报告时间：2015年5月25日下午16:00

报告地点：数学与统计学院106报告厅

报告人：北京交通大学 常彦勋教授

报告题目：Block designs with specific automorphism

摘要：Let v, k and t be positive integers such that v > k > t. A Steiner t-wise balanced design (briey S(t, k, v)) is a pair (X, B), where X is a set of v points and B is a set of k-subsets of X (called blocks) such that every t-subset of X is contained in a unique block. An automorphism group of a S(t, k, v) (X, B) is a permutation group on X leav-ing B invariant. In this talk, we consider Steiner t-wise balanced design with speci_cautomorphism. Some direct and recursive constructions on this topics are summarized.

报告人简介：常彦勋，男，北京交通大学二级教授，博士生导师，数学系主任。第二届全国高校青年教师奖获得者, 2000年获铁道部有突出贡献的中青年专家称号, 2004年享受国家特殊津贴。曾获霍英东教育基金会第六届高等院校青年教师基金，主持完成国家自然科学基金项目5项及1项博士点基金，现正主持国家自然科学基金重点项目。在组合数学与编码理论领域发表170篇学术论文，其中130篇被SCI收录，一项成果在1991年获河北省科技进步一等奖，另一成果在2001年获全国高校科技奖自然科学二等奖。现任中国组合数学与图论专业委员会常务理事，国际组合数学与应用学会Fellow，中国运筹学会图论与组合分会副理事长，中国数学会理事。近年发表的代表性学术论文有：

[1] T. Feng, Y. Chang, and L. Ji, Constructions for strictly cyclic 3-designs and applications to optimal OOCs withλ=2, J. Combin. Theory, Series A 115(2008), 1527-1551.

[2] Y. Chang and X. Wang, New upper bound for (m,k,λ)-IRSs with λ≥2, IEEE Trans. Inform. Theory, Vol. 55, Issue 9(2009), 4274-4278.

[3] Y. Chang and X. Wang, Determination of the exact values for Ψ(v, k, k-1), IEEE Trans. Inform. Theory, Vol. 57, Issue 6(2011), 3810-3814.

[4] Y. Chang and J. Zhou, Large sets of Kirkman triple systems and related designs, J. Combin. Theory, Series A 120(2013) 649-670.

[5] R. Pan and Y. Chang, (m,n,3,1) optical orthogonal signature pattern codes with maximum possible size, IEEE Trans. Inform. Theory, Vol. 61, Issue 2(2015), 1139-1148.

[6] L. Wang and Y. Chang, Combinatorial constructions of optimal three-dimensional optical orthogonal codes, IEEE Trans. Inform. Theory, Vol. 61, Issue 1(2015), 671-687.