对称

In this thesis, we developed chiral proton N-O type ligands and employed them in the enantioselective addition of diethylzinc to N-diphenylphosphinoyl imines. The relationship between the structure of the ligands and the enantioselectivity was systematically studied. Furthermore, enantioselective butylation of N-diphenylphosphinoyl imines withBu〓Zn and enantioselective diphenylzinc addition to imine were also examined.

本文致力于亚胺的不对称催化有机锌试剂加成反应的研究：以手性质子型N-O配体为促进剂，对N-二苯基次膦酰亚胺进行不对称乙基锌加成反应而展开研究工作，系统地考查了手性配体的结构对反应的影响；另外，对N-二苯基次膦酰亚胺的不对称催化丁基锌加成进行了研究，并首次对亚胺的不对称苯基锌加成反应进行了初步探索。

Meanwhile this dissertation points out the form and properties of basic symmetric function、simple symmetric function and basic CRM symmetric function in OR-Coincidence algebra system, discusses the relations and transform methods among the coefficients of the three kinds of symmetric functions.

提出了在或、符合代数系统中基本对称函数、简单对称函数及基本CRM对称函数的形式及性质，并详细讨论了对称函数三种展开式系数之间的关系和各种转换方法。

In the full-scale aero-elastic model test, it is observed that there exist more than one interval of poor aerodynamic performance, and the non-symmetric erection sequence, while increasing the aerodynamic stability at the very places where aerodynamic performance of symmetric erection sequence is poor, performs worse in some other intervals with a vertical flutter phenomenon.

在全桥气弹模型的风洞试验中发现，采用对称架梁施工方法，在施工过程中会存在颤振稳定性最差的区间，并且这样的区间可能不止一个，而采用非对称架梁施工方法，固然在那些采用对称架梁施工时颤振稳定性较差的区间处提高了颤振稳定性能，但却在另一些施工区间中表现出比对称架梁施工更差的颤振稳定性能。

First, the typhoon flow field is decomposed into two parts: the maximum asymmetric vortex and irrotational environmental flow field. Then the maximum asymmetric vortex is also decomposed into two parts: the maximum symmetric vortex and β-gyres. Finally, typhoon Pearl(2006) is simulated by WRF model(weather research and forcasting model), and flow fields at various times at 500hPa...

首先，将台风的流场分解成最大的、不对称的涡旋流场和无旋流场；然后将不对称的涡旋流场分解成最大的对称涡旋和不对称的β涡旋对；最后，利用WRF(weather research and forcasting)模式(V2.1.2)模拟了200601号珍珠台风，并对各时次的500hPa风场用该方法进行分解，结果表明：该方法对台风的运动机理研究和实际的台风路径预测提供了有价值的信息。

But in our insiders control transitional economy, because the shares of the companies with higher information asymmetry are overpriced, the possibility to use long term bank debt is low while if companies of this kind import long tern bank debt, the information asymmetry can be reduced. The benefit of monitoring exceeds the cost so that the corporate governance can be improved which will bring better corporate performance; shares of companies with lower information asymmetry do not get much overprice, the possibility of using long term bank debt of this kind of companies is higher while the benefit is smaller than the cost.

但在我国的内部人控制的转型经济中，信息不对称程度高的公司由于股票在公开市场的溢价程度高，引入长期银行借款的可能性反而小，其实这种类型的公司如果引入银行债务的监督，则会减轻信息不对称程度，债务的监督收益将大于债务的成本，从而带来公司治理结构的改善，最终将带来公司绩效的提升；信息不对称程度低的公司由于其股票在公开市场的溢价程度比信息不对称程度高的公司低，反而更有可能引入长期银行借款，但这种类型的公司引入长期银行借款的成本大于收益，将会导致业绩的降低。

A fault calculation method to determine faults with the conversion matrices in phase coordinates, to determine multiple faults with equal time and elements with unsymmetrical parameters is developed with the sequence network decoupled from symmetrical components coordinates.

利用对称分量变换将相分量坐标下的故障处理方法和计算公式转换到对称分量坐标下，提出了完全使用对称分量坐标系的多态对称分量法。并利用反映网络等效变换的方程降阶方法进一步提高计算效率。

As we well know, the symmetry reduction methods related to group theory, such as the Lie point symmetry method, conditional symmetry, generalized conditional symmetry and etc, are effective tools to study the exact solutions of the nonlinear partial differential equations.

众所周知，与群论有关的对称约化方法，如李点对称方法，条件对称方法，一般条件对称方法等，是研究非线性偏微分方程精确解的有效方法。

The second milestone was the development of bilateral symmetry ( two halves of the body mirror each other ) with an identifiable head , in contrast to radial symmetry ( symmetrical in a ray pattern from the center ), for example , jellyfish .

第二个重要事件是动物身体进化成两侧对称，并出现明显的头部组织。当然也有例外，例如海蜇这种生物就是径向对称（即对称点在身体中心，呈放射对称）。

At first, the paper quote a kind of special matrix ---sign symmetric matrix , anti sign symmetric matrix , weakly sign symmetric matrix and introduced some important results in spectral property about them from some bibliographies. And then, the paper extended the formerly results and gave more general conclusions about spectral property of sign symmetric matrix.

本文首先引入了一类特殊矩阵的概念——符号对称矩阵，反符号对称矩阵以及弱符号对称矩阵，在相关文献中对这类矩阵谱特征的已经有了一些结论，本文在前人研究的基础上将相关结论做了进一步的推广，得出了有关这类符号对称矩阵谱特征的更一般性的结论。

According to GBEM,a fullysymmetric Galerkin multi-zone boundary element methodisproposed in this paper.Based on regarding the coefficient matrix as thesum of a symmetric part and a non-symmetric one,this problem is solvedby adopting a proper assembly.Following this treatment,GBEM will beextended for a wide scope.

针对这一问题，(1)本文在单域伽辽金边界元的基础上，采用先生成各子域的方程，将系数矩阵表达为对称部分与非对称部分之和，通过恰当的集成方式，消除非对称部分的方法，提出了一种完全对称的伽辽金边界元子域法，拓宽了伽辽金边界元法的使用范围。

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。