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( Chanwon Lee ),( Junouk Ha ),( Jayoung Park ),( Seongho Choi ),( Heeseung Park ),( Jaeseung Lee ),( Seungheon Lee ),( Younghwan Lee ) 대한내과학회 2014 대한내과학회 추계학술대회 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.
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>
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.
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>
Lee, Se Won,Kwak, Giseop,Kwon, Younghwan,Kim, Young-Jin,Kim, Ki Hong,Lim, Hea-Ryong,Gwak, Sang-Won,Lee, Soo Chang,Han, Yoon Soo Informa UK (TaylorFrancis) 2017 Molecular Crystals and Liquid Crystals Vol.651 No.1
<P>We prepared UV-curable resins consisting of an aromatic urethane acrylate oligomer, an acrylate monomer, an acrylate cross-linker, and a photoinitiator; the resins were then cured by exposure to 365-nm UV irradiation for several minutes. By measuring relative photo-sensitivity, we found that the cross-linker with a functionality of four was most suitable for the photo-curable resins. Thermal, optical, and mechanical properties of UV-cured films with various compositions were evaluated, and the swelling ratio, cross-linking density, and average molecular weight between cross-linking points in the films were also quantified. The cured films showed strong resistance to chemicals, such as acidic etchant (HF) and alkaline (NaOH) solution, without peeling away from the glass substrate.</P>
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.
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>