A modified variational approach called Global Error Minimization (GEM) method is developed for obtaining an approximate closed-form analytical solution for nonlinear oscillator differential equations. The proposed method converts the nonlinear differential equation to an equivalentminimization problem. A trial solution is selectedwith unknown parameters. Next, the GEM method is used to solve th...

The asymptotic equivalence of linear and quasilinear impulsive dynamic equations on time
 scales, as well two types equations, are proven under mild conditions. To establish the a method has been developed that does not require
 restrictive conditions, such boundedness solutions. Not only time scale extensions former
 results have obtained, but also improved for differential defi...

This paper revisits the resonant behavior of a harmonically-forced Duffing oscillator with specific attention to phase resonance and its relation amplitude resonance. To this end, different families resonances, namely primary (1:1), superharmonic (k:1), subharmonic (1:ν) ultra-subharmonic (k:ν) resonances are carefully studied using first higher-order averaging. When lag is calculated between k...

background: pulmonary function tests (pfts) are used in assessing physiological to clinical status of the respiratory system, which is expressed as a percentage of predicted values. predicted pfts values are varies in different ethnics. predicted pfts values were studied in a sample of iranian children. materials and methods: prediction equations for pfts were derived from urban children in the...