基于Petri网和语义网络的虚拟维修过程建模与应用

针对当前虚拟维修过程中模型庞大,维修流程不可反复,部件间关系描述混乱等问题,论文提出一种Petri网和语义网络结合的过程建模方法——TJ(Training Join)网。TJ网上层利用语义网络对部件进行层次结构分解和资源规范聚类,实现子部件间逻辑互联;下层运用Petri网的变迁和触发规则提炼出Petri网元素模型,提高模型的通用性和建模效率。同时模型中的状态收集模块可实现部件属性状态间信息共享。最后,以虚拟维修平台中飞机电子设备架的维护为例,验证了TJ网的有效性。     

基于广义随机Petri网GSPN的系统安全性研究

针对基于广义随机Petri网GSPN的动态系统安全性建模与分析方法进行了系统研究。基于Petri网、GSPN模型的基本原理，提出了关键状态搜索算法，并进行了安全性仿真分析．将广义随机Petri网的扩展模型应用于安全性分析领域，丰富了动态系统安全性问题的研究手段。     

基于时间竞争的企业营销环境风险预警模型

分析了企业营销环境风险的时间流特征,提出了基于时间竞争的企业营销环境风险识别模型;为了快速响应市场营销环境的变化,将Petri网技术引入企业营销环境风险管理活动中,根据营销环境信息流结构,把企业营销环境的风险因素、对营销环境风险的把握能力分别与Petri网的基本元素--库所和变迁联系起来,建立了基于时间竞争的企业营销环境风险预警的随机Petri网模型.最后,将模型应用于某高新技术企业,所得结果与实际情形相一致.     

基于OOPN的FMS单元控制模型

由于Petri网既可以采用图形方式描述控制过程,同时又可以从数学上分析Petri网的死锁、可达性(reachability)、活性(liveness)等性质.因此,Petri网广泛地应用于FMS单元控制模型的设计.但Petri网在应用过程中,也存在着描述"爆炸"和无法嵌入调度策略等问题.本文提出了一种新型的基于面向对象Petri网(OOPN)的单元控制体系结构,该结构以分布式服务代理机制实现对生产过程的控制,它不仅具备减少Petri网模型规模以及面向对象编程特点,而目以代理机制的形式加入了控制模式.     

基于DSTBC-DF的无线传感网能量有效性研究

提出了一种基于分布式空时分组编码的译码转发(DSTBC-DF)的新的协同分集方案,设计了适合协同分簇多跳无线传感网的网络协议,并讨论了协同同步情况,分析了协同分集方案的性能和协同分簇无线传感网的能量效率.理论分析与Mento Catlo仿真的结果验证了这一新方案的有效性:相比传统的方案,不但实现简单,而且通过合理的协议设计有效地解决了协同同步问题,实现了完全的分集增益,有更高的能量效率,网络系统能耗明显降低.     

一种基于TPM的手机第三方安全移动支付协议

为解决in-APP第三方支付中密钥泄漏、信息显示不全、商家APP缺乏预信任等问题,采用着色Petri网(CPN)模型对现有的订单篡改、通知假冒、订单替换、非授权查询4种攻击进行建模分析,并通过推导不安全状态的可达性验证in-APP第三方支付系统存在的安全漏洞.提出了基于可信平台模块(TPM)的新的支付协议模型,该模型利...     

基于时延库所Petri网的动态联盟任务调度研究

针对动态联盟中任务调度的特点,提出了采用时延库所Petri网对动态联盟任务调度进行建模。给出了模型的形式化描述及变迁规则,对动态联盟中的产品加工类型进行了分类,并建立了各种加工类型的时延库所Petri网模型,分析了通过模型中零时差的库所求解关键路径和利用可达图求解合理调度方案的方法。最后,以实例表明了该方法的可行性和有效性。     

基于时间Petri网的建模与分析

介绍一种Petri网——时间Petri(TPN)。用时间Petri网表示工作流模型并对基本工作流模型进行时序分析,给出线性时间推理的规则,运用这些规则,可对复杂的工作流模型进行逐步化简,并在线性时间复杂度内解决时间推理问题。     

基于锁的Cache一致性协议的硬件优化策略

对一种基于锁的Cache一致性协议的开销进行了评估和分析,并结合一款处理器接口的设计,实现了一种分布式内存结构上的远程内存共享机制.该机制能提高处理器机间的通讯性能,降低一致性协议中的通讯延迟,同时通过硬件锁对协议中的同步开销进行优化,避免锁管理器节点陷入处理程序而减少同步等待时间.实际测试结果表明,通过硬件优化的软件Cache一致性协议基本操作的性能得到极大的提高,并在实际应用上具有更好的加速比和可扩展性.     

No.7SS ISUP的协议一致性测试系统实现

针对Ｎｏ．７公共信道信令ＩＳＵＰ（ＩＳＤＮ ＵＳＥＲ ＰＡＲＴ）协议的特点，分析了利用传统的分布式测试方法实现ＩＳＵＰ一致性测试系统的困难，并借用渡船测试方法的思想提出了一种ＩＳＵＰ协议一致性测试的新方法，其主要优点是较好地解决了上下测试器的同步问题。最后描述了基于这种方法实现的ＩＳＵＰ协议一致性测试系统。     

灼热桥式电火工品瞬态脉冲试验的现状和趋势

主要介绍了近年来电火工品瞬态脉冲试验在国内外的发展现状,包括试验仪器、热参数计算和分析的进展;同时介绍了瞬态脉冲试验在电火工品质量检测中的作用;并讨论了现在瞬态脉冲试验的应用范围和局限性;结合现有的仪器和软件,展望了瞬态脉冲试验今后在硬件和软件方面的发展趋势。     

灼热桥式电火工品瞬态脉冲试验的现状和趋势

主要介绍了近年来电火工品瞬态脉冲试验在国内外的发展现状,包括试验仪器、热参数计算和分析的进展;同时介绍了瞬态脉冲试验在电火工品质量检测中的作用;并讨论了现在瞬态脉冲试验的应用范围和局限性;结合现有的仪器和软件,展望了瞬态脉冲试验今后在硬件和软件方面的发展趋势。     

浅谈桥丝式电火工品瞬态脉冲试验的研究现状

文章主要介绍了近年来电火工品瞬态脉冲试验在国内外的发展现状.包括试验仪器、热参数计算和分析的进展,以及瞬态脉冲试验在电火工品质量检测中的作用.收集并分析了瞬态脉冲试验的应用范围和局限性,结合现有的仪器和软件,展望了瞬态脉冲试验今后在硬件和软件方面的发展趋势.     

Accelerated Life Testing (ALT) Design Based on Computational Reliability Analysis

Accelerated life testing (ALT) design is usually performed based on assumptions of life distributions, stress–life relationship, and empirical reliability models. Time‐dependent reliability analysis on the other hand seeks to predict product and system life distribution based on physics‐informed simulation models. This paper proposes an ALT design framework that takes advantages of both types of analyses. For a given testing plan, the corresponding life distributions under different stress levels are estimated based on time‐dependent reliability analysis. Because both aleatory and epistemic uncertainty sources are involved in the reliability analysis, ALT data is used in this paper to update the epistemic uncertainty using Bayesian statistics. The variance of reliability estimation at the nominal stress level is then estimated based on the updated time‐dependent reliability analysis model. A design optimization model is formulated to minimize the overall expected testing cost with constraint on confidence of variance of the reliability estimate. Computational effort for solving the optimization model is minimized in three directions: (i) efficient time‐dependent reliability analysis method; (ii) a surrogate model is constructed for time‐dependent reliability under different stress levels; and (iii) the ALT design optimization model is decoupled into a deterministic design optimization model and a probabilistic analysis model. A cantilever beam and a helicopter rotor hub are used to demonstrate the proposed method. The results show the effectiveness of the proposed ALT design optimization model. Copyright © 2015 John Wiley & Sons, Ltd.     

Applications of non-destructive testing techniques for post-process control of additively manufactured parts

This paper presents an overview on the principle of operation for post-process inspection non-destructive testing (NDT) techniques. The techniques include visual inspection, liquid penetrant testing, magnetic particle testing, eddy current testing, ultrasonic testing, and radiography. The applications of these NDT techniques in additive manufacturing (AM) and their suitability for defects detection of additively manufactured parts are reviewed. The sensitivity, and the advantages and disadvantages of each technique are evaluated. The types of defect, and the detectability of these defects by NDT techniques are assessed. The applicability of each NDT technique for different categories of AM process is discussed. The categories of AM are, namely, material extrusion, powder bed fusion, vat photopolymerisation, material jetting, binder jetting, sheet lamination, and directed energy deposition.     

Identification of constitutive model for rubber elasticity from micro-indentation tests on natural rubber and validation by macroscopic tests

Micro-hardness testing is widely used to measure the materials local response and is very valuable to describe gradients of physical properties. For polymers, the most common use is to measure a scalar value (hardness or modulus), which gives access to useful qualitative information but can clearly not be used to identify local constitutive models, strongly needed to achieve the numerical simulation of heterogeneous massive parts. In this study, load/displacement curves obtained at a micro-scale are used to identify the parameters of an Edwards-Vilgis hyperelastic model. The protocol proposed is coupling FE simulations achieved with Abaqus and optimization procedures using the dedicated software Boss Quattro. In order to limit the microstructure and viscous effects, the material studied is an unfilled natural rubber which exhibits a behavior very close to perfect hyperelasticity. Several numerical parameters (indent geometry, friction, thickness, …) as well as experimental protocols were tested in order to check the protocol reliability. The identified parameters are used to simulate macroscopic tests (tensile, compression and pure shear tests). The agreement with experimental data is very good, which is rarely found in the literature and which validates several numerical assumptions.     

Additive manufacturing process monitoring and control by non-destructive testing techniques: challenges and in-process monitoring

This paper examines on the obstacles specific to the implementation of non-destructive testing (NDT) techniques in additive manufacturing (AM). The general challenges impeding the adoption of AM for volume production of parts, and the use of NDT techniques to ameliorate some of these challenges are studied. These challenges include the lack of understanding of AM materials, and insufficient standards for the mechanical testing and NDT of additively manufactured parts. An overview on the principle of operation for in-process inspection NDT methods is presented. The techniques include thermography, and acoustic emission testing. The applications of these NDT techniques in AM and their suitability for defects detection of additively manufactured parts are reviewed. The sensitivity, and the advantages and disadvantages of each technique are evaluated. The types of defects, and the detectability of these defects by NDT techniques are assessed.     

声学综合无损检测技术

论述了检测复合材料和胶接结构不连续（缺陷）的新型多模综合无损检测技术。该技术以声与超声检测技术为基础,包含五种不同检测模式,用以检测复合材料与胶接结构的失粘、脱粘、分层、疏松、夹芯压皱及其他缺陷。它适用于复合材料与构件的制造、维修和使用现场。它的适用对象范围广泛,几乎覆盖了现有常用的复合材料和胶接结构。它的检测可靠性高,重复精度好。文章还讨论了组成多膜声学综合胶接检测仪的五种不同检测模式的原理,并从我们和国内外同行的大量实践经验出发,说明了综合无损检测技术的巨大发展前景。     

Change-points-based software scheduling

Software reliability literature consists of various change-point-based software reliability growth models and related release time problems. The primary assumption of the existing models is the existence of change-point before software release time only. This does not look practical as the testing team becomes more proficient in detecting the faults due to their continuous involvement in software development by the software release time. Hence the fault detection rate in the pre- and postrelease phase is not the same. To capture this change in fault detection rate in the pre- and postrelease testing phase, we propose a new software reliability modeling framework by considering two change-points during the software lifecycle; that is, there exists a change-point before release time and release time as a change-point. Further, in the last one-decade software firms have changed their strategy of stop testing the software after release and continue to test even after release to remove the number of faults to provide better user experiences. This phenomenon attracted academicians to develop theoretical as well empirical study on postrelease testing and formulation of related release time problem. In this paper, we propose a software cost model to determine optimal release and testing stop time considering under the assumption of two change-points as mentioned above. The proposed model is validated on real-life data set.     

Theoretical Analysis and Numerical Simulation of the Feasibility of Inspecting Nonferromagnetic Conductors by an MFL Testing Apparatus

ABSTRACT

It has been widely accepted that the magnetic flux leakage (MFL) testing system can be applied only to the inspection of ferromagnetic materials. The possibility of using the MFL testing apparatus to inspect nonferromagnetic metals is discussed in this article. According to Faraday’s law of induction, eddy current rises in the conductor passing through the MFL magnetizer. The perturbation of eddy current and its corresponding magnetic field caused by defects are theoretically analyzed. Then, the finite element method is carried out to verify the theoretical analyses and extract the perturbed magnetic field signals. Furthermore, the influences of specimen conductivity and moving velocity on the detection signal amplitude are also simulated. The results show that the nonferromagnetic conductors are possible to be inspected by the MFL apparatus, and higher conductivity or inspection speed will facilitate the inspection.