Web集群服务器可用性的提高

以Web集群服务器的后端节点作为研究对象，通过减少后端节点的MTTR（Mean Timeto Repair），来提高它们的可用性，从而提高整个集群服务器的可用性。首先，通过分析现有的故障恢复方案的不足，提出了新的改进方案，在新的方案中，采用了动态地检测和发送状态信息的策略。并引入了故障猜测状态，弥补了现有方案的不足。最后设计了一个试验环境，与现有的方案测试相比，使用改进的方案，MTTR（平均敞障修复时间）减少了63％，很好地提高了后端节点的可用性。     

金、铜丝球键合焊点的可靠性对比研究

金丝球焊是电子工业中应用最广泛的引线键合技术,但随着高密度封装的发展,铜丝球焊日益引起人们的关注。采用热压超声键合的方法,分别实现Au引线和Cu引线键合到Al-1%Si-0.5%Cu金属化焊盘。对焊点进行200℃老化实验的结果表明:铜丝球焊焊点的金属间化合物生长速率比金丝球焊焊点慢的多;铜丝球焊焊点具有比金丝球焊焊点更稳定的剪切断裂载荷,并且在一定的老化时间内铜丝球焊焊点表现出更好的力学性能;铜丝球焊焊点和金丝球焊焊点在老化后的失效模式不同。     

一台220kV电容式电压互感器的故障分析

通过一台电容式电压互感器的故障分析，提出对电容式电压互感器的维护以及预防性试验的一些看法。     

Numerical Cracking and Debonding Analysis of RC Beams Reinforced with FRP Sheet

Bonding a fiber reinforced polymer (FRP) sheet to the tension-side surface of reinforced concrete (RC) structures is often performed to upgrade the flexural capacity and stiffness. Except for upper concrete crushing, FRP sheet reinforcing RC structure may fail in sheet rupture, sheet peeloff failure due to opening of a critical diagonal crack, or concrete cover delamination failure from the sheet end. Accompanying the occurrence of these failure modes, reinforcing effects of the FRP sheet will be lost and load-carrying capacity of the RC structures will be decreased suddenly. This study is devoted to developing a numerical analysis method by using a three-dimensional elasto-plastic finite element method to simulate the load-carrying capacity of RC beams failed in the FRP sheet peeloff mode. Here, the discrete crack approach was employed to consider geometrical discontinuities such as opening of cracks, slipping of rebar, and debonding of the FRP sheet. Comparisons between analytical and experimental results confirm that the proposed numerical analysis method is appropriate for estimating the load-carrying capacity and failure behavior of RC beams flexurally reinforced with a FRP sheet.     

G105钻杆腐蚀失效分析

采用金相分析并结合X射线衍射、扫描电镜和电子探针能谱分析等方法，分析了某油田G105钻杆的腐蚀失效原因。结果表明，因腐蚀产物脱落造成井下堵水眼事故，而钻杆停钻后因未及时清理泥浆而造成钻杆内表面附着泥浆，含有氯离子的泥浆加速了其对钻杆的氧腐蚀。就停钻腐蚀问题提出了预防措施。     

Analysis and Reduction of Ultrasonic Pitting Defects on Hard Disk Surfaces

It has become of paramount importance to be able to perform failure analysis of defects on hard disk surfaces quickly and accurately. In this study, ultrasonic pitting defects on hard disk surfaces were investigated. A new electrical tagging pattern system, which directly translated the channel bits to magnetic transitions during writing of the magnetic pattern around a defect, was used in the failure analysis of magnetic recording disks to mark defective sectors. With the help of the Kerr magneto-effect, the defective sectors were effectively located for further failure analysis. Results of the failure analysis revealed that there was 30% to 40% loss of the recorded magnetic bit signal due to an increase in the gap between a recording head and a hard disk surface with ultrasonic pitting defects. The experiments performed indicated that low ultrasonic power for disk cleaning could reduce the ultrasonic pitting defects significantly. The maximum failure rate due to single-type ultrasonic pitting defects was reduced from 33.4% to 16.7%, while the maximum failure rate due to cluster-type ultrasonic pitting defects was reduced from 11.1% to 5%.     

Lifetime evaluation of concrete structures under sustained post-peak loading

Experimental tests on crack propagation in concrete under constant post-peak loading are simulated using the finite element method and the cohesive crack model, in both Mode I and Mixed-mode conditions. The time-dependent behaviour of concrete in the process zone is due to the interaction and growth of microcracks, a phenomenon which, for high constant load levels, turns out to be predominant over linear viscoelastic creep in the bulk material. In mechanical systems based on this type of material behaviour (creep and strain-softening taking place simultaneously), the initial value problem is non-parabolic, i.e., the error at one time level is affected by the accumulation of errors introduced at earlier time levels. Despite these difficulties, the scatter in numerical failure lifetime vs. load level turns out to be negligible in Mode I conditions and practically acceptable in Mixed-mode conditions. Therefore the time-dependent behaviour of the process zone can be inferred solely from the results of direct tensile tests.     

Preventive maintenance models with random maintenance quality

In real-world environments it is usually difficult to specify the quality of a preventive maintenance (PM) action precisely. This uncertainty makes it problematic to optimise maintenance policy. This problem is tackled in this paper by assuming that the quality of a PM action is a random variable following a probability distribution. Two frequently studied PM models, a failure rate PM model and an age reduction PM model, are investigated. The optimal PM policies are presented and optimised. Numerical examples are also given.     

一种基于遗传算法的缺陷集合最小化方法

文章根据遗传算法,提出了一种简化导致软件系统故障的缺陷集合的方法。在软件缺陷注入测试中应用此方法,可以快速地从注入缺陷集合中分离出导致软件系统故障的缺陷子集,进而可以方便测试者定位出被测软件系统中的脆弱点。     

基于动作推导引擎下的故障检测方法

本文根据文[2]介绍的软件管理者方法，提出了基于动作推导引擎的软件管理者方法。软件管理者单元是一种自动的实时监控软件故障的软件工具，适用于实时软件系统特别是通信类软件系统的故障侦测。它通过监控目标系统的输入和输出，使用获得的输入和目标系统的管理模型推算出对应此输入序列的期望输出值．与目标系统的实际输出做比较．如果实际输出没有在期望输出集中，则管理者单元断定目标系统出现错误。基于动作推导引擎的软件管理者方法，采用了动作推导引擎产生的目标系统管理模型，使该管理模型独立于软件管理者方法。可以实现管理模块与动作推导引擎同步实时更新．而不会导致软件管理者单元的改动。