摘要
This paper deals with the qualitative behavior of orbits at degenerate singular point with the method of quasi normal sector, which is a generalization of Frommer's normal sectors. Several examples show that this method is more effective than the wellknown methods of Z-sectors, normal sectors and generalized normal sector.
基金
supported by the National Natural Science Foundation of China(No.11401111,No.11171355)
the Ph.D.Programs Foundation of Ministry of Education of China(No.20100171110040)
