• Journal of the Korea Institute of Military Science and Technology
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• v.12 no.6
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• pp.719-726
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• 2009

A delay system in fuze for high explosive shell is an important safety device, but failure in the delay system usually causes failure of the shell. Root-cause analysis of failure in the delay system is required since failure in over 10-years stored delay system recently occurs. In this paper, failure in the delay system was reproduced experimentally to examine aged characteristics of the delay system, and the failed delay system shows the same characteristics as ones of failed delay systems in field. Based on the reproduced experiments, accelerated life testings and the data analysis of failure times of delay systems were performed to predict the storage lifetime.

• Composites Research
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• v.12 no.4
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• pp.62-70
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• 1999

It was well recognized that damages associated mainly with the aging of civil infrastructrues were one of very serious problems for assurance of safety and reliability. In recent, carbon fiber sheet(CFS) has been widely used for reinforcement and rehabitation of damaged concrete beam. However, the fundamental mechanism of load transfer and its load-resistant for carbon fiber sheet reinforced concrete are not fully understood. In this study, three point bend test has been carried out to understand the damage progress and micro-failure mechanism of CFS reinforced concretes. For these purposes, four kinds of specimens are used, that is, concrete, respectively. Acoustic Emission(AE) technique was used to evaluate the characteristics of damage progress and failure mechanism of specimens. In addititon, two-dimensional AE source location was also performed to monitor crack initiation and propagation processes for four types of these specimens.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.250-255
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• 2007

Steam generator tubes play an important role in safety because they constitute one of the primary barriers between the radioactive and non-radioactive sides of the nuclear power plant. For this reason, the integrity of the tubes is essential in minimizing the leakage possibility of radioactive water. The integrity of the tubes is evaluated based on NDE (non-destructive evaluation) inspection results. Especially ECT (eddy current test) method is usually used for detecting the flaws in steam generator tubes. However, detection capacity of the NDE is not perfect and all of the "real flaws" which actually existing in steam generator tunes is not known by NDE results. Therefore reliability of NDE system is one of the essential parts in assessing the integrity of steam generators. In this study POD (probability of detection) of ECT system for ODSCC in steam generator tubes is evaluated using multivariate logistic regression. The cracked tube specimens are made using the withdrawn steam generator tubes. Therefore the cracks are not artificial but real. Using the multivariate logistic regression method, continuous POD surfaces are evaluated from hit (detection) and miss (no detection) binary data obtained from destructive and non-destructive evaluation of the cracked tubes. Length and depth of cracks are considered in multivariate logistic regression and their effects on detection capacity are evaluated.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.23 no.1
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• pp.25-29
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• 1987

The engine room of ship is a synthetic system being composed of many machineries. Therefore, the reliability and safety of the all system of machinery is as important as each machine. In this paper, in order to reudce engine troubles while operation and to contribute in developing a high reliable marine engine the author analysed the factors of marine engine troubles by principal com-ponent analysis method. Analysed data are marine engine troubles of sea casualties from 1980 to 1985. It is found that the major part of marine engine troubles resulted from personal mistake, and also the troubles of shaft, propeller and cylinder occupied considerable proportion.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.905-910
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• 2007

The cubicle of high speed train is the equipment where the important train- operating equipments are concentrated, so it requires the higher safety and reliability than any other equipment. Recently, the power car cubicle of KTX-II is, basically similar to that of KTX-I and HSR350x in its size, but consequently, as more sophisticated ATP/ATC and other parts are added, the order company points out the problem of rising temperature in summer. Especially, the interpretation about the possibility of guaranteeing the minimum freezing performance becomes necessary, when Fan Tray is out of order. This paper presents the method of improving the freezing performance while minimizing the effect of dust, and the method of guaranteeing the present freezing performance by the best arrangement of Fan Tray, when Fan Tray is out of order. And as a method of verifying this, we would like to predict the pressure, speed of a running fluid and temperature distribution of cubicle through the flow analysis.

• Journal of Institute of Control, Robotics and Systems
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• v.4 no.4
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• pp.525-533
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• 1998

A conventional contact type brake system which uses a hydraulic system has mny Problems such as time delay response due to pressure build-up, brake pad wear due to contact movement, bulky size, and low braking performance in high speed region. As vehicle speed increases, a more powerful brake system is required to ensure vehicle safety and reliability. In this work, a contactless brake system of an eddy current type is proposed to overcome problems. Optimal torque control which minimizes a braking distance is investigated with a scaled-down model of an eddy current type brake. It is possible to realize optimal torque control when a maximum friction coefficient (or desired slip ratio) corresponding to road condition is maintained. Braking force analysis for a scaled-down model is done theoretically and experimentally compensated. To accomplish optimal torque control of an eddy current type brake system, a sliding mode control technique which is, one of the robust nonlinear control technique is developed. Robustness of the sliding mode controller is verified by investigating the braking performance when friction coefficient is varied. Simulation and experimental results will be presented to show that it has superior performance compared to the conventional method.

• Journal of the Korean Home Economics Association
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• v.49 no.10
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• pp.57-69
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• 2011

The purpose of the present study was to examine married female immigrants' life style and marriage satisfaction on the perception of preparing their old age. We also investigated how socio-demographic factors influence their Preparation for old age. For the study, -data were collected from 350 questionnaires obtained from female immigrants living in Chungcheongnam-do. Cronbach's ${\alpha}$ tests were conducted for reliability, and regressional analysis was conducted to test our hypotheses. The results of this study shows that there is evidence of relations among the sub-variables. However, we found attitudes to safety and material pursuit are not related to married female immigrants' preparations for their old age. On the other hand, the results indicate that their life style and marriage satisfaction influences their perception of preparing their old age in a positive way. Finally, sociodemographic factors such as gender, age, education, marriage status, occupation and income are shown to affect the women's perception of preparing their old age positively.

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.212-218
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• 2000

The importance and role of pre-/in-service inspection(PSI/ISI) for nuclear power plant(NPP) components are intimately related to plant design, safety, reliability, operation, etc. In this paper, for an effective and efficient management of large amounts of PSI/ISI data in NPPs, an intelligent database program(WS-IDPIN) for PSI/ISI data management of NPP was developed. WS-IDPIN program enables the prompt extraction of previously conducted PSI/ISI conditions and results so that the time-consuming data management, painstaking data processing and analysis in the past are avoided. Furthermore, development of ISI UT auto flaw evaluation and acceptance module based on ASME Code Sec. XI were presented. This module can be used for any angle beam examination from flat plate to spherical shapes as selected by the proper azimuthal angle. This program can be further developed as a unique PSI/ISI data management expert system.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.19 no.2
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• pp.146-150
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• 2007

Extreme value distributions for new deep sea wave were analyzed by using spread parameter and correlations between spread parameter and sliding distance of caisson breakwater were shown in numerical example. When spread parameter is larger than as usual, there occurred extra-ordinarily large wave height among 50 annual maximum significant waves generated by extreme value distribution. Spread parameter of new design wave is identified to be comparably larger than some foreign coastal areas and may cause large sliding displacement though deterministic safety factor for sliding is satisfied with enough margin.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.438-438
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• 2011

White light-emitting diodes (LEDs), the so-called next-generation solid-state lighting, offer benefits in terms of reliability, energy-saving, maintenance, safety, lead-free, and eco-friendly. Recently, rare-earth-doped oxynitride or nitride compounds have attracted a great deal of interest as a photoluminescent material because of their unique luminescent property, especially for white LEDs applications. Ce doped ${\beta}$-SiAlON has been studied as a wavelength conversion phosphor in white LEDs thanks to its high absorption rates, high quantum efficiency, and excellent thermal stability. Previously researches were not enough to understand the detail mechanism and characteristics of ${\beta}$-SiALON. The bandgap structures and electronic structures were not exact due to limitation of calculation methods. In this study, to elucidate the Ce doping effect on the SiAlON system, accurate band structures and electronic structure of the Ce doped ${\beta}$-SiAlON was intensively investigated using density functional theory calculations. In order to get a better description of the band gaps, MBJLDA method were used. We have found a single Ce atom site in ${\beta}$-SiAlON super cell. Furthermore, the density of state, band structure and lattice constant were intensively investigated.