“0.618”法、Fibonacci法、抛物线法搜寻复摆周期极值点

在实验室条件下,用"0.618"法、Fibonacci法和抛物线法来搜寻钟摆复摆周期极值点位置.通过实验发现,Fibonacci法在搜索精度上比"0.618"法高,但在搜寻速度上不占优势,而抛物线法在搜寻速度和精度上比"0.618"法和Fibonacci法都好.     

An improved interpolating element-free Galerkin method with a nonsingular weight function for two-dimensional potential problems

In this paper, an improved interpolating moving least-square (IIMLS) method is presented. The shape function of the IIMLS method satisfies the property of the Kronecker δ function. The weight function used in the IIMLS method is nonsingular. Then the IIMLS method can overcome the difficulties caused by the singularity of the weight function in the IMLS method. The number of unknown coefficients in the trial function of the IIMLS method is less than that of the moving least-square (MLS) approximation. Then by combining the IIMLS method with the Galerkin weak form of the potential problem, the improved interpolating element-free Galerkin (IIEFG) method for two-dimensional potential problems is presented. Compared with the conventional element-free Galerkin (EFG) method, the IIEFG method can directly use the essential boundary conditions. Then the IIEFG method has higher accuracy. For demonstration, three numerical examples are solved using the IIEFG method.     

An improved interpolating element-free Galerkin method with nonsingular weight function for two-dimensional potential problems

In this paper, an improved interpolating moving least-square (IIMLS) method is presented. The shape function of the IIMLS method satisfies the property of Kronecker δ function. The weight function used in the IIMLS method is nonsingular. Then the IIMLS method can overcome the difficulties caused by the singularity of the weight function in the IMLS method. And the number of unknown coefficients in the trial function of the IIMLS method is less than that of the moving least-square (MLS) approximation. Then by combining the IIMLS method with the Galerkin weak form of the potential problem, the improved interpolating element-free Galerkin (IIEFG) method for two-dimensional potential problems is presented. Compared with the conventional element-free Galerkin (EFG) method, the IIEFG method can directly use the essential boundary conditions. Then the IIEFG method has a higher accuracy. For demonstration, three numerical examples are solved using the IIEFG method.     

An impulse integrator for Langevin dynamics

The best simple method for Newtonian molecular dynamics is indisputably the leapfrog Stormer-Verlet method. The appropriate generalization to simple Langevin dynamics is unclear. An analysis is presented comparing an ‘impulse method’ (kick; fluctuate; kick), the 1982 method of van Gunsteren and Berendsen, and the Brünger-Brooks-Karplus (BBK) method. It is shown how the impulse method and the van Gunsteren-Berendsen methods can be implemented as efficiently as the BBK method. Other considerations suggest that the impulse method is the best basic method for simple Langevin dynamics, with the van Gunsteren-Berendsen method a close contender.     

微波器件微放电阈值计算的快速单粒子蒙特卡罗方法

为了计算微波器件的微放电阈值,提出了一种快速单粒子蒙特卡罗方法.该方法对二次电子出射能量、出射角度和相位等参数进行随机处理,结合四阶龙格库塔法和Furman模型模拟了电子运动和二次电子发射系数,并以多次连续碰撞的二次电子发射系数的算数平均值作为微放电效应发生的判据.以平板传输线横电磁模式为研究对象,分别采用快速单粒子蒙特卡罗方法、统计模型、传统蒙特卡罗方法以及粒子模拟方法计算其微放电阈值和敏感区域.计算结果表明,该方法不仅具有与统计模型和粒子模拟方法相当的计算精度,而且比统计模型方法的适应性更强,比传统蒙特卡罗方法的稳定性更好,比粒子模拟方法的计算效率高几十倍以上.     

复化辛普森法和傅里叶法在衍射计算上的比较

通过快速傅里叶变换(FFT)法和复化辛普森法对衍射的数值进行计算,可以看出快速傅里叶变换法是一种积分变换法,而复化辛普森法则是迭代相加的方法.通过计算得出了FFT法的计算速度高于复化辛普森法,计算精度则远低于复化辛普森法;复化辛普森法适合近距离菲涅尔衍射和近场衍射,而FFT法不适合.     

无线电掩星滑动频谱方法和后传播方法的分析比较

本文详细介绍了滑动频谱方法,并通过模拟仿真和实测资料处理与后传播方法进行比较. 通过对模拟仿真信号反演发现:后传播方法和滑动频谱方法均能削弱大气多路径的影响,后传播方法在一定程度上优于滑动频谱方法;在模拟信号的相位中加入高斯噪声对后传播方法影响不大,但对滑动频谱方法影响较大,尤其在边界层以下. 分别用后传播方法和滑动频谱方法对2007年第71天至73天共约4500个COSMIC掩星数据进行处理. 将折射率反演结果与ECMWF分析场资料进行统计比较,结果显示:滑动频谱方法反演的掩星廓线深度大于后传播方法;后 关键词： GPS/LEO掩星 多相位屏模型 后传播方法 滑动频谱方法     

HL-RBWO-冷腔特性的一种快速算法

 在传统谐振法基础上发展了一种计算慢性结构（SWS）冷腔参数的脉冲响应法，它的主要思想是利用有丰富谐波成分的窄脉冲作为激励源来代替实验系统中的扫频源，从而使得获取RBWO的色散曲线速度大大加快。这种方法使得脉冲响应法成为计算SWS冷腔参数的一种快速数值算法，更加适合于数值计算，并在研究HL-RBWO时得到有效的应用。     

Stability Analysis and Order Improvement for Time Domain Differential Quadrature Method

The differential quadrature method has been widely used in scientific and engineering computation. However, for the basic characteristics of time domain differential quadrature method, such as numerical stability and calculation accuracy or order, it is still lack of systematic analysis conclusions. In this paper, according to the principle of differential quadrature method, it has been derived and proved that the weighting coefficients matrix of differential quadrature method meets the importantV-transformation feature. Through the equivalence of the differential quadrature method and the implicit Runge-Kutta method, it has been proved that the differential quadrature method is A-stable and $s$-stage $s$-order method. On this basis, in order to further improve the accuracy of the time domain differential quadrature method, a class of improved differential quadrature method of $s$-stage $2s$-order has been proposed by using undetermined coefficients method and Padéapproximations. The numerical results show that the proposed differential quadrature method is more precise than the traditional differential quadrature method.     

能量色散X射线荧光分析中改进型基本参数法研究

能量色散X射线荧光分析方法是目前常用的一种多元素分析方法,但该方法检出限和分析精度,受到分析基体的影响。基本参数法是目前一种常用的分析方法,但在使用过程必须获取净峰面积和基体所有成分,而在实际使用时,尤其在分析低含量样品时,净峰面积计算、基体中“暗物质”影响了测量精度,制约了基本参数法的应用。针对基本参数法的不足,将谱线解析方法与基本参数法融合,将重叠峰剥离过程嵌入基本参数法迭代过程中。在含量计算过程中,采用分析样品特征X射线分支比的理论系数,对重叠峰进行剥离,解决能量色散X射线荧光测量中净峰面积计算和定量分析问题;在计算过程中,对“暗物质”进行均一化处理。通过对标准物质测量分析,结果表明对于Ni,Cu,Zn三个元素改进型基本参数法(改进型FP)测量结果准确度高于影响系数法。     

连续流动分析法测定土壤中的有效磷

为了提高土壤中有效磷的检测效率和方法的稳定性,研究了现代仪器分析方法-连续流动法测定土壤中有效磷的含量,对连续流动法与农业部标准方法NY/T 148-1990《石灰性土壤有效磷测定方法》、NY/T 1121.7-2006《酸性土壤有效磷的测定》的测定结果进行配对两处理t检验,结果表明：连续流动法与标准方法检测的结果不存在系统误差,样品测定的相对标准偏差均小于10％,连续流动法测定值的相对标准偏差较标准方法略小.同时,用连续流动法对土壤标准样品GBW 07413-GBW 07414（碱法）、GBW07416-GBW 07417（酸法）进行有效磷的测定,测定值与标准值相吻合.     

解线性代数方程组的TCG迭代法

ICCG方法是解线性代数方程组较为理想的方法,但它仅适用于具有正定对称的系数阵。本文介绍的TCG方法便足改造过的ICCG方法,它适用于一般非奇异的非正定对称阵。TCG方法比常用的JLUCG方法,对于非定常问题,可提高效率18%,特别是取用SIP不完全L、U分解作预条件时,可提高效率40%,是计算非正定对称阵较为理想的迭代法之一。本文推导出在消去法不完全L,U分解下的TCG方法,并用数值结果论证出它比ILUCG方法加速收敛的所在。     

van der Pol方程分析研究的新结果

依据等效小参量法原理,用主振荡包含两个谐波的符号分析算法求解van der Pol方程,在强非线性时获得的周期解准确度高于扰动法、KBM法、多尺度法、谐波平衡法及主振荡为一个谐波的等效小参量法,且求解过程简单,易于计算机编程．     

基于小波变换的新型数字散斑相关方法

通过将小波分析的方法应用到传统的空域相关计算中,提出了基于小波变换的数字散斑相关方法。详细介绍了该方法的原理,并对传统空域相关方法与小波相关方法进行了实验计算比较。实验结果表明,与传统的空域相关方法相比,基于小波变换的数字散斑相关方法大大提高了相关计算的精度,精度由0 05像素提高到了0 01像素以下。最后利用该方法测量了编织结构复合材料板在三点弯曲载荷作用下的位移场。     

FAAS法对三种制备样品方法的研究

在FAAS法分析中，样品预处理始终占有极为重要的位置。本文比较了三种样品消化方式，即传统酸消化法，灰化法及微波消化法。传统的消化方式过程长、速度慢、效率低、而且被测元素易受到损失及易污染等不足，而微波是一种非常快捷、省时、省试剂和无污染的消化方式。通过对校准物质贻贝中的铜、锌、铁的测定结果证明微波消化方式比传统的消化方式优点多。     

Quasi-geometrical optics methods in the theory of wave propagation through a randomly inhomogeneous layer

Some possibilities of using asymptotic methods, such as the Maslov method and the interference-integral method, in problems of wave propagation in randomly inhomogeneous media are considered. It is shown that using the Maslov method and the interference-integral method in a small-angle approximation, and neglecting amplitude fluctuations of partial waves, provides results of heuristic spectral methods that utilize expansions in terms of incoming or outgoing waves. The combined use of these asymptotic methods gives a third heuristic method, a mixed-integral representation obtained earlier by applying the method of two-scale expansions. It is pointed out that results of a mixed-integral representation change to those of the method of smooth disturbances and of the phase-screen method. Unlike the method of two-scale expansions, the proposed approach based on the combined use of asymptotic methods facilitates the process of taking into account the heterogeneity of a background medium.     

高精度测量孔径光阑面积方法概述

一些辐射学和光度学的测量是以高精度测量精密光阑面积为基础的, 因此高精度测量孔径光阑的面积有着至关重要的意义. 目前高精度测量孔径光阑面积主要有以下两类方法: 接触法与非接触法, 几何法与有效面积法.本文首先对各种方法进行简单介绍, 并对非接触法、 几何法和有效面积法进行重点阐述.最后通过对比不同方法的测量精度、 实现难易程度以及测量设备成本情况, 得出结论: 几何法和有效面积法是非常有前景的.然而要进一步提高孔径光阑面积的测量精度, 稳定的激光光源、精准的移动平台是必不可少的. 关键词： 高精度测量 测量方法 光阑面积     

Computational comparison of the conventional multislice method and the real space multislice method for simulating exit wavefunctions

The simulation of exit wavefunctions of a TEM sample is carried out by both the conventional multislice (C-MS) method and the real space multislice (RS–MS) method, with a series of different slice thicknesses. Surprisingly, the results calculated by the RS–MS method remain constant to seven significant figures when the slice thicknesses are changed within a wide range, while those calculated by the C-MS method change significantly. From the mathematical point of view, the C-MS method is only a first order approximation of the RS–MS method. Thus, the calculation precision of the RS–MS method is much higher than that of the C-MS method. Or to achieve the same precision, the slice thickness for the RS–MS method can be taken as two orders of magnitude larger than for the C-MS method in the simulation. As a result, the calculation speed for the RS–MS method may be even faster than that for the C-MS method in some cases. For the two advantages stated above, the RS–MS method may be more suitable for precise calculations.     

A stiffness equation transfer method for natural frequencies of structures

A stiffness equation transfer method is proposed for obtaining vibration frequencies of structures. This method is an extension of the finite element-transfer matrix (FE-TM) method. In the present method, the transfer of state vectors from left to right in the ordinary FE-TM method is changed into the transfer of stiffness equations of every section from left to right. This method reduces the propagation of round-off errors produced in the ordinary transfer matrix method. Furthermore, the drawback that the number of degrees of freedom on the left boundary must be the same as that on the right boundary in the ordinary FE-TM method, is now avoided. Besides, this method finds out the values of the frequency by Newton-Raphson iteration method, so no plotting of the value of the determinant versus assumed frequency is necessary. An IFETM—W program based on this method for use on an IBM PC586 microcomputer is developed. Finally, numerical examples are presented to demonstrate the accuracy as well as the potential of the proposed method for free vibration analysis of structures.     

罗替戈汀微球体外释放度的检查方法

分别采用摇床法和流通池法测定罗替戈汀微球的体外释放度,并通过与体内药动学曲线拟合进行选择.结果表明,摇床法和流通池法测定的体外释放度均与体内吸收具有明显相关性,相关系数r分别为0.9937和0.9978,且流通池法可检测到微球存在的较小突释.摇床法和流通池法均可用于罗替戈汀微球的体外释放度检查,流通池法作为一种新型溶出...