Abstract. This paper formulates a kind of dynamical macro-economic model based onSidrauski's work,then presents the sufficient and necessary conditions of t
Inexistence and existence of limit cycles in a predator-prey model with undercrowding effect are studied. The number of limit cycles obtained by Zheng Weiwei in
Abstract. In this paper,Steiner minimal trees for point sets with special structure are studied.These sets consist of zigzag lines and equidistant points lying