Mechanism of resistance microwelding of crossed fine nickel wires

Resistance microwelding of fine crossed nickel wires is of increasing industrial importance for electrical connections in downsized electronic and medical devices, but the understanding of the process is very limited. A study has, therefore, been performed to clarify the basic joining mechanisms, in which the effects of main process parameters (welding current and force and weld time) were investigated by detailed mechanical testing and metallurgical examinations. A bonding mechanism with main process stages (wire cold collapse, surface melting, molten-phase squeeze-out and, solid-state bonding) was proposed. A new technique has also been developed to optimize the process by initiating the welding current well before the electrode force has reached its full nominal value.     

In situ polymerization and characterization of polyester‐based polyurethane/nano‐silica composites

Polyester‐based polyurethane/nano‐silica composites were obtained via in situ polymerization and investigated by Fourier‐transform infrared spectroscopy (FTIR), or FTIR coupled with attenuated total reflectance (FTIR‐ATR), Transmission electron microscopy (TEM), atomic force microscopy (AFM), an Instron testing machine, dynamic mechanical analysis (DMA) and ultraviolet‐visible spectrophotometry (UV‐vis). FTIR analysis showed that in situ polymerization provoked some chemical reactions between polyester molecules and nano‐silica particles. FTIR‐ATR, TEM and AFM analyses showed that both surface and interface contained nano‐silica particles. Instron testing and DMA data showed that introducing nano‐silica particles into polyurethane enhanced the hardness, glass temperature and adhesion strength of polyurethane to the substrate, but also increased the resin viscosity. UV‐vis spectrophotometry showed that nano‐silica obtained by the fumed method did not shield UV radiation in polyurethane films. Copyright © 2003 Society of Chemical Industry     

应用均匀设计法研究安息香缩合工艺

利用均匀设计法通过SPSS10.0计算机软件研究了反应条件对安息香缩合的影响。从而获得优化的工艺条件，与正交试验相比，该法试验次数少。工作效率高，并且便于分析各种因素的影响。     

水溶液辐射分解产物对金属材料腐蚀的影响

实验研究了水辐射分解作用对高放废物深地质处置容器材料的影响。在高放废物深地质处置库附近的地下水,受辐射线作用后分解出氧、氢和氧化产物(例如H_2O_2等),于是在高放废物容器周围形成一个氧化场,导致高放废物中的某些重要放射性核素(例如U,Np和Tc)易溶于水,并向远域迁移。本实验中的含FeSO_4(0.13 mol/L)水溶液在吸收剂量为0、20、60、180、500kGy的射线作用下,其氧化还原电位(Eh)值由+357mV增至+414 mV;在不同吸收剂量的射线作用下,金属Cu、金属Al、0.357 mv金属Fe和不锈钢(后者是我国拟采用的高放废物包装容器材料),在水溶液中的氧化侵蚀强度,分别比在无辐射情况下的大0.2-6.1倍。     

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本文通过对在用钻机井架的现场实际测试,建立数据库、测评模型,对实测的数据用计算机技术进行分析,提出了初始弯曲应力;数据正态分布检验——x～2检验;建立回归方程;在给定置信度下测评当前承载能力的技术概念。解决了在用钻机A型井架的安全性评估问题,是一种较为合理、可靠、科学的测评技术和方法。     

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.     

钨铜合金药型罩及其性能

钨铜合金药型罩的应用可以提高射流对均质钢靶的侵彻能力.这一提高得益于射流密度的提高以及断裂时间的延长. 本文对钨铜合金射流及其断裂形态通过X光照像进行了研究.它的旋转效应及其炸高特性也进行了实验研究. 钨铜合金药型罩的威力实验在φ30 mm的破甲弹上进行.在相同装药条件下与紫铜罩相比,威力提高20～30%.     

Eigenvalue-based algorithms for testing positive realness of SISO systems

A computational test for scalar positive real and strictly positive real functions is proposed in this paper. The input for this algorithm is state space representation, not necessarily minimal. It is derived for the discrete time problem, based on numerical stable eigenvalue computations. The test can be used in the continuous counterpart, which is in fact an improvement of an algorithm posed by Bai and Freund. Differences between the discrete and continuous time problems are also pointed out.     

不锈钢绕带容器环板与绕带端头的焊接

本文通过焊接试验对奥氏体不锈钢绕带容器环板与绕带焊接工艺进行了研究分析,并得出了合理的焊接方法和工艺参数。