• Geomechanics and Engineering
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• 제13권5호
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• pp.775-791
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• 2017

Surface wave techniques are widely used as non-invasive method for geotechnical site characterization. Field surface wave data are collected and analyzed using different processing techniques to generate the dispersion curves, which are further used to extract the shear wave velocity profile by inverse problem solution. Characteristics of a dispersion curve depend on the subsurface layering information of a vertically heterogeneous medium. Sometimes soft layer can be found between two stiff layers in the vertically heterogeneous media, and it can affect the wave propagation dramatically. Now most of the surface wave techniques use the fundamental mode Rayleigh wave propagation during the inversion, but this may not be the actual scenario when a soft layer is present in a vertically layered medium. This paper presents a detailed and comprehensive study using finite element method to examine the effect of soft layers which sometimes get trapped between two high velocity layers. Determination of the presence of a soft layer is quite important for proper mechanical characterization of a soil deposit. Present analysis shows that the thickness and position of the trapped soft layer highly influence the dispersion of Rayleigh waves while the higher modes also contribute in the resulting wave propagation.

• 방사성폐기물학회지
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• 제11권2호
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• pp.115-131
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• 2013

미즈나미 지하처분연구시설 프로젝트는 일본원자력연구개발기구가 결정질암 내의 심부 지하 환경에 관해 종합적으로 연구하는 프로젝트이다. 미즈나미 프로젝트는 3개의 중첩되는 단계로 구성된다: 지표기반 조사단계 (단계 1), 건설단계 (단계 2), 운영단계 (단계 3)의 총 20년. 미즈나미 프로젝트의 1단계에서 3단계까지의 전체 목표는 1) 심부지질환경을 조사, 분석, 평가하기 위한 기술 정립, 2) 심부 지하 활용을 위한 일련의 공학적 기술 개발이다. 전체 목표 1을 달성하기 위하여, 1단계 목표를 굴착 전에 지질환경을 모사하고 굴착거동을 예측하는 모든 지표기반 조사결과로부터 지질환경 모델을 구축하는 것으로 설정하였다. 전체 목표 2를 달성하기 위하여, 2단계 목표는 지하시설을 위한 상세 설계 개념과 건설 계획을 수립하는 것으로 설정하였다. 본 논문은 결정질암내 지하수의 수리지화학적 특성을 조사하고 평가하기 위한 지질통합적 방법을 소개한다.

• 한국지하수토양환경학회지:지하수토양환경
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• 제25권2_spc호
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• pp.1-15
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• 2020

Monitoring and assessing terminal electron accepting processes (TEAPs) are one of the most important steps to remediate contaminated sites via various in-situ techniques. TEAPs are a part of the microbial respiration reactions. Microorganisms gain energy from these reactions and reduces pollutants. Monitoring TEAPs enables us to predict degradability of contaminants and degradation rates. In many countries, TEAPs have been used for characterization of field sites and management of groundwater wells. For instance, US Environmental Protection Agency (EPA) provided strategies for groundwater quality and well management by applying TEAPs monitoring. Denmark has also constructed TEAPs map of local unit area to develop effective groundwater managing system, particularly to predict and assess nitrogen contamination. In case of Korea, although detailed soil survey and groundwater contamination assessment have been employed, site investigation guidelines using TEAPs have not been established yet. To better define TEAPs in subsurface environments, multiple indicators including ion concentrations, isotope compositions and contaminant degradation byproducts must be assessed. Furthermore, dissolved hydrogen concentrations are regarded as significant evidence of TEAPs occurring in subsurface environment. This review study introduces optimal sampling techniques of groundwater and dissolved hydrogen, and further discuss how to assess TEAPs in contaminated subsurface environments according to several contamination scenarios.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2015년도 제49회 하계 정기학술대회 초록집
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• pp.60-60
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• 2015

Nanosheets of graphene and related 2D materials have attracted much attention due to excellent physical, chemical and mechanical properties. Single-layer graphene (SLG) was first synthesized by Blakely et al in 1974 [1]. Following his achievements, we initiated the growth and characterization of graphene and h-BN on metal substrates using surface segregation and precipitation in 1980s [2,3]. There are three important steps for nanosheet growth; surface segregation of dopants, surface reaction for monolayer phase, and subsequent 3-D growth (surface precipitation). Surface phase transition was clearly demonstrated on C-doped Ni(111) by in situ XPS at elevated temperatures [4]. The growth mode was clarified by inelastic background analysis [5]. The surface segregation approach has been applied to C-doped Pt(111) and Pd(111), and controllable growth of SLG has been demonstrated successfully [6]. Recently we proposed a promising method for producing SLG fully covering an entire substrate using Ni films deposited on graphite substrates [7]. A universal method for layer counting has been proposed [8]. In this paper, we will focus on the effect of competitive surface-site occupation between carbon and other surface-active impurities on the graphene growth. It is known that S is a typical impurity of metals and the most surface-active element. The surface sites shall be occupied by S through surface segregation. In the case of Ni(110), it is confirmed by AES and STM that the available surface sites is nearly occupied by S with a centered $2{\times}2$ arrangement. When Ni(110) is doped with C, surface segregation of C may be interfered by surface active elements like S. In this case, nanoscopic characterization has discovered a preferred directional growth of SLG, exhibiting a square-like shape (Fig. 1). Also the detailed characterization methodologies for graphene and h-BN nanosheets, including AFM, STM, KPFM, AES, HIM and XPS shall be discussed.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2011년도 춘계학술발표대회
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• pp.53.2-53.2
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• 2011

Ti metal has superior mechanical properties along with biocompatibility, but it still has the problem of bio-inertness thus forming weaker bond in bone/implant interface and long term clinical performance as orthopaedic and dental devices are restricted for stress shielding effect. On the other hand, despite the excellent biodegradable behavior as being an integral constituent of the natural bone, the mechanical properties of ${\beta}$-tricalcium phosphate $(Ca_3(PO_4)_2;\;{\beta}-TCP)$ ceramics are not reliable enough for post operative load bearing application in human hard tissue defect site. One reasonable approach would be to mediate the features of the two by making a composite. In this study, ${\beta}$-TCP/Ti ceramic-metal composites were fabricated by spark plasma sintering in inert atmosphere to inhibit the formation of $TiO_2$. Composites of 30 vol%, 50 vol% and 70 vol% ${\beta}$-TCP with Ti were fabricated. Detailed microstructural and phase characteristics were investigated by FE-SEM, EDS and XRD. Material properties like relative density, hardness, compressive strength, elastic modulus etc. were characterized. Cell viability and biocompatibility were investigated using the MTT assay and by examining cell proliferation behavior.

• 한국대기환경학회지
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• 제20권6호
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• pp.811-821
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• 2004

Low-Z particle electron probe X-ray microanalysis (low-Z particle EPMA) was applied to characterize aerosol particles collected at Gosan in Jeju island during an IOP (intensive observation period) for an international ACE-Asia project in April, 2001. Various types of atmospheric particles such as organics, carbon-rich, aluminosilicates, silicon oxide, sodium nitrate, sodium chloride, and ammonium sulfate were observed. The reacted sea salt particles such as sodium nitrate were the most abundantly encountered, but original sea salt particles were rarely observed. Since the Low-Z particle EPMA can provide quantitative information on the chemical composition of aerosol particles, many different particle types on the basis of their chemical compositions were observed and identified. In this study, it is demonstrated that the Low-Z particle EPMA can provide detailed information on the chemical compositions for the aerosol particles collected for six consecutive days in April, 2001, at Gosan super-site.

• 대한미생물학회지
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• 제21권1호
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• pp.47-52
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• 1986

A heat-labile enterotoxin and no heat-stable enterotoxin producing($LT^+ST^-$) plasmid (110 kilobases in size) was isolated from an enterotoxigenic Escherichia coli of human strain O15:H11 and used for analysis of the $LT^+$ deoxyrionucleic acid region using recombinant DNA technology. A DNA segment containing the $LT^+$ DNA region which was one restriction endonuclease BamHl fragment(6.2 kb in size) was joind to a small multicopy plasmid, pUC9. E. coli K-12 strain, JM103 harboring the chimeric plasmid produced greater amounts of LT than did the enterotoxigenic E. coli O15:H11 strain. The BamHl fragment was further digested with various restriction endonucleases and contained no HindIll restriction site which is an essential in $LT^+ST^+$ plasmid. The detailed DNA sequencing of this $LT^+ST^-$ plasmid is required.

• Bulletin of the Korean Chemical Society
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• 제34권5호
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• pp.1401-1406
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• 2013

This study tested the feasibility of observing H/D exchange of intact protein by top-down electron capture dissociation (ECD) mass spectrometry for the investigation of protein structure. Ubiquitin is selected as a model system. Local structural information was obtained from the deuteration levels of c and $z^{\cdot}$ ions generated from ECD. Our results showed that ${\alpha}$-helix region has the lowest deuteration level and the C-terminal fraction containing a highly mobile tail has the highest deuteration level, which correlates well with previous X-Ray and HDX/NMR analyses. We studied site-specific H/D exchange kinetics by monitoring H/D exchange rate of several structural motives of ubiquitin. Two hydrogen bonded ${\beta}$-strands showed similar HDX rates. However, the outer ${\beta}$-strand always has higher deuteration level than the inner ${\beta}$-strand. The HDX rate of the turn structure (residues 8-11) is lower than that of ${\beta}$-strands (residues 1-7 and residues 12-17) it connects. Although isotopic distribution gets broader after H/D exchange which results in a limited number of backbone cleavage sites detected, our results demonstrate that this method can provide valuable detailed structural information of proteins. This approach should also be suitable for the structural investigation of other unknown proteins, protein conformational changes, as well as protein-protein interactions and dynamics.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 세계 도시지반공학 심포지엄
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• pp.157-171
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• 2009

A 151 storey super high-rise building located in an area of reclaimed land constructed over soft marine clay in Songdo, Korea is currently under design. This paper describes the design process of the foundation system of the supertall tower, which is required to support the large building vertical and lateral loads and to restrain the horizontal displacement due to wind and seismic forces. The behaviour of the foundation system due to these loads and foundation stiffness influence the design of the building super structure, displacement of the tower, as well as the raft foundation design. Therefore, the design takes in account the interactions between soil, foundation and super structure, so as to achieve a safe and efficient building performance. The site lies entirely within an area of reclamation underlain by up to 20m of soft to firm marine silty clay, which overlies residual soil and a profile of weathered rock. The nature of the foundation rock materials are highly complex and are interpreted as possible roof pendant metamorphic rocks, which within about 50m from the surface have been affected by weathering which has reduced their strength. The presence of closely spaced joints, sheared and crushed zones within the rock has resulted in deeper areas of weathering of over 80m present within the building footprint. The foundation design process described includes the initial stages of geotechnical site characterization using the results of investigation boreholes and geotechnical parameter selection, and a series of detailed two- and three-dimensional numerical analysis for the Tower foundation comprising over 172 bored piles of varying length. The effect of the overall foundation stiffness and rotation under wind and seismic load is also discussed since the foundation rotation has a direct impact on the overall displacement of the tower.

• 터널과지하공간
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• 제33권3호
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• pp.109-125
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• 2023

고준위방사성폐기물처분장은 공학적/천연 방벽 등을 통해 처분장의 안전성을 확보한다. 이러한 안전 수단은 다양한 방법을 통해 장/단기적 성능을 평가하고 검증되어야 한다. 한국원자력연구원은 원내에 위치한 지하연구시설인 KURT를 이용해 다양한 현장 실증실험을 수행해왔다. 선행 시험 종료 후, 개선된 형태의 실증실험인 K-COIN을 수행하기 위해 개념 설계안을 도출하고 상세 실험계획을 수립 중이다. KURT 내부에 K-COIN 실험부지 선정을 위한 예비 부지조사를 수행하였다. 연구 모듈(research gallery, RG) 세 구역에 약 20 m 심도의 시추공 총 15개를 시추하여 시추코어를 확보하고 암석 실내시험에 적합한 구간을 선정하여 무결암 시험편을 준비하였다. 준비된 시험편을 사용하여 물리적 특성 측정, 단축압축시험, 간접인장시험, 삼축압축시험을 수행했으며 이를 통해 무결암의 비중, 공극률, 탄성파 속도, 단축압축강도, 탄성계수, 포아송비, 간접인장강도, 점착력, 내부 마찰각을 측정하였다. 간단한 통계 처리를 수행한 결과, 시추 구역과 심도(상부 0~10 m, 하부 10~20 m)에 따른 무결암 물성의 차이는 크지 않은 것으로 확인되었다. 가장 대표적인 암석 물성인 단축압축강도를 바탕으로 판단하면, 모든 시추 구역과 심도에서 매우 강한 암석으로 분류되어 모든 후보 지역에서 역학적인 안전성을 확보한 것으로 판단된다.