层合板壳脱层屈曲的有限元分析

通过建立一类新的参考面有限单元,得到适用于分析层合板壳脱层屈曲问题的有限元方法。指出了利用Mindlin假设意义下的变形协调条件,可以将大多数胜任层合板壳分析的一般板壳单元改造为相应的参考面单元。这一方法确保了位移场的合理性和协调条件的满足。为验证参考面单元的有效性,还对壳体脱层屈曲的几个算例作了数值分析。     

层合板壳脱层曲面的有限元分析

通过建立一类新的参考面有限单元,得到适应于分析层合板壳脱层屈曲问题的有限元方法,指出了利用Ｍｉｎｄｌｉｎ假设意义下的变形协调条件,可以将大多数胜任层合板壳分析的一般板壳单元改造为相应的参考面单元,这一方法确保了位移场的合理性和协调条件满足,为验证参考而单元的有效性和协调还对壳体脱层屈曲的几个算例作了数值分析。     

《数值计算与计算机应用》2021年第42卷第4期摘要

潘佳佳,李会元,二阶椭圆问题的弱迦辽金四边形谱元方法[J].数值计算与计算机应用,2021,42(4):303-322.摘要:本文对二阶椭圆方程特征值问题的弱伽辽金谱元方法开展相关数值研究.与弱有限元方法类似,弱伽辽金谱元方法的逼近函数空间包括各个单元上的独立内部分量、并辅以各单元边界分量作为单元与单元间的联系.本文聚焦任意凸四边形网格剖分下的弱伽辽金四边形谱元方法,弱逼近函数中的各内部分量与边界分量分别由参考正方形单元与参考单元边界上的正交多项式通过双线性变换来构造;而弱梯度逼近空间则由参考正方形上的正交多项式通过Piola变换构造.在此基础上,本文提出了二阶椭圆方程特征值问题的弱伽辽金四边形谱元方法逼近格式和实现算法,并通过对离散弱梯度核空间的系统研究。     

非正则条件下类Wilson元的构造及其应用

本文在非正则性条件下，研究了窄四边形上的类Wilson元。通过参考元上类Wilson元的构造，证明了由此产生的有限元对任意窄四边形剖分通过Irons分片检查，得到了二阶问题的误差估计。结果表明，该单元的收敛性质与Wilson元的类似。     

对《高中数学单元学习和测试》中部分测试题的几点修正意见

由某出版社出版的《高中数学单元学习和测试》一书是我市高中数学教师一份必备的参考资料，也是学生必备的较好的学习用书，笔者近来在备课中发现测试题中的部分试题(或答案)存在不少解题(或印刷)错误、现提出修正意见，供同行老师们参考、不妥之处，请予指正．     

具有阶段最终产出的广义链式网络DEA模型

传统网络DEA方法通过打开生产过程中的"黑箱",考虑生产过程的中间环节,对生产过程进行相对效率评价.但是传统网络DEA方法只能相对于决策单元集而不能相对于非决策单元集进行相对效率评价.给出能够相对于任意参考集对决策单元进行相对效率评价的基于C2R模型的具有阶段最终产出的广义链式网络DEA方法,初步讨论相应性质并进行算例演示.     

改进的非协调广义混合单元及性能分析

非协调广义混合单元最突出的特点是避免了传统混合单元中系数矩阵主对角线上存在零元素的问题，因此位移和应力结果的收敛是稳定的.以最小势能原理和H R变分原理为基础，联合增强假设应变理论建立了新的8结点非协调广义混合单元.一方面，该单元保持了已有非协调广义混合单元的全部优点；另一方面，该单元简化了积分计算.数值实例表明，改进的非协调广义混合单元的数值结果精度高，计算速度快并且对单元的几何扭曲敏感度低.     

《对称》单元小结

<正>陆剑鸣老师的文章,按"疏理知识、理清脉络"、"归纳提炼、形成方法"和"综合运用、提升能力"三部分,对《对称》单元进行了小结.对用轴对称法解题作了系统的总结;并结合综合应用的例题,对"分类讨论"和"从特殊到一般"的解题思路,作了很好的总结和提升.该文可供同学们自己动手做单元小结时参考.在文《如何进行单元小结》[1]中,我们以《直角三角形》这一单元为例,从三个方面谈了怎样进行单元小结.这里我们对《对称》单元进行小结.     

一道复数题贯穿单元复习课

一道复数题贯穿单元复习课卜华（江苏盐城二中２２４００２）如何提高单元复习课的效率，是一个值得研究的课题．由于单元复习的时间少，内容较多，在选择例题时有较大的难度．在复数的单元复习中，本人选择了一道例题，其多种解法几乎贯穿了这一单元的所有内容．下面是本...     

基于数学思想统领下的单元教学——以“消元——解二元一次方程组”为例

为了实现知识的网络化,在数学课堂中,我们常将一些教学内容整合成单元来实施教学.因教学内容的不同,这些整合而成的单元有大小之分,有些沿用了教材原有的编排体系独立成为教学单元(章),这样的单元是比较大的,而有些仅选择了其中几小节并为一个教学单元,这样的单元就相对较小了.但是不管单元大小如何,其教学内容和教学目标都是紧密关联的.因此,设计教学时,我们常根据知识、思想、方法等相同主题,将一些原本分散的数学知识并在一起,形成异于教材安排的课时安排.近期执教人教版第8章"二元一次方程组"时,笔者将两种解法合并成一个教学单元,开展了一次基于数学思想统领下的单元教学,取得了较好的教学效果.现呈现这次教学的历程并谈一些感悟,供大家参考.     

非协调区域分解Lagrange乘子法的超收敛

本文讨论分析非协调区域分解Ｌａｇｒａｎｇｅ乘子法对二阶椭圆型方程Ｄｉｒｉｃｈｌｅｔ问题的有限元超收敛现象。文中通过利用积分恒等式，适宜地引进Ｌ２投影过渡以及高次插值后处理等技巧，经过一系列误差分析及估计，得到了高出半阶的超收敛结果，实现了非协调区域分解法与高精度算法的结合。     

构造自然数算术系统的一种新方法

用公理化方法来定义非空集上的二元关系〈，使得〈与该集合构成全序集，在全序集中给出最小元素原理的定义，再构造一个含有最小元素原理的适当公理系统来重新给出自然数的公理化定义，然后从构造的自然数公理系统中严格推导出一些基本命题，最后根据这些基本命题来完成对自然数算术系统的精确刻画，从而得到一种具体构造自然算术系统的新方法。     

Automatic energy–momentum conserving time integrators for hyperelastic waves

An energy–momentum conserving time integrator coupled with an automatic finite element algorithm is developed to study longitudinal wave propagation in hyperelastic layers. The Murnaghan strain energy function is used to model material nonlinearity and full geometric nonlinearity is considered. An automatic assembly algorithm using algorithmic differentiation is developed within a discrete Hamiltonian framework to directly formulate the finite element matrices without recourse to an explicit derivation of their algebraic form or the governing equations. The algorithm is illustrated with applications to longitudinal wave propagation in a thin hyperelastic layer modeled with a two-mode kinematic model. Solution obtained using a standard nonlinear finite element model with Newmark time stepping is provided for comparison.     

定常不可压Navier—Stokes方程迎风格式

本文利用齐次定解条件对定常不可压Navier—Stokes方程的非线性项进行处理,给出了相应的一种迎风Galerkin有限元算法;针对这种迎风Galerkin有限元算法,在迎风参数满足一定条件下,利用其三项式具有的一些很好性质,更简单地证明了该问题解的存在唯一性。     

A beam segment element for dynamic analysis of large aqueducts

Large aqueduct structure is a complex structure that is commonly used in hydraulic engineering, especially in large-scale water conveying projects. The analysis of dynamic response for an aqueduct structure is necessary if the aqueduct is built in an earthquake area. Traditional 3D finite element analysis is time consuming and the existing simplified response method cannot take into account all the effects, such as the bending-torsion coupling effect and the constrained torsion, of the deformations of the thin wall structure of the aqueduct body. For this special structure, a simple and yet accurate model for dynamic analysis is needed. In this paper, a beam segment element is developed and used for the calculation of dynamic response for aqueduct structures. With the frame of the aqueduct being modeled using beam element, the proposed model can calculate the dynamic response of the whole aqueduct structures. Results are compared with that of a general purpose finite element analysis software using 3D finite element model. Good agreement is achieved between the two models. However, the proposed model needs less elements and much less computing time.     

A subregion DRBEM formulation for the dynamic analysis of two-dimensional cracks

The dual reciprocity boundary element method employing the step by step time integration technique is developed to analyse two-dimensional dynamic crack problems. In this method the equation of motion is expressed in boundary integral form using elastostatic fundamental solutions. In order to transform the domain integral into an equivalent boundary integral, a general radial basis function is used for the derivation of the particular solutions. The dual reciprocity boundary element method is combined with an efficient subregion boundary element method to overcome the difficulty of a singular system of algebraic equations in crack problems. Dynamic stress intensity factors are calculated using the discontinuous quarter-point elements. Several examples are presented to show the formulation details and to demonstrate the computational efficiency of the method.     

Development of a new frame finite element for crash analysis, using a mixed variational principle and rotations as independent variables

This paper deals with the development and application of a new space curved frame finite element to be used for crash analysis (non-linear). The frame finite element has been developed using a mixed variational principle (complementary form) and using rotations as independent variables. The formulation has been validated for problems of large deflection and rotation, and for problems involving initially curved members. Based on the validation performed, it is expected that crash problems may be modelled using a single element per member thus retaining computational efficiency while performing an accurate analysis. An illustrative example (modelling of an S-leg seat) is presented here to illustrate the benefits of the proposed approach to a designer.     

Valuing Asian options using the finite element method and duality techniques

The main objective of this paper is to develop an adaptive finite element method for computation of the values, and different sensitivity measures, of the Asian option with both fixed and floating strike. The pricing is based on Black–Scholes PDE-model and a method developed by Ve?e? where the resulting PDEs are of parabolic type in one spatial dimension and can be applied to both continuous and discrete Asian options. We propose using an adaptive finite element method which is based on a posteriori estimates of the error in desired quantities, which we derive using duality techniques. The a posteriori error estimates are tested and verified, and are used to calculate optimal meshes for each type of option. The use of adapted meshes gives superior accuracy and performance with less degrees of freedom than using uniform meshes. The suggested adaptive finite element method is stable, gives fast and accurate results, and can be applied to other types of options as well.     

Using Lagrange multipliers in the triangular element of a nonshallow shell under variable interpolation of displacements

We present an algorithmfor calculation of arbitrary thin shells on the basis of a triangular element of discretization with corrective Lagrange multipliers. The stiffness matrix of this element is formed using some ways of approximating displacements as scalar or vector quantities.     

An optimally convergent adaptive mixed finite element method

We prove convergence and optimal complexity of an adaptive mixed finite element algorithm, based on the lowest-order Raviart–Thomas finite element space. In each step of the algorithm, the local refinement is either performed using simple edge residuals or a data oscillation term, depending on an adaptive marking strategy. The inexact solution of the discrete system is controlled by an adaptive stopping criterion related to the estimator.