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Toward Graph Refactoring in Latent Space for Underwater Moving Object Detection for Digital Twins
No full textInternational audienceUnderwater object detection faces unique challenges such as low visibility, high turbidity, backscatter, and dynamic backgrounds, which complicate the task of identifying objects in underwater environments. Autonomous underwater vehicles require precise environmental modeling to navigate effectively, highlighting the need for robust detection systems. Digital twin environments can be created using passive camera sensors to model underwater surroundings, with a virtual machine replicating these conditions to detect moving objects across frames. This chapter examines the constraints of cutting-edge technologies, namely, deep learning techniques such as convolutional neural networks (CNNs), which encounter difficulties in underwater environments due to their dependence on kernel size and network depth, resulting in insufficient detection capabilities. We propose an approach that refines latent space using graph theory techniques to improve object detection by capturing complex spatio-contextual relationships that CNNs may overlook. This method leverages graph convolutional neural networks (GCNNs) to enhance the representation of underwater objects, enabling more precise boundary delineation and improved detection accuracy in challenging environments. Furthermore, we provide a detailed analysis of the proposed approach using a benchmark underwater dataset: Fish4Knowledge. Our research illustrates the efficacy of combining graph theory with deep learning to tackle the difficulties associated with detecting moving objects underwater
Trajectoires résidentielles et stratégies de recomposition spatiale face aux risques littoraux
No full textInternational audienceIn the face of climate change, the implementation of risk adaptation strategies in coastal areas is receiving a growing interest, particularly from land managers. Managed retreat, or spatial reorganisation, involves a planned move of goods and people to non-vulnerable areas. This article examines the role played by households' residential pathways in their propensity to plan a retreat by 2040. Based on a survey carried out on the Landes coast (Capbreton), we emphasize the importance of identifying the main dimensions of these residential pathways in order to co-construct relocation strategies with the population.Face au changement climatique, la mise en œuvre de stratégies d’adaptation aux risques sur le littoral suscite un intérêt croissant, en particulier pour les gestionnaires de ces territoires. La relocalisation résidentielle ou recomposition spatiale consiste à planifier un déplacement des biens et des personnes en zone non vulnérable. Nous étudions la place qu’occupent les trajectoires résidentielles des ménages dans leur propension à envisager un déménagement à horizon 2040. À partir d’une enquête menée sur le littoral des Landes (Capbreton), nous soulignons l’importance d’identifier les principales dimensions de ces trajectoires résidentielles pour coconstruire avec les populations les stratégies de déplacement
Création de modèles et de langages de description pour les Arts performatifs
No full textInternational audienceThis presentation provides an overview of the work carried out to design description models tailored to the specificities of the Performing Arts. This work focuses in particular on the development of controlled vocabularies and archival schemas to enhance the description, indexing, and interoperability of data in this field. These research and development activities are conducted within the framework of several scientific collaborations, including the CANEVAS consortium (IR* HumaNum), the THEATRALIA working group (DARIAH-EU), and the Institut des Amériques (GIS IdA).Cette présentation propose un aperçu des travaux conduits en vue de la conception de modèles de description adaptés aux spécificités des Arts performatifs. Ces travaux portent notamment sur la structuration de vocabulaires contrôlés et l’élaboration de schémas archivistiques permettant une meilleure description, indexation et interopérabilité des données dans ce domaine. L’ensemble de ces recherches et développements s’inscrit dans le cadre de plusieurs collaborations scientifiques menées au sein du consortium CANEVAS (IR* HumaNum), du groupe de travail THEATRALIA (DARIAH-EU), et de l’Institut des Amériques (GIS IdA)
A multi-scaling approach showing a transient metabolic mismatch in a freshwater fish ( Zingel asper ) during an acute heat stress
No full textInternational audienceHeat stress events will be more frequent and intense in the future. These events will challenge the capacity of organisms to exhibit sufficient metabolic flexibility to adapt to such variations. To better understand the acclimation processes implemented in response to acute warming, with an integrative approach we examined in vivo metabolic rate and cardiac mitochondrial respiration in the Rhône streber, during and after a heat stress on a precise time line. The temperature was raised from 13°C to 18°C (+1°C per hour) and maintained at 18°C for 5 days, before returning to 13°C at the same rate. We repeatedly measured, during the heat stress and 5 days after the end of the event, in vivo metabolic rate in the same individuals and cardiac mitochondrial respiration from different individuals. At the organismal level, oxygen consumption increased in line with warming, and was followed by a return to pre-acclimated levels just after the end of the heat stress. Conversely, cardiac mitochondrial respiration decreased during the heat stress, especially 24 h in, and recovered at the end of the event. Our results suggest that the heat stress was responsible for a metabolic mismatch in the strebers. Indeed, we observed (i) a strong thermodynamic effect without any acclimation process, suggesting that the range of temperatures chosen was not stressful for the fish, and (ii) the establishment of a transitory energy saving process. Our results underline the need for more integrative studies to understand how organisms will adapt to climate change
Morphological evolution of a coastal salt marsh/mudflat characterized from different remote sensing methods.
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Limited evidence that body size shrinking and shape-shifting alleviate thermoregulatory pressures in a warmer world
No full textInternational audienceAbstract Amassing evidence indicates that vertebrates across the globe are shrinking and changing shape concurrent with rising temperatures. Ecogeographical theories assert that these changes should provide thermoregulatory benefits by easing heat dissipation, however, thermophysical models underpinning such theories are highly simplified and lack empirical validation. Using data from three temperature-manipulation experiments, we quantified the contributions of body size and appendage lengths toward thermoregulatory performance in Japanese quail, while simultaneously querying neutral plasticity as an alternative driver of avian shape-shifts. In the cold, body mass and leg length (here, tarsus length) influenced energy costs of warming, but only among juveniles. In the warmth, smaller body sizes, longer legs and longer bills independently reduced energy and water costs of cooling across ages, but whole-body phenotypes necessary to provide even moderate thermoregulatory benefits were rare (2.5%) and required large departures from allometry. Last, rearing in the warmth reduced body sizes and increased appendage lengths comparable to recent changes observed in nature, but emergent morphologies provided no clear thermoregulatory benefit. Our findings question whether shrinking and shape-shifting are indeed easing thermoregulation in birds or reflect selection for such. Neutral plasticity, or relaxed selection against small body size in juveniles, may better explain recent avian shape-shifting
Multi-physical driven time-dependent reliability analysis framework for reinforced concrete floating wind turbine foundations considering climate change
No full textInternational audienceAs a critical component of floating offshore wind turbines (FOWTs), reinforced concrete (RC) floating foundations are typically designed to last two to three times longer than the upper structure. However, their durability and reliability are challenged due to the coupled effects of corrosion and fatigue in harsh marine environments. This study proposes a multi-physics coupling framework to explore the deterioration mechanisms of RC-FOWT foundations under dynamic wind-wave loading and adverse environments. A cylindrical chloride diffusion model quantifies chloride transport in concrete, considering temperature, humidity, and fatigue-induced cracks. A pitting corrosion model assesses the cross-sectional loss and pitting depth of steel reinforcements, while the Paris-Erdogan fatigue crack growth model simulates corrosion-induced crack propagation under cyclic loading. Additionally, probability density function informed method-driven probabilistic analysis and various climate change scenarios predict the time-dependent failure probability of FOWT foundations. Results indicate that extreme climate change scenarios increase energy production by 12.9% compared to non-climate-change scenario. However, chloride diffusion and corrosion rates accelerate by 62%, significantly speeding up crack propagation and reducing structural lifespan by approximately 49.15%. This study highlights the trade-off between increased energy production and accelerated structural deterioration due to climate change, emphasizing the need for balanced design considerations
Évaluer les protections côtières fondées sur les écosystèmes
No full textInternational audienceNature-based Coastal Defense is increasingly used to reduce climate risk, because considered effective, inexpensive and cost-effective, easy to implement, and no-regrets. This article discusses this positive framing through the analysis of 23 projects implemented in French overseas territories, using an ex-post expert judgment method considering enabling conditions (context, governance, funding, social acceptability), risk reduction (technical effectiveness; studies, monitoring and evaluation) and externalities (co-benefits and disbenefits; contribution to adaptation). 80% of projects aimed at reducing coastal erosion; 47.8% were implemented in natural or rural areas; 87.1% included restoration; 82.6% targeted one single ecosystem and 51.7% beach/dune systems; 47.8% were led by public actors; all relied on multiple funding sources. Performance indices range from 39.4 to 77.2%. The highest scores concern governance and social acceptability, and the lowest scores risk reduction. No project included an evaluation of risk reduction and was calibrated for future risk. Internal (i.e. project related) and external (more general) levers and barriers to effectiveness were identified. Internal barriers include the lack of political support to nature-based options, the difficulty to secure the required long-term funding and to upscale action in the face of strong land tenure constraints
A PETREL BREEDING DIVERSITY HOTSPOT: RAIVAVAE ISLAND (AUSTRAL ISLANDS, FRENCH POLYNESIA), WITH A NEED FOR CONSERVATION ACTION
No full textInternational audienceRaivavae is a small island in the Austral Islands of French Polynesia that is surrounded by a lagoon with 28 islets. Its marine avifauna is one of the least known and least studied in French Polynesia. Overall, seabird surveys in the various Austral Islands have been extremely sparse. This study addresses this need, using both historical and recent findings. The results show high species richness, with 10 breeding procellarid species, though none are numerous. We also update the knowledge on breeding petrels from other Austral Islands (except Rapa) and discuss the consequences of these findings in terms of their conservation on an island with cats Felis sp. and rats Rattus sp