基于Bayes小子样二项分布单元可靠性评定的仿真方法

对于小子样二项分布单元可靠度下限评定，经典方法有很大局限性，文中介绍了Bayes方法。并在其基础上提出基于Bayes方法的Monte Carlo仿真方法，示例证明，该方法有很好的应用前途。     

Reliability assessment of embedded digital system using multi-state function

This work describes a combinatorial model for estimating the reliability of the embedded digital system by means of multi-state function. This model includes a coverage model for fault-handling techniques implemented in digital systems. The fault-handling techniques make it difficult for many types of components in digital system to be treated as binary state, good or bad. The multi-state function provides a complete analysis of multi-state systems as which the digital systems can be regarded. Through adaptation of software operational profile flow to multi-state function, the HW/SW interaction is also considered for estimation of the reliability of digital system. Using this model, we evaluate the reliability of one board controller in a digital system, Interposing Logic System (ILS), which is installed in YGN nuclear power units 3 and 4. Since the proposed model is a generalized combinatorial model, the simplification of this model becomes the conventional model that treats the system as binary state. This modeling method is particularly attractive for embedded systems in which small sized application software is implemented since it will require very laborious work for this method to be applied to systems with large software.     

Simulation study of an automated storage/retrieval system

In this paper we present a simulation study of an automated storage/retrieval system and examine a wide variety of control policies. We compare several storage location assignment policies. For the class-based storage policy, we apply a recent algorithm that enables us to evaluate the trade-off between storage space requirements and travel times. We also study a new storage location policy which combines low storage space requirements with short mean travel times. Furthermore, we study the sequencing of storage and retrieval requests whereby we focus on the trade-off between efficient travel of the S/R machines and response time performance.     

Reliability assessment for a stochastic manufacturing system with reworking actions

This article evaluates the system reliability of a manufacturing system with reworking actions, where the system reliability is an essential indicator to determine whether the manufacturing system is capable or not. Based on the path concept, we transformed the manufacturing system into a stochastic-flow network in which the capacity of each machine is stochastic (i.e., multistate) due to failure, partial failure, and maintenance. In such a manufacturing network, the input flow (raw materials/WIP; work-in-process) processed by each machine might be defective and thus the output flow (WIP/products) would be less than the input amount. To analyze the different sources processed by the manufacturing network, we decomposed the network into one general processing path and several reworking paths by a graphical technique. Subsequently, an algorithm for the manufacturing network was proposed to generate the lower boundary vector which allows sufficient products to satisfy the demand. In terms of such a vector, the system reliability can be derived easily.     

Zone merge sequencing in an automated order picking system

This paper considers the zone automated order fulfilment systems with a number of zones linked by a main conveyor. Each zone has a number of dispensers and a buffer. Each dispenser holds one type of item and dispenses the items for an order into a buffer before the items are merged to the main conveyor. Due to variability of the mix of item types and number of items for each type in successive orders, idle time or open space on the conveyor can occur if the buffers merge the items to the conveyor sequentially. The idle time prolongs the order fulfilment duration. This paper aims to provide a solution to reduce the idle time or open space by optimising the merging sequences among zones. A model is developed to find merging sequences with minimum order fulfilment time. However, the model is strongly NP-hard. A greedy heuristic-based solution approach is thus developed. Experiment performance shows that the presented solution can reduce the order fulfilment time approximately 5% with both empirical data and simulation data. Moreover, the sensitivity analysis is conducted to measure the effect of the solution under the variation of zone numbers and order structures. Although the idle time reduction can be achieved with any number of zones and order structures, it was most significant in certain range of zone numbers and appropriate order structures.     

Construction and remote calibration of an automated resistance measuring system

The calibration of resistances was being performed manually at National Institute of Standards (NIS), Egypt till now. In this paper, a fully automated system for the remote calibrations of resistances is described. This sytem is mainly used for routine calibrations for low precision calibrations. The calibration of many resistors can be performed in this system automatically through the Resistors Automatic Changer which is controlled by a LabVIEW program developed and described in the present research work. Not only these calibrations of resistances are performed automatically but are also controlled remotely via an internet connection. Some simple remote and automated resistance measurements are carried out just to confirm our new measuring system.     

An expert system based controller for an automated storage/retrieval system

Expert systems have demonstrated their ability to solve problems of a specific domain and achieve quality performance. The technology has been applied in numerous engineering areas. In this paper, an expert system based AS/RS controller, ECSSIM, is presented. The system plans a control strategy based on the long term system characteristics. However, the system alters the control strategy tactically according to the short term control needs. The system performed very well particularly at high demand levels. It also demonstrated its capability of sensing poor control strategies, and tactically compensate for the strategy selection error.     

Reliability assessment of passive isolation condenser system of AHWR using APSRA methodology

In this paper, a methodology known as APSRA (Assessment of Passive System ReliAbility) is used for evaluation of reliability of passive isolation condenser system of the Indian Advanced Heavy Water Reactor (AHWR). As per the APSRA methodology, the passive system reliability evaluation is based on the failure probability of the system to perform the design basis function. The methodology first determines the operational characteristics of the system and the failure conditions based on a predetermined failure criterion. The parameters that could degrade the system performance are identified and considered for analysis. Different modes of failure and their cause are identified. The failure surface is predicted using a best estimate code considering deviations of the operating parameters from their nominal states, which affect the isolation condenser system performance. Once the failure surface of the system is predicted, the causes of failure are examined through root diagnosis, which occur mainly due to failure of mechanical components. Reliability of the system is evaluated through a classical PSA treatment based on the failure probability of the components using generic data.     

基于故障危害度的飞机电源系统可靠性评估

基于故障危害度对飞机电源系统进行可靠性评估,首先建立可靠性评估模型,该模型考虑各故障样本对飞机电源系统供电可靠性危害度影响,将出现的故障按照对电源系统安全、性能、任务及维修等指标的影响程度进行等级分类,从故障的失效机理出发建立相应的分布模型;然后采用分布计算和二次分布等算法进行系统整体可靠性指标评估。应用该模型对飞机电源系统进行了故障统计分析,计算了飞机电源系统的可靠性指标。     

Modelling an automated storage and retrieval system using Petri nets

We investigated the feasibility of using stochastic Petri nets (SPNs) to describe the behaviours of automated storage/retrieval systems as well as to evaluate the performance of different control policies of such systems. SPNs have been studied in the past 2 decades, and have become a powerful tool in modelling concurrent and distributed systems that exhibit synchronization and contention of shared resources. It appeared that some important characteristics of AS/RS could be well modelled with SPNs. The SPN is a graph-based tool suitable for modelling systems (manufacturing, computer, biological, etc.). It can be used to model a system at different levels of abstraction. In this study, the efficiency, control rules, bay assignment, and many other performance issues associated with AS/RS have been studied in detail using SPN models. SPNs are shown to be equivalent to the stochastic processes in which embedded Markov chains can be recognized. In addition, a stochastic Petri net package, SPNP, was adopted to solve the reachability trees from which an embedded Markov chain was generated. Finally, the performance of those systems of our interest was evaluated. The unique features and flexibility of SPNs are presented. Furthermore, the SPN models for different control algorithms of an AS/RS are discussed with examples.     

Design of an automated guided vehicle-based material handling system for a flexible manufacturing system

Automated guided vehicle (AGV)-based material handling systems (MHSs), which are widely used in several flexible manufacturing system (FMS) installations, require a number of decisions to be made. These include the number of vehicles required, the track layout, traffic pattern along the AGV tracks, and solving traffic control problems. This paper addresses the key issues involved in the design and operation of AGV-based material handling systems for an FMS. The problems arising from multi-vehicle systems are analysed, and strategies for resolving them are examined using analytical and simulation models.     

Reliability assessment of smoke detectors

A preliminary analysis of smoke detector test data is reported. The data corresponds to the threshold limit test (i.e. minimum aerosol concentration for operation of the detector) carried out using the smoke detector tester developed by UKAEA, Harwell.Differences in response levels of different detector types are discussed assuming that response levels follow normal and Weibull distributions. Based on a quality control criterion a pass/fail criterion is proposed.     

Reliability assessment of locking systems

The aim of this work is to predict the failure probability of a locking system. This failure probability is assessed using complementary methods: the First-Order Reliability Method (FORM) and Second-Order Reliability Method (SORM) as approximated methods, and Monte Carlo simulations as the reference method. Both types are implemented in a specific software [Phimeca software. Software for reliability analysis developed by Phimeca Engineering S.A.] used in this study. For the Monte Carlo simulations, a response surface, based on experimental design and finite element calculations [Abaqus/Standard User’s Manuel vol. I.], is elaborated so that the relation between the random input variables and structural responses could be established. Investigations of previous reliable methods on two configurations of the locking system show the large sturdiness of the first one and enable design improvements for the second one.     

Measuring system and software reliability using an automated data collection process

The factors which affect the behaviour of the customer's computing environment, which is undergoing a revolution away from a server or timeshare centric model to a client/server or distributed model, can no longer be identified solely through using traditional methods of data collection. Digital Equipment Corporation has developed an automated data collection process, collecting on-system data logging information from customer sites that has yielded consistent, quantitative, high integrity information. This information has been used to proactively focus on direct product and process improvements. This paper describes the on-system data logging process and analysis methodology used by Digital to measure system, product and operating system reliability with examples of the application of the techniques that provide insight into the causes of failures.     

Generating clustered journal maps: an automated system for hierarchical classification

Scientometrics - Journal maps and classifications for 11,359 journals listed in the combined Journal Citation Reports 2015 of the Science and Social Sciences Citation Indexes are provided at...     

Reliability assessment of dispenser-type thermionic cathodes

An extensive analysis has been performed of life test results obtained in the long-term (15,000 h) operation of both tungsten matrix and tungsten-osmium matrix dispenser cathodes. Sensitive indications of potential life capability for these cathodes are shown to be available via systematic interpretation of temperature-limited emission characteristics over time. These characteristics follow Arrhenius law temperature dependencies, with activation energies either identical with or closely similar to those determined separately for active material dispensation from these cathodes. Optimum temperature settings are determined, for each cathode type, at which projected life is maximized. Only modestly accelerated constant stress and step-stress results yield credible reliability projections at these optimum operational temperatures. Furthermore, there remains some uncertainty concerning the application of a (time)½ dependence to all data generated in testing of the tungsten-osmium, mixed metal matrix cathodes. Nevertheless, it is demonstrated that such cathodes can have mean lifetimes of at least 12 years, and may reach 20 years of serviceable life, sustaining only minor levels of degradation.     

Optically computing the hit-miss transform for an automated cervical smear screening system

The hit-miss transform serves as a region-of-interest locator for cells from cervical smear images that show abnormal changes, which are indicative of malignancy, in their nuclei. An optical implementation of the hit-miss transform algorithm uses an analog spatial light modulator for gray-scale modulation at the filter plane of a 4f optical correlator. Gray-scale modulation at the filter plane improves correlator performance in comparison with a binary phase-only filter (BPOF) by reduction of the edge enhancement of kernels used in morphological detection of cancerous cervical cells. The hit-miss transform with a gray-scale amplitude and binary phase optical filter (GABPOF) for the hit filter and a BPOF for the miss filter shows a 47% reduction in total error versus the use of only BPOF filters to locate abnormal cells.     

Reliability as an added‐value factor in an automotive clutch system

In the present competitive scenario, companies face the challenge of developing new products in a short time period, with superior technology in relation to prior developments and reduced costs to guarantee the survival of their business. Success is directly coupled with client requirements where quality and reliability should be the highest feasible, whereas deadlines and price have to be the lowest possible. This paper discusses tools and methods applied to planning and assurance of quality, which have to be taken into account at the product conception project, which concerns the phase in which quality, reliability and the final price of a product are technically defined. A methodology is presented for this purpose, and it can be extended to any product or system with few adaptations concerning quality, reliability and cost models. The product selected for the case‐study analysis in this work is an automotive clutch. The methodology proposed for the analysis is a combination of the KANO method, target cost and value analysis with respect to the assessment of client requirement compliance levels and the determination of the choice of functions—whose relative costs are above relative needs, therefore offering optimization or elimination potential. Thus, the reliability concepts of statistical distributions and fault tree analysis are employed to locate critical components and quantify design temporary performance. To provide life tests results to the highest failure risk in the system, the planning and deployment of accelerated tests are carried out. The final goal of this paper is the reliability assessment based on critical levels for the analysis of components to be improved or optimized and, mainly, to create a methodology for the development of optimized products. Copyright © 2007 John Wiley & Sons, Ltd.