• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.523-526
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• 2004

According to the continuous demand for power and the growth of electric power utilities, the electric power transmission capacity was increased. The increase of the electric power transmission capacity results in an increase of the fault current level a fault happened. So the superconducting fault current limiter(SFCL) has been reached as the countermeasure for the reduction of the fault current. In this paper, we investigate the fault currents characteristics of resistive type SFCL according to fault angles when AC power source applied. As the fault angles increase, the first peak value of fault current decreased lower. On the other hand, the power burden of SFCL increased.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.420-420
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• 2010

AC PDP에서 유전체 보호막으로 사용되는 MgO 박막은 높은 이차전자방출계수($\gamma$)로 인해 방전전압을 낮춰주는 중요한 역할을 하고 있다. 이러한 MgO 보호막의 이차전자방출계수를 증가시키기 위해 MgO 의 Energy Band Structure 규명이 중요한 연구 주제가 되고 있다. MgO의 이차전자방출계수($\gamma$)는 Auger 중화 이론에 의해 방출 메커니즘이 설명이 되고, 그 원리는 다음과 같다. 고유의 이온화 에너지를 가진 이온이 MgO 표면에 입사 되면, Tunneling Effect에 의해 전자와 이온 사이에 중화가 일어나고, 중화가 되고 남은 에너지가 MgO Valance Band 내의 전자에게 전달되면 이때 남은 에너지(${\Delta}E$)가 MgO의 일함수(Work function) 보다 크게 되면 이차전자로 방출된다. 본 실험 에서는 $\gamma$-FIB System을 이용하여 결정 방향이 (100), (110), (111)을 갖는 Single Crystal MgO에 이온화 에너지가 24.58eV인 He Ion source를 주사 하였을 때 Auger self-convolution을 통해 이차전자의 운동 에너지 분포를 구하고, 이를 통해 MgO 내의 Energy Band Structure를 실험적으로 측정하였다. 이를 통해 MgO Single Crystal의 일함수 및 Defect Level의 분포를 확인하였다.

• Korea Trade Review
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• v.44 no.3
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• pp.203-226
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• 2019

This study incorporates the structural relationships between leadership styles (LS), affect climate (AC), and organizational performance (OP) in Korean export manufacturing companies with three or more overseas subsidiaries. A theoretical model is suggested with the following empirical results. First, the positive effect of engaging leadership (EL) on organizational citizenship behavior (OCB), as well as of engaging leadership, involving leadership (IL), and goal-oriented leadership (GL) on team performance (TP), proved to be significant. Second, both engaging leadership and goal-oriented leadership have significant positive effects on optimism, while involving leadership has significant negative effects on pessimism. Third, only optimism has a positive (+) effect on OCB and TP. The mediating effects were proved to be significant in two paths: one in EL->optimism->OCB and the other in EL->optimism->TP. Finally, in responding to rapid changes in the external environment of exporting companies, the engaging leadership is a key source of organizational performance by forming a favorable affect climate. Therefore, top management should recognize the role of team leaders and strengthen their leadership training. In addition, it was confirmed that leaders with emotional intelligence that can respond to the affects of members play a more important role in forming an optimistic climate in Korea export manufacturing enterprises with foreign subsidiaries.

• Journal of the Korean Society of Industry Convergence
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• v.24 no.4_1
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• pp.377-385
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• 2021

High voltage direct current(HVDC) systems has been an alternative method of a power transmission to replace high voltage alternate current(HVAC), which is a traditional AC transmission method. Due to technical limitations, Line commutate converter HVDC(LCC-HVDC) was mainly used. However, result from many structural problems of LCC-HVDC, the voltage source converter HVDC(VSC-HVDC) are studied and applied recently. In this paper, after analyzing the reactive power and output voltage ripple, which are the main problems of LCC-HVDC, the characteristics of each HVDC are summarized. Based on this result, a new LCC-HVDC structure is proposed by combining LCC-HVDC with the MMC structure, which is a representative VSC-HVDC topology. The proposed structure generates lower reactive power than the conventional method, and greatly reduces the 12th harmonic, a major component of output voltage ripple. In addition, it can be easily applied to the already installed LCC-HVDC. When the proposed method is applied, the control of the reactive power compensator becomes unnecessary, and there is an advantage that the cut-off frequency of the output DC filter can be designed smaller. The validity of the proposed LCC-HVDC is verified through simulation and experiments.

• Nuclear Medicine and Molecular Imaging
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• v.41 no.1
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• pp.49-53
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• 2007

Purpose: It was reported that CT-based measured attenuation correction (CT-MAC) produced radioactivity concentration values significantly higher than $^{68}Ge$-based segmented attenuation correction (Ge-SAC) in PET images. However, it was unknown whether the radioactivity concentration difference resulted from different sources (CT vs. Ge) or types (MAC vs. SAC) of attenuation correction (AC). We evaluated the influences of the source and type of AC on the radioactivity concentration differences between reconstructed PET images in normal subjects and patients. Material and Methods: Five normal subjects and 35 patients with a known or suspected cancer underwent $^{18}F-FDG$ PET/CT. In each subject, attenuation corrected PET images using OSEM algorithm (28 subsets, 2 iterations) were reconstructed by 4 methods: CT-MAC, CT-SAC, Ge-MAC, and Ge-SAC. The physiological uptake in normal subjects and pathological uptake in patients were quantitatively compared between the PET images according to the source and type of AC. Results: The SUVs of physiological uptake measured in CT-MAC PET images were significantly higher than other 3 differently corrected PET images. Maximum SUVs of the 145 foci with abnormal FDG uptake in CT-MAC images were significantly highest among 4 differently corrected PET images with a difference of 2.4% to 5.1% (p<0.001). The SUVs of pathological uptake in Ge-MAC images were significantly higher than those in CT-SAC and Ge-MAC PET images (p<0.001). Conclusion: Quantitative radioactivity values were highest in CT-MAC PET images. The adoption of MAC may make a more contribution than the adoption of CT attenuation map to such differences.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.33 no.5
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• pp.385-391
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• 2011

Purpose: The periosteum is a well-known source of osteogenic precursor cells for tissue-engineered bone formation. However, cultured endothelial or endothelial-like cells derived from periosteum have not yet been investigated. This study focused on endothelial-like cell culture from the periosteum. Methods: Periosteal tissues were harvested from the mandible during surgical extraction of lower impacted third molars. The tissues were treated with 0.075% type I collagenase in phosphate-buffered saline (PBS) for 1 hr at $37^{\circ}C$ to release cellular fractions. The collagenase was inactivated with an equal volume of DMEM/10% fetal bovine serum (FBS) and the infranatant was centrifuged for 10 min at 2,400 rpm. The cellular pellet was filtered through a $100{\mu}m$ nylon cell strainer, and the filtered cells were centrifuged for 10 min at 2,400 rpm. The resuspended cells were plated into T25 flasks and cultured in endothelial cell basal medium (EBM)-2. Results: Among the hematopoietic markers, CD146 was more highly expressed than CD31 and CD34. The periosteal-derived cells also expressed CD90 and CD166, mesenchymal stem cell markers. Considering that the expression of CD146 was constant and that the expression of CD90 was lower at passage 5, respectively, the CD146 positive cells in passage 5 were isolated using the magnetic cell sorting (MACS) system. These CD146 sorted, periosteal-derived cells formed tube-like structures on Matrigel. The uptake of acetylated, low-density lipoprotein, labeled with 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI-Ac-LDL) was also examined in these cells. Conclusion: These results suggest that the CD146-sorted positive cells can be referred to as periosteal-derived CD146 positive endothelial-like cells. In particular, when a co-culture system with endothelial and osteoblastic cells in a three-dimensional scaffold is used, the use of periosteum as a single cell source would be strongly beneficial for bone tissue engineering.

• Korean Journal of Soil Science and Fertilizer
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• v.18 no.4
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• pp.336-347
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• 1985

Soils and rice plants subject to smoke from the Jang-hang Smelter were samples at two depths to assess the nature and extend of Cd, Cu, Pb, and Zn contamination, particularly with respect to distance from pollution source. Soils at east site within 1km of the center of the smelter were highly contaminated with Cd, Cu, Pb, and Zn. Metal levels in the smoke-polluted area were higher in surface soil than in subsurface soil, and decreased rapidly with distance reaching nearly background levels at 5km from pollution source. A position correlation was found between contents of total and 0.1 N HCl-extractable, or 1.0N $CH_3COONH_4$- extractable heavy metals in surface soils of pollution. Contents of heavy metals in soils were positively correlated with soil organic matter and cation exchange capacity. The contents of heavy metals in brown rice collected from the paddy field around the Jang-hang Smelter were in the range of 0.23-1.33 ppm for Cd, 2.39-6.25 for Cu, 0.95-8.32 ppm for Pb and 14.60-27.31 for Zn. The contents of Cd, Cu, and Zn in rice straw were positively correlated with those in the brown rice. Negative correlation was found between the contents of Cd, Cu, Pb, and Zn in brown rice and the distance from the source.

• The Korean Journal of Food And Nutrition
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• v.28 no.3
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• pp.458-464
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• 2015

In this study, the total polyphenol content, electron donating ability (EDA) and inhibitory activity of glutathione S-transferase (GST) of freeze-dried Citrus unshiu extracts were examined. The Citrus unshiu extracts was obtained from four solvents such as ethyl acetate, acetone, methyl chloride and methanol, to evaluate its functional properties. Total polyphenol contents were measured in the two different extracts, and the extracts were screened for their potential antioxidant activities using tests such as electron donating ability (EDA), glutathione S-transferase (GST). The total polyphenol contents of Citrus unshiu extracts were $928.48{\pm}1.19{\mu}g\;GAE/mL$ in ethyl acetate (EA), $886.03{\pm}0.44{\mu}g\;RE/mL$ in acetone (AC), $413.08{\pm}1.39{\mu}g\;GAE/mL$ in methylene chloride (MC), $12,648.60{\pm}0.56{\mu}g\;GAE/mL$ in methanol (MeOH), respectively. Also, the total polyphenol contents of EtOH Citrus unshiu extracts were $664.64{\pm}0.74{\mu}g\;GAE/mL$ in EA, $702.67{\pm}0.85{\mu}g\;RE/mL$ in AC, $429.64{\pm}0.61{\mu}g\;GAE/mL$ in MC, $16,108{\pm}0.73{\mu}g\;GAE/mL$ in MeOH, respectively. The total polyphenol contents were significantly difference (p<0.05) between the solvents. The electron donating ability of Citrus unshiu extracts were $62.80{\pm}0.36%$ in EA, $97.43{\pm}0.51%$ in AC, $52.20{\pm}0.30%$ in MC, $97.63{\pm}0.46%$ in MeOH, respectively. Also, the electron donating ability of EtOH Citrus unshiu extracts were $51.49{\pm}0.26%$ in EA, $63.17{\pm}0.31%$ in AC, $67.68{\pm}0.55%$ in MC, $96.18{\pm}0.41%$ in MA, respectively. The electron donating ability were significantly difference (p<0.05) between the solvents. The inhibitory activity of glutathione S-transferase in Citrus unshiu extracts were $76.22{\pm}0.65%$ in EA, $31.73{\pm}0.48%$ in MC, $97.48{\pm}0.56%$ in MeOH, respectively. Also, inhibitory activity of glutathione S-transferase in EtOH Citrus unshiu extracts were $75.54{\pm}0.55%$ in EA, $73.53{\pm}0.38%$ in MC, $48.70{\pm}0.46%$ in MeOH, respectively. The inhibitory activity of glutathione S-transferase were significantly difference (p<0.05) between the solvents. These results indicated that the Citrus unshiu extracts is a high-valued food ingredient and the extraction with methanol will be useful as a nutritional source with natural antioxidant activities. Considering high consumer demand beneficial health effects, Citrus unshiu extracts can be utilized to develop functional food health- promoting and natural antioxidant agents.

• Journal of the Korean Vacuum Society
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• v.22 no.3
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• pp.168-173
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• 2013

In this paper, we would like to introduce Electron Relay Enhancer (ERE), a supplementary device, which improves commercial solar cell efficiency minimizing electron-hole recombination of solar cell. The ERE in this study is mainly composed of two capacitors which are connected to AC power source and bridge diode system which controls electron flow direction. Two capacitors repeat collecting electrons from solar cell and pumping the collected electrons to load resistance or inverter through the bridge diode system. While one positively charged capacitor collect electrons, the other negatively charged one pumps electrons. A positively charged capacitor pulls the more exited electrons from the solar cell, before the exited electrons recombine the holes in solar cell. That is why the ERE system enhances solar cell efficiency. As a result, the measured power increase of the solar cell with the ERE is varied from 5.9 W to 25.6 W in each experimental condition. Maximal increase rate of the solar cell power with ERE is 30.8% of solar cell power without ERE.

• Biomedical Science Letters
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• v.9 no.4
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• pp.177-181
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• 2003

The baculovirus/Spodoptera frugiperda (Sf) cell system has become popular for the production of large amounts of the human erythrocyte glucose transporter, GLUT1, heterologously. However, it was not possible to show that the expressed transporter in insect cells could actually transport glucose. The possible reason for this was that the activity of the endogenous insect glucose transporter was extremely high and so rendered transport activity resulting from the expression of exogenous transporter very difficult to detect. Sf21-AE cells are commonly employed as the host permissive cell line to support the baculovirus AcNPV replication and protein synthesis. The cells grow well on TC-100 medium that contains 0.1 % D-glucose as the major carbon source, strongly suggesting the presence of endogenous glucose transporters. However, unlike the human glucose transporter, very little is known about properties of the endogenous sugar transporter(s) in insect cells. Thus, the uptake of 2-deoxy-D-glucose (2dGlc) by Sf21-AE cells and the inhibition of 2dGlc transport in the insect cells by fructose and cytochalasin B were investigated in the present work. The binding assay of cytochalasin B was also performed, which could be used as a functional assay for the endogenous glucose transporter(s) in the insect cells. Sf21-AE cells were infected with the recombinant virus AcNPV-GT or no virus, at a multiplicity of infection (MOI) of 5. Infected cells were resuspended in PBS plus and minus 300 mM fructose, and plus and minus 20 $\mu$M cytochalasin B for use in transport assays. Uptake was measured at 28$^{\circ}C$ for 1 min, with final concentration of 1 mM deoxy-D-glucose, 2-[1,2-$^3$H]- or glucose, L-[l,$^3$H]-, used at a specific radioactivity of 4 Ci/mol. The results obtained demonstrated that the sugar uptake in uninfected cells was stereospecific, and was strongly inhibited by fructose but only poorly inhibitable by cytochalasin B. It is therefore suggested that the Sf21-AE glucose transporter has very low affinity for cytochalasin B, a potent inhibitor of human erythrocyte glucose transporter.