• Journal of Sensor Science and Technology
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• v.4 no.2
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• pp.37-44
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• 1995

A coprecipitation method was used for preparing Ca and Pt doped $SnO_{2}$-based material. Crystallite size and specific surface area were investigated by TEM, XRD and BET analysis. $SnO_{2}(Ca)/Pt$ based thick film devices were prepared by a screen printing technique for hydrocarbon gas detecting. Then the electrical and sensing characteristics of devices were investigated. As Ca and Pt addition, the crystal growth of $SnO_{2}$ was suppressed during calcining and sintering, and the sensitivity of $SnO_{2}(Ca)/Pt$ thick film to gas was enhanced. Also any difference in the sensing properties has to be attributed to the Pt and Au electrode. For the 2000 ppm $CH_{4}$, the sensitivity of $SnO_{2}(Ca)/Pt$ thick film devices were about 83% at an operating temperature of $400^{\circ}C$.

• Journal of the Korean institute of surface engineering
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• v.44 no.2
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• pp.60-67
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• 2011

Ternary B-C-N coatings were deposited on Si(100) wafer substrate from $B_4C$ target by RF magnetron sputtering technique in $Ar+N_2+CH_4$ gas mixture. In this work, the effect of reactant gas ratio, $CH_4/(N_2+CH_4)$ on the composition, kinds and amounts of bonding states comprising B-C-N coatings were investigated using two different bias power sources of continuous and unipolar DCs. In addition, the tribological properties of coatings were studied with the composition and bonding state of coating. It was found that the substrate bias power had an effect on chemical composition, and all of the obtained coatings were nearly amorphous. Main bonding states of coatings were revealed from FTIR analyses to be h-BN, C-C, C-N, and B-C. The amount of C-C bonging mainly increased with increase of the reactant gas ratio. From our studies, both C-C and h-BN bonding states improved the tribological properties but B-C one was found to be harmful on those. The best coating from tribological points of view was found to be $BC_{1.9}N_{2.3}$ composition.

• 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.

• Korean Chemical Engineering Research
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• v.56 no.2
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• pp.169-175
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• 2018

This study deals with a process for the recovery of hydrogen isotopes from methane ($CQ_4$) and water ($Q_2O$) containing tritium in the nuclear fusion exhaust gas (Q is Hydrogen, Deuterium, Tritium). Steam Methane Reforming and Water Gas Shift reactions are used to convert $CQ_4$ and $Q_2O$ to $Q_2$ and the produced $Q_2$ is recovered by the subsequent Pd membrane. In this study, one circulation loop consisting of catalytic reactor, Pd membrane, and circulation pump was applied to recover H components from $CH_4$ and $H_2O$, one of $CQ_4$ and $Q_2O$. The conversion of $CH_4$ and $H_2O$ was measured by varying the catalytic reaction temperature and the circulating flow rate. $CH_4$ conversion was 99% or more at the catalytic reaction temperature of $650^{\circ}C$ and the circulating flow rate of 2.0 L/min. $H_2O$ conversion was 96% or more at the catalytic reaction temperature of $375^{\circ}C$ and the circulating flow rate of 1.8 L/min. In addition, the amount of $CQ_4$ generated by Korean Demonstration Fusion Power Plant (K-DEMO) in the future was predicted. Then, the treatment process for the $CQ_4$ was proposed and HAZOP (hazard and operability) analysis was conducted to identify the risk factors and operation problems of the process.

• Korean Journal of Food Science and Technology
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• v.27 no.6
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• pp.997-1002
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• 1995

In order to study the effects of reaction temperature, time and particle size on the physicochemical properties of chitosan, commercially available chitin was treated with 50%(w/w) NaOH. To obtain 78% of deacetylation, a treatment of 6 hours at $100^{\circ}C$(Ch-100), 20 minutes at $120^{\circ}C$(Ch-120) or 10 minutes at $140^{\circ}C$(Ch-140) was necessary. The resulting chitosans showed a different viscosity; 180cps for Ch-100, 130cps for Ch-120, 30cps for Ch-140. The residence time at $80^{\circ}C$ also decreased the viscosity of the chitosan but the reduction in the particle size of chitin largely favored deacetylation and resulted in a higher viscosity of the chitosan. Compared with chitin, the capacity of water and oil absorption of chitosan was not significantly improved. However, the capacity of dye absorption was increased by 4 times by the deacetylation. In addition the IR spectra of chitosans showed less sharp absorption bands than that of chitin.

• Korean Journal of Materials Research
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• v.7 no.12
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• pp.1047-1051
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• 1997

CH$_{4}$와 H$_{2}$의 혼합가스에 미량의 질소와 산소를 첨가하여 rf-플라즈마 CVD법으로 DLC막을 합성하였다. 이 때 챔버내 압력은 430mtorr, 기판에 인가된 전력은 80W였으며, H$_{2}$와 CH$_{4}$의 비율은 1:1이었다. 이 시편들에 대해 가시광선 영역과 자외선 영역에서의 투과도를 비교하였으며, 결합구조의 변화를 알아보기 위하여 FTIR 분석을 실시하였다. 질소의 경우 첨가량이 6.3%에서 17.4%으로 증가됨에 따라 전체적인 투과도값이 증가하였으며, FRIR 분석결과 wavenumber 3500 $cm^{-1}$ /의 위치에 N-H stretching band가 나타나고 2300$cm^{-1}$ /에는 nitrile의 피크가 나타났다. 이 피크들의 존재는 질소의 첨가에 의하여 interlink를 감소시킴으로써 막의 잔류응력을 현저히 감소시킬 수 있음을 의미한다. 2% $O_{2}$를 첨가한 경우 막의 투과도는 질소를 첨가한 경우보다 월등히 더 향상되었다. 질소첨가량을 증가시킴에 따라 optical band gap또한 증가되는 경향을 보였으며, 2% $O_{2}$를 첨가하였을 때 막의 optical band gap은 0.5까지 감소하였다.

• KSBB Journal
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• v.9 no.1
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• pp.26-34
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• 1994

When effects of exogenous hormone on hairy root cultures of Raphanus sativs cv. Chungpihongsim examined, the highest anthocyanin synthesis and disorganization were observed when 2, 4-D was supplemented to the culture medium Cytokinins showed early weak induction after transfer and ABA showed inhibitory effect and GA3 showed no effects in anthocyanin synthesis. Hormones except for 2, 4-D in 1 mg/$\ell$ concentration did not induce disorganization of hairy root and retarded growth of hairy root. Time-course changes in anthocyanin synthesis, phenylalanine ammonia-lyase activity and chalcone synthase activity were examined in culture condition contalning 2, 4-D and kinetin. In a medium containing 2, 4-D, anthocyanin synthesis began to increase on the 9th day and reaching maxima on the 18th day after transfer. Maximum peak of PAL activity appeared on the 3-9th day and another minor peak appeared on the 18th day. CHS activity increased from 9th day, reaching maximum on the 18th day and remained at a relatively high level for culture period. In a medium containing kinetin, anthocyanin synthesis increased temporarily on the 6-9th days, early days after transfer and maintained at a low level for remaining culture period. Peak of PAL activity appeared on the 6th day and CHS activity increased from the 6th days, reaching maxima about 18th day and remained at a relatively high level. In particular, addition of kinetin after preculture in hormone free medium for 2 weeks which was thought of wound healing period showed no effects in anthocyanin synthesis. This results showed that stimulation of anthocyanin synthesis by 2, 4-D and kinetin was meaningfully connected with changes of PAL, CHS activity, and then suggested rate-limiting role of CHS on anthocyanin synthesis in that there is close correlation between anthocyanin synthesis and changes of CHS activity in time-course. Besides, it is considered that cytoklnins involving kinetin stimulated anthocyanin synthesis be due to "wound response" by cutting of young roots, and that difference in time-course peak and PAL, CHS activities expressed by 2, 4-D and kinetin result from occurrence of isozyme which have different regulatory mechanism.mechanism.

• Korean Journal of Environmental Agriculture
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• v.42 no.4
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• pp.358-370
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• 2023

Composting has been proposed for the management of organic waste, and the resulting products can be used as soil amendments and fertilizer. However, the emissions of greenhouse gases (GHGs) such as CO₂, CH₄, and N₂O produced in composting are of considerable concern. Hence, various additives have been developed and adopted to control the emissions of GHGs. This review presents the different additives used during composting and summarizes the effects of additives on GHGs during composting. Thirty-four studies were reviewed, and their results showed that the additives can reduce cumulative CO₂, CH₄, and N₂O emission by 10.5%, 39.0%, and 28.6%, respectively, during composting. Especially, physical additives (e.g., biochar and zeolite) have a greater effect on mitigating N₂O emissions during composting than do chemical additives (e.g., phosphogypsum and dicyandiamide). In addition, superphosphate had a high CO₂ reduction effect, whereas biochar and dicyandiamide had a high N₂O reduction effect. This implies that the addition of superphosphate, biochar, and dicyandiamide during composting can contribute to mitigating GHG emissions. Further research is needed to find novel additives that can effectively reduce GHG emissions during composting.

• Asian-Australasian Journal of Animal Sciences
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• v.28 no.10
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• pp.1442-1448
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• 2015

The objectives of this study were to determine the molecular weight of condensed tannins (CT) extracted from mangosteen (Garcinia mangostana L) peel, its protein binding affinity and effects on fermentation parameters including total gas, methane ($CH_4$) and volatile fatty acids (VFA) production. The average molecular weight ($M_w$) of the purified CT was 2,081 Da with a protein binding affinity of 0.69 (the amount needed to bind half the maximum bovine serum albumin). In vitro gas production declined by 0.409, 0.121, and 0.311, respectively, while CH4 production decreased by 0.211, 0.353, and 0.549, respectively, with addition of 10, 20, and 30 mg CT/500 mg dry matter (DM) compared to the control (p<0.05). The effects of CT from mangosteen-peel on in vitro DM degradability (IVDMD) and in vitro N degradability was negative and linear (p<0.01). Total VFA, concentrations of acetic, propionic, butyric and isovaleric acids decreased linearly with increasing amount of CT. The aforementioned results show that protein binding affinity of CT from mangosteen-peel is lower than those reported for Leucaena forages, however, the former has stronger negative effect on IVDMD. Therefore, the use of mangosteen-peel as protein source and $CH_4$ mitigating agent in ruminant feed requires further investigations.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.31 no.5
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• pp.345-350
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• 2018

Nanomaterials have considerable potential to solve several key challenges in various electrochemical devices, such as fuel cells. However, the use of nanoparticles in high-temperature devices like solid-oxide fuel cells (SOFCs) is considered problematic because the nanostructured surface typically prepared by deposition techniques may easily coarsen and thus deactivate, especially when used in high-temperature redox conditions. Herein we report the synthesis of a self-regenerated Pd metal nanoparticle on the perovskite oxide anode surface for SOFCs that exhibit self-recovery from their degradation in redox cycle and $CH_4$ fuel running. Using Pd-doped perovskite, $La(Sr)Fe(Mn,Pd)O_3$, as an anode, fairly high maximum power densities of 0.5 and $0.2cm^{-2}$ were achieved at 1,073 K in $H_2$ and $CH_4$ respectively, despite using thick electrolyte support-type cell. Long-term stability was also examined in $CH_4$ and the redox cycle, when the anode is exposed to air. The cell with Pd-doped perovskite anode had high tolerance against re-oxidation and recovered the behavior of anodic performance from catalytic degradation. This recovery of power density can be explained by the surface segregation of Pd nanoparticles, which are self-recovered via re-oxidation and reduction. In addition, self-recovery of the anode by oxidation treatment was confirmed by X-ray diffraction (XRD) and scanning electron microscopy (SEM).