Permanence for a N-species competitive system with feedback controls

By applying the theory of inequality on time scales, we obtain some sufficient conditions which guarantee the permanence of the following N-species competitive system with feedback controls {x(i)(Delta)(t) = b(i)(t) - Sigma(N)(j=1) a(ij) (t) exp {x(j)(t)} - Sigma(N)(j=1,j not equal i) c(ij)(t) exp {x(i)(t) + x(j)(t)} - d(i)(t)u(i)(t), u(i)(Delta)(t) = r(i)(t) - e(i)(t)u(i)(t) + f(i)(t) exp {(x)i(t)}, i = 1,2,...,N, where b(i)(t), d(i)(t), r(i)(t), e(i)(t), f(i)(t), a(ij)(t) and c(ij)(t) ijctare all bounded non-negative almost periodic functions on T.