in this paper the effects of non-linearity of suspension on dynamic behavior of a railway wheelset has been studied. this wheelset has four degrees of freedom that with two constraints it has reduced to two degrees of freedom. vermeulen-johnson theory has been used to calculate contact forces between wheel and rail. in this study the creep coefficients have considered constant. any linearizatio...

this paper considers the problem of stable limit cycles generating in a class of uncertain nonlinear systems which leads to stable oscillations in the system’s output.this is a wanted behavior in many practical engineering problems. for this purpose, first the equation of the desirable limit cycle is achieved according to shape, amplitude and frequency of the required output oscillations. then,...

the focus of studies in the field of passive walking has often been on straight walking, while less attention has been paid to the field of turning motions. in this paper, the passive motions of a finite width rimless wheel as the simplest 3d model of passive biped walkers was investigated with a focus on turning motions. for this purpose, the hybrid model of the system consisting of continuous...

in this paper, we introduce fractional order of a planar fractional prey-predator system with a nonmonotonic functional response and anti-predator behaviour such that the adult preys can attack vulnerable predators. we analyze the existence and stability of all possibleequilibria. numerical simulations reveal that anti-predator behaviour notonly makes the coexistence of the prey and predator po...

In this paper we give sufficient conditions to ensure uniqueness of limit cycles for a class of planar vector fields. We also exhibit a class of examples with exactly one limit cycle.

We study quadratic perturbations of the integrable system (1 + x)dH, where H = (x2 + y2)/2. We prove that the first three Melnikov functions associated to the perturbed system give rise at most to three limit cycles.

We consider a planar differential system ˙ x = P (x, y), ˙ y = Q(x, y), where P and Q are C 1 functions in some open set U ⊆ R 2 , and ˙ = d dt. Let γ be a periodic orbit of the system in U. Let f (x, y) : U ⊆ R 2 → R be a C 1 function such that P (x, y) ∂f ∂x (x, y) + Q(x, y) ∂f ∂y (x, y) = k(x, y) f (x, y), where k(x, y) is a C 1 function in U and γ ⊆ {(x, y) | f (x, y) = 0}. We assume that i...