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Integrating Aggregated Electric Vehicle Flexibilities in Unit Commitment Models using Submodular Optimization
No full textThe Unit Commitment (UC) problem consists in controlling a large fleet of heterogeneous electricity production units in order to minimize the total production cost while satisfying consumer demand. Electric Vehicles (EVs) are used as a source of flexibility and are often aggregated for problem tractability. We develop a new approach to integrate EV flexibilities in the UC problem and exploit the generalized polymatroid structure of aggregated flexibilities of a large population of users to develop an exact optimization algorithm, combining a cutting-plane approach and submodular optimization. We show in particular that the UC can be solved exactly in a time which scales linearly, up to a logarithmic factor, in the number of EV users when each production unit is subject to convex constraints. We illustrate our approach by solving a real instance of a long-term UC problem, combining open-source data of the European grid (European Resource Adequacy Assessment project) and data originating from a survey of user behavior of the French EV fleet.</div
Mitigation of Defect Formation at the NiO x /Perovskite Interface in p-i-n Perovskite Solar Cells
No full textInternational audienc
The challenging appropriation of Generative AI at Work
No full textInternational audienceThe development of AI-based systems has enabled the delegation of tasks traditionally associated with human cognition to machines. With the advent of so-called "generative AI" (GenAI), public interest has surged, culminating in what Time magazine headlined on 27 February 2023 as an ongoing "arms race" among major corporations. Within this context, numerous reports – particularly from grey literature – highlight gains in productivity, efficiency, and, less frequently, quality, when employees utilise GenAI systems. Empir-ical studies conducted in real-world settings remain limited, with findings largely focused on quantitative indicators (e.g., Brynjolfsson et al., 2023), yet they nonetheless provide insight into the application of GenAI in the workplace. Other studies have turned their attention to the emergent mode of interaction known as "prompting", which underscores a transformation in production activities and the concomitant need for new skillsets (e.g., Mah-davi Goloujeh et al., 2024; Suh et al., 2021).To address the current gap between productivity-focused perspectives on GenAI in work contexts and broader understandings of human–AI interac-tion outside the workplace, this study aims to explore how the integration of a generative AI–based tool within an existing sociotechnical system recon-figures employees’ work practices. The objective is to investigate how work-ers engage with and adapt to this evolving technological landscape
Caractérisation des rugosités par données satellitaires pour les calculs d’inondations
No full textFlood simulation commonly relies on two-dimensional (2D) hydrodynamic models, which must be carefully calibrated and validated using past flood events to ensure accurate forecasting. A critical component of this calibration process is the spatial distribution of the roughness parameter, which significantly influences simulated water depths and velocities. In the minor bed, the hydrodynamic models are calibrated using time-series data from stage-gauging stations. For floodplains, few data are available, and the roughness spatial distribution is often poorly known and typically inferred from land-use classifications using empirical values drawn from expert judgment. Hydrodynamic models' calibration could benefit from incorporating the maximum available observational data.In this context, satellite remote sensing can be leveraged as a valuable source of information. Synthetic Aperture Radar (SAR) imagery, in particular, is capable of detecting surface water extents even under cloud cover, making it highly suitable for flood monitoring. This thesis aims to develop a methodology to calibrate floodplain roughness coefficients in 2D hydrodynamic models, leveraging satellite-derived observations.The first step aims to recover information from the satellite observations to calibrate the flood models. Thus, this thesis proposed an evaluation of the extraction of flood extent maps and water depth fields from SAR imagery, along with an evaluation of the associated uncertainties arising from method choices and hyperparameter settings. The flood extent maps should be compared with the hydrodynamic model to calibrate it. Thus, in this thesis, we developed a step-by-step methodology to guide the selection of appropriate performance measures to compare simulated and observed flood extent maps. Then, the uncertain SAR-derived flood observations are integrated into the hydrodynamic modeling framework through data assimilation techniques to enhance the calibration of spatially distributed roughness coefficients on floodplains.By combining remote sensing data, uncertainty quantification, and hydrodynamic modeling, this thesis proposes an approach to enhance flood model calibration, with the potential to improve flood forecasting and risk management practices.La simulation des inondations repose souvent sur des modèles hydrodynamiques bidimensionnels (2D), qui doivent être soigneusement calibrés et validés à l'aide d'événements d'inondation passés afin de garantir la précision des prévisions futures. Le coefficient de rugosité est un élément essentiel de ce processus de calibration, car il influe considérablement sur les profondeurs d'eau et les vitesses dans le modèle. Dans le lit mineur, les modèles hydrodynamiques sont calibrés à l'aide de données chronologiques provenant de stations de jaugeage. Cependant, pour les plaines d'inondation, la distribution spatiale du coefficient de rugosité est souvent mal connue et généralement déduite à partir de l'occupation des sols, associée à des valeurs empiriques tirées du jugement d'experts. La calibration des modèles hydrodynamiques pourrait bénéficier de l'intégration du maximum de données d'observation disponibles. Dans ce contexte, la télédétection par satellite peut être exploitée comme une source précieuse d'informations. L'imagerie par radar à synthèse d'ouverture (SAR), en particulier, est capable de détecter les étendues d'eau de surface même sous la couverture nuageuse, ce qui la rend très adaptée à la surveillance des inondations. Cette thèse vise à développer une méthodologie pour calibrer les coefficients de rugosité des plaines d'inondation dans les modèles hydrodynamiques 2D, en tirant parti des observations dérivées des satellites. La première étape vise à récupérer des informations à partir des observations satellitaires pour calibrer les modèles d'inondation. Ainsi, cette thèse propose une évaluation de l'extraction des cartes d'étendue des inondations et des champs de profondeur d'eau à partir de l'imagerie SAR, ainsi qu'une évaluation approfondie des incertitudes associées, découlant des choix de méthodes et de leurs hyperparamètres. Les cartes d'inondation observées doivent être comparées au modèle hydrodynamique afin de le calibrer. Dans cette thèse, nous avons développé une méthodologie pour guider la sélection d'une mesure de performance appropriée afin de comparer les étendues d'inondation simulées et observées. Finalement, les observations incertaines dérivées des images satellites SAR sont combinées avec le modèle hydrodynamique grâce à des techniques d'assimilation de données, afin d'améliorer la calibration des coefficients de rugosité variables dans l’espace sur les plaines d'inondation. En combinant les données de télédétection, la quantification des incertitudes et la modélisation hydrodynamique, cette thèse fournit une approche pour améliorer la calibration des modèles d'inondation, avec le potentiel de renforcer la prévision des inondations et les pratiques de gestion des risques
Messages et enseignements du projet Explore2 - Analyse de l’hydrologie de surface selon les niveaux de réchauffement fixés par la TRACC
No full textCe document résume les principales conclusions sur l'évolution de variables climatiques et hydrologiques (surface) et des aléas hydroclimatiques, obtenues à l'issue du projet Explore2, analysées par niveau de réchauffement prescrit par la TRACC (réchauffement de +2,7 °C et +4 °C en France hexagonale et Corse par rapport aux niveaux préindustriels)
What evidence exists on the impacts of artificial light on terrestrial non-flying mammals native to Europe? A systematic map and a narrative review
No full textInternational audienceIntroductionNowadays, light pollution due to the multiplication of outdoor lightings has become a worldwide disturbance for many species. A large amount of scientific literature shows that this sensory stressor has adverse effects on several taxa. However, existing reviews tend to conclude a lack of primary research on terrestrial non-flying mammals even if these organisms are highly nocturnal and frequently exposed to artificial light.MethodsTo have a more accurate overview on the available literature, we followed the guidelines proposed by the Collaboration for Environmental Evidence to perform a comprehensive evidence synthesis, focusing on the 186 terrestrial non-flying mammal species native to Europe. We searched 2 academic databases and Google Scholar for scientific and grey literature on the impacts of artificial light. We exported 6624 citations and screened 4866 articles on titles, abstracts, and then full-texts. We coded variables and extracted results for all the included studies to build a systematic database and we synthetized the data.ResultsWe collected 48 articles on 22 mammal species across 12 families, revealing a more substantial knowledge than expected. composed of 448 study units. We identified four main research hotspots that address different questions: 1/ impacts of manipulating the photoperiod; 2/ impacts of ex-situ artificial light on small mammals; 3/ impacts of in-situ outdoor lightings; 4/ impacts of global light pollution (sky glow). We described the results of the included studies in a narrative review to provide a factual overview of the findings.DiscussionThese initial results draw detrimental impacts of ALAN on circadian rhythm, behaviour, foraging or movements and ultimately occurrence, which are consistent with available literature on moonlight influence or ALAN effects on other taxa. Hence, we call for much more attention to be paid to wild terrestrial non-flying mammals in relation to this key anthropogenic driver
Critical assessment of an aging phenomenological model for building materials
No full textInternational audienceThe description of aging of construction materials represents a significant issue. According to previous studies, aging is addressed by using experimental approaches which consist in submitting materials to accelerated aging designs in the laboratory. Then, the effect is highlighted by performing measurements at different stages of material aging. These discrete configurations are considered to evaluate the impact of aging at the building scale. Within this context, this research proposes a phenomenological model that describes the aging of a material over time. It assesses the variation in porosity depending on drying and imbibition loads, each expressed by means of an indicator. Also, a cumulative and a moving approach are used to express each load. Afterwards, the model unknown parameters are estimated by solving an inverse problem. The results of the estimation are obtained based on experimental observations of an aging experimental design on hemp concrete. For each load approach, it is shown that the model fits good most of porosity measurements. In particular, the moving approach is better adapted to study the aging of materials. Further, the model of porosity is integrated into equations of heat and mass transfer within porous media. The objective consists in evaluating the impact of aging, with a continuous approach, on the energy efficiency of the material at the wall scale. Based on a case study, the impact is evaluated by assessing the energy efficiency for a first configuration without aging and a second with. Computations of sensible and latent heat fluxes reveal that thermal losses through the wall are underestimated by about 30% when aging effects are neglected. This finding highlights the significance of this phenomenon and encourages its consideration in future building energy simulations
REMOVING BEHAVIOURAL BARRIERS TO ENERGY RENOVATION – A DISCRETE CHOICE EXPERIMENT
No full textInternational audienceThe building sector is the largest consumer of energy and one of the main sources of greenhouse gas emissions in France. Without energy renovation, it will be impossible to achieve carbon neutrality by 2050. To encourage households to take action, the French government has introduced various measures, but the targets set have not been met. One reason is the financial difficulty households face when they need to carry out a complete energy renovation of their homes. Our study aims to measure the impact of two types of financial assistance, namely third-party financing and mortgage loans, on the energy renovation decisions of households that own single-family homes. We also assess households' willingness to pay to improve their comfort and reduce their energy bills
Reverse chemical ecology to study the defense of the plant host Sextonia rubra and the chemical mediators of its endophyte Fusarium falciforme against phytopathogen Trametes versicolor
No full textInternational audienceSextonia rubra is a tropical tree endemic to the Guiana Shield and the Brazilian Amazon. Despite its renowned wood durability, it remains susceptible to degradation by white-rot fungi such as Trametes versicolor. To mitigate biotic stresses, plants can rely on their associated microbial communities, including endophytes, which play a crucial role in their defense mechanisms. In this study, we explored the cultivable microbiota of S. rubra, considering it a holobiont.Endophytic strains were isolated from the bark, sapwood and heartwood of S. rubra, and metabolome were extracted. We used a reverse chemical ecology approach to elucidate the mechanisms underlying these extracts' fungicidal activity. In this context, glutathione-S-transferases (GST), key detoxification enzymes of the lignivorous fungus T. versicolor, were chosen as targets. GST tests confirmed the presence of antifungal compounds in extracts from 13 of the 152 endophytes. Two isolates of Fusarium falciforme and one isolate of Fusarium graminearum were selected for co-culture experiments with T. versicolor.A comprehensive metabolic analysis of the confrontation zones using RPLC-ESI(+)-HRMS/MS and molecular networking revealed that the antifungal activity against T. versicolor was primarily mediated by cyclopeptides, and the observed contact inhibition was attributed to fusarins. These findings shed new light on the role of endophytic fungi in the chemical defense strategies of S. rubra, highlighting their potential as a source of bioactive compounds with antifungal properties
Coastal to Riverine Entry Timing During the Spawning Migration of the European Shads (Alosa spp.): Drivers and Phenological Trends for the French Atlantic Coast Populations
No full textInternational audienceDuring the spawning migration of the anadromous allis Alosa alosa and twaite Alosa fallax shads, timing of river entry is decisive to ensure that arrival in the spawning grounds matches with favourable conditions for reproductive success. Identifying the environmental cues that drive the timing of river entry is therefore crucial to understanding the implications of climate change for shad populations and to implementing management measures for these threatened species. In this study, data from fisheries and fish counting stations located in the estuaries or low reaches of 10 rivers were combined to investigate the effects of coastal, river conditions and abundance on the timing of migration. Phenological trends were quantified at five sites with more than 20 years' monitoring, and we analysed whether these trends aligned with the period when river temperatures were in the most favourable range for offspring survival. The results indicated that the temporality of spring warming in coastal habitats and photoperiod were key drivers influencing river entry timing. Their relative influence varied between models predicting migration initiation, median and end dates. Significant shifts toward earlier and longer migration periods were quantified. At the site with the longest monitoring time series, the shift in migration timing increased the time lag between early shad arrival and the period of most favourable breeding temperatures. Therefore, further studies should assess the repercussions of earlier spawning migration on the phenology and success of reproduction and juvenile stages