• 터널과지하공간
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• 제16권6호
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• pp.451-466
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• 2006

DOM 시추코어에서 측정된 불연속면의 위치 및 방향성 자료를 이용하여 현장암반의 구조적 특성을 고려한 사면거동 해석이 가능하였다. 3차원 공간에서 설정된 절리들의 위치에 의거하여 붕락 현상이 발생된 개착사면의 추가적인 파괴양상을 예측하였으며, 개별 절리면의 붕락위해 가능성과 개착면 상에서의 trace 위치를 파악하여 세부적인 사면거동 양상을 파악하였다. 개착사면 횡단면에서 개별절리들의 파괴거동 양상과 사면체 블록형성을 대수학적으로 산출하여 사면 붕락심도를 규명하였다. 현장사면에 자동화 계측시스템을 설치하여 사면 거동에 대한 계측자료를 수집하였으며, DOM 시추공 내에 지중경사계를 설치하여 사면거동 양상을 횡단면 해석 결과와 대비시켜 분석하였다. 지중경사계를 이용하여 측정된 개착면의 표면변위 자료에 의거하여 사면 파괴시기를 예측할 수 있는 방법론을 고찰하였으며, 강우가 사면거동에 끼치는 영향성을 분석하였다.

• 디지털융복합연구
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• 제12권12호
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• pp.277-284
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• 2014

소프트웨어 고장분석을 위한 비동질적인 포아송과정에서 결함당 고장발생률이 상수이거나, 단조 증가 또는 단조 감소하는 패턴을 가질 수 있다. 본 논문에서는 결함의 기대값을 가정하는 유한고장소프트웨어 NHPP모형과 수리시점에서도 고장이 발생할 상황을 반영하는 무한고장 NHPP모형들을 비교 제시하였다. 소프트웨어 신뢰성분야에서 많이 인용되는 레일리분포를 이용한 유한고장과 무한고장 소프트웨어 신뢰성모형에 대한 비교문제를 탐색한 결과 무한고장모형이 유한고장모형보다 효율적으로 나타났다. 이러한 비교문제를 위하여 모수추정은 최우추정법을 이용하였다. 이 연구를 통하여 소프트웨어 개발자에게 소프트웨어 고장현상을 파악하는데 어느 정도 도움을 줄 수 있을 것으로 사료 된다.

• Journal of the Korean Data and Information Science Society
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• 제8권1호
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• pp.21-30
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• 1997

가속수명시험에서 강한충격수준에서 부품들의 고장시간이 관측되고 가속화된 고장시간을 토대로 정상충격수준에서 부품들의 성능을 조사한다. 본 논문은 지수수명분포에서 중도절단된 가속수명자료를 이용하여 고장률의 사전분포의 평균을 알 때, 정상조건하에서 하나의 미래 관찰치의 예측문제를 사전분포의 모수에 대하여 적률추정량을 이용하는 경험적 베이즈 접근방법을 적용시켜 경험적 베이즈 예측분포와 예측구간에 대하여 연구하였다.

• 품질경영학회지
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• 제41권1호
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• pp.135-148
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• 2013

Purpose: This paper presents a method to evaluate the stockpile reliability of propelling charge for performance and storage safety with storage time. Methods: We consider a performance failure level is the amount of muzzle velocity drop which is the maximum allowed standard deviation multiplied by 6. The lifetime for performance is estimated by non-linear regression analysis. The state failure level is assumed that the content of stabilizer is below 0.2%. Because the degradation of stabilizer with storage time has both distribution of state and distribution of lifetime, it must be evaluated by stochastic process method such as gamma process. Results: It is estimated that the lifetime for performance is 59 years. The state distribution at each storage time can be shown from probability density function of degradation. It is estimated that the average lifetime as $B_{50}$ life is 33 years from cumulative failure distribution function curve. Conclusion: The lifetime for storage safety is shorter than for performance and we must consider both the lifetime for storage safety and the lifetime performance because of variation of degradation rate.

• International Journal of Reliability and Applications
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• 제7권2호
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• pp.111-125
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• 2006

This paper introduces different vectors of the reliability equivalence factors of a series system consists of n independent and nonidentical components. The failure rates of the system components are assumed to be constant. The reliability function and mean time to failure are used as performances to derive the reliability equivalences of the system. The results presented here generalize those available in the literatures. Numerical study is given to explain how one can utilize the theoretical results obtained.

• 한국신뢰성학회지:신뢰성응용연구
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• 제16권2호
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• pp.162-170
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• 2016

Purpose: The purpose of this study was to analyze the failure modes of an auto transfer switch (ATS), determine the most common failure mechanisms, and iterate the design to improve reliability. Methods: We carried out failure mode and effect analysis (FMEA) to determine the failure modes and mechanisms. We identified the parts or modules that required improvement via two-stage quality function deployment based on FMEA, and improvements to reliability were monitored using the Gomperz growth model. Results: The main failure modes of the ATS were damage to, and deformation of, the stator / movable element due to repetitive movements. Five iterations of design modification were carried out, and the mean time to failure (MTTF) increased to 14,539 cycles, corresponding to 85% of the target MTTF. The Gompertz growth model indicates that the 10th iteration of design modification is expected to achieve the target MTTF. Conclusion: We improved the reliability of mechanical parts via failure mode analysis, and characterized the iterative improvements in the MTTF using the Gompertz growth model.

• 한국정보처리학회논문지
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• 제3권7호
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• pp.1917-1923
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• 1996

대량의 데이터를 저장하는 시스템은 다중디스크 시스템이 필수적이다. 그러나 디스 크의 갯수가 늘어나면 디스크시스템의 신뢰성이 떨어진다. 디스크시스템을 구성하는 디스크 중 하나의 디스크가 고장났을 경우에는 정상 동작하지만, 두 개이상의 디스 크가 고장일 경우에는 저장된 데이타를 잃게되는 디스크시스템을 고려하였다. 또한 각 디스크의 수명은 서로 다른 매개변수를 갖는 지수분포를 따르며, 수리시간은 일반 적인 확률분포를 갖는다고 가정한다. 이 가정을 바탕으로 하여 주어진 디스크시스템의 신뢰성을 MTTF(Mean Time To Failure)로서 분석 하였다. 그리고 디스크시스템의 설계에 필요한 파라미터를 도출하였으며, 특별한 경우 대하여 선형비용 구조하에서 디스크시 스템의 수명을 주어진 값보다 크게 하는 최소 비용 문제를 고찰하였다.

• ETRI Journal
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• 제32권2호
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• pp.241-247
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• 2010

We propose and experimentally demonstrate a service-aware optical transport system. The proposed service-aware optical transport system makes a flow based on service type and priority of traffic. The generated flow is mapped to a corresponding sub-${\lambda}$ for transport over an optical network. Using sub-${\lambda}$ provided by the centralized control plane, we could effectively provide quality-of-service guaranteed Ethernet service and best-effort service simultaneously in a single link. The committed information rate (CIR) traffic and best-effort traffic are assigned to different sub-${\lambda}s$. The bandwidth of the CIR traffic is guaranteed without being affected by violation traffic because the bandwidth is managed per each sub-${\lambda}$. The failure detection time and restoration time from a link failure is measured to be about 60 ${\mu}s$ and 22 ms, respectively, in the ring network. The measured restoration time is much smaller than the 50 ms industry requirement for real-time services. The fast restoration time allows the proposed service-aware optical transport system to offer high availability and reliability which is a requirement for transport networks.

• 한국신뢰성학회:학술대회논문집
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• 한국신뢰성학회 2005년도 학술발표대회 논문집
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• pp.69-73
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• 2005

The failure of geogrids used for soil reinforcement application can be defined as an excessive creep strain which causes the collapse of slopes and embankments. Accordingly, the lifetime is evaluated as a time to reach the excessive creep strain using two accelerated creep testing methods, time-temperature superposition(TTS) and stepped isothermal methods(SIM). TTS is a well-accepted acceleration method to evaluate creep behavior of polymeric materials, while SIM was developed in the last ten years mainly to shorten testing time and minimize the uncertainty associated with inherent variability of multi-specimen tests. The SIM test is usually performed using single rib of geogrids for temperature steps of $14^{\circ}C$ and a dwell time of 10,000 seconds. However, for multi-ribs of geogrids, the applicability of the SIM has not been well established. In this study, the creep behaviors are evaluated using multi-ribs of polyester geogrids using SIM and TTS creep procedures and the newly designed test equipment. Then the lifetime of geogrids are predicted by analyzing the failure times to reach the excessive creep strains through reliability analysis.

• 대한방사선기술학회지:방사선기술과학
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• 제45권5호
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• pp.439-448
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• 2022

The purpose of this study was to analyze the results from statistical process control (SPC) to recommend upper and lower control limits for planning parameters based on delivery quality assurance (DQA) results and establish our institutional guidelines regarding planning parameters for helical tomotherapy (HT). A total of 53 brain, 41 head and neck (H & N), and 51 pelvis cases who had passing or failing DQA measurements were selected. The absolute point dose difference (DD) and the global gamma passing rate (GPR) for all patients were analyzed. Control charts were used to evaluate upper and lower control limits (UCL and LCL) for all assessed treatment planning parameters. Treatment planning parameters were analyzed to provide its range for DQA pass cases. We confirmed that the probability of DQA failure was higher when the proportion of leaf open time (LOT) below 100 ms was greater than 30%. LOT and gantry period (GP) were significant predictor for DQA failure using the SPC method. We investigated the availability of the SPC statistic method to establish the local planning guideline based on DQA results for HT system. The guideline of each planning parameter in HT may assist in the prediction of DQA failure using the SPC statistic method in the future.