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Towards standardisation of the out-of-plane permeability measurement for reinforcement textiles
No full textInternational audienceIn the collaborative effort towards standardisation of out-of-plane permeability measurement, an international benchmarking exercise was carried out whereby 19 participants worldwide were instructed to measure the out-of-plane permeability following a number of strict guidelines, informed by the outcomes of the first international benchmarking exercise completed in 2021. This paper presents the results of the exercise and an assessment of the reproducibility of the data and the suitability of the proposed test method. The data returned were subjected to a number of statistical analysis methods, which showed that adherence to the test guidelines resulted in a high likelihood of a participant not being an outlier and therefore providing evidence that the test method proposed in this paper is a suitable way forward for a standardised test method
Experimental study on flow and burning behaviors of pool fires under ventilation conditions inside an engine compartment
No full textInternational audienceDespite the considerable body of work on pool fires taking place in confined and mechanically ventilated environments, there are still important uncertainties in our comprehension of such phenomena and in our ability to forecast their behavior. In this context, experiments are carried out to investigate the impact of airflow velocity on the flow and thermal characteristics of a heptane pool fire in a full-scale engine compartment of an industrial vehicle. The particle image velocimetry (PIV) technique is employed across several areas of interest to investigate the effect of airflow velocities (0, 1.6, 3.2, and 6.4 m/s) on the flow properties in the flame’s neighborhood. An analysis of these zones can provide a representation of the global average velocity fields, which are not often documented in the existing literature for this type of enclosure. The burning characteristics, such as flame shape, mass loss, heat release rate, total heat flux, temperature profiles, and gaseous species concentrations, are investigated and compared among different ventilation conditions. The PIV results exhibit detailed flow structures around the flame in terms of direction and intensity. Vertical and horizontal velocity components are sensitive to changes in ventilation rate and the exhaust hood’s position. Experimental findings reveal the formation of a large corner vortex at low velocity magnitudes. Thomas’ predictions show reasonable agreement with flame height measurements compared to Heskestad’s correlation. A high ventilation rate can lead to a significant increase in both heat release rate and total heat flux. Increasing ventilation rates results in a more significant temperature decrease in the intermittent zone compared to the continuous flame zone. A high ventilation speed of 6.4 m/s does not decrease O concentration as expected, possibly due to the fan’s blowing effect and the dilution of fresh air with combustion product gases. This study enhances the physical understanding of fire behavior in ventilated engine compartments, leading to improved fire safety measures and the design of effective extinguishing systems
Impact of polymer binders on the aggregation modes of two-pieces CSH composites
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A European aerosol phenomenology – 9: Light absorption properties of carbonaceous aerosol particles across surface Europe
No full textInternational audienceCarbonaceous aerosols (CA), composed of black carbon (BC) and organic matter (OM), significantly impact the climate. Light absorption properties of CA, particularly of BC and brown carbon (BrC), are crucial due to their contribution to global and regional warming. We present the absorption properties of BC (b) and BrC (b) inferred using Aethalometer data from 44 European sites covering different environments (traffic (TR), urban (UB), suburban (SUB), regional background (RB) and mountain (M)). Absorption coefficients showed a clear relationship with station setting decreasing as follows: TR > UB > SUB > RB > M, with exceptions. The contribution of b to total absorption (b), i.e. %Abs, was lower at traffic sites (11–20 %), exceeding 30 % at some SUB and RB sites. Low AAE values were observed at TR sites, due to the dominance of internal combustion emissions, and at some remote RB/M sites, likely due to the lack of proximity to BrC sources, insufficient secondary processes generating BrC or the effect of photobleaching during transport. Higher bAbs and AAE were observed in Central/Eastern Europe compared to Western/Northern Europe, due to higher coal and biomass burning emissions in the east. Seasonal analysis showed increased b, b}_{Abs,BrC}_{BrC}_{Abs,BC}_{Abs,BrC}_{BrC}_{BrC}_{Abs,BrC}$ and AAE increased, suggesting a shift in CA composition, with a relative increase in BrC over BC. This study provides a unique dataset to assess the BrC effects on climate and confirms that BrC can contribute significantly to UV–VIS radiation presenting highly variable absorption properties in Europe
Multi-objective optimization for a composite pressure vessel with unequal polar openings
No full textInternational audienceMulti-objective parametric optimization problem is presented for overwrapped composite pressure vessels under internal pressure for storage and heating water. It is solved using the developed iterative optimization algorithm. Optimal values of design parameters for the vessel are obtained by varying the set of parameters for composite layers, such as the thickness of layers and radii of polar openings, which influence the distribution of fiber angles along the vessel. The suggested optimization methodology is based on the mechanical solution for composite vessels and the satisfaction of the main failure criteria. An innovative approach lies in the possibility of using the developed optimization methodology for designing vessels with non-symmetrical filament winding, which have unequal polar openings on the domes. This became possible due to the development of a special numerical mechanical finite element model of a composite vessel. A specific Python program provides the creation of a model and controls the exchange of data between the modules of the iterative optimization process. The numerical model includes the determination of the distribution of fiber angles on the domes and cylindrical part of the vessel as well as changes in layer thicknesses. The optimization problem solution is provided using a Multi-Island Genetic Algorithm, this type of method showed its efficiency for such applications, by allowing to avoid local solutions. Thus, optimal parameters of a composite vessel were found by minimizing composite mass and thickness and maximizing the strain energy. Test solutions using the developed methodology are presented for three types of composite materials to evaluate their possibility for integration into the vessel design model.</div
Sensors integration for structural health monitoring in composite pressure vessels: A review
No full textInternational audienceFilament-wound Composite Pressure Vessels (CPVs) are employed largely for gas or fluid storage under pressure in aerospace, automotive and naval industries. Composite vessels are subjected to harsh conditions such as critical loadings, extreme temperatures, and bursting; therefore, a permanent in-situ and online monitoring approach for the structural integrity of the vessels is essential. Hence, this review paper focuses on the description of the most trending used sensors such as piezoelectric (PZT and PVDF), piezoresistive (BP and MXene) and fiber optic (SOFO®, OBR and FBG) sensors, for developing a Structural Health Monitoring (SHM) approach to create self-sensing composite pressure vessels. The novelty of this review paper lies in providing an overview of existing works covering the integration of sensors in composite vessels, including sensor types, localization, and their impact on composite integrity. Particularly, an analysis of the literature is provided concerning the sensor's integration and especially their monitored parameters, layout design and arrangement in CPVs. Additionally, the interaction between the host composite material and sensors is analyzed to understand how to integrate sensors with the minimum possible defects that alter the mechanical performance of composite vessels. Lastly, a discussion of a CPV's SHM system is provided to offer researchers a foundation for upcoming experimental work.</div
Assessment of health effects of potato crop phytopharmaceuticals and storage products in a murine model
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High-performance pyramid solar still with hemispherical fins and parabolic collector: A numerical investigation for sustainable water desalination
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Organisations alternatives : faire face aux injonctions contradictoires
No full textInternational audienceSession thématique ouverte.Cette session vise à mettre en lumière et enrichir l’analyse des tensions contradictoires qui peuvent traverser les organisations dites « alternatives » (société à mission, entreprise de l’ESS, associations, etc.) : autonomie vs. contrôle, financiarisation vs. logique de long terme, réindustrialisation vs. concurrence des territoires, soutenabilité forte vs. greenwashing, etc.• Est-il possible de faire émerger une typologie de ces injonctions contradictoires ?• Quels outils conceptuels transdisciplinaires pour les éclairer ? Comment les tensions que l’on peut théoriser au niveau macro sont-elles concrètement vécues par les acteurs ?• Comment les organisations alternatives inventent de nouvelles pratiques pour y faire face
Formation and composition of organic aerosols from the uptake of glyoxal on natural mineral dust aerosols: a laboratory study
No full textInternational audienceThe uptake of glyoxal on realistic submicron mineral dust aerosol particles from a natural soil (Gobi Desert) is investigated during experiments in a large simulation chamber, under variable experimental conditions of relative humidity (RH), irradiation, and ozone concentrations. The uptake of glyoxal on the dust particles starts as soon as the glyoxal is injected into the chamber. At 80 % RH, the measured uptake coefficient of glyoxal on mineral dust is γ = (9±5) × 10−3. The totality of the mass of reacting glyoxal is transformed into organic matter on the surface of the dust particles. The uptake of glyoxal is accompanied by the appearance of marker peaks in the organic mass spectra and a persistent growth in the volume concentration of the dust particles. While the mass of the organic matter on the dust rapidly reverts to values prior to uptake, the organic composition of the dust is modified irreversibly. Glycolic and other organic acids, but also oligomers, are detected on the dust. At 80 % RH, compounds ranging from C4 to C10 are observed as oligomerization products of glyoxal mono- and di-hydrate forms. The study suggests that dust aerosols could play a very substantial role in the formation of organic aerosols at high RH, but also that the reaction could have potentially important implications for the dust optical and hygroscopic properties, including their pH