These conclusions are expounded on the basis of the peculiarity of cube and regular tetrahedron of dna sequences , so they are rationalization , and they will be very useful in the study of the classification and the evolution of organisms 它们都是根据dna序列的立方体和正四面体的性质而提出来的，有一定的合理性。本文的结论对人们研究生物体的分类和进化有着很重要的作用。
2.
As its abundance is rare , it is very valuable . it appears in native usually as colourless precious stone , and is useful for cutting things and in jewellery . each atom in diamond is bonded to four others in a tetrahedral arrangement which gives the structure considerable intrinsic strength and hardness 金刚石是非常罕有且珍贵的碳，在金刚石中，每个碳原子都以正四面体的排列方式与另外三个碳原子连接，因此破坏这种化学键需要极大的能量，因此金刚石十分坚硬，主要用作金属及珠宝切割的用途。
3.
As its abundance is rare , it is very valuable . it appears in native usually as colourless precious stone , and is useful for cutting things and in jewellery . each atom in diamond is bonded to four others in a tetrahedral arrangement which gives the structure considerable intrinsic strength and hardness 金刚石是非常罕有且珍贵的碳，在金刚石中，每个碳原子都以正四面体的排列方式与另外三个碳原子连接，因此破坏这种化学键需要极大的能量，因此金刚石十分坚硬，主要用作金属及珠宝切割的用途。
4.
When sno2 wt % was controlled for 10 % , the square resistance of sn - in2o3 was minimum . through the characterization of in2o3 / sno2 nano powders , some conclusions were drawn : sno2 nano powder is rutile structure , and in2o3 and sn - in2o3 nano powders are cubic structure . in2o3 / sno2 nano powders were well dispersing with spherical uniform grain , and the mean grain was 4 - 50 nm 通过对inzo3 / snoz纳米粉体表征，得出inzo3 / snoz纳米粒子多呈球形、颗粒均匀、分散性良好、组分均匀、纯度较高、平均粒径在4一50lun左右、比表面积达67一156mz / g ; snoz纳米粉为正四面体金红石结构， inzo3和sn一inzo3纳米粉为体心立方结构。
5.
By making some assumptions , collision frequency were presented . then the the flocculation kinetics model was established through population balance equation . comparison of experimental data and modeling results indicate that there are the same trend between the two . so the model can predict floes number and size during flocculation of yellow river ' s loess particles without using empirical parameters . the tem and sem were used to obsever floes in the study of floe structure . the flocculation was divided as flocculi , floc and floe aggregate . the floes structure model was established by assumption that particles position in floe accords with tetrahedron . the fractal dimension of model and experimental floes was found to be coincidentso the model can reflect the structure of flocs formed in flocculation of yellow river ' s loess particles by macromolecule flocculant at a certain extent 最后，本文还对絮凝动力学和絮体结构进行了研究，在前人研究的基础上，针对高分子絮凝黄河泥沙，对絮凝过程作了一些符合试验条件的假设，建立了颗粒碰撞频率表达式，应用了颗粒数量平衡方程，从而建立了絮凝过程的动力学生长模型，模型计算结果与试验数据对比表明，二者趋势一致，在没有使用经验参数的情况下基本上能够描述黄河泥沙絮凝过程中絮体数量和尺寸分布的变化过程；对絮体结构的研究中，应用扫描电子显微镜和透射电子显微镜对絮体进行了观察，将絮体分为絮粒、絮团和絮网三个不同的生长阶段，通过假设颗粒结合位置符西安建筑科技大学博士学位论文合正四面体，建立了絮体结构模型，计算得到的模型絮体分形维数基本与试验中的实际絮体相符，在一定程度上能够反映高分子絮凝黄河泥沙生成的絮体结构。
6.
We also derive the expression of the signal obtained from random position by the magnetic field sensor . then we construct five - dimension nonlinear equation group for the signal obtained by the magnetic field sensor and solve them , so that we can realize 3d localizing and navigation for endoscope probe 我们根据电磁场理论推导出位于正四面体六条棱上的差分磁偶极子在空间任意点的场强表达式及探头感应磁场信号的原理，然后建立起五元非线性方程组进行定位求解。
