十二面体

The structures and stabilities of the ground-states for Cu13-nAgn clusters have been studied by Gupta model potential based on tight binding second moment approximation in combination with a genetic algorithm. It is found that the lowest energy structures of the pure clusters (n=0,13) are perfect icosahedron, and the structures for the bimetallic clusters (n=1～10) have stable structure which are slightly deformed with respect to the perfect icosahedron, The Cu atom prefers to occupy the center of the clusters with higher coordination numbers.

在混合团簇基态结构优化的遗传算法方案中增加了交换算子，结合Gupta紧束缚模型势研究了Cu13-nAgn团簇的最低能量结构，选择合适的交换和杂交概率，可有效地提高优化效率，优化结果表明，Cu13和Ag13是全对称的二十面体，n=1～10的混合团簇能形成稳定结构，其构型是在二十面体基础上发生畸变，Cu原子趋于处在团簇中心，随着Ag原子数目的增加，原子间的平均距离单调增加，团簇的结合能单调减小，Cu2Ag12和CuAg12只存在亚稳结构。

In addition to the black-white double-lobe caused by the displacement field around pores, we demonstrate that LSC should correspond to a novel, peculiar class of anti-phase domain, of which the interior is a local isomorphism with a non-zero phason-type displacement ε〓w〓 i.e.

利用这个结果，我们发现黑白双瓣衬度是二十面体准晶中的多面体微孔引起，而环形衬度则对应于一种二十面体准晶中新奇的反相畴界，其两侧是由相位子型位移ε〓w〓＝B〓联系着的局域同晶类。

At each penton, a hole (φ=20〓) can be seen connecting the inside and the outside of the capsid, and there is a hole (φ=12〓) at each hexton and the center of 2-fold axis, so there are 132 holes in total at the surface of CSBV.

应用冷冻电镜技术和计算机三维结构重构的方法，我们测定了CSBV核衣壳的三维结构，分辩率为25 〓，病毒的核衣壳是按T=1（P=3）的对称结构排列二十面体，病毒表面比较光滑，有12个五邻体、60个六邻体的结构，每个五邻体的中央有孔洞，六邻体的中央也有孔洞，另外在2次轴的位置上也有孔洞，这样病毒共有132个孔洞，五邻体的孔洞的直径为20 〓，而六邻体和二次轴的孔洞的直径月为12 〓。

Icosehedral quasicrystal, showing icosahedral point group symmetry and quasi-periodic order along three directions, has been intensively studied.

二十面体准晶是目前研究最广泛的准晶之，它具有二十面体点群对称性，属于三维准晶，就是说其原子在三维上都是准周期分布的。

Interestingly, in liquid Fe75B25 the situation is reversed. About 35% of 1441, 1431, 1421 and 1422 pairs are found, indicating that tetrahedral local order is preponderant.

一个比较有趣的结果是，在Fe20B80中，代表二十面体和扭曲二十面体微观局域结构的1551和1541占主导地位，大约占键对总数的43%。

In contrast to ordinary liquid and amorphous alloys, the number of 1551 bonds related to the icosahedral structure becomes very smaller with the decrease of temperature,but the numbers of 1311,1301,1201 bonds related to the rhombohedral structure are increased remarkably.

结果表明，与通常液态及非晶态金属相反，随着温度降低，与二十面体相关的1551键型数越来越少，而与菱面体相关的1311，1301和1201键型数目显著增加，最后形成以菱面体结构单元为主的非晶态结构。

This fact disproves an assumption that λ-phase is an approximant of the IQC.

但是我们研究发现λ相与在其基础上生成的二十面体相之间没有固定的取向关系，这反驳了λ相是二十面体相的近似相的假设。

There are three forms of symmetry in virus capsids: icosahedral , helical and complex forms.

壳粒排列的方式使病毒的结构呈几何对称，病毒衣壳有三种对称形式：二十面体立体对称、螺旋对称、复合对称，螺旋结构呈杆状，而二十面体由对称的亚单位组成近似的球状，非对称的衣壳是较复杂的形式，往往与细菌病毒有关。

A virus is a unit of infectious genetic material smaller than any bacteria and embodying properties placing it on the borderline between life and non-life. The vast majority of the virus capsid protein assembled into icosahedral symmetry of the structure. Caspar-Klug Theory has become a fundamental concept for the classification of icosahedral viral capsids based on the principle of quasi-equivalence.

二：病毒是比任何细菌都小的感染性遗传物质，介于生命与非生命之间的一类无细胞结构的生物，绝大多数病毒的衣壳蛋白装配成二十面体对称的结构，&准等价&原理是解决严格遵从二十面体对称性的病毒衣壳几何特征的有效而成熟的方法。

The growth of truncated icosahedra could be induced and maintained through interplay of following processes:the～50 nm multiple twinned seeds were generated; shape and size focused by Ostwald ripening,then oxidativly etched and preferentially grew on the {100} face.Oxidative etching plays an important role in the formation of gold nanocrystals on hydrothermal condition.

对二十面体金纳米粒子及截角二十面体的生长机理进行了探讨，考察了不同刻蚀程度对金纳米粒子的形态影响，研究结果表明，增强体系刻蚀程度有利于单晶的生长，减弱刻蚀程度有利于孪晶的生长。

It has been put forward that there exists single Ball point and double Ball points on the symmetrical connecting-rod curves of equilateral mechanisms.

从鲍尔点的形成原理出发，分析对称连杆曲线上鲍尔点的产生条件，提出等边机构的对称连杆曲线上有单鲍尔点和双鲍尔点。

The factory affiliated to the Group primarily manufactures multiple-purpose pincers, baking kits, knives, scissors, kitchenware, gardening tools and beauty care kits as well as other hardware tools, the annual production value of which reaches US$ 30 million dollars.

集团所属工厂主要生产多用钳、烤具、刀具、剪刀、厨具、花园工具、美容套等五金产品，年生产总值3000万美元，产品价廉物美、选料上乘、质量保证，深受国内外客户的青睐