外焊缝自动跟踪系统

介绍了外焊缝自动跟踪系统的组成及工作原理，简述了传动部分ＧＴＲ－ＰＷＭ调速系统，给出了系统的硬件电路。该跟踪器具有结构简单，体积小，性能稳定等特点，在生产线上获得了成功的应用。     

脉冲波形对流化床性能的影响

本文从理论上分析了矩形波和正弦脉波气流对流化床操作性能的影响，发现矩形波在一定条件下优于正弦波的规律，并用实际进行了验证。     

High-temperature,high-pressure thermophysical measurements on liquid zinc

Wire-shaped zinc samples were resistively volume heated as part of a fast-capacitor discharge circuit. Time-resolved measurements with submicrosecond resolution of the current through the specimen, the voltage drop across it, and the thermal expansion of the specimen as a function of time allow determination of the enthalpy, electrical resistivity, and density at different temperatures up to superheated liquid states of zinc far above the normal boiling point. High static pressures, up to 3800 bar of the ambient medium water, were used. An estimate of the critical pressure for zinc is given by investigations of the stability of the sample with a framing CCD camera, taking pictures of different samples varying the ambient static pressure. The critical volume and the critical temperature are obtained by means of an extrapolation of measured data at different pressures.Paper presented at the Fourth International Workshop on Subsecond Thermophysics, June 27–29, 1995, Köln, Germany.     

Effect of processing history on the properties of Ag-based tapes

The Bi-system tapes and coils were prepared by the powder-in-tube method. The effect of processing and heat treatment on the properties of the tapes and coils was studied. It is found that the shearing stress produced by the rolling process may destroy the 2223 phase, and the destroyed 2223 phase cannot be recovered by heat treatment, whereas the pressing stress produced by the uniaxial pressing process only makes the 2223 phase grains break, and the broken 2223 phase can be closed by the heat treatment. TheJ _c values of the rolling samples, pressing sample, and the coil with a diameter of 35 mm are over 1.3×10⁴, 2.5×10⁴, and 4×10³ A/cm² (77 K, 0 T), respectively.     

Measurements of the refractive index of alternative refrigerants

Measurements of coexistence curves of the refractive index of HCFC-22, HFC23, HFC-32, HFC-125, and HFC-152a have been carried out in the range from ambient to critical temperature. Near the critical temperature the refractive index has distribution in both the vapor and the liquid phases in the test cell. Thus the values at the boundary between vapor and liquid are selected at those of saturated vapor and liquid, respectively. The values of the critical temperature and critical refractive index for each substance are estimated. The refractive index is related to density by the Lorentz-Lorenz equation. In the case of HFC-32 the value of the LL function is assumed to be constant in the limited region near the critical point, and the values of density of saturated vapor and liquid are calculated and are compared with the experimental values of density obtained byPVT measurement.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994, Boulder, Colorado, U.S.A.     

Transport properties of 1,1-difluoroethane (R152a)

Based on reliable. carefully selected data sets. equations for the thermal conductivity and the viscosity of the refrigerant R 112a are presented. They are valid at temperatures from 240 to 440 K, pressures up to 20 MPa. and densities up to 1050 kg · m^–3. including the critical region.     

低速爆轰管对黑火药的点传火性能研究

文章采用中心点火管结构的实验装置研究了黑火药的点传火性能。用低速爆轰 (L VD)中心点火管来点燃黑火药时 ,1# ～ 3# 大粒黑药的传火速度为 70 0 m· s-1～ 80 0 m· s-1数量级 ,燃烧波宽度在 3.1ms～ 3.5 ms,最大压力峰值 :1# 为 36 .4 MPa,2 # 为 2 4 .0 MPa,3# 为 38.0 MPa。用普通中心点火管点燃黑火药时 ,2 # 、3# 和钝化 2 # 大粒黑的传火速度分别为 6 1.2 m· s-1、6 8.2 m·s-1和 4 0 .1m· s-1,最大燃烧波宽度分别为 9.2 ms、6 .3ms和 9.5 ms。燃烧波表明 ,L VD中心传火管与普通中心传火管相比较 ,在传火管的不同位置处 ,前者的 P- t曲线一致性远高于后者。     

High-field magnetic and transport critical current density of Sm-Ba-Cu-O: Agx superconductors at low temperature

Variation of magnetic critical current density (J _mc) and transport critical current density (J _tc) in high magnetic fields at liquid helium temperature were investigated on Sm-Ba-Cu-O: Ag _x (x=0.0, 0.2, 0.4, and 0.6) superconducting samples prepared by the coprecipitation technique.T _c and crystallographic parameters remain unaffected by Ag addition. However, bothJ _mc andJ _tc were found to increase on Ag addition. The volume pinning force (F _p) also increased with increase in Ag concentration, resulting in stronger flux line sheer. Microwave-induced d.c. voltage measurement shows a significant reduction of the total number of weak links between the superconducting grains with increasing concentration of Ag, which creates stronger pinning potentials between the boundary of the superconducting intergrains. Hence, the volume pinning force is greatly enhanced by Ag addition, leading to flux line lattice movement which is responsible for highJ _mc andJ _tc.     

Formal methods: The next generation of system design tools

Because of the growing demand for increasingly complex computer-based systems there is now an urgent need to provide tools to assist during the design of such systems. Formal specifications and formal methods provide such assistance but their widespread adoption has been hindered by the so-called ‘math fear’ and the perception that the tools are too difficult, too time consuming and too costly to use in a commercial environment. The aim of this article is to dispel the mystery surrounding the topic and to explain what formal methods are, how and why they are used, the benefits that accrue and why the technology should be accepted on a broader front. The application of formal methods to the design of computer-based systems will be discussed without resorting to jargon or mathematics. The discussion will concentrate more on the software content of systems but the arguments apply equally well to hardware. Some of the available tools will also be introduced.     

利用短周期地脉动推断深层地基S波速度

从二维随机波场的相关理论出发，提出了如何从短周期地脉动（频率＞０．５Ｈｚ）时域信号中计算Ｒａｙｌｅｉｇｈ波弥散曲线，进而反演深层地基剪切波（Ｓ波）速度的理论方法和分析技术，并结合实测信号的分析结果，探讨了该方法的可行性和实用性。