查询词典 approximation

It is helpful for us to construct difference approximation schemes for HJ equation with aids of schemes for conservation laws.

众所周知，即使在初值条件0是充分光滑的情况下，一般来说，虽可以得到式(1 )的连续解，但其解的导数却是间断的。

Apply the thought of differential and integral calculus to the problem of global optimization, imitate the algorithm of digital approximation of definite integral and construct a category of algorithms that can solve global optimization with great brevity and utility.

把微积分的基本思想应用到最优化问题中，仿照定积分的数值逼近算法构造出一类简洁实用的全局优化算法-积分选择算法。

For example differential calculus does a great deal with linear approximation to functions.

例如微分做了大量的线性近似的职能。

Space fractional differential equation ; finite difference approximation ; stability ; convergence

空间分数阶微分方程；显式有限差分格式；隐式有限差分格式；稳定性分析；收敛性分析

Among used machine learning methods, the gradient descent method is widely used to train various classifiers, such as Back-propagation neural network and linear text classifier. However, the gradient descent method is easily trapped into a local minimum and slowly converges. Thus, this study presents a gradient forecasting search method based on prediction methods to enhance the performance of the gradient descent method in order to develop a more efficient and precise machine learning method for Web mining.However, a prediction method with few sample data items and precise forecasting ability is a key issue to the gradient forecasting search method. Applying statistic-based prediction methods to implement GFSM is unsuitable because they require a large number of data items to model a prediction model. In the contrast with statistic-based prediction methods, GM(1,1) grey prediction model does not need a large number of data items to build a prediction model, and it has low computational load. However, the original GM(1,1) grey prediction model uses a mathematical hypothesis and approximation to transform a continuous differential equation into a discrete difference equation in order to model a forecasting model.

其中梯度法是一个最常被使用来实现机器学习的方法之一，然而梯度法具有学习速度慢以及容易陷入局部最佳解的缺点，因此，本研究提出一个梯度预测搜寻法则(gradient forecasting search method， GFSM)来改善传统梯度法的缺点，用来提升一些以梯度学习法则为基础的分类器在资讯探勘上的效率与正确性；而一个所需资料量少、计算复杂度低且精确的预测模型是梯度预测搜寻法能否有效进行最佳解搜寻之关键因素，传统统计为基础之预测方法的缺点是需要较大量的数据进行预测，因此计算复杂度高，灰色预测模型具有建模资料少且计算复杂度低等优点，然而灰色预测理论以连续之微分方程式为基础，并且透过一些数学上的假设与近似，将连续之微分方程式转换成离散之差分方程式来对离散型资料进行建模及预测，这样的作法不尽合理，且缺乏数学理论上的完备性，因为在转换过程中已经造成建模上的误差，且建模过程仅考虑相邻的两个资料点关系，无法正确反应数列未来的变化趋势。

The boundary value problem for first-order differential equations with a parameter refers to the finite solution condition of equation which includes unknown quantity and its first-order derivative that not only relies on interval value but also relies on the parameter of the equation,which is always settled by fixed point theory or successive approximation method.

含一个参数的一阶微分方程边值问题是指：含有未知量及它的一阶导数的方程的定解条件不仅依赖于在区间端点的取值，而且依赖于方程中的参数。通常它用不动点定理或逐步逼近法来解决。

In this paper, the theoretical model of CQI is described in an atom-diatom system in the condition of the molecular beam, based on the first-Born approximation of time dependent perturbation theory, taking into accounts the anisotropic Lennard-Jones interaction potentials. The method of observing and measuring correctly the differential interference angle is presented. The relation between differential and parameter, velocity is obtained. The relation of the integral interference angle and temperature is discussed.

文中利用一阶含时波恩近似和L-J相互作用势，建立了原子-双原子分子碰撞系统转动传能的量子干涉模型，描述了观察和测量微分干涉角的方法，得到了微分干涉角与碰撞半径和碰撞速度间的关系，同时也得到了积分干涉角和实验温度的关系。

The differential and partial wave scattering cross sections of Ne-H2(D2,T2) collisions have been calculated by close-coupling approximation method using Tang-Toennies potential model at the incident energy of 83.8 meV.

使用密耦近似（Close-Coupling）方法、采用Tang-Toennies势模型计算了惰性气体原子Ne与H2分子及同位素D2分子在碰撞能量为83.8 meV时的微分散射截面及分波截面，并与实验值和文献值进行比较。

The fine structure Hamiltonian for Hydrogen-like atoms is derived using the nonrelativistic approximation of the Dirac equation for one electron moving in the Coulomb field.

从Coulomb场中运动的电子的Dirac方程出发，取其非相对论极限导出了类氢离子的精细结构哈密顿的表达式。

A parallel algorithm for certain real symmetric block-tridiagonal linear systems on distributed-memory multicomputers is proposed. This algorithm is based on the block factorization of the coefficient matrix. This algorithm is used to solving the block-tridiagonal linear systems resulted from the finite difference approximation to Poisson's equation with Dirichlet boundary conditions. Then we get a parallel algorithm which speedup tends to linear speedup.

7研究了一类实对称块三对角线性方程组的分布式并行求解，提出了一种基于块矩阵分解的高效分布式并行算法，将其应用于求解带Dirichlet边界条件的Poisson方程导出的块三对角线性方程组，得到加速比趋于线性加速比的分布式并行算法，理论上说，这也是并行算法的理想情况。

For the head-teacher of the class said that I had seriously broken the school rules,which led me to a three-day suspend class.

为什么呢？因为我的班主任说我严重的违反了校规，于是让我停课三天。

Many of them believe that the conversion of thousands of working-class folk in England spared that nation from the mass carnage and the tyranny that came with the revolution in France.

他们之中有许多人相信，在英国数以千计的劳工阶级之悔改信主使英国免於遭受如法国大革命所造成的大屠杀和专制暴政。