带鳍通道性能的遗传算法优化

与光滑通道相比,带鳍通道有更高的传热系数,附加的鳍,极大地增强了通道的传热.然而,传热的增强又与压降的升高相关联,这又导致泵动力需求的增加,因此应该寻求对该系统的优化设计.该文的主要目的是,通过如下方式来精确地确定鳍的位置和尺寸:利用遗传算法实现最小压降时达到最优传热.鳍的每种布局作为问题(遗传算法中的一个个体)的一个解.通常,首先随机地产生一个初始种群,然后该算法在所有这些解中搜索,利用布局函数迭代出新解,最后得到鳍的优化设计.     

用于高功率激光装置中的电脉冲整形系统

采用射频GaAs场效应管和微带传输线技术,研制出用于高功率激光装置中的电脉冲整形系统.该系统电脉冲整形宽度为3.5 ns,幅度在0~5 V范围内调节,时域调整精度200 ps.整形后的方波,前沿383 ps,后沿642 ps,顶部不平坦度4~5%,波形幅度稳定性4~5%（p-p).利用该系统产生的整形电脉冲驱动电光波导调制器进行激光脉冲整形,得到了理想的整形激光脉冲.     

液滴在气流中破碎的数值分析

液滴的破碎是液体抛撒、破碎和雾化中的一个非常重要的阶段,它直接影响到最终的液滴的尺寸和散布。为了揭示液滴破碎的机理和影响破碎的因素,本文通过应用VOF方法和湍流模型对液滴在气流中的破碎过程进行了数值计算。数值计算得到了与国外实验研究相一致的液滴破碎形状。并根据数值计算的结果,分析了几个特征参数对液滴破碎过程的影响。     

一个新的IEC61000-4-2标准ESD电流解析表达式

 分析了两个ESD标准电流波形表达式，并提出一个新的基于脉冲函数来描述ESD标准电流的解析表达式，该表达式符合最新的标准IEC61000-4-2，在零时刻的电流及其微分部为0，且波形与实际测量波形基本吻合。     

螺旋管锅炉反应器管内汽液两相流压力降脉动研究

本又根据闭式循环热动力推进系统中锅炉反应器的各种可能的航行方向及运行参数，对螺旋管内汽液两相流压力降脉动特性进行了系统的试验研究，首次区分了两类不同特征的压力降脉动并得到了各主要因素的影响现律和发生脉动的界限准则。     

Displacement wave of the blood vessel —A mechanical model

According to clinical observations and model experiment, we have developed a theoretical model and obtained its mathematical equations to investigate the displacement wave of the blood vessel. The waveform and its occurrence criterion have been obtained by using perturbation theory and numerical method. The present study suggests that the displacement wave is associated with the blood velocity waveform and the machanical behaviour of the blood vessel, but not with the pressure waveform. The clinical criterion is in agreement with the observations.     

基于智能手机和Matlab的居家悬滴法表面张力测量实验

本文基于智能手机和Matlab软件设计了一种居家环境下可实现的悬滴法水滴表面张力测量实验.借助智能手机拍照功能获得水滴图像,利用Matlab进行边缘检测及计算,从而得出表面张力系数.对于不同清晰度的情况提出了对应的分析和处理方法,实验结果表明该方法稳定可靠.为后疫情时代开展居家大学物理实验教学提供了一个典型案例.     

Ultrasonic devulcanization of waste rubbers: Experimentation and modeling

Continuous ultrasonic devulcanization of ground tire rubber (GRT) and styrene-butadiene rubber (SBR) is considered. Experiments are performed under various processing conditions. Two recipes of SBR with different amounts of polysulfidic linkages are utilized. Gel fraction and crosslink density of devulcanized rubbers are measured and a unique relationship between them is established. Die characteristics with and without imposition of ultrasonic waves are determined. Devulcanized samples are revulcanized and mechanical properties are measured. In some cases, properties of revulcanized SBR samples exceeded those of virgin vulcanizates. This is explained based on the presence of a double network in the revulcanized rubber. A modification of acoustic cavitation and flow modeling of ultrasonic devulcanization of SBR and GRT is proposed using a concept of effective viscosity characterizing the flow of vulcanized particles before devulcanization combined with a shear rate, temperature and gel fraction-dependent viscosity of devulcanized rubber. Velocity, shear rate, pressure, and temperature field along with gel fraction, crosslink density and number of bonds broken are simulated. Predicted data on gel fraction, crosslink density, and pressure using the present modification of the model are found to be closer to experimental data then previously reported.Dedicated to the memory of Professor Tasos C. Papanastasiou     

Drop coalescence and deposition in turbulent wet steam pipe flows

The numerical turbulent coalescence/deposition model of Crane and Williams has been used to indicate likely trends in the development of drop size distribution and entrained water flow rate in the cross-over pipes of a nuclear wet steam turbine. Large increases in mean drop diameter have been shown to be possible, the results being very sensitive to the width of the initial size distribution, the entrained wetness fraction and the turbulence intensity. Deposition rate was also found to be strongly dependent on turbulence intensity, but inertial deposition onto and re-entrainment from the turning vanes of a bend did not significantly influence subsequent coalescence and turbulent deposition rates in the single example computed     

Correlations predicting frictional pressure drop and liquid holdup during horizontal gas-liquid pipe flow with a small liquid holdup

Experimental data and correlations available in the literature for the liquid holdup ε_L and the pressure gradient ΔP_TP/L for gas-liquid pipe flow, generally, do not cover the domain 0 < ε_L < 0.06. Reliable pressure-drop correlations for this holdup range are important for calculating flow rates of natural gas, containing traces of condensate. In the present paper attention is focused on reliable measurements of ε_L and ΔP_TPIL values and on the development of a phenomenological model for the liquid-holdup range 0 < ε_L < 0.06. This model is called the “apparent rough surface” model and is referred to as the ARS model. The experimental results presented in this paper refer to air-water and air-water + ethyleneglycol systems with varying transport properties in horizontal straight smooth glass tubes under steady-state conditions. The holdup and pressure gradient values predicted with the ARS model agree satisfactorily with both our experimental results and data obtained from the literature referring to small liquid-holdup values 0 < ε_L < 0.06. Further, it has been shown that in the domain 38 < < 72 mPa m the interfacial tension of the gas-liquid system has no significant effect on the liquid holdup. The pressure gradient, however, increases slightly with decreasing surface tension values.