Malekashtar University of Technology

engineering, Iran

Malekashtar University of Technology

engineering, Iran
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Hossein Mousavi S.M.,Islamic Azad University at Najafabad | Jafarboland M.,Malekashtar University of Technology
International Review on Modelling and Simulations | Year: 2012

In this paper, the effect of increased number of phases of brushless direct current motor (BLDC) has been investigated on the improvement of performance of this motor. First, a new model of 9-phase BLDC motor drive is studied and the model will be implemented using Matlab/Simulink software. The motor has been simulated through dynamic modeling and using the switching functions concept. In addition, in order to create constant torque and take advantage of the maximum torque capacity of motor, hysteresis current control method is used in the internal loop of speed and torque control system. Then, the results of simulation, including transient and steady state characteristics, will be compared with 3-phase, 5-phase and 7-phase models of this motor and the advantages and disadvantages of the increased number of phases in this motor will be reviewed. The results of comparison suggest the proposed nine-phase model of this motor to be more efficient in the applications intended in this paper, which enjoy a high performance. © 2012 Praise Worthy Prize S.r.l.

Sarshogh M.H.,Islamic Azad University at Najafabad | Jafarboland M.,MalekAshtar University of Technology
International Review on Modelling and Simulations | Year: 2012

In this paper a linear driver with high frequency, efficiency and power is designed and implemented to drive an array of pulsed power laser diodes. The driver's linear regulator includes a pulsed current source and a proper controller in control loop. This driver generates an optimum rise time, overshoot and ripple current pulsed for laser diode array. Besides the protecting circuits which are required for high power applications are optimized to protect the system against load disconnection and inadmissible increase in pulse width, frequency, duty cycle and current. The resulting current pulse shape and laser diode power output, for a laser diode array that is used in an oscillator amplifier head with 27 laser diodes of 100w power and 20 mj energy are demonstrated. © 2012 Praise Worthy Prize S.r.l.

Torkian S.,MalekAshtar University of Technology | Ghasemi A.,MalekAshtar University of Technology | ShojaRazavi R.,MalekAshtar University of Technology | Tavoosi M.,MalekAshtar University of Technology
Journal of Superconductivity and Novel Magnetism | Year: 2016

The aim of this work is to investigate the correlation between replacement of Fe3+ ions by Al3+ and structural and magnetic properties of Sr-hexaferrites. To this regard, a simple sol–gel auto-combustion method followed by subsequent heat treatment in air was employed to synthesize nanocrystalline SrFe12−xAlxO19 (0 ≤ x ≤ 4). X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Fourier-transform infrared (FT-IR), and vibrating sample magnetometer (VSM) methods were used in order to characterize the produced samples. The results show that the formation of the M-type hexaferrite phase is associated with some α-Fe2O3 as a secondary phase at low calcination temperature. By increasing the calcination temperature, high-purity hexaferrite phase without any unwanted phases can be formed. The average particle size of the substituted strontium ferrite gradually became smaller by addition of aluminum. The room temperature saturation magnetization values continuously reduced by increasing Al3+ that is contributed to substitution of Fe3+ by nonmagnetic ions in the lattice. However, the coercivity initially increases and then decreases with increasing the Al3+ content. A high coercivity up to 9.1 kOe was obtained for SrFe10Al2O19 which is much higher than the maximum theoretical value of HC for pure SrFe12O19 (7.5 kOe). © 2016 Springer Science+Business Media New York

Ghassemi H.,Amirkabir University of Technology | Yari E.,Malekashtar University of Technology
Polish Maritime Research | Year: 2011

Added mass is an important and effective dynamic coefficient in accelerating, non uniform motion as a result of fluid accelerating around a body. It plays an important role, especially in vessel roll motion, control parameters as well as in analyzing the local and global vibration of a vessel and its parts like propellers and rudders. In this article, calculating the Added Mass Coefficient has been examined for a sphere, ellipsoid, marine propeller and hydrofoil; using numerical Boundary Element Method. Since an Ellipsoid and a sphere have simple geometric shapes and the Analytical values of their added mass coefficients are available, so that the results of added mass matrix are obtained and evaluated, using the boundary element method. Then the added mass matrix is computed in a given geometrical and flow specifications for a specific propeller and its results are studied versus experimental results, which it's current numerical data In comparison with other numerical methods has a good conformity with experimental results. The most important advantage of the method in determining the added mass matrix coefficients for the surface and underwater vessels and the marine propellers is extracting all the added mass coefficients with very good Accuracy, while in other numerical methods it is impossible to extract all the coefficients with the Desired Accuracy.

Gorji M.,MalekAshtar University of Technology | Ghassemi H.,Amirkabir University of Technology | Mohammadi J.,MalekAshtar University of Technology
International Journal of Engineering, Transactions A: Basics | Year: 2016

The research performed in this paper is carried out to determine the marine propeller hydro-acoustic characteristics by Reynolds-Averaged Navier-Stokes (RANS) solver in both uniform and non-uniform wake flow at different operating condition. Wake flow can cause changes in pressure fluctuation.and gas effect on propeller noise spectrum. Noise is generated by the induced trailing vortex wake and induced pressure pulses. The two-step Fflowcs Williams and Hawkings (FW-H) equations are used to calculate hydrodynamic pressure and its performance as well as sound pressure level (SPL) at various points around the propeller. The directivity patterns of this propeller and accurate explanation of component propeller noise are discussed. Comparison of the numerical results shows good agreement with the experimental data. Based on these results, effects of wake flow and operating conditions on the noise reduction are investigated.

Farrokhi H.,Semnan University | Khani O.,MalekAshtar University of Technology | Nemati F.,Semnan University | Jazirehpour M.,MalekAshtar University of Technology
Synthetic Metals | Year: 2016

One of the substantial topics in business field and also for military purposes is radar absorbing technology. Intrinsic conducting polymers (ICP) such as polyaniline and polypyrrole which have advantages such as high conductivity, high flexibility, ease synthesis routes, high stability and good mechanical properties, have aroused intense of many researches for Radar absorbing materials (RAMs) applications. Also, these polymers can help to design the ideal RAMs. In this paper, the dielectric and microwave absorbing properties of 3D polypyrrole (PPy) microspheres consist of interweaved PPy nanostructures/paraffin composite have been reported in the frequency range of 2-18 GHz, for the first time. As well as, a one-step route for the chemical synthesis of PPy via a reactive template of MnO2 was successfully used. For this purpose, the reactive template of MnO2 was prepared by a facile hydrothermal method. The synthesized MnO2 was used as initiator for polymerization reaction. The XRD pattern and the EDX spectra confirmed that the MnO2 template consumed as the initiator. The SEM images indicated that the δ-MnO2 sample is composed of uniform flower-like microsphere nanostructures and the PPy nanostructures are totally inherited from the MnO2 templates. © 2016 Elsevier B.V. All rights reserved.

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