对称中心

Moreover, it is proved by means of a totally different method that every central symmetric closed convex curve admits an inscribed square.

进而用全新的方法证明了每一个中心对称的闭凸曲线均能内接一个正方形。

The influence of position of the substitution, strength and number of donors and acceptors, and their coplanarity and asymmetry is discussed. The results indicate that the molecules may have larger first hyperpolarizabilities when the molecules have stronger and more donors and acceptors, large asymmetry of HOMO and LUMO, better coplanarity and higher accentricity. This work attemps at finding out the relationship between the structure and the property, thus providing theoretical basis for designing nonlinear optical molecules.

进一步研究体系中取代基的位置，给体与受体的数量和得失电子的能力，分子的共面性和对称性对分子第一超极化率的影响，结果表明，有机分子拥有更多数量与更强得失电子能力的给体和受体，最高占据分子轨道和最低未占据分子轨道空间分布的不对称，具有较高的原子共面性和较低的分子中心对称性，都能显著增加

The factors such as conjugate framework withsmall conjugation energy, central asymmetry, long conjugate chain,introduction of electron donors-acceptors, strong electron-donating orelectron-withdrawing abilities, long distance between electron donors andelectron acceptors, good coplanarity and so on lead to high third-order optical nonlinearities.

离域能小的共轭骨架，非中心对称结构，长的共轭链，吸供取代基的引入，取代基强的供电子性或吸电子性，长的吸供电子取代基之间的距离，以及良好的共平面程度等因素有利于获得较大的三阶非线性光学性能。

It is designed as a periodic cylindrically symmetric sinusoidal corrugation waveguide and operates in 10GHz.

在设计方案中，它是旁壁对称正弦波纹的圆波导，变换器的中心频率为10GHz。

In addition, the energy of s and p orbits of F2 or F3 ion is lower in the ferroelectric phase than in the cented symmetry phase and the covalence character of F1 ion whose contribution to the displacement is largest almost lose, which stabilize the structure of the ferroelectric system.

铁电相F2(F3)离子的能量低于中心对称相，最大位移贡献者F1的化学键性由弱共价作用到离子键的变化也是最大的，这均有利于体系的稳定。

They belong to the monoclinic crystallographic system with space group Cm.

该系列晶体属非中心对称的单斜晶系，空间群Cm。

At the same time, we can determine the symmetry degree of the two edges on the parts by comparing the distance form the parts center to the edge.

通过比较零件从中心到两切边的距离差，确定零件两切边的对称度。

This dissertation has conducted some information superiority oriented research focusing on some key technologies such as information acquiring, object recognition, situation assessment, threat assessment, target assignment, effectiveness evaluation of C~4ISR system, effectiveness evaluation of NCW in cognitive domain and so on. The main research and devotement of this dissertation are listed as follows: 1. Based on the analysis of physical meaning and campaign course of Lanchester linear law, we proposed a model reflecting the impact of surveillance and reconnaissance on force attrition. The model also discussed the effect of asymmetry information on the outcome of the battle, and conquered the disadvantage of Lanchester equation in modeling C~4ISR system.

本文面向信息优势对C~4ISR系统的信息获取、目标识别、态势评估、威胁估计、武器分配、效能评价以及网络中心战等关键技术进行深入研究，取得了一些创新性成果：(1)通过对Lanchester线性率中各参数物理意义及作战过程的分析，建立了反映侦察和监视效果的兵力消耗过程模型，并引入博弈论分析了战场上信息的不对称对交战结果的影响，克服了描述C~4ISR系统的Lanchester方程没有考虑作战单元、对手和环境间的动态交互以及数学结构简单的缺点。

By using the generalized central limit theorem, the heavy-tailed distributions (heavy-tailed Rayleigh distribution for amplitude image and heavy-tailed exponential distribution for intensity image) are obtained from the symmetric stable distributions of real and imaginary parts of echoes. Taking the heavy-tailed Rayleigh distribution as an example, the algebraic tails of heavy-tailed distributions are explained as well as the statistics of sharp peak and heavy tail.

本文使用广义中心极限定理，由雷达回波的实部和虚部的对称稳定分布，得到SAR图像的拖尾分布（幅值图像的拖尾Rayleigh分布以及强度图像的拖尾指数分布），并以拖尾Rayleigh分布为例，讨论了拖尾分布的代数拖尾特征以及尖峰厚尾的统计特性。

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。

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。