Reissner板弯曲问题的渐近解

本文从分析Ｒｅｉｓｓｎｅｒ板理论与Ｋｉｒｃｈｈｏｆｆ板理论的关系入手，导出了对Ｒｅｉｓｓｎｅｒ板问题的求解，可用摄动技术转化为相应边界条件下求解一系列Ｋｉｒｃｈｏｆｆ板问题，最后给出了算例也证明了本文方法具有简单，精度高的特点。     

弹性地基上无限长板受局部荷载作用的解析解

基于Ｋｉｒｃｈｈｏｆｆ薄板驼用Ｆｏｕｒｉｅｒ变换和三角级数法得到了Ｗｉｎｋｌｅｒ地基上无限长板受局部荷载作用的解析解。     

闭环式电起爆网路参数的计算方法

文中详细介绍了大型瓣环式电起爆网路的参数计算问题，按照Ｋｉｒｃｈｈｏｆｆ定律及大型闭环式电卢爆网路的特点，给出了电参数方程组及其求妥的数学模型。并通过分析方程组的特点，采用ＦＯＲＴＲＡＮ语言设计开发了计算程序，方程组的构造与计算均由计算机自动完成，较好地解决了闭环式网路参数计算的难题；     

Plant Engineering Education for Aircraft Industry in Hong Kong

ＰｌａｎｔＥｎｇｉｎｅｅｒｉｎｇＥｄｕｃａｔｉｏｎｆｏｒＡｉｒｃｒａｆｔＩｎｄｕｓｔｒｙｉｎＨｏｎｇＫｏｎｇＴ．Ｔ．ＷｏｎｇＤｅｐａｒｔｍｅｎｔｏｆＭｅｃｈａｎｉｃａｌＥｎｇｉｎｅｅｒｉｎｇＴｈｅＨｏｎｇＫｏｎｇＰｏｌｙｔｅｃｈｎｉｃＵｎｉｖｅｒｓｉ...     

纪念放射性发现一百周年(一)

１９９５、１９９６两年是Ｘ一射线和放射现象发现一百周年。在原子时代的这一百年间，核能的研究和利用给人类带来了巨大的财富，但也造成过深远的灾难。下面列出了在近代原子物理学、核物理学以及辐射防护发展史上一些闪发着人类智慧的重大里程碑。历史的回顾会给我们无穷的启示：年代重大事件１８１０道尔顿（Ｄａｌｔｏｎ）首次提出了物质的最小单位原子理论。１８５９本生（Ｂｕｎｓｅｎ）和基尔荷夫（Ｋｉｒｃｈｈｏｆｆ）发明了谱仪。１８６９．２门捷列夫（Ａ．Ｅ．Ｍｅｎｄｅｌｅｅｖ，１８３４～１９０７）发现化学元素的周期规律…     

商品条码在包装中的定位与印刷

商品条码在包装中的定位与印刷陈克愚ＰＯＳＩＴＩＯＮＩＮＧＡＮＤＰＲＩＮＴＩＮＧＯＦＢＡＲＣＯＤＥＳＯＮＣＯＭＭＯＤＩＴＩＥＳ￥ＣｈｅｎＫｅｙｕＡｂｓｔｒａｃｔ：Ｂａｒｃｏｄｅｉｓｂｒｉｎｇｉｎｇａｂｏｕｔａｒｅｖｏｌｕｔｉｏｎｔｏｔｈｅｃｉｒｃｕｌａ...     

水泥粉磨设备的现代化

１９９２年在Ｋｉｒｃｇｂｉｃｈｌ水泥厂安装了一台Ｌｉｅｚｅｎ机器公司的水平冲击破碎机，用来进行熟料及混和材的破碎。在所有加装该设备的水泥厂，其现有水泥粉磨设备的产量获提高。主要水泥厂家的产量提高达２８％，同时节约能耗１０％左右。该设备的和它的高使用率使水泥粉磨设备获高度经济的运转成为可能。     

基于虚拟裂缝模型的混凝土等效断裂韧度

本文采用虚拟裂缝模型,将临界裂缝尖端张开位移ＣＴＯＤｃ作为控制参数,利用三点弯曲梁试件通过迭代求得了混凝土裂缝亚临界扩展量的临界值△ａｃ,据此求得了混凝土起裂断裂韧度ＫｉｎｉＩｃ、等效断裂韧度ＫｕｎＩｃ值。计算结果表明,随着试件尺寸的增大,△ａｃ增大,但ＫｉｎｉＩｃ、ＫｕｎＩｃ值却是与试件尺寸无关的断裂参数。这表明线弹性断裂韧度准则可应用于混凝土结构的裂缝评定。     

空调器系统设计计算中的湿空气计算

空调器系统设计计算中的湿空气计算ＴｈｅＣａｌｃｕｌａｔｉｏｎｏｆＷｅｔＡｉｒｉｎＡｉｒ－ｃｏｎｄｉｔｉｏｎｅｒＤｅｓｉｇｈ谭周芳许春城（中山威力集团公司威力空调器厂广东５２８４０３）一、前言随着人们生活水平的进一步提高，空调器已经作为生活必需品进入...     

动态有限元模型修正中灵敏度分析的迭代LANCZOS方法

本文提出了特征向量导数计算的选代Ｌａｎｃｚｏｓ方法，与截断Ｌａｎｃｚｏｓ方法相比，大大提高了灵敏度分析的效率。文中给出了ＦＯＲＫ和３Ｄ—ＦＲＡＭＥ两种结构为实例的计算机仿真，证明本方法不仅能充分保证精度，而且提高了计算速度。     

双层插值NAH噪声源定位方法研究

针对近场声全息(near-field acoustic holography, NAH)在实际测量环境下降低环境噪声的影响且保证全息面上声压重建精度的需求,基于空间面积分声压重建理论,在基于等效源法的近场声全息方法(near-field acoustic holography based on equivalent source method, NAH-ESM)基础上,利用Newton插值和克希荷夫积分的声压重构方法提出一种双层插值NAH噪声源定位方法。由少量麦克风测量点数据,重构多个全息面上任意位置点的声压值及声矢量,实现噪声源定位,进而重构噪声源。最后结合噪声源重构结果建立噪声源等效模型,通过实地测量,建立某制氧厂主厂房噪声数值仿真,仿真结果与实测值误差在5%以内。通过实验证明在一定复杂环境下,该方法能有效提高噪声源定位效率及精度。     

Focal shifts in diffracted converging electromagnetic waves. I. Kirchhoff theory

Starting with the vector formulation of the Kirchhoff diffraction theory, expressions for the total energy density distribution along the axis are presented without using any of the usual assumptions except the assumption made by Kirchhoff for the boundary conditions of a black screen. To make the Kirchhoff integral compatible with Maxwell's equations, a line integral around the edge of the aperture is added in the analysis. The consequence of ignoring the contribution of this line integral to the axial field distribution is examined numerically. The focal shift effect is investigated for both aplanatic systems and parabolic mirrors having an arbitrary numerical aperture (NA) and finite value of the Fresnel number. The combined effects of the Fresnel number and NA on the focal shift are evaluated, and the validity of the results is carefully checked by comparing the wavelength with the system dimensions.     

基于MLE的滚动轮胎冲击振动噪声仿真分析

提出一种滚动轮胎冲击振动噪声预测的新方法。轮胎滚动接触引发的噪声是道路交通的一个重要课题,引发广泛关注,目前尚没有有效的分析预测方法。提出新方法包括用混合拉格朗日—欧拉描述法(Mixed Logrange Euler Method,MLE)分析大变形滚动接触结构的速度场、加速度场和接触变形。通过欧拉网格和拉格朗日网格的信息传递,完成滚动结构动力学分析。通过将轮胎花纹和胎冠整体三维建模,可以得到连续轮胎表面的加速度场。以参考空间中连续表面的加速度场作为声源,采用声学有限元方法得到滚动噪声的分布预测。实验和仿真结果对比证明本方法的可靠和准确,也证明1 000 Hz以下轮胎的滚动噪声主要是花纹的冲击振动引起的噪声。提出的方法为预测分析轮胎的滚动噪声开辟一条可行的道路。     

《Kirchhoff公式在电容器装置噪声水平预估中的应用》

引入Kirchhoff公式，对于换流站中滤波电容器装置围栏外噪声水平进行预估，并将该方法的计算结果与单极子阵列声源计算方法的计算结果、肇庆实际测量结果进行了比较。结果表明，实测结果与Kirchhoff公式计算结果具有良好的一致性，进而验证了该方法的合理性和准确性。     

基于绝对节点坐标法的输流管道非线性动力学分析

基于绝对节点坐标法,建立一种新的一维二节点输流管道单元。应用Irschik提出的适用于含非材料体系统的Lagrange方程推导输流管道单元的运动方程。采用Euler梁来模拟管道,并完全采用非线性Green应变张量和第二Piola Kirchhoff应力张量,没有任何量级近似,也没有假设悬臂输流管道的轴线不可伸长,并考虑材料的泊松效应对流速的影响,因此通过该方法得到的运动方程比传统的通过量级近似得到的输流管道的运动方程更合理。通过数值计算,分析不同边界条件下的输流管道非线性行为,并与经典输流管道运动方程的计算结果比较,结果表明本文中的方法更合理     

A Detailed Study of the Scattering of Scalar Waves from Random Rough Surfaces

A multiple scattering theory of scalar waves from random rough surfaces is presented. By using the Ewald-Oseen extinction theorem the scattering integral equation is solved by means of an expansion in σ powers (σ being the standard deviation of the corrugation). Values of the mean scattered intensity until the fourth order of σ are given. The quick convergence of this series for low σ permits us to deal with those situations of small roughness in which the Kirchhoff approximation given by Beckmann and Spizzichino [2] fails. These are the cases in which σ ? T and λ ? T (λ being the wavelength and T the surface correlation length). Thus this theory can give the intensity for white noise surfaces, and yields the conditions under which the single scattering Kirchhoff approximation works, as well as its percentage of error. As such it is shown that Beckmann's theory gives good results in all cases in which σ /T < 0·05 and, thus, the reason why it is valid for interpreting laser speckle measurements is given. All the analysis is done for normal statistics and a gaussian correlation function of the corrugation.     

Multiscale modeling of beam and plates using customized second-generation wavelets

We have designed bicubic Hermite-type finite-element wavelets that decouple the multiresolution stiffness matrix obtained from the discretization of the biharmonic equation. The scale decoupling basis makes the stiffness matrix block diagonal and hence eliminates the coupling between scales. The scale-decoupled system leads to an incremental procedure for systematic enrichment of the solution without the need for costly remeshing of the whole domain and recalculation of the solution. The solution is obtained by injection of finer-scale wavelets at locations with high detail coefficients. We conducted some numerical experiments to demonstrate the customized wavelet-based finite-element method for the problem of bending of Euler’s beam and Kirchhoff’s plates; we also demonstrate the role of wavelets in resolving localized phenomena.     

两个宽带噪声矢量场模型的空间相关特性

针对宽带噪声矢量场的空间相关特性问题,文章讨论了各向同性噪声模型和表面噪声模型。在高频近似条件下,根据射线声学理论和简谐平面行波满足的欧拉公式,采用时域建模方法分别建立了宽带各向同性噪声和表面噪声矢量场模型。给出了噪声场相关函数的积分表达式和竖直方向空间相关系数的解析表达式。数值分析结果表明,相较于窄带噪声矢量场,宽带噪声矢量场各分量空间相关系数振荡幅度更小,随空间两点间距的增大更快地趋近于零;噪声源指向性对表面噪声场竖直方向上的空间相关特性的影响显著。相较于已有的宽带噪声空间相关系数计算方法,文中模型无需使用傅里叶合成方法,可通过时域建模直接获得宽带噪声空间相关函数。     

Numerical simulation of incompressible Navier-Stokes and Euler equations to the vortical flow about a delta wing

Summary An algorithm based on the method of artificial compressibility is used to solve the incompressible Navier-Stokes and Euler equations in 3D generalized curvilinear coordinates. The choice of the pseudocompressibility parameter is discussed and a function form of which accelerates the convergence effectively is presented. Numerical simulation of the vortical flow about a 70° delta wing is made by both Euler and Navier-Stokes methods. Comparison of the computed results and the experimental data indicates that the Euler method can capture the global flow feature, i.e., separation from the sharp leading edge and the formation of the leading-edge vortex; the Navier-Stokes method depicts not only the flow features captured by the Euler method, but also the boundary layer effects and specifically the secondary separation induced by the leading-edge vortex on the wing upper surface. Thus, the Navier-Stokes method shows a much improved correlation with the experimental data.     

An analysis of compressive stability of elastic solids containing a crack parallel to the surface

An analysis is presented for compressive stability of elastic solids containing a crack parallel to the free surface based on the mathematical theory of elasticity. Basic buckling equations derived from the mathematical theory of elasticity are employed and are reduced to a system of homogeneous Cauchy-type singular integral equations by means of Fourier integral transform. The integral equations are solved numerically by utilizing Gauss-Chebyshev integral formulae. Numerical results for buckling loads are presented for various geometrical parameters and are compared with those obtained from classical theory of beam-plate stability based on the Kirchhoff assumption. The comparison of both results shows that the buckling loads obtained from the classical theory of beam-plate stability are much larger than those obtained from the mathematical theory of elasticity, referring to which the limitations of the classical theory applied to the present buckling problem are discussed. A simple but accurate approximate method for estimating the buckling load is developed by the use of the elastic support coefficient obtained from the present analysis and the Euler formula derived from the classical theory for the case of elastically supported ends. Finally, the numerical results of the buckling wave shapes and the Mode I and II stress factors, which cannot be obtained from the classical theory, are presented.