Al-Qadisiyah Journal for Engineering Sciences <p>Al-Qadisiyah Journal for&nbsp;Engineering Sciences&nbsp;(QJES) is a scientific Open Access peer-reviewed journal. It publishes research papers describing different disciplines &nbsp;of engineering sciences online and hard copy every three months since 2007.</p> <p>&nbsp;</p> en-US (Khaled Al-arhany) (admin) Sun, 14 Apr 2019 06:39:07 +0000 OJS 60 Optimization of Friction Stir Processing Parameters for Aluminum Alloy (AA6061-T6) Using Taguchi Method <p>This work is devoted toward optimization of the parameters of the friction stir processing (FSP) which effect on tensile strength of aluminium alloy AA6061-T6 of 6mm thick plate by applying a certain number of tests utilizing the Taguchi method. Design of experiment (DOE) has been applied for the determination of the most important parameters influencing ultimate tensile strength. FSP was achieved under three different rotation speeds (800,1000 and 1250) rpm, different transverse speeds (16,25 and 32) mm\min, and number passes(1,2 and 3)&nbsp; in the same direction and tool tilt angle was 2°&nbsp; with using threaded cylindrical pin profile.&nbsp; The best FSP parameters were 1250 rpm and 32 mm\min and two passes. It was found that the higher hardness value was 75HV in stir zone center and then decreases toward the TMAZ, HAZ and the base metal</p> Muna K. Abbassa, Noor Alhuda B. Sharhan ##submission.copyrightStatement## Sun, 14 Apr 2019 05:07:51 +0000 Reinforcing the Octagonal Web Openings of Castellated Beam by Steel Rings <p>Castellated steel beams are section steel members with hexagonal or octagonal web openings which they are made from standard hot rolled steel section I or H. The main advantage of these members is their economic material. An additional important advantage is a possibility to guide service ducts through the openings. The presence of the web openings influences the members’ failure behavior around the openings, new local failure modes will come into existence, such as the buckling of the web post between the openings, or yielding around the openings. Castellated beams with octagonal openings usually fail due to web post-buckling because of the increase in depth. The current study focused on improving the behavior of the castellated beam with octagonal openings using steel ring stiffener and adjusting the best dimension and distribution for the stiffeners. All the models of specimens have been fabricated from a parent I section (IPE 140). The models have been modeled and analyzed using finite element software ANSYS (version 15). The analysis results showed that reinforcing octagonal castellated beams by adding steel ring stiffeners around octagonal web opening was very active way to increase the ultimate load for long span, where the ultimate load of reinforced octagonal castellated beam increased up to (286%) compared with parent I-section beam. Economically, the percentage of additional steel material which used to expansion and reinforce the castellated beams (spacer plate and steel ring stiffeners) was (36%) when compared with the weight of parent I-section beam. While the allowable load at deflection (L/180) was (260 %) compared to the allowable load of parent section at the same deflection. The gained benefit was increasing the ultimate and allowable load of reinforced octagonal castellated beams by (186%) and (160%) respectively by using additional steel material only (36%) from the weight of parent I- section, which the additional steel material consisted from the spacer plates and steel rings. Also, the results indicate that the best dimensions for the ring were when thickness equal to the web thickness of the parent section and the width equal to the half of the parent section flange width.</p> Hayder W. Al-Thabhawee, Abbas A. Mohammed ##submission.copyrightStatement## Sun, 14 Apr 2019 05:59:23 +0000 Design of an RLC Compensator for a Synchronous Motor: Torque Ripple Improvement <p>AC-drive systems based Permanent Magnet Synchronous Motor (PMSM) are widely utilized in industrial applications due to many advantages including excellent efficiency, best reliability, and low-effective cost compared with DC-drive systems. Design and implementation of an RLC compensator for a PMSM-drive system is demonstrated in this paper. The main aims of using an RLC compensator are decreasing of Total-Harmonics-Distortion (THD) of the input line current and Ripple Factor (RF) of the electromagnetic torque over a wide range variation in rotor speed and load. The entire transfer function of the proposed system is derived for stability verification under the change of rotor speeds. The proposed PMSM-drive system is implemented with and without RLC compensator for two cases; which are at a fixed load and a step-change in load. Good performance is achieved using the proposed RLC compensator; in terms of THD and RF are 0.77% and 3.13%, respectively.</p> Bashar A. Fadheel ##submission.copyrightStatement## Sun, 14 Apr 2019 06:15:42 +0000 A Review and Comprehensive Study of Wireless Channel in Mobile Communication System: Fading Phenomena and Estimation <p>In wireless communication systems, the channel estimation problem has been played an essential challenge to accurately retrieve the channel state information (CSI) such that reliable communication &amp; wide coverage can be provided. Due to the improvement and rapid growth of communication systems and in order to maintain a reliable data transmission, estimation of CSI has become necessary. This in turn results, precise receiver demodulation, accurate decoding, and equalization processes. This paper gives a survey on a fading phenomena and a comprehensive review of the recent works that have already been done and studied related to the problem of estimating channel parameters in wireless communication systems. Varieties of best channel estimation techniques that have been recently evolved are explored. Comparison between them in terms of computational cost, simplicity and appropriateness conditions is also discussed. This paper also provides a basic introduction of wireless channel model, SIMO and MIMO channel.</p> Awwab Q. Jumaah ##submission.copyrightStatement## Sun, 14 Apr 2019 06:36:57 +0000