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Rational energy balance method to nonlinear oscillators with cubic term
, Article Asian-European Journal of Mathematics ; Volume 6, Issue 2 , 2013 ; 17935571 (ISSN) ; Ahmadpoor, M. A ; Askari, H ; Yildirim, A ; Sharif University of Technology
2013
Abstract
In this paper, a novel approach is proposed for solving the nonlinear problems based on the collocation and energy balance methods (EBMs). Rational approximation is employed as an initial guess and then it is combined with EBM and collocation method for solving nonlinear oscillators with cubic term. Obtained frequency amplitude relationship is compared with exact numerical solution and subsequently, a very excellent accuracy will be revealed. According to the numerical comparisons, this method provides high accuracy with 0.03% relative error for Duffing equation with strong nonlinearity in the second-order of approximation. Furthermore, achieved results are compared with other types of...
Higher-order energy balance method for a series of nonlinear oscillatory systems
, Article Asian-European Journal of Mathematics ; Volume 6, Issue 4 , December , 2013 ; 17935571 (ISSN) ; Safaie, N ; Ahmadpour, M. A ; Askari, H ; Sharif University of Technology
2013
Abstract
The aim of this paper is to use higher-order energy balance method as a novel solution procedure for investigation the nonlinear oscillation of various systems. The method is associated with collocation method and employed for a group of nonlinear problems including pure cubic nonlinearity, fractional elastic force and duffing harmonic terms. Obtained results are evaluated by comparing with the classical balance method and also the exact solutions computed numerically. It is shown our solution procedure achieves more accurate results versus the classical solution and higher agreement are observed between the newer solutions and the exact ones for the systems. Effect of initial conditions in...
Mapping surface temperature in a hyper-saline lake and investigating the effect of temperature distribution on the lake evaporation
, Article Remote Sensing of Environment ; Volume 136 , 2013 , Pages 374-385 ; 00344257 (ISSN) ; Ahmadalipour, A ; Tajrishy, M ; Sharif University of Technology
2013
Abstract
Remote sensing is an effective tool for capturing spatial and temporal variations of water surface temperature (WST) in large lakes. The WST of Urmia Lake in northwestern Iran was examined from 2007 to 2010, using MODIS land surface temperature (LST) products. Spatial and temporal (diurnal, monthly, seasonal and inter-annual) variations of Urmia Lake WST were also investigated. Results indicate that the MODIS-derived WSTs are in a good agreement with the in situ data (R2=0.92 and bias=-0.27). Spatial analysis of WST revealed that there are three thermal zones along the lake: the shallow region in barriers of the causeway, islands and the shoreline; the south part; and the deep north parts....