对称中心

If the straight line linking the nose and tail is defined as the major axis of the aircraft, any aircraft boundary is symmetric about its major axis.

尽管不同用途、不同国度生产的飞机，其形状、大小千差万别，但如果将机首与机尾的中心直线方向定义为飞机的主轴方向，则任何一架飞机的边缘图像都是关于主轴对称的。

A molded plastic bottle (10) has a base (24) having an outside surface rotationally symmetric about a longitudinal axis of the bottle including a convex heel (26) and a central concavity (28) separated by a standing ring (30) supporting the bottle on an underlying surface.

一种模制的塑料瓶(10)，具有一个带有绕瓶子的纵轴转动对称的外表面的底座(24)，该底座包括凸出的跟部(26)和中心凹面(28)，它们用将瓶子支撑在任何下垫面上的立环(30)互相分开。

The residual stress in the adherend is center symmetric, and the polynomial fitting of the S is obtained as parabola distribution.

被粘物中的残余应力呈中心对称，等效应力经多项式拟合后呈抛物线分布。

STRUCTURE: Titanium and composites used extensively, with particular emphasis on corrosion resistance; fully articulated three-blade coaxial contrarotatmg rotors have all-composites blades with carbon fibre and glass fibre main spars, pockets (13 per blade) of Kevlar-type material, and filler similar to Nomex; blades have non-symmetrical aerofoil section; each has ground-adjustable tab; each lower blade carries adjustable vibration damper, comprising two dependent weights, on root section, with further vibration dampers in fuselage; tip light on each upper blade; blades fold manually outboard of all control mechanisms, to folded width within track of main landing gear; rotor hub is 50% titaniuin/50% steel; rotor brake standard; all-metal fuselage; composites tailcone; fixed incidence tailplane, elevators, fins and rudders have aluminium alloy structure, composites skins; fins toe inward approximately 25°; fixed leading-edge slat on each fin prevents airflow over fin stalling in crosswinds or at high yaw angles.

结构：钛和复合材料广泛使用，耐腐蚀性能与特别强调，充分阐明三叶片转子同轴contrarotatmg有碳纤维和玻璃纤维的主要棒材全复合材料桨叶，口袋（每刀片13）凯夫拉型材料，类似的Nomex纤维填料；叶片非对称机翼部分，每有地面可调选项卡，每降低叶片振动阻尼器进行调节，包括两部分依赖重根，在机身进一步减振装置；小费每个刀片上轻；刀片倍手动舷外所有控制机制，折叠宽度内的主起落架的轨道；转子中心为50％titaniuin/50％钢；转子制动标准；全金属机身，复合材料tailcone，固定发生机尾，电梯，蛙鞋和方向舵的铝合金结构，复合材料的皮肤；鳍鳍在每个脚趾向内约25 °；固定领先的板式翅片防止了侧风或气流停滞在高偏航角度。

In the 9September 1999issue of Nature,molecular geneticist Enrico Coen and colleagues at the John Innes Centre inNorwich,U.K.,reported that a mutant version of the toadflax plant--which results in flowers with radial rather thanbilateral symmetry--is due to an epimutation.

在1999年9月9日的《自然》杂志上，英国Norwich，John Innes 中心的分子遗传学家Coen和同事报道了云兰属植物Linaria vulgaris的一个突变体特征。这一特异突变导致它的花从双面对称变为辐射状。

In phase of junior high school, graphical motion basically is contract commutation, contain translation, axial symmetry, rotate and the center is symmetrical.

在初中阶段，图形的运动主要是合同变换，包含平移、轴对称、旋转和中心对称。

The asymmetric ring-opening aminolysis of meso-epoxides represents one of the most important reactions in organic synthesis,giving rise to enantio-enriched aminoalcohol products with two chiral centers.

中文摘要：胺类对内消旋环氧化合物的不对称开环是一类重要的反应，反应生成两个手性中心的氨基醇化合物在有机合成中有着重要的应用。

In order to develop an useful synthestic process, we have synthesized amides with various substitutents. The isoquinoline skeleton was constructed through Bischler-Napieralski reaction, followed by asymmetric reduction of the imine intermediates with a Ru complex to form the only chiral center. Finally, we connected the two phenyl groups by Heck reaction and effectively obtained optically active aporphine alkaloids.

为了发展一套实用的合成方法，我们首先制备於苯环上具有不同种取代基的苯乙醯胺，接著透过Bischler-Napieralski反应进行分子内合环，并利用钌金属对亚胺中间体进行不对称的还原反应，建立出产物中唯一的光学活性中心，最后再利用Heck反应连结两个苯环，就可以顺利得到具有光学选择性的阿朴吩类天然物。

A matrix is said to be centrosymmetric matrix if = for all .

摘 要：设矩阵，如果，则称X是中心对称矩阵。

In this paper, the convergence of iterative methods for the linear system Ax=b is investigated, where A is a centrosymmetric M-matrix.

主要研究了线性方程组Ax=b的迭代解法的收敛性，其中A为中心对称的M-阵。

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。