Some block matrices with signed Drazin inverses

The sign pattern of a real matrix M is the (0,1,-1)-matrix obtained from M by replacing each entry by its sign. Let Q(M) be the set of real matrices with the same sign pattern as M. For any , if the Drazin inverses of M and have the same sign pattern, then M is said to have signed Drazin inverse. In this paper, we give a complete characterization for a class of anti-triangular matrices with signed Drazin inverse, and present a complete characterization for sign symmetric bipartite matrices with signed Drazin inverse.