掺气分流墩墩头的动水压强特性研究

对掺气分流墩墩头的动水压强特性进行了试验研究,以求了解墩头的抗空蚀性能及动水压强特性。试验结果得出：时均压强P／Pman沿墩高和Cp沿横断面的分布规律;墩头轴线与来流有夹角时Cp沿横断面的分布规律;墩头壁压脉动压强特性,在墩后充分供气时,墩头的空化特性。     

非球形颗粒布朗运动的涨落-格子Boltzmann数值研究

采用涨落-格子Boltzmann方法对非球形颗粒(二维)的布朗运动进行直接数值模拟.数值结果包括椭圆形、矩形颗粒的速度均方值及速度自相关函数等.研究发现,对于非球形颗粒,其方向性并没有影响能量均分原理的适用性,每个自由度的能量由其速度或角速度的均方值确定,而且计算的颗粒平动温度和转动温度一致.此外,颗粒的速度自相关函数在相对长的时间内以~ct^-1的规律衰减,其系数c与颗粒的形状无关.     

Computational study of combined effects of conduction-radiation and hydromagnetics on natural convection flow past magnetized permeable plate

The computational study of the combined effects of radiation and hydromagnetics on the natural convection flow of a viscous,incompressible,and electrically conducting fluid past a magnetized permeable vertical plate is presented.The governing non-similar equations are numerically solved by using a finite difference method for all values of the suction parameter ξ and the asymptotic solution for small and large values of ξ.The effects of varying the Prandtl number P r,the magnetic Prandtl number P r m,the magnetic force parameter S,the radiation parameter R d,and the surface temperature θ w on the coefficients of the skin friction,the rate of heat transfer,and the current density are shown graphically and in tables.An attempt is made to examine the effects of the above mentioned physical parameters on the velocity profile,the temperature distribution,and the transverse component of the magnetic field.     

Experimental study of wind loads on cylindrical reticulated shells

The cylindrical reticulated shell structures without side walls, which are normally arranged in pairs, are usually used as dry-coal sheds in a thermal power plant. The wind loads of these shells do not exist in standards or codes. Therefore, this study investigates the mean and fluctuating wind loads on a cylindrical reticulated shell with a rise-to-span ratio of 0.39 through a series of wind tunnel tests. The characteristics of the wind pressures on the upper and lower surfaces and the net pressures are presented. The results show that the wind direction and another shell structure significantly affect the wind loads on the principal shell. The most unfavorable wind direction is around 30°, whereas the effects of the wind field and the height of the coal stack are small. The surfaces of the shells are divided into nine blocks, and the block mean and fluctuating (rms) pressure coefficients suitable for engineering applications are given as references for wind load codes.     

COMPARATIVE STUDY OF THE PRINCIPLES AND APPLICATIONS OF POD AND MSM

为揭示本征正交分解(proper orthogonal decomposition, POD) 与模态叠加法(mode superposi-tion method, MSM) 在基本原理和工程应用中的异同,对POD 和MSM 的数理基础进行了对比性分析;通过风洞试验及动力响应时程分析获得了一座冷却塔的表面脉动风载荷及其脉动响应,以此两个时空随机场为例对POD 和MSM 两种方法的应用进行了对比性阐述. POD 和MSM 均通过引入空间模态和相应的时间坐标,经线性叠加来实现对时空随机场的分解与重建,但两者的应用对象并不一致:前者多用于已知随机载荷场的分析而后者多用于未知结构响应的计算. 两者空间模态和时间坐标的提取方法和数理意义以及各模态对原随机场的贡献等亦不相同. 尽管POD 和MSM 两种方法所得空间模态均有正交性,但时间坐标的正交性仅存在于POD 方法,故POD 各阶模态的本征值之和可以完全反应对原随机场的贡献,而MSM 的模态贡献则存在一定的耦合性.     

Fluctuations in the motions of mass and of patterns in one-dimensional driven diffusive systems

The stochastic spreading of mass fluctuations in systems described by a fluctuating Burgers equation increases ast ^2/3 with time. As a consequence the stochastic motion of a mass front, a point through which no excess mass current is flowing, is shown to increase ast ^1/3. The same is true for the stochastic displacement of mass points and shock fronts with respect to their average drift, provided the initial configuration is fixed. An additional average over the stationary distribution of the initial configuration yields stochastic displacements, increasing with time ast ^1/2.     

波动温度下食品连串降解动力学的分析解

本文提出了在矩形波和正弦波温度分布下食品连串热降解反应的动力学模型，并导出了模型的分析解。利用分析解可以直接预测波动温度下食品品质改变的程度或保藏寿命。     

Dynamical analysis of a delayed singular prey–predator economic model with stochastic fluctuations

This article studies a delayed singular prey–predator economic model with stochastic fluctuations, which is described by differential‐algebraic equations due to a economic theory. Local stability and Hopf bifurcation condition are described on the delayed singular prey–predator economic model within deterministic environment. It reveals the sensitivity of the model dynamics on gestation time delay. A phenomenon of Hopf bifurcation occurs as the gestation time delay increases through a certain threshold. Subsequently, a singular stochastic prey–predator economic model with time delay is obtained by introducing Gaussian white noise terms to the above deterministic model system. The fluctuation intensity of population and harvest effort are calculated by Fourier transforms method. Numerical simulations are carried out to substantiate these theory analysis. © 2013 Wiley Periodicals, Inc. Complexity 19: 23–29, 2014     

Source function extracted from single-event HBT correlation functions of hydrodynamical sources

We investigate the single-event two-pion correlation functions for the hydrodynamic particle-emitting sources with the fluctuating initial conditions generated by the Heavy Ion Jet Interaction Generator （HIJING）. Using a three-dimension fast Fourier transform （FFT）, we further extract the source functions from the single-event correlation functions. It is found that the inhomogeneity of the hydrodynamic sources with the fluctuating initial conditions lead to event-by-event fluctuations of the correlation functions and source functions.     

ABEEM浮动电荷分子力场在含离子体系中的发展和应用

离子水合及生物分子体系内离子选择性的微观作用机制是人们长期探索的重要课题,其难点在于如何合理精确地描述上述体系内的离子-水、离子-生物分子等各种相互作用.本文主要总结近年来原子-键电负性均衡浮动电荷分子力场（ABEEM/MM）在含离子体系中的发展和应用,包括离子水溶液、金属蛋白、离子-核酸碱基体系的研究.我们优选相关参数,构建上述体系的势能函数,并对气相水合离子团簇、离子水溶液、金属蛋白、离子-核酸碱基体系进行研究,模拟其结构、活性、热力学和动力学等性质.研究和比较结果表明,我们的ABEEM浮动电荷力场总体上优于其它力场方法,其精度可达到或接近高水平从头计算MP2方法.这为进一步探讨生物分子体系内的离子选择性、金属酶及其它含离子体系的结构和性质奠定了基础.