• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2006.11a
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• pp.177-180
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• 2006

This study is to make a basic study if solid zinc (Zn) can be used for buried reference electrode, so we examined the adequacy of zinc as reference electrode by using zinc which showed regular electrode for buried period. The deference of electric potential if zinc electrode for corrosion factor such as soil resistivity or pH didn't show fixed trend and there was no clear trend on the change of measurement period. From field test, it is known that the natural electric potential difference of CSE electrode and zinc electrode is 1,100mV, but the electric potential of zinc electrode for CSE electrode in the natural soil and copying soil was 1,094~1,158mV. There was no fixed trend on the change of measurement period and electric potential difference of zinc electrode for corrosion factors such as soil resistivity or pH. Consequently, there was 40~60mV of electric potential difference in every copying soil during the experiment measurement.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.466-467
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• 2008

In case of a line-to-ground fault at transmission lines, a portion of fault current will flow into the earth through the footings of the faulted tower causing electrical potential rise nearby the faulted tower footings. In this situation, any buried pipelines or structures nearby the faulted tower can be exposed to the electrical stress by earth potential rise. Although many research works has been conducted on this phenomena, there has been no clear answer of the required separation distance between tower footings and neary buried pipeline because of its dependancy on the soil electrical charactersics of the concerned area and the faulted system.

• Journal of the Earthquake Engineering Society of Korea
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• v.4 no.4
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• pp.15-26
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• 2000

지진파 전파로 인한 매설관에 작용하는 지진하중은 지진특성 및 지반조건에 따른 지반변형률로부터 산정되어야 한다. 그러나. 기존에 사용되고 있는 경험적인 방법에 의해 계산된 지반변형률 모형은 지진 및 지반의 지역적 특수성을 고려할 수 없는 문제점을 내포하고 있다. 따라서, 본 연구에서는 이러한 문제점을 개선하기 위하여 지진특성 및 지반조선을 반영할 수 있는 수정된 지반변형률 모형을 제안하고 개발된 모형을 매설관로의 지진해석에 지진하중으로 적용하였다. 여기서, 지반변형률을 예측하기 위한 지진판 전파속도는 지반조건을 고려할 수 있도록 파 에너지분포에 근거한 분산곡선을 제안하여 산정하였다. 이러한 과정을 통해 얻어진 지반변형률 산정방법에 타당성을 파악하기 위해 예측한 지반변형률과 과거 지진으로 실측된 지반변형률을 비교하였다. 타당성이 입증된 지반변형률 모형을 매설관의 하중으로 적용하여 지진해석을 실시하였으며, 계산결과는 범용 유한요소해석을 통한 동해석 및 응답변위법에 의한 결과와 비교하였다. 이를 통해 지반 변형률 모형을 적용한 매설관 지진해석의 타당성을 검증하였다. 또한, 지진 및 지반환경이 다른 다양한 관의 특성을 반영하기 위해, 지진 지반 및 관의 영향 인자에 대해 매개변수 해석에 실시되었으며, 이로써 본 연구의 활용성을 검토하였다.

• Proceedings of the KIEE Conference
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• 2004.11c
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• pp.532-534
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• 2004

The advancement of electronics and telecommunication technologies has forced the risk management system for underground metallic structures to evolve into the remote monitoring and control system. Especially, facilities such as gas pipelines, oil pipelines and water distribution lines might make hazardous effect on human safety without continuous monitoring and control. As a result, pipeline engineers have applied cathodic protection system to prevent the degradation of their facilities by corrosion and carried out a periodic monitoring of the pipe-to-soil (P/S) potentials at numberous test boxes along their pipelines. The latter action on a road in downtowns, however, is so much dangerous that the inspectors should be ready to suffer the threatening of their lives and maintenance. In order to minimize these social costs and hazards, a stand-alone type corrosion monitoring equipment which can be installed in test box, store the P/S data for given Belied and send the data by wired/wireless telecommunications is under development. In order to obtain the exact P/S data, however, a reference electrode should be located as close to the pipeline as possible. Actually, the measured potential by a conventional portable reference electrode contain inevitably an IR drop portion caused by the current flow from the cathodic protection rectifier or the subway railroad. To minimize this error, it is recommended that the reference electrode should be buried within 10 cm from the pipeline. In this paper, we describe the design parameters for fabricating the permanent type reference electrode and the characteristics of the developed reference electrode.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.10
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• pp.1551-1558
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• 2001

Recently, a number of underground pipelines have been drastically increased. The integrity of these buried pipelines, especially gas transmitting pipelines, is of importance due to an explosive characteristic of natural gas. The third party damage is known as one of the most critical factor which causes fatal accidents. For this reason, a number of systems detecting third party damage are under development. The major concern in the development of third party damage detection system is to transmit vibration signals out of accelerometer to signal conditioner and data acquisition system without any interference caused by noise. The objective of this paper is to develope a fiber optic accelerometer applicable to third party damage detection system. A fiber optic accelerometer was developed by use of combining principles of one degree of freedom vibration model and an extrinsic Fabry-Perot interferometer. The developed fiber optic accelerometer was designed to perform with a sensitivity of 0.06mVg, a frequency range of less than 6kHz and an amplitude range of -200g to 200g. The developed, accelerometer was compared with a piezoelectric accelerometer and calibrated. In order to verify the developed accelerometer, the field experiment was performed. From the field experiment, vibration signals and the location of impact were successfully detected. The developed accelerometer is expected to be used for the third party damage detection system which requires long distance transmission of signals.

• Journal of Korean Society of Water and Wastewater
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• v.30 no.1
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• pp.59-67
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• 2016

Owing to time and cost constraints, new methods that would make it possible to evaluate the safety of the water supply pipeline in a less time- and cost-consuming manner are urgently needed. In response to this exigency, the present study developed a new statistical model to assess the safety of the water supply pipeline using the quantification theory type II. In this research, the safety of the water supply pipeline was defined as 'a possibility of the pipeline failure'. Quantification analysis was conducted on the qualitative data, such as pipe material, coating, and buried condition. The results of analyses demonstrate that the hit ratio of the quantification function amounted to 77.8% of hit ratio, which was a fair value. In addition, all variables that were included in the quantification function were logically valid and demonstrated statistically significant. According to the results derived from the application of the safety evaluation model, the coefficient of determination ($R^2$) between K-region's water supply pipeline safety and the safety inspection amounted to 0.80. Therefore, these findings provide meaningful insight for the measured values in real applications of the model. The results of the present study can also be meaningfully used in further research on safety evaluation of pipelines, establishing of renewal prioritization, as well as asset management planning of the water supply infrastructure.

• Journal of the Korean Institute of Gas
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• v.18 no.5
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• pp.66-71
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• 2014

Gas pipelines are the core facilities in the gas facilities and the most pipelines are buried underground and are exposed to the risk of corrosion caused by the soil characteristics and the environmental impact. The anti-corrosion potential and the corrosion status of the underground pipelines are measured periodically in accordance with the relevant laws and regulations. A study on the cathodic protection measurement system was carried out in order to solve the problems of the conventional measurement system. This paper describes the survey on the standards and the specifications of the cathodic protection measurement and the the reference electrode to meet the relevant regulations, and the development of the measuring circuit and the data transmission module to build the cathodic protection measurement system. This study verified the field applicability through the testing of the developed prototype and investigated on the problems of the previous studies and the future research and development direction.

• Journal of Magnetics
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• v.16 no.1
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• pp.36-41
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• 2011

If gas is leaking out of gas pipelines, it could cause a huge explosion. Accordingly, it is important to ensure the integrity of gas pipelines. Traditionally, over the years, gas-operating companies have used the ILI system, which is based on axial magnetic flux leakage (MFL), to inspect the gas pipelines. Relatively, there is a low probability of detection (POD) for the axial defects with the axial MFL-based ILI. To prevent the buried pipeline from corrosion, it requires a protective coating. In addition to the potential damage to the coating by environmental factors and external forces, there could be defects on the damaged coating area. Thus, it is essential that nondestructive evaluation methods for detecting axial defects (axial cracks, axial groove) and damaged coating be developed. In this study, an electromagnetic acoustic transducer (EMAT) sensor was designed and fabricated for detecting axial defects and coating disbondment. In order to validate the performances of the developed EMAT sensor, experiments were performed with specimens from axial cracks, axial grooves, and coating disbondment. The experimental results showed that the developed EMAT sensor could detect not only the axial cracks (minimum 5% depth of wall thickness) and axial grooves (minimum 10% depth of wall thickness), but also the coating disbondment.

• Journal of the Earthquake Engineering Society of Korea
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• v.14 no.5
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• pp.65-76
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• 2010

In this paper, earthquake fragility analysis has been comparatively performed with regard to a buried gas pipeline of API X65 which has been widely used in Korea. For this purpose, a nonlinear time-history analyses has been carried out for 15 different analytical models of a buried gas pipeline in terms of the selected 12 sets of earthquake ground motions with 0.1g of scaling interval. Following that, earthquake fragility analyses have been conducted using the maximum axial strain of the pipeline obtained from the nonlinear time-history analyses. Parameters under consideration for subsequent earthquake fragility analyses are soil conditions, end-restraint conditions, burial depth and the type of pipeline. Comparative analyses reveal that whereas the first three parameters influence the fragility curves, particularly soil conditions amongst the three parameters, the last parameter has a little effect on the curves. In all, the present study can be considered as a benchmark fragility analysis of a buried gas pipeline in the absence of an earthquake fragility analysis of the pipeline and thus is expected to be a useful source regarding earthquake fragility analyses of a buried gas pipelines.

• Journal of Korea Water Resources Association
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• v.55 no.spc1
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• pp.1177-1185
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• 2022

The water and sewage system is an infrastructure that provides safe and clean water to people. In particular, since the water and sewage pipelines are buried underground, it is very difficult to detect system defects. For this reason, the diagnosis of pipelines is limited to post-defect detection, such as system diagnosis based on the images taken after taking pictures and videos with cameras and drones inside the pipelines. Therefore, real-time detection technology of pipelines is required. Recently, pipeline diagnosis technology using advanced equipment and artificial intelligence techniques is being developed, but AI-based defect detection technology requires a variety of learning data because the types and numbers of defect data affect the detection performance. Therefore, in this study, various defect scenarios are implemented using 3D printing model to improve the detection performance when detecting defects in pipelines. Afterwards, the collected images are performed to pre-processing such as classification according to the degree of risk and labeling of objects, and real-time defect detection is performed. The proposed technique can provide real-time feedback in the pipeline defect detection process, and it would be minimizing the possibility of missing diagnoses and improve the existing water and sewerage pipe diagnosis processing capability.