• Journal of the Korean Ceramic Society
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• v.40 no.6
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• pp.594-600
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• 2003

L $a_{0.7}$S $r_{0.3}$G $a_{0.6}$F $e_{0.4}$ $O_{3-}$$\delta$/ perovskite-type mixed conducting membranes, which could permeate oxygen selectively, have been fabricated and the microstructural features developed by varying the sintering conditions have been analyzed. The effects of surface modification and the membrane thickness on oxygen permeability have been evaluated under He/air environment. With increasing a grain boundary fraction, the overall oxygen permeability decreased. The syngas (CO+ $H_2$) has been produced by partial oxidation reaction of methane with the oxygen permeated through the membrane. Methane conversion and syngas yield have been evaluated as functions of the compositional ratio of feed gas and reaction temperature. In long-term duration test for 600 h, under C $H_4$+He/air environment, L $a_{0.7}$S $r_{0.3}$G $a_{0.6}$F $e_{0.4}$ $O_{3-}$$\delta$/ membrane showed a highly stable performance.

• Journal of the Korean GEO-environmental Society
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• v.22 no.2
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• pp.15-23
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• 2021

A method of improving the post-management end system of a landfill that reflected total pollutant load was applied to the SUDOKWON 1st Landfill Site. Modeling results showed that the ratio of remaining methane, when compared to the total maximum potential of 2,521 × 106 Nm3, was estimated to be 8.8% in 2020, 7.0% in 2030, and 6.5% in 2040. If the average oxidation rate of 89.1% in 2005-2019 was applied, the ratio decreased by 1.01% in 2020, 0.76% in 2030, and 0.70% in 2040. This suggests that if the amount of methane generated is all emitted from the surface of the landfill after 2025, the real amount emitted to the atmosphere is less than that in 2019; therefore, the post-management end is possible. According to the results of trend analysis of the quality of leachate water, effluent criteria for Biochemical Oxygen Demand (BOD) can be satisfied in 2024, while those for Chemical Oxygen Demand (COD) and Total Nitrogen (T-N) can be satisfied in 2047 and 2117, respectively. If the post-management end system changed based on total pollutant load, the post-management can be terminated BOD today and COD within a few years; however, the fact that T-N could be terminated only after 2041 shows the need to fundamentally change management methods.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.1
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• pp.61-66
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• 2006

The combined ADEPT(Anaerobic Digestion Elutriated Phased Treatment)-SHARON(Single reactor system for High Ammonium Removal Over nitrite)-ANAMMOX(Anaerobic ammonium oxidation) processes were operated for resources recovery and nitrogen removal from slurry-type piggery waste. The ADEPT process operated at an acidogenic loading rates of 3.95 gSCOD/L-day, the SCOD elutriation rate and acid production rate were 5.3 gSCOD/L-day and 3.3 gVFAs(as COD)/L-day, respectively. VS reduction and SCOD reduction by the hydrolysis were 13% and 0.19 $gSCOD_{prod.}/gVS_{feeding}$, respcetively. Also, the acid production rate was 0.80 $gVFAs/gSCOD_{prod}$. In methanogenic reactor, the gas production rate and methane content were 2.8 L/day($0.3m^3CH_4/kgCOD_{removal}@STP$) and 77%, respectively. With these operating condition, the removals of nitrogen and phosphorus were 94.1% as $NH_4-N$(86.5% as TKN) and 87.3% as T-P respectively.

• Journal of the Korean Chemical Society
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• v.40 no.9
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• pp.615-622
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• 1996

(Benzotriazol-1-yl)arenesulfonylalkanes, 2a, 2b, 3a and 3b, were prepared by lithiation of 1-(benzotriazol-1-yl)arenesulfonylmethanes followed by reaction with alkyl iodides. Very bulky molecules such as 1,1-di(benzotriazol-1-yl)-1-aryl-1-thiophenoxymethanes 5, 1,1-di(benzotriazol-1-yl)-1-thiophenoxymethane 9a and 1,1-di(benzotriazol-1-yl)-1,1-dithiophenoxymethane 9b were synthesized. 1,1-Di(benzotriazol-1-yl)-1-benzenesulfoxymethane 10a and 1,1-di(benzotriazol-1-yl)-1-benzenesulfonylmethane 10b were also synthesized by the oxidation of compound 9a, while oxidation of sulfide group on compound 5 and 9b by m-CPBA were not successful. On the other hand, pyrolysis and hydrolysis of 3-(benzotriazol-1-yl)-3-toluenesulfonylpentane 3b gave 3-toluenesulfonyl-2-pentene 11 and diethyl ketone 13a, respectively, which means there are both C-N and C-S bond cleavages.

• Journal of Korean Society on Water Environment
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• v.34 no.1
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• pp.121-131
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• 2018

Domestic sewage treatment plants (STPs) consume about 0.5 % of total electric energy produced annually, which is equivalent to 207.7 billion Korean won per year. To minimize the energy consumption and as a way of mitigating the depletion of energy sources, the sewage treatment strategy should be improved to the level of "energy positive". The core processes for the energy positive sewage treatment include A-stage for energy recovery and B-stage for energy-efficient nitrogen removal. The integrated process is known as the A/B-process. In A-stage, chemically enhanced primary treatment (CEPT) or high rate activated sludge (HRAS) processes can be utilized by modifying the primary settling in the first stage of sewage treatment. CEPT utilizes chemical coagulation and flocculation, while HRAS applies returned activated sludge for the efficient recovery of organic contents. The two processes showed organic recovery efficiencies ranging from 60 to 70 %. At a given recovery efficiency of 80 %, 17.3 % of energy potential ($1,398kJ/m^3$) is recovered through the anaerobic digestion and combustion of methane. Besides, anaerobic membrane bioreactor (AnMBR) can recover 85% of organic contents and generate $1,580kJ/m^3$ from the sewage. The recovered energy is equal to the amount of energy consumption by sewage treatment equipped with anaerobic ammonium oxidation (ANAMMOX)-based B-stage, $810{\sim}1,620kJ/m^3$. Therefore, it is possible to upgrade STPs as efficient as energy neutral. However, additional novel technologies, such as, fuel cell and co-digestion, should be applied to achieve "energy positive" sewage treatment.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.97-97
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• 2015

전 세계적으로 화석연료의 고갈 및 환경오염 문제를 해결하기 위해 신재생에너지에 대한 관심이 급증하고 있다. 이러한 신재생에너지에는 수소 에너지, 자연 에너지(태양열, 지열 등), 바이오 매스 에너지 등이 포함된다. 이 중 수소 에너지는 지구상에 풍부하게 존재하고 있는 물과 탄화수소로부터 얻어지며, 연소 시에도 다시 물을 형성하여 오염 물질을 배출하지 않는 차세대 무공해 에너지원으로써 주목을 받고 있다. 수소 제조를 위한 공정에는 수증기 개질 공정(steam reforming), 부분 산화(partial oxidation) 및 자열개질(autothermal reforming) 등이 있으며 실제로 생산되는 대부분의 수소는 탄소/수소비(1:4)가 높은 메탄($CH_4$) 가스를 이용한 메탄 수증기 개질 공정(steam methane reforming)을 통하여 제조된다. 이 때 수소 제조의 고효율화 및 저비용화를 위해서는 반응물에 대한 높은 선택도, 고활성도 및 높은 안정성을 갖는 촉매가 반드시 필요하며, 대표적으로 Ni, Pt, Ru 등이 보고되고 있다. 이러한 촉매들은 대부분 세라믹 pellet 형태로 제작되어 왔으나 열전도도가 낮고 물리적 충격에 취약하다는 단점이 존재한다. 따라서 우리는 이러한 단점을 극복하고, 촉매의 활성을 높이기 위하여 다공성 금속 합금 폼을 촉매 지지체로 도입하였다. 또한, 다공성 금속 합금 폼 표면에 촉매의 분산 및 안정성을 향상시키기 위해 지지체와 촉매 사이에 원자층 증착법을 이용하여 inter-layer를 도입하였다. 이들의 구조, 형태, 및 표면의 화학적 상태는 주사전자현미경, EDS (energy dispersive spectroscopy)가 탑재된 주사전자현미경, X-선 회절, 및 X-선 광전자 분광법을 이용하여 규명하였다. 더하여 정전압-전류 측정법 및 유도 결합 플라즈마 분광 분석기을 이용하여 전기 화학 반응을 유도하고, 반응 후 전해질의 성분분석을 통해 촉매와 지지체 간의 안정성을 평가하였다. 따라서 본 결과들은 한국진공학회 하계정기학술대회를 통해 좀 더 자세히 논의될 것이다.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.110-110
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• 2015

표면에너지는 계면특성을 지배하는 핵심인자로 디스플레이의 터치 스크린 패널 공정, 이종소재의 접합, 금속의 클래딩 등 실제 산업에 있어서 매우 중요하다. 표면에너지는 코팅과 본딩 이론에 있어서 기본이 되는 물리량으로 표면에너지가 높을수록 코팅 또는 박막 증착시 코팅, 증착이 용이하며 이종소재의 접합도 쉽게 일어난다. 본 연구에서는 플라즈마 표면처리시 산소 분율의 변화에 따른 기판의 표면에너지와 코팅층과 기판의 부착력의 변화에 대해 연구하였다. 연구의 주요 기판으로 ITO, PET 기판을 사용하였고, 표면 에너지 변화를 확인하기 위해 기판을 상온 상압 플라즈마에 노출시켰다. 플라즈마는 아르곤(Ar)의 공급량을 20 LPM으로 고정하고 산소($O_2$)의 공급량을 0 sccm에서 40 sccm 까지 10 sccm 간격으로 변수를 주었다. 표면에너지 값은 기판 위에 형성된 액체의 접촉각을 통해 도출하였다. 표면에너지 측정 액체로 증류수(deionized water)와 디오도메탄(diiodo-methane)을 사용하였다. 표면에너지는 산소분압이 10 sccm에서 최대값인 76 mJ/m2으로 증가한 후 20 sccm까지 유지하다 다시 직선적으로 감소하였다. 기판에 증착된 크롬 박막의 부착력은 스크래치 테스트를 통해 측정하였다. 표면에너지의 증가와 비례하게 부착력은 증가하였고 표면에너지가 감소하는 범위에서는 부착력도 감소하였다. 기판과 코팅층의 부착력 증가 원인 중 하나인 계면 산화물 층의 생성 여부를 알아보기 위해 auger electron spectroscopy (AES) 분석을 진행하였다. AES 분석을 통해 플라즈마 표면처리시 기판과 코팅층의 계면 산화물층의 두께가 표면에너지의 변화와 비례하게 증가하였다가 감소하는 것을 확인하였다. 산소분압이 10 sccm 이었을 경우 산화물층의 두께가 가장 두꺼웠다. 또한 계면의 화학적 결합 상태를 알아보기 위해 X-ray photoelectron spectroscopy (XPS) 분석을 진행하였으며 산소 분율의 변화에 따라 크롬 산화물의 양이 증가하였다 감소하는것을 확인하였다. 이 연구를 통해 산소를 포함한 플라즈마 표면개질이 기판과 코팅층의 부착력 증가에 영향을 끼침을 확인 할 수 있었다. 또한 이를 응용하여 부착력 증가가 필요한 다양한 분야에서도 쉽게 적용시킬 수 있을 것이다.

• Journal of environmental and Sanitary engineering
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• v.14 no.3
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• pp.123-129
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• 1999

The utilization methods of algae biomass have been studied constantly in whole world. These are $\circled1$the wastewater treatment if waste stabilization pond and oxidation ditch etc. and $\circled2$the biosorption of heavy metals and recovery of strategic' precious metals and $\circled3$the single-celled protein production and the production of chemicals like coloring agent and $\circled4$the production of electric energy through methane gasification. The culture system also has been developed constantly in relation with such utilization method developments. In the result of experimental operation under continuous and cyclic irradiation of light, using high rate algae biomass culture pond(HRABCP), which had been made so as to be an association system with the various items which had been managed to have high efficiency for algae culture, the algae production of the 12 hours-irradiance pond was 41.48 Chlorophyll-a ${\mu}g/L$ only in spite of having the more chance of $CO_2$ synthesis to algae cell than the 24 hours-irradiance pond. This means that the energy supply required for dark-reaction of photosynthesis is very important like this. The difference of algae production between continuous and cyclc irradiation explains that the dark-reaction of photosynthesis acts on algae production as the biggest primary factor. The continuous irradiance on HRABCP made the good algae-production($1403.97{\;}{\mu}g$ Chlorophyll-a/mg) and the good oxygen-production(5.8 mg $O_2/L$) and the good solid-liquid seperation. especially, DO concentration through the oxygen-production was enough to fishes' survival.

• Journal of Electrochemical Science and Technology
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• v.10 no.3
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• pp.335-343
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• 2019

In this study, $Sr_2Ni_{1.8}Mo_{0.2}O_{6-{\delta}}$ (SNM) with a double perovskite structure was investigated as an alternative anode for use in the $CH_4$ fuel in solid oxide fuel cells. SNM demonstrates a double perovskite phase over $600^{\circ}C$ and marginal crystallization at higher temperatures. The Ni nanoparticles were exsolved from the SNM anode during the fabrication process. As the SNM anode demonstrates poor electrochemical and electro-catalytic properties in the $H_2$ and $CH_4$ fuels, it was modified by applying a samarium-doped ceria (SDC) coating on its surface to improve the cell performance. As a result of this SDC modification, the cell performance improved from $39.4mW/cm^2$ to $117.7mW/cm^2$ in $H_2$ and from $15.9mW/cm^2$ to $66.6mW/cm^2$ in $CH_4$ at $850^{\circ}C$. The mixed ionic and electronic conductive property of the SDC provided electrochemical oxidation sites that are beyond the triple boundary phase sites in the SNM anode. In addition, the carbon deposition on the SDC thin layer was minimized due to the SDC's excellent oxygen ion conductivity.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.12
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• pp.41-46
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• 2018

In this research, numerical analysis was performed to determine the effects of hydrogen on biogas combustion for homogeneous charged compression ignition (HCCI) engines. The target engine specifications were a 2300cc displacement volume, 13:1 compression ratio, 15kW of electricity, and 1.2 bar boost pressure. The engine speed was fixed to 1800rpm. By varying the excess air ratio and hydrogen contents, the cylinder pressure, nitric oxide, and carbon dioxide were measured as a function of the hydrogen contents. According to preliminary studies related to the reaction mechanism for methane combustion and oxidation, a GRI 3.0 mechanism as the base mechanism was selected for HCCI combustion calculations describing the detailed reaction mechanism. By adding hydrogen, NO was increased while $CO_2$ was decreased. The cylinder pressure was also increased, having advanced timing for the maximum cylinder pressure and pressure rise region. Furthermore, lean operation limits were extended by adding hydrogen to the HCCI engine.