查询词典 approximation theory

In this paper,a rational approximation method of the norm of parametric speed is given,which is more effective than the polynomial approximation.

文章根据等距曲线逼近的关键在于对其参数速度模的逼近，提出了对参数速度模有理逼近的2种形式，在此基础上给出了平面Bézier曲线等距曲线的逼近函数和误差估计函数，并导出了保持法矢平移方向的代数方式的等距有理逼近算法。

The fluid film bearing-flexible rotor nonlinear system with squeeze film damper is modeled practically using the finite element method and the Hamilton principle.(3) The film forces produced by fluid film bearing and squeeze film damper are determined by finite element method at any moment, and the Jacobian matrix is also determined.(4) A method for analyzing the dynamics of a large system with local nonlinearities is presented. The stability and bifurcation of the equilibrium position and the unbalance responce of a fluid film bearing-flexible rotor system with squeeze film damper are investigated based on the assumption of an incompressible lubricant together with the long bearing approximation for fluid film bearing, short bearing approximation for squeeze film damper and the"π"film cavitation model.

主要研究内容包括下面几个方面：（1）对挤压油膜阻尼器-滑动轴承-转子非线性动力系统中的非线性现象进行了机理方面的研究；（2）应用有限元方法及Hamilton原理对复杂的挤压油膜阻尼器-滑动轴承-转子非线性动力系统进行了建模分析；（3）对滑动轴承及挤压油膜阻尼器中任一时刻的油膜力及相应的Ja-cobi矩阵的确定进行了分析；（4）对一类具有局部非线性的多自由度动力系统，提出了一种可以有效地分析其动力特性的方法；（5）采用实验与理论分析相结合的方法，对挤压油膜阻尼器-滑动轴承-转子非线性动力系统的动力特性进行了分析。

The NIEL induced by low energy proton in Si and GaAs have been calculated using analytical method and Monte-Carlo code. Thin_target approximation was used when calculating NIEL by SRIM code and the result compared with that of other authors'. The results show that thin_target approximation is reasonable and NIEL scaling is feasible. The NIEL values become lower after taking into account the screening effect.

为此，本文采用解析法和基于Monte-Carlo方法的SRIM程序计算了考虑库仑屏蔽效应后低能质子在半导体材料Si，GaAs中的NIEL，SRIM程序在计算过程中采用薄靶近似法，并与其他作者的计算数据和实验数据进行了比较。

In this paper we give the concept ob approximation nilpotent alternate algebra,and sduty the relation ot nipotency and solvability to the approximation nilpotency .

在这篇文章中给出了交错代数的近似幂零性的概念。并且，讨论了交错代数的幂零性、可解性与近似幂零性之间的关系。

Introduces the notion of Feynman's path integrals and path integrals approach to financial modeling; Derives the path-dependent options pricing formula by making use of the Lagrange form of path integrals; Discusses Ilinski(2003)'s Gauge model which based on path integrals and fibre bundle, and its application for real-options evaluation; Summarizes the general modeling framework of options evaluation, taking advantage of the Hamilton form of path integrals; Applies the Geske-Johnson's analytical approximation in the path integrals form to the real-options evaluation for investment decisions, detailed procedure is presented under the assumption that underlying asset price dynamic follows a geometric Brownian motion, and the integral reduction for multivariate normal integrals and polynomial approximation for real-options evaluation is given.

系统论述了路径积分概念方法及其在期权估值中的应用，利用路径积分方法的Lagrange表述推导了路径依赖期权定价公式：探讨了基于路径积分和纤维丛的Gauge模型思想方法在实物期权价值评估中的应用；利用路径积分的Hamilton表述形式，总结了基于Hamilton表述的期权估值一般化框架；基于路径积分的形式框架建立了一个新的投资期权估值模型，并在具体的估值算法中给出了多重正态积分的降阶计算和期权价值的多项式逼近方法。

Then the distributed sources models of one order approximation model, twoorders approximation model, spatial frequency model and low order JA seriesexpansion model are compared with respect to the model accuracy.

随后将分布源的一阶近似模型、二阶近似模型、空间频率模型和低阶JA级数展开模型的模型精度进行了比较。

Paraxial approximation absorption boundary condition based on acoustic wave equation can obtain better absorption results by increasing paraxial approximation order of Taylor series. However, this kind of operation will increase the complexity of difference computation, and result in instability of computation process.

基于声波波动方程的旁轴近似吸收边界条件可以通过提高泰勒级数展开的旁轴近似阶数获得更好的吸收效果，但这样不仅增加了差分计算的复杂性，同时还导致计算过程不稳定。

According to the characteristic that the definition point of the Q matrix of wave front is always located on the extremum point on the axis of the beam, a three-dimensional formula for the rectificative factor of phase in complex ray paraxial approximation is proposed, which calculates the rectificative factor of phase directly without considering the calculation of the main directions and curvatures and the rotation of the coordinates, thus simplifying the paraxial approximation calculation by the complex ray expansion method.

根据波前Q矩阵的定义点总位于波束轴上极值点的特点，提出了三维复射线近轴近似相位校正因子计算公式。该公式不用考虑主方向和主曲率的计算和坐标旋转，直接计算相位校正因子，从而简化了复射线展开法的近轴近似计算。

The difference of results under two approximations-high order approximation and paraxial approximation are also given.

最后用计算机绘制了列阵成像系统中各观察面上的场强分布。

A neural network is then used to represent the estimation of potentials,both the parameterized TD(0) learning formulas and algorithm are also derived for approximating the policy evaluation.By the approximation values of potentials and approximation policy iteration,a unified neuro-dynamic programming optimization approach is consequently proposed for both two criteria.

根据定义式，建立性能势在平均和折扣性能准则下统一的即时差分公式，并利用一个神经元网络来表示性能势的估计值，导出参数TD(0)学习公式和算法，进行逼近策略评估；然后，根据性能势的逼近值，通过逼近策略迭代来实现两种准则下统一的神经元动态规划(neuro-dynamic programming，NDP)优化方法。

He became prime minister in 1997 and won international acclaim for his role in the Northern Ireland peace process.

他在1997年成为总理，并且因为在北爱尔兰的和平进程中发挥的作用受到国际社会的赞许。

Mixed Page Sorting Method Using the cuttable user model, this thesis proposes a mixed page sorting method by using cutted user model in server-side and complete user model in client-side.

隐私分级利用的混合式页面排序方法针对个性化搜索中搜索结果排序的问题，本文利用隐私可控开放的用户偏好模型，提出一个在客户端和服务器端分步进行的隐私分级利用的混合式页面排序方法。