近似法

In the sense of Von Karman large displacement, the governing equation of nonlinear dynamic response of the clamped circular plates under impact of a mass is established by using the virtual displacement principle and Galerkin's method in this paper. The effect of coupling between the impact load and the displacement of. the circular plates is considered. The governing equation is solved by applying the time increment method and the singular perturbation theory, and the asymptotic solutions of nonlinear dyna...

本文在Von Kármán大位移的意义上，利用虚位移原理伽辽金方法建立了圆板在物体撞击下的非线性动力响应的控制微分方程，在研究响应问题时，考虑了冲击载荷与圆板位移响应之间的耦合影响，文中使用时间增量法和奇异摄动理论求解问题的控制方程，获得了固支圆板非线性动力响应的近似解，并且求解了具体算例，绘出了圆板位移、应力响应曲线以及冲击力随时间的变化曲线。

A Novel Method for Intrinsic Viscosity Determination of Polymer SolutionThere are many methods for molecular weight determination of polymers, among which viscometry is used most, it has been broad applied both in production and scientific research. This method is easy to operate with simple instruments and is applicable for broad-range molecular weight, additionally, it has high precision.

在许多情况下，常需要对同种类聚合物的特性粘度进行大量重复测定，如果都按此法操作，每个样品至少要测定3个以上不同浓度溶液的相对粘度，这是非常繁琐的，而且需时较长，尤其在所得样品量极少的情况下，就难以用此法求得高聚物溶液的，为此，人们找到了更快速的近似方法，即"一点法"。

We apply this technique into theimplementation of discrete dipole approximation method, and the method of moment ofvolume integral equation. The FFT technique combined with iterative solvers reported inthe literatures is compared for the ordinary volume integral equation and weakform ones.

我们将它应用到分析介质体散射的离散偶极子近似方法及体积分方程的矩量法中，并且讨论了文献中报道的FFT技术结合迭代解法求解体积分方程几种不同实现方案的优缺点。

The solutions were found to be good agrees with experimental results. The transfer characteristic of air dry/wet bulb temperature and spraying water temperature were discussed. The LMTD method based on this mathematical model is applicable to design and verify for the plate wet air cooler. The ratio of the wet bulb heat transfer coefficient to the heat transfer coefficient under air-cooled conditions was investigated theoretically and experimentally. The relative errors of the ratio between theoretical and experimental valves are small than 7 percent.

分别得到了平行流型式微分方程组的解析解与交叉流型式的近似解析解，实验验证了该解析解具有较高的计算精度；探讨了空气干湿球温度与喷淋水温的迁移特性；分析得到基于湿球温度迁移模型的对数平均温差法在湿式空冷器的设计与校核计算中是适用的，给出了空气湿球换热系数与空冷时空气对流换热系数比值的理论与实验确定方法，比值系数理论值与实验值比较最大相对误差小于7％。

A thermal temperature and emissivity separation algorithm based on Wien approximation and Alpha derived emissivity method are proposed.

提出了一种基于维恩近似修正和阿尔法获得法的温度和发射率的反演方法。

The paper introduces the return circuit sensitivity in the experiment of the internal resistance by sensitive amperemeter with semi-bias method.

在半偏法测灵敏电流计内阻的实验中引入回路灵敏度，并采取近似处理找出回路灵敏度不足产生误差的最小值范围，同时从理论和实验两方面对回路灵敏度不足产生误差的原因进行分析，从而找到减小这一误差的途径。

By means of the Fourier series expansion, an approximate analytical propagation equation of flattened Gaussian beams passing through an apertured paraxial ABCD optical system is derived, and illustrated with numerical examples, when the transmissivity of the aperture is T = cos.

用傅立叶级数展开法研究了平顶高斯光束通过有光阑限制的近轴ABCD光学系统的传输特性，导出了光阑透射率为T=cos时的近似解析传输公式，硬边光阑的情况可作为Ω=0的特例得到。

By means of the Fourier series expansion,an app roximate analytical propagation equation of flattened Gaussian beams passi ng through an apertured paraxial ABCD optical system is derived,and illustr ated with numerical examples,when the transmissivity of the aperture is T=cos.

用傅里叶级数展开法研究了平顶高斯光束通过有光阑限制的近轴ABCD光学系统的传输特性，导出了光阑透射率为T =cos时的近似解析传输公式，硬边光阑的情况可作为Ω=0的特例得到。

Its application to SPC circuits gives the same results as those obtained by the state-space average approach, which is proposed by Middlebrook and Colk, but our approach is also in the form of CMNA.

在分析方面，通过应用加权平均和小信号近似手段，我们建立了KL平均法，导出了开关变换器电路的S域分析的紧凑型改进节点方程，为人们应用拉普拉斯变换这一得心应手的工具来研究这类周期性开关电路提供了又一种方法。

By time-varying filtering, we realize the signal selectivity and interference suppression, especially for the signals with time-varying power spectrum. It is shown herein that conventional eigenstructure based methods are lower dimensional special case of the time-frequency subspace fitting method. The closed-form array response estimation algorithms for blind source separation in wireless communication is also developed in the dissertation by exploiting the data structure of second-order statistics of the array output in the presence of multipath. The proposed method achieves array response estimation with little constraint on signal property and propagation environment such as scatters or angular spread. Moreover, the array utilized here can be of arbitrary geometry and even uncalibrated. Since the closed-form solution is obtained, no misconvergency may occur and large amount of computation can be saved. The equivalent feed model and corresponding optimization designation are proposed to realize the downlink multi-user selective transmission. By coherent and non-coherent superposition of the electromagnetical field, multiple beams can be formed using a single array, so that each co-channel user signal is transmitted in each beam and will not interfered with each other. The proposed system scheme implements the digital beamforming and the channel allocation in the base band, therefore is suitable for the utilization of the radio software technology. The feasibility and effectiveness of the proposed model are proved by the RF experiment.

在窄带条件下，GSC－SSF方法还可以提高阵列的虚拟孔径，从而提高估计的性能；可以证明，Cyclic DOA 和SC-SSF方法可看作该方法的特例或近似； 3、提出了二维GSC－SSF方法和宽带谱相关DOA矩阵方法，利用信号的循环平稳特性解决了宽带条件下二维 DOA 估计问题，并具有阵元数少、计算量较小的特点； 4、提出了时频子空间拟合和宽带时频DOA估计算法，将联合时频分析的理论和方法引入到阵列信号的空间谱估计研究中，利用时变滤波实现信号选择性测向和干扰抑制，特别适合于谱时变信号；可以证明传统特征结构法可看作是时频子空间拟合方法的特例； 5、提出了多用户环境下阵列响应的估计方法——CARE方法，该方法对信号结构和传播参数（主要是散射源分布与角度散布）的约束较少，适用于各种几何结构的阵列甚至未校准的阵列，能够直接得到阵列响应的闭式解，因此计算量小、稳健性好，不存在收敛问题； 6、提出了针对多用户下行选择性发送的阵列等效激励模型、优化设计方法及其系统实现方案，通过空间场的相干叠加与非相干叠加使得单一阵列能够形成多个波束，并保证各波束内的用户信号各不相同且相互干扰最小；其系统方案具有在基带实现数字波束成形、信道分配并便于软件无线电实现的特点，其有效性已得到外场实测数据的证实。

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。