Liste des publications
A Hybrid Integrated Ultra-Wideband/Dual-Band Antenna with High Isolation
In this paper, we propose a novel integrated ultra-wideband (UWB) monopole antenna with dual-band antenna. The antenna consists of planar rectangular with semi-elliptical base and a rectangular dielectric resonator antenna (DRA) with dual-band operation. Both of them are excited via coplanar waveguide (CPW) lines. The experimental measurements show that the planar monopole provides an impedance bandwidth between 2.44 and 11.9 GHz which largely covers the entire UWB spectrum, and the rectangular DRA operates at two bands; 5.3–6.2 and 8.5–9.4 GHz. Additionally, the proposed structure ensures low mutual coupling between the two ports (with S21 less than 22 dB in the whole operating frequency band). Voir les détails
Mots clés : CPW-fed line, Dielectric resonator antenna, Dual-band antenna, Integrated antennas, isolation, UWB antenna
Cr(VI) photocatalytic reduction under sunlight followed by Cr(III) extraction from TiO2 surface
The main objective of this work was the extraction of Cr(III) from TiO2 surface deposited after Cr(VI) reduction by TiO2 solar photocatalysis. The results show that the reduction of Cr(VI) to Cr(III) by TiO2 under natural sunlight is total after 2 h using tartaric acid (A.T) as a hole scavenger under the following conditions: [Cr(VI)]: 20 ppm, [TiO2]: 2 g/L, [A.T]: 60 ppm and pH: 2.2. The produced Cr(III) is divided between deposited onto TiO2 surface (39.75%) and in the solution (60.25%). The Cr(III) removal from TiO2 surface by the sequential extraction after three washing were 90.13% and 42.62% using citric acid and EDTA respectively. Voir les détails
Mots clés : Chromium, Reduction, Deposition, Solar light, extraction, TiO2 surface
Microstructure and residual stresses in Ti-6Al-4V alloy pulsed and unpulsedTIG welds
Increasing the pulse frequency in pulsed Tungsten Inert Gas arc welding refines the prior- grain size in the fusion zoneof Ti-6Al-4V compared to unpulsed arc welding. The microhardness increases in the fusion zones obtained with pulsed welding mode, with respect to this microstructural evolution. The increase of the pulse frequency contributes to the formation of a more important amount of residual phase in the fusion zone which is accompanied by a decrease of microhardness. The tensile residual stress (RS) level in the pulsed process is lower than the one of the unpulsed process. The tensile RS induced by both welding processes in the HAZ are found to decrease when increasing the pulse frequency. In the fusion zone, the transversal RS are of compressive type for both processes whereas the longitudinal ones change from tensile to compressive type when increasing the pulse frequency. Voir les détails
Mots clés : Ti-6Al-4V alloy, welding, pulsed current, microstructure, residual stress.
High/Low Gain Rectangular Dielectric Resonator Antenna for WLAN Applications
In this paper, a novel integrated dual-port rectangular dielectric resonator antenna (DRA) is presented for 802.11a WLAN system applications. The antenna structure is formed by integrating the concept of antenna array with a single DRA element to produce a radiation characteristic necessity. The array is composed of four identical rectangular DRA elements placed on a horizontal ground plane and separated by a distance of 0.54λ at design frequency of 5.97 GHz, excited through rectangular shaped aperture slots by a microstrip transmission line from port 1. The central element fed from port 2 by 50 Ohm microstrip line via a slot etched on the ground plane. The designed proposed antenna sized of 60×80×0.672 mm3 operates over the frequency band between 5 and 6 GHz for VSWR. Voir les détails
Mots clés : High/Low Gain antenna, dielectric resonator antenna (DRA)
Simulation of cracks detection in tubes by eddy current testing
The means of detection must ensure controls either during initial construction, or at the time of exploitation of all parts.The Non destructive testing (NDT) gathers the most widespread methods for detecting defects of a part or review the integrity of astructure.In the areas of advanced industry (aeronautics, aerospace, nuclear …),assessing the damage of materials is a key point to control durability and reliability of parts and materials in service.In this context, it is necessary to quantify the damage and identify thedifferent mechanisms responsible for the progress of this damage. It is therefore essential to characterize materials and identify the most sensitive indicators attached to damage to prevent their destruction and use themoptimally.In this work, simulation by finite elements method is realized with aim to calculate the electromagnetic energy of interaction: probe and piece (with/without defect). From calculated energy, we deduce the real and imaginary componentsof the impedance which enables to determine the characteristic parameters of a crack in various metallic parts. Voir les détails
Mots clés : Eddy Current, Non-destructive testing (NDT), Cracks, Finite, Element Method
Vector Fourier transform analysis of stacked rectangular microstrip patches on isotropic and anisotropic substrates
Galerkin’s method in the vector Fourier transform domain is used for computing the resonant frequencies of two stacked rectangular patches embedded in a multilayered media containing isotropic and/or uniaxial anisotropic dielectrics. The proposed method for determining the dyadic Green’s functions of the stacked configuration leads to a new concise expression, allowing the computation of these dyadic easily by using simple matrix multiplications. Numerical results are presented for two stacked rectangular patches fabricated on a two-layered substrate. Numerical results are also obtained for another stacked configuration involving three patches and five layers. The set of TM modes of a rectangular cavity with magnetic side walls are used in the approximation of the currents on the patches. Through numerical convergence checks, it is found that for symmetrical patches, only one mode per patch suffices to obtain good convergence, while for unsymmetrical patches, additional basis functions should also be included in both the approximation of the current on the lower patch and the one on the upper patch. The validity of the solution is tested by comparing the computed results with the known experimental data. The numerical results indicate that the two constitutive resonators of the stacked structure, which determine the dual-frequency behavior of the antenna, depend on the relative sizes of the lengths of the patches. Also, the numerical results show that substrate dielectric anisotropy has a more pronounced effect on the lower resonance than on the upper resonance. With regard to the bandwidth, we show that in order to bring the stacked antenna the benefits of broad band, it is necessary that the antenna operates at its lower (upper) resonance when b2 > b1 (b2 < b1). Other results also indicate that the displacement of the upper patch along the resonant direction constitutes an efficient tool for widening the separation between the upper and lower resonances. Voir les détails
Mots clés : Stacked patches Unsymmetrical patches Dual-frequency operation Full-wave analysis
Optimization of Distribution Functions for the Hysteresis Preisach Model by Genetic Algorithms
The description of hysteresis is one of the classical problems in magnetic materials. The progress in its solution determines the reliability of modeling and the quality of design of a wide range of contemporary devices, as well as devices that will be created in the future. The intensive investigations in hysteresis modeling were induced by the fact that accuracy models of magnetic hysteresis must be studied yet. In this paper, several identification procedures of the distribution functions of the Preisach model will be investigated by means of a genetic algorithm.The proposed approach has been applied to model the behavior of many samples and distribution functions are optimized which will give accurate results of the hysteresis loop. The results show the robustness and efficiency of genetic algorithm to model the phenomenon of hysteresis loop. This work can give solutions about the ferromagnetic material evaluations and shows the optimization of distribution functions according to the material behaviors. Voir les détails
Mots clés : Preisach Model, distribution functions, genetic algorithms GA, optimization
Contribution to Inverse Kinematic Modeling of a Planar Continuum Robot Using a Particle Swarm Optimization
According to the literature, research on modeling continuum robots isfocused on ways to develop the kinematic models, because of the lack of analyticalmodels for these robots and the complexity of the problem which reside in thecoupling of operational variables and infinite of possible solutions for a desiredconfiguration. This paper presents a numerical approach for solving the inversekinematic model of a planar continuum robot (PCR), assuming that each sectionof the manipulator is curved as a circular arc, with an inextensible central axis ofthe structure. At first, this paper presents an inverse kinematic model solution forone bending section, whereas the extreme points, of each section, used in calculatingthe inverse kinematic model for multi-sections is calculated numerically usinga particle swarm optimization (PSO) technique. Finally, Simulation examples ofthis method are carried to validate the proposed approach. Voir les détails
Mots clés : Planar continuum robot, modeling, Inverse kinematic model, optimization, Particle Swarm Optimization
A comparison of 1D analytical model and 3D Finite Element Analysis with experiments for a Rosen-type piezoelectric transformer
This article is dedicated to the study of Piezoelectric Transformers (PTs), which offer promising solutions to the increasing need for integrated power electronics modules within autonomous systems. The advantages offered by such transformers include: immunity to electromagnetic disturbances; ease of miniaturisation for example, using conventional micro fabrication processes; and enhanced performance in terms of voltage gain and power efficiency. Central to the adequate description of such transformers is the need for complex analytical modeling tools, especially if one is attempting to include combined con- tributions due to (i) mechanical phenomena owing to the different propagation modes which differ at the primary and secondary sides of the PT; and (ii) electrical phenomena such as the voltage gain and power efficiency, which depend on the electrical load. The present work demonstrates an original one-dimensional (1D) analytical model, dedicated to a Rosen-type PT and simulation results are successively compared against that of a three-dimensional (3D) Finite Element Analysis (COMSOL Multiphysics software) and experimental results. The Rosen-type PT studied here is based on a single layer soft PZT (P191) with corresponding dimensions 18 mm x 3 mm x 1.5 mm, which operated at the second harmonic of 176 kHz. Detailed simulational and experimental results show that the presented 1D model predicts experimental measurements to within less than 10% error of the voltage gain at the second and third resonance frequency modes. Adjustment of the analytical model parameters is found to decrease errors relative to experimental volt- age gain to within 1%, whilst a 2.5% error on the output admittance magnitude at the second resonance mode were obtained. Relying on the unique assumption of one-dimensionality, the present analytical model appears as a useful tool for Rosen-type PT design and behavior understanding. Voir les détails
Mots clés : Piezoelectric transformer, Rosen-type transformer, 1D analytical modelling, 3D FEA simulations, Experimental characterisation
Analysis and evaluation of the impact of climatic conditions on thephotovoltaic modules performance in the desert environment
The main objective of this study is to investigate the impact of climatic conditions on the performance ofphotovoltaic modules installed in the desert region in south of Algeria. Firstly, the performance ofISOFOTON 100 module under daily weather conditions is evaluated. Next, the effects of partial shadingand accumulation of sand dust for a period of two months on power loss and the current–voltagecharacteristics of photovoltaic modules are examined. Finally, the visual inspection of the degradationof the UDTS 50 modules such as discoloration of encapsulant and delamination show the influence ofhigh temperature and the other climatic factors in the Saharan environment after a long time exposureof more than 10 years observed in the field at the Unit of Research in Renewable energy URERMS Adrar.The performance degradation is also assessed using (I–V and P–V) curves normalized at STC conditioncompared with the nominal STC data given by the manufacturer. The experimental results show thatthe performance parameters such as maximum output current (Imax), maximum output voltage (Vmax),maximum power output (Pmax), open-circuit voltage (Voc), short-circuit current (Isc) and fill factor (FF)of UDTS 50 modules are degraded after these years of exposition. Voir les détails
Mots clés : Photovoltaic module, Performance evaluation, degradation, Desert environment