInternational audienceSoil pollution has become a serious concern due to the intensification of anthropogenic activities, and few techniques are available for the remediation of large volumes of metal-contaminated soil. Among the available options, phytoextraction using hyperaccumulator plants is a promising approach, as it enables the removal of metals directly from soils. However, this strategy generates metal-enriched biomass that must be treated to detoxify the residues and recover valuable metals in line with circular economy principles. The aim of this work was to propose a complete process for recovering zinc (Zn) from two hyperaccumulator plants, Noccaea caerulescens (Ganges and Vosges populations) and Sedum plumbizincicola, cultivated from Zn-contaminated agricultural or industrial soils. The harvested biomass, containing up to 9 g Zn/(kgdry biomass), but also other metals (namely aluminium (Al)), was subjected to combustion at 620 °C to produce Zn-rich ash. The ash was subsequently treated through sequential water washing, alkaline leaching with sodium hydroxide, and acidification with nitric acid. This process yielded a Zn-enriched solid product containing 8 wt% Zn, from a plant containing 0.9 wt%, with an overall recovery efficiency exceeding 84%.Characterization of the recovered material indicated the presence of a zinc aluminosilicate phase, along with residual sodium nitrate. Although further purification would be necessary to obtain higher Zn purity, the approach demonstrates that it is possible to convert contaminated biomass into a valuable Zn-based product while strongly depleting other undesirable elements such as cadmium.Overall, this work illustrates the potential of integrating phytoextraction with hydrometallurgical recovery processes to develop sustainable agromining strategies for metal-contaminated soils.La pollution des sols est devenue un problème grave en raison des activités humaines, et les techniques disponibles pour assainir de grands volumes de sols contaminés par des métaux sont limitées. La phytoextraction à l'aide de plantes hyperaccumulatrices offre une approche prometteuse, car elle permet d'éliminer les métaux directement des sols. Cependant, la biomasse riche en métaux qui en résulte doit être traitée afin de détoxifier les résidus et de récupérer les métaux précieux dans le cadre d'une économie circulaire. L'objectif de ce travail était de proposer un processus complet de récupération du zinc (Zn) à partir de deux espèces hyperaccumulatrices, Noccaea caerulescens (populations du Gange et des Vosges) et Sedum plumbizincicola, cultivées à partir de sols agricoles ou industriels contaminés par le Zn. La biomasse récoltée, contenant jusqu'à 9 g de Zn/(kg de biomasse sèche), mais aussi d'autres métaux (notamment de l'aluminium (Al)), a été soumise à une combustion à 620 °C afin de produire des cendres riches en Zn. Des traitements séquentiels (lavage à l'eau, lixiviation alcaline à l'hydroxyde de sodium et acidification à l'acide nitrique) ont ensuite été appliqués. Ce processus a permis d'obtenir un produit solide enrichi en Zn contenant 8 % en poids de Zn, à partir d'une plante contenant 0,9 % en poids, avec un rendement global de récupération supérieur à 84 %. La caractérisation du matériau récupéré a révélé la présence d'une phase d'aluminosilicate de zinc, ainsi que de nitrate de sodium résiduel. Bien qu'une purification supplémentaire soit nécessaire pour obtenir une pureté de Zn plus élevée, cette approche démontre qu'il est possible de convertir la biomasse contaminée en un produit à base de Zn de grande valeur tout en éliminant fortement d'autres éléments indésirables tels que le cadmium. Dans l'ensemble, ces travaux illustrent le potentiel de l'intégration de la phytoextraction aux procédés de récupération hydrométallurgiques pour développer des stratégies d'agrominage durables pour les sols contaminés par des métaux
Development and Performance Evaluation of a Hybrid Solar Dryer with Latent Heat Storage and Dehumidification Systems
No full textInternational audienceDrying agricultural products has become an essential technique for preservation, but current drying methods often prove to be energy-intensive, costly, and unsuitable for the needs of local small and medium-sized enterprises (PME/PMI). In this study a hybrid solar dryer has been designed specifically to meet the needs of PME/PMI. The current limits to the development of solar drying in Africa are low efficiency and low autonomy. To remove these bottlenecks, thermal storage and air dehumidification systems are often used. This article firstly, presents a brief review, not only of thermal storage materials but also of dehumidification systems. This review led to the choice of paraffin and silica gel respectively for thermal storage and dehumidification of drying air. The selected materials were subsequently implemented in an indirect hybrid dryer with a drying capacity of up to 50 kg of fruits and vegetables. It is made up of an aluminum absorber painted in matt black, 1.5 mm thick. Its exterior structure is made of steel separated from the interior face made of stainless steel, by a layer of glass wool, 30 mm thick. Performance tests are carried out on the classic dryer, then with the dryer integrating silica gel on the one hand and on the other hand, the dryer with paraffin. The tests were conducted in Cotonou (latitude: 6°21'50"N; longitude: 2°26'32"E) during the month of November with an average irradiation of 137.23 kWh/m² received on the horizontal plane with an average temperature of 27.4°C.The experiments are carried out over several days so as to be able to extract, for each of the improved dryers, 03 days similar, from the point of view of daily irradiation, to the tests on conventional dryers. Tests carried out on the dryer with the new latent heat storage system reveal an increase in efficiency of 3% compared to the classic dryer. The proposed dehumidification solution showed a good dehumidification rate of 16% which helps to improve the overall efficiency of the dryer. In practice, this improvement in performance will result in a reduction in drying time and energy consumption. These first promising experimental results will be validated with other tests which will be carried out over several consecutive days, also varying the quantities of paraffin and silica gel
Steady Conduction Problems with Non-Linear Kapitza contact Resistance: Existence and Bifurcation
No full textWe focus on the mathematical analysis of the steady-state heat conduction problem in a two-layered domain, with a non-linear Kapitza contact resistance at the interface, which slows down heat transfer. A maximum principle is first established, followed by a proof of existence by applying the Schauder fixed point theorem to the variational formulation. Non-uniqueness is then illustrated through a simple one-dimensional example. Solutions are computed as fixed points of certain algebraic mappings, using Picard's iterative method. A co-dimension-one bifurcation analysis of these maps is presented, with the ratio of the conductivities of the two layers used as the control parameter. Two classes of (power-law) Kapitza conductance give rise to different types of bifurcations, including transcritical, supercritical, flip, and saddle-node bifurcations.</div
Écologie sociale et humanités numériques : intégrer la poésie à la science
No full textInternational audienceThis article proposes an ethical and political approach to the impact of digital humanities (DH) research, based on the philosophy of social ecology, in order to address the issue of degrowth in DH. Do DH have a role to play in a process of degrowth? How would an ecological DH project be organised? To address these questions, we will begin by summarising the principles of social ecology, as defined by Murray Bookchin, and their application to technology. We will then look at what it means to apply these principles to DH. Finally, we will present a digital publishing project based on these principles. We thus draw on the philosophy of social ecology, as well as on the concepts of degrowth, low-tech and minimal computing, to show that digital humanities can play a fundamental role in the development of an ecological digital environment, through a qualitative approach that values human creativity.Nous proposons dans cet article une approche éthique et politique de l'impact des recherches en humanités numériques (HN), basée sur la philosophie de l'écologie sociale, pour aborder la problématique de la décroissance dans les HN. Les HN ont-elles un rôle à jouer dans un processus de décroissance ? Comment serait organisé un projet d'HN écologique ? Pour aborder ces questions, nous allons dans un premier temps résumer les principes de l'écologie sociale, tels que définis par Murray Bookchin, ainsi que leurs applications à la technologie. Nous verrons ensuite ce qu'appliquer ces principes aux HN peut signifier. Nous présenterons enfin un projet d'édition numérique suivant ces pistes et principes. Nous faisons ainsi appel non seulement à la philosophie de l'écologie sociale mais aussi aux concepts de décroissance, de low-tech et de minimal computing, afin de montrer que les humanités numériques peuvent jouer un rôle fondamental dans le développement d'un numérique écologique, à travers une approche qualitative valorisant la créativité humaine
Boundary Objects in Preliminary Design: Meaning-Making, Storytelling and Strategic Framing in Interdisciplinary Innovation
No full textInternational audienceThis paper explores the emerging roles and opportunities associated with Boundary Objects (BOs) inthe context of preliminary design within interdisciplinary innovation project. Creative tools such aspersona encyclopaedias, storytelling, design fiction and idea cards, serves as BOs in collaborativedesign setting. Drawing from domains such as design, management, and engineering, we synthesiseexisting definitions of BOs and highlight their generative, strategic, and reflective functions.Through a systematic literature review, enriched by empirical observations and exploratoryinterviews conducted in corporate R&D and design departments, we identify key mechanisms bywhich BOs operate in early project stages. Our findings emphasise the central role of BOs insupporting storytelling and imagination during phases of meaning-making convergence and vision-building. We demonstrate how BOs facilitate externalisation of thought, shared understanding,coordination, and the co-construction of meaning across disciplinary boundaries in organisation.The study highlights severalinsights: the use ofcombinations of semantic and generative BOsaimed attelling compelling stories and framing design questions, opportunities and challenges; theempowering effect of BOs in enhancing systemic understanding andbuilding shared confidenceamong stakeholders; and theorchestration role of designers in deploying and staging BOs asmediating artifacts. These findings provide a foundation forfuture research into thestrategic use,and potential instrumentalization, of BOs during non-regulated, exploratory stages of innovationprocesses