• Title/Summary/Keyword: $J_c$ (B)

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Characterization of the High Energy Milled Boron Precursor Powders in the Synthesis of $MgB_2$ Superconductor ($MgB_2$ 초전도체의 합성에 미치는 고에너지 밀링에 의한 초기 보론 분말의 특성)

  • Lee, J.H.;Shin, S.Y.;Kim, C.J.;Park, H.W.
    • Progress in Superconductivity
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    • v.9 no.1
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    • pp.74-79
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    • 2007

  • We characterized the highly refined boron precursor powders which were attrition milled for different milling times. $MgB_2$ powder precursor was formed from elemental crystalline Mg and amorphous B powder. The microstructure was investigated by SEM. SEM results indicate that the size of the milled powders was reduced with increasing milling time, which were varied from 0 to 8 hours. We also studied thermal behavior of the starting precursor by DSC as a function of milling time. The thermal behavior of the powder precursors was influenced by milling time. In order to determine the thermal events at DSC peaks, we annealed the milled powder mixture at $600^{\circ}C$ and $650^{\circ}C$ under protective gas and then analyzed the formation of $MgB_2$ by the XRD. We observed that superconducting $MgB_2$ phase was formed at lower temperature by the longer high energy milling. These results show that the high energy milling of the boron precursor powder can improve the reactivity for the formation of $MgB_2$.

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A simulation study on the figure of merit optimization of a 1200V 4H-SiC DMOSFET (1200V급 4H-SiC DMOSFET 성능지수 최적화 설계 시뮬레이션)

  • Choi, Chang-Yong;Kang, Min-Suk;Bang, Wook;Kim, Sang-Chul;Kim, Nam-Kyun;Koo, Sang-Mo
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2009.06a
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    • pp.63-63
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    • 2009

  • In this work, we demonstrate 800V 4H-SiC power DMOSFETs with several structural alterations to observe static DC characteristics, such as a threshold voltage ($V_{TH}$) and a figure of merit ($V_B^2/R_{SP,ON}$). To optimize the static DC characteristics, we consider four design parameters; (a) the doping concentration ($N_{CSL}$) of current spreading layer (CSL) beneath the p-base region, (b) the thickness of p-base ($t_{BASE}$), (c) the doping concentration ($N_J$) and width ($W_J$) of a JFET region, (d) the doping concentration ($N_{EPI}$) and thickness ($t_{EPI}$) of epi-layer. Design parameters are optimized using 2D numerical simulations and the 4H-SiC DMOSFET structure results in high figure of merit ($V_B^2/R_{SP,ON}$>~$340MW/cm^2$) for a power MOSFET in $V_B{\sim}1200V$ range.

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A Simulation Study on the Structural Optimization of a 800 V 4H-SiC Power DMOSFET (800 V급 4H-SiC DMOSFET 전력 소자 구조 최적화 시뮬레이션)

  • Choi, Chang-Yong;Kang, Min-Seok;Bahng, Wook;Kim, Sang-Cheol;Kim, Nam-Kyun;Koo, Sang-Mo
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.22 no.8
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    • pp.637-640
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    • 2009

  • In this work, we demonstrate 800 V 4H-SiC power DMOSFETs with several structural alterations to obtain a low threshold voltage ($V_{TH}$) and a high figure of merit ($V_B\;^2/R_{SP,ON}$), To optimize the device performance, we consider four design parameters; (a) the doping concentration ($N_{CSL}$) of current spreading layer (CSL) beneath the p-base region, (b) the thickness of p-base ($t_{BASE}$), (c) the doping concentration ($N_J$) and width ($W_J$) of a JFET region, (d) the doping concentration ($N_{EPI}$) and thickness ($t_{EPI}$) of epi-layer. These parameters are optimized using 2D numerical simulation and the 4H-SiC DMOSFET structure results in a threshold voltage ($V_{TH}$) below $^{\sim}$3.8 V, and high figure of merit ($V_B\;^2/R_{SP,ON}$>$^{\sim}$200 $MW/cm^2$) for a power MOSFET in $V_B\;^{\sim}$800 V range.

  • https://doi.org/10.4313/JKEM.2009.22.8.637 인용 PDF KSCI

ON PATHOS BLOCK LINE CUT-VERTEX GRAPH OF A TREE

  • Nagesh, Hadonahalli Mudalagiraiah
    • Communications of the Korean Mathematical Society
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    • v.35 no.1
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    • pp.1-12
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    • 2020

  • A pathos block line cut-vertex graph of a tree T, written P BLc(T), is a graph whose vertices are the blocks, cut-vertices, and paths of a pathos of T, with two vertices of P BLc(T) adjacent whenever the corresponding blocks of T have a vertex in common or the edge lies on the corresponding path of the pathos or one corresponds to a block Bi of T and the other corresponds to a cut-vertex cj of T such that cj is in Bi; two distinct pathos vertices Pm and Pn of P BLc(T) are adjacent whenever the corresponding paths of the pathos Pm(vi, vj) and Pn(vk, vl) have a common vertex. We study the properties of P BLc(T) and present the characterization of graphs whose P BLc(T) are planar; outerplanar; maximal outerplanar; minimally nonouterplanar; eulerian; and hamiltonian. We further show that for any tree T, the crossing number of P BLc(T) can never be one.

  • https://doi.org/10.4134/CKMS.c170432 인용 PDF KSCI