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An Integrated Study on Seawater Intrusion in Yeonggwang-gun, Korea
Hwang, Seho,Shin, Jehyun,Chi, Sejung,Lee, Wonsuk,Park, Inhwa,Huh, Daegee,Lee, Sangkyu 한국암반공학회 2003 Geosystem engineering Vol.6 No.4
A combination of drilling, hydrogeochemical survey, geophysical survey, and the numerical modeling for the flow and transport of groundwater was performed to evaluate seawater intrusion in Baeksu-eup, Yeonggwang-gun, Korea. Twelve wells were drilled for the collection of geologic, hydrogeochemical, hydrologic, and geophysical logging data to characterize seawater intrusion. To evaluate the salinity distribution of a coastal aquifer, drilling, geophysical data such as vertical electrical soundings (VES), well logging, and hydrogeochemical results were used. Hydrogeochemical results were used to understand the origin of salt and the seawater mixing ratio of groundwater. Spatial layer interfaces derived from YES data, various in situ physical properties from geophysical well loggings, the estimated equivalent NaCl concentration, and aquifer test such as slug test and so on were used as useful input parameters for the numerical simulation with density-dependent flow. Our multidisciplinary approach for evaluating seawater intrusion can be considered as a valuable attempt to enhance the utilization of various data and the reliability of numerical groundwater modeling.
Hwang Seho,Shin Jehyun,Park Inhwa,Lee Sangkyu Korean Society of Earth and Exploration Geophysici 2004 지구물리와 물리탐사 Vol.7 No.1
A combination of drilling, geophysical well logging, and electrical soundings was performed to evaluate seawater intrusion in Baeksu-eup, Youngkwang-gun, Korea. The survey area extends for over 24 $km^2$. To delineate the extent of seawater intrusion, 60 vertical electrical soundings (VES) have been carried out. Twelve wells were also drilled for the collection of hydrogeological, geochemical, and geophysical well logging data, to delineate the degree and vertical extent of seawater intrusion. To map the spatial distribution of seawater in this coastal aquifer, geophysical data and hydrogeochemical results were used, and the relation between the resistivity of groundwater and equivalent NaCl concentration was found. Layer parameters derived from VES data, various in-situ physical properties from geophysical well logging, and the estimated equivalent NaCl concentration were very useful for quantitative evaluation of seawater intrusion. Our approach for evaluating seawater intrusion can be considered a valuable attempt at enhancing the use of geophysical data.
부지특성 조사 및 평가를 위한 지구물리검층 방법의 품질관리
황세호(Seho Hwang),신제현(Jehyun Shin),현승규(Seung Gyu Hyun) 대한지질학회 2021 대한지질학회 학술대회 Vol.2021 No.10
방사성폐기물 처분시설 부지에 대한 부지특성 조사 및 평가는 지표 지질, 물리탐사 등의 지표 조사 후에 심부 지질학적 부지특성의 상세한 정보를 파악하기 위하여 대표적인 위치를 선정하여 시추공을 굴착한다. 시추공 내 물리검층, 수리시험, 역학시험 등의 원위치 시험과 모니터링 등을 통해 심부의 부지특성을 평가한다. 물리검층 결과의 주요 활용 영역은 시추공 설치 적합성 확인과 더불어 지질학적 특성(단열분포와 암종 등), 수리지질학적 특성, 암반역학적 및 열적 특성 등의 분야에서 이용된다. 물리검층 자료는 코어주상도, 실내 물성/역학 시험, 수리 및 역학 원위치 시험에서 대상 구간의 참조에 강력한 도구로 활용되며 다양한 시험결과의 해석에도 활용성이 높다. 물리검층의 장점으로는 조밀한 간격으로 연속적 측정이 가능하고, 측정 체적이 크며, 반복적으로 측정을 할 수 있다는 것이다. 이런 장점을 갖는 물리검층을 통해 단층 파쇄대 물성 확인, 단열의 수리특성 평가 등을 수행할 수 있다. 반면 물리검층의 단점은 지층 물성의 직접적 측정 및 간접적 추정에 있어서 일부 측정 장비의 정밀도 및 정확도는 검층 속도, 시추공의 지름 변화, 공내수의 특성 등 다양한 시추공 환경에 영향을 받을 수 있으므로 사용전 검층장비에 대한 보정이 필요하다는 것이다. 이러한 측정 장비에 대해 적절한 보정 등이 이루어지지 않는다면 조사 자료의 품질이 저해될 수 있으며, 자료의 신뢰도가 낮아진다. 따라서 지질학적 특성(단열분포와 암종 등), 수리지질학적 특성, 암반역학적 및 열적 특성 등 활용 분야 별 물리검층을 위해서 방사능동위원소, 전기, 초음파, 광학 등의 매우 다양한 센서들을 시추공 내 사용함에 따라 장비의 성능구현의 적절성과 관련된 교정(calibration)이나 시추공 환경영향 보정(correction) 등에 대한 과정과 절차를 명확하게 할 필요가 있다. 이와 같은 과정은 물리검층 측정값에 대한 신뢰성을 보증하는 과정으로 이해할 수 있으며 체계화된 품질관리에 대한 문서화가 필요하다. 본 연구에서는 방사성 폐기물 처분시설 부지평가와 관련하여 물리검층 방법에 대한 품질관리 중요성과 앞으로의 과제를 현재까지 국내에서 수행한 물리검층의 품질관리와 스웨덴 SKB에서 수행한 사례를 중심으로 소개하고자 한다.
Efficient Decoding Schemes of LDPC Codes for the Layered-Division Multiplexing Systems in ATSC 3.0
Hwang, Youngjun,Cho, Sunghye,Myung, Seho,Yang, Kyeongcheol [Institute of Electrical and Electronics Engineers 2017 IEEE transactions on broadcasting Vol.63 No.1
<P>A low-complexity decoding scheme of low-density parity-check codes for the layered-division multiplexing (LDM) systems in ATSC 3.0 is proposed. Based on the unique characteristic of the LDM and the special structure of a parity-check matrix (PCM) for the core layer, the proposed scheme applies the sum-product algorithm (SPA) to only a part of the PCM. For this reason, it is referred to as 'the partial SPA,' compared with the conventional scheme, denoted by 'the full SPA.' Clearly, it has a significantly lower complexity than the full SPA. Furthermore, we propose hybrid decoders employing both the full SPA and the partial SPA to achieve a better performance, while maintaining their complexity low. Numerical results show that the proposed schemes have a good performance enough to perform successive interference cancellation for the enhanced layer of the LDM systems in ATSC 3.0 as well as they have a low-complexity merit depending on system parameters. Since they only schedule the decoding procedure without modifying the decoder structure, they also have a benefit in the implementation of decoders.</P>
비파괴검사용 자기카메라의 자원 및 자기렌즈의 3차원 시뮬레이션
황지성,이진이,최세호 한국비파괴검사학회 2004 학술대회 논문집 Vol.- No.-
It is important to estimate the distribution of intensity of a magnetic field for application of magnetic method to industrial nondestructive evaluation. Magnetic camera provides the distribution of a quantitative magnetic field with homogeneous lift-off and same spatial resolution, Leakage magnetic flux near the crack on the specimen could be amplified by magnetic fluid. This study introduces the 3-dimensional simulations consideration of the magnetic resource and the effects of lens for concentrating of magnetic flux.
Seho Sun,Kangchun Lee,Ganggyu Lee,Yehwan Kim,Sungmin Kim,Junha Hwang,Hyungoo Kong,Kyung Yoon Chung,Ghulam Ali,Taeseup Song,Ungyu Paik 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.111 No.-
Chemical mechanical planarization (CMP) is indispensable for processing of integrated circuit semiconductordevices to attain globally planarized surfaces. One of the critical consumables in the CMP processis a slurry containing abrasives like colloidal silica (SiO2). However, there is a limit to the use of CMP slurriescontaining SiO2 under acidic conditions due to deterioration of colloidal stability, resulting in defectson the planarized surfaces. Herein, we developed an Fe-substituted SiO2 consisting of single-atom Fe(III),enabling improved colloidal stability over universal pH regions for low-defect tungsten CMP applications. The facile and unique single-atom modification process is proposed by controlling the lattice dissolution–reprecipitation replacement of Fe3+ and Si4+ ions. The physicochemical states of Fe atoms in the surficiallattice of Fe-substituted SiO2 were confirmed through Raman spectroscopy, electron microscopy, x-rayabsorption spectroscopy, and energy-dispersive x-ray spectroscopy. Consequently, enhanced performancein W CMP was achieved using Fe-substituted SiO2. Regarding defect performance, defects werereduced from 11 scratches to 0 and 94 other defects to only 7. Additionally, the removal rate increasedfrom 67 to 122 Å/min, and the surface topography improved from 6.6 to 2.9 nm.