Positive solution for system of nonlinear first-order PBVPs on time scales

In this paper we are concerned with the following system of nonlinear first-order periodic boundary value problems on time scale TxiΔ(t)+fi(t,x1(σ(t)),x2(σ(t)),…,xn(σ(t)))=0,t∈[0,T],xi(0)=xi(σ(T)),i=1,2,…,n,where fi:[0,T]×[0,+∞)n→R is continuous and there exists a constant Mi>0 such thatMixi-fi(t,x1,x2,…,xn)⩾0for(x1,x2,…,xn)∈[0,+∞)n,t∈[0,T].Some existence criteria of positive solution are established by using a fixed point theorem for operators on cone.