对称中心

The coherent electron micro-diffraction from a translation domain boundary perpendicular to the direction of the incident beam was studied. The qualitative and analytical descriptions are given to reveal the phenomena on the breakdown of center symmetry and an appearance of the forbidden diffraction spots.

对垂直电子束方向的畴界的特征，进行了实空间法的准动力学的理论推导，给出了对称性的定性描述，同时用动力学多层法程序对一些上下畴界进行了模拟；对出现的斑点不消光，中心对称的破损，镜面对称的破损等给出了定性的实空间法的动力学的理论的解析描述。

In topographic map, especially for city area, most of features are central symmetry and axial symmetry. By means of extracting features with symmetric figure first and then vectoring them according to their geometric characteristic, accuracy and efficiency can be increased and data sizes can be reduced.

在地形图中，轴对称和中心对称的要素占据着相当大的比例，特别是城市地形图中，房屋建筑等具有对称形状的要素占据了地形图中要素的绝大部分，在扫描图中首先对这些要素进行提取，进而根据特定要素的几何特征矢量化，可显著地提高矢量化精度和效率，减少数据的储存量。

According to the some properties of the differentiation ,I found that the symmetry of the graph is closely related to the first-order differentiation and the second-order differentiation .from this ,I search for a way to identify the symmetry of the functional graph for the direct line or the central symmetry of the functional graph for the some dot .

摘 要：利用导数的一些性质，发现了函数图象的对称性与函数的一阶、二阶导数的密切关系。根据这些关系，找到了一种判定函数图象是否关于某一直线对称或关于某点成中心对称的方法。

A novel structure of Yan-13 molecule was determined by X-ray single crystal diffraction analysis.

从表面上看起来Yan-13分子是中心对称的，事实上，它是不对称的。

Six days after inoculation, the cucumber root tip was slightly swollen and symmetrical root-knots were observed at the meristematic and elongation zones. Giant cells were differentiated by previous cambium cells in the center of the root; 10days after inoculation, symmetrical and secondary root-knots were observed at the root hair and upper zones. Vessels were separated by giant cells, around which protoxylem vessels were observed; l6days after inoculation, hypo-vascular tissue appeared earlier than normal; 20-30 days after inoculation, the vertical arrangement of vessels was disordered, shape was distorted and a new vascular tissue appeared in the cortex.

结果显示：接种后6 d的根尖分生区、伸长区出现膨大、对称的根结，根中心的原形成层细胞分化出巨型细胞；10 d在根毛区及以上部位出现既有对称又有偏于一侧的根结，周围有原生木质部导管出现，根结中巨型细胞阻断了导管；16 d次生维管组织提早出现；20~30 d导管纵向排列无序，形状扭曲，皮层中有新维管组织产生。

This paper analyzes the cause of distortion of octahedron complexes and tetrahedron complexes and states the general methods to judge the distortion .

分析了八面体配合物和四面体配合物畸变的原因，给出了判断八面体配合物和四面体配合物畸变的一般方法：配合物是否发生畸变要看中心离子电子云是否对称分布，若对称分布，就具有规则的八面体或四面体构型，否则，将会发生变形。

It is recognized by the symmetrical rosette (hair radiating symmetrically from a center) and erect ridge patterns on its body and head.

它是公认的对称花环（头发从一个中心辐射对称）和竖脊模式，其身体和头部。

The first asymmetric synthesis of trans-β-hydroxy-γ-butyrolactones:-(3R, 4R, 5S)-4-(1-acetoxy-isopropyl)-3-hydroxy-butyrolactone 65a was achieved starting from isobutylaldehyde through nine steps. The key steps involve the construction of three chiral carbon centers by the Sharpless's asymmetric epoxidation and Substrate directable chemical reaction.

以异丁醛为起始原料，经过九步反应首次设计合成了具有三个手性中心的trans-β-羟基-γ-丁内酯：-（3R，4〓，5S）-4-（1-乙酰氧基-异丙基）-3-羟基-丁内酯65a，关键步骤是Sharpless不对称环氧化和底物定向不对称合成反应。

Effect of biasing electric field on the propagation behavior of Lamb wave in a piezoelectric plate.

由于板结构的对称性，板中存在关于中心平面对称和反对称的多阶模态。

On the basis of symmetry model of cosmos of material and antimatter energy with the center of star of antimatter and material of extra negative energy,this paper analyzed proton and antiproton of negative energy,which have not agglomerated to the star of antimatter and material of extra negative energy,and it puts forward that the space so called"empty with nothing"can produce young galaxy.

以特大负能反正物质星体为中心的正能正反物质对称宇宙模型的基础上，对尚未凝聚到特大负能反正物质星体中去的负能反正质子和所谓空无一物的空间区能产生年轻的星系作了进一步分析，从而发展成了正负能正反物质对称宇宙模型，使得更多的天文观测资料都能做出统一的解释

The absorption and distribution of chromium were studied in ryeusing nutrient culture technique and pot experiment.

采用不同浓度K2CrO4(0，0.4，0.8和1.2 mmol/L)的Hoagland营养液处理黑麦幼苗，测定铬在黑麦体内的亚细胞分布、铬化学形态及不同部位的积累。

By analyzing theory foundation of mathematical morphology in the digital image processing, researching morphology arithmetic of the binary Image, discussing two basic forms for the least structure element: dilation and erosion.

通过分析数学形态学在图像中的理论基础，研究二值图像的形态分析算法，探讨最小结构元素的两种基本形态：膨胀和腐蚀；分析了数学形态学复杂算法的基本原理，把数学形态学的部分并行处理理念引入到家实际应用中。