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Park, Heesun,Kim, Jongmin,Jung, Young Hee,Kim, Yeong Il Korean Chemical Society 2017 대한화학회지 Vol.61 No.2
Monoclinic $VO_2(M)$ nanoparticles codoped with 1.5 at. % W and 2.9 at. % Mg were synthesized by the hydrothermal treatment and post-thermal transformation method of $V_2O_5-H_2C_2O_4-H_2O$ with $Na_2WO_4$ and $Mg(NO_3)_2$. The composite thin film of the W/Mg-codoped $VO_2(M)$ with a commercial acrylic block copolymer was also prepared on PET substrate by wet-coating method. The reversible phase transition characteristics of the codoped $VO_2(M)$ nanoparticles and the composite film were investigated from DSC, resistivity and Vis-NIR transmittance measurements compared with the undoped and Wdoped $VO_2(M)$ samples. Mg-codoping into W-doped $VO_2(M)$ nanoparticles synergistically enhanced the transition characteristics by increasing the sharpness of transition while the transition temperature ($T_c$) lowered by W-doping was maintained. The codoped composite film showed the prominently enhanced NIR switching efficiency compared to only W-doped $VO_2(M)$ film with a lowered $T_c$.
Development and Test of a Cooling System for a 154 kV Superconducting Fault Current Limiter
Kim, Heesun,Han, Young Hee,Yang, Seong-Eun,Yu, Seung-Duck,Park, Byung Jun,Park, Kijun,Yoo, Jaeun,Kim, Hye-Rim,In, Sehwan,Hong, Yong Joo,Yeom, Hankil Korea Electric Power Corporation 2015 KEPCO Journal on electric power and energy Vol.1 No.1
The superconducting fault current limiter (SFCL) is an electric power device that limits the fault current immediately in a power grid. Korea Electric Power Corporation (KEPCO) has been developing a 154 kV, 2 kA SFCL since 2011 to protect power grids from increasing fault current and improve the stability and quality of electric power. This SFCL adopts 2G YBCO wires and operates at 71 K and 5 bars. In this paper, a cooling system for the 154 kV SFCL and its cooling test results are reported. This cooling system uses a Stirling-type cooler to make sub-cooled liquid nitrogen ($LN_2$), which cools the superconductor modules of the SFCL. The $LN_2$ is circulated between the cooler and the cryostat that contains superconductor modules. The $LN_2$ also plays the role of a high voltage insulator between the modules and the cryostat, so the pressure was maintained at 5 bars for high insulation performance. After installation in a test site, the cooling characteristics of the system were tested. In this operation test, some important data were measured such as temperature distribution in $LN_2$, pressure change, performance of the heat exchanger, and cooling capacity of the total system. Consequently, the results indicate that the cooling system operates well as designed.
외부혼합형 이류체 노즐 설계형상에 따른 미립화 성능 분석
권희선 ( Heesun Kwon ),박준규 ( Junkyu Park ),박성욱 ( Sungwook Park ) 한국액체미립화학회 2018 한국액체미립화학회 학술강연회 논문집 Vol.2018 No.-
Twin-fluid nozzles are used and applied throughout various fields of industry. In this research, an externalmixing type twin-fluid nozzle was used with water and air as working fluids. Design parameters such as nozzle diameter, exit angle, distance between the exits and the use of swirl blades were varied to assess the effect on both macroscopic and microscopic spray behaviors. Spray visualization experiments were conducted to measure the spray angle and observe the liquid column while the phase Doppler particle analyzer (PDPA) was used to calculate the droplet diameter and evaluate the droplet distribution. The nozzle diameter substantially improved the SMD, but distinct difference in macroscopic spray characteristics were not achieved. Overall, the optimization of each spray characteristics can be expected through this parametric study.
Hyponatraemia and its prognosis in acute heart failure is related to right ventricular dysfunction
Lee, Heesun,Lee, Sang Eun,Park, Chan Soon,Park, Jin Joo,Lee, Ga Yeon,Kim, Min-Seok,Choi, Jin-Oh,Cho, Hyun-jai,Lee, Hae-Young,Choi, Dong-Ju,Jeon, Eun-Seok,Kim, Jae-Joong,Oh, Byung-Hee BMJ Publishing Group Ltd 2018 Heart Vol.104 No.20
<P>Trial registration number Korean Acute Heart Failure registry NCT01389843; Results.</P>