  A commutativity result for the Hoare power construction and a modified
version of the Smyth power construction on all US-admitting dcpos has been
confirmed in [11], where the property of being US-admitting determined by the
strongly compact subsets instead of compact subsets is weaker than the
well-filteredness. In this paper, we introduce the Hoare and Smyth power
constructions denoted by H and Q respectively on the category WF of all
well-filtered dcpos and Scott continuous maps, and further show that H and Q
commute, more precisely, HQ(L) is isomorphic to QH(L), if and only if L
satisfies the property (KC) and the Scott topology coincides with the upper
Vietoris topology on Q(L). We also investigate the Eilenberg-Moore category of
the double power construction on WF and characterize it to be a subcategory of
the category Frm composed by all frames and all frame homomorphisms.
