• Title, Summary, Keyword: Superconductors

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Transient Thermal Behaviors of Melt Processed Superconductors with Artificial Holes During the Cooling in Liquid Nitrogen (액체질소 냉각 시 임의의 홀을 가진 초전도체의 열응력 해석)

  • Jang, G.E.;Lee, H.J.;Kim, C.J.;Han, Y.H.;Sung, T.H.
    • Progress in Superconductivity
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    • v.11 no.1
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    • pp.52-56
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    • 2009
  • Temperature distributions and thermal stresses were calculated and analyzed to investigate the effect of the artificial holes to the transient behaviors of the superconductors which was cooled in liquid nitrogen. Three dimensional finite element method was used to calculated the transient temperature and thermal stresses in the superconductors. The cooling speed of the superconductors with holes is faster than those without holes. Because the thermal stresses calculated in the superconductors can be relaxed by the distributed holes, the volume of the peak tensile stress decreases during the cooling in liquid nitrogen. If optimal metal, which can maintain the relaxation of thermal stresses, is used to fill and reinforce the artificial holes, the probability of failure of the superconductors may be decreased by the decrease of volume of peak tensile stress.

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Critical Behavior and Spectrum of Holographic Superconductors

  • Ahn, Hyo Chul;Hong, Deog Ki;Park, Cheonsoo
    • New Physics: Sae Mulli
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    • v.67 no.1
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    • pp.52-55
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    • 2017
  • We study a minimal gravity dual of planar superconductivity at finite temperature to estimate the Meissner and Debye masses of photons in a planar superconductor, which are the characteristic properties of superconductors. We also study the temperature dependences of those masses to find their critical behavior near the critical temperature to see if the behaviors of holographic superconductors deviate from those of the usual conventional BCS superconductors because high-temperature superconductors exhibit properties very different from those of the usual BCS superconductors, as they are strongly correlated. We find that the critical exponents to be 0.49 and 0.92 for the Debye mass and the Meissner mass, respectively. Finally, we study the critical behavior of the radial excitations of the order parameter.

Normal State EPR Study of the n-type High-Tc Superconductors

  • Lee, Cheol-Eui;Kim, W.S.;Noh, S.J
    • Journal of Magnetics
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    • v.3 no.2
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    • pp.39-40
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    • 1998
  • Normal state EPR signals have been studied for the n-type$ high-T_c$ superconductors $Nd_{1.85}Ce_{0.15}CuO_{4-x} and Nd_2CuO_{3.6-x}F_{0.4-y}.$ Since EPR signals were observed only in quenched non-superconducting samples and were absent in furnace-cooled samples, our results suggest that no normal state EPR signals come from pure phase n-type hihg-Tc superconductors. Our observation is consistent with previously reported absence of nomal state EPR signals in the p-type high-Tc superconductors.

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The analysis of quenching mechanism of a YBCO HTSC ring (YBCO 고온초전도링의 퀜치현상해석)

  • Joo, Min-Seok;Lee, Chan-Ju;Chu, Yong;Ko, Tae-Kuk
    • Proceedings of the KIEE Conference
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    • pp.178-180
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    • 1996
  • An Inductive high-Tc superconducting fault current limiter using YBCO superconducting ring in the secondary part has many advantages in power networks. It is based on the appearance of resistivity in the superconductors and this paper is studied on the relation between the resistivity and the temperature of superconductors. In many other devices using superconductors, it is important to prohibit the superconductors from quenching for the protection of the whole system, or at least the superconductors.ᢁ

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Near Net Shape Processing of RE-Ba-Cu-O Bulk Superconductors

  • Murakami, M.;Fujishiro, M.;Miyazaki, T.;Nariki, S.;Sakai, N.;Hirabayashi, I.
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • pp.1319-1320
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    • 2006
  • Several practical applications of melt-textured bulk superconductors require the complex-shaped products such as curved, ring-shaped, and drilled blocks rather than simple shaped pellets. However, melt-textured bulk superconductors are often damaged when they are cut, grinded, or drilled. With the aim of reducing such damages, we have investigated the preparation of the complex-shaped bulk superconductors by previously machining binder-added precursors and pre-sintered precursors. We could produce various complex-shaped bulk superconductors without cracking from these machined precursors

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The Magnetoresistance in Iron-based Superconductors

  • Lv, B.;Xie, R.B.;Liu, S.L.;Wu, G.J.;Shao, H.M.;Wu, X.S.
    • Journal of Magnetics
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    • v.16 no.2
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    • pp.192-195
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    • 2011
  • The phase transition of vortex matter from solid to liquid was studied in iron-based superconductors. Based on the traditional vortex glass theory, we have examined the magnetoresistivity data of iron-based superconductors using our extended thermal activation model: $\rho(B,T)=\rho((T-T_g(B))/(T_c(0)-T_g(B)))^{v(z-1)}$. We predict that the magnetic field-dependent area S + $S_0$ which integrates $\rho$ with T is proportional to $B^{\beta}$, where ${\beta}$ is the vortex glass transition exponent. From our calculation, the vortex glass transition exponent is 0.33, close to the exponent of area $S_0$ + S is 0.31 in $SmO_{0.9}F_{0.1}FeAs$; the exponent of area S is 0.63, which is close to the irreversibility line exponent 2/3. Both of the results show the validity of our model. In addition, our model is shown to be effective in describing irreversibility behavior in layered superconductors.

Critical review of pseudo-gap in high Tc superconductors : Experiments and theories

  • Choi, Han-Yong
    • 한국초전도학회:학술대회논문집
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    • v.10
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    • pp.8-8
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    • 2000
  • Recently the study of the pseudo-gap in high temperature superconductivity become critical issue because it contains key information of the pair formation of the high temperature superconductivity. Specially angle resolved photoemission study shows the various information of the gap formation. In this talk, I will review the recent theories as will as experiments on the pseudo-gap in high temperature superconductors. Specially I will introduce the possible observation of the Andreeve reflection in the underdopped high temperature superconductors.

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A Review on AC Loss Characteristics of High $T_c$ Superconductors

  • Amemiya, N.;Jiang, Z.
    • Progress in Superconductivity and Cryogenics
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    • v.8 no.4
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    • pp.1-7
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    • 2006
  • This paper reviews AC loss characteristics of high $T_c$ superconductors. The mechanisms of AC loss generation are explained briefly, and AC losses are classified by the magnetic field components which generate them. A couple of analytical formulae of AC losses, which are useful for simple and rough AC loss estimations, are presented. AC loss characteristics of single BSCCO multifilamentary conductors and single YBCO coated conductors are reviewed based on previous experimental and numerical studies. AC loss characteristics of those two types of practical high $T_c$ superconductors are compared with each other.