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Successful Rescue of a Juvenile Humpback Whale (Megaptera novaeangliae) Trapped Upstream of the Rance Tidal Power Station, Brittany, France
No full textInternational audienceRescue operations involving baleen whales trapped in dammed environments are difficult to perform successfully, yet increasingly relevant under growing coastal development. We report on a two-day (9–10 February 2023) rescue of a juvenile humpback whale trapped upstream of the Rance Tidal Power Station (TPS) in Brittany, France, providing rare peer-review evidence on response strategies in highly engineered estuaries. A collaborative, non-invasive strategy was implemented by adjusting water levels and creating artificial tidal currents to prevent the whale from stranding and to guide the individual back to open water. Approximately 100 people were mobilized as part of the rescue operation. This paper describes a detailed spatiotemporal account of the whale’s movements and a chronological record of the actions taken by the rescue team. After several attempts to guide it out, rescue efforts enabled its successful exit from the estuary on the second day of operations, and it was not subsequently reported stranded along the French coast. This case demonstrates the value of rapid multidisciplinary coordination between the French National Stranding Network (composed of marine scientists, veterinarians and local correspondents), local organizations, the local marine biology station, international marine mammal experts, national institutions, authorities and a tidal energy operator. Beyond documenting an unusual event, this paper provides operational lessons, highlighting (i) the adaptative management of a TPS as a guidance tool, (ii) the prioritization of animal welfare and responders’ safety, (iii) the effective public and media management and (iv) the involvement of trained volunteers during the rescue, promoting environmentally responsible behavior. These insights are transferable to other cases to inform future baleen whales rescue protocols in anthropogenic environments
Efficacité de l'utilisation d'images satellites pour évaluer les changements passés et futurs de la végétation aquatique en rivière
No full textInternational audienceSince several decades, the acquisition of satellite images has considerably accelerated the monitoring of vegetation, but their use remains limited in aquatic environments due the interferences induced by the water column. The aim of this study was to analyse whether data from recent high spatial and temporal resolution satellite campaign could be used to monitor aquatic vegetation. For that purpose, very high spatial resolution images (15-25cm) were used as validation data and Planet satellite images (3m, daily acquisition, planet.com) acquired within ± 15 days of the reference images were downloaded. For each Planet image, a vegetation index based on reflectance in the green and near infra-red spectra, the GNDVI, was calculated to test whether aquatic vegetation and water can be differentiated spectrally. First results showed that GNDVI values are different between water and vegetation but with contrasting thresholds for distinguishing the two classes among images. These results indicate that a single threshold cannot be applied to all images to distinguish aquatic vegetation from water. Future challenges will consist in testing whether statistical methods can be used to distinguish aquatic vegetation from water without referring to field observations. These advances would be particularly useful for monitoring the dynamics of aquatic vegetation and supporting managers in their decision-making, and in aquatic ecosystems conservation, and restoration efforts.Depuis plusieurs décennies, l’acquisition d’images satellites a considérablement accéléré le suivi de la végétation, mais leur utilisation reste limitée en milieu aquatique du fait des interférences induites par la colonne d’eau. L’objectif de cette étude était d’analyser si les images issues de nouvelles campagnes de données satellites à haute résolution spatiale et temporelle peuvent être utilisées pour suivre la végétation aquatique. Pour cela, des images aériennes à très haute résolution spatiale (15-25 cm) ont été utilisées comme données de validation et les images satellites Planet (3 m, revisite journalière, planet.com) acquises à ± 15 jours des images de références ont été téléchargées. Pour chaque image Planet, un indice de végétation basé sur la réflectance dans le vert et dans le proche-infrarouge, le GNDVI, a été calculé afin de tester si la végétation aquatique et l’eau peuvent être différenciées sur le plan spectral. Les premiers résultats ont montré que les valeurs de GNDVI étaient différentes entre l’eau et la végétation mais avec un seuil de distinction des deux classes variable entre les images. Ces résultats indiquent qu’un seuil unique ne peut donc pas être appliqué à l’ensemble des images pour distinguer la végétation aquatique de l’eau. Les défis futurs consisteront à tester si des méthodes statistiques peuvent être utilisées pour distinguer la végétation aquatique de l’eau sans avoir recours à des observations de terrain. Ces avancées seraient particulièrement utiles pour suivre la dynamique de la végétation aquatique et soutenir les gestionnaires dans la prise de décision, ainsi que dans les efforts de conservation et restauration des cours d’eau
Quand le Rhône change, le Spirlin s’adapte : variations saisonnières des performances métaboliques et natatoires de cette espèce de poisson peu étudiée
No full textInternational audienceEctotherms are organisms whose body temperature depends directly on environmental temperature, which makes them vulnerable to climate change. Temperature is an abiotic factor that is variable in space and time, and affects different physiological parameters in ectotherms, including their metabolism. Our aim was to study the effect of seasonal temperature fluctuations on the metabolism and swim performance of the spirlin, Alburnoides bipunctatus, which is known as a cold stenotherm but is found downstream of nuclear power plants in warmed conditions. Seasonal fluctuations lead to changes in hydro-climatic conditions, and with rising temperatures, questions arise regarding the ability of ectotherms to adapt to these variations. To investigate this, we fished spirlins downstream the Bugey nuclear power plant on the Rhône River, in February and in May before acclimatizing them to the temperature at which they were caught. We then measured (i) metabolic rate via using oxygen consumption as a proxy and (ii) swim performance in a swim tunnel at the acclimation temperature. Our results show that standard metabolic rate, maximum metabolic rate, and swim performance are enhanced in spring individuals compared to winter ones. These findings show an acceleration in metabolic processes due to a thermodynamic effect of temperature, resulting in increased energy availability for growth and reproduction.Les ectothermes, dont la température corporelle dépend de leur environnement, sont particulièrement sensibles au changement climatique. La température est un facteur abiotique qui varie fortement dans l’espace et dans le temps et affecte divers paramètres physiologiques des ectothermes, notamment leur métabolisme. Notre but était de voir l’influence de la fluctuation saisonnière des températures sur le métabolisme et la performance de nage du spirlin Alburnoides bipunctatus, un poisson connu comme un sténotherme froid mais que l’on retrouve en nombre dans des conditions échauffées en aval de centrales nucléaires. Les fluctuations saisonnières engendrent des changements dans les conditions hydro-climatiques, qui sont de plus en plus variables et chaudes en lien avec le dérèglement climatique, et cela questionne sur la capacité des ectothermes à endurer ces changements et à s’adapter. Dans cette étude, nous avons pêché des spirlins en aval de la centrale nucléaire du Bugey sur le Rhône en février et en mai 2024, avant de les stabuler pendant un mois à leur température de pêche. Nous avons ensuite fait (i) des mesures de taux métabolique via le proxy de la consommation d’oxygène et (ii) une évaluation de la performance de nage dans un tunnel de nage à leur température d’acclimatation. Nos résultats montrent que le taux métabolique standard, le taux métabolique maximal et la performance de nage sont plus élevés chez les individus du printemps par rapport à ceux de l’hiver. Ces résultats témoignent d’une accélération des processus métaboliques dû à un effet thermodynamique de la température, ce qui leur octroie plus d’énergie disponible pour la croissance et la production de gamètes
A class of turbulent K-models for compressible flows based on a thermodynamical approach
No full textInternational audienceThis work proposes a thermodynamics-based derivation of a single-equation K model for turbulence in compressible flows. Unlike classical RANS approaches, this framework ensures hyperbolicity and well-defined shocks while avoiding complex closure modeling. The model naturally incorporates turbulence effects into temperature, which is essential for reactive flows such as premixed flame propagation. A theoretical analysis of turbulent shocks is provided, and the proposed model is compared with a classical K model, showing strong similarities under specific closures
Decay heat calculations and application of the lines of defence method to Chloride Molten Salt Reactor ARAMIS-A
No full textInternational audienceThis paper presents decay heat calculations and an application of the lines of defence method on 300 MWth chloride molten salt reactor ARAMIS-A. Decay heat calculations were performed with the CEREIS code, an under-development CNRS Python code, coupled with SERPENT2, which ensures reactivity control by fuel salt batch feeding. Results were compared to the benchmarked CNRS REM code and lead to a maximum total decay heat of 21.32 MW (7.1% of nominal power). The lines of defence method was applied to identify needed fuel salt locations and decay heat removal systems reliability requirements to ensure the decay heat removal safety function. This analysis leads to a proposition of 4 locations, with dedicated decay heat removal systems, and 3 containment barriers
Modèle de Données Sémantiques Commun pour l'Espace de Données Européen de l'Energie Omega-X
No full textInternational audienceL'interopérabilité sémantique est un défi important dans les espaces de données de l'énergie, où divers acteurs (fournisseurs d'énergie, gestionnaires de réseau, fournisseurs de services technologiques) échangent des données, tout en ayant l'obligation de se conformer à différents standards et réglementations. Cet article présente le Common Semantic Data Model (CSDM), une ontologie développée dans le cadre du projet européen Omega-X, visant à construire un espace de données fédéré pour le domaine de l'énergie. Le développement de l'ontologie Omega-X a pour objectif d'assurer une interopérabilité sémantique efficace pour tous les acteurs de l'échange de données, et de permettre une exploitation optimale des jeux de données mis à disposition. Le CSDM adopte une approche modulaire et multiniveau, alignée sur les principes FAIR (Findable, Accessible, Interoperable, Reusable), qui s'appuie sur des ontologies du domaine de l'énergie, ainsi que des standards tels que l'IEC CIM. L'article détaille le processus de développement du CSDM, basé sur les méthodologies AIME et ACIMOV, et présente ses principaux modules. Une évaluation du CSDM est réalisée à travers deux cas d'usage concrets : (1) l'échange de données de flexibilité entre un producteur de données et un fournisseur de services de prédiction et (2) la gestion de la performance des installations photovoltaïques. Ces cas d'usage ainsi qu'une validation technique démontrent la capacité du modèle à assurer l'interopérabilité sémantique et à améliorer la gestion des données dans un espace énergétique fédéré
Asymptotic approaches for dealing with distorted crack geometries
No full textA growing, albeit not predominant, way to contribute to the climate transition in the field of fracturemechanics is to refine predictions from damage tolerance approaches used to assess the durability andreliability of sensitive components such as those found in railway, aeronautics, aerospace or nuclearindustries. If it can be certified that the reduced safety margins remain acceptable, the intervals betweenmaintenance operations could be extended, and the replacement of defective parts delayed, therebyreducing the environmental footprint.The aim of Damage Tolerance Approaches is to ensure that the existence of unavoidable defects does notcompromise safety. This involves considering the most unfavorable case of brittle fracture and determiningthe propagation of a preexisting crack under cyclic loading until the Griffith energy fracture thresholdis reached. Currently, this is done using simplified, smoothed-out crack geometries, relying either ontabulated values or Finite Element Methods. Since meshing of the entire structure is required, the lattercurrently struggles to accurately account for the small-scale tortuosity of the crack geometry.This paper aims to show that asymptotic approaches are efficient alternatives to address this challenge.Various aspects of these approaches, along with selected applications, will be reviewed. In addition tosupporting the reduction of safety margins, these approaches also help to ensure that small geometricalperturbations do not lead to unexpected catastrophic failure. Asymptotic methods aim to provide analyticalformulas for the variation of stress intensity factors caused by small-scale crack shape perturbations.Several applications are presented including crack shape evolution, the influence of heterogeneities, andpropagation in general mixed-mode I+II+III condition
Chlorine 36 dry deposition on lettuce and maize crops
No full textInternational audienceChlorine is a mineral nutrient which, in a certain amount in the form of chloride, is essential for plant development. However, the atmosphere-plant transfer of its radioactive isotope, chlorine-36, is still poorly understood. In this study, dry deposition of 36Cl on lettuce and maize was determined experimentally. These two cultures were carried out downwind of Orano La Hague plant (West of France), which chronically emits small quantities of 36Cl. The dry deposition velocities were similar on these two canopies with mean values of and 1.4 × 10− 2 m s− 1 on lettuce and 1.6 × 10− 2 m s− 1 on maize crops. The measured deposition fluxes reflect the importance of the dry deposition mechanism on plants, particularly in situations of anthropogenic discharge. All these results will contribute to improving the knowledge on the fate of 36Cl in environment, and particularly in agrosystems
Reduced-order modelling of parameter-dependent systems with invariant manifolds: Application to Hopf bifurcations in follower force problems
No full textInternational audienceThe direct parametrisation method for invariant manifolds is adjusted to consider a varying parameter. More specifically, the case of systems experiencing a Hopf bifurcation in the parameter range of interest is investigated, and the ability to predict the amplitudes of the limit cycle oscillations after the bifurcation is demonstrated. The cases of the Ziegler pendulum and Beck's column, both of which have a follower force, are considered for applications. By comparison with the eigenvalue trajectories in the conservative case, it is advocated that using two master modes to derive the ROM, instead of only considering the unstable one, should give more accurate results. Also, in the specific case where an exceptional bifurcation point is met, a numerical strategy enforcing the presence of Jordan blocks in the Jacobian matrix during the procedure is devised. The ROMs are constructed for the Ziegler pendulum having two and three degrees of freedom, and then Beck's column is investigated, where a finite element procedure is used to spatially discretize the problem. The numerical results show the ability of the ROMs to correctly predict the amplitude of the limit cycles up to a certain range, and it is shown that computing the ROM after the Hopf bifurcation gives the most satisfactory results. This feature is analyzed in terms of phase space representations, and the two proposed adjustments are shown to improve the validity range of the ROMs
DeviceScope: An Interactive App to Detect and Localize Appliance Patterns in Electricity Consumption Time Series
No full textInternational audienceIn recent years, electricity suppliers have installed millions of smart meters worldwide to improve the management of the smart grid system. These meters collect a large amount of electrical consumption data to produce valuable information to help consumers reduce their electricity footprint. However, having non-expert users (e.g., consumers or sales advisors) understand these data and derive usage patterns for different appliances has become a significant challenge for electricity suppliers because these data record the aggregated behavior of all appliances. At the same time, ground-truth labels (which could train appliance detection and localization models) are expensive to collect and extremely scarce in practice. This paper introduces DeviceScope, an interactive tool designed to facilitate understanding smart meter data by detecting and localizing individual appliance patterns within a given time period. Our system is based on CamAL (Class Activation Map-based Appliance Localization), a novel weakly supervised approach for appliance localization that only requires the knowledge of the existence of an appliance in a household to be trained