模糊AHP在电网企业员工岗前培训评估中的应用

电网企业技术密集、人员众多、架构庞大,员工岗前培训与企业健康持续发展密不可分.培训工作中最突出的问题在于对培训效果缺乏合理的评估,从而无法了解企业投资的效果,以及培训对组织的贡献.以柯氏培训四级评估模型为基础,采用模糊AHP规范化整个评估过程.最后以电力企业进行的培训项目为例验证分析,证明所提算法的有效性.     

Mixed two‐grid finite difference methods for solving one‐dimensional and two‐dimensional Fitzhugh–Nagumo equations

The aim of this paper is to propose mixed two‐grid finite difference methods to obtain the numerical solution of the one‐dimensional and two‐dimensional Fitzhugh–Nagumo equations. The finite difference equations at all interior grid points form a large‐sparse linear system, which needs to be solved efficiently. The solution cost of this sparse linear system usually dominates the total cost of solving the discretized partial differential equation. The proposed method is based on applying a family of finite difference methods for discretizing the spatial and time derivatives. The obtained system has been solved by two‐grid method, where the two‐grid method is used for solving the large‐sparse linear systems. Also, in the proposed method, the spectral radius with local Fourier analysis is calculated for different values of h and Δt. The numerical examples show the efficiency of this algorithm for solving the one‐dimensional and two‐dimensional Fitzhugh–Nagumo equations. Copyright © 2016 John Wiley & Sons, Ltd.     

Local and parallel finite element algorithm for stationary incompressible magnetohydrodynamics

This article presents a local and parallel finite element method for the stationary incompressible magnetohydrodynamics problem. The key idea of this algorithm comes from the two‐grid discretization technique. Specifically, we solve the nonlinear system on a global coarse mesh, and then solve a series of linear problems on several subdomains in parallel. Furthermore, local a priori estimates are obtained on a general shape regular grid. The efficiency of the algorithm is also illustrated by some numerical experiments.© 2017 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 33: 1513–1539, 2017     

复合材料三角形网格加筋圆锥壳体位移型稳定性方程及其总体稳定性分析

本文采用Donnell型扁壳理论,首先利用最小势能原理和广义平均筋条刚度法推导出用位移分量表示的复合材料三角形网格加筋叠层圆锥壳体的稳定性方程,考虑了蒙皮最一般的拉弯与拉扭耦合关系和加筋筋条的偏心效应,并讨论了该方程的基本性质.根据外压实验观察结果,通过选取适当的位移分量表达式,并运用Galerkin法分析了在均布外压作用下复合材料三角形网格加筋叠层圆锥壳体总体稳定性,得到了临界载荷的解析表达式,并对某一类C/E复合材料三角形内网格加筋圆锥壳体的临界外压进行了计算,所得理论值与实验结果很好地吻合.最后,讨论了有关参数对临界载荷的影响.本文所建立的新方程和所得结果对于航空航天结构非常有用.     

Hamilton等参元与智能叠层板的半解析法

根据压电材料修正后的Hellinger-Reissner(H-R)变分原理,建立了各向异性压电材料4节点Hamilton等参元的一般形式．为智能叠层板自由振动问题和带有压电块的叠层悬臂梁的瞬态响应等问题提出了一种新的半解析法．数学模型的基本步骤:将压电层和主体层看成独立的三维体,在平面内离散各层,分别建立各层的方程;根据主体层和压电层在连接界面上广义应力和广义位移的连续条件,联立主体层和压电层的方程得到全结构的控制方程．等参元不限制智能板侧面的几何边界形状、板的厚度和层数,有广泛的应用领域．     

基于混合网格的低声爆反设计方法研究

低声爆设计方法已成为新一代军民用超声速飞机研制过程中必须解决的关键难题之一。针对传统SGD低声爆外形反设计方法无法对声爆近场非线性效应进行描述和分析的缺点,提出了利用CFD方法求解得到的声爆近场压力分布代替F函数进行低声爆反设计的方法。声爆近场预测采用点-点对接的结构/非结构混合网格,充分利用非结构网格对复杂外形适应性强和结构化网格计算效率高的优点。结果分析表明,基于改进后的低声爆反设计方法得到的方案在声爆超压以及感觉噪声级等方面都比基于原始SGD方法得到的方案有较大改善。     

基本变量区域重要性测度及其稀疏网格解

为了提高现有基本变量对样本均值贡献的区域重要性测度指标的稳定性和收敛性, 提出了一个新的衡量基本变量内部各个区域对输出均值影响的重要性测度指标.并将其进一步扩展提出了一个衡量基本变量内部各个区域对输出总方差分解式中一阶方差影响的区域重要性测度指标.分析了所提指标的性质, 并探讨了它们与现有基本变量对样本均值贡献区域重要性测度指标和对样本方差贡献的区域重要性测度 指标之间的关系. 另外, 针对所提指标的特点, 还建立了其求解高效的稀疏网格积分法.算例结果表明, 所提新的基本变量对输出均值贡献的区域重要性测度指标不仅继承了现有指标的优点, 而且比现有指标具有更高的收敛性和稳定性.所提基本变量对一阶方差贡献的区域重要性指标能够在基本变量对样本方差贡献区域重要性测度的基础上, 进一步提供基本变量内部各个区域对总方差的一阶分量的影响信息.而所建稀疏网格积分法可以在保证计算精度的同时大幅度提高基本变量区域重要性分析的效率.     

基于ANSYS二次开发的板片空间结构的参数化建模

板片空间结构是由轻质、高强的复合板材和薄壁金属骨架或完全由板通过特定方式组合而成的一种新型空间结构体系.为研究适用于设计的理论,需要进行大规模参数化分析,因此需要适用于此分析的可行的建模方法.分析板片空间结构构件的几何拓展规律,将球面坐标系和直角坐标系结合,运用APDL语言,编制相应的建模和分析模块程序,实现了板片空间结构的参数化建模,为对板片空间结构的大规模参数化分析提供工具.并分析了板片空间结构与网壳结构的异同,将两者的建模程序相组合,实现同一程序下的两种结构的自动建模.同时运用本文所提出的建模思路可以实现大部分空间网架结构的参数化建模.     

Convergence issues in using high‐resolution schemes and lower–upper symmetric Gauss–Seidel method for steady shock‐induced combustion problems

This paper reports numerical convergence study for simulations of steady shock‐induced combustion problems with high‐resolution shock‐capturing schemes. Five typical schemes are used: the Roe flux‐based monotone upstream‐centered scheme for conservation laws (MUSCL) and weighted essentially non‐oscillatory (WENO) schemes, the Lax–Friedrichs splitting‐based non‐oscillatory no‐free parameter dissipative (NND) and WENO schemes, and the Harten–Yee upwind total variation diminishing (TVD) scheme. These schemes are implemented with the finite volume discretization on structured quadrilateral meshes in dimension‐by‐dimension way and the lower–upper symmetric Gauss–Seidel (LU–SGS) relaxation method for solving the axisymmetric multispecies reactive Navier–Stokes equations. Comparison of iterative convergence between different schemes has been made using supersonic combustion flows around a spherical projectile with Mach numbers M = 3.55 and 6.46 and a ram accelerator with M = 6.7. These test cases were regarded as steady combustion problems in literature. Calculations on gradually refined meshes show that the second‐order NND, MUSCL, and TVD schemes can converge well to steady states from coarse through fine meshes for M = 3.55 case in which shock and combustion fronts are separate, whereas the (nominally) fifth‐order WENO schemes can only converge to some residual level. More interestingly, the numerical results show that all the schemes do not converge to steady‐state solutions for M = 6.46 in the spherical projectile and M = 6.7 in the ram accelerator cases on fine meshes although they all converge on coarser meshes or on fine meshes without chemical reactions. The result is based on the particular preconditioner of LU–SGS scheme. Possible reasons for the nonconvergence in reactive flow simulation are discussed.Copyright © 2012 John Wiley & Sons, Ltd.     

An aspect ratio agglomeration multigrid for unstructured grids

A robust aspect ratio‐based agglomeration algorithm to generate high quality of coarse grids for unstructured and hybrid grids is proposed in this paper. The algorithm focuses on multigrid techniques for the numerical solution of Euler and Navier–Stokes equations, which conform to cell‐centered finite volume special discretization scheme, combines vertex‐based isotropic agglomeration and cell‐based directional agglomeration to yield large increases in convergence rates. Aspect ratio is used as fusing weight to capture the degree of cell convexity and give an indication of cell stretching. Agglomeration front queue is established to propagate inward from the boundaries, which stores isotropic vertex and also high‐stretched cell marked with different flag according to aspect ratio. We conduct the present method to solve Euler and Navier–Stokes equations on unstructured and hybrid grids and compare the results with single grid as well as MGridGen, which shows that the present method is efficient in reducing computational time for large‐scale system equations. Copyright © 2013 John Wiley & Sons, Ltd.