一种用射影线束族生成曲线的方法

以两射影对应线束对应真线交点的轨迹是二阶曲线为基础，研究了射影线束族的形成原理，讨论了射影线束与线束族，射影线束族与线束族对应直线交点所构成的平面曲线及其性质，同时利用计算机绘制了部分曲线。     

二次NURBS曲线的退化曲线

NURBS曲线是几何造型中广泛使用的曲线拟合工具.当某一权因子趋向于无穷时,NURBS曲线趋于相应的控制顶点,当所有权因子趋向于无穷时,其极限曲线的几何性质目前还没有结论.利用NURBS曲线的节点插入算法,将NURBS曲线转化为分段有理Bézier曲线,结合有理Bézier曲线的退化理论,得到当所有权因子趋向于无穷时其退化曲线的几何结构.     

两射影平面场的合同点列与线束

同素对应的两射影平面场存在两对对应合同点列，两对对应合同线束。且合同点列与线束之间具有特殊的位置关系。根据这一点，我们给出反映两射影平面场之间量的关系参数：射影比。     

关于射影KillingP-形式的注记

定义了与文[1]中不同的射影Killing p-形式．命名为z-射影Killing p-形式,实质上是射影Killing．p-形式的一种推广,并证明了有关该形式的三十定理。     

基于李群指数映射的二阶最小化射影目标跟踪

基于空间变换模型的目标跟踪问题常归结为非线性最小二乘优化问题,射影变换模型的高度非线性使得基于向量空间的优化算法倍显局限.通过李群指数映射将正则射影变换群局部线性化,在内蕴几何优化理论的框架下,结合目标跟踪的具体特点,提出一种无需计算赫森阵的二阶最小化射影变形目标跟踪算法.与基于向量空间和基于李代数参数化的高斯-牛顿两种优化算法作对比实验,结果证实本文算法的可行性和高效性.     

钢筋混凝土柱二阶弹塑性计算的图解法

对于钢筋混凝土柱的材料和几何非线性问题,基于正弦曲线的变形假设推导了钢筋混凝土柱二阶弹塑性极限荷载计算的图解法。通过分析钢筋混凝土截面弯矩-曲率关系曲线的切线特征,该法以柱子长细比和一阶偏心距为未知量,不对弯矩-曲率关系简化,直接将截面上弯矩-曲率关系曲线上的每一点作为极限承载力。采用分级加荷载的图解方法,能够同时得到荷载-挠度曲线的上升段和下降段。计算结果与试验值符合良好。结果表明:细长柱也可能出现材料强度破坏,其二阶极限承载力近似等于截面极限承载力。     

分解算法的丢失数据射影重建

在射影重建问题中,广泛应用的分解算法尽管能够平等地看待所有的图像,但它们要求全部空间点在所有的图像上都可视.为了克服这一限制,该文提出了一种基于分解算法的射影重建方法.该方法迭代地估计空间点、投影矩阵、深度因子和丢失的数据.投影矩阵和空间点通过奇异值分解被求取.深度因子则根据每幅所有图像点构成的行向量生成的线性子空间和与射影重建空间点构成的行向量生成的线性子空间是同一线性子空间的特性被估计出来.模拟数据和真实图像的实验结果表明,该射影重建方法具有重投影误差小,收敛性好和实用性强的特点.     

曲线上较大桥台布置形式的探讨

随着曲线计算理论的日益完善，施工技术的不断提高，曲梁将逐步应用在曲线桥上。桥上线路为曲线，但梁仍为筒支直线梁的曲线桥布景方式目前应用仍最为普遍。本文着重对较大桥台在曲线桥上各种布置形式进行计算分析，并就各布置形式的精度进行探讨，以便于日后施工时参考。     

基于二阶锥规划的稳健低旁瓣自适应波束形成

针对水下成像时圆弧阵常规波束旁瓣级较高,当存在强干扰时容易带来较多虚警的缺点,提出一种基于二阶锥规划的稳健低旁瓣自适应波束形成方法。该方法通过对波束旁瓣进行优化设计,可以将波束旁瓣级进行严格控制,并进一步结合协方差矩阵重构法,使波束形成器的稳健性得到提高,最后将该波束优化问题转化为二阶锥规划问题进行求解。计算机仿真结果表明,相较于其他算法来说,文中算法在波束旁瓣级得到严格控制的同时,可以在存在各类失配的情况下获得更高的输出信干噪比,稳健性更高。水池实验进一步验证了该方法的有效性,该研究成果可以在声呐成像领域应用。     

最小二乘法拟合压力传感器二次曲线及精度分析

提出了用最小二乘法拟合压力传感器输入输出关系二次曲线的方法.文中对这两种方法作了比较,并用实例说明二次多项式拟合结果可大大提高测量的精度;其次,采用矩阵运算及MATLAB编程可提高计算效率.     

Pseudo second order kinetics and pseudo isotherms for malachite green onto activated carbon: comparison of linear and non-linear regression methods

Pseudo second order kinetic expressions of Ho, Sobkowsk and Czerwinski, Blanachard et al. and Ritchie were fitted to the experimental kinetic data of malachite green onto activated carbon by non-linear and linear method. Non-linear method was found to be a better way of obtaining the parameters involved in the second order rate kinetic expressions. Both linear and non-linear regression showed that the Sobkowsk and Czerwinski and Ritchie's pseudo second order model were the same. Non-linear regression analysis showed that both Blanachard et al. and Ho have similar ideas on the pseudo second order model but with different assumptions. The best fit of experimental data in Ho's pseudo second order expression by linear and non-linear regression method showed that Ho pseudo second order model was a better kinetic expression when compared to other pseudo second order kinetic expressions. The amount of dye adsorbed at equilibrium, q(e), was predicted from Ho pseudo second order expression and were fitted to the Langmuir, Freundlich and Redlich Peterson expressions by both linear and non-linear method to obtain the pseudo isotherms. The best fitting pseudo isotherm was found to be the Langmuir and Redlich Peterson isotherm. Redlich Peterson is a special case of Langmuir when the constant g equals unity.     

Plane wave propagation and domain of influence in fractional order thermoelastic materials with three-phase-lag heat transfer

The domain of influence theorem for the fractional order theory of anisotropic thermoelastic materials with three-phase-lag heat transfer is proposed. The fractional order theory of thermoelasticity with three-phase-lag heat transfer has been used to investigate the problem. The plane wave propagation in anisotropic thermoelastic medium having a fractional order derivative in the context of three-phase-lag model of thermoelasticity is studied. The governing equations for a transversely isotropic three-phase-lag model are reduced as a special case. Some wave characteristics are computed numerically and presented graphically.     

我国口岸截获一、二类危险性有害生物情况评价

对 1990年至 2 0 0 1年我国口岸在进境植物检疫中截获的一、二类危险性有害生物进行了总结和分析 .我国口岸截获的一类危险性有害生物共有 8种 ,其中昆虫类 4种、线虫类 1种、真菌类 3种 ;二类危险性有害生物共有 16种 ,其中昆虫类 9种、线虫类 2种、病毒类 1种以及杂草类 4种     

Method of particular solutions for solving PDEs of the second and fourth orders with variable coefficients

The paper presents a new meshless numerical method for solving partial differential equations of the second and fourth orders with variable coefficients. The key idea of the method is the use of modified particular solutions which satisfy the homogeneous boundary conditions of the problem. This allows us to seek an approximate solution in the form which satisfies the boundary conditions of the initial problem. As a result we separate the approximation of the boundary conditions and the PDE inside the solution domain. Numerical experiments are carried out for accuracy and convergence investigations. A comparison of the numerical results obtained in the paper with the exact solutions or other numerical methods indicates that the proposed method is accurate in dealing with PDEs with variable coefficients.     

Higher‐order responses of three‐dimensional elastic plate structures and their numerical illustration by p‐FEM

The displacements of three‐dimensional linearly elastic plate domains can be expanded as a compound power‐series asymptotics, when the thickness parameter ε tends to zero. The leading term u ⁰ in this expansion is the well‐known Kirchhoff–Love displacement field, which is the solution to the limit case when ε→0. Herein, we focus our discussion on plate domains with either clamped or free lateral boundary conditions, and characterize the loading conditions for which the leading term vanishes. In these situations the first non‐zero term u ^k in the expansion appears for k=2, 3 or 4 and is denoted as higher‐order response of order 2,3 or 4, respectively. We provide herein explicit loading conditions under which higher order responses in three‐dimensional plate structures are visible, and demonstrate the mathematical analysis by numerical simulation using the p‐version finite element method. Owing to the need for highly accurate results and ‘needle elements’ (having extremely large aspect ratio up to 10000), a p‐version finite element analysis is mandatory for obtaining reliable and highly accurate results. Copyright © 2001 John Wiley & Sons, Ltd.     

Large‐deformation and friction analysis of non‐linear elastic cable networks by second‐order cone programming

A new formulation is presented for equilibrium shape analysis of cable networks considering geometrical and material non‐linearities. Friction between cables and joint devices is also considered. The second‐order cone programming (SOCP) problem which has the same solution as that of minimization of total potential energy is solved to obtain the equilibrium configuration. The optimality conditions are derived to verify that the solution satisfies equilibrium conditions and friction laws. Since no assumption on stress state is needed in the proposed method, no process of trial and error is involved. No effort is required to develop any analysis software because SOCP can be solved by using the well‐developed software based on the interior‐point method. Copyright © 2002 John Wiley & Sons, Ltd.     

两类Chebyshev零点的Newman型有理算子逼近|x|的渐近性质

设X={xk∶k=1,2,…,n}是区间(0,1]上n个互不相同点的集合,令pn(x)=∏nk=1(xk+x),rn(X;x)=xpn(x)-pn(-x)pn(x)+pn(-x),本文给出了当X=U={xk=cosk2n+1π∶k=1,2…,n},X=T={xk=sin2k-14nπ∶k=1,2,…,n}时,max|x|≤1‖x|-rn(U;x)|及max|x|≤1‖x|-rn(T;x)|的渐近表达式.     

规范秩序 提升水平 健康发展——写在我国PS发泡餐具解禁之际

本文通过分析PS发泡餐具及装备制造行业国内外的现状。提出了如何通过规范行业秩序，努力提升水平，缩短与国际先进水平的差距，使我国发泡餐具及装备制造业能得到健康较快的发展。为我国食品包装做出新贡献。