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Editorial January 2012

Volume 8, Number 1, January 2012



This is the first issue of the eighth year of publication of International Journal of Performability Engineering. As usual, we bring to our readers new papers and ideas in this issue. These papers represent to the frontier areas of performability engineering and are widely spread in their theme and range of applications. Starting with the problem of attack and defence of systems, new models in reliability engineering, use of fuzzy similarity approach for fault diagnosis and failure mode identification, Intuitionistic fuzzy methodology for software optimization, use of Bayesian Networks for maintenance strategies applied to safety of metro rails, replacement policies for combining additive and independent damages, and lastly application of Demster-Shafer’s theory to the DGA on power transformer. All this packed in an issue of 110 pages. We believe, this should generate enough interest in International Journal of Performability Engineering. We will continue this year to bring to our readers all that is best in the area.

The first two papers in this issue relate to an important area of defence and attack of systems (particularly our concern here would be in engineering systems), which has grown rapidly after 9/11 event. Papers that have appeared so far, can be broadly categorized based on system structure, defence measures, and attack tactics and circumstances. In fact looking to the importance and an exponential growth of literature, we intend to publish in this journal a state-of-the-art paper outling the current status of the research in this area for the benefit of our readers.

The authors of these two papers have contributed considerably to this subject. In the first paper, Optimizing Structure of Parallel Homogeneous Systems under Attack, the two authors suggest an algorithm to determine the optimal system structure under uncertain contest intensity with the assumptions that the defender determines the system structure based on the type and the number of elements in the system and the defender distributes its limited resource between purchasing the elements and protecting them from outside attacks. The attacker chooses the number of elements to attack and distributes its limited resource evenly among all the attacked elements.

In the second paper, K-Round Duel with Uneven Resource Distribution, the two authors consider the problem of optimal resource distribution between offense and defense and among different rounds in a K-round duel. In each round of the duel, two actors exchange attacks. Each actor allocates resources into attacking the counterpart and into defending itself against the counterpart's attack with the basic assumption that the offense resources are expendable (missiles), whereas the defense resources are not expendable (bunkers). The game ends when at least one target is destroyed or after K rounds.

In the third paper, The Evolution and History of Reliability Engineering: Rise of Mechanistic Reliability Modelling, the authors trace the transformations that the reliability engineering discipline has undergone since World War II and discuss the emergence of mechanistic-based reliability modeling approaches in reliability engineering in recent years and emphasize the fact that reliability approaches of now are becoming more and more realistic. The authors present chronologically the developments that have taken place in reliability engineering during past several decades. The paper presents a good review of developments in reliability modelling techniques. The authors claim that the physics-based (or mechanistic-based) reliability models have proven to be the most useful and appropriate reliability models of the components.

The fourth paper, Fault Diagnosis and Failure Mode Estimation by a Data-Driven Fuzzy Similarity Approach, presents a data-driven, fuzzy similarity approach for available Recovery Time (RT) estimation, Fault Diagnosis (FD) and Failure Mode (FM) identification,  which is

supposed to be a useful computerized support tool to be embedded in an operator support system for emergency accident management. The approach is illustrated through number of fault scenarios in the analysis of Lead Bismuth Eutectic eXperimental Accelerator Driven System (LBE-XADS).

The fifth paper, An Intuitionistic Fuzzy Methodology for Component-Based Software Reliability Optimization, a new technique that is gaining popularity in reliability is described. We have already published a paper in this area in our January 2011 issue of IJPE. The present paper presents a software reliability estimation methodology based on user profile, and optimal decision related to cost-reliability models in classical and intuitionistic fuzzy environments availability of railway infrastructure through diagnostics and preventive maintenance is discussed. The authors have presented a Petri net based modeling method for Monte Carlo simulation and validated it with a case study on French high speed railway line.

The sixth paper, Optimal Metro-Rail Maintenance Strategy using Multi-Nets Modeling, describes a generic decision support tool VirMaLab, developed by the authors to evaluate complex systems maintenance strategies, is introduced. In this paper an original maintenance strategy modeling is introduced, which is dedicated for the prevention and detection of broken rails, in a context of renewal of the signaling and train control systems for Paris steel-wheel metro lines. Of recent, Baysian Networks (BN) have proved their usefulness to represent complex systems and perform reliability studies. This paper deals with a multi-nets extension of VirMaLab, as applied to the maintenance of metro rails. This, according to authors, helps achieve high-performance levels of safety and availability (which is especially critical at peak hours), the operator needs to estimate, hour by hour its ability to detect broken rails.

In the seventh paper of this issue, Replacement Models for Combining Additive Independent Damages, the authors present replacement policies for combining additive and independent damages. Systems often degrade with time and total damage accumulated within them by shocks, stress, or environment change. A unit, if subjected to shocks, always suffers some damage due to shocks. Since the total damage due to shocks is additive, a unit fails when it has exceeded a failure level. This is known as the cumulative damage. However, a system may also fail if the damage due to any given shock exceeds failure level. This is called independent damage. The authors consider age replacement policies for combining additive with independent damages, in which the unit is replaced at a planned time or when the total damage exceeds a failure level, whichever occurs first, and undergoes minimal repair when independent damage occurs. The expected costs rates have are obtained by using the techniques of cumulative processes in reliability theory. Optimal policies have been derived analytically and computed numerically. Some areas of application of this policy is indicated in the paper.

The eighth Paper, Diagnosis Decision-Making using Threshold Interpretation Rule and Expected Monetary Value, uses Dempster-Shafer’s evidence theory to account for various pieces of evidences in the Dissolved Gas Analysis (DGA) in case of power transformers., where there exists lack of information about the exact condition of power transformer whether it is in normal condition of operation or in an early stage of fault besides inability to differentiate between incipient fault condition, and major fault condition that leads to power transformer's failure. Also the authors claim that current recognition methodologies cannot identify a precise fault type for some range of DGA values. Therefore, they feel Dempster-Shafer’s (DS) theoretic approach is most suited for the fusion of DGA pieces of evidences since it can represent various types of ignorance in the knowledge sources.

In addition to the above papers, we also present reviews of three important books that are considered relevant for the benefit of our readers. It is hoped that this issue will generate considerable interest among our readership in the theme discussed.

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