Electronic Journal of Differential Equations,
Vol. 2005(2005), No. 53, pp. 1-12.

Title: Throughout positive solutions of second-order nonlinear
differential equations
       
Authors: Zhenguo Zhang (Hebei normal Univ.,  China)
         Chunjiao Wang (Hebei normal Univ.,  China)
	 Qiaoluan Li (Hebei normal Univ.,  China)
	 Fang Li (Hebei normal Univ., China)

Abstract: 
 In this paper, we consider the second-order nonlinear and the
 nonlinear neutral functional differential equations
 $$\displaylines{
 (a(t)x'(t))'+f(t,x(g(t)))=0,\quad  t\geq t_0\cr
 (a(t)(x(t)-p(t)x(t-\tau))')'+f(t,x(g(t)))=0,\quad t\geq t_0\,.
 }$$
 Using the Banach contraction mapping principle, we obtain the
 existence of throughout positive solutions for the above equations.
 
Submitted December 13, 2004. Published May 19, 2005.
Math Subject Classifications: 34C10, 34K11.
Key Words: Nonlinear differential equations; neutral term; 
    eventually positive solution; throughout positive solution.