后向差分

This section presents two kinds of characteristic schemes, one is the natural use of the usual backward Euler characteristic difference scheme ( [60] ) onto the triangular mesh, the other replaces the backward Euler's method by modified Euler formula to approximate the characteristic differential equation, so that the discretization for characteristic curve can get up to second order accuracy.

本节给出了两种三角形网格上的特征差分格式，第一种是通常的向后Euler型特征差分格式（[60]）在三角形网格上的自然运用，第二种采用§3.3、§3.4的离散思想，使用改进的Euler公式代替向后Euler公式来近似特征微分方程，使其对特征线的离散达到了二阶精度。

In the process of discretization of the auxiliary function, the traditional central difference formula is replaced by the backward difference formula, and numerical results show the method is of good stability.

在辅助函数的离散过程中用后向差分公式代替传统的中心差分公式，数值结果显示出良好的稳定性。

There are three difference formats in this thesis. They are backward difference, Crank-Nicolson"s difference and Galerkin"s difference.

本文对时间域采用的离散格式有两点向后差分、Crank-Nicolson格式差分和Galerkin差分等。

This scheme divides center difference to forward and backward one-side difference operators which are combined in 4-6 steps Runge-Kutta time integration.

此格式将中心差分算子分成前向和后向两个空间单边差分，然后在4-6步Runge-Kutta时间积分中使用单边差分组合。

While using three—points backward finite difference to imitate the radiation condition, we accept Raven's〓 idea to shift collocation points upstream a short distance.

在用三点向后差分格式模拟辐射条件时，接受了Raven〓的建议，将单元控制点向后移动了一段距离。

Because the diffusive term is discretized with divided forward difference or divided backward difference according to the sign of convection velocity, these methods keep first order accuracy for diffusive term.

3.2考虑规则网格上的一维和二维定常型对流占优扩散问题，离散方法采用了有限体积方法及普通的有限差分方法，基本离散思想是将对流项提高到二阶精度，扩散项则根据对流速度的方向决定采用向前或向后差商离散。

The initial population size is studied based on the defined partial function, favor and back difference equations, and the schema theorem.

该文研究二进制和自然数编码遗传算法的群体规模，结合偏好函数和模式定理，利用前向及后向差分方程，得到这2种编码的群体规模下限值，证明其存在性。

Unlike the previous method, however, the proposed algorithm obtains the new transformed matrix by taking the conjugate operation to the forward and backward spatial smoothing covariance matrix of the received data, so that the modified covariance differencing matrix which is a Hermitian matrix of zero real part can lower the computation load effectively during the eigenvalue decomposition.

不同于以前的算法，提出的算法通过对接收数据的前后向空间平滑协方差矩阵进行共轭运算得到新的变换矩阵，因此修正后的协方差差分矩阵是个实部为零的厄米特矩阵，从而有效地降低了特征分解过程的计算量。

Since any approximations, such as numerical Laplace inversion, backward differentiation formula, nonlinear model of switch, do not exist, the new algorithms are accurate.

由于该方法不存在任何极限近似问题（数值拉普拉斯反变换法，后向差分法，非线性开关模型法等），因而它是一种精确计算方法。

During the calculation of the early age temperature field, the early age physical and mechanical performance of concrete varies with its age, therefore in the second chapter we discuss the early age physical and mechanical performance of concrete and its development regulation with time, we emphasize elastic module and the development about the early age strength of concrete varying with time, at the same time consider the effect of shrink and creep upon the early age of concrete, in succession discuss how to confirm the physical parameter of thermodynamics of concrete.

之后讨论了混凝土的热物理参数的确定。为了能够正确合理的应用有限元方法求解早期混凝土温度场问题，第三章论述了求解温度场的有限元方法。第三章首先对热传导的微分方程作了阐述。之后确定温度场的边界条件。本章采用变分原理推导有限单元法计算温度场的公式。因此在第二小节叙述了变分原理，然后阐明了不稳定温度场的计算的三种方法，确定第四章分析中将采用向后差分法求解0#箱梁早期的温度场。

This is not an ordinary box, which is used as a background picture of the dialog box, very pretty.

详细说明：这可不是一个一般的对话框，它是用图片作为背景的对话框，非常好看。

Conceal me what I am,and be my aid for such disguise as haply shall become the form of my intent.

遮掩我的身份，帮助我，我的面具将成为我的目的。