四边形

Some typical structures of titanium nanowires , i.e. four-strands helical, centered pentagonal, hexagonal and the thicker hexagonal structures are chosen to study the structural and size effects of ultrathin nanowires. The angular correlation functions and vibrational properties are discussed.

我们选择不同的结构和生长序列的几个典型的超细钛纳米线，即四边形、五边形和六边形序列，以及六边形序列的两个较大体系，以分别考察结构和尺寸效应。

In the case of non-regularity meshes, the quasi-Wilson element for arbitrary narrow quadrilateral are studied in this paper.

本文在非正则剖分条件下，研究了任意窄四边形上的类Wilson元。

Using the method of analysing Specht element, the application of nonconforming arbitrary quadrilateral element to the unilateral problem is studied, and the convergence analysis and optimal error estimates are given.

利用分析 Specht元的技巧，研究将非协调任意四边形单元应用于单侧问题，给出了相应的收敛性分析和最优误差估计。

Based on the construction of reference ele ment and bilinear transformation, a quasi-Wilson element for arbitrary narrow q uadrilateral is presented.

基于参考元的构造和双线性变换，本文给出了一个任意窄四边形类Wilson元。

An efficient 13-parameter arbitrary quadrilateral plate element is proposed by the double set parameter method and its convergence is proven.

我们用双参数法构造了一个13-自由度任意四边形板元，证明了其收敛性，并进行了数值实验。

In the second chapter, elementary theories and ideas of one step forming inverse approach were described and warped modification method, implemented by Cook, was introduced into one step forming simulation and based on idea of surface spreading; new quadrilateral element modification arithmetic was put forward. By spreading warped quadrilateral onto plane in local coordinate system, a plane quadrilateral element whose shape and area were equal to original warped quadrilateral element was gotten and internal force vectors of four nodes and stiffness matrix of elements were improved to increase precision of simulations on this plane element.

第二章从一步成形逆有限元法的基本理论和思想出发，将Cook基于弹性理论的四边形单元的翘曲修正算法引入基于塑性的一步成形，并且基于曲面展开的思想，本文提出一种新的四节点单元翘曲修正方案，通过把翘曲的单元展开的方法在局部参考系中得到一个与实际翘曲单元的形状与面积非常接近的平面单元，在该平面单元中进行单元刚度及内力向量的计算，进一步改善模拟结果的精度。

In this paper, based on variational principle and bilinear coordinate transformation, a spline Kantorovich method using cubic B-spline function is presented to obtain an approximate solution for the free vibration problem of arbitrary quadrilateral plates with various boundary conditions.

本文从变分原理和双线性坐标变换出发，采用基于三次B样条的康托洛维奇法得到了带有各种边界条件任意四边形板自由振动的近似解答。

A comparative study of the bilinear, biquadratic quadrilateral element and quadratic triangular element for solving incompressible viscous flows was presented. These elements make use of the Galerkin/Least squares stabilized finite element formulation, in which the pressures and velocities are interpolated with the equal orders.

本文比较了用于求解不可压缩粘性流的四边形双线性、双二次单元及三角形二次单元的性能，这些单元采用GLS稳定化有限元格式，而压力和速度采用等阶数插值。

1Algorithm of approximating to a domain bounded by multiple curves anddistinguishing different material regions and inheriting of stresses ispresented.

提出了对多种曲线构成区域的网格逼近和材料分区识别、应力继承的算法，实现了四边形单元弹塑性自适应有限元计算程序。

The influence on absorption coefficient brought from shape choice with cylindrical or cone-shaped cavity, square or hexagonal profile, from different closure as air or water, from different material properties and structure sizes, are analyzed based on the numerical calculations. Some general characteristics are summarized. It shows that lowest resonance frequency of sound absorbent coefficient is inversely proportional to volume of cavity and sound absorbent coefficient is proportional to perforated percentage.

2通过数值方法研究了吸声结构内腔为圆柱腔和圆锥腔、基材的剖面形状为正四边形和正六边形、不同背衬、基材材料特性、尺寸大小对整体吸声效果的影响，总结了这些情况下非旋转对称吸声结构的声学特性变化规律，得出腔体体积越大，吸声系数最低共振频率越低；穿孔率越大，吸声系数越大的结论。

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。