  In this article, we study new methods for constructing uninorms on bounded
lattices. First, we present new methods for constructing uninorms on bounded
lattices under the additional constraints and prove that some of these
constraints are sufficient and necessary for the uninorms. Second, we show that
the additional constraints on $t$-norms ($t$-conorms) and $t$-subnorms
($t$-subconorms) of some uninorms are exactly sufficient and necessary. At
last, we give new constructions of uninorms on arbitrary bounded lattices by
interation based on $t$-conorms and $t$-conorms.
