Positivity of an explicit Runge–Kutta method

This paper deals with the numerical solution of initial value problems (IVPs), for systems of ordinary differential equations (ODEs), by an explicit fourth-order Runge–Kutta method (we will refer to it as the classical fourth-order method) with special nonlinear stability property indicated by the positivity. Stepsize conditions, guaranteeing this property based on general theory,have been st…