Lahyani A.,University of Carthage |
Venet P.,University Claude Bernard Lyon 1 |
Guermazi A.,University of Sfax |
Troudi A.,University of Sfax
IEEE Transactions on Power Electronics | Year: 2013
This study presents a study of the reduction in battery stresses by using supercapacitors (SCs) in a 500-kVA rated UPS. We aim at investigating the optimal supercapacitors-battery combination versus the SCs cost. This investigation is threefold; first, supercapacitors and battery models developed using MATLAB/ Simulink are presented and validated. Second, the architecture and the simulation of the designed system that combines the SCs and the battery are shown. The supercapacitors are used as high-power storage devices to smooth the peak power applied to the battery during backup time and to deliver full power during short grid outages. By charging the SCs through the battery at a suitable rate, all impulse power demands would be satisfied by the supercapacitors. Third, extensive simulations are carried out to determine the gain in batteryRMS current, the gain in energy losses, the energy efficiency and the elimination rate of surge load power. These four performance parameters are determined by simulation and then analyzed. The influence of the SCs recharge on the performance indicators is highlighted. A thorough analysis involving optimal study proposes to draw the optimal SCs number and filter constant from the variation of the aforementioned parameters versus the cost of the SCs. © 2012 IEEE.
Agency: European Commission | Branch: FP7 | Program: CP-FP-SICA | Phase: SiS-2010-188.8.131.52 | Award Amount: 2.36M | Year: 2011
The overall objective of this proposal is enhancing research cooperation on gender and science between the European Union and the Mediterranean countries. Research cooperation is aimed at better understand the roots of gender inequality in science in the area, taking into account cultural diversities and traditions, and analyse how the Mediterranean countries are addressing this issue. It will deal with gender equality from a twofold perspective: the representation of women in scientific research and technological development and the integration of the gender dimension in research policy. The project will provide state of the art description, data collection and relevant comparative analysis on gender and science in all the Mediterranean countries, focusing on three key themes: statistics on women in science, gender equality policies and research on gender inequalities in science careers. These results will be made accessible to the research community and policy makers via an online database, publishable reports and workshops. With the overall purpose of enhancing networking and steering policy-making on gender and science in the years to come, the project will finally develop recommendations for policy-makers aimed at enhancing the presence of women in scientific research and technological development at all levels and ensuring a better integration of the gender dimension in research policy. The Mediterranean countries included in the proposal are the Mediterranean Partner Countries (MPCs), i.e. the Mediterranean countries included in the list of International Co-operation Partner Countries: Algeria, Egypt, Jordan, Lebanon, Morocco, Palestinian-administered areas, Syrian Arab Republic, Tunisia.
Arouri M.E.H.,EDHEC Business School |
Jouini J.,University of Carthage
Energy Economics | Year: 2012
The objective of this paper is to investigate the volatility spillovers between oil and stock markets in Europe. As not all industries are expected to be equally affected by oil price changes, we conduct our study at both the aggregate as well as sector levels. Empirically, we make use of a recently developed VAR-GARCH approach which allows for transmissions in volatilities. In addition, we analyze the optimal weights and hedge ratios for oil-stock portfolio holdings based on our results. On the whole, our findings show significant volatility spillovers between oil price and sector stock returns, and suggest that a better understanding of those links is crucial for portfolio management in the presence of oil price risk. © 2011 Elsevier B.V.
Karoui A.,University of Carthage
Journal of the Franklin Institute | Year: 2011
In this work, we give a brief description of the theory and the properties of the 1-D and 2-D prolate spheroidal wave functions (PSWFs). Then, we study some efficient methods for the computation of the different PSWFs and their associated eigenvalues. More precisely, we shall develop a quadrature method for the approximation of the 1-D PSWFs. Then, we extend this method to the construction of the 2-D PSWFs that are concentrated on the unit disk. Also, we give a brief review of the quality of approximation of almost band-limited functions by the 1-D PSWFs. Moreover, we use some numerical tests to compare between PSWFs and wavelets as signal processing tools. In particular, we give some numerical tests that highlight the efficiency of the PSWFs in processing band-limited signals. © 2010 The Franklin Institute. Published by Elsevier Ltd. All rights reserved.
Jammazi C.,University of Carthage
IMA Journal of Mathematical Control and Information | Year: 2010
The article gives Lyapunov-type sufficient conditions for partial finite-time and asymptotic stability in which some state variables converge to zero, while the rest converge to constant values that possibly depend on the initial conditions. The article then presents partially asymptotically stabilizing controllers for many non-linear control systems for which continuous asymptotically stabilizing (in the usual sense) controllers are known not to exist.
Ben Salem A.,University of Carthage |
Cherif R.,University of Carthage |
Zghal M.,University of Carthage
Optics Express | Year: 2011
We design As2Se3 and As2S3 chalcogenide photonic nanowires to optimize the soliton self-compression with short distances and ultralow input pulse energy. We numerically demonstrate the generation of single optical cycle in an As2S3 photonic nanowire: a 5.07 fs compressed pulse is obtained starting from 250 fs input pulse with 50 pJ in 0.84 mm-long As2S3 nanowire. Taking into account the high two photon absorption (TPA) coefficient in the As 2Se3 glass, accurate modeling shows the compression of 250 fs down to 25.4 fs in 2.1 mm-long nanowire and with 10 pJ input pulse energy. © 2011 Optical Society of America.
Naghmouchi I.,University of Carthage
International Journal of Bifurcation and Chaos | Year: 2011
We show that, for monotone graph map f, all the ω-limit sets are finite whenever f has periodic point and for monotone dendrite map, any infinite ω-limit set does not contain periodic points. As a consequence, monotone graph and dendrite maps have no LiYorke pairs. However, we built a homeomorphism on a dendroid with a scrambled set having nonempty interior. © 2011 World Scientific Publishing Company.
Kaaniche M.-B.,University of Carthage |
Bremond F.,French Institute for Research in Computer Science and Automation
IEEE Transactions on Pattern Analysis and Machine Intelligence | Year: 2012
We introduce a new gesture recognition framework based on learning local motion signatures (LMSs) of HOG descriptors introduced by . Our main contribution is to propose a new probabilistic learning-classification scheme based on a reliable tracking of local features. After the generation of these LMSs computed on one individual by tracking Histograms of Oriented Gradient (HOG)  descriptor, we learn a codebook of video-words (i.e., clusters of LMSs) using k-means algorithm on a learning gesture video database. Then, the video-words are compacted to a code-book of codewords by the Maximization of Mutual Information (MMI) algorithm. At the final step, we compare the LMSs generated for a new gesture w.r.t. the learned code-book via the k-nearest neighbors (k-NN) algorithm and a novel voting strategy. Our main contribution is the handling of the N to N mapping between codewords and gesture labels within the proposed voting strategy. Experiments have been carried out on two public gesture databases: KTH  and IXMAS . Results show that the proposed method outperforms recent state-of-the-art methods. © 2012 IEEE.
Jammazi C.,University of Carthage
ESAIM - Control, Optimisation and Calculus of Variations | Year: 2012
We consider chained systems that model various systems of mechanical or biological origin. It is known according to Brockett that this class of systems, which are controllable, is not stabilizable by continuous stationary feedback (i.e. independent of time). Various approaches have been proposed to remedy this problem, especially instationary or discontinuous feedbacks. Here, we look at another stabilization strategy (by continuous stationary or discontinuous feedbacks) to ensure the asymptotic stability even in finite time for some variables, while other variables do converge, and not necessarily toward equilibrium. Furthermore, we build feedbacks that permit to vanish the two first components of the Brockett integrator in finite time, while ensuring the convergence of the last one. The considering feedbacks are continuous and discontinuous and regular outside zero. © EDP Sciences, SMAI, 2011.
Jammazi C.,University of Carthage
Proceedings of the IEEE Conference on Decision and Control | Year: 2013
In this paper, we give a construction of discontinuous feedback laws stabilizing in finite-time all without drift systems. Our construction is based on "sampling control" defined by Clarke et al.  and on Bhat and Bernstein feedback laws for cascaded structures . Moreover, our construction are extended to another family of systems as satellite with two controllers when stabilizability by pure discontinuous feedback laws fails. © 2013 IEEE.