As life estimation methods for waterproof LCD used for outdoor meters, environmental accelerated life tests in high temperature, low teperature and high humidity were conducted. Besides, temperature and humidity in the outdoor meter under test were measured and conditions in actual usage were estimated in order to predict the meter life. Since the required life of outdoor meters was 10 years, 20 years of life was aimed and it is estimated that the LCD satisfy the life requirement in the field. Owing to the above test methods, an estimation method of life in the field was conducted.

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[in Japanese]

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[in Japanese]

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Abstract : In general, it is not easy to determine any maintenance policy from the actual failure data. Thus, nonparametric methods to obtain directly the optimal maintenance policy without specifying the form of failure distribution functions are useful in practice. The purpose of this article is to introduce and explain several nonparametric methods to estimate the optimal replacement time, which minimizes a relevant expected cost function, in the typical age replacement problem. Further, we compare the estimators for the optimal policy on the methods and refer to the relation between the estimators and the number of the data in terms of precision.

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[in Japanese]

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[in Japanese]

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[in Japanese]

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