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원발성 후복막강 기형종과 교차성 융합 이소신을 동반한 터너씨 증후군 1예
김연중 대한영상의학회 1988 대한영상의학회지 Vol.24 No.1
In 1938, Turner described a clinical entity in phenotype females characterized by sexual infantilism con-genital webbed neck and cubitus valgus. After then the occurrence of renal anomalies in patients with Turner's syndrome has been recognized. Associated crosses fuses renal ectopia is very rare. Primary retroperitoneal teratoma is also rare and usually during childhood. The authors report a case of primary retroperitoneal teratoma and crossed fused renal ectopia with Tumer's syndrome(mosaic type). The clinical pathological and radiographical findings are reviewed.
Changes in Physical Properties of Ta5+-doped BaTiO3 Solid Solution
김연중 한국진공학회 2018 Applied Science and Convergence Technology Vol.27 No.6
Structural properties for the substitution of Ta5 + ions in the BaTiO3 crystal lattice were observed by SEM/EDS. The formation of perovskite phase and the change of (111), (200) and (002) planes of BaTiO3 solid solution containing a small amount of Ta5+ were studied. As a result, the relationship between the dielectric properties and the polycrystalline structure of Ta5+-doped BaTiO3 was confirmed. It was found that the maximum dielectric constant of the Ta5+-doped BaTiO3 solid solution was more than about 8000, and the transition temperature shifted slightly toward the lower temperature as compared with the pure BaTiO3. The dielectric constants of all the samples measured in the temperature region above the transition temperature showed some diffusivity and satisfied the modified Curie-Weiss law.
Characterization and Physical Properties of Ba0.9Sb0.1TiO3 Solid Solution
김연중 한국진공학회 2019 Applied Science and Convergence Technology Vol.28 No.2
BaTiO3 is known to be an environmentally friendly electronic material with a phase transition temperature that can be controlled through the substitution of an appropriate additive. Physical changes of grain growth in Ba0.9Sb0.1TiO3 were analyzed by adding a small amount of antimony to pure BaTiO3. The Ba0.9Sb0.1TiO3 solid solution with antimony substitution was prepared under various calcination and sintering conditions. The optimal conditions for sintering were confirmed and the grain growth process was clearly understood. As a result, the relationship between the dielectric properties and the polycrystalline structure of Ba0.9Sb0.1TiO3 substituted with antimony was confirmed. The maximum dielectric constant of the Ba0.9Sb0.1TiO3 solid solution was found to exceed about 5500 and the dielectric constant at room temperature reached nearly 4000. The transition temperature of Ba0.9Sb0.1TiO3 was shifted closer to room temperature than that of pure BaTiO3. Unlike the phase transition behavior of pure BaTiO3, the dielectric constant curve, which is a function of temperature for all samples, showed a very gradual change.
Changes in Dielectric Properties of Sb, Nb, and Ta-doped BaTiO3 Systems
김연중 한국진공학회 2019 Applied Science and Convergence Technology Vol.28 No.4
Acceptor and donor dopants have a significant effect on the dielectric properties of BaTiO3. In this paper, Sb, Nb, and Ta were added to BaTiO3 solid solutions to analyze the specific change of dielectric property based on temperature. First, the crystal stabilization process was analyzed by X-ray difraction and scanning eletron microscopy. Second, the optimum sintering conditions were confirmed according to the results, and specimens were prepared to compare their characteristics. In this experiment, it was found that the calcining condition was ~1100 °C and the sintering condition was ~1300 °C, although the heat treatment conditions were slightly different depending on the additive materials. The dielectric constants of BaTiO3 doped with 1.0 mole% of Sb, Nb, and Ta reached 4741, 2055, and 2963 at room temperature, and the transition temperatures were ~67, ~116, and ~109 °C, respectively, which shifted to very low temperatures from the transition temperature of pure BaTiO3 (~125 °C). The results of 1/K vs. T and ln[(1/K)-(1/Km)] vs. ln(T-Tm) were partially different from those of pure BaTiO3, having a temperature slightly higher than the phase transition temperature. This abnormal ferroelectric phase transition property of impurity-substituted BaTiO3 was confirmed by using the modified Curie-Weiss rule.