Marzocca P.,Clarkson University |
Fazelzadeh S.A.,Shiraz University |
Hosseini M.,Sirjan University of Technology
Journal of Thermal Stresses | Year: 2011
Functionally Graded Materials (FGM) have attracted significant interest as heat-shielding materials for space vehicle, skin sub-structures, gas turbine blades technologies, and many other high-temperature industrial applications. This paper reviews the state-of-the-art in linear and nonlinear aero-thermo-elasticity of FGM panels with emphasis on the authors' contributions to the topic. An overview of the pertinent literature discussing the linear and nonlinear behavior of flat and curved panels when exposed to high temperature supersonic flow fields is presented first. The effect of material property dependency on temperature is also discussed. The study addresses divergence and flutter and methodologies used to determine these aerothermo- elastic instabilities. In particular, critical and post-critical behaviors for panels in presence of thermal loads are addressed, along with a series of divergence, flutter, and post-flutter results obtained with linear/nonlinear dynamics approaches. Regular and chaotic motions regime are determined through qualitative tools, such as bifurcation analysis using Poincaré maps, panel time history, phase-space evolutions, and frequency spectra, and with quantitative tools, such as the Lyapunov's exponents and dimensions. Finally, conclusions and directions for further work in the field are presented. Copyright © Taylor & Francis Group, LLC.
Sajjadi H.,Shahid Bahonar University of Kerman |
Beigzadeh Abbassi M.,Sirjan University of Technology |
Kefayati G.H.R.,Flinders University
Journal of Mechanical Science and Technology | Year: 2013
In this paper, lattice Boltzmann simulation of turbulent natural convection with large-eddy simulations (LES) in a square cavity which is filled by water/copper nanofluid has been investigated. The present results are validated by experimental data at Ra = 1.58×109. This study is conducted for high Rayleigh numbers (Ra = 107-109) and volume fractions of nanoparticles (0 ≤ Φ ≤ 0.06). In this research, the effects of nanoparticles are displayed on streamlines and isotherms counters, local and average Nusselt numbers. The average Nusselt number is enhanced by the augmentation of nanoparticle volume fraction in the base fluid while the manner has an erratic trend toward different Rayleigh numbers. © 2013 The Korean Society of Mechanical Engineers and Springer-Verlag Berlin Heidelberg.
Asadi M.,Sirjan University of Technology
Journal of Rock Mechanics and Geotechnical Engineering | Year: 2016
Development of accurate and reliable models for predicting the strength of rocks and rock masses is one of the most common interests of geologists, civil and mining engineers and many others. Due to uncertainties in evaluation of effective parameters and also complicated nature of geological materials, it is difficult to estimate the strength precisely using theoretical approaches. On the other hand, intelligent approaches have attracted much attention as novel and effective tools of solving complicated problems in engineering practice over the past decades. In this paper, a new method is proposed for mining descriptive Mamdani fuzzy inference systems to predict the strength of intact rocks and anisotropic rock masses containing well-defined through-going joint. The proposed method initially employs a genetic algorithm (GA) to pick important rules from a preliminary rule base produced by grid partitioning and, subsequently, selected rules are given weights using the GA. Moreover, an information criterion is used during the first phase to optimize the models in terms of accuracy and complexity. The proposed hybrid method can be considered as a robust optimization task which produces promising results compared with previous approaches. © 2016 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences.
Makiabadi B.,Sirjan University of Technology
Journal of Sulfur Chemistry | Year: 2015
Quantum chemical calculations were used to investigate the interaction of tautomer forms of thiazolidine-2-thione (T2T) with iodine in the gas and solution phases. The calculations show that the planar complexes are more stable than the perpendicular complexes. Also in the perpendicular complexes, the thione form is more stable than the thiol form. The calculated thermodynamic parameters in the solution phase indicate that the stability of the formed complexes increases as the dielectric constant of the solvent is increased. This result is in good agreement with the experimental results. The NBO results predict that the LP(S) → σ∗(I-I) and LP(S) → σ∗(N-H) charge transfer (CT) interactions are very important in the stabilizing of the planar complexes with respect to the perpendicular complexes. In all complexes, CT takes place from T2T to I2. Therefore, it is predicted that the donor properties of T2T are the origin of its anti-thyroid action. The atoms in molecule (AIM) analysis shows that the interactions in the planar complexes are stronger than the perpendicular complexes. © 2015 Taylor and Francis.
Mahmoodabadi M.J.,Sirjan University of Technology |
Momennejad S.,Islamic Azad University |
Bagheri A.,Guilan University
Information Sciences | Year: 2014
Regulation and tracking of system states to the desired points or trajectories are two common tasks in the field of control engineering. For optimum performance of a controller, the appropriate selection of its parameters is of utmost importance. Furthermore, when the initial conditions of the system change, the controller with the previous parameters would be not optimum in the new conditions. To overcome these obstacles, in this paper, an online optimal Decoupled Sliding Mode Control (DSMC) approach is introduced. Firstly, to determine the optimum parameters of DSMC, an improved Particle Swarm Optimization (PSO) algorithm is applied. Next, to adapt the optimal controller to any initial condition, the Moving Least Squares (MLS) approximation is utilized. Finally, the proposed online optimal DSMC is successfully applied to a ball and beam system. The comparative studies are provided to verify the effectiveness of the proposed control scheme. © 2014 Elsevier Inc. All rights reserved.