• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.2
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• pp.245-250
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• 1999

The effect of cation substitution on the inonic conductivity was studied in $(Li_{0.5}La_{0.5})_{1-y}Sr_yTi_{1-x}Mn_xO_3$ system. In case of Sr substitution, the ionic conductivity abrubtly decreased over y=0.05. This may be caused by the decrease of lithium contents which contribute to lithium inonic conductivity. Jahn-Teller distortion as well as lattice parameter variation influenced the inonic conductivity in case of Mn substitution. A and B-site cations effects on the conductivities were found to be independent, and the ionic conductivity as high as $2.8{\times}10^{-2}$S/cm was obtained in x=0.0006 and y=0.05.

• Journal of the Korean Ceramic Society
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• v.35 no.9
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• pp.981-987
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• 1998

$La_{0.5}Sr_{0.5}MnO_{3-\delta}$ as air electrode for soild oxide fuel cell was synthesized by a citrate process and its cathodic polarization was determinated by the current interruption method on the Gd-doped ceria as electrolyte. The addition of citric acid increased the exothermic heat for the formation of $La_{0.5}Sr_{0.5}MnO_{3-\delta}$ perovskite oxide. The degree of the initial particle agglomeration was affected by the exothermic heat. Also the increase of cal-cination temperature enlarged the particle size and the higher sintering temperature accelerated the den-sification of $La_{0.5}Sr_{0.5}MnO_{3-\delta}$ layer after its being painted on $Ce_{0.8}Gd_{0.2}O_{1.9}$ electrolyte. In this study $La_{0.5}Sr_{0.5}MnO_{3-\delta}$ synthesized by citrate process of which the molar ratio of citric acid to metal nitrate was 2 calcined at $650^{\circ}C$ for 2hr and sintered at 1100 at $1200^{\circ}C$ for 4 hrs after slurry coating on Ce0.8Gd0.2O1.9 electrlyte showed the lowest cathodic polarization.

• Proceedings of the Korean Nuclear Society Conference
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• 1998.05b
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• pp.677-682
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• 1998

영광원전주변 해양에서 조사된 환경방사능 조사결과를 토대로 Cs-137과 Sr-90 방사성물질의 해수와 부유물에서 분포특성과 해양생물로의 전이.농축특성을 분석하였다. 방사성물질의 분포특성 분석은 해양에서 방사성물질의 용해성과 부유물에의 흡착성 평가뿐 아니라 방사성물질의 해양확산을 평가하는데 필수적 요소이다. 지금까지는 방사성물질의 해양확산 평가시 완전 용해성으로 가정하여 단순한 해수유동 특성만을 고려하여 평가하였으나, 흡착성 등 물리화학적 거동특성을 평가함으로써 좀더 사실적인 해양확산을 평가할 수 있다. 평가결과 Cs-137과 Sr-90의 분포특성을 나타내는 분배계수가 각각 8.1$\pm$1.4E-4, 7.4$\pm$2.3E-5 로 나타났다. 이는 두 핵종 모두 용해성이 높고 흡착성이 낮음을 보여준다. 그리고 Cs-137과 Sr-90에 비해 상대적으로 흡착성이 높게 나타나고 있다. 또 전이.농축특성 분석결과는 김에서 Cs-137과 Sr-90의 전이.농축계수가 66과 3, 서대와 병어에서는 122.5와 6, 패류에서는 Sr-90의 전이.농축계수가 6으로 나타났다. Sr-90은 전반적으로 전이.농축계수가 낮게 나타나 생물체에유입되더라도 쉽게 배출돼 축적경향이 매우 낮음을 보여준다. 반면 Cs-137은 Sr-90에 비해 상대적으로 농축특성이 높게 나타나고 있다. 향후 이를 토대로 해역의 고유 환경특성에 맞는 방사성물질의 해양중 거동특성을 고려한 해양확산평가 및 해양감시가 이뤄져야할 것이다.

• Proceedings of the KSEEG Conference
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• 2000.04a
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• pp.110-110
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• 2000

Temporal and spatial distribution patterns of the magmatic rocks and associated ore deposits in the Mesozoic magmatic - metallogenic belt along the Yangtz River, Anhui Province are used to determine and discuss the crust - mantle interaction processes. The magmatic rocks are Cu - Au mineralized high - K calc - alkalic intermediate ¬acidic (CAK) and Fe - Cu mineralized high - Na alkalic - calc intermediate - basic intrusive rocks (FCN) in the central part of the belt and grade to Cu - Mo - Pb - Zn - Ag mineralized calc - alkalic granitoids (CMG) and A - type granites (AG) in the southern and northern parts of the belt. Samples from the CAK and CMG yield Rb - Sr isochron ages of 137 - 140Ma with $(^{87}Sr/^{86}Sr)_{o}$ = 0.7060 - 0.7101, while those from the FCN and AG yield the ages of 120 - 129Ma with $(^{87}Sr/^{86}Sr)_{o}$ = 0.7047 - 0.7077. The Sr isotope ratios, CriTh ratios 0.4 - 3.1), Eu/Eu* ratios < 0.79 - 1.05) and initial epsilon (Nd) values (-16.6 - -6.3) for the CAK and CMG are consistent with magma derivation from old metamorphic basement rocks rich in metallogenic elements through a two - stage process of mantle - derived magma underplating caused by primary lithosphere extension and subsequent partial melting. On the basis of Sr isotope data, CriTh ratios (3.4 - 13.8), Eu/Eu* ratios (0.86 - 1.13) and initial epsilon (Nd) values (-7.7 - +1.4), the FCN and AG are considered to be formed through syntexis with material input from the mantle that resulted from further lithosphere extension followed by mantle - derived magma underplating on a large scale.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.04b
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• pp.60-63
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• 2000

The $0.94MgTiO_3-0.06SrTiO_3$ ceramics were prepared by the conventional mixed oxide method. The structural properties were investigated with sintering temperature and composition ratio by XRD, SEM and DT-TGA. According to the X-ray diffraction patterns of the $0.94MgTiO_3-0.06SrTiO_3$ ceramics, the cubic $SrTiO_3$ and hexagonal $MgTiO_3$ structures were coexisted. Increasing the sintering temperature from $1325^{\circ}C$ to $1400^{\circ}C$, average grain size was increased from $5.026{\mu}m$ to $8.377{\mu}m$. In the case of the $0.94MgTiO_3-0.06SrTiO_3$ ceramics sintered at $1325^{\circ}C$, dielectric constant, quality factor and temperature coefficient of resonant frequency were 21.66, 2,522(at 7.34GHz), $+71ppm/^{\circ}C$, respectively.

• Clinical and Experimental Pediatrics
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• v.51 no.3
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• pp.237-242
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• 2008

To investigate the trends in the survival rate (SR) for very low birth weight infants (VLBW) and extremely low birth weight infants (ELBWI) in Korea, a total of 43 articles pertaining to SR were analyzed, covering the years from 1967 to 2007. The changes in SR were compared using 5 year periods. The SR for VLBWI has increased remarkably, from 31.8% in early 1960 to 65.8% in early 1990 and 78.8% in early 2000. The SR for ELBWI has increased from 8.2% in early 1960 to 37.4% in early 1990 and 62.4% in early 2000. The SR has improved steeply since early 1990. When the SRs for VLBWI in Korea were compared with those in the U.S.A. and Japan, the figures were 40%, 72%, and 79% in 1985; 65.8%, 82%, and 86% in 1990; 71.3%, 86%, and 88% in 1995; 78.8%, 86%, and 89% in 2000, respectively. Although the recent SRs for VLBWI and ELBWI in Korea has improved rapidly, they have not yet reached the levels in these highly developed countries. To obtain accurate statistics that could be represented as an SR for premature infants in Korea, we have to develop a nationwide network database project.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.693-696
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• 2001

The (Ba$_{0.3}$Bi$_{0.3}$Sr$_{0.4}$)TiO$_3$[BBST] ceramics were prepared by conventional mixed oxide method. The structural properties of the BBST ceramics with sintering temperature were investigated by XRD, SEM, EDS. In the case of BBST ceramics sintered at 1150~135$0^{\circ}C$, the $Ba_{0.5}$Sr$_{0.5}$TiO$_3$and SrBi$_4$Ti$_4$O$_{15}$ phase were coexisted. The 2$\theta$ value of the BST (110) peaks were shifted to the lower degree at the sintering temperature of 130$0^{\circ}C$ and 135$0^{\circ}C$. The grains of the BBST ceramics sintered at 130$0^{\circ}C$ and 135$0^{\circ}C$ were not appeared. Increasing the sintering temperature, the densities of the BBST ceramics were increased. In the BBST ceramics sintered at 130$0^{\circ}C$ and 135$0^{\circ}C$, the mole ratio of Bi was decreased.d.ed.d.d.d.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.50 no.8
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• pp.376-381
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• 2001

The(1-x) MgTiO$_3$-xSrTiO$_3$(x=0.03~0.04) ceramics were fabricated by the conventional mixed oxide method. The structural and microwave dielectric properties were investigated by XRD, SEM, EDS and network analyzer. The sintering temperature and time were 1275$^{\circ}C$~135$0^{\circ}C$ and 2hours, respectively. In the XRD results of 0.96MgTiO$_3$-0.04SrTiO$_3$ceramics, the perovskite structure of SrTiO$_3$and ilmenite structure of MgTiO$_3$phase were coexisted. The dielectric constant($\varepsilon$(sub)${\gamma}$) and temperature coefficient of resonant frequency($\tau$(sub)f) were increased with addition of SrTiO$_3$. In thie case of 0.96MgTiO$_3$-0.04SrTiO$_3$ ceramics sintered at 13$25^{\circ}C$, the dielectric constant, quality factor(Q) and temperature coefficient of resonant frequency($\tau$(sub)f) were 20.13, 7956(at 7.27GHz), and +1.76ppm/$^{\circ}C$, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.04a
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• pp.8-11
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• 1997

This study makes SrTiO$_{3}$ with nonpolarity among ferroelectrics by RF sputtering as dielectric layer, produces thin film of Si/SrTiO$_{3}$ and Si/Ti/SrTiO$_{3}$ of MOS structure using Ti as buffer layer, measures and examines the electrical features with optical refractive index, absorption rate, permittivity, photon energy and as a result, ferroelectrics oscillation occurrs by the interaction within a film by light temperature and the absorption of thin film with Ti as buffer layer is increased. It is found that the pea\ulcorner of permittivity value of Ti/SrTiO$_{3}$ thin film has low values and is appeared late and as dipole which is found in dielectric is shown, the experiment satisfies the theory In the nature of permittivity by photon energy, imaginary value is higher and current variation slope of thin film of thickness SrTiO$_{3}$ has lower values in reverse bias.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.597-600
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• 2002

Electrical properties of $\{(Sr_xCa_{1-x})_{0.95-y-z}Bi_2Pb_{0.05+y}\})Ti_{1.02}O_3$ ceramic were studied as a function of Sr/Ca ratio and Bi, Pb contents. Dielectric properties of specimens with different x, y, z values were explained in terms of ionic polarizability with Molecular Additionally Rules and Clausius-Mosotti equation. For the composition of $\{(Sr_{0.62}Ca_{0.38})_{0.90}Bi_{0.01}Pb_{0.09}\})Ti_{1.02}O_3$ and $\{(Sr_{0.62}Ca_{0.38})_{0.905}Bi_{0.015}Pb_{0.08}\})Ti_{1.02}O_3$, dielectric constant$({\varepsilon}_r)$, quality factor(Q) and temperature coefficient(TC) were 389, 3048, -1490 and 394, 1869, -1340 at 1MHz, respectively.