对称中心

It was founded that the hardness distribution is approximately symmetrical to the center of welding line , the weakest zone of the whole joint is about 10mm from the center of the welding line . The HAZ of the welding line has an intenerate zone. the center of the welding line presents a typical dendritic casting structure.

结果表明：焊接接头的硬度以焊缝中心线为对称轴呈近似对称分布，焊接接头的最薄弱环节位于距焊缝中心约10mm处，焊接接头的热影响区内存在一个软化区。

The chaotic attitude motion of an asymmetric satellite moving on a Keplerian orbit in the central gravitational field was discussed. The Hamiltonian function of the system can be expressed by using Serret-Andoyer variables.

基於土星卫星上所观察到的混沌运动，研究了中心引力场中Kepler椭圆轨道上非对称卫星的姿态运动，其系统的Hamilton函数可用Serret-Andoyer变量写出。

Chiral centers of C5 and C8 are directly constructed in the key step of the diastereoselective propargylation from D--tartrate. The methylation and subsequent methoxycarbonylation result in desymmetrization of the terminal dialkynes. The α,β-unsaturated δ-lactone is synthesized after partial hydrogenation and lactonization.

由非天然酒石酸出发，利用双向非对映选择性的炔丙基化反应，在一步反应中同时构建C5和C8手性中心；然后通过末端炔基的甲基化、甲酯基化，延长碳链并对分子去对称化；内酯化得到关键中间体α，β-不饱和六元内酯，再经多步反应转化得到8-epi--Boronolide。

When the spatial pattern is meridionally anti-symmetric, in the north-warm/south-cold years, an anticyclonic anomaly circulation exists over the warm pool at 850hPa, the easterly near 15°N and the westerly near the equator are greatly strengthened, while the center of the 200 hPa anticyclonic circulation moves to the East Asia, and the Hadley circulation is affected evidently, so the summer rainfall may be above normal in the middle and lower reaches of the Yangtze River, and vice versa.

当SSTA为南北反对称分布时，北暖南冷年850hPa暖池区上空为一反气旋偏差环流，15°N附近东风气流和赤道附近西风气流增强，200hPa反气旋偏差环流中心移到东亚大陆上空，长江中下游地区为上升气流，降水明显增多，华北地区为下沉气流，降水减少；冷异常年则相反。

Rotate speed of 1 hydraulic turbine group measures a principle measurement unit of group rotate speed is like this hydraulic turbine graph 1 place is shown, it is comprised by sensor of 65 micro computer instrument, among them 64 sensor distributing to go up in 4 symmetrical runner shaft, the 65th sensor is in axial center nodical.

该水轮机组转速测量安装如图1所示，它由六十五个微型机械传感器组成，其中六十四个传感器漫衍在对称的四个转轴上，第六十五个传感器在轴的中心交点。

The asymmetric alkynylation of carbonyls is proved to be one of the most powerful procedures for organic synthetic chemistry,where the formation of one carbon-carbon bond and one chiral center of propargylic alcohol can be achieved in one step,and has attracted organic chemists\' most attentions.Plenty of works have been reported in recent years.

由于催化末端炔对羰基化合物的不对称加成在制备手性炔丙醇的同时，能够构建一个碳碳键和一个手性中心，因而该领域的研究受到了研究者的广泛关注，有大量的研究工作见报道。

Symmetrical low densi-ty shadows in the areas of periventricle and/or semioval center were the main finding.

CT表现为两侧基本对称的侧脑室周围和半卵圆中心区域的密度减低。

Results (1) Of 19 cases, 7 showed confluent foci within periventricular white matter and centrum semioval, presenting as massive symmetrically-distributed lesions with long T 1 and long T 2 signal.

结果 (1)脑白质异常信号 7例，主要分布于侧脑室旁的脑白质及半卵圆中心，为大片状长T1、长T2 信号，呈对称分布。

Both were measured using X-ray single crystal diffraction. For the crystal in MeOH, X-ray in compound. In an ansymmetry unit, there are two Cu atoms, two ligands and twosolvent methanol molecules. The tetranuclear complex contains two kinds of Cucenter.

本文在MeOH中得到了阶梯型四核铜骨架配合物；在THF中得到了扭曲的立方烷型四核铜骨架配合物，经晶体结构分析表明，阶梯型四核铜骨架配合物是由两个Cu2被μ~3-剪刀撑二个醇羟基O所连接形成中心对称的二铜二聚体结构。

The crystal consists of two similar but independent molecules in the asymmetric unit and the Ce ion coordinated toward ten donor atoms, six of which belong to the nitrogen atoms of two tridentate ligands and four oxygen atoms from two bidentate picrates.

晶体中一个不对称单元内有两个结晶学上独立的分子，这两个分子的构型基本相同，中心Ce3＋均与两个三齿配位的配体及两个双齿配位的苦味酸根配位，配位数为10。

On the other hand, the more important thing is because the urban housing is a kind of heterogeneity products.

另一方面，更重要的是由于城市住房是一种异质性产品。

Climate histogram is the fall that collects place measure calm value, cent serves as cross axle for a few equal interval, the area that the frequency that the value appears according to place is accumulated and becomes will be determined inside each interval, discharge the graph that rise with post, also be called histogram.

气候直方图是将所收集的降水量测定值，分为几个相等的区间作为横轴，并将各区间内所测定值依所出现的次数累积而成的面积，用柱子排起来的图形，也叫做柱状图。