HAL-Université de Bretagne Occidentale
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Décentrer le regard pour faire bouger les lignes : la métropole brestoise au défi de la mobilité dans ses marges
No full textInternational audienceNous proposons ici une réflexion autour des marges métropolitaines et de leur difficile prise en compte dans les politiques territoriales de transports et de déplacements. Centrales au regard des enjeux environnementaux et sociaux des transitions, ces marges restent délaissées par les politiques contemporaines. Les échanges politiques autour de la desserte métropolitaine sont, d’une façon sous-jacente, structurés par la responsabilité individuelle de l’usage de l’automobile et la comptabilité autour du versement mobilité et son affectation. À trop ignorer les spécificités des pratiques de déplacements observées dans les marges, à trop percevoir la dépendance automobile comme un mauvais choix individuel, les politiques contemporaines ne sont-elles pas en train de nous dire que les habitants des marges méritent leur sort au risque d’alimenter une forme de populisme
Vers la robustesse : les réseaux de neurones comme systèmes dynamiques face aux attaques adversariales
No full textThis thesis explores the problem of adversarial robustness in modern AI models, with a focus on classification tasks, through the lens of dynamical systems theory. Adversarial attacks are subtle, often imperceptible perturbations to input data that can cause a model to make incorrect predictions. These attacks present a serious obstacle to the widespread adoption of AI systems, especially in safety-critical applications such as healthcare and autonomous driving. By framing neural networks as dynamical systems, we gain new insights into their behavior under adversarial conditions and develop novel defense strategies grounded in this perspective. Our work offers a principled path toward more reliable and trustworthy AI.Cette thèse s’intéresse à la robustesse des modèles d’intelligence artificielle face aux attaques adversariales, en particulier dans le cadre des tâches de classification, à travers le prisme de la théorie des systèmes dynamiques. Les attaques adversariales consistent en des perturbations subtiles, souvent imperceptibles, appliquées aux données d’entrée, pouvant induire les modèles en erreur. Ces attaques représentent un obstacle majeur à l’adoption massive des systèmes d’IA, notamment dans des domaines critiques tels que la santé ou les véhicules autonomes. En modélisant les réseaux de neurones comme des systèmes dynamiques, nous obtenons une meilleure compréhension de leur comportement en situation adverse et proposons de nouvelles stratégies de défense fondées sur cette approche. Ce travail ouvre la voie à une IA plus fiable et digne de confiance
Climate, Cities and Societies : the French Urban Climatology Network
No full textInternational audienceThe urban climatology community has been structured internationally at different levels for several years with venues such as ICUC, AGU, EGU or IC2UHI which regularly bring together different members of academia addressing urban climate-related research and engineering challenges from different disciplines, countries and perspectives. Late 2018, a series of meetings of the French community were launched. Two in-person meetings occurring in Paris, France in early and late 2019, bringing together 30-40 academics from different French research groups and universities across the country.During the COVID-19 pandemic and lockdown episodes, networking and research sharing took place in the form of a series of online webinars in 2021 offered a venue for young researchers to present their work to their peers and research community. In-person meetings took place once again starting in 2022. Building on the community’s engagement and interest, the research network began formalizing its existence and organization, currently structured into four thematic groups focused on:numerical modelingfield observationsknowledge transfer for operational applicationsteaching and public dissemination of scientific and technical informationThe community currently comprises around 150 members from 50+ different research institutes, as well as the public (government agencies), private (startups and SMEs) and local government (municipalities, urban planning agencies, …) sectors. These members are involved in work spanning a wide range of disciplines from the technical, natural and human and social sciences and conducted at a variety of spatial scales ranging from urban materials to the regional scale (“nano”, “indoor”, micro, local and meso-scale climates) and focusing on the study of urban climate: from fundamental science to climate change adaptation solutions.The proposed contribution will present the network, its membership as well as work undertaken by its thematic groups, including a literature review of radiation shields
Toward a validation of coupled arc-melt pool model for a TIG spot weld configuration
No full textInternational audienceThe TIG process is a complex arc welding method due to the multitude of operating parameters and their interdependence, making it challenging to master. To improve understanding of it, a magneto-thermo-hydrodynamic model with arc-melt pool coupling is realized. A comparison is made between numerical and exhaustive experimental results of welding performed on 304L stainless steel in spot configuration at 150 A and 250 A . The effect on the melt pool of increasing the intensity is numerically studied and compared to experimental trends. A significant reduction of the model error is observed when considering the deformation of the anode-plasma interface, which strongly impacts the arc and the melt pool at high intensity. However, the numerical melt pool size is still underestimated compared to the melt areas observed on the post-mortem micrographs. The effect of an additional potential drop term that can be found in the literature is studied and demonstrated to be ineffective. The experimental melt area overestimation is discussed to explain the differences observed
Évolution du travail et du management des collaborateurs en cabinet comptable : analyse des effets sur le présentéisme, le conflit travail-hors travail et le stress au travail
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Lifecycle Collaborative Planning for Traction Power Supply Systems With Integrated Energy Access
No full textInternational audienceAs global energy transition and electrified transportation continue to advance, traction power supply systems (TPSS) are becoming increasingly vital in rail transit. To solve problems that traditional planning for TPSS often overlooks the integrated energy access and the collaborative optimization of economic security throughout the life cycle, a lifecycle economic-security collaborative planning (LE-SCP) model for TPSS with integrated energy access (IEA-TPSS) is proposed. This model integrates an equipment performance correction matrix (EPCM) to address the performance degradation over the lifecycle of equipment. In addition, it considers N−1 security to ensure the resilience of IEA-TPSS under contingent conditions. Furthermore, a scenario-based hierarchical decomposition (SHD) method is introduced to solve this model. A case study analysis using actual data was conducted to validate the LE-SCP model and SHD method. The simulation results show that the LE-SCP model and the SHD method effectively address the comprehensive lifecycle planning issues of IEA-TPSS, considering both equipment degradation and N−1 security. Moreover, compared to traditional solution algorithms, the proposed SHD method can effectively reduce the model-solving time by 8.61
Albert Camus in America (1946) : from rejection of "new man" to creation of "Le premier homme"
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Differences in local immune response of bait Mycobacterium bovis heat-inactivated vaccinated badgers showing exacerbated tuberculous lesions after challenge
No full textInternational audienceEuropean badgers (Meles meles) are reservoirs for animal tuberculosis (TB) in some European countries, complicating TB control in cattle. Badger vaccination and a deeper understanding of the subsequent protection mechanisms are necessary for effective TB control. In a previous study, two of eight badgers immunized with the heat-inactivated Mycobacterium bovis (HIMB) vaccine exhibited an unusual immune response (divergent), developing exacerbated lesions. The present study aimed to describe the local immune response in divergent badgers (those with severe disease progression), with respect to that observed in standard (where the vaccine showed efficacy) and control badgers. Immunohistochemistry was performed to evaluate immune cells (macrophages, T and B lymphocytes, plasma cells), and proteins (TGF-β, IL-10, Fox-P3) within TB granulomas in the lung and bronchial lymph node (LN), after TB challenge. Lung lesion volume, bacterial load and immunological response were also evaluated. The divergent immune response was characterized by elevated IL-10 and Fox-P3, few macrophages and high B lymphocytes (mainly in lungs), suggesting a Th1/Th2 imbalance with reduced Th1 cellular immunity leading to severe TB. In contrast, vaccinated badgers with a standard immune response showed a balanced response, with significantly lower bacterial loads (85.5% LN and 99.9% lung) than control group. This study provides new insights into the immune mechanisms in HIMB-vaccinated badgers, to improve TB control strategies
Estimation of compressive strength in thick continuous fibre composites: Quantifying the role of initial fibre misalignment
No full textInternational audienceThe present study investigates the compressive strength of continuous fibre composites. These materials comprise almost ten different fibre/matrix pairs with four epoxy-based thermoset resin systems, three different carbon fibres and three manufacturers. The experimental values obtained from flexural testing on thick laminates (with 10 samples for each pair) are compared to an analytical compressive failure criterion. This latter model incorporates ease of use in engineering design and mechanistic contributions, including material (non-linear shear behaviour of the ply), manufacturing (initial fibre misalignment) and structural effect (loading, neighbourhood of ply). A comparison between the experimental and estimated values, using the standard deviation of the frequency distribution of fibre misalignment, demonstrates a satisfactory or excellent outcome. The comparison for a pair produced less favourable results, with greater discrepancies observed</div