• Title/Summary/Keyword: lanthanum

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Electrical Properties of the Lanthanum Ferrite-Based Cathode Materials for Low-Temperature SOFCs (저온 작동형 SOFC Lanthanum Ferrite계 공기극 소재의 전기적 특성)

  • Kang, Ju-Hyun;Choi, Jung-Woon;Shim, Han-Byel;Yoo, Kwang-Soo
    • Journal of the Korean Ceramic Society
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    • v.43 no.3 s.286
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    • pp.162-168
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    • 2006
  • The perovskites with nominal compositions $La_{0.8}Sr_{0.2}Fe_{1-x}M_xO_3$ (M=Co, Mn, Ni, x=0.1-0.3) were fabricated by a solid-state reaction method as cathode materials of low-temperature operating Solid Oxide Fuel Cells (SOFCs). X-ray diffraction analysis and microstructure observation for the sintered samples were performed. The ac complex impedance were measured in the temperature range $600-900^{\circ}C$ in air and fitted with a Solatron ZView program. The electrical conductivity and polarization resistance of $La_{0.8}Sr_{0.2}Fe_{1-x}M_xO_3$ (M=Co, Mn, Ni, x=0.1-0.3) were characterized systematically. The porosities of the sintered samples were in the range of 25% to 38%. The polarization resistance of $La_{0.8}Sr_{0.2}Fe_{0.7}M_{0.3}O_3$ was $0.291{\Omega}cm^2\;at\;700^{\circ}C$.

The Effects of Siegesbeckiae Herba on EDRF in the Carotid Artery of the Rabbit (희렴이 가토(家兎)의 혈관내피세포성(血管內皮細胞性) 이완인자(弛緩因子)에 미치는 영향(影響))

  • Kim, Ho-Hyun;Kim, Gil-Whon
    • The Journal of Korean Medicine
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    • v.18 no.2
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    • pp.15-32
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    • 1997
  • This study was undertaken to define the mechanism of Siegesbeckiae Herba-induced relaxation in rabbit common carotid artery contracted by agonists. In order to investigate the effect of Siegesbeckiae Herba on contracted rabbit carotid arterial strips, transverse strips with intact or damaged endothelium were used for the experiment using organ bath. To analyze the mechanism of Siegesbeckiae Herba-induced relaxation, Siegesbeckiae Herba extract infused into contracted arterial strips induced by agonists after treatment of lanthanum chloride, indomethacin, atropine, $N\omega-nitro-{_L}-arginine$, cobalt chloride or methylene blue. The relaxation effect of Siegesbeckiae Herba was dependent on the presence of endothelium, showing that Siegesbeckiae Herba-induced relaxation was not observed in the strips without endothelium. The endothelium-dependent relaxation induced by Siegesbeckiae Herba was suppressed by the pretreatment of lanthanum chloride, $N\omega-nitro-{_L}-arginine$, cobalt chloride or methylene blue, but it was not observed in the strips pretreated with indomethacin or atropine. These results demonstrated that Siegesbeckiae Herba may inhibit agonist-induced contraction through an increase in the cyclic GMP by the production of nitric oxide in the vascular endothelial cells.

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The Ferroelectric Frequency characteristics of $Bi_{4-x}La_{x}Ti_{3}O_{12}$ ceramics with the variation of Lanthanum additives (La 첨가량에 따른 $Bi_{4-x}La_{x}Ti_{3}O_{12}$ 강유전체의 주파수특성)

  • Kim, Eung-Kwon;Park, Bok-Gi;Park, Gi-Yub;Park, Choon-Bae
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2001.11b
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    • pp.463-466
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    • 2001
  • In recent year, Ferroelectric $BLT(Bi_{4-x}La_{x}Ti_{3}O_{12})$ is a promising candidate materials. This study was practiced to make good conditions of BL T targets. In this study, calcination and sintering temperature were kept at $750^{\circ}C$, $1100^{\circ}C$ for 2 hour respectively. the density obtained 7.612, 7.98, $7.877g/cm^{3}$ as $La_{2}O_{3}$ contents were 0.0mol%, 0.25mol%, 0.5mol%. Especially, the lanthanum content of 0.5 mol% measured C-axis (117) preferred orientation more than the others targets in the XRD. In $\varepsilon_{r}-f$ relationship using by HP 4194 A impedance analyzer, the 0.5 mol% observed above 200 relative dielectric constant. but the dissipation factor was higher than others targets at 100Hz~13MHz range. SEM photograph with the content of $La_{2}O_{3}$ was observed like rod and plate types.

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