Numerical simulation of two-phase turbulent flow in hydraulic and hydropower engineering

In connection with the specific features of high velocity aerated flow generated by hydraulic engineering structures, the mathematical model is developed for high turbulence air-water two-phase flow with the use of twin flow theoretical model in this paper. Furthermore the numerical method is proposed to treat bubbled flows. In addition, on the basis of air-water stratified twin flow model, the new calculation methods and free surface tracking technique are proposed to describe complicated movements of the free surface. Finally, the proposed model is used to calculate artificial aerated flows. The computed results coincide quite well with experimental results. This means that the proposed method can provide solid basis for practical engineering design.     

Separation of nanocolloids driven by dielectrophoresis: A molecular dynamics simulation

The nonequilibrium molecular dynamics (MD) method was used to model the nanocolloids and the solvent particles. By introducing a non-uniform electric field, colloids were polarized to have opposite polarities. Separation of colloids driven by dielectrophoresis (DEP) could be seen clearly under a strong electric field at low temperatures. Analyzing the ratio of DEP velocities of colloids to thermal velocities of neutral solvent particles showed that when the ratio was correspondingly big, collision between colloids and solvent particles would be intense, making the DEP velocity of colloids fluctuate frequently. By changing the electric field strength, it was found that the enhancement of electric field strength would quicken the separation of colloids. But when the electric field strength increased to a certain degree, the separation motion would be slow because of the strong friction resistance of the solvent particles to the colloids. Moreover, studying the separation reason of colloids based on the potential energy showed that after colloids were polarized, the attractive potential energy among the colloids would be weaker than before, while the increase of temperature would reduce the attractive potential energy and increase the repulsive potential energy, which accorded with the DLVO theory. Supported by the National Hi-Tech Research and Derelopment Program of China (“863” Project) (Grant No. 2006AA04Z351) and the National Natural Science Foundation of China (Grant Nos. 50675033, 30770553)     

Rapid prediction method for nonlinear expansion process of medical vascular stent

A neural network model with high nonlinear recognition capability was constructed to describe the relationship between the deformation impact factors and the deformation results of vascular stent.Then,using the weighted correction method with the attached momentum term,the network training algorithm was optimized by introducing learning factor η and momentum factor ψ,so the speed of the network training and the system robustness were enhanced.The network was trained by some practi-cal cases,and the statisti...     

清华山维一体化软件EPS脚本语言的应用

通过分析和研究清华山维EPS脚本语言的构成、规则、函数和运行,总结出其程序开发特点,并根据实际需要编写脚本函数,实现诸如图形属性提取、坐标变换、数据转换等功能扩展,从而达到程序二次开发的目的.     

Uncertain eigenvalue analysis of the dielectric-filled waveguide by an interval vector finite element method

Science China Technological Sciences - Eigenvalues of the dielectric-filled waveguide are of great importance to its transmission characteristic analysis and optimization design, which could be...     

开放式现场总线CC-Link在计量配料中的应用

本文主要介绍了利用开放式现场总线CC－Link来实现计量与配料的监控系统，达到可靠性，有效性，可维护性的目的，着重讨论了它们的特性，功能及其应用。     

2—丙烯酰胺基十六烷磺酸的合成与表征

以丙烯腈，１－十六烯与发烟硫酸反应，合成了２－丙烯酰胺基十六烷基磺酸单体，借助ＩＲ，Ｈ－ＮＭＲ和元素分析确定了产物的结构。     

A frequency domain reliability analysis method for electromagnetic problems based on univariate dimension reduction method

In this paper, a class of electromagnetic field frequency domain reliability problem is first defined. The frequency domain reliability refers to the probability that an electromagnetic performance indicator can meet the intended requirements within a specific frequency band, considering the uncertainty of structural parameters and frequency-variant electromagnetic parameters.And then a frequency domain reliability analysis method based on univariate dimension reduction method is proposed, which provides an effective calculation tool for electromagnetic frequency domain reliability. In electromagnetic problems, performance indicators usually vary with frequency. The method firstly discretizes the frequency-variant performance indicator function into a series of frequency points' functions, and then transforms the frequency domain reliability problem into a series system reliability problem of discrete frequency points' functions. Secondly, the univariate dimension reduction method is introduced to solve the probability distribution functions and correlation coefficients of discrete frequency points' functions in the system. Finally, according to the above calculation results, the series system reliability can be solved to obtain the frequency domain reliability, and the cumulative distribution function of the performance indicator can also be obtained. In this study,Monte Carlo simulation is adopted to demonstrate the validity of the frequency domain reliability analysis method. Three examples are investigated to demonstrate the accuracy and efficiency of the proposed method.     

基于模糊可靠度的深海高压密封舱优化设计

为了减轻深海高压密封舱的重量,提出基于模糊可靠度的优化设计方法.该方法采用最小强度和最大工作应力模糊可靠度计算理论, 以密封舱的可靠度为1和最小壁厚为优化设计目标,通过有限元计算求取密封舱工作时最大应力隶属函数曲线的分布参数,根据材料的变异特性求取密封舱最小强度隶属函数曲线的分布参数.理论计算和实验结果表明,采用该方法可以有效减轻密封舱的重量.     

生物柴油副产甘油的综合利用

随着全球生物柴油成为替代石油能源产业的兴起,使副产甘油成为丰富而廉价的可再生资源,因而合理利用甘油已成为生物柴油研究的一个重要方向。本文着重介绍了甘油制备丙二醇、二羟基丙酮、环氧氯丙烷等衍生物的研究及应用,并结合我国的实际情况对副产甘油的综合利用提出了一些设想和建议。