逼近

The new method is a combination of characteristic approximation to handle the convection part, to ensure the high stability of the method in approximating the sharp fronts and reduce the numerical diffusion, a smaller time truncation is gained at the same time, and a mixed finite elementspatial approximation to deal with the diffusion part, the sealer unknown and the adjoint vector function are approximated optimally and simultaneously.

此方法即为对方程的对流项沿流体流动的方向即特征方向进行离散，从而保证格式在流动锋线前沿逼近的高稳定性，消除了数值弥散现象，并得到了较小的时间截断误差；另一方面，对方程的扩散项采用混合元离散，可同时高精度逼近未知函数及其伴随向量函数，理论分析表明，此方法是稳定的，具有最优的L~2逼近精度。

If we hope to use a sequence of finite objects to approximate infinite objects, then we should know what kinds of infinite objects are approximable and how to approximate them effectively.

无穷形式对象可逼近的充分条件为了研究哪一类无穷对象可以逼近以及如何有效地逼近它们，我们用过程模式作为无穷对象上的计算的模型，用以刻画接受无穷输入、生成无穷输出的无穷对象上的计算。

In theory of approximations, the classic methods of polynomial approximation for rational expression are various interpolations and operator approximations, such as Lagrange interpolation, Hermite interpolation and Bernstein polynomial approximation.

在逼近论中，用多项式逼近有理式的经典的方法是各种插值与算子逼近方法，如Lagrange插值、Hermite插值和Bernstein多项式逼近等。

The method based on the frequency sampling is taken from the interpolation theory. The method based on the Chebyshev best uniform approximation theory can control the precision of approximation by limiting parameters.

频率采样脉冲波形设计法源于数值逼近理论插值法，所得脉冲波形有确定解析式；Chebyshev最佳一致逼近脉冲波形设计法属于均匀一致逼近，逼近程度能够利用参数进行限定。

Secondly, we combine the theories of monotone operator and maximal monotone operator's Yosida approaching with domain method to prove the solution's existence of set-valued input-output equation in R n in the similar economical backgrounds in present articles too and then gain the solution's continuity by interior approaching method,at last we give the responding economical meaning about the solution's existence and continuity.

对于R n空间中消耗为单调集值型的投入产出方程，也在现有文献类似的经济背景之下，利用单调算子的理论以及极大单调算子的Yosida逼近结合邻域逼近法给出了投入产出方程的解的存在性的证明，接着利用内部逼近法结合方程截断技巧对投入产出方程的解的连续性给予了证明，然后顺便简单的介绍了运用外部逼近法来得到方程的解的连续性的思路，最后也给出了相对应于存在性和连续性的经济意义。

The Paper mainly studies forecast of a kind of time sequence which is made by using fuzzy approximation and Functional differential Equation, gives several theorems which explicate fuzzy and optimal approximation and relation between them by using the forecasting method.

主要对以模糊逼近和泛函微分方程进行时间序列预测问题作进一步的理论研究，给出了几个有关使用该预测方法时，模糊逼近与最佳逼近及其关系的定理，证明了逼近方面及预测方面的一些有意义的结果。

This book reviews the many areas of numerical analysis, including the configuration polynomial, finite difference, factorial polynomials, summation, Newton formula, operator and configuration polynomial, Cheung section, close polynomials, TaylM more item type, interpolation, numerical differentiation, numerical integration, and with the series, differential equations, differential equations, least squares polynomial approximation, minimax polynomial approximation, rational function approximation, triangular approximation, non-linear algebra, linear equations, linear programming, boundary value problems, MonteCarIo methods and so on.

本书综述了数值分析领域的诸多内容，包括配置多项式、有限差分、阶乘多项式、求和法、Newton公式、算子与配置多项式、祥条、密切多项式、TaylM多项式、插值、数值微分、数值积分、和与级数、差分方程、微分方程、最小二乘多项式逼近、极小化极大多项式逼近、有理函数逼近、三角逼近、非线性代数、线性方程组、线性规划、边值问题、MonteCarIo方法等内容。本书的特色主要表现在利用例题及大量详细的题解来透彻地阐明所述内容的内涵，同时附有大量的补充题以便读者进一步巩固和深化从书中获得的数值分析知识。

The results are much better than the other approaches'. Then we give another method for approximating offset curves. The circle is first approximated by regular polygon within some tolerance. The exact offset curve is then approximated by the convolution of the regular polygon with a B-spline curve or a NURBS curve having the same degree.

与此同时作者从基圆的正多边形逼近出发，通过求解包络的技巧给出了等距曲线逼近的另一个算法，可整体估计误差，所得的等距逼近曲线为与基曲线同次数的B样条或NURBS曲线，克服了国际上现有同类算法中逼近曲线次数几倍于基曲线次数的缺陷。

ABSTRACT This paper summarizes our researches on two key techniques in curve and surface modeling-the geometric approximation techniques and the geometric interpolation techniques. The former includes three types of geometric approximation techniques: Hybrid polynomial approximation to rational curves and surfaces, offset curves and surfaces approximation, interval Bézier curves and surfaces approximation. The latter includes a series of algorithms for shape blending modeling: the MSI algorithm for shape blending between space polylines or trees, the MSI algorithm for shape blending between triangular meshes, and skeleton-based shape blending algorithms using triangular decomposition and star-shape decomposition.

本文是作者对曲线曲面造型中两类核心技术几何逼近技术和几何插值技术的研究成果的总结，其中前者包括有理曲线曲面的Hybrid多项式逼近、等距曲线曲面逼近和区间曲线曲面逼近等三类几何逼近方法；后者包括用于形状混合造型的几何插值方法的一系列算法：空间多边形形状混合的MSI插值算法、三角网格形状混合的MSI插值算法、树的形状混合的MSI插值算法以及基于骨架树形状混合的三角剖分算法和星形剖分算法。

In practice, the offset curve usually is approximated by lower degree rational polynomial cur ve in order to have the unified expression of data structure and geometric algor ithm in the commercial modeling systems.

通过用双圆弧逼近表示 NURBS( non- uniform rational B- spline)曲线及其 offset，并利用双圆弧逼近的特有性质，把 offset的双圆弧逼近转化为原曲线的双圆弧逼近，简化了问题的求解。

Neither the killing of Mr Zarqawi nor any breakthrough on the political front will stop the insurgency and the fratricidal murders in their tracks.

在对危险的南部地区访问时，他斥责什叶派民兵领导人对中央集权的挑衅行为。

In fact,I've got him on the satellite mobile right now.

实际上 我们已接通卫星可视电话了