The independent domination number $i(G)$ (independent number $\beta (G)$) is the minimum (maximum) cardinality among all maximal independent sets of $G$. Haviland (1995) conjectured that any connected regular graph $G$ of order $n$ and degree $\delta \le \frac{1}{2}{n}$ satisfies $i(G)\le \lceil \frac{2n}{3\delta }\rceil \frac{1}{2}{\delta }$. For $1\le k\le l\le m$, the subset graph $S_{m}(k,l)$ is the bipartite graph whose vertices are the $k$- and $l$-subsets of an $m$ element ground set where two vertices are adjacent if and only if one subset is contained in the other. In this paper, we give a sharp upper bound for $i(S_{m}(k,l))$ and prove that if $k+l=m$ then Haviland’s conjecture holds for the subset graph $S_{m}(k,l)$. Furthermore, we give the exact value of $\beta (S_{m}(k,l))$.
In the paper, we obtain the existence of symmetric or monotone positive solutions and establish a corresponding iterative scheme for the equation $(\phi _p(u^{\prime }))^{\prime }+q(t)f(u)=0$, $0<t<1$, where $\phi _p(s):=|s|^{p-2}s$, $p>1$, subject to nonlinear boundary condition. The main tool is the monotone iterative technique. Here, the coefficient $q(t)$ may be singular at $t=0,1$.