可变序结构下向量优化中的一个新非线性标量化函数及其应用

在具有可变序结构的一般拓扑向量空间中定义了一个新的非线性标量化函数,讨论了该函数的主要性质.同时作为应用,通过该函数构造出了一族半范数和一类赋范线性空间,并在最后建立了该非线性标量化函数和半范数的上、下半连续性结论.     

Three-dimensional mixed convection flow with variable thermal conductivity and frictional heating

In this article,three-dimensional mixed convection flow over an exponentially stretching sheet is investigated.Energy equation is modelled in the presence of viscous dissipation and variable thermal conductivity.Temperature of the sheet is varying exponentially and is chosen in a form that facilitates the similarity transformations to obtain self-similar equations.Resulting nonlinear ordinary differential equations are solved numerically employing the Runge-Kutta shooting method.In order to check the accuracy of the method,these equations are also solved using bvp4c built-in routine in Matlab.Both solutions are in excellent agreement.The effects of physical parameters on the dimensionless velocity field and temperature are demonstrated through various graphs.The novelty of this analysis is the self-similar solution of the threedimensional boundary layer flow in the presence of mixed convection,viscous dissipation and variable thermal conductivity.     

Computational study of the formation of aluminum-graphene nanocrystallites

The molecular dynamics method is used to study the formation of the Al/graphene nanocomposite in the structural grains of different size under the action of internal stresses. The behavior of graphene sheets inside an individual structural grain as well as in the process of two Al grains containing graphene are joined is investigated. The motion of graphene films, starting from the middle of the aluminum matrix, ends with their location at the crystallite boundaries. Graphene moves in the Al matrix along closely packed planes. In this case, graphene sheets acquire curvature. An intergrowth of graphene sheets is also observed. A contact between two Al-C nanocrystallites through a graphene interlayer is created. The self-diffusion coefficients of atoms and the partial potential energies increased with decreasing nanocrystallite size. The angular distribution of the nearest geometric neighbors and the distribution of distances to the nearest neighbors are determined using the construction of Voronoi polyhedra.     

Metastable states in high carbon C–(Fe,Ni, Co) films obtained by three-electrode ion-plasma sputtering

Abstract

The effect of ion-plasma deposition on the structure of high-carbon films (at. %) Fe–(20–84) % С, Co–(5–52) % С, Ni–(7–61) % С was investigated. The lattice periods and crystallite sizes of nonequilibrium phases in the as-deposited state and after heating are determined. The temperatures of the beginning and end of the decay of metastable phases during heating at a constant speed are established. The transition from an amorphous to an equilibrium crystalline state in Fe–C films passes through the stage of formation and subsequent decomposition of an intermediate, metastable hcp phase of variable composition. The electrical and hysteretic magnetic properties of the films were measured in the as-deposited state and after heat treatment. The compositions and conditions for producing films with low values of the temperature coefficient of electrical resistance and high coercive force are established. Thus, high-carbon films of Ni–61% C in the as-depoteted state and Fe–69% C films after heating to 900?K are characterized by small TCR values (± 10^?6 К^?1) over a wide temperature range.     

基于VIKOR和关联系数的犹豫三角模糊语言多属性决策方法

针对属性评价值为犹豫三角模糊语言集的多属性决策问题,提出一种基于VIKOR方法的犹豫三角模糊语言多属性决策方法.首先定义了犹豫三角模糊语言集的相关概念.然后运用VIKOR和关联系数方法,在可接受优势和决策过程稳定的条件下对方案进行择优,在理论分析的基础上,提出了这种新方法的计算步骤.并构建了确定最优属性权重的非线性规划模型,研究了当专家权重和属性权重未知情况下的犹豫三角模糊语言多属性决策方法.最后通过实例说明了该方法的有效性和可行性.     

基于激光雷达的垂直能见度反演算法及其误差评估

针对大气垂直方向上消光系数分布不均匀难以用传统方法直接测量垂直能见度的问题,提出了一种基于激光雷达探测垂直能见度的计算方法。根据大气辐射传输基本原理,借助于辐射传输方程,推导出了垂直能见度的计算公式;然后利用激光雷达原理方程和Klett算法反演出大气垂直方向上的消光系数分布,基于此提出了垂直能见度的迭代算法。最后,利用灰色模型GM(1,1)和批统计算法,对激光雷达反演得到的后向散射系数进行了评估,给出了误差置信区间为(0.760±0.339)×10^-4(srad·km)^-1。结果表明,该方法是一种特别有效的计算垂直能见度的方法,符合探测的基本需求,且误差小精度高。     

Meshless acoustic analysis using a weakly singular Burton-Miller boundary integral formulation

The Burton-Miller boundary integral formulation is solved by a complex variable boundary element-free method (CVBEFM) for the boundary-only meshless analysis of acoustic problems with arbitrary wavenumbers. To regularize both strongly singular and hypersingular integrals and to avoid the computation of the solid angle and its normal derivative, a weakly singular Burton-Miller formulation is derived by considering the normal derivative of the solid angle and adopting the singularity subtraction procedures. To facilitate the implementation of the CVBEFM and the approximation of gradients of the boundary variables, a stabilized complex variable moving least-square approximation is selected in the meshless discretization procedure. The results show the accuracy and efficiency of the present CVBEFM and reveal that the method can produce satisfactory results for all wavenumbers, even for extremely large wavenumbers such as k = 10 000.     

群集建筑中大跨裙摆屋盖风荷载特性的数值模拟研究

以苏州太平金融大厦为工程背景,针对其大跨裙摆屋盖的风荷载作用,首先采用RNG k-ε模型模拟分析了其平均风压分布规律,以及风向变化对屋盖表面风荷载体型系数的影响;其次,引入干扰因子IF,探讨了周边建筑对大跨裙摆屋盖风荷载的气动干扰作用。结果表明:0°风向下,走廊上方屋盖两侧区域出现“上吸下顶”的叠加作用;90°风向下屋盖北侧飘带末端区域受到狭道风效应出现正压集中现象;风向变化对大跨裙摆屋盖的风荷载体型系数分布影响较大;且周围建筑物对大跨裙摆屋盖的气动干扰效应明显,主要表现为风压“遮挡效应”,而局部区域表现为风压“放大效应”。     

若干高维可积和不可积模型的严格解

可积和不可积模型可以描述自然科学中的诸多现象, 寻找高维非线性模型的严格解已成为可积系统的一个重要研究内容. 结合达布变换法和多线性分离变量法, 可以得到多个(2+1)维非线性模型包含任意函数的严格解, 通过选取不同的任意函数, 构造这些非线性模型新的相互激发模式. 进一步推广了形变映射理论, 建立了变系数 场和sine-Gordon以及双sine-Gordon场的形变映射关系, 从而得到高维不可积模型包含任意函数的新严格解. 对任意函数的不同选择, 构造了sine-Gordon和双sine-Gordon可积模型丰富的局域解和周期解, 如多solitoff解及其周期波推广、周期形变的蛇形孤波解以及变模的拟周期解等.     

非齐次动力学方程的一种精细积分单步方法

针对非齐次动力学方程■,结合精细积分法和微分求积法,利用同阶的显式龙格-库塔法对计算过程中待求的v_(k+i/s)(i=1,2,…,s)进行预估,提出了一种避免状态矩阵求逆的高效精细积分单步方法。该方法采用精细积分法计算e~(Ht),而Duhamel积分项采用s级s阶的时域微分求积法,计算格式统一且易于编程,可灵活实现变阶变步长。仿真结果表明,与其他单步法及预估校正-辛时间子域法进行数值比较,该方法具有高精度、高效率及良好的稳定性,在求解大规模动力系统时间响应问题中具有较大的优势。