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Zri A.,University of Lille Nord de France | Abriak N.-E.,EMDouai | Zentar R.,EMDouai
European Journal of Environmental and Civil Engineering | Year: 2011

In a context of sustainable development, the management of sediment depends on their potential to induce pollution. The old management techniques used as immersion in the sea by overfflow, dumping or storage is restricted due to regulation which is increasingly rigid in terms of environmental protection. The new trend of all actors in the field of sediment management is moving ineluctably towards an alternative solution as the valorisation of the sediments as. Any valorisation requires a stage of characterisation in order to enhance the knowledge about the material: its various components, its potential to induce pollution and its mechanical behaviour. Our work consists, on the one hand, in carrying out a comparative study of mechanical and physical behaviours, between polluted and unpolluted sediment and on the other hand, to underline the evolution of the behaviour of polluted sediment following a lime treatment. The sediment in question is considered as a raw material as it has not been subject to any process of pre-treatment. © 2011 Taylor & Francis Group, LLC.

Huguet S.,Joseph Fourier University | Huguet S.,INERIS | Huguet S.,Center National Of Recherche Sur Les Sites Et Sols Pollues | Huguet S.,University of Pau and Pays de l'Adour | And 11 more authors.
Environmental and Experimental Botany | Year: 2012

Arabidopsis halleri is a model plant investigated for Zn and Cd hyperaccumulation. In this work, A. halleri plants from metallicolous origin exposed to Cd and Zn were studied using an original combination of chemical and physical techniques to obtain insights on Cd hyperaccumulation mechanisms. In most cases, Zn and Cd accumulation in leaves increased with time and with their respective concentrations in hydroponics. At the rosette scale, 109Cd autoradiography showed that the amount of Cd increased with time but there was no clear trend in the localization of Cd in young or mature leaves. At the leaf scale, an enrichment of the petiole, central vein and trichomes was observed after 3 weeks. After 9 weeks, leaf edges were the most Cd-enriched tissues, and regions along leaf vascular bundles appeared less concentrated. Bulk Cd K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy showed that Cd was predominantly bound to COOH/OH groups belonging to organic acids and/or cell wall components. Cd bound to thiol groups was found as a secondary species (less than 25%). Thiols ligands might correspond, at least partly, to glutathione found in significant amount in aerial parts, but phytochelatins were not detected. These results show that the mechanisms of Cd storage and detoxification in A. halleri differ from what was previously found for Zn. © 2012 Elsevier B.V..

Chicot D.,University of Lille Nord de France | De Baets P.,Ghent University | Staia M.H.,Ghent University | Staia M.H.,Central University of Venezuela | And 6 more authors.
International Journal of Refractory Metals and Hard Materials | Year: 2013

Instrumented indentation is very useful to determine the elastic modulus and hardness of materials. To obtain reliable values of the mechanical properties, the measurement of the indenter displacement into the material must be very precise. In practice, the frame compliance of the instrument and the indenter tip defect are among the most influential parameters. In microindentation, the frame compliance term must be calculated for each analysis. On the other hand, the tip defect can lead to a wrong estimation of the contact area, which is involved in both the elastic modulus and the hardness calculations. The present work is mainly focused on the influence of the tip defect on the determination of the mechanical properties of a composite TiB 2-60% B4C hard material using Berkovich, Vickers, Knoop and spherical indenters. This composite system was obtained by sintering in vacuum, employing a pulsed electric current, without any sintering additives. It has been shown that the tip defect greatly affects the results related to the mechanical properties of the system under study, even for low defect sizes, which are usually neglected in practice. After correction, the elastic modulus of the TiB2-60% B4C is found to be equal to 490 GPa whatever the indenter shape used. This result corroborates the value of 500 GPa found for this system by employing the resonance frequency method according to the ASTM Standard e1876-99. For analyzing the hardness-load dependence, the representative parameter of the Proportional Specimen Resistance model becomes null when the tip defect is introduced into the hardness calculation. Additionally, this parameter is found to be directly proportional to the tip defect size, suggesting a special attention when characterizing the indentation size effect of materials. Finally, the Meyer hardness found for the TiB 2-60% B4C is close to 20 GPa. © 2013 Elsevier Ltd.

Hemmouche L.,Polytechnic School of Algiers | Chicot D.,Lille Laboratory of Mechanics | Amrouche A.,CNRS Civil and geo-Environmental Engineering Laboratory | Iost A.,Arts et Metiers ParisTech | And 6 more authors.
Materials Science and Engineering A | Year: 2013

The elastic modulus of thin films can be directly determined by instrumented indentation when the indenter penetration does not exceed a fraction of the film thickness, depending on the mechanical properties of both film and substrate. When it is not possible, application of models for separating the contribution of the substrate is necessary. In this work, the robustness of several models is analyzed in the case of the elastic modulus determination of a porous aluminium oxide film produced by anodization of an aluminium alloy. Instrumented indentation tests employing a Berkovich indenter were performed at a nanometric scale, which allowed a direct determination of the film elastic modulus, whose value was found to be approximately 11. GPa. However, at a micrometric scale the elastic modulus tends toward the value corresponding to the substrate, of approximately 73. GPa. The objective of the present work is to apply different models for testing their consistency over the complete set of indentation data obtained from both classical tests in microindentation and the continuous stiffness measurement mode in nanoindentation. This approach shows the continuity between the two scales of measurement thus allowing a better representation of the elastic modulus variation between two limits corresponding to the substrate and film elastic moduli. Gao's function proved to be the best to represent the elastic modulus variation. © 2013 Elsevier B.V.

PubMed | Synchrotron Soleil, INERIS, EMDouai, French National Center for Scientific Research and University of Pau and Pays de l'Adour
Type: | Journal: The Science of the total environment | Year: 2015

In regions impacted by mining and smelting activities, dredged sediments are often contaminated with metals. Phytotechnologies could be used for their management, but more knowledge on the speciation of metals in the sediment and on their fate after colonization by plant roots is needed. This work was focused on a dredged sediment from the Scarpe river (North of France), contaminated with Zn and Cd. Zn, Cd hyperaccumulating plants Arabidopsis halleri from metallicolous and non-metallicolous origin were grown on the sediment for five months in a pot experiment. The nature and extent of the modifications in Cd speciation with or without plant were determined by electron microscopy, micro X-ray fluorescence and bulk and micro X-ray absorption spectroscopy. In addition, changes in Cd exchangeable and bioavailable pools were evaluated, and Cd content in leachates was measured. Finally, Cd plant uptake and plant growth parameters were monitored. In the original sediment, Cd was present as a mixed Zn, Cd, Fe sulfide. After five months, although pots still contained reduced sulfur, Cd-bearing sulfides were totally oxidized in vegetated pots, whereas a minor fraction (8%) was still present in non-vegetated ones. Secondary species included Cd bound to O-containing groups of organic matter and Cd phosphates. Cd exchangeability and bioavailability were relatively low and did not increase during changes in Cd speciation, suggesting that Cd released by sulfide oxidation was readily taken up with strong interactions with organic matter and phosphate ligands. Thus, the composition of the sediment, the oxic conditions and the rhizospheric activity (regardless of the plant origin) created favorable conditions for Cd stabilization. However, it should be kept in mind that returning to anoxic conditions may change Cd speciation, so the species formed cannot be considered as stable on the long term.

Habchi C.,EMDouai | Habchi C.,Lebanese International University | Russeil S.,EMDouai | Russeil S.,University of Lille Nord de France | And 7 more authors.
Applied Thermal Engineering | Year: 2012

Global and local analysis of the heat transfer in turbulent vortical flows is studied using three-dimensional numerical simulations. Vorticity is generated by inclined vortex generators in a turbulent circular pipe flow with twelve different configurations that fall into three categories. In the first category are rows of trapezoidal vortex generators in different arrangements; in the second category the vortex generators are fixed at certain distance from the tube wall, and the third category has vortex generator rows between which a row of small protrusions are inserted on the tube wall. First, a global analysis of the thermal performance is performed for all these configurations, which are also compared with other heat exchangers from the literature. New correlations for the friction factor and Nusselt number are then obtained. Local analysis of the effect of the flow structure on the temperature distribution is carried out for the four configurations showing the best performances. The local analysis involves studying the streamwise vorticity flux to characterize the convective transport process, the turbulent kinetic energy characterizing the turbulent mixing, and finally the local Nusselt number. © 2012 Elsevier Ltd. All rights reserved.

Habchi C.,EMDouai | Habchi C.,Lebanese International University | Russeil S.,EMDouai | Russeil S.,University of Lille Nord de France | And 9 more authors.
Computers and Fluids | Year: 2013

In this work a fluid-structure interaction solver is developed in a partitioned approach using block Gauss-Seidel implicit scheme. Finite volume method is used to discretize the fluid flow problem on a moving mesh in an arbitrary Lagrangian-Eulerian formulation and by using an adaptive time step. The pressure-velocity coupling is performed by using the PIMPLE algorithm, a combination of both SIMPLE and PISO algorithms, which permits the use of larger time steps in a moving mesh. The structural elastic deformation is analyzed in a Lagrangian formulation using the St. Venant-Kirchhoff constitutive law, for non-linear large deformations. The solid structure is discretized by the finite volume method in an iterative segregated approach. The automatic mesh motion solver is based on Laplace smoothing equation with variable mesh diffusion. The strong coupling between the different solvers and the equilibrium on the fluid-structure interface are achieved by using an iterative implicit fixed-point algorithm with dynamic Aitken's relaxation method. The solver, which is called vorflexFoam, is developed using the open source C++ library OpenFOAM. The solver is validated on two different benchmarks largely used in the open literature. In the first one the structural deformation is induced by incompressibility. The second benchmark consists on a vortex excited elastic flap in a Von Karman vortex street. Finally, a more complex case is studied including two elastic flaps immersed in a pulsatile flow. The present solver detects accurately the interaction between the complex flow structures generated by the flaps and the effect of the flaps oscillations between each other. © 2012 Elsevier Ltd.

Bako L.,University of Lille Nord de France | Lecoeuche S.,EMDouai
Systems and Control Letters | Year: 2013

A new continuous state observer is derived for discrete-time linear switched systems under the assumptions that neither the continuous state nor the discrete state are known. A specificity of the proposed observer is that, in contrast to the state of the art, it does not require an explicit prior estimation of the discrete state. The key idea of the method consists in minimizing a non-smooth ℓ2-norm-based weighted cost functional, constructed from the matrices of all the subsystems regardless of when each of them is active. In the light of recent development in the literature of compressed sensing, the minimized cost functional has the ability to promote sparsity in a way that makes the knowledge of the discrete mode sequence unnecessary. © 2012 Elsevier B.V. All rights reserved.

Gineys N.,University of Lille Nord de France | Aouad G.,EMDouai | Damidot D.,University of Lille Nord de France
Cement and Concrete Composites | Year: 2011

This study compares two methods to immobilise the same amount of Zn in cement paste. In the first method, Zn is introduced into the raw material before clinkerisation, whereas in the second process, Zn is introduced in the liquid phase used to make the cement paste, which is often referred to as solidification/stabilisation. In laboratory-made clinker, Zn was mainly fixed within a new compound (Ca6Zn3Al4O 15). Also, Zn was observed in tricalcium silicate (C3S) and in the interstitial phase (C3A and C4AF) with the exception of dicalcium silicate (C2S). In the present study, the threshold limit value corresponds to the maximum amount of Zn that could be incorporated without the stability of the clinker phases being modified. This threshold was reached when a decrease in C3A content and/or the presence of Ca6Zn3Al4O15 were observed by X-ray diffraction. The threshold limit of Zn in the studied clinker was established at 0.7% by weight. The reactivity of synthesised cement doped with Zn was studied by isothermal calorimetry measurements. These tests revealed that the incorporation of Zn had no effect on calcium silicate hydration (C3S and C2S), even if the Zn content exceeded the threshold limit value, i.e., 1%. These results were compared with those obtained through the solidification/stabilisation treatment of Zn in a cement paste. In these experiments, a Zn content of 0.7% induced a significant delay in the cement hydration. This difference in behaviour is due to the slower flow of zinc ions released in solution when it is incorporated in the clinker phases. Thus, the immobilisation during clinkerisation is a good alternative to treat waste with a high Zn content in Ordinary Portland Cement (OPC) without causing the well-known, deleterious effect on cement setting time. © 2011 Elsevier Ltd. All rights reserved.

Bako L.,University of Lille Nord de France | Lecoeuche S.,EMDouai
Proceedings of the IEEE Conference on Decision and Control | Year: 2011

A new continuous state observer is derived for discrete-time linear switched systems under the assumptions that neither the continuous state nor the discrete state are known. A specificity of the proposed observer is that, contrary to the state-of-art, it does not require an explicit estimation of the discrete state. The key idea of the method consists in minimizing a non-smooth l 2-norm-based weighted cost functional, constructed from the matrices of all the subsystems regardless of when each of them is active. In the light of some recent development in the literature of compressed sensing, the minimized cost functional has the ability to promote sparsity in a way that makes prior knowledge/estimation of the discrete mode sequence unnecessary. © 2011 IEEE.

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