In this paper,the authors consider a class of Hohling model with functional responses:where x≥0, y≥0, a,b,d,r,w are positive real numbers. and prove that it has at most one limit cycle.
In this paper we point out that paper [1] has some mistakes and correct the corresponding results.In paper [1], the quadratic system having a parabola as an integral curve can be changed in to
In this paper we study the decision problem of the center or focus for a class of planar polynomial fields which can be changed into Abel equation. Taking a Poincaré return map h(x) , we can calculate any order derivative of h(x) at x=0 and obtain the focus value of each order. The new method in this paper avoids the recurence operation and reduces the work in calculating the focus value.
