رغد حامد هلال
الجامعة التكنولوجية · العراق
Amina Saadi, Mohamed Lazhar Chikhi, Roumaissa Kasraoui
كلية التكنولوجيا-جامعة سعد دحلب - البليدة · الجزائر
La théorie du chaos traite des systèmes dynamiques non linéaires déterministes, mais qui ont la propriété fondamentale de leur extrême sensibilité aux conditions initiales, ce qui les rend non prédictibles en pratique à long terme. Après une description sur les principales propriétés des systèmes dynamiques en général, et chaotiques en particulier, l’étude détaillée du générateur chaotique multi -scrolls a été développée ainsi que sa simulation sous environnement Matlab-Simulink. Son implémentation sur circuit FPGA a ensuite été développée sous environnement System Generator sous Matlab Simulink pour les générateurs chaotiques 2 scrolls (circuit deChua), 4 scrolls et 5 Scrolls. La Simulation des codes VHDL ainsi générés a été faite sous le logiciel Modelsim. L’implémentation FPGA du générateur chaotique multi-scrolls a été réalisée sur la carte ML501-Virtex 5 de Xilinx en utilisant le codec audio AC’97intégré dans la carte pour la visualisation des différents signaux sur oscilloscope numérique.
أسما الياس, علا يحيى عبله
الجامعة الافتراضية السورية · سوريا
Knarig Garabed Meghdessian, George Najjar
كلية سليمان العليان لإدارة الأعمال -الجامعة الأمريكية في بيروت-الجامعة الأمريكية في بيروت · لبنان
Elham K. A Serria, Mousa Hussein
كلية الهندسة-جامعة الإمارات العربية المتحدة · الامارات
Antenna engineering is very important in the development of communication systems and the requirements for low profile antennas that cover a wide spectrum of frequencies increase the number of researches in this field. Accordingly, scientists have focused on UWB microstrip antennas that cover the range from 3.1 GHz to 10.6 GHz but others concentrate on enhancing its performance using a special type of materials called metamaterials. The main objective of this work is to enhance frequency bandwidth, antenna gain, and radiation pattern for the UWB circular microstrip antenna by employing the Split Ring Resonator (SRR) technique, which is one type of metamaterial. Circular and square split-ring resonators are investigated as an enhancement method after studying their characteristics. Multiple techniques are also applied to these two structures prior to being implemented at the antenna’s backside including different SRR schematics such as the SRR position with respect to the ground, inner and outer ring rotation, positive and negative rotation angle, number of SRR units, SRR size, SRR design, in addition to using the complementary SRR. Furthermore, two techniques are combined together in some designs to observe how the antenna’s performance will be affected. The proposed techniques rely on the variation in capacitance and inductance which will affect the resonant frequency of the SRR unit cell. Then some SRR Schematics were implemented in the proposed circular antenna design to test the functionality within WiFi frequencies 2.4 GHz and 5 GHz. The enhancement can be summarized in increasing antenna bandwidth and transmitting or rejecting specific frequency bands. The results of the study reveal an enhancement in circular antenna performance. UWB circular antenna with elliptical rings has a frequency bandwidth between 3.5 GHz to 9 GHz and a maximum gain of around 5 dB; during the enhancement process using the previously mentioned techniques, the frequency bandwidth increased to cover the range from 2.2 GHz to 9.8 GHz along with some bands rejection. It was noted that some rejected bands have shifted to higher frequencies when applying inner or outer ring rotation. To emphasize this, WiFi frequencies 2.4 GHz and 5GHz are inspected by using the suitable size of S-SRR to decide which frequency to reject or transmit depending on the communication applications. The outcomes of this work should assist in designing antennas with SRR depending on required communication applications and operating frequencies.
Ali Fourar , Kamel Rahmani
كلية التكنولوجيا-جامعة باتنة 2 - الشهيد مصطفى بن بولعيد · الجزائر
Un modèle numérique, unidimensionnel, instationnaire d’onde de rupture debarrage et sa propagation dans l’aval du barrage, est présenté dans ce travail, pourétudier les phénomènes de rupture de barrage dans les déférentes parties dans le canalaval après la rupture. Les équations de continuité et conservation de quantité demouvement (l’équation de saint venant) ont été résolues à l’aide du programme enfortran, basé sur la méthode des différences finis, l’effet de pente du canal, lefrottement et la largeur du canal, zone inondable approchés sont étudiés.
عبدالحميد عقاقبة, ليلى خلو
كلية العلوم الإنسانية والاجتماعية-جامعة محمد خيضر - بسكرة · الجزائر
Mark John Hammar, Suhail Ahmad
كلية تصاميم البيئة-جامعة الملك فهد للبترول والمعادن · السعودية
Tertiary treatment was given to the secondary wastewater effluent of the North Aramco Wastewater Treatment Plant, Dhahran, in order to utilize it for unrestricted reuse and landscape irrigation. The process employed for this study consisted of coagulation, flocculation, sedimentation, granular media filtration and chlorination. A bench scale study was conducted to optimize coagulant dosages and filtration rate to produce a satisfactory filtered effluent for chlorination. Based upon the experimental data, a coagulant dosage and filtration rate was suggested for the tertiary treatment of two kinds of wastewater effluent (chlorinated and unchlorinated). A mathematical relationship was developed based upon the batch chlorination data to determine the chlorine residual and contact time to achieve an effluent coliform concentration of less than 2.2 MPN/100 m1 that is safe for unrestricted reuse as described by Title 22 of California Administrative Code.
Waka Tesfai, Youssef Shatilla
جامعة خليفة · الامارات
Cooling has become a major challenge for system design and performance in the fast growing technology. This development is pushing the conventional cooling methods to its limitation and there is an ever increasing call for new cooling methods to cope with current technologies. One of the possible ways of satisfying this demand is by introducing nanofluids as heat transfer fluids. Nanofluids are colloidal suspension of nanoparticles with enhanced thermal conductivity engineered for heat transfer application. Understanding the thermophysical property of nanofluids is crucial for their practical applications. The main objective of the present study is to investigate the viability of nanofluids for heat transfer applications. The applicability of Pump-probe technique for measurement of nanoscale thermal transport in nanofluids was investigated. Stable nanofluids of Copper, Zirconia, Silicon Carbide and Yttria in water and ethylene glycol base fluids were prepared by the conventional two step method without addition of surfactants. Particle size and zeta potential characterization of the nanofluids were carried out by electro-acoustic and DLS techniques. Yttria based nanofluids were found promising for their stability and dielectric properties. The viscosity of yttria nanolfuids increased with concentration almost linearly and showed an increment of around 3% at 0.1 vol% to 45 % at 5 vol% of particle. This increment was found beyond the prediction of Einstein or Batchelor theoretical models. The effective viscosity of these nanofluids showed non-linear dependence on temperature and this was due to particle-particle interaction which is observed from the higher orders fitting values of Arrhenius model. Theoretical analyses for the efficacy of Yttria and copper nanofluids are made for laminar and turbulent flow regimes. In laminar flow regimes, Yttria nanofluids showed promising results above 37oC and a maximum of 16% increase in efficiency was gained at working temperatures of 100oC. Similarly, Copper nanofluids were found viable for temperatures above 50oC with an efficiency gain of 7.5% maximum. In case of turbulent flow applications, Yttria nanofluids remain better coolants for temperature above 45oC despite of Copper nanofluids incompetence in the experimental range of temperature.
BOUYAKOUB Amel zahira, S. KACIMI
كلية العلوم-جامعة أبو بكر بلقايد - تلمسان · الجزائر
La bentonite de maghnia (ouest d'Algérieà) a été purifiée et caractérisée par différentes tequniques. Cette argile est dence (1g/cm3), basique (PH=10.7). Ses capacités au gonflement et d'échange cationique sont trés importanes : Cg=8 et CEC=0.90 meq/g. Sa conductivité électrique est de 66.4uS.
