近似法

Based on the above results, the problems of the electromagnetic interaction between a perfect conducting plate and 1-D/2-D conducting slightly random rough surface and the problems of the electromagnetic interaction between a dielectric spherical particle and dielectric slightly random rough surface are investigated. By using the reciprocity theorem, Small Perturbation Method and Physical Optics approximation, the solution for the composite scattering field from the composite target is derived and evaluated, and the numerical results are discussed and analyzed.

在此基础上，用互易性原理分别研究了一维、二维导体微粗糙面与其上方金属导体平板目标的复合电磁散射及介质粗糙面与其上方球形粒子的复合电磁散射，结合互易性原理和粗糙面散射微扰法及物理光学近似导出了复合散射场的计算公式并进行了数值计算，对计算结果进行了讨论和分析。

Bifurcation behaviour of nonlinear systems under the resonance condition isstudied when there are parametric and external excitations at the same time.

本文提出的映射迭代法可以有效地用于强非线性系统的定性分析，且对于弱非线性系统，其一次近似的平均方程与其它方法等价。

The aspect of non-linearity caused by deformation of the pipeline may not be considered in the swallow sea if rigidity of the pipeline is high enough, linear beam model is established for the pipeline and solved by using finite element method.

在浅水铺管时，如果管道刚度较大，可以不考虑管道的变形引起的非线性因素的影响，近似地把浅水中的管道模型视为线性梁，用线性有限单元法求解。

The governing equation is the mild-slope equation. Finite element method has advantage to treat complicated boundary. The second order radiation boundary condition is expanded to improve the wave model for large incident wave angles. The validity of the second order radiation condition is examined through varying arbitrary wave incident angles.

模式将以包含波浪绕射及反射之缓坡方程式建立数值模式，利用有限元素法易於处理不规则边界的优点，引用二阶近似辐射边界条件，扩展波场模式处理大角度波浪入射的能力，探讨在未碎波的情形下，二阶辐射边界条件对於任意角度波浪入射之适用情形。

Especially, the Hurst value in Rescaled range analysis is 1, indicating the correlation of income serial is very strong,.

特别是重标极差法的Hurst值近似为1，说明收益序列之间相关影响十分强，远没达到有效。

Theory analysis and the measured data are shown that excitation pulse in pile integrity testing is silimar to half-period of the sine curve, and different exciting methods produce signals with different period of time, so its frequency composition is also different.

理论计算及实测资料表明，反射波法基桩动测激振信号近似为半周期正弦波，不同激振方式产生的桩顶速度脉冲信号宽度不同，相应频率成分也就不同。

After several years analysis and research in practice,this paper uses approximate equilateral triangle method,by the way of sine theorem,last according to tagent formule to calculate the REM ,this method is ssimple,its accuracy is high,the method applies to any circumstance to measure REM .

本文经过实践多年分析研究，采用近似正三角形法通过正弦定理、长边推短边，最后按正切公式让算获得悬高，方法简便，精度高，适用于任何条件下的悬高测量。

In consideration of large computational efforts of Deodatis simulation,a modified spectral representation method was proposed for simulating the fluctuating wind field 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。

The approximate stationary probability density function for the response of multi-degree-of-freedom dissipated Hamiltonian systems to Poisson white noises are obtained by solving the four-order generalized Fokker-Planck-Kolmogorov equation using perturbation approach.

通过用摄动法求解四阶广义福克－普朗克方程，得到泊松白噪声激励的多自由度耗散的哈密顿系统的近似平稳响应概率密度函数。

Then the problem is reduced to less degrees of freedom to solve nonlinear equations by the modal synthesis method.To verify the successfulness of this method,an example is given.

利用非线性振动理论的平均方法，求得经模态综合法降维后系统方程的近似解析解。

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。