  From the open boundary t-J model, an impurity model is constructed in which
magnetic impurities of arbitrary spins are coupled to the edges of the strongly
correlated electron system. The boundary R matrices are given explicitly. The
interaction parameters between magnetic impurities and electrons are related to
the potentials of the impurities to preserve the integrability of the system.
The Hamiltonian of the impurity model is diagonalized exactly. The integral
equations of the ground state are derived and the ground state properties are
discussed in details. We discuss also the string solutions of the Bethe ansatz
equations, which describe the bound states of the charges and spins. By
minimizing the thermodynamic potential we get the thermodynamic Bethe ansatz
equations. The finite size correction of the free energy contributed by the
magnetic impurities is obtained explicitly. The properties of the system at
some special limits are discussed and the boundary bound states are obtained.
