查询词典 approximation methods in physics

In rough-set theoretic sense,the histogram correlates with the lower approximation and encrustation of histogram correlates with upper approximation.

从粗糙集理论意义上来说，直方图的外层与上近似有关，而直方图取值与下近似有关。

By virtue of a two-mode approximation and a rotating-wave approximation, an exact solution of the system is given.

利用双模近似和旋转波近似，得到了系统的精确解。

The finite difference approximation for this equation is presented.The stability and convergence of the finite difference approximation are analyzed.

并证明了显式格式条件稳定和条件收敛，而隐式格式则是无条件稳定和无条件收敛。

In order to solve the problem,starting from the analysis of the simplest plane wave numerical theory,we derived the formula of relative phase velocity and group velocity under the condition of arbitrary high-order finite-difference approximation,and gave the computational method for acquiring the optimum Courant number,and then analyzed the anisotropic effects due to finite difference approximation.

针对此，从最简单的平面波数值理论分析出发，推导了任意高阶有限差分近似条件下相对相速度和相对群速度的计算公式，给出了求解最佳Courant数的计算方法，分析了差分近似造成的各向异性效应。

College of Guandong Business, Guanzhou 510320, China）Abstract: Since large-scale vertical quench furnace is voluminous, whose working condition is a typically complex process with distributed parameter, nonlinear, multi-inputs/multi-outputs, close coupled variables, etc, dynamically decoupling control algorithm of temperature distributed parameter system in the furnace was presented, by which the whole system was decoupled to several subsystems and the implementation of controller was simplified. With finite difference approximation, the space and time step size was solved to ensure the convergency of finite difference approximation. After decoupling, the subsystems were controlled with self-learning PID control algorithm. The results show that the temperature control precision and homogeneity are improved; the overshoot and process in temperature rising period are reduced simultaneity.

摘 要：针对大型立式淬火炉体积庞大，工况复杂，炉内温度分布呈本征非均匀性，具有多输入/多输出、非线性、强耦合等特性，难以实现炉内温度高精度高均匀性控制目标等问题，提出一种温度分布参数系统动态解耦控制算法，其原理是：采用有限维逼近方法将对象解耦为多个独立的子系统，简化控制器的实现过程；通过分析有限维逼近方法的收敛性，获得保证收敛性的空间和时间步长应满足的条件；解耦后的子系统采用自学习PID控制算法，实现炉内温度高精度和高均匀性控制以及升温过程的快速性和小超调。

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。

Neural networks; Function approximation ; generalized Fourier series ; approximation capability

神经网络；函数逼近；广义Fourier级数；逼近能力

In this paper, we discuss rough set approximation under granulation, and establish positive approximation under dynamic granulation.

本文讨论了粒度意义下的粗糙集近似，并定义了动态粒度下的正向近似。

The main procedures are as following: to generate small increment of parameters automatically and to calculate the FE several times and obtain the sensitivity of objective function to the parameters, and then form a Hermite polynomial approximation, the calculation of FE solutions are substitute by the calculation of polynomial approximation, so time cost decreases dramatically.

用n维埃尔米特插值技术建立设计变量在可行域上的目标函数的逼近函数；将局部寻优的梯度算法和全局寻优的随机算法结合起来，大幅度地降低寻优过程中电磁场的计算次数。

First the approximation problems are obtained by approximation to the initial datum.

第三部分研究基本半导体方程混合初边值问题解的整体性质。

I can not negligent, he should do what?

我不能不在意了，他要做什么呢？

It is very dangerous to swim in the river alone.

一个人到河里游泳是很危险的。