查询词典 method of approximation

The procedure of designing a FIR filter with the proximate best uniform approximation method is given.The example shows that the filter designed by this method is of good performance in both pass band ...

给出了用近似最佳一致逼近方法设计FIR滤波器的具体过程，然后通过实例表明该方法设计的滤波器在通带和阻带内具有较好的特性，且计算简单、计算量小，有较好的应用前景。

Numerical results for the original stochastic Duffing-van der Pol system obtained separately by the Mento-Carlo method and the Chebyshev polynomial approximation are compared to show the effectiveness and efficiency of the latter method in solving the nonlinear dynamical problems of system with bounded random parameters.

数值模拟结果显示，Chebyshev正交多项式逼近法是研究含有界随机参数的耦合非线性动力学系统的一种有效方法。

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。

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

Common Reflection Surface stack is a brand-new and special ZO imaging method, the theory of CRS stack stems from paraxial ray theory, the biggest difference between CRS stack and conventional ZO imaging method is that it consider a reflector R as a circular reflector segment Cr placed in the vinicity of reflector R, Cr can be seen as the second order approximation of the reflector. The CRS traveltime surface is the multi-coverage reflection response of the reflector mirror assigned to R.

共反射面元（CommonReflection Surface=CRS）叠加技术是一种全新的、特殊的零偏移距剖面成像方法，CRS迭加理论源于傍轴射线理论，它与普通的零偏移距剖面成像方法的最大区别是它认为地下反射层是由许多个小反射弧段互相叠合组成的，认为来自某反射点附近的一个邻域内的反射信息都可以对该反射点的成像作出贡献，因此对该反射点进行零偏移距成像时就应该聚焦更多的能量参与迭加。

After the background of problem has been described, graphical method is used to determine the stroke of cylinder, and then approximation method is used three times to get the answer.

在介绍了问题的背景后，使用图解法首先确定气缸的行程及其规格，然后通过从一边试探的方式，三次试探就得到了问题的解答。

Then, on the basis of Atluri's work, a modified MLPG method is employed, in which the moving least squares approximation is used as a trial function and the Heaviside function is used as a test function of the weighted residual method.

然后基于Atluri等人的工作，采用移动最小二乘近似函数构造试函数，采用Heaviside函数作为加权残值法中的权函数，采用直接插值法施加本质边界条件而不采用罚函数法和拉格朗日乘子法。

We study a kind of efficient approximation method: maximum entropy method for multiobjective minimax problems from the point view of numerical computation.

本文从数值计算的角度对求解多目标minimax问题的一种有效的逼近方法：极大熵方法进行了研究。

Simulation results for both artificial and real data show the generalization performance of our method is a good approximation of SVMs and the computation complexity is largely reduced by our method.

文中最后对人工和实际样本进行了实验，结果说明了线性规划支撑矢量机在推广能力上较好地逼近了原支撑矢量机，而在计算复杂度上明显低于原支撑矢量机。

It is proved that if the RungeKutta method and the linear multistep method are of order p, then the numerical Hopf bifurcation value is an approximation to the Hopf bifurcation value of the equation itself of the same order p.

证明了如果Runge-Kutta方法和线性多步法是p阶的，那么数值Hopf分支值以相同的阶数p逼近于方程本身的Hopf分支值。

Neither the killing of Mr Zarqawi nor any breakthrough on the political front will stop the insurgency and the fratricidal murders in their tracks.

在对危险的南部地区访问时，他斥责什叶派民兵领导人对中央集权的挑衅行为。

In fact,I've got him on the satellite mobile right now.

实际上 我们已接通卫星可视电话了