  Within the context of a cosmic space whose energy source is modeled with a
perfect fluid, a uniform model of Universe based on a standard FRW cosmology
containing decoupled mixed matter sources namely stiff matter and cosmic dust
together with a positive cosmological constant, has been studied. Within the
scenario of a $k=0-$ spatially-flat geometry, we analysed the geometrodynamics
of the theoretical cosmology. For the model with an added cosmological
constant, the main scope was to point out the effects of it on the universe'
dynamics. In this last case, the thermodynamics of the model was also
considered together with the relation between the cosmological energy density
and fluid pressure in terms of the inverse function of the equation of state.
