Application of Outlier Detection Algorithms to Design a Multi-Packer System for Hydrogeological Analyses

Seungbeom Choi,Kyung-Woo Park,Changsoo Lee 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.2

The high-level radioactive waste repository must ensure its performance for a long period of time enough to sufficiently reduce the potential risk of the waste, and for this purpose, multibarrier systems consisting of engineered and natural barrier systems are applied. If waste nuclides leak, the dominating mechanisms facilitating their movement toward human habitats include advection, dispersion and diffusion along groundwater flows. Therefore, it is of great importance to accurately assess the hydrogeological and geochemical characteristics of the host rock because it acts as a flow medium. Normally, borehole investigations were used to evaluate the characteristics and the use of multi-packer system is more efficient and economical compared to standpipes, as it divides a single borehole into multiple sections by installing multiple packers. For effective analyses and groundwater sampling, the entire system is designed by preselecting sections where groundwater flow is clearly remarkable. The selection is based on the analyses of various borehole and rock core logging data. Generally, sections with a high frequency of joints and evident water flow are chosen. Analyzing the logging data, which can be considered continuous, gives several local points where the results exhibit significant local changes. These clear deviations can be considered outliers within the data set, and machine learning algorithms have been frequently applied to classify them. The algorithms applied in this study include DBSCAN (density based spatial clustering of application with noise), OCSVM (one class support vector method), KNN (K nearest neighbor), and isolation forest, of which are widely used in many applications. This paper aims to evaluate the applicability of the aforementioned four algorithms to the design of multi-packer system. The data used for this evaluation were obtained from DB-2 borehole logging data, which is a deep borehole locates near KURT.

Experimental Study on Frictional-Healing Behavior of a Rock Joint

Seungbeom Choi,Yongki Lee,Taehyun Kim 한국방사성폐기물학회 2022 한국방사성폐기물학회 학술논문요약집 Vol.20 No.2

A rock joint exerts significant influences on the rock mass behavior in terms of thermal, hydraulic, and mechanical (THM) aspects. Therefore, its features should be thoroughly investigated in various rock mechanical projects, such as high-level radioactive waste (HLW) disposal repository, tunnel, and rock slope. Meanwhile, it is essential to guarantee the safety of the disposal repository for a very long period of time and it should prepare measures for various risks, which may possibly encounter during that period. In general, direct shear tests for a rock joint are conducted to investigate the possibility of frictional sliding of the joint under specific loading conditions or to predict the shear strength of the joint. However, it is necessary to consider whether regional sliding of a rock joint or reactivation of a fault might occur due to an earthquake or redistribution of the in-situ stresses because the expected operation period of the repository is quite long, and various situations can happen. A slide-hold-slide test for a rock joint is a practical test that can investigate the time-dependent behavior or frictionalhealing of a joint. The test enables an estimation of the stress build-up phenomenon after strain energy release in a quantitative manner. In this study, a series of slide-hold-slide tests were carried out in order to investigate the characteristics. Joint specimens were made from mortar, which is a rock-like and brittle material, so as to consider the effect of joint roughness and to secure the reproducibility of the tests. At the same time, mechanical conditions as well as thermal and hydraulic were applied in order to take the environment of the repository into account. As a result, the behavior of shear stress recovery was observed, and the effects of THM coupled condition on the recovery were investigated. This study presents fundamental results of the experiments, and further research outcomes, including time dependent behavior of a joint, will be presented sequentially.

The Evolution of Community Development Governance in Korean

Seungbeom Choi 서울행정학회 2003 서울행정학회 학술대회 발표논문집 Vol.- No.-

The purpose of the article is to analyze how a community has been developed since the Korean War in the area, where US Camp Humphreys is located. A collaborative relationship among local government, US camp, and residents is necessary for the town to prosper at peace with the camp. The relationship has changed basically by the environmental factors such as diplomatic policy, economic recession, political and social change, and military strategies. However, residents, businessmen, local government, central government and US camp have made a lot of efforts to develop their community, in which they have to live together. They have successfully made a cooperative relationship, though there were troubles in other US campsite villages in Korea. This study analyzes the evolutionary process of the community development from the perspective of the governance theory.

Static and Dynamic Water Motion-Induced Instability in Oxide Thin-Film Transistors and Its Suppression by Using Low-<i>k</i> Fluoropolymer Passivation

Choi, Seungbeom,Jo, Jeong-Wan,Kim, Jaeyoung,Song, Seungho,Kim, Jaekyun,Park, Sung Kyu,Kim, Yong-Hoon American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.31

<P>Here, we report static and dynamic water motion-induced instability in indium-gallium-zinc-oxide (IGZO) thin-film transistors (TFTs) and its effective suppression with the use of a simple, solution-processed low-k (epsilon similar to 1.9) fluoroplastic resin (FPR) passivation layer. The liquid-contact electrification effect, in which an undesirable drain current modulation is induced by a dynamic motion of a charged liquid such as water, can cause a significant instability in IGZO TFTs. It was found that by adopting a thin (similar to 44 nm) FPR passivation layer for IGZO TFTs, the current modulation induced by the water-contact electrification was greatly reduced in both off- and on-states of the device. In addition, the FPR-passivated IGZO TFTs exhibited an excellent stability to static water exposure (a threshold voltage shift of +0.8 V upon 3600 s of water soaking), which is attributed to the hydrophobicity of the FPR passivation layer. Here, we discuss the origin of the current instability caused by the liquid-contact electrification as well as various static and dynamic stability tests for IGZO TFTs. On the basis of our findings, we believe that the use of a thin, solution-processed FPR passivation layer is effective in suppressing the static and dynamic water motion-induced instabilities, which may enable the realization of high-performance and environment-stable oxide TFTs for emerging wearable and skin-like electronics.</P>

Site Characterization for Bentonite Erosion and Piping Test (BEPT) in KURT

Seungbeom Choi,Chang-Ho Hong,Jaewook Ahn,Jin-Seop Kim 한국방사성폐기물학회 2024 한국방사성폐기물학회 학술논문요약집 Vol.22 No.1

Characterization of Geometric Properties of Rough Rock Joints for Hydromechanical Analyses

Seungbeom Choi,Chae-Soon Choi,Yong-Ki Lee,Sung-Hoon Ji 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.1

Discontinuities exert great influence on the thermal, hydraulic, and mechanical behavior of rock mass. Rock joint is one of the most frequently encountered discontinuities in many engineering applications, such as tunnel, rock slope and repository for high level radioactive waste. Therefore, the effects of rock joint should be thoroughly investigated in various aspects. Rock joint has gone through many geological processes and its behavior can be characterized by many properties. Among them, geometric properties, such as joint roughness, aperture, and contact area can affect mechanical and hydraulic properties and vice versa. Therefore, accurate understanding and characterization of the geometric properties are of importance. Generally, the geometric properties of a joint are obtained or estimated using the surface height or elevation, which could be measured by various contact or noncontact methods. Then, the coordinates of the surfaces are used to calculate several parameters, for instance roughness indexes and mechanical aperture, in a quantitative manner. This paper is a part of SKB task force project that aims to evaluate the geometric properties of rock joints and to analyze the hydromechanical behavior within a rough joint considering the properties. Four pairs of joint surfaces were laser-scanned in order to obtain coordinates of the surfaces and then the coordinates were used to calculate the roughness, directional roughness, aperture, and spatial correlations. At the same time, fluid flow within a rough joint were simulated by a commercial FEM code, considering the variation of aperture space due to normal load. Flowrate, flow path, and channelization were investigated in an aperture scale. Since rock mass consists of several joints and/or joint sets, characterization of a single rock joint can be utilized for analyzing the behavior of rock mass as a reference.

Estimation of Evaluation Parameters in Site Assessment for HLW Disposal in Terms of Rock Mechanics

Seungbeom Choi,Yoo Hong Kihm,Dae-Sung Cheon 한국방사성폐기물학회 2021 한국방사성폐기물학회 학술논문요약집 Vol.2021 No.06

고준위방사성폐기물 심층처분 부지조사를 위한 암반공학적 요소: 국내외 현황 및 사례 조사

최승범(Seungbeom Choi),김유홍(You Hong Kihm),김은경(Eungyeong Kim),천대성(Dae-Sung Cheon) 한국암반공학회 2020 터널과지하공간 Vol.30 No.2

우리나라는 1978년부터 원자력발전소를 운영해왔으며 그에 따른 고준위방사성폐기물 발생이 누적되고 있다. 이를 안전하게 처분하기 위한 영구 처분시설이 시급한 실정이나 처분 부지를 선정하는 과정에서 광범위하고 정밀한 부지조사가 요구되기 때문에 장기간에 걸친 조사가 선행되어야한다. 이러한 부지조사는 단계별로 진행되는 것이 일반적이며 이 과정에서 다학제적 평가가 이루어진다. 본 논문에서는 부지조사 과정에서 요구되는 암반공학적 요소를 중점으로 사례조사를 수행하였다. 단계별로 고려되는 암반공학적 평가요소와 그 적용 사례를 정리하였으며 이 과정에서 수행된 해외 연구 사례를 조사하였다. 동시에 국내 연구현황을 정리하였고 부지조사와 관련된 향후 연구 계획을 간략히 보고하였다. 향후 연구를 통해 부지조사 시 참고할 수 있는 기반자료를 생산하고자 하며 본 논문에서 수집된 사례 역시 활용할 예정이다. Nuclear power plants have been operated in Korea since 1978, thus the high-level radioactive waste (HLW) produced from the plants has been accumulated accordingly. Hence, it is urgent to secure a final repository for HLW disposal, however, siting process should be preceded, which usually takes long time, as it requires broad and precise investigation. The investigation is generally carried out in stages, which consists of multidisciplinary approaches. In this study, the case studies mainly pertaining to rock mechanics were conducted. Rock mechanical aspects required in each stage and their applications were investigated and corresponding R&D researches were presented as well. At the same time, current research status in Korea was presented, followed by a brief future research plan with regard to the site investigation. The future research aims to produce fundamental information for siting process, and the compiled cases in this study will be utilized as references in the research.

지방자치단체 빅데이터의 활용트렌드와 활성화 조건에 대한 연구

최승범(Choi, Seungbeom) 충북대학교 국제개발연구소 2016 사회적경제와 정책연구 Vol.6 No.1

본 논문은 지방자치단체 수준에서 빅데이터 활용의 현황을 살펴보고 활성화를 위한 조건을 제시하는 것을 목적으로 한다. 이를 위하여 빅데이터의 개념 및 특징을 구체적으로 고찰하고, 국내·외 및 민간·공공부문에서의 활용 트렌드를 살펴보고, 지방자치단체의 빅데이터 운용구조를 분석하고 활용가능성을 위한 조건을 제시하기로 한다. 지방자치단체가 빅데이터를 활성화하기 위하여는 관심 및 이해의 증진, 전담조직이나 인력의 확보, 데이터 생산주체 간의 협력, 데이터 품질관리노력 및 투자의 확대, 민간과의 협력, 프라이버시의 보호체계 정비 등의 요건이 갖추어져야 할 것이다. The purpose of this paper is to analyze the current status of Big-data use and to suggest conditions for the vitalization of it. In order to realize the purpose, the contents will include reviewing the concept and characteristics of Big-data, following the trends of its use in both Korea and abroad, analyzing the operation structure in local government, and suggesting conditions for the vitalization of Big-data. It is suggested that the revitalization needs Big-data team organization and personnel with full charge, local ordinances for institutional basis, public-data sharing structure, cooperation with private sector, privacy protection etc.

지역재생 관점에서 지방자치단체의 철도유휴부지 활용에 관한 연구

최승범 ( Seungbeom Choi ),김종호 ( Chong Ho Kim ) 국민대학교 사회과학연구소 2018 社會科學硏究 Vol.31 No.1

본 연구의 배경은 철도부지로서의 기능을 상실한 유휴부지가 지속적으로 증가하고 있으며, 이에 대한 활용의 필요성이 높아지고 있는 현실을 반영하고 있다. 철도유휴부지는 철도라는 고유의 행정목적으로 더 이상 활용되지 않는 것을 의미하기에, 새로운 목적으로 활용될 필요가 있으며, 지방자치단체 행정구역에 소규모로 산재해 있기에 이를 지방자치단체가 주도적으로 해당 지역의 특성에 부합할 수 있도록 지역재생의 관점에서 활용하는 접근이 필요하다. 철도유휴부지 사례분석 결과, 세 유형으로 구분할 수 있다. 첫째, 경제적 이익을 추구하는 지방자치단체 중심의 하향식 활용이다. 둘째, 공공성을 추구하는 지방자치단체 중심의 하향식 활용이다. 셋째, 적극적인 시민참여 거버넌스 중심의 상향식 활용이다. 지역재생 관점에 가장 부합하는 세 번째 유형과 더불어 사례들의 공통점에서 다음과 같은 시사점을 도출할 수 있다. 첫째, 철도유휴부지 활용의 효과성 증진을 위한 거버넌스 체제 구축이다. 둘째, 철도유휴부지 사업의 다양화와 공공성 확보이다. 셋째, 적극적 시민참여에 의한 상향식 활용이다. 넷째, 환경가치와 지역재생에 부합하는 활용이다. 이를 통하여 지역재생을 위한 지방자치단체의 주도적 역할, 분류기준의 구체화, 주요행위자들 간의 긴밀한 거버넌스 체제 구축을 정책적으로 제언한다. The background of this study reflects the fact that the railway idle land that has lost its function as a railway site is increasing, and the necessity of utilization is increasing. The railway idle site means that it is no longer used for its own administrative purpose of railway, so it needs to be utilized for a new purpose. Since it is scattered in a small scale in the administrative districts of the local autonomous entities, it is necessary to use it from the point of view of regional regeneration. As a result of analysis of railway idle site cases, there are three types. First, it is a top-down use centered on local governments seeking economic benefits. Second, it is a top-down use centered on local governments seeking publicity. Third, it is the bottom-up use of governance system through active citizen participation. In addition to the third type that best fits the regional regeneration perspective, the following implications can be drawn from the commonality of the cases. First, it is building a governance system to enhance the effectiveness of the utilization of idle land on the railway. Second, diversification of railway idle site projects and ensuring publicity. Third, it is bottom-up use by governance system through active citizen participation. Fourth, it is the application to meet environmental value and regional regeneration. This study suggests the active role of local governments for regional regeneration, the specification of classification criteria, and the establishment of close governance system among major actors.