  We discuss the dynamical effects of bulk viscosity and particle creation on
the early evolution of the Friedmann -Robertson -Walker model in the framework
of open thermodynamical systems. We consider bulk viscosity and Particle
creation as separate irreversible processes. Exact solutions of the Einstein
field equations are obtained by using the "gamma-law" equation of state
$p=(\gamma -1)\rho$, where the adiabatic parameter $\gamma$ varies with scale
factor of the metric. We consider the cosmological model to study the early
phases of the evolution of the universe as it goes from an inflationary phase
to a radiation -dominated era in the presence of bulk viscosity and particle
creation. Analytical solutions are obtained for particle number density and
entropy for all models. It is seen that, by choosing appropriate functions for
particle creation rate and bulk viscous coefficient, the models exhibit
singular and non-singular beginnings.
