  We study the generic non-equilibrium steady states in asymmetric exclusion
processes on a closed network with bottlenecks. To this end we proposes and
study closed simple networks with multiply-connected non-identical junctions.
Depending upon the parameters that define the network junctions and the
particle number density, the models display phase transitions with both static
and moving density inhomogeneities. The currents in the models can be tuned by
the junction parameters. Our models highlight how extended and point defects
may affect the density profiles in a closed directed network. Phenomenological
implications of our results are discussed.
