利用Gains和Mawhin重合度理论中的延拓定理,得到了一类具有比率依赖密度制约的离散非自治捕食-被捕食系统周期解的存在性和保证周期解存在的充分条件,推广了某些已知的相关结果.这个结论不仅适用于离散时滞,同样也适用于分布时滞和偏差变元.
By using the continuation theorem based on Gaines and Mawhin's coincidence degree,sufficient and realistic conditions are obtained for the existence of positive periodic solutions for a discrete time nonautonomous predator-prey system with density dependence and ratio-dependence,and extend and improve some previous results.Our results are applicable to distributed delays and deviating arguments.