查询词典 approximation method

With this approximation, detailed error analysis was completed, and two new methods were proposed: the like triangle method and the sinusoid method.

通 过对经典计算方法的误差分析，推出了2种新的计算方法：相似三角形法和正弦曲线法。

The disadvantages of this method are analyzed. Based on the analyses, an improved training method for the self-organizing map neural network is proposed to reduce the approximation error.

在此基础上，进一步研究该方法的逼近性能，分析其两个不足之处，进而提出一种提高逼近性能的改进神经网络训练策略。

The new method is based on combining perturbation method of eigen-problems with rational approximation of a vector-value function.

提出了一种新的结合特征灵敏度直接法和向量值函数有理逼近的结构动力重分析方法。

It takes less time to get the model approximation than rectangular automata method and flow pipe method.

相比于基于矩形自动机和流管道方法的模型近似，计算时间显著减小。

The error analysis of asymptotic approximation of finite series expansion is also given. Our method avoids choosing the integral length of the reentrant comer, and can be used to calculate the charge on the conductor conveniently and efficiently. Numerical examples are presented to demonstrate the efficiency of the method.

本文算法克服了邓肯矫正需要选择角点积分区域的不足，有效地校正了导体角点奇异性引起的电容参数提取的计算误差，最后给出了算法的数值实验与分析结果。

The numerical result demonstrates the Born Approximation can be effectively used for 3D imaging for borehole-ground electrical method. It also demonstrates that the method can be used as the basis for fast 3D inversion in reservoir monitoring application and in water injection exploration.

数值计算的结果表明Born近似是一种有效的井地电法三维快速反演方法，同时也说明井地电法监测油水前驱和储层边界预测的观测数据可以用该方法进行快速三维反演成像。

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

A simple radiation model was used to calculate daily changes of the aerosol radiative heating rates and cooling rates in different months. Two-stream approximation, hemispheric constant method, adding method and doubling method were applied in the computation.

摘 要：采用两流近似辐射模式，应用半球常数法近似，采用累加法和倍加法，计算了不同月份大气气溶胶的辐射加热率和减温率的日变化。

According to the clear water experiment, aeration performance of the new equipment is good with high total oxygen transfer coefficient and oxygen utilization ratio.

曝气设备的动力效率在叶轮转速为120rpm～150rpm时取得最大值，此时氧利用率和充氧能力也具有较高值。

The environmental stability of that world - including its crushing pressures and icy darkness - means that some of its most famous inhabitants have survived for eons as evolutionary throwbacks, their bodies undergoing little change.

稳定的海底环境─包括能把人压扁的压力和冰冷的黑暗─意谓海底某些最知名的栖居生物已以演化返祖的样态活了万世，形体几无变化。