Ghalee A.,Tafresh University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013
We propose a model for the dust matter in the cosmological context. The model contains a scalar field with a kinetic term nonminimally coupled to gravity. By investigating the background and perturbative equations, it is demonstrated that the scalar field has the same dynamics as the dust matter. We have also considered the cosmological constant in the model. It turns out that the model has not exotic behavior. Thus, a universe including the scalar field and the cosmological constant evolves just as our Universe. Moreover, we have added the quadratic term in the action. It is shown that the quadratic term can be ruled out by its consequences. © 2013 American Physical Society.
Madady A.,Tafresh University
International Journal of Control, Automation and Systems | Year: 2013
This paper presents a new iterative learning control (ILC) for discrete-time single-input single-output (SISO) linear time-invariant (LTI) systems. To establish this ILC, the input of the controlled system is modified by using a novel four-parametric algorithm. This algorithm is called the extended proportional plus integral and derivative (EPID) type, since by eliminating the fourth parameter of it one would get to the PID type ILC, therefore PID type ILC is a special case of it. The convergence of the proposed ILC is analyzed and an optimal method is presented to determine its parameters. It is shown that the given ILC has a better performance than the PID-type one. Three illustrative examples are included to demonstrate the effectiveness and the preference of the presented ILC. © 2013 Institute of Control, Robotics and Systems and The Korean Institute of Electrical Engineers and Springer-Verlag Berlin Heidelberg.
Yang X.-S.,National Physical Laboratory United Kingdom |
Gandomi A.H.,Tafresh University
Engineering Computations (Swansea, Wales) | Year: 2012
Purpose - Nature-inspired algorithms are among the most powerful algorithms for optimization. The purpose of this paper is to introduce a new nature-inspired metaheuristic optimization algorithm, called bat algorithm (BA), for solving engineering optimization tasks. Design/methodology/approach - The proposed BA is based on the echolocation behavior of bats. After a detailed formulation and explanation of its implementation, BA is verified using eight nonlinear engineering optimization problems reported in the specialized literature. Findings - BA has been carefully implemented and carried out optimization for eight well-known optimization tasks; then a comparison has been made between the proposed algorithm and other existing algorithms. Originality/value - The optimal solutions obtained by the proposed algorithm are better than the best solutions obtained by the existing methods. The unique search features used in BA are analyzed, and their implications for future research are also discussed in detail. © Emerald Group Publishing Limited.
Rezaei Z.,Tafresh University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012
The open string tachyon and U(1) gauge field as longitudinal fluctuations and the velocity as a transverse fluctuation of an arbitrary dimensional D-brane are considered as boundary deformations of a closed superstring free action. The path integral approach will be applied to calculate the corresponding generalized boundary states using supersymmetrized boundary actions. Obtaining the disk partition functions from the boundary states and studying the effect of tachyon condensation on both of them in the Neveu-Schwarz-Neveu-Schwarz and Ramond-Ramond sectors, leads to results that differ from the established ones. © 2012 American Physical Society.
Dehghanpour H.R.,Tafresh University
Journal of Experimental and Theoretical Physics | Year: 2014
We have generated Nd-Fe-B-C nanoparticles by Nd:YAG (1064 nm) laser irradiation in distilled water. Exposure times were 1, 5, and 10 min. Characterization of such nanoparticles in terms of their size distribution, shape, and chemical composition was carried out by transmission electron microscopy, energy-dispersive X-rays, and Fourier transform infrared spectroscopy. To investigate the nanoparticle stability, the size distribution of nanoparticles was measured two weeks after the nanoparticle generation, using dynamic light scattering. Investigations with the help of the atomic force microscope and magnetic force microscope showed other aspects of the generated nanoparticles. © 2014 Pleiades Publishing, Inc.