• Clean Technology
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• v.24 no.1
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• pp.63-69
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• 2018

The reduction reaction characteristics and physicochemical properties were studied for the selection of oxygen carrier, which is the core of the chemical looping combustion (CLC) technology. Fuel conversion and $CO_2$ selectivity of oxygen carrier according to the concentration of reducing gas and the reduction temperature using three kinds of oxygen carrier (SDN70, N018-R2, N016-R4) were measured and compared. In addition, Attrition Index (AI) and BET surface area were measured to analyze the attrition resistance and the surface characteristics of the oxygen carrier. As a result, it was confirmed that all three kinds of oxygen carrier were suitable for use in chemical roofing combustion system, and the best particle was determined to be N016-R4.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.12
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• pp.1329-1336
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• 2007

This study was carried out to develop an efficient process abating high NO concentration. A hybrid process of selective catalytic reduction(SCR) and activated carbon fiber(ACF) adsorption was newly designed and tested. Used ACF in NO adsorption was regenerated by simultaneously applying heat and vacuum. The result of ACF regeneration was for superior in the desorption condition at $140^{\circ}C$ and vacuum 600 mmHg. A commercial catalyst was used at the conditions of reaction temperature at $300^{\circ}C$, $NH_3/NO$ mole ratio = 1.0 for SCR process. NO evolved from ACF regeneration reactor could be removed by SCR reactor up to 98%. But high concentration of NO was exhausted from SCR reactor for one minute when the flue gas of NO 300 ppm and deserted NO from ACF regeneration were simultaneously treated by the same SCR reactor. Therefore, it is necessary to use additional small sized SCR reactor or to increase $NH_3$ concentration for a short time along with NO concentration rather than to mix flue gas with the gas evolving from ACF regeneration at fixed $NH_3$ inlet concentration. The hybrid process of SCR and ACF showed high NO removal efficiency over 80% at any time courses. Through the repeated cycles, stable DeNOx efficiency was maintained, indicating that the hybrid process would be a good countermeasure to the spotaneously high NO concentration instead of increasing the SCR capacity.

• Korean Journal of Logic
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• v.4
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• pp.89-107
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• 2000

이 논문의 목적은 확률에 대한 빈도 해석(특히 라이헨바하와 새먼에 의해 체계화된 형태)을 비판적으로 고찰하는 데에 있다. 보다 구체적으로, 확률 빈도 해석에 대해 기존에 제기된 반론들을 보다 강화하고 새로운 추가적 반론들을 제기함으로써, 확률 빈도 해석이 종래에 생각되어 왔던 것보다 훨씬 더 심각한 상태에 있음을 보이려 한다. 특히, 빈도 해석이 흔히 여겨지는 바와 달리, 확률 값을 부여하기 위해 여러 국면들에 있어서의 주관적이고 임의적인 선택들에 의존해야 한다는 것이 이 논문에서의 반론들을 통해 드러날 것이다.

• Resources Recycling
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• v.30 no.6
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• pp.36-42
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• 2021

Spent lithium-ion batteries are treated by reduction-smelting at high temperatures to recover valuable metals. Solvent extraction and precipitation of the HCl leaching solution of reduction-smelted metallic alloys resulted in a filtrate containing Ni(II) and a small amount of Si(IV). Adsorption and precipitation experiments were conducted to recover pure Ni(II) compounds from the filtrate. Si(IV) was selectively loaded onto polyacrylamide, but this method did not efficiently filter the solution due to an increase in viscosity. The addition of Na₂CO₃ as a precipitant to the filtrate led to the simultaneous precipitation of Ni(II) and Si(IV). However, it was possible to recover nickel oxalate with a purity higher than 99.99% by selectively precipitating Ni(II) with the addition of Na₂C₂O₄ as a precipitant.

• Journal of the Korean Institute of Gas
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• v.19 no.5
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• pp.20-28
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• 2015

This work investigated the size and shape effect of ${\gamma}$-alumina-supported metal oxides on the hydrocarbon selective catalytic reduction of nitrogen oxides. Several metal oxides including Ag, Cu and Ru were used as the catalysts, and n-heptane as the reducing agent. For the Ag/${\gamma}$-alumina catalyst, the $NO_x$ reduction efficiency in the range of $250{\sim}400^{\circ}C$ increased as the size of Ag decreased (20 nm>50 nm>80 nm). The shape effect of metal oxides on the $NO_x$ reduction was examined with spherical- and wire-shape nanoparticles. Under identical condition, higher catalytic activity for $NO_x$ reduction was observed with Ag and Cu wires than with the spheres, while spherical- and wire-shape Ru exhibited similar $NO_x$ reduction efficiency to each other. Among the metal oxides examined, the best catalytic activity for $NO_x$ reduction was obtained with Ag wire, showing almost complete $NO_x$ removal at a temperature of $300^{\circ}C$. For Cu and Ru catalysts, considerable amount of NO was oxidized to $NO_2$, rather than reduced to $N_2$, leading to lower $NO_x$ reduction efficiency.

• Proceedings of the Membrane Society of Korea Conference
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• 1998.10a
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• pp.82-85
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• 1998

1. 서론 : Cyclodextrin(CD) 동족체(homologues)는 $\alpha$-, $\beta$-, $\gamma$-CD로 구분되며, 이들 각각은 $\alpha$-D-glucopyranose 단위체 6,7, 및 8개가 비환원성 환상구조로 연결된 cyclic maltooligosaccaride의 일종으로 외부는 친수성이고, 내부는 소수성인 공동 구조를 갖고 있다. 따라서 각 CD는 동공의 크기가 달라 다른 크기의 소수성 물질들과 선택적인 포접화합물 (inclusion compound)을 형성하는 특징이 있다. CD 동족체는 전분 분해 효소인 cyclodextrin glycosyltransferase(CGTase)에 의해 전분으로부터 생산되는데, 반응용액 내에서의 CD 동족체 농도가 어느 한계값 이상으로 높아지면 생산물 저해와 다른 환원당으로의 분해 때문에 생산성이 감소하여 이의 효과적 생산에 어려움이 있다. 본 연구는 dead-end 및 cross-flow형 막 생물반응기를 사용하여 CGTase에 의한 전분의 CD 동족체로의 분해반응시 생산물 저해를 억제시켜 생산성을 향상시키고, 동시에 조작조건 변화에 따른 생산물인 CD 동족체의 효과적인 연속분리 가능성을 검토하였다.

• Journal of the Microelectronics and Packaging Society
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• v.30 no.4
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• pp.17-31
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• 2023

Amidst escalating global warming fueled by indiscriminate fossil fuel consumption, concerted efforts are underway worldwide to mitigate atmospheric carbon dioxide (CO₂) levels. Electrochemical CO₂ reduction technology is recognized as a promising and environmentally friendly approach to convert CO₂ into valuable hydrocarbon compounds, deemed essential for achieving carbon neutrality. Copper, among the various materials used as CO₂ reduction electrodes, is known as the sole metal capable of generating C₂₊ compounds. However, low conversion efficiency and selectivity have hindered its widespread commercialization. This review highlights diverse research endeavors to address these challenges. It explores various studies focused on utilizing copper-based electrodes for CO₂ reduction, offering insights into potential solutions for advancing this crucial technology.

• Journal of Korea Technology Innovation Society
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• v.13 no.4
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• pp.700-716
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• 2010

This paper examines the development of smelting reduction process in POSCO from 1990 to 2007 with the perspective of post catch-up technological innovation. POSCO paid attention to smelting reduction process as a sort of next-generation iron and steel technology, and implemented COREX (coal ore reduction) by the cooperation with V$\"{o}$oest. In addition to this, POSCO started to develop FINEX (fine iron ore reduction) which can use abundant powder ore, and FINEX was developed through model plant, pilot plant, demo plant, and commercial facility. POSCO came up to innovation leader beyond fast follower by securing almost technologies concerning FINEX. The case of smelting reduction process shows various characteristics including appropriate technological choice, successive scale-up, spiral development system, complementary technological cooperation, long-tenn investment, the existence of top management's leadership, and Korean government's support in early stage. This case can be interpreted as a path-revealing innovation in the middle of technological paradigm change.

• Journal of Korean Society of Environmental Engineers
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• v.38 no.12
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• pp.667-675
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• 2016

Nanoscale zero-valent iron (nZVI) has been effectively applied for environmental remediation due to its ability to reduce various toxic compounds. However, quantification of nZVI reactivity has not yet been standardized. Here, we adapted colorimetric assays for determining reductive activity of nZVIs. A modified indophenol method was suggested to determine reducing activity of nZVI. The method was originally developed to determine aqueous ammonia concentration, but it was further modified to quantify phenol and aniline. The assay focused on analysis of reduction products rather than its mother compounds, which gave more accurate quantification of reductive activity. The suggested color assay showed superior selectivity toward reduction products, phenol or aniline, in the presence of mother compounds, 4-chlorophenol or nitrobenzene. Reaction conditions, such as reagent concentration and reaction time, were optimized to maximize sensitivity. Additionally, pretreatment step using $Na_2CO_3$ was suggested to eliminate the interference of residual iron ions. Monometallic nZVI and bimetallic Ni/Fe were investigated with the reaction. The substrates showed graduated reactivity, and thus, reduction potency and kinetics of different materials and reaction mechanism was distinguished. The colorimetric assay based on modified indophenol reaction can be promises to be a useful and simple tool in various nZVI related research topics.

• Applied Chemistry for Engineering
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• v.9 no.3
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• pp.355-360
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• 1998

Reduction activity of precious metal-loaded HZSM-5 for NO has been studied and was compared to that of Cu-HZSM-5 in the presence of excess oxygen. It was found that among the catalysts used in this study, Ru-HZSM-5 was the most active catalyst for the reduction of NO to $N_2$ in the absence of hydrocarbon reductant. The highest conversion obtained was 45%. No severe inhibition of water vapor to the reduction was observed. It is suggested that the higher catalytic activity of Ru-HZSM-5 may result from the better ability to oxidize NO to $NO_2$ in the presence of excess oxygen. A proposed reaction mechanism for the reduction of NO to $N_2$ in the presence of excess oxygen is that NO is oxidized to $NO_2$ on the surface of Ru-HZSM-5 catalyst and the adsorbed $NO_2$ on the surface is then decomposed to $N_2$. $NO_2$ is supposed to the reaction.