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Middle Eocene hyperthermal seasonality from Paris Basin marine mollusks
No full textInternational audienceThe Earth has experienced hyperthermal events in the past, characterized by maximum durations of hundreds thousand years, significant magnitude, global extent, and drivers associated with increases in greenhouse gas concentrations, therefore making them potential analogues for current climate change. The Middle Eocene Climatic Optimum (MECO) that occurred 40 Ma ago, is marked by a CO2-driven global warming of +4 to +6° C, affecting global temperatures. Here, we present a detailed reconstruction of seasonal fluctuations in seawater temperatures during this warming event in littoral environment, based on geochemical analyses (δ18O and Δ47) of shallow-marine mollusks from the Paris Basin. Our data show a stability in mean winter temperatures compared to pre-MECO conditions, but a marked warming of +10°C in maximum estuarine water temperatures, with a seasonal temperature range increasing from 12°C before the MECO to 22°C at the climax of the event. We demonstrate that at mid-latitudes, annual maximum shallow-water temperatures increased from 30 ± 2°C before the event to a maximum of 41 ± 4°C at the warming peak. This pattern is associated with a seasonal regime characterized by dry summers and wet winters, implying that the Paris Basin experienced a super-hot summer Mediterranean climate during the MECO
Stabilization of compressed earth bricks (CEB) using alkali-activated glass powder: A sustainable binder approach
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Assessing the thermal efficiency of innovative eco-friendly bricks enhanced with phase change materials
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Measurement report: Lessons learned from the comparison and combination of fine carbonaceous aerosol source apportionment at two locations in the city of Strasbourg, France
No full textInternational audienceAbstract. Source apportionment analyses of carbonaceous aerosol were conducted at two neighboring urban sites in Strasbourg, France, during the winter of 2019/2020 using ACSMs (Aerosol Chemical Speciation Monitors; for non-refractory submicron aerosols), aethalometers (AE33; for equivalent Black Carbon – eBC) and filter-based offline chemical speciation. Positive Matrix Factorization (PMF) was applied to organic aerosols (OA) following two strategies: (i) analyzing each site individually, (ii) combining both sites into a single dataset. Both methods resolved five OA factors: hydrocarbon-like (HOA), biomass burning (BBOA), cooking-like (COA-like), oxygenated (OOA), and an amine-related OA (58-OA) factor. The latter factor, accounting for ∼ 4 % of the total OA mass at each site, showed clear diel profiles and a distinct origin marked by specific wind directions, suggesting a unique local source, potentially linked to industrial emissions. The present study also highlights the challenge of attributing a cooking-only origin to the COA-like factor, which exhibited a diel cycle similar to biomass burning OA at the background site. The combined PMF analysis improved the apportionment of cooking emissions at nighttime, especially for the traffic site, compared to individual PMF analyses, but it did not enhance the other OA factors due to instrumental specificities (i.e., different fragmentation patterns) leading to differences in OA mass spectra between the two instruments. Overall, this study argues for careful inspection of instrumental peculiarities in ACSM and AE33 data treatment and provides hints to benefit from their use at various locations at the city scale. It also allows comparison between different types of PMF analyses, showing that combined PMF may not be appropriate for improving the consistency of OA factors in some cases such as the one presented here
Mechanical, microstructural and environmental performance of 100% recycled-aggregate concrete with low-carbon binders
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Bacterial alginate-based hydrogels reinforced with polysaccharide nanocrystals for water and wastewater decontamination
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The BIOMASP+ project on biosphere-atmosphere exchanges and their role in air pollution in the subtropical megacity of São Paulo: motivations, methods and preliminary observations
No full textInternational audienceAir pollution, especially in urban areas, is the result of a complex mixture of natural and anthropogenic emissions and their atmospheric processing. It causes millions of premature deaths worldwide and affects plant metabolism, which in turn alters the emissions of Biogenic Volatile Organic Compound (BVOCs) by plants. By taking the subtropical Metropolitan Area of São Paulo (MASP) as a natural laboratory, the BIOMASP+ project (BIOsphere-atmosphere interactions in the Metropolitan Area of São Paulo - plus) a ims to evaluate the interplay between the biosphere and secondary pollution (ozone and SOA formation and aging). The Brazilian Atlantic Forest (Mata Atlântica) is the target ecosystem as the fifth biodiversity hotspot in the world. Here we present the scientific motivations of the project, its methodology and the preliminary observations from the Special Observation Periods of year 2023 (SOP1, 2, 3 and 4). BIOMASP+ is (i) integrative, by combining in-situ/remote/laboratory observations andmodeling, (ii) multidisciplinary, addressing micrometeorology, urban climate, atmospheric chemistry and biology. The project involves multiple nested scales: from leaf to above-canopy levels, from very short time (microseconds) to multi-year scale, from few millimeters (turbulence scale) to synoptic scale. In particular, the experimental effort relies on the implementation of two contrasting supersites (primary forest and urban forest) with a 30-m and 20-m flux towers, respectively, and a variety of state-of-the-art instruments. Ambient observations and the quantification of BVOC emissions have highlighted the complex interactions between meteorology, atmospheric composition of pollution, biogenic emissions of representative remnants of the Atlantic Forest and anthropogenic emissions
Uptake of atmospheric pollutants on road asphalt pavements: an underestimated sink in urban environments
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Moving Vehicle Obstacle Pre-Detection with Telemetry Sensing Signal Prediction by Negative Group Delay Method
No full textInternational audienceThis article develops a vehicle-obstacle anti-collision system based on negative group delay (NGD) function. As theory, the anti-collision pre-detector design and implementation are described by exploiting the NGD time-advance ta to anticipate obstacle positioning relatively to a moving object and required safety distance. The NGD pre-detector design equation and methodology are formulated as function of ta. The NGD anti-collision system is validated with realistic demonstration constituted by a mini-vehicle equipped with a telemetry sensor moving along an 85-cm track towards an obstacle. NGD circuit implemented on microcontroller and Arduino UNO platform in good agreement with theory confirms obstacle pre-detection at 30-cm and 50-cm safety distances with ta={-0.1, -0.2, -0.3} seconds. The NGD anti-collision system has notable benefits as ta flexibility, low-power consumption, learning phase unnecessity and embedding simplicity. As future work, the NGD method will be integrated in anti-accident industrial systems by providing optimal safety distance allowing to react quickly and effectively to obstacle warnings by maximizing response time
Saturation-Based Adaptive Tracking Control of Underwater Vehicles: From Theoretical Design to Real-Time Experiments
No full textInternational audienceTracking control of an autonomous tethered underwater vehicle (ATUV) for a successful marine operation is a challenging task due to the complex and nonlinear dynamics of the vehicle characterized by parametric uncertainties. Besides these issues, the vehicle mainly operates in an uncertain and unpredictable environment. To deal with the ATUV control tracking problem, this article proposes a new tracking control approach that will be named saturation-based adaptive computed torque+ (SACT+). The proposed SACT+ is designed using a variable saturation function, a computed torque structure, a saturation-based dynamic feedback, and an adaptive mechanism. Then, several arguments, based on the well-known Lyapunov techniques, are proposed to prove the stability behavior of the final closed-loop dynamics. This ensures the convergence (theoretically) of the vehicle tracking error to the origin, leading to stable and safe operations. However, this tracking error (experimentally) only stays around the origin due to many factors, such as the measurement noise from the vehicle’s sensors, the inherent uncertainties of the vehicle combined with external disturbances from the marine environment, etc. Different tests are conducted in real-time using our underwater vehicle Leonard prototype to validate the proposed SACT+. The obtained experimental results show the effectiveness and robustness of the proposed SACT+ approach in real-life cases. Finally, the performance and energy consumption indices, as well as comparative experimental studies with two well-established controllers (from the literature), confirm the relevance of the proposed approach for controlling small-sized and/or low-cost underwater vehicles