journal6 ›› 2007, Vol. 28 ›› Issue (3): 10-11.

• 数学 • 上一篇    下一篇

导线生成的可展曲面

  

  1. (吉首大学数学与计算机科学学院,湖南 吉首 416000)
  • 出版日期:2007-05-25 发布日期:2012-08-27
  • 作者简介:刘罗飞(1964-),男,湖南望城人,吉首大学数学与计算机科学学院副教授,理学博士,主要从事几何学与拓扑学研究.
  • 基金资助:

    国家自然科学基金天元基金项目(TY1002605-01-05);湖南省教育厅科学研究项目(06C656;00C194)

Developable Surfaces Generated by a Directrix

  1. (College of Mathematics and Copmuter Science,Jishou University,Jishou 416000,Hunan,China)
  • Online:2007-05-25 Published:2012-08-27

摘要:讨论了沿着一条曲线的某些直线族构成可展曲面的条件.主要结果是:(1)以Γ:r=r(s)为导线,以α(s)cos θ(s)+γ(s)sin θ(s)为母线方向的直纹面可展当且仅当tan θ(s)=k(s)/τ(s),其中α,γ分别是Γ的单位切向量、副法向量,k,τ分别是Γ的曲率、挠率函数;(2)设Γ是曲面S上的一条曲线,则以Γ为导线,以ε(s)cos θ(s)+n(s)sin θ(s)为母线方向的直纹面可展当且仅当θ(s)=∫ss0τg(s)ds+θ0,其中n(s)是曲面在S处的单位法向量ε=n×α,τg是沿导线Γ的测地挠率.

关键词: 可展曲面, 曲线, 直线族

Abstract: In this paper we discuss how to obtain  a developable surface from some families of straight along a curve.The main results are:(1) The ruled surface generate by a directrix Γ:r=r(s)  and the rulings α(s)cos θ(s)+γ(s)sin θ(s) is developable if and only if tan θ(s)=k(s)/τ(s),where α and γ are the unit tanqent vectors and binormal vectors of Γ respectively,k and τ are curvature and torsion functions of Γ respectively;(2) Let Γ be a curve on the surface S,then the  ruled surface can be generated by the directrix Γ and the rulings ε(s)cos θ(s)+n(s)sin θ(s)  is developable if and only if θ(s)=∫ss0τg(s)ds+θ0,where n(s) is the normal vector of S at s,ε=n×α,τg is the gesdesic torsion of S along Γ.

Key words: development surface, curve, family of straight lines

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