离散

In point of the physical characters,it is better to differentiate the time derivative in the characteristic direction than intime direction.

1.4中针对流体的流动以对流为主的物理特性，采用特征线法去对时间导数项离散，使截断因子比通常的时间方向离散小得多，更好地反映了问题的物理特性。

Spectral element methods for partial differencial equation is introduced in this study from viewpoint of the collocation approximation of Chebyshev polynomial. Wave Equation and its space discretization are deduced. Two time integral methods, central difference method and implicit Newmark method, are introduced, and their stability and applicability are also discussed in some details. The significance of absorbing boundary conditions in spectral element methods for Aeroacoustics is explained, and Clayton-Engquist-Majda absorbing boundary conditions is emphasized and introduced, then the discrete scheme of this boundary conditions is deduced and applied to spectral element methods for wave equation.

本文从Chebyshev多项式逼近理论出发，详细介绍了谱元方法求解偏微分方程的过程；推导了流体中的声波动方程并在空间上对其进行了谱元离散；详细讨论了两种时间积分方法──中心差分法和Newmark方法，分析了它们的稳定性条件，并从理论上对比了两种方法的优缺点和适用范围；将吸收边界条件推广应用于谱元方法求解气动声学问题中，重点介绍了Clayton-Engquist-Majda吸收边界条件的原理和公式，推导了该吸收边界条件的变分形式，并将其引入波动方程的离散形式中。

Introduce the image transformation method in Clarendon Laboratory of Oxford University and in Resources Institute of China Mining University.

定义了正向转换和逆向转换的球面离散格网影像转换方法，实现了影像到球面离散格网的正向转换。

The model is applied to numerically analyze the wave field and the coastwise current formed by the breaking of oblique incident wave in the Leadbetter Beach, Santa Barbara, California, USA. In the analysis the Crank-Nicolson scheme is adopted to solve the parabolic mild slope equation and the ADI finite difference scheme is applied to solve the model of wave induced coastwise current.

运用该近岸流方程，对美国Santa Barbara Leadbetter海岸波浪斜向入射所产生的波浪场及波浪破碎所形成的沿岸流进了数值模拟，其中抛物型缓坡模型采用Crank-Nicolson格式进行数值离散，近岸流方程采用ADI差分格式离散。

This algorithm is the linear combination of the discrete Conformal mapping and the discrete Authalic mapping.

它是离散保角映射与离散保积映射的线性组合，兼有二者的优点，如鲁棒性与低变形。

Based on the conjugate symmetric frequency spectrum of Complex Discrete Fourier Transformation and the conventional Real Discrete Fourier Transformation,a modified RDFT is implemented in Wiener filter to restore aerial images degraded by motion or vibration.

基于复数离散傅里叶变换频谱的共轭对称性，对传统的实数离散傅里叶变换做了改进，将改进后的RDFT算法用于维纳滤波器中来实现对运动模糊图像的恢复处理。

The examples indicate that the algorithm has strong pertinence and high efficiency, hi the discrete variable optimization, the problem is solved in the relative quotient method On the base of analyzing the relative quotient method, the conjugate gradient direction is used to modify the old search directions, the iterative matrix of the algorithm, and the method to resolve the discrete variable optimization, the relative conjugate difference quotient algorithm is presented.

离散变量优化算法是从相对差商法开始的，在详细分析相对差上法的基础上，用共轭梯度方向修正原有的搜索方向，并对算法的迭代矩阵进行相关的修改，最终形成一种用于求解离散变量优化问题的RCDQ法。

The numerical results verifies the conservation properties of mass and energy of complete discrete scheme.

最后给出了全离散格式的算例，数值结果验证了全离散格式的质量、能量守恒性质。

To ensure the conservation of total momentum and energy of the system, the best discretization form of conservation equations are suggested.

在保证系统总动量和总能量守恒的基础上，提出了离散方程的理想离散形式。

The discrete velocities are connected by Delaunay grids to form referring region, and the error vectors in the discrete data can be distinguished, corrected and interposed by continuity principle of flow.

2针对PIV数据错误矢量进行识别、修正与插值方法进行了研究，通过Delaunay网格将离散的各流速点连接起来，形成参考区域，利用流体的连续性原理实现了离散数据中错误矢量识别、修正与插值。

The split between the two groups can hardly be papered over.

这两个团体间的分歧难以掩饰。

This approach not only encourages a greater number of responses, but minimizes the likelihood of stale groupthink.

这种做法不仅鼓励了更多的反应，而且减少跟风的可能性。