Zheng Qiu ZHANG, Xian Wu ZENG, Zhi Cheng WANG
应用数学学报(英文版). 2003, 19(4): 691-702.
By using the continuation theorem of coincidence degree theory, the existence of a positive periodic solution for a nonautonomous diffusive food chain system of three species. { dx_1(t)/dt = x_1(t)[r_1(t)-a_(11)(t)x_1(t)-a_(12)(t)_2(t)]+D_1(t)[y(t)-x_1(t)],dx_2(t)/dt = x_2(t)[-r_2(t)+a(21)(t)x_1(t-τ_1)-a_(22)(t)x_2(t)-a_(23)(t)x_3(t)], dx_3(t)/dt = x_3(t)[-r_3(t)+a_(32)(t)x_2(t-τ_2)-a_(33)(t)x_3(t)], dy(t)/dt = y(t)[r_4(t) -a_(44)(t)y(t)]+D_2(t)[x_1(t)-y(t)], is established, where r_i (t), a_(ii) (t) (i = 1, 2, 3, 4), D_i (t) (i = 1, 2), a_(12)(t), a_(21)(t), a_(23)(t) and a_(32)(t) are all positive periodic continuous functions with period w > 0, τ_i (i = 1, 2) are positive constants.