A mechanism for transgranular stress-corrosion cracking

A model is proposed to explain transgranular-stress corrosion cracking (T-SCC) in face-centered cubic (fcc) materials. Crack propagation is shown to be anisotropic, in that growth near {110} < 001> is discontinuous due to crack arrest by dislocation blunting whereas growth away from this growth orientation is continuous. For the former case, renucleation of arrested cracks involves active dissolution of shear bands at the crack tip, which changes the stress state at Lomer-Cottrell locks, causing them to fail by cleavage. Once the crack is nucleated, its instantaneous macroscopic crack-growth velocity is considered to be comprised of multiple nucleation of microcracks with intervening arrests. This microcracking results from the interaction of the stress fields from neighboring cracks which are forming simultaneously, the crack-opening constraint due to ligaments which act as “bridges” behind the crack front, and the localized dissolution at the microcrack tip which affectsK _IC and leads to the “cobblestone” appearance. Experimental evidence and theoretical considerations are presented to support the model. The system studied was Cu-25 at. pct Au in 0.6 M NaCl solution at potentials between 300 and 400 mV (sce), which precludes hydrogen embrittlement. This article is based on a presentation made in the symposium “Quasi-Brittle Fracture” presented during the TMS fall meeting, Cincinnati, OH, October 21–24, 1991, under the auspices of the TMS Mechanical Metallurgy Committee and the ASM/MSD Flow and Fracture Committee.     

A Linear Cross-Coupled Control System for High-Speed Machining

We present a linear cross-coupled controller to improve highspeed contouring accuracy independently of tracking accuracy in a biaxial machine tool feed drive servomechanism. Unlike conventional cross-coupled controllers, the cross-coupled controller presented here is a linear system, so it is very easy to perform the stability and steady-state error analysis, and to optimise the controller parameters. The proposed controller is evaluated experimentally on a CNC LOM machine and compared to an uncoupled controller and a conventional cross-coupled controller. Controller performance is evaluated for a circular contour at a feedrate of 30 m min _1 . The experimental results show that the proposed controller can greatly reduce the contour error at large feedrates. The linear cross-coupled controller is simple to implement and is practical.     

有限区间信号边界效应问题的研究

研究了截断信号边界的“吉布斯”现象及数字滤波器相位特性对有限区间信号滤波处理的影响，在阐明了有限区间信号处理中边界效应物理本质的基础上，探讨了数字信号处理中通常所采用的边界处理方法的有效性问题，提出了一种命名为端值延拓法的新的边界处理方法，通过比较分析和实例验证表明这种方法的优越性，文中以零相位数字滤波及运用MALLAT算法对有限区间信号进行小波分解与重构为实例，介绍了其边界效应问题及解决方案，取得了很好的效果。     

SAAB雷达与PROVOX系统的通讯

介绍了SAAB雷达液位计和SAAB雷达系统与上位系统的通讯接口FSC以及PROVOX系统的智能设备接口卡 (IDI)等的基本内容 ,并对SAAB雷达液位计与PROVOX系统通讯的硬件连接和PROVOX系统中关于IDI卡的组态方法进行说明     

内循环好氧三相流化床处理造纸中段废水

本实验采用内循环好氧三相流化床处造纸中段废水，经过一段时间的驯化，获得了稳定的出水。CDO去除经保持在65％以上，系统对进水污染负荷的变化具有较大的承受能力。出水Cl^-的浓度有所增加，说明驯化后的微生物可能对有抽氯化物具有一定的降解作用。水气比在1／120至1／140之间可获得最好的COD去除效果。后进行絮凝处理后，出水COD降为60－80mg/L,BODo 50-60/L，色度为100－150CU，挥发性酚的质量浓度小于0．0265mg／L。     

纳米α-FeOOH颗粒的形态和结构

以硫酸法钛白的副产物绿矾为原料，采用滴加法制备纳米铁黄（α－FeOOH）颗粒。研究了反应体系的pH值、反应温度、通氧速率、搅拌速率和添加剂等对铁黄颗粒形态结构的影响，采用XRD、TEM等分析手段对颗粒进行表征。结果表明，调节体系pH值能控制铁黄晶型结构和色相；改变通氧速率、搅拌速率、添加剂种类以及反应温度等可以调节纳米α－FeOOH的大小和分散性。     

吐丝圈径对大规格高碳盘条组织性能的影响

计算与分析了斯太尔摩冷线上盘条的吐丝圈径、搭接密度及"佳灵"装置横向布风曲线之间的关系,研究了吐丝圈径的大小对大规格82B盘条组织和性能的影响,确定了大规格82B盘条最小吐丝圈径应为980mm.     

Si基膜片型气敏传感器微结构单元的热学性能

微结构气敏传感器由于其微型化、低功耗、易阵列化和易批量生产等优点而受到国内外研究者的广泛关注。利用微机电系统（MEMS）加工技术，制备Si基膜片型微结构单元，并分析其热学性能。这种单元工作区温度为-300℃时，加热功率约75mW；并且膜片工作区的热质量很小，温度可以于毫秒量级的时间内，在室温和450℃之间调制。利用这种微结构单元，可以在温度调制方式下，研究气敏薄膜的电学特性和敏感机理。     

砂基中泥浆盾构法隧道施工开挖面稳定性试验研究

 通过模型试验，对泥浆盾构施工中泥浆维持开挖面稳定的力学机理，开挖面前缘土体的应力变化规律，泥浆压力作用机理及泥皮形态进行了研究，提出了中粗砂地基中临界泥浆压力 公式。     

露天矿半连续工艺技术应用现状及发展前景

介绍了露天矿半连续工艺技术国内外应用现状、研究成果以及发展趋势。