Portail HAL confremo Archives ouvertes du Moyen-Orient
Not a member yet
3450 research outputs found
Sort by
Mobility and phytoavailability of Cu, Cr, Zn, and As in a contaminated soil at a wood preservation site after 4 years of aided phytostabilization
No full textInternational audienceThe remediation of copper-contaminated soils by aided phytostabilisation in 16 field plots at a wood preservation site was investigated. The mobility and bioavailability of four potentially toxic trace elements (PTTE), i.e., Cu, Zn, Cr, and As, were investigated in these soils 4 years after the incorporation of compost (OM, 5 % w/w) and dolomite limestone (DL, 0.2 % w/w), singly and in combination (OMDL), and the transplantation of mycorrhizal poplar and willows. Topsoil samples were collected in all field plots and potted in the laboratory. Total PTTE concentrations were determined in soil pore water (SPW) collected by Rhizon soil moisture samplers. Soil exposure intensity was assessed by Chelex100-DGT (diffusive gradient in thin films) probes. The PTTE phytoavailability was characterized by growing dwarf beans on potted soils and analyzing their foliar PTTE concentrations. OM and DL, singly and in combination (OMDL), were effective to decrease foliar Cu, Cr, Zn, and As concentrations of beans, the lowest values being numerically for the OM plants. The soil treatments did not reduce the Cu and Zn mineral masses of the bean primary leaves, but those of Cr and As decreased for the OM and DL plants. The Cu concentration in SPW was increased in the OM soil and remained unchanged in the DL and OMDL soils. The available Cu measured by DGT used to assess the soil exposure intensity correlated with the foliar Cu concentration. The Zn concentrations in SPW were reduced in the DL soil. All amendments increased As in the SPW. Based on DGT data, Cu availability was reduced in both OM and OMDL soils, while DL was the most effective to decrease soil Zn availability
Determination of wind turbine far wake using actuator disk
No full textInternational audienceThe growth in size of wind turbines over the last years is significant. The rotor diameter becomes somehow comparable to atmospheric boundary layer at the land surface. In this case the assumption of uniform velocity of upcoming wind cannot be valid. The aim of this paper is to create a simplified model of wind turbine rotor which can represent the aerodynamic inter-action of atmospheric boundary layer with a horizontal axis wind turbine. Such model will be also useful for the study of optimal placement of wind turbines in a wind farm when a large number of calculations is needed and when the time required for full CFD calculations be-comes prohibitive. In this study we adopt actuator disk model which takes in account with sufficient precision the influence of blade geometry on wind turbine aerodynamic performance. The proposed actuator disk model is tested in the case of horizontal axis wind turbine using wall-modelled large eddy simulation. The obtained results of aerodynamic performance and wake show the rapidity of calculation and the reliability of proposed approach
A link between hepatic glucose production and peripheral energy metabolism via hepatokines.
No full textInternational audienceABSTRACTType 2 diabetes is characterized by a deterioration of glucose tolerance, which associates insulinresistance of glucose uptake by peripheral tissues and increased endogenous glucose production.Here we report that the specific suppression of hepatic glucose production positively modulateswhole-body glucose and energy metabolism. We used mice deficient in liver glucose-6 phosphatasethat is mandatory for endogenous glucose production. When they were fed a high fat/high sucrosediet, they resisted the development of diabetes and obesity due to the activation of peripheralglucose metabolism and thermogenesis. This was linked to the secretion of hepatic hormones likefibroblast growth factor 21 and angiopoietin-like factor 6. Interestingly, the deletion of hepaticglucose-6 phosphatase in previously obese and insulin-resistant mice resulted in the rapidrestoration of glucose and body weight controls. Therefore, hepatic glucose production is anessential lever for the control of whole-body energy metabolism during the development of obesityand diabetes
Effect of organic amendments on the mobility of trace elements in phytoremediated techno-soils: role of the humic substances
No full textInternational audienceThe efficiency of aided phytostabilization using organic amendments such as ramial chipped wood (RCW) and composted sewage sludge (CSS) was studied on contaminated techno-soils, on nine experimental plots. The objective was to characterize the role of fulvic (FA) and humic acids (HA) on the mobilization of trace elements, specifically As, Cu, Mo, Pb and Zn. Results showed that the addition of CSS increased the total organic carbon and nitrogen content more than with RCW and as a result, the C/N ratio in the CSS soil was higher than in the RCW and non-amended (NE) soil, reflecting the high decomposition of soil organic matter in the CSS soil compared with the other soils. The RCW and CSS amendments increased the hydrogen index (HI) values and the oxygen index (OI) values compared with the NE soil, especially for the soil treated with CSS which contained more aliphatic than aromatic compounds. The addition of CSS to the techno-soil significantly increased the percentage of C org associated with the HA fractions compared with the RCW and NE soils. The soil amended with CSS showed the highest E 4/E 6 ratio and the lowest E 2/E 3 ratio of FA. Zn and As were more abundant in the FA fraction than in the HA fraction, whereas Pb, Cu and Mo were more associated to HA than to FA in the treated and untreated soils, which may explain the difference in their mobility and availability
Oxidative solution polymerization of aniline hydrochloride onto electrospun nanofibers mats of polylactic acid: Preparation method and characterization
No full textInternational audienceIn this work, we present the preparation of polylactic acid (PLLA)/polyaniline (PANI) conductive composite nanofibers mats. They are prepared by bulk oxidative solution polymerization of PANI onto electrospun non-woven fibers mats of PLLA. The PANI ratio in the composite is about 70%w/w. Scanning electron microscopy (SEM) shows that PLLA nanofibers are randomly oriented, beads free with diameters of 186 ± 85 nm, The PLLA/PANI composite nanofibers diameter values are 518 ± 128 nm with a good adherence between PANI and PLLA nanofibers. DSC and XRD measurements reveal an amorphous structure of the electrospun PLLA fibers due to the rapid evaporization of the solvent. FTIR and UV-vis spectra reflect good mutual interactions between PANI and PLLA chains. The DC-conductivities (σ=0.07-0.13-S.cm-1) far better than other published ones for similar composites prepared by bulk oxidative solution polymerization of PANI onto other electrospun nanofiber mats or with electrospun nanofibers from a solution mixture of PLLA and PANI
Une approche géométrique de la dégradation des modules PV
No full textInternational audienceThis paper presents an overview of two degradation modes of PV panels: the Moisture Induced Degradation and the Cell Cracks. The two mentioned degradation modes affect PV cells differently according to their position in the module. At a previous stage, we have build a PV model that takes into consideration three degradation modes, the Potential Induced Degradation, the Light Induced Degradation, and the Ultraviolet Light Degradation. In this paper, we update our model to take into consideration all degradation modes.Cet article présente un aperçu des deux modes de dégradation de panneaux photovoltaïques: la dégradation induite par l'humidité et les fissures de la cellule. Les deux modes de dégradation mentionnés affectent les cellules photovoltaïques différemment en fonction de leur position dans le module. Lors d'une étape précédente, nous avons construit un modèle de PV qui prend en compte trois modes de dégradation, le potentiel induit la dégradation, la lumière induit la dégradation, et la dégradation Lumière ultraviolette. Dans cet article, nous mettons à jour notre modèle à prendre en considération tous les modes de dégradation
Contribution à la modélisation des effets du vieillissement des cellules et modules PV
No full textInternational audienceIn this paper, we present an overview of three degradation modes: the Potential Induced Degradation, the Light Induced Degradation, and the Ultraviolet Light Degradation. Then we develop a mathematical model that describes the latter degradation modes in order to evaluate the lifetime of PV (photovoltaic) modules. At the end we simulate the efficiency of a PV module as a function of time where the three degradation modes are taken into consideration.Dans cet article, nous présentons un aperçu des trois modes de dégradation: le potentiel induit la dégradation, la dégradation induite par la Lumière, et la dégradation par la Lumière ultraviolette. Ensuite, nous développons un modèle mathématique qui décrit les derniers modes de dégradation afin d'évaluer la durée de vie des modules photovoltaïques . A la fin on simule l'efficacité d'un module PV en fonction du temps lorsque les trois modes de dégradation sont pris en considération
Vibration Amplitude - Dependent Natural Frequency and Damping Ratio of Repaired Pier Model
No full textInternational audienceThe present work aims to investigate the dependency of dynamic characteristics such as the natural frequency and the damping ratio of pier model on the vibration amplitude under a series of different vibration levels. Several free vibration tests with a wide range of amplitudes were, therefore, carried out under excitation with relatively small amplitude levels. The pier model was subjected to a progressive damage by conducting a shaking table test to study the influence of different damage scenarios on its dynamic characteristics. After the damage occurs at the plastic hinge zone of the pier model, free vibration tests with different amplitude excitation were carried out to derive the dynamic characteristics of the damaged pier model. Furthermore, after the damage of the pier model was repaired by carbon fiber sheets (CFS) jacketing, free vibration test was carried out again, to derive the dynamic characteristics of the repaired pier model. Generally, this study indicates that overall natural frequency and damping ratio are very sensitive to vibration amplitude level. Particularly, whenever the acceleration amplitude increases, damping ratio significantly increases while natural frequency slightly decreases. Also, the repairing method by CFS proved to be effective in restoring performance characteristics of damaged pier
Conception d'un réseau de capteurs acoustiques passifs pour un contrôle - santé intégré basse consommation et non - intrusif des structures aéronautiques et conduites de transport de fluides
No full textLa corrélation d'un champ acoustique permet de caractériser un milieu de façon passive, cette étude a commencé à se développer depuis plusieurs années dans différentes applications de contrôle santé intégré (CSI). Une brève explication d'une étude faite précédemment pour la détection des endommagements dans une structure sera donnée puis une nouvelle méthode permettant de tester le degré de ressemblance entre les images temps-fréquence sera donnée. D'autre part, des résultats expérimentaux seront illustrés pour montrer le lien qui existe entre la corrélation et la fonction de Green
Fatigue strength assessment of tubular welded joints by an alternative structural stress approach
No full textWOSInternational audienceThe tubular joints, frequently employed in the offshore industry, are submitted to stresses resulting from elementary loadings: tension/compression, in-plane bending and out-of-plane bending. This work concerns the analysis of the recommendations commonly used for the fatigue design of welded joints submitted to combined loadings. Particularly, it deals with the fatigue behaviour of T-joints submitted to deviated-bending: first, a finite element analysis was developed and a post-processing based on the structural stress approach, as proposed by the International Institute of Welding (IIW). Then, fatigue tests were conducted on T-joints submitted to deviated-bending. Comparisons between experimental and numerical results showed that this kind of recommendations is not systematically conservative. Thus, an alternative approach based on structural stresses and taking into account the multi-axial stress state in the weld toe was developed in order to complete the recommendations for the fatigue design of tubular welded joints