• 대한기계학회논문집B
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• 제28권7호
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• pp.850-856
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• 2004

When a shock wave arrives at the open end of a tube, an impulsive wave is discharged from the tube exit and causes serious noise and vibration problems. In the current study, the effect of the cross-sectional area of a circular tube on the impulsive wave is investigated using computational methods. Marten-Yee's TVD scheme was employed to solve axisymmetric, unsteady, compressible Euler equations. With a change in the cross-sectional area of the tube, the Mach number of an incident shock wave is varied between 1.01 and 1.50. The results obtained show that the magnitude of the impulsive wave strongly depends upon the Mach number of the incident shock wave and the cross-sectional area of the tube. It is also found that for a given cross-sectional area of the tube, the impulse wave has strong directivity to the tube axis.

• 비파괴검사학회지
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• 제22권2호
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• pp.187-192
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• 2002

서로 연결되어 있는 강관의 결함을 검사할 수 있도록 하기 위한 개폐식 탐촉자를 제작하였다. 본 탐촉자는 기존의 외삽형 와전류 탐촉자로서는 탐상이 불가능한 설치 가동중인 튜브류의 검사를 위한 것이다. 리본 케이블과 커넥터로 구성된 여기 코일은 접합/단락이 가능하게 하였으며 감지 코일은 튜브 외벽 근처에 원주 방향으로 어레이 형태로 배치하였는데 여기 코일로부터 튜브 직경의 약 1.5배정도 떨어진 위치이다. 제작된 탐촉자를 강관에 적용한 결과, 감도나 결함 크기 구분 등의 성능은 자기 포화형 탐촉자에 미치지 못하나 비교적 큰 결함의 발견이나 위치 파악 등에는 적용 가능한 것으로 나타났다. 크랙 형태의 표면 결함의 경우 두께의 19% 이상의 결함을 찾을 수 있었다.

• 전기학회논문지
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• 제56권7호
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• pp.1224-1230
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• 2007

In this paper, we study the classification of defects at steam generator tube in nuclear power plant using eddy current testing (ECT). We consider 4 defect patterns of SG tube: I-In type, I-Out type, V-In type, and V-Out type. Through numerical analysis program based on finite element modeling, 400 ECT signals are generated by varying width and depth of each defect type. In order to improve the classification performance, we propose new feature extraction technique. After extracting new features from the generated ECT signals, multi-layer perceptron is used to classify the defect patterns. Through the computer simulation study, it is shown that the proposed method achieves 100% classification success rate while the previous method yields 91% success rate.

• 대한기계학회논문집A
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• 제28권3호
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• pp.289-295
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• 2004

Pressure tubes are major component of nuclear reactor, but only selected samples are periodically examined due to numerous numbers of tubes. Current in-service inspection result show there is high probability of flaw existence at uninspected pressure tube. Probabilistic analysis is applied in this study for the integrity assessment of uninspected pressure tube. All the current integrity evaluations procedures are based on conventional deterministic approaches. So it is expected that the results obtained are too conservative to perform a rational evaluation of lifetime. More realistic failure criteria, based on FAD are also proposed for the probabilistic analysis. As a result of this study failure probabilities for various conditions are calculated, and examined application of FAD and LBB concept.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.1211-1215
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• 2003

Pressure tubes are major component of nuclear reactor, but only selected samples are periodically examined due to numerous numbers of tubes. Current in-service inspection result show there is high probability of flaw existence at un-inspected pressure tube. Probabilistic analysis is applied in this study for the integrity assessment of un-inspected pressure tube. But all the current integrity evaluations procedures are based on conventional deterministic approaches. So many integrity evaluation parameters are not directly apply to probabilistic analysis. As a result of this study failure assessment diagram are proposed based on test data.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 B
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• pp.831-833
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• 2000

In this paper, a numerical analysis algorithm of eddy current testing(ECT) for heat exchanger tube with axi-symmetric defects using finite element method(FEM) is presented. In the ECT FEM analysis, we used trianglular and rectangular elements for exact signal of ECT for variable shape of defects. This paper presents a systematic and efficient numerical analysis algorithm for ECT. We employ the LU decomposition and Cholesky method for solving the system matrix. This numerical analysis algorithm is effectively applied to heat exchanger tube with defects.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.53-55
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• 2005

The signals of the eddy current testing(ECT) for the examination of the steam generator(SG) tubes in the nuclear power plant(NPP) determine the existence, size, and kind of defects using the variation of impedance signals when a testing coil, driven by alternating current, passes through the SG tube contains defects. The aim of this paper is building a database of the RPC probe signals on the basis of the sizes variation of defects and frequency variation of probe. In this paper 3-D numerical analysis of the ECT signals using the finite element method is performed. Through this study, it is shown variation of magnitude and phase of impedance according to variation of defect size and frequency. From the result of this paper, we can obtain the information which is useful in defect discrimination of SG tube in nuclear power plant.

• Journal of Electrochemical Science and Technology
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• 제14권4호
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• pp.349-360
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• 2023

This study investigated the tri-metallic galvanic coupling of different metals in the tubes, fillers, and fins of a heat exchanger. The goal was to prevent corrosion of the tubes using the fin as a sacrificial anode while ensuring that the filler metal has a more noble potential than the fin, to avoid detachment. The metals were arranged in descending order of corrosion potential, with the noblest potential assigned to the tube, followed by the filler metal and the fin. To address a reduction in protection current of the fin, the filler metal was modified by adding Zn to decrease its corrosion potential. However, increasing the Zn content of filler metal also increases its corrosion current. The study examined three different filler metals, considering their corrosion potential, and kinetics. The results suggest that a filler metal with 1.5 wt.% Zn addition is optimal for providing cathodic protection to the tube while reducing the reaction rate of the sacrificial anode.

• 대한전기학회논문지
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• 제38권7호
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• pp.549-556
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• 1989

Radiation induced current of the insulating oil used for X-ray tube housing was investigated in this paper. The X-ray induced current increased in proportion to the X-ray intensity and X-ray wave length and was greatly affected by the temperature of the insulating oil and the gap length` however, the current was not varied by the amount of the X-ray absorbed. The results suggest that one must consider the following problems as important factors for X-ray machine design and normal operation: cooling system of the X-ray tube housing, X-ray intensity, increasing temperature due to continuous operation, years used, and oil exchange and management.

• Journal of Magnetics
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• 제14권2호
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• pp.97-100
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• 2009

A new eddy current testing probe was developed to separate the eddy current signal distortion caused by permeability variation clusters and ordinary defects created in steam generator tubes. Signal processing circuits were inserted into the probe to increase the signal-to-noise ratio and allow digital signal transmission. The new probe could measure and separate the magnetic phases created in the steam generator tubes in the operating environment of a nuclear power plant. Furthermore, the new eddy current testing probe can measure the defects in steam generator tubes as rapidly as a bobbin probe with enhanced testing speed and reliability of defect detection.