• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2001년도 총회 및 춘계학술발표회
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• pp.19-21
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• 2001

The Shiheung mine was closed in 1972 and has been abandoned since then. Although some restoration work has been done, there still remain mine failings in and around the mine, posing a potential environmental hazard. Mine tailings and the porewater extracted from the tailing were investigated to see any evidence of elemental release and migration to adjacent groundwater and soil in the field. The pHs of the tailing range from 6.24 to 7.23. Calcite in the studied area seems to influence on such neutral pH range. Depth profile of mine tailing demonstrate elements have been leached and removed as a consequence of weathering during disposal. This is also supported by the findings from porewater analysis, corresponding the trends in the mine tailings. The concentrations of Cu, Cd, Pb, Zn in the tailing porewater exceed the standard value of EPA for drinking water and this implies groundwater can be contaminated through infiltration of the porewaters, which ultimately will be discharged as leachate from the mine tailing. Groundwater samples collected near the mine area do not show high metal concentrations, except for Fe, which were detected over drinking water standard.

• 한국물환경학회지
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• 제33권2호
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• pp.211-218
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• 2017

This experiment was carried out with the purpose of testing cadmium adsorption abilities of multi wall carbon nanotube (MWCNT), activated carbon, and synthesized layered double hydroxide (LDH). In the acidic condition, only MWCNT was effective for removing cadmium ion in the aqueous phase while other adsorbents rarely removed it. The MWCNT and cadmium ion adsorption reactions followed pseudo-first order kinetic. When the initial pH value was neutral (pH = 7), cadmium ion was rapidly removed by MWCNT and activated carbon in 4 hr (100% and 99.2%, respectively). Increasing adsorbent dosages affects the pH evolution and cadmium ion removal (0 to 99%). Cytotoxicity test showed that both MWCNT and LDH has low cytotoxic effects on three kind of human cells (A549, HS-294t, and HT-29).

• 한국전기전자재료학회논문지
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• 제26권2호
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• pp.83-86
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• 2013

The optical properties of ZnO thin film have been studied using photoluminescence(PL) spectroscopy with the change of sample temperatures from 10 K to 290 K. The spectrum at 10 K showed the characteristic emission lines of ZnO which were as follows: free exciton(FX) at 3.369 eV, neutral donor-bound exciton($D^0X$) at 3.360 eV, two electron satellite(TES) at 3.332 eV, $D^0X$-1LO at 3.289 eV, and donor-acceptor pair(DAP) transiton at 3.217 eV. From the spectral evolution with temperatures, two features could be identified as temperature went higher: (1) the bound excitons changed gradually into free excitons, (2) DAP turned into free electron-acceptor transition(e,$A^0$). The PL intensity of free exciton increased with the increase of temperatures, which was accompanied by the decrease of the intensity of bound excitions and bound excition-related transitons such as TES and $D^0X$-1LO. At 80 K DAP transition disappeared, while (e,$A^0$) transition started to appear at 30 K.

• 한국입자에어로졸학회지
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• 제10권1호
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• pp.27-31
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• 2014

A simple bimodal model has been developed to analyze charged particle coagulation by modifying previously suggested bimdal model for evolution of particle generation and growth. In the present model, two monodisperse modes are used and 40 charge nodes are assigned to each mode to account both change of the particle size and charge distribution. In addition, we also implemented the effect of electrostatic dispersion loss in the present model. Based on the developed model, we analyzed coagulation of asymmetric bipolar charged particles by computing evolutions of particle number concentration, geometric mean diameter of particles, charge asymmetric ratio and geometric standard deviation of particle size distribution for various initial charge asymmetric ratios. The number concentration of asymmetric bipolar charged particles decreases faster than that of neutral particles but that does not give faster growth of particles since the electrostatic dispersion loss overwhelms particle growth by coagulation.

• Journal of the Optical Society of Korea
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• 제17권6호
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• pp.543-547
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• 2013

A temperature dependent (10K-290K) photoluminescence (PL) study for two differently prepared ZnO thin films (as-grown and O-plasma treated) is presented. Four characteristic peaks were identified for both samples: (i) neutral donor-bound excitons ($D^oX$), (ii) two electron satellites (TES), (iii) phonon replica of $D^oX$ ($D^oX$-1LO), and (iv) donor-acceptor pair transition (DAP). As the sample temperature increased, $D^oX$-1LO and DAP transitions became indistinct. This was accompanied by newly-rising emission of free electron-acceptor transitions (e, $A^o$). The spectral evolution with temperature for as-grown samples also showed the optical emission from free excitons, which became dominant at higher temperatures. Some features related to O-plasma were identified in PL spectra: (i) different positions of TES transitions (28meV lower than $D^oX$ for as-grown samples and 35meV for O-plasma treated samples), (ii) the decrease of spectral intensity in both emissions of $D^oX$ and DAP after O-plasma treatment, and (iii) no noticeable transition from free excitons after the O-plasma treatment.

• 한국습지학회지
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• 제20권4호
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• pp.410-416
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• 2018

본 연구는 탄소나노튜브(MWCNT)와 활성탄을 이용한 니켈과 구리의 흡착특성을 평가하였다. 산성조건에서 활성탄의 제거성능이 낮은 반면, MWCNT만 니켈과 구리를 흡착 제거하는데 효율적이었다. MWCNT와 중금속의 흡착반응은 유사 일차반응식을 따랐다. 초기 pH가 중성일 때, 니켈은 MWCNT에 의해 신속히 제거되었고, 활성탄은 4시간에 각각 99.02%와 80.30%를 나타냈다. 또한, 구리이온은 초기 pH가 중성일 때 4시간내에 효율적으로 제거되었다. 흡착제 주입량을 증가함에 따라 pH가 증가하였고, 중금속 제거율도 증가하였다. 또한, 산화 전처리 공정은 MWCNT의 중금속 제거율을 증가시켰다.

• 한국지하수토양환경학회지:지하수토양환경
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• 제26권1호
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• pp.34-44
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• 2021

Acid mine drainage (AMD) resulting from pyrite oxidation in mining areas, subsequently leads to soil acidification accompanied by lowering pH and high concentration of metals and metalloids in its surrounding environment. Regarding to this, the microbial amelioration has been considered as a promising option for a more cost-effective and eco-friendlier countermeasure, compared to the use of alkaline chemicals. This study was aimed to evaluate influencing factors in microbially-mediated amelioration of acidic soil spiked by simulated AMD. For this, microcosm experiments were conducted by acid-neutralizing bacterial consortium (dominated by Klebsiella sp. and Raoultella sp.) under the various conditions of AMD spikes (0-2,500 mg SO42-/L), together with acidic mine soil (0-100 g) or sphagnum peat (0-5 g) in the 200 mL of nutrient medium. The employed bacterial consortium, capable of resisting to high level of sulfate concentration (up to 1,500 mg SO42-/L) in low pH, generated the ammonium while concomitantly reduced the sulfate, subsequently contributing to the effective soil stabilization with an evolution of soil pH up to neutral. Furthermore, it demonstrates that suitable condition has to be tuned for successful microbial metabolism to facilitate with neutralization during practical application.

• 천문학회보
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• 제45권1호
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• pp.63.2-63.2
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• 2020

FLASH is a blind neutral hydrogen (HI) absorption line survey, eventually targeting about 100,000 background radio continuum sources in the entire southern sky using the full 36-antenna of the Australian Square Kilometre Array Pathfinder (ASKAP). Our primary goal is to search for associated and intervening HI absorption lines in the intermediate redshift range 0.4 < z < 1.0. The survey aims to understand the evolution of HI gas in galaxies as well as various physical mechanisms in active galactic nuclei, such as accretion and feedback processes. In this poster, we give an overview of the FLASH survey and present the preliminary results from our first 100-hrs of pilot observations. The latest survey data covers 1,000 square degrees and is ideal for validating observation and data processing in the continuous 300MHz-width low frequency ASKAP band (700-1000MHz). One of the crucial objectives of the pilot survey is to establish the analysis methodology that will be applied to upcoming large absorption surveys in the future. We discuss our data quality validation and present some detections of associated/intervening HI absorption lines. These absorption lines allow us to trace the cold gas properties of active and normal galaxies at higher redshifts where the HI emission line is too weak to be detectable.

• 전기화학회지
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• 제11권3호
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• pp.165-169
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• 2008

CODH(Carbon Monoxide Dehydrogenase)에 의한 이산화탄소 환원에 있어서 작업전극을 유리탄소전극을 사용한 경우와 금전극을 사용한 경우를 비교하여 그 영향을 관찰하였다. 금전극을 사용한 경우에는 수소발생과 섞이기 때문에 전기분해의 전위를 잘 선택해야 효율적인 이산화탄소의 환원 반응을 관찰할 수 있는데 반하여, 유리탄소전극은 금전극보다 수소 환원에 대한 과전압이 크기 때문에 -650 mV vs. NHE 까지도 중성수용액에서 수소발생 없이, 효율적인 이산화탄소의 환원을 관찰할 수 있었다. CODH를 이용한 이산화탄소의 환원에는 가해주는 전기분해 전위가 큰 영향을 미침을 알 수 있었는데, $-570{\sim}600\;mV$ vs. NHE 근처가 가장 효율적임을 알 수 있었고 이보다 더 음의 전위를 걸어주었을 때는 효소활성의 감소 및 수소발생이 복합적으로 영향을 미쳐 일산화탄소 생성의 전류효율이 급격히 감소함을 알 수 있었다.

• Ocean Systems Engineering
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• 제6권1호
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• pp.61-97
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• 2016

This is the second of two papers on the 3D numerical modeling of nearshore hydro- and morphodynamics. In Part I, the focus was on surf and swash zone hydrodynamics in the cross-shore and longshore directions. Here, we consider nearshore processes with an emphasis on the effects of oceanic forcing and beach characteristics on sediment transport in the cross- and longshore directions, as well as on foreshore bathymetry changes. The Delft3D and XBeach models were used with four turbulence closures (viz., ${\kappa}-{\varepsilon}$, ${\kappa}-L$, ATM and H-LES) to solve the 3D Navier-Stokes equations for incompressible flow as well as the beach morphology. The sediment transport module simulates both bed load and suspended load transport of non-cohesive sediments. Twenty sets of numerical experiments combining nine control parameters under a range of bed characteristics and incident wave and tidal conditions were simulated. For each case, the general morphological response in shore-normal and shore-parallel directions was presented. Numerical results showed that the ${\kappa}-{\varepsilon}$ and H-LES closure models yield similar results that are in better agreement with existing morphodynamic observations than the results of the other turbulence models. The simulations showed that wave forcing drives a sediment circulation pattern that results in bar and berm formation. However, together with wave forcing, tides modulate the predicted nearshore sediment dynamics. The combination of tides and wave action has a notable effect on longshore suspended sediment transport fluxes, relative to wave action alone. The model's ability to predict sediment transport under propagation of obliquely incident wave conditions underscores its potential for understanding the evolution of beach morphology at field scale. For example, the results of the model confirmed that the wave characteristics have a considerable effect on the cumulative erosion/deposition, cross-shore distribution of longshore sediment transport and transport rate across and along the beach face. In addition, for the same type of oceanic forcing, the beach morphology exhibits different erosive characteristics depending on grain size (e.g., foreshore profile evolution is erosive or accretive on fine or coarse sand beaches, respectively). Decreasing wave height increases the proportion of onshore to offshore fluxes, almost reaching a neutral net balance. The sediment movement increases with wave height, which is the dominant factor controlling the beach face shape.