A family of generalized strongly regular graphs of grade 2

A generalized strongly regular graphof grade p,as anew generalization of strongly regular graphs,is a regular graph such that the number of common neighbours of both any two adjacent vertices and any two non-adjacent vertices takes on p distinct values.For any vertex u of a generalized strongly regular graph of grade 2 with parameters(n,k;a_(1),a_(2);c_(1),c_(2)),if the number of the vertices that are adjacent to u and share ai(i=1,2)common neighbours with u,or are non-adjacent to u and share c,(i=1,2)common neighbours with is independent of the choice of the vertex u,then the generalized strongly regular graph of grade 2 is free.In this paper,we investigate the generalized strongly regular graph of grade 2 with parameters(n,k;k-1,a_(2);k-1,c_(2))and provide the sufficient and necessary conditions for the existence of a family of free generalized strongly regular graphs of grade 2.

A survey of the study of combinatorial batch code

A combinatorial batch code has strong practical motivation in the distributed storage and retrieval of data in a database.In this survey,we give a brief introduction to the combinatorial batch codes and some progress.

Automorphisms of generalized orthogonal graphs of characteristic 2

We determine the automorphism group of the generalized orthogonal graph GO2v＋δ（q, m, G） over Fq of characteristic 2, where 1 〈 m 〈 v.