• Journal of the Korean Society for Nondestructive Testing
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• v.36 no.5
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• pp.384-390
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• 2016

It is important to have a pipeline leak-detection system that determines the presence of a leak and quickly identifies its location. Current leak detection methods use a acoustic emission sensors, microphone arrays, and camera images. Recently, many researchers have been focusing on using cameras for detecting leaks. The advantage of this method is that it can survey a wide area and monitor a pipeline over a long distance. However, conventional methods using camera monitoring are unable to target an exact leak location. In this paper, we propose a method of detecting leak locations using leak-detection results combined with multi-frame analysis. The proposed method is verified by experiment.

• Proceedings of the Korean Society of Computer Information Conference
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• 2018.07a
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• pp.51-52
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• 2018

화력발전용 순환유동층 보일러는 환경오염의 주요인인 질소산화물(NOx)과 황산화물(SOx)의 배출량이 적은 친환경 화력발전용 보일러로 화력발전 업계에서 각광받고 있는 추세이다. 그러나 순환유동층 보일러의 연료인 유동매체는 미분탄과 같이 작지만 단단한 고체이므로 유동매체의 타격으로 인해 워터월(waterwall) 튜브의 마모는 물론 누설까지 야기할 수 있다. 순환유동층 보일러 튜브에서 누설된 증기는 보일러 내부에 클링커(Clinker)를 발생시키고 이는 순환유동층 보일러 튜브 표면에 응고되어 열전도율을 감소시킬 뿐만 아니라 보일러 운전정지의 원인이 된다. 따라서 본 논문에서는 음향방출 센서를 이용하여 화력발전용 순환유동층 보일러 튜브의 누설 위치를 추정하는 방법을 제안한다. 제안 방법에서는 매질의 분자단위 이동에 의해 발생되는 탄성파를 감지할 수 있는 음향방출 센서를 이용하고, 보일러 워터월 튜브의 멤브레인 용접부와 비용접부(seamless)의 감쇠율을 고려한 위치별 센서 감도 추정 알고리즘을 통해 워터월 튜브의 위치별 진폭 크기를 히트맵으로 표현할 수 있다.

• The Journal of the Acoustical Society of Korea
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• v.31 no.7
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• pp.449-460
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• 2012

The importance of the leak detection of a buried pipe in a power plant of Korea is being emphasized as the buried pipes of a power plant are more than 20 years old. The objective of this work is to enhance the capability of the leak detection technique in a noisy environment. For this purpose, a modified cross-correlation method that can effectively remove the rotating machinery noise component is suggested. In addition, a method for leak point detection using phase information of cross-spectrum is suggested. The validity of the proposed method is verified by performing an experiment. The experimental result demonstrates that the performance of the cross-correlation method can be enhanced by reducing the periodic noise components due to mechanical equipment.

• The Journal of the Acoustical Society of Korea
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• v.43 no.4
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• pp.414-421
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• 2024

In this paper, we design and verify a system that can detect piping leakage noise in an environment with significant reverberation and reflection using a multi-channel acoustic sensor module as a technology to prevent major plant accidents caused by leakage. Four-channel microphones arranged in a tetrahedron are designed as a single sensor module to measure three-dimensional sound intensity vectors. In an environment with large effects of reverberation and reflection, the measurement error of each sensor module increases on average, so after placing multiple sensor modules in the field, measurement results showing locations with large errors due to effects such as reflection are excluded. Using the intersection between three-dimensional vectors obtained from several pairs of sensor modules, the coordinates where the sound source is located are estimated, and outliers (e.g., positions estimated to be outside the site, positions estimated to be far from the average position) are detected and excluded among the points. For achieving aforementioned goal, an excluding algorithm by deciding the outliers among the estimated positions was proposed. By visualizing the estimated location coordinates of the leakage sound on the site drawing within 1 second, we construct and verify a system that can detect the location of the leakage sound in real time and enable immediate response. This study is expected to contribute to improving accident response capabilities and ensuring safety in large plants.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2010.10a
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• pp.248-249
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• 2010

• The Journal of the Acoustical Society of Korea
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• v.28 no.5
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• pp.461-470
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• 2009

We investigate and analyze the problems encountered in frame-based estimation of TDOA (Time Difference of Arrival) using CPSP function. Spectral leakage occurring in framing of a speech signal by a rectangular window could make estimation of CPSP spectrum inaccurate. Framing with other windows to reduce the spectral leakage distorts the signal due to the asynchronous weighting around the frame specifically both ends of the frame. These problems degrade the performance of the CPSP-based TDOA estimation. In this paper, we propose a method to alleviate those problems by pre-emphasis of the speech signal. It reduces the influence of the spectral leakage by reducing dynamic range of the spectrum of a speech signal with pre-emphasis. To validate the proposed method of pre-emphasis, we carry out TDOA estimation experiments in various noise and reverberation conditions, Experimental results have shown that the framing of pre-emphasized microphone output by a rectangular window achieves higher success rate of TDOA estimation than any other framing methods.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.10a
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• pp.209-210
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• 2012

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.6
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• pp.1044-1053
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• 2022

Time domain reflectometry (TDR) is a diagnostic technique to evaluate the physical integrity of cable and finds application in leak detection and localization of piping system. In this study, a cable-shaped leak detection sensor was proposed using the TDR technique for monitoring leakage detection of ship's engine room seawater piping system. The cable sensor was developed using a twisted pair arrangement and wound by an absorbent material. The availability and performance of the sensor for leak detection and localization were evaluated on a lab-scale pipeline set up. The developed sensor was installed onto the pipes and flanges of the lab-scale set up and various TDR waveforms were acquired and analyzed according to the dif erent variables including the number of twists and sheath thickness. The result indicated that the twisted cable sensor was able to produce clear and smooth signal as compared to the TDR sensor with a parallel arrangement. The optimal number of twist was determined to be above 10 per the unit length. The optimal diameter of sheath thickness that results in the desired sensitivity was determined to be ranging from 80% up to 120% of the diameter of the conductor. The linear regression analysis for estimation of leak localization was carried out to estimate the location of the leakage, and the result was a determination coefficient of 0.9998, indicating a positive relationship with the actual leakage point. The proposed TDR based leak detection method appears to be an effective method for monitoring leakage of ship's seawater piping system.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.71-71
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• 2000

본 연구에서는 차세대 마이크로파 유전체 소자로서의 응용을 목적으로 펄스 레이저 방식에 의하여 증착된 MgTiO3 박막의 전기적 특성을 종합적으로 연구 분석하였다. 이를 바탕으로 MgTiO3 박막의 유전손실 등과 같은 열화를 야기시키는 박막 내부 또는 박막과 기판간의 결함의 특성을 파악하여 열화 메카니즘을 분석하였다. MgTiO3는 마이크로파 영역에서의 우수한 유전특성과 같은 낮은 유전손실을 가지며, 온도 안정성 또한 우수하다. 현재까지 벌크 세라믹 MgTiO3 의 응용 광범위하게 연구되어 왔으나 박막의 제조공정 및 전기적 특성 분석은 미흡한 형편이다. 따라서 벌크 세라믹과는 특성이 상이한 박막의 전기적 특성분석 및 연구가 필요하다. 분석을 위한 소자의 기본 구조로서 Metal-Insulator-Semiconductor(MIS) 구조를 채택하였다. MgTiO3 박막을 증착하기 위한 기판으로는 n형 Si(100)기판과 p형 Si(100)기판을 사용하였고, Si 기판 위에 급속 열처리기 (RTP)를 이용하여 SiO2를 ~100 두께로 성장시킨 것과 성장시키지 않은 것으로 구분하여 제작하였다. MgTiO3 박막은 펄스 레이저 증착 방식(PLD)에 의하여 약 2500 두께로 증착되었으며, 200mTorr 압력의 산소 분위기 하에서 기판의 온도를 40$0^{\circ}C$~55$0^{\circ}C$까지 5$0^{\circ}C$간격으로 변화시키며 제작하였다. 상하부의 전극 금속으로는 Al을 이용하였으며, 열증발 증착기로 증착하였다. 증착된 MgTiO3 박막의 결정구조를 확인하기 위하여 XRD 분석을 수행하였으며, 박막의 전기적 특성을 분석하기 위해 Boonton7200 C-V 측정기와 HP4140P를 이용한 경우에는 C-V 곡선에 이력현상이 나타났으나, MgTiO3/SiO2를 이용한 경우에는 이력현상이 나타나지 않았고, 유전율은 감소하는 것으로 나타났다. I-V 측정 결과, 절연층으로 MgTiO3/SiO2를 이용한 경우에는 MgTiO3만을 절연층으로 사용한 경우에 비해 동일한 전계에서 낮은 누설전류 값을 가짐을 알 수 있었다. 또한 박막의 증착온도가 증가함에 따라서 C-V 곡선의 위치가 양의 방향으로 이동함을 확인하였다. 위의 현상은 기판의 종류에 관계없이 발생하는 것으로 보아 벌크 또는 계면에 존재하는 결함에 의한 것으로 추정된다. 현재 C-V 곡선의 이동 원인과 I-V 곡선의 누설전류 메카니즘을 분석 중에 있으며 그 결과를 학회에서 발표할 예정이다.

• Journal of IKEEE
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• v.23 no.4
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• pp.1457-1460
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• 2019

In this paper, we proposed the development of a mixed sensor parts for integrated radiation exposure protection fireman's life-saving alarm that can be location-tracked and irradiated. To measure radiation exposure dose, we use the PIN-Diode radiation measurement sensor module, a semi-conductive radiation measurement sensor that can minimize size and weight. The design for removing leakage current is carried out to enhance the characteristics of the radiation measurement sensor using PIN-Diode. The IMU sensor module is used to estimate the location of the current fireman at the same time as the accident estimate by adding together the data and the values for acceleration on the three axis. Experiments were conductied by an authorized testing agency to determine the efficiency of the proposed mixed sensor parts for integrated radiation exposure protection fireman's life-saving alarms. The cumulative dose measurement range was measured in the range of 10 μSv to 10 mSv, the highest level in the world. The accuracy was measured from ±6.3% to ±9.0% (137 Cs) and normal operation was found at the international standard of ±15%. In addition, positional accuracy was measured within ±10%, resulting in a high level of results, demonstrating its effectiveness. Therefore, it is expected that more firemen will be able to provide with superior performance integrated radiation exposure protection fireman life-saving alarm.