Numerical solutions for impulsively started and decelerated viscous flow past a circular cylinder

A finite difference study of the unsteady two-dimensional flow past a circular cylinder has been conducted using vorticity and streamfunction as the dependent variables. The two cases considered were impulsively started and decelerated flows. The impulsively started problem was considered to validate the method and has yielded results which agree quite closely with existing results from both calculations and experiments. The decelerated flow analysis produced results which can be explained in terms of induced velocity effects from existing wake vortices for both suddenly stopped and uniformly decelerated flows.     

Surface functionalization of silicon nanoparticles produced by laser-driven pyrolysis of silane followed by HF-HNO3 etching

CO2 laser induced pyrolysis of silane was used to produce silicon nanoparticles with an average diameter as small as 5 nm at high rates (up to 200 mg/h). Etching these particles with a mixture of hydrofluoric acid (HF) and nitric acid (HNO3) reduces their size and passivates their surface such that they exhibit bright visible photoluminescence (PL). This paper describes the attachment of organic molecules to hydrogen-terminated and hydroxyl-terminated surfaces of these nanoparticles. Stable particle dispersions in various solvents were obtained by treatment of hydrogen-terminated surfaces with octadecene or undecylenic acid and by treatment of hydroxyl-terminated surfaces with octadecyltrimethoxysilane. Transmission electron microscopy showed that the surface-functionalized particles were well dispersed and crystalline. FTIR spectroscopy confirmed the expected reactions of the organic molecules with the particle surfaces. Photoluminescence measurements showed that surface treatment significantly stabilized the PL properties of the nanoparticles against degradation. Size selective precipitation was applied to particle dispersions and allowed some narrowing and tuning of the PL spectrum.     

金属表面自组装缓蚀功能分子膜*

本文总结了近年来自组装单分子膜技术在金属腐蚀与防护领域中的应用,重点介绍了几类比较成熟的自组装体系,评价了几种常用的表征技术,概括了近年来本课题组在该研究领域中的一些成果,并对自组装技术今后的发展作了预测。     

A Novel Method for Epoxidation of Cyclohexene Catalyzed by Fe2O3 with Molecular Oxygen and Aldehydes

A novel method for the epoxidation of cyclohexene using molecular oxygen (latm) and aldehyde in the presence of Fe₂O₃ is presented. The yields of epoxide highly increased by using this method.     

植物病毒病化学防治剂的探寻Ⅶ.2,4-二氧六氢-1,3,5-三嗪芳基取代化合物的合成

研究了２，４－二氧六氢－１，３，５－三嗪（ＤＨＴ）的Ｎ－芳基取代反应，找到了３种合成标题化合物的方法，测定了所得到化合物抑制ＴＭＶ的活性，最高者达到５１％．     

Intelligent detection of rail corrugation using ACMP-based energy entropy and LSSVM

In this paper, an intelligent method to diagnose rail corrugation based on signal decomposition and entropy theory is proposed. The axle box acceleration signals are first decomposed into several components with different frequency bands by ACMP, EEMD and MODWT. By comparison, ACMP is able to successfully extract rail corrugation component from original signal without mode mixing. Energy entropy is then introduced here to quantify the degree of the rate of energy concentration. The analysis results show that the energy will change when rail corrugation occurs and the entropy will become small. It has been also proved that the entropy difference of rail corrugation and normal signal based on ACMP is the most significant. In addition, to intelligently diagnose rail corrugation, we combine energy entropy with energy index and the first mode energy, regarded as the input feature vector of LSSVM, to distinguish rail corrugation from mass data sets. It is obvious that the accuracy of ACMP-based technique is the highest.