子分曲面尖锐特征生成

虽然生成光滑曲面是自由曲面造型的一个主要追求目标 ,但在某些场合却又要求能够产生非光滑的特殊效果 ,即所谓的尖锐特征 ( sharp feature) .该文研究子分曲面造型中特殊效果的生成 ,提出一种基于网格拓扑构造的方法 ,把折痕、角、尖刺和锥等尖锐特征的生成统一到边界处理方法中 ,从而避免了为各种效果建立特殊子分规则 ,并在不改变已有子分模式的情况下实现特殊尖锐特征造型 .

Compact Space-like Submanifolds in Pseudo-Riemann Manifold

We first establish a integral inequality for compact maximal space-like subman ifolds in pseudo-Riemannian manifolds Np(n+p). Then, we investigate compact space-like sub manifolds and hupersurfaces with parallel second fundamental form in Np(n+p) and some other ambient spaces. We obtain some distribution theorems for the square norm of the second fundamental form.

Effect of surface nanocrystallization and PPEC time on complex nanocrystalline hard layer fabricated by plasma electrolysis

Size distribution of nano-carbides produced by duplex treatments of surface nanocrystallization(by surface severe plastic deformation) and plasma electrolytic carburizing on CP-Ti was investigated.Skewness and kurtosis of Gussian shape distribution curves were studied and the effect of time was determined.The usage of longer time is more suitable for achieving less size of complex nano-carbides.Surface roughness of treated samples was measured.It is observed that there is an optimum level for time on surface roughness increasing(difference between two measured data).