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Alaya B.,Gabes University
ICEIS 2017 - Proceedings of the 19th International Conference on Enterprise Information Systems | Year: 2017

Due to enterprises environment specificities, the operations management is actually a challenging problem. In this paper, we choose to using a compromise between the available resources and the quality of service (QoS) granularity. We join this compromise to a guaranteed technique in order to reach an intelligent loss of Sub-operations according to the importance of each operation. The resulting approach permits the increase of availability, performance, reliability and system dependability. The aim of our contribution is to ensure the client satisfaction by increasing the QoS while dealing with the enterprises environment characteristics. The effectiveness of what we propose is measured through a simulation study. Copyright © 2017 by SCITEPRESS - Science and Technology Publications, Lda. All rights reserved.

Lachiheb M.,Taibah University | Lachiheb M.,Gabes University
Applied Mathematics and Computation | Year: 2014

Many authors assume viscosity to be constant or a radius exponential function in Stokes' equations in order to study the peristaltic motion of a Newtonian fluid through an axisymmetric conduit. In this paper, viscosity is assumed to be a function of both the radius and the axial coordinate. More precisely, it is dependent on the distance from the deformed membrane given the fact that the change in viscosity is caused by the secretions released from the membrane. The effect of this hypothesis on the peristaltic flow of a Newtonian fluid in axisymmetric conduit is investigated under the assumptions of long wavelength and low Reynolds number. The expressions for the pressure gradient and pressure rise per wavelength are obtained and the pumping characteristics and the phenomena of reflux and trapping are discussed. We present a detailed analysis of the effects of the variation of viscosity on the fluid motion, trapping and reflux limits. The study also shows that, in addition to the mean flow parameter and the wave amplitude, the viscosity parameter also affects the peristaltic flow. It has been noticed that the pressure rise, the friction force, the pumping region and the trapping limit are affected by the variation of the viscosity parameter but the reflux limit and free pumping are independent of it. © 2014 Elsevier Inc. All rights reserved.

Ben-Ali S.,Gabes University | Jaouali I.,Gabes University | Souissi-Najar S.,Gabes University | Ouederni A.,Gabes University
Journal of Cleaner Production | Year: 2017

This study investigates the adsorption potential of natural materials waste. The biosorbent used is an untreated pomegranate peel (PGP) derived from local agricultural activities to remove copper Cu(II) ions. Natural PGP biosorbent has given, for the first time in literature, high removal efficiency for copper ions removal. The characterization of the biosorbent have been made by means Fourier Transform Infrared Spectroscopy (FTIR), TG/DTA analysis, Boehm titration and point of zero charge (pHpzc). Studied parameters are: the initial metal concentration, the pH of the solution, the particle size, the temperature and contact time. The highest Cu(II) adsorption capacity is obtained at pH = 5.8, for a particle size of 630 μm, a temperature of 313 K, a contact time of 2 h, and by increasing the initial concentration of Cu(II) solution. Langmuir, Freundlich, Dubinin Radushkevich and Temkin isotherm models have been used. Langmuir maximum adsorption capacity is 30.12 mg/g. Experimental data have been fitted to Pseudo-first order, Pseudo-second order, Intra-particle diffusion and Elovich kinetics models. Thermodynamic analysis has indicated a spontaneous endothermic adsorption of Cu(II) on pomegranate peel. The results of this study suggest that copper could be removed through an environmentally friendly process using a low cost biosorbent from an agricultural waste i.e. PGP. © 2016 Elsevier Ltd

Sebri M.,University of Monastir | Ben-Salha O.,Gabes University | Ben-Salha O.,International Finance Group
Renewable and Sustainable Energy Reviews | Year: 2014

The current study investigates the causal relationship between economic growth and renewable energy consumption in the BRICS countries over the period 1971-2010 within a multivariate framework. The ARDL bounds testing approach to cointegration and vector error correction model (VECM) are used to examine the long-run and causal relationships between economic growth, renewable energy consumption, trade openness and carbon dioxide emissions. Empirical evidence shows that, based on the ARDL estimates, there exist long-run equilibrium relationships among the competing variables. Regarding the VECM results, bi-directional Granger causality exists between economic growth and renewable energy consumption, suggesting the feedback hypothesis, which can explain the role of renewable energy in stimulating economic growth in BRICS countries. © 2014 Elsevier Ltd.

In this research, various assessment tools are applied to comprehensively investigate hydrogen production from steam reforming of poultry tallow (PT). These tools investigate the chemical reactions, design and simulate the entire hydrogen production process, study the energetic performance and perform an environment impact assessment using life cycle assessment (LCA) methodology. The chemical reaction investigation identifies thermodynamically optimal operating conditions at which PT may be converted to hydrogen via the steam reforming process. The synthesis gas composition was determined by simulations to minimize the Gibbs free energy using the Aspen Plus 10.2 software. These optimal conditions are, subsequently, used in the design and simulation of the entire PT-to-hydrogen process. LCA is applied to evaluate the environmental impacts of PT-to-hydrogen system. The system boundaries include rendering and reforming along with the required transportation process. The reforming inventories data are derived from process simulation in Aspen Plus, whereas the rendering data are adapted from a literature review. The life cycle inventories data of PT-to-hydrogen are computationally implemented into SimaPro 7.3. A set of seven relevant environmental impact categories are evaluated: global warming, abiotic depletion, acidification, eutrophication, ozone layer depletion, photochemical oxidant formation, and cumulative non-renewable fossil and nuclear energy demand. The results are subject to a systematic sensitivity analysis and compared to those calculated for hydrogen production from conventional steam methane reforming. The LCA results indicate that the thermal energy production process is the main contributor to the selected environmental impact categories. Improvement actions to minimize the reforming thermal energy and the transport distance are strongly recommended as they would lead to relevant environmental improvements. © 2013 Elsevier Ltd. All rights reserved.

Hajjaji N.,Gabes University | Marie-Noelle Pons,University of Lorraine
International Journal of Hydrogen Energy | Year: 2013

A thermodynamic analysis of hydrogen production via steam and autothermal reforming of beef tallow has been carried out via the Gibbs free energy minimization method. Equilibrium calculations are performed at atmospheric pressure with a wide range of temperatures (400-1200 °C), steam-to-beef tallow ratios (1-15) and oxygen-to-beef tallow ratios (0.0-2.0). The results show that the optimum conditions for steam reforming can be achieved at reforming temperatures between 700 °C and 900 °C and a steam-to-beef tallow ratio of approximately 5. Optimal operating conditions of T = 700 °C and a steam-to-beef tallow ratio of 5 are proposed. With this condition, a hydrogen yield of 170 moles/kg beef tallow and a CO concentration in the synthesis gas of 4.77% with a trace content of CH4 (0.01%) can be obtained without coke formation. The most favorable conditions for hydrogen production from autothermal systems are achieved at the temperature, steam-to-beef tallow ratio and oxygen-to-beef tallow ratio of 600-800 °C, 3-5 and 0.0-0.45, respectively. Thermoneutral conditions can be accomplished with an oxygen-to-beef tallow ratio of 0.384-0.427. The recommended conditions are a steam-to-beef tallow ratio of 5, T = 600 °C and an oxygen-to-beef tallow ratio of 0.422. Under these conditions, 150 moles H2/kg beef tallow can be produced with only 2.92% CO and 0.07% CH4 in the synthesis gas. Copyright © 2012, Hydrogen Energy Publications, LLC.

Masrouhi A.,Gabes University | Koyi H.A.,Uppsala University
Geological Society Special Publication | Year: 2012

Stratigraphical, sedimentological and structural data and a Bouguer gravity map of Medjez-El-Bab (MEB) in Northern Tunisia are used to illustrate a Cretaceous example of salt extrusion on a passive continental margin. Located just south of the Teboursouk thrust front (a preferential décollement surface used by the continuous Tertiary shortening in this area), the MEB structure is a simple N40°E box anticline. Removing the two Tertiary foldings (Eocene and Miocene) leads to the exposure of the original feature of a simple submarine 'salt glacier'. The Triassic salt rocks appear as an Albian interstratified body between two Cretaceous series with stratigraphic normal polarity, suggesting a bedding parallel extrusion (at the sediment-water interface) of the Triassic salt in Cretaceous times. The formation of such salt extrusions are associated with extensional faulting (probably both in the cover and basement), the presence of a slope and basinwards salt flow. This scenario is similar to the allochthonous salt described in other salt provinces, characterizing passive margins. © The Geological Society of London 2012.

This paper presents a practical method to solve the problem of global output feedback tracking trajectories for a class of Euler-Lagrange systems when the variables of velocity are the unmeasured part of the state. We exhibited a new output feedback control scheme, which globally exponentially stabilize trajectories. It relies on the determination of a change of coordinates which gives to the systems a triangular form. Results are illustrated on the academic example of the two-link direct drive robot manipulator. © Springer Science+Business Media B.V. 2009.

The scarcity of surface water resources in arid and semi-arid regions from North African countries contributes to the considerable increase of groundwater exploitation, which leads to the development of hydrogeological studies. However, due to the lack of hydrodynamic data in these regions, these studies focus more and more on the geochemical and environmental isotope techniques to insure a better understanding of the hydrodynamic functioning of subsurface systems. In this study, which interests an important unconfined aquifer in central Tunisia, tritium data and chloride mass balance (CMB) method were applied in order to (1) understand the mode of recharge of this aquifer and (2) obtain a reliable estimation of its recharge amount as well as (3) estimate its annual renewal rate. It has been demonstrated that the shallow groundwaters are classified into two groups according to their tritium contents. The first group includes wells located mainly downstream and highlights the significant role of the post-nuclear lineal recharge through Wadis courses. The second group encloses wells located practically overall the rest of the basin and refers to relatively modern waters originated from areal recharge of present-day rainfall. Based on the CMB method, the recharge to this unconfined aquifer is estimated to 31.7 mm year-1, which corresponds to 10.5% of the total rainfall. The annual renewal rate of groundwater, evaluated based on the tritium contents, is up to 16%. © 2009 Springer-Verlag.

Nasri W.,Gabes University
Journal of Enterprise Information Management | Year: 2011

The purpose of this study is to investigate the degree of knowledge of competitive intelligence in Tunisian companies. Design/methodology/approach- This exploratory study was conducted using semi-in-depth interviews and focus group with six executives in six companies in Tunisia. Three sectors were chosen for this study: communication technologies, manufacturing and commercial retailing. These companies are prevalent in Tunisia and are very different. Findings: The results show that Tunisian managers are conscious of the importance of competitive intelligence in the management of their companies. Second, managers believe that internal sources of information are more valuable than external sources information and personal source information is deemed most valuable. Third, the results of the process and structure questions indicate that companies may not yet be investing appropriately in building the internal infrastructure required for fully effective intelligence efficacy. Finally, this practice is not organised in a separate department and, if it is mostly done in the marketing department. Practical implications: To know and develop this practice, a company must, on the one hand, build internal competitive intelligence process. On the other hand, develop a sensitisation programme that is continuous and that should focus on telling employees what competitive intelligence is, what they can, and should, contribute and demonstrate the value in sharing information. Originality/value: This study is the first to investigate competitive intelligence in Tunisia. The results lead to a number of recommendations to develop competitive intelligence in Tunisian companies. Various methods are proposed including awareness and training program, recognising by managers the value of competitive intelligence as an important tool to develop competitive intelligence. © Emerald Group Publishing Limited.

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