对称中心

The results are as follow:(1) In static status, the velocity of jet flow shows a symmetry distribution through central axis of enclosure.

结果表明，腔体静止时，射流速度沿腔体中心轴对称分布，腔体中心轴上的速度最大，两侧流速逐渐减小，近壁处为零；腔体转动时，在哥氏力的作用下，射流中心发生偏转，流场相对于腔体中心轴不再对称分布，腔体中各点处的流速分布随角速度而变化，压电射流角速度传感器利用这一特性敏感角速度。

Using the seale separation method, the meso-scale structure of Mcc occ- ured near the Delta Area of the Pearl River is studied. It is shown that there is a meso-scale cyclonic circulation at 1000 hpa level and a meso-scale anticyclon at 200 hpa level associated with the Mcc. The axis of the Meso-scale cyclone center tilts northwestward with height, stretching up to 400 hpa level.

用滤波方法分析了一例发生在珠江口附近地区的Mcc的中尺度结构，结果表明，在对流层下部有中尺度的气旋性涡旋与Mcc相应，涡旋的中心轴线随高度向西北方向倾斜，在地面涡旋的上方200hPa层上，是一中尺度的反气旋性涡旋，中尺度的辐合中心和上升运动中心偏于Mcc的西部，扰动温度场也是非对称的，在对流层上部没有中尺度的暖高压。

Therelationship of the amount of catalyst and the ee% of product was seen to be negative nonlin-ear. Catalyst 3 was used in the enantioselective addition of diethylzinc to aromatic aldehydesand gave good results. The configuration of products was determined by the configuration ofthe catalysts' chiral carbon linked with hydroxy group. Using β- amino alcohols bearing only one chiral center as catalysts for the enantiose-lective addition were studied. D-N, N-dialkyl-2-amino butanol gave poor catalytic effect be-cause of their structure. The configuration of the product is the same as the catalyst. Anotherkind of β- amino alcohols - phenylglycine derivatives and valine derivatives have chiralcenter on the carbon linked with amino group. Catalyzed by-phenylglycine derivatives 6,7, 9, 10, the reactions gave satisfied results. The optical yields exceeded 80%.

在探讨了含有两个手性中心的β-氨基醇之后，选择了只有一个手性中心的β-氨基醇，一是手性中心为连羟基的手性碳原子：D-N，N-二烷基-2-氨基丁醇；二是手性中心为连氨基的手性碳原子：D-苯基甘氨酸衍生物和L-缬氨酸衍生物。D-2-氨基丁醇的催化效果不太好，这与其结构的空间位阻较小有关系，反应产物与连羟基手性碳构型一致；由苯基甘氨酸和缬氨酸出发合成五种β-氨基醇6-10，研究了不同ee％的-6作用下的二乙基锌-苯甲醛加成反应，发现该催化剂具有不对称放大效应；-7，9，lO的催化效果也比较令人满意，光学产率80％以上，所得产物构型与催化剂构型一致。

The synthesis of the pentacyclic skeleton of Et-743 and the construction of the five chiral centers thereof.1. The core pentacyclic skeleton of phthalascidin was constructed with L-dopa as the starting material via thirteen steps. First, two basic synthons, the C-1 functionalized tetrahydroisoquinoline compounds 8 and N-protected Z-dopa derivative 9, were prepared from L-dopa. They were coupled via amide bond to form the dipeptide compounds 10, which were the first key intermediates. Then the primary hydroxyl groups were transformed into the corresponding amino aldehydes 11 via Swern oxidation. Followed by the intramolecular Pictet-Spengler cyclization, the pentacyclic compounds 12 were synthesized.

五环骨架的构建及五个正确手性中心的确立：1.1我们以L-多巴为起始原料，经过多步官能团保护和转化合成了基本结构单元8然后和苯丙氨酸衍生物9，通过缩合反应生成酰胺中间体10，经Swern氧化得到醛化合物11，然后再次利用分子内改良的Pictet-Spengler反应一步构建c，d两环，得到五环骨架化合物12，最后，实现了21-位羰基向氰基的转化，得到了C-1位官能化的化合物14，化合物14不但具有和Et-743一致的五环骨架，而且分子中五个手性中心立体构型也与其完全相同：其中，3，位和13，位的手性中心由原料L-多巴带入，而1，位，11，位和21，位手性中心则通过不对称诱导而确立。

The metal ions of the dinuclear copper complex of [Cu_2_2Cl_4] are linked by two N~1,N~2 1,2,4-triazole bridges,and the central Cu ions have distorted trigonal bipyramid geometries. The central Cu ion of [CuL22]·H2O has a centrosymmetric and distorted tetragonal-octahedral geometry. The metal ions of the dinuclear manganese complex of [Mn_2L_2_2Cl_2(H_2O)_2] are bridged by two chlorine atoms, and the central Mn ions have distorted tetragonal-octahedral geometries. Part III.

配合物[Cu_2_2Cl_4]是通过配体L的1，2，4-三唑环上两个氮原子(N~1，N~2)桥联形成的双桥双核配合物，每个中心铜离子都具有畸变的三角双锥构型；配合物[CuL22]·H_2O的中心铜离子具有中心对称的畸变八面体构型；配合物[Mn2L2_2Cl_2(H_2O)2]是通过两个氯原子桥联形成的双桥双核配合物，每个中心锰离子都具有畸变的八面体构型。

In this paper, we first introduce the concepts and structures of generalized per-symmetric matrix, generalized centro-symmetric matrix or generalized bisymmetric matrix.

本文介绍了广义广对称矩阵、广义中心对称矩阵以及广义双对称矩阵的概念及结构，研究了这些特殊矩阵集合中，矩阵方程AXB=C及矩阵方程组A_1XB_1=C_1，A_2XB_2=C_2的迭代解法，同时考虑了相应的最佳逼近问题。

Furthermore, its optimal approximation to a given matrix X can be obtained by finding the least-norm centrosymmetric solution of a new matrix equation AXB+CXD=F.

对任意给定的矩阵Xo，矩阵方程AXB+CXD=F的最佳逼近中心对称解可以通过迭代求解新的矩阵方程AXB+CXD=F的极小范数中心对称解而得到。

In this paper, an iterative algorithm is proposed to find the generalized centrosymmetric solution pair of matrix equation AXA~T+BYB~T=C. The solvability of the matrix equation can be determined automatically in the iterative process. When the matrix equation is consistent, the solution pair can be obtained within finite steps in the absence of round-off errors.

该论文运用迭代方法研究了矩阵方程的一般中心对称解解，特别地，当矩阵方程是相容的时，经过有限步就能求出该方程的一般中心对称解解，然后以此为主要依据进一步研究了矩阵方程的最优近似解，最后举例验证了该论文的主要结论。

The systems include application sub-system and cretification authority, application sub-system apply symmetric and asymmetric cryptosystem and public-key certificate which was authoticated by CA and can certify the valid user-identity to set up secure communication channel, exchange session key and provide message integrity, confidetiality, authentication and nondeniability.

系统包括证书中心和应用子系统，证书中心签发证书用来证明用户的合法身份，应用子系统应用证书和对称、非对称密码体制，识别用户合法身份，建立了安全通信通道和交换会话密钥，实现了通信数据的完整性、保密性、真实性、不可否认性。

Compared to other models pointed out by foreign scholars, my model was characteristic of multiple periods during evolution of urban systems, complexities of the course of forming urban systems, multiple types of urban functions, periodicity of regional changes of the important regions of urban development, periodicity of dominances of inland central city and seaport gateway city.

此后，随着海疆由开启转为封闭，再由封闭转为开启，最大城市由青岛转为济南，再由济南转为青岛；中心地职能体系由&青岛单中心体系&转换为&青岛、济南双中心体系&，再转换为&青岛单中心体系&；工业发展重点区域也由沿海转向内陆，再由内陆转向沿海；口岸城市的门户职能强度也经历了增强、减弱、增强的不对称&U&型变动；城市体系的空间结构经历了碎化—整合—碎化的过程。

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。