期刊信息
- 刊名: 河北师范大学学报(自然科学版)Journal of Hebei Normal University (Natural Science)
- 主办: 河北师范大学
- ISSN: 1000-5854
- CN: 13-1061/N
- 中国科技核心期刊
- 中国期刊方阵入选期刊
- 中国高校优秀科技期刊
- 华北优秀期刊
- 河北省优秀科技期刊
On the Helly Number for Line Transversals to Paral lelograms
摘要/Abstract
摘要:
对于平面内平行的平行四边形簇 F(|F|≥3),如果F中任意3个平行四边形都有一条上升(或下降)直线横截,那么F中所有的平行四边形必有一条公共的上升(或下降)直线横截,从而确定了平行四边形集簇的Helly数大于等于3.
Abstract:
If each three parallelog rams of a family of parallel parallelog rams are intersected by an ascending(or a descending)line, then there is an ascending(or a descerding)line that intersect s all the parallelog rams of the family, and determined the Helly number of family of parallelog rams≥3.
关键词
Key words:
parallelo gram
;
line transversal
;
convex set
;
Helly number