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Search Results: 1 - 10 of 9111 matches for " Mohamed Hamdi "
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Donnan Dialysis Removal of Nitrate from Water: Effects of Process Parameters  [PDF]
Thouraya Turki, Raghda Hamdi, Mohamed Tlili, Mohamed Ben Amor
American Journal of Analytical Chemistry (AJAC) , 2015, DOI: 10.4236/ajac.2015.66055
Abstract: Excess or lack of levels of nitrate in drinking water is harmful to the human health, the concentration of NO-3 ions must be maintained at 50 mg/l. Donnan dialysis (DD) used as a driving force of the concentration gradient is an effective and simple technique for nitrate removal. In this paper, the transport of nitrate through an AMX anion-exchange membrane has been studied as a function of driving ion nature, receiver phase concentration, flow rate, temperature and agitation rate under Donnan dialysis condition. It was observed that the hydrodynamic conditions and temperature were the main variables affecting the transmembrane flow. As the driving ion, the chloride ion is more efficient than the hydrogeneocarbonate ion. The systematic study of the different parameters involved showed that the nitrate removal efficiency obtained with a feed synthetic nitrate solution (62 ppm) was off 96%. This efficiency slightly decreases for a tap water containing the same nitrate concentration; it was about 84%. This can be attributed to the complex ionic composition of the natural water.
Control of Bistability in a Delayed Duffing Oscillator
Mustapha Hamdi,Mohamed Belhaq
Advances in Acoustics and Vibration , 2012, DOI: 10.1155/2012/872498
Abstract: The effect of a high-frequency excitation on nontrivial solutions and bistability in a delayed Duffing oscillator with a delayed displacement feedback is investigated in this paper. We use the technique of direct partition of motion and the multiple scales method to obtain the slow dynamic of the system and its slow flow. The analysis of the slow flow provides approximations of the Hopf and secondary Hopf bifurcation curves. As a result, this study shows that increasing the delay gain, the system undergoes a secondary Hopf bifurcation. Further, it is indicated that as the frequency of the excitation is increased, the Hopf and secondary Hopf bifurcation curves overlap giving birth in the parameter space to small regions of bistability where a stable trivial steady state and a stable limit cycle coexist. Numerical simulations are carried out to validate the analytical finding. 1. Introduction This paper concerns the effect of a high-frequency excitation on the nontrivial solutions and on bistability dynamic of a Duffing type oscillator with a delayed displacement feedback in the form where is the damping, is the natural frequency, the nonlinearity, and , are the amplitude and the time delay, respectively. The parameters , and are assumed to be small and positive. This equation may serve as the simplest model for describing the dynamic of various controlled physical and engineering systems; see [1–3]. Other works have been devoted to study the dynamic of a Duffing oscillator under a delayed feedback control [4–6]. In addition, (1) has been considered in [7] as a simple model for a vibration problem in turning machine for modelling the nonlinear generative effect in metal cutting [1] or for exploring the control of a flexible beam in a simple mode approach [8]. On the other hand, numerous physical applications focusing on bistability dynamic can be found in the literature [9, 10]. In [1, 11–13], attention has been paid to the linear stability analysis of the trivial steady state of delayed oscillators of type (1). While the investigation of stability of nontrivial solutions in (1) has received little attention from analytical view point, the influence of high-frequency excitation on nontrivial steady state has not been tackled. In [12], for instance, a detailed and systematic study on the dynamic of a delayed Duffing oscillator was confined to the linear stability analysis. In this paper, we explore the bifurcation of a nontrivial solution of (1) created in Hopf bifurcation, and we analyze the influence of a high-frequency excitation on the bifurcation
A Comparative Study in Wavelets, Curvelets and Contourlets as Denoising Biomedical Images
Mohamed Ali HAMDI
International Journal of Image, Graphics and Signal Processing , 2012,
Abstract: A special member of the emerging family of multi scale geometric transforms is the contourlet transform which was developed in the last few years in an attempt to overcome inherent limitations of traditional multistage representations such as curvelets and wavelets. The biomedical images were denoised using firstly wavelet than curvelets and finally contourlets transform and results are presented in this paper. It has been found that contourlets transform outperforms the curvelets and wavelet transform in terms of signal noise ratio
Study of Stability and Vibration Reduction in Multi-Tool Ultrasonic Machining under Simultaneous Primary and Internal Resonance  [PDF]
Yaser Salah Hamed, Mohamed Syed Abd Elkader, Hamdi Mahmoud Genedi
Applied Mathematics (AM) , 2012, DOI: 10.4236/am.2012.31001
Abstract: The main object of this paper is the mathematical study of the vibration behavior in ultrasonic machining (USM) described by non-linear differential equations. The ultrasonic machining (USM) consists of the tool holder and the absor-bers representing the tools. This leads to four-degree-of-freedom system subject to multi-external excitation forces. The aim of this project is the reduction of the vibrations in the tool holder and have reasonable amplitudes for the tools represented by the multi-absorbers. Multiple scale perturbation method is applied to obtain the solution up to the second order approximation and to study the stability of the steady state solution near different simultaneous resonance cases. The resulting different resonance cases are reported and studied numerically. The stability of the steady state solution near the selected resonance cases is studied applying both frequency response equations and phase-plane technique. The effects of the different parameters of the system and the absorbers on the system behavior are studied numerically. Optimum working conditions for the tools were obtained. Comparison with the available published work is reported.
Global Competitiveness and Economic Growth: Empirical Verification for African Countries
Mohamed BEN AMAR,Mohamed Tlili HAMDI
International Journal of Economics and Finance , 2012, DOI: 10.5539/ijef.v4n6p125
Abstract: The target of this work consists of analyzing economic growth in African countries. We have three main results that were generated from this work. First, the pillars of global competitiveness are strongly inspired by the theories of endogenous growth. Secondly, concerning economic growth, African countries realized some impressive performances during the last decade and show very important potential. Finally, by means of panel data evaluation for a sample of 23 African countries during the period (2004-2009), we confirmed the positive and statistically significant effect of economic growth, driven by the level of the global competitiveness.
Intravascular Ultrasound Image Segmentation Using Morphological Snakes
Mrabti Mohamed Amine,Hamdi Mohamed Ali
International Journal of Image, Graphics and Signal Processing , 2012,
Abstract: From the first use of the technics of intravascular ultrasound (IVUS) as an imaging technique for the coronary artery system at the 70th century until now , the segmentation of the arterial wall boundaries still an important problem . Much research has been done to give better segmentation result for better diagnostics , evaluation and therapy planning. In this paper we present a new segmentation technics based on Morphological Snakes which developed by Luis álvarez used for the first time for IVUS segmentation. It is a simple , fast and stable approach of snakes evolution algorithm. Results are presented and discussed in order to demonstrate the effectiveness of this approach in IVUS segmentation.
Tuberculosis Arthritis of the Sternoclavicular Joint  [PDF]
Osman Walid, Triki Mohamed Amine, Kaziz Hamdi, Jemni Sonia, Naouar Nader, Ben Ayech Mohamed Laziz
Open Journal of Orthopedics (OJO) , 2015, DOI: 10.4236/ojo.2015.56018
Abstract: Tuberculosis remains a public health problem in developing country particularly in Tunisia. Bone location of tuberculosis infection is increasing and is often misdiagnosed due to the weakness of clinical presentation in early stages. Sternoclavicular joint tuberculosis is rare and unusual location of this disease. However, antibiotherapy and surgical debridement is still the basis of treatment. We report a case of sternoclavicular joint tuberculosis with a follow up of four years. The patient was treated surgically and put under antibiotherapy during twelve months. The site was sterilized. We report this case to show that debridement and antibiotherapy still efficient in tuberculous bone affection no matters the location.
Coverage Assessment and Target Tracking in 3D Domains
Noureddine Boudriga,Mohamed Hamdi,Sitharama Iyengar
Sensors , 2011, DOI: 10.3390/s111009904
Abstract: Recent advances in integrated electronic devices motivated the use of Wireless Sensor Networks (WSNs) in many applications including domain surveillance and mobile target tracking, where a number of sensors are scattered within a sensitive region to detect the presence of intruders and forward related events to some analysis center(s). Obviously, sensor deployment should guarantee an optimal event detection rate and should reduce coverage holes. Most of the coverage control approaches proposed in the literature deal with two-dimensional zones and do not develop strategies to handle coverage in three-dimensional domains, which is becoming a requirement for many applications including water monitoring, indoor surveillance, and projectile tracking. This paper proposes efficient techniques to detect coverage holes in a 3D domain using a finite set of sensors, repair the holes, and track hostile targets. To this end, we use the concepts of Voronoi tessellation, Vietoris complex, and retract by deformation. We show in particular that, through a set of iterative transformations of the Vietoris complex corresponding to the deployed sensors, the number of coverage holes can be computed with a low complexity. Mobility strategies are also proposed to repair holes by moving appropriately sensors towards the uncovered zones. The tracking objective is to set a non-uniform WSN coverage within the monitored domain to allow detecting the target(s) by the set of sensors. We show, in particular, how the proposed algorithms adapt to cope with obstacles. Simulation experiments are carried out to analyze the efficiency of the proposed models. To our knowledge, repairing and tracking is addressed for the first time in 3D spaces with different sensor coverage schemes.
Multi-target Tracking Using Wireless Sensor Networks Based on Higher-Order Voronoi Diagrams
Manel Abdelkader,Mohamed Hamdi,Noureddine Boudriga
Journal of Networks , 2009, DOI: 10.4304/jnw.4.7.589-597
Abstract: Recent advances in integrated electronic devices motivated the use of Wireless Sensor Networks (WSNs) in many applications including target surveillance and tracking. A number of sensor nodes are scattered within a sensitive region to detect the presence of intruders and forward subsequent events to the analysis center(s). Obviously, the sensor deployment should guarantee an optimal event detection rate. This paper proposes a tracking framework based on Voronoi tessellations. Two mobility models are proposed to control the coverage degree according to target presence. The objective is to set a non-uniform coverage within the monitored zone to allow detecting the target(s) by multiple sensor nodes. We show how the proposed algorithm adapts to the situation where multiple targets move in the monitored zone. Moreover, we introduce an algorithm to discover redundant nodes (which do not provide additional information about target position). This algorithm is shown to be effective in reducing the energy consumption using an activity scheduling approach. Simulations are carried out to underline the efficiency of the proposed models.
Comparative Study between Teaching Football with Oral and Oral/Graphic Verbalization  [PDF]
Makram Zghibi, Mohamed Jabri, Najmeddine Ouesleti, Chamseddine Guinoubi, Samira Welhezi, Moez Hamdi
Creative Education (CE) , 2013, DOI: 10.4236/ce.2013.46058
Abstract:

The aim of this study was to compare two methods of teaching using two different modalities of verbalization: oral and oral/graphic. We opted for a quantitative-comparative analysis of the pupils’ language typologies taken from oral and written productions of third secondary grade pupils who play football in a professional club (juniors of Olympic Kef, IInd league, 18 years old on average). The comparisons between the group proceeding to an oral verbalization versus the group using an oral/graphic one as well as intra-groups’ comparisons did not show clear significant differences. Despite of a statistical signification absence, we note that the two teams made a progress (increase in the number of played and conquered balls and the shots on target) especially during the last three sessions. Indeed, the debate of ideas is a process. It is relevant that the interaction between learning oral and graphic verbalization is more dynamic, whenever pupils verbalize orally and graphically, they are more motivated to learn.

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