令γ*( D)表示有向图D的双控制数,Dm [ Dn ]表示有向图Dm 和Dn 的字典式积,其中Dm ,Dn 的阶数m,n分别大于等于2.本文首先给出 Dm [ Dn ]的双控制数的上下界,然后确定如下有向图的双控制数的确切值:Dm [ Kn ];Km [ Dn ];Km1,m2,…,mt [ Dn ];Cm [ Dn ];Pm [ Cn ]及Pm [ Pn ].
Let γ*(D) denote the twin domination number of digraph D and let Dm[Dn] denote the lexicographic product of Dm and Dn, digraphs of order m,n≥2. In this paper, we first give the upper and lower bound of the twin domination number of Dm[Dn], and then determine the exact values of the twin domination number of digraphs:Dm[Kn];Km[Dn];Km1,m2,…,mt[Dn];Cm[Dn];Pm[Cn] and Pm[Pn].