• Title/Summary/Keyword: 김지헌

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Inhibitory Effects of Tannins on Tyrosinase Activity (탄닌화합물의 Tyrosinase 억제 활성)

  • Cho, Su-Min;Kim, Jee-Hun;Lee, Min-Won
    • Korean Journal of Pharmacognosy
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    • v.32 no.1 s.124
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    • pp.68-71
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    • 2001
  • For the use of tannins in the whitening-effect cosmetics, inhibitory effect against tyrosinase activity was determined. Three condensed tannins including gallocatechin, gallocatechin 3',4'-di-O-gallate and epicatechin 3-O-gallate and three hydrolyzable tannins, 1,2,6-tri-O-galloyl-${\beta}$-D-glucose, 2,3-(S)-HHDP-D-glucose and pedunculagin showed 15-29% mild inhibitory effects against tyrosinase activity.

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Elimination of Residual Phase Rotation Errors in SC-FDE Received Signals (SC-FDE 수신 신호의 잔여 위상회전에러 제거)

  • Kim, Ji-Heon;Kim, Whan-Woo
    • Proceedings of the IEEK Conference
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    • 2006.06a
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    • pp.101-102
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    • 2006
  • Similar to Orthogonal Frequency Division Multiplexing (OFDM), a Single Carrier with Frequency Domain Equalization (SC-FDE) system is computationally efficient since equalization is performed on a block of data in the frequency domain. In coherent QAM schemes, the mean phase rotation error caused by the residual carrier frequency offset may lead to serious degradation. When the frequency equalizer is combined with the mean phase error tracking algorithm, its performance can be enhanced noticeably.

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The Dielectric Properties of PZT(52/48)/BST(60/40) Heterolayered Thin Film Prepared bv RF Sputtering Method (RF 스퍼터링법을 이용한 PZT(52/48)/BST(60/40) 이종층 박막의 유전 특성)

  • Kwon, Hyun-Yul;Kim, Ji-Heon;Choi, Eui-Sun;Lee, Sung-Gap;Lee, Young-Hie
    • Proceedings of the KIEE Conference
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    • 2004.07c
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    • pp.1621-1623
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    • 2004
  • The $Pb(Zr_{0.52}Ti_{0.48})O_3/(Ba_{0.6}Sr_{0.4})TiO_3$ [PZT(52/48)/BST(60/40)] heterolayered thin films were deposited on Pt/Ti/$SiO_2$/Si substrates by using the RF sputtering method with RF powers of 60,70,80,90[W]. All thin films showed the peaks of the tetragonal phase. Increasing the RF power, dielectric constant and loss of the PZT(52/48)/BST(60/40)] heterolayered thin films were decreased. The thickness ratio of PZT and BST thin films was 1/1. The relative dielectric constant and the dielectric loss of the PZT(52/48)/ BST(60/40) heterolayered thin films were 562 and 13%, respectively.

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Structural Properties of BZCT Ceramics with Sintering Temperature (소결온도에 따른 BZCT 세라믹스의 구조적 특성)

  • Kim, Ji-Heon;Lee, Moon-Kee;Chung, Jang-Ho;Lee, Young-Hie
    • Proceedings of the KIEE Conference
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    • 2001.11a
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    • pp.115-117
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    • 2001
  • $Ba(Zn_{1-x}Co_x)TaO_3$[BZCT] ceramics were prepared by the conventional mixed oxide method. The ceramics were sintered at the temperature of $1450{\sim}1550^{\circ}C$ for 5hr. in air. The structural properties of the BZCT ceramics as a function of composition and sintering temperature were investigated by the XRD and SEM. The crystal structure of BZCT ceramics was investigated by the XRD. The microstructure of the specimens were observed by SEM. All the BZCT ceramics sintered above the $1550^{\circ}C$ were showed as a polycrystalline complex perovskite structure without second phases and any unreacted materials. The density of BZCT (70/30) specimen sintered at $1550^{\circ}C$ was $6.31g/cm^3$.

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