Gafsa, Tunisia
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Hentati H.,University of Sfax | Abdelmoula R.,University of Paris 13 | Maalej A.,University of Sfax | Maalej K.,Groupe Chimique Tunisien
Applied Mechanics and Materials | Year: 2012

Fracture mechanics has been revisited by proposing different models of quasi static brittle fracture. In this work, the problem of the quasi static crack propagation is based on variational approach. It requires no prior knowledge of the crack path or of its topology. Moreover, it is capable of modeling crack initiation. In the numerical experiments, we use a standard linear (P1) Lagrange finite element method for discretization. We perform numerical simulations of a piece of brittle material without initial crack. An alternate minimizations algorithm is used. Based on these numerical results, we determine the influence of numerical parameters on the evolution of energies and crack propagation. We show also the necessity of considering the kinetic term and the crack propagation becomes dynamic. © (2012) Trans Tech Publications, Switzerland.


Hentati H.,University of Sfax | Abdelmoula R.,University of Paris 13 | Maalej A.,University of Sfax | Maalej K.,Groupe Chimique Tunisien
Applied Mechanics and Materials | Year: 2012

Fracture mechanics has been revisited aimed at modeling brittle fracture based on Griffith viewpoint. The purpose of this work is to present a numerical computational method for solving the quasi static crack propagation based on the variational theory. It requires no prior knowledge of the crack path or of its topology. Moreover, it is capable of modeling crack initiation. At the numerical level, we use a standard linear (P1) Lagrange finite element method for space discretization. We perform numerical simulations of a piece of brittle material without initial crack. We show also the necessity of adding the backtracking algorithm to alternate minimizations algorithm to ensure the convergence of the alternate minimizations algorithm to a global minimizer. © (2012) Trans Tech Publications, Switzerland.


Trab S.,Research Unit MACS | Bajic E.,University of Lorraine | Zouinkhi A.,Research Unit MACS | Abdelkrim M.N.,Research Unit MACS | And 2 more authors.
Procedia Computer Science | Year: 2015

One of the most relevant topics in warehouse management system (WMS) is the security issue and concerns the optimal placement allocation of products with respect of product and human safety in a sustainable system. Knowing that differences often exist between virtual view of products placements in centralized WMS and the real situation in the facility due to unplanned movements resulting from human errors or products' misplacements, we propose a reactive and compatibility constraint approach for product storage allocation. Our aim is to reduce the size of floating locations largely used in WMS and to avoid the inherent risks of hazardous accidents which can be generated by incompatibility between products and then to minimize the total logistic costs and to guarantee higher warehousing service levels in a safety monitored environment. This work proposes a multi-agent architecture for product allocation planning with compatibility constraints (PAP/CC), which uses a decision mechanism for product's placement, based on negotiations between agents associated to compatibility tests. This approach represents an improvement key for decentralized management of warehouses in a dynamic and reactive environment. Negotiations mechanisms relying on an Internet of Things (IoT) infrastructure and multi agent systems are defined in order to solve security problem of product allocation operations. Industrial deployment of IoT platform represents an ideal solution for decentralized management and to support collaboration between products and shelves. A simulation case of the proposed interactions mechanisms is provided with the use of NetLogo environment which offers many advantages to control agents and to describe their interactions in a graphical environment. © 2015 The Authors.


Louhichi S.,University of Sfax | Ghorbel A.,University of Monastir | Chekir H.,Groupe chimique Tunisien | Trabelsi N.,Groupe chimique Tunisien | Khemakhem S.,University of Sfax
Applied Clay Science | Year: 2016

The present work aimed at modifying original kaolin with iron and copper chlorides in order to introduce active centers for hydrogen sulfide (H2S) adsorption. In the first modification, interlayer sodium cations were exchanged with two metals. In the second one, iron oxide (FeOx) was introduced to the clay surface. Kaolin and modified kaolin were analyzed using ICP, X-ray diffraction (XRD), Infrared Ray, Fluorescence-X, BET surface area analysis and SEM. The modified clay samples were tested as hydrogen sulfide adsorbents. Iron-doped and copper-doped samples showed a significant improvement in the capacity for H2S removal, despite a noticeable decrease in microporosity compared to the initial pillared clay. The smallest capacity was obtained for the clay modified with FeOx. Variations in adsorption capacity are likely due to differences in the chemistry of metals species, degree of their dispersion on the surface, and accessibility of small pores for H2S molecule. Results suggest that on the surface of metal-modified clay, hydrogen sulfide reacts with Cu2+ and Fe+3 ions to form sulfides or can be catalytically oxidized to SO2 on iron (hydro) oxides. Subsequent oxidation may lead to sulfate formation. © 2016 Elsevier B.V.


Hentati H.,University of Sfax | Abdelmoula R.,University of Paris 13 | Maalej A.,University of Sfax | Maalej K.,Groupe Chimique Tunisien
International Journal of Modelling, Identification and Control | Year: 2013

The purpose of this work is to present a numerical method for solving a problem of dynamic structures. For that, we use the Newmark algorithm and the finite element method for time and space discretisations, respectively. We prove the efficiency of the Newmark scheme in which the sum of elastic and kinetic energies is conserved. We conduct also numerical computations aiming to determine the influence of numerical parameters in terms of time step and mesh size on energy conservation. Copyright © 2013 Inderscience Enterprises Ltd.


Ben Farhat M.,University of Sfax | Fourati A.,Groupe Chimique Tunisien | Chouayekh H.,University of Sfax
Applied Biochemistry and Biotechnology | Year: 2013

The genes gdh and pqqABCDE encoding glucose dehydrogenase and its pyrroloquinoline quinone cofactor were cloned from the mineral phosphate-solubilizing (MPS) bacterium Serratia marcescens CTM 50650. We investigated, for the first time, the impact of their coexpression in Escherichia coli on MPS ability. The production of recombinant PQQGDH conferred high MPS activity to the engineered E. coli. In fact, the amounts of soluble phosphorus (P) produced from tricalcium phosphate, hydroxyapatite, and Gafsa rock phosphate (GRP) were 574, 426, and 217 mg/L, respectively. In an attempt to increase the soluble P concentration, the E. coli strain coexpressing the gdh and pqqABCDE genes was immobilized in agar, calcium alginate, and k-carrageenan and was then further applied in a repeated batch (six batches) fermentation process to solubilize GRP. Compared to other encapsulated systems, alginate cell beads were noted to yield the highest concentration of soluble P, which attained 300 mg/L/batch. MPS efficiency was maximal in the presence of 5 and 40 g/L of GRP and glucose, respectively. © 2013 Springer Science+Business Media New York.


Bouguerra W.,U. R Traitement et Dessalement des Eaux | Brahmi K.,U. R Traitement et Dessalement des Eaux | Elaloui E.,Gafsa University | Loungou M.,Groupe Chimique Tunisien | Hamrouni B.,U. R Traitement et Dessalement des Eaux
Desalination and Water Treatment | Year: 2015

This study was carried out to investigate the effect of the electrocoagulation reactor design parameters in the removal of zinc from water. In order to optimize experimental electrocoagulation reactor parameters such as inter electrode distance (die), electrode connection mode, surface-area-to-volume ratio (S/V), and the initial temperature of the solution (T), many electrocoagulation tests were performed using aluminum electrodes. The obtained experimental results showed that optimal zinc removal was achieved with a distance between electrodes of 0.5 cm, a bipolar connection mode, the surface-area-to-volume ratio (S/V) of 13.6 m−1, and for an initial temperature (T) of 50°C. The application of these results on the treatment of a sulfuric acid and superphosphate manufacturing industry wastewater made it possible to achieve a total zinc removal in five minutes of electrolysis time. © 2015 Balaban Desalination Publications. All rights reserved.


Brahmi K.,U. R Traitement et Dessalement des Eaux | Bouguerra W.,U. R Traitement et Dessalement des Eaux | Hamrouni B.,U. R Traitement et Dessalement des Eaux | Loungou M.,Groupe Chimique Tunisien
Desalination and Water Treatment | Year: 2015

Electrocoagulation (EC) is an efficient technique for cleaning waste water containing heavy metals before discharge in the environment. The performance of electro coagulation for zinc ions removal using aluminum electrodes was investigated in this paper. Several electrochemical parameters such as pH, current density, electrolyte doses, energy consumption, initial concentration, EC time, the state of the aluminum plates, and heavy metal ions concentration were studied in an attempt to achieve high zinc removal efficiency. Optimum conditions for zinc removal were found at a pH value of 7, a current density of 7.35 mA cm−2, an inter-electrode potential of 5 V, a conductivity of 5.3 mS cm−1, and an EC time of 30 min. These operating conditions can simultaneously achieve a good mix, good flotation, high flocs stability, and thus efficient removal in a relatively short reaction time and low cost with a removal percentage up to 98.96. The testing of zinc removal from industrial waste water showed that the removal by EC using aluminum electrodes was effective and the removal efficiency of zinc reached 100% in the first 5 min of treatment with a very low power consumption of 1.02 kW h m−3 for an initial pH over 5. In the light of these results, this method promises interesting industrial applications. © 2014 Balaban Desalination Publications. All rights reserved.


Brahmi K.,Faculte des science de Tunis | Bouguerra W.,Faculte des science de Tunis | Hamrouni B.,Faculte des science de Tunis | Loungou M.,Groupe Chimique Tunisien
Desalination and Water Treatment | Year: 2014

Electrocoagulation (EC) is an efficient technique for cleaning waste water containing heavy metals before discharge in the environment. The performance of electro coagulation for zinc ions removal using aluminum electrodes was investigated in this paper. Several electrochemical parameters such as pH, current density, electrolyte doses, energy consumption, initial concentration, EC time, the state of the aluminum plates, and heavy metal ions concentration were studied in an attempt to achieve high zinc removal efficiency. Optimum conditions for zinc removal were found at a pH value of 7, a current density of 7.35 mA cm−2, an inter-electrode potential of 5 V, a conductivity of 5.3 mS cm−1, and an EC time of 30 min. These operating conditions can simultaneously achieve a good mix, good flotation, high flocs stability, and thus efficient removal in a relatively short reaction time and low cost with a removal percentage up to 98.96. The testing of zinc removal from industrial waste water showed that the removal by EC using aluminum electrodes was effective and the removal efficiency of zinc reached 100% in the first 5 min of treatment with a very low power consumption of 1.02 kW h m−3 for an initial pH over 5. In the light of these results, this method promises interesting industrial applications. © 2014 Balaban Desalination Publications. All rights reserved.


Bouguerra W.,Faculte des science de Tunis | Brahmi K.,Faculte des science de Tunis | Elaloui E.,Gafsa University | Loungou M.,Groupe Chimique Tunisien | Hamrouni B.,Faculte des science de Tunis
Desalination and Water Treatment | Year: 2015

This study was carried out to investigate the effect of the electrocoagulation reactor design parameters in the removal of zinc from water. In order to optimize experimental electrocoagulation reactor parameters such as inter electrode distance (die), electrode connection mode, surface-area-to-volume ratio (S/V), and the initial temperature of the solution (T), many electrocoagulation tests were performed using aluminum electrodes. The obtained experimental results showed that optimal zinc removal was achieved with a distance between electrodes of 0.5 cm, a bipolar connection mode, the surface-area-to-volume ratio (S/V) of 13.6 m−1, and for an initial temperature (T) of 50°C. The application of these results on the treatment of a sulfuric acid and superphosphate manufacturing industry wastewater made it possible to achieve a total zinc removal in five minutes of electrolysis time. © 2015 Balaban Desalination Publications. All rights reserved.

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