  In this paper, we study $\Delta$- convergence of iterations for a sequence of
strongly quasi-nonexpansive mappings as well as the strong convergence of the
Halpern type regularization of them in Hadamard spaces. Then, we give some
their applications in iterative methods, convex and pseudo-convex
minimization(proximal point algorithm), fixed point theory and equilibrium
problems. The results extend several new results in the literature and some of
them seem new even in Hilbert spaces.
