• Journal of Applied Reliability
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• v.14 no.3
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• pp.191-196
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• 2014

The importance of railway safety has become increasingly significant domestically as well as internationally, as a series of high speed railway accidents and other major accidents have occurred recently. Especially for the domestic railway, the Korean Railway Safety Law has been revised recently, mandates all the domestic railway operation authorities to render the performance of RAMS and RCM. This study inspects and analyzes the current status of the sensing technology of the electric detection system to tell the status of railway facilities in the highway railway in a real time through a sensor. It also performs the reliability analysis of the electric detection system that is being progressed as a study assignment and suggests the system construction for the higher reliability.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1998.05a
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• pp.159-165
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• 1998

The RCM strategies are considered as an effective maintenance tool in nuclear power plants to allocate limited resource efficiently. In this paper, the importances of HPSI system on the CDF were analyzed with PSA model of Yonggwang units 1,2. The HPSI system was chosen because it is of one of the pilot system for the study of Yonggwang units 1,2 RCM. With the remodeling of the HPSI system, the total CDF of 16 initiating events was quantified and the importance of 74 basic events of HPSI was analyzed.

• Proceedings of the Korea Water Resources Association Conference
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• 2010.05a
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• pp.1216-1220
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• 2010

기후변화에 따른 기상변화가 집중호우 및 돌발홍수 등의 형태로 가시화 되고 있으며, IPCC 보고서(2007)는 21세기 후반까지 온도상승으로 인한 폭우 및 태풍이 점차 강력해질 것이라는 예측을 하였다. 이러한 예측의 대응으로 전 세계는 $CO_2$ 감축을 위한 노력이 진행중에 있으며, $CO_2$ 변화에 따른 미래 강수의 빈도해석을 해야한다는 주장이 제기되고 있다. 이에 본 연구는 기상청 지역기후모델(KMA-RegCM3) A1B시나리오의 강우 자료를 이용하여 Quantile-Mapping을 실시한 후 지역빈도해석을 실시하였다. 대상지역은 국내 전역에 위치한 기상청 산하 58개 관측소를 선정하였다. Hosking(1997)이 제안한 L-moment 알고리즘을 이용하여 지역빈도해석을 수행하였으며, 그 결과 A2 시나리오보다 상대적으로 $CO_2$ 배출량이 낮은 A1B시나리오 역시 모든 지역에서 확률강수량이 증가함을 알 수 있었다.

• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.425-428
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• 2019

본 연구에서는 남해 주변해역의 조석과 조류의 구조특성을 해석하기 위해 현장관측결과와 수치실험결과를 이용하였다. 남해 주변해역의 해수유동은 2003년~2008년 사이 노량수로, 대방수로, 여수수로, 창선수로, 강진만, 앵강만에서 ADCP 및 RCM 9 유속계를 사용하여 각 정점에서 1개월 정도 연속측류를 하였다. 노량수로와 대방수로에서는 ADCP를 사용하여 표층에서 저층까지 3m 간격으로 측류하였고, 여수수로, 창선수로, 강진만과 앵강만에서는 RCM-9 유속계를 사용하여 표층에서 연속 측류하였다. 노량수로 상층에서 동-서 방향의 최대 유속은 약 165~175 cm/sec, 대방수로에서는 창 낙조류 최대유속은 약 200~270 cm/sec, 여수수로에서는 약 85~96 cm/sec 정도 나타났다. 강진만의 표층에서 최대유속의 크기는 창 낙조류 비슷하게 35~46 cm/sec, 앵강만 입구 부근에서 낙 창조류 최대유속은 20~22 cm/sec으로 발생하였다. 또한, 조류수치모형실험을 수행하여 남해 주변해역의 조류분포 특성을 전반적으로 해석하였다.

• Smart Structures and Systems
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• v.11 no.5
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• pp.555-567
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• 2013

An Remote Corrosion Monitoring (RCM) system consists of an anode with low potential, the metallic structures against corrosion, an electrode to provide reference potential, and a data-acquisition system to ensure the potential difference for anticorrosion. In more detail, the data-acquisition (DAQ) system monitors the potential difference between the metallic structures and a reference electrode to identify the correct potential level against the corrosion of the infrastructures. Then, the measured data are transmitted to a central office to remotely keep track of the status of the corrosion monitoring (CM) system. To date, the RCM system is designed to achieve low power consumption, so that it can be simply powered by batteries. However, due to memory effect and the limited number of recharge cycles, it can entail the maintenance fee or sometimes cause failure to protect the metallic structures. To address this issue, the low-overhead energy harvesting circuitry for the RCM systems has designed to replenish energy storage elements (ESEs) along with redeeming the leakage of supercapacitors. Our developed energy harvester can scavenge the ambient energy from the corrosion monitoring environments and store it as useful electrical energy for powering local data-acquisition systems. In particular, this paper considers the energy harvesting from potential difference due to galvanic corrosion between a metallic infrastructure and a permanent copper/copper sulfate reference electrode. In addition, supercapacitors are adopted as an ESE to compensate for or overcome the limitations of batteries. Experimental results show that our proposed harvesting schemes significantly reduce the overhead of the charging circuitry, which enable fully charging up to a 350-F supercapacitor under the low corrosion power of 3 mW (i.e., 1 V/3 mA).

• Journal of Korean Society for Geospatial Information Science
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• v.20 no.3
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• pp.49-56
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• 2012

Performance analysis on RAIM, which is one of the techniques for monitoring integrity to ensure the reliability of GPS, was conducted in this study. RAIM is such a method which allows its user to monitor integrity in the stand-alone mode. Among the existing RAIM procedures, the representative methods including the RCM (Range Comparison Method), LSRM (Least Square Residual Method), Parity approach and WRAIM (Weighted RAIM) were evaluated, and their performance was analyzed. To validate the performance of the implemented algorithms, fault detection was tried on the clock malfunctioning event of PRN 23 occurred on January 1st, 2004. As a result, it was identified that the LSRM and the WRAIM detected all the faults happened in the event. In the case of RCM, all the states of fault were detected except for the error which occurred as a false alarm at one epoch. Furthermore, simulated biases were added for each satellite to analyze the sensitivity of each algorithm. Consequently, when biases of the 9-13 meters range were simulated for the RCM and LSRM algorithm, all the malfunctions were detected. For the WRAIM method, it could detect range biases greater than 15 meters.

• Journal of Korea Water Resources Association
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• v.49 no.8
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• pp.657-671
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• 2016

It is expected that water resources will be changed spatially and temporally due to the global climate change. The quantitative assessment of change in water availability and appropriate water resources management measures are needed for corresponding adaptation. However, there are large uncertainties in climate change impact assessment on water resources. For this reason, development of technology to evaluate the uncertainties quantitatively is required. The objectives of this study are to develop the climate change uncertainty assessment method and to apply it. The 5 RCMs (HadGEM3-RA, RegCM4, MM5, WRF, and RSM), 5 statistical post-processing methods (SPP) and 2 hydrological models (HYM) were applied for evaluation. The results of the uncertainty analysis showed that the RCM was the largest sources of uncertainty in Spring, Summer, Autumn (29.3~68.9%), the hydrological model was the largest source of uncertainty in Winter (46.5%). This method can be possible to analyze the changes in the total uncertainty according to the specific RCM, SPP, HYM model. And then it is expected to provide the method to reduce the total uncertainty.

• KSBB Journal
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• v.4 no.3
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• pp.288-292
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• 1989

Induction and culture of hairy roots from ginseng(Panax ginseng C. A. Meyer) roots discs by A. rhizogenes strain $A_4$ were studied. After 6-12 weeks infected with A. rhizogenes tumor and hairy roots emerged from the root discs. The ratio of hairy root induction on root discs was higher in 5-year old than in 3, 4, and 6-year old ginseng. On treatment with IAA, IBA, 2, 4-D and tryptophan, hairy roots formation showed a significant increase at 15-30mg/1 tryptophan treated. Subsequently, hairy roots were cultured on hormone-free RCM medium(pH 4.5, sucrose 30g/1).

• Journal of the Korea Safety Management & Science
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• v.13 no.3
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• pp.45-53
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• 2011

The research proposes seven elimination rules of redundant gates and blocks in Fault Tree Analysis (FTA) and Reliability Block Diagram (RBD). The computational complexity of cut sets and path sets is NP-hard. In order to reduce the complexity of Minimal Cut Set (MCS) and Minimal Path Set (MPS), the paper classifies generation algorithms. Moreover, the study develops six implementation steps which reflect structural importance (SI) and reliability importance (RI) from Reliability Centered Maintenance (RCM) that a priority of using the functional logic among components is to reduce (improve) the system unavailability (or availability). The proposed steps include efficient generation of state structure function by Rare Event Enumeration (REA). Effective use of importance measures, such as SI and ill measures, is presented based on the number and the size of MCS and MPS which is generated from the reference[5] of this paper. In addition, numerical examples are presented for practitioners to obtain the comprehensive understanding of six steps that is proposed in this research.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.3
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• pp.500-506
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• 2017

In 2014, ISO 55000s has been enacted and the power plant asset management is becoming a hot issue for all over the world. The asset management system is being developed as a combination of CBM(Condition Based Maintenance) and RCM(Reliability Centered Maintenance). Therefore, the research on the calculation of the failure rate which is the most basic index of RCM is actively carried out. The failure rate calculation has been going on for a long time, and the most widely used probability distribution is the Weibull distribution. In the Weibull distribution, the failure rate function is determined in three types according to the value of the shape parameter. However, the Weibull distribution has a limitation that it is difficult to apply it when the trend of failure rate changes-such as bathtub curves. In this paper, the failure rate is calculated using the mixture Weibull distribution which can appropriately express the change of the shape of the failure rate. Based on these results, we propose the necessity and validity of applying mixture Weibull distribution.