Fault-tree structures of override control systems

The development of a systematic fault-tree synthesis procedure for the override control systems is presented in this paper. The unique configuration of the digraph model under study is first described and then analyzed in detail. On the basis of qualitative simulation of the fault propagation patterns, the corresponding generalized fault-tree structures are then established. It can be observed clearly from the simulation results that none of the existing techniques are capable of producing the correct fault-trees. To demonstrate the correctness of our analysis, successful application of the proposed structure to furnace operation is also presented.     

Dispatching rules for scheduling in assembly jobshops - Part 2

In this part of the paper, we present the development and evaluation of dispatching rules for scheduling in jobshops manufacturing multi-level assembly jobs with the performance measures reated to tardiness. We present a new definition of 'operation due date' in the context of assembly jobs and use it in the development of dispatching rules. A simulation study is carried out to evaluate the performances of the existing and the proposed dispatching rules with respect to different measures of tardiness. We also measure their performances with respect to different measures of flowtime and staging delays. The results of the study indicate that the proposed rules perform better than the existing rules.     

Resistance varying characteristics of DC superconducting fault current limiter in MTDC system

Recent years, voltage source converter-based multi-terminal high voltage DC power transmission (MTDC) is widely developed in the world. However, it is difficult for the existing DC breaker to cut off the fault transmission line with large short-circuit fault current. Then, it would be helpful to develop DC fault current limiter for the MTDC system. In this paper, DC superconducting fault current limiter (DCSFCL) is proposed to limit fault current. In order to study the resistance-time performance of the DCSFCL under the rapid change of fault current, a simulation model of Zhoushan MTDC system with DCSFCL is established, and the current-limiting performance of the DCSFCL at different location of the grid is studied. The simulation results show that DCSFCL can effectively limit short-circuit current and improve the operation reliability of MTDC system.     

铁路货场仓储作业过程仿真与优化

为检测和分析铁路货场仓储作业系统现状,实现系统资源配置优化,提出了CIMFlow工作流概念模型与Flexsim系统仿真模型相结合的建模方法,同时提出铁路货场仓储作业系统资源配置优化计算方法,辅助实施系统优化。实验结果表明,该模型和方法能够准确反映系统实际运营状况,并在总费用最低的前提下,保证各资源利用率均达到70%左右的最优水平,从而提高铁路货场仓储作业系统的运营效率。     

Dispatching rules for scheduling in assembly jobshops - Part 1

Research on jobshop scheduling has tended to concentrate on the development of dispatching rules for jobs that are independent, i.e. single-component jobs. However, in real-life situations, many jobs involve assembly operations that require scheduling of multiple components through the jobshop where both serial and parallel operations take place. In this two-part paper, we consider the problem of scheduling in assembly jobshops, i.e. jobshops that manufacture multi-level assembly jobs. The development of new and efficient dispatching rules with a view to address various measures of performance related to flowtime and staging delay of jobs is first undertaken. A new concept, called 'operation synchronization date' is introduced and made use of in the new dispatching rules. The best existing dispatching rules and the proposed dispatching rules are relatively evaluated by an exhaustive simulation study. The results indicate that the proposed rules emerge to be superior to the existing ones for most measures of performance.     

直升机振动与噪声综合评估方法研究

为了能够对直升机振动与噪声进行综合性的研究,本文系统地建立了一种以飞行员、机上设备和环境为基础的综合评估模型,并对振动与噪声的主要影响进行分析,构建了一个三层的指标体系结构;在研究各种综合评估方法的基础上,选择层次分析法（Analytic Hierarchy Process）与模糊综合评估法（Fuzzy Comprehensive Evaluation）对构建的模型进行评估;同时应用MATLAB开发平台对提出的方法进行仿真;最后选择样例直升机进行案例分析,对提出的方法进行验证。仿真结果表明,该方法能够从定性与定量的角度综合描述直升机振动与噪声对飞行员、机上设备和环境的影响,为直升机振动与噪声的评估提供了一种新的途径,可以在直升机的研制、试验和使用等阶段进行应用和推广。     

Reliability and fault-tolerant issues of multiprocessor and multicomputer systems

This paper deals with the reliability and fault-tolerance evaluation of multiprocessor and multicomputer architectures considering the degradation of both computation and communication capabilities. Reliability and performance availability (pa) are used to characterize and evaluate the dependability of these architectures. Bandwidth availability (ba) and computation-communication availability (cca) are used to quantify thepa of multiprocessors and multicomputers, respectively. These measures are based on the system requirements for the parallel execution of a task (job) that consists of a few subtasks. We present two different dependability models for multiprocessors, namely: a bus-oriented model (bom) and a switch-oriented model (som). Thebom is an analytical model and is used to evaluate multiprocessors with crossbar and multiple-bus interconnections. Thesom uses simulation to analyze all types of multiprocessors. A simulation technique is also presented to compute the reliability andcca of various types of multicomputer networks suggested in the literature. This research was conducted when Das was with the University of Southwestern Louisiana. It was supported in part by thensf Grant No.dmc-8513041.     

Simulation of High Altitude Power-on-live Robot Based on Pro/E and ADAMS

In order to solve the existing problems that the manual operation with high risk of the electric power industry,large labor intensity and low degree of automation,combining with the existing various cl...     

Design and simulation on the publication delay control system

Based on the simulation study of the publication delay control process [Yu & al., 2005], transfer function models of delay control processes by adjusting the accepted contribution flux and the published contribution flux are identified using system identification. According to Cybernetics, the feedback control system of the publication delay is designed and control processes are simulated and analyzed when the average publication delay are regarded as the controlled object. On the basis of the relation between the average publication delay and the deposited contribution quantity, another control method is proposed that the deposited contribution quantity is regarded as the controlled object and the simulation result proves that the method is an excellent means and can help editors expediently manage their journals and control publication delays.     

前端调速型风电机组动力学建模与运行特性研究

基于先进的机械调速与伺服控制技术,提出了一种带有发电机前端无极调速器的混合传动风电机组方案,以实现变速恒频。利用集中质量与拉格朗日方法,建立该机组传动系统动力学模型。并利用动力学方程建立1.5 MW前端调速型风电机组的Simulink仿真,实现对机组调速精度、功率消耗、电流谐波与低电压穿越能力等运行特性的深入研究。结果表明:在不同的风速条件下,所提机组不仅可以在调速功率消耗较小的情况下输出恒频电能(占比小于输出功率的15.25%),还可以有效抑制电流谐波污染,改善机组低电压穿越能力。理论分析与仿真研究验证了该机组的实用性和优越性。     

新建隧道上跨既有隧道的爆破振动分析

为保证既有隧道的安全运营,开展了新建隧道上跨既有隧道爆破振动的影响分析研究。在距离掌子面100m处的交叉段区域内对新建隧道进行爆破振动监测。根据实测数据,运用萨道夫斯基公式回归分析新鼓山隧道质点峰值振动速度,并根据公式推算出单段最大药量。通过数值模拟软件ANSYS/LYS-DYNA分析爆破振动对既有隧道产生的影响,并且对既有隧道进行振动监测,将模拟结果与实测结果进行比较。结果表明,模拟结果接近实测结果,可为类似工程提供参考。     

The effects of strength models in numerical study of metal plate destruction by contact explosive charge

Based on a complete mathematical model, the authors set up a problem of metal plate destruction by contacting explosive charge in highly nonlinear dynamic software AUTODYN and solved in two cases using the Johnson–Cook and von Mises strength models. The numerical simulation results were compared with the experimental results and showed a good fit of numerical calculations versus experiments by using the von Mises strength model. The study also shows that the Johnson–Cook strength model, if applied unreasonably, will lead to large errors, which would help to avoid mistakes in the future high speed impact study.     

基于 JACK的老年人下肢屈伸康复系统绩效仿真分析

通过人机工效仿真测评,得到老年人下肢康复行为的人机工程设计数据,为康复训练产品设计的优化提供参数化支撑和方向性指导。根据现有康复产品,建立康复虚拟环境,创建虚拟数字老年人体模型,定义老年身体形态和生理参数,将虚拟数字老年人体模型与虚拟康复环境结合,输入康复任务,分析老人康复操作任务的流程,对老人康复行为进行人机工效虚拟仿真。通过对老年人下肢康复系统的人机工效虚拟仿真测评,得到大量仿真数据,从而发现系统存在的不足和潜在的风险,为改进其设计提供依据。通过仿真分析有助于康复产品真正做到安全、健康、有效,从本质上提升康复训练系统的可用性。     

A MODEL FOR PREDICTING THE RELIABILITY OF A MAN–MACHINE SYSTEM

A continuous-time Markov chain model, which considers the concept of human errors and recovery factors, is proposed for analysing the reliability of a man–machine system. This model can be applied to industrial systems such as the nuclear power plant, the NC machine cell, and the chemical plant. In order to show the application of the model and to validate its result, a computer animation program was written to simulate the control operation of a system. Some simulation experiments were conducted and the data were fed into the reliability model. The results show that the proposed model can perform well in comparison to the simulation output. In addition, some observations from the simulation experiments can also be applied to the design of a control system. © 1997 John Wiley & Sons, Ltd.     

Semi-Markov modeling of dependability of VoIP network in the presence of resource degradation and security attacks

Nowadays VoIP has become an evolutionary technology in telecommunications. Hence it is very important to study and enhance its dependability attributes. In this paper, an analytical dependability model for VoIP is proposed. The study is focused on analyzing the combined effects of resource degradation and security breaches on the Quality of Service (QoS) of VoIP, to enhance its overall dependability. As a preventive maintenance policy to prevent or postpone software failures which cause resource degradation, software rejuvenation is adopted. The dependability model is analyzed using semi-Markov process which captures the effects of non-Markovian nature of the time spent at various states of the system. The steady-state as well as the time-dependent analysis of the dependability model is presented. The steady-state results are obtained analytically, whereas the time-dependent results are obtained from simulation. Also, the analytical model is validated via simulation. The model analysis using a numerical example indicates the feasibility of our approach. Various dependability attributes such as availability, reliability and confidentiality are also obtained. A comparative study is also done between our proposed model and the existing models.     

Application of an effective method in predicting breakthrough curves of fixed-bed adsorption onto resin adsorbent

Removal of many organic pollutants including phenolic compounds from industrial wastewater can always be achieved by fixed-bed adsorption onto the polymeric resin adsorbent, and the relevant breakthrough curves would provide much valuable information to help to design a fixed-bed adsorption process in field application. In the present study, a model developed based on the constant-pattern wave approach theory and the Freundlich model was adopted to describe the breakthrough curves of phenol and p-nitrophenol adsorption onto a macroreticular resin adsorbent NDA-100 from aqueous solution. Column experiments were performed at different conditions to verify the model and the results proved that the model would describe the breakthrough curves well. Effect of the operation parameters on breakthrough curves was also discussed to get helpful information in choosing the adsorption process.     

Numerical study on the effect of prestrain history on ductile fracture resistance by using the complete Gurson model

During installation and operation, pipeline steels may suffer from plastic pre-deformation (prestrain) due to accidental loading, cold bending or ground movement. The plastic prestrain history not only modifies steels’ yield and flow properties but also influences their fracture performance. This paper focuses on the effect of plastic prestrain history on ductile fracture resistance. Single edge notched tension (SENT) specimens have been selected for the numerical study and the crack is assumed to exist before a prestrain history was applied. The complete Gurson model has been applied to simulate the ductile fracture behaviour. The results show that prestrain history can reduce the fracture resistance significantly and neither the history-independent resistance model nor material-memory resistance model existing in the literature can be used to describe the prestrain history effect. Based on the numerical results an approximate history-dependent resistance model is proposed. The results also suggest that it is important to take the prestrain effect into consideration in future structural integrity assessment procedure for pipelines.     

Design of high performance badminton shuttlecocks: virtual and rapid prototyping approach

In this paper, a framework utilising virtual and rapid prototyping to aid design of a shuttlecock skirt was proposed and implemented. A standard template for flow simulation on ANSYS® CFX was developed to predict the aerodynamic performance of the virtual prototypes, with focus on reduced simulation time and complexity. This forms the basis of the computer aided design model – computational fluid dynamics – performance evaluation loop in the proposed framework. Steady state flow simulation was conducted for three simple computer aided design models of shuttlecocks, with different gap dimensions on the skirt. Wind tunnel drag study of the models reproduced through rapid prototyping validated the simulation result. The proposed methodology can also be applied to the existing design process for integration of virtual and rapid prototyping to reduce the burden of design iteration.     

追踪算法在纳米晶粒薄膜散射研究中的应用

本文通过光线追踪算法结合基于麦克斯韦方程解的蒙特卡洛方法,模拟了光在梯度折射率指数硅/非晶硅(C-Si/a-Si)复合薄膜中的传播情况.文中将梯度折射率指数薄膜考虑成多层均匀折射率薄膜的叠加,每一层的折射率由该层所在位置决定.通过对透射、反射光子在梯度折射率指数薄膜中运动的统计研究,讨论梯度折射率指数薄膜的减反射性能.模拟结果获得了薄膜中粒子的浓度、粒子直径大小以及折射率梯度变化对薄膜反射率的影响规律,这有助于低反射率薄膜的设计,以期解决目前较为引人关注的镀膜玻璃光污染问题.     

Multi‐modal parameter identification by automata approach

Abstract

In this paper, we consider the multi‐modal function optimization problem. An automata model with improved learning schemes is proposed to solve the global optimization problem. Theoretically, we prove that the automaton converges to the global optimum with a probability arbitrarily close to 1. The numerical simulation results show that the automata approach is better than both the well‐known gradient approach and the simulated annealing method. The simulation results also show that our automata model converges faster than the other existing models in the literature.