SURFACE TENSION AND BUOYANCY DRIVEN INSTABILITIES IN A LAYER OF LIQUID TIN HEATED FROM BELOW

The linear theory of Pearson (1958) and Nield (1964) is modified here to study liquid tin and include the finite thermal resistances of the bounding layers of boron nitride, copper and air (∼10^-2 torr) in the experiments of Ginde et al. (1989). The magnitude of the ΔT_c across the layer of liquid tin required for the onset of convection depends on the ratios of the thermal conductivities and thicknesses of the supporting layers of boron nitride and copper to those of the tin.

According to our theory surface tension contributes more than buoyancy to the instability observed experimentally. The critical ΔT_c observed required for the onset of convection in the layer of tin, is up to 25% lower than that predicted, which shows the layer is less stable than the theory indicates. Thus the surface of the tin was uncontaminated, or a significantly larger observed critical ΔT_c would be expected.

The boundary condition on the thermal fluctuations at the base of the supporting layer of copper does not appear to be important in these experiments. However, the thermal resistance of the boron nitride would have to be assumed to be unrealistically large to obtain agreement within experimental error with the theory.     

半连续式棒材轧机在线捆扎机及其工艺设置

由北京冶金设备制造厂设计的YSK6型钢丝捆扎机，共设有并列6台棒材捆扎车，每台捆扎车由中间收送机、成形捆扎机、液压装置、捆扎辊道和台车组合而成。按生产工艺参数要求，整个成型捆扎周期为30秒。捆扎后的棒材在成品称重时用电子秤，每称量一次均可打印出单次净值、累加值和累加次数值。     

液体火箭发动机研制情况的一些回顾

４０年来，我国液体火箭发动机的研制工作取得了很大成绩。文中对发动机的一些研制情况作了回顾，对ＹＦ－７３和ＹＦ－７５氢氧发动机的设计特点、飞行结果作了简单叙述。对今后工作也提出了看法。     

Multi‐layered flat‐surface micro‐optical components directly molded on an LCD panel

Abstract— We have developed a process to fabricate optical components, such as a lens, prism, or diffuser, directly on to a glass substrate. Processes include precision mastering by diamond cutting and multi‐layer photopolymer (2P) molding to realize flat surfaces and the integration of multiple components with an alignment within a few micrometers.     

IR Radiometry Optical System View Factor and Its Application to Emissivity Investigations of Solid and Liquid Phases

An optical system for fast IR radiometry designed for investigations of thin film thermal properties and pulsed laser melting was analyzed in this work. A methodology for determination of the view factor from calibration measurements was developed. The view factor (0.0255) of the optical system containing two paraboloid mirrors was determined experimentally from calibration measurements on pure metals and metallic alloys. The knowledge of the view factor was then applied to normal emissivity investigations at IR wavelengths. The emissivity of tungsten films prepared by magnetron sputtering was determined for different deposition conditions, varying between 0.036 and 0.071. Liquid phase emissivities of Cu, Mo, Ni, Si, Sn, Ti, and steel were also determined and were found to be higher than solid-state emissivities as predicted from the literature. A knowledge of the liquid-state emissivity of silicon enabled recalculation of the IR signal evolution to the temperature evolution, during and after a nanosecond laser pulse. This was not possible by use of the usual calibration because of silicon’s semi-transparent behavior in the IR range (1–10 μm) in the solid-state phase.     

电子辐照加速器大功率工频高压电源

文章介绍目前两种用于烟气脱硫加速器的不同形式直流高压电源，分析了它们各自的特点。针对它们存在的不足之处，提出了一种全新的倍压型桥式整流线路，并对此线路进行了理论推导和计算机模拟仿真。     

基于集群计算机的保护定值在线校核

采用分布式计算技术，研究并实现了基于集群计算机的保护定值在线校核并行计算方法。首先分析了保护定值校核计算的计算量和计算特点，接着对可能采用的并行计算方法进行比较，最后选择了基于电网分块的并行计算方法。采用协调机加计算子机的计算模式，在协调机上执行分块算法，通过基于主导节点的图划分方法把电网分成几块，每台计算子机只校核1块电网内的保护定值，最后由协调机收集汇总计算结果。现场应用证明，该并行计算方法正确、有效。     

油罐液位温度自动检测系统及其程序设计

本文介绍了燃油火力发电厂油罐液位及温度数据的计算机数据自动采集及处理系统的结构和基于WINDOWS的可视化程序设计方法，该系统结构简单，成本低，采用RS－485数据接口可视现2千米内的数据通讯，是中小企业实现自动化管理的最佳解决方案。     

MODELING LIQUID MASS TRANSFER IN HIGEE SEPARATION PROCESS

Correspondence concerning this paper should be addressed to Professor Richard S.H. Mah. Hsien-Hsin Tung is now affiliated with Department of Chemical Engineering, California Institute of Technology

Penetration theory is used to describe the liquid mass transfer in Higee separation process. Within a possible range of effective areas, it is shown that the predicted mass transfer coefficients are in reasonable agreement with the estimated mass transfer coefficients. The estimated coefficients were calculated from the experimental data and the possible effective areas. Hence it is concluded the penetration theory is generally applicable to describe liquid mass transfer in Higee separation process. The comparison also suggests that liquid mixing at the junctions of packing materials may be more complete in Higee process than in traditional process.     

纳米ZnO薄膜制备及液态源掺杂

用真空蒸发法在玻璃和单晶硅片 (10 0 )上制备Zn薄膜 ,然后对Zn薄膜进行氧化、热处理获得纳米ZnO薄膜。对在硅片上制备的Zn薄膜一次性进行高温掺杂、氧化获得纳米ZnO∶P和ZnO∶B薄膜。研究不同氧化、掺杂温度和时间对薄膜结构、电学性能的影响。结果表明 :氧化温度和时间对ZnO薄膜结构影响较大 ,液态源掺P可明显改善纳米ZnO薄膜的导电性能、结构特性和化学组分