• Applied Chemistry for Engineering
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• v.19 no.6
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• pp.583-591
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• 2008

Recently, as a demand for the portable device is surged, there are needs to develop a new fuel cell system for replacing the conventionally used secondary battery. For this purpose, it becomes important to develop direct formic acid fuel cell (DFAFC) that uses formic acid as a fuel. The formic acid can offer typical advantages such as excellent non-toxicity of the level to be used as food additive, smaller crossover flux through electrolyte, and high reaction capability caused by high theoretical electromotive force (EMF). With the typical merits of formic acid, the efforts for optimizing reaction catalyst and cell design are being made to enhance performance and long term stability of DFAFC. As a result, to date, the DFAFC having the power density of more than $300mW/cm^2$ was developed. In this paper, basic performing theory and configuration of DFAFC are initially introduced and future opportunities of DFAFC including the development of catalyst for the anode electrode and electrolyte, and design for the optimization of cell structure are discussed.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.29 no.6
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• pp.365-371
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• 2019

In this study, the flame temperature distribution of the diffusion flame burner for SiO₂ deposition was analyzed by the computational fluid analysis. This corresponds to the previous step for simulating the SiO₂ preform deposition process for manufacturing optical fibers using environmentally friendly raw materials. In order to model premixed combustion, heat flow, convection, and chemical reactions were considered, and Reynolds-averaged Navier-Stokes equations and k-ω models were used. As a result, the temperature distribution of the flame showed a tendency to increase the distance from the nozzle surface to the maximum temperature when the flow rate of the auxiliary oxygen increased. In addition, it was confirmed that the temperature distribution due to incomplete combustion was large in the combustion reaction with a large equivalence ratio of the mixed gas.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.450.2-450.2
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• 2014

열전재료는 열-전기가 상호 가역적으로 변하는 재료로서, 최근 에너지 변환소재 분야에서 각광받고 있다. 열전재료의 특성 효율은 무차원 열전 성능지수(dimensionless figure of merit, $ZT={\alpha}2{\sigma}T/{\kappa}$)로 나타낼 수 있다. 여기서 ${\alpha}$는 제벡계수(Seebeck coefficient), ${\sigma}$는 전기전도도(electrical conductivity), ${\kappa}$는 열전도도(thermal conductivity), T는 Kelvin 온도를 나타낸다. 500 K에서 800 K까지의 중온 영역에서 우수한 열전특성을 보이는 $Mg_2X$ (X=Si, Ge, Sn)와 이들의 고용체는 성분원소가 독성이 없고, 매장량이 많아 친환경 열전 재료로 각광받고 있다. $Mg_2X$ 고용체 중 $Mg_2Si_{1-x}Ge_x$는 기존 $Mn_2Si$, $Mg_2Ge$, $Mg_2Sn$계 보다 더 우수한 열전 성능지수를 보인다. 다양한 제조 방법들이 시도되고 있으나, 조성설계 및 구조, 성능 조절의 어려움이 있고, Mg의 산화와 휘발 및 Mg, Si, Ge의 융점 차이가 크고 중력 편석과 반응하지 않은 원소들로 인해 제조가 상당히 어렵다. Sb가 도핑된 $Mg_2Si_{0.5}Ge_{0.5}Sb_y$ (y=0, 0.005, 0.01, 0.02, 0.03) 고용체를 고상반응으로 합성하고 진공열간 압축성형을 통해 성공적으로 제조하였다. 고용 상을 확인하기 위하여 X선 회절분석을 실시하였고, 고용체 형성과 도핑에 따른 전기적 특성변화를 평가하기 위해 Hall 효과를 측정하여 전자 이동특성을 분석하였고, 323~823 K까지 전기전도도, 제벡계수, 열전도도의 측정을 통해 열전 성능지수를 평가하였다.

• Polymer(Korea)
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• v.39 no.2
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• pp.235-239
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• 2015

In this work, we evaluated catalytic activity of LiOH, $Cu(acac)_2$ and n-butyltin hydroxide oxide hydrate in the early stage of the melt transesterification of isosorbide and bisphenol A as diol monomers and diphenylcarbonate for the melt polymerizaiton of polycarbonate. $Cu(acac)_2$ proved to be the most active catalyst for homopolymerization process, while the catalytic activity of LiOH was higher than the others in case of melt copolymerization depending on the catalytic mechanism and chemical structure of catalyst. We suggested that evaluation of catalytic activity can be used for selection of catalyst system in bio-based copolymerization of polycarbonate.

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.2
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• pp.29-37
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• 2018

This paper reports the preliminary firing test performed with an ADN-based monopropellant using a 5 N scale thruster. ADN-based propellant and catalyst was fabricated and catalytic combustion of propellant was characterized by DSC-TG analysis. Although an explosion in the catalyst bed was occurred, high temperature in the catalyst bed obtained and demonstrated catalytic combustion of the propellant. Preliminary test results motivates the research for catalysts with better thermal stability.

• Resources Recycling
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• v.30 no.1
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• pp.83-91
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• 2021

Ladle furnace slag is a byproduct of the steel-making process, and it contains the mineral β-C2Sandtherapid-settingmineral (dependingonwhichreducingagenthasbeenused). Ladle furnace slag is often treated through slow cooling, which causes the slag to lose its reactivity. In this study, the properties of air-quenched CAC and pulverized ladle furnace slag containing gypsum were evaluated, and the optimal mixing ratio was determined for broadening their usage. Consequently, the properties of CAC aredemonstrated by the dissolution of gypsum after a period of three hours and the content of gypsum after a period of one day. The optimal mixing ratio of anhydrate and hemihydrate gypsum is found to be within 30% and that of dihydrate gypsum is found to be higher than 35%. Furthermore, based on the results of CAC with dihydrate gypsum, the applicability of the by-product dihydrate gypsum has been verified.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.1
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• pp.25-32
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• 2021

For developing the durable eco-concrete, water-repellent and hydrophobic emulsion were prepared by stirring and mixing polymethyl hydrosiloxane and polyvinyl alcohol. After adding the PMHS emulsion cement paste, the hydration reaction characteristics and the change in chemical composition were analyzed through BSE and EDS analysis, and the micropores were evaluated by MIP test. Cement mixed with PMHS emulsion was analyzed to increase the hydration reactivity and to decrease the capillary porosity, but it was found that the capillary porosity varies depending on the degree of dispersion of the emulsion in the cement paste. In the case of the emulsion containing metakaolin, there was little difference in hydration degree and porosity from the case of using only the PMHS emulsion. However, when the cement surface was coated with PMHS emulsion, the contact angle was found to increase significantly compared to OPC, and it was analyzed that especially when PVA fiber was used together, it changed to a hypohydrophobic surface.

• Journal of the Korean Geotechnical Society
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• v.39 no.8
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• pp.7-16
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• 2023

This study aimed to evaluate the sulfate removal capacity of the enzyme-induced carbonate precipitation (EICP) technique through the chemical precipitation of sulfate with calcium ions. The optimal EICP recipe was obtained to retain the excess calcium cations in the solution for the generation of a sufficient amount of calcium carbonate (CaCO₃) mineral. The effect of gypsum precipitation on the EICP-treated sand specimen was investigated by measuring the shear wave velocity and by visual inspection via scanning electron microscopy. The EICP solution using soybean crude urease, as an alternative to laboratory-grade purified urease, exhibited a lower sulfate removal efficiency at a similar CaCO₃ production rate compared with the optimal EICP recipe because of soybean impurities.

• Weed & Turfgrass Science
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• v.1 no.4
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• pp.38-43
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• 2012

This study was conducted to predict the yield response of red pepper and to determine the economic weed threshold levels for red pepper cultivation field from competition with the most serious weeds, Amaranthus patulus and Digitaria ciliaris in Youngyang of Korea. Crop yield as a function of weed density was predicted by using a rectangular hyperbola, and their economic threshold levels were determined by using the equation developed by Cousens (1987). The red pepper yield loss models of weeds were predicted as y=304.7/(1+0.063x), $R^2$=0.967 in D. ciliaris and y=281.3/(1+0.1723x), $R^2$=0.952 in A. patulus. Economic thresholds calculated using Cousens' equation were negatively related with the competitiveness of weed. Economic thresholds of each weed were calculated as 18.2 plant $100m^{-2}$ in D ciliaris, and 7.2 plant $100m^{-2}$ in A. patulus.

• Journal of the Korean GEO-environmental Society
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• v.25 no.5
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• pp.39-47
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• 2024

In this study, the environmental implications of electric arc furnace steel slag, commonly used in road construction and soil reinforcement, were examined. Experiments were conducted to assess the leaching of heavy metals based on particle size and to investigate ion leaching from specimens with varying mixtures of steel slag and clay. The official waste test revealed no detectable heavy metals in the sample items. However, when subjected to leaching experiments and analyzed using ICP-OES, certain heavy metals were found. The reaction of steel slag with water, facilitated by free CaO within the slag, was identified as the cause of leaching. Results showed that aluminum, exhibiting the highest leaching rate, displayed an inverse relationship with particle size. In mixed soil containing steel slag and clay, higher steel slag content resulted in increased aluminum leaching. Nonetheless, the quantity of leached aluminum was notably lower in mixed soil compared to pure steel slag. Furthermore, leaching of other heavy metals remained within acceptable limits. These findings suggest that recycling mixed soil of steel slag and clay for road construction or soil stabilization presents reduced environmental risks compared to using steel slag alone. Utilizing such mixtures could offer an environmentally sustainable and safe alternative.