[in Japanese]

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[in Japanese]

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Micro electro mechanical system (MEMS) is notable as a technology of the next generation having a potential to make great change in our society. Due to miniaturi zation and reduction of mechanical joints in MEMS, its resistivity to vibration and mech anical shock remarkably increases. However, new types of problems based on phenomena which are proper to micro meter scale have appeared. The most typical problem is stiction of a movable part in a device with its counter part after a contact between them. Stiction occurs by formation of liquid bridge at a contacting part due to attachment of washing used in MEMS fabrication process and capillary condensation of water vapor from air. Stiction can be sufficiently prevented by improvements of fabrication process, increasing of hydrophobicity of contacting parts and decreasing of contact area between the movable and counter parts.

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Recently in the literature [8] we have proposed fairly good methods of estimating especially the scale parameter of the Weibull distribution from right censored type II data, whereas in the present paper we shall study the same kind of problems and compare 12×5+8=68 kinds of the results of |BIAS| and MSE yielded by the combination of the eight methods of estimation and the five plus three data-types of unknown data predictions through performing N=20000 trials of simulation for each of the sample sizes n=5,7,10,15,20 and for more than 4 observed data. In most cases of the primal stage of our simulation with sample sizes n=5,7,10,15 and censored observations considered here, the estimator MPM defined in Sec.2.5 may be recommended, while in many cases of the stage of the size n=20, LSE in Sec.2.2 may be proposed, as the most desirable estimator among many candidates in each of the respective cases. However, if MSE/m^2 of the estimator obtained in the stage is not small, the reader may proceed to the second stage to use our EMI (Empirical Method of Improvement) shown in Sec.2.8 and Appendix.

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