• Journal of Korean Society of Transportation
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• v.27 no.1
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• pp.63-71
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• 2009

The purpose of this paper is to identify unreliable routes in the view of users. After headway error ratio per route and travel time error ratio per route were calculated by using BMS data, reliability which incorporated two indicators each route was calculated through data envelopment analysis. Reliability among routes and among traffic zones was compared through the results, the needs to improve severely unreliable routes and to show passengers adjusted bus schedule information considering current reliability were suggested. As a future study, reliability evaluation framework of each route needs to be developed considering operation environment by analyzing bus card data (passengers and operation speed etc.) and pooly unreliable route should be managed strictly and reformed.

• Journal of Electrical Engineering and Technology
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• v.9 no.4
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• pp.1248-1257
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• 2014

Overhead transmission lines are crucial components in power transmission systems. Well-designed maintenance strategy for overhead lines is required for power utilities to minimize operating costs, while improving the reliability of the power system. This paper presents a maintenance priority index (MPI) of overhead lines for a reliability centered approach. Proposed maintenance strategy is composed of a state index and importance indices, taking into account a transmission condition and importance in system reliability, respectively. The state index is used to determine the condition of overhead lines. On the other hand, the proposed importance indices indicate their criticality analysis in transmission system, by using a load effect index (LEI) and failure effect index (FEI). The proposed maintenance method using the MPI has been tested on an IEEE 9-bus system, and a numerical result demonstrates that our strategy is more cost effective than traditional maintenance strategies.

• Journal of the Korean Physical Society
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• v.80
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• pp.1076-1080
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• 2022

For preventing a sneak current in the 3D cross-point array, the selection device is essentially necessary and an n-MOSFET has been used for the selection device. However, the three-terminal electrodes of n-MOSFET make to achieve a high density of a cross-point array difficult. As a solution, using a selector having two terminal electrodes has been intensively researched. We presented that the CuGeS₂/GeS₂-based super-linear-threshold-switching (SLTS) selector device with the insertion of optimal TiN liner thickness exhibited outstanding electrical characteristics and reliability. The dependency of electrical characteristics and reliability on various TiN liner thicknesses were investigated. In addition, the principles of reliability and electrical characteristics improvement were understood through the energy dispersive spectroscopy elemental mapping and line profile of Cu. The adequate amount of Cu distributed in GeS₂ resistive switching layer is a key factor to achieve excellent electrical characteristics and reliability for an ultra-high-density 3D cross-point array cell.

• Nuclear Engineering and Technology
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• v.20 no.1
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• pp.47-53
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• 1988

The objective of this study is to evaluate the reliability of the High Head Safety Injection System (HHIS) of KNU 5, 6, 7 and 8 following the removal of safety injection signal (s-signal) from the mini-flow bypass line valves of charging/safety injection pumps. The unavailability of HHSIS and the rupture probability of a charging/safety injection pump have been computed for two different cases; with s-signal on and removed. The results show that when the s-signal is removed from the mini-flow bypass line valves, the unavailability of HHSIS slightly increases while the rupture probability of a charging/safety injection pump is significantly reduced. Hence, based upon the results of this study we conclude that it is more reasonable to remove the s-signal from the mini-flow bypass line valves of KNU 5, 6, 7 and 8 in the normal plant operation. And to improve the availability of HHSIS, the modification of operational procedures and the emphasis on operator training are recommended.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.7
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• pp.2534-2540
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• 2010

In this paper we propose contents and results on installation and commissioning test for ATP on-board unit, which has propelled as one of the research projects, so called, "Reliability assessment and operation technology development for Korean-type tilting trains" in order to ensure the safety and operation efficiency of tilting trains. In KRRI, we have developed tilting trains for the speed-up of existing lines and for the passenger service improvement where the KTX is not available. And we also make progress the operation trial test at the speed of 10km with the use of ATS units, used in existing lines, for the purpose of the reliability assessment of the developed tilting trains. In MLTM, they have decided to accelerate the speed at more than 200km/h for the 7 existing lines including Jungang-line and Chungbuk-line where KTX has not operated. According to this decision, Train control system is to be changed from ATS to ATP. We should install an ATP on-board unit in tilting trains and verify the operational suitability. Therefore, we have installed and tested the same ATP on-board unit on tilting trains that used in the ATP construction project on Gyeongbu-line and Honam-line.

• Journal of the Korean Society of Clothing and Textiles
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• v.31 no.2 s.161
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• pp.206-216
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• 2007

The purpose of this study was to investigate the differences in the cosmetic purchasing behavior influenced by make-up preference images, and the orders of importance in the cosmetic store selection. The questionnaires were given to female residents in the ages between $20{\sim}45$ in Seoul and Kyung-gi province. 322 questionnaires were used for data analysis. The collected data were analyzed by using SPSS 10.0 software with various techniques such as Frequency analysis, Factor analysis, Cronbach's ${\alpha}$ reliability analysis, Paired t-test, ANOVA test and Duncan test. The results of this study were as follows: 1. After investigating how the make-up preference image influences the selection of the off-line cosmetic store, it was found out that the personal service, shopping convenience, and product composition had significant differences. 2. After investigating how the make-up preference image influences the selection of the on-line cosmetic store, it was found out that only the product composition had significant difference. 3. After studying the factors that influence the off-line cosmetic store selection, it was found that the personal service was considered most important. After studying the factors that influence the on-line cosmetic store selection, it was found that the price was considered most important.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.55 no.4
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• pp.189-198
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• 2006

In order to improve the reliability of stator windings for hydro generators, it is necessary to detect the defective point and life assessment of the high voltage windings. Especially the on-line partial discharge (PD) test provides the ability to monitor effects, such as slot discharge, internal discharge, and end-winding discharge without interrupting generators, this method has been proven the major testing technology in high voltage rotating machines nowadays. The purpose of this paper is to describe the method of the on-line PD measurement on stator windings for hydro-generator with 13 [kV] class ceramic coupler (CC), on-line PD measuring system, terminal box, and index parameters. Also, the developed PD measuring system and 13 [kV] class CC were installed Daechung-dam generator #2. It was found that this installed sensor and system had good electrical characteristics to detect PD activity during the operating condition with its detection frequency band is between several and several tens MHz.

• Transactions of Materials Processing
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• v.29 no.4
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• pp.188-193
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• 2020

Piping work of large ships or offshore plants is often done in a narrow and confined space, requiring precise bending and safety. In order to realize an accurate bending angle, it is very important to predict and correct a deformation that may be caused by elasticity in the bending process, that is, an angular deviation due to springback. Therefore, by using CAE analysis to develop a correction angle model for springback based on multiple tube bending angles and using trend line data derived from this correction angle model, at bending the tube as the diameter of the base former and the tube outer diameter change, the springback compensation angle at any angle can be obtained. In this study, the bending mechanism was analyzed to increase the bending precision, and a correction angle model was developed and a trend line was derived in consideration of springback occurring in the bending process. In order to derive a more accurate and reliable trend line, a tube tensile test was performed, and the reliability of the corrected angle trend line was verified by comparing the bending angle measurement and analysis results with a 3D scanner.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.1
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• pp.7-15
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• 2017

Ambient Adjusted line Rating(AAR) method for overhead transmission lines considering Risk Tolerance(RT) was proposed in this paper. AAR is suitable for system operators to plan their operation strategy and maintenance schedule because this can be designed as a seasonal line rating. Several candidate transmission lines are chosen to apply the proposed method in the paper. As a result, it is shown that system reliability was significantly enhanced through maximizing transfer capability, solving the system constraints.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.11
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• pp.2050-2056
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• 2008

A realization for moving object sensing and tracking system in two dimensional plane using stereo line CCDs and lighting source is presented in this paper. The system is realized that instead of processing camera images directly, two line CCD sensor and input line image is used to measure two dimensional distance by comparing the brightness on line CCDs. The algorithms are used the moving object sensing, path tracking and coordinate converting method. To ensure the effective detection of moving path, a detection algorithm to evaluate the reliability of each measured distance is developed. The realized system results are that the performance of moving object recognizing shows 5mm resolution, and enables to track a moving path of object per looms period.