四面体的

Nutlets 4, semiglobose-tetrahedral or subulate trigonous-tetrahedral, shiny, glabrous or pubescent, rarely tuberculate, adaxial 3 surfaces subequal in size or bottom smaller than 2 lateral surfaces, longitudinal vein at juncture of 2 lateral surfaces, sessile or with a short carpophore from corner of 3 adaxial surfaces, abaxial surfaces flattened or convex, acute or obtuse ribbed, rarely narrow winged; attachment scar at bottom of carpophore or at corner of 3 adaxial surfaces when sessile.

小坚果4，三棱四面体，发亮的半球形四面体或钻形，无毛或被短柔毛，具瘤，正面3 表面大小近等或者最后的小于2侧面的很少，在2侧面的接合的纵向脉，角落的3正面的在底部附件痕的果瓣柄或什么时候无梗。

The results show that the particles character as the growth of anion coordination tetrahedron during solvent thermal treatment, where blende-type ZnS particle is in the shape of double cone or tetrahedron, blend-type CdS appears as the tetrahedron, but wurtzite-type CdS is in the shape of cone. In addition, the particles with the better crystallinity are obtained with the increase of solvent thermal treatment temperature and time.

结果表明：采用溶剂热处理，粉末形状呈现负离子配位多面体生长特征，闪锌矿型ZnS粉末由球形变为双锥状或四面体状，颗粒上有明显的电子衍射花纹；闪锌矿型CdS晶体粉末主要呈四面体形状，而纤锌矿型CdS晶体粉末则以锥状为主，并且粉末的晶型随溶剂热处理温度的升高和时间的延长更趋于完整。

We obtain three classes of polyhedra which have high symmetry. they are regular tetrahedral class belonging to tetrahedral group , regular hexahedral class and regular octahedral class belonging to octahedral group.

本文将Goldberg在正十二面体上构筑多面体的方法推广到其它柏拉图多面体上，分别得到了三类具有较高对称性的多面体：属于四面体群的正四面体类和属于八面体群的正六面体类、正八面体类。

The two-dimensional structural units (such as silicon-oxygen tetrahedral sheet, octahedral sheet), interlayer space are assembled according to the sphere close packing manner, and the close packing layers parallel to {0001}. There are several mechanisms to release the difference in size while the silicon-oxygen tetrahedral sheet and octahedral sheet assemble the TO and TOT-type structural layers. The two types of structural layers with different interlayer space fitted together in six kinds of assembling modes and formed six kinds of crystal layers. The combinatorics analysis of the two-dimensional structural units revealed that there may be 28 kinds of TOT type interstradified minerals in six kinds of polysomatic assembling modes of interatradified structure. The structural layer is symmetrical for octahedron sheet in the structure of interstratified minerals and shows polarity characteristics.

结果表明，不同二维结构单元体（包括硅氧四面体片、八面体片、层间域的构筑基本符合球体紧密堆积原理，紧密堆积层平行{0001}；四面体片与八面体片构筑TO和TOT结构层时采取多种机制消除二者在二维尺寸上的差异；两种模式的结构层与不同类型的层间物组装形成六种组装模式的晶层；并通过二维结构单元体的组合规律的分析，计算出可能存在的28种TOT型间层结构，它们分属于6种间层结构多体性组装模式；间层结构中，结构层对于八面体片是不对称的，并在属性上表现出极性特征；间层矿物的晶层类型可用6种多体性组装模式加以表达。

The conception of the edge element was firstly proposed by Whitney in 1957. At the beginning of 1980\'s, Bossavit and Verite put it to practical application to three-dimensional eddy-current problems. In 1987, Barton and Cendes applied the tetrahedral element to three-dimensional magnetic calculation.

棱边元的构想，最早由Whitney在1957年提出。80年代初期，Bossavit和Verite将四面体棱边元应用于三维涡流问题，1987年，Barton和Cendes将四面体棱边元首次应用于三维磁场计算揭开了基于棱边的有限元方法在电磁问题中应用的序幕。

The quality and quantity of the newly generated tetrahedrons will greatly affect the subsequent computations.

2四面体单元稳定性的提高四面体重构后新产生的单元的数量和质量将直接影响到模型后续计算。

The revetment is made up of many single permeable tetrahedrons,and has much gap,so the group of permeable tetrahedrons can be treat as the porous media with large porosity.

四面体透水框架群是由很多单个四面体框架抛投而成，具有很大的空隙，因而，可以将框架群看成由很多框架杆件和大的孔隙组成的大孔隙率多孔介质。

Two ways to measure stability of tetrahedrons will be introduced. An earlier method to improve tetrahedron stability, the Snap Method, will be briefly discussed. Then techniques used in Delaunay. triangulation to deal with degenerated elements will bethoroughly investigated.

本文引入了两种单元质量的描述方法，简单介绍了已有的提高四面体稳定性方法之一—投射法；然后介绍了Delaunay方法中使用较广泛的逐点插入法的核心思想，将Delaunay网格构造法中处理退化单元的方法；删除法和换面法，改造后应用于四面体稳定性的提高上。

If two tetrahedra coincide after suitable reflection and rotation, we regard them to

的四面体可以有多少个同的形？（如果个四面体经适当的反射和旋转

We obtain three classes of polyhedra which have high symmetry.

本文将Goldberg在正十二面体上构筑多面体的方法推广到其它柏拉图多面体上，分别得到了三类具有较高对称性的多面体：属于四面体群的正四面体类和属于八面体群的正六面体类、正八面体类。

The split between the two groups can hardly be papered over.

这两个团体间的分歧难以掩饰。

This approach not only encourages a greater number of responses, but minimizes the likelihood of stale groupthink.

这种做法不仅鼓励了更多的反应，而且减少跟风的可能性。