• The Transactions of the Korean Institute of Electrical Engineers
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• v.39 no.7
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• pp.653-667
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• 1990

Superconductor is consolidated, for required current capacity, with proper numbers of basic strands which are multifilamentary composites. Althouth superconductors are perfectly loss-free under DC conditions of current and field, AC losses occur under time-varying condition of the current and field. The AC losses are a controllable inherent characteristics of supercondectors. The AC losses dependent on the changing rate of current and field can be reduced by reducing the filament diameter. On the other hand, finer filament results in manufacturing cost increase. Therefore, in this paper optimization technique of superconductor for SMES is proposed from the viewpoint of AC loss reduction and manufacturing cost increase. The case study shows that the technique can be effectively used for the design of superconductor for SMES, appreciating the influence of various parameters related to superconductor itself and operating condition of SMES. As a result of the case study, it is confirmed that the technique is more effective for the design of superconductor for SMES for electric power power system stabilization rather then SMES for energy storage.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.112-115
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• 2000

In this work the results of the systematic investigations on the effect of organic addition by using polymer compound as starting materials on the superconducting properties of YBCO electrophoretic deposited films on silver substrate are presented. The characteristics of the films were examined by X-ray diffraction and SEM observation. Our results show that the adhesion and microstructure of these films are sensitive to the nature of polymer compounds and sintering conditions (electrophoretic deposition, drying and heat-treatment procedures). To develop optimum microstructures for samples processed in this manner it is necessary to have an understanding of how these processes affect the microstructure and hence the properties of ceramic superconductors.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1990.10a
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• pp.26-30
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• 1990

Bi$\_$0.7/Pb$\_$0.3/Sr$_1$Ca$_1$Cu$\_$1.8/Ox thick films were screen printed on magnesia(MgO), silver and yttrium stabilized zirconia (YSZ) substrates and were sintered in a boat with cover to prevent the evaporation. The high-Tc phase increase and the low-Tc phase and Ca$_2$PbO$_4$ decrease with an increase in sintering temperature from 835$^{\circ}C$ to 860$^{\circ}C$. YSZ substrate interact strongly with the oxide resulting in poor superconductor, while the Ag and MgO substrates were satisfactory to make screen printed superconductors. The Bi$\_$0.7/Pb$\_$0.3/Sr$_1$Ca$_1$Cu$\_$1.8/Ox thick films screen printed both on Ag and MgO substrates show high Tc phase of ~85% and Tc of 96K.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.452-455
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• 2000

Superconducting power cable is one of the most promising energy application of high-T$_{c}$ superconductors (HTS). A prototype HTS cable have been constructed multi-layer cable using Bi-2223 tape and tested. The AC transport losses under self field were investigated at 77K on the 19 filamentary tape and multi-layer HTS cables. And we carried out numerical analysis using bean model. The result shows that the total transport current of HTS cable in L$N_2$ was 475[A], and transport current passed through almost the outer layer (2-layer). Also, AC transport losses in outer layer of HTS cable was proportion to I$^2$ and higher than losses of inner layer. In case of Ip=Ic, calculated numerical loss density was concentrated on the edge of tape and most of loss density in cable was distributed outer layer more than inner layer. As magnetic distribution was concentrated on outer layer.r.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.6
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• pp.550-554
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• 2007

Large and single-grain Y-Ba-Cu-O(YBCO) bulk superconductors have been fabricated by using a seeded infiltration and growth method. $Y_2BaCuO_5$(Y211) precursor pellets and $YBa_2Cu_3O_x$(Y123) liquid source pellets were prepared using commercial powder and were processed by infiltration and growth method to achieve low pore and high trapped field property. The superconductor properties of the single crystal are measured and analyzed in relation with the density and size of the Y211 particle in the Y123 matrix. An optimum processing condition is suggested based on the analyzed results.

• Proceedings of the KIEE Conference
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• 2003.07b
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• pp.879-881
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• 2003

For quite a long time various researches and developments of superconducting magnetic energy storage(SMES) device for enhancement of power quality control of sensitive electric toad. This paper describes the design, fabrication and experimental results for the 3MJ SMES magnet made by using the design code of a SMES device that we developed. A computer code was developed to find the parameters of the SMES magnet which has minimum amount of superconductors for the same stored energy, and the 3MJ SMES magnet was designed based upon that.

• Proceedings of the KIEE Conference
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• 1995.07a
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• pp.150-152
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• 1995

In order to study the basic I-V behavior and quench characteristics, we fabricated two kinds of small superconducting coils which were wound with different superconductors. In this study, it was made clear that the propagation. velocity of normal zone preferentially depends on the operation current rather than heat pulse energy and also increases exponentially with respect to operation current.

• 한국초전도학회:학술대회논문집
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• v.15
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• pp.63-63
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• 2005

• Bulletin of the Korean Chemical Society
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• v.20 no.9
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• pp.1045-1048
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• 1999

Electronic structures calculated based upon the extended Huckel tight-binding method for Ba1-xKxBiO3 with x = 0, 0.04, and 0.4 are reported. It is noticed that the commensurate ordering of Bi 3+ and Bi 5+ is responsible for the insulating and semiconducting behavior in BaBiO3 and Ba0.96K0.04BiO4. The band gaps of 3.2 eV and 1.4 eV for the former and the latter compounds, respectively, are consistent with the experimental results. Doping in Bi 6s-block band up to x = 0.4 causes the collapse of the ordering of Bi 3+ and Bi 5+, thereby resulting in the superconductivity in the Ba0.6K0.4BiO3 compound. Strikingly, the character of oxygen contributes to the conducting mechanism than that of the bismuth. This is quite different from the cuprate superconductors in which the character of copper dominates that of oxygen.

• Progress in Superconductivity and Cryogenics
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• v.21 no.3
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• pp.22-26
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• 2019

With an increasing potential to realize quantum computer, it has recently been an important issue to extend the capabilities of RF cavities to maintain longer coherent quantum system. Using superconductors instead of normal metals allows the quantum system to have a substantially enhanced quality factor. In this paper, surface impedances of superconducting cavities are calculated by the Mattis-Bardeen theory with Python & MATLAB programs. With a simulation of electromagnetic field distribution, the sensitivity to dielectric and surface losses of the superconducting cavities are determined. Then calculations of the resonance frequency and quality factor of three-dimensional superconducting resonators made of Al or Nb are discussed.