近似法

The phase of optical wave can be recovered by the intensity transport equation under the paraxial approximation For the optical system with diffraction limit, it is difficult to get the boundary radical slope of phase and sample in the circular domain boundary when using the intensity transport equation to recover the phase, consequently, we reviewed an algorithm mentioned in the reference ［4］, namely, the equation, computation domain and boundary condition are changed, then the phase is reconstructed by the multigrid method and corrected at last Moreover, the experiment system is set to testify the algorithm, and the recovered phase from the intensity data detected by CCD is compared with the result from phase retrieval algorithm, it is found that the phase reconstruction error can reach 017 λ in the case of non-uniform intensity distribution, as a result, the method is suitable for the phase recovery with low wavefront sensing accuracy.

在傍轴近似条件下，可以利用光强传播方程对畸变波前进行相位恢复。对于衍射受限的光学系统，很难获得相位的边界径向斜率值作为边界条件，此外，要获得精确的圆域边界采样值也并非易事。为了克服上述困难，进一步研究了相位恢复改进方法，即改变了方程的表示形式、计算区域和边界条件，并用多重网格法进行求解获得重构相位，最后再将其修正。为了验证算法的精确性，搭建了实验系统对算法进行实验验证，将由CCD探测的光强分布进行计算得到的相位分布与相位恢复算法的结果进行比较，证明在光强分布非均匀的情况下，该方法恢复的相位均方根误差能够达到017 λ，可以适用于波前传感精度要求不是很高的相位恢复。标签自适应光学相位恢复相位修正光强传播方程 adaptive optics phase retrieval phase correction intensity transport equation

Researched influence of frequency on characteristic of electromagnetic wave transmission in tunnels, and analyzed characteristic of electromagnetic wave transmission in circular, arches and curved tunnels by method of metal wave guide, and gives approximate formulas of attenuation rate. Main conclusions we obtain are as follows: in circular,rches tunnels, if frequency is higher, attenuation rate is smaller, it is beneficial for EM waves to transmit, in curved tunnel, higher frequency, more attenuation rate ...

研究了频率对井下电磁波传输特性的影响，采用金属波导法分析了圆形、拱形及弯曲隧道中电磁波的传输特性并给出衰减率近似公式，得出主要结论：在圆形和拱形隧道中，频率越高，衰减率越小，越有利于电磁波的传播；在弯曲隧道中，频率越高，衰减率越大，不利于电磁波的传播；通过特性曲线与井下实验数据相比较得出在900MHz左右为井下无线通信系统传输信号最佳频段。

Two methods of discretization, collocation method and Galerkin method, have been dominant in existing meshless methods.

在最小二乘法和移动最小二乘近似的基础上提出了加权最小二乘无网格法。

The exact solution of the period is got by using the first kind of complete elliptic integral.

应用线化和校正法对单质点弹簧振子的周期和近似解进行了求解。

This paper mainly introduces a new method to approximating the failure probability of structural systems and the method is defined as dimensions reduction method by conditional probability .

本文主要介绍一种新的结构体系失效概率近似计算的方法——条件概率降维法。

The path is defined as linear combination of a sequence of conjugate directions whichare obtained by applying standard conjugate direction method to approximate quadratic functionof unconstrained optimization.

Bulteau和Vial在[7]中构造了无约束最优化问题的共轭梯度路径，其基本思想是将标准共轭方向法应用于无约束优化目标函数f的局部二次近似函数，得到一组共轭方向序列。

New inspection method was deduced by using constant coefficient of variation in sequence inspection method, and the approximate relationship of inspection variables between mean method and sequence one was gained by analyzing difference of two methods.

将变差系数不变的条件引入到序贯检验方法中，推导出新的结构强度检验方法，分析检验变量与均值法的差异，得到两者的近似关系。

Digital holography ; Microscopic digital holography ; Wave front reconstruction ; Fresnel approximation ; Convolution method ; Angular spectrum theorem

数字全息；显微数字全息；波前重建；菲涅耳近似；卷积法；角谱方法

Via the stochastic averaging method, the four-dimensional system is reduced to a two-dimensional one. Through the logarithmic polar transformation , and then Girsanov theorem and Feynmann-Kac formula, the backword differential operator is then obtained. By expanding the eigenfunctions as a Fourier cosine series, the approximate analytic expansion of the moment Lyapunov exponent is then obtained.

首先在经典二元机翼颤振方程加入随机激励，通过随机平均法，Girsanov定理和Feynmann-Kac公式得到关于矩Lyapunov指数的特征值问题，其次采用Fourier余弦级数对特征函数进行正交展开得到系统矩Lyapunov指数的近似解析式。

The Cholesky decomposition of cross spectral density matrix was approximated and reduced, and then the modified spectral representation method is efficient and requires less computer memory, which is suitable for simulating spatial wind fields of long span bridges.

针对现有Deodatis方法模拟大跨度桥梁空间脉动风场中存在的计算量问题，通过对谱分解矩阵引入插值近似，减少谱分解的次数，从而提高该谐波合成法的计算效率，并节省内存花费，实现了对三维空间脉动风场的有效模拟。

Singer Leona Lewis and former Led Zeppelin guitarist Jimmy Page emerged as the bus transformed into a grass-covered carnival float, and the pair combined for a rendition of "Whole Lotta Love".

歌手leona刘易斯和前率领的飞艇的吉他手吉米页出现巴士转化为基层所涵盖的嘉年华花车，和一双合并为一移交&整个lotta爱&。

This is Kate, and that's Erin.

这是凯特，那个是爱朗。