查询词典 first approximation

Both continuous paraxial approximation formula and two order discrete paraxial approximation formula are developed for one way wave motion transmitting apparently along normal direction based on kinematics model and local polynomial interpolation function.

引言 Clayton和Engquist在1977年和1980年提出的傍轴近似公式[1，2]是迄今为止最具代表性的局部人工边界条件之一。但是上述傍轴近似公式是从特定的波动微分方程出发推导建立的，因此其普适性受到限制。

Firstly, this paper investigated roundly the basic theory of the ambient vibration method, analyzed systematically the main methods of ambient vibration identification, and discussed their advantages and disadvantages. Then we established the finite element model of structural dynamics and test model and analyzed their mutual relation, improved MUSIC method and correlation function method in the harmonic identification, and gave the subspace method and correlation function method based on continuous model, which is multi-harmonic retrieve technique. And then, this paper also puts forward least-squares method to estimate directly structural physical and modal parameters; this approach replaced the derivative operator in the continuous time model with an equivalent approximation, and estimated the physical parameters of structures by the least-squares method. And then, we discussed the approximation methods of derivative and their convergence. Finally, this paper researched the modal parameters of a frame structure by the simulation and test. The results demonstrated that subspace method, correlation function method and the least-squares method are effective and stable respectively.

全面地研究环境振动识别方法的基本理论，系统地分析环境振动识别方法的主要方法，讨论它们的优点和不足；建立结(来源：6666AB44C论文网www.abclunwen.com)构动力学的有限元模型和试验模型，分析有限元模型与试验模型之间的相互关系；改进谐波识别中的MUSIC识别方法和相关函数识别方法，给出大型结构模态识别的连续型的子空间分解识别方法和相关函数识别方法，这个方法是多元谐波识别方法；提出直接识别结构的物理参数和模态参数的最小二乘方法，这个方法利用导数的近似值代替导数值，并运用最小二乘方法识别结构的物理参数，讨论导数近似值的选择方法，分析算法的收敛性；通过仿真计算和模型实验，研究高层框架结构的模态参数识别，验证子空间分解识别方法、相关函数识别方法和最小二乘识别方法的有效性，算法的稳定性；从理论和试验两个方面分析和研究噪声对识别精度的影响，影响识别精度的因素，以及部分模态成分的模态参数不能够被识别的原因。

In the third chapter, we study the approximation and weighted approximation for a kind of generalized Baskakov operators of two-variable. Using different weight functions, we discuss the convergence on weighted space of polynomials and rate of convergence with Jacobi weight for this kind of two-dimensional product-type operators, which extends the results of one-dimensional operators.

第三章研究一类二元广义Baskakov算子的逼近及其加权逼近，主要针对于不同的权函数讨论了这类乘积型的二元算子及其导数在多项式权空间上的收敛性和加Jacobi权的收敛阶，把一元的结果推广到多元的情形。

In the last section ,according to the basis theory of rough set ,we propose the definition of an approximation space which is basing on the convex cone that contain the origin ,and define the upper and the lower approximation of convex cone ,then discuss some operation properties.

文章的最后是基于粗糙集的基本理论，提出了可利用含原点的凸锥构造一个近似空间，定义了此空间的上、下近似，总结了一些运算性质。

After summarizing the existing research results, this article proposes new methods on moving force identification based on radial basis function approximation method and cubic spline function approximation method, and discusses the influence which some parameters to the precision of identification through calculating an example.

文章首先在第一章中介绍了已有的移动荷载识别方法及国内外的研究状况，在此基础上提出了研究目标和意义，即提出新的移动荷载识别方法，并通过数字模拟来讨论新方法的精度，以便评估桥梁的动力特性，为桥梁的设计和汽车性能的改进提供依据。

The properties of the λ-cut sets of the lower and upper approximation are discussed,and then the F-Union Decomposition theorem of the lower and upper approximation of rough fuzzy sets is given.

基于此，本文在逐一增加属性形式下的等价类F-分解的基础上，讨论了粗模糊集的F-分解形式，并给出了粗模糊上、下近似集合的F-分解定理及相关推论。

Thus, there is no way to demonstrate that sufficient data has been collected to form a mathematically valid approximation (or known degree of approximation) of the complete data set.

因此， 没有方法示范充份的数据已经被收集形成完全数据组的一个算术有效近似值。

Two-dimensional Bernstein type operators on simplex are constructed, and a necessary and sufficient condition of uniform approximation by mem is obtained, at the same time, the degree of approximation is characterized by two-order moduli of smoothness.

并且构造出单纯形上推广的二元Bernstein型算子，给出其一致收敛的一个充要条件，同时用二阶连续模刻划了它们的逼近度性质。

In this chapter we discussed the existence,uniqueness and approximation degree of binary cubic splines with C~2 connectivity for type-Ⅱtriangulations on rectangular domain,and we also gave a analysis of approximation of the interpolation splines.

本文还研究了二元三次样条函数在曲面重建中的应用问题，在TYPE-Ⅱ型剖分下，对于三次样条插值曲面的C~1-拼接问题，许多学者在这方面展开了大量的研究

In order to validate the correctness, the absolute differential cross sections of e-Ar scattering with multi-photon exchange in some special scattering geometries are calculated with Yukawa potential by applying the Second-order Born approximation and low-frequency approximation theory, respectively.

为了验证该计算方法的有效性，在入射电子的动量平行于激光场的极化方向这种特殊的散射模式下，利用Yukawa势，分别应用二阶玻恩近似方法和低频近似理论方法对激光场中电子—氩原子交换不同光子数的散射截面都进行了计算。

Many will continue to choose to live in duality and in conflict.

许多人将继续选择活在二元对立性和冲突中。

I find that students of the University of Physical Education all wear sportswear at first sight.

我发现：体育大学的学生乍一看，都是穿运动衣，大家都一样