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Choi, Seunghwan,Kim, Joohwan,Kim, Ji-Hee,Lee, Dong-Keon,Park, Wonjin,Park, Minsik,Kim, Suji,Hwang, Jong Yun,Won, Moo-Ho,Choi, Yoon Kyung,Ryoo, Sungwoo,Ha, Kwon-Soo,Kwon, Young-Guen,Kim, Young-Myeong Nature Publishing Group 2017 Experimental and molecular medicine Vol.49 No.11
<P>Heme oxygenase-1-derived carbon monoxide prevents inflammatory vascular disorders. To date, there is no clear evidence that HO-1/CO prevents endothelial dysfunction associated with the downregulation of endothelial NO synthesis in human endothelial cells stimulated with TNF-α. Here, we found that the CO-releasing compound CORM-2 prevented TNF-α-mediated decreases in eNOS expression and NO/cGMP production, without affecting eNOS promoter activity, by maintaining the functional activity of the <I>eNOS</I> mRNA 3′-untranslated region. By contrast, CORM-2 inhibited MIR155HG expression and miR-155-5p biogenesis in TNF-α-stimulated endothelial cells, resulting in recovery of the 3′-UTR activity of <I>eNOS</I> mRNA, a target of miR-155-5p. The beneficial effect of CORM-2 was blocked by an NF-κB inhibitor, a miR-155-5p mimic, a HO-1 inhibitor and siRNA against HO-1, indicating that CO rescues TNF-α-induced eNOS downregulation through NF-κB-responsive miR-155-5p expression via HO-1 induction; similar protective effects of ectopic HO-1 expression and bilirubin were observed in endothelial cells treated with TNF-α. Moreover, heme degradation products, except iron and <I>N</I>-acetylcysteine prevented H<SUB>2</SUB>O<SUB>2</SUB>-mediated miR-155-5p biogenesis and eNOS downregulation. These data demonstrate that CO prevents TNF-α-mediated eNOS downregulation by inhibiting redox-sensitive miR-155-5p biogenesis through a positive forward circuit between CO and HO-1 induction. This circuit may play an important preventive role in inflammatory endothelial dysfunction associated with human vascular diseases.</P>
A STUDY ON FILM DEPOSITION MECHANISM OF SILICON DIOXIDE (SiO2) FORMED BY PHOTO CVD
Ryoo,Ji Ho,Ju,Yu Jin,Kim,Jong Kwan,Sung,Yung Kwon 대한전자공학회 1995 ICVC : International Conference on VLSI and CAD Vol.4 No.1
A new deposition mechanism of SiO₂ film deposited by ArF(193nm) excimer laser with Si₂H_6 and N₂O gas mixture is introduced. A modeling based on the new deposition was established using deposition rate and refractive index by suggesting new precursors and frlm deposition mechanism. The suggested precursors are SiH₂O and SiH₃OH, which are generated by photolysis and collision with intermediate molecules, and then diffuse to the substrate. The radical oxygen also provides the film with sufficient oxygen atoms and bonds the precursors together.
Preparation of Three Different Style Packed Capillary Frits
Ryoo, Jae-Jeong,Song, Young-Ae,Lee, Kwang-Pill,Park, Ji-Yeon,Choi, Seong-Ho,Hyun, Myung-Ho,Ohta, Kazutoku,Fujimoto, Chuzo,Jin, Ji-Ye,Takeuchi, Toyohide,Lee, Jung-Whan Korean Chemical Society 2006 Bulletin of the Korean Chemical Society Vol.27 No.4
Three different style capillary columns, a packed capillary with temporary quartz wool frit, a packed capillary with immobilized frit, and an immobilized packed-capillary, were easily prepared with a commercially available (S)-N-(3,5-dinitro-benzoyl)leucine-N-phenyl-N-alkylamide derived chiral stationary phase. Liquid chromatographic chiral separations of some racemic amino acid derivatives on these columns were performed and the results were compared to each other. The packed capillary with immobilized frit showed some merits in chiral chromatography.
Design and Implementation of a 40-kV, 20-kJ/s Capacitor Charger for Pulsed-Power Application
Ji-Woong Gong,Hong-Je Ryoo,Suk-Ho Ahn,Sung-Roc Jang IEEE 2014 IEEE transactions on plasma science Vol.42 No.11
<P>This paper presents the design and implementation of a 40-kV, 20-kJ/s high-voltage capacitor charger based on a series/parallel resonant converter. The inclusion of the parallel resonant capacitor component in this circuit results in the production of a trapezoidal resonant current, which reduces conduction loss. This capacitor is practically realized as a part of the balancing network of the high-voltage rectifiers in the secondary side of the circuit. Particular attention in this paper is paid to the high-voltage transformer, which must be carefully designed to provide the required functionality without negative impact on the resonant circuit. A PSpice simulation has been used to prove that the proposed control method for the circuit is valid. This is supported with the experimental results, which verify that the operation of the circuit is as expected and that the converter is able to meet all the design criteria with an efficiency of up to 96%.</P>
Ryoo, Jae-Jeong,Kim, Se-Hoon,Jeong, Young-Han,Do, Hwan-Suk,Ryu, Jeong-Eun,Kwon, Hae-Young,Jeong, Ji-Yoon,Park, Hye-Jin,Lee, Soon-Ho,Hong, Moo-Ki,Hong, Jong-Ki Korean Chemical Society 2008 Bulletin of the Korean Chemical Society Vol.29 No.5
Simultaneous determination of amitraz, bromopropylate, coumaphos, cymiazole and 2,4-dimethylaniline in 200 honey samples purchased in Korea was performed by reversed-phase high-performance liquid chromatography with multiple UV detection. 2% Acetone in hexane was used for a liquid-liquid extraction and 20-40% water in acetonitrile solutions were used as mobile phases. The LOD for the analytes varied between 0.4 and 1.5 $\mu$g/L and the recoveries were yielded between 64 and 94%. Relative standard deviation of the repeatability of the method is less than 15%. Amitraz was not present in amount above 10 $\mu$ g/L and one for coumaphos and cymiazole and two for bromopropylate, and three for 2,4-dimethylanilne were detected in amount above 10 $\mu$ g/ L. Levels of the acaricide residues found were less than 50 $\mu$ g/L.
A New Split Source Type Converter for SRM Drives
Ryoo,Hong-Je,Kim,Won-Ho,Rim,Geun-Hie,Kang,Wook,Park,Ji-Ho,Won,Chung-Yuen 성균관대학교 1998 학술회의지원논문목록집 Vol.1998 No.-
This paper describes a new split source type converter topology for switched reluctance motor drives. The new converter topology consists of 2 DC link capacitors, 6 switches and 6 diodes with 2 switches and 2 diodes adding to a conventional split source converter to drive an 8/6 pole SRM. The main advantage of the proposed converter is fast suppression of the tail current in the phase-winding, hence, resulting in minimization of negative torque using doubly boosted voltage in the demagnetizing mode. The control characteristics of the proposed converter is compared with those of the asymmetric bridge converter that is widely used. Through the laboratory experiments, the proposed converter has shown higher efficiency and more output power than the other counterpart in the heavy load condition and/or in the high-speed operation.
Suk-Ho Ahn,Hong-Je Ryoo,Ji-Woong Gong,Sung-Roc Jang IEEE 2014 IEEE transactions on power electronics Vol.29 No.8
<P>This paper describes the design, implementation, and analysis of a 35 kJ/s high-voltage capacitor charger based on a delta-connected three-phase series resonant converter that provides a constant charging current with high efficiency and high-power density. In order to obtain the maximum output power for various charging voltages, each high-voltage transformer supplied by a delta-connected resonant inverter is designed with two secondary windings and voltage-doubled rectifiers. This configuration allows not only a flexible output current and voltage with fixed output power but also a high power factor on the input side. On the basis of the analysis of the series-loaded resonant converter operating at a discontinuous conduction mode, the details of the design procedure for the resonant inverter are provided. Furthermore, the implementation of the high-voltage transformers and rectifiers is also explained while considering insulation and compactness. Experiments were carried out on the developed charger with different types of capacitors, depending on their applications, and the results are discussed. In addition, malfunctioning tests were conducted for the open, short, and misfiring during charging conditions. Finally, the developed high-voltage capacitor charger was shown to be very reliable, even under faulty operating conditions in the system.</P>
Low-Ripple and High-Precision High-Voltage DC Power Supply for Pulsed Power Applications
Suk-Ho Ahn,Hong-Je Ryoo,Ji-Woong Gong,Sung-Roc Jang IEEE 2014 IEEE transactions on plasma science Vol.42 No.10
<P>This paper describes the design and implementation of a three-phase resonant converter with low ripple and high control accuracy. Based on a three-phase LCC-type resonant converter-which has advantages of low ripple, highefficiency, and high-power density compared with a single-phase converter-a high-voltage power supply with low ripple (<;0.1%) was designed. In addition to the general merits of an LCC-type resonant converter operating at continuous conduction mode- including soft switching, low conduction loss, and current source characteristics-the proposed scheme uses only one phase under a light-load condition by having different leg designs of the gate drive circuit and snubber parameters. This allows the design to overcome the operational constraints of the general LCC-type resonant converter. The distinctive design of the three-phase converter structure provides high efficiency and low ripple not only during rated operation, but also under light-load conditions. In order to analyze the high performance of the proposed scheme from no load to rated load, a PSPICE simulation was carried out. Comparison results with a conventional LCC-type resonant converter based on a single-phase structure are analyzed from the viewpoints of output ripple, losses, and operable load range. Using the proposed converter, a 20-kV, 20-kW high-voltage dc power supply design and implementation was presented with a superior gate drive circuit. Finally, the superiority of the proposed converter was verified through a simulation and experimental results. It was experimentally confirmed that the developed power supply achieves high performance in terms of efficiency (98%), operable load range (0.5-20 kV), and low ripple (0.05%), with a high power density.</P>