Int J Performability Eng ›› 2011, Vol. 7 ›› Issue (3): 201-.doi: 10.23940/ijpe.11.3.p201.mag

• Editorial •     Next Articles


Krishna B. Misra   


The theme of this special issue of IJPE has been chosen as Multi-state system reliability and Professor Mustapha Nourelfath of Mechanical Engineering Department, Université Laval, Canada, who is on the editorial board of this journal very kindly agreed to guest-edit this special issue. Multi-state systems reliability has received importance and attention in past couple of decades as it brings in more realistic modelling of some physical systems. For example, in case of systems such as power system, computer systems, communication systems, air conditioning systems, production systems, oil transmission pipelines etc. and systems with degraded components, the usual two-state (success and failure) modelling of system does not reflect the realistic situation, where several levels of performance and several modes of failures characterized by capacity, flow, communication or data processing speed etc., ranging from perfect functioning to complete failure, could exist. It will be over simplification of the physical phenomenon to assume a two-state model of performance for such systems. Further on, some systems are also being modeled as multi-state k-out-of-n:G systems, where multiple states are interpreted as multiple levels of capacity. Reliability or availability optimization of such multi-state systems is another area in which new formulations are being suggested in the literature.

?The difficulty in analyzing such Multi-state systems (MSS) arises from the large number of states that may have to be considered for the system since each system element can have many different states (and not just two states as in case of two-state model).

Some of the approaches for multi-state system reliability assessment have been proposed based on the (1) extension of the Boolean models to the multi-valued case, (2) stochastic processes (mainly Markov and semi-Markov) approach, (3) universal generating function approach (4) fuzzy set theory etc.

The eight papers, which have been selected among the several papers that the Guest editor received in response to his call, reflect the current thinking in the area of research in the analysis of multi-state system reliability or availability. This, of course does not reflect the complete picture of the on-going research in the area but encourages the readers to think in that direction, which has been at the back of our mind and our effort. It is hoped that the readers would be benefited by this presentation which will help generate further research on the theme of the special issue.

I would like to thank the contributors of the papers included in this issue and my sincere thanks are due to the referees who helped us in improving the presentation and maintained the timeline of this special issue.

Last but not the least; I take this opportunity to thank Professor Nourelfath for his painstaking effort in bringing out this special issue.