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Fabrication and Oxygen Permeation Properties of ${La_{1-x}Sr_{x}B_{1-{\gamma}}Fe_{\gamma}O_{3-{\delta}}$(B=Co, Ga) Perovskite-Type Ceramic Membranes (${La_{1-x}Sr_{x}B_{1-{\gamma}}Fe_{\gamma}O_{3-{\delta}}$(B=Co, Ga) 페롭스카이트 세라믹 분리막의 제조 및 산소투과특성)

  • 임경태;조통래;이기성;한인섭;서두원
    • Membrane Journal
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    • v.11 no.4
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    • pp.143-151
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    • 2001
  • We have fabricated mixed-ionic conducting membranes, L $a_{0.6}$S $r_{0.4}$ $Co_{0.2}$F $e_{0.8}$ $O_{3-}$$\delta$/ and L $a_{0.7}$S $r_{0.3}$G $a_{0.6}$F $e_{0.4}$ $O_{3-}$$\delta$/ by the solid state method. Ceramic membranes consisted of perovskite-type structures and exhibited high relative density, >95%. Especially, dense L $a_{0.6}$S $r_{0.4}$Co $O_{3-}$$\delta$/ layer was coated on the L $a_{0.7}$S $r_{0.3}$G $a_{0.6}$F $e_{0.4}$ $O_{3-}$$\delta$/ membranes by using screen printing technique in order to improve oxygen ion flux. We measured oxygen ion flux on uncoated L $a_{0.6}$S $r_{0.4}$ $Co_{0.2}$F $e_{0.8}$ $O_{3-}$$\delta$/, uncoated L $a_{0.7}$S $r_{0.3}$G $a_{0.6}$F $e_{0.4}$ $O_{3-}$$\delta$/, and coated L $a_{0.7}$S $r_{0.3}$G $a_{0.6}$F $e_{0.4}$ $O_{3-}$$\delta$/ membranes. The L $a_{0.6}$S $r_{0.4}$ $Co_{0.2}$F $e_{0.8}$ $O_{3-}$$\delta$/ membranes showed the highest flux, 0.26 mL/min.$\textrm{cm}^2$ at 90$0^{\circ}C$, after steady state had been reached. The oxygen flux of coated L $a_{0.7}$S $r_{0.3}$G $a_{0.6}$F $e_{0.4}$ $O_{3-}$$\delta$/ membranes showed higher value, 0.19 mL/min.$\textrm{cm}^2$ at 95$0^{\circ}C$. This flux was as much as 2 or 3 times higher than those of uncoated L $a_{0.7}$S $r_{0.3}$G $a_{0.6}$F $e_{0.4}$ $O_{3-}$$\delta$/ membranes. 3-$\delta$/ membranes.X> 3-$\delta$/ membranes.membranes.

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A Study of Convergence Social Voluntary Service Activity and Sense of Profession Values, Self-Esteem, Sociality in Nursing Students (간호대학생의 융·복합 사회봉사활동과 직업가치관, 자아존중감, 사회성에 관한 연구)

  • Yoon, Mi-Sun;Yim, So-youn
    • The Journal of the Korea Contents Association
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    • v.18 no.11
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    • pp.562-570
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    • 2018
  • This study is a descriptive research to understand the degree and relevance of profession value, self - esteem, and sociality of nursing college students according to voluntary service activities. The results showed that the formation of profession values according to the general characteristics was related to religion (F = 4.79, p = .003) and major (F = 3.75, p = .011) and self esteem was related to grade (F = 4.84, p = .002). The profession values according to the characteristics of voluntary service activities showed a significant difference in volunteer time (F=18.70, p<.001), volunteer duration (F=18.87, p<.001), volunteer organization(F=3.41, p=.001), volunteer motivation(F=8.08, p<.001), participation path(F=3.63, p=.002), participation field(F = 2.13, p = .031). The profession value was positively correlated with self-esteem(r = .327, p <.01) and sociality(r= .248, p <.01). Self-esteem showed a statistically significant positive correlation with sociality(r= .327, p <.01).

On the growth of entire functions satisfying second order linear differential equations

  • Kwon, Ki-Ho
    • Bulletin of the Korean Mathematical Society
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    • v.33 no.3
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    • pp.487-496
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    • 1996
  • Let f(z) be an entire function. Then the order $\rho(f)$ of f is defined by $$ \rho(f) = \overline{lim}_r\to\infty \frac{log r}{log^+ T(r,f)} = \overline{lim}_r\to\infty \frac{log r}{log^+ log^+ M(r,f)}, $$ where T(r,f) is the Nevanlinna characteristic of f (see [4]), $M(r,f) = max_{$\mid$z$\mid$=r} $\mid$f(z)$\mid$$ and $log^+ t = max(log t, 0)$.

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GENERALIZED CUBIC MAPPINGS OF r-TYPE IN SEVERAL VARIABLES

  • Kang, Dong Seung
    • Journal of the Chungcheong Mathematical Society
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    • v.20 no.1
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    • pp.37-45
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    • 2007
  • Let X, Y be vector spaces. In this paper, we investigate the generalized Hyers-Ulam-Rassias stability problem for a cubic function $f:X{\rightarrow}Y$ satisfies $$r^3f(\frac{\Sigma_{j=1}^{n-1}x_j+2x_n}{r})+r^3f(\frac{\Sigma_{j=1}^{n-1}x_j-2x_n}{r})+8\sum_{j=1}^{n-1}f(x_j)=2f{\sum_{j=1}^{n-1}}x_j)+4{\sum_{j=1}^{n-1}}(f(x_j+x_n)+f(x_j-x_n))$$ for all $x_1,{\cdots},x_n{\in}X$.

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Flux Melting Route to 2-and 3-dimensional Fibrous Potassium Titanates, K$_2Ti_{2n}O_{4n+1}$ (n = 2 and 3) (Flux 용융법에 의한 2차원 및 3 차원 구조의 티탄산칼륨 섬유의 합성)

  • Jin-Ho Choy;Yang Su Han;Seung Wan Song
    • Journal of the Korean Chemical Society
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    • v.37 no.8
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    • pp.765-772
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    • 1993
  • Two-dimensional potassium tetratitanate ($K_2Ti_4O_9$) and three-dimensional potassium hexatitanate ($K_2Ti_6O_{13}$) fibers have been prepared by the combined method consisting of the flux melting (1150$^{\circ}C$)-slow cooling (cooling rate = 5$^{\circ}C$/h) process from the starting raw materials of $K_2CO_3$, and $TiO_2$ with the flux of $K_2MoO_4$. It was found that the fiber growth reaction is strongly dependent upon the mole ratio of flux (F) to raw material (R), which is 7 : 3 (F : R) as for the optimum growth condition. Relatively long fibers (average length ${\thickapprox}$ 4 mm) with a mixture of $K_2Ti_4O_9$ (major) and $K_2Ti_6O_{13}$ (minor) could be obtained when the reaction was carried out for the $K_2MoO_4-$K_2O{\cdot}4TiO_2$ (F : R = 7 : 3) system, but for the $K_2$MoO_4$-$K_2O{\cdot}6TiO_2$ (F : R = 7: 3) one, only the short fibers with ${\thickapprox}$ 2 mm long could be grown as the mixed phase of $K_2Ti_6O_{13}$ and $K_2Ti_4O_9$.

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Sintering and dielectric properties of glass/ceramics dielectrics due to the borosilicate glass (Borosilicate glass에 따른 glass/ceramics 유전체의 소결 및 유전 특성)

  • Yoon, Sang-Ok;Kim, Kwan-Soo;Jo, Tae-Hyun;Kim, Kyung-Ho;Park, Jong-Guk
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.363-364
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    • 2005
  • LTCC(low temperature co-fired ceramics)용 glass/ceramic 복합체를 제조하기 위해 3종류 의 glass를 선정하고 filler로 $Al_2O_3$$TiO_2$를 사용하여 glass frit에 따른 소결 및 유전 특성에 대하여 조사하였다. Glass frit은 lead-borosilicate(PBS), zinc-borosilicate(ZBS), bismuth-borosilicate(BBS) glass 조성을 사용하였고 1100~$1400^{\circ}C$에서 melting시킨 후 quenching하여 frit화하였다. $Al_2O_3$$TiO_2$ filler에 10~50 vol%로 glass frit을 각각 혼합한 후 600~$950^{\circ}C$에서 2시간 동안 소결한 결과 50 vol% glass frit 일 때 $900^{\circ}C$ 이하에서 소성이 가능하였다. 유전특성은 $900^{\circ}C$에서 $Al_2O_3$-50vol%PBS($\varepsilon_{r}$=8.8, $Q{\times}f_o$=4,900, $\tau_f$=-24), $Al_2O_3$-50vol% ZBS($\varepsilon_{r}$=5.7, $Q{\times}f_o$=17,800, $\tau_f$=-21), $Al_2O_3$-50vol%BBS($\varepsilon_{r}$=11.1, $Q{\times}f_o$= 2,080, $\tau_f$=-48), $TiO_2$-50vol%PBS($\varepsilon_{r}$=18.6, $Q{\times}f_o$=3,800, $\tau_f$=+135), $TiO_2$-50vol%ZBS($\varepsilon_{r}$=36.4, $Q{\times}f_o$= 7,500, $\tau_f$=+159), $TiO_2$-50vol%BBS($\varepsilon_{r}$=56.4, $Q{\times}f_o$=520, $\tau_f$=+119)을 나타내었다. 따라서 LTCC용 기판재료 및 마이크로파 유전체로 응용이 가능한 것으로 확인되었다.

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Grignard Coupling Reaction of Bis(chloromethyl)diorganosilanes with Dichloro(diorgano)silanes: Syntheses of 1,3-Disilacyclobutanes

  • 조연석;유복렬;안삼영;정일남
    • Bulletin of the Korean Chemical Society
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    • v.20 no.4
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    • pp.427-430
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    • 1999
  • The Grignard coupling reaction of bis(chloromethyl)diorganosilanes [(ClCH2)2SiR1R2: R1 = R2 = Me, la; R1 = Me, R2 = Ph, lb; R1 = R2 = Ph, lc] with diorganodichlorosilanes [(Cl2SiR3R4: R3 = R4 = Me, 2a; R3 = Me, R4 = Ph, 2b; R3 = R4 = Ph, 2c] at THE reflux temperature gave the intermolecular C-Si coupling product of 1,1,3,3-tetraorgano-1,3-disilacyclobutanes 3a-f in poor to moderate yields ranging from 7% to 50% along with polydiorganosilapropanes. The cyclization reaction of la-c with methyl-substituted dichlorosilanes 2a, b gave 1,3-disilacyclobutanes 3a-c, e, d in moderate yields (42-50%), while the same reaction with dichlorodiphenylsilane (2c) to 1,3-disilacyclobutanes 3d, f resulted in low yield (7-18%) probably due to the steric hindrance of two-phenyl groups on the silicon of 2c.

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Preparation and Structure of $Re(NC_6F_5)(PPh_3)_2Cl_3 $ ($Re(NC_6F_5)(PPh_3)_2Cl_3 $화합물의 합성 및 구조)

  • 박병규;김영웅
    • Korean Journal of Crystallography
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    • v.7 no.2
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    • pp.113-119
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    • 1996
  • Reaction of Re(O)(PPh3)2Cl3,I, with 2,3,4,5,6-pentafluoroaniline (C6F5NH2), produced Re(NC6F5)(PPh3)2Cl3, II. The product has been characterized by 1H-NMR, elemental analysis, and X-ray diffraction. II crystallizes in the orthorhombic system, space group Pna21 with cell parameters a=18.763Å, b=14.737(2)Å, c=16.707(3)Å, Z=4. Least-square refinement of the structure led to an R(wR2)factor of 0.0455(0.1148) for 3319 unique reflections of I > 2σ(I) and for 174 variables.

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Regioselective Lithiation of $\alpha$-Methylpyridine Analogue and Its Trapping Reactions with $Me_2RSiCl(R = Me, tBuCH_2(Me_3Si)CH)$ ($\alpha$-Methylpyridine유도체의 국지 선택적 리튬화 반응과 $Me_2RSiCl(R = Me, tBuCH_2(Me_3Si)CH)$을 이용한 반응생성물의 확인반응)

  • Kim, Jeong Gyun;Park, Eun Mi;Son, Byeong Yeong
    • Journal of the Korean Chemical Society
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    • v.38 no.8
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    • pp.570-575
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    • 1994
  • The metallation of $\alpha$-methylpyridine 1(a∼f) with n-BuLi produced $\alpha-methylenylpyridinium$ salt 3(a∼f) by elimination of butane. The trapping reactions of 3(a∼f) with $Me_3SiCl\;and\;Me_2SiClCH(SiMe_3)CH_2tBu$ produced only 4(a∼f) and 5(a∼f). The $\alpha$-hydrogen atom of silylated methylene group in 4(a∼f) is more reactive than unreacted $CH_3$ of 4(a∼f) itself and 1(a∼f) toward n-BuLi at low temperature in pentane medium.

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