This paper consists of two parts .The first part is devoted to discussion of the properties of the incompressible pairwise incompressible surfaces in alternating knot complements. Let F c S3 K be an incompressible surface and if F r~ has three or four components ,we not only give the concrete location of topological graph but also prove that the genus of F equals zero; given certain conditions, the genus of the incompressible surface whose topological graph has n+l components equals zero if the genus of the incompressible surface whose topological graph has n components equals zero. The second part is devoted to computing the polynomial span of 4- regular graph in R3 by using the method of the calculation of the polynomial span in almost alternating links. |