• Transactions of the Korean hydrogen and new energy society
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• v.23 no.6
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• pp.654-659
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• 2012

The interest in water gas shift (WGS) reaction has grown significantly, as a result of the recent advances in fuel cell technology and the need to develop small-scale fuel processors. Recently, researchers have tried to overcome the disadvantages of the commercial WGS catalysts. As a consequence, supported Pt catalysts have attracted a lot of researchers due to high activity and stability for WGS at low temperatures. In this study, $Pt-Na/Ce_{(1-x)}Zr_{(x)}O_2$ catalysts with various Ce/Zr ratio have been applied to WGS at a gas hourly space velocity (GHSV) of $45,515h^{-1}$. According to TPR patterns of $Pt-Na/Ce_{(1-x)}Zr_{(x)}O_2$ catalysts, the reducibility increases with decreasing the $ZrO_2$ content. As a result, Cubic structure $Pt-Na/Ce_{(1-x)}Zr_{(x)}O_2$ catalysts exhibited higher CO conversion than tetragonal structure $Pt-Na/Ce_{(1-x)}Zr_{(x)}O_2$ catalysts. Expecially, Pt-Na/$CeO_2$ exhibited the highest CO conversion as well as 100% selectivity to $CO_2$. Moreover, Pt-Na/$CeO_2$ catalyst showed relatively stable activity with time on stream. The high activity of cubic structure Pt-Na/$CeO_2$ catalyst was correlated to its higher oxygen storage capacity (OSC) of $CeO_2$ and easier reducibility of Pt/$CeO_2$.

• Journal of the Korean Applied Science and Technology
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• v.26 no.3
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• pp.269-278
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• 2009

In this study, the anti oxidative effects, inhibitory effects on elastase, and components of Securinega suffruticosa extracts were investigated. The free radical (1,1-diphenyl-2-picrylhydrazyl, DPPH) scavenging activities ($FSC_{50}$) and reactive oxygen species ROS) scavenging activities ($OSC_{50}$) of extract/fractions from Securinega suffruticosa were measured. The aglycone fraction ($9.04\;{\pm}\;0.51\;{\mu}g/mL$) and 50 % ethanol extract ($1.05\;{\pm}\;0.41\;{\mu}g/mL$) showed the most effective scavenging activities. The protective effects on the rose-bengal sensitized photohemolysis of human erythrocytes were investigated. The aglycone fraction exhibited the most prominent cellular protective effect (${\tau}_{50},\;102.77\;{\pm}\;5.37$ min at $10{\mu}g/mL$). The inhibitory effect of ethyl acetate fraction on tyrosinase were of examined ($210.0\;{\pm}\;1.02\;{\mu}g/mL$). The inhibitory effect of aglycone fraction on elastase were also investigated ($17.6\;{\pm}\;1.26\;{\mu}g/mL$). These results indicate that extract/fractions of Securinega suffruticosa can function as antioxidants in biological systems, particularly skin exposed to UV radiation by scavenging $^1O_2$ and other ROS, and protect cellular membranes against ROS. Securinega suffruticosa extract could be used as a new cosmeceutical ingredient for whitening and anti-wrinkle products.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.201.1-201.1
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• 2014

본 연구에서는 Slot die coating 공법으로 코팅된 Poly (3-4 ethylenedioxythiophene): Poly (styrenesulfonate) (PEDOT:PSS) 박막과 비정질 ITO 박막의 전기적, 광학적, 기계적 특성을 비교 평가하여 Slot die coating 공법으로 코팅된 PEDOT:PSS 박막의 유기태양전지의 전극으로서의 적용가능성을 확인하였다. 상업용 PEDOT:PSS 박막은 보통 280 Ohm/sq.의 면저항과 가시광 영역에서 약 80%의 광투과도를 나타내며, 비정질 ITO 박막과 유사한 전기적, 광학적 특성을 나타내었다. Slot die coating 공법을 통해 제작된 PEDOT:PSS 투명 전극과 비정질 ITO 투명 전극의 기판 휘어짐에 따른 전기적 안정성을 비교 평가하기 위해 25 mm에서 1 mm까지 radius 변화에 따른 저항의 변화를 측정하였다. 그 결과, 비정질 ITO 투명 전극 대비 PEDOT:PSS 투명 전극이 더 우수한 전기적 안정성을 나타냄을 확인하였다. 또한, 다양한 Bending test (Inner/Outer bending, Rolling, Stretching, Twisting) 를 통해 비정질 ITO 투명 전극 보다 Slot die coating 공법으로 코팅된 PEDOT:PSS 투명 전극의 우수한 기계적 특성을 확인하였다. 이를 바탕으로 Flexible 유기태양전지에의 적용 가능성을 알아보기 위해 Slot die coating 공법으로 코팅된 PEDOT:PSS 투명 전극과 비정질 ITO 투명 전극을 유기태양전지의 anode 층에 적용하여 각각 제작하고 그 특성을 평가하였다. 비정질 ITO 투명 박막을 적용한 유기태양전지 대비 Slot die coating 공법으로 코팅된 PEDOT:PSS 투명 박막으로 제작한 유기태양전지에서 더 높은 효율이 나타났으며, 이로써 Slot die coating 공법으로 코팅된 PEDOT:PSS 투명 전극의 Flexible 유기태양전지로써의 적용 가능성을 확인하였다.

• Fire Science and Engineering
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• v.17 no.1
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• pp.33-39
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• 2003

The purpose of this study is to evaluate flame retardant performance, thermal stability and toxicity of combustion gases for some commercial wallpapers. ID evaluate flame retardant performance 45 degree combustion experiment method was used and thermal stability was evaluated using DSC and TGA apparatus (OSC-50/Shimadzu, TGA2050/TA Instruments Inc) . Concentrations of CO, $CO_2$, HCN and HCI were measured with (GASTEC/Japan, MSA400 Gas Monitor/Infitron Inc) and toxicity indices using NIST N-Gas Model were applied to evaluate the toxicity of combustion gases. The evaluation produced the following results : First, paper cork and PVC wallpaper treated with flame retardants were found to be suitable for flame retardant performance standards. Second, paper, cork and PVC wallpaper non-treated with flame retardants were shown to be relatively more hazardous because they had greater calorific values and a faster decomposition time than the flame retardant treated wallpapers. Third, the toxicity indices of non-treated wallpapers were found to be higher than those of treated wallpapers, and the toxicity index of PVC wallpapers was higher than those of paper and cork wallpapers.

• Journal of Power Electronics
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• v.18 no.6
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• pp.1791-1804
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• 2018

To achieve a fast dynamic response and to solve the multi-objective control problems of the output currents, capacitor voltages and system constraints, this paper proposes a deadbeat and hierarchical predictive control with space-vector modulation (DB-HPC-SVM) for five-level nested neutral point piloted (NNPP) converters. First, deadbeat control (DBC) is adopted to track the reference currents by calculating the deadbeat reference voltage vector (DB-RVV). After that, all of the candidate switching sequences that synthesize the DB-RVV are obtained by using the fast SVM principle. Furthermore, according to the redundancies of the switch combination and switching sequence, a hierarchical model predictive control (MPC) is presented to select the optimal switch combination (OSC) and optimal switching sequence (OSS). The proposed DB-HPC-SVM maintains the advantages of DBC and SVM, such as fast dynamic response, zero steady-state error and fixed switching frequency, and combines the characteristics of MPC, such as multi-objective control and simple inclusion of constraints. Finally, comparative simulation and experimental results of a five-level NNPP converter verify the correctness of the proposed DB-HPC-SVM.

• Journal of agriculture & life science
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• v.53 no.3
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• pp.147-157
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• 2019

In this study, we tried to find out the most appropriate pre-processing method and to verify the feasibility of developing a low-price sensing system for predicting the hardy kiwis sugar content based on VNIRS and subsequent spectral analysis. A total of 495 hardy kiwi samples were collected from three farms in Muju, Jeollabukdo, South Korea. The samples were scanned with a spectrophotometer in the range of 730-2300 nm with 1 nm spectral sampling interval. The measured data were arbitrarily separated into calibration and validation data for sugar content prediction. Partial least squares (PLS) regression was performed using various combinations of pre-processing methods. When the latent variable (LV) was 8 with the pre-processing combination of standard normal variate (SNV) and orthogonal signal correction (OSC), the highest R2 values of calibration and validation were 0.78 and 0.84, respectively. The possibility of predicting the sugar content of hardy kiwi was also examined at spectral sampling intervals of 6 and 10 nm in the narrower spectral range from 730 nm to 1200 nm for a low-price optical sensing system. The prediction performance had promising results with R2 values of 0.84 and 0.80 for 6 and 10 nm, respectively. Future studies will aim to develop a low-price optical sensing system with a combination of optical components such as photodiodes, light-emitting diodes (LEDs) and/or lamps, and to locate a more reliable prediction model by including meteorological data, soil data, and different varieties of hardy kiwi plants.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.37 no.4
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• pp.357-363
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• 2011

In this study, the antioxidative effects and inhibitory activities on tyrosinase of Rheum undulatum (R.undulatum) L. extracts were investigated. 50 % ethanol extract, ethyl acetate and aglycone fractions of R. undulatum L. were used in experiments. The DPPH (1,1-diphenyl-2-picrylhydrazyl) scavenging activities ($FSC_{50}$) of R. undulatum L. extracts was lower than (+)-${\alpha}$-tocopherol, known as a typical antioxidant. Reactive oxygen species (ROS) scavenging activities ($OSC_{50}$) of aglycone fraction on ROS generated in $Fe^{3+}$-EDTA/$H_2O_2$ system using the luminol-dependent chemiluminescence assay showed the most prominent effect at a concentration of $0.265\;{\mu}g/mL$. The cellular protective effects of extract/fractions of R. undulatum L. on the rose-bengal sensitized photohemolysis of human erythrocytes were increased in a concentration dependent manner ($1{\sim}50\;{\mu}g/mL$). Especially, aglycone fraction in $10\;{\mu}g/mL$ concentration showed the most protective effect among extracts (${\tau}_{50}$, 757.0 min). The inhibitory effects ($IC_{50}$, $11.20\;{\mu}g/mL$) on tyrosinase of aglycone fraction was much higher than arbutin ($226.88\;{\mu}g/mL$), known as a whitening agent. These results indicate that R. undulatum L. extracts can be used as antioxidant. Particularly, aglycone fraction of R. undulatum L. showed superior antioxdative activity and high inhibitory effect on tyrosinase. Therefore, aglycone fraction of R. undulatum L. could be applicable to new functional cosmetics.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.38 no.3
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• pp.275-282
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• 2012

In this study, the antioxidative effects of extracts from different parts of Juncus effusus L. were investigated. The three parts (above-ground part, below-ground part, medulla part) were selected. 50 % ethanol extract, ethyl acetate and aglycone fractions of J. effusus L. were used in experiments. The highest DPPH (1,1-diphenyl-2-picrylhydrazyl) scavenging activities ($FSC_{50}$) was shown by medulla part (42.9 ${\mu}g/mL$) in 50 % ethanol extracts, below-ground part (12.1 ${\mu}g/mL$) in ethyl acetate fractions, and below-ground part (12.1 ${\mu}g/mL$) in aglycone fractions. Reactive oxygen species (ROS) scavenging activities ($OSC_{50}$) on ROS generated in $Fe^{3+}$-EDTA/$H_2O_2$ system using the luminol-dependent chemiluminescence assay showed the most prominent effect of medulla part (0.29 ${\mu}g/mL$) in 50 % ethanol extracts, below-ground part (0.25 ${\mu}g/mL$) in ethyl acetate fractions, and medulla part (0.20 ${\mu}g/mL$) in aglycone fractions. The cellular protective effects of extract/fractions of J. effusus L. on the rose-bengal sensitized photohemolysis of human erythrocytes were increased in a concentration dependent manner (0.5 ~ 10 ${\mu}g/mL$). Especially, aglycone fraction of medulla part at a concentration of 10 ${\mu}g/mL$ showed the most prominent protective effect among all extracts (${\tau}_{50}$, 321.0 min). These results indicate that extracts from below-ground part and medulla part of J. effusus L. extracts can be used as an natural antioxidant. Particularly, J. effusus L. can protect suggesting a high ${\tau}_{50}$ skin where many $^1O_2$ was generated by sunlight exposure.

• Applied Chemistry for Engineering
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• v.26 no.1
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• pp.29-34
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• 2015

N,N'-Diferuloyl-putrescine (DFP) present in plants such as Sophora japonica has been reported to have skin depigmentative and antioxidative activities. In this study, DFP, usually presents in nature a very little amount and its derivative (DFP-D) were synthesized in a large quantity for the use as functional cosmetical materials. The antioxidative activities of synthesized DFP and DFP-D were evaluated by the 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay, chemiluminescence assay, and cell protective effect induced by $^1O_2$, stress. DFP and DFP-D showed DPPH radical scavenging activities ($FSC_{50}$) at $61.25{\pm}2.25{\mu}M$ and $12.92{\pm}0.72{\mu}M$, respectively. ROS (reactive oxygen species) scavenging activities ($OSC_{50}$) in the $Fe^{3+}-EDTA/H_2O_2$ system of DFP and DFP-D were 2 times ($1.84{\pm}0.12{\mu}M$) and 13 times ($0.174{\pm}0.01{\mu}M$), respectively higher than that of L-ascorbic acid. $^1O_2$, one of ROS playing a key role in the skin photo-aging, induces cellular membrane damages. DFP-D ($50{\mu}M$) showed good cell protective effects (${\tau}_{50}=80.2min$) about 2 times more than that of (+)-${\alpha}$-tocopherol (${\tau}_{50}=43.6min$). These results suggest that the great antioxidative activities of DFP and DFP-D could be applied to cosmetic industries as functional cosmetic materials.

• Microbiology and Biotechnology Letters
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• v.46 no.1
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• pp.18-28
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• 2018

In this study, the antioxidant activities and cytoprotective effects against oxidative stress of Lonicera japonica Thunb. 50% ethanol extract and ethyl acetate fraction were investigated. Using the 1,1-diphenyl-2-picrylhydrazyl assay, the free radical scavenging activity (FSC50) of L. japonica Thunb. 50% ethanol extract and ethyl acetate fraction was determined as 152.00 and $77.25{\mu}g/ml$, respectively. To measure the reactive oxygen species (ROS) scavenging activity, the total antioxidant capacity (OSC50) was determined by using a luminol-dependent chemiluminescence assay. The antioxidant activity of the ethyl acetate fraction ($0.33{\mu}g/ml$) was approximately four times stronger than that of the 50% ethanol extract ($1.12{\mu}g/ml$). The protective effect against $^1O_2$-induced cellular damage of human erythrocytes (${\tau}_{50}$) was 46.0 min at $10{\mu}g/ml$ of the 50% ethanol extract and 52.3 min at $1{\mu}g/ml$ of the ethyl acetate fraction. We also investigated the cytoprotective effects against oxidative stress induced by $H_2O_2$ and the intracellular ROS scavenging activity in response to UVB irradiation and found that the extract and fraction protected human skin cells from damage and reduced ROS. These results confirmed that L. japonica Thunb. was a valuable plant-derived natural antioxidant with potential for development as an antioxidative functional ingredient.