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RISS 인기검색어
- 검색키워드
- 저자 : Lee Younghwan (검색결과 351 건)
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( Chanwon Lee ),( Junouk Ha ),( Jayoung Park ),( Seongho Choi ),( Heeseung Park ),( Jaeseung Lee ),( Seungheon Lee ),( Younghwan Lee ) 대한내과학회 2014 대한내과학회 추계학술발표논문집 Vol.2014 No.1
Background: To investigate the relationship between markers of overall glucose exposure, postprandial glucose excursions and glycemic variability in patients with type 2 diabetes mellitus (T2DM). Methods: Sixty three patients with T2DM (mean age of 56 years) were enrolled, and all wore a continuous glucose monitoring system (CGMS) for 72 hours. We investigated the interrelationships between markers of overall glucose exposure, markers of postprandial glucose excursions and glycemic variability parameters from a CGMS. Results: Spearman`s correlation analysis revealed a signifi cant correlation between all markers of overall glucose exposure and various parameters related to glucose excursion. Percent coeffi cient of variation (CV) showed the strongest correlation with the GA (r = 0.470, p < 0.01). In participants with HbA1c levels < 7.5% (n = 33), almost all of glycemic markers and glycemic variability parameters were signifi cantly correlated with each other. All postprandial glucose excursion parameters also showed signifi cant correlation with other glycemic markers. In participants with HbA1c levels < 7.5% (n = 33), all markers of overall glucose exposure showed signifi cant interrelationships with mean glucose, postprandial glucose excursion and glycemic variability parameters (except CV). However, in participants with HbA1c levels = 7.5% (n = 30), postprandial glucose excursion and glycemic variability parameters were not related with any chronic glycemic marker. Conclusions: The postprandial glucose excursions may explain the glycemic variability and the total glucose exposures in well-controlled diabetic participants.
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Lee, Won-Gil,Lee, So-Deok,Cho, Joong-Heui,Jung, Younghwan,Kim, Jeong-hyun,Hien, Tran T.,Kang, Keon-Wook,Ko, Hyojin,Kim, Yong-Chul American ChemicalSociety 2012 Journal of medicinal chemistry Vol.55 No.8
<P>Screening of a library of chemical compounds showed that the dichloropyridine-based analogue 9 was a novel P2X(7) receptor antagonist. To optimize its activity, we assessed the structure-activity relationships (SAR) of 9, focusing on the hydrazide linker, the dichloropyridine skeleton, and the hydrophobic acyl (R-2) group. We found that the hydrazide linker and the 3,5-disubstituted chlorides in the pyridine skeleton were critical for P2X(7) antagonistic activity and that the presence of hydrophobic polycycloalkyl groups at the R-2 position optimized antagonistic activity. In the EtBr uptake assay in hP2X(7)-expressing HEK293 cells, the optimized antagonists, 5i and 52, had IC50 values of 4.9 and 13 nM, respectively. The antagonistic effects of 51 and 52 were paralleled by their ability to inhibit the release of the pro-inflammatory cytokine, IL-1 beta, by LPS/IFN-gamma/BzATP stimulation of THP-1 cells (IC50 = 1.3 and 9.2 nM, respectively). In addition, 52 strongly inhibited iNOS/COX-2 expression and NO production in THP-1 cells, further indicating that this compound blocks inflammatory signaling and suggesting that the dichloropyridine analogues may be useful in developing P2X(7) receptor targeted anti-inflammatory agents.</P>
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Lee, Seoyoung,Lee, Seunghyun,Jo, Hyunjin,Bae, Sangki,Kim, Kimin,Song, Jiho,Cho, Younghwan,Kim, Jinsung,Ahn, Hyungsoo,Yang, Min 한국물리학회 2016 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol. No.
<P>The growth temperature dependence of self-aligned beta-Ga2O3 nanostructures grown on an r-plane sapphire substrate by using metal-organic chemical vapor deposition is reported. Periodic self-alignment of the beta-Ga2O3 grains was observed for certain growth temperature windows and the grain size of the beta-Ga2O3 structure varied in response to the growth temperature. At temperatures under 800 A degrees C, self-alignment of the beta-Ga2O3 structures was not observed. The self-alignment tendency began to appear at 900 A degrees C, and obvious self-alignment characteristics in a certain direction were observed at approximately 950 A degrees C. However, as the growth temperature was increased to more than 900 A degrees C the growth mode of the beta-Ga2O3 structure gradually deviated from the self-alignment mode, finally exhibiting a two-dimensional thin film mode at 1100 A degrees C. We surmise that the driving force of beta-Ga2O3 grain self-alignment is the surface-potential difference between the planar and the step regions of the substrate on an atomic scale, which originates from misorientation occurring during the r-plane sapphire cutting process.</P>
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Interaction Effects between Ownership Concentration and Leverage on Firm Performance
Younghwan Lee,Sooyee Lee KINFORMS 2014 Management Review Vol.9 No.1
This paper examines the relationship between ownership structure and capital structure on firm performance. Both direct and moderating effects are examined. In this paper, we posit, as a primary relationship, a significant association between ownership concentration and firm performance and then examine whether the level of leverage moderates this relationship. Using a sample of 1827 observations listed on the Korean Stock Exchange (KSE) from 2010 to 2012, the paper finds that ownership concentration has a significant negative effect on firm performance. By using hierarchical regression analysis we further find that the level of leverage has a significant interaction effect on the relationship between ownership concentration and firm performance. Firms with a low level of ownership concentration and lower leverage have better firm performance than firms with a high level of ownership concentration and higher leverage. We conclude that the negative relationship between ownership concentration and firm performance is weaker for firms with higher leverage compared to the firms with lower leverage.
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Analysis and Design of Down Ender and Dismantler for Spent Fuel Assembly Dismantling in Head-End
Younghwan Kim,SunSeok Hong,Seckmin Hong,JuHo Lee,JaeWon Lee,ChangHwa Lee 한국방사성폐기물학회 2022 한국방사성폐기물학회 학술논문요약집 Vol.20 No.2
Dry head end process is developing for pyro-processing at KAERI (Korea Atomic Energy Research Institute). Dry processes, which include disassembling, mechanical decladding, vol-oxidation, blending, compaction, and sintering shall be performed in advance as the head-end process of pyro-processing. Also, for the operation of the head-end process, the design of the connecting systems between the down ender and the dismantling process is required. The disassembling process includes apparatus for down ender, dismantling of the SF (Spent Fuel) assembly (16×16 PWR), rod extraction, and cutting of extracted spent fuel rods. The disassembling process has four-unit apparatus, which comprises of a down ender that brings the assembly from a vertical position to a horizontal position, a dismantler to remove the upper and bottom nozzles of the spent fuel assembly, an extractor to extract the spent fuel rods from the assembly, and a cutter to cut the extracted spent fuel rods as a final step to transfer the rod-cuts to the mechanical decladding process. An important goal of dismantling process is the disassembling of a spent nuclear fuel assembly for the subsequent extraction process. In order to design the down ender and dismantler, these systems were analyzed and designed, also concept on the interference tools between down ender and dismantler were considered by using the solid works tool.
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Analysis and Design of Mechanical Decladding for Spent Fuel in Head-End
Younghwan Kim,SunSeok Hong,Seokmin Hong,JuHo Lee,JaeWon Lee,ChangHwa Lee 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.2
The PRIDE scale mechanical decladder is decladding apparatus for separating and recovering fuel material and cladding hull by horizontally slitting rod-cut. In order to enhance mechanical decladdng efficiency, the main requirements were considered as follows. Decladding of the fuel rods may be performed by rotation of three circular cutting blades inserted among the rollers arranged at 120° portion. In a mechanical decladder, a slitting assembly as a unit for slitting the cladding tube may include cutting blades for slitting and rollers for guiding extrusion of the cladding tube. Rotation of the cutting blades may be caused by the fuel rods being extruded from a plurality of rollers. Slitting intervals of rod-cuts having different diameters may be controlled by adding or removing a spacing plate between the cutting blade and a ranch bolt for fixing the slitting blade to the slitting assembly. An extrusion velocity with respect to the fuel rods may be controlled by a hydraulic pressure applied to the fuel rods. A force for cutting the fuel rods may be adjusted by controlling steel plates. Forces applied to a plurality of rollers may be generated by the hydraulic cylinder. The hydraulic pressure may be controlled by hydraulic pressure controller. The PRIDE scale mechanical decladder mainly consists of auto feeding module, hydraulic cylinder module and blade module. A load cell was installed between the hydraulic cylinder and the extrusion pin to measure the decladding force and slitting velocity, and a data acquisition system capable of obtaining data by using the RSC 232 was constructed. Also, the control panel can control the forward and backward movement of the extrusion pin, the hydraulic flow rate, and the hydraulic velocity. In the mechanical decladding test, 40 pieces of simulated rod-cuts were loaded in two auto feeding basket and slit by utilizing the 3-CUT blade modules in the housing, and hulls and simulated pellets were collected in the collection container. As a result, 80 pieces of simulated rodcut (brass pellets + Zry4 tube) were slit continuously without any problem. About 35 min was required to slit 80 rod-cuts and average decladding force was 260 kg. The decladding force of the ceramic simulated rod-cuts (castable) requires 25 kg less force than the brass pellets. Therefore, it is estimated that the spent fuel rod-cut can be fully split into three pieces using the mechanical decladder.
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Analysis and Design of Rod Extractor and Cutter for Spent Fuel Assembly Dismantling in Head-End
Younghwan Kim,SunSeok Hong,Seckmin Hong,JuHo Lee,JaeWon Lee,ChangHwa Lee 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.1
An important goal of dismantling process is the disassembling of a spent nuclear fuel assembly for the subsequent extraction process. In order to design the rod extractor and cutter, the major requirements were considered, and the modularization design was carried out considering remote operation and maintenance. In order to design the rod extractor and cutter, these systems were analyzed and designed, also the concept on the rod extraction and cutting were considered by using the solid works tool. The main module consists of five sub-modules, and the function of each is as follows. The clamping module is an assembly fixing module using a cylinder so that the nuclear fuel assembly can be fixed after being placed. The Pusher module pushes the fuel rods by 2 inches out of the assembly to grip the fuel rods. The extraction module extracts the fuel rods of the nuclear fuel assembly and moves them to the consolidation module. The consolidation module collects and consolidates the extracted fuel rods before moving them to the cutting device. And the support module is a base platform on which the modules of the main device can be placed. The modules of level 2 can be disassembled or assembled freely without mutual interference. For the design of fuel rods cutter, the following main requirements were considered. The fuel rod cut section should not be deformed for subsequent processing, and the horizontally mounted fuel rods must be cut at regular intervals. The cutter should have the provision for aligning with the fuel rod, and the feeder and transport clamp should be designed to transfer the fuel rods to the cutting area. The main module consists of 6 sub-modules, and function of each is as follows. The cutting module is a device that cuts the fuel rods to the appropriate depth for notching. The impacting module is a device that impacts the fuel rods and moves them to the collection module. The transfer module is a device that moves the fuel rods to the cutting module when the aligned fuel rods enter the clamp module. The clamping module is a device to clamp the fuel rods before moving them to the cutting module. The collection module is a container where the rod-cuts are collected, and the support module is a base platform on which the modules of the main device can be placed. The module of level 3 can be disassembled or assembled after the cutting module of level 2 is installed, and the modules of level 2 can be disassembled or assembled freely without mutual interference.
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Oxidation-resistant titanium carbide MXene films
Lee, Yonghee,Kim, Seon Joon,Kim, Yong-Jae,Lim, Younghwan,Chae, Yoonjeong,Lee, Byeong-Joo,Kim, Young-Tae,Han, Hee,Gogotsi, Yury,Ahn, Chi Won The Royal Society of Chemistry 2020 Journal of Materials Chemistry A Vol.8 No.2
<P>Two-dimensional transition metal carbides (MXenes) have attracted much attention due to their excellent electrical conductivity and outstanding performances in energy storage, telecommunication, and sensing applications. It is known that MXene flakes are readily oxidized in either humid air or aqueous environments. While the chemical instability of MXenes may limit their use in applications involving ambient environments and long-term operation, oxidation behaviour of MXene films has not been addressed. In this work, we demonstrate a hydrogen annealing method to increase the oxidation stability of Ti3C2 MXene in two different aspects: (1) dramatic improvement in the oxidation stability of pristine MXene films against harsh conditions (100% relative humidity, 70 °C), and (2) large recovery in the electrical conductivity of previously oxidized Ti3C2 MXene films. We also demonstrate an electric-field-induced heater capable of stable operation under highly oxidizing conditions, based on the oxidation-resistant MXene film. A total loss of heat generation ability was observed for the as-prepared MXene film, while the hydrogen-annealed one maintained its bright infrared radiation, under the highly oxidizing conditions. This work offers a solution to industrial applications of unprotected MXene films, securing their stable and long-term operation in humid conditions.</P>
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