We present some new lower
bound estimates of the first eigenvalue for compact manifolds with positive Ricci
curvature in terms of the diameter and the lower Ricci curvature bound of the
manifolds. For compact manifolds with boundary, it is assumed that, with respect to
the outward normal, it is of nonnegative second fundamental form for the first
Neumann eigenvalue and the mean curvature of the boundary is nonnegative for the
first Dirichlet eigenvalue.