The Cumulative Conformance Count (CCC) chart has been used for monitoring high yield processes with very low process fraction nonconforming. Current work has yet to provide a systematic treatment for establishing the chart particularly when the parameter is estimated. We extend the results from the recent studies by Tang and Cheong , and Yang et al. so that engineers are able to construct the CCC chart under different sampling and estimation conditions. We first outline the statistical properties of the CCC chart. We then give new insights on the behaviours of CCC chart when the parameter is estimated. We propose some procedures for constructing the CCC chart when the process fraction nonconforming is given, when it is estimated sequentially, and when it is estimated with a fixed sample size. The proposed steps are implemented using data from a high yield process which, in some degree, demonstrate the effectiveness of the scheme.
Received on December1, 2004
References: 09

For s-dependent systems, reliability models capable of reflecting the effect of failure dependence, i.e. the so called "common cause failure" are in demand, since the system reliability depends not only on the reliabilities of the individual components but also on the interactions among the component failures. Based on the attribute of system failure, the meaning of order statistics, as well as the mechanism of failure dependence, this paper developed s-dependent system reliability models by incorporating order statistics of component strength into load-strength interference model. The models simply characterize the fact that series system fails as long as the applied load exceeds the first (the minimum) order statistic of component strength, parallel system (with n i.i.d. components) fails when and only when load exceeds the nth (the maximum) order statistic of component strength, and k-out-of-n(F) system fails if load exceeds the kth order statistic of component strength. Since no assumption about s-independent failure was applied, the models are in a position to reflect the effect of failure dependence which may bring about common cause failures. To evaluate the reliability of general system comprising of non-i.i.d. components, an extended load - strength order statistics interference model was presented too.
Received on January 15, 2005
References: 13

Kijima and Sumita have proposed a stochastic model called the generalized renewal process (GRP) to describe the availability characteristics of repairable systems by introducing the notion of the virtual age of the system. Yanez et al. offer maximum likelihood estimation (MLE) approach for estimating parameters of the GRP models. Due to the complexity of the equations, a close solution is not available, and numerical solutions are proposed with limited success. This paper describes an alternative for calculating the parameters of GRP models using a Genetic Algorithm (GA) approach to solve complex MLE equations. The results using this approach confirm and extend conclusions of the Kijima and Sumita, and Yanez et al. works. Examples of applications of GA have been presented. The paper also concludes that under certain conditions, application of the minimal repair assumption provide a reasonable answer for the availability of repairable units.
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Received on February 28, 2005
References:25

This paper presents a model for deterioration and repair of a railway line. The critical failure is "broken rail". Two main failure mechanisms are considered: either shock failure, i.e. an immediate critical failure (without "warning"), or the critical failure occurs as the result of a degradation process, i.e. a degraded failure (crack) occurs first. Various types of inspection and maintenance are performed on the line. Inspection by Ultrasonic Inspection Cars (UIC) is carried out at regular intervals, and there is a probability q that the inspection shall detect a degraded failure. Additional inspection will be initiated on a segment of the line if degradation above a certain level is observed. A piece of rail which is degraded is more prone to suffer a critical failure (broken line), and when the degradation has reached a certain level, this will require immediate repair. The degradation/repair process within the fixed inspection interval is modeled as a time continuous Markov chain. Also the change of state implemented at the end of an inspection interval is modeled as a (time discrete) Markov chain. The model is based on actual inspection and failure data for a specific railway line in Norway. These data are used to estimate the parameters of the model. The given failure/maintenance model and estimation technique should generally be useful for systems that experience deterioration and are subject to imperfect inspection.
Received on September 29, 2004
References:11

Based on a system accident model where an accident occurs due to the loss of safety control actions, this paper proposes a simple method to obtain accident conditions of a complex system with interactions among human, software and hardware. For the accident to occur, two fundamental conditions are necessary: (1) a disturbance path can cause a deviation leading to the system accident, and (2) safety control actions related to the disturbance path fail to prevent or mitigate it. To obtain these failure conditions objectively, the proposed method utilizes a global system model, which clearly shows the relations between the physical behavior and safety control actions. While a formal approach using bond graphs is applied to the analysis of physical behaviour, information flow analysis is applied to safety control actions including operator actions such as monitoring and diagnosis. As long as the design assumptions and the evaluation of the safety control actions are correct, the consistency of accident conditions is guaranteed.
Received on September 29, 2004

A fault-tolerant dynamically-reconfigurable SEC-DED RAM system with a built-in Self-Testing-And-Repairing 'STAR' engine is presented and analysed. The STAR engine with a single reconfiguration unit provides on-line fault detection, correction, and repair of the memory system without destroying useful data stored in memory. The system utilizes a hardware parallel comparator array for providing rapid processing of incoming address stream without degrading the original memory access time. The flexible STAR architecture and the low hardware overhead enables utilization of the proposed approach in VLSI memory chips as well as in WSI and large memory modules. Computer analysis of the presented system show significant reliability and system life-time enhancement over conventional and SEC-DED RAMs.
Received on March 3, 2005
References: 05

Cleaner Production and Industrial Ecology are challenging new preventive concepts that can improve the environmental and economic performance of industry. In this paper, the author sketches the conditions to challenge the experienced reluctance to change routines in many dissemination projects of these concepts. Organizational learning processes are needed to go beyond limited results such as some good housekeeping practices and waste exchange links.
A dilemma for the dissemination of new concepts in general is that pilot studies never meet the full conditions that are needed. The disseminator is often restricted through resistance to change and many organisational management obstacles. The organisation that is willing to co-operate with an assessment, is often not really interested in the implementation of the results. The funds for research are bounded to the limits of the vision of the funding public or private organisations.
In this article a change process that might generate more radical approaches, is promoted. The steps of this dissemination process within and between organizations are:
1. Bringing information about a new concept for the start of a process of awareness-raising and commitment building;
2. After that, educating the concept to provide the knowledge for the assessments of the concept and strategic discussions in interaction processes with the key-actorswithin and between organizations to generate a basis for implementation;
3. Evaluating the learning processes to stimulate continuous improvement programmes;
4. The above-mentioned actions can be better embedded in organizations when asurroundings and an organizational analysis for the dissemination of the new concept is performed and the results are included in the approach.
Received on Septenber 30, 2004
References: 21