• Journal of Korean Tunnelling and Underground Space Association
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• v.24 no.4
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• pp.341-353
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• 2022

Pipelines are buried in urban area, and the position (depth and orientation) of buried pipeline should be clearly identified before ground excavation. Although various geophysical methods can be used to detect the buried pipeline, it is not easy to identify the exact information of pipeline due to heterogeneous ground condition. Among various non-destructive geo-exploration methods, ground penetration radar (GPR) can explore the ground subsurface rapidly with relatively low cost compared to other exploration methods. However, the exploration data obtained from GPR requires considerable experiences because interpretation is not intuitive. Recently, researches on automated detection technology for GPR data using deep learning have been conducted. However, the lack of GPR data which is essential for training makes it difficult to build up the reliable detection model. To overcome this problem, we conducted a preliminary study to improve the performance of the detection model using finite difference time domain (FDTD)-based numerical analysis. Firstly, numerical analysis was performed with homogeneous soil media having single permittivity. In case of heterogeneous ground, numerical analysis was performed considering the ground heterogeneity using fractal technique. Secondly, deep learning was carried out using convolutional neural network. Detection Model-A is trained with data set obtained from homogeneous ground. And, detection Model-B is trained with data set obtained from homogeneous ground and heterogeneous ground. As a result, it is found that the detection Model-B which is trained including heterogeneous ground shows better performance than detection Model-A. It indicates the ground heterogeneity should be considered to increase the performance of automated detection model for GPR exploration.

• Journal of the Korean Society for Nondestructive Testing
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• v.22 no.3
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• pp.275-283
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• 2002

To detect the position and depth of buried underground utilities, method of Ground Penetrating Radar(GPR) survey is the most commonly used. However, the skin-depth of GPR is very shallow, and in the places where subsurface materials are not homogeneous and are compose of clays and/or salts and gravels, GPR method has limitations in application and interpretation. The aim of this study is to overcome these limitations of GPR survey. For this purpose the site where the GPR survey is unsuccessful to detect the underground big pipes is selected, and soil tests were conducted to confirm the reason why GPR method was not applicable. Non-destructive high-frequency electromagnetic (HFEM) survey was newly developed and was applied in the study area to prove the effectiveness of this new technique. The frequency ranges $2kHz{\sim}4MHz$ and the skin depth is about 30m. The HFEM measures the electric field and magnetic field perpendicular to each other to get the impedance from which vertical electric resistivity distribution at the measured point can be deduced. By adopting the capacitive coupled electrodes, it can make the measuring time shorter, and can be applied to the places covered by asphalt an and/or concrete. In addition to the above mentioned advantages, noise due to high-voltage power line is much reduced by stacking the signals. As a result, the HFEM was successful in detecting the buried underground objects. Therefore this method is a promising new technique that can be applied in the lots of fields, such as geotechnical and archaeological surveys.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.8
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• pp.633-641
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• 2008

Recently, the necessity for diagnosis and management of pipes has emerged as the issue due to contamination of water supply generated by corrosion of pipes. Although inspection has been performed with industrial endoscopes, the method has limits for full diagnosis of pipes due to the lack of working range. As a solution for this problem, many locomotive mechanisms for a micro robot with endoscope functions were proposed. In this paper, we analyze the locomotive mechanism of crawling robot proposed as locomotive device for pipe inspection. Based on a mechanical modeling of motor and micro robot inside small pipe, the theoretical formula for velocity is obtained. This derived theoretical formula is demonstrated the feasibility through the comparison with experimental result. Also, we could find the most important element influencing the moving velocity of micro robot when the robot operates in small pipe. Consequently, it is expected that this study can supply useful information to design of crawling robot to move in small pipe.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.3
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• pp.1270-1274
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• 2012

The pipe laid underground more than three decades ago are already starting to reveal the problem like corrosion. There have been many studies to design robotic system for a cost-effective revival of old pipes. And the ability to inspect in the pipes, the ability to treat and repaint the pipes and the fault-tolerant robotic system are well known important factors for the robotic system. It's real hard part to manage the underground pipes for companies because it needs high technical and too much money. According to this reasons, in this paper, we had design an in-pipe robotic system having abilities to inspect outworn pipes, to treat and paint old pipes. This new robot system is pressing wall type robot, and it has a good carrying power for working.

• Journal of Korean Society of societal Security
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• v.1 no.4
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• pp.73-81
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• 2008

Electromagnetic induction surveys are one of the useful methods to detect the location and buried depth of underground utilities by measuring horizontal and vertical magnetic fields. It can effectively detects single buried utility with the accuracy of within 20 cm. However when another utility is buried near to target one, the accuracy of utility location considerably decreases due to the distortion of magnetic fields caused from adjacent utility. This study shows the ways to verify the location and buried depth of target utility when magnetic fields does not show symmetric distribution due to adjacent another utility. Using Bluetooth wireless communication tools, we developed the way to records measured magnetic fields to handheld PDA. We investigated the criteria for minimum distance of two adjacent utilities to separate the individual responses through field model test.

• Geophysics and Geophysical Exploration
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• v.3 no.2
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• pp.48-52
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• 2000

We have calculated and analyzed the electromagnetic responses of buried conductive pipes due to a horizontal magnetic dipole source on the pound using a three-dimensional (3-D) finite element method to provide useful guidelines for designing electromagnetic pipe locator and for field operation of the system. For single buried pipe, the horizontal component and the horizontal difference of the vertical component of magnetic field show peaks above the pipe. When comparing the width of response curves of both cases around the peak, horizontal difference of vertical component of magnetic field shows much narrower peak, 2 times narrower at a half of maximum amplitude, than that of horizontal component of magnetic field. Accordingly, we can pinpoint the horizontal location of pipe on the ground more accurately by measuring the horizontal difference of vertical component of magnetic fold. Moreover, it will have a merit in determining the depth of pipe, because the equation for depth estimation is defined just above the pipe. When there are two buried pipes separated by two meters with each other, the response of horizontal difference of vertical component of magnetic field has two separate peaks each of which is located above the pipe whereas horizontal magnetic field response has only one peak above the pipe just below the transmitter. Thus, when there exist more than a buried pipe, measuring the horizontal difference of vertical magnetic field can effectively detect not only the pipe under transmitter but also adjacent ones. The width of response curves also indicates higher resolving ability of horizontal difference of vertical component of magnetic field.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.1
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• pp.77.1-77.1
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• 2011

김해천문대는 2002년에 개관하여 대전, 영월을 이어 세 번째로 건립된 초기 시민천문대이다. 당시 지방자치단체에서 지방과학관 사업으로 국비를 받아 건립하였다. 초기에 개관한 시민천문대에 대한 국민들의 뜨거운 호응에 힘입어 이후 지방과학관 사업에서 대부분 시민천문대 형태로 건립되었는데, 현재 약 20개 정도의 지방자치단체에서 시민천문대를 건립하였다. 현재 도서관, 수련원, 교육과학연구원 등 기존의 교육 기관에 딸린 부설 천문대를 포함하면 청소년, 시민들이 이용할 수 있는 성격의 천문대는 전국적으로 약 80개에 이른다. 이러한 시민천문대의 등장은 국민들의 천문에 대한 관심을 높여 우리나라의 천문학 발전에 밑거름이 될 수 있기 때문에 매우 중요하다. 따라서 시민천문대에 대한 학계, 교육계의 관심과 협조가 향후 천문학 발전에 중요한 밑거름 역할을 할 수 있을 것이다. 또한 시민천문대의 운영은 일반적인 과학관과는 달리 천체를 보여주는 등, 관측 활동을 중심으로 진행하기 때문에 창의적인 다양한 방법의 운영을 시도하는 것이 무엇보다도 중요하다. 특히 김해천문대의 경우 초기의 관람중심을 탈피하여 교육프로그램 중심의 운영함으로서, 소행성 탐사, 자체 기술개발 등 연구 활동이 가능할 정도로 발전하였다. 본 발표에서는 김해천문대에서 지난 9년간 진행된 다양한 사업과 프로그램을 소개하고 김해천문대 운영의 운영 변화 과정과 그 결과를 통해 향후 시민천문대의 운영 방향을 말하고자 한다.

• Proceedings of the KIEE Conference
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• 2005.10c
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• pp.38-40
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• 2005

이 논문은 지하매설관의 손상에 따른 자기누설 신호를 유한요소법을 이용하여 Simulation 하고, 자기누설탐사장치를 이용하여 지하매설관에 대한 비파괴검사를 할 경우 나타나는 여러 가지 자기적 신호를 분석하여 손상의 크기나 형상 등을 판별할 수 있도록 기본적인 자기누설정보를 제공하기 위한 연구이다. 3가지 형태의 결함을 배관과의 상대적인 위치에 따라 3차원 FEM으로 해석을 하고 결함의 형상 및 크기대한 정보제공을 위하여 분석을 하였다.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.18 no.2
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• pp.111-120
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• 2000

Water, waste, electric and gas facilities are urban based facilities that needed in our life and are often located in underground. Therefore, underground facilities are more difficult to manage efficiently than ground facilities. It is needed to carry out survey/probe into underground facilities and to build database in order to prevent city-misfortunes being occurred because of negligent management and in order to minimize budget-waste and a traffic jam according to repetition of road excavation constructions. Also, the development of application system is required to manage efficiently underground facility. Chonju city has launched underground water supply facility computerizing project as a part of National Geographic Information System project until December 1998 and executed survey/probe into 402.89 km water supply that is 80 mm up inside central town area 39.6 $km^2$. Also, chonju city built database into 537 km water supply that is 80 mm below based on water supply card without other survey/probe works. Also, existing work process each department is changed into GIS applied work process and underground water supply facility management system is developed by its work process basis. Water supply underground facility management system that is developed is composed of sub-system like base-map management, water supply inspect, water supply management and water supply inquiry, construction work management, administration management and map management. This research presents the procedure and method of underground water supply facility survey/probe and problem being occurred during survey/probe procedure and also show the functions of each sub-systems composing underground water supply facility management system.

• Journal of the Korean GEO-environmental Society
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• v.23 no.8
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• pp.5-10
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• 2022

Ground Subsidence has been continuously occurring in densely populated downtown. The main cause of ground subsidence is the damaged underground facility like sewer. Currently, ground subsidence is being dealt with by discovering cavities in ground using GPR. However, this consumes large amount of manpower and cost, so it is necessary to predict hazardous area for efficient operation of GPR. In this study, ◯◯city is divided into 500 m×500 m grids. Then, data set was constructed using the characteristics of the underground facility and ground subsidence in grids. Data set used to machine learning model for ground subsidence risk grade prediction. The purposed model would be used to present a ground subsidence risk map of target area.