• 한국철도학회:학술대회논문집
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• 한국철도학회 2009년도 춘계학술대회 논문집
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• pp.396-405
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• 2009

열차제어 지상신호시스템에서 핵심적인 철도보안기능을 수행하는 연동장치는 철도산업의 안전성 확보 지침에 따라 높은 안전성과 신뢰성을 갖추어야만 한다. 따라서 연동장치는 높은 안전성과 신뢰성을 달성할 수 있도록 실시간 운영체제 및 그 구성 하드웨어의 랜덤 고장에 대처하기 위한 Fail-Safe형 다중 제어시스템으로 구성된다. 이러한 구성에서는 운영자 인터페이스를 포함한 다양한 장치와의 메시지 교환을 위한 인터페이스 가능을 구현하기 어려운 특성이 존재한다. 본 논문에서는 연동장치와 상위 인터페이스 설비간의 통신기능을 구현하기 위한 Dual Ethernet 네트워크 구성 및 DPST (Dual Packet Seamless Transfer) 통신 프로토콜을 제안한다. 제안된 시스템의 구성에서는 특정 네트워크 장비의 랜덤 고장이나 통신오류에 강인한 특성을 보이며 통신채널의 장애를 검출할 수 있는 기능이 추가되어 설비의 유지보수에 효과적인 정보로 활용될 수 있음을 실험적으로 검증한다. 제안된 네트워크 구성 및 운영 프로토콜을 현대제철 전용철도용 전자연동장치에 구현하고 그 성능과 특성을 유럽표준규격 EN50159의 지침을 토대로 타당성을 분석한다.

• Nuclear Engineering and Technology
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• 제52권7호
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• pp.1462-1470
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• 2020

Reliability in safety-critical systems and equipment is of vital importance, so the probabilistic safety assessment (PSA) has been widely used for many years in the nuclear industry to address reliability in a quantitative manner. As many nuclear power plants (NPPs) become digitalized, evaluating the reliability of safety-critical software has become an emerging issue. Due to a lack of available methods, in many conventional PSA models only hardware reliability is addressed with the assumption that software reliability is perfect or very high compared to hardware reliability. This study focused on developing a new method of safety-critical software reliability quantification, derived from hardware-software integrated environment testing. Since the complexity of hardware and software interaction makes the possible number of test cases for exhaustive testing well beyond a practically achievable range, an importance-oriented testing method that assures the most efficient test coverage was developed. Application to the test of an actual NPP reactor protection system demonstrated the applicability of the developed method and provided insight into complex software-based system reliability.

• 핵의학기술
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• 제14권2호
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• pp.197-202
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• 2010

목적: 각 검사실에서는 임상의 신속한 검사 결과 보고 요청에 부응하고 검사 결과의 신뢰도 및 효율성을 증가시키기 위해 자동화 장비를 많이 사용한다. 국산 자동화 장비는 기존 자동화 장비의 단점을 개선, 보완하여 폭넓은 수행능을 가진 국산 자동화 장비이다. 본 연구에서 국산 자동화 장비와 기존 자동화 장비와의 상관성 및 분석능력을 평가하여 검사실에서의 결과보고시간 단축에 대한 유용성과 신뢰성을 알아보고자 하였다. 대상 및 방법: 2009년 9월 삼성서울병원에서 갑상선 호르몬 검사(TT3, TSH, FT4)가 의뢰된 환자를 대상으로 저농도에서 고농도 검체 100개씩 국산 자동화 장비와 RIA-mat 280을 사용하여 상관성을 알아보았다. 국산 자동화 장비의 부분별 평가로 첫째, Tip부분은 정확도, 회수율, 검체 간 상호 오염도를 측정하였다. 둘째, Incubator부분은 회전수(RPM)와 회전축 원경(mm)에 따른 최적의 검사반응 조건을 알아보았다. 검체처리 속도를 분석하기 위해 특정기간의 검사결과 보고시간을 조사하였다. 결과: 국산 자동화 장비와 RIA-mat 280의 상관계수($R^2$)는 TT3 0.98, TSH 0.99, FT4 0.92로 좋은 상관관계를 보였다. Tip의 평가로 정밀도 CV 0.38 %(1번 Tip), CV 0.39 %(2번 Tip), 정확도 98.3 %(1번 Tip), 98.6 %(2번 Tip). 검체 간 상호 오염도는 0.01 %(1번 Tip), 0 %(2번 Tip)로 검체 간 상호 오염도가 거의 없었다. Incubator 조건에서 회전수(RPM)와 회전수 원경(mm) 500 RPM의 1.0 mm, 1.5 mm와 600 RPM의 1.0 mm, 1.5 mm 중 600 RPM의 1.0 mm가 최상의 조건임을 알 수 있었다. 기존의 자동화 장비에서 6회/일 시행되던 검사가 최대20회/일로 늘어남으로써 검체 접수에서 결과보고까지 소요시간이 평균 4.20시간에서 평균 2.19시간으로 약 2시간 단축되었다. 결론: 국산 자동화 장비(Gamma Pro) 사용으로 결과보고 시간이 평균 2.19시간으로, 약 2시간 단축되는 결과를 얻었다. 본 기기는 일정시간당 대량 검체 처리능력이 뛰어나고 실용성을 갖춘 효율적인 장비라고 여겨진다. 검사결과 보고 시간 단축으로 인해 응급환자의 신속한 진단과 외래환자의 진료대기시간 단축에 유용할 것이다.

• Earthquakes and Structures
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• 제14권5호
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• pp.425-436
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• 2018

The design of seismically isolated structures considering the stochastic nature of excitations, base isolators' design parameters, and superstructure properties requires robust reliability analysis methods to calculate the failure probability of the entire system. Here, by applying artificial neural networks, we proposed a robust technique to accelerate the estimation of failure probability of equipped isolated structures. A three-story isolated building with susceptible facilities is considered as the analytical model to evaluate our technique. First, we employed a sensitivity analysis method to identify the critical sources of uncertainty. Next, we calculated the probability of failure for a particular set of random variables, performing Monte Carlo simulations based on the dynamic nonlinear time-history analysis. Finally, using a set of designed neural networks as a surrogate model for the structural analysis, we assessed once again the probability of the failure. Comparing the obtained results demonstrates that the surrogate model can attain precise estimations of the probability of failure. Moreover, our proposed approach significantly increases the computational efficiency corresponding to the dynamic time-history analysis of the structure.

• 한국신뢰성학회지:신뢰성응용연구
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• 제16권4호
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• pp.272-279
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• 2016

Purpose: In order to fulfill the RAMS (Reliability Availability Maintainability and Safety) requirements in Korean railway systems, specific target metrics should be measured and met the requirements when ordering a new system. This paper presents a procedure to predict and demonstrate the availability, maintainability and safety of subway elevators, escalators and PSD (platform screen doors) systems. Methods: The system manufacturer predicts availability and maintainability with lab and field tested data. After installation, availability and maintainability are demonstrated based on the actual operational data. The data was collected from the FRACAS (Failure Report and Corrective Action System). Results: Methods and process of assessing and analyzing the availability, maintainability and safety are presented for elevating services and PSD systems. The data obtained through the actual operation of the equipment is analyzed and maintained to predict the RAMS based on the component and system level failure data acquired. Conclusion: This study presented an application using IEC 62278 and operational data which can be used in the design and development stage to achieve the RAMS target value of the subway elevators, escalators and PSD systems.

• 드라이브 ㆍ 컨트롤
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• 제16권4호
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• pp.93-100
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• 2019

Nuclear and thermal power plants must provide the turbines with an appropriate degree of high temperature and high pressure steam, to produce the optimum electricity. Additionally, in the event of system and power system failure during electrical production, the steam is immediately disabled, to protect the turbines and generators rotating at high speed. The plant thus uses a special steam control valve system for turbine control, which is opened by force of the hydraulic servo actuator and closed by a large steel spring force. In this study, the causes of failure of the turbine control valve system, a key device of the power plants, were analyzed, and the causes of failure were improved relative to reliability of the equipment.

• 대한물리의학회지
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• 제8권2호
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• pp.209-217
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• 2013

PURPOSE: The purpose of this study was to investigate the clinical availability of the pendulum test (through reliability and validity) using a NK table attached electrogoniometer for spasticity measurement in patients with brain lesions. METHODS: Thirty-one stroke and traumatic brain injury subjects participated in the study. Intraclass correlation coefficient (ICC) was used to verify the test-retest reliability of spasticity measures of the pendulum test. Pearson's product correlation coefficient was used to examine the validity of the pendulum test through the amplitude of the deep tendon reflex (DTR) test known for objective and quantitative measure of spasticity. RESULTS: In these results, the test-retest reliability was showed significantly high correlation between pendulum tests (ICCs=.95~.97, p<.01). There were significant negative correlations between the amplitude of the DTR test and all measures of spasticity of the pendulum test(r=-.77~-.85, p<.01). CONCLUSION: Thus, it is possible to use the pendulum test using a NK table as an objective measure of spasticity, rather than other expensive equipment, which is more complicated to use. Further studies are needed to explore the therapeutic effects of spasticity using a newly designed pendulum test equipment in this study.

• 대한안전경영과학회지
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• 제14권2호
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• pp.147-158
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• 2012

This paper aims to develop a new chain metrics for obtaining lean Overall Equipment Effectiveness(OEE) and present implementation strategy which considers the properties for Total Productive Maintenance(TPM) to reduce machine losses, Performance Analysis and Control(PAC) to reduce labor losses, Lean Production System(LPS) to reduce floor wastes, and Theory of Constraints(TOC) to minimize the problem of Capacity Constrained Resource(CCR). The study reviews the related literatures and reformulates the structure of machine losses, labor losses and field wastes. The research also develops the integrated productivity metrics according to time, units, reliability and maintainability. It is found that the study develops the actual productivity measure in terms of efficiency, effectiveness and standard productivity. In addition to that, it outlines and develops by using the integrated LPS and TPM, lean OEE measures such as Time Based Productivity(TBP), Unit Based Productivity(UBP), and Reliability & Maintainability Based Availability(RMBA). Implication examples are proposed to make it easier and available for practioners to understand the implementation strategies about TPM OEE, lean OEE and TOC OEE. Futhermore related to other studies, the research contributes to create a new chain productivity measures to clear the interrelationship concepts of productivity, efficiency and effectiveness. Moreover the paper develops the enhanced OEE measures by integration of TPM, PAC, LPS and TOC with the perspective of schedule, throughput, reliability, maintainability and availability.

• 대한전기학회논문지:전력기술부문A
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• 제54권11호
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• pp.548-556
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• 2005

Reliability evaluation of power distribution system is very important to both power utilities and customers. It present the probabilistic number and duration of interruption such as failure rate, SATDI, SAIFI, and CAIDI. However, it has a fatal weakness at reliability index because of accuracy of failure rate. In this paper, the Time-varying Failure Rate(TFR) of power distribution system equipment is extracted from the recorded failure data of KEPCO(Korea Electric Power Corporation) in Korea. For TFR extraction, it is used that the fault data accumulated by KEPCO during 10 years. The TFR is approximated to bathtub curve using the exponential(random failure) and Weibull(aging failure) distribution function. In addition, Kaplan-Meier estimation is applied to TFR extraction because of incomplete failure data of KEPCO. Finally, Probability plot and regression analysis is applied. It is presented that the extracted TFR is more effective and useful than Mean Failure Rate(MfR) through the comparison between TFR and MFR

• 한국품질경영학회:학술대회논문집
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• 한국품질경영학회 2006년도 춘계학술대회
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• pp.375-380
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• 2006

Recently European Council(EU) published the RoHS(restriction of the use of certain hazardous substances in electrical and electronic equipment) which is prohibit the use of Pb, Hg, Cd, $Cr^{+6}$, PBB or PBDE in the electrical and electronic equipments. So EU member States shall ensure that, from 1 July 2006, new electrical and electronic equipment put on the market does not contain 6 hazardous substances. So many kinds of projects is proceeding to ensure the reliability of Pb-free electronics in the worlds. Especially it is necessary to evaluate of Pb-free solder joints in electronics. Therefore, on this paper, we compared with solder joint strength of chip components, respectively SnPb, Pb-free solder as follows reliability test methods. We also measured the shear strength of solder joint and also compared the effects of environmental test methods. In this results, we analyzed and compared the shear strength variation as follows solder materials and reliability test conditions.