In an optical fiber ring topology network such as FDDI (Fiber Distributed Data Interface) rings and SONET (Synchronous Optical Network) rings, the number of consecutively bypassed failed stations is limited by the optical power loss constraint. In recent years, this situation was represented as a consecutive k-out-of-n:F system and the two-terminal reliability was presented in the literature, but K-terminal reliability has not been presented. In this paper, we obtain K-terminal reliability expressions for dual-counter rotating networks (DR's) that use both self-heal and station-bypass switches in which all components (stations, links and bypass switches) can fail. The results are useful in evaluating the reliabilities of FDDI ring networks parametrically and making reliability comparisons. This method can be used to obtain a closed-form reliability expression in a more general ring-network such as 'ring of trees. '

A new approach to the problem of optimal software testing time is described. Most models implicitly assume the testing is terminated at the end of a prescribed period of time without user's approval. It means the release time and the in-service reliability are determined unilaterally by the developer. If software developer uses and maintains it, the assumption is appropriate. But, it may be inappropriate, if a software requiring more stringent reliability is developed by second party on a contract basis. In this case, the time of release is usually determined with the user's approval. To overcome the weaknesses of the assumption, a two stage testing with failure-free release policy is proposed. A software, after being tested by the developer for some time (in-house testing), is transferred to acceptance testing performed jointly with the user. During the acceptance testing, it is released when τ units of time specified by user is observed to be failure-free for the first time. The policy may be attractive to a user because he can determine the time of release, and extend the testing time by increasing τ. A software cost model for the policy is developed. For the software developer, an optimal in-house testing time minimizing software cost, and various quantities of interests, such as expected periods of acceptance testing, are derived based on the Jelinski-Moranda software reliability model. Finally, numerical examples are shown to illustrate the results.

A novel design for temperature-compensated complementary metal-oxide semiconductor (CMOS) voltage reference sources by using the 1st order voltage reference taking into account the electrical property of the conventional current generator was proposed to minimize a temperature coefficient. A temperature coefficient of the proposed voltage reference source was estimated by using the current generator, which operated at smaller or larger temperature in comparison with the optimized operating temperature. The temperature coefficient at temperature range between -40 and 125, obtained from the simulated data by using hynix 0.35 µm CMOS technology, was 3.33 ppm/. The simulated results indicate that the proposed temperature-compensated CMOS voltage reference sources by using the 1st order voltage reference taking into account the electrical properties of the conventional current generator can be used to decrease the temperature coefficient.