Computation of optimum reliability acceptance sampling plans in presence of hybrid censoring

The decision regarding acceptance or rejection of a lot of products may be considered through variables acceptance sampling plans based on suitable quality characteristics. A variables sampling plan to determine the acceptability of a lot of products based on the lifetime of the products is called reliability acceptance sampling plan (RASP). This work considers the determination of optimum RASP under cost constraint in the framework of hybrid censoring. Weibull lifetime models are considered for illustrations; however, the proposed methodology can be easily extended to any location-scale family of distributions. The proposed method is based on asymptotic results of the estimators of parameters of lifetime distribution. Hence, a Monte Carlo simulation study is conducted in order to show that the sampling plans meet the specified risks for finite sample size.     

基于SystemVerilog可重用测试平台的实现

对于中小型设计,传统的验证效率低、可重用性差,而基于方法学的高级验证测试平台搭建较繁琐,验证流程不太灵活。以ARINC429收发器IP核为验证对象,采用System Verilog语言,通过层次化设计,改善工程组织架构,运用虚接口与回调等关键技术,实现了一种可重用测试平台。将不同的测试案例在测试平台上运行,结合断言与覆盖率驱动等验证技术完成了对ARINC429收发器IP核的功能验证,代码覆盖率和功能覆盖率均达到100%。实践表明,该测试平台具有良好的可重用性、易操作性,验证效率较高。     

带钢端部形状双目视觉检测系统的建模仿真

为了实现热轧带钢端部形状检测,利用Matlab中视觉图像处理工具箱,建立了由CCD线阵相机构成的双目立体视觉系统模型和实际带钢生产线上的运动过程模型。热轧带钢在生产过程中会受到粗轧辊的不平均压力的影响,从而造成带钢头尾变形。针对这种情况.提出了一种新的带钢末端形状视觉检测和宽度计算方法。该方法不但可以在带钢发生平移、倾斜等位置和姿态变化情况下仍能够准确测量出带钢宽度,并且可以精确还原出带钢头尾形状。仿真试验结果证实了所提出的视觉模型和算法的有效性.取得的结果令人满意。     

Influence of groove type on welding-induced residual stress,deformation and width of sensitization region in a SUS304 steel butt welded joint

To join a medium or thick plate weldment with a full penetration, a groove is usually prepared in the space between two sections of metal. Because weld metal needs to be deposited within the groove to form the joint, it is expected that different groove type will require different heat input, which may consequently have influence on welding residual stress and deformation. Generally, different groove corresponds to different bead layout, so it can be foreseen that the groove type has a significant effect on temperature history, shape and size of heat affected zone, and region of sensitization in certain alloys such as austenitic stainless steel. The influences of groove type on residual stress, angular distortion and width of sensitization region in a SUS304 butt-welded joint were investigated by means of numerical simulation and experiment. Based on ABAQUS code, a computational approach with considering thermo-mechanical coupling behaviors, moving heat source, strain hardening and annealing effect was developed to simulate temperature profile, stress field and deformation in multi-pass joint. Welding temperature cycles, residual stress distributions and deformations in V, K and X groove joints were calculated through using the proposed computational procedure. Meanwhile, experiments were carried out to obtain residual stress distributions and angular distortions. Through comparing the numerical results and the measured data, the effectiveness and accuracy of the developed computational approach were verified. The simulation results show that groove type has a significant influence on welding residual stress distribution, angular distortion and width of sensitization region.     

Process parameter optimization of lap joint fillet weld based on FEM–RSM–GA integration technique

This study introduces a welding process design tool to determine optimal arc welding process parameters based on Finite Element Method (FEM), Response Surface Method (RSM) and Genetic Algorithms (GA). Here, a sequentially integrated FEM–RSM–GA framework has been developed and implemented to reduce the weld induced distortion in the final welded structure. It efficiently incorporates finite element based numerical welding simulations to investigate the desired responses and the effect of design variables without expensive trial experiments. To demonstrate the effectiveness of the proposed methodology, a lap joint fillet weld specimen has been used in this paper. Four process parameters namely arc voltage, input current, welding speed and welding direction have been optimized to minimize the distortion of the structure. The optimization results revealed the effectiveness of the methodology for welding process design with reduced cost and time.     

Exception handling analysis and transformation using fault injection: Study of resilience against unanticipated exceptions

ContextIn software, there are the error cases that are anticipated at specification and design time, those encountered at development and testing time, and those that were never anticipated before happening in production. Is it possible to learn from the anticipated errors during design to analyze and improve the resilience against the unanticipated ones in production?ObjectiveIn this paper, we aim at analyzing and improving how software handles unanticipated exceptions. The first objective is to set up contracts about exception handling and a way to assess them automatically. The second one is to improve the resilience capabilities of software by transforming the source code.MethodWe devise an algorithm, called short-circuit testing, which injects exceptions during test suite execution so as to simulate unanticipated errors. It is a kind of fault-injection techniques dedicated to exception-handling. This algorithm collects data that is used for verifying two formal contracts that capture two resilience properties w.r.t. exceptions: the source-independence and pure-resilience contracts. Then we propose a code modification technique, called “catch-stretching” which allows error-recovery code (of the form of catch blocks) to be more resilient.ResultsOur evaluation is performed on 9 open-source software applications and consists in analyzing 241 catch blocks executed during test suite execution. Our results show that 101/214 of them (47%) expose resilience properties as defined by our exception contracts and that 84/214 of them (39%) can be transformed to be more resilient.ConclusionOur work shows that it is possible to reason on software resilience by injecting exceptions during test suite execution. The collected information allows us to apply one source code transformation that improves the resilience against unanticipated exceptions. This works best if the test suite exercises the exceptional programming language constructs in many different scenarios.     

一种改进的超轻量级RFID认证协议

针对当前超轻量级RFID认证协议中存在的安全缺陷,提出一种改进的超轻量级RFID双向认证协议。通过引入新的函数,使消息之间的数学关联性更加复杂,避免了泄露标签标识符,提高了阅读器和标签在开放环境中通信的保密性。对该协议的安全性和效率进行分析,并利用OPNET软件对该协议仿真实验,结果表明,该协议能抵抗代数攻击,重传攻击,假冒攻击等多种常见恶意攻击,在同等计算量下具有更高的安全性,可用于实际的移动身份认证环境。     

基于Petri网的维修保障过程可视化建模与仿真

为解决民用飞机维修保障过程中资源影响复杂性及时间消耗不确定性的难题,提出基于模糊时间着色Petri网的民用飞机维修保障过程可视化建模方法与仿真。分析维修保障各个过程的资源充足度及时间消耗不确定性对整个维修保障活动的影响,动态地显示资源状态及模糊时间。以民用飞机起落架液压系统故障为例进行可视化建模与仿真,动态的仿真过程及最终结果验证了模型的可行性及算法的正确性,其能够为民用飞机维修保障过程的效率评估以及薄弱环节的确定提供支持。