四边形

This unique long stroke shock mounted parallelogram landing gear is a break through in gyroplane safety.

这种独特的长冲程休克式平行四边形起落架是一个突破gyroplane安全。

The results are listed as follows:(1) In peneplain with plenty water-resource, hexagonal spatial structure of urban system can be formed. Due to differential competed function of central places, the hexagonal system is distorted. The result is that the area covered is decr eased and the girth is unchanged——but every border is usually unequal;(2) A pattern of pentagonal system evolves from hexagonal system controlled by a river;(3) A pattern of quadrilateral develops from hexagonal system under two parallel rivers;(4) The equal distance distribution of central places in narrow geographic space has its special reasons. The results are very important for understanding urban's formation and development and urban plan in Huang-Huai-Hai plain.

本文通过自然地理因素中水文、地形这两个重要要素对城镇体系空间结构形成的影响，分析了华北平原区在不同要素影响下的城镇体系空间结构样式：①在水源充足的准"均质"河北冲积平原上，基本满足六边形形成条件，但由于周边中心地发展竞争力不同，故使得正六边形发生畸变——覆盖面积减小而周长却保持不变；②构建了在一条河流影响下的六边形网络结构朝五边形网络演变的模型；③构建了在平行状河流作用下六边形网络向四边形网络演替的模式；④指出了在水源充足的狭长地理空间，城镇体系空间结构发育成等间距的现象与原因。

In this dissertation, the meshing techniques, especially for unstructured quadrilateral and hexahedral elements, are discussed, and the relative techniques, like the node smoothing and the reduction of matrix profile of a mesh, are also discussed.

本文全面回顾了四边形和六面体有限元网格特别是非结构网格生成技术，对相关的技术如网格节点位置平滑和带宽优化等技术进行了总结，并详细的描述了有关的算法。

A convenient and applied geometric transformation function, which is suit for interface of quadrangle or hexahedron, is proposed.

提出方便实用的、适合于内外域交界面为四边形或六面体情况的几何变换函数。

Firstly, the surface was dispersed into quadrangular meshes, then, the self-hidden lines were removed from the surface by the algorithm of removing hidden lines.

首先将方程曲面离散成四边形网格，然后采用消隐算法消除曲面的自隐藏线。

In order to generate spherical equal-area grid,this paper finds the corresponding relationships between unfolded icosahedron and sphere using Snyder equal-area projection.

文中利用Snyder等积多面体投影建立了平面与球面的对应关系，设计了球面等积三角形和四边形离散网格的生成算法。

The major focus of the teaching activity is, through the model of conducting games, to make the students in junior high school able to analyze the characteristics and quality of geometric shapes with the use of mathematical argument, reasoning and skills of communication, in order to develop the learning of the inclusion relation of quadrilaterals.

此教学活动最主要的内容，乃是藉由游戏竞赛的方式，让国中生在对几何形状的特徵与性质分析上，能充分运用数学辨证、推理和沟通的技巧，进而发展「四边形包含关系」的学习。

According to the principles of infinitesimal calculus ,a new method on how to ratiocinate the arbitrary quadrilaterals area was put forward.

利用微积分原理给出任意四边形面积公式推证的一种新方法。

These three types of rib rings with intercostal muscles were used to replace a segment of trachea in thorax.

将犬的第 3肋骨修整卷曲成三角形、四边形和多边形，用附着不同形状肋骨的骨肌瓣环替代胸内部分气管。

Can use the inverse operation of area formula freely.

会逆用平行四边形的面积公式，求出它的底或高。

Cynanchum Lingtai apricot production in the average weight 65 grams, the brightly-colored fruit, juicy rich, sweet-sour taste, sweet from the nucleolus, when the late Qing Dynasty famous Shaanxi, Gansu provinces, the Qing imperial court Tongzhi tribute for years.

灵台生产的牛心杏平均单果重65克，果实色泽鲜艳，汁多味浓，甜酸适口，离核仁甜，清末时就驰名陕、甘两省，清同治年间曾为朝廷贡品。

Chenopodium album,Solanum nigrum, and Amaranthus retroflexus were very susceptible to the herbicides. Polygonum persicaria and Abutilon theophrasti were relatively less susceptible to the herbicides, and Lycopersicon esculentum was not susceptible to it. The relationship between reduction rates of weed biomass and PPM values of weed leaves 2,4, and 6 days after treatment was established.

供试的6种杂草对该混剂的敏感性存在显著差异：红心藜Chenopodium album、龙葵Solanum nigrum和反枝苋Amaranthus retroflexus对该混剂最敏感，ED90值分别为47.65、71.67和29.17g/hm2；春蓼Polygonum persicaria和苘麻Abutilon theophrasti敏感，ED90值分别为96.91、114.20g/hm2；而番茄不敏感。