Trapping region of impinging jets in a cross-shaped channel

This study follows our previous report (Zhang et al., Phys. Fluids, vol. 31, 2019, 034105) by describing the formation and evolution of the engulfment flow in the cross-shaped channel. First, the flow regimes were studied by planar laser induced fluorescence (PLIF). Results show the formation of a spiral vortex in the center of the chamber and the appearance of a well-mixed zone inside the spiral vortex. Second, we proposed a novel experimental method to analyze the residence time of the fluid in the chamber, and discover an unexpected trapping region inside the well-mixed zone. There is almost no fluid transport into or out of this region. Furthermore, three-dimensional numerical simulation is used to reveal the origination of this trapping region. Simulation results reveal that the fluid recirculates in the trapping region and the flow feature is caused by the bubble-type vortex breakdown.     

Deposit morphology on SiC fibers in methane-acetylene/air laminar diffusion flames

The morphologies of soot deposit on 15 μm diameter silicon carbide (SiC) fibers have been investigated with a scanning electron microscope (SEM) in methane-acetylene/air laminar diffusion flames with co-flowing air. The morphologies are shown to be strongly dependent on the fuels ratio. Two kinds of processes by which mature soot particles are produced were proved to exist in a sooting flame: one is the transition from the condensed-phase deposits; the other is the aggregation of the smaller soot particles (or chains of them) carried along the particle path line. Different transition processes are compared between the present work and previous work done by other researchers that used propane/air laminar diffusion flames. It seems the presence of C=C in methane-acetylene laminar diffusion flames is the key factor that causes the difference of transition processes in those two kinds of flames.     

用Boosting算法预测多硝基芳香族化合物的密度

采用Boosting算法对多硝基芳香族化合物(PNACs)的密度进行预估.选用分子结构描述码作为输入特征参数.结果表明,PNACs的密度与其分子结构存在良好的相关性,与人工神经网络相比,Boosting算法对预测的准确性有显著提高,预测结果的相对误差都在8%以内.     

基于SCP模式建立高校管理模式SHCP

社会对人才需求变化对高校的管理模式具有较强的冲击力,要适应这种变化,应把重点集中在学科布局和人才竞争的发展方面,打破原有的SCP(结构-行为-绩效)模式,引入人才竞争的概念,建立起新型的SHCP(结构-人才-行为-绩效)模式.本文从我国高校管理的现实背景出发,研究实施SCP分析框架在高校的作用,并针对高校管理系统背景提出新型的SHCP管理模式.     

Heat transfer of evaporating droplet flow in low pressure systems

Convective heat transfer of laminar droplet flow is analyzed for a low pressure system, where latent heat of evaporation and ratio of liquid density to vapor density is high (for example, water at l atm). The droplet size is considered to be approximately constant but the vapor velocity is considered increasing along the tube. The heat transfer effect of droplets in the vapor stream is treated as distributed heat sink. Results are presented in non-dimensional form for circular tubes, with constant wall heat flux or constant wall temperature boundary conditions. Distinct heat transfer behavior of droplet flow is revealed.     

核电站适用涂层特点分析

分析核电站核岛、常规岛、辅助系统适用涂层的特点,从涂料选择、涂层施工、涂层检查三方面阐述了核电站涂层管理要求及其发展要求。     

用麦克斯韦应力法计算凸极同步电机的电磁转矩

本文先用有限差分法计算了额定负载时凸极同步发电机内的二维磁场分布,在此基础上,用麦克斯韦应力和安培力算出了电枢齿壁、电枢铁芯、主极表面和两侧、主极铁芯和载流导体上的切向磁场力以及相应的电磁转矩,画出了电机内切向磁场力的分布,并把算得的结果与传统法进行了比较.     

典型缺口试样应力集中系数的数值分析

采用有限元分析方法,对几种典型的缺口试样中缺口顶端的应力场进行了详细分析,求得了表征低碳钢冷脆特征温度(T_c~*)的重要参量—有效屈服区内边缘的第一主应力集中系数(简称有效应力集中系数)的最大值Q_(m(?)x)的数值解,为冷脆特征温度的确定奠定了理论基础.     

圆柱镦粗时表面剪应力分布规律的实验验证

通过实验的方法,直接验证圆柱镦粗时剪应力分布曲线。由于摩擦剪应力存在,圆柱镦粗后发生不均匀变形,研究其半径的变化可得出r-R_i曲线,其形状和r-τ曲线一致。     

滤色片在金刚石X光选中的应用研究

本文在研究金刚石及其伴生矿物的X光谱特性的基础上,根据两种光谱峰值波段和光强的区别,探讨了引进滤色片屏蔽伴生矿物X光谱波段,提高金刚石X光拣选分辨率的可能性,并通过试验对采用不同滤色片所产生的不同拣选效果进行了试验对比,确立了国产QB_4滤色片为金刚石x光拣选的优选滤色片。