• 대한환경공학회지
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• 제39권11호
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• pp.607-612
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• 2017

연소후 아민 $CO_2$ 포집공정에서 탄산수화 효소의 첨가에 따른 다양한 아민 흡수제의 $CO_2$ 흡수에 미치는 영향과 반응열을 평가하였다. 30 wt%의 MEA, AMP, DMEA, MDEA 수용액에 소의 적혈구에서 추출한 탄산무수화 효소 250 mg/L 첨가한 후 흡수속도를 분석한 결과, 모든 흡수제에서 $CO_2$ 흡수속도가 증가하였다. 특히, 1차아민인 MEA와 입체장애아민인 AMP보다는 3차아민인 DMEA와 MDEA에서 속도증진 효과가 컸다. 반응열량계를 이용하여 탄산무수화 효소 첨가후 흡수제(MEA, DMEA, MDEA)와 $CO_2$ 사이의 화학 반응 시 발생하는 반응열을 측정한 결과 효소 촉매의 첨가로 모든 흡수제의 반응열량이 낮아짐을 확인할 수 있었다. 특히, 연소후 아민 흡수제를 이용하는 이산화탄소 포집공정에 탈기 성능이 우수한 3차 아민 계열의 흡수제가 탄산무수화 효소 촉매 적용에 유리한 흡수제이며 이중 MDEA에서 효과가 가장 큼을 알 수 있었다.

• Carbon letters
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• 제10권3호
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• pp.217-220
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• 2009

In this study, porous electrospun carbon fibers were prepared by electrospinning with PAN and $MgCl_2$, as a MgO precursor. MgO was selected as a substrate because of its chemical and thermal stability, no reaction with carbon, and ease of removal after carbonization by dissolving out in acidic solutions. $MgCl_2$ was mixed with polyacrylonitrile (PAN) solution as a precursor of MgO with various weight ratios of $MgCl_2$/PAN. The average diameter of porous electrospun carbon fibers increased from 1.3 to 3 ${\mu}m$, as the $MgCl_2$ to PAN weight ratio increased. During the stabilization step, $MgCl_2$ was hydrolyzed to MgOHCl by heat treatment. At elevated temperature of 823 K for carbonization step, MgOHCl was decomposed to MgO. Specific surface area and pore structure of prepared electrospun carbon fibers were decided by weight ratio of $MgCl_2$/PAN. The amount of hydrogen storage increased with increase of specific surface area and micropore volume of prepared electrospun carbon fibers.

• Carbon letters
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• 제8권3호
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• pp.177-183
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• 2007

[ $TiO_2$ ]ACF composites were prepared by the electrochemical method with Titanium (IV) n-butoxide (TNB) electrolyte under different electrochemical operation time. The BET surface area for $TiO_2$/ACF composites decrease with the increase of electrochemical operation time. There is a single crystal structure which is anatase in all of the samples from the data of XRD. The SEM micrphotographs of $TiO_2$/ACF composites show that the $TiO_2$ particles were well mixed with the ACF. There are O and P with strong C and Ti peaks in all samples from EDX results, and it also shows that a decrease of the C content with a increasing of Ti content with increasing of the electrochemical operation time in the over all composites. DSC cures show that the exothermic peak of all composites at $560^{\circ}C$ represents the transformation heat of amorphous parts to anatase phase and the discontinuous grain growth of the transformed anatase particles. Finally, the excellent photoactivity of $TiO_2$/ACF composites (especially, ACFT10) could be attributed that the decrease of concentration of MB can be concluded to be much faster for the adsorption by ACF than for photocatalytic decomposition by $TiO_2$.

• 공업화학
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• 제22권4호
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• pp.423-428
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• 2011

경북 대포 지역에서 채취한 제올라이트의 시멘트 혼합재료로의 이용 가능성을 검토하기 위하여 제올라이트가 함유된 시멘트의 수화 특성을 연구하였다. 제올라이트가 함유된 시멘트 페이스트에 대하여 수화발열 속도, XRD, EDS, 질소 흡착, 수은 침투 등의 분석을 수행하였다. 제올라이트가 함유된 시멘트 페이스트에서는 제올라이트 양이 증가함에 따라 응결시간이 빨라지고 시멘트의 수화가 촉진되는 경향을 나타내었다. 제올라이트가 함유된 모르터에서는 제올라이트 양이 증가함에 따라 플로우가 크게 감소하였다. 또한 플레인 모르터와 비교하여 단기에 강도증진이 나타났다. 이러한 결과는 시멘트의 수화시 알칼리에 의한 제올라이트의 탈알루미늄 과정에서 제올라이트 입자로부터 이탈한 활성 알루미늄 종과 관련이 있는 것으로 보인다.

• 한국포장학회지
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• 제26권1호
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• pp.1-9
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• 2020

We evaluated the applicability of baking soda, charco'al, coffee, and green tea as a natural deodorant in Kimchi packaging. Moreover, to evaluate the potential usage of these deodorants in packaging materials and confirm their applicability in high-temperature melt-extrusion processing, the thermal stabilities of the deodorants were investigated, and heat-treated deodorants were evaluated in terms of the deodorizing function compared with non-treated deodorants. Aroma patterns were decreased after deodorizing treatment with all-natural deodorants. Dimethyl disulfide, methyl trisulfide, and diallyl disulfide, the most significant odorous Volatile organic compounds (VOCs) of Kimchi, decreased after treatment with the deodorants. In particular, baking soda and charcoal showed the highest efficiency in removing odorous compounds and VOCs from Kimchi, even after high-temperature processing. The acetic acid removal rates for both baking soda and charcoal were 99.9±0.0%. The heating process increases the deodorizing effects of baking soda. Sensory evaluation results showed that there is a significant increase (p < 0.05) in the overall preference for Kimchi samples packaged with charcoal and baking soda. This study provides useful information for the deodorization effects of natural deodorants for Kimchi smell and their applicability for packaging materials.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1989년도 하계종합학술대회 논문집
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• pp.310-313
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• 1989

The semiconducting bodies were prepared by doping the bariume titanate with $Sb_2O_3,Nb_2O_5$and by subsequent sintering in air. The sintered bodies were annealed between $1100^{\circ}C$ and $1250^{\circ}C$ for 30 minutes to 2 hours in air. The resistivity was measured as a function of temperature from $20^{\circ}C$ to $240^{\circ}C$. The anomalous effect in resistivity occurred all of the $Nb_2O_5$ and $Sb_2O_3$doped barium titanate specimens, which were sintered in air atmosphere, and the most effective PTC effect occurred through 1 hour of sintering time at $1350^{\circ}C$ and 30 minute of annealing time at $1200^{\circ}C$. The resistivity - temperature characteristics seem to be intimately related to oxygen adsorption at grain boundaries and also to the thickness of insulating layers formed at grain boundaries during heat treatment.

• 한국세라믹학회지
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• 제48권5호
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• pp.404-411
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• 2011

The humidity controlling ceramic materials was developed by applying the phenomena of dew condensation in the capillary. It is said that the humidity range which human feels comfortable is from 40 to 70% in relative humidity. In this study, the ceramic tile using natural soils such as diatomite for interior wall was investigated. In particular, we had introduced novel processing routes for fabricating microcellular ceramics tile using hollow microsphere as a pore former. The microcellular pores in the humidity controlling ceramic materials showed the superior properties such as light-weight, heat insulation. The cell density was ${\sim}1.0{\times}10^9$ cells/$cm^3$ and density of sample was 0.65 g/$cm^3$ in the case of 1.71 wt% hollow microsphere content. Also, it is observed that the BET surface area and the pore volume of the sintered diatomite tile have the values of 40.92 $m^2$/g and 0.173 $cm^3$/g.

• 한국산업융합학회 논문집
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• 제25권6_3호
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• pp.1247-1260
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• 2022

The steel industry accounts for about 5% of the total annual global energy consumption and more than 6% of the total anthropogenic carbon dioxide emissions. Therefore, there is a need to increase energy efficiency and reduce greenhouse gas emissions in these industries. The utilization of coke oven gas, a byproduct of the coke plant, is one of the main ways to achieve this goal. Coke oven gas used as a fuel in many steelmaking process is a hydrogen-rich gas with high energy potential, but it is commonly used as a heat source and is even released directly into the air after combustion reactions. In order to solve such resource waste and energy inefficiency, several alternatives have recently been proposed, such as separating and refining hydrogen directly from coke oven gas or converting it to syngas. Therefore, in this study, recent research trends on the separation and purification of hydrogen from coke oven gas and the production of syngas were introduced.

• Journal of Microbiology and Biotechnology
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• 제20권2호
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• pp.332-339
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• 2010

The lipase from Mucor racemosus NRRL 3631 was partially purified by fractional precipitation using 60% ammonium sulfate, which resulted in a 8.33-fold purification. The partially purified lipase was then immobilized using different immobilization techniques: physical adsorption, ionic binding, and entrapment. Entrapment in a 4% agar proved to be the most suitable technique (82% yield), as the immobilized lipase was more stable at acidic and alkaline pHs than the free enzyme, plus 100% of the original activity was retained owing to the thermal stability of the immobilized enzyme after heat treatment for 60 min at $45^{\circ}C$. The calculated half-lives (472.5, 433.12, and 268.5 min at 50, 55, and $60^{\circ}C$, respectively) and the activation energy (9.85 kcal/mol) for the immobilized enzyme were higher than those for the free enzyme. Under the selected conditions, the immobilized enzyme had a higher $K_m$ (11.11 mM) and lower $V_{max}$ (105.26 U/mg protein) when compared with the free enzyme (8.33 mM and 125.0 U/mg protein, respectively). The operational stability of the biocatalyst was tested for both the hydrolysis of triglycerides and esterification of fatty acids with glycerol. After 4 cycles, the immobilized lipase retained approximately 50% and 80% of its original activity in the hydrolysis and esterification reactions, respectively.

• Journal of the Korean Wood Science and Technology
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• 제43권5호
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• pp.539-547
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• 2015

To investigate dimensional responses of wood under dynamic temperature condition, poplar (populous euramericana Cv.) specimens, 20 mm in radial (R) and tangential (T) directions with two thicknesses of 4 and 10 mm along the grain, were exposed to cyclic temperature changes in square wave between $25^{\circ}C$ and $40^{\circ}C$ at 60% relative humidity (RH) for three different cycling periods of 6 h, 12 h and 24 h. R and T dimensional changes measured during the cycling gave the following results: 1) Transverse dimensional changes of the specimens were generally square but at an opposite phase and lagged behind the imposed temperature changes. The phase lag was inversely correlated with cycling period, but positively related to specimen thickness, while the response amplitude was directly proportional to cycling period, but in a negative correlation with specimen thickness. 2) The specimens showed swelling hysteresis behavior. The heat shrinkage coefficient (HSC) became greater as cycling period increased or specimen thickness decreased. 3) Dimensional changes of the specimens produced deformation accumulation during repeated adsorption and desorption. The deformation accumulating ratio decreased with an increase in cycling period and specimen thickness. 4) Wood suffered 1.5 times as many dimensional changes per unit temperature variation as per unit humidity variation, and this deformation behaved even more seriously under static condition.