Liste des documents
Water quality of the plain of El-Hadjar wilaya of Annaba (Northeast Algeria)
The region of El- Hadjar is known for its diversity of industries that stretch of the steel industry to the food and materials processing. Industrial and domestic waste is channeled into streams Oued Seybouse is its major tributary Oued Meboudja, both flanked with major industrial areas. Pollution of surface and groundwater has become a particular problem of interest for health and environmental conservation. This study aims to physico- chemical characterization of waters in this area using 11 sampling points covering the entire area of a spread on rivers and plains of El Hajar). The results are expressed in terms of concentrations of the various pollutants such as nitrate, nitrite and chloride in a first step. The physico -chemical parameters were recorded over a period of seven months during 2009 and relate to salinity, conductivity, pH, Eh ... It was found that the region is moderately polluted following the accepted standards. The data are correlated with industrial and agricultural activity in the region. The study is in the process of being completed by a water quality map of the entire region with the concentrations of hydrocarbons and heavy metals. The evolution of these parameters will develop a policy for the preservation of the environment that is needed in these times. Voir les détails
Mots clés : pollution, environment, surface water, groundwater quality, physical and chemical analysis, environmental policy, El- Hajar.
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
Enhancement of phased array ultrasonic signal in compositematerials using TMST algorithm
In this paper, we apply a new technique for the ultrasonic phased array signal enhancement. It is based on the threshold modifiedS-transform (TMST). The signal processing algorithms generally give very satisfactory results on synthetic signals verifying theimplicit or explicit hypotheses on which they are constructed. The obtained performances on the real signals can be howeverdifferent radically. Time–frequency analysis methods are mainly used to improve the defects detection resolution. Significantperformance enhancement is confirmed when the proposed approach is tested with the simulation of the B-scan signals contain acloser delamination to the front face. The experimental results show that the TMST Algorithm can enhance the quality of imageprovided by composite materials contained delamination defect. Voir les détails
Mots clés : Ultrasonic Phased Array, composite materials, S-transform, TMST Algorithm
DSC analysis of commercial Cu-Cr-Zr alloy processed by equal channel angular pressing
Samples of a commercial Cu-1Cr-0.1Zr (mass fraction, %) alloy were subjected to equal channel angular pressing(ECAP) up to 16 passes at room temperature following route Bc. Differential scanning calorimetry (DSC) was used to highlight theprecipitation sequence and to calculate the stored energy, recrystallization temperature and activation energy after each ECAP pass.On another hand, electrical properties were correlated with the dislocation density. Results show that the stored energy increasesupon increasing ECAP pass numbers, while the recrystallization temperature decreases significantly. Voir les détails
Mots clés : equal channel angular pressing (ECAP), Cu-Cr-Zr alloy, differential scanning calorimetry (DSC), electrical conductivity, stored energy
Comportement structural et mécanique dessoudures en aciers inoxydables austénitique etduplex réalisées par le procédé TIG
L’objet de cette étude étant de connaître lesdifférentes variations structurales et mécaniques après un cyclethermique de soudage de deux aciers inoxydables de hauteperformance (austénitique AISI 316L et duplex AISI 2205), quisont très utilisés dans tous les secteurs, particulièrementl’industrie pétrolière. On a utilisé le procédé TIG, c’est unprocédé à arc électrique, caractérisé par son apport thermiqueintense et précis aisément automatisé, l’état microstructurale desassemblages soudés a été analysées par des observationsmétallographique optique de différentes zones à savoir : la zonefondue ZF, la zone affectée thermiquement ZAT et le métal debase MB. Finalement les changements microstructurales ont étéargumentés par une filiation de micro-dureté. Voir les détails
Mots clés : Acier inoxydable austénitique, duplex, soudage TIG, micro-dureté et contrôle
POLYPYRROLE COATED CELLULOSIC SUBSTRATE MODIFIED BY COPPER OXIDE AS ELECTRODE FOR NITRATE ELECTROREDUCTION
The aim of this work is to synthesize polypyrrole (PPy) films on nonconducting cellulosic substrate and modified by copper oxide particles for use in the nitrate electroreduction process. Firstly, the chemical polymerization of polypyrrole onto cellulosic substrate is conducted by using FeCl3 as an oxidant and pyrrole as monomer. The thickness and topography of the diferent PPy films obtained were estimated using a profilometer apparatus. The electrochemical reactivity of the obtained electrodes was tested by voltamperometry technique and electrochemical impedance spectroscopy. Secondly, the modification of the PPy film surface by incorporation of copper oxide particles is conducted by applying a galvanostatic procedure from a CuCl2 solution. The SEM, EDX and XRD analysis showed the presence of CuO particles in the polymer films with dimensions less than 50 nm. From cyclic voltamperometry experiments, the composite activity for the nitrate electroreduction reaction was evaluated and the peak of nitrate reduction is found to vary linearly with initial nitrate concentration. Voir les détails
Mots clés : Polypyrrole, cellulosic, CuO, electrocatalysis, Nitrate
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
The effect of copper concentration on CdS/CZTSheterojunction properties
Cu2ZnSnS4 (CZTS) / CdS heterojunctions have been prepared by a successive deposition of CZTS and CdS thin films on glass substrates by spray pyrolysis and chemical bath deposition techniques respectively. The concentration of cupric chloride in the starting solution has been varied in order to investigate its influence on device properties. The realized CZTS/CdS heterojunctions were characterized by recording their IV characteristics at ambient and at different temperatures. The current-voltage (IV) characteristics of the different heterostructures exhibit a rectifying behavior with a good ideality factor ranged from 1.5 to 2.7. From these IV characteristics we have deduced the saturation current series resistance and barrier height of the devices. We found that these quantities vary from 0.22 to 1.68µA for the saturation current and from 300 to 2500 for the series resistance. We have deduced also that the potential barrier was found between 0.3 and 1.31eV. From these results we inferred that the realized structures are suitable for their applications as solar cells. Voir les détails
Mots clés : CZTS; heterojunction; spray pyrolysis; solar cells;IV
Structural, Optical and Electrical Properties of PbS Thin Films Deposited by CBD at Different Bath pH
PbS thin films were grown on glass substrates by chemical bath deposition (CBD). The precursor aqueous bath contained 1mole of lead nitrate, 1mole of Thiourea and complexing agents (triethanolamine (TEA) and NaOH). Bath temperature and deposition time were fixed at 60°C and 3 hours, respectively. However, the PH of bath was varied from 10.5 to 12.5. Structural properties of the deposited films were characterized by X-ray diffraction and Raman spectroscopy. The preferred direction was revealed to be along (111) and the PbS crystal structure was confirmed. Strains and grains sizes were also calculated. Optical studies showed that films thicknesses do not exceed 600nm. Energy band gap values of films decreases with increase in pH and reached a value ~ 0.4eV at pH equal 12.5. The small value of the energy band gap makes PbS one of the most interesting candidate for solar energy conversion near the infrared ray Voir les détails
Mots clés : CBD, PbS, pH, Thin films, X-ray diffraction
Sensor Monitoring of the Concentrations of Different Gases Present in Synthesis of Ammonia Based On Multi-Scale Entropy and Multivariate Statistics
This paper presents powerful techniques for the development of a new monitoring method based on multi-scale entropy (MSE) in order to characterize the behaviour of the concentrations of different gases present in the synthesis of Ammonia and soft-sensor based on Principal Component Analysis (PCA). Voir les détails
Mots clés : Ammonia synthesis, Concentrations of different gases, Soft sensor, Multi-scale entropy, multivariate statistics.