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Quantitative Study of a Full-scale Pedaling Mannequin for Wind Tunnel Testing
No full textHuman subjects introduce variability in cycling wind tunnel testing due to slight inconsistencies in position and fatigue. To address these limitations, this study introduces a dynamic, full-scale pedaling mannequin, capable of generating repeatable and controlled pedaling movements.The study focuses on three main objectives: (1) validating the mannequin's kinematics by comparing its pedaling motion to an idealized mechanical model, (2) quantifying the dynamic forces generated by the mannequin during operation and assessing their impact on measurement stability, and (3) evaluating the variability of aerodynamic measurements across different pedaling cadences and wind speeds. Experiments were conducted in a low-turbulence wind tunnel, with kinematic analysis performed using computer vision and force measurements recorded at multiple cadences and wind speeds.Results demonstrate that the mannequin produces highly repeatable pedaling motions with a minimal and maximal standard deviation of 0.24 % and 0.88 % across all tested conditions. The smallest detectable meaningful power change in optimal conditions was 1.61 W at 50 km/h and at a pedaling frequency of 67 rotations per minute. Pedaling-induced forces were shown to influence the aerodynamic drag measurements, highlighting the importance of distinguishing dynamic and aerodynamic components of the force signal. These findings establish the mannequin as a reliable tool for controlled aerodynamic analysis, with applications in both scientific research and performance optimization in competitive cycling
Les fibres de lin: une solution alternative pour la réduction de la fissuration des mortiers de revêtement?
No full textInternational audienceLes fibres de lin: une solution alternative pour la réduction de la fissuration des mortiers de revêtement
A First Look at River Discharge Estimation From SWOT Satellite Observations
No full textInternational audienceThe Surface Water and Ocean Topography (SWOT) satellite has the potential to transform global hydrologic science by offering simultaneous and synoptic estimates of river discharge and other hydraulic variables. Discharge is estimated from SWOT observations of water surface elevation, width, and slope. A first assessment using just the highest quality SWOT measurements, over the first 15 months (March 2023–July 2024) of the mission evaluated at 65 gauged reaches shows results consistent with pre‐launch expectations. SWOT estimates track discharge dynamics without relying on any gauge information: median correlation is 0.73, with a correlation interquartile range of 0.51–0.89. SWOT estimates capture discharge magnitude correctly in some cases but are biased (median bias is 50%) in others. There are already a total of 11,274 ungauged global locations with highest quality SWOT measurements where SWOT discharge is expected to accurately track discharge variations: this value will increase as SWOT data record length grows, algorithms are refined and SWOT measurements are reprocessed. This first look indicates that SWOT discharge is performing as expected for SWOT data that achieve performance requirements, providing observed information on discharge variations in ungauged basins globally
The glycosomal ATP-dependent phosphofructokinase of Trypanosoma brucei operates also in the gluconeogenic direction.
No full textInternational audienceIn the glucose-free environment of the midgut of the tsetse fly vector, the procyclic forms of Trypanosoma brucei primarily consume proline to feed its central carbon and energy metabolism. In this context, the parasite produces through gluconeogenesis, glucose 6-phosphate (G6P), the precursor of essential metabolic pathways, from proline catabolism. We show here that the parasite uses three different enzymes to perform the key gluconeogenic reaction producing fructose 6-phosphate (F6P) from fructose 1,6-bisphosphate, (i) fructose-1,6-bisphosphatase (FBPase), the canonical enzyme performing this reaction, (ii) sedoheptulose-1,7-bisphosphatase (SBPase), and (iii) more surprisingly ATP-dependent phosphofructokinase (PFK), an enzyme considered to irreversibly catalyze the opposite reaction involved in glycolysis. These three enzymes, as well as six other glycolytic/gluconeogenic enzymes, are located in peroxisome-related organelles, named glycosomes. Incorporation of 13C-enriched glycerol (a more effective alternative to proline for monitoring gluconeogenic activity) into F6P and G6P was more affected in the PFK null mutant than in the FBPase null mutant, suggesting the PFK contributes at least as much as FBPase to gluconeogenesis. We also showed that glucose deprivation did not affect the quantities of PFK substrates and products, whereas an approximately 500-fold increase in the substrate/product ratio was expected for PFK to carry out the gluconeogenic reaction. In conclusion, we show for the first time that ATP-dependent PFK can function in vivo in the gluconeogenic direction, even in the presence of FBPase activity. This particular feature, which precludes loss of ATP through a futile cycle involving PFK and FBPase working simultaneously in the glycolytic and gluconeogenic directions, respectively, is possibly due to the supramolecular organization of the metabolic pathway within glycosomes to overcome thermodynamic barriers through metabolic channeling
Convergence rates for polynomial optimization on set products
No full text22 pagesInternational audienceWe consider polynomial optimization problems on Cartesian products of basic compact semialgebraic sets. The solution of such problems can be approximated as closely as desired by hierarchies of semidefinite programming relaxations, based on classical sums of squares certificates due to Putinar and Schm\"udgen. When the feasible set is the bi-sphere, i.e., the Cartesian product of two unit spheres, we show that the hierarchies based on the Schm\"udgen-type certificates converge to the global minimum of the objective polynomial at a rate in , where is the relaxation order. Our proof is based on the polynomial kernel method. We extend this result to arbitrary sphere products and give a general recipe to obtain convergence rates for polynomial optimization over products of distinct sets. Eventually, we rely on our results for the bi-sphere to analyze the speed of convergence of a semidefinite programming hierarchy approximating the order quantum Wasserstein distance
Green Aviation Manufacturing: Addressing Environmental Impacts with MDO Methodologies
No full textInternational audienceThe aeronautical industry faces increasing pressure to reduce its environmental footprint while meeting the growing demand for aircraft. Although the operational phase remains the most significant contributor to environmental impact, the manufacturing phase may gain prominence as aviation transitions to alternative fuels and innovative designs. This study addresses the need for sustainability in aircraft production by integrating environmental considerations into key stages of the aircraft lifecycle, particularly during preliminary design. The study evaluates aircraft mass and material composition using a bottom-up approach, considering buy-to-fly ratios, greenhouse gas emissions, energy consumption, and waste generation of the legacy aircraft. To mitigate environmental impact, this research explores a multi-objective optimization technique for selecting environmentally friendly material composition while maintaining performance standards. A key focus is the role of multidisciplinary design optimization (MDO) in balancing sustainability with functional and economic requirements during the overall aircraft design. Ultimately, this study highlights the need for introducing material composition selection as a new parameter within the classical MDAO framework.<br /
Exact algorithms in bar nesting: How to cut general items from linear stocks so that wastage is minimised
No full textInternational audienceThis paper proposes exact, polynomial-time algorithms that solve the problem of cutting items with angled sides from a single linear stock so that wastage is minimised. In industry, this problem is called ''bar nesting''. Here we give an algorithmic framework that solves several important variants of the problem, including cutting items from stocks with asymmetric cross-sections, cutting items whose sides occur on different planes, and the minimum score separation problem
Evaluation of the mechanical damage of recycled aggregate concrete by acoustic emission
No full textInternational audienceThe depletion of natural resources and the accumulation of construction and demolition waste have led the concrete industry to explore the use of recycled coarse aggregates (RCA) as a sustainable alternative to natural coarse aggregates (NCA). This paper presents an experimental investigation into the distinct and combined effects of two RCA granular classes, 4/8, 8/16, and their combination 4/16, on the concrete fracture process. Three-point bending tests, under crack mouth opening displacement (CMOD) control, are performed on concretes incorporating these RCA classes. Crack evolution is monitored using the acoustic emission (AE) technique. Recycled aggregate concretes (RAC) made with 100 % RCA of classes 4/8, 8/16, and 4/16 are compared with natural aggregate concrete (NAC) in terms of mechanical properties, fracture properties, acoustic activity, and characteristics of the fracture process zone (FPZ). The results show that the use of RCA of classes 4/8 and 8/16, either separately or in combination, achieves compressive and splitting tensile strengths comparable to those of NAC, despite higher porosity. However, this increased porosity reduces the modulus of elasticity of the RAC. The distinct use of these RCA classes maintains a fracture energy equivalent to that of NAC. However, their combination leads to a significant reduction in this energy. Furthermore, the separate use of RCA of classes 4/8 and 8/16 does not significantly impact the acoustic activity of RAC compared to NAC, while their combination generates an increase in this activity, indicating a more intense microcracking process, which aligns with the observed reduction in fracture energy. The incorporation of RCA, regardless of its class (4/8, 8/16, or 4/16), does not significantly influence the length of the FPZ but reduces its width. At the end of the test, the length of the FPZ of concrete with these RCA classes is approximately 67.78–68.44 mm (0.85 times the height of the ligament), and its width is about 26.33–27.66 mm (1.64–1.73 times the maximum size of the aggregates). The 4/16 class has a more pronounced impact on reducing the width of the FPZ of RAC than the 4/8 and 8/16 classes