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Ferroelectric Properties of Ce3+- Doped Aurivillius K0.5Bi4.5Ti4O15 Thin Films
곽민환,Chinnambedu Murugesan Raghavan,김상수,김원정 한국물리학회 2017 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.71 No.7
The effect of Ce3+-ion doping on the structural, electrical and ferroelectric properties of the Aurivillius K0.5Bi4.5Ti4O15 thin films are reported. For the purpose of this study, K0.5Bi4.5Ti4O15 and K0.5Bi4.0Ce0.5Ti4O15 thin films were deposited on Pt(111)/Ti/SiO2/Si(100) substrates by using chemical solution deposition method. Formation of the Aurivillius structure was confirmed through X-ray diffraction and Raman scattering studies. From the experimental results, tremendous improvements in the electrical and the ferroelectric properties were observed for the K0.5Bi4.0Ce0.5Ti4O15 thin film. The ferroelectric polarization-electric field (P-E) hysteresis loops study showed a largely enhanced remnant polarization (2Pr), with a value of 52.8 μC/cm2 for the K0.5Bi4.0Ce0.5Ti4O15 thin film measured at an applied electric field of 595 kV/cm. Furthermore, a low leakage current density value of 1.38×10−8 A/cm2 was measured at an applied electric field of 100 kV/cm for the K0.5Bi4.0Ce0.5Ti4O15 thin film.
곽민환,Chinnambedu Murugesan Raghavan,Sang Su Kim,김원정 한국물리학회 2017 New Physics: Sae Mulli Vol.67 No.11
A study of the structural, electrical and ferroelectric properties of layered Aurivillius-type Na$_{0.5}$Bi$_{4.5}$Ti$_4$O$_{15}$ (NaBTi) and Na$_{0.5}$Bi$_{4.0}RE_{0.5}$Ti$_4$O$_{15}$ ($RE$ = Eu, Gd and Dy) thin films is reported. These films were fabricated on Pt-coated Si(100) substrates by using a chemical solution deposition method followed by a heat treatment. The rare-earth elements used as dopants, such as Eu, Gd and Dy, were found to be effective in improving the leakage current densities and the ferroelectric properties of the layered Na$_{0.5}$Bi$_{4.5}$Ti$_4$O$_{15}$ thin films without affecting their original Aurivillius structures. Based on the measured ferroelectric polarization-electric field ($P-E$) hysteresis loops, we found that the Gd-doped NaBTi thin film, among all the films, exhibited the highest ferroelectric remnant polarization of 2$P_r$ = 37.4 $\mu$C/cm$^2$ and a low coercive electric field of 2$E_c$ = 187 kV/cm at an applied electric field of 475 kV/cm. Furthermore, the lowest value of the leakage current density of 6.12$\times$10$^{7}$ A/cm$^2$ at an applied electric field of 100 kV/cm was measured for the Gd-doped NaBTi thin film.
곽민환,이민우,Ko Seong Eun,임현철,강태욱,송경두,김종만,Choi Gyu Seong 대한초음파의학회 2022 ULTRASONOGRAPHY Vol.41 No.3
Purpose: Radiofrequency ablation is a curative treatment option for very early-stage or earlystage hepatocellular carcinoma (HCC). However, percutaneous radiofrequency ablation (PRFA) for subphrenic tumors is technically challenging. Laparoscopic radiofrequency ablation (LRFA) has been used to overcome this disadvantage. This study compared the treatment outcomes between LRFA and PRFA for subphrenic HCC.Methods: This retrospective study screened patients who underwent PRFA or LRFA for subphrenic HCC between 2013 and 2018. Therapeutic outcomes, including local tumor progression (LTP), intrahepatic distant recurrence (IDR), extrahepatic metastasis (EM), disease-free survival (DFS), and overall survival (OS), were compared between the two groups.Results: Thirty patients in the PRFA group and 23 patients in the LRFA group were included. LTP was observed in six patients in the PRFA group (20%), but in no patients in the LRFA group. The cumulative LTP rates at 1, 3, and 5 years were 3.7%, 23.4%, and 23.4%, respectively, in the PRFA group and 0.0% in the LRFA group (P=0.015). The IDR, EM, and DFS rates were not significantly different between the two groups (P=0.304, P=0.175, and P=0.075, respectively). The OS rates at 1, 3, and 5 years were 96.6%, 85.7%, and 71.6%, respectively, in the PRFA group and 100%, 95.7%, and 95.7%, respectively, in the LRFA group (P=0.049).Conclusion: LRFA demonstrated better therapeutic outcomes than did PRFA for subphrenic tumors in terms of LTP and OS. Therefore, LRFA can be considered as the first-line treatment option for subphrenic HCC.
곽민환,이상기,조성걸 한국세라믹학회 1997 한국세라믹학회지 Vol.34 No.12
ZnO varistors containing 5.0 at% Co3O4 and Pr6O11, ranging from 0.1 to 1.0 at%, were sintered at 130$0^{\circ}C$ and 135$0^{\circ}C$. The I-V characteristics and nonlinear coefficients of the specimens were investigated with respect to Pr addition and sintering temperature. In general the specimens sintered at 130$0^{\circ}C$ showed better varistor characteristic than those fired at 135$0^{\circ}C$, which seemed to be related with the liquid phase formation during sintering. The barrier heights obtained from C-V relations, 0.29-1.36 eV, were different from those acquired using resistivity-temperature plots measured at low voltage per grain boundary. Therefore the estimation of potential barrier heights using C-V relations is better suited for the specimens prepared in this study. The carrier densities obtained using C-V relations were ~1018 cm-3.
곽민환(Min Hwan, Kwak),강명권(Myung Kweon, Kang),김대용(Dea Yong, Kim),성연관(Yeon Kwan,Sung),송주태(Ju Tae,Song) 한국자동차공학회 2011 한국자동차공학회 지부 학술대회 논문집 Vol.2011 No.10-1
LPI Fuel Pump is equipment which is installed inside of cylinder, pressurize LPG fuel 5bar more than saturated vapor pressure to keep liquid phase of LPG throughout Fuel supply system. Installing fuel pump inside of cylinder is more reliable in aspect of fuel supply performance, but cost is expensive and maintenance is poor and dangerous. This paper shows the procedure of optimum design of new LPI fuel supply system which external fuel pump locates on the fuel feed line to improve maintenance quality and reduce cost of system. The purpose of this paper is to make better fuel supply performance of external LPI fuel pump than that of internal LPI fuel pump using Robust Design Method .