• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.12
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• pp.1193-1200
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• 2008

The procedure of design for reliability which consists of reliability analysis and Failure Modes and Effects Analysis(FMEA) is established and reliability assesment is performed for the nano-satellite air-launching rocket, Mirinae II. By means of using the reliability analysis result, the feasibility to insert the Mirinae II to the target orbit for given mission time under operating environment is assessed. During the reliability analysis process, the system is categorized by Work Breakdown Structure(WBS), and reliability structure is defined by both Reliability Block Diagram(RBD) and schematics of the system. FMEA is used to determine the risk priority number of components and parts. The target reliability is satisfied by changing the design of components and parts with high-risk, hence the design for reliability to put the satellite in to the target orbit safely has been performed.

• Journal of the Korean Society for Railway
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• v.18 no.3
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• pp.186-193
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• 2015

In this paper, a reliability growth analysis for a next-generation high-speed train was conducted. First, the high-speed train was decomposed into 6 sub-systems and main equipment of the high-speed train was derived from functional diagrams. Next, failure rates were calculated for each sub-system from the failure data obtained during commissioning tests. Then, reliability growth analysis was conducted for the high-speed train using the Duane model. The results show that activities to increase reliability were carried out throughout the test runs from the reliability growth results.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.24 no.4
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• pp.26-34
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• 2016

In this study, reliability prediction of the ignition system of hybrid rocket is performed. The FMECA is preceded to the reliability prediction. To this end, the ignition system is divided into 5 components and 19 potential failure modes. The failure cause and effects are identified and criticality analysis is carried out for each failure mode, in which the criticality number is estimated using the failure rate databases. Among the numbers, the failure modes and components with higher criticality and severity are chosen and allocated with higher weighting factor. The reliability predictions are performed using the failure rate databases, from which the current ignition system is found to satisfy the target reliability.

• Journal of Wind Energy
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• v.9 no.4
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• pp.5-8
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• 2018

Optimum performance and reliable operation of wind turbines and/or wind farms are crucial parameters for stakeholders such as OEMs, operators, owners and investors. The efficiency and life time of wind power heavily depends on operation and maintenance efforts. Every manufacturer or owner wants to have wind turbines with high reliability, which can be defined as the probability that a wind turbine will perform its designed function for a certain period of time under stated conditions. In this regard, IEC WG26 is now developing a technical specification defining information categories from which reliability metrics can be identified and reported.

• Review of KIISC
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• v.30 no.4
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• pp.61-67
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• 2020

블록체인을 포함하는 분산원장기술은 신뢰할 수 없는 네트워크 상에서 공동으로 거래 정보를 검증하고 기록, 보관함으로써 원장의 무결성과 신뢰성을 제공하고 있다. 이러한 분산원장기술을 이용한 제반 응용시스템이 실세계에서 적용되고 확산되기 위해서는 거버넌스 체계가 구축되어야 한다. 일반적으로 거버넌스란 특정 조직내에서의 지시와 통제활동이라고 할 수 있는데, 분산원장시스템의 경우, 다양한 조직 또는 시스템을 포함하고 있으며 거버넌스 체계도 분산 또는 탈중앙화된 형태로 존재하므로 기존의 조직 거버넌스 체계와 다른 특성과 한계를 가지고 있다. 본 연구에서는 ISO TC 307에서 진행하고 있는 분산원장시스템 거버넌스 표준화 활동을 소개하고 향후 전망과 대응방안을 검토한다.

• Proceedings of the Korea Information Processing Society Conference
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• 2014.11a
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• pp.30-32
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• 2014

최근 낸드 플래시 메모리는 임베디드 저장 장치로 많이 사용되고 있다. 비휘발성인 플래시 메모리는 기존의 하드디스크와 달리 저 전력, 좋은 내충격성 및 집적도 등 많은 장점이 있지만 데이터 업데이트 시 덮어쓰기가 안 되어 쓰기 연산 전 해당 블록을 지우는 작업이 선 진행되어야 하며 이로 인해 부분 페이지 업데이트가 자주 일어난다. 이런 플래시메모리와 더불어 최근 차세대 메모리연구가 많이 진행 중인데, 이 중에서 PCM 이라는 메모리는 비휘발성으로 정전 시 데이터가 날라 가버리는 DRAM에 반해 전원이 공급 안 되더라도 데이터가 보존되는 특성이 있다. 하지만 PCM 역시 플래시 메모리와 마찬가지로 블록 당 쓰기연산 작업이 제한되어 있어서 근래에 DRAM과 같이 사용하는 하이브리드 구조를 채택하여 많은 연구가 진행되고 있다. 따라서 본 논문에서는 플래시 메모리의 문제점을 해결함으로서 수명을 연장시키고 정 전시 데이터가 보존되지 않는 DRAM의 단점을 하이브리드 메모리를 기반으로하여 데이터의 신뢰성을 높이는 FTL알고리즘을 제안한다.

• Journal of the Korean Society for Railway
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• v.7 no.4
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• pp.356-359
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• 2004

In this paper, as the first step to assess and enhance the reliability of Korea High Speed Train, auxiliary power system is selected and reliability analysis is carried out. The auxiliary power system is classified into subsystems and functional analysis is conducted. Reliability block diagrams are drawn and reliability parametric analysis is performed. Analysis results show that the reliability of auxiliary power system depends on critical items. To grow the system reliability, activities should be concentrated on improvement of critical items.

• Journal of the Korean Society for Railway
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• v.8 no.5
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• pp.434-438
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• 2005

In this paper, as the first step to assess and enhance the reliability of Korea High Speed Train, an electric traction system is selected and reliability analysis is carried out. The electric traction system is classified into subsystems and functional block diagrams and reliability block diagrams are drawn. Expressions for evaluating the reliability are derived and Mean Kilometer Between Service Failure is calculated using the trial track test results. The calculation results show reliability growth of the proposed system.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.15 no.1
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• pp.21-32
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• 2003

In this study, the reliability design method developed by Hanzawa et al. in 1996 for calculation of the expected damage to armor blocks of a horizontally composite breakwater is extended to take into account the variability in wave direction such as directional spreading of waves, obliquity of the design principal wave direction from the shore-normal direction, and its variation about the design value. To calculate the transformation of random directional waves. the model developed by Kweon et al. in 1997 is used instead of Goda's model, which was developed in 1975 for unidirectional random waves normally incident to a straight coast with parallel depth contours and has been used by Hanzawa et al. It was found that the variability in wave direction had great influence on the computed expected damage to armor blocks. The previous design, which disregarded wave directionality, could either overestimate or underestimate the expected damage by a factor of two depending on water depth and seabed slope, if the assumption of the present study that the stability formula for breakwater armor blocks proposed for normal incidence can be used for obliquely incident waves is valid.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.3
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• pp.291-297
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• 2014

Due to the rapid increase in demand for transportation of human and freight in modern railway systems, the CBTC system has been proposed, which is the solution for improvement of the line capacity that has been limited by the conventional track circuit based train control system. In the CBTC system, higher reliability of the communication system should be guaranteed for the safety of passengers and trains. However, due to the inherent characteristics of the wireless channel environment, performance degradations are inevitable. The diversity techniques can increase the reliability of data transmission using multiple antennas. In this paper, we investigate the performance of the STBC in the railway channel environment. Rician fading model is used for the viaduct scenarios which take important roles in the railway system. Also, considered is the Doppler effect which is an important factor in the mobile communication system. Simulations are performed to analyze the performance of the STBC in various channel environments. Results show that the performance degradation due to the phase error in viaduct scenarios is independent of the diversity order but is affected by the constellation of the modulation.