Highly stable implicit-explicit Runge-Kutta methods

We investigate implicit-explicit (IMEX) Runge-Kutta (RK) methods for differential systems with non-stiff and stiff processes. The construction of such methods with large regions of absolute stability of the 'explicit part' of the method assuming that the 'implicit part' of the scheme is A-stable, is described. We also describe the construction of IMEX RK methods, where the 'explicit part' of the schemes have strong stability properties. Examples of highly stable IMEX RK methods are provided up to the order p=4. Numerical examples are also given which illustrate good performance of these schemes.