射流速度剖面形状变化及其对界面稳定性的影响

用线性稳定性理论研究了内部为轴对称液体射流、外部为同轴气体射流的粘性双流体模型．在液体射流和气体射流分别处于不同压力梯度作用的条件下,讨论了数学模型中射流速度剖面形状变化,并用Chebyshev配点法研究了剪切层厚度变化及其对界面稳定性产生的影响．     

高浓度悬浮固粒对射流界面的粘性稳定性影响

该文首次利用双流体模型和扰动速度势理论,推得含高浓度悬浮固粒的射流界面粘性稳定性方程和对应的固气扰动速度比值方程．通过数值计算,得到了不同雷诺数及固粒属性的射流界面粘性稳定性曲线和对应的固气扰动速度比值曲线．在分析和比较所得的粘性稳定性曲线的基础上,得到了流场雷诺数及固粒特性对射流界面粘性稳定性影响的结论．同时,通过分析所得的固气扰动速度比值曲线,得到了流场雷诺数及固粒等效斯托克斯数对固粒跟随气流的扰动 性能的影响的结论．这些结论是首次在计入气流的粘性的条件下得到的,不同于文献［８］和文献［１０］相关的囿于无粘情形的研究,对于两相射流发展的认识和工程实际中实施对两相射流场的人工控制有重要意义．     

含周期脉动的大密度比气液同轴射流的Floquet稳定性分析

基于周期脉动速度激励下气液同轴射流的数学模型,运用线性稳定性理论,采用Chebyshev配点法和Floquet理论,将含周期脉动分层流的Floquet稳定性分析扩展到大密度比的情况.研究了液铝-氮气射流的参数共振特性,分析了不同的物理参数对系统稳定性的影响,计算了实验工况并和实验结果进行了比较.     

含悬浮固粒射流界面稳定性研究

利用气固两相耦合模型,理论推导出含悬浮固粒射流的稳定性方程,通过数值计算得到了两相射流稳定性特征曲线、固气扰动速度比值幅值曲线及固气相位差曲线,进而得到了关于固粒对流场中扰动增长和传播的影响及失稳过程中固粒扰动特性的结论。这些结论对于两相射流发展的认识和工程实际中实施对两相射流场的人工控制有重要意义。     

有障碍圆形浮力射流的绕流流态研究

针对静止环境中有障碍圆形浮力射流出现的正常绕流现象与非正常绕流现象（反射与分叉现象）,分析了其主要的3个影响因素:障碍盘直径D/d（D和d分别是障碍盘和射流出口的直径）,射流出口密度Froude数以及障碍盘离射流孔口的距离H/d与发生非正常绕流之间的相互关系．得到了H/d=2,4,6,8在不同D/d值时发生非正常绕流的临界密度Froude数．对直径为D/d的障碍盘,当其离射流孔口的距离H/d达到某一值时,流动仅为正常绕流流态．基于大量计算给出了不同障碍盘所要求的H/d值,综合以上因素得到了临界密度Froude数的拟合公式．对非正常绕流中射流出现反射与分叉的规律性进行了探讨．对D/d=1的有障碍浮力射流进行的数值计算表明,所有工况下的流态均为正常绕流,并得到了不同H/D条件下的轴线稀释度．     

大气运动基本方程组的解析解

在已知大气运动基本方程于光滑函数类中具有最好的稳定性前提下,讨论了它的局部解的解空间构造．根据它的解空间构造,分析了这个方程具有代表性和应用性的第三初值问题,在解析函数类中给出了适定的第三初值问题的解析解的计算方法以及具体的关系表达式,在局部解意义下完整的解决了这一点初值问题的解析解所涉及的理论与计算问题．指出其它类型定解问题都可以仿照文中的计算方法和步骤,求出所需要的稳定的解析解．     

热传导对气-液射流界面不稳定性的作用机理研究

研究了平面分层气-液射流在非线性温度分布条件下的界面不稳定性性质.考虑了气体的可压缩性、液体的粘性、以及气体热导率和密度随温度变化等事实.并应用正则模态方法将问题转化为四阶变系数常微分方程,用数值积分和多重打靶法对模型的空间模式进行了计算,研究了不稳定模态随各物理参量的变化趋势.计算表明模型所体现的不稳定性特征与其它模型的计算结果是一致的.同时计算还得出气体和液体的温差越小、雷诺数越大、热导率变大均将有利于液体射流有效雾化的结果.该结论与HJE.Co.Inc(Glens Falls,NY,USA)的实验数据是定性吻合的.     

亚声速热射流声源模型的应用

对亚声速转捩热射流中失稳波相关的噪声产生机制进行了研究,并与冷射流中的结果进行了对比.基于时均大涡模拟(LES)流场,通过求解线性抛物化稳定性方程(LPSE)得到了失稳波的空间演化特性,然后基于LPSE的解与声比拟方法构建了射流的线性及非线性声源模型.LPSE结果表明,加热可以提高失稳波的空间增长率,使其更早达到饱和.由线性模型分析可知,加热会提高高频模态的声压级(SPL).与冷射流相比,热射流中线性模型预测的声压级与大涡模拟结果间的差距更小,表明线性机制在热射流中作用更大.在亚声速冷射流中,非线性模型在之前的研究中已经被证明可以提高声辐射效率.在当前热射流中,发现非线性模型与大涡模拟间的声压级差距被进一步的缩小,且温度相关的声源项在声辐射中发挥更重要的作用.     

线性时变系统二次最优控制问题的保辛近似求解

状态空间的最优控制体系是保守的,其近似算法应当保辛．提出了基于分段常值精细积分方法的保辛摄动近似方法,在同一框架下求解了线性时变LQ最优控制中的计算问题,即变系数矩阵Riccati方程和状态反馈方程．该算法是保辛的,具有很好的数值稳定性和精度．算例验证了算法的有效性．     

亚声速热射流声源模型的应用（英文）

对亚声速转捩热射流中失稳波相关的噪声产生机制进行了研究,并与冷射流中的结果进行了对比.基于时均大涡模拟(LES)流场,通过求解线性抛物化稳定性方程(LPSE)得到了失稳波的空间演化特性,然后基于LPSE的解与声比拟方法构建了射流的线性及非线性声源模型.LPSE结果表明,加热可以提高失稳波的空间增长率,使其更早达到饱和.由线性模型分析可知,加热会提高高频模态的声压级(SPL).与冷射流相比,热射流中线性模型预测的声压级与大涡模拟结果间的差距更小,表明线性机制在热射流中作用更大.在亚声速冷射流中,非线性模型在之前的研究中已经被证明可以提高声辐射效率.在当前热射流中,发现非线性模型与大涡模拟间的声压级差距被进一步的缩小,且温度相关的声源项在声辐射中发挥更重要的作用.     

基于AHP-TOPSIS评判模型的中药企业研发人员胜任力研究

研发人员作为企业中运用知识进行创新活动的群体,具有知识型员工的行为特质,因而导致研发人员的努力程度和贡献大小很难准确地测量.为了解决科学地评价研发人员胜任力的问题.在层次分析法(AHP)和逼近理想解的排序法(TOPSIS)两个理论的基础上,构建了AHP—TOPSIS综合评判指标体系模型,对3类中药企业研发人员胜任力进行综合评判优选.从职业态度、知识—技术、个人魅力、创新能力和团队合作能力5个方面综合考虑影响研发人员胜任力的评判指标,旨在为企业和不同行业全面评价以及甄选研发人才提供一种可行的方法.     

结构振动特性在线识别的理论模型和计算方法

环境自然激励作用下的大型结构动力特性在线识别方法受到广泛的关注,这个方法仅仅利用结构自然响应的被测试数据,识别结构动力特性．Ibrahim方法和ARMAV方法是基本的识别方法．该文研究了受随机激励作用动力学模型,给出了有别于传统谐波恢复的子空间分解识别方法．数值仿真结果表明,该方法对结构振动特性的识别具有较好的鲁棒性和较高的计算精度．     

复合材料层合板三维线性理论的完整性

本文针对文献[1]所述复合材料层合板三维模型,在三维线性弹性理论基本方程和经典变分原理的基础上,通过分块矩阵运算和线性Lagrange乘子法,推导出比文献[1]更全面更系统的基本方程和变分原理,使复合材料层合板三维线性理论臻于完整。     

Plane Waves and Boundary Value Problems in the Theory of Elasticity for Solids with Double Porosity

This paper concerns with the dynamical theory of elasticity for solids with double porosity. This theory unifies the earlier proposed quasi-static model of Aifantis of consolidation with double porosity. The basic properties of plane waves are established. The radiation conditions of regular vectors are given. The basic internal and external boundary value problems (BVPs) of steady vibrations are formulated. The uniqueness theorems are proved. The basic properties of elastopotentials are given. The existence of regular (classical) solution of the external BVP by means of the potential method (boundary integral method) and the theory of singular integral equations are proved.     

具有垂直传染和接触传染的传染病模型的稳定性研究

本文研究了一类具有垂直传染和接触传染的传染病模型.利用常微分方程定性与稳定性方法,分析了该模型非负平衡点的存在性及其局部稳定性.同时,利用LaSalle不变性原理和通过构造适当的Lyapunov函数,获得了平凡平衡点、无病平衡点和地方病平衡点全局渐近稳定的充分条件.结果表明当基本再生数小于等于1时,所有种群趋于灭绝;当基本再生数大于1和病毒主导再生数小于1时,病毒很快被清除;当基本再生数大于1和病毒主导再生数大于1以及满足一定条件时,病毒持续流行并将成为一种地方病.     

Book Review

A method of estimation of the coefficients of a linear regression model is described as invariant if the basic regression results obtained by the method are unaltered by a location/scale transformation of the data matrix. A necessary and sufficient condition for a method to be invariant is presented. Finally specific methods of estimation are examined for invariance.     

Modeling inventory routing problems in supply chains of high consumption products

Given a distribution center and a set of sales-points with their demand rates, the objective of the inventory routing problem (IRP) is to determine a distribution plan that minimizes fleet operating and average total distribution and inventory holding costs without causing a stock-out at any of the sales-points during a given planning horizon. We propose a new model for the long-term IRP when demand rates are stable and economic order quantity-like policies are used to manage inventories of the sales-points. The proposed model extends the concept of vehicle routes (tours) to vehicle multi-tours. To solve the nonlinear mixed integer formulation of this problem, a column generation based approximation method is suggested. The resulting sub-problems are solved using a savings-based approximation method. The approach is tested on randomly generated problems with different settings of some critical factors to compare our model using multi-tours as basic constructs to the model using simple tours as basic constructs.     

Analysis of finite element approximations of a phase field model for two-phase fluids

This paper studies a phase field model for the mixture of two immiscible and incompressible fluids. The model is described by a nonlinear parabolic system consisting of the nonstationary Stokes equations coupled with the Allen-Cahn equation through an extra phase induced stress term in the Stokes equations and a fluid induced transport term in the Allen-Cahn equation. Both semi-discrete and fully discrete finite element methods are developed for approximating the parabolic system. It is shown that the proposed numerical methods satisfy a discrete energy law which mimics the basic energy law for the phase field model. Error estimates are derived for the semi-discrete method, and the convergence to the phase field model and to its sharp interface limiting model are established for the fully discrete finite element method by making use of the discrete energy law. Numerical experiments are also presented to validate the theory and to show the effectiveness of the combined phase field and finite element approach.

     

P-algorithm based on a simplicial statistical model of multimodal functions

A well-recognized one-dimensional global optimization method is generalized to the multidimensional case. The generalization is based on a multidimensional statistical model of multimodal functions constructed by generalizing computationally favorable properties of a popular one-dimensional model—the Wiener process. A simplicial partition of a feasible region is essential for the construction of the model. The basic idea of the proposed method is to search where improvements of the objective function are most probable; a probability of improvement is evaluated with respect to the statistical model. Some results of computational experiments are presented.     

On the calculation of the bounds of probability of events using infinite random sets

This paper presents an extension of the theory of finite random sets to infinite random sets, that is useful for estimating the bounds of probability of events, when there is both aleatory and epistemic uncertainty in the representation of the basic variables. In particular, the basic variables can be modelled as CDFs, probability boxes, possibility distributions or as families of intervals provided by experts. These four representations are special cases of an infinite random set. The method introduces a new geometrical representation of the space of basic variables, where many of the methods for the estimation of probabilities using Monte Carlo simulation can be employed. This method is an appropriate technique to model the bounds of the probability of failure of structural systems when there is parameter uncertainty in the representation of the basic variables. A benchmark example is used to demonstrate the advantages and differences of the proposed method compared with the finite approach.