Finally, by using the method of topological degree, we obtain the existence of positive periodic solution of three species predator-prey system with nonautonomous delay. We also discuss the effect of delay on permanence and periodic solutions of the system.

利用拓扑度的理论给出了具有时变离散时滞的三种群捕食食物链系统正周期解的存在性,得到了时滞的大小对种群的持续生存及系统周期行为的影响。

, and the disease is uniformly persistent if the period of pulsing is larger than r* (or T*). The permanence of the models is investigated analytically.

通过分别对这四类模型的研究,得到了系统无病周期解全局吸引和系统一致持久的充分条件;并且得到当脉冲周期小于Υ_*(或γ_*)时疾病将会灭绝,当脉冲周期大于Υ_*(或γ_*)时疾病将成为地方病。

In our paper, we have comprehensively discussed the permanence of predator-prey systems and the impact of prey refuges on their dynamics and obtain the following main results:1.

本文系统的讨论了具有阶段结构的捕食——食饵系统(包括多物种食物链系统)的一致续存和庇护所效应对其动态结果的影响。

In our paper, we have comprehensively discussed the permanence of predator-prey systems and the impact of prey refuges on their dynamics and obtain the following main results:1.

本文系统的讨论了具有阶段结构的捕食——食饵系统(包括多物种食物链系统)的一致续存和庇护所效应对其动态结果的影响。