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Enhancing the accuracy of thermal conductivity measurements with insulating construction materials: Addressing edge effects and methodological improvements
No full textInternational audienceAccurate and reliable thermal conductivity measurements are essential for evaluating the insulation properties of materials used in construction. Traditional insulating materials like glass or rock wool, or more recently developed biobased materials such as hemp wool, cellulose, flax or wood fiber panels, have very low thermal conductivity influenced by density, porosity, and temperature. However, edge effects often compromise the reliability of measurements, especially for low-conductivity materials. This study revisits the standard measurement technique with a heat flow meter proposing a refined methodology to minimize edge effects. We first show that the standard procedure based on a preliminary calibration of the heat flow meter apparatus on a reference sample to mitigate edge effects must be used with great care as it can afterwards lead to significant error on tested samples. With a model (cellulosic) material we then study systematically how the sample thickness and the temperature difference between sample and ambient air can impact measurements. In particular we show that the material anisotropy can significantly enhance edge effects, and in some cases edge effects are so large that the heat flux along one plate is negative. The analysis is completed by numerical simulations and measurements of the temperature distribution inside the sample. This work finally allows to establish the optimal thermal conductivity testing conditions for insulating materials
Permeability of foam-filled granular packing: Numerical modeling
No full textInternational audienceIn recent experiments [M. Ceccaldi et al., Phys. Rev. Fluids 8, 024302 (2023); 9, 074003 (2024)], it was shown that the permeability of foam-filled granular packings is strongly influenced by the ratio of bubble size to grain size. This effect appears to be primarily driven by geometric factors and is independent of interfacial mobility. It was suggested that the liquid from the foam introduced into a granular medium redistributes toward the grain surfaces and the contact points between grains, contributing to the drying of the foam and significantly reducing its hydraulic permeability. To investigate this phenomenon in detail, we developed a numerical model of foam within a granular medium, which describes the liquid distribution within the pores and allows to calculate the liquid permeability. This model offers improved predictions of liquid redistribution compared to existing analyticalmodels and closely matches permeability measurements.Moreover, our results quantify the contributions to permeability of all liquid components formed within the pores, particularly bulk and wall foam liquid channels
Design Optimization and Rheological Property of Recyclable Epoxy Asphalt
No full textInternational audienceEpoxy asphalt serves as a vital material in infrastructure construction; however, its inefficient regeneration process hampers broader adoption. To overcome this challenge, the concept of recyclable epoxy asphalt, harnessing the reversibility of dynamic covalent bonds, has been introduced. In prior research, we successfully developed and validated recyclable epoxy asphalt incorporating Diels–Alder reaction bonds. This study focuses on enhancing performance through design optimization and rheological property assessment of recyclable epoxy asphalt. By employing response surface methodology, 13 distinct compositions varying two parameters and evaluating three mechanical properties were devised to determine the optimal material formulation for recyclable epoxy asphalt. Subsequently, the recyclable epoxy asphalt underwent controlled aging and regeneration processes. Finally, the study evaluated the chemical composition and rheological properties of recyclable epoxy asphalt before and after regeneration. The optimization procedure identified the ideal composition of recyclable epoxy asphalt as 54% asphalt, 15% epoxy monomer, and 31% curing agent. The durability of the Diels–Alder reaction bonds’ reversibility under prolonged use is pivotal to the regeneration process. Rheological analysis suggests that moderate use enhances the performance of recyclable epoxy asphalt, with partial recovery achievable through the regeneration process. The preparation-aging-regeneration cycle underscores the practicality of recyclable epoxy asphalt, offering substantial environmental benefits and promising future applications
Global solutions and uniform convergence stability for compressible Navier-Stokes equations with oldroyd-type constitutive law
No full textWe consider one dimensional isentropic compressible Navier-Stokes equations withOldroyd-type constitutive law. By establishing uniform a priori estimates (with respect to relaxation time), we show global existence of smooth solutions with small initial data. Moreover, we get global-in-time convergence of the system towards the classical isentropic compressible Navier-Stokes equations
The MMX InfraRed Spectrometer (MIRS) for the spectral characterization of the Martian system
No full textInternational audienceMIRS (MMX InfraRed Spectrometer) is a push-broom imaging spectrometer onboard of the JAXA sample return MMX mission. It has been built by the French laboratory LESIA, today LIRA (Laboratory for Instrumentation and Research in Astrophysics) of Paris Observatory-PSL in collaboration with five other French laboratories, collaboration and financial support of CNES and close collaboration with JAXA and MELCO. MIRS, designed to accomplish the MMX scientific objectives, has been built to be adapted on MMX Exploration Module. MIRS will remotely observe the Martian system for three years. MIRS will observe Phobos, Deimos and Mars in the spectral range 0.9-3.6 µm to characterize surface composition of the satellites and investigate Martian atmospheric variations
Application of Universal Multifractal framework on data collected from an off-shore wind farm
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Heuristic universality detection over regular expressions specified by systems
No full textInternational audienceIn this article, we provide a computational approach for evaluating the expressivity of systems of equations for generating random regular expressions. More concretely, we obtain bounds on the proportion of universal expressions these systems produce. These bounds rely on the heuristic proposed by Koechlin et al., 2021, extended here to more general systems of several equations, which are harder to analyze. We have developed a tool that enables one to automatically test many of them. We discuss the results obtained for several systems from the literature
Les microplastiques dans les sols selon les pratiques agricoles dans un bassin versant français
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Using Wastewater to Monitor Suggested Changes in Dietary Intake: A Participatory Experiment
No full textInternational audienceThis study aimed to assess the feasibility of a participatory experiment involving residents of a Paris district, in which their dietary habits were monitored through the analysis of chemicals in wastewater. Unlike conventional sociological metrics, wastewater can be used to monitor the behavior of the entire population, regardless their participation, with an almost 100% response rate. The results revealed changes in the chemistry of wastewater during the experimental week, when residents were encouraged to consume "more fruits and vegetables”. A key challenge lies in understanding the possible influence of confounding factors that could affect the chemical dynamics and thus impact the results. These factors were also evaluated. For the first time, wastewater has demonstrated its potential as a monitoring medium for participatory experiments addressing issues of diet and health, which are critical components in shaping the trajectory of sustainable urban living for the future
DIM PAMIR Patrimoines matériels -innovation, expérimentation et résilience Charte de réutilisation des données du projet MIAM
No full textInternational audienceThe preservation of built cultural heritage in an urban area is a socio-economic challenge for municipalities. During their lifetime, buildings out of stone are exposed to chemical and biological actions that lead to different alteration patterns. In order to evaluate the treatments developed in the laboratory by the ICMPE team, under controlled and real conditions. The polymers will be applied to healthy coupons in the presence of microbial communities in the laboratory under controlled conditions as well as on the roof of UPEC. The application of treatments will take place in real conditions at Père Lachaise Cemetery on pre-aged coupons as well as on graves (in agreement with the cemetery manager). This would make it possible to see the curative effect and preventive effect of the treatments developed in the laboratory and its effectiveness on the different microbial communities (bacteria, fungi and microalgae). The safety of the treatments on the material as well as on the surrounding environment will be evaluated.La préservation du patrimoine culturel bâti en zone urbaine est un défi socio-économique. Durant leur vie, les bâtiments en pierre sont exposés à des actions chimiques et biologiques qui conduisent à différents faciès d’altération. Afin d’évaluer les traitements développés au laboratoire par l’équipe ICMPE, en conditions contrôlées et réelles. Les polymères seront appliqués sur des coupons sains en présence de communautés microbiennes au laboratoire en conditions contrôlées ainsi que sur le toit de l’UPEC. L’application des traitements aura lieu en conditions réelles au cimetière Père Lachaise sur des coupons pré-vieillis ainsi que sur des tombes (en accord avec le gestionnaire du Cimetière). Cela permettrait de voir l’effet curatif et l’effet préventif des traitements développés au laboratoire et son efficacité sur les différentes communautés microbiennes (Bactéries, champignons et micro-algues). L’innocuité des traitements sur le matériau ainsi que sur le milieu environnant sera évalué