... called a logarithmicallyconvex function on D if ln f is convex on D,andf is called logarithmically concave if ln fis concave.The following criterion for convexity of function was established by ... of complete monotonicity of a function involving psi function,”RGMIA Research Report Collection, vol. 11, no. 3, article 12, 2008.Journal of Inequalities and Applications 3Definition 1.1. Let ... aim of this paper is to discuss the monotonicity and logarithmical convexity of thefunction Fαx, y with respect to parameter α.For convenience of the readers, we recall the definitions and...