• 한국통신학회논문지
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• 제21권8호
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• pp.1989-2002
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• 1996

In this paper, we describe several warm standby fault-tolerant models and their operation methods applicable to telephone switching control systems which have dual module structure and need high availability. Unavailabilities of the system implemented by four different methods for each model are computed by using the Markov state model, and then are compared for system performance evaluation. As the results ofsimulations, the warm standby model with triple processors is best in the aspect of data loss, while in most cases the warm standby model with doble processors based on no standby check method provides the highest system avaiability. Periodic changeover increases the system unavailability, but the preriodic standby check on standby module decreases the system unavailability of warm standby model with a single processor and with double processors. On the other hands, the variationas of warm standby model with a single processor and with double processors. On the other hand, the variations of data recovery time and personnel recovery rate have little effect on the system unavailtability.

• International Journal of Reliability and Applications
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• 제8권1호
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• pp.67-82
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• 2007

This paper deals with the effectiveness analysis of an engineering system, which has two units of different strengths in parallel and one unit as a cold standby unit. Failure times for all the units have negative exponential distribution whereas their repair times have general distribution. Single server caters the need for the system. The effectiveness analysis of the system is done by using regenerative point technique. The different measures of effectiveness such as mean sojourn time, mean time to system failure, availability, busy period, etc, are derived. Cost factors also taken into consideration.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2003년도 춘계학술대회 논문집
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• pp.145-150
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• 2003

The safety of staff customers and of general Public in general viewed as one of the most important requirements in the urban transit. The maintenance CALS system for car of urban transit is a part of standardization and development of urban transit system, and We have been performed the establishment of maintenance CALS system from 2001 to 2005. The RAMS for management computerization system are utilized in a variety of CALS system for user's convenience and safety in maintenance. Ever since its inception though, the urban transit has searched for ways to improve reliability, availability, maintainability and safety of the railway subsystem. In this paper, This system include RAMS(reliability, availability, maintainability and safety) of the vehicles shall be enhanced in the future.

• 한국국방경영분석학회지
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• 제27권1호
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• pp.58-72
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• 2001

This research deals with the weapon system RAM which is the reliability, availability and maintainability for weapon systems. This weapon system RAM is one of very important factors because it is related to the life cycle cost and combat readiness of weapon systems. Therefore, in this research we introduce the weapon system RAM and analyze the problems of weapon system RAM management during system life cycle including acquisition period. Finally we suggest an alternative to improve the weapon system RAM in various agencies which are the department of defense and army headquarter level, etc., in the process of defense acquisition.

• 한국콘텐츠학회:학술대회논문집
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• 한국콘텐츠학회 2008년도 춘계 종합학술대회 논문집
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• pp.529-533
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• 2008

임무컴퓨터는 항공전자시스템에서 전체 시스템을 관리하고, 특정 임무를 처리하는 중요한 역할을 수행한다. 일반적으로 단일 시스템에서 SPOF(Single Point Of Failure) 요소의 고장은 전체 시스템의 고장으로 이어질 수 있으며, 이는 서비스의 중단으로 인한 임무의 실패뿐만 아니라 조종사의 생명까지도 위협할 수 있다. 이에 본 논문에서는 SPOF 요소를 제거하기 위해 단일 시스템을 이중화하여 고장발생에 유연하게 대처하도록 설계하였다. 또한 이를 효율적으로 운영하기 위한 방안으로 리눅스 기반의 Heartbeat, Fake, DRBD(Distributed Replicated Block Device), Bonding 등의 기법을 이용하여 시스템을 관리한다.

• Nuclear Engineering and Technology
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• 제51권2호
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• pp.463-478
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• 2019

The most important non-functional requirements for dependability of any Embedded Real-Time Safety Systems are safety, availability and reliability requirements. System architecture plays the primary role in achieving these requirements. Compliance with these non-functional requirements should be ensured early in the development cycle with appropriate considerations during architectural design. In this paper, we present an application of system architecture modeling for quantitative assessment of system dependability. We use probabilistic model checker (PRISM), for dependability analysis of the DTMC model derived from system architecture model. In general, the model checking techniques do not scale well for analyzing large systems, because of prohibitively large state space. It limits the use of model checking techniques in analyzing the systems of practical interest. We propose abstraction based compositional analysis methodology to circumvent this limitation. The effectiveness of the proposed methodology has been demonstrated using the case study involving the dependability analysis of safety system of a large Pressurized Water Reactor (PWR).

• 산업공학
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• 제18권4호
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• pp.477-484
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• 2005

This paper is concerned with the life-cycle cost(LCC) of the urban transit system which was developed by KRRI and is now under test in Gyeongsan, Korea. Its reliability, availability and maintainability(RAM) were analyzed. LCC is the core part of analyzing the total cost of acquisition and ownership of a system. LCC analysis of a system is the most effective when it is applied in the it's early design phase. In this paper, we present IEC 60300-3-3(Life Cycle Costing) in detail and propose how to apply LCC in assessing the urban transit system according to RAM process. This case study demonstrates that reliability management system is very effective in reducing the operating cost of subway corporations in Korea.

• 시스템엔지니어링학술지
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• 제10권2호
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• pp.43-50
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• 2014

The Centralized Traffic Control(CTC) System of Urban Railway is an element(subsystem) of the Urban Railway system to aim safety operation and efficient management of rolling stock in accordance with a train scheduling program in train operation ways. That's why the CTC System must be developed considering systematic and safety-guaranteed methods such as RAMS(Reliability, Availability, Maintainability, and Safety) refereed to IEC standards. The CTC System is consists of rolling stock, signaling, power supply, communication, and mechanical equipment and preforms control and remote monitoring functions. The technical activities considering safety process are very important at such an early stage of development in a railway project. This paper introduces RAMS activities and an independent safety assessment by $3^{rd}$ Party focused on a safety applied to a development of the CTC system of Urban Railway and proposes the experiences as well practices.

• 한국철도학회논문집
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• 제8권3호
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• pp.286-292
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• 2005

In this paper, we introduce IEC 60300(Dependability program management) into urban transit system, and propose effective method to apply IEC 60300 to Subway Corporation. The dependability is the collective term used to describe the availability performance and its influencing factors such as reliability performance, maintainability performance and maintenance support performance. A dependability program covers all phases of a system's life cycle from planning to operation and possibly disposal, and is composed of program elements divided into tasks.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2010년도 춘계학술대회 논문집
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• pp.1904-1911
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• 2010

LRT projects pursue fully automated manless operating system with an aim to achieve a minimum availability of 99%. System performance is required to be guaranteed by verified SE procedures to meet user requirements for maintaining system availability above 99%. Configuration Management is one of the most practical SE application methods that manage various changes that may have a major influence on system performance on the process of undertaking assigned projects and find out problems in the system through future tracking systems. This paper discusses further use of Configuration Management in the areas concerned after examining the cases that apply Configuration Management, one of SE application methods, to the ongoing local LRT projects.