• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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• pp.836-839
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• 1996

Throughout CGL (Continuous Galvanizing Line) in steel works, zinc-coated steel sheets are produced which are used where long-running corrosion resistivity is required. During the galvanizing process, top dross is created and floated on the zinc pot. Because the dross leaves ill patterns on the coated sheets, a robot system is developed to automatically collect and remove the top dross. It consists of a robot and its carriage system, a pot level sensor, a system controller, and special robot tools. For the first time the level of zinc pot must be measured and fed back to the robot controller to avoid submersion of the robot hand into the hot zinc pot. In this paper, acoustic distance sensor is tested as a candidate for the pot level sensor in the view point of hot environment. Some considerations on the use of the acoustic distance sensor will be denoted.

• 한국구조물진단유지관리공학회 논문집
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• 제15권3호
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• pp.142-154
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• 2011

본 연구에서는 철근 콘크리트 터널 구조물을 해상 대기중 비래염분이 침투하는 터널 내벽과 해수에 항시 접촉하는 터널 외벽으로 구분하여, 몬테카를로 시뮬레이션에 의해 철근 부식 개시 확률을 예측하였다. 염해관련 변수의 변동성을 평가하기 위하여 염소이온 확산계수, 표면 염소이온농도, 피복두께, 임계 염소이온농도를 실제 실험 및 문헌 조사를 통해 확률특성을 구하였다. 그 결과 염소이온 확산계수의 평균치는 $3.77{\times}10^{-12}m^2/s$ 이었으며, 대상 부재인 터널 내벽과 외벽의 피복두께는 각각 45.5mm, 94.7mm으로 조사되었고, 임계 염소이온농도의 평균은 결합재 단위중량당 0.69%이었다. 각 변수의 확률적 특성에 근거하여 노출기간에 따른 철근위치에서의 염소이온 농도 분포를 구하였다. 재령이 증가할수록 침투 염소이온 농도의 평균값은 증가하며, 변동계수는 감소하게 됨을 알 수 있었다. 또한 확률론적 염해 해석기법을 적용하여 콘크리트 터널 내벽과 외벽에 대해 내구수명 및 부식개시 확률을 평가하였다. 염소이온 침투의 시간의존성을 고려하지 않은 경우 터널 내벽과 외벽에 대해 각각 8년, 12년의 내구수명이 도출되었으나, 시간의존적 모델에서는 178년, 283년의 내구수명이 계산되어 구조물의 설계내구수명(100년)을 만족하고 있음을 보였다. 또한, 시간의존성을 고려하지 않은 경우 100년에서의 부식 개시 확률은 터널 내벽과 외벽에 대해 각각 59.5, 95.5%였으며, 시간의존성 모델에서는 2.9, 0.2%로 계산되었다. 따라서 구조물의 과다설계를 방지하고 보다 합리적인 내구수명 설계 및 평가를 위해서는 염소이온 확산의 시간의존성을 고려하여야 한다. 마지막으로 본 연구에서 문헌 조사를 통해 구한 부식 발생 임계 농도를 현재 콘크리트 관련 기준에 제시한 값과 비교하여 분석하였다.

• Journal of Advanced Marine Engineering and Technology
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• 제26권3호
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• pp.375-381
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• 2002

Measuring of the dissolved oxygen is widely used for the environmental control of natural waters, sewage waste treatment, medical and biochemical studies, soil husbandry, food and drug process control, and prevention of corrosion in boilers. Especially, a power plants need special management for preventing accidents from corrosion, therefore, it is essential to measure the concentration of dissolved oxygen in real-time. In this paper we present a method of measuring dissolved oxygen very accurately up to pub units. This method, called polarograph method, is based on the measures of the electric current generated by the oxidation process in cathode and de-oxidation process in anode, assuming that the amount of the current is proportional to the density of dissolved oxygen.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.1760-1765
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• 2007

This paper shows a derating design approach for LED reliability improvement. The LED is widely used in display devices or circuits. The main failure of interest is defined as 100% reduction of the light output intensity of LED resulting from corrosion due to stresses, i.e. temperature and humidity. The lifetime is varied according to the stress levels under where the LED operates so that correlation of the lifetime to these stress levels over time is modeled through accelerated life testings. A derating design approach to accomplish a required reliability level of LED is proposed to determine adequate the stress levels. In the approach, $B_{10}$ life, Failure rate, Sensitivity Analysis of LED are used as a reliability metric.

• Computers and Concrete
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• 제18권1호
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• pp.69-97
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• 2016

Performance-based remaining life assessment of reinforced concrete bridge girders, subject to chloride-induced corrosion of reinforcement, is addressed in this paper. Towards this, a methodology that takes into consideration the human judgmental aspects in expert decision making regarding condition state assessment is proposed. The condition of the bridge girder is specified by the assignment of a condition state from a set of predefined condition states, considering both serviceability- and ultimate- limit states, and, the performance of the bridge girder is described using performability measure. A non-homogeneous Markov chain is used for modelling the stochastic evolution of condition state of the bridge girder with time. The thinking process of the expert in condition state assessment is modelled within a probabilistic framework using Brunswikian theory and probabilistic mental models. The remaining life is determined as the time over which the performance of the girder is above the required performance level. The usefulness of the methodology is illustrated through the remaining life assessment of a reinforced concrete T-beam bridge girder.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2004년도 춘계학술대회 논문집
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• pp.77-82
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• 2004

노후선박의 구조적 안전성을 확보하기 위해서는 부식이나 피로균열 및 기계적인 손상에 의하여 선체 구조 강도가 어떠한 영향을 받는지 충분히 검토하여 적절한 수리 보수 등 이에 대한 대책을 강구할 필요가 있다. 본 연구에서는 이러한 관점에서 부식, 피로균열, 기계적인 손상과 같은 노후 선박에 발생할 수 있는 여러 가지 손상이 선체강도에 미치는 영향을 이론적, 수치적, 실험적인 방법을 통하여 조사하고, 이를 통하여 선각거더의 소성붕괴강도 저하를 고려한 신뢰성 평가법 및 보수, 수리를 통한 인정수준 이상의 선각강도를 유지하게 하는 지침도 연구하였다.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• 제10권S_1호
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• pp.29-33
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• 2001

A numerical simulation was carried out to investigate the mechanism of snowfall around the Seoul region during a cold air-outbreak in the winter season. A particular case was selected for this study(Dec. 19, 1999). The inflow directions of the synoptic flow in the upper and lower levels were westerly and north-westerly, respectively. Plus, there was a deep trough and thermal ridge at a level of 500/700/850 hPa over the Bal-Hae region, in the northern part of the Korean peninsula. According to the model results, snowfall occurred around the Seoul region with the simultaneous existence of a strong static instability in the lower atmosphere, northerly or westerly dry air advection, and strong thermal advection toward the Seoul region. There was a strong convergence thereby indicating the existence of convective rolls in the clouds. The main energy source of convection over the Yellow sea was a sensible heat flux. The main moisture source was convection. Radiative cooling in the cloud layer intensified the static instability in the lower atmosphere.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2018년도 춘계 학술논문 발표대회
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• pp.147-148
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• 2018

In order to compare the electrochemical performance with that of Calomel Electrode, MnO2 solid-state-electrode was fabricated and its potential and impedance were measured in chloride aqueous solution. As a result, the SCPS without chloride ions showed a potential of -200 mV or more and an impedance over 2000 Ωcm, but the potential below -600 mV and the impedance below -200 Ωcm showed as the chloride concentration in the solution increased. It is considered electrochemical studies on the corrosion of rebar are necessary for the MOE, which shows the same tendency as SCE and exhibits electrochemical performance, over the Mortar level in the future.

• Nuclear Engineering and Technology
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• 제32권1호
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• pp.67-76
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• 2000

Significant wall thinning due to flow accelerated corrosion(FAC）was recently reported in main feedwater pipes in 3 Korean pressurized water reactor(PWR) plants. The main feedwater pipes in one plant were repaired using overlay weld method at the outside of pipe, while those in 2 other plants were replaced with new pipes. In this study, the effect of the wall thinning in the main feedwater pipes on piping integrity was evaluated using finite element method. Especially, the effects of both the overlay weld repair and the stress concentration in notch-type thinned area on the piping integrity were investigated. The results are as follows : (1) The piping load carrying capacity may significantly decrease due to FAC. In special, the load carrying capacity of the main feedwater pipe was reduced by about 40% during about 140 months operation in Korean PWR plants. (2) By performing overlay weld repair at the outside of pipe, the piping load carrying capacity can increase and the stress concentration level in the thinned area can be reduced.

• Corrosion Science and Technology
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• 제20권1호
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• pp.1-6
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• 2021

Many Korean industrial plants including nuclear and fossil power plants use seawater as the ultimate heat sink to cool the heat generated by various facilities. Owing to the high corrosivity of seawater, facilities and piping made of metal material in contact with seawater are coated or lined with polymeric materials to avoid direct contact with seawater. However, polymeric materials used as coating and lining have some level of permeability to water and are degraded over time. Korean industrial plants have also experienced a gradual increase in the frequency of damage to pipes in seawater systems due to prolonged operating periods. In the event of a cavitation-like phenomenon, coating or lining inside the piping is likely to be damaged faster than expected. In this paper, the cause of water leakage due to base metal damage caused by the failure of the polyester lining in seawater system piping was assessed and the experience with establishing countermeasures to prevent such damage was described.