Structures of systems with exponential life and HNBUE components

Structures of systems with exponential life and HNBUE (harmonic new better than used in expectation) components are studied. If a monotonic system with independent HNBUE components has exponential life then it is essentially a series system with exponential components. Thus the surmise of Ahmed and Alzaid (1988) is correct. Further, without the assumption of independence, the author derives a similar result for parallel systems with HNBUE components.<
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