• Journal of Korean Tunnelling and Underground Space Association
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• v.24 no.6
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• pp.451-464
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• 2022

The high-level nuclear waste repository is a deep geological disposal system exposed to complex environmental conditions such as high temperature, radiation, and ground-water due to handling spent nuclear fuel. Continuous exposure can lead to cracking and deterioration of the structure over time. On the other hand, the high-level nuclear waste repository requires an ultra-long life expectancy. Thus long-term structural health monitoring is essential. Various sensors such as an accelerometer, earth pressure gauge, and displacement meter can be used to monitor the health of a structure, and a piezoelectric sensor is generally used. Therefore, it is necessary to develop a highly durable sensor based on the durability assessment of the piezoelectric sensor. This study designed an accelerated life test for durability assessment and life prediction of the piezoelectric sensor. Based on the literature review, the number of accelerated stress levels for a single stress factor, and the number of samples for each level were selected. The failure mode and mechanism of the piezoelectric sensor that can occur in the environmental conditions of the high-level waste repository were analyzed. In addition, two methods were proposed to investigate the maximum harsh condition for the temperature stress factor. The reliable operating limit of the piezoelectric sensor was derived, and a reasonable accelerated stress level was set for the accelerated life test. The suggested methods contain economical and practical ideas and can be widely used in designing accelerated life tests of piezoelectric sensors.

• The Korean Journal of Archival Studies
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• no.46
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• pp.153-187
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• 2015

This study aims to discuss issues about non-existent information of the information disclosure system and to provide alternative strategies for the issues. For the theoretical discussion it reviews the definitions and standards of non-existent information and analyzes legal aspects and statistical changes of non-existent information. Furthemore, in order to discuss a current status and problems of non-existent information at the central administrative agencies, it analyzes the cases of the non-existent information notification. According to analysis results, non-existent information status of the surveyed institutions is a total of 4,421 cases for three years and it shows the continuous increasing trend year after year. The number of institutions that have the number of non-existent information equal to the number of nondisclosures or over it reached about 40%. It means excluding non-existent information from the reasons of nondisclosure influenced disclose rates and nondisclosure rates of many agencies. In the type analysis of the non-existent information reasons, the most main reason, the case of not producing or receiving the requested information by public institutions takes over 75% among the whole reasons. The next reason is the case of collecting or processing information takes over 7-10%. This study found the operational issues, as analyzing notifications of non-existent information. The operational issues are 1) the incomplete explanation of non-existent information, 2) the unclear scope of the collection and processing, 3) the problem of the transfer processing, and 4) the problem of recording management. Therefore, this study suggested some improvements of the perspective and the technical and procedural aspects. First, information disclosure issues including non-existent information are to be understood as an extension of records management. Second, disclosure service should improve overall based on advanced understanding. Third, the management procedures of non-existent information should be improved. Fourth, specific guidelines for handling non-existent information should be developed.