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Abstract
The notion of coherent systems plays an essential role in conventional reliability theory. A system is said to be coherent if all of its components are relevant and the system reliability is improved as the component reliabilities are improved. However, in many complex systems or networks, not all the components are unconditionally relevant. As a result, in this paper we introduce the notion of variable-structure coherent systems to describe those systems that extensively exist and demonstrate essentially distinct features not observed in conventional coherent systems. A variable-structure coherent system consists of a number of substructures that are each a coherent system in conventional sense themselves. We then analyze the structural properties of variable-structure coherent systems; define the system operational profile, the system reliability, and the system structural profile. We study the system life distribution, the substructure importance, and the component importance. Finally, we deal with phase-cyclic systems in the context of variable-structure coherent systems.
Acknowledgements
The author thanks the anonymous reviewers for their helpful comments.
Notes
† This assumption is over-strong in general, however it may hold if no single identical component is contained in two substructures and all components are distinct and independent.
† However Kim & Park did not introduce or study the notion of system operational profile.
† Kim & Park discussed mission reliability. They did not introduce the notion of phase-cyclic systems.
†
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† We can say that χ1 is in an idle state, no matter it is functioning or failed, if y = j and .