HAL - La Rochelle Université, Archives Ouvertes
Not a member yet
19516 research outputs found
Sort by
Assessing accessibility to quiet and green areas at the city scale using an agent-based transport model
No full textInternational audienceStandard European approaches to assessing environmental noise focus on individuals exposed to critical noise levels. However, there are complementary approaches that question the accessibility of the population to quiet areas, highlighting the restorative properties of natural and quiet spaces for human health. In this regard, from an agent-based model, this study proposes a spatio-temporal methodology to assess accessibility to quiet areas in agglomerations, integrating everyday mobility into the analysis of place effects and opportunities. The two primary objectives are to identify current quiet areas that are accessible in order to preserve them acoustically and to identify green spaces with the greatest potential for accessibility in order to improve them acoustically. Green spaces of Lyon and Villeurbanne (France) are assessed during the lunch break period using an open-source framework. The results indicate that on average about 30% of agents have access to a quiet area. Further, green spaces in courtyards represent the current quiet areas with the greatest accessibility. Concerning spaces with great potential for accessibility, linear green spaces along rivers and small squares near high-attended urban centers represent the greatest potential gain in accessibility to quiet areas. Improvements pertain to the utilization of in-situ surveys to integrate human perception and place attendance evaluations in the formulation of action plans
Key conservation actions for European steppes in the context of the Post-2020 Global Biodiversity Framework
No full textInternational audienceThe Kunming–Montreal Global Biodiversity Framework (KM–GBF) envisions a world living in harmony with nature by 2050, with 23 intermediate targets to be achieved by 2030. However, aligning international policy and national and local implementation of effective actions can be challenging. Using steppe birds, one of the most threatened vertebrate groups in Europe, as a model system, we identified 36 conservation actions for the achievement of the KM–GBF targets and we singled out—through an expert-based consensus approach—ten priority actions for immediate implementation. Three of these priority actions address at least five of the first eight KM–GBF targets, those related to the direct causes of biodiversity loss, and collectively cover all the targets when implemented concurrently. These actions include (i) effectively protecting priority areas, (ii) implementing on-the-ground habitat management actions, and (iii) improving the quality and integration of monitoring programmes. Our findings provide a blueprint for implementing effective strategies to halt biodiversity loss in steppe-like ecosystems. Our approach can be adapted to other taxonomic groups and ecosystems and has the potential to serve as a catalyst for policy-makers, prompting a transition from political commitment to tangible actions, thereby facilitating the attainment of the KM–GBF targets by 2030
Etude expérimentale de la flexibilité de la recherche de nourriture en réponse aux contraintes en mer chez un plongeur profond, le manchot royal
No full textInternational audienceWhen foraging, marine top predators rely on increasingly unpredictable oceanographic structures. Central place foragers are particularly affected. Their efficiency at replenishing their body reserves at sea while feeding their offspring on land relies on accurately targeting predictable foraging locations. Therefore, increased time and effort spent searching for resources is likely to compromise reproduction. Here, we used an experimental design to assess the flexibility of breeding king penguin (Aptenodytes patagonicus) foraging behavior in response to harsh conditions at sea, and examined the consequences on the growth and survival of their chick. We tested for behavioral adjustments to compensate for experimentally increased foraging workload, obtained by the application of a hydrodynamic drag effect. Compared to controls, treated adults more directly targeted a predictable hydrographic feature, the Polar Front, while limiting the increased costs of deep diving. Treated adults significantly increased hunting activity at shallower depths where the effect of treatment on diving efficiency was negligible. Our experiment resulted in decreased body mass gain during the brooding stage of chicks raised by treated parents compared to controls, with no direct effects on chick survival up to the winter period, but significant negative effects during winter. We identified two different strategies for foraging in king penguins: (1) foraging at the Polar Front where prey patches are more predictable and accessible at shallower depths or (2) foraging closer to the colony by targeting preys at deeper depths. These results highlight the possibility of a trade-off between distance and depth in breeding king penguin foraging behavior
Reassessing the Garonne River Floods chronology (13th-17th century) : a critical evaluation of Jules Serret work using Historical and palaeohydrological data.
No full textInternational audienceIn the downstream section of the Garonne Valley, encompassing both the overflowing and maritime Garonne (Lambert, 1988), one of the most extensive surveys of historical flood chronologies was undertaken by J. Serret, a scholar and lawyer from Agen. Initially published in 1874 in a condensed format—likely influenced by Champion's work (1856)—it was reissued in 1900 in an expanded version, prompted by the significant floods of the 1870s, particularly the devastating flood of 1875. In his compilation, Serret records over 120 floods occurring between 560 and 1874 AD, including 52 floods predating the 16th century. However, his work does not consistently cite sources, which were likely partly legal records, nor does it provide a clear hierarchy of the events. Serret's chronicle is notable for documenting the transitional period between the Medieval Climate Anomaly and the Little Ice Age.In this study, we critically re-examine Serret’s chronology through a dual approach: a thorough historical review of critical data and palaeohydrological analysis derived from a core extracted from a palaeochannel of the Garonne at Cadillac (33), covering the mid-13th to early 17th century CE. Particular attention is given to the methodological challenges posed by the diverse origins of the floods (Centralian, Pyrenean, and Mediterranean). As a result, Serret's chronology is reassessed and placed in its broader historical and hydrological context
Dynamic and Overlapping Community Detection in Link Streams through Formal Concept Analysis
No full textInternational audienceCommunity detection is a fundamental task in network analysis, with a large body of work focused on static networks. However, real-world communities are inherently overlapping and dynamic, requiring specific models. Methods such as Clique Percolation and its variants have been developed to address overlapping structures, and some extensions also incorporate limited notions of temporal dynamics. Yet, these approaches often rely on coarse time discretizations that fail to accurately represent the temporal structure of interactions. The link stream (LS) model was introduced to overcome this limitation by explicitly modeling time-stamped interactions. To date, the Link Stream Clique Percolation Method (LSCPM) is the only known approach for detecting overlapping communities within the LS framework. In this paper, we extend a Formal Concept Analysis-based method, originally developed for static and overlapping scenarios, to the LS model, enabling the detection of overlapping dynamic communities with high temporal resolution. We also introduce evaluation measures tailored to assess the quality of communities identified in this dynamic setting
Almost Sure Uniform Convergence Of Random Hermite Series
No full textWe continue the analysis of random series associated to the multidimensional harmonic oscillator on with d \geq 2. More precisely we obtain a necessary and sufficient condition to get the almost sure uniform convergence on the whole space . It turns out that the same condition gives the almost sure uniform convergence on the sphere (despite is a zero Lebesgue measure of ). From a probabilistic point of view, our proof adapts a strategy used by the first author for boundaryless Riemannian compact manifolds. However, our proof requires sharp off-diagonal estimates of the spectral function of . Such estimates are obtained using elementary tools
De pierre, de bois et de feu. Arsenaux, rivalités navales et patrimoine maritime: Etudes réunies en l'honneur de Martine Acerra
No full textInternational audienceLa recherche en histoire maritime et navale a connu un renouvellement de grande ampleur à partir des années 1970, et parmi les chantiers les plus novateurs figure celui des marines de guerre. Martine Acerra a apporté une contribution fondamentale à cette rupture historiographique permettant, avec d'autres chercheurs, de rompre avec une lecture nationale, voire nationaliste, de l'histoire des flottes européennes forgée essentiellement au XIXe siècle et très peu révisée depuis. D'une histoire articulée autour des grandes batailles et des figures héroïques, un puissant mouvement s'est engagé pour appréhender les enjeux politiques, économiques, sociaux, techniques et culturels de la construction et de l'entretien des marine de guerre. Si l'histoire universitaire a bénéficié de ce recentrement thématique, cette nouvelle façon d'appréhender la mer a également permis d'accompagner la patrimonialisation des héritages maritimes qui débute à la même période. Aussi, tout en rendant hommage à l'apport de Martine Acerra, cet ouvrage a l'ambition de montrer la vitalité de l'histoire maritime et navale qui poursuit sa mue épistémologique et thématique à travers l'ouverture de nouveaux chantiers
Singing around the volcano: Detecting baleen whales in the Mozambique channel based on their song rhythms, from seismic and hydroacoustic data
No full textInternational audienceSince March 2019 and October 2020, two long-term submarine networks—comprising ocean bottom seismometers and water-column hydrophones—have been deployed in the northern Mozambique Channel (Western Indian Ocean) to monitor the seismo-volcanic crisis that began offshore Mayotte in 2018. These deployments provide a valuable multi-year dataset for environmental monitoring in this remote region, including seasonal variations in the presence of baleen whales. To analyze these patterns, we developed an automated detector for stereotyped and regular signals, focusing on the characteristic inter-call intervals of each whale species, independently of the song structure. The detector's simplicity makes it computationally efficient and easily adaptable to species vocalizing in the 15–100 Hz frequency range over extended periods. Analysis of nearly six years of continuous seismo-acoustic data highlights the seasonal presence of Antarctic blue whales (May–August), Southwest Indian Ocean pygmy blue whales (bi-modal pattern from April–August and October–January), minke whales (June–December), and fin whales (July–November), and highlights the potential variability over years. Our results enhance and refine our understanding of the seasonal migration patterns of whale populations in this specific area of the Western Indian Ocean
