National Engineering School of Tunis

Tunis, Tunisia

National Engineering School of Tunis

Tunis, Tunisia
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Agency: European Commission | Branch: FP7 | Program: CP-FP | Phase: NMP-2009-2.6-1 | Award Amount: 5.77M | Year: 2010

One of the major challenges of this century is the provision of safe drinking water for a growing population. The shortage in water resources in arid areas requires the availability of more efficient and cheaper drinking water production processes. For groundwater, it is often sufficient to aerate and disinfect to produce drinking water. However, in large parts of the world the use of groundwater from aquifers is not possible due to excessive use and global climate change that allow penetration of salt sea water into the aquifers. Population growth, not surprisingly, leads to more pollution of aquifers rendering the water quality unsuitable for drinking water purposes without excessive treatment. In contrast, there are always large quantities of water vapor present in air. The objective within CapWa is produce a commercially available membrane modular system suitable for industrial applications within 3-4 years. The produced demin water from this system should be competitive with existing demin water technologies. The starting point will be the water vapour selective composite membranes that are developed in the proof of principle project. At the same time fundamental research will also be done on other alternative water selecting coatings. For both of these membrane paths the upscale from lab to industrial scale membrane production will be developed in CapWa. In CapWa the modular membrane system will also be developed and tested in the flue gas duct of a gas and coal-fired power plant, a cooling tower (or geothermal well) and in a paper or board mill. To achieve this goal the selective membranes must be thermal/chemically stable under the existing environmental conditions (50-150 C) and resistant to fouling. To be competitive with existing demin production lines, the construction of the end system must be efficient and user friendly.

Khaldi K.,National Engineering School of Tunis | Boudraa A.-O.,Ecole Navale
IEEE Transactions on Audio, Speech and Language Processing | Year: 2013

In this paper a new adaptive audio watermarking algorithm based on Empirical Mode Decomposition (EMD) is introduced. The audio signal is divided into frames and each one is decomposed adaptively, by EMD, into intrinsic oscillatory components called Intrinsic Mode Functions (IMFs). The watermark and the synchronization codes are embedded into the extrema of the last IMF, a low frequency mode stable under different attacks and preserving audio perceptual quality of the host signal. The data embedding rate of the proposed algorithm is 46.9-50.3 b/s. Relying on exhaustive simulations, we show the robustness of the hidden watermark for additive noise, MP3 compression, re-quantization, filtering, cropping and resampling. The comparison analysis shows that our method has better performance than watermarking schemes reported recently. © 2006-2012 IEEE.

Agency: European Commission | Branch: FP7 | Program: CP-SICA | Phase: ENERGY.2013.2.9.1 | Award Amount: 7.48M | Year: 2013

REELCOOP stands for REnewable ELectricity COOPeration, and will address 5 areas: photovoltaics (PV), concentrated solar power (CSP), solar thermal (ST), bioenergy and grid integration. REELCOOP will develop decentralised (distributed) building integrated PV systems and ST/biomass micro-cogeneration systems, as well as centralised generation of electricity in hybrid solar/biomass power plants. This is in accordance with the EU SET-Plan approach of developing a European electricity grid able to integrate renewable and decentralised energy sources. The overall aim of REELCOOP will be to significantly enhance research cooperation and knowledge creation on renewable electricity generation, involving Mediterranean partner countries (MPC), while at the same time developing and testing new renewable electricity generation systems. The proposed systems will be developed in European organisations with collaboration of MPC partners, and tested under real-life operating conditions in the MENA region, thus establishing a cooperation network amongst partner countries. Three novel prototype systems will be developed and tested, being representative of both micro (distributed) and large (centralised) scale approaches to electricity generation: prototypes 1 and 2 are representative of typical micro-generation systems, while prototype 3 is representative of a large scale power plant on a reduced scale. The development of the 3 prototypes will also contribute to bring to the market energy efficient, renewable electricity generation systems. The environmental sustainability and economics of the prototype systems will be assessed, and the results obtained will be disseminated to industry and research, as proof-of-concept of renewable electricity generation solutions. Grid integration will also be assessed. The prototype systems will have a great potential for exploitation/commercialization. The commercialisation of the systems will bring economic and environmental benefits to the EU.

Bouzid M.B.K.,National Engineering School of Tunis | Bouzid M.B.K.,École de Technologie Supérieure of Montreal | Champenois G.,University of Poitiers
IEEE Transactions on Industrial Electronics | Year: 2013

This paper proposes new expressions of symmetrical components (SCs) of the stator currents of the induction motor (IM) in steady state and under different stator faults, useful to ensure an efficient fault diagnosis. In this paper, the considered stator faults are interturns short circuit, phase-to-phase, and single-phase-to-ground faults. An analytical study of the behavior of these expressions shows that, under balanced supply voltage, the phase angle and the magnitude of the negative-and zero-sequence currents can be considered as reliable indicators of stator faults of the IM. The behavior of the developed expressions of the SCs is also verified experimentally on a 1.1-kW IM under different fault conditions, different frequencies, and different load conditions. The good agreement between the analytical and experimental values leads to consider the negative-and zero-sequence currents as powerful and effective indicators of stator faults. © 1982-2012 IEEE.

Today, the reverse osmosis (RO) becomes a process of first importance for fresh water production worldwide. For this reason, downtimes due to repairing operations (following breakdowns, blockage of membrane, pressure losses, etc.) or preventive maintenance (cleaning of membranes, changes in components, etc.) have to be minimized in duration and frequency to ensure maximum availability. Indeed, improving the availability (or the reliability) of the RO plant as a whole system, objectively leads to a substantial reduction in operating costs and maintenance. In this paper we consider two methods for availability and effectiveness assessment of an RO unit, where the main objective is economic optimization. The two methods are Reliability Block Diagram Method (RBD) and Fault Tree Analysis Method (FTA). For the validation of both methods, we used data related to an RO unit operating in Kuwait and corresponding to four years operation. A comparison between both methods was performed in order to highlight the efficiency and the limitation of each one.It was shown that all the subsystems (pretreatment, dosing, etc.) have a good availability. Slightly lower availability was determined for the high pressure pump. A sensitivity study was conducted to determine the critical components for the availability of the RO plant. The obtained results show a high influence of the availability of the high pressure pump on the total availability of the system. Hence, particular attention should be taken on the selection and the maintenance of the high pressure pump.The comparison between the two methods RBD and FTA shows that the first method is more appropriate for the availability assessment because it allows accurate modeling of different complex configurations. © 2012 Elsevier B.V.

Kessentini H.,National Engineering School of Tunis | Bouden C.,National Engineering School of Tunis
Renewable Energy | Year: 2013

The aim of this work is to develop a numerical code able to predict the thermal behavior of a double tank integrated collector storage system (ICS) with compound parabolic concentrator (CPC). The developed numerical model is based on the detailed analysis of the different forms of heat transfers occurring in the ICS system. The balance equations of each element of the system have been established and solved by means of a transient algorithm. A prototype of an ICS device was constructed and experimentally tested outdoors in order to observe the variation of water temperature in the storage tanks. The experimental results are presented and the validity of the model is examined by comparison of the theoretical results with experiments which demonstrates a good agreement. The numerical model is then used to perform theoretical study on the present ICS solar heater. The simulation results of the variation of the thermal efficiency are presented. The results of the yearly parametric study of the effect of the concentrators reflectivity, the absorber emissivity and the use of double glazing on the thermal performance of the ICS system are also presented and discussed. The developed numerical tool within this work can be considered as important for the study of double tanked ICS solar water heater regarding its transient thermal behavior. © 2013 Elsevier Ltd.

Yano J.-I.,Meteo - France | Baizig H.,National Engineering School of Tunis
Dynamics of Atmospheres and Oceans | Year: 2012

A fully prognostic prototype of bulk mass-flux convection parameterization is presented. The bulk mass-flux parameterization is formulated by assuming a subgrid-scale system consisting only of a convective plume and environment. Both subcomponents (segments) are assumed to be homogeneous horizontally. This assumption is called the segmentally constant approximation (SCA). The present study introduces this purely geometrical constraint (SCA) into the full nonhydrostatic anelastic system. A continuous-space description of the full system is, thus, replaced by a discretization consisting only of two segments (plume and environment) in the horizontal direction. The resulting discretized system is mathematically equivalent to a 0th order finite volume formulation with the only two finite volumes. The model is presented under a two-dimensional configuration. Interfaces between the plume and the environment segments may either be fixed in time or Lagrangianly advected as two limiting cases. Under this framework, the single-plume dynamics is systematically investigated in a wide phase space of Richardson number, the aspect ratio, and a displacement rate of the plume interfaces relative to the Lagrangian displacement. Advantage of the present model is in evaluating the lateral mixing processes of the plume without invoking an entrainment-detrainment hypothesis. The fractional entrainment-detrainment rate diagnosed from the present model simulations highly varies both over space and time, suggesting a limitation of applying an entrainment-detrainment hypothesis to unsteady plumes, as in the present case, in which circulations of the plume scale dominates over the turbulent mixing process. Furthermore, when the entrainment-plume hypothesis of Morton et al. is adopted for defining the plume-interface displacement rate, the plume continuously expands with time without reaching equilibrium. © 2012 Elsevier B.V.

Hammami S.,National Engineering School of Tunis
ISA Transactions | Year: 2015

This paper deals with a new state feedback-based synchronization problem for coupled hyperchaotic systems. In the beginning, complete synchronization conditions of coupled chaotic systems, are provided. The active control law developed is based on the use of both aggregation techniques for error dynamics stability study and the arrow form matrix for systems description. After that, the proposed feedback-based synchronization between two identical hyperchaotic systems is successfully applied for transmitting an encoded image. To finish, numerical simulations are carried out to assess the performance and the efficiency of the proposed contributions in the important field of secure image encryption. © 2014 ISA.

Hamdi M.A.,National Engineering School of Tunis
International Journal of Imaging and Robotics | Year: 2012

This paper proposes a new technique's segmentation that combines multiresolution contourlet transform with the watershed transform. The contourlet transform is one kind of new multi-scale transform that is based on discrete curvelet transform, whose structural elements include the parameters of location and dimension, and orientation parameter more, which let contourlet transform has good orientation characteristic. Therefore, contourlet transform is superior to curvelet in the expression of image edge, and denoising such as geometry characteristic of discrete curve and beeline, which has already obtained very good research results in image denoising. The flooding watershed transform is then applied, and the segmented image is projected up to higher resolutions using contourlet transform. Typically, if a low resolution is chosen for the initial segmentation so large relevant objects will be captured (noise); therefore, a higher initial resolution will lead to smaller and more detailed segmented objects. This paper puts forward an improved method based on contourlet and watershed transform because certain regions of the image have the ringing and radial stripe after contourlet transform. © 2012 by IJIR (CESER Publications).

El Fatmi R.,National Engineering School of Tunis | Ghazouani N.,National Engineering School of Tunis
Composite Structures | Year: 2011

This two-part-paper proposes a higher order composite beam theory that can be viewed as an extension of Saint-Venant's theory. Saint-Venant's solution, is known to represent the exact 3D solution in the interior part of a beam, far from the end-sections where the boundary conditions are applied. The difference between these solutions contains the end-effects. The objective of the proposed theory is to capture a significant part of these end-effects in order to predict the 3D-stresses in a larger interior-part of the beam, and therefore better describe its structural behavior. Based on a kinematics built from the exact form of Saint-Venant displacement, the present theory is rigorously derived for the case of symmetric cross section made of orthotropic materials. Closed-form expressions are obtained for the stiffness matrix of the structural behavior and for the 3D-stresses. Easy to compare to those of Saint-Venant, these results highlight the contribution of this approach. Part-I is devoted to the theoretical developments and part-II illustrates the predictive capability of this theory through the analysis of tip loaded cantilever beams, focusing the built-in effects influence on the structural behavior of the beam. © 2010 Elsevier Ltd.

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