空间网架结构边界约束对网架温度应力的影响

结合边界约束条件对网架温度应力的影响来控制网架结构边界条件的选型。分析了网架结构在弹性约束、固定和强迫位移条件下的总刚度矩阵处理方法；介绍了网架结构在均匀温度场变化下，由于杆件不能自由的热胀冷缩而产生了温度应力，同时阐述了它的分析方法。并且根据有限元理论和Visual Basic6.0编程语言编制了温度应力分析程序，针对具体的工程实例来探讨温度应力在边界的切线与法线方向约束条件分别选取固定、弹性、放松三种情况进行五种组合的条件下杆件温度应力的变化规律，从而确定了网架的边界形式。     

群桩基础的剪切位移法分析

提出分析群桩基础的剪切位移法：设定桩身位移方程为含有未知量的有限级数，利用桩顶、桩端的边界条件求解各未知量，从而得到桩身位移及桩周土位移。通过算例和实例的计算结果可证明该方法的正确性。     

岩土材料滑移线场理论中的应力间断线

根据非特征线应力边界条件的显示解析表达式，明确给出了岩土材料滑移线场理论中应力间断线上的应力条件，应力间断值及其位置，使得锐角楔体极限荷载等问题的求解更简单，更方便。     

一类稳态扩散问题的死核估计

考察了一类在化学反应研究中的具有Robin边界条件的非线性稳态扩散问题，由于扮演重要角色的死核边界是先验未知的，即这是一个自由边界问题，首先借助相应Dirichlet问题的解结合极值原理和比较原理，导出了该问题边值的上界和下界，说明死核是存在的，随后利用解在边界上的上，下界，估计了一般区域上死核所在的位置及其形状，这是对已有结果的完善和推广。     

平面间隙运动副副元素相对运动

考虑到含间隙运动副在碰撞接触时的边界条件，采用非线性弹簧力和非线性阻尼描述含间隙运动副副元素的碰撞接触过程。以多间隙运动副曲柄摇杆机构为例，通过数值计算研究了间隙运动副副元素的相对运动及多个间隙副之间的相互影响，并首次指出了高速运转条件下，运动副副元素由于弹性变形而存在的连续变形接触现象和多间隙运动副之间的相互影响特性。     

用变分法计算在张力作用下长方形薄板弯曲问题的近似解

1长方形薄板在张力作用下承受法向振动荷载时里兹(Ritz)法的近似解 设单跨矩形薄板G｛0≤a,0≤y≤b｝,承受一简谐振动荷载为:这时薄板在张力作用下的强迫振动方程为: 取板的振动幅度w(x,y,t)为: 将(2)式代入(1)整理后[1]可得:其中:为抗弯刚度,为振动荷载的频率,是板单位面积上的重量,q(x,y)是作用在板的单位面积上的荷载幅度. 方程(3)的四边简支边界条件为在 线性算式是对称正定算式.因此,边值问题(3)、(4)的唯一解等价于泛函J[u]的极小值[2] 1)取均布的振动荷载q,则F(x,y,t)-qsin(t),式中q是振动荷载幅度.选取坐标函数系[3]将N)式代人*)…     

Connecting Conditions and Constraint Equations in Applied Science

IntroductionIn applied science , e . g . machinery , vibrationmechanics , fluid mechanics , and management science , toobtain the opti mal solution of some issues , the objectfunction is usually shown since the abstract mathematicsmodel is set , and all kinds of boundary conditions andconnecting conditions or constraint conditions are putforward . Above these conditions are shown with the shapesof constraint equations . For example ,in machinery opti maldesign, to get the opti mal solution of …     

Fingerprint representation methods based on B-Spline functions

The global characteristics of a fingerprint image such as the ridge shape and ridge topology are often ignored in most automatic fingerprint verification system.In this paper,a new representative method based on B-Spline curve is proposed to address this problem.The resultant B-Spline curves can represent the global characteristics completely and the curves are analyzable and precise.An algorithm is also proposed to extract the curves from the fingerprint image.In addition to preserve the most information of the fingerprint image,the knot-points number of the B-Spline curve is reduced to minimum in this algorithm. At the same time,the influence of the fingerprint image noise is discussed.In the end,an example is given to demonstrate the effectiveness of the representation method.     

FDTD modeling of transient scattering by subsurface targets

In this paper, a two-dimensional (2-D) finitedifference time-domain method (FDTD) scheme is used to simulate the transient scattering characteristics of buried objects, which are modeled by columns of arbitrary permittivities, conductivities, and sizes. The FDTD soil is modeled by isotropic, homogeneous and lossy media. The standing-traveling wave boundary condition (STWBC) that can simplify calculation and save CPU storage is used for modeling physical absorbers inside the FDTD computational dornairL Reflection of electromagnetic pulses incident on a layered medium and transient scattering by the ground and an underground airsqu are cylinder are computed. These results verify the validity of the FDTD scheme by comparisons with those shown in some references. Numerical results presented in the final part of this paper are desirable and meaningful, explicitly distinguishing echo waves stemming from the ground and the buried ohjects.