Experimental and numerical study of flat momentumless wake

Flat momentumless wake behind wing profile has been studied both experimentally and with numerical simulation based on the second order Reynolds stress turbulence model. Some obtained regular trends of momentumless wake decay are mainly consistent with previous experiments by Dmitrenko et al. (Dmitrenko, Yu.M., Kovalev, I.I., Luchko, N.N., Cherepanov, P.Ya., 1987. J. Eng. Phys. 52, 743–751 (in Russian)), Cimbala and Park (Cimbala, J.M., Park, W.J., 1990. J. Fluid Mech. 213, 479–509; Park, W.J., Cimbala, J.M., 1991. J. Fluid Mech. 224, 29–47). Transverse distributions of statistical characteristics and its evolution along the flow axis depend on initial conditions and body shape. It was shown that characteristic turbulence parameters associated with the wake's width, mean velocity deficit, turbulence kinetic energy, and its dissipation rate are not constant as some of the theories predict.     

Experimental and analytical investigation of liquid sheet breakup characteristics

The main objective of this research is to study analytically and experimentally the liquid sheet breakup of a flat fan jet nozzle resulting from pressure-swirling. In this study the effects of nozzle shape and spray pressure on the liquid sheet characteristics were investigated for four nozzles with different exit widths (1.0, 1.5, 2.0 and 2.5 mm). The length of liquid sheet breakup, liquid sheet velocity and the size of formed droplets were measured by a digital high speed camera. The breakup characteristics of plane liquid sheets in atmosphere are analytically investigated by means of linear and nonlinear hydrodynamic instability analyses. The liquid sheet breakup process was studied for initial sinuous and also varicose modes of disturbance. The results presented the effect of the nozzle width and the spray pressure on the breakup length and also on the size of the formed droplets. Comparing the experimental results with the theoretical ones for all the four types of nozzles, gives a good agreement with difference ranges from 4% to 12%. Also, the comparison between the obtained results and the results due to others shows a good agreement with difference ranged from 5% to 16%. Empirical correlations have been deduced describing the relation between the liquid sheet breakup characteristics and affecting parameters; liquid sheet Reynolds number, Weber number and the nozzle width.     

便携式紫外-可见分光光度计的设计

介绍了一种便携式紫外-可见分光光度计的设计方法,该方法采用平场凹面全息光栅及Hamamatsu图像传感器S3904-1024Q为核心设计了小型化的色散系统;将多股光纤的一端排列成长方形直接作为入射狭缝,解决了光谱带宽与光源能量利用率之间矛盾的问题;采用触摸屏作为仪器的输入与输出设备及集成化的小型光纤光源作为仪器的光源。实验结果表明,采用该种方法设计的紫外-可见分光光度计体积小(190 mm×170 mm×100 mm)、操作简单(触摸屏操作)、可以多波长同时在线测量、技术指标符合国家标准。     

Hermitian-Poisson Metrics on Flat Bundles over Complete Hermitian Manifolds

In this paper, the author solves the Dirichlet problem for Hermitian-Poisson metric equation √?1Λ_ωG_H = λId and proves the existence of Hermitian-Poisson metrics on flat bundles over a class of complete Hermitian manifolds. When λ = 0, the HermitianPoisson metric is a Hermitian harmonic metric.     

Toric rings arising from vertex cover ideals

We extend the sortability concept to monomial ideals which are not necessarily generated in one degree and as an application we obtain normal Cohen-Macaulay toric rings attached to vertex cover ideals of graphs. Moreover, we consider a construction on a graph called a clique multi-whiskering which always produces vertex cover ideals with componentwise linear powers.     

On the Galois covers of degenerations of surfaces of minimal degree

We investigate the topological structures of Galois covers of surfaces of minimal degree (i.e., degree n) in ${\mathbb{CP}}^{n+1}$. We prove that for $n\ge 5$, the Galois covers of any surfaces of minimal degree are simply-connected surfaces of general type.