基于区间数正态分布假设的多属性决策集对分析

针对属性权重未知的区间数多属性决策问题,根据区间数取值为正态分布假设时获得期望值μ和标准差σ所提供的信息,应用集对分析理论把μ和σ写成二元联系数,并计算二元联系数的模,再根据属性值模的变差(为最大的属性在属性体系中应该有较大权重的原理),计算各属性权重,在此基础上建模、计算、决策,方法简明,结论可靠,便于作不确定性分析,有利于科学决策.     

Scattering of plane SH waves by an isosceles trapezoidal hill

This paper presents a theoretical approach to study the surface motion of an isosceles trapezoidal hill impacted by incident SH waves. A rigorous solution has been derived by applying an accurate region-matching technique. The solution region is divided into three parts by an appropriate partitioning method. Based on complex function method and multipolar coordinates, a fractional factor is introduced to construct suitable wave functions which satisfy the governing equation and zero-stress condition on the free surface in each sub-region. According to the continuity condition at the auxiliary boundary, surface displacements are expressed in series of infinite algebraic equations, and the unknown coefficients of the series can be determined by Fourier series expansion technique in complex domain. Numerical results demonstrate the analytical results depend on the following parameters: The slope, the height and the width of the trapezoidal hill, the frequency content of the excitation and the incidence angle.     

A high-order compact scheme for solving the 2D steady incompressible Navier-Stokes equations in general curvilinear coordinates

In this paper, a high-order compact finite difference algorithm is established for the stream function-velocity formulation of the two-dimensional steady incompressible Navier-Stokes equations in general curvilinear coordinates. Different from the previous work, not only the stream function and its first-order partial derivatives but also the second-order mixed partial derivative is treated as unknown variable in this work. Numerical examples, including a test problem with an analytical solution, three types of lid-driven cavity flow problems with unusual shapes and steady flow past a circular cylinder as well as an elliptic cylinder with angle of attack, are solved numerically by the newly proposed scheme. For two types of the lid-driven trapezoidal cavity flow, we provide the detailed data using the fine grid sizes, which can be considered the benchmark solutions. The results obtained prove that the present numerical method has the ability to solve the incompressible flow for complex geometry in engineering applications, especially by using a nonorthogonal coordinate transformation, with high accuracy.     

直觉梯形模糊语言Frank算子及其在决策中的应用

本文在直觉梯形模糊语言集的基础上,引入了Frank算子,提出一组新的算子——直觉梯形模糊语言Frank集结算子,并将其应用到多属性决策中。首先,本文提出了直觉梯形模糊语言集Frank算子的表达式,并给出相应的运算规则。然后提出了直觉梯形模糊语言Frank加权算术平均(ITrFLFWA)算子、直觉梯形模糊语言Frank加权几何平均(ITrFLFWG)算子、直觉梯形模糊语言Frank广义加权平均(ITrFLGFWA)算子等,并证明了其具有幂等性、有界性、单调性等性质。最后,通过实例验证了直觉梯形模糊语言Frank算子可以有效解决直觉梯形模糊语言环境下的多属性决策问题。     

基于模糊证据推理及改进TOPSIS的多属性群决策方法

针对不同识别框架多属性群决策问题属性准则度量的不确定性、随机性,定义基于梯形模糊数表征的属性准则评价等级相似度量,求解专家决策权重的最优解。对公共识别框架备选方案属性准则采用模糊证据推理过程综合专家评价等级置信度信息;利用可严格区分属性准则评价等级的相似度量,改进TOPSIS方法中备选方案属性准则评价等级置信度距离因子,获取备选方案逼近正负理想解的贴近度。实例分析以某通信企业电信产品市场竞争力评估为例,说明基于模糊证据推理、改进TOPSIS的多属性群决策问题求解过程,从属性准则专家模糊评价等级置信度集中获取直观的待评估产品市场竞争力排序结果,验证该方法解决此类决策问题的可行性与有效性。     

等腰直角三角形腔中的负离子光剥离研究

基于等腰直角三角形势阱中的能量本征值和本征波函数,利用量子力学传统方法计算了氢负离子处于一个横截面为等腰直角三角形腔内的光剥离截面.等腰直角三角形势阱中的能量本征态无法通过分离变量的方法求解,但是该问题是完全可解的.通过计算,得到了光剥离截面随能量变化的解析表达公式.公式表明,振荡与离子的位置和光子的极化有关.公式还给出了剥离截面的阈值行为.进一步研究发现,当氢负离子处在等腰直角三角形的直角顶角附近时,本文中使用量子力学传统方法得到的结果与已有的氢负离子处于直角域内时使用闭合轨道理论的方法得到的结果是一致的.     

High-order quadratures for integral operators with singular kernels

A numerical integration method that has rapid convergence for integrands with known singularities is presented. Based on endpoint corrections to the trapezoidal rule, the quadratures are suited for the discretization of a variety of integral equations encountered in mathematical physics. The quadratures are based on a technique introduced by Rokhlin (1990). The present modification controls the growth of the quadrature weights and permits higher-order rules in practice. Several numerical examples are included.     

Tabu Guided Generalized Hill Climbing Algorithms

This paper formulates tabu search strategies that guide generalized hill climbing (GHC) algorithms for addressing NP-hard discrete optimization problems. The resulting framework, termed tabu guided generalized hill climbing (TG²HC) algorithms, uses a tabu release parameter that probabilistically accepts solutions currently on the tabu list. TG²HC algorithms are modeled as a set of stationary Markov chains, where the tabu list is fixed for each outer loop iteration. This framework provides practitioners with guidelines for developing tabu search strategies to use in conjunction with GHC algorithms that preserve some of the algorithms known performance properties. In particular, sufficient conditions are obtained that indicate how to design iterations of problem-specific tabu search strategies, where the stationary distributions associated with each of these iterations converge to the distribution with zero weight on all non-optimal solutions.     

基于可信性理论的投资组合优化问题研究

建立了基于可信性理论的投资组合模型,包括风险最小的单目标均值-方差模型和收益最大的单目标均值-方差模型,运用拉格朗日乘数法对两个模型进行了求解,给出了2个模型解析解的表达式,并通过数值算例验证了模型的可行性.对两个模型的结果进行对比,发现风险最小化和收益最大化的单目标均值—方差模型得到的结果基本吻合.     

Novel Implementation and Assessment of a Digital Filter Based Approach for the Generation of LES Inlet Conditions

A novel implementation of a digital filter based inlet condition generator for Large Eddy Simulation (LES) is presented. The effect of using spatially varying turbulence scales as inputs is investigated; it is found that this has impact on both accuracy and affordability, and has prompted the algorithm implementation changes described in the paper. LES of a channel flow with a periodically repeating constriction was used as a test case. The accuracy of the present simulation using a streamwise periodic boundary condition (PBC) was first established by comparison with a previously published highly resolved LES study. Post-processed statistics from the PBC simulation were then input into a Digital Filter Generator (DFG) algorithm. Three time series were created using the DFG for subsequent use as LES inlet conditions. In the first, as well as inputting the spatially varying first and second moments of the velocity field over the inlet plane from the PBC simulation, the turbulence scales input into the DFG were chosen to be spatially uniform with values specified by an area weighted average across the channel inlet height. In the second and third time-series, the turbulence scales were allowed to change in the wall normal direction, their variation again being deduced from the PBC simulation. These various time series were then used as inlet boundary conditions for LES prediction of the same flow case. Analysis of the results and comparison to the PBC predictions showed that the use of spatially varying turbulence scales increased the accuracy of the simulation in some important areas. However, the cost of generating unsteady inlet conditions using the DFG approach increased significantly with the use of spatially varying turbulence scales. Consequently, a new technique applied as part of the DFG approach is described (used as an ‘on the fly’ method), which significantly reduces the cost of generating LES inlet conditions, even when spatially non-uniform turbulent scales are used.