• 한국광물학회지
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• 제32권4호
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• pp.303-312
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• 2019

본 연구에서는 안동댐 퇴적물의 중금속 및 용출 특성을 분석하기 위하여 X-선 회절 분석, ICP 분석, 용출 실험을 수행하였다. X-선 회절 분석 결과 안동댐 퇴적물의 주구성 광물은 석영, 사장석, 녹니석, 일라이트이다. 퇴적물에 대한 ICP 분석 결과 비소와 카드뮴의 농도가 매우 높게 나타났다. 용출 실험은 교란 상태에서 호기성 및 혐기성 환경에서 수행하였다. 용출 실험 결과 혐기성보다 호기성 상태에서 더 많은 중금속이 용출되는 경향을 나타내었다. 호기성 상태에서 시간이 지남에 따라 농도가 증가하는 항목은 망간, 아연, 카드뮴이며 혐기성 상태에서는 망간, 철, 비소이다. 퇴적물 중금속 농도대비 용출비는 호기성 및 혐기성 환경에서 각각 Mn > Cd > Zn > Ni > Cu > As > Pb ≒ Fe ≒ Cr이며 Mn > As > Cu > Ni > Zn > Pb ≒ Cd ≒ Fe ≒ Cr이다.

• 한국응용과학기술학회지
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• 제32권1호
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• pp.116-126
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• 2015

본 연구에서는 이산화탄소 고정화에 있어 이산화탄소 전환을 위해 MEA를 이용한 습식화학흡수법의 셔틀메카니즘을 도입하였다. 또한 알칼리 무기물질을 다량 함유한 산업부산물을 습식탄산화법을 이용해 처리하고자 하였다. 즉, 산업부산물의 화학적 처리를 통해 칼슘이온을 용출하였다. 산성물질을 이용한 용출상징수를 ICP로 분석한 결과, 칼슘이온이 최대 17,900 ppm(1.79%)을 확보하였다. 또한 MEA를 이용한 습식 흡수공정을 통해 상온, 상압조건의 이산화탄소 분위기에서 94%의 전환률을 얻었다. 슬러지의 액상탄산화를 통해 슬러지 mg 당 0.175 mg의 이산화탄소를 고정하였으며, 최종생성물의 XRD 분석결과 일반적인 탄산칼슘의 결정구조인 calcite 형상을 확인하였다.

• 자원리싸이클링
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• 제17권3호
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• pp.42-47
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• 2008

침출온도 $100^{\circ}C{\sim}140^{\circ}C$, 산소압력 $40psi{\sim}100psi$, NaOH농도 $0.5M{\sim}2M$ 범위의 침출조건에서 황비철광과 방연광의 혼합황화광의 알카리산화에 의한 Pb 침출실험이 수행되었다. 혼합황화광중의 방연광침출에는 침출용액중의 $OH^-$농도가 큰 영향을 미치며 낮은 $OH^-$농도의 침출용액에서는 침출반응의 진행에 따른 $OH^-$저하에 의하여 침출된 $HPbO_2^-$가 화합물로 다시 석출이 일어나서 침출율을 저하시킬 수 있다. 침출온도 $120^{\circ}C$, 산소압력 100psi, 침출시간 30분, NaOH 2M의 침출조건에서 처리한 침출잔사 중의 Pb함량이 가장 낮은 결과를 얻었다.

• 한국지하수토양환경학회지:지하수토양환경
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• 제13권3호
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• pp.45-51
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• 2008

토양공극에 위치한 벤젠-NAPL(Non-Aqueous Phase Liquid)에 대한 cosolvent 세정기술을 연구하였다. 토양칼럼을 이용하여 cosolvent 내 알코올 특성 및 농도 변화에 따른 NAPL 제거 변화를 실험하였다. NAPL에 흡수되어 부피를 증가시키는 NAPL swelling 알코올(1-프로판올, TBA)과 Non-swelling 알코올(에탄올) 특성에 따른 NAPL 제거 효과를 평가한 결과, 에탄올 cosolvent의 NAPL 제거 메커니즘은 용해이며, swelling 알코올의 주요 NAPL 제거 메커니즘은 이동임이 확인되었다. 토양 내 NAPL 제거에 있어 용해보다는 NAPL 이동에 의한 제거가 훨씬 효과적이었다. 알코올 농도 변화 실험에서, cosolvent 내 알코올 함유량이 40% 이상 되어야 토양 내 NAPL의 이동이 현저히 증가하는 것으로 나타났다.

• 한국재료학회지
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• 제29권10호
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• pp.623-630
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• 2019

Because of their excellent stability and highly specific surface area, carbon based materials have received attention as electrode materials of electrical double-layer capacitors(EDLCs). Biomass based carbon materials have been studied for electrode materials of EDLCs; these materials have low capacitance and high-rate performance. We fabricated tofu based porous activated carbon by polymer dissolution reaction and KOH activation. The activated porous carbon(APC-15), which has an optimum condition of 15 wt%, has a high specific surface area($1,296.1m^2\;g^{-1}$), an increased average pore diameter(2.3194 nm), and a high mesopore distribution(32.4 %), as well as increased surface functional groups. In addition, APC has a high specific capacitance($195F\;g^{-1}$) at low current density of $0.1A\;g^{-1}$ and excellent specific capacitance($164F\;g^{-1}$) at high current density of $2.0A\;g^{-1}$. Due to the increased specific surface area, volume ratio of mesopores, and surface functional groups, the specific capacitance and high-rate performance increased. Consequently, the tofu based activated porous carbon can be proposed as an electrode material for high-performance EDLCs.

• 자원환경지질
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• 제55권2호
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• pp.127-135
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• 2022

Excessive presence of As level in groundwater is a major health problem worldwide. In the Red River Delta in Vietnam, several million residents possess a high risk of chronic As poisoning. The As releases into groundwater caused by natural process through microbially-driven reductive dissolution of Fe (III) oxides. It has been extracted by Red River residents using private tube wells for drinking and daily purposes because of their unawareness of the contamination. This long-term consumption of As-contaminated groundwater could lead to various health problems. Therefore, a predictive model would be useful to expose contamination risks of the wells in the Red River Delta Vietnam area. This study used four machine learning algorithms to predict the As probability of study sites in Red River Delta, Vietnam. The GBM was the best performing model with the accuracy, precision, sensitivity, and specificity of 98.7%, 100%, 95.2%, and 100%, respectively. In addition, it resulted the highest AUC of 92% and 96% for the PRC and ROC curves, with Eh and Fe as the most important variables. The partial dependence plot of As concentration on the model parameters showed that the probability of high level of As is related to the low number of wells' depth, Eh, and SO₄, along with high PO₄^3- and NH₄⁺. This condition triggers the reductive dissolution of iron phases, thus releasing As into groundwater.

• Advances in concrete construction
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• 제13권1호
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• pp.71-81
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• 2022

Aluminosilicate materials as precursors are heterogenous in nature, consisting of inert and partially reactive portion, and have varying proportions depending upon source materials. It is essential to assess the reactivity of precursor prior to synthesize geopolymers. Moreover, reactivity may act as decisive factor for setting molar concentration of NaOH, curing temperature and setting proportion of different precursors. In this experimental work, the reactivities of two precursors, low calcium (fly ash (FA)) and high calcium (ground granulated blast furnace slag (GGBS)), were assessed through the dissolution of aluminosilicate at (i) three molar concentrations (8, 12, and 16 M) of NaOH solution, (ii) 6 to 24 h dissolution time, and (iii) 20-100℃. Based on paratermeters influencing the reactivity, different proportions of ternary binders (two precursors and ordinary cement) were activated by the combined NaOH and Na2SiO3 solutions with two alkaline activators to precursor ratios, to synthesize the geopolymer. Reactivity results revealed that GGBS was 20-30% more reactive than FA at 20℃, at all three molar concentrations, but its reactivity decreased by 32-46% with increasing temperature due to the high calcium content. Setting time of geopolymer paste was reduced by adding GGBS due to its fast reactivity. Both GGBS and cement promoted the formation of all types of gels (i.e., C-S-H, C-A-S-H, and N-A-S-H). As a result, it was found that a specified mixing proportion could be used to improve the compressive strength over 30 MPa at both the ambient and hot curing conditions.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.439-440
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• 2002

Nano-Crystalline $CeO_2$ particles were dispersed in deionized water with controlled slurry chemicals for CMP test. According to the CMP test, the removal rate of $SiO_2$ layer was mainly controlled by the size and crystallinity of $CeO_2$ particles which can be controlled by the heat-treatment condition during $CeO_2$ synthesis. In contrast, the removal rate of $Si_3N_4$ layer was significantly influenced by the passivation reagent which protects the $Si_3N_4$ surface layer from excessive dissolution during CMP.

• 열처리공학회지
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• 제33권4호
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• pp.185-192
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• 2020

In this study, materials characterization of pure copper and copper based carbon nano-tube composite prepared by powder metallurgy method were investigated. Prior to evaluate materials characterization, spark plasma sintering processing variables such as sintering temperature, pressure, thickness and diameter of compacts was optimized to ensure the microstructure and materials property of pure Cu and Cu-CNT composite. In addition, corrosion behavior of Cu-based CNT composite produced by powder sintering method was investigated. It was confirmed from this study that the corroded surfaces of the composite shows less dissolution compared with pure copper in 3.5 wt% NaCl solution. The measured corrosion current density (I_corr) indicates improved corrosion property of Cu based composite containing small additions of CNTs in chloride containing media. Micro-galvanic activity between Cu and CNT was not observed in given sintering condition.

• 한국산업융합학회 논문집
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• 제6권3호
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• pp.207-214
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• 2003

Children of three-to-eighteen-years-old have been brought up in the institution (Orphanage) for several reasons such as family dissolution, divorce and poverty since the Korean Was of 1950. The Cottage, where these children are housed and brought up has dining room, library and bedrooms, plays as a significant social interaction place as well as study. Since the most facilities were built during the 1950-1960s period, most of the cottages are now in the condition of being rebuilt or remodelled. Because living space and studying space are mixed, it will be necessary to provide another studying space separated from living space. And then it will be also necessary to provide a space for play or rest between the two spaces. This study was conducted to obtain some basic data necessary for design of spaces in the orphanages by examining the relations between the studying activities of children and residence types.