• 대한조선학회논문집
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• 제56권2호
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• pp.161-167
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• 2019

In general, fatigue analysis is performed by using deterministic model to estimate the optimal parameters. However, the deterministic model is difficult to clearly describe the physical phenomena of fatigue failure that contains many uncertainty factors. With regard to this, efforts have been made in this research to compare with the deterministic model and the stochastic models. Firstly, One deterministic S-N curve was derived from ordinary least squares technique and two P-S-N curves were estimated through Bayesian-linear regression model and Markov-Chain Monte Carlo simulation. Secondly, the distribution of Long-term fatigue damage and fatigue life were predicted by using the parameters obtained from the three methodologies and the long-term stress distribution.

• 한국신뢰성학회지:신뢰성응용연구
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• 제11권2호
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• pp.111-126
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• 2011

The clutch coil mounted on the automotive air conditioner is an important part which actuates the clutch to connect or disconnect the pulley and the compressor according to the climate control condition in an automobile. Here, it is generally required that the clutch coil should ensure the long term durability requirement, such as a warranty for the 10 years of field operation or 160,000 km driving, especially in a brand new item, and so forth. However, some difficulties have arisen in restoring its credibility, since domestic specifications for the part have not been yet unified. In order to ensure the reliability, test methods and assessment criteria should be standardized. Moreover, assessed lifetime under specific conditions and potential failure analysis would be important. In this study, lifetime test specifications for the clutch coil have been reviewed and methodological suggestions are provided to ensure reliability, utilizing a quality function deployment through the potential failure mode effect analysis.

• Nuclear Engineering and Technology
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• 제53권1호
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• pp.344-350
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• 2021

As the High Flux Advanced Neutron Application Reactor (HANARO) has been recently required to support new R&D relevant to future nuclear systems requiring a much higher neutron fluence, the development of irradiation capsule technology for long-term irradiation testing was performed in three steps (3, 5, 10 dpa). At first, several design improvements of a standard capsule were suggested based on a failure analysis of the capsule and successfully applied for irradiation testing at HANARO at up to eight reactor operation cycles equivalent to 3 dpa. Based on a schematic stress analysis of the vulnerable parts of the previous capsule, an optimized design of the capsule was made for 5 dpa irradiation. The newly designed capsule was safely out-pile tested up to 450 days, which was equivalent to 5 dpa irradiation in the reactor. The test results were submitted to the Reactor Safety Review Committee of HANARO and irradiation testing for 5 dpa was approved. The capsule was also successfully out-pile tested to evaluate the possibility of irradiation testing for 10 dpa. For a higher neutron fluence exceeding 10 dpa, new capsule technologies, including a new capsule that has a different bottom design and neutron flux boosting capsule, were also suggested.

• Journal of Chest Surgery
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• 제34권9호
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• pp.686-691
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• 2001

배경: Duromedics 판막은 1982년부터 사용되어 왔으나 국내에서는 장기 임상 성적에 대한 보고가 없는 실정이다. 이에 본원에서 시행된 Duromedics 판막의 장기 임상 성적을 보고하는 바이다. 대상 및 방법: 1987년부터 1988년 사이에 23명의 성인 환자에게 Duromedics 기계판막을 이용하여 판막치환술을 시행하였다. 승모판막 치환이 8예, 대동맥판 치환이 5예, 삼첨판막 치환이 1예, 대동맥판막과 승모판막을 동시에 치환한 경우가 6예, 승모판막과 삼첨판막을 동시에 치환한 경우가 1예였다. 남자 환자가 12명, 여자 환자가 11명이었고 환자들의 평균 연령은 35$\pm$10(15~52) 세였다. 저자들은 이 환자들에게 치환된 Duromedics 기계 판막의 임상적인 결과를 추적 조사하였다. 결과: 조기 사망은 1예로서 4.3%(1/23)의 조기 사망률을 보였고 만기 사망도 1예로서 4.3%(1/23)의 만기 사망률을 보였다. 사망 원인은 저심박출 증후군과 구조적 판막실패였다. 평균 추적기간은 133$\pm$43개월(8~157)이었다. 재수술을 시행한 경우는 모두 3예가 있었는데 판막혈전증이 1예, 구조적 판막이상이 1예, 비구조적 판막 이상이 1예였다. 10년 생존율(actuarial survival rate)은 90.9%이었다. 결론: 비록 임상 연구를 하기에 충분한 환자 수는 아니었지만, Duromedics 판막의 장기 임상 성적은 다른 판막에 비해 우수하거나 비슷하였으며, 구조적 결함도 발견되지 않았다. 하지만 향후 좀더 연구가 이루어져야 할 것으로 생각된다.

• 한국품질경영학회:학술대회논문집
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• 한국품질경영학회 1998년도 The 12th Asia Quality Management Symposium* Total Quality Management for Restoring Competitiveness
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• pp.287-292
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• 1998

As business looks towards the $21^{\st}$ century, a long-term strategy that focuses on global sourcing will be the vital factor in whether companies win or lose. At the same time, with electronic components, it is important to ensure stable quality and reliability, together with other important parameters. In order to achieve this, creating an effective mechanism of failure analysis and database management for electronic components is essential. The authors introduce the actual mechanism employed by NEC and explain the ideas and insight they have obtained from their experience.

• Structural Monitoring and Maintenance
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• 제2권4호
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• pp.339-355
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• 2015

Corrosion of prestressed concrete structures is one of the main challenges that engineers face today. In response to this national need, this paper presents the results of a long-term project that aims at developing a structural health monitoring (SHM) technology for the nondestructive evaluation of prestressed structures. In this paper, the use of permanently installed low profile piezoelectric transducers (PZT) is proposed in order to record the acoustic emissions (AE) along the length of the strand. The results of an accelerated corrosion test are presented and k-means clustering is applied via principal component analysis (PCA) of AE features to provide an accurate diagnosis of the strand health. The proposed approach shows good correlation between acoustic emissions features and strand failure. Moreover, a clustering technique for the identification of false alarms is proposed.

• KEPCO Journal on Electric Power and Energy
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• 제6권1호
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• pp.41-47
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• 2020

The contribution of damage mechanisms to failure of steam turbine casing made of Cr-Mo-V steel was investigated. Creep-fatigue interaction on the HP side corner of turbine casing was revealed as the root cause of the catastrophic failure performed by metallurgical analysis. The steady-state pressure and transient thermal stress were analyzed based on the actual operating condition of the thermal plant. Damage of creep-fatigue interaction to crack initiation was evaluated with multiaxial effects. The contribution ratio of creep and fatigue to the crack initiation was estimated to 3:1. Temporary geometrical correct action with repair weld was executed. For long-term operation, design improvement of casing equipment for creep resistance should be needed.

• 복식
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• 제63권3호
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• pp.46-60
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• 2013

With a goal of establishing a marketing strategy which allows businesses to hold a dominant position in beauty service industry, this study has attempted to investigate causal relations among behavioral intentions by customer satisfaction once service recovery strategy is recovered depending on customers' emotional responses against service failure. In order to provide relevant data to make correct decisions during management and marketing planning so that better customer satisfaction can be achieved in the beauty service industry, the results of the previous studies on service failure and recovery strategy in the beauty service industry have been examined. Then after selecting i) the efforts to recover service failure, ii) satisfaction after recovery and iii) behavioral intention after satisfaction as causal variables, the relation among these variables were verified using a structural equation model. As a result, an appropriate recovery strategy which is developed after service failure makes customers have positive behavioral intentions when customer satisfaction is achieved just as described in previous studies. Furthermore, it is a critical fact which helps businesses keep their customers in a mature market, where it is hard to attract new customers and create long-term profit. This study empirically supports information on how service failure and related variables occur in the beauty service industry. It is significant in that it has helped beauty service providers build service recovery-related strategies.

• 한국지반공학회논문집
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• 제19권4호
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• pp.167-178
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• 2003

발파설계가 터널 굴착 시 암반손상 및 여굴에 미치는 영향을 분석하고 암반손상 및 여굴이 터널 안정성에 미치는 영향을 분석함으로서 발파설계가 터널 지보설계에 미치는 영향을 연구하였다. 도로터널의 일반적인 발파패턴에 대해 동적발파 수치해석을 시행하고 연속체 손상역학(continuum damage mechanics)의 손상변수(damage variable)를 이용하여 여굴과 암반손상 정도를 분석함으로서 터널 굴착면 주위의 암반손상 정도와 영역을 구분하였다. 또한 발파하중 같은 동적하중이 암반내를 전파할 때 변화하는 암반의 동적파괴기준에 대한 연구를 수행하였다. 발파 암반손상 영향을 터널 안정성 해석에 반영하기 위하여 손상된 암반강성과 파괴기준을 적용하였다. 손상된 암반강성은 손상역학의 강도감소 모델을 이용하여 감소시켰다. 손상된 암반의 파괴기준은 암반강성과 지질강도지수의 관계식에서 도출한 손상된 지질강도지수(GSI$GSI_d$)를 적용함으로서 산출한 수정 Hoek-Brown 파괴기준을 적용하였다. 암반손상을 고려하여 터널안정성을 해석한 결과, 암반손상을 고려하지 않는 경우와 비교하여 소성영역 범위가 확대되고 변위량이 증가하였다. 이는 발파암반손상을 고려하지 않고 터널설계를 하는 경우 단기적 혹은 장기적으로 터널안정성이 위협받을 수 있음을 나타내었다.

• Geomechanics and Engineering
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• 제5권1호
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• pp.37-55
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• 2013

An important issue in the design of soil-nailing systems, as long-term retaining walls, is to assess their stability during seismic events. As such, this study is aimed at simulating the dynamic behavior and failure pattern of nailed structures using two series of numerical analyses, namely dynamic time history and pseudo-static. These numerical simulations are performed using the Finite Difference Method (FDM). In order to consider the actual response of a soil-nailed structure, nonlinear soil behaviour, soil-structure interaction effects, bending resistance of structural elements and construction sequences have been considered in the analyses. The obtained results revealed the efficiency of both analysis methods in simulating the seismic failure mechanism. The predicted failure pattern consists of two sliding blocks enclosed by three slip surfaces, whereby the bottom nails act as anchors and the other nails hold a semi-rigid soil mass. Moreover, it was realized that an increase in the length of the lowest nails is the most effective method to improve seismic stability of soil-nailed structures. Therefore, it is recommended to first estimate the nails pattern for static condition with the minimum required static safety factor. Then, the required seismic stability can be obtained through an increase in the length of the lowest nails. Moreover, placement of additional long nails among lowest nails in existing nailed structures can be considered as a simple retrofitting technique in seismic prone areas.