  We investigate the accelerated expansion of the late-time universe in the
Friedmann-Robertson-Walker metric with nonzero curvature, applying a
holographic principle based on a generalized holographic dark energy model
introduced by Nojiri and Odintsov (2005,2006). We describe the evolution of the
universe using a generalized equation of state in the presence of a viscous
fluid. Solutions of the gravitational equation of motions are obtained in
explicit form for a constant value of the thermodynamic parameter, and for
various forms of the bulk viscosity. We calculate analytic expressions for
infrared cut-offs in terms of the particle horizon, and derive the energy
conservation law in the holographic picture. We show that the inclusion of
nonzero curvature in the Friedmann equation leads to the appearance of
additional singularities of type Big Rip in the Universe.
