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MOD-Processed SmBCO Films on <tex> ${\rm LaAlO}_{3}$</tex> (100) Substrates
Geo-Myung Shin,Duck-Jin Kim,Kyu-Jeong Song,Chan Park,Seung-Hyun Moon,Sang-Im Yoo Institute of Electrical and Electronics Engineers 2007 IEEE transactions on applied superconductivity Vol.17 No.2
<P>SmBa<SUB>2</SUB>Cu<SUB>3</SUB>O<SUB>7-delta</SUB>(SmBCO) thin films were successfully prepared on the LaAlO<SUB>3</SUB>(100) substrate by the TFA-MOD method in an extremely reduced oxygen atmosphere. The precursor solution was prepared dissolving SmBCO powder into the trifluoroacetic acid solution. The precursor solution was spin-coated on the LaAlO<SUB>3</SUB>(100) single crystalline substrates, calcined at the temperature up to 400degC, and fired at various high temperatures for 2 h in reduced oxygen atmospheres. Optimally processed SmBCO thin film exhibited T<SUB>C,zero</SUB> value of 90.2 K and J<SUB>C</SUB> value of 0.8 MA/cm<SUP>2</SUP> at 77 K, respectively. Relatively lower J<SUB>C</SUB> values in SmBCO films compared with MOD-processed YBCO films are attributed to the existence of a-axis oriented grains.</P>
Shin, Geo-Myung,Lee, Jung-Woo,Choi, Soon-Mi,Moon, Seung-Hyun,Yoo, Sang-Im Institute of Electrical and Electronics Engineers 2015 IEEE transactions on applied superconductivity Vol.25 No.3
<P>We report the effects of barium-based perovskite particle inclusions of BaCeO<SUB>3</SUB> (BCO), BaZrO<SUB>3</SUB> (BZO), and YBa<SUB>2</SUB>SnO<SUB>5.5</SUB> (YBSO) on the thickness dependence of critical current density <inline-formula> <TEX-math notation='LaTeX'>$(J_c)$</tex-math></inline-formula> in metal organic deposition (MOD) -processed <inline-formula> <TEX-math notation='LaTeX'><TEX>$\mbox{YBa}_2\mbox{Cu}_3\mbox{O}_{7-\delta} $</TEX></tex-math></inline-formula> (YBCO) films on the SrTiO<SUB>3</SUB> (STO) single-crystal substrate. With increasing film thickness, while BZO-doped YBCO films show a serious degradation in <inline-formula> <TEX-math notation='LaTeX'><TEX>$J_\mathrm{c} $</TEX></tex-math></inline-formula>, caused by the interlayer at the boundaries of multicoated layers, BCO- and YBSO- doped films exhibit a significant enhancement of <inline-formula> <TEX-math notation='LaTeX'>$J_c$</tex-math></inline-formula> (77 K, self-field) over ∼1 μm thickness even though BCO- or YBSO-doped YBCO films have degraded <I>in-plane</I> textures compared with undoped films, implying that these perovskite dopants affect not only the pinning properties but also the growth of multicoated layers. The highest critical current <inline-formula> <TEX-math notation='LaTeX'><TEX>$(I_\mathrm{c} )$</TEX></tex-math></inline-formula> value over 440 A/cm-width, corresponding to <inline-formula> <TEX-math notation='LaTeX'><TEX>$J_\mathrm{c} $</TEX></tex-math></inline-formula> value of 1.8 MA/cm<SUP>2</SUP>, was obtained from the 2.4-<inline-formula> <TEX-math notation='LaTeX'><TEX>$\mu\mathrm{m}$</TEX></tex-math></inline-formula>-thick YBSO-doped film.</P>
MOD-processed YBCO coated conductor on the IBAD-MgO template
Shin, Geo-Myung,Ko, Rock-Kil,Song, Kyu-Jeong,Yoo, Jai-Moo,Oh, Sang-Soo,Moon, Seung-Hyun,Yoo, Sang-Im The Korean Society of Superconductivity and Cryoge 2007 한국초전도저온공학회논문지 Vol.9 No.4
We report the results of MOD-processed YBCO coated conductors on the IBAD-MgO template. The precursor solution was coated on the $CeO_2-buffered$ IBAD-MgO template using a slot-die coating method, calcined at a temperature of $550^{\circ}C$, and fired at high temperatures for 2.5 h in a reduced oxygen atmosphere. The $J_C$ value of YBCO coated conductors was found to be very sensitive to the microstructure, and thus higher $J_C$ value could be achieved when the in-plane texture was higher and the difference in $T_{C,zero}$. was negligible. Optimally processed YBCO coated conductor exhibited $J_C$ value of $0.75MA/cm^2$ at 77 K in self-field, which might be due to somewhat depressed $T_{C,zero}$ of 87.3 K caused by possible $Sm^{3+}$ substitution on the $Ba^{2+}$ site.
Myung Su Kim,Geo Young Kim,Hyun Tae Kim,구정서 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.8
In this paper, a theoretical formula was proposed that predicts the derailment index due to a cross wind applied to a rail vehicle considering the cross running wind condition of two running trains as well as the dynamic wheel-rail effects. The recently developed derailment theory on a wheelset was applied to this new cross wind derailment formula. Contrary to the conventional formulas, this new derailment formula was derived considering a dynamic derailment coefficient (Q/P) under normal running, the friction coefficient between the wheel and the rail, the wheel load variation, the cross running wind effects, and the cross wind. Using this proposed formula, the derailment pattern and the critical cross wind speed of derailment could be predicted for various cross running wind conditions of two running trains. Finally, for some typical examples, the results of this proposed formula were compared and verified with those of the conventional formulas and the numerical simulation of multi-body dynamics software, Recurdyn.
김건웅(Geo Ung Kim),송병권(Byung Kwen Song),진명숙(Myung Sook Jin) 한국정보처리학회 2000 정보처리학회논문지 Vol.7 No.8
The functions of telecommunication network can be divided into two broad classifications : delivery segment function and service segment function. The delivery segment function can be layered into a number of Layer Network(LN)s with a client-server relationship between adjacent layer. The Layer Network concept can be extended, and provide an ability to integrate dissimilar networks. We propose the routing scheme that guarantee the user’s QoS in layered network. There are Layer Manager(LM)s that hold the information of layer network and select the route. In this paper, the proposed routing scheme is presented and demonstrated to be better than that of hop-by-hop routing.
Phase and microstructure evolution during the TFA-MOD process of YBCO films
Wee, Sung-Hun,Shin, Geo-Myung,Hong, Gye-Won,Yoo, Sang-Im The Korean Society of Superconductivity and Cryoge 2007 한국초전도저온공학회논문지 Vol.9 No.2
We report the phase and microstructure evolutions of metal trifluoroacetate (TFA) precursor films in the TFA-MOD process of YBCO films on the LAO (100) substrates. It was confirmed that the precursor films were decomposed into $Y_2O_3$, $BaF_2$, and CuO nanoparticles after the initial heat treatment up to 400$^{\circ}C$. After a subsequent heat treatment at higher temperatures ranging from 700 to 850$^{\circ}C$ for 2 h, these nano-sized phases are converted into YBCO films. High Jc(77K, sf)-YBCO thin films (over 2 MA/$cm^2$) were successfully fabricated with firing temperatures ranging from 775 to 850$^{\circ}C$ for 2 h, where films were composed of dense microstructures with large grains.
Fabrication of YBCO films on metal tapes by the TFA-MOD process
신거명,송규정,박찬,문승현,유상임,Shin Geo-Myung,Song Kyu-Jung,Park Chan,Moon Seung-Hyun,Yoo Sang-Im The Korean Superconductivity Society 2005 Progress in superconductivity Vol.7 No.1
YBCO thin films on metal substrates were prepared by the metal-organic deposition using trifluoroacetates (TFA-MOD). To compensate the loss of Ba element from the precursor films due to the reaction with $CeO_2$ cap layer, we have employed Ba-excessive precursor solutions of $YBa_{2+x}Cu_{3}O_{7-{\delta}}$ ($0{\le}x{\le}0.1$). The precursor solutions were dip-coated on the metal substrates with $CeO_2$ cap layer, initially heated up to $400^{\circ}C$, and finally fired at the various high temperatures for 2 h in a reduced oxygen atmosphere. With this approach, YBCO films possessing critical temperature over 85 K could be successfully prepared on the metal substrates. The highest $T_{c,zero}$ value of 86 K was obtained from the Ba-excessive YBCO film of x=0.005 in $YBa_{2+x}Cu_{3}O_{7-{\delta}}$ fired at $750^{\circ}C$ for 2 h. However, unexpected $T_c$ suppression even in Ba-excessive YBCO samples requires further identification.