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Ahmadivand A.,Islamic Azad University at Ahar
Optics and Laser Technology | Year: 2014

In this work, a broadband efficient hybrid Photonic-Plasmonic polarization beam splitter (HPPPBS) based on metal-silica-silicon interactions is proposed and investigated numerically. This device contains two silicon (Si) nanofibers with specific examined dimensions, a silica (SiO2) waveguide and a straight chain of Au nanoshells which is encompassed by silica host. All of the mentioned fibers and waveguide are deposited on a Mg2F crystal host. It is shown that this structure is working properly at near infrared region (NIR), specifically at telecommunication wavelength (λ≈1550 nm). Furthermore, relevant optical characteristics have been examined and studied, thoroughly. The quality of polarization splitting is demonstrated for both transverse electric (TE) and magnetic (TM) modes in separate figures. Simulation results corroborate that the sensitivity and accuracy of the superstructure during polarization dividing and light propagating are noticeable in comparison to analogous devices. Finite-difference time-domain method (FDTD-M) is utilized to examine the optical properties of the presenting structure. © 2013 Elsevier Ltd. Source

Safari A.,Islamic Azad University at Ahar | Shayeghi H.,University of Mohaghegh
Expert Systems with Applications | Year: 2011

In this paper, iteration particle swarm optimization (IPSO) has been applied to determine the feasible optimal solution of the economic load dispatch (ELD) problem considering various generator constraints. Many realistic constraints, such as ramp rate limits, generation limitation, prohibited operating zone, transmission loss and nonlinear cost functions are all considered for practical operation. The performance of the classical particle swarm optimization (CPSO) greatly depends on its parameters, and it often suffers the problem of being trapped in local optima. A new index named, Iteration Best, is incorporated in CPSO to enrich the searching behavior, solution quality and to avoid being trapped into local optimum. Two test power systems, including 6 and 15 unit generating, are applied to compare the performance of the proposed algorithm with PSO, chaotic PSO, hybrid GAPSO, self organizing hierarchical PSO (SOH-PSO) methods. The numerical results affirmed the robustness and proficiency of proposed approach over other existing methods. © 2010 Elsevier Ltd. All rights reserved. Source

Kourehli S.S.,Islamic Azad University at Ahar
International Journal of Structural Stability and Dynamics | Year: 2015

This paper presents a novel approach for structural damage detection and estimation using incomplete noisy modal data and artificial neural network (ANN). A feed-forward back propagation network is proposed for estimating the structural damage location and severity. Incomplete modal data is used in the dynamic analysis of damaged structures by the condensed finite element model and as input parameters to the neural network for damage identification. In all cases, the first two natural modes were used for the training process. The present method is applied to three examples consisting of a simply supported beam, three-story plane frame, and spring-mass system. Also, the effect of the discrepancy in mass and stiffness between the finite element model and the actual tested dynamic system has been investigated. The results demonstrated the accuracy and efficiency of the proposed method using incomplete modal data, which may be noisy or noise-free. © World Scientific Publishing Company. Source

Aghababa M.P.,Islamic Azad University at Ahar
Chinese Physics B | Year: 2011

In this paper, the problem of the finite-time synchronization of two uncertain chaotic gyros is discussed. The parameters of both the master and the slave gyros are assumed to be unknown in advance. The effects of model uncertainties and input nonlinearities are also taken into account. An appropriate adaptation law is proposed to tackle the gyros' unknown parameters. Based on the adaptation law and the finite-time control technique, proper control laws are introduced to ensure that the trajectories of the slave gyro converge to the trajectories of the master gyro in a given finite time. Simulation results show the applicability and the efficiency of the proposed finite-time controller. © 2011 Chinese Physical Society and IOP Publishing Ltd. Source

Aghababa M.P.,Islamic Azad University at Ahar
Journal of Computational and Nonlinear Dynamics | Year: 2014

The problem of stabilization of nonlinear fractional systems in spite of system uncertainties is investigated in this paper. First, a proper fractional derivative type sliding manifold with desired stability and convergence properties is designed. Then, the fractional stability theory is adopted to derive a robust sliding control law to force the system trajectories to attain the proposed sliding manifold and remain on it evermore. The existence of the sliding motion is mathematically proven. Furthermore, the sign function in the control input, which is responsible to the being of harmful chattering, is transferred into the fractional derivative of the control input. Therefore, the resulted control input becomes smooth and free of the chattering. Some numerical simulations are presented to illustrate the efficient performance of the proposed chattering-free fractional variable structure controller. Copyright © 2014 by ASME. Source

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